SU1257069A1 - Method of control of hydrocarbon dehydrogenation process - Google Patents

Description

The invention relates to the automation of cyclic reaction processes of chemical-technological production, in particular the production of isoprene and divinyl, and may be unused in the chemical, petrochemical and other industrial sectors.

The purpose of the invention is to reduce the consumption of energy and energy resources.

FIG. 1 is a schematic diagram of a process control system; in fig. 2 - cyclogram of the process

The dehydrogenation process is carried out in reactors 1 and 2 with a fixed catalyst bed, switched by logic machine 3 alternately with -contacting for regeneration and back (in the diagram, reactor 1 nor is shown during the contacting period, and reactor 2 is regenerated). The duration of the full cycle is 15-20 minutes. The raw material is fed to the reactor in a mixture with steam after heating in the furnace 4. During regeneration, air is mixed into the reactor with a mixture of steam to release the coke that is deposited during the contact.

The process control system includes (Fig. 1) a flow controller 5 with a sensor 6, a steam controller 7 for a furnace with a sensor 8, a fuel gas pressure regulator 9 for a furnace with a valve 10, a sensor 11 for regeneration air, 12 consumption of regeneration gas, sensor 13, steam temperature at the outlet of the furnace, air supply valve 14 and fuel gas supply valves 15. The diagram also shows the functional blocks: air flow control unit 16, program change unit 17, per unit air flow rate, steam temperature control unit 18

during the furnace, block 19 of the fuel gas pressure correction unit, block 20 for determining the flow rate of steam for contacting, block 21 for adjusting the ratio of the flow rate into the furnace and steam for contacting and block 22 for synchronizing the listed functional blocks are implemented in the control calculator ( UVM) 23. The method is carried out as follows

in a way.

Using regulators 5 and 7, they regulate the consumption of raw materials and steam, respectively, fed through furnace 4 to reactors 1 and 2.

s - 0 5

about

0

Using the measuring unit 16 from the sensor 11, the air flow is controlled by the impact on the oriental 14. In connection with the presence of discontinuous disturbances due to air pressure, the 1SD-law of regulation is used. During the regeneration interval of each cycle, the setpoint for air flow is changed using block 17, for example, according to the following program: linear flow increase from zero to nominal value with a speed that ensures output to the nominal no faster than 1 min and subsequent stabilization (Fig. 2 ).

FIG. 2 the dotted line shows the air supply at the beginning of the regeneration interval by a known method.

Using the unit 18, implemented in UVM 23, adjust the steam temperature according to information from the sensor 13 by simultaneously acting on the valves 15. Using the regulator 9, regulate the pressure of the fuel gas on the furnace by acting on the valve 10 installed on the common supply line of the fuel gas to the furnace. Periodically (with an interval t) with the help of block 19, the task of the controller 9 is adjusted, for example, according to the following law:

MMN ipx

Oh if

f. (BOS | KS

 oh if x and

-b if and (1)

where dR is the value of the job setting

by pressure in one step; and - the current position of the valve 15, determined by the magnitude of the control signal on them;

S

five

iax

and

and - maximum and minimum

permissible valve position 15.

The value of T is chosen so that it exceeds the duration of the transient processes in the furnace CL O-ZO min).

The valves 15 use bypass flows, which improves accuracy, and at the same time narrows the control scale. Correction (1) of the fuel gas pressure at the exit of the valves 15 to the permissible limits is a coarse adjustment for expanding the scale,

The steam, superheated in furnace 4, to a temperature of about, is distributed between reactors 1 and 2. Because of .ft.

The presence of valves, operating reliably at the indicated temperature, is carried out by the ratio of the resistances of the contact gas lines and the regeneration gas. Due to the absence of flow meters that operate reliably at the specified temperature, the steam consumption for contacting is determined from the material balance using block 20 as follows

G, .. Gj- (G..p -G,), (2) where G is the steam consumption per furnace, determined from information from sensor 8;

regeneration gas flow rate determined from information from sensor 12;

Gg is the air flow determined from information from sensor 11. With the help of block 21, the ratio of the consumption of raw materials, determined by information from sensor 6, and steam consumption, determined by formula (2), is adjusted.

Using unit 22, synchronization of the operation of the CCM 23 with the cyclical nature of the operation of the reactors is carried out by analyzing the signal of the beginning of the cycle from the logical machine 3, the main function of which is to realize the cyclical nature of the operation of the reactors according to a given time program. It has a timer that reads the time from the beginning to the end of the cycle, then the time of the next cycle, etc. (for example, a cycle duration of 16 minutes). At specified times, logic machine 3 opens or closes the corresponding gate valves.

Thus, at the beginning of the cycle of the reactor 1 (Fig. 2), the valves shown open in Fig. 2 open. 1 and at the same time, the valves shown in FIG. 1 closed. After 8 min

those. after 1/2 cycle, the reverse is done: open valves close, and closed valves open. After another 8 min, the process is repeated, etc.

In addition to this basic function, logic machine 3 performs some logical operations related to the explosion hazard of production. In particular, monitoring and blocking the simultaneous opening of certain valves is carried out. For example, it is not allowed to simultaneously feed and feed to one reactor.

Block 22 receives a signal from the timer of block 3 and records the moments of the beginning of cycles of the 1st and 2nd reactors. The implementation of time programs within cycles for controlling, in particular, the air supply is carried out with the aid of a computer having its own timer. Such synchronization is necessary because of the errors of the timers of block 3 and the computer.

The limited air supply at the beginning of regeneration reduces its total amount during the regeneration interval (fuel gas saving) reduces catalyst over-oxidation and eliminates its overheating due to overflow (economy). The two-stage steam temperature control improves the quality of maintaining the desired temperature of the process (save). The use of indirect metering of steam for contacting increases the quality of regulation of the ratio of raw material and steam consumption (economy of steam). The use of the control method in the production of isoprene reduces the expenditure coefficients for the main raw material (isopentane), steam and fuel gas.

"XMZoMizht is open

Zodbizhko

closed Shz regeneration

Raw material consumption

Consumption

raw material br-p1

Consumption

couple

6p-p1

Consumption

couple

6p p2

So3dyxa dr-p1 consumption

Consumption,

bozdha

6p-p2.

ABOUT

Compiled by G.Ogadzhanov Editor T.Parfenova Tehred L.Serdyukova Corrector T.Kolb

Order 4880/19 Circulation 379Subscription

VNIIPI USSR State Committee

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

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

fpuz.2

Claims (1)

METHOD FOR CONTROLLING A HYDROCARBON HYDROGENING PROCESS, carried out in a two-reactor system of cyclic action, by adjusting the ratio of the feed to the furnace by changing the steam flow rate, the steam temperature at the furnace outlet by changing the fuel gas supply to the furnace burners and the air flow rate for regeneration, characterized in that, with in order to reduce the consumption of raw materials and energy resources, additionally measure the flow rate of regeneration gas and the pressure of the fuel gas in the furnace, change the air flow rate from zero to rear at a given speed value at the beginning of the regeneration interval of each cycle, regulate the pressure of the fuel gas in the furnace with a correction for the consumption of fuel gas in the burner of the furnace, determine the flow rate of steam for contacting the flow rates of steam in the furnace, air for regeneration and regeneration gas and adjust the ratio of the flow of raw materials to steam in furnace depending on the steam flow for contacting.