SU1655903A1 - Device for controlling processes automatically and for drying and absorption of calcination gas - Google Patents

Abstract

The invention relates to the automation of industrial processes, can be used in the production of sulfuric acid by the contact method, and reduces the loss of sulfur. The device contains collections 1-3, respectively, of the drying tower, monohydrate and oleum absorbents, sensors 4, 6 and 14 concentrations of monohydrate, oleum and drying acid, respectively, regulators 5, 7, 10. 13 and 15, sensors 12, 16 and 17, adders 22 and 23, control units 24 and 25, threshold elements 29 and 30, multiplication blocks 26 and 27, logic block 28, null organ 31 and block 32 of dynamic communication 2 or

Description

The invention relates to the automation of industrial processes and can be used in the production of sulfuric acid by the contact method, in particular for controlling the processes of drying and absorption of calcined gas at the output of products in the form of technical sulfuric acid and oleum.

The purpose of the invention is to reduce sulfur losses by increasing the accuracy of controlling the concentration and level in acid collectors.

FIG. 1 shows a functional diagram of an apparatus for automatically controlling the processes of drying and absorption of calcined gas; in fig. 2 is a block diagram of the proposed device in the form of a directed graph.

The control object is a collection 1 of a drying tower, a collection 2 of a monohydrate absorber and a collection 3 of oleum

absorbent materials that are interconnected by mutual flows (see Fig. 1). Excess drying acid from collector 1 is pumped out to the warehouse, excess oleum from collector 3 is also pumped out to warehouse

The device for automatic control of the processes of drying and absorption of calcined gas contains control loops of the concentration and level of acids in the collections, as well as the control loop of the flow of oleum pumped from collection 3 to the warehouse

The monohydrate concentration control circuit includes series-connected monohydrate concentration sensor 4 and regulator 5. The oleum concentration control circuit includes oleum concentration sensor 6 connected in series, regulator 7 and actuator 8 installed on the monohydrate supply line from collection 2 to collection 3 Contour

ABOUT

ate about

with

controlling the consumption of oleum pumped from collection 3 to a warehouse includes a series-connected sensor 9 of oleum consumption, a regulator 10, and an actuator 11.

The oleum level control loop in collector 3 includes a level 12 sensor and a regulator 13 connected in series. The drying acid concentration control loop includes a series connected concentration sensor 14 and a regulator 15, In addition, the automatic control device contains a level 16 drying acid acid sensor in collector 1 , level sensor 17 in collector 2, actuators 18-21, installed respectively on the drying acid pumping line from collection 1 to the warehouse, on the drying acid supply line from The Data collection 1 in 2 for supplying the monohydrate of 2 collection in the collection line 1 and oleum from feed line 3, the collection in the collection 2.

The device for automatic control also contains the first and second adders 22 and 23, respectively, the first and second regulating units 24 and 25, the first and second multiplying blocks 26 and 27, the logic unit 28, the first and second threshold elements 29 and 30, the zero-authority 31 and a dynamic communication unit 32.

The proposed device works as follows.

The drying acid from collector 1 is fed to the irrigation of the kiln gas in the drying tower and absorbs the moisture contained in it, i.e. gas drying occurs. The dried calcining gas is sent to the contact apparatus, where sulfur dioxide is oxidized to sulfur trioxide, and after it enters first the oleum absorber and then the monohydrate absorber (drying tower, monohydrate and oleum absorbers and the contact apparatus are not shown in the drawings). Sulfur trioxide is extracted from the calcining gas in the oleum absorber using oleum supplied for irrigation from collector 3, and in a monohydrate absorber using monohydrate supplied for irrigation from collection 2.

The degree of concentration of these acids, which are maintained at the required values due to the mutual flows between the collectors, determines the degree of drying of the calcining gas and the degree of absorption of sulfur trioxide, which, at certain values of the concentration of drying acid (within 93-95%, depending on the temperature ), monohydrate (98.6%) and oleum (within 18-20%) reach the maximum value. The level value in collections 1-3 does not directly affect the quality of drying and absorption of calcined gas, however, significant fluctuations in the level affect the concentration of drying acid, monohydrate, and oleum in the corresponding collections. In addition, an excessive increase in

or lowering the level leads to emergency situations.

The concentration of the monohydrate is controlled by means of a regulator 5, to the information input of which a signal is supplied from the sensor 4 of the concentration of the monohydrate. If a mismatch occurs between the current and target concentration values at the output of the controller 5, a control signal is generated according to the standard, for example, PID law, which is fed to the actuator 20 installed on the monohydrate supply line from collection 2 to collection 1, and increases the flow rate of a given stream when the current concentration of the monohydrate becomes greater than its predetermined value, and when the concentration of the monohydrate becomes less than the predetermined value, decreases.

Similarly, using the controller 7, to the information input of which a signal from the oleum concentration sensor 6 is applied, the oleum concentration is controlled. Formed by the PID law at the output

5 of the regulator 7, the control signal is fed to the actuator 8 mounted on the monohydrate supply line from collector 2 to collector 3. and increases the flow rate of the given flow when the concentration

0 oleum becomes greater than its predetermined value, and when the concentration of oleum becomes less than the predetermined value, decreases.

The consumption of oleum pumped out from collection 3 to the warehouse is controlled by means of regulator 10, to the information input of which a signal from flow sensor 9 is supplied. At the output of the controller 10 according to the standard PID law

0, a control signal is generated, which is fed to the actuator 11 mounted on the oleum pumping line from collector 3 to the warehouse and increases the flow rate of this stream if the oleum flow rate is less

5 of its predetermined value, and when the flow rate becomes greater than the predetermined value, it decreases.

The adjustment of the oleum level into the collector 3 is carried out by means of the regulator 13, to the information input of which is supplied a signal from the sensor of the oleum level 12. At the output of the regulator 13, according to the standard PID law, a control signal is generated, which is fed to the actuator 21 installed on the oleum supply line from collector 3 to collector 2 through the adder 23 and increases the flow rate of this stream if the level exceeds its specified value , and when the level value becomes less than the specified value, it decreases.

The second input of the second adder 23 is supplied with a signal from the drying acid concentration sensor 14 via the dynamic communication unit 32. The latter, depending on the dynamic properties of the control channel: the concentration of the drying acid — the concentration of oleum is an integral-differentiating or real differentiating element. If the concentration of the drying acid decreases, then the flow rate of the oleum supplied from collector 3 to collector 2 will increase under the action of the signal at the output of dynamic communication unit 32, which will lead to an increase in the concentration of monohydrate. When the current value of the monohydrate concentration exceeds its specified value, regulator 5 turns on and under the action of its output signal using the actuator 20, the supply of monohydrate from collector 2 to collector 1 will increase, resulting in an increase in drying acid, thereby compensating its initial decrease.

If the concentration of the drying acid will increase, then under the action of the output signal of the dynamic communication unit 32 by means of the actuator 21, the flow rate of the oleum supplied from the collector 3 to the collector 2 will decrease. At the same time, the concentration of monohydrate will begin to decrease, which will be accompanied by a decrease in the consumption of monohydrate supplied from collection 2 to collection 1. Due to the control loop, the concentration of drying acid will begin to decrease, thereby compensating for its initial increase.

Additionally, the concentration of the drying acid is controlled by the controller 15, to the information input of which a signal is sent from the concentration sensor 14. At the output of the controller 15, according to the standard PID-law, a control signal is generated, which through the first adder 22 enters the actuator 18 installed on the pumping line of the drying acid from

collector 1 to the warehouse, and with its help it increases the flow rate of this stream, if the concentration of the drying acid becomes more than its specified value, and when the concentration of the drying acid becomes less than the specified value, it decreases.

The level in collector 1 is measured by means of a level sensor 16, and in collector 2 by a level sensor 17. Their output signals come simultaneously to the input of threshold element 29, threshold element 30 and to the inputs of the null organ 31. Discrete signals are generated at the null organ outputs when the following 5 conditions are fulfilled: if (Hi-On) b, then a discrete signal is generated at the first output of the null organ 31 and through block 27, where it is multiplied by -1, is fed to one of the inputs of the second regulating block 25; if (Hi - Hg) 0 d, then a discrete signal is generated at the second output of the null organ 31 and is directly fed to another input of the second recording unit 25

At the output of the regulating unit 25 under the action of discrete signals of different polarities, coming from the null organ 31, according to the standard PID law, a discrete signal is generated and fed to the actuator 19, set 0 on the drying acid supply line from collector 1 to collector 2. With the help of this actuator, an increase in the flow rate of this flow occurs when Hi On, and a decrease when Hi H2. The result of such a control is the achievement of equality of the levels in both collections 1 and 2, i.e. Hi - H2

At the outputs of the threshold element 29 discrete signals are generated in that case. when the level of the drying acid in collector 1 reaches its lower (Hi Nmin) or upper (Hi Nmax) limit values. If, on the other hand, its lower (H2 NMin) or upper (H2 5 Nmax) limit values reaches the level of monohydrate in collector 2, then discrete signals are formed at the outputs of the threshold element 30.

The discrete signals from the outputs of both 0 threshold elements 29 and 30 are supplied to "a input of the logic unit 28. At its first output, a discrete signal is generated when or at the same time and through the multiplication unit 26 by -1 5 it goes to one of the inputs of the first regulating unit 24. At the second output of the logic block 28, a discrete signal is generated when H 1 Nmax and H2 Nmax. which is directly fed to another input of the first regulating unit 24. At the output of the latter, under the action of discrete signals of different polarities, a control signal is formed according to the standard PID law and through the first adder 22 is fed to an actuator 18 installed on the pumping line of the drying Acid from collection 1 to the warehouse.

Thus, when the level of drying acid in collection 1 and the level of monohydrate in collection 2 simultaneously reach a minimum value (i.e. Hi Nmin, H2 Nmin), the flow rate of the drying unit is reduced by the control signal of the first regulating unit 24 acid pumped from collection 1 to the warehouse. At the same time, the level of the drying acid in collector 1 begins to increase and when Hi On is reached, then under the action of the control signal of the second control unit 25, the flow rate of the drying acid supplied from collector 1 to collection 2 will increase, and the level in the latter will also begin to rise.

In the case when the level of drying acid in collection 1 and the level of monohydrate in collection 2 simultaneously reach their maximum value (i.e., H 1 N max S S N max), then under the action of the control signal of the first regulating unit 24 with the help of an actuator 18 the consumption of drying acid pumped out from collection 1 to the warehouse will increase. At the same time, the level of the drying acid in collector 1 will begin to decrease and when H1 N2 will occur, then under the action of the control signal of the second regulating unit 25 using the actuator 19, the consumption of drying acid supplied from collector 1 to collection 2 will decrease, and the level in the latter will be also decrease.

At the vertices of the graph (see Fig. 2), indicated by circles, adjustable parameters and flow rates between collections are placed. The arrows show the connections between them, and the connections that come out of the vertices of the graph, which correspond to the flow rates, are natural and reflect the properties of the control object. Connections leaving the vertices of the graph, which correspond to the adjustable parameters, are implemented using control blocks. Dotted lines indicate short-term links that are included using discrete

elements of the proposed device when fulfilling the above described conditions of the state of the control object (certain relations between the levels in the collections

drying tower and monohydrate absorber).

The nature of the relationship between flow rates and adjustable parameters is established from the following considerations:

with increasing consumption of acid entering the collector, the level in it increases, and decreases with decreasing; with an increase in the consumption of acid pumped out of the collector, the level in it decreases, and

5 increases with decreasing; if the consumption of acid entering the collector increases and its concentration is greater than the acid concentration in the collector itself, this leads to an increase in the concentration of the acid in the collector and to a decrease if the incoming acid flow decreases, if the acid consumption in the collector, increases, and its concentration is less than the concentration of acid in the collector itself, this leads to a decrease in the concentration of acid in this collection and to an increase otherwise; with an increase in the consumption of acid pumped out of the collector, the concentration in it decreases and increases otherwise.

From the block diagram of the proposed automatic control device, it can be seen that there are many

5 permanently acting closed circuits and they all have the property of self-leveling. For example, consider the largest contour:

Cl.

0 If the concentration of drying acid Ci is increased, the response will be a decrease in the consumption of monohydrate G21 supplied from collection 2 to collection 1, and this causes a decrease in the concentration of advanced acid Ci and helps to compensate for the initial deviation of Ci. Similarly, there will be compensation for the deviation of the controlled parameters from their given values and for the rest

0 closed loops. As a result, favorable conditions are created to improve the accuracy of adjusting the process parameters.

Temporary connections are included when certain ratios between the level values in the collections of the drying tower and the monohydrate absorber (Hi N2, Hi H2,

Hi S: Nmin H2 - Nmin. Hi - H max H2 Nmax)

when these ratios cease to satisfy the specified conditions. Therefore, the individual closed contours formed by short-term connections without self-leveling do not have a noticeable negative effect on the control accuracy.

The use of the proposed device for automatic control of the drying and absorption processes of calcined gas in the automation system of the drying and absorption department of the sulfuric acid production by improving the accuracy of controlling the concentration and acid level in collections allows for a two-fold reduction in sulfur losses in the form of mist and unabsorbed sulfur trioxide from flue gas. As a result, the annual production of sulfuric acid increases. Preliminary calculations showed that the introduction of the proposed device in sulfuric acid production with a capacity of 360 thousand tons of acid per year will provide an additional increase in the production of acid in the amount of not less than 1500 tons per year.

Claims (1)

Apparatus of the Invention A device for automatic control of roasting gas dehydration and absorption processes comprising a monohydrate concentration sensor connected in series and a regulator, an oleum concentration sensor connected in series, a regulator and an actuator mounted on the monohydrate absorber supply line to the oleum absorber collector in series United oleum flow sensor, regulator and actuator mounted on the pumping line of oleum from oleum an oleum absorber into the warehouse, successively connected oleum level sensor in the oleum absorber collector and regulator, successively connected drying acid concentration sensor and re / l torus, drying acid level sensors in the drying tower collection and monohydrate absorbent level in the monohydrate absorber collection, actuators, installed on the lines, respectively, pumping the drying acid from the collection of the drying tower to the warehouse, supplying the drying acid from the collection of the drying tower to the collection of monohydrate abs supplying the monohydrate from the monohydrate absorber collector to the collection of the drying tower and feeding the oleum from the oleum absorber collection to the monohydrate absorber collection, characterized in that, in order to reduce sulfur losses by increasing the concentration and level control accuracy in acid collections, the device additionally contains two adder, two control blocks, two multiplication blocks, 0 logical block, two threshold elements, a zero-organ and a dynamic communication block, while the output of the first adder is connected to flax mechanism mounted on the suction line drying acid 5 from the collection of the drying tower to the warehouse; one of its inputs is connected with the output of the regulator of concentration of the drying acid, and the other with the output of the first regulating unit, the first input of which is connected to the first 0 by the output of the logic unit, and the other input is connected through the first multiplication unit with the second output of the logic unit, the outputs of the first and second threshold elements are connected to two inputs of the logic unit, the sensor of the drying acid level in the collection of the drying tower is connected in parallel to the input of the first threshold element and the first input of the null organ, the monohydrate level sensor in the monohydrate absorber collector is connected in parallel to the input of the second threshold element and to the second input of the zero organ, one output of which is connected to the first input of the second control unit, and the other output through 5, the second multiplying unit is connected with the second input of the second regulating unit, the output of which is connected to the actuator installed on the drying acid supply line from the collection of the drying tower to the monohydrate absorber collection, the output of the monohydrate concentration regulator is connected to the actuator installed on the supply line monohydrate from the monohydrate absorber collector to the drying tower collection, the output of the oleum regulator in the oleum absorber collection through the second adder is connected to the executive mechanism installed on the oleum feed line from 0 of the oleum absorber collector to the monohydrate absorber collector, and the second input of the adder is connected via a dynamic communication unit to the concentration sensor of the drying acid five .3d i TU-tL urine AND 3d Јg t-tj IT U “,, u Н„ ax Fig 1 qing Fm.2