SU1638211A1 - Method and device for control of continuous electrochemical synthesis of dimethyl sebacate - Google Patents

Abstract

The invention relates to methods and devices for controlling the process of synthesizing dimethyl ester of sebacic acid, can be used in the chemical industry and makes it possible to reduce electricity costs. The method of controlling the continuous synthesis of dimethyl by sebacate ester consists of feeding the cascade of serially connected electrolysers of the main and feed streams of the initial reagent, distributing the feed streams through the electrolyzers, measuring the flow rates of these streams, the concentration of the starting reagent between the electrolyzers, the input and output of the cascade, current through the cascade, determining the average output and gas flow rates for different parts of the cascade, calculating the concentration radio monometiladipi- nata and correction of the make-up flow rate. A device for carrying out this method comprises sensors 6-8 for measuring the concentration of menomethyladipate, respectively, with S (L

Description

,,

The invention relates to methods for controlling the synthesis of sebacic acid dimethyl ester (DMS) by an electrochemical method and can be used in the chemical industry in the production of synthetic sebacic acid.

The aim of the invention is to reduce the cost of electricity for the process by improving the accuracy of stabilization of the operating mode of the electrolyzer cascade,

The drawing shows a block diagram of a device for controlling a continuous electrochemical process for the synthesis of dimethyl ether of sebacic acid | TY.

| The control unit comprises a cascade of 1 serially connected electrolyzers, a switching unit 2, a main 3 line and 4 feeds the electrolyte solution supplied from mixer 5, sensors 6-8 for measuring the concentration of monomethyl adipate, respectively, at the stage into the cascade, between the cells and the output from the cascade, sensors 9, 10 for measuring the flow rate of the feed and main streams of the electrolyte solution, current sensors 11 through the stage, the control valve 12 mounted on the feed line to OK, the blocks (13, 14 of the correction, respectively, of the current output and the gas flow rate (respectively for the part of electrolyzers located up to sensor 7 and after it, i.e. for the second part of the cascade), are connected via four inputs to sensors 10, 11, 6, 7, blocks 15, 16 for calculating the concentration of monomethyl adipate (MMA), respectively, for part of the electrolyzers up to sensor 7 and after it, with five inputs connected to sensors 6, 11, 10 and two corresponding outputs of the first and second blocks 13, 14 corrections, concentration controller 17, input to

15

20

thirty

- 35 40 50

Secondly, it is connected to the MMA concentration sensor 8 at the output of cascade 1, the feed flow rate calculation unit 18, the inputs connected to sensors 6, 10, 11, with two outputs of the correction unit 14, with the output of the correction unit 13, and the output with the summation unit 19, which is connected to the second input with G concentration controller 17, and the output with control valve 12, logic unit 20 and switching unit 2 (relay), the inputs connected to sensor 7 to the MMA concentration, with the fifth and sixth inputs of unit 14 being connected respectively with sensors 8, 9, and its seventh input The sixth, seventh and eighth inputs of the block 16 are connected to the output of the correction unit 13, respectively, with sensors 7, 9 and the output of the correction block 13, the output of the block 15 is connected to the input of the switching unit 2, and the output of the MMA concentration calculator 16 is connected to the input recharge flow rate calculation unit 18, the output (switching unit 2 is connected to the feed flow rate calculation unit 18, the input of switching unit 2 is connected to the outputs of MMA concentration calculating unit 15 and logic block 20, and its output - to feed flow meter. The corresponding outputs of the correction unit 13 are connected to the corresponding inputs of the blocks: correction 14, calculating the concentration of MMA 16 and calculating the flow rate of the feed flow 18. i

The device works as follows.

The initial flow of the electrolyte solution through line 3 from the mixer 5 is fed to the input of a cascade of serially connected electrolyzers 1, in which the electrochemical synthesis of dimethyl ester of α-sebacic acid takes place. From the source stream

5163

The electrolyte solution branches off the feed stream, which is directed along line 4 through control valve 12 to separate electrolytic cells, where it is mixed with the main flow of electrolyte.

At the cascade inlet (from line 3) between the cells and at the cascade inlet, a small portion of the flow is taken to sensors 6-8 to measure the concentration of unreacted MMA. Based on the measured MMA concentrations, the current through the cascade, and the flow rates of the main and feed streams in correction blocks 13 and 14, the corrected parameters are determined, and then using these parameters in blocks 15 and 16, the concentrations of MMA are calculated respectively at the output of the first part of the electrolysers the location of the sensor 7 and the electrolyte solution at the outlet of the cascade.

The corrected parameters determined in the correction unit 13 are the average current efficiency and the gas flow rate for the first part of the cells (up to the installation point of the sensor 7). The calculation is performed sequentially by the formulas:

B, G0 - M-Gq, iN; X, UWMAPM / (F B,);

A, G0C0 / B, - X, - E ,, N; 35

EI.N +. E ", N - CA - A) X / (Y, + X); ST, R (P + N) + R0;

G4 ,, GG ,, N + 2ST, (CA-A,) A, / B ,, 4Q de, E1iN + 1- average current output for the first part of the electrolyzers at the Nth and (N + l) -M steps 45 - the average gas flow rate from the electrolysis cells on the N-m and (N + l) -m correction steps;

GT5, NG ".

- 50 MMA concentration signal at the cascade input from sensor 6;

- signal consumption of the electrolyte at the entrance to the cascade of g sensor 10; 55 - current signal from sensor 11;

- signal concentration of MMA from sensor 7;

0

50

five

Q 5

0

five

M - chispo electrolysers p cascade located up to sensor 7;

V 0.02 - parameter entered to protect against measurement interference; N - number of the current step

correction parameters; (M, CMA molecular weight MMA;

F is the Farade number; R, R, P - constant parameters ° (R 0.2, Re - 0.001,

R 0.8).

Parameters B, A, Xt, ST, are intermediate design variables determined through the block input signals and having the following physical meaning:

Bj, A 4 - respectively, the consumption of electrolyte and the concentration of MMA at the output of the 1st part of the electrolyzer;

X, - the number of reacted MMA with K ,, (M 1;

ST is intermediate variable, defined by R, RQ, P.

The output signals of the block are the values of K (rU |, supplied to the inputs of block 15, the signal G y., Comes in addition to the inputs of blocks 14, 16 and 18.

In correction block 14, the electrolyte consumption G and the concentration of MMA C at the inlet of the second part of the electrolysers are determined based on the signals from the cascade sensors and the gas flow signal from the output of block 13:

Ga G0 - M. + QM;

G2 (G0 - M-GQ, iN) CA +,

and then the current efficiency and gas flow rate from the electrolyzers of the second part of the cascade are adjusted according to the ratios of block 13:

B2 G2- (K-M) GQ2iN;

X1 PWKK-M) / (F.B2); Ar С С2 / Вг - X2E2N;

T2

Е1, НН Е2.ц ((N ST R / (P + N) + R0;

GQ2.N +, GQ2, N + 2ST2 (CN - A2) At / B2

where E2 | 4 E2N4lr is the average current efficiency for the second part of the electrolyzers on the Nth and (N + 1) -M steps of correction;

G $ 2.N GQz.NvT average gas flow rate from the electrolyzer at the Nth and (M – H) th correction steps; GM Signal Flow Signal

the flow from t sensor 9; CH - concentration signal

MMA from sensor 8; , K - the total number of electrolyzers in the cascade; Bg, g, Ar are the intermediate calculated variables determined through the input signals of the block (in the physical sense they are similar to Bn, X4, A,); (ft JN constant; ST Ј - ST, .20

The output signals of the block are the corrected values of E2 (fl4,,

The MMA concentration calculation unit 15 calculates the MMA concentration (CA / I) at the output of the first part of the cascade electrolysers located up to sensor 7,

From G ° C ° -lUu / uAl M.Ej.N / F

 AM

Go - M-GQ4i |

The block input receives analog signals Cn, Cn, I from sensors 10, 6, 11, respectively, and the output signal is the value C ..,. The parameters come from the output of block 13.

In block 16 for calculating the concentration of MMA, the concentration of MMA C p is calculated at the output of a cascade of electrolyzers using the formula

С (G о, - м; Се, ц) С д + GA, CQ I (K-M) E2lN / F

RAA

Go - M GM.W + Q / i-

52. N

thirty

where G m - signal flow rate of the feed stream from the sensor 9; C d - signal concentration of MMA from

sensor 7; K - the total number of electrolyzers

in a cascade.

The signal Gr N comes from the output of the block 13, the signals Gq2N, from the outputs 35 of the block 14. The output signal of the block 16, the value C „„ - is fed to the input of the block

g

18 calculate the flow rate of the feed stream.

In the controller of 17 concentrations, the increment of the flow rate of the feed flow is carried out sequentially by the formulas

ACJ - Wed - Sc; 45

BN BH-i DTKrACN / (Ti + DT); UGp + BN, where C is the specified value of the con centration of MMA at the output of the JQ stage, entered into block 17 of Fig. 2;

C C - the value of the concentration of MMA, measured by the sensor 8; 5 value of the integral

component of the regulator block at the Nth and N-1st steps of the block;

E2lN / F

52. N

(one)

D is the period for calculating the increment of the feed stream; K, T- - gain and

constant block time. At the same time, in block 18 of the condition that the calculated concentration of MMA is equal to the specified value C P, the value / flow of the feed flow Gpi GA G0 - M G, .. 1M;

p (b- (K-M) E 2 N-GACA,

 P

ftp + gft -. jK-M) GCT.

C0 - G

The signals GQ, C0, I enter the block input from sensors 10, 6, II, the signal Cft from sensor 7 or is calculated by block 15, the value GQ comes from the output of block 13, and the loop N from the output of block 14, Dr, GA - intermediate calculated variables.

The signals corresponding to the calculation results in blocks 18 and 17 are fed to the adder 19. The output signal of the summation unit 19 is fed to the control valve 12, which accordingly changes the flow rate of the feed flow through the cascade of electrolyzers.

Logic block 20 and block 2 re- | The key includes the unit 15 for calculating the concentration of MMA at the output of the 1st part of the electrolysers between the unreliable signals of concentration of MMA from the sensor 7. In this case, the input of the calculation unit is fed by Ivayushchego flow instead of the signal from sensor 7 through the switch unit receives the calculated concentration value MMA from block 15 output.

To do this, in logic block 20, which is, for example, a double comparator, the following method is checked for reliability of the input signal of MMA concentration Sdot of sensor 7.

If signal C is outside the limits defined by technological conditions, i.e. inequality is violated

SMIN-SA s / saks where Smin, Smvks constant threshold

comparator signals that meet the technological minimum and maximum (

 3%. Clioke 8weight%) at the output of the comparator the signal corresponds to

Logic 1 functions. According to this signal, switching unit 2 connects the output of block 15 to the input of block 18, in which the values of MMA calculated in block 15 are used for the calculation. If the above inequality is not violated, then the signal at the output of the comparator corresponds to 0, while the input of block 18 receives a reliable concentration signal from sensor 7.

Using the proposed method and control system provides the following advantages over existing methods:

allows, by increasing the accuracy of maintaining the required concentration profile, to increase the average electrical conductivity of the solution in the electrolyzers, to prevent the formation of shielding films on the electrodes of the last electrolyzers, thereby reducing the voltage on the cascades. an average of 8-10% and, therefore, to obtain the corresponding gain in energy consumption;

i

by preventing the formation of shielding films on the last electrolyzers, you increase Q

P

25

Jq

Q

45

55

the course of the current LCA and the performance of the cascade;

simplified process flow and easier maintenance of the process.

Claims (2)

1. A method for controlling a continuous electrochemical process for the synthesis of dimethyl ester of sebacic acid in a cascade of successively connected electrolyzers, consisting in feeding the main flow of the source reagent solution and feed flow to the cascade, distributing the feed flow to the cell inputs, measuring the flow rates of these flows, measuring the concentration of the source reagent cascade and adjusting the flow rate of the feed stream according to the measured concentration of the source reagent at the cascade output, characterized in that, in order to reduce electricity costs by improving the accuracy of stabilizing the cascade mode of operation, the current through the cascade and the concentration of the source reagent at the cascade inlet between two are measured the electrolyzers selected and successively standing along the main stream determine the average current yields and gas flow rates for the part of the electrolyzers bounded along the For the rest of the electrolysers, the concentration of monomethyl adipate between the selected electrolyzers and at the cascade output is calculated and the feed flow rate is adjusted using the values of these parameters. 2. A device for controlling a continuous electrochemical process for the synthesis of dimethyl ester of sebacic acid in a cascade of successively connected electrolysers, containing main and feed streams of the initial reagent, sensors for measuring the flow of these streams, a sensor for measuring the concentration of the initial reagent at the output of the cascade, connected to the regulator concentration, and a control valve installed on the feed line, characterized in that, in order to reduce the cost of energy by increasing the accuracy of stabilization of the cascade operation mode and by To improve reliability, it additionally contains concentration sensors of mnomnomethyl adipate at the inlet to the cascade and between electrolyzers, a sensor for measuring the current intensity, current output and gas flow correction units, two units for calculating the concentration of monomethyl adipate, a unit for calculating the feed flow, the unit the summation, the LOGIC block and the switch block, with the first four inputs of the correction blocks connected to the sensors, respectively, of the main flow rate, current measurement and concentration of monomethyl adipate at the inlet to the switch and between the electrolyzers, the second and sixth inputs of the second correction unit are connected to the sensors, respectively, of the feed flow rate and monomethyl adipate concentration at the cascade output, the first three inputs of the monomethyl adipate concentration units are connected to the sensors, respectively, of the monomethyl adipate concentration at the cascade input, current and flow measurements the main flow, the fourth and fifth inputs of the first unit for calculating the concentration of monomethyl adipate are connected to the outputs of the first correction unit, seventh th input of the second correction unit and eighth input of the second calculating unit concentration monometiladipinata connected to the second output of the first correction unit, Thu five 0 0 The second and seventh inputs of the second methadipate concentration calculator are connected respectively (1 monomethyl adipate concentration sensor between the electrolyzers and the feed flow sensor, the first and second outputs of the second correction unit are connected to the fifth and sixth inputs of the second monomethyl adipate concentration unit, the feed calculation unit the flow of eight inputs connected respectively to the sensor for measuring the current, the flow sensor of the main flow and the sensor concentration nomethyl adipate at the cascade inlet, with the output of the second monomethyl adipate concentration calculation unit, with the output of the switching unit, with two outputs of the second correction unit and with the second output of the first correction unit, and its output connected to the first input of the summation unit, the second input of which is connected to the regulator concentration, and the output with the control valve, the input of the logic unit and the second input of the switching unit are connected to the monomethyl diphenate concentration sensor between the electrolyzers, the output of the logic unit is connected the first input of the switching unit, and the third input of the switching unit is connected to the output of the first monomethyl adipate concentration calculating unit.