SU1481200A1 - Method of automatic control of sulfur dioxide drying process - Google Patents

Abstract

The invention relates to the automation of technological processes of sulfuric acid production, in particular, the process of drying of sulfur dioxide, and can be used in the chemical industry. The aim of the invention is to improve the quality of gas drying and reduce material and energy costs. The method involves the regulation of the moisture content of the gas at the outlet of the drying tower by changing the acid supply to the irrigation of the drying tower, when the flow rate reaches the limit values, the flow of monohydrate to the acid capacity of the drying tower is changed. When the concentration of acid supplied to the irrigation of the drying tower is reached, the boundary values are controlled by the gas temperature at the inlet of the drying tower by changing the acid supply to the irrigation of the wash column, when the flow rate of which reaches the boundary values, the water supply to the irrigation cooler of the washing tower is changed. 2 Il.

Description

(2) 4296756 / 31-26

(22) 08/10/07

(46) 05.23.83. Bul V 19

(71) Ufa Oil Institute

(/ 2) A.I.Kobkov, R.T.Usmanov

and M.Kh.Valeev

(53) 66.012.52 (088.8)

(56) USSR Author's Certificate No. 1085932, cl. From 01 to 17/76, 1982.

Technical project for the production of sulfuric acid. Part IV

Technological part. Section B Automation of technological processes. Prince 1.-M .: Giprokhim, 1976.

(54) METHOD FOR AUTOMATIC CONTROL OF A SULFUR GAS DRYING PROCESS

(57) The invention relates to the automation of technological processes of sulfuric acid production, in particular the process of drying of sulfur dioxide, and can be used in the chemical industry. The aim of the invention is to improve the quality of gas drying and reduce material and energy costs. The method involves the regulation of the moisture content of the gas at the outlet of the drying tower by changing the acid supply to the irrigation of the drying tower, upon reaching the consumption of which the boundary values change the supply of monohydrate to the acid capacity of the drying tower. When the concentration of acid supplied to the irrigation of the drying tower is reached, the boundary values are controlled by the gas temperature at the inlet of the drying tower by changing the acid supply to the irrigation of the wash column, when the flow rate of which reaches the boundary values, the water supply to the irrigation cooler of the washing tower is changed. 2 Il.

five

The invention relates to the automation of technological processes of sulfuric acid production, in particular the process of drying of sulfur dioxide, and can be used in the chemical industry.

The aim of the invention is to improve the quality of gas drying and reduce material and energy costs.

FIG. 1 is a schematic diagram of an automatic control system implementing this method; in fig. 2 - graphs of changes in the main process parameters, explaining the operation of the control system,

J

00

The control system (FIG. 1) contains drying 1 and washing 2 towers, air 3 and irrigation 4 refrigerators, acid tanks 5 and 6, acid towers 7 and 8, temperature sensor 9, gas humidity sensor 10, acid concentration sensor 11 , flow sensors 12 and 13, regulators 14-17, comparison blocks 18 and 19, controllers 20-24, limit blocks 25-27, logic blocks and switches 31-33.

The method is carried out as follows.

Hche

ABOUT

about

The sensor 10 measures the humidity of the gas at the outlet of the drying tower 1. The signal V n from the output of the sensor is supplied to the input of the comparator unit 18. At the other entrance of the block, the specified value C „humidity of the gata is supplied. At the output of the block

b

form a signal & C & their differences

LS6 St. C

3

(one)

This signal is directed to the inputs of the acid supply controller 20 for irrigation of the drying tower, the monohydrate supply controller 21 to the tank 5 to strengthen the acid, and the gas temperature controller 22 at the inlet of the drying tower through switches 31 and 32, respectively. Depending on the value of this signal,

if Y, (tK) fc Y4, mai (; (3)

if (Y, Y ,, mi (Y, Y, il4cnf); (4)

if Y, (tK) Y, im, n, (5)

where Y, t, and Y, | 1Tl; n are the boundary values, 25 which determine the range of variation of this control. The signal from the output of the restriction unit 26 is directed to the regulator 14 on the irrigation acid supply line to the drying tower, and thereby determines the flow rate of the irrigation depending on the magnitude of the deviation of humidity from the target.

The boundary values Ylm; nH Y of the irrigation flow rate are determined from the conditions for ensuring the normal operation of the drying tower to avoid flooding and deficiency of irrigation.

if if

(.yy hGSib GKl, „);

10 ,, With

to so

H (Gk G

CC

).

The signal (y, is routed to the switch at the output of the controller 21

.tor 31. UCB and Comm-45 are also served here. Non-vi form control

 B

The tator is designed to connect the concentration controller 21 to the output of block 18 when the flow rate of the drying tower reaches the boundary values. For this output signal, the switch is formed by the formulas, - DSB, if (K, 0, (8), 0, if 1. (9)

50

Ya (tK) Ya (tK,) + ka-, where k 0 is the coefficient per regulator.

This signal is directed by the constraints to which the tied values Yj | ffl; n and Yj form the output signal

Y2 (tK) Y2 ma, if Yz (tK) i Y2niq,; (11)

Y2 (t) Y2 (tK) if (Ya (tJ Y2, m, nU (Y2 (tK) Y7, MOX; (12) Ya (tK) Y2iW; n, ecnHY (tK) Y,. M; n, (13)

the process of stubbing sulfur dioxide. Affect controls as follows.

In controller 20, depending on the magnitude of the humidity deviation from the task JSV, control V4 is formed by the formula

Y, (tk) Y, (tK.,) + UCB (tK) -k ,, k 0,1, ..., (2) where tfc nt .., are the times of formation of the control; k Y 0 - coefficient settings. The signal Y1 from the output of the regulator 20 is fed to the input of the limiting unit 26, the output of which receives a signal Y4 equal to

When the flow rate of the drying tower reaches the boundary values and the deviation of the gas humidity from the task remains, the flow of monohydrate into the tank 5 of irrigating acid is changed. For this purpose, the consumption of irrigating acid is measured by sensor T2, which is supplied by pump 7 through refrigerator 3. Signal G ,,. from the output of the sensor, the logical block 28 is supplied. At the other inputs of the block, the boundary values of the SC | „; П Gkirna ,, are valid, corresponding to the values Ylm; n.

At the output of the block 28 form the value | C, according to the formulas

xGSib GKl, „);

H (Gk G

CC

).

At the output of the controller 21, no vi

Ya (tK) Ya (tK,) + ka-, (tk), (10) where k 0 is the coefficient for adjusting the controller.

This signal is sent to restriction block 27, where the boundary values Yj | ffl; n and .IIoHHM are also supplied form the output signal Y, j:

which is directed to the regulating authority supplying the monohydrate to the tank 5 of the irrigating acid of the drying tower and thereby affecting the concentration of irrigation.

Gas drying in tower 1 is more effective the higher the concentration of irrigating acid. However, maintaining the concentration of irrigating acid at a limiting value is not economically advantageous, which explains the regulation of the supply of monohydrate in a certain range limited by the values

Y. V

il, I2, moi) t

In the case when, upon reaching the limiting concentration of the irrigating acid, the deviation of the humidity C in the gas from the task is maintained, then

p 0 if (.mni () V (CkЈCKiW; n); (14) if (C CKiWa,) A (CK CKim; n). (15)

The signal | ka from the output of logic block 29 is directed to the input of switch 32, another input of which is connected to the output of block 18. For a single value value | Cg switch connects block 18 to comparison with controller 22, switch output is determined by the formulas

if | Ut 0; (16), if (. (17) The regulator, by the value of the signal v / i, corrects the task Tg for the gas temperature at the inlet of the tower 1. Correction is carried out according to the formula

T (tJK) Tr (tlc.,) - kv b (t), (18) where is the setting factor

regulator.

The signal T is fed to the input of the unit (19 Comparison, at the other input of which a signal Tg is output from the output of the temperature sensor 9, which measures the temperature of the gas at the inlet of the drying tower. In Bloa (tK) Y, (tK), if Y5 (tK) ,. „,;„) L (Y3 (tK) Y ,, tAL Y, (tK) Y3im; n, if Y (tK) i Y ,, m; n, (23)

where Y, im; n and UE || 71s are the boundary values, which are determined from the conditions of the normal mode of the washing tower.

If the limiting values of acid consumption for irrigation of tower 2 do not exclude deviations of the gas temperature from

481200

eliminate it

ten

15

deviation by the temperature change of the gas supplied to the drying tower from the outlet of the washing tower. The change in the gas temperature is possible either by affecting the flow rate of the irrigation tower 2 cooled in the irrigation cooler 4 of the irrigation acid or on the water supply to the irrigation cooler. This part of the method is implemented as follows. The sensor 11 measures the concentration of the irrigation acid of the drying tower. The signal Ck from the output of the concentrator is fed to the input of the logic unit 29 where the boundary values CK, P, C and Ci.innovno of the irrigation acid are also supplied. In block 29 form the signal RLЈ by the formulas

ke 19 they are compared and the deviation value UTf is determined for them. LTG Tg - (19) which is fed to the regulator 23 for supplying the irrigation acid of the washing tower 2 and through the switch 33 to the controller 24 for supplying water to the irrigation cooler 4.

In controller 23, in proportion to the deviation of temperature from the adjusted reference Tg, a signal U3 is formed:

Y3 (t) Y, (tK.,) - k4 L Tr (tK), (20) where Z 0 is the coefficient for adjusting the controller.

This signal through the comparison unit 25 and the regulator 16 controls the supply of acid for irrigation by washing the tower 2. The signal in unit 25 is limited so that

if -Y, (tK) Yjma) t; (21)

cash ue

Y3 (tK) Y

); (22)

the tasks, the controller 24, change the supply of water to the irrigation cooler 4. To do this, the sensor 13 measures the flow of acid supplied from the tank 6 by the pump 8 through the irrigation cooler 4 to the irrigation of the washing tower. The signal Gn from the output of the sensor 13 is sent to a logic unit 30. The other inputs of the block 30 are supplied with the boundary values C 1 and correspond to the values Y

lp, min SOOT, Y.vn. n

| U, 0, if (Gn Gn, wa) V (Cn g Gan, 5 «) 5 (24) (if (Gn GntWet) A (Gn Grim; n), (25)

 which is fed to the switch 33. Syu-block 28 according to (14) and (15) of usLTG.

 Yes, the same with the output of block 19 serves

 At the output of the switch 33 is valid

equal signal

   if (K, 0, (26), -5, 0, if | And, 1. (27) i Depending on the magnitude of Vj by the regulator, the puller 24, which is connected to the output of the switch 33, affects the regulator 17 and thereby changing the water supply to the irrigation cooler 4. The control Y at the output of the block 24 is formed according to the following law:

Y4 (tk) Y, (tK.1) -ks-) y (t.K), (28) where kj 0 is the coefficient for adjusting the controller.

Example. Let at the initial moment of time the process be affected by a perturbation, as a result of which the humidity of the task takes place (Fig. 2). Then, according to (1) and (2), the controller 20 increases

ten

15

20

25

injects a signal (D is zero. As a result, switch 32 according to (16) connects controller 22 to block 18. The controller according to the law (18) reduces the reference T for gas temperature along the second control level loops. First, the flow control loop goes into operation acid for irrigation of the washing tower, since, starting from time t, the value

UTr becomes negative according to (19) and regulator 23 according to (20) increases the acid supply to the irrigation of the wash tower. During this period, the controller 24 is inactive, because the value in accordance with (25) and (27) has a zero value.

However, at the moment of time t, the flow rate of the G-reaches the limiting value Gn, which causes the signal / ee to be zeroed according to (24) and the controller 24 to connect in accordance with (26)

towers 1. By the time t (the flow rate Gk reaches the limit value Gn, Snr 26 stabilizes in П ЦХ..

According to (3) acid supply. AT

time ti

the supply of acid to the irrigation of the drying unit 0 to block 19. Starting from time t3, the controller 24 in accordance with (28) increases the water supply to the irrigation cooler until the value of & C6 equals the signal value 35 to zero. As can be seen from FIG. 2, this has

at the output of block 28 according to (6) and

(7) becomes zero, which by the switch 31 according to (8) and

(9) includes a regulator 21.

The latter increases according to the law (10) 40

feeding the monohydrate to fortify;

acid irrigation drying tower.

This increase occurs until

until either & CB becomes zero,

or until reaching the limit con-sequence, as in the consideration of the center of irrigation, in this example case, only in the opposite direction (figure 2).

The use of the proposed control method allows improving the quality of gas drying and reducing the irrigation costs of the drying and washing

the place at the time point C, after which all changes in the controls in the system stop.

At the moment of time t - a process was affected by a disturbance which caused a deviation of the gas humidity below the task. Starting from this moment, the system changes the control of the gas treatment process at the same last time at time t2. This means that the control resources of the first level of the system, affecting the mode of operation of the drying tower, turned out to be insufficient to compensate for the disturbance to the process. Therefore, the system commissions the control loops of the second hierarchical level of the system to change the mode of operation of the washing batni.

When reaching the value of C to the limit value of C, tachlogy

50

55

towers, monohydrate and water when the moisture content of the dried gas deviates below a predetermined value.

Claims (1)

Invention Formula The method of automatic control of the drying process of sulfur dioxide in In this block, a signal VWj is formed by the formulas 0 five injects a signal (D is zero. As a result, switch 32 according to (16) connects controller 22 to block 18. The controller according to the law (18) reduces the reference T for gas temperature along the second control level loops. First, the flow control loop goes into operation acid for irrigation of the washing tower, since, starting from time t, the value UTr becomes negative according to (19) and regulator 23 according to (20) increases the acid supply to the irrigation of the wash tower. During this period, the controller 24 is inactive, because the value in accordance with (25) and (27) has a zero value. However, at the moment of time t, the flow rate of the G-reaches the limiting value Gn, which causes, according to (24), the signal / s to zero out and the controller 24 to be connected in accordance with (26) the place at the time point C, after which all changes in the controls in the system stop. At the moment of time t - a process was affected by a disturbance which caused a deviation of the gas humidity below the task. Starting from this point, the system changes the gas treatment control in the same way. towers, monohydrate and water when the moisture content of the dried gas deviates below a predetermined value. Invention Formula The method of automatic control of the drying process of sulfur dioxide in sequentially connected washing and drying towers, including measuring the gas temperature at the inlet of the drying tower, controlling the acid supply for irrigating the towers, monohydrate into the acid tank of the drying tower, and water to the irrigation cooler of the washing tower, in order to increase the quality of gas drying and reducing material and energy costs, additionally measure the humidity of the gas at the outlet of the drying tower and the concentration of acid supplied to the irrigation of the drying tower, calculate the deviation measured The value of the humidity of the gas at the outlet of the drying tower from the specified value regulates the flow of acid to the irrigation of the drying tower in proportion to the calculated deviation of the measured value of the gas humidity from the set value and upon reaching the measured value of the acid consumption of the drying tower supplied for irrigation of these boundary values, they regulate the flow of monohydrate to capacity acid of the drying tower is proportional to the calculated deviation of the measured value of the gas humidity from the specified value, compare the measured value of the acid concentration supplied to the irrigation of the drying tower with the specified minimum and maximum boundary values and upon reaching the measured acid concentration of these boundary values calculate the deviation of the measured gas temperature at the inlet of the drying tower from a predetermined value, regulate the flow of acid to the irrigation of the washing tower in proportion to Initially, the calculated deviation of the measured gas temperature from the predetermined value compares the measured value of the acid flow applied to the irrigation of the wash tower with the specified minimum and maximum boundary values and upon reaching the measured value of the acid flow supplied to the irrigation of the wash tower, these limit values regulate the flow water in the irrigation cooler of the wash tower is proportional to the calculated deviation of the measured value of the gas temperature from the set Yeni. Drained gas 1