SU476280A1 - Method for automatic control of ethylene polymerization process - Google Patents

Description

decompose and will not fall into the polymer. Therefore, it is proposed to vary the flow rate of a low-temperature antistatic substance depending on the temperature at the beginning of the reaction zone of the reactor, and the flow rate of the high-temperature one depending on the conversion of monomer at the reactor exit. In this case, the consumption of antistatic substances is adjusted by the amount of flow of the reaction mixture into the reactor. Siptamide, for example, can be used as a high-temperature antistatic agent, for example, stearox as a low-temperature agent. The conditions for carrying out the polymerization process in the reactor are, in particular, the following; the pressure in the reactor is 1200–1500 mp, the temperature in the reactor is 185–280 ° C; the melt index of the polymer obtained is 0.3–20; the initiator (oxygen) is up to 0.005 weight. %, the temperature of the coolant is 180-220 ° C, the initial temperature in the reactor is 180 ° C, the degree of conversion is 14-20%. The proposed method for controlling the polymerization process of ethylene can be implemented in the control system, a block diagram of one of the variants of which is shown in the drawing (the bold line shows the flow of monomer, polymer and initiator, the dotted one shows the flow of low-temperature antistatics, the dash-dotted one - flow of high-temperature antistatics, thin lines the system unit control system. The reactor control system I consists of a monomer 2 flow sensor, a pressure sensor 3 at the beginning of the reactor, a temperature sensor 4 at the beginning of the reaction zone. reactor, temperature sensor 5 at the end of the reactor, pressure sensor 6 at the end of the reactor, monomer conversion sensor 7 in the reactor, valve 8 after the reactor, valve 9 on the initiator feed line to the reactor, pressure regulator 10, temperature regulator 11, analyzer 12 , high-temperature antistatic dispenser 13, low-temperature antistatic dispenser 14, valve 15 on line from dispenser 13 to reactor, valve 16 on line from dispenser 14 to reactor, regulator 17, adder 18, regulator 19, adder 20. The system works as follows. Using pressure sensor 3, pressure regulator 10 and valve 8 regulate the pressure in reactor 1. Temperature sensors 4 and 5, temperature regulator 11 and valve 9 regulate the temperature in the reactor. Using pressure sensors 3 and 6, analyzer 12, adders 18 and 20, valves 15 and 15 regulate the pressure drop in reactor 1 by varying the flow rate of antistatic substances into it. With increasing, for example, the pressure drop in the reactor, which occurs due to an increase in the thickness of the polymer film on the walls of the reactor, partly due to the effect of static electricity, the consumption of antistatic substances in the reactor increases. As a result of this, the effect of static electricity is reduced, and the polymer that is formed from the film is washed out of the reactor. Especially dangerous is the increase in temperature at the beginning of the reaction zone of the reactor, measured by temperature sensor 4. When the specified temperature rises and it is impossible to remove it: by changing the initiator feed mode using valve 9, the temperature is reduced by using controller 17, adder 18 and valve 16, increasing the supply of low-temperature antistatic agent to reactor 1. With a sensor of percent polymer 7, controller 19, adder 20, the flow rate of high-temperature antistatic is measured depending on the degree of monomer conversion to Ore 1. This achieves constant concentration of antistatic agent in the resulting polymer. Using the flow sensor 2 connected to the regulators 17 and 19, the flow rate of antistatic substances is adjusted according to the flow rate of the reaction mixture. Subject and requirement 1. Method for automatic control of the process of polymerization of ethylene by the method of high pressure in a tubular reactor by stabilizing the temperature and pressure in the reactor, the effect m respectively on the initiator feed to the reactor and the operation of the pressure relief valve at the reactor exit characterized in that, in order to increase the productivity of the reactor, the polymerization process is carried out with the supply of low-temperature and high-temperature antistatic substances to the reactor and depending on the values The pressure drop in the reactor changes the flow rate of the mixture of these substances to the reactor. 2. A method according to claim 1, characterized in that, in order to maintain the concentration of the antistatic substance in the polymer obtained within the prescribed limits, the consumption of the high-temperature antistatic substance is changed depending on the conversion of the monomer to the output from the reactor. 3. Method according to paragraphs. 1 and 2, characterized in that the flow rate of the low-temperature antistatic substance varies depending on the temperature value at the beginning of the reaction zone of the reactor. 4. Method according to paragraphs. 1-3, characterized in that when the flow rate of the reaction mixture changes, the total consumption of antistatic substances is adjusted according to the flow rate of the reaction mixture into the reactor.

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