SU1421416A1 - Method of automatic control of sedimentation centrifuges operating in parallel - Google Patents

Abstract

The invention can be used in the field of automatic control of the process of separation of suspensions in precipitation centrifuges and is aimed at improving the accuracy of controlling the concentration of the centrate. The method involves measuring the flow rates of the suspension and flocculant, the concentration of the suspension, determining the flow rate of dry matter with the suspension, controlling the flow of dry matter with suspension, changing the flow rate of the suspension, controlling the flow rate of flocculant, changing the flow rate of each centrifuge and con - centrifuge concentration at the total centrifuge yield, use of the mismatch between the measured and specified centrate concentration for the forts, and the correction effect on the increase A given flocculate flow rate setpoint, starting with the centrifuge whose load current is minimal, determining the magnitude and sign of the rate of change of the centrifuge concentration relative to the flocculant flow rate change and modulo comparing with its preset value. Moreover, if this difference is positive or equal to zero, or in the case of a positive sign of the speed itself, a corrective action is transmitted to the next centrifuge, characterized by a higher load current compared to the previous one, forging the corrective effect on reducing the specified dry matter consumption value with suspension the mismatch between the measured and predetermined values of the concentration of the centrate on the total output of the centrifuges after the correction of the specified values of the flow rate. flocculant, starting with the centrifuge, the load current is minimal. With incomplete elimination of the specified. the error is transmitted to the next centrifuge, which is characterized by a large load current compared to the previous one. 1 hp ff, 4 ill. | R (/)

Description

The invention relates to the field of automatic control of the process of separation of suspensions in sedimentation centrifuges and can be used in the pulp and paper industry, the production of building materials, metallurgical, chemical, and chemical-pharmaceutical, microbiological, food and other industries. x industries

The purpose of the invention is to improve the accuracy of adjusting the concentration of ha of the fugate at the overall centrifuge yield.

FIG. 1 shows an automatic control system for precipitation centrifuges for separating a sewage suspension operating in parallel; Fig. 2 shows the dependences of the change in time of the concentration of the centrate on the total yield of centrifuges during the etching process (curve 1) and. proposed (curve 2) methods; in fig. 3 — dependences of the change in the concentration of centrate on the total centrifuge yield on flocculation flow per centrifuge (1-centrifuge with high mexai wear, 2 — centrifuge after major overhaul 3 — centrifuge with small mechanical wear) f in FIG. 4 the dependence of the change in the concentration of centrate on the total centrifuge yield on the total flocculant flow rate per centrifuge (1 - when controlled by a known method, 2 - when controlled by the proposed method).

FIG. 3 the following notation is accepted: G d5d, is the total consumption of the flow of pump at the control of a known method, equal to Sfd ,, G srlg fl .; Gftj, is the total flow rate of flocta nta under the control of the proposed method.

The control object is a group of three to three precipitating screw centrifuges with screw drives operating in parallel.

Automatic control system

includes sets of automatic flow meters 4–9, respectively, suspensions and flocculants for each centrifuge, measuring transducers 10–12 load current of centrifuge screw drives, respectively, 1.2 and 3 centrifuges 5 sensors 13 and 14, optical concentrations, respectively, suspension at the common inlet and fugate on

- Q

5 0 5 About

d

0

total output, units 15–17 for determining the dry matter consumption with a suspension in each centrifuge, regulators 18–23, respectively, for the dry matter consumption with suspension and flocculant, for each centrifuge, setting units 24–29, respectively, for the given values of dry matter and flocculant each the centrifuge, unit 30 of the specified value of the concentration of centrate on the total output of centrifuges, unit 31 for calculating the mismatch between the specified and measured values of the concentration of centrate on the total output of centrifuges, block 32 of the minimum cs-1g And according to the current from the track signals of the load current of centrifuge screw drives and dedicated channel signaling, blocks 33-35 for calculating the rate of change of concentration of centrate on the total output of centrifuges relative to changing flow rate of flocculate, respectively, for a centrifuge, block 36 for determining the sign of the relative rate of change of concentration of centrifuge, the module 37 for calculating the modulus of the relative rate of change of the concentration of the centrate S of the problem 38 for the minimum relative rate of change of the concentration of the centrate, block 39 for calculating the between the minimum value and the modulus of the measured value of the relative rate of change of the concentration of the centrate, unit 40 for determining the sign of the indicated mismatch, units 41 and 42 of forming corrective actions on changing the set values, respectively flocculant flow rate and flow rate, dry matter with suspension in a controlled centrifuge, relay logic blocks 43-53, logic elements And 54-59, limit switches. 60-62 servo-motors 63-65 for controlling the performance of pumps 66- 68 for feeding flocculant solution to centrifuges, sets of organs 69-71 regulating with electric actuator} 2 body MexHBBMaNM changed the suspension supply to the appropriate centrifuge.

The method is carried out as follows.

ia, each centrifuge is operated by two automatic systems of controlled dry matter, with suspension and the flow rate of the olokul solution.

An example implementation of the method in a centrifuge 1.

The signals from the automatic meter 4 and the sensor 13 are fed to block 15, in which the dry matter flow rate of the suspension from the centrifuge is calculated by the following formula:

ac G - suspension consumption,

Cj. - suspension concentration.

The dry substance flow signal is then fed to the dry matter regulator 18, which generates a control signal for controlling the regulator assembly 69 installed on the slurry supply line. The predetermined dry matter flow rate is entered using the setting unit 24.

The signal from the set 5 of the automatic flow meter flocculant enters the flow controller 19. . flocculant, which generates a control signal to control the servomotor 63 of the flocculator pump installed on the flocculant feed to the centrifuge.

A set value of the flocculant flow rate is inputted using the setting unit 25. The signal from the centrate concentration sensor 14 at the total centrifuge output enters the calculation unit 31 for the calculation between the predetermined value and the measured concentration value of the centrifuge. The predetermined concentration of the centrate is introduced by the setting unit 30.

i.

Next, the error signal is supplied to blocks 41 and 42, where corrective actions are formed on the change in the set values of the flocculant flow rate and flow rate from the ear substance with suspension, which are fed to the centrifuge according to the following expressions:

TO

CFDLF 5

 ;

K, Cd, are the proportionality coefficients determined experimentally; iCJ is the mismatch signal between the measured Cm and the given S. value

20

mi concentration of centrate on the total output of centrifuges, equal to C; pC. The signals from the transducers 10-12 of the load current of the centrifugal screw drives are fed to the selection and signaling unit 32 (signal of the minimum current signal).

1Q With this unit, a centrifuge having a minimum auger drive load current i.e. least effective in dehydration suspension-. Zia (Fig. 4).

15Ci drive from one of three outputs

This unit enters one of the three logical elements And 54 and 55 or 56. Each element And of this group also receives the signal of the final control unit 60-62 of the servomotor 63-65 of the pump 66-68 flocculant of each centrifuge 1-3. The output signal of the AND 54-56 logic element occurs when the input contains a signal from the output of block 32 and a signal from the end switch of the pump servomotor, indicating the possibility of changing the pump performance of the flocculant. Logical output

The 2Q element AND of this group of elements enters the corresponding logical element AND of the next group of elements, which also receives the enabling signal from the group of blocks and devices operating with the relative rate of change of the centrate of the centrate.

Each of the blocks 33-35 for calculating the relative rate of change of the centrate of the centrate of the centrifuge receives a signal

concentration dd from sensor 14. Flocculant flow rate signal from the corresponding centrifuge from sets 5, 7, and 9 of flow meters comes in even-cut relay logic blocks 44, 43

g and 53 to block 33, 34 or 35. The relay logic unit triggers and passes the flow signal to the relative speed calculator if it receives a signal from the selection unit 32 that selected the appropriate centrifuge for the minimum load current of the auger drive.

From the output of one of the three blocks 33-35, the signal goes to the relay logic unit 52 and block 36, which determines the sign of the relative rate of change of the concentration of the centrate. Relay 52 passes relative signal

50

55

the rate of change of the fugue concentration in the case of a negative sign on the modulus 37 of the relative velocity modulus. From the output of the latter, the signal arrives at block 39 for calculating the error between the set

the permissible speed of the GDI MODULVM of the measured velcchni, the preset value is set by the setting unit 38, the rate of change of the centrate of the centrate relative to the change in the flow rate of the flocant is calculated by the following formula;

where is S.

 p-1

the centrate of the centrate and the flow rate of flocta nta and time point n;

 the same quantities, but at time point n-1,

From the output of block 39, the signal arrives at block 40 for determining the mismatch sign and to the relay logic element 51 9 pass (the mismatch signal is -1I to the corresponding element And 57j 58 or 59, if the mismatch i is positive or in extreme cases

When a signal arrives at the corresponding elements of the AND element of the group 57, 58 or 59, it triggers and opens the corresponding relay logic elements 45, 46 or 47 to skip the corrective action of the DC

rl

from block 41 to one of the three regulators 19 21 or 23 of flocculant flow rate.

In the same way, in the presence of a DST mismatch, successively corrective actions are introduced on changes in the given value of the flocculant flow rate on all centrifuges. If, after such successive corrective control, a mismatch and C remain, then an additional corrective effect of dCd is put into effect. the change in the target value of the dry matter consumption with the suspension entering the centrifuge.

Relay logic elements 48-50 pass a corrective action signal from the output of block 42 when

0

five

0

five

0

35

0

45

0

55

the presence at the input of the burdock signal about the choice of the centrifuge for the minimum load current of the auger drive from block 32.

Corrective action G is applied to the corresponding dry matter regulator 18, 20 or 22 with a suspension to correct the target value of the dry matter consumption.

In the same way, taking into account the increase in the load current of the auger drive, as in the case of a corrective action, a corrective action is introduced on a change in the set value of dry matter suspension with a suspension for each centrifuge.

This method was tested under laboratory conditions. For comparison under the same conditions, a known method was tested in parallel operation of centrifuges. According to the results of the experiments built dependencies, shown in figure 2,

As can be seen from the graphical dependencies, the proposed method of automatic control can significantly improve the accuracy of stabilization of the concentration of centrate on the overall yield of centrifuges. OTKnoHefrae. the concentration of the centrate from the target averaged i 1.50%. When controlled by a known method, the accuracy of stabilization of the concentration of centrate on the total output of the centrifuges indirectly was significantly lower. The deviation of the concentration of the fugate from the target averaged 15.5%.

During testing, flocculant flow rate measurements were carried out for 20 hours. A comparative analysis of the two control methods showed that the average flocculant flow rate reduction under the control of this method was 1 57

I b - / / about

Thus, the method of automatic control in comparison with the known method allows to improve the quality of control by increasing the accuracy of stabilizing the concentration of the nj-worm rod at the total output of centrifuges, as well as to reduce the total flow rate of flocculation

Claims (2)

Formula invented and. 1 o Method of automatic control of wasps; 1 centrifuges, ra., 142 concurrently, including measuring the flow rates of the suspension and flocculant, the concentration of the suspension, determining the flow rate of dry matter with the suspension, controlling the flow rate of the dry matter with the suspension by changing the flow rate of the suspension, and controlling the flow rate of flocculant by changing its flow rate, differing from , in order to increase the accuracy of controlling the concentration of the centrifuge at the total output of the centrifuges, the load current of each centrifuge and the concentration of the centrate are measured at the total output of the centrifuges, the deviations are determined Between measured and specified values, adjust the value of the specified value of the flocculant flow rate, starting with the centrifuge, the load current of which is minimal, determine the magnitude and sign of the rate of change of the centrifuge concentration relative to the change of the flocculant flow rate and compare it with the specified eight value, and if this difference is positive or equal to zero, or in the case of a positive sign of the speed itself, the flocculant flow rate of the next centrifuge with a higher load current compared to the previous one is corrected. 2. A method according to claim 1, characterized in that if there is a mismatch between the measured and predetermined values of the centrifuge concentration at the total centrifuge output after correcting the set values of the flocculant flow rate on the centrifuges, the predetermined value of the dry matter consumption with the suspension is corrected starting with the centrifuge, the load current of which is minimal, and in case of incomplete elimination of the indicated mismatch, the target value of the substance is corrected with the suspension of the next centrifuge. Pac / nSof) (loku / 1 mgg) oCvcnpffyifg Fi: .1 6 20 g t h f uc.2  i Ta, d, / 7 / Compiled by G. Bogacheva Editor A.Vorovich Tehred M.Didzh Corrector L.Pilipenko Order 4363/8. Circulation 323 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Subscription