SU1587471A1 - Control system of circulating water supply of manufacturing process - Google Patents

Abstract

This invention relates to automatic process control. The purpose of the invention is to improve the accuracy of the control system. To achieve the goal, the process cycle control system includes a water level sensor in a hot chamber, a first level controller, a level indicator, an actuator on the water supply line to the cooling tower, a water level sensor in a cold chamber, a second level regulator, an actuator, mounted on the make-up line, water flow sensor for purge, flow controller, actuator installed on the purge line, water flow sensors at the outlet of hot and cold chambers, accumulators, setting devices minimum water consumption for purging, nominal and minimum water levels in the cold chamber, keys, a unit for calculating the expected production water flow, a comparator, a nonlinear dead band type unit and a delay unit. 2 Il.

Description

The invention relates to the field of automatic control of technological processes and can be used primarily for controlling the water circulating cycle.

The aim of the invention is to improve the accuracy of the control system.

FIG. 1 is a functional diagram of the control system | 1 and the water-circulating cycle; in fig. 2 is a graph showing the dependence of the correction value of the task on the water flow regulator for purging on the magnitude of the level in the cold chamber. The throughput cycle includes three stages of water processing. In the first stage, water is collected from all technological objects, where it is used for cooling and therefore is heated, in hot

chamber 1. In the second stage, water is cooled in a cooling tower 2. The third stage serves to collect chilled water in a cold chamber 3 before being supplied to technological objects (production) that need cooling. To remove water from the cycle, a purge line is located, located after the hot chamber 1. To enter the water in the cycle, use the feed line to the cold chamber 3.

The process water cycle control system contains a water level sensor 4 in the hot chamber 1. connected to the first input of the first level controller 5, the second input of which is connected to the output of the level 6 setter, the actuator 7 installed on the water supply line in the cooling tower, sensor 8 water levels in cold chamber 3,

H

connected by the output to the first input of the second regulator 9 level, the output of which is connected to the input of the executive body 10 installed on the make-up line, the sensor 11 of the water flow to the purge connected by the output to the first input of the regulator 12 of the flow rate whose output is connected to the input the executive unit 13 installed on the purge line, the water flow sensors at the hot outlet 14 and the cold 15 chambers, the adders 16-18, the control devices of the minimum water flow for the purge 19, the nominal water level in the cold chamber 21 and the minimum water level in the cold chamber 20, the keys 22-25, the unit 26 for calculating the expected water consumption for production, the comparator 27, the non-linear dead band 28, and the delay block 29.

At the same time, the inputs of the first adder 16 are connected to the outputs of the first level controller 5 and the water flow sensor 11 for purging, respectively, and the output is connected to the input of the executive unit 7 installed on the water supply line to the cooling tower 2, the inputs of the second adder 17 are connected to the outputs, respectively, of the water flow sensor 14 at the outlet of the hot chamber 1 and the flow rate sensor 11 for purging, and the output with the first input of the comparator 27, the second input of which is connected to the output of the unit 26 for calculating the expected water consumption for production, the input of which is with the output of the water flow sensor 15 at the outlet of the cold chamber, the inputs of the third adder 18 are associated respectively with the output of the water flow sensor 14 at the exit of the hot chamber 1, with the output of the unit 26 for calculating the expected water consumption for production and with the output of the nonlinear block 28 of the dead zone type whose input is connected to the output of the water level sensor 8 in the cold chamber 3, the information inputs of the keys 22-25 are connected to the outputs of the third adder 18, the setter 19 of the minimum flow rate for blowdown, the setpoint adjuster 21, minimum the water level in the cold chamber 3 and the setting device 20 of the nominal water level in the cold chamber 3, the control inputs of the keys 22 and 24 are connected to the direct output of the comparator 27, and the control inputs of the keys 23 and 25 to the inverse output of the comparator 27, outputs the keys 22 and 23 are combined and connected to the second input of the flow controller 12, the outputs of the keys 24 and 25 are connected and connected via the block 29 to the second input of the second controller 9.

The control system implements the following algorithm:

L | (e) K11 (e) -nK21 / et; (Rt-Rt); °

(flt2-ht2).

J, 3 l: s (H, -nL- «1; Ar (1 () K.

I

If R t-Ь ГЛ R t + r / t

that

Rt-rmin

 But.

If fif -f- r / t fit + r / t, TO 15 Rt Rt-Rt + r / t (Hmln, Hmax, Ht);

H + T Hmln:

0 if Hmin Ht Hmax. .

Kl (Hmln - Ht) if Hmin Ht

Kl (Hmax -.Ht), IFLI Hmax HI

where l: 1 {e) is the law regulating the PI with the parameters Kii. K2I О - regulator number);

Ut — control actions on the purge lines;

Ut - control actions on feed lines;

Ut - control actions on the water supply lines to the cooling tower; . Rt - water consumption for purging;

Rt is the water flow rate after the hot chamber;

R + t / - expected water consumption after cooling tower with lead g determined at the moment of BpeMeHift;

Rt - specified flow rate for purging;

R + - the expected consumption of water for production after the cold chamber with a lead g determined at the time

meny t:

Ht is the level in the hot chamber;

Ht - level in the cold chamber;

Ht - set level in hot kame

re;

Ht is the target level in the cold chamber;

Rmin - minimum water flow per

purge ;.

Hmin is the minimum level in the cold chamber;

Hmax - the maximum level in the cold chamber;

But - the nominal level in the cold

the camera; K - coefficient of water losses in the cooling tower;

r - transport delay time of the disturbance of the flow of vodm when passing through the cooling tower ..

The expected water consumption for production is determined by the known ratio (predictive model);

R + aiRt-in + b,

i 0

where Rt is the water flow rate after the cold chamber; .

31 - parameters of the predictive model;

m is the order of the model;

n is the time-slicing step (n m); . B - trend.

The system works as follows.

Water levels in hot 1 and cold 3 chambers are measured by sensors 4 and 8. Water consumption for blowdown at the outlets of hot 1 and cold 3 chambers is measured by sensors 11. 14 and 15. The first regulator 5 controls the level in hot camera 1 at a signal from the sensor 4 level. Setting the first level 5 controller forms the 6 level sensor. The control action from the first level 5 regulator is supplied to the first adder 16, where the signal is subtracted, which is proportional to the flow rate measured by the water flow sensor 11 for purging. This allows for regulating the level of water in the hot chamber 1 to take into account both the flow of water to the cooling tower 2 and the flow of water to purge. From the first adder 16, a control action is applied to the actuator 7. The second level 9 regulator controls the level in the cold chamber 3 by a signal from the water level sensor 8 in the cold chamber by acting on the actuator 10 in the make-up line. The flow regulator 12 controls the flow of water by acting on the actuator 13 on the purge line. The second adder 17 according to the signals from the sensor 14 of the water flow at the outlet of the hot chamber 1 and the sensor 11 of the water flow per purge forms the expected water flow after cooling tower 2 with prediction g;

R + r / t (Rt -Rt) K.

This uses scaling to the inputs of the adder 17, which takes into account the water losses in the cooling tower 2. The expected water flow after cooling tower 2 is equal to the expected water flow to the cold chamber 3.

The unit 26 for calculating the expected water consumption for production is paid by

determination of the forecast Rt + r / t specified

flow rate at the current values of the flow rate of the electrode measured by the sensor 15 water flow at the outlet of the cold chamber.

The unit 26 for calculating the expected production water consumption can be implemented on the basis of a programmable controller. Thanks to the embedded software, the controller allows to perform all the functions of block 26.

0 including the collection of information from the sensors, the counting of time intervals, the formation of time delays and, if necessary, the adjustment of the parameters of the predictive model.

5 The comparator 27 controls the process of forming the tasks for the second level controller 9 and the flow controller 12 depending on the result of comparing the expected costs for

0 cold chamber 3 and the production.

The stationary state of the water cycle is characterized by stable water consumption of production. In this case, the arrival of water to the hot chamber 1 is

5 water flow rate from the hot chamber 1 (at a constant level in the hot chamber). The water consumption for the cold chamber 3, taking into account the water losses in the cooling tower 2, is less than the water consumption for production after the cold chamber 3.

0 Under these conditions, in accordance with the control system operation algorithm, the expected water consumption for production is greater than the expected water consumption for the cold chamber 3, and therefore

5, the signal from the direct output of the comparator 27 opens the keys 23 and 25, and the signal from the inverse output of the comparator 27 keeps the keys 22 and 24 closed. Thus, the task to the flow controller 12 comes from set 19 to the minimum flow rate for purging and is equal to the minimum flow water to purge. The setting of the second level 9 controller comes from the setting device 20 of the nominal water level in the cold chamber and is equal to

5 to the nominal level in the cold chamber 3. With the occurring disturbances in water consumption, the water circulating cycle passes into an unsteady state, which is characterized by fluctuations in water flow

0 for production and / or after a hot chamber 1.

If the expected water consumption for production becomes less than the expected water consumption for the cold chamber 3

5 (which may occur, for example, with a decrease in water consumption by production, and / or an increase in the water consumption after the hot chamber 1), the comparator 27 provides new control signals. The signal from the direct output of the comparator 27 closes the keys 23

and 25, and the signal from the inverse output of the comparator 27 opens the keys 22 and 24, This leads to a change in the tasks to the second level controller 9 and the flow controller 12.

The second level 9 controller receives a task from a minimum water level setpoint adjuster 20 in cold chamber 3 through delay unit 29 and equal to the minimum allowable level in cold chamber 3. Thus, by the time the ratio of expected water consumption to production changes to the cold chamber, due to the unit 29 delay, the second level 9 regulator receives a new task, which is less than the nominal one, which leads to overlapping of the feed, since the level in the cold chamber 3 is approximately equal to the nominal one.

The flow regulator 12 receives an increased purge task, since production is not able to consume all the water that comes after the hot chamber 1 from the adder 18 through the first key 22. The accumulator 18 forms an enlarged task for the purge water consumption water consumption for production from block 26 calculating the expected water consumption, the current water consumption after the hot chamber 1 from the flow sensor 14 and the correction signal from the water level sensor 8 in the cold chamber 3 flowing through the nonlinear block 28. ohm, in the adder 18 the ratio is realized

, 1-r3j,. , Ngpah, Ht).

The presence of a non-linear block 28 of the deadband type makes it possible to compensate for the inaccuracy of the calculation of the purge task. If the level in the cold. chamber 3 has become less than the minimum allowable value, the make-up is activated and the blowdown task is reduced. If the level in cold chamber 3 has exceeded the maximum allowable value, the purge task is increased. If the level in the cold chamber 3 lies between the maximum and minimum value, then the correction is equal to zero. A feature of dynamic job switching is that the jobs switch in strict sequence, first the jobs for flow controller 12, and then after time for the second level regulator 9 in cold chamber 3.

In the event that the expected water consumption for production exceeds the expected water consumption for the cold chamber 3, then the tasks for the second level controller 9 and the flow controller 12 become correspondingly equal to the nominal level in the cold chamber 3 (with a lag relative to

current time) and the minimum consumption for purge.

Ph o rm a l and 3 o bre ns The process water cycle control system containing a water level sensor in a hot chamber connected by an output to the first input of the first level regulator, the second input of which is connected to the output level gauge, 0 water level sensor in the cold chamber, connected by an output to the first input of the second level regulator, the output of which is connected to the input of the actuator installed on the make-up line, water flow sensor 5 for purging connected by the output to the first input of the regulator p converge. yes, the output of which is connected to the inlet of the executive body installed on the purge line, as well as the executive body installed on the water supply line to the cooling tower, characterized in that, in order to improve the accuracy of the system, it contains water flow sensors at the hot end and cold chambers, three adders, 5 controllers for the minimum flow rate for purging, the nominal water level in the cold chamber and the minimum water level in the cold chamber, four keys, the unit for calculating the expected flow rate for production, comparator, not Linear unit of the dead zone type and the delay unit, the inputs of the first adder are connected to the outputs of the first level regulator and the flow rate sensor for purging water, respectively, and the output is connected to the input of the actuator installed on the water supply line to the cooling tower, the inputs of the second adder are connected to the outputs, respectively, of the water flow sensor at the outlet 40 of the hot chamber and the flow sensor for purging, and the output with the first input of the comparator, the second input of which is connected to the output of the unit for calculating the expected time water production, the inlet of which is connected to the output of the water flow sensor at the cold chamber outlet, the inputs of the third adder are associated respectively with the output of the water flow sensor at the hot chamber outlet, with the output of the unit 50 for calculating the expected water consumption for production and nonlinear output Block of the “Dead zone” type, the input of which is connected to the output of the water level sensor in the cold chamber, 55 information inputs of the keys are connected to the outputs of the third totalizer, the minimum water flow indicator, respectively. purge, setpoint minimum water level in the cold chamber and the setpoint nominal water level in the cold chamber, the control inputs of the first and second keys for communication-connected to the second input of the regulator

with the direct output of the comparator, and the control flow rate, the outputs of the second and fourth pulsing inputs of the third and fourth keys are combined through the delay unit

- with the inverse output of the comparator, the output connectors are connected to the second input of the second control of the first and third keys and 5 level tori.

ABOUT

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Claims (1)

Claim A control system for the water cycle of the technological process, comprising a water level sensor in the hot chamber connected to the output of the first input of the first level controller, the second input of which is connected to the output of the level switch, a water level sensor in the cold chamber connected to the output of the first input of the second level controller, output which is connected with the input of the executive body installed on the make-up line, a purge water flow sensor connected by an output to the first input of the flow controller, the output of which is connected to the input of the executive body installed on the purge line, as well as the executive body installed on the water supply line to the cooling tower, characterized in that, in order to improve the accuracy of the system, it contains water flow sensors at the outlet of the hot and cold chambers, three adders, minimum purge water flow rate, nominal water level in the cold chamber and minimum water level in the cold chamber, four keys, a unit for calculating the expected water consumption for production, a comparator, a non-linear unit of the type Zone insensitive units and a delay unit, the inputs of the first adder being connected to the outputs of the first level controller and the water flow sensor for purging, and the output to the input of the actuator installed on the water supply line to the cooling tower, the inputs of the second adder are connected to the outputs of the water flow sensor respectively the output of the hot chamber and the water flow sensor for purging, and the output with the first input of the comparator, the second input of which is connected to the output of the unit for calculating the expected water consumption for production, the input of which connected to the output of the water flow sensor at the output of the cold chamber, the inputs of the third adder are connected respectively to the output of the water flow sensor at the output of the hot chamber, to the output of the unit for calculating the expected water flow to production and to the output of a non-linear block of the type Dead band, the input of which is connected to the sensor output the water level in the cold chamber, the information inputs of the keys are connected to the outputs of the third adder, the setpoint for the minimum water flow for purging, the setter for the minimum water level in the cold chamber and the setpoint for the nominal water level in the cold chamber, the control inputs of the first and second keys are connected to the direct output of the comparator, and the control inputs of the third and fourth keys are connected to the inverse output of the comparator, the outputs of the first and third keys are combined and 5 are connected to the second input flow controller, the outputs of the second and fourth keys are combined and through the delay unit are connected to the second input of the second level controller.