SU1550306A1 - Method of controlling the process of spray drying - Google Patents

Abstract

The invention can be used in the chemical industry in the production of mineral fertilizers in granular form from pulps, melts and solutions in a fluidized bed and improves the quality of the drying process. The method of control consists in measuring the temperature and porosity of the fluidized bed at several points of the horizontal section of the layer located at the height of the bulk layer below the corresponding spray points of the solution, calculating the intensity of mixing of the material at these points and proportional control of the solution flow (irrigation density) above the areas of the bed depending on the measured values of the intensity of mixing. Measurements can be carried out either in the operating mode (in the irrigated layer) or on a dry blown layer.

Description

The invention relates to the field of automation of drying processes, relates to a method for controlling the spray drying process and can be used in the chemical industry, for example, in the production of mineral fertilizers.

The purpose of the invention is to improve the quality of the drying process.

The drawing shows a block diagram of a control system for implementing the proposed method of controlling the spray-drying process.

The control system contains a primary converter 1 for flue gas temperature, a comparison unit 2, an actuator 3, an adjustable air flow valve 4, a blower fan 5, a fluidized bed apparatus 6, a primary layer temperature converter 7, a comparison block 8, a switching unit 9, an actuating device 10, an adjustable v. 11 general flow rate of the solution, a probe 12 with low-inertial primary converters temperature and porosity of the fluidized bed, an amplifier-transformer unit 13 with electromechanical the animated part of the recording device 14, the ADC 15, computer

16 with control panel, device

17, in conjunction with the object, the command block 18, adjustable valves 19-21 of the solution flow rate through the nozzles 22, spraying the solution above the layer — containing the fluidized bed of granules 23, with

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In this case, the primary converter of the flue gas temperature is connected to the first input of the comparator unit 2, the output of which through the actuator 3 is connected to the adjustable air flow valve 4, the primary converter of the fluidized bed temperature 7 is connected to the first input of the comparator unit, the output of which is connected to the input of the switching unit unit 9 connected to the actuating device 10, and the output of the switching unit 9 is connected to the adjustable valve 11 of the total solution flow, and the probe 12 is connected to the amplifier-transformer to the transmitter unit 13, the first output of which is connected to the registering device 14, and the second output is connected via an ADC to a computer 16, the output of which is connected to the input of a command unit 18 via the communication device 17 and the outputs of which are connected to the inputs of the corresponding amplifier and converter unit 13, the switching unit 9, the actuator 10, the comparison unit 8 and the comparison unit 2, as well as to the adjustable valves 19-21.

The method for controlling the spray-drying process is as follows.

Initially, the flow rate of the air supplied to the combustion and dilution of the flue gases is controlled by the temperature of the gases under the grate of the fluidized bed furnace, and the total flow rate of the solution supplied to the layer 23 is controlled by the temperature of the boiling layer. For this, the signal from the converter 1 measuring the temperature of the flue gases enters the comparison unit 2, which also receives the reference signal from the computer 16 through the device 17 and the block 18. The differential signal from the block 2 is fed to the actuator 3, which controls the position of the valve 4, those. air flow. At the same time, the fluidized bed temperature is continuously measured using converter 7, the signal of which enters comparison unit 8, where it is compared with the reference signal set on the control panel 16 and passed through device 17 and block 18 Differential signal from comparison unit 8 through switching unit 9 controls the position of the valve 11,

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the total consumption of the solution in the layer. The solution is sprayed over the bed 23 in the apparatus 6 by the nozzles 21. When the temperature of the flue gases decreases relative to the predetermined actuator of the unit 3 by means of the valve 4, it reduces the air supply for burning and diluting the flue gases. If the set value is exceeded, the air flow rate increases. If the temperature of the fluidized bed 23 measured by converter 7 becomes lower, the difference signal from block 8 through switching block 9 enters the actuating device 10, which by means of a valve 11 reduces the solution flow to the furnace until the set value is restored fluidized bed temperature 23. With increasing temperature of the fluidized bed 23 relative to a given solution, the flow rate of the solution must be increased.

In order to control the process, an additional control of the flow of the sawn solution through each nozzle 21 is introduced, depending on the calculated value of the intensity of mixing of the material.

To calculate the intensity of mixing at several points located in the horizontal section of the apparatus at the height of the bulk layer of material under the corresponding spray points of the solution, measure the temperature and porosity of the fluidized bed of the material. The values obtained through the ADC are fed to the computer 16, where the frequency of temperature fluctuations (heat flux) fT and the porosity of the f сло layer are calculated by known methods using the deviations from the mean values during the measurement period.

The value of the intensity of mixing is calculated by the expression

Im kf

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Ј - layer porosity;

G - productivity, kg / s; rtb density of the solid phase

g — free fall acceleration, m / s;

L and B are the length and width of the horizontal section of the fluid bed apparatus, m. In order to stabilize the growth rate of the granules (granulometric composition of the finished material) it is necessary that in areas with increased intensity of mixing Im the flow rate of the sprayed solution through the corresponding nozzle 21 is greater than than in areas of low intensity. To do this, from the control console 16, through the device 17 and the block 18, a command is sent to turn on the block 13, which advances the probe 12 to the depth specified by the operator in the layer of material 23 in a section located at the height H0 of the bulk layer. When the probe 12 reaches a predetermined depth, a command is withdrawn from block 13 to advance the probe. The signals from the primary transducers of the porosity and the temperature of the probe 12 are fed to the amplifier-converting part of the block 13, from the output of which the corresponding electrical analog signals are fed to the ADC 15 and to the recording device 14 for control. From the output of the A / D converter 15, signals are digitally fed to a computer 16, in which the mixing intensity is calculated at points in the layer using the indicated formula. After measuring the transducer signals at a predetermined depth of the probe for a predetermined time and calculating the mixing intensity, the computer 16 receives a command through the device 17 to block 18, which, in turn, issues a command to the electromechanical part of the block 13 to advance the probe 12 into the depth of to the next checkpoint. When the predetermined depth is reached, the command from the electromechanical part of the block 13 is removed, the probe 12 stops. Again, the measurement of the signals of the primary transducers from probe 12 and the calculation of the intensity of mixing, as described above, are performed.

Thus, the operator probes a predetermined section of the layer at several points (their number is equal to the number of nozzles 21 with adjustable valves) and determines the distribution of mixing intensities in the specified section. In proportion to the obtained values and mixing intensities, solution flow rates (irrigation density) over the control zones of the layer are determined, and the computer 16, through the device 17, communicates with the object to block 18, which regulates the position of the irrigation areas of the layers solution.

Determination of the intensity of mixing Im more accurately carried out on a dry layer of granules, i.e. when the irrigation is disconnected through the nozzles 21. At the same time, in the operating state of the apparatus, the 6 probe 12 is extended beyond

apparatus. Since the presence and location of zones with different mixing intensities is mainly determined by the hydrodynamics of the fluidized bed (i.e.

Q depends on the material properties, the size of the apparatus, the uniform distribution of the gas flow), while maintaining a pre-selected regime (air flow

5 and the total flow rate of the fluid being dispensed, the temperature of the fluidized bed, it is sufficient to make measurements of the phases per shift or even less.

When more operative control is required, the temperature and porosity of the layer can be measured more often, while the probe 12 can be constantly kept in the working area of the device 6 and measurements can be carried out in the working mode of the device on the irrigated fluidized bed.

Claims (1)

Invention Formula A method of controlling the spray drying process in a fluidized bed apparatus having several spray points of a solution, by adjusting the total flow rate of the sprayed solution according to the temperature of the fluidized bed of pellets and controlling the air consumption for combustion and diluting the flue gases by the temperature of the coolant in the sublattice space, characterized by In order to improve the quality of the drying process, the temperature and porosity of the fluidized bed of granules are additionally periodically measured at several points, placed GOVERNMENTAL in the horizontal section of the apparatus, located at a height of the layer of bulk granules under the corresponding points of the spraying solution, the measured value m calculated stirring intensity in each measuring point and maintain the flow of solution into the product sootGrtovyi P L corresponding spray point is directly proportional to the calculated value. I