CN-122006280-A - System and method for producing wide-component distribution high-density polyethylene

CN122006280ACN 122006280 ACN122006280 ACN 122006280ACN-122006280-A

Abstract

The invention relates to the technical field of data centers, and provides a system for producing wide-component distribution high-density polyethylene, which comprises a first reactor, a flash tank, a second reactor and a third reactor which are sequentially connected in series, wherein a discharge port of the first reactor is communicated with a feed port of the flash tank through a pipeline, a first pump is arranged on the pipeline and is used for returning part of materials in the pipeline to the first reactor, a discharge port of the flash tank is communicated with the feed port of the second reactor through a main pipeline, the discharge port of the flash tank is also communicated with the feed port of the third reactor through a hole sub-branch with a control valve, the discharge port of the second reactor is communicated with the feed port of the third reactor through a pipeline, a second pump is arranged on the pipeline and is used for returning part of materials in the pipeline to the second reactor, and the discharge port of the third reactor is communicated with a post-treatment tank.

Inventors

WANG YONGGUANG
ZHANG CONG
LI MING
LI JIANBING
ZHANG KANGNING
LI CHAO
JIA XIAOHUA
LI ZHENTAO
LI TENGTENG

Assignees

山东东明石化集团有限公司
上海菏明国际贸易有限公司

Dates

Publication Date: 20260512
Application Date: 20260209

Claims (10)

1. A system for producing a broad molecular weight distribution high density polyethylene, comprising a first reactor, a flash tank, a second reactor and a third reactor in series; the discharge port of the first reactor is communicated with the feed port of the flash tank through a pipeline, a first pump is arranged on the pipeline, and the first pump is used for returning part of materials in the pipeline to the first reactor; The discharge port of the flash tank is communicated with the feed inlet of the second reactor through a main path, and the discharge port of the flash tank is also communicated with the feed inlet of the third reactor through a sub-path with a control valve; the discharge port of the second reactor is communicated with the feed port of the third reactor through a pipeline, a second pump is arranged on the pipeline and used for returning part of materials in the pipeline to the second reactor, and the discharge port of the third reaction kettle is communicated with a post-treatment tank.
2. The system of claim 1, wherein the first pump and the second pump are each circulation pumps.
3. The system of claim 1, wherein the control valve is a stop valve or a regulating valve for controlling the on-off of the branch and the material delivery amount.
4. The system of claim 1, wherein the first reactor, the second reactor, and the third reactor are all stainless steel reaction vessels.
5. The system of claim 1, wherein the first reactor is provided with a hexane feed port, an ethylene feed port, a hydrogen feed port, a catalyst feed port, and a triethylaluminum feed port.
6. A process for producing a high-density polyethylene having a broad molecular weight distribution, comprising the steps of (1) adding a reaction mass to a first reactor, and starting a first pump to circulate the mass through a line between the first reactor and a flash tank to effect a polymerization reaction to produce a low-molecular weight, high-melt index high-density polyethylene; the method comprises the steps of (1) feeding a product obtained in the step (1) into a flash tank for decompression and hydrogen removal treatment, selecting a material conveying path through a control valve according to the product requirement, feeding the material into a second reactor through a main path if the molecular weight distribution is required to be further widened, directly feeding the material into a third reactor through a branch path if the molecular weight distribution is required to be further widened, 3) feeding reaction materials into the second reactor when the material is fed into the second reactor, starting a second pump to enable the material to circulate through a pipeline between the second reactor and the third reactor, carrying out polymerization reaction to prepare high-density polyethylene with high molecular weight and low melt index, mixing the high-density polyethylene with the material processed by the flash tank and continuing the reaction, and 4) feeding the material conveyed by the branch path in the step (2) or the material mixed and reacted in the step (3) into the third reactor for termination reaction to obtain the high-density polyethylene with wide molecular weight distribution.
7. The method of claim 6, wherein the polymerization of step (1) and step (3) is performed by a slurry process.
8. The process of claim 6 wherein the catalyst added in step (1) and step (3) is a Ziegler-Natta catalyst.
9. The process of claim 6, wherein the reaction mass added in step (1) and step (3) each comprises hexane and hexane is used as a solvent for the polymerization reaction.
10. The process of claim 6, wherein the termination of step (4) is accomplished by cooling the third reactor and stopping stirring.

Description

System and method for producing wide-component distribution high-density polyethylene Technical Field The invention relates to the technical field of polyethylene production, in particular to a method for producing wide-component distribution high-density polyethylene. Background Polyethylene (PE) resin is a thermoplastic plastic formed by polymerizing ethylene monomer and comonomer thereof, and the catalyst plays a very important role in the synthesis process of polyethylene, however, the polymerization process plays a position which is difficult to replace in the synthesis process of polyethylene. The catalysts for preparing high-density polyethylene which are known at present mainly include Ziegler-Natta catalysts, chromium-based catalysts, metallocene catalysts and other non-metallocene catalysts, and a method for producing high-density polyethylene with a wide molecular weight distribution by using a metallocene compound as a catalyst is disclosed in patent application No. CN202180005039, however, the method not only requires expensive metallocene as a catalyst, but also has defects in controlling the molecular weight distribution, and in particular: The existing High Density Polyethylene (HDPE) production pipeline system is mainly divided into two types of core structures, and the inherent design defects of the existing High Density Polyethylene (HDPE) production pipeline system can not solve the problem that the melt flow rate ratio is too narrow and the melt index is unbalanced, specifically as follows: The structure form of the existing pipeline system is as follows: The first type is a single kettle type production pipeline, which is a one-way straight pipeline of a raw material storage tank, a single reaction kettle and a product collecting device, wherein only one continuous feeding-reacting-discharging channel is arranged, all polymerization reactions are completed in the same reaction kettle, no auxiliary structure of sectional reaction, condition isolation or material circulation exists in the pipeline, raw materials (monomers, catalysts, regulators and the like) are injected into the reaction kettle at one time, and the raw materials are directly discharged through the discharging pipeline after the reaction. The second type is a simple multi-kettle serial pipeline, which adopts a direct communication structure of raw material feeding, a first reaction kettle, a second reaction kettle and product discharging, a plurality of reaction kettles are sequentially butted through pipelines, key components (such as flash tanks) for isolating the reaction conditions of the front kettle and the rear kettle are not arranged, a special pipeline for material circulation reflux or parameter regulation is not arranged, and the product of the former kettle directly enters the latter kettle through the communication pipeline, and no intermediate condition regulation link is arranged. The reason why the core problem cannot be solved by the existing pipeline system is that: For a single kettle type production pipeline, the pipeline only supports polymerization under a single reaction environment, so that the segmented preparation of a low-molecular-weight high-melt index component and a high-molecular-weight low-melt index component can not be realized in the same process, a polymerization product is only a component with a single molecular weight range, the molecular weight distribution is naturally narrow (the melt flow rate ratio is too narrow), meanwhile, the pipeline design of unidirectional straight-through ensures that the raw materials are not fully contacted with a catalyst, the reaction uniformity is poor, the reaction process can not be accurately regulated, the fluctuation of the melt index of a product is easy to be too high or too low, and the product can not be stabilized in an adaptation range required by chlorinated polyethylene for rubber. For simple multi-kettle series pipelines, because of the lack of a condition isolation pipeline component, a reaction medium (such as hydrogen for regulating molecular weight) of a former reaction kettle can enter a latter reaction kettle through a pipeline which is directly communicated, so that the reaction condition of the latter reaction kettle is disturbed, components with target molecular weight and melt index cannot be accurately prepared, the pipelines have no design of material circulation or secondary mixing, the mixing of products of the front and rear kettles is uneven, the reaction is insufficient, the molecular weight distribution is difficult to be widened, and meanwhile, the fluctuation of melt index parameters is large, so that the strict performance requirements of chlorinated polyethylene for rubber on raw materials cannot be finally met. Disclosure of Invention In order to achieve the above object, the present invention provides a system for producing a wide-component distribution high-density polyethylene, comprising a first reactor, a f