JP7515239B2 - Drying equipment and heating amount control method - Google Patents

Description

The present invention relates to a drying facility and a method for controlling the amount of heat.

Materials to be dried, such as various biomass, waste, and sludge, contain a large amount of moisture, so drying is sometimes performed by heating using a dryer. One example of a dryer is an indirect heating type dryer. This dryer has a hollow casing for housing the material to be dried, and the hollow casing is provided with a hollow drive shaft and hollow stirring blades for stirring the material to be dried. In an indirect heating type dryer, a heating medium such as steam is introduced into the hollow parts of the hollow drive shaft and hollow stirring blades, and the material to be dried is dried by indirect heating with the heating medium. Some such dryers are also provided with a dehumidifier in the exhaust path of the exhaust gas from the dryer to reduce (condense) the amount of moisture in the exhaust gas.

Patent Document 1 discloses a system that includes an indirect heating dryer that indirectly heats the material to be dried with steam to evaporate the moisture contained therein, and a drain trap (dehumidifier) that condenses the exhaust gas from the dryer. The outlet of this drain trap is connected to a drain pot that stores condensed water (drain) from the drying exhaust gas, and a drain flow sensor is provided in the path between the drain trap and the drain pot. The measurement result of the drain flow sensor is regarded as the amount of moisture evaporated from the material to be dried and is sent to a calculator. The calculator uses the amount of evaporated moisture as one of the control elements to control the steam pressure supplied to the dryer, i.e., the amount of heat applied to the material to be dried.

JP 2012-163257 A

Here, when the dehumidifier that condenses the dried exhaust gas is taken as an example to be a scrubber, the water supplied to the dehumidifier (dehumidified water) and the evaporated water from the material to be dried are mixed and discharged from the dehumidifier. If the dehumidified water is, for example, 90 ^m3 /h, the amount of evaporated water is generally 2 to ³ m3/h, which is about a few percent of the dehumidified water supplied to the dehumidifier, and the amount of dehumidified water is large compared to the amount of evaporated water. The flow rate sensor that measures the discharge flow rate from the dehumidifier is selected based on the flow rate of the dehumidified water, so a flow rate sensor capable of measuring a flow rate of several tens to several hundreds of ^m3 /h is selected.

In other words, the amount of evaporated water corresponds to the measurement error of the flow sensor, and the amount of evaporated water measured by the flow sensor is easily affected by the measurement error of the flow sensor, so there is a possibility that the precision and stability are insufficient and the measurement may not be accurate. For this reason, even if the amount of heating is controlled based on the measurement value of the flow sensor, the control will not be appropriate, and as a result, there is a possibility that the moisture content of the material to be dried cannot be controlled appropriately.

The present invention aims to provide a drying facility and a method for controlling the amount of heat that can appropriately control the moisture content of the material to be dried.

The drying equipment of the present invention is a drying equipment having a dryer that heats and dries the material to be dried, and a dehumidifier that reduces the amount of moisture in the exhaust gas discharged from the dryer by using a liquid medium, and is equipped with a calculation means that calculates the amount of moisture evaporated from the material to be dried in the dryer based on the physical amount of the liquid medium or the physical amount of the exhaust gas before and after passing through the dehumidifier, and a control means that controls the amount of heat applied to the material to be dried in the dryer based on the amount of moisture evaporated calculated by the calculation means.

According to this configuration, the amount of evaporated moisture of the material to be dried in the dryer is calculated based on the physical amount of the liquid medium or the physical amount of the exhaust gas before and after passing through the dehumidifier, rather than directly from the measured value of the flow sensor. This allows the calculated amount of evaporated moisture to be calculated with the same accuracy as the accuracy (percentage) of the flow sensor. This configuration then controls the amount of heat applied to the material to be dried in the dryer based on the calculated amount of evaporated moisture, so that the moisture content of the material to be dried can be appropriately controlled.

In the above drying equipment, the calculation means calculates the amount of water evaporated from the material to be dried in the dryer based on the condensation heat flow rate of the exhaust gas in the dehumidifier, which is calculated using the physical quantity of the liquid medium.

According to this configuration, the amount of evaporated water in the material to be dried in the dryer is calculated based on the condensation heat flow rate of the exhaust gas in the dehumidifier, not directly from the measured value of the flow sensor. Therefore, the calculated amount of evaporated water is calculated with the same accuracy as the accuracy (percentage) of the flow sensor. In addition, since the physical amount of the liquid medium flowing into and out of the dehumidifier is unlikely to fluctuate instantaneously, the physical amount of the liquid medium is suitable as a variable for calculating the amount of evaporated water in the material to be dried. In other words, even if an attempt is made to control the amount of heat in the dryer using a control factor calculated from a variable that fluctuates instantaneously, the control value does not converge, making it difficult to perform appropriate control. On the other hand, by using a control factor calculated from a variable that does not fluctuate instantaneously, the control value tends to converge, resulting in appropriate control. Therefore, this configuration can appropriately control the moisture content of the material to be dried by using the condensation heat flow rate of the exhaust gas calculated from a variable that does not fluctuate instantaneously as the control factor for the amount of heat for the material to be dried.

In the drying equipment, the calculation means may calculate the condensation heat flow rate based on at least the measured inlet temperature and the measured outlet temperature of the liquid medium with respect to the dehumidifier.

This configuration makes it easy to calculate the condensation heat flow rate of exhaust gas.

In the drying equipment described above, the calculation means calculates the amount of evaporated water based on the measured inlet flow rate, outlet flow rate, and outlet temperature of the exhaust gas to the dehumidifier.

This configuration makes it easy to calculate the amount of water that has evaporated.

The drying equipment of the present invention is a drying equipment having a dryer that heats and dries the material to be dried while stirring it with a stirring means into which steam is introduced, and is equipped with a calculation means that calculates the amount of evaporated water of the material to be dried in the dryer based on the physical quantity of the steam, and a control means that controls the amount of heat applied to the material to be dried in the dryer based on the amount of evaporated water calculated by the calculation means.

According to this configuration, the amount of evaporated water in the material to be dried in the dryer is calculated based on the physical amount of steam passing through the agitation means, rather than directly from the measured value of the flow sensor. This allows the amount of evaporated water to be calculated with the same accuracy as the accuracy (percentage) of the flow sensor. This configuration then controls the amount of heat applied to the material to be dried in the dryer based on the calculated amount of evaporated water, so that the moisture content of the material to be dried can be appropriately controlled.

In the above drying equipment, the calculation means calculates the amount of water evaporated from the material to be dried in the dryer based on the flow rate of the steam.

This configuration makes it easy to calculate the amount of water that has evaporated.

In the above drying equipment, the dryer dries the material to be dried using a heating medium, a dam is provided at the discharge outlet of the material to be dried, and the control means may change the height of the dam when the amount of heat is to be changed relatively greatly, or change the physical property value of the heating medium when the amount of heat is to be changed relatively small.

This configuration improves the ability to control the amount of heat depending on changes in the moisture content of the material to be dried.

In the above drying equipment, the control means may control the amount of heat based on the amount of evaporated water calculated a predetermined time after the material to be dried is put into the dryer.

It takes time for the dryer to dry the items to be dried. Therefore, this configuration allows for more appropriate control of the amount of heat applied to the items to be dried.

The drying equipment of the present invention is equipped with a dryer that heats and dries the material to be dried, and is equipped with a calculation means that calculates the amount of evaporated water from the material to be dried in the dryer based on the physical quantity of a fluid from which water condenses as heat is removed while flowing through the drying equipment, and a control means that controls the amount of heat applied to the material to be dried in the dryer based on the amount of evaporated water calculated by the calculation means.

The heat amount control method of the present invention is a heat amount control method for a drying facility having a dryer that heats and dries the material to be dried, and a dehumidifier that uses a liquid medium to reduce the amount of moisture in the exhaust gas discharged from the dryer, and includes a first step of calculating the amount of evaporated moisture of the material to be dried in the dryer based on the condensation heat flow rate of the exhaust gas in the dehumidifier calculated using the physical quantity of the liquid medium, and a second step of controlling the amount of heat applied to the material to be dried in the dryer based on the amount of evaporated moisture calculated in the first step.

The heat amount control method of the present invention is a heat amount control method for a drying facility having a dryer that heats and dries materials to be dried while stirring them with a stirring means into which steam is introduced, and includes a first step of calculating the amount of evaporated water of the materials to be dried in the dryer based on the physical amount of the steam before and after passing through the stirring means, and a second step of controlling the amount of heat applied to the materials to be dried in the dryer based on the amount of evaporated water calculated in the first step.

The present invention can appropriately control the moisture content of the material to be dried.

FIG. 1 is a schematic configuration diagram of a drying facility according to a first embodiment. FIG. 2 is a functional block diagram relating to heat amount control of the drying facility of the first embodiment. FIG. 4 is a schematic diagram showing a flow of calculation of a dam plate height or steam pressure in the first embodiment. 4 is a flowchart showing a flow of a heat amount control process in the first embodiment. FIG. 11 is a schematic configuration diagram of a drying facility according to a second embodiment. FIG. 11 is a functional block diagram relating to heat amount control of the drying facility of the second embodiment. FIG. 11 is a schematic configuration diagram of a drying facility according to a third embodiment. FIG. 13 is a functional block diagram relating to heat amount control of the drying facility of the third embodiment. FIG. 11 is a schematic configuration diagram of a drying facility according to another embodiment.

The following describes a drying equipment and a heating amount control method according to an embodiment of the present invention with reference to the drawings. In this embodiment of the present invention, the amount of water evaporated from the sludge in the dryer is calculated based on the physical quantity of the fluid from which water condenses as heat is removed while the fluid flows through the drying equipment, and the amount of heat applied to the sludge in the dryer is controlled based on the calculated amount of evaporated water. Note that the above-mentioned fluids are, by way of example, dehumidified water flowing through a dehumidifier (e.g., a scrubber), exhaust gas flowing through the dehumidifier, and steam flowing inside the agitation means.

First Embodiment
1 is a schematic diagram of a drying facility 10 according to the present embodiment. The drying facility 10 according to the present embodiment is installed in, for example, a food waste treatment facility or a sewage treatment facility, and is a facility for drying materials such as sludge, various biomass, food waste, and waste materials containing moisture. In the present embodiment, the material to be dried is described as sludge as an example.

As shown in FIG. 1, the drying equipment 10 of this embodiment includes a supply pump 12, a dryer 14, a conveying device 16, a scrubber 18, and a main control device 20.

The supply pump 12 is a device for supplying sludge, which is the material to be dried, to the dryer 14. A sludge supply line 22 for supplying sludge to the dryer 14 is provided at the outlet of the supply pump 12. This sludge supply line 22 is provided with a flow rate sensor 24 for measuring the input amount F0 of sludge supplied to the dryer 14 and a moisture content sensor 26 for measuring the moisture content X0 of the sludge.

The dryer 14 is a device that heats and dries sludge, and is equipped with a hollow casing 14A that contains the sludge, a hollow drive shaft 14B that agitates the sludge in the hollow casing 14A, and a hollow agitating blade 14C.

A sludge inlet 14D is provided on one side of the hollow casing 14A, and a discharge outlet 14E for dried sludge (hereinafter referred to as "dried sludge") and an exhaust outlet 14F for exhaust gas containing moisture evaporated during the drying process are provided on the other side. A sludge supply path 22 is connected to the sludge inlet 14D, and sludge is supplied to the dryer 14 from the supply pump 12. A transport device 16 is connected to the discharge outlet 14E, and the dried sludge discharged from the discharge outlet 14E is transported by the transport device 16. A scrubber 18 is connected to the exhaust outlet 14F via an exhaust path 36, and exhaust gas is sent to the scrubber 18.

The hollow drive shaft 14B is provided along the longitudinal direction of the hollow casing 14A and is rotated by a rotary drive device (not shown) such as a motor. The hollow agitator blades 14C are multiple fan-shaped blades connected to the hollow drive shaft 14B and a hollow section (described in detail later), and rotate in response to the rotation of the hollow drive shaft 14B without coming into contact with the inner wall of the hollow casing 14A. The sludge introduced into the dryer 14 from the sludge inlet 14D is transported toward the outlet 14E by the rotating hollow agitator blades 14C.

The hollow drive shaft 14B and hollow agitator blade 14C are hollow (hereinafter referred to as "hollow portion"), and a heating medium is introduced into them to dry the sludge. In this embodiment, the heating medium is steam as an example, but the heating medium is not limited to this and may be hot water or heated oil or fat. A steam inlet pipe 28 is connected to the end of the hollow drive shaft 14B, and steam, which is the heating medium, is introduced into the hollow portion of the hollow drive shaft 14B and hollow agitator blade 14C via the steam inlet pipe 28.

The steam filling the hollow parts of the hollow drive shaft 14B and hollow agitator blade 14C indirectly heats the sludge in contact with the hollow drive shaft 14B and hollow agitator blade 14C, evaporating the water contained in the sludge. When the sludge is heated, the viscosity of the sludge decreases, making it easier to separate the filtrate from the sludge, and the sludge is thermally denatured, reducing the water retention capacity of the sludge, so that the water content of the sludge can be efficiently reduced. In this way, the sludge fed into the dryer 14 is heated by the heating medium via the hollow drive shaft 14B and hollow agitator blade 14C, and is compressed and dehydrated by the hollow agitator blade 14C while being transported to the downstream side of the dryer 14.

Here, the steam inlet pipe 28 is provided with a pressure control valve 30 that controls the steam pressure, and the drying equipment 10 controls the amount of heat applied to the sludge by controlling the steam pressure. The pressure control valve 30 changes the steam pressure by controlling the opening degree with a valve control device 31. In addition, the valve control device 31 receives the measured value of a pressure sensor 32 provided in the steam inlet pipe 28, and feedback controls the pressure control valve 30 so that the steam pressure becomes the predetermined value transmitted from the main control device 20.

The drying equipment 10 of this embodiment only needs to control the amount of heat by changing the physical properties of the steam, which is the heating medium. For example, a flow control valve may be provided in the steam inlet pipe 28 instead of the pressure control valve 30. In this embodiment, the drying equipment 10 controls the amount of heat applied to the sludge by controlling the steam flow rate. Furthermore, both the pressure control valve 30 and the flow control valve may be provided in the steam inlet pipe 28, and the amount of heat applied to the sludge may be controlled by the steam pressure and steam flow rate.

A dam plate 14G is provided in front of the discharge port 14E of the dryer 14 to block and retain the sludge transported by the hollow agitator blades 14C. The height of the dam plate 14G (hereinafter referred to as the "dam plate height") is controlled by the motor 34, which is the driving device, and the higher the dam plate height, the greater the amount of sludge in the dryer 14. In other words, the higher the dam plate height, the longer the retention time of the sludge and the greater the amount of heat applied to the sludge. The motor 34 has its rotation speed and direction controlled by the motor control device 35. As an example, the dam plate height is expressed as a percentage (%), and 100% is the state in which the dam plate 14G is most closed, i.e., the dam plate height is at its highest, and 0% is the state in which the dam plate 14G is most open, i.e., the dam plate height is at its lowest.

In this embodiment, the shape of the barrier plate 14G is, for example, a plate shape, but is not limited to this. The shape of the barrier plate 14G may be other shapes as long as it can block the sludge discharged from the discharge port 14E and control the amount of heat applied to the sludge.

The exhaust gas discharged from the exhaust port 14F of the dryer 14 passes through the scrubber 18 as described above and is released into the atmosphere, or is introduced back into the dryer 14 as a carrier gas.

The scrubber 18 functions as a dehumidifier that reduces the amount of moisture in the exhaust gas. In this embodiment, the scrubber 18 reduces the amount of moisture in the exhaust gas by, for example, spraying a liquid medium into the exhaust gas. In this embodiment, the liquid medium is, for example, cold water (hereinafter referred to as "dehumidified water"), but the liquid medium is not limited to this and may be other liquids other than water, such as alcohol.

The dehumidified water is supplied to the scrubber 18 from the water supply line 38 and sprayed from the top of the scrubber 18. The exhaust gas discharged from the dryer 14 is sent from below the scrubber 18 and cooled by the dehumidified water sprayed inside the scrubber 18, condensing the moisture in the exhaust gas. The condensed moisture is stored in the lower part of the scrubber 18 together with the sprayed dehumidified water, and is drained from the drainage line 40. Meanwhile, the exhaust gas that has passed through the scrubber 18 is discharged into the atmosphere through a deodorizing device (not shown) from a gas outlet 42 provided at the top of the scrubber 18. Alternatively, the exhaust gas is heated through a heat exchanger (not shown) from the gas outlet 42 and introduced again into the dryer 14 as a carrier gas.

The main control device 20 is responsible for controlling the entire drying equipment 10. The main control device 20 is composed of, for example, a computer such as a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in a storage medium or the like in the form of a program, for example, and the CPU reads this program into the RAM or the like and executes information processing and arithmetic processing to realize various functions. The program may be installed in advance in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means.

The main control device 20 controls, for example, the amount of heat applied to the sludge in the dryer 14 (hereinafter referred to as "heat amount control"). The amount of heat is controlled by the steam pressure and the dam height as described above. For this reason, the main control device 20 transmits a control signal for controlling the steam pressure to the valve control device 31, and transmits a control signal for controlling the dam height to the motor control device 35.

In order to control the amount of heat, the main control device 20 receives the measurement results from the flow rate sensor 24 and moisture content sensor 26 as well as various physical property values measured by other sensors. The placement of each sensor and the physical property values it measures are explained below.

The water supply passage 38 of the scrubber 18 is provided with a flow sensor 44 for measuring the dehumidified water flow rate F1 and a temperature sensor 46 for measuring the dehumidified water temperature T1. The drainage passage 40 of the scrubber 18 is provided with a flow sensor 48 for measuring the drainage flow rate F2 and a temperature sensor 50 for measuring the drainage temperature T2. The exhaust passage 36 is provided with a temperature sensor 52 for measuring the inlet exhaust gas temperature T3. The gas outlet 42 of the scrubber 18 is provided with a temperature sensor 54 for measuring the outlet exhaust gas temperature T4 and a flow sensor 56 for measuring the outlet exhaust gas flow rate F4.

The heat amount control in this embodiment is, in other words, a control of the amount of moisture contained in the dried sludge (dried sludge moisture content), and calculates the amount of evaporated moisture of the sludge in the dryer 14 based on the condensation heat flow of the exhaust gas in the scrubber 18 (hereinafter referred to as the "exhaust gas condensation heat flow"), which is calculated using the physical quantity of dehumidified water. The heat amount control controls the amount of heat applied to the sludge in the dryer 14 based on the calculated amount of evaporated moisture. The exhaust gas condensation heat flow is, specifically, the heat flow (kJ/h) that condenses the moisture in the exhaust gas by cooling the exhaust gas in the scrubber 18. The calculated amount of evaporated moisture is referred to as the actual amount of evaporated moisture in the following explanation.

In this way, according to the heat amount control of this embodiment, the actual evaporated water amount of the sludge in the dryer 14 is calculated based on the condensation heat flow rate of the exhaust gas in the scrubber 18, rather than directly from the measured value of the flow sensor. Therefore, the calculated actual evaporated water amount is calculated with the same accuracy as the accuracy (percentage) of the flow sensor. In addition, since the physical amount of the dehumidified water flowing into and out of the scrubber 18 is unlikely to fluctuate instantaneously, the physical amount of the dehumidified water is suitable as a variable for calculating the actual evaporated water amount of the sludge. In other words, even if an attempt is made to control the amount of heat of the dryer 14 using a control factor calculated from a variable that fluctuates instantaneously, the control value does not converge, making it difficult to perform appropriate control. On the other hand, by using a control factor calculated from a variable that does not fluctuate instantaneously, the control value is likely to converge, resulting in appropriate control.

Therefore, the heat amount control of this embodiment can appropriately control the moisture content of the sludge by using the condensation heat flow rate of the exhaust gas, calculated from variables that are unlikely to fluctuate instantaneously, as the control factor for the amount of heat applied to the sludge. In addition, since the heat amount control of this embodiment is automatic drying control, it is possible to reduce the labor required for management personnel to operate the drying equipment 10. Furthermore, since the heat amount control of this embodiment makes it possible to perform appropriate control, it is possible to avoid a state in which the moisture content of the dried sludge becomes excessively low, and it is possible to improve safety, such as preventing the dried sludge from catching fire.

Figure 2 is a functional block diagram related to the heat amount control of this embodiment. As an example, each function shown in Figure 2 is executed by a computer provided in the main control device 20, but this is not limited thereto, and each function may be executed by individual hardware such as an ASIC (Application Specific Integrated Circuit) provided in the main control device 20.

The main control device 20 includes a condensation heat flow rate calculation unit 60, an actual evaporated water content calculation unit 62, a target evaporated water content calculation unit 64, and a heating amount control unit 66.

The condensation heat flow calculation unit 60 calculates the exhaust gas condensation heat flow.

As an example, as shown in the following formula (1), the condensation heat flow calculation unit 60 of this embodiment calculates the exhaust gas condensation heat flow from the heat flow of the dehumidified water supplied to the scrubber 18 (dehumidified water heat flow Q1), the heat flow of the wastewater discharged from the scrubber 18 (wastewater heat flow Q2), the heat flow of the exhaust gas flowing into the scrubber 18 (inlet exhaust gas heat flow Q3), and the heat flow of the exhaust gas flowing out of the scrubber 18 (outlet exhaust gas heat flow Q4).

Exhaust gas condensation heat flow rate = wastewater heat flow rate Q2 + outlet exhaust gas heat flow rate Q4 - dehumidified water heat flow rate Q1 - inlet exhaust gas heat flow rate Q3 ... (1)

The dehumidified water heat flow rate Q1, the wastewater heat flow rate Q2, the inlet exhaust gas heat flow rate Q3, and the outlet exhaust gas heat flow rate Q4 are calculated using the following formulas.

Q1 = H1 (specific enthalpy of dehumidified water temperature T1 [kJ/kg]) x F1 (flow rate of dehumidified water [kg/h])
Q2 = H2 (specific enthalpy of wastewater temperature T2 [kJ/kg]) x F2 (wastewater flow rate [kg/h])
Q3 = H3g (specific enthalpy of inlet exhaust gas temperature T3 [kJ/kg]) x F3g (gas flow rate in the inlet exhaust gas of the scrubber 18 [kg/h])
Q4 = H4g (specific enthalpy of outlet exhaust gas temperature T4 [kJ / kg]) × F4g (gas flow rate in the outlet exhaust gas of the scrubber 18 [kg / h])

The inlet exhaust gas flow rate F3g and the outlet exhaust gas flow rate F4g are the flow rates of dry gas in the exhaust gas flowing into and out of the scrubber 18. This dry gas is not condensed by the scrubber 18, so the flow rate of the dry gas does not change before and after it flows into and out of the scrubber 18. For this reason, the inlet exhaust gas flow rate F3g and the outlet exhaust gas flow rate F4g are the same as shown in the following formula.
F3g [kg/h] = F4g [kg/h]

The outlet exhaust gas flow rate F4g is calculated by the simultaneous equations of the following formulas (2) and (3). Note that the outlet exhaust gas moisture flow rate F4w is calculated on the assumption that the moisture amount in the outlet exhaust gas is the same as the saturated water vapor amount.
F4 [kg/h] = F4g [kg/h] + F4w [kg/h] ... (2)
F4w [kg/h] = m (100% absolute humidity at outlet exhaust gas temperature T4 [kg- _H2O /kg-dry gas]) × F4g [kg/h] ... (3)

In this way, the condensation heat flow calculation unit 60 of this embodiment does not simply calculate the exhaust gas condensation heat flow from the dehumidified water heat flow Q1 and the wastewater heat flow Q2, but also takes into account the inlet exhaust gas heat flow Q3 and the outlet exhaust gas heat flow Q4 in the calculation of the exhaust gas condensation heat flow. In other words, the condensation heat flow calculation unit 60 of this embodiment calculates the exhaust gas condensation heat flow taking into account the heat quantity (sensible heat) of the dry gas, so that a more accurate exhaust gas condensation heat flow can be calculated.

The actual evaporated water amount calculation unit 62 calculates the actual evaporated water amount, which is the amount of water lost from the sludge during drying by the dryer 14. Specifically, the actual evaporated water amount calculation unit 62 calculates the actual evaporated water amount by dividing the steam latent heat (latent heat of condensation) from the exhaust gas condensation heat flow rate, as shown in the following equation (4).
Actual amount of evaporated water [kg/h] = exhaust gas condensation heat flow [kJ/h] ÷ steam latent heat [kJ/kg] ... (4)

Here, in the prior art, the actual evaporated water amount can also be obtained directly from the difference between the measured values (dehumidified water flow rate F1, drainage flow rate F2) of the flow rate sensors 44, 48. However, the dehumidified water flow rate F1 and drainage flow rate F2 can be significantly affected by the measurement error of the flow rate sensors 44, 48. For example, at a dehumidified water flow rate of 90 ^m3 /h, the actual evaporated water amount may be 2 to 3 ^m3 /h. In such cases, the actual evaporated water amount obtained from the difference between the measured values of the flow rate sensors 44, 48 falls within the measurement error of the flow rate sensors 44, 48 and may not be accurate.

On the other hand, the drying equipment 10 according to this embodiment calculates the heat flow rate (exhaust gas condensation heat flow rate) exchanged in the scrubber 18, and calculates the actual amount of evaporated water based on this heat flow rate. Here, the exhaust gas condensation heat flow rate may be calculated based on at least the measured value of the inlet temperature (dehumidified water temperature T1) and the measured value of the outlet temperature (wastewater temperature T2) of the dehumidified water as a physical quantity of the dehumidified water. This is because the measured value of the temperature sensor generally has a small measurement error, and the temperature of the dehumidified water flowing into and out of the scrubber 18 is not likely to fluctuate instantaneously, making it a physical quantity suitable for calculating the actual amount of evaporated water used to control the amount of heat.

In this embodiment, the measured values of the flow sensors 44, 48 are also used to calculate the exhaust gas condensation heat flow rate, and the calculated actual amount of evaporated water also includes this measurement error. However, the calculated exhaust gas condensation heat flow rate is calculated by multiplying the measured values of the flow sensors 44, 48 by physical quantities (temperature difference and specific heat) based on the measured values of the temperature sensors 46, 50, and the calculation result is sufficiently large relative to the measurement errors of the flow sensors 44, 48. Therefore, the effect of the measurement errors of the flow sensors 44, 48 on the calculated actual amount of evaporated water is sufficiently small, and using the measured values of the flow sensors 44, 48 contributes to a more accurate calculation of the exhaust gas condensation heat flow rate.

As described above, the condensation heat flow calculation unit 60 only needs to calculate the exhaust gas condensation heat flow based on at least the dehumidified water temperature T1 and the wastewater temperature T2 as the physical quantities of the dehumidified water. This allows the condensation heat flow calculation unit 60 to easily calculate the exhaust gas condensation heat flow. Note that when only the dehumidified water temperature T1 and the wastewater temperature T2 are used to calculate the exhaust gas condensation heat flow, the other values are set as constants.

The pattern for calculating the exhaust gas condensation heat flow rate using the dehumidified water temperature T1, the drainage water temperature T2, and other measured values includes the pattern described above, and is shown below. The pattern to be used is selected appropriately depending on whether or not various sensors are present.

Pattern 1: T1 and T2 are measured values, other values are constants. Pattern 2: T1, T2, F1, and F2 are measured values, other values are constants. Pattern 3: T1, T2, F1, F2, T3, and T4 are measured values, other values are constants. Pattern 4: T1, T2, F1, F2, T3, T4, and F4 are measured values, no constants.

The target evaporation moisture amount calculation unit 64 calculates the amount of moisture (hereinafter referred to as the "target evaporation moisture amount") that is desired to be evaporated from the sludge in the dryer 14. In this embodiment, the target evaporation moisture amount calculation unit 64 calculates the moisture input amount [kg/h], which is the moisture amount of the sludge, from the sludge input amount F0 and the sludge moisture content X0, and calculates the target evaporation moisture amount [kg/h] by multiplying this moisture input amount by the target moisture [%], which is the percentage that is desired to be evaporated.

In addition, since the amount of sludge fed into the dryer 14 changes slightly over time, the sludge feed amount F0 and sludge moisture content X0 used to calculate the target evaporation water amount are not instantaneous values, but rather, as an example, average values over a predetermined period of time (e.g., 10 minutes) are used.

In addition, to stabilize fluctuations in the moisture content of the sludge, the hopper that receives the sludge may be allocated according to the difference in the moisture content of the sludge. That is, sludge with a high moisture content and sludge with a low moisture content are fed into the dryer 14 via different hoppers. The amount of sludge with a high moisture content and the amount of sludge with a low moisture content fed into the dryer 14 are then adjusted so that the moisture content of the sludge is a predetermined value. This makes the moisture content of the sludge fed into the dryer 14 more stable.

The heat amount control unit 66 controls the amount of heat applied to the sludge in the dryer 14. In this embodiment, the heat amount control unit 66 controls the amount of heat applied to the sludge by controlling the dam height and steam pressure, as described above. To this end, the heat amount control unit 66 transmits control signals indicating the steam pressure and dam height to the valve control unit 31 and the motor control unit 35.

More specifically, the heat amount control unit 66 of this embodiment controls the heat amount based on the difference between the actual evaporated water amount and the target evaporated water amount (hereinafter referred to as the "evaporated water amount difference"). That is, when the actual evaporated water amount is greater than the target evaporated water amount, the heat amount control unit 66 controls the heat amount to be smaller. On the other hand, when the actual evaporated water amount is smaller than the target evaporated water amount, the heat amount control unit 66 controls the heat amount to be larger.

Here, controlling the dam height is suitable for making large changes to the amount of heat applied to the sludge because the dam 14G blocks the sludge in the dryer 14, but is not suitable for fine-tuning the amount of heat applied. On the other hand, controlling the steam pressure is suitable for fine-tuning the amount of heat applied to the sludge, but is not suitable for making large changes to the amount of heat applied because there is a limit to the control range of the steam pressure.

The heat quantity control unit 66 of this embodiment changes the dam height when the amount of heat is to be changed relatively greatly, and changes the steam pressure when the amount of heat is to be changed relatively small. This improves the drying equipment 10's ability to control the amount of heat in response to changes in the moisture content of the sludge.

In addition, the heating amount control unit 66 of this embodiment controls the dam height or steam pressure based on a predetermined control function, as an example. The target amount of evaporated water is input as a variable to this control function, and a value indicating the dam height or steam pressure according to the target amount of evaporated water is output. As an example, the control function is a different function when controlling the dam height and when controlling the steam pressure.

Figure 3 is a schematic diagram showing the flow of calculation of the dam height or steam pressure by the heating amount control of this embodiment. The target moisture shown in Figure 3 is input by the manager of the drying equipment 10, etc. In addition, the input amount of solids contained in the sludge (solids input amount) and the input amount of moisture (moisture input amount) are calculated based on the sludge input amount F0 measured by the flow sensor 24 and the sludge moisture content X0 measured by the moisture content sensor 26. Then, the target evaporated moisture amount is calculated from the target moisture, solids input amount, and moisture input amount.

In addition, an appropriate control function is selected from among multiple control functions for the dam height or steam pressure based on the calculated water input amount.

Meanwhile, an evaporation water amount difference is calculated, which indicates the degree of deviation between the calculated target evaporation water amount and the calculated actual evaporation water amount. The selected control function is corrected based on this evaporation water amount difference. Then, the target evaporation water amount is input to the corrected control function, and the control amount of the dam height or the control amount of the steam pressure is calculated.

One example of the correction of the control function is to change the coefficients and constants included in the control function according to the difference in the amount of evaporated water so that the difference in the amount of evaporated water is less than a predetermined value that can be considered to be substantially zero. The amount of change in the coefficients and constants is selected to be a value that reduces the difference in the amount of evaporated water by the next heating amount control.

In this embodiment, when selecting a control function based on the amount of water input, the change in the amount of heat is calculated from the difference in the amount of evaporated water, and if this change is equal to or greater than a reference value, the control function for the dam height is selected as the control function. On the other hand, if the change in the amount of heat is less than the reference value, the control function for the steam pressure is selected as the control function.

In the example of FIG. 3, the sludge input amount F0 and the sludge moisture content X0 are measured by sensors, but this is not limiting, and the sludge input amount F0 and the sludge moisture content X0 may be input by the manager. In addition, sludge may be brought into the drying equipment 10 at different times by multiple transport vehicles, and stored, transported, and mixed in the drying equipment 10 before being input into the dryer 14. In such a case, the manager of the drying equipment 10 or the operator of the transport vehicle may input the sludge input amount F0, the sludge moisture content X0, and the time of sludge input, and a simulation may be performed from storing, transporting, and mixing the sludge to inputting it into the drying equipment 10, and the amount of solid input and the amount of moisture input to the dryer 14 may be calculated based on the result.

Figure 4 is a flowchart showing the flow of the heating control process executed by the main control device 20 in this embodiment. Note that the heating control process starts when the operation of the drying equipment 10 starts.

First, in step S100, the target evaporation water amount calculation unit 64 calculates the average value of the target evaporation water amount (e.g., the average value over a 10-minute period).

In the next step S102, a control function is selected based on the amount of water input.

In the next step S104, the heat amount control unit 66 calculates the amount of heat corresponding to the target amount of evaporated water by substituting the target amount of evaporated water into the control function, and transmits a control signal corresponding to the calculated amount of heat to the valve control device 31 and the motor control device 35. In this step, the initial values of the dam height and the steam pressure are determined by substituting the target amount of evaporated water into both the control function for the dam height and the control function for the steam pressure. As a result, the motor control device 35 drives the motor 34 so that the dam height corresponds to the control signal. Also, the valve control device 31 drives the motor 34 so that the steam pressure corresponds to the control signal. The processing in step S104 corresponds to feedforward control of the amount of heat for the sludge.

In the next step S106, the actual evaporated water content calculation unit 62 determines whether a predetermined time (e.g., 1 to 2 hours) has passed since the previous calculation of the target evaporated water content. If the determination is positive, the process proceeds to step S108, whereas if the determination is negative, the process waits until the predetermined time has passed. Note that this predetermined time corresponds to the time required for the sludge to be discharged after the drying process by the dryer 14 is completed after it is fed into the dryer 14.

In step S108, the condensation heat flow rate calculation unit 60 calculates the exhaust gas condensation heat flow rate, and the actual evaporated water content calculation unit 62 calculates the actual evaporated water content using the exhaust gas condensation heat flow rate.

In the next step S110, the heat amount control unit 66 calculates the evaporation water amount difference, which indicates the degree of deviation between the previously calculated target evaporation water amount and the actual evaporation water amount, and corrects the control function according to the evaporation water amount difference. Note that the heat amount control unit 66 does not need to correct the control function if the evaporation water amount difference is less than a predetermined value.

In the next step S112, the target evaporation water amount calculation unit 64 calculates the average value of the target evaporation water amount (e.g., the average value over 30 minutes).

In the next step S114, the target evaporated water content calculated in step S112 is input into a control function, and the heat amount control unit 66 calculates a heat amount corresponding to the target evaporated water content, and transmits a control signal corresponding to the calculated heat amount to either the valve control device 31 or the motor control device 35. This controls the dam height or steam pressure according to the calculated heat amount. In other words, the processing of step S112 is a correction of the operation amount for the dam height or steam pressure using a control function corrected according to the difference in evaporated water content, and corresponds to feedback control of the heat amount for the sludge.

In the next step S116, the heat amount control unit 66 determines whether or not an instruction to stop the drying equipment 10 has been input, and if the determination is negative, the process returns to step S104 to repeat the control of the heat amount. On the other hand, if the determination is positive, the heat amount control process ends.

As explained using the flowchart of FIG. 4, the heat amount control process of this embodiment controls the heat amount based on the evaporated water amount calculated a predetermined time after the sludge is input into the dryer 14. The reason for this is that it takes time for the dryer 14 to dry the sludge. In other words, the calculated actual evaporated water amount is not the evaporated water amount of the sludge input into the dryer 14 at the time of calculation, but the evaporated water amount of the sludge input before that. The moisture content of the sludge input into the dryer 14 may change depending on the properties of the sludge input. For this reason, the actual evaporated water amount after a predetermined time has elapsed after the sludge is input into the dryer 14, i.e., after the time required for drying the sludge has elapsed, is the actual evaporated water amount corresponding to the sludge input into the dryer 14.

For this reason, in this embodiment, the amount of heat applied to the sludge can be more appropriately controlled by controlling the amount of heat applied based on the actual amount of evaporated water calculated after a predetermined time has elapsed since the sludge was put into the dryer 14, i.e., taking into account the time delay. Note that this predetermined time may be changed depending on the dam height, since the residence time of the sludge in the dryer 14 changes depending on the dam height.

Second Embodiment
A second embodiment of the present invention will now be described. The drying equipment 10 of this embodiment calculates the amount of water evaporated from the sludge in the dryer 14 based on the physical quantity of the exhaust gas from the dryer 14.

Figure 5 is a schematic diagram of the drying equipment 10 of this embodiment. The same components in Figure 5 as those in Figure 1 are given the same reference numerals and their description will be omitted. Figure 6 is a functional block diagram related to the heat amount control of this embodiment. The same components in Figure 6 as those in Figure 2 are given the same reference numerals and their description will be omitted.

As shown in FIG. 5, the drying equipment 10 of this embodiment is provided with a flow sensor 70 in the exhaust path 36 of the dryer 14 to measure the inlet exhaust gas flow rate F3 to the scrubber 18.

As shown in FIG. 6, the main control device 20 of this embodiment includes an actual evaporated water amount calculation unit 62A, a target evaporated water amount calculation unit 64, and a heating amount control unit 66.

The actual evaporated water amount calculation unit 62A calculates the actual evaporated water amount of the sludge in the dryer 14 based on the physical quantities of the exhaust gas before and after passing through the scrubber 18. In this embodiment, the actual evaporated water amount calculation unit 62A calculates the actual evaporated water amount based on, as an example, the measured inlet flow rate (inlet exhaust gas flow rate F3) of the exhaust gas to the scrubber 18, the measured outlet flow rate (outlet exhaust gas flow rate F4), and the measured outlet temperature (outlet exhaust gas temperature T4).

Next, we will explain an example of calculating the actual amount of water evaporated from the sludge in the dryer 14 based on the physical quantities of the exhaust gas.

The actual amount of evaporated water is calculated by subtracting F4w, which is the water flow rate [kg/h] in the exhaust gas at the outlet of the scrubber 18, from F3w, which is the water flow rate [kg/h] in the exhaust gas at the inlet of the scrubber 18, as shown in the following equation (5).
Actual amount of evaporated water = F3w - F4w ... (5)

The moisture flow rate F3w in the inlet exhaust gas is calculated by subtracting the gas flow rate F4g in the outlet exhaust gas from the inlet exhaust gas flow rate F3, as shown in the following formula (6).
F3w = F3 - F4g ... (6)

The outlet exhaust gas gas flow rate F4g and the outlet exhaust gas moisture flow rate F4w are calculated by the simultaneous equations of the following equations (7) and (8). The inlet exhaust gas moisture flow rate F3w is calculated by substituting the outlet exhaust gas gas flow rate F4g into equation (6).
F4g = F4 - F4w ... (7)
F4w = m (100% absolute humidity at outlet exhaust gas temperature T4 [kg- _H2O /kg-dry gas]) × F4g ... (8)

The actual amount of evaporated water is calculated by substituting the inlet exhaust gas moisture flow rate F3w and the outlet exhaust gas moisture flow rate F4w calculated using equations (6) to (8) into equation (5).

The heating amount control unit 66 of this embodiment controls the heating amount based on the difference (evaporation water amount difference) between the actual evaporated water amount calculated based on the physical quantities of the exhaust gas and the target evaporated water amount.

The heating control process executed by the main control device 20 in this embodiment is similar to the heating control process described in FIG. 4, so a description thereof will be omitted.

Third Embodiment
A third embodiment of the present invention will now be described. The drying equipment 10 of this embodiment calculates the actual amount of water evaporated from the sludge in the dryer 14 based on the physical amount of steam (hereinafter referred to as "heating steam") introduced into the agitation means (hollow drive shaft 14B and hollow agitation blade 14C).

Figure 7 is a schematic diagram of the drying equipment 10 of this embodiment. The same components in Figure 7 as those in Figures 1 and 5 are given the same reference numerals and their description will be omitted. Figure 8 is a functional block diagram related to the heat amount control of this embodiment. The same components in Figure 8 as those in Figure 6 are given the same reference numerals and their description will be omitted.

As shown in FIG. 7, the drying equipment 10 of this embodiment is provided with a flow sensor 80 in the steam inlet pipe 28 that measures the flow rate F5 of the heating steam.

The hollow drive shaft 14B is also provided with a drain pipe 82 that discharges moisture (drain) that is condensed from the heating steam when heat is absorbed by the sludge. Although the drain pipe 82 is omitted in Figures 1 and 5, it is also provided in the drying equipment 10 of the first and second embodiments.

As shown in FIG. 8, the main control device 20 of this embodiment includes an actual evaporated water amount calculation unit 62B, a target evaporated water amount calculation unit 64, and a heating amount control unit 66.

In this embodiment, the actual evaporated water amount calculation unit 62B calculates the evaporated water amount of the sludge in the dryer 14 based on the heating steam flow rate F5 measured by the flow rate sensor 80, as an example.

In the dryer 14, the sludge is dried by the heating steam introduced into the stirring means. As a result, the heating steam that has absorbed heat from the sludge is condensed and discharged as drain. In other words, there is a correlation between the amount of water evaporated from the sludge and the amount of heating steam supplied, and the actual amount of evaporated water can be calculated from the flow rate of the heating steam.

Therefore, the actual evaporated water amount calculation unit 62A calculates the actual evaporated water amount by multiplying the heating steam flow rate F5 by a coefficient A as shown in the following equation (9).
Actual amount of evaporated water = A x F5 (9)

This coefficient A is set arbitrarily according to the flow rate of the heating steam, but may vary, for example, according to the temperature of the heating steam. Coefficient A may also vary, for example, according to the flow rate of the drain formed by condensing the heating steam. In this case, a flow rate sensor for measuring the flow rate of the drain is provided in the drain pipe 82.

The heat amount control unit 66 of this embodiment controls the heat amount based on the difference (evaporation water amount difference) between the actual evaporated water amount calculated based on the physical quantity of the heating steam and the target evaporated water amount.

The heating control process executed by the main control device 20 in this embodiment is similar to the heating control process described in FIG. 4, so a description thereof will be omitted.

The present invention has been described above using the above embodiment, but the technical scope of the present invention is not limited to the scope described in the above embodiment. Various modifications or improvements can be made to the above embodiment without departing from the gist of the invention, and forms with such modifications or improvements are also included in the technical scope of the present invention. Furthermore, the configurations of the first, second, and third embodiments may be combined as appropriate.

In the above embodiment, the control functions for the dam height and steam pressure are corrected according to the difference in the amount of evaporated water, and the control amounts for the dam height and steam pressure are calculated from the corrected control functions. However, this embodiment is not limited to this. For example, the increase or decrease in the amount of heat applied to the sludge may be calculated from the difference in the amount of evaporated water, and the control amount for the steam pressure or dam height may be calculated according to this increase or decrease.

In the above embodiment, the dehumidifier that reduces the amount of moisture in the exhaust gas is the scrubber 18, but this embodiment is not limited to this. For example, as shown in FIG. 9, the scrubber 18 may be a condenser 90. In this embodiment, cooling water flows in and out of the condenser 90 as dehumidified water, and the exhaust gas from the dryer 14 is indirectly cooled by this cooling water. As a result, the water vapor in the exhaust gas is condensed and discharged as drain from the drain outlet 90A. In the example of FIG. 9, a flow sensor 44 is provided in the water supply passage 38 and a flow sensor 48 is provided in the drain passage 40. However, since the flow rate of the cooling water flowing through the water supply passage 38 and the drain passage 40 is the same, it is sufficient to provide either the flow sensor 44 or the flow sensor 48.

In the above embodiment, the fluids used to calculate the amount of evaporated water from the sludge in the dryer 14, in which water condenses as heat is removed while flowing through the drying equipment 1, are dehumidified water flowing through the scrubber 18, exhaust gas flowing through the scrubber 18, and heating steam flowing inside the agitation means. However, the present invention is not limited to this, and other fluids may also be used.

10 Drying equipment 14 Dryer 14G Barrier 18 Scrubber (dehumidifier)
62 Actual evaporated water amount calculation unit (calculation means)
66 Heat amount control unit (control means)

Claims (8)

A drying facility having a dryer that heats and dries a material to be dried, and a dehumidifier that reduces the amount of moisture in an exhaust gas discharged from the dryer by using a liquid medium,
a calculation means for indirectly calculating an evaporated water amount of the material to be dried in the dryer based on a physical quantity including a temperature of the liquid medium before and after passing through the dehumidifier or a physical quantity including a temperature of the exhaust gas;
A control means for controlling an amount of heat applied to the material to be dried in the dryer based on the amount of evaporated water calculated by the calculation means;
Drying equipment equipped with: A drying facility having a dryer that heats and dries a material to be dried while stirring it with a stirring means into which steam is introduced,
A calculation means for indirectly calculating the amount of water evaporated from the material to be dried in the dryer by multiplying the flow rate of the steam by a coefficient;
A control means for controlling the amount of heat applied to the material to be dried in the dryer based on the difference between the evaporated water content calculated by the calculation means and a target evaporated water content;
Drying equipment equipped with: The dryer dries the material to be dried by a heating medium, and a dam is provided at an outlet of the material to be dried,
The drying equipment according to claim 1 or claim 2, wherein the control means changes the height of the dam when the amount of heat is to be changed relatively greatly, and changes the physical property values of the heating medium when the amount of heat is to be changed relatively small. The drying equipment according to any one of claims 1 to 3, wherein the control means controls the amount of heat based on the amount of evaporated water calculated a predetermined time after the material to be dried is put into the dryer. The drying equipment according to claim 1, wherein the calculation means indirectly calculates the amount of evaporated water of the material to be dried in the dryer based on the condensation heat flow rate of the exhaust gas in the dehumidifier, which is calculated using physical quantities including the temperature of the liquid medium. The drying equipment according to claim 2 , wherein the coefficient varies depending on a flow rate of the steam, a temperature of the steam, or a flow rate of drain resulting from condensation of the steam. A method for controlling a heat amount of a drying facility having a dryer that heats and dries a material to be dried, and a dehumidifier that reduces the amount of moisture in an exhaust gas discharged from the dryer by using a liquid medium, comprising:
A first step of indirectly calculating an amount of water evaporated from the material to be dried in the dryer based on a physical quantity including a temperature of the liquid medium before and after passing through the dehumidifier or a physical quantity including a temperature of the exhaust gas;
A second step of controlling the amount of heat applied to the material to be dried in the dryer based on the amount of evaporated water calculated in the first step;
The heating amount control method includes the steps of: A method for controlling a heat amount of a drying facility having a dryer that heats and dries a material to be dried while stirring it with a stirring means into which steam is introduced, comprising the steps of:
A first step of indirectly calculating an evaporated water amount of the material to be dried in the dryer by multiplying the flow rate of the steam by a coefficient ;
A second step of controlling the amount of heat applied to the material to be dried in the dryer based on the amount of evaporated water calculated in the first step;
The heating amount control method includes the steps of:

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