JP3150182B2 - Method for controlling injection amount of sodium carbonate in softening treatment of calcium-containing treated water of fluorine-containing wastewater and fluorine removing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the softening of a calcium-containing treated water obtained by subjecting waste water containing fluorine (which means "fluoride ion" in the present specification) to at least a primary fluorine removal treatment. The present invention relates to a method for controlling an injection amount of sodium carbonate used in performing a treatment.

[0002]

2. Description of the Related Art Flue gas desulfurization wastewater (hereinafter referred to as "desulfurization wastewater") generated in a coal-fired power plant and wastewater generated in a semiconductor factory (hereinafter referred to as "hydrofluoric acid wastewater") contain fluorine. The fluoride content in the wastewater is removed as calcium fluoride precipitate using calcium salt such as slaked lime, or the fluorine content is coprecipitated with aluminum hydroxide using an aluminum compound, and the coprecipitation is performed. Wastewater treatment methods for removing substances in the form of substances are widely used (in the present specification, the chemicals used for removing fluorine as described above are referred to as "fluoride removing agents"). Here, the `` aluminum compound '' may be anything as long as it can produce the above-mentioned `` aluminum hydroxide '', and examples thereof include aluminum sulfate, polyaluminum chloride, and alum. It may be used or in a solid state.

[0003] The desulfurization wastewater further contains calcium (which means "calcium ion" in this specification) and aluminum (which means "aluminum ion" in this specification). On the other hand, calcium fluoride is generally not contained in the hydrofluoric acid wastewater, but the treated water obtained by removing the fluorine content with slaked lime contains calcium derived from slaked lime.

[0004] Treated water obtained by removing most of the fluorine content from the fluorine-containing wastewater by the above method (including calcium,
In this specification, "calcium-containing treated water" is generally referred to as "primary treated water". In order to reduce a large amount of dissolved calcium in the calcium-containing treated water, sodium carbonate is injected into the calcium-containing treated water. Precipitated as calcium carbonate
A softening process for removing (generally, a “secondary process”) is performed. At this time, the pH is usually adjusted (usually, caustic soda is injected).

The present invention is intended to control the injection amount of sodium carbonate in the softening treatment, and to control the injection amount of a pH adjuster such as caustic soda as required. The method of the present invention to be described in detail is not limited to the above-mentioned softening treatment of the calcium-containing treated water obtained from the primary treatment of desulfurization waste water or hydrofluoric acid waste water for removing the fluorine content, and it is not limited to a softening treatment of a similar composition. For example, it can be applied to softening treatment of various calcium-containing treated water . However, in the present specification, description will be given focusing on the treatment of “desulfurization wastewater” as a representative of the treatment target of the method of the present invention.

[0006] First, the entire treatment of desulfurization wastewater using a fluorine removal device including a fluorine removal primary treatment device and a softening treatment device will be described. The concentration of fluorine in the desulfurization wastewater in a coal-fired power plant can be determined by, for example, the type of coal used for power generation (coal type), the method of a flue gas desulfurization apparatus (soot separation method or soot mixing method), In general, even if the species are the same, they differ depending on the power generation load.

Heretofore, in treating fluorine-containing wastewater such as desulfurization wastewater using a fluorine-removing device, it has been a practice to manually adjust the amount of chemicals.

FIG. 4 is a graph showing, as an example, a model change in the fluorine concentration of the desulfurization wastewater with the elapse of the operation time of the coal-fired power plant. The horizontal axis of this figure represents the operation time, and the vertical axis represents the fluorine concentration.

[0009] The fluorine concentration in the desulfurization wastewater fluctuates as the operation time elapses as shown in FIG.
Since the analysis of fluorine requires time and labor, it is often the case that the fluorine removing device is operated while injecting a fluorine removing agent such as slaked lime or aluminum sulfate at a constant injection rate based on the expected fluorine concentration (A). Was.

In this case, if the actual fluorine concentration in the wastewater is lower than the expected fluorine concentration (A) (C) (that is, the peak of the concentration fluctuation is lower), the fluorine-removing agent is excessively injected, and running is performed. This leads to an increase in cost. Conversely, the actual fluorine concentration is higher than the expected fluorine concentration (A) (B) [ie,
If the fluctuation of the concentration is higher, the amount of the fluorine-removing agent injected is insufficient, the efficiency of the fluorine-removing agent deteriorates, the quality of the treated water deteriorates, and the discharge standard water quality cannot be satisfied.
Conventionally, such inconveniences have been frequently observed.

[0011] Further, it has become clear that calcium and aluminum are present in the desulfurization wastewater, and these are effectively used for removing fluorine. However, the concentration of calcium and aluminum, which are the main control factors in the desulfurization wastewater (hereinafter, also referred to as “main active ingredient contained”), and further, the concentration of magnesium (which means “magnesium ion” in the present specification). In general, the concentration also varies depending on the operating conditions of the flue gas desulfurization unit and the type of coal used. As will be described later, magnesium also contributes to the removal of fluorine.

For this reason, when the main active ingredient contained in the desulfurization wastewater is effectively used for removing the fluorine content, a certain standard concentration of the main active ingredient contained in the desulfurization wastewater (generally, a planned value) is assumed. Alternatively, it is general to determine an operation value by actual measurement and set an insufficient amount of the fluorine-removing agent to be injected. In this method, as described above, the amount of the fluorine-removing agent becomes excessive or insufficient, so that there have been problems such as an increase in operating costs and an inability to stabilize the quality of treated water.

On the other hand, especially when removing the fluorine content of desulfurization wastewater by injecting slaked lime, a large amount of slaked lime is required.
Since the resulting calcium concentration in the treated water is also high, when the calcium-containing treated water is further treated by a nitrogen treatment device, a COD treatment device, or the like at the subsequent stage, it is necessary to reduce the calcium concentration in order to prevent calcium analysis. When an aluminum compound is used as a fluorine-removing agent, there is more or less the same problem because of the calcium content originally contained in the desulfurization wastewater, and it is necessary to reduce the calcium concentration of the calcium-containing treated water.

[0014]

For this reason, when sodium carbonate is injected into the above-mentioned calcium-containing treated water to perform softening treatment, precipitation of calcium carbonate occurs, and the calcium concentration is greatly reduced. Further, when a pH adjuster such as caustic soda was injected so that the pH value exceeded 10, magnesium (magnesium ion) contained in the desulfurization wastewater was precipitated as magnesium hydroxide and remained there. It has been found that unreacted fluorine co-precipitates (probably adsorbs) with magnesium hydroxide to effectively remove residual fluorine (therefore, magnesium is also one of the main controlling factors as described above). One). In addition,
Generally, magnesium is hardly contained in hydrofluoric acid wastewater.

Therefore, the amount of the pH adjuster such as sodium carbonate and caustic soda to be injected is similar to that in the case of the above-mentioned fluorine removal, and when slaked lime is used as the fluorine remover, it is contained in a certain standard of desulfurization wastewater. With respect to the calcium concentration and the slaked lime injection amount for the shortage, the injection amount of sodium carbonate is set assuming the residual calcium concentration after the reaction with the fluoride ions in the wastewater, and an aluminum compound is used as a fluorine removing agent. When performing, the concentration of calcium contained in the desulfurization wastewater of a certain standard (the injection of aluminum compound has almost no effect on the calcium concentration of the primary treatment water)
In general, the injection amount of sodium carbonate is set, and the set value of sodium hydroxide injection for pH adjustment is generally determined by assuming a certain standard concentration of magnesium contained in desulfurization wastewater (usually a planned value).

Therefore, in this method as well, as in the case of the above-mentioned fluorine removal, there is an excess or deficiency of sodium carbonate or caustic soda, causing problems such as an increase in operating costs and instability of treated water quality.

In particular, since the calcium concentration, aluminum concentration, and magnesium concentration in the desulfurization wastewater do not always fluctuate in synchronization with the fluorine concentration, and often change in a state having almost no correlation, the softening treatment device is used. It can be said that the desulfurization wastewater treatment equipment, including the above, requires operation management different from that of the conventional integrated wastewater treatment equipment.

Further, in order to stabilize the quality of treated water, excessive injection of a fluorine remover and sodium carbonate is inevitable, and the problems of industrial waste treatment associated with an increase in treatment cost and an increase in the amount of waste sludge are caused. Had occurred. On the other hand, injection of excessive caustic soda has caused a problem of water quality instability. Fluorine, calcium, aluminum,
In order to absorb fluctuations in the concentration of each component such as magnesium and to make the properties of the inflow desulfurization wastewater as uniform as possible, it was necessary to provide a storage tank with a sufficiently large capacity and a homogenization facility for the storage tank in the preceding stage. Hydrofluoric acid wastewater, which generally does not contain calcium or magnesium, has the same problem as described above because the amount of hydrofluoric acid used in a semiconductor factory greatly varies depending on the time of day.

Accordingly, the present invention has been made to solve the above problems, and has as its main object to minimize the amount of sodium carbonate to be injected when softening calcium-containing treated water containing fluorine-containing wastewater. In addition, it is intended to stabilize the quality of the softened water. Further, in some cases, the injection amount of a pH adjuster such as caustic soda for adjusting the pH during the softening of the calcium-containing treated water is kept to a minimum.

In order to solve the above-mentioned problems encountered in the total fluorine removing treatment including the softening treatment, the fluctuation of the flow rate of the wastewater flowing into the fluorine removing device, the fluorine concentration in the inflowing wastewater, and the like. Fluctuation, calcium or aluminum concentration fluctuation, magnesium concentration fluctuation,
And fluorine ions and various binding ions with calcium ions: components (sulfate ion, phosphate ion, silicate ion, etc. These concentration in the waste water of various binding ions which react with calcium ions also come more different coal types, etc.) Devise measures to minimize the injection amount of slaked lime or aluminum compound and the injection amount of sodium carbonate even if the composition ratio fluctuates, and to determine the fluorine content due to the magnesium content in the influent wastewater. To set the optimum pH value to maximize the removal effect and to reduce the amount of slaked lime or aluminum compound injected.Furthermore, since wastewater treatment involves several treatment steps, feedback Even when performing control, the control time constant is extremely large,
In addition, since the time constant changes with the fluctuation of the amount of inflow wastewater, it is necessary to devise a means for solving the problem that the feedback correction must be performed at an appropriate timing. It is necessary to increase the control accuracy of the feed forward as much as possible and to devise a means for responding to the need to reduce the feedback correction amount. "Processed water flow rate" means that there is no detector that can accurately measure the calcium concentration at a low cost without being affected by calcium precipitation (becomes a scale) when the calcium concentration is high. It was necessary to do.

[0021]

Means for Solving the Problems The present inventors have made intensive studies from such a viewpoint, and as a result, have completed the present invention.

That is, according to the present invention, there is provided a softening tank, a calcium concentration analyzer for detecting the calcium concentration of the calcium-containing treated water of the fluorine-containing wastewater, a facility for injecting sodium carbonate into the softening tank, and a remote setting of the amount of sodium carbonate to be injected. In a control method of a softening treatment device including a control system controlling by a signal of a value, a calcium concentration signal from the calcium concentration analyzer, a flow rate value of the calcium-containing treated water flowing into the softening treatment device, and an optimal multiplication coefficient. As a remote set value to the control system, the calculated sodium carbonate injection amount obtained by multiplying
Performing feedforward control of the amount of sodium carbonate injected; and (1) a reaction tank, a wastewater flow rate detector for detecting the flow rate of the inflowing fluorine-containing wastewater, and a wastewater fluorine concentration analyzer for detecting the fluorine concentration of the inflowing fluorine-containing wastewater. A facility for injecting slaked lime into the reaction tank, and a primary fluorine removal device including a slaked lime injection amount control system for controlling the slaked lime injection amount by a signal of a remote set value are provided in front of the softening treatment device, The amount of calcium required for fluorine removal is calculated by multiplying a predetermined calculation formula or the fluorine concentration signal by an optimum multiplication coefficient according to a fluorine concentration signal from the wastewater fluorine concentration analyzer, and calculating the necessary calcium amount by The slaked lime injection amount calculation value obtained by multiplying the inflow wastewater flow signal from the wastewater flow detector by the correction coefficient is the slaked lime injection amount control. Primary treated water obtained as a result of treating the fluorine-containing wastewater while performing feedforward control of the slaked lime injection amount as a remote set value to the stem [however, in this case, the calcium-containing treated water flowing into the softening treatment device] The flow rate value is an estimated value of the calcium-containing treated water flow rate obtained by correcting and calculating the fluctuation of the inflow waste water flow rate signal detected by the waste water flow rate detector by detecting the flow rate of the waste water flowing into the fluorine removal primary treatment device. And (2) a reaction tank, a wastewater flow rate detector for detecting the flow rate of the inflowing fluorine-containing wastewater, a wastewater fluorine concentration analyzer for detecting the fluorine concentration of the inflowing fluorine-containing wastewater, and detecting the calcium concentration of the inflowing fluorine-containing wastewater. Wastewater calcium concentration analyzer, slaked lime injection equipment to the reaction tank, and slaked lime injection that controls the slaked lime injection amount by a signal of a remote set value A fluorine removal primary treatment device including a control system is provided in front of the softening treatment device, wherein the fluorine-containing wastewater further contains calcium, and is predetermined by a fluorine concentration signal from the wastewater fluorine concentration analyzer. Calculate the calcium concentration required for fluorine removal by multiplying the calculation formula or the fluorine concentration signal by an optimum multiplication coefficient, and subtracting the calcium concentration signal from the wastewater calcium concentration analyzer from the calculated necessary calcium concentration to obtain a shortage. The amount of calcium is calculated, and the calculated value of slaked lime injection obtained by multiplying the calculated amount of insufficient calcium by the inflow wastewater flow signal from the wastewater flow detector and the correction coefficient is remotely set to the slaked lime injection amount control system. As a result of treating the fluorine-containing wastewater while performing feedforward control of the slaked lime injection amount as a value The obtained primary treated water, and (3) a reaction tank, a wastewater flow rate detector for detecting a flow rate of the inflowing fluorine-containing wastewater,
Wastewater fluorine concentration analyzer for detecting the fluorine concentration of inflowing fluorine-containing wastewater, wastewater aluminum concentration analyzer for detecting the aluminum concentration of inflowing fluorine-containing wastewater, equipment for injecting aluminum compound into the reaction tank, and remote setting of the amount of aluminum compound to be injected A primary fluorine removal device including an aluminum compound injection amount control system controlled by a value signal is provided in front of the softening device, wherein the fluorine-containing wastewater further contains aluminum and calcium, and the wastewater fluorine. The aluminum concentration required for fluorine removal is calculated by multiplying a predetermined calculation formula or the fluorine concentration signal by an optimum multiplication coefficient by the fluorine concentration signal from the concentration analyzer, and the wastewater aluminum concentration analysis is performed from the calculated required aluminum concentration. Subtract the contained aluminum concentration signal from the Calculate the amount of minium, and multiply the calculated value of the amount of insufficient aluminum by the inflow wastewater flow rate signal from the wastewater flow rate detector and the correction coefficient to obtain the calculated amount of the aluminum compound injection amount to the aluminum compound injection amount control system. The calcium-containing treated water for treating the treated water selected from the group consisting of primary treated water obtained as a result of treating the fluorine-containing wastewater while performing feedforward control of the aluminum compound injection amount as a remote set value with the softening treatment device. A method for controlling the injection amount of sodium carbonate in the softening treatment of the calcium-containing treated water, which is characterized in that:

In a preferred embodiment of the method for controlling the injection amount of sodium carbonate in the softening treatment of the calcium-containing treated water according to the present invention, the magnesium content contained in the wastewater is effectively used for removing the fluorine content. The softening apparatus further includes a control system that controls the pH of the water in the softening tank by a signal of a pH remote set value,
It is preferable to control the injection amount of the pH adjusting agent by constant value control with respect to the pH remote set value.

[0024]

[0025]

[0026]

Further, in still another embodiment of the method for controlling the injection amount of sodium carbonate in the softening treatment of the calcium-containing treated water according to the present invention, one of the above (2) or (3) is provided.
In the case of the primary treated water,
Similarly, instead of using a treated water flow rate detector to avoid the influence of scale due to precipitation of calcium contained in the calcium-containing treated water, the flow rate of the calcium-containing treated water flowing into the softening treatment device As the value, use the assumed value of the calcium-containing treated water flow rate obtained by correcting and calculating the fluctuation of the inflow wastewater flow rate signal detected by the wastewater flow rate detector by detecting the flow rate of the wastewater flowing into the fluorine removal primary treatment device. Is preferred.

Further, in still another embodiment of the method for controlling the injection amount of sodium carbonate in the softening of treated water according to the present invention, the softening treatment device adjusts the pH of the water in the softening tank to pH remote control.
Control system controlled by the signal of the set value
In the case of further comprising a treated water fluorine concentration analyzer for measuring the fluorine concentration of the softened treated water downstream of the softening treatment device, in order to perform feedback correction at an appropriate timing when performing feedback control. And
Each time the comparison circuit determines that the integrated value by the integration circuit that integrates the inflow wastewater flow rate based on the inflow wastewater flow rate signal from the wastewater flow rate detector has reached the effective retention volume value of the fluorine removal primary treatment device, Change in the calcium concentration of the calcium-containing treated water per unit time and the injection ratio of the pH adjuster for adjusting the pH of the water in the softening tank (pH adjustment with respect to the amount of the calcium-containing treated water flowing into the softening device) And the change of the ratio of the agent injection amount to a factor on the apparatus with respect to the previous value is measured, calculated, and stored. Each time the comparison circuit determines that the total effective retention volume of the fluorine removal primary treatment device and the softening treatment device has been reached, the integrated value of the inflow wastewater flow rate is reset and the treated water fluorine is reset. Calculation based on the change in the fluorine concentration of the softened water at the position of the degree analyzer and the target value thereof and the fluorine concentration of the softened water per a specified time, and remote control to the slaked lime injection control system or the aluminum compound injection control system. The set value and the remote set value of the pH of the water in the softening tank are preferably subjected to feedback correction control by logic operation.

Further, according to the present invention, if necessary,
Controls the pH of the water in the tank with the signal of the pH remote set value
And the primary processing described in (1), (2) or (3) above , further comprising a control system
A fluorine removal device including a primary treatment device for removing water to obtain water, comprising a calculation means and a control system for performing a method for controlling an injection amount of sodium carbonate according to any of the above embodiments. There is also provided a fluorine removing device characterized by the following.

Hereinafter, the present invention will be described specifically and in detail. In the following description, wastewater containing both fluoride ions and calcium ions, such as desulfurization wastewater, will be taken as typical fluorine-containing wastewater, and slaked lime, which is mainly used in soot separation type desulfurization wastewater, will be used as a fluorine remover. The following description focuses on the case in which the

In the case of fluorine-containing wastewater that does not contain calcium, such as hydrofluoric acid wastewater, it is considered except for the factor of the calcium concentration contained in the wastewater, that is, the concentration of calcium contained is always considered to be zero and injected as a fluorine removing agent. It may be considered that only the calcium content of the slaked lime is softened by the method of the present invention. In addition, since hydrofluoric acid wastewater generally does not contain magnesium, it is only necessary to consider a factor excluding this factor when setting up a control program, that is, consider a control system with the magnesium concentration always set to zero, which will be described later. Routine for secondary correction of slaked lime injection amount taking into account the ability of magnesium to remove fluorine by logic operation and correction of pH remote set value to control injection amount of pH adjuster such as caustic soda consumed by magnesium May be omitted.

When an aluminum compound is used as the fluorine-removing agent, the concentration of aluminum is replaced in place of the calcium concentration of the fluorine-containing wastewater to control the primary treatment for removing fluorine prior to the softening treatment. It is only necessary to note that the calcium concentration of the treated calcium-containing water is derived from the calcium originally contained in the fluorine-containing wastewater.

First, in controlling the softening treatment of the calcium-containing treated water according to the present invention, a calcium concentration (Ca ″) signal from a calcium concentration analyzer for detecting the calcium concentration of the calcium-containing treated water of the fluorine-containing wastewater is used. The amount of sodium carbonate (NaCO ₃ ) to be injected into the softening tank is obtained from the following formula based on the flow rate (Q ′ _M ) of the calcium-containing treated water flowing into the softening device, and this is set as the remote setting value of the injected amount of sodium carbonate In combination with the sodium carbonate injection amount control system, feed forward control is performed.The injected sodium carbonate may be in a solid state or a solution state, but is usually injected in a solution state, in which case the injection amount is represented by a flow rate. Is done.

[0034]

NaCO ₃ = K ₂ · Ca ″ · α ₂ · Q ′ _M · 1 / γ ₂ [where K ₂ is a constant specific to the softening device, α ₂ is an optimal multiplication coefficient as a simple proportional coefficient, Q ′ _M is a calcium-containing treatment water flow rate, gamma ₂ is sodium carbonate actually injected (solution)
Indicates the concentration (or density) of ]

The flow rate of the inflowing calcium-containing treated water (Q ′ _M ) is often difficult to directly measure with a flow rate detector due to the formation of scale by precipitation of high-concentration calcium as described above. In this case, the response of the fluctuation in the flow rate of the fluorine-containing wastewater flowing into the fluorine removal device including the softening device and the fluorine removal primary treatment device upstream thereof appears as a fluctuation in the flow rate at the inlet of the softening device. From the time and the magnitude of the fluctuation, the fluctuation of the inflow wastewater flow signal detected by the wastewater flow detector provided for detecting the flow rate of the fluorine-containing wastewater flowing into the above-mentioned fluorine removal primary treatment device is corrected and calculated. It is preferable to use the estimated value of the average effective flow rate obtained as above as the calcium-containing treated water flow rate (Q ′ _M ).

For example, more specifically, the assumed effective flow rate (Q ' _M ) of the calcium-containing treated water flowing into the softening treatment device is determined at regular intervals by the fluorine-containing wastewater flowing into the fluorine-removing primary treatment device. The average value of the assumed flow rate (Q ' _M1 ) obtained from the integrated flow rate and the estimated flow rate (Q' _M2 ) obtained from the required integration time for each fixed integration value of the flow rate of the fluorine-containing wastewater.

In the above-described primary apparatus for removing fluorine, for example, the fluorine in the inflow wastewater measured using a wastewater fluorine concentration automatic analyzer which can be measured continuously or at short time intervals and a similar wastewater calcium concentration automatic analyzer. From the concentration (F ₁ ) signal and the calcium concentration (Ca ′) signal, the calcium concentration required for fluorine removal is determined by a predetermined calculation formula or preferably by an optimal multiplication coefficient (α ₁ ) as a simple proportional coefficient [F 1]. ₁ · α ₁ -Ca ′] is calculated, and the inflow wastewater flow rate (Q), the constant (K ₁ ), the slaked lime injection amount feedback correction multiplication coefficient (β ₁ ) as a variable, and the slaked lime (slurry) actually injected Concentration (or density)
Slaked lime injection flow rate determined by multiplying the reciprocal ₍₁ / γ 1) of the (gamma ₁₎ as a remote setpoint, slaked lime injection flow control system and combined to perform the feed forward control. It is preferable that the above-described softening treatment is performed on the calcium-containing treated water obtained by the primary treatment for removing the fluorine content thus controlled.

The correction timing of the feedback correction multiplication coefficient (β ₁ ) based on the fluorine concentration of the slaked lime injected from the softening treatment water discharged from the softening treatment device is determined by the fluorine removal device (for example, the fluorine removal primary treatment device + softening treatment). It is carried out every time the integrated value (Q _Tn ) of the inflow wastewater flow reaches the effective retention volume (Q _S0 ) from the inlet to the outlet of the device.

If the secondary correction of the slaked lime injection amount in consideration of the ability of magnesium to remove fluorine by a logic operation described later is not performed instead of the fluorine concentration of the softened water, the calcium-containing treated water flowing into the softening device will be used. Is used for correcting the slaked lime injection amount feedback correction multiplication coefficient (β ₁ ), and from the inlet of the fluorine removing device to the inlet of the softening device as described above (this portion is referred to as “pre-processing” in this specification. the effective retention volume of referred to as part (s) ") to (Q _S1) may be used.

The apparatus may be designed so that both of the above two methods of correcting the slaked lime injection amount feedback correction multiplication coefficient (β ₁ ) can be performed. For example, both a calcium-containing treated water fluorine concentration analyzer and a softened treated water fluorine concentration analyzer are provided, and when the fluctuation of the inflow wastewater flow rate or the influent wastewater fluorine concentration per unit time exceeds a certain value, calcium is measured. The concentration of fluorine contained in the treated water may be used to determine the above-mentioned correction multiplication coefficient (β ₁ ), and at other times, the concentration of fluorine in the softened water may be used to calculate the above-mentioned correction multiplication coefficient (β ₁ ).
In this case, since the former case has a smaller effective retention volume than the latter, there is an advantage that it is possible to respond to a rapid change in the flow rate of the inflow wastewater or the fluorine concentration of the inflow wastewater in a shorter time. When the fluctuation of the flow rate or the fluorine concentration of the inflow wastewater is not so large, the advantage that the feedback control of the fluorine concentration signal of the softened water which is more closely related to the desired water quality can be controlled more precisely can be obtained. For this purpose, one treated water fluorine concentration analyzer may be used in common for both treated waters, and the sample lines may be switched alternately.

Injection amount of slaked lime Injection of the fluorine removal device so that trace back to the measured control values of the calcium concentration and the magnesium concentration can be made in accordance with the correction timing of the feedback correction multiplication coefficient (β ₁ ). Flow rate (Q) from the effective residence volume (Q _S1 ) from the inlet to the softening unit inlet (ie, to the outlet of the pretreatment unit)
At the time when the integrated value (Q _Tn ) of the pre-treatment unit is reached, the calculation and storage of the change value (ΔCa ″) of the calcium concentration of the calcium-containing treated water from the previous measurement value, and the calculation of the magnesium content in the wastewater Injection ratio of pH adjuster (various alkalis can be used, but usually caustic soda is used, but it will be described below as “caustic soda” is used) which is almost proportional to the concentration (calcium-containing treatment flowing into the softening device) The change value (Δ) from the previous value of the ratio of the amount of the pH adjuster injected to the amount of water multiplied by a factor on the device.
The calculation and storage of QV) may be performed.

That is, at the time of calculating the correction of the slaked lime injection amount, a logic control operation is performed based on the caustic soda consumption amount (caustic soda injection ratio) due to the change in the magnesium content and the increase / decrease tendency of the fluorine concentration of the softening treatment water. The back correction may be performed as one of the forms of the feedback control. This is because, as described above, when magnesium contained in the calcium-containing treated water obtained from the desulfurization wastewater reacts with caustic soda to form magnesium hydroxide, the residual fluorine content is also coprecipitated and removed. Can indirectly find the estimated magnesium concentration of the calcium-containing treated water, and since this magnesium concentration affects the "fluorine concentration of the softened treated water", these are used for feedback correction of the slaked lime injection amount. If it is used, more precise correction can be made.

[0043]

According to the control method of the present invention, softening bath by the calcium-containing treatment water flow rate (Q _'M) signals flowing to the softening treatment apparatus calcium concentration (Ca ") signal of the calcium-containing treatment water of the fluorine-containing waste water The amount of sodium carbonate (NaCO ₃ ) to be injected into the water is calculated by an arithmetic circuit, and the calculated value is used as a remote setting value of the amount of injected sodium carbonate.
Combined with sodium carbonate injection volume control system,
Since feedforward control is performed, it is possible to stabilize the water quality of the softening treatment and reduce the cost of the softening treatment by injecting the minimum necessary amount of sodium carbonate.

In the control method of the softening device configured as described above, the flow rate of the calcium-containing treated water at the outlet of the pretreatment unit upstream of the softening device required for arithmetic control of the injection amount of sodium carbonate is determined. Even when the concentration is high, it can be measured indirectly without being affected by calcium precipitation and scale formation. That is, it can be achieved, for example, by using the above-mentioned assumed average effective flow rate as the flow rate (Q ′ _M ) of the calcium-containing treated water flowing into the softening treatment apparatus. As described above, the average effective flow rate assumed value was obtained from the integrated value of the flow rate of the fluorine-containing wastewater flowing into the pre-treatment unit (generally, the primary treatment unit) upstream of the softening treatment device at regular intervals. The average value of the assumed flow rate (Q ' _M1 ) and the estimated flow rate (Q' _M2 ) obtained from the required integration time for each fixed integration value of the flow rate of the fluorine-containing wastewater. As a result, even if there is a large fluctuation in the flow rate of the wastewater, the change in the amount of sodium carbonate injected is transiently slightly earlier when the amount of inflow wastewater is increased, and slightly later when the amount of inflow wastewater is decreased, and does not cause insufficient injection. Driving in the safety area,
When the inflow wastewater flow rate is stable, an accurate sodium carbonate injection amount is secured.

As the first step, feedback correction to the set value of the slaked lime injection amount and the pH set value of the softening tank pH controller for controlling the caustic soda injection amount is performed at the time of flowing out of the pretreatment unit, that is, at the inlet of the softening treatment device. Calculate the calcium concentration of the calcium-containing treated water at the point of time when it has reached and the change value (ΔCa ″) after a certain period of time and the previous and current change values (ΔQV) of the caustic soda injection ratio. At the time of flowing out as softened treated water from the outlet of the treatment apparatus (in some cases, at the time of flowing out as calcium-containing treated water from the outlet of the pretreatment unit)
Then, the primary correction of the slaked lime injection amount correction multiplication coefficient (β ′) is calculated and corrected from the fluorine concentration target value (f) and the fluorine concentration measurement value (F ′). From the fluorine concentration measurement value (F ' _{(n + t)} ) of the softened water, a change value (.DELTA.F') of the fluorine concentration of the softened water is calculated, and these values (.DELTA.Ca ", .DELTA.QV, .DELTA.F ', F') are calculated. , F) in order to cope with fluctuations in the fluorine concentration of the softened water which is determined to be due to fluctuations in the magnesium concentration in the wastewater, a pH set value (SV) for injecting caustic soda into the softening tank is calculated. _pH ) correction factor and slaked lime injection volume correction factor (β ₁ )
It is now possible to perform secondary correction of

In the control method of the fluorine removing apparatus configured as described above, the treatment of the desulfurization wastewater is performed by changing the power generation load, changing the fluorine concentration and the contained calcium concentration due to the change of the coal type blend, and furthermore, The optimum multiplication coefficient (α
_The optimum slaked lime injection amount can be performed in real time as feed-forward control by the concentration value signal of the fluorine concentration automatic analyzer and the similar calcium concentration automatic analyzer which can be measured continuously or in short time intervals with ₁ ). Similarly, even in the case of hydrofluoric acid wastewater in a semiconductor factory that performs a process in which the amount of hydrofluoric acid varies greatly depending on the time of day, the optimum amount of slaked lime can be similarly controlled as feedforward control in real time.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically and in detail with reference to the accompanying drawings, but the present invention is not limited to the embodiments.

Embodiment FIG. 1 is a flowchart showing each processing step and a signal system in an example of a wastewater treatment apparatus which is a fluorine removing apparatus provided with a softening treatment apparatus used in the method of the present invention. This embodiment is an example of carrying out a preferred embodiment of the method of the present invention including a primary treatment for removing fluorine on the upstream side of the softening treatment.

This apparatus is a soot separation type desulfurization wastewater treatment apparatus. In FIG. 1, the left side from the position where the calcium-containing treated water 16 (in the present embodiment, “primary treated water”) flows out has a fluorine content. Removal primary treatment device (In the case of this device,
This is the pretreatment unit, and the right side is a softening treatment device (the posttreatment unit, the magnesium content in the desulfurization wastewater is precipitated by pH adjustment, and at the same time, the residual fluorine content is coprecipitated and removed in a form that is likely to be adsorbed. , Also works as a secondary treatment device for removing fluorine).

This fluorine removal primary treatment apparatus is composed of a reaction tank 5
(Injecting slaked lime), pH adjusting tank 6 (for example, injecting caustic soda, adjusting the pH value to a neutral range of about 6 to 8), and first coagulating tank 7 having a coagulation aid adding equipment (not shown).
(E.g., using an anionic polymer flocculant as an auxiliary agent), having a first settling tank 15, and as ancillary equipment, slaked lime dissolving tank 12, slaked lime injection pump 13, slaked lime flow detector 8, slaked lime injection flow controller 10, a slaked lime injection flow control valve (control valve) 9, a pH adjusting agent injection valve 18, and a pH adjusting agent storage tank (not shown). The first sedimentation tank 15 is provided with a first sludge extraction pump 17, and the pH adjustment tank 6 is provided with a pH detector 19.

The softening device includes a softening tank 31 (injecting sodium carbonate and caustic soda as a pH adjuster in this embodiment) and a second flocculating tank 32 (for example, having a coagulant aid adding device (not shown)). An anionic polymer flocculant is used as an auxiliary), and a second precipitation tank 33 is provided. Softening tank 31
Is provided with a pH detector 36, and the second settling tank 33 is provided with a second sludge extraction pump 35.

As ancillary equipment of the softening apparatus, a sodium carbonate dissolving tank 51, a sodium carbonate injection pump 5
2. A sodium carbonate injection flow controller 53, a sodium carbonate injection flow control valve (control valve) 54, a sodium carbonate injection flow detector 55, and a sodium carbonate concentration detector 56 are provided for sodium carbonate injection, and a caustic soda storage tank 71, a caustic soda Infusion pump 7
2. A softening tank pH controller 73, a caustic soda injection flow control valve (control valve) 74, and a caustic soda injection flow detector 75 are provided for pH adjustment.

The desulfurization wastewater generally contains magnesium ions, and when the pH value exceeds about 10 (for example, pH = about 10.3 to about 10.5), a precipitate of magnesium hydroxide is formed. A significant portion of the fluorine content remaining in the calcium-containing primary treatment water in the form of being adsorbed to the water is co-precipitated, so that the fluorine concentration in the secondary treatment water is further reduced.
The pH adjustment for this is performed in the softening tank 31.

In the above-mentioned fluorine removing apparatus, in this embodiment, the inflowing wastewater flow rate (Q) as each control factor is the inflowing wastewater flow rate detector 1, and the fluorine concentration (F) of the inflowing wastewater 2 is the wastewater fluorine concentration. Analyzer 3 (for example, using the ion electrode method,
In Japanese Unexamined Patent Publication (Kokai) No. 3-51754, the calcium concentration (Ca ′) of the influent wastewater 2 is determined by measuring the calcium concentration of the wastewater calcium analyzer 4.
(For example, utilizing the emission plasma method, Japanese Utility Model Laid-Open No. 2-1188)
56, 2-118857, 2-118858, 2-12
0057), calcium-containing primary treated water 1
The calcium concentration (Ca ″) of 6 was measured by the calcium concentration analyzer 14 of the primary treatment water, and the softened water 37 (in the case of this embodiment,
The fluorine concentration (F ′) of “secondary treated water” is measured by the treated water fluorine concentration analyzer 34.

In the above-mentioned fluorine removing apparatus, the fluorine ion concentration (F) of the inflow wastewater 2 is measured by the wastewater fluorine concentration analyzer 3.
Is measured, and the signal of F is input to the computer 100 as a calculating means, and the necessary total calcium amount [F
(X)] according to the following formula,
Calculate with PU.

[0056]

F (x) = a · logF ² + b · logF + C

However, since this calculation is complicated, the optimum multiplication coefficient (α ₁ ) as a simple proportional coefficient described below is used instead.
It is convenient to use the simple proportional coefficient (α ₁ ) in the following description of the present embodiment. The simple proportional coefficient (α ₁ ) is obtained from the results of actual equipment and various field tests, and can be used easily.
As × alpha _1, it is possible to determine the total amount of calcium required. Note that the simple proportional coefficient (α ₁ ) is
00, and its proper value is 2.
It is in the range of 5 to 5.0.

The calcium concentration (Ca ′) contained in the influent wastewater 2 was measured by the wastewater calcium concentration analyzer 4, and this C was measured.
'inputs signals to the computer 100, [F · α ₁ -Ca in CPU' a performs an operation of], to calculate the deficiency of calcium concentration should increase the slaked lime injection.

The value of [F · α ₁ -Ca ′] is multiplied by the instantaneous wastewater flow signal (Q) from the wastewater flow detector 1 by the CPU, and further analyzed by the analyzer used in the slaked lime injection system of the present apparatus. -Specific constants (K ₁ ) determined by the measurement range, control range, and unit of use of various devices such as devices and measuring devices
(Stored in the memory unit) to calculate an instantaneous amount of slaked lime when the slaked lime concentration is 100.

Further, the concentration signal (γ ₁ ) of the slaked lime concentration detector 11 for measuring the actual slaked lime slurry concentration is inputted to the computer 100, and the above-mentioned slaked lime concentration 10
The slaked lime injection flow rate at the actual liquid concentration is calculated by multiplying the instantaneous slaked lime injection amount at 0% by 1 / γ ₁ .

When an automatic melting facility capable of constantly controlling the concentration of slaked lime is prepared, 1 / γ ₁ may be included in the internal constant of the arithmetic unit and the slaked lime concentration detector may be omitted. Although slaked lime can be injected in a solid state, it is preferably injected in a slurry state.

Further, as a preferred embodiment, a slaked lime injection amount feedback correction multiplication coefficient (β ₁ ) represented by the following equation may be used.

[0063]

Β ₁ = 1 + RV _(tn−1) + ΔRV _{1 (tn)} + ΔRV _{2 (tn + t)}

The equation (3) is calculated each time the integrated value (Q _Tn ) of the inflow wastewater flow reaches the effective retention volume (Q _S0 ) of the fluorine removing device. That is, when Q _Tn ≧ Q _S0 , the multiplication coefficient (β ₁ ) is corrected to a new value and fixed until the next time. At the same time, the integrated value of the inflow wastewater flow rate (Q _Tn )
Is also reset to zero and the integration is restarted.

In the above equation (3), ΔRV
_{1 (tn)} is the fluorine concentration signal F 'from the treated water fluorine concentration analyzer 34 for measuring the fluoride ion concentration of the softened water 37 and the fluorine concentration target value f of the softened water 37 (within a non-zero discharge allowable limit). Is better to be set to a positive value of
−f) is the current primary correction value when Q _Tn ≧ Q _S0, and ΔRV _{1 (tn)} = k (F′−f) _(tn) .
Here, k is a primary correction proportional coefficient for each correction value. In the equation ₍ 3 ₎ , RV _(tn-1) is the accumulated value of the correction values up to the previous time, and ΔRV _{2 (tn + t)}
Is a logic operation based on ΔF ′, ΔCa ”and ΔQV (ΔQV is the“ increase / decrease tendency of the caustic soda injection amount ratio ”described later) after the primary correction at the time of Q _Tn ≧ Q _S0 and (t) time has elapsed. Is a corrected secondary correction value (having ± polarity).

It should be noted that this secondary correction value is not necessarily required to be used. If you don't use this,
The primary treatment was performed using the calcium-containing primary treated water 16 as the primary treated water instead of the softened treated water 37 as the secondary treated water to measure the fluorine concentration for calculating the slaked lime injection amount feedback correction multiplication coefficient (β ₁ ). The fluoride ion concentration of the primary treatment water 16 is measured by a primary treatment water fluoride ion concentration analyzer (not shown) provided in the vicinity of the water calcium concentration analyzer 14, and the slaked lime injection is performed in substantially the same manner even when the fluoride ion concentration is fed back as F '. Volume control can be performed. However, in the present embodiment, the ability to remove the fluorine content of magnesium in the desulfurization wastewater is indirectly considered as a control factor, and the above-described secondary correction value is used to control the amount of slaked lime injection more precisely. Continue explanation.

The fluorine concentration target value f of the softened water 37
Is set to a positive value within the non-zero emission tolerance
Specifically, it means that the value is set to a value higher than the measurement limit value (lower limit) of the fluorine concentration analyzer 34, larger than the measurement error, and within the allowable emission limit, and this means that the excess of slaked lime This is for performing control to avoid injection. This is because if the f-value is set to be equal to or less than the value of the measurement lower limit of the fluorine concentration analyzer 34 plus the measurement error, when F ′ becomes equal to or less than the value of the measurement lower limit of the fluorine concentration analyzer 34 plus the measurement error due to excessive injection. This is because it is not possible to determine whether the injection is excessive injection or the degree of excessive injection.

The calculation of the slaked lime injection flow rate (Ca) as described above is represented by the following equation.

[0069]

## EQU4 ## Ca = K ₁ · [F ₁ · α ₁ -Ca '] · Q · β
₁・ 1 / γ ₁

By performing such calculations, feedforward control of the slaked lime injection flow rate is performed. The calculated slaked lime injection amount (Ca) is calculated by the slaked lime injection flow rate controller 10
Is set as the remote set value of the injection flow measured by the slaked lime injection flow detector 8 and the computer 100
And output as an opening command MV value (manipulating value) to the slaked lime injection flow control valve 9. In this manner, injecting slaked lime without excess or deficiency in a steady state is realized.

Next, the control of the injection amount of sodium carbonate into the softening tank 31 of the softening apparatus is performed by the following method. First, a calcium concentration (Ca ″) signal from the primary treated water calcium concentration analyzer 14 for detecting the calcium concentration of the calcium-containing primary treated water 16 flowing out of the first settling tank 15 and flowing into the softening tank 31 and a calcium-containing substance described later. The amount of sodium carbonate (NaCO ₃ ) to be injected into the softening tank 31 is determined by the above equation (1) from the primary treatment water flow rate (Q ′ _M ) signal, and this is set as the remote setting value of the sodium carbonate injection flow rate. In combination with the sodium carbonate injection flow rate controller 53, feed forward control is performed.

[0072]

## EQU1 ## NaCO ₃ = K ₂ · Ca ″ · α ₂ · Q ′ _M · 1 / γ ₂

In this equation, K ₂ is a constant determined by the measurement range, control range and unit of use of the sodium carbonate injection system of the present apparatus, and is stored in the memory of the computer 100.

[0074] Furthermore, alpha ₂ is the optimum multiplication factor as a simple proportionality coefficient in the sodium injection rate control, those of obtained from results of the actual machine and various field tests, conveniently be used, as Ca "× α ₂ , The instantaneous required amount of sodium carbonate can be determined when the amount of sodium carbonate is 100% .The simple proportional coefficient (α ₂ ) is stored in the memory of the computer 100,
Its proper value lies in the range of 0.8 to 1.60.

Γ ₂ indicates the concentration (or density) of the sodium carbonate (solution) to be actually injected, and specifically, a sodium carbonate concentration detector for measuring the sodium carbonate concentration of the sodium carbonate solution. 56 is a sodium carbonate concentration signal from FIG. A computer 100 using the sodium carbonate concentration signal (γ ₂ ) as a calculating means
, And the above sodium carbonate concentration of 100%
Instantaneous required sodium carbonate injection amount [Ca "
× α ₂ ] is multiplied by 1 / γ ₂ to calculate the sodium carbonate injection flow rate at the actual liquid concentration.

When an automatic dissolution equipment capable of constantly controlling the concentration of sodium carbonate is prepared, 1 / γ ₂
Is included in the internal constant of the arithmetic unit, and the sodium carbonate concentration detector 56 can be omitted. Although sodium carbonate can be injected in a solid state, it is preferable to inject it in a solution state.

As described above, the flow rate of the influent calcium-containing primary treated water (Q ′ _M ) is often difficult to directly measure with a flow rate detector due to the formation of scale due to the precipitation of high-concentration calcium. . Therefore, the fluctuation of the flow rate of the wastewater flowing into the fluorine removal device is represented by the fluctuation of the response time and the fluctuation amount of the flow rate of the wastewater flowing into the wastewater flow detector 1 which is detected as the fluctuation of the flow rate at the inlet of the softening treatment apparatus. Is preferably used as the calcium-containing treated water flow rate (Q ′ _M ).
Of course, when the flow rate (Q ′ _M ) of the inflowing calcium-containing primary treated water can be directly detected by the flow rate detector, a flow rate signal from the flow rate detector may be used.

For example, the assumed effective flow rate of the calcium-containing primary treatment water flowing into the softening treatment device, that is, the flow rate of the calcium-containing primary treatment water (Q ′ _M ) is determined by the fluorine-containing wastewater flowing into the fluorine removal primary treatment device. Estimated primary treatment water flow rate (Q ' _M1 ) calculated from the integrated waste water flow rate at fixed time intervals and estimated primary treatment water flow rate (Q' _M2) determined from the required integration time for each fixed integrated value of the fluorine-containing waste water flow rate ). In this case, the assumed value of the effective flow rate of the primary treated water, that is, the flow rate of the calcium-containing primary treated water (Q ′ _M ) is expressed by the following equation.

[0079]

## EQU5 ## Q ′ _M = (Q ′ _M1 + Q ′ _M2 ) / 2

In equation (5), Q ′ _M1 is represented by the following equation.

[0081]

## EQU6 ## Q ′ _M1 = Q ′ _T1 / t _(TM-3) <m ³ / hr>

In the equation (6), Q ′ _T1 is a value (Q ′) obtained by subtracting the first sludge withdrawal flow rate drawn through the first sludge withdrawal pump 17 from the inflow wastewater flow rate (Q). ”Is the integrated value of the“ specified time calculation method ”, and t
_(TM-3) is the above-mentioned rated inflow wastewater at the inlet of the primary fluorine removal equipment, that is, at the inlet of the reaction tank 5 when the inflow wastewater flow rate is almost equal to the upper limit of the range of the inflow wastewater flow rate determined by the equipment design. Response time until a relatively small change in the flow rate value from the flow rate appears in the flow rate change at the outlet of the first sedimentation tank 15 (actually, it is a value that is roughly fixed, It is a variable value to some extent according to)
It is.

In equation (5), Q ′ _M2 is represented by the following equation.

[0084]

## EQU7 ## Q ′ _M2 = Q ′ _S1 (= Q ′ _T2 ) / T _S <m
³ / hr>

In the equation (7), Q ′ _T2 is a value (Q ′) obtained by subtracting the first sludge withdrawal flow rate drawn by the first sludge withdrawal pump 17 from the inflow wastewater flow rate (Q). This is the integrated value of the "specified volume calculation method", which is "the minimum operation inflow at the inlet of the reaction tank 5 at the time of the almost operation minimum inflow wastewater flow rate (corresponding to the lower limit of the range of the wastewater flow rate enabling stable operation)". the value of _T2 'Q when equal to _(S1' variation of a relatively small flow rate from the waste water flow rate is first precipitation tank integrated value of the inflow wastewater flow rates up to appear at the flow rate fluctuation of the outlet of the 15 Q) ' Used. T _S is Q ′ _T2
Represents the time until the value of Q ′ _S1 reaches the value of Q′S1.

Thus, the first settling tank 15 and the softening tank 31
The estimated effective flow rate (Q ' _M ) is obtained even if there is no treated water flow rate detector during
And the calcium concentration (Ca ") of the calcium carbonate (Ca"), the flow rate of sodium carbonate injection can be determined, and feedforward control of sodium carbonate injection in the softening treatment of the calcium-containing treated water is realized.

If the assumed effective flow rate as described above is used as the primary treated water flow rate (Q ′ _M ), a large wastewater flow rate (Q)
Despite the fluctuations, the change in the amount of sodium carbonate injected changes slightly earlier when the inflow wastewater is increased, and slightly later when the inflow wastewater decreases, and operates in a safe area where sodium carbonate injection is not insufficient. On the other hand, when the wastewater flow rate is stable, an accurate sodium carbonate injection amount is secured.

The amount of sodium carbonate injection (NaCO ₃ ) obtained by the equation of “Equation 1” thus obtained is set as a remote set value of the sodium carbonate injection flow controller 53, and is actually measured by the sodium carbonate injection flow detector 55. The calculated injection flow rate is compared with and adjusted by the computer 100 as arithmetic means, and is output as an opening degree command MV value to the sodium carbonate injection flow rate control valve 54.

Q _{Tn is used} as a timing for _obtaining the following measured values at the time when the inflow wastewater flows into the fluorine removal device and flows out of the outlet of the pretreatment unit (fluorine removal primary treatment device). The point of ≧ Q _S1 was selected. However, Q _Tn
Is the integrated value of the inflow wastewater flow rate (Q) being integrated this time,
Q _S1 is the effective retention volume from the inlet to the outlet (ie, the outlet of the first sedimentation tank 15) of the fluorine-removing primary treatment apparatus [the sludge withdrawal flow rate and the circulation flow rate (at least after a certain stage of processing to return to the upstream side). Correction of wastewater, if any).

The timing at which each measured value described below is determined at the time when the inflow wastewater flows into the fluorine removal device and flows out as softened water from the outlet of the post-processing unit (softening device) is as follows. The time point of Q _Tn ≧ Q _S0 was selected.
Here, Q _Tn is the integrated value of the inflow wastewater flow rate (Q) being integrated this time, and Q _S0 is the inlet to the outlet of the fluorine removal device (that is, the outlet of the second settling tank 33), as described above. Effective retention volume up to and including the correction of the sludge withdrawal flow rate and the circulation flow rate (the flow rate of wastewater that has undergone at least some stage of return to upstream).

As described above, the inflow wastewater which is feedforward-controlled becomes the calcium-containing primary treatment water 16, and the calcium-containing primary treatment water 16 reaching the downstream treatment section (ie, the inlet of the softening treatment device) at a certain point in time. Concentration (C
a ″ _(n) ) and the calcium concentration (Ca ″ _{(n + t)} ) of the primary treated water 16 after the elapse of (t) time (variable time of the timer TM-1) from the certain point in time, according to the following equation. , The amount of change (ΔCa ″) indicating the tendency of the calcium content of the primary treatment water 16 to increase or decrease is calculated.

[0092]

ΔCa ″ = Ca ″ _{(n + t)} −Ca ″ _(n)

Further, the injection ratio of caustic soda into the softening tank 31 (the ratio of the amount of caustic soda injected to the amount of primary treatment water flowing into the softening tank 31 multiplied by a factor on the apparatus).
, A comparison operation between the above-described time point and the previous corresponding time point is performed, and the increasing / decreasing tendency (change amount) of the magnesium content of the primary treatment water 16 which is an unknown control factor is determined by the amount of caustic soda consumption, that is, the caustic soda injection ratio. This is inferred from the following equation representing the increase / decrease tendency (change amount: ΔQV) of (QV).

[0094]

９QV = QV _(n) −QV _(n−1)

In the equation ₍ Equation 9 ₎ , QV _(n) is the current caustic soda injection ratio and is expressed by the following equation.

[0096]

(Equation 10)

In the equation ₍ 10 ₎ , FV _(n) represents the current caustic soda injection amount in the maximum caustic soda injection amount range (caustic soda injection pump 72, caustic soda injection flow control valve 74, pH detector or caustic soda injection flow detector). Divided by the maximum injection value determined by design constraints such as the scale of the instrument, etc.).
Multiplied by zero. Q _O is the maximum range of the primary treatment water inflow (corresponding to the maximum value of the maximum flow rate of the primary treatment water determined by the restriction on equipment design), and Q ′ _{M (n)} is the primary treatment at the outlet of the first settling tank 15. The denominator of the above equation is expressed as a percentage in the present average effective flow rate assumed value of water 16 by 100.
Is multiplied by

Therefore, in general, the caustic soda injection ratio (QV) is determined by the ratio of the amount of caustic soda injection to the amount of primary treatment water 16 flowing into the softening tank 31 by a factor on the apparatus [maximum inflow of primary treatment water / caustic soda. Multiplied by the maximum injection volume range), and this "change" in the caustic soda injection ratio is a factor on the device is constant,
If this factor is excluded, it can be considered that the ratio of the amount of caustic soda injection to the amount of primary treatment water 16 changes. MV _(n) is the softening tank pH controller 7
3 when MV _(n) is proportional to the amount of caustic soda injection, MV _(n) = FV _(n) , and the above equation represents this case.

In the equation ₍ 9 ₎ , QV _(n-1) is the previous caustic soda injection ratio and is expressed by the following equation.

[0100]

[Equation 11]

[0102] In the formula of the "Number 1 1", FV _(n-1) is multiplied by 100 in the sense that the caustic soda injection amount of the previous expressed as a percentage divided by the caustic soda maximum injection volume range. Q _O is the maximum flow rate of primary treated water, and Q '
_{M (n-1)} is a value obtained by multiplying the previous assumed average effective flow rate of the primary treated water 16 at the outlet of the first settling tank by 100 in the sense that the denominator of the above equation is expressed as a percentage. MV
_(n-1) represents the output (% ₎ of the current pH controller (softening tank pH controller 73). When MV _(n-1) is proportional to the amount of caustic soda injection, MV _(n-1) = FV _(n-1) , and the above equation represents this case.

On the other hand, at the time of the above-mentioned Q _Tn ≧ Q _S0 , as described above, the slaked lime is obtained by the current softened water fluorine concentration (F ′ _n ) and the softened water fluorine concentration target value (f). The primary correction of the injection amount is calculated by the following equation.

[0103]

Β ₁ = 1 + RV _(tn−1) + ΔRV _{1 (tn)} [where ΔRV _{1 (tn)} = k (F′−f), which is a primary correction value]

After the time (t) (variable time of the timer TM-2) from this point, the fluorine concentration of the softened water (F ′)
_{(n + t)} ) is measured, and a change amount (ΔF ′) indicating a tendency of increase and decrease of the fluorine concentration of the softened water is calculated by the following equation.

[0105]

ΔF ′ = F ′ _{(n + t)} −F ′ _n

Here, "Equation 8", "Equation 9", and "Equation 1"
ΔCa ″, ΔQV, ΔF ′ calculated by the equations 3)
And the following “Equation 14” and “Equation 15” from the values of F ′ and f
Logic operation is performed according to the following equation.

[0107]

[Equation 14] SV _pH = A + KV _(tn-1) + ΔKV _(tn)

In the equation (Equation 14), the SV _pH is calculated as
Is the pH remote set value of the pH controller 73, and has upper and lower limiters. A is a reference set pH value of the pH controller 73 of the softening tank 31 and is 1
It is around 0.3. KV _(tn-1) is, Q _T ≧ Q _S0 previous (tn-1), the time ie became _{Q T (tn-1) ≧} Q S0, a cumulative value of the correction value for SV _pH was logic operation , ± polarity. ΔKV _(tn) is now F′−f, Δ
F ′, ΔCa ″, and ΔQV are correction values for the current SV _pH, which are logically calculated according to their polarities and magnitudes, and have ± polarity. The upper and lower limiters are provided for SV _pH . In order to avoid destabilization of water quality due to excessive or under injection of caustic soda.

[0109]

Β ₁ = 1 + RV _(tn−1) + RV _{1 (tn)} + ΔRV _{2 (tn + t)}

[0110] In the formula of the "number 15", RV _(tn-1) represents the accumulated value of the correction value for beta ₁ up to the previous, with the polarity of the ±. RV _{1 (tn)} is the above-described primary correction value. ΔRV
_{2 (tn + t)} is ΔF ′ after (t) time (variable time of the timer TM-2) after the primary correction at the time of Q _TM ≧ Q _S0 ,
A secondary correction value logically calculated by ΔCa ″ and ΔQV, and has ± polarity.

An example of the above logic operation is shown in FIG.
In FIG. 2, thresholds (m, n, and q in FIG. 2) are provided so as not to perform unnecessary logic operations, taking into account the accuracy and reproduction error of each measurement analyzer. I have. In addition, in order to prevent the correction per operation from being an excessive correction, a positive constant on each operation (in FIG. 2,
_{a, b 1, b 2,} c, is provided d, e, and h) a.

The logic operation of FIG. 2 will be specifically described.

When the fluorine concentration change amount (ΔF ′) of the softened water is a positive value larger than + m, the secondary correction (ΔRV _{2 (tn} ) that increases the slaked lime injection amount feedback correction multiplication coefficient (β ₁ ) by a × ΔF ′ _{+ t)} ). On the other hand, when the fluorine concentration change (ΔF ′) of the softened water is minus less than −m, the calcium concentration change (ΔCa ″) of the primary treated water is larger than + m and the fluorine concentration of the softened water is plus. (F ′) and the deviation (F′−) of the target value (f).
Only when f) satisfies the negative condition, the slaked lime injection amount feedback correction multiplication coefficient (β ₁ ) is calculated as − [b ₁ × | Δ
F ′ | + b ₂ × ΔCa ″] (ΔRV
Performs a _{2 (tn + t)),} when it does not satisfy the above conditions is not performed secondary correction of β _1.

The fluctuation in the fluorine concentration (ΔF ′) of the softened water is +
In the case of a positive value larger than m, the softening tank p is + h × ΔF ′.
A correction (ΔKV _(tn) ) for increasing the pH remote set value (SV _pH ) of the H controller is performed. On the other hand, when the fluorine concentration fluctuation (ΔF ′) of the softening treatment water is minus minus less than −m, the calcium concentration fluctuation (ΔCa ″) of the primary treatment water hardly occurs, and the change amount (ΔQV) of the caustic soda injection ratio is + q.
-C [d × ΔQV + e × | ΔF ′ only when the deviation (F′−f) between the larger plus and the fluorine concentration (F ′) of the softened water and the target value (f) satisfies the negative condition.
|] Is performed to reduce the pH remote set value (SV _pH ) of the softening tank pH controller. If the above condition is not satisfied, the SV _pH is not corrected.

The above-described logic operation is merely an example. Each measurement value used in the logic operation may be obtained by a manual analysis instead of the automatic analysis, and a sampling position therefor can be selected at almost any position of the fluorine removing device.

FIG. 3 is a flowchart showing the procedure of the control operation of the present embodiment described above. The program processing procedure performed by the computer 100 will be described next with reference to the flowchart of FIG.

At some point, when it is detected that the apparatus is operating [Step (1)], the integrated value (Q _Tn ) of the inflowing wastewater flow rate up to the previous cycle during the current integration is determined by the fluorine content. The comparison circuit determines whether or not the effective retention volume value (Q _S1 ) from the inlet to the outlet of the primary removal apparatus (ie, the outlet of the first settling tank 15) has been reached [Step (2)]. If it has not reached, the operation of the equation (4) is performed by the arithmetic circuit [Step (3)], and slaked lime is injected into the reaction tank 5 based on the result. Next, the operation of "Equation 1" is performed by the operation circuit [step (4)], and based on the result, sodium carbonate is injected into the softening tank 31.

Next, the inflow wastewater flow rate (Q) of the current cycle is integrated with the same integrated value up to the previous cycle (step (5)). Next, it is determined whether or not a memory (in FIG. 3, indicated as "M1") for entering a subroutine of the logic operation is set (step (6)).

If the memory M1 is not set,
Next, the set time [( _(TM-3) ) of the timer TM-3 which sets the response time (t _(TM-3) ) until the wastewater flow fluctuation at the time of the rated inflow wastewater flow appears as the flow fluctuation at the outlet of the first settling tank 15 t) Every time] (up) or not (step (7)).

If the set time [(t) hours] of the timer TM-3 has not been reached, the first sludge withdrawal flow rate drawn by the first sludge withdrawal pump 17 from the inflow wastewater flow rate (Q) of the current cycle is calculated. integrating subtracted value 'a' equivalence to the previous cycle (Q (Q) 'to) the integrated value of the "prescribed time calculation method"(Q' _T1) [step (8)].

Next, the same value (Q ′) up to the previous cycle of “value (Q ′) obtained by subtracting the first sludge withdrawal flow rate drawn by the first sludge withdrawal pump 17 from the inflow wastewater flow rate (Q)” Value (Q ' _T2 )
The comparison circuit determines whether or not the “integrated value of the inflow wastewater flow rate (Q ′ _S1 ) until the fluctuation in the wastewater flow rate at the minimum operation inflow wastewater flow rate appears in the flow rate fluctuation at the outlet of the first settling tank 15”. [Step (9)].

If Q ′ _T2 has not yet reached Q _S1 ,
The value of Q ′ in the current cycle is integrated with the integrated value (Q ′ _T2 ) of the “specified volume calculation method” (step (10)). Then
In order to find the time (T _s ) until Q ′ _T2 reaches Q _S1 , the time of the current cycle is added to the integrated value of the time added up to the previous cycle [step (11)].

Next, in the arithmetic circuit, the expression [Q ' _M =
(Q ′ _M1 + Q ′ _M2 ) / 2] is calculated to obtain an estimated effective flow rate (Q ′ _M ) of the primary treated water 16. The assumed effective flow rate (Q ′ _M ) of the primary treatment water 16 is used for calculating the injection flow rate of sodium carbonate in accordance with the equation of “Equation 1” in the next cycle. Thus, one cycle is completed, and the process returns to step (1).

Such a cycle is repeated, and in step (2), the integrated value (Q _Tn ) of the inflowing waste water amount up to the previous cycle by the integrating circuit (Q _Tn ) is the effective retention volume value (Q _S1 ) of the fluorine-removing primary treatment apparatus. _Is reached, that is, when the condition of Q _Tn ≧ Q _S1 is satisfied, the amount of change (ΔC) representing the tendency of the calcium concentration of the primary treated water 16 to increase or decrease according to the equation (Equation 8)
a ″) and the caustic soda injection ratio (Q
A subroutine for calculating the amount of change (ΔQV) representing the increase / decrease tendency of V) is entered.

First, it is determined whether or not the calculation of ΔCa ″ according to the equation (Equation 8) has been completed (step (13)).
If the calculation has been completed, it is next determined whether or not the calculation of ΔQV has been completed [step (14)]. If the calculation of ΔQV has been completed, it is determined whether or not the integrated value (Q _Tn ) of the inflow wastewater flow rate has reached the effective retention volume (Q _S0 ) of the fluorine removing device, that is, whether or not Q _Tn ≧ Q _S0 . [Step (1
5)]. If not, the process proceeds to step (3), calculates the slaked lime injection amount using the beta ₁ stored in the preceding cycle.

If the calculation of ΔCa ″ in the above step (13) has not been completed, the measured value of the calcium concentration (Ca ″ _(n) ) of the primary treated water 16 is stored in the memory unit [step (16)]. Then, a timer TM-1 used to check the tendency of the calcium concentration of the primary treatment water 16 to increase or decrease.
Is determined (step (17)). If not, the process proceeds to step (14). If it is determined that the set time has been reached, the calcium concentration (Ca ″) of the primary treated water 16 at that time is determined.
_{(n + t)} ) is instructed (step (18)). The analysis of the calcium concentration uses, for example, a calcium concentration analyzer of the emission plasma type. However, it takes a certain amount of time to complete the analysis. Until that time, the primary treatment water is used in the next step (19). Calcium concentration (Ca ")
_{(n + t)} ) When the comparison circuit determines whether or not the measurement is completed, it is determined that the measurement is not completed, and the process proceeds to step (14) to repeat the cycle.

In the above step (19), the primary treated water 1
When it is determined that the calcium concentration (Ca ″ _{(n + t)} ) measurement of No. 6 has been completed, the amount of change (ΔCa ″) indicating the increase / decrease tendency of the calcium concentration of the primary treated water this time is calculated according to the equation (8) The result is stored in the memory unit [Step (2)
0)], the timer TM-1 is reset [step (21)]. Next, the process proceeds to step (15).

In the above step (14), if the calculation of the change amount (ΔQV) indicating the increase / decrease tendency of the caustic soda injection ratio has not been completed, the caustic soda injection ratio (Q
V _(n) ) [Step (22)], and then
Using the obtained value, a calculation of ΔQV is performed according to the equation of “Equation 9”, and stored in the memory unit [Step (23)]. Next, the process proceeds to step (15).

If the condition of Q _Tn ≧ Q _S0 is satisfied in the above step (15), the fluorine concentration of the softened water 37 in the current cycle is measured [step (24)], and the slaked lime injection amount feedback is performed. The correction multiplication coefficient (β ₁ ) is calculated by correcting the primary correction value [Step (25)], and the integrated value (Q _T ) of the inflow wastewater flow rate is reset [Step (26)]. Next, the memory M1 is set [step (27)], and the process proceeds to the step (5).

When the comparison circuit determines in step (6) that the memory M1 is set, the subroutine for logic operation is entered. Note that the above step (2)
When the integrated value of the inflow wastewater flow rate is reset in 6), the memory M1 is set in the above-mentioned step (27).
Set it to 2. Until the time (t) elapses, it is determined in the step (28) whether or not the set time of the timer TM-2 has been reached.
Go to and repeat the cycle.

When the set time of the timer TM-2 has been reached (u
If p) is determined [Step (28)], the measurement of the fluorine concentration (F ' _{(n + t)} ) of the softened water 37 at that time is instructed [Step (29)]. In the next step (30), the comparison circuit determines whether or not the measurement of the fluorine concentration (F ' _{(n + t)} ) of the softened water has been completed, and proceeds to the step (7) until it is determined that the measurement has been completed. Repeat cycle.

In the above step (30), the softened water 3
When it is determined that the measurement of the fluorine concentration (F ′ _{(n + t)} ) of No. 7 has been completed, the amount of change (ΔF ′) indicating the tendency of increase and decrease of the fluorine concentration of the softened water this time is calculated according to the equation (13). The result is stored in the memory unit [Step (31)].

Next, based on the calculation result, the softening tank 3
Logic operation of the pH remote set value (SV _pH ) of the pH controller No. 1 [step (32)], and then a secondary operation of correcting the slaked lime injection amount feedback correction multiplication coefficient (β ₁ ) by logic operation. [Step (33)].
Next, the timer TM-2 is reset [Step (3)
4)] and reset the memory M1 [Step (3)
5)], and proceed to step (7).

In the step (7), the timer TM-
If it is determined that the set time of 3 has been reached (up), the assumed flow rate value ( _Q'M1 ) of the primary treated water 16 of the "specified time calculation method" is calculated according to the formula of [Equation 6] (step (36)). ]. Next, the integrated value (Q ′ _T1 ) of the “regulated time method” of the “value (Q ′) obtained by subtracting the first sludge withdrawal flow rate drawn by the first sludge withdrawal pump 17 from the inflow wastewater flow rate (Q)” is reset. [Step (37)],
Reset the timer TM-3 [Step (3)
8)]. Next, the process proceeds to the step (9).

In the step (9), the same value up to the previous cycle of the value (Q ′) obtained by subtracting the first sludge withdrawal flow rate drawn by the first sludge withdrawal pump 17 from the inflow wastewater flow rate (Q) (Q ′) The integrated value (Q ′ _T2 ) of the “prescribed volume calculation method” of Q ′) is “the flow rate of the influent wastewater until the fluctuation of the wastewater flow rate at the minimum operation influent wastewater flow rate appears in the fluctuation of the flow rate at the outlet of the first settling tank 15. If the judgment of the comparison circuit as to whether or not the integrated value ( _Q'S1 ) "has been reached is affirmative, that is, _Q'T2
If it is determined that ≧ Q ′ _S1 , the estimated flow rate (Q ′ _M2 ) of the primary treated water 16 in the “prescribed volume calculation method” is calculated according to the equation (Equation 7) (step (39)). Next, “the value (Q ′) obtained by subtracting the first sludge withdrawal flow rate drawn by the first sludge withdrawal pump 17 from the inflow wastewater flow rate (Q)”
'Reset the _(T2 [step (40)], Q integrated value Q)' of the "prescribed volume calculation method" of the value of _T2 is reset time (T _S) until it reaches the value of Q _'S1 [ Step (41)]. Next, the process proceeds to the step (12).

FIG. 5 shows, by way of example, the calcium concentration in the desulfurization wastewater, the calcium concentration of the calcium-containing primary treatment water obtained from the first precipitation tank, and the calcium concentration of the softening treatment water obtained from the second precipitation tank. FIG. 7 is a graph showing changes over time when no feedforward control is performed and when feedforward control is performed according to the embodiment. In FIG. 5, the horizontal axis represents the number of operating days, and the vertical axis represents the calcium concentration (mg / l). This graph is a semilogarithmic (semilog) graph, and the calcium concentration scale on the vertical axis is a logarithmic scale.

This is a case where the softening treatment was performed while adjusting the pH of the water in the softening tank to about 10.5. In FIG.
Curve (a) is the calcium concentration of the desulfurization wastewater, curve (b) is the calcium concentration of the calcium-containing primary treated water, and curve (c) is the softened treated water without the “feed forward control” of the present invention. Curve (d) is the "feedforward control" of the present invention.
Is the calcium concentration of the softening treated water when the above is performed.

In the softening treatment of the present invention, the fluctuation range of the calcium concentration of the softened water when “feed-forward control” of the injection amount of sodium carbonate was performed was much smaller than that without “feed-forward control”. The excellent effect of the method of the present invention is demonstrated. In addition, this “feed forward control” saved about 12% of sodium carbonate in comparison with the conventional method.

The slaked lime injection equipment in this embodiment
The control valves (control valves) 9, 54, and 74 of the drive unit for controlling each injection amount in the sodium carbonate injection equipment and the caustic soda injection equipment are not necessarily control valves. For example, each injection pump is provided without the control valve. Plunger type metering pumps may be used as 13, 52 and 72, and a combination of stroke control and rotation speed control with the plunger type metering pump may be used.

The various numerical operations and logic operations in the present embodiment can be performed by a one-loop computer that can perform the above operations using a commercially available control computer in addition to a dedicated arithmetic unit.
It can be used with a controller or an arithmetic circuit such as a personal computer or a sequencer. In short, there is no problem if any of the above can be used.

In this embodiment, the fluorine content of the desulfurization wastewater is removed by slaked lime. However, when the fluorine content is removed by an aluminum compound instead, the pH adjusting tank 6 shown in FIG. Generally, a pH adjusting agent injection valve and a pH detector are provided as equipment.

Further, although not described in detail in the present embodiment, the addition amount of the coagulation aid to the first coagulation tank 7 and the second coagulation tank 32 also depends on the inflow wastewater flow rate (Q) and the average of the primary treated water. The addition amount may be optimized in proportion to the effective flow rate (Q ' _M ) or the like, and it is clear that the use amount of the coagulation aid can be reduced by doing so.

[0143]

As described above, according to the present invention, in the removal of fluorine content from fluorine-containing wastewater such as desulfurization wastewater of a soot separation method, for example, calcium content is reduced from calcium-containing treated water generated as primary treated water. In removing the water, it was possible to reduce the consumption of the injected sodium carbonate by injecting the appropriate sodium carbonate based on the estimated flow rate calculation value of the calcium-containing treated water calculated from the inflow wastewater flow rate and the like.

According to the preferred embodiment of the present invention, the main control factors (F ₁ ) and (C
From the measurements of a ′), (Q), (Ca ″), and (F ′) alone, it is possible to feed-forward control the injection of an appropriate amount of slaked lime almost in real time, and furthermore, an unknown control factor (Mg ⁺⁺ ). By performing a logic operation on the change of the caustic soda injection ratio and various change tendency values, the consumption of slaked lime and caustic soda can be reduced appropriately and to a minimum.

Further, the timing is adjusted so that the control time constants are matched with respect to fluctuations in the blend ratio of coal types and fluctuations in the flow rate of wastewater, so that an appropriate traceback correction is fed back and the quality of treated water is stabilized. Can be planned.

According to the control method of the present invention, for example, according to the embodiment, although depending on the power generation load, the reduction of the amount of various chemicals used and the reduction of the waste sludge associated therewith are enormous throughout the year. Amount. Along with such a reduction in operating costs and a reduction in the amount of industrial waste disposal, it has become possible to stabilize the quality of treated water and reduce the complexity of operation management.

In addition, automatic follow-up to fluctuations in the flow rate, properties and the like of the inflowing fluorine-containing wastewater is remarkably improved as compared with the related art, so that the burden on the operator is reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing each processing step and a signal system in an example of a wastewater treatment apparatus which is a fluorine removal apparatus including a softening treatment apparatus used in the method of the present invention.

FIG. 2 is a diagram illustrating an example of a logic operation in the embodiment.

FIG. 3 is a flowchart illustrating a program processing procedure of a control operation system according to the embodiment.

FIG. 4 is a graph schematically showing a change in the fluorine concentration of the desulfurization wastewater with the elapse of the operation time of the coal-fired power plant.

FIG. 5 is a diagram for explaining the effect of softening treatment of calcium-containing treated water when the control method of the present invention is used, and shows the concentration of calcium in desulfurization wastewater and the concentration of calcium-containing primary treated water obtained from a first precipitation tank. FIG. 5 is a semi-logarithmic graph showing the change over time in the calcium concentration of the softened water obtained from the second precipitation tank (in the softening treatment, without feedforward control and with the feedforward control according to the present invention).

[Explanation of symbols]

 Reference Signs List 1 wastewater flow detector 2 inflow wastewater 3 wastewater fluorine concentration analyzer 4 wastewater calcium concentration analyzer 5 reaction tank 6 pH adjustment tank 7 first flocculation tank 8 slaked lime flow detector 9 slaked lime injection flow control valve 10 slaked lime injection flow controller 11 slaked lime Concentration detector 12 Slaked lime dissolving tank 13 Slaked lime injection pump 14 Primary treated water calcium concentration analyzer 15 First sedimentation tank 16 Primary treated water 17 Sludge extraction pump 18 pH adjuster injection valve 19 pH detector 31 Softening tank 32 Second flocculation tank 33 Second Precipitation Tank 34 Treated Water Fluorine Concentration Analyzer 35 Sludge Extraction Pump 36 pH Detector 37 Softened Water (Secondary Treated Water) 51 Sodium Carbonate Dissolution Tank 52 Sodium Carbonate Injection Pump 53 Sodium Carbonate Injection Flow Controller 54 Injection of Sodium Carbonate Flow control valve 55 sodium carbonate Umium injection flow detector 71 Caustic soda storage tank 72 Caustic soda injection pump 73 Softening tank pH controller 74 Caustic soda injection flow control valve 75 Caustic soda injection flow detector 100 Computer

Continued on the front page. (72) Inventor Mamoru Toriyao 1 at Kita-Sekiyama, Odaka-cho, Midori-ku, Nagoya-shi, Aichi Prefecture. 20 in Kitakanyama, Odaka-cho, Midori-ku, Chubu Electric Power Co., Inc. (72) Inventor Hidetoshi Takami 5-5-1-16 Hongo, Bunkyo-ku, Tokyo Organo Co., Ltd. (72) Invention Person Takada ▲ Toki ▼ Guide 5-6-1, Hongo, Bunkyo-ku, Tokyo Organo Co., Ltd. (56) References JP-A-61-212384 (JP, A) JP 3-33399 (JP, B2) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) C02F 1/00-1/74 C02F 5/00-5/14

Claims (4)

(57) [Claims] 1. A softening tank, a calcium concentration analyzer for detecting the calcium concentration of the calcium-containing treated water of the fluorine-containing wastewater, a sodium carbonate injecting facility into the softening tank, and a sodium carbonate injection amount controlled by a signal of a remote set value. In the control method of the softening treatment device including the control system, the control method is obtained by multiplying the calcium concentration signal from the calcium concentration analyzer by the flow rate value of the calcium-containing treated water flowing into the softening treatment device and an optimal multiplication coefficient. Performing feedforward control of the injection amount of sodium carbonate using the calculated value of the injection amount of sodium carbonate as a remote set value to the control system; and (1)
Reaction tank, wastewater flow rate detector for detecting the flow rate of inflowing fluorine-containing wastewater, wastewater fluorine concentration analyzer for detecting the fluorine concentration of inflowing fluorine-containing wastewater, slaked lime injection equipment for the reaction tank, and remote setting of slaked lime injection amount A fluorine removal primary treatment device including a slaked lime injection amount control system controlled by a value signal is provided in front of the softening treatment device, and a calculation formula predetermined by a fluorine concentration signal from the wastewater fluorine concentration analyzer is provided. Or multiplying the fluorine concentration signal by an optimal multiplication coefficient to calculate the amount of calcium required for fluorine removal,
The calculated amount of slaked lime obtained by multiplying the calculated value of the required calcium amount by the inflow wastewater flow rate signal from the wastewater flow rate detector and the correction coefficient is used as a remote setting value to the slaked lime injection amount control system to calculate the slaked lime injection amount. Primary treated water obtained as a result of treating the fluorine-containing wastewater while performing feedforward control [however, in this case, the flow rate value of the calcium-containing treated water flowing into the softening treatment device is the fluorine-removed primary treatment. This is an estimated value of the calcium-containing treated water flow rate obtained by correcting and calculating the fluctuation of the inflow wastewater flow rate signal detected by the wastewater flow rate detector detecting the flow rate of the wastewater flowing into the apparatus.], (2) Reaction tank, inflow Flow rate detector to detect the flow rate of waste water containing fluorine, waste water fluorine concentration analyzer to detect the fluorine concentration of waste water containing inflow fluorine, waste waste containing inflow fluorine A wastewater calcium concentration analyzer for detecting calcium concentration, slaked lime injection equipment for the reaction vessel, and a slaked lime injection primary control device including a slaked lime injection amount control system for controlling the slaked lime injection amount by a signal of a remote set value are described above. The fluorine-containing wastewater is further provided with calcium, and is provided in a preceding stage of the softening treatment apparatus, and a predetermined calculation formula or the fluorine concentration signal is multiplied by an optimum multiplication coefficient by a fluorine concentration signal from the wastewater fluorine concentration analyzer. To calculate the calcium concentration required for fluorine removal, subtract the contained calcium concentration signal from the wastewater calcium concentration analyzer from the calculated required calcium concentration to calculate the amount of insufficient calcium, and calculate the amount of insufficient calcium. Slaked lime injection meter obtained by multiplying the inflow wastewater flow signal from the wastewater flow detector by a correction coefficient Primary treated water obtained as a result of treating the fluorine-containing wastewater while performing feedforward control of the slaked lime injection amount with the value set as a remote setting value to the slaked lime injection amount control system; and (3) a reaction tank, Wastewater flow rate detector for detecting the flow rate of wastewater containing wastewater, fluorine concentration analyzer for wastewater detecting the fluorine concentration of wastewater containing inflow fluorine, aluminum concentration analyzer for wastewater detecting aluminum concentration of wastewater containing inflow fluorine, aluminum to the reaction tank Compound injection equipment,
A primary fluorine removal treatment device including an aluminum compound injection amount control system for controlling the aluminum compound injection amount by a signal of a remote set value is provided at a stage preceding the softening treatment device, and the fluorine-containing wastewater further contains aluminum. It contains calcium and calculates the aluminum concentration required for fluorine removal by multiplying the fluorine concentration signal from the wastewater fluorine concentration analyzer by a predetermined calculation formula or the optimum multiplication coefficient by the fluorine concentration signal. The amount of aluminum deficiency is calculated by subtracting the contained aluminum concentration signal from the wastewater aluminum concentration analyzer from the aluminum concentration, and the calculated value of the insufficient aluminum is multiplied by the inflow wastewater flow signal from the wastewater flow rate detector and the correction coefficient. The calculated value of the aluminum compound injection amount obtained by The softening treatment device is a treatment water selected from the group consisting of a primary treatment water obtained as a result of treating the fluorine-containing wastewater while performing feedforward control of the aluminum compound injection amount as a remote set value to the compound injection amount control system. A method for controlling the injection amount of sodium carbonate in the softening treatment of the calcium-containing treated water, wherein the calcium-containing treated water is treated with the water. 2. In the case of the primary treatment water of (2) or (3) in claim 1, the flow rate value of the calcium-containing treatment water flowing into the softening treatment device is set to the fluorine removal primary treatment device. 2. The calcium-containing treated water flow rate estimated value obtained by correcting and calculating a fluctuation of an inflow wastewater flow rate signal detected by the wastewater flow rate detector and detecting a flow rate of the incoming wastewater flow rate, according to claim 1, wherein A method for controlling the injection amount of sodium carbonate in the softening treatment of calcium-containing treated water of fluorine-containing wastewater. 3. The method according to claim 1, wherein the softening treatment device is configured to adjust pH of water in the softening tank.
Further comprising a control system for controlling the pH of the wastewater flow rate by a signal of a pH remote set value, and a treated water fluorine concentration analyzer for measuring a fluorine concentration of the softened treated water downstream of the softening treatment device. Each time the comparison circuit determines that the integrated value obtained by the integration circuit that integrates the inflow wastewater flow rate based on the inflow wastewater flow rate signal has reached the effective retention volume value of the fluorine removal primary treatment apparatus, the calcium-containing treated water is Injection ratio of pH change agent for adjusting the concentration change of calcium concentration per specified time and pH of water in the softening tank (ratio of injection amount of pH adjuster to amount of calcium-containing treated water flowing into the softening device) Of the influent wastewater is measured, calculated, and stored, and the integrated value of the inflow wastewater flow rate is calculated by the treated water fluorine concentration analyzer. Each time the comparison circuit determines that the total effective retention volume value of the fluorine removal primary treatment device and the softening treatment device up to the position has been reached, the inflow wastewater flow rate integrated value is reset, and the treated water fluorine concentration analyzer is reset. Performs a calculation based on the change in the fluorine concentration of the softened water at the position and the target value thereof and the fluorine concentration of the softened water per a specified time, the remote set value to the slaked lime injection control system or the aluminum compound injection control system, and 3. The method for controlling the injection amount of sodium carbonate in the softening treatment of the calcium-containing treated water according to claim 1 or 2, wherein the remote setting value of the pH of the water in the softening tank is feedback-controlled by a logic operation. . 4. A fluorine containing a softening treatment device according to claim 1 or 3 and a fluorine removal primary treatment device for obtaining the primary treatment water of (1), (2) or (3) in claim 1. A fluorine removing device, comprising: a calculating means and a control system for performing the sodium carbonate injection amount control method according to any one of claims 1 to 3.