SU1235515A1 - Apparatus for automatic controlling of extraction rectification - Google Patents

Description

The invention relates to the automatic control of the process of extractive rectification and may find application, for example, in the production of butadiene from butane, in the chemical, petrochemical, and other industries.

The purpose of the invention is to improve the quality of the separation products and reduce energy consumption.

The drawing shows a schematic diagram of the device.

The device for automatic control of the extractive distillation process includes a column 1, a sensor 2 of the extractant flow, which is connected via controller 3 to the column 4 of the extractant supply to the column, temperature sensors 5 of the extractant, pressure 6 of the top of the column and composition 7 of the raw material, 8 consumption The sensor that connects the temperature sensor 1t to the bottom of the column through the regulator 9 is connected to the valve 10 to supply the raw material to the column through the regulator 12 to the valve 13 to feed the heat flow. In addition, the device contains flow sensors 14 for external reflux, composition 15 of distillate and bottom product 16, flow sensor 17 for distribution connected via regulator 18 to the valve

19 selecting the distillate, compressor 20 of the unit 21 for adjusting the internal flare number and degree of saturation of the extractant 21, unit 22 for controlling the flow rate of the distillate, the calculation unit 23 for setting the extractant flow controller and the corrective unit 24.

The device works as follows.

When changing the task of regulating the consumption of raw materials or the composition of the raw materials supplied to column 1, in the switch

20: One of the following conditions is checked.

one, ,

14 - с1 SC ,,

Gf,, Gp. - the current and previous values of the task flow regulator sy- "Rb 9

Wed Gf. - current to the previous value of the concentration of the light component in the composition of the raw material S measure 5e ssyej sensor 7 {

h Gj. , SCp - ranges of sensitivity to changes in consumption and composition of raw materials.

In case one of the conditions (1) is fulfilled, the switch 20 excludes the signal to the flow control unit 22. In block 22, a signal from the switch 20 and information from the sensor 7 and the controller 9 calculates a new reference value to the controller 18 for the distillate consumption. The value of Cd is found when solving the system of equations of the competent material-balance

ft rA rA

C g - Cgch 1, C F, JJ, ZAf

p T

C ,. C ,, C „. . With „,, (2)

g

Gp. ---- i; - - -,

 "T" l "

y-y-y

317, gd. wieA A

(3)

where cf. - the current value of the concentration of the heavy component in the J raw material;

C Rl, given concentrations of lung and heavy components In distillate;

H eA given concentrations of light and heavy components in the bottom product; estimated flow

 w;

vat product.

If conditions (1) are not fulfilled, the switch 20 provides the signal to the trimming unit 21, and the signal to the unit 22 becomes zero. The new value of the task is to control the flow rate distiller Au. not calculated

4fi

 -at;

at;-,)

(four)

5CS

S

where gj - the previous value of the task for the consumption of distillate.

The device uses the concepts of internal phlegm, internal reflux number and degree of nasiacene extractant. The amount of internal reflux is determined from the following expression

R

,

- H

 K, K, C,),

(five)

31235515

p p where Sc,, Gg. - calculated value

the flow rate of the external phlegm and the calculated value of assigning the flow controller to the extras agent 3;

- the current value of the temperature of the extractant, measured by the sensor 5; R

K ,, K2 pos ent

The value of the internal number is determined by

s;

G ,, - -5-

The degree of saturation of the nose is determined and

TO

May

 iblGiL ± -Gi: j cb b (()

J

where p „- is the current pressure value

When condition (10) is fulfilled in the block top of the column, measured 5 ke 21, the adjustment is performed by means of a step 6j

neither extractant saturation

K, K,

K, K, Ku - constant coefficients. K „dr

At the beginning of the operation of the proposed device, the values of R and K. are assumed to be 20 where is a constant coefficient.

 To „„, + K, (Cv ,. - С)

If conditions (9) and (10) do not fit, then adjustment P is not performed. The signal on the value of Rdn and Cd from block 21 enters into the calculated block 23. In block 23, the formation of sensors 6 and 7 and block 21 and 22 determines the new values of the external reflux flow rate and set the extractant flow controller G

are equal

R

vit

Vng

V to

Us - us

where r

Int.

K., „, initial values

NA | C

defined as average values

vnt nvs

If conditions (9) and (10) do not fit, then adjustment P is not performed. The signal on the value of Rdn and Cd from block 21 enters into the calculated block 23. In block 23, the formation of sensors 6 and 7 and block 21 and 22 determines the new values of the external reflux flow rate and set the extractant flow controller G

working ranges of zo when solving equations together

changes in consumption and composition of raw materials.

Moreover, the RBHT value is adjusted when the device is operated with the aim of

(5), (6) and (7). This solution allows you to simultaneously maintain the specified values of P. and Cc. . Signal of

the design value of the assignment for distilling the distillate of a given extractor Gg; It is put on the slide, and the value of Scr is in order to change the value of the relative volatility of the light component and, consequently, to obtain a cubic basis of a product of a given composition.

Block 21 adjusts the signal from the switch 20 and the information from sensors 15 and 16 to analyze the deviations of the concentrations of the heavy component in the distillate cL and the light component in the bottoms

Hi «„

Cw product; from given values / Ci; - C, ate / SCi, j (9)

40

AS

giving the input to the regulator 3, and the signal about the calculated value of the flow rate of external reflux GPI goes to the correction unit 24.

In block 24 of information from sensors 11, 14, 17 and blocks 22 and 23, the value of the setting of temperature controller 12 in the cube of the column is adjusted.

tKi tKj./ K, o (vf - V;), (13) where t., C. - corrected and previous value of the reference: neither regulator 12;

/ Ci; - Cw,

where SCjj, 8c is the tolerance. Under conditions (9) in block 21, the internal reflux number is adjusted

vit

Int.

 V4 -.d).

where Kg is a constant coefficient.

K ,, K2 constant coefficients.

The value of the internal reflux ratio is determined from the ratio

G ,, - -5-

(6)

The degree of saturation of the extractant nose is determined from the expression

(7)

When the condition is met 21

neither extractant saturation

 constant coefficient.

 K „„, + K, (Cv ,. - С), (12)

20 where is a constant coefficient.

25

If conditions (9) and (10) are not satisfied, then adjustment P is not performed. The signal on the values of Rdn and Ktsd from block 21 enters the calculated block 23. In block 23, according to information from sensors 6 and 7 and blocks 21 and 22, new values of external reflux flow rate and assignment of the extractant flow controller are determined when the equations are solved together

(5), (6) and (7). This solution allows you to simultaneously maintain the specified values of P. and Cc. . Signal of

40

AS

50

. giving the input to the regulator 3, and the signal about the calculated value of the flow rate of external reflux GPI goes to the correction unit 24.

In block 24 of information from sensors 11, 14, 17 and blocks 22 and 23, the value of the setting of temperature controller 12 in the cube of the column is adjusted.

tKi tKj./ K, o (vf - V;), (13) where t., C. - corrected and previous value of the reference: neither regulator 12;

- new calculated value of the vapor flow in the reinforcing part of the column; + GDJ, (14)

v

v

-R;

55 where V; - the current value of the vapor flow in the fortifying part

columns

 “;

+ G

Bj

(15)

where is gij. , Gj). - current values of external reflux consumption and distillate consumption, measured by sensors 14 and 15 |

Ksch - constant coefficient Signal of the corrected value of the air temperature setpoint 1etc on the master input of the temperature controller 12.

In contrast to the known device, the control according to the proposed construction is designed so that, by simultaneously using expressions (5), (6) and (7), the control of the composition of the distillate and the bottom product, i.e. When controlling for the deviation of the composition of one of the products from a predetermined value, account is taken of the in-system connections of the process described by expressions (5), (6), (7), and the validity of the control actions is determined so as not to change the composition of the other . Since the role of the extractant in extractive distillation is mainly reduced to a change in the relative volatility of the components of the mixture being separated, expressions (5), (6) and (7) allow to calculate such a value that would maintain in accordance with the required concentration of hydrocarbons in the extractant, taking into account the effect on the solubility of the latter

pressure in the column P. and the temperature of the extractant, thereby providing the necessary value of the relative volatility of the light component to obtain the desired composition of the bottom product. At the same time, from expressions (5) (6) and (7), it is possible to determine the value pf for obtaining a given distillate composition. The calculation is made taking into account the effect on the composition of the distillate on the flow rate Ggj and the temperature tgj of the extractant as additional reflux. In addition, by changing steam flow V; In block 24, the setting of the temperature regulator in the bottom of the column is corrected.

Compensation of disturbances in the composition and consumption of raw materials is provided by the operation of the distillate flow control unit 22, the calculated 23 and the corrective 24 blocks.

Thus, in this device, always with changes in the composition and consumption of large-scale sensitivity ranges and changes in compositions. Cystylla and cubic product of large permissible deviations, the calculation of all three control actions is performed - setting the extractant flow controller Gg-, setting the distillate flow controller and setting the temperature controller in the cube

columns t | ,; .

Extrageit

9 leaves

Editor S.Patrusheva

Compiled by T.Chuykova

Tehred O. Sopko Proofreader M. Samborska

Order 3031/3 Circulation 663. Subscription 6NIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Rauiyuka nab., d.4 / 5

Production and printing company, Uzhgorod, Projecto st., 4

Claims (1)

DEVICE FOR AUTOMATIC CONTROL OF THE EXTRACTIVE RECTIFICATION PROCESS, containing flow sensors and composition of raw materials, a sensor and an extractant flow controller, an extractant temperature sensor, a column temperature sensor and temperature regulator, an external reflux flow sensor, a column top pressure sensor, a switch and a correction unit, characterized in that, in order to improve the quality of separation products and reduce energy consumption, it additionally contains a sensor and a distillate flow controller, a distillate composition sensor, a state sensor Ava bottled product, raw material consumption regulator, unit for adjusting the internal reflux ratio and degree of extractant saturation, calculation unit for setting the extractant consumption regulator and distillate consumption control unit, connected by inputs to the raw material composition sensor, setting input of the raw material flow regulator and the first output of the switch, and the output with a master input for the distillate flow controller, inputs of the correction unit and the calculation unit connected by inputs to the sensors of the composition of the raw material, extractant temperature, column top pressure s and the output of the adjustment unit, and the outputs with the input of the regulator of the extractant flow rate and with the correction unit connected to the inputs of the temperature sensors in the cube of the column, the flow rate of the external phlegm and the flow rate of the distillate, and the output with the input of the temperature controller in the cube of the column, at This switch inputs connected to the composition sensor and the master input of the flow controller, and the input adjustment block is connected to the second output of the switch and the composition sensors of the distillate and bottoms product.