SU1271857A1 - Method of automatic control for process of decomposing mineral raw material by acid in production of fertilizer - Google Patents

Abstract

The invention relates to a method for automatically controlling the decomposition of mineral raw materials with acid, can be used in the mineral fertilizer industry and improves the quality of the product and reduces the consumption of acid. The method is implemented by the SAR, which includes a circuit for controlling the supply of acid to the mixer.4, depending on its temperature and the density of the pulp at the inlet of the reactor 1 (sensor

Description

(D) 8 acid consumption, D 9 temperature, D 12 density, regulator (P) 22, actuator 14 of acid dispenser 14) and control circuit for the supply of mineral raw materials to mixer 4 depending on the acid consumption, temperature difference of the slurry in the mixer and the reactor and the rate of temperature change in the mixer (D8 acid consumption, DI, 13 temperature, D10 phosphate flour consumption, P 24 and differentiator 27, which determines the rate of change of the temperature of the slurry in the mixer), 7 Il.

The invention relates to the automation of chemical and technological processes for the processing of mineral raw materials, in particular, natural phosphates with phosphoric acid to double superphosphate, and can be used in the production of mineral fertilizers. The purpose of the invention is to improve the quality of the product and reduce the consumption of acid. In FIG. Figure 1 shows a schematic diagram of a device for carrying out the proposed control method as applied to the process of phosphoric acid phosphoric acid decomposition; in fig. 2 - active zone of decomposition of mineral raw materials; in fig. 3 is a graph of the functional relationship between the regulatory and adjustable parameters; in fig. 4 is a graph of the change in free pulp content over time; in fig. 5 is a graph of pulp temperature over time; in fig. 6 is a graph of changes in the content of free acid with changes in the physicochemical composition of the raw material; in fig. 7 is a graph of changes in free acid content and pulp temperature with a decrease in the temperature of the pulp at the beginning of the core. . The diagram {figure 1) contains the reactor super chamber 1, equipped with a knife 2 and a discharge conveyor 3, a mixer 4, a phosphate flour batcher 5, a phosphoric acid batcher 6, an acid tank 7, measuring sensors 8-13, actuators 14 and 15, electric motors 16 -20, pump 21, controllers 22-24, loading window 25, partition 26 and differentiator 27. Mineral raw materials decompose in the reactor-super chamber I, where pulp obtained from the mixer 4 is obtained by mixing mineral raw materials (phosphoric flour) with phosphoric acid. Phosphoric acid is pumped into pump tank 7 by pump 21, from where gravity flows to dispenser 6. The specified amount of acid is sent to mixer 4, and the excess is drained: from dispenser back to pressure tank 7. Phosphorite flour is fed to dispenser 5 where it is mechanically mixed with phosphoric acid. The pulp is continuously supplied from mixer 4 to reactor 1. In reactor 1, the pulp enters the cake and, as the reactor rotates, the engine 16 moves around the circumference. By the end of the rotation, the cake approaches the knife 2, which is rotated towards it by means of the engine 17, and enters the conveyor 3, from where as a semi-product is sent to the finished goods warehouse. A method for automatically controlling the decomposition of mineral raw materials is carried out as follows. The optimum flow rate of phosphoric acid from the pressure tank 7 to the mixer 4 is set through the dispenser 6, the excess acid is drained from the dispenser, and the pump 21 is rotated into the pressure tank 7. The optimum value of the phosphoric acid consumption is maintained in inverse proportion to the signals from sensor 8 its mass

3

the flow rate, the acid temperature sensor 9 and proportional to the signal of the pulp density sensor 12 at the exit of the mixer 4 by the actuator 14 of the dispenser 6. Depending on the consumption of phosphoric acid, which is measured by the sensor 8, the rate of change of the pulp temperature in the mixer, measured by the sensor 11 and differentiator 27, and temperature differences in the active decomposition zone, measured by sensors II and 13 temperatures in a predetermined ratio by the controllers 23 and 24, through the actuator 15 and the dispenser 5 I support phosphate fertilizer consumption, providing the necessary degree of decomposition harakterizuyuschuyus indirectly heat generated in the core yuschims decomposition of the mineral.

The consumption of phosphate flour is controlled by a screw feeder 5 proportional to the signals for acid consumption from sensor 8, back proportional to the consumption of phosphate flour from sensor 10, inversely proportional to the temperature difference in the active mineral decomposition zone. raw materials from sensors 11 and 13 and inversely proportional to the rate of change of temperature of the pulp in the mixer from sensor 11 and differentiator 27 through the adjusting regulator 23, regulator 24 by means of an actuator 15.

When the degree of decomposition of the raw material changes, for example, its decrease (the chemical composition of the raw mineral material deteriorates), the temperature difference between the pulp in the active decomposition zone and the rate of temperature change of the pulp in mixer 4 decreases. Proportional to this change, the signals come from the temperature difference of the pulp in active heat. mineral decomposition

the raw material to the controller 24 and from the sensor I through the differentiator 27 of the rate of change of the pulp temperature in the mixer to the same controller 24, which establishes a new increased optimum value of the consumption of phosphorus flour. As the temperature in the mixer and in the active zone increases, the consumption of phosphate rock changes in the reverse order.

8574

The decomposition of phosphate rock, carried out in a mixer and reactor,

is a complex process of chemical dissolving phosphorus raw materials,

proceeding according to the reaction equation:

Ca5F (PO) s + 7HjPO + 0.25Si02- -4.5H, 0 5Ca (H, POj-H O + 0.25.SiF.

In order to obtain a product of feed classification, fluorine must be distilled off. Therefore, decomposition reaction is essential. The determining parameters for obtaining feed monocalcium phosphate are: the decomposition coefficient of the initial phosphorus raw material (it determines the maximum depth of defluorization, for the fluorine residue goes into the finished product); The free phosphoric acid content determines the defluorination kinetics and the quality of the finished product.

For all the importance of these parameters, it is not possible to carry out their continuous measurement. At the same time, as shown by experimental studies, the rate of decomposition is characterized by the temperature of the pulp in the active zone (Fig. 3), which begins in mixer 4 at the mixing site of the starting components and ends in reactor 1 zone bounded by a sector with an angle of 10-30 from the point of entry pulp in the reactor (figure 2)

The kinetics, p & l of phosphate flour flows according to a known ratio

1- X:

C C G

;

where Cd and C are the initial and current for the time content of free acid in the pulp, respectively; K - reaction rate constant.

Since the decomposition process is continuous for a given fixed ratio of the starting products, the graph of changes in the free acid content is as shown in FIG. 4. Since the process is isothermal and the intensity of the reaction is characterized by equivalent heat release, a change in the temperature of the pulp along the length of the decomposition zone has the form shown in FIG. five.

In the proposed method, it is recommended to maintain the difference in temperature of the pulp in a fixed section 5 of the flow path (in the core). At the beginning of the core (point 1), the free acid content is described by the following ratio at the end of the core - uk The temperature difference over the core length is proportional to the difference in the content of free acid in the pulp, i.e. f00 (c) (1 where ot is the coefficient of proportionality, depending on the length of the core, the particle size distribution of the raw material, the temperature of the mixture of the raw material at the beginning of the core, etc., determined experimentally. Fig. 6 shows the change in the free acid content (a) and the temperature of the pulp (b) when the physicochemical composition of the raw material is changed. When the active length is constant, on which the temperature difference of the pulp from the granulometric composition of the raw material is measured, the coefficient of proportionality clearly depends on the temperature of the raw material. The change in the temperature of the mixture in the beginning of the active zone changes the difference in temperature of the pulp along the length of the active: th zone (Fig. 7), and at the same time the length of the active zone of decomposition of the raw material. It should take into account information about the current temperature value at the beginning of the active zone.However, the signal by the temperature difference along the core length is more significant and representative, since it takes into account the main perturbations of the perturbations in the physicochemical component of the raw material. Example. The initial, mode of production of feed monocalcium phosphate is characterized by the following parameters; total average consumption of thermal phosphoric acid 50 t / h; acid concentration 80% P Od; consumption of phosphate rock 40 t / h; temperature of thermal phosphoric acid at the inlet to the mixer 50-60 C; temperature of the pulp in the mixer 5055 s; temperature in the VO-EOS reactor; decomposition factor in 576 reactor 80%; the content of free phosphoric acid in the intermediate at the exit of the reactor 2%. Consider the response of the control system to the disturbance in terms of the physicochemical composition of the phosphate rock (PO content, particle size distribution), for example, on the downside side by 5%. At the same time, the difference in temperature of the pulp in the core section will decrease by 4 ° C, the input of the regulator 24 from the meters 11 and 13 will receive a signal about this change, the output of the regulator 24 through the actuator 15 increases the consumption of phosphate flour by about 2 tons / h , which leads to the restoration of the previous difference in temperature of the pulp in the active zone. When the physicochemical composition changes towards the improvement, the response of the control system is carried out in the reverse order. When the temperature of the mixture of fluxes in the core of the core decreases by 5 ° C, the temperature difference in the active zone also decreases; signals from the meters P and 13 and the correction regulator 23 are received at the input of the controller 24, and the output from the controller 24 through the actuator 15 increases the consumption of phosphate rock is about 1.5 t / h, which leads to the restoration of the previous temperature difference of the pulp in the active zone of decomposition, and the restoration of the previous temperature difference occurs much faster (by the amount of trans oriental delay mip), since the regulator 24, in addition to the main signal of the pulp temperature in the active zone, receives a correction signal on the rate of change of the temperature of the pulp in the beginning; 1le of the core, formed by sensor 1, differentiator 27 and corrective regulator 23, When the temperature changes pulp at the beginning of the core in the direction of increasing the adjustment reaction is carried out in reverse order. In the absence of correction of the consumption of phosphate raw materials by the temperature difference in the active zone of its decomposition and the rate of change of the temperature of the pulp in the mixer, the decomposition coefficient of mineral raw materials varies between 70-80% and the content of free forsforic acid is 12-14 / 0. If the temperature of the pulp in the mixer becomes, then the decomposition reaction occurs to a greater extent in the mixer, and the pulp does not set, a semi-liquid product is formed — waste, if below — the decomposition factor of mineral raw materials sharply decreases to 6570%. Loss of acid and phosphate rock is growing. When the control system is operated with correction based on the difference between the temperature of the pulp in the section of the active zone of its decomposition and the rate of change of the temperature of the pulp in the mixer, the optimum mode is maintained: the decomposition coefficient increases to 80-85% and the content of free phosphoric acid decreases to 11-12%. Subject to this technology. mode achieved using an automatic control system

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Claims (1)

The way the raw material process with acid in fertilizer production by controlling the supply of acid to the mixer depending on its temperature and pulp density at the inlet of the reactor and the supply of mineral raw materials to the mixer, I distinguish reduce acid consumption, additionally measure the temperature of the pulp in the mixer and reactor, determine the difference between these temperatures and the rate of change of the temperature of the pulp in the mixer and control the flow of mineral raw materials in direct proportion to the flow of acid and inversely proportional to the difference in temperature of the pulp in the mixer and reactor and the rate of change of temperature