SU1411276A1 - Method of automatic control of extraction phosphoric acid production - Google Patents

Abstract

The invention relates to automating the process of obtaining phosphoric acid, and can be used in the industry for the production of mineral fertilizers. The aim of the invention is to increase the productivity of the process and reduce the loss of raw materials and energy. The consumption of apatite was chosen as the leading flow in the control circuit, and the flow of sulfuric acid, dilution solution, pulp per filter, and water into the condenser as slaves. Computing devices (WU) 55, 57, 58, 61 are designed to calculate the slave flow, depending on the consumption of apatite. For the flow rate of steam into the ejector pump, the flow rate of water to the condenser was selected as the leading flow, and for the flow rate of water. To flush the phosphogypsum - the flow rate of pulp per filter. WU 55 is also intended to calculate the value of the required temperature of steam in a vacuum evaporator, which is then used by WU 56 to calculate the required vacuum. WU 62 is designed to reduce the effect of pulp flow disturbance on the flow rate of the dilution working solution and its concentration of phosphoric acid when changing the load on apatite, as well as when regulating the ratio of the liquid and solid pulp phases or its level in the extractor. 1 hp f-ly, 1 ill. ABOUT)

Description

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about

This invention relates to automating the process of producing phosphoric acid and can be used in industrial production of mineral fertilizers.

The aim of the invention is to increase the productivity of the process and reduce the loss of raw materials and energy.

The drawing shows a structural diagram of an automatic control system implementing this control method.

The scheme contains the reaction compartment 1, the dispenser collector 2, the matcher 3 crystals, the vacuum evaporator 4, the condenser 5, the ejector vacuum pump 6, the vacuum filter 7, the collector 8 of the working dilution solution, the collector. 9 of the first filtrate, pipelines 10–12 supplying sulfuric acid, apatite and dilution solution to the extractor, pipelines 13–21, respectively, supplying steam to the ejector vacuum pump, water for washing phosphogypsum, cooling water to the condenser, pulp in a vacuum evaporator, cooled pulp in a collection distributor, pulp from a maturing agent to a filter, phosphogypsum into a dump, production acid in a collection of dilution solution and a warehouse, sensors 22 and 23 of apatite and sulfuric acid consumption, a sensor 24 of pulp density, a sensor 25 concentrations of sulfuric acid You are in the liquid phase of the pulp, the dilution solution flow sensor 26, the sensor I 27 of the density of the pulp liquid phase and the concentration of phosphoric acid in it, the pulp temperature sensors 28 and 29 in the reaction zone of the extractor and in the dispenser collector, sensor 30 of water flow to the condenser, sensor 31 vacuum in a vacuum evaporator, sensor 32 level in a matcher, sensor 33 of steam flow to a vacuum pump, sensor 34 of slurry flow to a filter, sensor 35 of phosphoric acid concentration in the working dilution solution, sensor 36 of water flow to a filter 37 and 38 level Sat Ornika dilution solution and, in the collection of the first filtrate, local regulators 39-44 for stabilization of flows and regulators of 45-46 levels, respectively, in collections 8 and 9, as well as regulators for the deviation, respectively, of the concentration of sulfuric acid in the liquid phase of the pulp,

5 0 5 0 s

0

five

neither liquid and solid phases in the pulp, temperature of the pulp in the reaction zone, dilution in the vacuum evaporator, temperature of the pulp in the dispenser, concentration of phosphoric acid in the liquid phase of the pulp, level of pulp in the extractor reconditioner, concentration of phosphoric acid in the working dilution solution and computational devices 55-62.

The consumption of apatite was chosen as the leading flow in the production control scheme; sulfuric acid consumption, dilution circulating solution, filter pulp, water in-condenser,

, Computing devices 55, 57, 58, 61 are designed to calculate the slave flows depending on the consumption of apatite using mathematical formulas, which approximately ensure compliance with the material and heat balances of production. For the flow rate of steam to the ejector pump, the flow rate to the condenser was selected as the leading flowrate, and for the flow rate to flush the phosphogypsum, the flow to the filter was pulp. The last two links are provided respectively by computing devices 59 and 62,

Computing device 55 is also intended to calculate the value of the desired steam temperature in a vacuum evaporator Tj (.j, which is then used by device 56 to calculate the required vacuum.

The device 62 is intended to reduce the influence of pulp flow disturbance on the flow rate of the dilution working solution and the concentration of phosphoric acid in it when the load on the apatite is changed, as well as when regulating the ratio of the liquid and solid phases of the pulp or its level in the extractor.

The method is carried out as follows.

The operation of the device 62 is based on maintaining the material balance of fluid flows on a vacuum filter, expressed through the flow of water for washing phosphogypsum

stzh

 BF L p p - L p + L pr L $ r where Lp.p is the flow rate of the working solution

dilution;

Lf, is the flow rate of the liquid phase in the pulp fed to the filter;

LPP - production acid consumption at the warehouse

Lj, p - consumption of liquid carried away

in plow with phosphogypsum. This uses the expression

 L

P

. + 1

-(but,

n-pj)

de LP j - respectively consumption

pulp on the filter and the ratio in it of the liquid and solid phases;

, а - coefficients of approximation of the dependence k a, +, which are experimentally determined, for example, by the method of least squares for each specific process. the ratio of liquid and solid phases in

phosphogypsum 1 L Fg

k

Ll

Fg

one -

 Fg

and consumption of solid phase pulp with phosphogypsum L

Ln

according to statistics from 1 +

phosphogypsum IFP values measured at the site, as well as Ln and jfi variables

This evaporation is based on an experimentally established fact: the ratio k increases proportionally to the consumption of the solid phase of the pulp per filter Lf.

The device 63 is designed to calculate the ratio of the liquid and solid phases of the pulp from the pulp density PP measured in the extractor and the density of its liquid phase p. Rasta uses the formula

. (1-4) g

Where

Fn-f

p is the density of the solid phase

Rt

pulp (usually

 3000 kg / mz). The device 64 is designed to calculate the ratio of the measured flow rates of the dilution solution and the an "L P. p

Titus C (5

The apatite consumption value measured by the sensor 22 goes to cleaning devices 55, 57, 58, 61 which work as follows

Device 55 calculates the RIF root of the equation

W city, - (-A

 one

  + - qSq Oh,

/ ,,

where the required temperature is steam in a vacuum evaporator, at which the cooling of the pulp ensures the stability of the temperature of the pulp or a given load, c - as required by the regulations

the temperature of the pulp in the collection of 6-ike /;

LP is the capacity of the pump feeding the slurry to the vacuum evaporator.

C p - the heat capacity of the pulp,

 25.00 -32 kg

 -2.41

kJ

kg hail

 25

zo

ha

approximation coefficients of the table function of the specific energy of vaporization from the temperature of saturated water vapor (1

 7.sp);

180 degrees, tn 2,1 - coefficients of experimentally obtained dependence of the temperature of the pulp coming from the vacuum evaporator to the collector 2, on the temperature of the steam formed in it

H

(hlt +);

, kJ

774 - part of the energy

h kg

the reaction that the pulp cooling system must remove from the extract so that the pulp temperature in the extractor remains unchanged when apatite consumption changes (per 1 kg of apatite reacted in the extractor),

In addition, it calculates the flow rate of water to the condenser, which should provide cooling of the vaporized vaporizer from the pulping temperature of the pulp to the temperature tyj., using the formula

55

- KifcFJ

60 2C Ktnt.

qs "

where K ,, F is the heat transfer coefficient and

condenser heat exchange surface area} Qj is the energy transferred from the condenser to the ejector by uncondensed gases (constant for

ejector magnitude); t (5 is the temperature of the water used for cooling the condenser (constant),

and also gives the calculated value L. as a task to the controller 41 for its implementation on the object.

The device 56 calculates the vapor pressure required in the vacuum evaporator by the formula, which is obtained by approximating the tabular function of the saturated vapor state:

RISP 0.113 + 0.00579 („, - 48.5) + 0, OOOT23 (g„ j - 48.5) 2 where, the required value of the steam temperature, calculated by the device 55,

and also calculates and transmits to the task to the controller 50 the required values of the vacuum pressure in the vacuum evaporator:

LR

 R

ytm

- R

 wen

where POJTM is atmospheric pressure.

Device 57 calculates the consumption of sulfuric acid according to the formula L5 1.235 and delivers it as a task to controller 39.

The device 58 calculates the dilution solution flow rate using the formula

Lp, p 1,6S "(f - 0.21), where Yi is the ratio of the liquid and solid phases of the pulp required by the process regulations,

and also gives the calculated Lp4 value to the stabilizing controller 40 as a reference.

The device 59 calculates the flow rate of gases not condensed in the condenser using the formula

G / i k., Lji3,

where k is the coefficient selected

experimentally for technological equipment, calculates the required steam flow rate by an ejector vacuum pump according to dependencies, which describes its passport data:

steam

 f (L P, G-2) 6.2-32 (LR +

+ 0.85) + 0.5 (G7 - 15),

five

where P is the required vacuum in vacuum; 2e, calculated by device 56,

and also gives controller 42 as the task of calculating the 1st value

 ntxr

Devices 60 and 61 provide

compensating for the disturbance of the flow rate of the working solution, respectively, to the concentration of phosphoric acid in the liquid phase of the pulp and to its level in the extractor by controlling the ratio of the liquid and solid phases of the pulp by means of a device 58 or a regulator 48.

The device 60 calculates from the current value of the C ratio the desired concentration of phosphoric acid in the working dilution solution:.

Kpo, - K

 OA335 ()

p.p. , |

- and

where K. (, f is the concentration of phosphoric acid in the liquid phase of the pulp, the resulting value of the crp concentration is given to controller 54 as a task.

The device 61 calculates according to the current; its value of the ratio C ;, and the consumption of apatite SQ, the required flow of pulp per filter according to the formula Lr, (1.935 + C) Sg, which is obtained taking into account that Co is Lp / Sg, and, in addition, the obtained value of L t passes as a task to the controller 43.

Device 62 calculates the value of the derivative

0

l §l

dj, gg

9 §i t

()

as well as the required water flow

washing phosphogypsum by the formula - about 8P

LBH-snt (n Ln),

45

50

55

where Lgf,, L is, respectively, the flow rate of water for washing and the flow rate of pulp for the vacuum filter at the moment the regulator is turned on,

and, moreover, gives the controller 44 in

the quality of the task is the calculated value

water consumption lgn.

Thus, with the help of devices 55-62, the stabilizing regulators are calculated and transferred to implement technological regimes at the facility that correspond to different loads on raw materials — apatite consumption.

Due to the limited accuracy of the mathematical models underlying the computing devices 55-62, as well as the presence of errors in the measuring channels in an open control system for disturbance, deviations of the main controlled variables from the specified values still occur. To eliminate these deviations, regulators 47-49, 53, operating in deviation mode, are used. These regulators produce control actions and with their help correct the tasks of stabilizing regulators.

Thus, the final control of the process is carried out with the help of control deviation contours.

Consider the operation of these circuits. Let a disturbance arise in the control loop of the ratio of the liquid and solid phases of the pulp, which leads to the deviation of this variable from setting the controller. By increasing (decreasing) the ratio of liquid and solid phases calculated by block 63, the controller 48 through the adder reduces (increases the task to the controller 40 (increases) the task to the controller 40. As a result of this new controller, the flow rate of the dilution solution decreases (increases)). The device 64 indicates a decrease (increase) in the ratio of the measured costs of the dilution solution and the raw material, since the flow rate does not change.

The device 61 through the adder reduces (increases) the setting of the controller 43. As a result, the flow of pulp to the filter is reduced (increased). At the same time, the pulp level in the extractor does not change, since the change in the supply of the dilution solution to the extractor is equal to the change in the feed of the pulp to the filter.

Decreasing (increasing) the supply of pulp to the filter reduces (increases) the thickness of the phosphogypsum sediment layer on the filter cloth, and the removal of the liquid phase with phosphogypsum decreases (increases). In order to maintain the same amount of liquid flowing into the washing solution, the device 62 prevents the action of this disturbance: through the adder it reduces (increases) the task to the controller

44 stabilize the supply of water for washing phosphogypsum. As a result of this decrease (increase) in the water supply by the regulator 44, the amount of the washing solution does not change.

The decrease (increase) by the regulator 40 according to the signal from the regulator 48 of the circulating solution increases the level of the accumulator 8, since the supply of the washing solution to this collector does not change due to the operation of the device 62. To keep the level of the collector 8 the controller 45 reduces (increases) the supply of production acid from the collector 9 into it.

Since at this time the pulp feed is reduced (increases) by

0 filter, the flow of production acid in the collector 9 is also reduced (increased). Obviously, if the coefficients a and a are chosen correctly, devices 62 and in the absence of essential ЕЕ1, natural measuring

error level in compilation 9: unchanged, this will not entail a change by the regulator 38 of the amount of acid withdrawn to the warehouse. Change

The ratio of the flow rates of the washing acid entering the collector 8 and the production acid supplied from the collector 9 causes a change in the concentration of the diluting working solution, since these streams have different concentrations. In this case, the concentration of the dilution solution decreases (increases) so as not to cause the effect of the regulator.

Q 54 on the change in concentration of the dilution solution device 60 through the adder reduces (increases) his job.

As a result, the dilution circulating solution with a new concentration enters the extractor. Due to this, when adjusting the ratio of the liquid and solid phases of the pulp, the concentration of phosphoric acid in the liquid phase of the pulp does not change.

Consider the process control when changing the concentration of phosphoric acid in the liquid phase of the pulp.

Let controller 52 note that the concentration of (phosphoric acid in the liquid phase ny: ii.nbi, for example, is lower (higher) than the reference. This regulator through the adder increases (decreases) the reference of the controller 54, which, in CHOW

five

five

0

five

the queue through the adder reduces (increases) the water supply to the phosphogypsum washes.

The decrease (increase) in water consumption leads to a decrease in level in collector 8. To maintain this level, regulator 45 increases (decreases) the consumption of production acid from collection 9 to collection 8, As the concentration of production acid is higher than the concentration of the washing solution, the concentration of working dilution solution increases (decreases). Thus, at a constant flow rate of the dilution solution, the concentration of phosphoric acid in it increases (decreases), which means that the supply to the PjOj extractor increases (decreases) and at the same time the supply of water decreases (increases), which ultimately leads to an increase ( decrease in the concentration of phosphoric acid in the liquid phase of the pulp.

It is important that neither the level of the pulp in the extractor, nor the ratio of the liquid and solid phases of the pulp is disturbed.

When a disturbance to the pulp level in the extractor occurs in the extractor, the controller 53 from the level sensor 32 through the adder changes the task to the controller 43. As the new task by this controller is refined, the water used for flushing with the help of the device 62 changes. dilution and the concentration of phosphoric acid in it remain unchanged, thanks to which other adjustable variables do not change: the ratio of the liquid and solid phases in the pulp and the concentration of phosphoric acid in the liquid phase of the pulp. Changing the output of the pulp from the extractor at the same remaining flows evens out the level in it.

Consider the response of the control system to the perturbation of the temperature of the pulp in the extractor. If the measured temperature of the pulp in the reaction compartment of the extractor increases (decreases), the controller 49 reduces (increases) the setting of the controller 51, requiring a decrease (increase) of the temperature of the pulp in the dispenser 2. The controller 51 increases (decreases) the setting of the controller 50, Requiring him to increase (decrease) the vacuum in the evaporator, the controller 50 through the adder increases (decreases) the water supply to the condenser. By increasing (decreasing) the water flow to the condenser, the signal from the water flow sensor 30 increases the device (reduces) the steam water flow to the ejector pump. Increasing (decreasing) the water and steam flow will increase (decreasing) the negative pressure in the system, as a result (decreases) heat removal from the pulp in a vacuum evaporator

5 and decreases (increases) its temperature in the dispenser. Now the pulp comes to the reaction compartment of the extractor with a lower (high) temperature, as a result

Q of which there also decreases (increases) the temperature.

Consider how the control system suppresses the perturbation of the temperature of the cooling water condenser. With an increase (decrease) in temperature, the vacuum in the system decreases (increases), to which the controller 50 responds by increasing (decreasing) the task to the controller 41,

0 As a result of the increase (decrease) by the water flow regulator 41 and the supply of steam to the vacuum pump, the vacuum is restored. During the transient in the vacuum control loop, the temperature of the pulp in the extractive apparatus remains almost unchanged.

If, under constant vacuum in a vacuum evaporator, a disturbance arises as a result of a change in the intensity of water evaporation or a change in the flow from collector 2 to a dispenser 3, the temperature of the pulp in the distribution collector changes. The controller 51 will be adjusted to this by adjusting the task to controller 50, and that one, in its

five

0

five

0

five

turn, - by changing the amount of water supplied to the condenser, and through device 59 - and steam to the ejector pump. This affects the evaporation rate in a vacuum evaporator. As a result, this control restores the temperature in collector 2.

Thus, the considered disturbance practically does not cause a change in the temperature of the pulp in the reaction compartment and the primer, since it is compensated in time by the regulator.

Using this control method allows to increase the hourly productivity of the processing line by 8%, reduce the consumption of raw materials by 1.5% and sulfuric acid by 2% and reduce energy costs by 3.5%.

Claims (2)

Invention Formula 1, a method for automatically controlling the production of extraction phosphoric acid, including regulating the concentration of excess sulfuric acid in the liquid phase of an extractor pulp by varying the supply of sulfuric acid to the extractor depending on the consumption of raw materials supplied to the extractor, adjusting the level of pulp in the matcher by changing the feed of the pulp to the vacuum filter depending on the consumption of raw materials, water supply to the vacuum filter, depending on the flow rate, regulation of the ratio of the liquid and solid phases of the pulp in the extractor and temperature pulp tours in the extractor, characterized in that, in order to increase the productivity of the process and reduce the loss of raw materials and energy, the concentration of the pulp and its liquid phase in the extractor, the concentration and flow rate of the working dilution solution are measured by the concentration of the pulps 1 and its liquid phases determine the ratio of the liquid and melt phases of the pulp in the extractor, calculate the cost ratio of the raw material and the working dilution solution, regulate the ratio of the liquid and solid phases of the pulp in the extractor by changing the supply of the circulating solution p the reduction with the correction of the flow of raw material into the extractor, the concentration of the liquid phase of the pulp in the extractor by changing the concentration of the working solution dilution, the impact on the water supply to the vacuum filter the costs of the raw material and the circulating dilution solution, and the feed of the pulp to the vacuum filter is additionally adjusted depending on the ratio of the expenditures of Cf and the circulating dilution solution. 2. A method according to claim 1, characterized in that it further regulates the vacuum in the vacuum evaporator by varying the flow rate of water into the condenser depending on the flow into the extractor with correction for the temperature of the pulp in the extractor and the collection distributor, and adjusting the steam supply to the ejector pump depending on the flow of water to the condenser.