SU1283223A1 - Method for automatic control of process of the settling of extraction phosphoric acid - Google Patents

Abstract

The invention relates to a method for automatically controlling the process of settling extraction phosphoric acid, can be used in the chemical industry and improves the quality of the finished acid by reducing the content of solid impurities in it. The method is implemented by the SAR, including a temperature control loop in the heater by changing the steam supply to the coil sensor (D) 8 temperature, controller 11, regulator (PO) 19 with correction for the difference in density of sludge and finished acid (D 3 and 4, P 12, associated with P 11), the circuit for calculating the current content of solids in the source acid in the computing device 14, taking into account the temperature and concentration of phosphorus oxide in the original acid, the circuit for calculating the set value of the sludge consumption, depending on the flow rate and density of the original acid and sludge density in the computing device 15. 1 Il. "Q (L

Description

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The invention relates to the automation of the process of obtaining phosphoric acid (EPA) at the stage of its evaporation and can be used in the chemical and other industries in the automation of septic tanks with solid phase recycling.

Purification of EPA from solid impurities (sludge) is carried out in a constant-level sedimentation tank with sludge recirculation.

The process is affected by disturbances that de-stabilize the settling mode, which negatively affects the quality of the finished acid in terms of solids content. The main disturbances come from the source acid stream (oscillations, consumption, concentration and content of solid impurities) and recycled sludge (flow and density fluctuations depending on the content of solids), and also arise due to the nonstationarity of the thermal and concentration regimes of the apparatus .

The aim of the invention is to improve the quality of the finished acid by reducing the solids in it.

The drawing shows an automatic control system for implementing this control method.

The system includes a sump and heater, sensors 1 and 2, density sensors 3, 4 and 5, concentration sensor 6, temperature sensors 7 and -8, regulators 9-13, computing devices 14 and 15, adder 16, regulators 17, 18 and 19.

The method is carried out as follows.

Stabilize the consumption of the original acid in the sump. For this, sensor 1 measures the flow rate of the initial acid and sends the signal Gn to the input of regulator 9, where the task Gn, 3 is also supplied. The signals Gn and G ", j are compared and, according to the PI law, the signal U is formed by the PI law, which is fed to the regulator 17 installed on the feed line of the original acid to the sump, and thereby stabilizes its flow.

In order to stabilize the amount of solid impurities coming from the source acid and sludge streams, the sludge circulating through the settling tank is fed depending on the flow rate and density of the starting acid and sludge density. For this purpose, the sensor 2 measures the sludge flow rate and the sump and the signal Gm is sent to the input of the regulator 10. To the second input of the regulator, the signal G, ь from the computing device 15 is sent as a reference. In the regulator 10, the signals GW and Gm, 5 compare and form, for example, according to the PI law, the signal Ug, which is directed to the regulator 18 installed on the cuttings line, and regulate, thereby supplying

1283223

circulating sludge in the sump. The set value of the consumption of sludge is formed depending on the flow rate and density of the original acid and the density of the sludge in the computing device 15 by the formula

Gm, 3 (Q- K piB.m

GrT) / Pm,

(one)

formula

obtained from the condition of constancy of the quantity Q of solid impurities entering the settling tank with the flows of the initial acid and sludge (Q is the calculated value corresponding to the nominal mode of operation of the settling tank). To do this, the signal from the source acid consumption sensor 1 Ol, the signal from the computing device 14 of the solid content in the original acid Rt.p and the signal from the sludge density sensor 4 p are sent to the computing device 15 and form the signal Gm, j, using the formula (1) which is used further as a task for the controller 10.

The current value of the solid content Rtb-n, and in the initial acid is calculated in the computing device 14 taking into account the temperature Tp and the concentration of Cd in the initial acid. The temperature signals Tp, concentrations C p and density p of the original acid from the outputs of sensors 7, 6 and 5 are sent to the computing device 14, a 5tv signal is generated in it, pi is fed to the input of the computing device 15, the signal value rtv, n is calculated from

ole

Rtv, p rp-K / C -f KiTrt,

(2)

where KI, Kr are the coefficients determined by

experimentally.

The temperature of the suspension in the sump is maintained by a temperature stabilization scheme in the preheater. For this purpose, the temperature is heated; e is measured by the sensor 8 and the signal T from its output is sent to the input of the regulator 11. To the second input of the regulator, the correction signal Tc is supplied as a reference. In the controller, the comparison signals T and T3 are formed, for example, according to the PI-law, the signal Y, is sent to the regulator 19 installed on the steam supply line and thereby regulate the temperature in the preheater and, therefore, in the sump. Setting Tj to the temperature controller is formed in controller 12 according to the results of comparing the current and set values of the difference in density of the sludge and the finished acid, for example, according to the PI law. For this purpose, the sludge density signal J) m from the output of sensor 4 is directed to the input of the adder 16. To the other input of the adder, a signal RG of the finished acid is supplied from the output of the sensor 3. In the adder 16, a signal of the difference of densities & are his to the input of the regulator 12.

To another input of regulator 12, as a task, a signal is sent to, formed by regulator 13. Signal) g of the finished acid density from the output of sensor 3 is sent to the input of regulator 13. To the second input of regulator, a signal is supplied. the density of the finished acid. In the controller, the signals are compared and, according to the PI law, the other control signal is formed by the mismatch value — the supply of the sludge circulating through the settling tank in an amount that ensures the content of solids entering the settler is adjusted to the flow of the original acid and the slurry. preheater on the difference between the density of the sludge and the finished acid and the correction of this equality in the density of the finished acid, provides an increase in the quality of the finished acid by

The difference in densities, firstly, to the single content of solid impurities in it, characteristically characterizes the rate of sedimentation of the improvement of informativity and control solids in the settling tank at a constant inhalers, achieving invariance to

admission with the initial acid fluxes to the main disturbances in the process and decrease of the sludge; secondly, this parameter is the determination of the effectiveness of regulating actions that are very sensitive to changes in the actions. granulometric composition of the solid phase

Claims (1)

in the sump and, thirdly, it (parameter) Invention Formula possesses invariance properties to centration and temperature control mode moms in the sump. The use of such a process of settling the extraction phosphidative variable allows 20 percent acid by regulating the more effectively suppressing the effects of the temperature in the preheater by changing the controlled disturbances (in particular, by placing the human gene into the serpentine with the correct curvature of the outgoing man, who has lost his or her… control the settling rate and increase the slime circulating through the sump the effectiveness of the regulating effect .25 of the initial acid in the settling tank and the measured Re value sets the concentration of the initial acid, depending on the density of the finished acid, because, in order to increase its density (density) from the regulation-quality of the finished acid by reducing the the values of pr, b are explained by the content of solids in it, until the stabilization of the difference in density measures the density and temperature (which is equivalent to the stabilization of the velocity of the original acid s and sedimentation density) does not provide stabilization, as measured by density values. control - supply of sludge circulating through the settling tank in an amount that ensures the constant content of solid impurities entering the settling tank with the original acid and sludge flows, adjusting the temperature in the preheater according to the density difference of the sludge and the finished acid, and correcting this equality in the finished acid density quality of finished acid by the regulated content of solids in the finished acid. Indeed, under the action of perturbations, the absolute values of the densities can change at a constant difference. This method of automatic control of the process of settling extraction phosphoric acid in comparison with the prototype, due to the use of new the concentration and temperature of the initial acid, calculate the solids content in the initial acid, determine the difference between the densities of the sludge and the finished acid, and regulate the flow of the sludge circulating through the settling tank depending on the measured values of the consumption of the initial acid and sludge and the calculated solids content in unregulated variables - temperatures about suitable acid, and the flow of steam into the coil and the concentration of the original acid, the flow rate of the preheater is adjusted depending on the sludge in the sump, the difference densities from the difference between the densities of the sludge and the finished sludge and the finished acid, and new methods of acid. the concentration and temperature of the starting acid, calculate the solids content in the starting acid, determine the difference between the densities of the sludge and the finished acid and regulate the flow of the sludge circulating through the settling tank depending on the measured values of the consumption of the starting acid and sludge density and calculating