SU1209675A1 - Automatic control device for process of hydrocarbon dehydration - Google Patents

Description

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The invention relates to means of automatic control of technological processes occurring in a reactor with a fixed or fluidized bed of a catalyst, for example, the oxidative dehydrogenation of I-butane and N-butenes in the production of butadiene, and can be used in the chemical, petrochemical and other industries.

The purpose of the invention is to increase the productivity and explosion safety of the process.

The drawing shows a diagram of the proposed device.

The technological unit for the oxidative dehydrogenation of hydrocarbons includes a superheater furnace 1, a reactor 2 with a fixed or fluidized bed of catalyst, pipelines for inlet and outlet currents. The device contains a raw material consumption regulator 3, a cutter 4, a valve 5 for supplying hydrocarbon raw materials to the furnace, a flow sensor 6, a programmer 7, an oxidizer consumption controller 8, a cutter 9, an oxidizer supply valve 10, and an oxidizer flow sensor 11, block 12 for calculating the ratio of initial reagents and oxidizer consumption, block 13 for calculating the consumption of initial reagents, sensor 14 for raw materials, sensor 15 for oxidizer concentration in waste gases from the reactor, corrector 16, block 17 for determining the rate of change of oxidizer concentration for waste gases, first, second, third and fourth comparators 18-21, first, second, third and fourth setting devices 22-25, OR 26, delay 27 27, dual-position control module 28, inert gas supply valves 30 and 30 and reactor.

The control device can be made using the means of controlling computer technology, for example, using modules from the ASVT-M system nomenclature, as well as on the basis of standard elements of electrical or pneumatic automation.

The production process for the dehydrogenation of hydrocarbons is that the raw material blend pairs containing the initial reagents w-butane

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and -butenes are superheated in the furnace 1, mixed in a stoichiometric ratio with an oxidizing agent and fed to the reactor 2, where in the catalyst bed with

5 at a certain temperature, oxidative dehydrogenation reactions take place, and the reaction gases that form the reaction gases are further directed to cooling, combining and evolving the target gas.

to product. As an oxidizing agent

both air and oxygen-air mixtures with an increased oxygen content can be supplied to the reaction under stacked pressure

15 to 50% by volume.

The device works as follows

When conducting the process in normal mode, the controller 3 according to information

20 from sensor 6 generates control actions on valve actuator 5, in order to stabilize the raw material consumption at a level that is set by the output signal of programmer 7, Regulator B ensures the stabilization of the predetermined ratio between the oxidizer consumption measured by sensor 11 and the initial reagents consumption detected by block 13

30 according to information from sensors 6 and 14. The output control signal of the regulator 8 is formed in accordance with the expression

U (t) U (t-1) + AU (t)

3.:, (1)

yia) to p „° A (t) -F (t), where F, (t) is the given consumption of oxidizer; Fg (t) - oxide consumption 5

K is a positive tuning factor.

The cut-off devices 4 and 9, which receive control pulses from module 28 through the first output channel, are in the open state and pass signals from regulators 3 and 8 to valves 5 and 10 of feeding the raw material to the furnace 1 and oxidant reactor 2.

The value of the task for regulator 8 is calculated by block 1-2 according to information from block 13 and equalizer 1.6 in accordance with the formula

Where

() (t), (t), (2) K - coefficient of stoichios

metric cost ratio;

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AK (t) is the increment of the coefficient 4 (t)

cent cost ratio;

 F |. (i) 21 C; (t) is the value of the consumption of the initial reagents, determined by block 13, moreover, C, (t) is the concentration of the initial reagents in the raw material of N-butane, butene-1, butene-2 (c / s), butene-2 (trans).

The magnitude of the increment of the cost ratio, uK (t) in the formula (2), the corrector 16 periodically determines, depending on both the deviation from the predetermined concentration of oxidant in the gases leaving the reactor and the positive rate of change of the indicated oxidant concentration:

E (t) - & C (t) if dS (s) 0 uK (t).

E (t), if AC (t) iO, (3 where E (t)

a, (t) J is the amount of deviation from the target of the concentration of oxidant measured by sensor 15; AC (t) and c (t) -C (t-1) - rate of change

the concentration of the oxidizing agent, which is determined by block 17; a, and a 2 are positive coefficients selected experimentally.

The concentration of the oxidizing agent C (t) is measured by the sensor 15, and the magnitude of the reference concentration

A unit C is formed by a dial (not shown).

The operation of the two control loops described is based on the fact that the ratio of the oxidant to the initial reagents in the feedstock is related to an approximate proportional relationship with the concentrations of the target product and the unreacted oxidant to waste gas, and the proposed correction for the regulator 8 compensates for low-frequency disturbances (such as change in catalyst properties, pressure,

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temperatures, etc.) affecting the nature of this relationship.

As a result of an unforeseen process flow, it is possible that the oxidizer content in the reaction gases will increase and an explosive mixture will form in the process equipment (in the compression and subsequent rectification themes). Therefore, in order to detect and eliminate the dangerous pre-emergency deviation of process parameters from the regulatory norms, the output signals of sensors 11 and 15 and blocks 13 and 17 are fed to the input of comparators 18-21. The comparators compare the current values of the initial reagent and oxidizer consumption, the concentration of oxidant, as well as the rate of change of the concentration of the oxidizing agent with their permissible values, which are set using the setting devices 22-25. If at least one of the specified parameters of the pre-emergency level is reached, the corresponding comp The actor issues a command signal to the input of the OR 26 element, which implements the logic addition function and is connected to the module 28 by the output. The last signal on the first output channel is a signal for closing the cutters 4 and 9, and for the second output channel is a signal for opening the valves 29 and 30, which causes cessation of feed and oxidant supply through valves 5 and 10, the start of supplying inert gas under stabilized pressure to the pipelines for raw materials and oxidizer, and putting the process into a safe state.

After elimination of the pre-emergency situation, the concentration of the oxidizer in the exhaust gases decreases to the norm, which is determined by the signal from the inverse output of the comparator 20 connected to the input of the element 27, which after a predetermined delay time causes the command signal to the second input of the module 28. the first and second output channels provide signals for closing the valves 29 and 30 on the supply of inert gas, opening the slam-shutters 4 and 9, which unblock the control channels from the controller 3 to the valve 5 and from the controller 8 to the valve 10. Simultaneously In this case, the programmer 7 begins to melt in accordance with a given program.

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but increase the task for the controller 3 consumption of raw materials to a set value, also increase the consumption of oxidant using controller 8 in a stoichiometric ratio with the consumption of initial reagents in SF and, after putting the process on the mode, the ratio of the specified cost ratio is adjusted using the output signal of the 16 V unit according to addiction (3).

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The use of the proposed device makes it possible to increase the production of the target product by an average of 1j, 5% and thereby reduce the specific consumption of raw materials from 1.225 to 1.21 t / t. Implementing the device also improves the safety conditions of production by detecting earlier and preventing 10 emergency operation, increasing the reliability of protection.

VNIIPI Order 460/32 Circulation 379 Subscription Affiliate GOSh Patent, Uzhgorod, Proektna St., 4

Claims (1)

DEVICE FOR AUTOMATIC CONTROL OF THE PROCESS OF HYDROCARBON HYDROCARBONS, containing circuits for regulating the flow of raw materials into the furnace and oxidizer into the reactor, consisting of series-connected flow sensors, a regulator, a shut-off valve and a valve, a unit for calculating the flow of initial reagents, the first and second inputs of which are connected to flow sensors and the composition of the feedstock, and the output is connected in parallel to the first inputs of the first comparator and the unit for calculating the ratio of the flow rates of the initial components and the oxidizing agent, the first inputs of the second and three the five comparators are connected respectively to the sensors of the oxidizer flow rate and its concentration in the gases leaving the reactor, the second inputs of the first, second, and third comparators are connected to their setpoints, and the outputs of the comparators are connected to the first, second, and third inputs of the OR element, connected by its output to the first the input of the on-off control module, the first output of which is connected in parallel to the input of the programmer and to the cutoffs of the consumption of raw materials and oxidizer, and the second output is connected to the gate valves and inert gas to the furnace and reactor, the output of the programmer is connected to the second input of the feedstock flow regulator, the output of the unit for calculating the ratio of the costs of the starting components and feedstock is connected to the second input of the oxidizer flow controller, the second output of the third comparator through the delay element is connected to the second input of the on-off control module, characterized in that, in order to increase the productivity and explosion safety of the process, it further comprises a corrector, a unit for determining the rate of change in the concentration of oxides in the exhaust gases from the reactor and a fourth comparator with a setter, while the oxidizer concentration sensor in the exhaust gases from the reactor is also connected in parallel to the first input of the corrector and to the input of the unit for determining the rate of change of the oxidizer concentration in the exhaust gases from the reactor, the output of which is connected in parallel with the second the input of the corrector and the first input of the fourth comparator connected by its second input to its master, and the output to the fourth input of the OR element, the output of the corrector is connected to the second input unit for calculating the ratio of the costs of the starting components and the oxidizing agent. SU „.1209675