JPH0729036B2 - Powder fine water content control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder fine water content control apparatus.

[0002]

2. Description of the Related Art Conventionally, a so-called spray dryer has been used to granulate powder for other purposes such as ceramics. In this apparatus, the stock solution is supplied and sprayed into the tower, and hot air is sent into the tower to be dried to obtain a powder.

[0003]

In the spray dryer of this type, if the main purpose is to produce a powder having no water content, it is sufficient to control the amount of heat supplied, etc., though not so high. However, some product powders are required to have a water content as uniform as possible within a predetermined constant value. Making the powder moisture content uniform can contribute to improving the quality of the molded product when a certain amount of a minute moisture content is contained, for example, when press molding the powder, but in the above, It is difficult to deal with such a case, and it is difficult to stably produce a powder containing a certain small amount of water.

On the other hand, if the operator measures the water content and adjusts the amount of hot air in the spray dryer based on this, the change in the amount of water content in the actual powder is reflected in the granulation process by that amount, which is advantageous. However, in this case, it is labor-intensive, and it is still insufficient for stabilizing the water content, and as described above, a highly uniform water content is required. I can't answer enough. In order to realize highly accurate and uniform distribution of powder water content,
It is extremely effective in terms of yield, etc. to construct comprehensive control by taking into consideration not only the actual water content of the product powder but also other factors that may affect the water content. Is.

Therefore, the object of the present invention is to realize the above-mentioned idea, to appropriately granulate a powder containing an arbitrary minute amount of water, and to stabilize the amount of water and to control the powder finely. It is to provide a water content control device.

[0006]

According to the present invention, the following powder minute water content control device is provided. A control device for controlling the water content of the powder in a spray dryer that obtains the granulated powder based on the stock solution from the stock solution supply device, and means for detecting the water content of the granulated powder and exhaust air in the tower. And a temperature control means capable of controlling hot air to be fed into the tower, the temperature control means is configured to detect the moisture content, an operating state of the exhaust means or its equivalent value, and a stock solution. The powder minute water content control device includes means for setting a temperature in accordance with the supply pump pressure and / or the flow rate or its equivalent value.

[0007]

The above-described powdery minute water content control device has its water content detection means, exhaust means, and temperature setting means, and automatically detects the water content, while the hot liquid is being fed into the tower. The powder is granulated by atomization and drying of the temperature control means, and the temperature setting means of the temperature control means sets not only the detected moisture value but also the operating state of the exhaust means or its equivalent value when setting the control temperature. Further, in accordance with the pump for supplying the undiluted solution and / or the flow rate or its equivalent value, the temperature is set in consideration of them, and the hot air supplied is controlled based on this. As a result, automatic control is possible, and in order to stabilize the water content, more detailed water control that considers the above factors in an integrated manner is possible, and the water content of the obtained powder can be adjusted to a high level. Can be made evenly uniform, and efficient granulation of a powder containing an optional minute amount of water is performed.

[0008]

1 and 2 show a granulation system to which a powder moisture content control in a spray dryer according to an embodiment of the present invention is applied. These figures show the entire system in a divided form. Fig. 1 mainly shows the drying tower of the spray dryer and the exhaust (exhaust air) device side, and Fig. 2 shows the powder to be granulated (for example, ceramic powder). The control system side including the automatic control of the water content of powder) is shown.

In the illustrated system, a nozzle type nozzle is used, and a spray dryer can body 1 as a drying tower is provided with a nozzle (pressure nozzle) 2 that opens upward in the lower part, whereby the feedstock is directed upward. To spray. The lower end of the can has an outlet 1a for granulated powder, through which the produced powder (ceramic) is discharged. The nozzle 2 is connected to a tank 4 (No. 1, No. 2) for storing the stock solution slurry via a supply path 3, and a fresh water tank 5 is further connected to the supply path 3 and the stock solution slurry is quantitatively determined. The pump 6 is installed. The pump 6 is driven by a motor 7.

Hot air is supplied to the can body 1 above the nozzle 2, and the hot air supply passage 11 is connected to a hot air supply (temperature control) device (FIG. 2). The device includes a combustion air fan 12
(0.4KW), including a controllable combustion air damper 13, and a burner 14 as an air heater for heating the feed air,
Also, dry air damper 15 (0.75kW) for manual control,
A dry air fan 16 can be included. The combustion air damper 13 is controlled by a motor 17. The amount of water in the powder granulated by the spray dryer is controlled by controlling the temperature of the combustion air damper 13 by the motor 17.

The system may further include a cyclone or a filter, which is separate from the spray dryer can body, for collecting the granulated powder having a small particle size. In this example, the cyclone 21 is provided.
The can 1 and its cyclone having both the filter 22 and the filter 22.
21 and 21 are connected via an exhaust duct 23. The portion of the exhaust duct 23 that is introduced into the can can be disposed below the nozzle 2, for example, as shown in the drawing. The filter 22 downstream of the cyclone 21 is further connected to the exhaust fan 24 (5.5 kW).
For the exhaust fan 24, an exhaust fan inverter
A rotary drive controller 26 including 25 is provided to control the rotation speed of the exhaust fan 24 and serve to control the static pressure inside the can (inside the tower).

In this system, the production of granulated powder is basically carried out as follows. That is, the metering pump 6 by the motor 7 mixes the undiluted solution to be granulated stored in the slurry tank 4 and, if necessary, still water and others.
Under the drive control of the (volumetric pump), it is fed in a predetermined supply state and sprayed upward in the can body 1 by the nozzle 2 (slurry mist). In the can, with the automatic start-up described later, and in the subsequent system operation state, the exhaust fan 24 functioning as an exhaust pump controls the static pressure in the can, and thus in the spray dryer, to stabilize the static pressure. On the other hand, the temperature control according to the water content control described later is performed by the control of the combustion air damper 13 by the motor 17, and under these controls, when the nozzle is sprayed, the raw material is dried by the hot air supplied, and the obtained powder is a can. It drops to the bottom and is discharged from the outlet 1a. On the other hand, the exhaust air containing fine components is duct 23,
It is purified in the process of passing through the cyclone 21 and the filter 22, and is discharged through the exhaust fan 24.

The motor 7 for the pump 6 and the combustion air damper 13 including the above-mentioned operation and system start-up
The spray motor control computer 31 controls the motor 17 and the exhaust fan 24, and the control system
Temperature controller 32, pressure controller for stock solution supply system 33
And so on (Fig. 2). Control computer 31
The data from the automatic moisture meter 41 for detecting the water content of the granulated powder obtained from the outlet 1a, and the hot air inlet temperature used for the temperature cascade control of the spray dryer together with the outlet temperature detection value described later. To detect the signal from a hot air inlet temperature detector 42 (for example, a thermocouple) placed near the hot air inlet to the can, and the static pressure to detect the static pressure inside the can (spray dryer static pressure inside the can). A signal or the like from the pressure gauge 43 is input. The input from the moisture meter 41 is performed by communication, and the temperature detector 42 and the static pressure gauge 43 side are analog inputs.

Further, in the exhaust duct 23 between the can body 1 and the cyclone 21, an outlet temperature detector 44 (for example, a thermocouple) which detects the temperature of the exhaust gas passing through the relevant portion as the outlet temperature is installed. Is input to the temperature controller 32, and a pressure detector 45 for detecting the pressure (stock solution pump pressure) is arranged in the stock solution supply path 3 to the nozzle 2, and the signal from this is input to the pressure controller 33. The controllers 32 and 33 perform input / output of necessary data through the converter 34 by communication.

Computer 31 for controlling spray dryer
Performs processing according to a program whose example is shown below by a flowchart based on various input information, and performs comprehensive control on the granulation system. Comprehensive control includes automatic system startup, subsequent moisture control during operation, and more. For example, continuous automatic measurement of water content, stabilization of static pressure in the can of the spray dryer mentioned earlier, stabilization (constant) of the powder atomization pressure of the raw material, and temperature cascade control of the spray dryer.
For temperature control, the motor 17 is controlled through the temperature controller 32. The pump 6 is pressure-controlled including ON / OFF of the motor 7 via the pressure controller 33. Regarding the exhaust fan rotation speed control, the computer 31 directly sends a control signal as an analog output to the exhaust fan inverter 25 to execute the control.

When automatically controlling the water content, it is necessary to consider the water content, the rotation speed of the exhaust fan, the powder atomization pressure of the raw material, the flow rate, the temperature, the hot air volume, and the static pressure in the can to stabilize the water content of the product powder. This milling system is based on the idea that it is effective in obtaining powder products containing the desired and extremely small amount of water as efficiently as possible by making it uniform (uniforming the amount of powder water). Is what is built. Particularly, in the spray drying of the undiluted solution in the drying tower (spray dryer), the tower pressure (in the can), the tower temperature, the properties of the slurry, etc. are one of the important factors affecting the results. Therefore, the exhaust fan 24 controls the rotation speed so that the pressure in the tower becomes constant. For the pump, this results in a constant discharge pressure and a constant particle size, resulting in a constant drying rate. The magnitude of the speed affects the magnitude of the water content, and therefore it is preferable that the rate is constant also from this point. When the spray amount increases, for example, it works so as to lower the temperature in the tower, and therefore it is preferable to raise the temperature of the hot air supplied and keep the water amount constant. The exhaust fan 24, as a result of performing the above control, for example, if the internal pressure of the tower increases,
The number of revolutions is increased (the degree of drying is small) in order to reduce the pressure, and the water content is large. Therefore, in such a case, it is better to raise the temperature. Stabilization of the pressure in the tower (static pressure of the can)
Furthermore, it is also effective to avoid a situation (negative pressure) that flows through the exhaust duct 23 to the exhaust fan 24 side due to pressure fluctuations, for example, thus ensuring a high yield with a constant particle size. Moreover, it is advantageous to realize that the water content is uniform.

Based on these considerations, the amount of heat supplied is controlled so that a predetermined set water content (for example, an arbitrary minute water content of 0.2 to 2.5%) is controlled, and a constant particle size and high yield are realized. When the water content is large, the heat supply is increased, and when the exhaust fan rotation speed is high, the heat supply is increased. Furthermore, in order to perform finer control, increase the pump rotation speed and increase the heat supply amount. If the flow rate is increasing, the heat supply amount is increased accordingly. Furthermore, when the temperature (in-column temperature) itself shows high and low fluctuations, the supplied heat amount is changed so as to suppress it. The above-mentioned heat quantity control is, of course, executed within the allowable heat resistant temperature range of the spray dryer to be used, and the control target set temperature (target set value) is set according to the type of stock solution to be applied, and it is sequentially set. It is updated, set, and executed under the control of the control computer 31 (an example of the temperature setting calculation in the temperature controller 32 will be described later).

FIG. 3 shows a control program of the system,
This allows the granulation process after ignition of the burner 14 (step
From 102) to its stop (step 107), it is managed as a whole. In the same figure, the processing relating to the automatic start-up and moisture control task consists of steps 101 to 107, and similarly, the static pressure control task in the tower (in the can body 1) and the moisture value input task are respectively step 201 to 107. 205, steps 301-305
Consists of.

First, a necessary initial value in the system (for example, a predetermined temperature value which will be described later applied in a temperature control loop of a start-up routine, or a temperature controller set value (initial value) in a moisture control routine, setting) After setting (moisture value etc.) (step 101), the ON state of the control start signal based on the switch operation by the operator during the burner combustion (the ON state of the signal is determined by the corresponding determination (for example, step
(611, 711) also applies), the automatic startup routine is started (step 101
~ 105). During the burner combustion, the tower static pressure control task is executed. This is the setting of the initial value (for example, the static pressure determination value in FIG. 6 described later) necessary for the control (step 20).
1) The same input and check processing as in steps 103 and 104, static pressure control routine (step 204), and burner stop check (step 205).

The automatic start-up routine has the contents shown in FIG. 4 (step 401), and executes a temperature control loop (step 402) after a manual control command to the temperature controller (step 401). The temperature control loop can basically be configured as the processing content shown in FIG. The explanation in the above case is as follows.

First, the hot air inlet temperature from the thermocouple 42 is read (step 501). Subsequent steps 50 2, 5
03 is a comparison check with each set temperature value, here,
It is checked whether a predetermined value, for example, 395 ° C or higher and 375 ° C or lower. Specifically, the range is set according to the upper limit (for example, 399 ° C.) of the allowable heat resistant temperature of the can body 1. If the answer to step 502 is YES, the control amount DUMP of the combustion air damper 13 is set to, for example, 0 (step 504) and the combustion air damper is controlled (step 507). Specifically, the motor 17 according to the command is set. The controller 32 determines and outputs the drive control signal to the controller under the control of the computer 31.

The answer to step 502 is NO and step 503
If the answer is YES, for example, set DUMP = 100 (step 505
In step 507, control is performed to raise the temperature. If the answer to both steps 502 and 503 is No,
In step 506, DUMP = DUMP + K (388-INTMP) is calculated, and the combustion air damper 13 is controlled based on this calculation. Here, K is a constant and INTMP is a hot air inlet temperature.
In this way, the temperature control is executed and adjusted to a predetermined value (here, the central value is 388 ° C.). Basically, this method can be applied to the case of water content control which will be described later.

Returning to FIG. 4, next, the output temperature is read from the output temperature thermocouple (detector) 43 and a predetermined value, for example,
A comparison check with 120 ° C is performed (steps 403 and 404), and when the appropriate starting temperature according to the applied stock solution is reached, the following is executed. That is, the stock solution slurry pump is turned on, pump pressure control is started, and the water content input task (see FIG. 3) is started (steps 405 to 407). Then, a temperature control loop is executed to read out the outlet temperature and set it to a predetermined temperature value (eg 72
(° C) is checked (steps 408 to 410).
Here, as for the above-mentioned discrimination temperature value, since the slurry powder mist starts to be started at this point and the temperature near it, that is, the outlet temperature, decreases as the undiluted solution is charged into the can body 1,
It is set lower than the discriminant value temperature in step 404,
Further, it can be set in combination with the product powder containing the desired amount of water to be granulated, the feed stock solution for that, and the like.
Then, when the temperature falls below the predetermined value (72 ° C), this routine is finished.

Returning to FIG. 3, when the process goes to the next water content control routine (step 106), the detected value in the water content input task executed by the above start command is applied to this routine. The task consists of the processes (steps 301 to 305) as shown in the figure, and the powder detection moisture value input from the automatic moisture meter 41, the moisture value calculation, the moisture value output to the host computer, and the moisture control are performed. Each of the applied moisture value outputs (steps 301 to 304) is repeatedly executed according to the result of the burner stop check (step 305). The output process in step 304 is performed every 15 minutes, for example, but the output process is not limited to this.

The moisture control routine also includes the exhaust fan rotation speed output in the static pressure control routine (step 204).
It is applied as a control variable (parameter). Here, the static pressure control routine will be described. This has the contents shown in FIG. 6 (steps 601 to 611). First, the detected static pressure value from the can static pressure manometer 44 is read (step). 601
). In the subsequent steps 602 to 605, the static pressure value (actual value) and a predetermined value (for example, 6 mm H ₂ O, 4 mm H ₂ O, 2) are respectively set.
mm H ₂ O, 0 mm H ₂ O), the control amount FRQ for the exhaust fan inverter 25 is set to increase / decrease the rotation speed of the exhaust fan in each level range according to the corresponding determination result. , FRQ = FRQ + constant or FRQ = FR
Q-Calculate with a constant (steps 606 to 609). Here, the addition and subtraction constants at each level are set to predetermined values. Then, in step 610, the output of the calculated value FRQ is executed, the rotation speed of the exhaust fan 24 is controlled via the rotary drive controller 26, and the pressure inside the can (static pressure) is desired (2 mm H in this case). ₂ O to ₄ mm H ₂ O) is continued during operation (step 611).

In step 106 of FIG. 3, thus,
Although each control variable is applied, an example of such a moisture control routine is shown in the process of FIG. 7 (steps 701 to 711).
). In FIG. 7, this is also repeatedly executed during operation (step 711). First, the state of the rotation speed control is monitored, and the exhaust fan rotation speed input FAN1 is set to step 701.
Read in. Specifically, since the control amount for the inverter 26 corresponds to this, the FAN1 value can be taken in based on this.

Next, in step 702, the stock solution pump pressure PRS1 is read based on the output of the pressure detector 45 of the stock solution supply passage 3, and in step 703, the stock solution pump flow rate FLW1 is read. Regarding the FLW1 value, since the control signal for the motor 7 can be treated as indicating the flow rate under the pump control by the pressure controller 33, the FLW1 value is taken in here based on that.

Then, in step 704, the moisture value MOIS (step 304) obtained in the moisture value input task is read. After entering the moisture value every 15 minutes, the respective values of FAN2, PRS2, FLW2
(Value after 15 minutes) is read (steps 705 to 707), and the temperature controller setting value SETTMP is read every time step 708 is executed. Then, using each of the above values, in step 709,
Perform the following operation.

[Equation 1] SETTMP = SETTMP + constant (FAN2-FAN1) + constant (PRS2-PRS1) + constant (FLW2-FLW1) -constant (SETMOIS
-MOIS) ・ ・ ・ ・ ・ ・ ・ ・ 1

Here, SETMOIS is a preset moisture value of the powder to be obtained, and the difference value between each of the second to fifth terms on the right side (the current value and the previous value 15 minutes before). The difference between the multiplication constants depends on the type of each control parameter.
If the reflection to the water content control is weighted in consideration of the degree, more appropriate control becomes possible. SE calculated in this way
The TTMP value is output as the temperature controller temperature setting value in this loop (step 710), and the temperature control is executed based on this. Therefore, the temperature controller 32, under the control of the computer 31, sets the motor 17 so that the above set value is obtained.
And outputs a control signal for the combustion air damper 13 to control the combustion air damper 13.

In such control, the detected temperature value (actual value) is applied so that the outlet temperature becomes the target set value, and the temperature feedback control is performed, and at the time of setting the set SETTMP value, the above equation is used. Since the setting is based on, the exhaust fan rotation speed (hence the static pressure in the can), the pump pressure, and the flow rate are added to the water content information, and as a result,
Fine water content control (correction) is realized. Therefore,
Not only the deviation between the target value and the actual value of the water content (water content feedback control), but for example, if the rotation speed of the exhaust fan 24 increases, the set temperature is correspondingly high in order to compensate for the resulting deviation. The amount of heat supplied is set in accordance with this, and the fluctuation of the amount of water can be suppressed well, and this point is the same for other factors, and the control becomes appropriate.

As described above, according to the present control, the powder product which exceeds the concept of a mere spray dryer and contains an arbitrary minute amount of water of, for example, 0.2 to 2.5%, is accurate and highly accurate with respect to the amount of water. Can be obtained in the granulation step.
The obtained water content of the powder is sufficiently uniform, and even when the powder is molded (for example, by press molding), the content of a certain amount of the minute water content is ensured, so that the quality can be improved.

Further, there is no problem such as labor and instability of the water content when an operator measures the water content to adjust the hot air quantity of the spray dryer, and the water content can be stabilized and automatically controlled. Of course, in the case of this example, as described above, comprehensive overall control in the process is performed, and a high yield can be easily achieved with a constant particle size.

The present invention is not limited to the above embodiment. For example, although the target of granulation is ceramics, it can be widely applied when it is desired to contain a certain amount of water in the production of granules for various other uses. Further, although the exhaust fan rotation speed is observed as an applicable parameter in the moisture control, it can be implemented by observing the column internal pressure instead. Furthermore, the drying tower and the exhaust device system are not limited to those having the illustrated structure (for example, atomization may not be a nozzle type). This point is the same for the control system.

[0034]

According to the present invention, it is possible to easily and stably obtain a powder having a uniform powder water content, and to make a fine adjustment in consideration of other control variables of the detected water content even in the automatic water content control. Therefore, even in the case of granulation for an application in which powder content is required to have a constant water content, it can be sufficiently satisfied, and therefore product quality can be improved. .

[Brief description of drawings]

FIG. 1 is a divided representation of an entire granulation system having a powder water content control device according to an embodiment of the present invention.
It is a figure which shows a part.

FIG. 2 is a diagram showing another part of the same.

FIG. 3 is a diagram showing an example of contents of a control program in the system.

FIG. 4 is a flowchart showing an example of an automatic startup routine.

FIG. 5 is a flowchart showing an example of a temperature control loop.

FIG. 6 is a flowchart showing an example of a static pressure control routine in a tower.

FIG. 7 is a flowchart showing an example of a moisture control routine.

[Explanation of symbols]

 1 Spray dryer canister 2 Nozzle 4 Slurry tank 5 Fresh water tank 6 Undiluted slurry metering pump 7,17 Motor 12 Combustion air fan 13 Combustion air damper 14 Burner 24 Exhaust fan 31 Computer for spray dryer control 32 Temperature controller 33 Pressure controller 41 Automatic moisture Total 42 Hot air inlet temperature detector (thermocouple) 43 Outlet side temperature detector (thermocouple) 44 Can static pressure gauge 45 Pressure detector

Claims (1)

[Claims] 1. A controller for controlling the water content of powder in a spray dryer that obtains granulated powder based on the stock solution from a stock solution supply device, and means for detecting the water content of the granulated powder, An exhaust means for exhausting the air in the tower and a temperature control means for controlling the hot air to be fed into the tower are provided, and the temperature control means is configured to detect the moisture content and the operating state of the exhaust means or its A powder minute water content control device comprising means for setting a temperature according to a corresponding value and a pump pressure and / or a flow rate of the undiluted solution supply or its corresponding value.