JPH1076101A - Control method of spray dryer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling a spray dryer by which stable control is rapidly performed even when operating conditions of equipment such as the throughput of equipment and the target value of product quality are changed. SOLUTION: A controller 14 is constituted of a CPU and memories, and has a calculation program in which heat balance is calculated from measuring data indicating system operating conditions to obtain heat loss. The controller is also provided with a calculation program in which the target value (the dry powder moisture, slurry feed quantity and the like) is changed and if necessary, (if the relative formula is known,) the values of corresponding physical quantities (blown air temperature, heat loss, granular product temperature and the like) are changed from the calculated heat balance to calculate heat balance again and calculate the target hot air temperature and/or gas volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a spray drying apparatus for spray-drying raw materials.

[0002]

2. Description of the Related Art Spray drying techniques such as spraying and drying a slurry raw material to obtain a powdered detergent product containing a predetermined range of moisture are conventionally known. For example, Japanese Patent Publication No. 02-14400 discloses that a hot air temperature, a slurry supply speed, and a spray pressure are controlled based on a specific exponential function equation as feedback of a process value from the current moisture value of a drying tower. Thus, a quality control method in spray drying is disclosed. Japanese Patent Application Laid-Open No. 06-15101 discloses a spray-drying apparatus and a spray-drying method with moisture control in which control is performed by fuzzy inference and a member-ship function in order to further control the moisture to a reference value. Japanese Patent Publication No. 54-35702 discloses a quality control method in hot-air drying in which operation variables such as apparent specific gravity, blast temperature, and slurry supply speed are vector-operated. JP 01-12700
No. 1 discloses a control device for a spray-drying tower that adaptively controls the blowing temperature of hot air so as to reduce the change in the temperature of the dough under the tower. Japanese Patent Application Laid-Open No. 01-284301 discloses a spray drying method in which the temperature of air discharged from a drying device is detected to control the temperature of air blow. In Japanese Patent Publication No. 07-51202, the current value of the moisture content of the powder is measured, and the flow rate and air temperature of the drying air are determined according to the past value of the flow rate and temperature of the dry air, the current value and the past value of the moisture content. A controlled computer controlled spray drying process is disclosed.

[0003] Japanese Patent Application Laid-Open No. 01-203001 discloses a spray drying method for a multi-stock solution in which the operating conditions of a spray drying apparatus are automatically set by a condition file and a calculation formula set in advance for each item to be dried. A method for automatically setting the applicable operating conditions of the spray drying apparatus is disclosed. JP 03-106401
The method includes a method for controlling the water content of a spray-dried powder and a spray-drying apparatus, wherein a water content control constant is determined by the temperature of the exhaust gas from the drying zone and the temperature of the spray-dried particles, and the drying zone is operated. It has been disclosed.

[0004]

When a particulate product is obtained using a spray drying apparatus, the tolerance of the water content in the product is usually relatively narrow, and therefore the desired water content in the product is low. In order to achieve the content, it is necessary to precisely control the operation state of the apparatus. In spray drying, if feedback control is performed on the target value,
A somewhat stable control is possible. That is, since the feedback control is effective for stabilizing disturbance factors during the steady operation of the apparatus, a desired quality product can be obtained by the feedback control when the spray drying apparatus is normally operated. However, in the operation of the device, it is necessary to change the operating conditions of the device for various reasons. The above-described feedback control has a problem that the followability when a set value (target moisture or capacity) in operation is changed is poor. That is, there is a problem that it takes too much time to reach a new set value, and it is not possible to secure desired quality of a product until the control is stabilized by changing the setting, thereby lowering the operation efficiency. Will be done.

Conventionally, when changing operating conditions such as changing the capacity of the apparatus, the operating conditions (blowing temperature and blowing volume) of the influencing factors related to the performance change are based on the experience of the driver. Had changed. Also, JP-A-01-203001
As disclosed in Japanese Unexamined Patent Application, First Publication No. H03-106401, the drying characteristics and relational expressions are determined in advance through experiments and the like and the conditions are set based on the results. , It takes a long time to obtain a product of the desired quality. In particular, when changing the set value of the apparatus during operation, it is important that the control be quickly stabilized, and the technique disclosed in the above publication is insufficient from this viewpoint.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is applicable to a case where the operating conditions of the apparatus are changed, such as a change in the production capacity of the apparatus, a change in the target value of the product quality, and the like. Stable control can be performed quickly, and therefore,
Even in such a case, it is an object of the present invention to provide a method for controlling a spray drying apparatus which has a high reliability and can efficiently obtain a product of a desired quality and has a good operation efficiency. The above object of the present invention is to provide a method for controlling a spray drying apparatus for spraying and granulating a raw material and drying the granulated raw material to obtain a predetermined particulate product, wherein the raw material is introduced into a system including the spray drying apparatus. Measuring the temperature of the substance and the substance discharged from the system, measuring the amount of the substance introduced into the system and the substance discharged from the system, calculating the heat loss in the system based on the measured value, An equation for the heat balance and / or mass balance of the system, wherein a predetermined physical quantity of the temperature and the quantity of the substance introduced into the system and the substance discharged from the system is given as a set value, and another predetermined physical quantity is set as an unknown number. Calculating the unknown by solving the equation, and setting the operating conditions of the spray drying apparatus based on the physical quantity including the calculated unknown. It can be achieved by controlling how to.

In a preferred embodiment, an average measurement value during a predetermined operation time is used as the measurement value. Usually, the operating conditions include the amount of the raw material, the amount of air for drying for drying the raw material, the air temperature, and the like. Further, it is desirable that the heat loss is calculated after the system has been continuously operated for a predetermined period of time. In a preferred embodiment,
The amount of raw material is given as a set value, and the amount of air and the temperature are determined by solving the equation with the amount of air for drying or the temperature as an unknown number. Further, the set value may be changed according to a predetermined characteristic, and an unknown value corresponding to the set value may be sequentially calculated to obtain a correlation between the set value and the unknown value, thereby setting an operation condition. .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the operation of an apparatus for obtaining a product under desired conditions, the present invention changes the operating conditions by performing simulation calculations using equations relating to the heat balance and mass balance of the system. After that, the operating state of the system is accurately predicted to achieve a reliable control, whereby a high-quality product can be efficiently obtained. In this case, from data obtained based on the operation data of the system at a certain point in time or continuous operation, it is data necessary for predicting the operation state of the system. Alternatively, parameters and the like are estimated and calculated, and the calculated values are used to predict fluctuations in the set values and physical property values of the drying tower, and operating conditions corresponding to the fluctuations in the operating state of the system are determined. It is intended to be controlled. In this case, when calculating the physical property values or the like for which the direct measurement is difficult, it is a case where it is obtained from the measurement data relating to a single operation state.

When a single solution is obtained from data in each state when a plurality of data are obtained using trend data representing a change in a predetermined time range, an average value of the obtained solutions is used. Further, when a simulation calculation requiring sequential calculation or the like is used, an evaluation function of the result is defined, and an estimated value is determined by searching so as to minimize this value. In the case where the present invention is applied to a spray-drying apparatus for spraying a slurry detergent raw material in a cylinder and drying it to obtain a particulate detergent product adjusted to a predetermined range of water content in the form of particles, the operating conditions are often changed. Changes in the feed amount (drying capacity) of the material to be dried, that is, the raw material,
The moisture content in the product, ie the target moisture content. And
It is common to change these values by changing the amount of heat (temperature or air volume) of the hot air introduced into the spray dryer. According to the present invention, when the operating conditions are changed, equations relating to the heat balance and the material balance of the system including the spray-drying device are set, and the equations are solved to determine the control variables of the device. In this case, factors of the system that are difficult to measure directly are also calculated in the above equation, and simulation based on a change in operating conditions is performed based on the calculated values.
That is, according to the present invention, unlike the conventional method, various control variables are determined in consideration of the state change of the entire system, so that accurate control can be achieved. (1) Simulation control by heat balance In one embodiment of the present invention, the heat balance of the spray drying apparatus is calculated from the current operation state, and the calorie required to obtain new target capacity and moisture is calculated based on the calculated value. Then, based on this, the hot air temperature and the air volume are calculated and given as new set values.

In this case, in order to calculate the condition at the new target value based on the heat balance, in addition to the set value given as the operating condition and the factors which are not affected even after the operating condition is changed, the heat of the spray drying apparatus is changed. The values of the loss, the exhaust air temperature when the target moisture content in the product is changed, the target moisture content, and the dry product temperature when the hot air temperature is changed are required. In this case, it is difficult to accurately predict the heat loss after changing the operating conditions of the spray drying apparatus as an absolute value in advance, but the value before the change can be calculated from the current operating data, so the value is changed using this value. Determine the later value. Note that the exhaust air temperature and the product temperature can be obtained by measuring the value of the current operation state. Further, it is extremely difficult to accurately calculate the absolute value of the changed value of the exhaust air temperature or the powdery product temperature. In view of this, relative values such as the moisture content in the product, the exhaust air temperature, the hot air temperature, the heat loss, and the amount of change in each of the hot air temperature and the particulate product temperature can be calculated relatively accurately. It is possible to accurately determine the control variables after changing the operating conditions using these values. The configuration of a system 1 including the spray drying device of the present invention will be described with reference to FIG.

In the example shown in FIG. 1, a so-called counter-current spray dryer in which hot air and sun-dried material move in opposite directions in the tower is used. However, a co-current type spray dryer in which hot air and material to be dried move in the same direction. The same can be applied to a spray drying device in the same manner. The system according to the present invention is for spraying and drying a slurry-like detergent raw material to obtain a granular detergent product having a desired content. The system 1 of the present invention comprises a spray drying device 2 for spraying the slurry raw material toward the inside, and a hot air blown into the spray drying device to contact with the granulated raw material to generate hot air for drying. And a hot-air generating furnace 3 that performs heat generation. The spray drying device 2 has a tower shape, and a spray nozzle 23 for spraying a raw material slurry is attached to an upper end side wall 22 of a body 21 of the tower. The slurry supply line 4 is connected.
Depending on the size of the tower, a plurality of spray nozzles may be provided. A skirt portion 24 having a slightly larger diameter is provided at a lower portion of the body portion. A hot air line 5 is connected to an upper end portion of the skirt portion 24 to introduce hot air from the hot air generating furnace 3. Have been. In addition, the spray drying device 2
Has a product take-out port 26 for taking out a granular product at the lower end thereof.

A discharge line 7 provided with a belt conveyor 6 for discharging the granular product from the spray drying device 2 to the outside of the system is provided below the outlet 26. Further, an exhaust line 8 for discharging the air after contacting the raw material sprayed from the tip with the inside of the spray drying device 2 is connected to the tower top 27. The exhaust line is provided with an exhaust blower 9 for sucking the inside of the spray dryer. The hot-air generating furnace 3 has a tower shape, and a supply side of a blower blower 10 is connected to a lower skirt portion 31 so as to send air into the inside. A fuel line 11 for introducing fuel is connected to a position of the skirt portion 31 facing the blower blower 10. In the hot air generating furnace 3, the fuel is burned to generate heat, and the air from the blower blower 10 is heated to generate hot air. The top of the hot-air generating furnace 3 is connected to the hot-air line 5. With respect to the hot air generating furnace 3, the amount of air from the blowing blower 10, the air temperature and the humidity are measured by a flow meter 12 attached to a blowing line 12.
1, a flow meter 1 which is measured by a thermometer 122 and a hygrometer 124 and measures a fuel amount in the fuel supply line 11
11 and a flow rate adjusting valve 112 for adjusting the flow rate. Further, a flow rate adjusting device 123 for adjusting the air volume from the blower blower 10 is provided. A thermometer 52 for measuring the temperature is provided in the hot air line 5.

In the spray drying apparatus 2, the raw material slurry supply line 4 is provided with a thermometer 41 for measuring the temperature of the raw material slurry and a flow meter 42 for measuring the flow rate of the slurry. The slurry is sent out by a high-pressure pump 44, and the flow rate is controlled by the number of rotations, the number of spray nozzles, and the size. The exhaust line 13 is provided with a thermometer 132 for measuring the temperature of the exhaust air. In addition, a flow rate adjusting device 134 that adjusts the flow rate of the exhaust air blower 9 is provided so that the exhaust air amount can be appropriately adjusted. Usually, it is adjusted so that the air blowing amount and the exhaust air amount are balanced. Further, a thermometer 28 and a moisture meter 71 for measuring the temperature and the water content of the granular product taken out from the bottom of the column are provided. In addition, the amount of water in the slurry is measured in advance and is known. The system 1 according to the present example obtains data indicating the operating state from the output from the above-described instrument, solves the heat balance, the equation related to the material balance,
Control amounts such as the amount of air blown from the blower, the amount of fuel supply, and the amount of slurry supply are determined so that a desired amount of granular product having a desired moisture content can be obtained from the tower bottom, and input to each control device. And a controller 14 for controlling the system 1.

The controller 14 controls the system by outputting signals relating to the respective control amounts to the respective control devices.
The controller 14 includes a CPU and a memory, and has a calculation program for calculating a heat balance from the above-described respective measurement data indicating the operating state of the system and obtaining a heat loss. In addition, the apparatus of this example changes the value of the target value (dry powder moisture, slurry supply amount, etc.) from the calculated heat balance and, if necessary (if the relational expression is known), the value of the corresponding physical quantity. (Exhaust air temperature, heat loss, granular product temperature), a heat balance is calculated again, and a program for calculating a target hot air temperature and / or air volume is provided.

The procedure of calculating the heat balance of the system according to the present invention will be described below. The relevant physical quantities are represented as follows: Measurements obtained from the measuring device T2: hot air temperature, T4: exhaust air temperature, T1: granular product temperature, T
3: Slurry temperature, PW: Moisture in granular product, FES: Set value known from measured values of slurry supply device, raw material, and outside air G: Hot air flow, SW: Slurry moisture, H2: Hot air humidity chemical engineering computable or known value CA2 to: hot air heat capacity, CA4: exhaust air heat capacity, CJ2: hot steam heat capacity CJ4: wind exhaust vapor heat capacity, CS: solid specific heat, RAM: latent heat of vaporization. Calculated calorific value QI: Total heat input, QO: Total heat output , QH: Hot air heat, QS: Stock solution heat QP: Seed granular product heat, QE: Exhaust heat, WJ: Evaporated moisture, H4: Exhaust air humidity , HRP: granular product production. Value obtained by heat calculation QLOSS: Heat loss. The heat balance equation is as follows. QLOSS = QI-QO QI = QH + QS QO = QP + QE QH = G * CA2 * T2 + (RAM + CJ2 * T2) * H2 * G QS = T3 * (FES * SW / 100 + FES * CS * (100 -SW) / 100) QP = T1 * (HRP * PW / 100 + HRP * CS * (1-PW / 100)) HRP = FES * (1-SW / 100) / (1-PW / 100) QE = G * CA4 * T4 + (RAM + (CJ4 * T4)) * H4 * G H4 = H2 + WJ / G WJ = FES * SW / 100-PW / 100 * FES * (1-SW / 100) / (1-PW / 100) In the above system, the following cases can be cited as examples of changing the operating conditions. When changing the slurry supply amount and controlling the hot air temperature Using the hot air temperature as a variable, insert a new set value in the slurry supply amount, and use the hot air temperature as the other values using the values obtained from the operating data before the change. Is calculated, and the hot air temperature is controlled using the value as a set value. When controlling the hot air temperature when changing the moisture content in the granular product, that is, the target moisture, and using the hot air temperature as a variable, adding a new value to the dry powder moisture, and other values were obtained from the operating data before the change The hot air temperature is controlled using the calculated value as a set value.

When the target moisture is to be changed and the relational expression between the exhaust air temperature and the change in the water content of the granular product is known, the hot air temperature is used as a variable and a new value is added to the dry powder moisture. The exhaust air temperature is calculated by T4NEW = T4 + f (PW-PWNEW), and other values are calculated using the values obtained from the operating data before the change, and the values are used as the set values to calculate the target moisture content of the granular product. The optimum hot air temperature after the change is determined, and the actual hot air temperature is controlled so as to reach this temperature. When controlling the amount of hot air when changing the amount of slurry supply, use the amount of hot air as a variable, enter a new set value for the amount of slurry supply, and calculate other values using the values obtained from the operating data before the change. Then, using the value as a set value, an appropriate amount of hot air after changing the slurry supply amount is determined.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A system heat loss is calculated as a factor affecting the operation state based on various measured values indicating the operation state of the apparatus, and then the actual operation when the operation conditions are changed to control the apparatus operation is described. The calculation example of is shown below. Various physical quantities as shown in Table 1 are obtained based on the outputs of various measuring devices attached to predetermined positions of the system with respect to the conditions currently being operated. When calculated using this value, QLOSS 1218108 QI 5349298 QO 4131190 QH 5059298 QS 290000 QP 85431 HRP 6336 QE 4045758 H4 0.116 WJ 3664, and QLOSS 1218108 kcal / hr is obtained. Found here
When operating conditions are changed using QLOSS, the calculation of how to change the operating factors to obtain a powdery product of the desired properties is performed. Control Example 1 When the supply amount of the slurry was changed to 8000 kg / hr, the obtained QLOSS was used as a constant, and the granular product having the desired water content was obtained without changing other conditions such as the target water content in the product. The temperature of hot air was calculated to obtain T2 = 383.3. When the actual amount of slurry supplied to the drying tower was changed to 8000 kg / hr and the hot air temperature set value was changed to 383.3 ° C, the time constant was almost stable at 2.1 minutes, and the water content was 5.0 to 5.4% (average 5.25%). %), And a control result with sufficient accuracy for practical use was obtained. Control Example 2 Next, when the operating condition is changed to the target moisture of 7%, the obtained QLOSS is set as a constant, and the other conditions are kept as they are, and the calculated value T2 is set as the optimum hot air temperature for achieving the target moisture. = 418.2 was obtained.

When the temperature of the hot air in the drying tower was actually changed to 418 ° C., the time constant was almost stable with a time constant of 1.7 minutes, and the water content was 6.7 to 7.1%.
(Average: 6.9%), and a control result with sufficient accuracy for practical use was obtained. Also generated from fuel using hot air humidity, which expresses exhaust air temperature, powder temperature, as a function of hot air temperature and powder moisture, expresses hot air, exhaust air, hot air steam, heat capacity of exhaust air steam, latent heat of vaporization as a function of temperature Accuracy can be further improved by making a correction in consideration of the moisture to be added, and the reliability of control can be improved. In the above embodiment, other control methods are not shown, but they may be used in combination with feedback control or the like. Next, a case where a method based on a sequential calculation simulation is applied to control of the system of the present example will be described. In this method, the drying tower is cut into small sections, and the physical quantity of the drying tower can be simulated by solving equations such as heat balance, mass balance, and mass transfer in each section. The basic formula used in this case is as follows.

[0019]

(Equation 1)

Here, the suffixes 1 and 2 indicate values of entering and exiting the set minute section. The simulation is performed by solving this equation for a very small section, but the heat transfer coefficient (h) and the heat loss (L) are also difficult to determine. In this case as well, h and L are determined from the current driving state (a plurality of values in the trend) (when h and L are assumed to be certain values using a method such as the least squares method), the final calculation result is obtained. The combination of h and L, which makes the exhaust air temperature closest to the actual value, which is equivalent to the product water content (moisture), is searched for and obtained), and the value obtained therefrom is used under a new set value. By giving a control amount, a highly reliable control result can be obtained.

[0021]

The present invention is suitable for setting operation conditions of a process using a simulation calculation in order to obtain a product having desired properties in a chemical treatment process such as drying. In particular, when it is difficult to easily set appropriate values for the device constants, physical property values, and the like (constants and variables) used in the above simulation, and there are parameters and the like that affect the operation of the system. It is suitable.
In such a case, as described above, in a drying process such as spray drying, a heat loss or a heat transfer coefficient, which is often difficult to estimate from preliminary experiments, is calculated using measured values obtained during operation, By determining the control amount when the operating condition of the system is changed using the obtained values of the heat loss, the heat transfer coefficient, and the like, highly accurate and reliable control can be achieved.

[Brief description of the drawings]

FIG. 1 is a system diagram of a system including a spray drying apparatus to which the present invention can be applied;

FIG. 2 is a block diagram showing an input / output relationship of a controller.

FIG. 3 is a table showing various measurement values indicating an operation state of the system of FIG. 1;

[Explanation of symbols]

1 system, 2 spray dryer 3 hot air generator, 4
Fuel supply line, 5 hot air line, 6 belt conveyor.

Claims (6)

[Claims] 1. A method for controlling a spray drying apparatus for spraying a raw material to form particles and drying the granulated raw material to obtain a predetermined particulate product, wherein a substance introduced into a system including the spray drying apparatus And measuring the temperature of the substance discharged from the system, measuring the amount of the substance introduced into the system and the amount of the substance discharged from the system, and calculating the heat loss in the system based on the measured value. A predetermined physical quantity of the temperature and the quantity of the substance to be introduced and the substance discharged from the system is given as a set value, and another predetermined physical quantity is set as an unknown value, and an equation for a heat balance and / or a material balance of the system is obtained. Solving the equation to calculate an unknown, and setting operating conditions of the spray drying apparatus based on the physical quantity including the calculated unknown. Control how. 2. The control method according to claim 1, wherein the measured value is an average measured value during a predetermined operation time. 3. The control method according to claim 1, wherein the operating conditions include an amount of a raw material, an amount of air for drying for drying the raw material, and an air temperature. 4. The control method according to claim 1, wherein the heat loss is calculated after the system has been continuously operated for a predetermined time. 5. The control method according to claim 1, wherein the amount of raw material is given as a set value, and the amount of air and the temperature are obtained by solving the equation with the amount of air for drying or the temperature as an unknown. 6. The control method according to claim 1, wherein the set value is changed according to a predetermined characteristic, and a correlation between the set value and the unknown value is obtained by sequentially calculating an unknown value corresponding thereto. .