Multi-zone circulating reaction device and method for olefin polymerization

Abstract

The invention discloses a multi-zone circulating reaction device and a multi-zone circulating reaction method for olefin polymerization. The reaction device comprises two reaction systems which are symmetrically distributed in parallel, wherein each system comprises a first reactor or a third reactor, a second reactor or a fourth reactor, a cyclone separator, a compressor, a heat exchanger, a liquid collecting tank and a circulating pump in turn; the first reactor or the third reactor is positioned on the lower part of the reaction system; the second reactor or the fourth reactor is connectedwith the top of the first reactor or the third reactor; the cyclone separator is connected with the top of the second reactor or the fourth reactor; the compressor is connected with the top of the cyclone separator; the heat exchanger is connected with the compressor; the liquid collecting tank is connected with the heat exchanger; the circulating pump is connected with the bottom of the liquid collecting tank and the second reactor respectively; the lower part of the cyclone separator is provided with a gas stripping section and a returning leg in turn; and the returning legs of the two systems are connected with the third reactors or the first reactors of the opposite systems respectively. The device and the method are suitable for vinyl polymerization, propylene polymerization or othergas-phase olefin polymerization.

Description

technical field [0001] The invention relates to an olefin polymerization device and an olefin polymerization method in the field of petrochemical industry, in particular to a method for preparing olefin CH 2 =Reaction device and reaction method of polymer or copolymer of CHR. Background technique [0002] For polyolefins, especially polyethylene, molecular weight (MW) and molecular weight distribution (MWD) greatly influence the mechanical properties and processability of the polymer. In the field of research, it has been recognized that the higher the molecular weight, the higher the mechanical properties. However, polyolefins with high molecular weight are difficult to process due to their poor flow properties, difficult to blow and extrude at high shear rates. In order to improve rheological properties, that is, processability, while maintaining the mechanical properties of the final product, it is known in the art that expanding the molecular weight distribution of pol...

AI Technical Summary

Problems solved by technology

The problem is: 1. The process of connecting two gas-phase fluidized bed reactors in series does not completely solve the problem of cross-flowing reactants between the two reactors, that is, the reaction gas, especially hydrogen or comonomer, can flow from one reactor to the other. Channeling to another reactor, interacting with each other's gas composition

For example: in the traditional series process of two gas-phase reactors, if the first gas-phase fluidized bed reactor is used to produce low-molecular-weight and high-density resin, a high concentration of hydrogen is required in the gas phase composition, and the resin is transported Before the second reactor, if the hydrogen is difficult to remove by the published method, it is impossible to further produce low molecular weight resin in the second reactor

2. On the other hand, due to the uneven distribution of the residence time of polymer particles in the two gas phase reactors, it is easy to cause uneven distribution of high and low molecular weight inside the particles, which affects product performance

3. The resin and reaction gas discharged from the first gas phase reactor still have a relatively high temperature, so that the catalyst contained in the resin still maintains a relatively high activity. If the residence time in the pipeline and equipment is long, the reaction The material will continue to react, and the heat generated will cause failures such as molten agglomeration or blocky polymers to block pipes or equipment

However, the problem with this technology is that due to the inhomogeneous distribution of the residence time of the polymer particles in the two gas phase reactors, it is easy to cause the inhomogeneous distribution of high and low molecular weight inside the particles, which affects product performance; in addition, the first reactor produces The resin contains more fine powder, and the process adopts the method of transporting the solid resin to the second reactor with gas after flashing. At a higher temperature, the catalyst in the resin still maintains a higher activity, and the reactants are easy to Accidents that continue to react in the pipeline and cause process instability

However, the problems in this patent are: firstly, the descending section is a moving bed with low porosity, which is not conducive to heat transfer. It can only be applied to the polypropylene process with small reaction heat release, but cannot be applied to the reaction heat release ratio Polypropylene large polyethylene production

First, the intermittent operation of the particle recirculation pipeline in this patent is too cumbersome and complicated, which is not conducive to the realization of industrialization

Second, the measure of replacing the reaction gas with the cleaning gas cannot completely replace the reaction gas in the circulating material. The reaction gas that has not been completely replaced is likely to continue to react with the polymer waiting to be transported, resulting in pipeline blockage

Third, the patent focuses on the issue of how to achieve mutual circulation of materials in the fluidized bed reactor under the two conditions and improve the uniformity of the product. It does not disclose how to solve the problem of channeling of reaction gases between the two reactors. That is, the problem of how to broaden the molecular weight distribution of the product is not solved

Fourth, in the process of conveying the circulating material from one reactor to another reactor, it is necessary to reduce the circulating material from the reaction pressure to normal pressure and then raise it back to the reaction pressure, which consumes a lot of energy

Images