RU2509089C2 - Method of controlling polymerisation process when producing butyl rubber - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method is carried out via copolymerisation of isoprene and isobutylene in a reactor in an inert solvent in the presence of a catalyst. The method involves loops for controlling flow of the mixture, catalyst, a stopper, liquid and gaseous ethylene. An automatic reactor launch subsystem is used in addition to the control system in operating mode. This operation is carried out in two steps, the first of which involves transitioning the control object to operating temperature, which is carried out either only using the catalyst flow control channel or with further use of the ethylene pressure control channel. The control device is a certain regulator. The second step involves switching to the operating point of the process parameter space, which is carried out by switching the ethylene pressure release loop to a nominal value.

EFFECT: high efficiency of the polymerisation section, reduced consumption of material and energy resources and safer production.

2 dwg

Description

The invention relates to the field of automation of technological processes for the production of synthetic rubber and can be used in the production of butyl rubber.

A known method of controlling the production of butyl rubber obtained by copolymerization of isoprene and isobutylene in an inert solvent in the presence of a catalyst, carried out in an installation comprising a mixer, refrigerator, reactor, degasser, which are interconnected by pipelines using control loops consisting of isoprene flow sensors, control valves, , isobutylene, an inert solvent, a mixture, a catalyst, the level and flow rate of the refrigerant to the refrigerator and to the reactor and steam to the degasser, temperature sensors s and a concentration of the charge, the temperature in the reactor and degassing connected to controllers correction isoprene costs isobutylene, inert solvent, and refrigerant vapor [RF patent 2310666, IPC S08F 210/12, S08S 19/14, 8/22 S08F, Bul. 32, 2007].

A disadvantage of the known control method is the lack of a subsystem for automatically starting the polymerization unit, which entails a loss in equipment productivity due to the untimely change of one reactor to another.

A known method of controlling the process of synthesis of butyl rubber, carried out in an inert solvent in a reactor with a stirrer. The copolymerization of monomers (isoprene and isobutylene) is carried out in the presence of a catalyst, the charge and catalyst consumption are regulated, the temperature in the reaction zone is measured, the Mooney viscosity is determined by calculation, and the lower drive parameter of the mixer is also determined [RF patent 2046126, IPC С08С 2/06 G05D 27/00 bull. 29, 1993].

The disadvantage of this method is that it does not provide for automatic start of the polymerization device, which increases the start time and thereby reduces the productivity of the equipment.

A known method of controlling the production of butyl rubber during the copolymerization of isoprene and isobutylene in an inert solvent in a batch mixer, a refrigerator, reactors and a degasser using control loops consisting of sensor controllers, charge flow valves, catalyst, isoprene, isobutylene, an inert solvent, steam, temperature sensors and the concentration of the mixture, the temperature in the reactors and degassers, the level and flow rate of ethylene connected to the controllers. When controlling processes, the concentration and temperature in the reactors and degassers are set and the flow rates of ethylene, isoprene, and steam are adjusted by the action of the corresponding valves [RF patent 2223284, C08F 210/12, G05D 27/00, 2004].

The disadvantage of this method is that it does not take into account all the disturbing influences that impede the process of starting the polymerizer, which reduces the safety of production.

The closest technical solution to the present invention is a method for controlling the process of producing butyl rubber in a reactor in the presence of a catalyst, a mixture consisting of isobutylene and isoprene in an inert solvent, including charge and catalyst flow control loops, Mooney polymer temperature sensors, and lower mixer parameters in a reactor with the additional use of a mixer of charge components, isobutylene, isoprene, inert solvent flow control loops and ovnya ethylene top drive parameter and the batch temperature sensors in the reactor agitator [RF patent 2209817 C1, C08F 210/12, G05D 27/00, 2002 g.].

A disadvantage of the known control method is the low productivity of the equipment and the low level of personnel safety due to manual start-up of the equipment.

The aim of the invention is to increase the productivity of the polymerization department, reduce the cost of material and energy resources, as well as increase the level of safety.

This technical result is achieved by the fact that in a method for controlling the process of producing butyl rubber by copolymerizing isoprene and isobutylene in an inert solvent in a reactor in the presence of a catalyst, including the charge control circuits of a charge, catalyst, stopper, liquid and gaseous ethylene, according to the invention, in addition to a control system in a working the mode uses the automatic start-up subsystem of the reactor, which performs this operation in two stages, the first of which is the output of the control object to operating temperature, carried out either by using the control channel for the flow of catalyst, or with the additional use of the control channel for ethylene pressure, while the control device is a fuzzy controller, and the second is the access to the working point of the space of technological parameters, which is realized by connecting the ethylene pressure output circuit to nominal value.

In the proposed method, due to the start-up process in the automatic mode, the start-up time of the reactor corresponds to the value provided for by the regulation, since it eliminates operator errors. Thus, the productivity of equipment is increased and the safety of production is increased by reducing the influence of the human factor.

The essence of the invention is illustrated in the drawing, which shows a functional diagram of a control system that implements this method (Fig. 1.). A device that determines the completion of the first stage of the start-up process and connects the ethylene pressure output circuit to the nominal value is illustrated in FIG.

The following devices are shown on the functional diagram: a polymerization unit 1, equipped with a mixer 2 with a lower drive, an inverted cup type heat sink with double walls 3 and a cooling jacket (jacket) 4, a series of heat exchangers 5, a refrigerator 6, three separators 7-9 and a mixer 10 All technological objects are interconnected by pipelines.

The mixture entering the reactor is pre-cooled. This is done by passing the charge through a series of heat exchangers 5, in which the cooling agent is the polymerizate coming from the reactor, as well as by cooling it in the refrigerator 6, in which liquid ethylene is the cooling agent.

The mixture and the catalyst enter the polymerization unit 1. The copolymerization reaction proceeds with the release of a large amount of heat, as a result of which it is carried out at low temperatures. The polymerization is cooled by feeding liquid ethylene into the jacket 4 and into the glass 3 of the polymerization. The spent ethylene enters the separators 7-9 to separate it into liquid and gaseous fractions.

To stop the reaction, a stopper solution is added to the polymerizate exiting the reactor. This procedure is carried out in the mixer 10.

The polymerization control system includes:

- a loop for regulating the pressure of gaseous ethylene (a glass and a polymerization jacket) 11;

- temperature control loop in the polymerizer 12 and / or 13;

- a control loop for the level of liquid ethylene in the separator (glass) 14;

- a control loop for the level of liquid ethylene in the separator (shirt) 15;

- control loop flow stopper 16;

- contour of the flow rate of the charge 17;

- pressure regulation loop of gaseous ethylene (refrigerator) 18;

- a control loop for the level of liquid ethylene in the separator (refrigerator) 19.

In addition, the control system includes control loops:

- flow rate of ethylene gas (20, 21);

- temperature of gaseous ethylene (22, 23);

- drive power of the scraper mechanism (24);

- the temperature of the polymerizate at the outlet of the reactor (25);

- charge pressure (26);

- the temperature of the polymerizate after the mixer (27);

- the temperature of the polymerizate after heat exchangers (28);

- charge temperature after heat exchangers (29);

- temperature of the bottom of the polymerization agent (30);

- charge pressure after the refrigerator (31);

- temperature of the charge after the refrigerator (32);

- drive power of the mixer (33);

- catalyst consumption (34).

The process control in the operating mode according to the proposed method is as follows:

- set the charge rate using the circuit 17;

- control the charge pressure (26);

- the charge is passed through a series of heat exchangers 5 and its temperature is controlled (29);

- the cooled charge is chilled in the refrigerator 6 and its pressure (31) and temperature (32) are controlled at the outlet;

- the charge mixture is cooled with liquid ethylene, the flow rate of which is regulated by the level in the separator-separator 8 using the circuit 19;

- regulate the pressure of gaseous ethylene after the separator-separator 8 using the circuit 18;

- regulate the temperature in the polymerization unit by the flow of the catalyst using circuit 12;

- control the temperature of the polymerizate exiting the reactor (25);

- to terminate the reaction, the polymerizate is mixed with a stopper solution using its flow control loop 16;

- control the temperature of the polymerizate exiting the mixer (27);

- control the temperature of the polymerizate after heat exchangers (28);

- the flow rate of liquid ethylene in the shirt and the glass of the polymerizer is regulated by the level in the separators-separators 7, 9 using the circuits 15 and 14, respectively;

- regulate the pressure of gaseous ethylene after separators-separators 7, 9, using circuit 11.

The control of the polymerization process at the start-up stage according to the proposed method is as follows:

- in a reactor pre-cooled to a temperature of -95 ° C, a charge is fed, the flow rate of which is controlled in accordance with the technological process regulations (circuit 17);

- start up of the reactor is carried out in two stages:

1. An exit on working temperature is -60 ° C.

In turn, this process has two options:

a) with a small mismatch and a low rate of its growth, only the flow rate of the catalyst is used as the control action (control loop 12);

b) with a large mismatch or high growth rate, an ethylene pressure control channel is additionally used (control loop 13).

A fuzzy controller acts as a device that determines the first or second control option and issues the necessary control actions.

2. Conclusion to the working point of the space of technological parameters.

When using the ethylene pressure control channel during the start-up, the output at the operating temperature can occur at any point corresponding to a temperature of -60 ° C and a charge flow rate of 13,000 kg / h at different values of ethylene pressure and catalyst flow rate. However, reaching a temperature of -60 ° C is a necessary, but not sufficient condition for the start-up process in accordance with the regulations. To obtain high quality rubber, it is necessary to comply with a predetermined molecular weight distribution (MMP), which corresponds to a certain ratio of charge and catalyst consumption. To do this, go to the nominal ethylene pressure, which will entail reaching the nominal value of the catalyst flow rate at a given charge flow rate and the required reaction temperature.

The control and monitoring circuits not described during the start-up function in the same way as in the operating mode.

A device that implements switching between the first and second stages of the start-up consists of two comparison blocks 35, 36, a block that implements transport delay, 37, two blocks of constants 38, 39, key 40, adder 41, and multiport 42.

The operation of the device is as follows. The comparison unit 35 receives a signal about the current reaction temperature. If this value falls in the range from -60.5 to -59.5 ° C, then “1” is formed at the output, otherwise “0”. The received signal is sent to the comparison element 36 and to the block that implements transport delay, 37, after which the time-shifted signal is also sent to block 36. If both values in element 36 are equal to “1”, then “1” is generated at its output, and otherwise "0". The signal from the comparison unit 36 is supplied to the closing input of the key 40 (if the output of the block 36 was “1”, the key 40 is closed). Blocks 38 and 39 form a constant signal equal to "1". With the key 40 closed, the adder 41 receives two constants “1” and the output of the adder is “2” (otherwise “1”). Multiport 42 connects one of two input signals, the first of which comes from a fuzzy controller and is connected with a control signal equal to "1", and the second is the output of the ethylene pressure output circuit to a nominal value and is connected with a control signal equal to "2". The multiport output is an ethylene pressure control signal.

After the start-up process is over, control is transferred to the classic control system.

From an economic point of view, the use of the automatic start subsystem will allow this operation to be carried out in the time described in the TP regulations, which will increase the polymerization separation productivity due to the timely replacement of one reactor by another, and reduce the cost of material and energy resources by eliminating unsuccessful starts.

Claims (1)

A method for controlling the process of producing butyl rubber by copolymerization of isoprene and isobutylene in an inert solvent in the presence of a catalyst, comprising control circuits for charge, catalyst, stopper, liquid and gaseous ethylene, characterized in that in addition to the control system in the operating mode, the automatic reactor start-up subsystem is used performing this operation in two stages, the first of which is the conclusion of the control object to the operating temperature, which is carried out either using the channel of flow control on the catalyst, or with an additional channel using ethylene pressure control, wherein the control device is a fuzzy controller, and a second - output in the operating point of the space of process parameters that realize connecting circuit ethylene pressure output to a nominal value.

Images