SU1430391A1 - Method of controlling the process of oxidative dehydrogenation of hydrocarbons - Google Patents

Abstract

The invention relates to the automation of reactive catalytic processes of chemical technological productions, in particular the production of divinyl, coins used in the chemical and petrochemical industries and allows for an increase in output J. target product. The control circuit contains reactor 1, furnace 2, sensors (D) 3,4,5 of raw materials consumption, air and oxygen, oxygen content analyzer in oxygen-air mixture, D-7-10 temperature above the catalyst bed, top of the catalyst bed, height of the catalyst bed , the bottom layer of the catalyst, the regulators (P) 11-14 of the air flow rate, oxygen, raw materials and steam, the P 15 temperature above the catalyst bed, and the blocks (B) 17.18 correct the oxygen supply and temperature above the catalyst bed, K 19 maximum temperature difference. The method allows to control the ratio of raw material consumption and the amount of oxygen supplied, and the supply of fuel gas, depending on the temperature above the catalyst bed and the height of the catalyst zone with the maximum temperature difference. 2 Il. w (L 4 bo o co with

Description

This invention relates to the automation of reactive catalysts for catalytic processes in chemical technological processes, in particular the production of divinyl, and can be used in the chemical, petrochemical, and other related industries.

The purpose of the invention is to increase the output and the target product.

Fig. 1 is a schematic diagram of a process control system implementing the proposed method; Fig. 2 illustrates the variation in the temperature profile of the catalyst bed in the dehydrogenation cycle.

The process of oxidative dehydrogenation is carried out in the reactor 1 (Fig. 1) with a fixed catalyst bed. Raw materials are fed to the reactor simultaneously with water and steam after overheating in furnace 2. In addition, oxygen-containing gas (a mixture of air and technically pure oxygen) is fed into the reactor.

The process control system includes sensors 3-5 for raw material consumption, air and oxygen, respectively, analyzer for oxygen content in the oxygen-air mixture, sensor 7 for temperature above the catalyst layer sensor 8 for the temperature of the upper catalyst layer, sensors 9 for the height of the catalyst bed, sensor 10 for the bottom temperature catalyst layer regulators 11-14 of air, oxygen, raw materials and steam consumption, respectively, into the reactor, temperature controller 15 above the catalyst bed. The diagram also shows the functional blocks implemented in UVM 16: block 17 for adjusting oxygen supply to the reactor, block 18 for correcting temperature above the catalyst bed, block 19 for determining the maximum value of the temperature difference, and blocks 20 for determining the temperature difference.

The method is carried out as follows.

Regulators 11-14 are used to regulate the flow rates of air, oxygen, raw materials and steam, respectively, to reactor 1. Using controller 15, the measurement from sensor 7 regulates the temperature T over 55 catalyst bed in reactor 1 by affecting the fuel supply gas in a superheater 2.

35

40

l- 45

Q

15

20 25

zo 0 5

five

0

five

With the help of block 17, implemented in UVM 16, the corrective task of the controller 12, for example, according to the rai-law

li +. (one)

In this case, as the control error, use the following value

e - Cjr / (2)

where G is the consumption of raw materials, measured by

using sensor 3; (- oxygen consumption measured by sensor 5; С - air consumption measured

using sensor 4; C is the concentration of oxygen measured by sensor 6.

In this way, the oxygen-oxidizing agent is fed into the reactor in a predetermined ratio with the raw material consumption. With blocks 20, temperature differences are determined by zones of the catalyst bed as follows.

The catalyst layer is divided into zones (in this example, 4 zones are allocated - A, B, C and D), sensors 9 are installed at the boundaries of zones i, and sensors 8 and 10 are placed in the upper and lower parts of the layer, respectively. Temperature differences are determined between adjacent sensors.

The number of zones in the bed is selected depending on its height, diameter of the reactor, properties of a particular catalyst batch and other technological factors determining the nature of the change in temperature profiles across the catalyst bed in the dehydrogenation cycle (see fig.2). At that, they use the peculiarity of the process that the main share of raw material conversion during oxidative dehydrogenation is carried out on a small portion of the catalyst bed, and this portion is shifted from top to bottom in the dehydrogenation working cycle (curve 1 corresponds to the beginning of the working cycle, curve 2 - its middle, curve 3 - the second half of the cycle).

Using block 19, a zone with a maximum temperature difference i.e. the zone in which the site with the highest conversion.

31A3039I4

Using block 18 corrects as a result of C, 2373 .4t) 2613,

setting a controller 15, for example, according to a linear law

C. Concentration is equal to 0.492, and the regulation error

T,

(3)

where n is the number (starting from the top of the layer) of the zone with the maximum temperature difference; JQ

 - coefficient.

At the beginning of the working cycle (curve G in FIG. 2), the section with the highest conversion is located in the upper part of the layer (zone A), and therefore the differential temperature in this zone is maximum

DT, max ,, (4)

20

During the work cycle, the area with the highest conversion is shifted to subsequent zones. For curve 2

IT, t7 max fir ;, t1,25 (5)

but for curve 3

M; max DT; - & T,

uTj, ltp (6)

Example. Consider the following technological regime: G 5600. m / 435 G 4700. G, 2373 m / h with a content of 0 100%, with 0.475 (in units of units x); ot 0.6.

I

The calculated adjustment error by Q expression (2) is equal to

5 0.6-3600 - O, 475- (4700 + -I- 2373) О

Let us assume that the consumption of raw materials increased stepwise and became equal to 6000 m / h. The regulation error in expression (2) takes the value

e 0, - 0.475- (4700 + 2373) 240

Block 17, in the case of the P-law of regulation, increases the consumption of technical oxygen by an amount (we take

TO

P

you to 240

as a result of C, 2373 .4t) 2613,

Q

five

0

five

0

five

Q

five

0

five

the concentration of C. is equal to 0.492, and the regulation error

  0.6 "6000 - 0.492 (4700 + 2613) i О

The temperature change of the dehydrogenation is carried out, for example, as follows.

The initial value of the temperature TD 350 ° C, a factor of 5.

In the considered example, 4 zones are allocated - A, B, C, D with numbers from O to 3 (zone A - n O, zone B - n 1, etc.).

at the beginning of the operating cycle, the temperature above the catalyst bed

T Td - f bp 350 5-0 3504.

At transition of the maximum temperature difference to the zone B

  T + | 3p 350 + 5-1 355 С

Using the proposed control method allows to increase the yield of the target product and thereby reduce the expenditure ratio of the main raw material (n-butylene) by 0.3 rel.%.

Claims (1)

Invention Formula A method for controlling the oxidative dehydrogenation of hydrocarbons, including controlling the supply of raw materials and steam to the superheater, oxygen and air into the reactor, temperatures above the catalyst bed of the reactor, changing the supply of fuel gas to the superheating furnace and measuring the temperature profile in the reactor along the height of the catalyst bed, By the fact that, in order to increase the yield of the target product, the oxygen content in the oxygen-air mixture at the reactor inlet is measured, ur on catalyst zones and height of the catalyst zone with a maximum temperature difference, on the flow of air and oxygen into the reactor and the oxygen content in the oxygen-air mixture, calculate the amount of oxygen fed to the reactor, regulate the ratio of raw material consumption to the furnace and the calculated amount of oxygen by changing filing oxygen into the reactor, and the flow of fuel gas into the furnace is adjusted depending on the height of the catalyst zone with the maximum temperature difference. Temperature 3offaA ZomaV Zone C) FIG. 2  r / tySuffa layer f afTfa / ttisofrTO / ffa