JPS61179206A - Removal of heat of polymerization - Google Patents

Abstract

PURPOSE:To make it possible to remove the heat of polymerization without decreasing the capacity of a cooling and condensation section for a long time, by cooling the path of a stream of an evaporated vapor to the cooling and condensation section and spraying a nonvolatile matter-free liquid over the vapor in the polymerization of a 2-8Calpha-olefin in the presence of a liquid phase. CONSTITUTION:In the production of a polyolefin by reacting a 2-8Calpha-olefin (e.g., ethylene or butene-1) in the presence of a liquid phase, part of the liquid phase is evaporated in a reaction vessel 1 and the evaporated vapor is sent through a path 4 to a cooling and condensation section 2. The liquid formed by cooling and condensation is returned through a line 12 to the reaction vessel. The path 4 is cooled by a cooling jacket 14 and a nonvolatile matter-free liquid 8 is sprayed from a spray nozzle 9 over the vapor. Even when the operation is continued for a long time, the heat of polymerization can be removed without decreasing the cooling capacity of the cooling and condensation section 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for removing heat of polymerization. Specifically, the present invention relates to a method of removing heat of polymerization by vaporizing, cooling and condensing a part of the liquid phase when polymerizing an α-olefin having 2 to 8 carbon atoms in the presence of a liquid phase.

Conventional technology When carrying out polymerization reactions on an industrial scale, it is an important issue to efficiently remove the heat of the polymerization reaction.Especially in the Bun-type reactor, the polymerization reaction is carried out in the presence of a liquid phase, and the A well-known method is to evaporate a portion of the phase, cool and condense the vapor, and return the condensate to the polymerization reactor using a so-called reflux condenser. For example, West German Patent Publication No. 2
Many examples are known, such as No. 305211. In addition, it is known that spraying droplets can be used to reduce the heat transfer efficiency due to the adhesion of polymers to the heat transfer surface of the cooler, which is a problem when using such a reflux condenser. 1977-
No. 88186, JP-A-51-84887, JP-A-52
-96687, etc.) Problems to be Solved by the Invention However, simply spraying droplets does not require the provision of a separate line for introducing steam into the cooling condensation section and a line for returning the cooled and condensed liquid to the reactor. The problem was that the devices that were used were insufficient to prevent a decrease in heat transfer efficiency and could not withstand continuous operation for a long period of time.

Means for Solving the Problems The present inventors have conducted intensive studies on a method for removing polymerization heat that can withstand continuous polymerization over a long period of time and that solves the above-mentioned problems, and have completed the present invention.

That is, in the present invention, when manufacturing a polyolefin by reacting an α-olefin having 2 to 8 carbon atoms in the presence of a liquid phase,
In the method of vaporizing a part of the liquid phase and cooling and condensing the vaporized vapor to remove heat of polymerization, at least a part of the flow path of the vaporized vapor to the cooling and condensing section is cooled, and the cooling section and/or a method for removing heat of polymerization characterized by spraying a liquid containing substantially no non-volatile matter above.

In the present invention, the α-olefin having 2 to 8 carbon atoms used for polymerization includes ethylene, vinyl chloride, propylene,
Butene-1, Hexene-1, Heptene-1, Octene-1
1, etc., and is applied to the removal of polymerization heat during copolymerization reactions of these alone or with each other.

Therefore, in addition to the α-olefin described above, compounds that are liquid under reaction conditions that do not inhibit the reaction during polymerization can be used as components constituting the liquid phase, such as fluoropane, phthane, pentane, hexane, heptane, octane, etc. Hydrocarbon compounds, and in some cases also water, can be used.

In the present invention, there are no particular limitations on the reaction conditions, but
Good polymerization is achieved under conditions where the liquid phase is vaporized, the vaporized vapor is cooled and condensed at a relatively high temperature, and the heat of polymerization can be efficiently removed, that is, the temperature of the cooling water introduced into the cooling and condensing section is close to room temperature. Preferably, it is operated under temperature and pressure.

The substantially non-volatile content-free liquid to be sprayed in the present invention may be the same as that which is cooled and condensed in the cooling condensation section, or an additional monomer or liquid medium introduced into the reactor, or , liquid cooled and condensed in the cooling condensation section can be used.

Aspects of the present invention will be explained below using the drawings. Figure 1 shows an overview of the reactor. 1 is a reaction tank, 2 is a cooling condensing section, and 3 is a blower 14, which are important parts to illustrate the embodiment of the present invention, and are shown enlarged in FIG. 5 is a channel for cooling and condensing the vapor vaporized in the reaction tank; 6 is an inlet line for cooling water to cool the channel; 7 is an outlet line; 14
1 is a cooling jacket, 8 is a spray liquid introduction line, 9 is a spray nozzle, 10 is a cooling water introduction line to the cooling condensation section,
11 is a lead-out line, 12 is a return line for the liquid condensed in the cooling condensation section to the reaction tank, and 13 is a return line for non-condensed gas.

In the present invention, the vapor vaporized in the reaction tank 1 is sent to the cooling condensation section through the flow path 4. The structure of the cooling condensing section is not particularly limited, but it is usually preferable to have a structure similar to that of a multi-tubular heat exchanger. The liquid cooled and condensed in the core is returned to the reaction tank via line 12. Further, as shown in the drawings, it is preferable to forcibly return the non-condensable gas to the reaction tank using a blower or the like.

Effects and Effects By carrying out the method of the present invention, the cooling capacity of the cooling condensing section will not decrease even if the operation continues for a long time (
It becomes possible to remove the heat of polymerization and is extremely valuable industrially.

One of the reasons why the method of the present invention is superior is that a part of the steam condenses on the wall of the flow path 5 and adheres to the wall along with the entrained polymer, catalyst, etc., and is washed away by spraying the liquid thereon. Therefore, since the polymer, catalyst, etc. are not entrained to the cooling condensing section 2, it is thought that problems such as inability to remove polymerization heat due to a decrease in heat transfer efficiency of the cooling condensing section do not occur.

Example The present invention will be further explained with reference to Examples below.

Continuous polymerization was carried out using a polymerization tank with an internal volume of 40 m5 using a bulk polymerization method using liquid propylene as a liquid medium using a catalyst consisting of titanium trichloride and diethylaluminium chloride. The polymerization tank is covered with a coolable jacket (maximum heat removal amount 600 Mcall/H), and a certain amount of heat is removed by introducing cooling water, and the remaining amount is removed by the reflux condenser shown in Figure 1. Polypropylene was polymerized at a rate of 24 liters per hour by removing the heat of polymerization. (Titanium trichloride catalyst 1.
2 klil/H) At this time, about 1200 McA per hour of heat generation is removed by the jacket, and about 900 Mcal is removed by the cooling condensing section, which is a shell-and-tube heat exchanger.

In the example, 14 in Fig. 2 (5 is 8B piping, and about 2 m is covered with IOB piping) is 4000K.
Flow water at 20℃ at g/H, and 20cm above 14.
Liquid propylene was sprayed at 700 kg/h. After operating under these conditions for three months, the heat exchanger was disassembled and almost no solid matter was observed.

When the heat exchanger was operated by simply spraying liquid propylene without passing cooling water through the heat exchanger, polypropylene was found to adhere to the tubes of about IA of the heat exchanger after three months of operation. On the other hand 14
However, after about two months of operation, it became difficult to remove heat in the cooling condensing section, and when the operation was stopped and dismantled, polypropylene was found in the approximately 1A tubes of the multi-tube heat exchanger. In addition, the tube was almost completely blocked.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a reactor to which the method of the present invention is applied, and FIG. 2 shows its details. Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] In a method for producing a polyolefin by reacting an α-olefin having 2 to 8 carbon atoms in the presence of a liquid phase, a part of the liquid phase is vaporized and the vaporized vapor is cooled and condensed to remove the heat of polymerization. Removal of heat of polymerization, characterized by cooling at least a part of the flow path of vaporized vapor to a cooling condensation section, and spraying a liquid substantially free of non-volatile matter into the cooling section and/or above. Method.