CN109456431B

CN109456431B - Clean closed-loop production method and system for polyolefin

Info

Publication number: CN109456431B
Application number: CN201811183859.5A
Authority: CN
Inventors: 钱坤; 常喜斌; 王江波; 李万邦; 汪根存; 杨美美; 张旭升; 田亮亮
Original assignee: Qinghai Minging Group Co ltd
Current assignee: Qinghai Minging Group Co ltd
Priority date: 2018-10-11
Filing date: 2018-10-11
Publication date: 2021-07-20
Anticipated expiration: 2038-10-11
Also published as: CN109456431A

Abstract

The invention provides a clean closed-loop production method and a system for polyolefin, wherein the method comprises the following steps: a methanol preparation step S1, a polyolefin preparation step S2, and a polyvinyl chloride preparation step S3. The system comprises a gasification device, a purification device, a methanol device, a caustic soda device, a synthesis conversion device, an olefin preparation device, an ethylene storage tank, a propylene storage tank, a polyethylene device, a polypropylene device, an oxychlorination device, a polyvinyl chloride device and the like. The invention utilizes the comprehensive utilization of coal resources to drive the comprehensive development of various resources such as chlorine, sodium and the like, realizes the zero emission of waste gas in the process of preparing methanol from coal, and produces polyvinyl chloride without mercury, thereby further promoting the comprehensive and effective utilization of resources, constructing a circular economy industrial chain, and realizing the fusion development of multiple industries such as coal chemical industry, chlor-alkali chemical industry and the like.

Description

Clean closed-loop production method and system for polyolefin

Technical Field

The invention relates to the field of comprehensive utilization of coal chemical resources, in particular to a clean closed-loop production method and a clean closed-loop production system for polyolefin.

Background

Polyolefin is one of the most important materials in high polymer materials, occupies a great proportion in plastic processing, plays an important role in national economy, is particularly guided by policies of 'replacing wood with plastic' and 'replacing steel with plastic' in the building material industry, and promotes the vigorous demand of China on polyolefin. The volume consumption of the steel is already higher than that of steel. The consumption of plastic volume is about 1.8 times of that of steel volume worldwide. In plastic consumption, polyolefin accounts for more than 60 percent, and is the plastic variety with the largest consumption. China has become the main plastic consumer and producer countries in the world. China is also a large country for the consumption and production of polyolefins. The polyolefin comprises general high polymer materials with large consumption, such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene and the like, and also comprises high value-added high polymer materials, such as polybutene-1, polyolefin elastomer and the like, so that the application is very wide, and the development speed is very high. In addition to the commonly used polyethylenes and polypropylenes, polybutene-1 is an important polyolefin material. The polyolefin elastomer comprises low-modulus multiphase polypropylene, stereoblock polypropylene, olefin block copolymer OBC and the like, and has wide application prospects in the aspects of flexible molded products, extruded profiles, pipes, elastic fibers, films, foaming materials and the like.

At present, polyolefin is widely applied to industries such as industry, transportation, building, packaging, electronics, medical and health care and the like. As the production energy of polyolefin is continuously increased in China, the consumption of raw materials and energy and the discharge of wastes are in a straight-line rising trend, so that the shortage of resources and energy and the serious situation of environmental pollution are aggravated.

In order to alleviate the contradiction between the polyolefin market supply and energy, resource shortage, environmental pollution and ecological protection, various efficient, environment-friendly and economic resource comprehensive utilization production methods are researched in various countries in the world. The circular economy mode which is characterized by resource conservation, environmental friendliness and sustainable development is concerned by countries in the world and takes corresponding measures to enhance the capability of sustainable development of economy.

Disclosure of Invention

In view of the above problems, the present invention aims to provide a clean closed-loop production method and system for polyolefin, which can further promote the comprehensive and effective utilization of resources, construct a circular economy industrial chain, and realize the fusion development of multiple industries such as coal chemical industry, chlor-alkali chemical industry, etc.

In order to achieve the above purpose, the invention provides the following technical scheme:

according to a first aspect of the present invention, there is provided a clean closed-loop production process for polyolefins, said process comprising the steps of:

methanol preparation step S1:

coal, oxygen and limestone enter a gasification device together for reaction to generate synthesis gas;

purifying the synthesis gas by a purification device to obtain purified gas;

the purified gas enters a methanol device to synthesize methanol;

the solid raw salt is subjected to an electrolytic reaction in a caustic soda device to produce hydrogen, chlorine and a sodium hydroxide solution;

the hydrogen enters a synthesis conversion device, the carbon dioxide recovered by the gasification device and the purification device is mixed and then simultaneously enters the synthesis conversion device, and the hydrogen and the carbon dioxide react to generate methanol;

polyolefin production step S2:

the methanol synthesized by the methanol device and the methanol synthesized by the synthesis conversion device both enter an olefin preparation device to prepare ethylene and propylene;

the ethylene enters a polyethylene device to react to generate polyethylene;

the propylene enters a polypropylene device to react to generate polypropylene;

polyvinyl chloride preparation step S3:

and the ethylene, the oxygen and the chlorine produced by the caustic soda device enter an oxychlorination device to carry out oxychlorination reaction, and the generated chloroethylene enters a polyvinyl chloride device to synthesize polyvinyl chloride.

According to one embodiment of the first aspect of the present invention, in step S1,

the gasification device adopts a Coelin pulverized coal pressurized gasification process for reaction, and carbon dioxide is generated in the gasification reaction process; the granularity of the coal is less than 10mm, and the coal is stored in a raw coal bin; the oxygen is generated by separating air by a first air separation unit; the limestone is transported by a limestone tank wagon;

the purification device adopts a low-temperature methanol washing process to purify the synthesis gas, carbon dioxide is released, and the acidic gas rich in hydrogen sulfide in the by-products is recovered by a sulfur recovery device;

the reaction of the methanol device takes purified gas as a raw material, adopts a David process, and produces MTO-grade methanol by pressure synthesis;

and the sodium hydroxide solution produced by the caustic soda device is evaporated and concentrated to prepare a solid caustic soda finished product or a flake caustic soda finished product.

the reaction of the caustic soda device adopts an ion membrane electrolysis technology, and the sodium hydroxide solution is 32% sodium hydroxide solution.

According to one embodiment of the first aspect of the present invention, in step S2,

the olefin preparation device is a DMTO device, and the ethylene and the propylene meeting the polymer grade are prepared by adopting DMTO technology and the methanol as a raw material.

the preparation of polyethylene takes the ethylene as a raw material, a low-pressure gas-phase polymerization process is adopted for reaction, and the polyethylene generated by the reaction is sent to a polyethylene product receiving bin;

the preparation of the polypropylene takes the propylene as a raw material, the propylene is refined and then undergoes a polymerization reaction under the action of a catalyst, and the polypropylene generated by the reaction is sent to a polypropylene product receiving bin.

In one embodiment of the first aspect of the present invention, the step S3 further includes,

the oxygen is generated by separating air by a second air separation unit;

and conveying the polyvinyl chloride generated by the reaction of the polyvinyl chloride device to a polyvinyl chloride product bin.

the reaction in the oxychlorination unit also produces a portion of the dichloroethane;

the dichloroethane enters a cracking furnace for cracking to generate chloroethylene and hydrogen chloride;

the hydrogen chloride is sent to the oxychlorination device for continuous reaction;

and the chloroethylene generated by cracking of the cracking furnace is sent to the polyvinyl chloride device to synthesize polyvinyl chloride.

In accordance with an embodiment of the first aspect of the present invention, further comprising,

and refining the chloroethylene generated after the cracking of the cracking furnace by using a rectifying device, then sending the chloroethylene into a chloroethylene monomer spherical tank for storage, and then sending the chloroethylene into the polyvinyl chloride device to synthesize polyvinyl chloride.

According to a second aspect of the present invention, there is provided a clean closed-loop production system for polyolefins, comprising:

the gasification device takes coal, oxygen and limestone as raw materials to generate gasification reaction so as to generate synthesis gas;

the purification device is connected behind the gasification device and is used for purifying the synthesis gas to obtain purified gas;

the methanol device is connected behind the purification device, and the purified gas is used as a raw material to synthesize methanol;

the device comprises a caustic soda device, a reaction kettle and a reaction kettle, wherein the caustic soda device takes solid raw salt as a raw material to perform an electrolytic reaction to generate hydrogen, chlorine and a sodium hydroxide solution;

a synthesis conversion device which is connected with the caustic soda device, the gasification device and the purification device respectively, and which takes the hydrogen generated by the caustic soda device, the carbon dioxide recovered by the gasification device and the carbon dioxide recovered by the purification device as raw materials to react and synthesize methanol;

the olefin preparation device is respectively connected with the methanol device and the synthesis conversion device, and the methanol synthesized by the methanol device and the methanol synthesized by the synthesis conversion device are used as raw materials to prepare ethylene and propylene;

an ethylene storage tank connected after the olefin production unit for receiving and storing the ethylene;

a propylene storage tank connected after the olefin production unit for receiving and storing the propylene;

the polyethylene device is connected to the ethylene storage tank and then used for carrying out polymerization reaction on the ethylene to generate polyethylene;

the polypropylene device is connected with the propylene storage tank and then used for carrying out polymerization reaction on the propylene to generate polypropylene;

the oxychlorination device is respectively connected with the ethylene storage tank and the caustic soda device, and takes the ethylene, the chlorine and the oxygen as raw materials to perform oxychlorination reaction to generate chloroethylene;

and the polyvinyl chloride device is connected behind the oxychlorination device and synthesizes polyvinyl chloride by taking the chloroethylene generated by the oxychlorination device as a raw material.

According to an embodiment of the second aspect of the invention, further comprising:

the first air separation unit is connected with the gasification unit and is used for separating oxygen in air and supplying the oxygen to the gasification unit;

the limestone tank wagon is connected with the gasification device and used for providing the limestone for the gasification device;

a raw coal bunker coupled to the gasification device for storing and transporting the coal for provision to the gasification device;

the sulfur recovery device is connected with the purification device and is used for recovering the acid gas rich in hydrogen sulfide in the by-products generated by the purification device;

and the caustic soda flake device is connected behind the caustic soda device and is used for receiving the sodium hydroxide solution produced by the caustic soda device and preparing a solid caustic soda finished product or a caustic soda flake finished product through evaporation and concentration.

According to an embodiment of the second aspect of the present invention, the reaction in the caustic soda plant adopts an ionic membrane electrolysis technology, and the sodium hydroxide solution is a 32% sodium hydroxide solution.

According to an embodiment of the second aspect of the present invention, the olefin production plant is a DMTO plant, which uses DMTO technology to produce the ethylene and the propylene meeting polymer grade from the methanol.

In accordance with an embodiment of the second aspect of the present invention, further comprising,

the polyethylene product receiving bin is connected behind the polyethylene device and is used for receiving and storing the polyethylene finished product generated by the reaction;

and the polypropylene product receiving bin is connected behind the polypropylene device and is used for receiving and storing the polypropylene finished product generated by the reaction.

a second air separation unit connected to the oxychlorination unit for separating the oxygen from the air and supplying the oxygen to the oxychlorination unit;

and the polyvinyl chloride product bin is connected behind the polyvinyl chloride device and is used for receiving and storing the polyvinyl chloride.

the cracking furnace is connected with the oxychlorination device and used for cracking a part of dichloroethane generated by the oxychlorination device to generate vinyl chloride and hydrogen chloride, the hydrogen chloride is sent to the oxychlorination device to continue reacting to generate vinyl chloride, and the vinyl chloride is sent to the polyvinyl chloride device to synthesize polyvinyl chloride.

the rectifying device is connected behind the cracking furnace and is used for refining the chloroethylene generated by the cracking furnace;

and the vinyl chloride monomer spherical tank is respectively connected with the rectifying device and the polyvinyl chloride device, and is used for receiving and storing the vinyl chloride refined by the rectifying device and conveying the vinyl chloride to the polyvinyl chloride device.

The invention has the beneficial effects that the clean closed-loop production method and the system for the polyolefin are provided, the comprehensive development of various resources such as chlorine, sodium and the like can be driven by the comprehensive utilization of coal resources, the zero emission of waste gas in the process of preparing the methanol from the coal is realized, and the polyvinyl chloride is produced in a mercury-free manner, so that the comprehensive and effective utilization of the resources is further promoted, a circular economy industrial chain is constructed, and the fusion development of multiple industries such as coal chemical industry, chlor-alkali chemical industry and the like is realized.

Drawings

FIG. 1 is a schematic representation of the steps of a clean closed-loop polyolefin production process of the present invention.

FIG. 2 is a schematic view of a clean closed loop polyolefin production system of the present invention.

FIG. 3 is a schematic diagram of one embodiment of a clean closed loop polyolefin production system of the present invention.

FIG. 4 is a schematic view of a clean closed loop polyolefin production system utilizing a DMTO plant for an olefin production plant according to the present invention.

FIG. 5 is a schematic view of a clean closed loop production system of the present invention comprising a polyolefin product receiving bin.

Fig. 6 is a schematic diagram of a system comprising a second air separation unit and a polyvinyl chloride product bin in a clean closed loop polyolefin production system of the present invention.

FIG. 7 is a schematic view of a clean closed loop polyolefin production system including a pyrolysis furnace according to the present invention.

FIG. 8 is a schematic diagram of a clean closed loop polyolefin production system including a refining process for vinyl chloride produced by a cracking furnace according to the present invention.

M1-gasification unit, M2-purification unit,

m3-methanol unit, M4-caustic soda unit,

m5-synthetic conversion unit, M6-olefin preparation unit,

m7-ethylene tank, M8-propylene tank,

m9-polyethylene unit, M10-polypropylene unit,

m11-oxychlorination unit, M12-polyvinyl chloride unit,

m13-first air separation plant, M14-limestone tank car,

m15-raw coal bunker, M16-sulfur recovery device,

m17-caustic soda flake device, M18-polyethylene product receiving bin,

m19-polypropylene product receiving bin, M20-second air separation plant,

m21-a polyvinyl chloride product bin, M22-a cracking furnace,

m23-rectification unit, M24-vinyl chloride monomer spherical tank,

s1-methanol preparation step, S2-polyolefin preparation step,

s3-polyvinyl chloride preparation step.

Detailed Description

In the following detailed description of the preferred embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific features of the invention, such that the advantages and features of the invention may be more readily understood and appreciated. The following description is an embodiment of the claimed invention, and other embodiments related to the claims not specifically described also fall within the scope of the claims.

The invention is further described with reference to the following figures and detailed description of embodiments.

As shown in fig. 1, the present invention provides a clean closed-loop production method of polyolefin, comprising the steps of: a methanol preparation step S1, a polyolefin preparation step S2, and a polyvinyl chloride preparation step S3. The concrete description is as follows:

methanol preparation step S1:

purifying the synthesis gas by a purification device to obtain purified gas;

the purified gas enters a methanol device to synthesize methanol;

polyolefin production step S2:

the ethylene enters a polyethylene device to react to generate polyethylene;

the propylene enters a polypropylene device to react to generate polypropylene;

polyvinyl chloride preparation step S3:

In the methanol production step S1, the production of methanol can be achieved by two ways, the first way is to produce the synthesis gas by a gasification reaction in the gasification apparatus, the synthesis gas is purified by the purification apparatus to obtain the purified gas, and the purified gas is fed as a raw material to the methanol apparatus to synthesize methanol by pressurization; the second route is derived from the synthesis conversion device, the raw material for preparing the methanol in the synthesis conversion device is derived from the carbon dioxide recovered by the gasification device and the purification device and the hydrogen generated by the electrolysis reaction in the caustic soda device, and the carbon dioxide and the hydrogen are used for preparing the methanol under the condition of high temperature in the synthesis conversion device through the action of a catalyst.

The gasification device takes raw material coal and oxygen as raw materials to produce the synthesis gas; and the raw material coal, limestone and oxygen enter a gasification furnace together to be pressurized to generate the synthesis gas. The limestone is added when the coal and the oxygen are subjected to oxidation reaction, so that sulfur dioxide generated during combustion of the coal is absorbed, the emission of the sulfur dioxide is reduced, and the aims of protecting the environment and producing cleanly are fulfilled. Thus, the main components of the synthesis gas include carbon monoxide, hydrogen, carbon dioxide, hydrogen sulfide, and the like.

The synthesis gas from the gasification device is subjected to low-temperature methanol washing by the purification device to produce the purified gas, and the purified gas is input into the methanol device through a pipeline. The main components of the purified gas are as follows: h₂66.88 Vol%, CO 29.78 Vol%, CO₂2.50 Vol% and other trace components.

The synthesis gas from the gasification device M1 is purified by the purification device M2, the generated purified gas firstly enters a compressor for compression, is compressed to 7.25 MPa and then is sent to a methanol synthesis tower to synthesize methanol under the action of a catalyst, crude methanol from the methanol synthesis tower is separated into crude methanol and hydrogen by a crude methanol separator, and the crude methanol is sent to a stabilization tower to be continuously refined into MTO-grade methanol; the hydrogen enters a hydrogen recovery unit, and the purity of the hydrogen is improved to 99.99 percent by pressure swing adsorption and then the hydrogen is sent to each required device.

The synthesis conversion device is a hydrogen gas H from the caustic soda device₂And carbon dioxide CO recovered from the gasification apparatus and the purification apparatus₂As raw material, methanol CH is generated under the action of high-temperature catalyst₃OH，CO₂The mechanism for synthesizing methanol is mainly 3 reactions:

(1)CO+2H₂→CH₃OH－ΔH＝90kJ/mol

(2)CO₂+3H₂→CH₃OH+H₂O－ΔH＝49.43kJ/mol

(3)CO₂+H₂→CO+H₂O－ΔH＝41.12kJ/mol

previous studies have considered that the reaction of carbon dioxide to methanol must be carried out via CO₂+H₂CO and water are produced, indicating that CO is a reaction intermediate, and then CO and hydrogen synthesize methanol. From CO₂The synthesis of methanol usually has two parallel reactions (2) and (3), while the hydrogenation synthesis from CO has the main reaction (1). Comparing the two reactions (1) and (2), it can be seen that CO is₂Half of the methanol is synthesized, so carbon dioxide synthesis of methanol can be reacted at lower temperatures than synthesis of methanol from CO. From both reactions (2) and (3), it is also known that CO₂The synthesis of methanol generates a large amount of water, so that copper crystals are dissociated, migrated and recrystallized, and the activity of the catalyst is lost. The presence of water also increases the water content of the crude methanol, burdening the distillation. In addition, the presence of water not only improves the selectivity to methanol, but also mitigates the amount and concentration of organic by-products. Thereby reducing the difficulty of crude methanol distillation.

In the polyolefin preparation step S2, an olefin or an olefin mixture is prepared from methanol by the olefin preparation apparatus, the olefin preparation apparatus mainly includes an olefin preparation reaction unit and an olefin separation unit, and the olefin separation unit can separate the olefin mixture generated by the reaction into olefin monomers. At present, the process for preparing olefin by methanol includes various processes, for example, MTO process for preparing ethylene and propylene from methanol and MTP process for preparing propylene from methanol are currently important chemical technologies. The technology is a chemical technology for producing low-carbon olefin by taking methanol synthesized by coal or natural gas as a raw material and by means of a fluidized bed reaction form similar to a catalytic cracking device. Similar works have been carried out by domestic research institutions such as the institute of chemical ligation and mass of Chinese academy of sciences, the university of petroleum, the institute of petrochemical science and technology of China. The DMTO process developed by the large-chain compound is original, the initial research is to prepare olefin based on dimethyl ether, the subsequent technical improvement is started from methanol, the process started from methanol also comprises the process of converting methanol into dimethyl ether and converting dimethyl ether into olefin, and the development and application of the DMTO complete technology have extremely important significance for developing novel coal chemical industry and realizing the energy strategy of 'petroleum substitution' in China both economically and strategically.

The reaction of the polyethylene PE device adopts Unipol process technology of Unimutation company, namely low-pressure gas-phase polymerization process, the process technology is mature and reliable, and polyethylene products with high, medium and linear low density can be produced. The UNIPOL process, i.e. the low-pressure gas-phase fluidized bed polymerization process, uses ethylene as main raw material and butene-1 or hexene-1 as comonomer to produce linear low-density and partial medium-and high-density polyethylene granular resin. The density of the product is 0.915-0.965 g/cm³The melt flow ratio MFR (I21.6/I2.16) is 0.05 to 155. The process is simple, short in flow, self-limiting in pressure and without overpressure hazard. The process has mild operation condition, no high temperature and low pressure. High automation level, complete safety chain and computer control. The UNIPOL process mainly comprises the steps of raw material refining, reaction, resin degassing, exhaust gas recovery, blending granulation, packaging, storage and the like. Ziegler-Natta catalysts, Cr-based catalysts, metallocene catalysts, bimodal catalysts may be used. Ethylene and a comonomer are polymerized in a fluidized bed reactor to generate a polymer, wherein the comonomer can be butene-1 and hexene-1. The carrier type titanium, metallocene, double peak or chromium catalyst is continuously added into the reactor, the powder material of the product is continuously withdrawn, and after degassing, granulation can be carried out. The reaction gas is circulated in the reaction system, and the heat of reaction is removed by the circulating gas.

The polypropylene PP device uses propylene as a raw material, and crude propylene contains a small amount of impurities such as water, oxygen, sulfur, carbon monoxide, nitrogen monoxide, carbon dioxide, arsenic, etc., which can cause poisoning of a polypropylene catalyst, and thus must be removed in advance. The carbon dioxide, inorganic sulfur and a large amount of water can be removed by adopting solid alkali or flake alkali, the manganese agent is used for deoxidation, the activated alumina and the 3A0 molecular sieve are used for removing a small amount of water, R3-11 is used for removing carbon monoxide by chemical adsorption, and the carbon monoxide is removed by physical fractionation in a stripping tower; r3-12 is dearsenized. The polypropylene catalyst is refined by the methods, impurities contained in the polypropylene catalyst, such as sulfur, arsenic, water, oxygen, carbon oxides, ammonia, alcohols, ketones and the like, which poison the polypropylene polymerization catalyst are removed, the polypropylene catalyst meets the requirements of the polymerization grade propylene specification, then the polypropylene catalyst enters a fluidized bed main reactor, and reacts under the catalysis of a high-efficiency catalyst system, namely a main catalyst is a high-efficiency carrier catalyst, a cocatalyst is triethyl aluminum and an electron donor to generate a homopolymer and a random copolymer product, and the operation conditions can be adjusted within a larger range to keep the product performance uniform. After the reaction is finished, the finished polypropylene is conveyed to a product receiving bin from a product discharging system in a dense phase mode through an airflow conveying system and is degassed, degassed powder and additives are simultaneously conveyed to an extrusion granulator for granulation, and the powder and the additives are conveyed to a blending bin through a pneumatic conveying system after granulation and conveyed to a packaging and stacking system for packaging and stacking and then conveyed to a finished product warehouse.

In the polyvinyl chloride preparing step S3, the ethylene is derived from the ethylene generated by the reaction in the polyolefin preparing step S2, and the oxygen may be replaced by air. The oxychlorination device adopts a balanced oxychlorination method to produce the chloroethylene. The reaction principle is as follows: the method for producing vinyl chloride by ethylene oxychlorination comprises three steps of reactions:

(1) direct chlorination of CH with ethylene₂＝CH₂+Cl₂→CH₂ClCH₂Cl；

(2) Splitting 2CH with dichloroethane₂ClCH₂Cl→2CH₂＝CHCl+2HCl；

(3) Oxychlorination of ethylene₂＝CH₂+2HCl+O₂→CH₂ClCH₂Cl+H₂O；

General reaction formula 2CH₂＝CH₂+Cl₂+O₂→2CH₂＝CHCl+H₂O。

The key point of the method is that the reaction amount of the addition reaction of ethylene and chlorine and the oxychlorination reaction of ethylene are well matched, so that HCl generated by cracking 1, 2-dichloroethane just meets the HCl required by the oxychlorination of ethylene. This is to keep the HCl in equilibrium throughout the production process. The method is a production method which is recognized as an advanced, economic and reasonable technology in the world at present.

The main reaction of the ethylene direct chlorination part in the oxychlorination device is as follows:

CH₂＝CH₂+Cl₂→CH₂ClCH₂Cl △H＝-171.7kJ/mo1

the molar ratio of ethylene to chlorine is usually 1.1: 1.0. The slight excess of ethylene can ensure complete reaction of chlorine, reduce the content of free chlorine in the chlorination liquid, reduce the corrosion to equipment and be beneficial to post-treatment. Meanwhile, the explosion danger caused by direct contact between the chlorine and the hydrogen in the feed gas can be avoided. In the production, the chlorine content in the tail gas is controlled to be not more than 0.5 percent, and the ethylene content is controlled to be less than 1.5 percent. The reaction temperature is generally controlled to be about 53 ℃. The reaction pressure is normal pressure.

The main reaction of the dichloroethane cracking part in the oxychlorination device is as follows:

CH₂ClCH₂Cl→CH₂＝CHCl+HCl △H＝79.5kJ/mo1

the conversion to vinyl chloride is carried out by cracking in a cracking furnace, which is supplied with the parameters of western chemistry in the united states and designed by the company heldi, france. Feeding refined dichloroethane EDC into a cracking furnace, cracking at high temperature into vinyl chloride VCM and hydrogen chloride HCL, wherein the cracking reaction occurs in a gas or fuel box furnace, the temperature is 490-; and the Hydrogen Chloride (HCL) is dried and then is continuously sent to an oxychlorination device for reaction.

The main reaction of the ethylene oxychlorination part in the oxychlorination device is as follows:

CH₂＝CH₂+2HCl+O₂→CH₂ClCH₂Cl+H₂O △H＝-251kJ/mo1

in a quantitative relationship according to the equation for ethylene oxychlorination, C₂H₄:HC1:O₂1:2:0.5 (mol). Under normal operating conditions, C₂H₄Slight excess of O₂About 50% excess to complete conversion of HC 1. Fruit of Chinese wolfberryThe proportion of the boundary raw materials is C₂H₄:HC1:O₂(1.05: 2: 0.75-0.85 (mol)). If HC1 is excessive, the excessive HCl will be adsorbed on the surface of the catalyst, so that the catalyst particles will swell and the density will decrease; if a fluidized bed reactor is adopted, the bed layer can be sharply raised, and even a slugging phenomenon can occur, so that the normal operation can not be realized. C₂H₄Slight excess can ensure complete conversion of HC1, but too much excess, CO and CO in the exhaust₂The content of (a) increases, so that the selectivity decreases. If the amount of oxygen is too large, the above phenomenon may occur.

As shown in fig. 2, there is provided a clean closed-loop production system for polyolefins, comprising:

a gasification device M1, wherein the gasification device M1 takes coal, oxygen and limestone as raw materials to generate gasification reaction so as to generate synthesis gas;

a purification device M2, wherein the purification device M2 is connected to the gasification device M1 and is used for purifying the synthesis gas to obtain a purified gas;

a methanol unit M3 connected to the purification unit M2 in the methanol unit M3, and synthesizing methanol using the purified gas as a raw material;

the device comprises a caustic soda device M4, wherein the caustic soda device M4 takes solid raw salt as a raw material to perform an electrolytic reaction to generate hydrogen, chlorine and a sodium hydroxide solution;

a synthesis converter M5, in which the synthesis converter M5 is connected to the caustic soda unit M4, the gasification unit M1, and the purification unit M2, respectively, and methanol is synthesized by reaction using the hydrogen gas generated in the caustic soda unit M4, the carbon dioxide recovered in the gasification unit M1, and the carbon dioxide recovered in the purification unit M2 as raw materials;

an olefin production unit M6, wherein the olefin production unit M6 is connected to the methanol unit M3 and the synthesis conversion unit M5, respectively, and ethylene and propylene are produced by using the methanol synthesized by the methanol unit M3 and the methanol synthesized by the synthesis conversion unit M5 as raw materials;

an ethylene storage tank M7, said ethylene storage tank M7 being connected after said olefin production unit M6, for receiving and storing said ethylene;

a propylene storage tank M8, said propylene storage tank M8 being connected after said olefin production unit M6 for receiving and storing said propylene;

a polyethylene device M9, wherein the polyethylene device M9 is connected with the ethylene storage tank M7 and then is used for carrying out polymerization reaction on the ethylene to generate polyethylene;

a polypropylene apparatus M10, connected to the propylene tank M8, for polymerizing propylene to produce polypropylene, the polypropylene apparatus M10 being connected to the propylene tank M8;

an oxychlorination device M11, wherein the oxychlorination device M11 is respectively connected with the ethylene storage tank M7 and the caustic soda device M4, and the ethylene, the chlorine and the oxygen are used as raw materials to perform an oxychlorination reaction to generate vinyl chloride;

a polyvinyl chloride unit M12 connected to the oxychlorination unit M11, and synthesizing polyvinyl chloride using the vinyl chloride generated in the oxychlorination unit M11 as a raw material.

The gasification device M1 takes raw material coal and oxygen as raw materials to produce the synthesis gas; and the raw material coal, limestone and oxygen enter a gasification furnace together to be pressurized to generate the synthesis gas.

The purifying device M2 mainly adopts a low-temperature methanol washing process and adopts low-temperature methanol to absorb CO in the converted gas₂、H₂S, COS, and the like, to obtain qualified purified gas for a downstream methanol synthesis device, wherein rich methanol after absorbing the impurity gas releases CO with higher purity through desorption₂Products and tail gases. The desorbed methanol is thermally regenerated to obtain poor methanol which can be reused as an absorbent, and the byproduct is rich in H₂And (4) sending the acid gas of the S to a sulfur recovery device. The freezing station device adopts a propylene compression refrigeration process to provide cold energy for the low-temperature methanol washing device. The propylene compression adopts a three-stage compression process, the technology is mature and reliable, and the high-purity CO is obtained₂The recovered hydrogen is sent to a synthesis conversion device M5 and a caustic soda device M4 for electrolysis to generate hydrogen to continue to synthesize the methanol.

The methanol device M3 takes the purified gas washed by the low-temperature methanol as a raw material to produce MTO-grade methanol by pressure synthesis. The main production device in the boundary area of the methanol device M3 comprises methanol synthesis, synthesis gas compression, hydrogen recovery and pressure swing adsorption hydrogen production. The methanol synthesis can adopt a David process with mature and reliable industrial experience, and the David methanol synthesis technology is one of the most selected technologies in large-scale methanol synthesis devices with over 100 million tons at present. The methanol synthesis adopts a single series, 2 synthesis towers are arranged, the synthesis pressure is 7.0-7.5 MPa (A), the operation temperature is 215-282 ℃, and the 2 synthesis towers are arranged in series, so that the capacity requirement of the device is met.

The caustic soda device M4 takes solid raw salt as raw material and adopts the ion membrane electrolysis technology to produce sodium hydroxide solution and chlorine Cl₂And hydrogen H₂(ii) a The produced Cl2 is purified and compressed and then is sent to the oxychlorination device M11 for ethylene chlorination; the produced H2 is purified and compressed and then enters the synthesis conversion device M5, and carbon dioxide CO recovered by the gasification device M1 and the purification device M2₂Generating methanol CH under the action of high-temperature catalyst₃OH, the methanol is sent to the olefin preparation device M6 to prepare diene, and then polymerization or chlorination is continued; evaporating and concentrating the sodium hydroxide solution to prepare a solid caustic soda finished product; the sodium hydroxide solution can be used for producing the caustic soda flakes by adopting a multi-effect countercurrent falling film evaporation technology and a solid caustic soda evaporation technology. The sodium hydroxide solution may be a 32% sodium hydroxide solution.

The synthesis conversion device M5 is hydrogen H from the caustic soda device M4₂And recovered from the vaporizing device M1 and the purifying device M2Carbon dioxide CO of₂As raw material, methanol CH is generated under the action of high-temperature catalyst₃OH，CO₂The mechanism for synthesizing methanol is mainly 3 reactions:

(1)CO+2H₂→CH₃OH－ΔH＝90kJ/mol

(2)CO₂+3H₂→CH₃OH+H₂O－ΔH＝49.43kJ/mol

(3)CO₂+H₂→CO+H₂O－ΔH＝41.12kJ/mol

The olefin preparation device M6 mainly includes an olefin preparation reaction unit that uses methanol as a raw material to prepare olefin or an olefin mixture, and an olefin separation unit that can separate the olefin mixture generated by the reaction into olefin monomers. At present, the process for preparing olefin by methanol includes various processes, for example, MTO process for preparing ethylene and propylene from methanol and MTP process for preparing propylene from methanol are currently important chemical technologies. The technology is a chemical technology for producing low-carbon olefin by taking methanol synthesized by coal or natural gas as a raw material and by means of a fluidized bed reaction form similar to a catalytic cracking device. Similar works have been carried out by domestic research institutions such as the institute of chemical ligation and mass of Chinese academy of sciences, the university of petroleum, the institute of petrochemical science and technology of China. The DMTO process developed by the large-chain compound is original, the initial research is to prepare olefin based on dimethyl ether, the subsequent technical improvement is started from methanol, the process started from methanol also comprises the process of converting methanol into dimethyl ether and converting dimethyl ether into olefin, and the development and application of the DMTO complete technology have extremely important significance for developing novel coal chemical industry and realizing the energy strategy of 'petroleum substitution' in China both economically and strategically.

The oxychlorination device M11 uses the ethylene, the chlorine and the oxygen as raw materials, and adopts a balanced oxychlorination method to produce the chloroethylene. The reaction principle is as follows: the method for producing vinyl chloride by ethylene oxychlorination comprises three steps of reactions:

(2) Splitting 2CH with dichloroethane₂ClCH₂Cl→2CH₂＝CHCl+2HCl；

(3) Oxychlorination of ethylene₂＝CH₂+2HCl+O₂→CH₂ClCH₂Cl+H₂O；

General reaction formula 2CH₂＝CH₂+Cl₂+O₂→2CH₂＝CHCl+H₂O。

The main reaction of the ethylene direct chlorination part in the oxychlorination device M11 is as follows:

CH₂＝CH₂+Cl₂→CH₂ClCH₂Cl △H＝-171.7kJ/mo1

The main reaction of the dichloroethane cracking part in the oxychlorination device M11 is as follows:

CH₂ClCH₂Cl→CH₂＝CHCl+HCl △H＝79.5kJ/mo1

the conversion to vinyl chloride is carried out by cracking in a cracking furnace which is designed by the company Hull-Tu, France and which is supplied with parameters by Western American chemistry. Feeding refined dichloroethane EDC into a cracking furnace, cracking at high temperature into vinyl chloride VCM and hydrogen chloride HCL, wherein the cracking reaction occurs in a gas or fuel box furnace, the temperature is 490-; and the hydrogen chloride HCL is dried and then is continuously sent to the oxychlorination device M11 for reaction.

The main reaction of the ethylene oxychlorination part in the oxychlorination device M11 is as follows:

CH₂＝CH₂+2HCl+O₂→CH₂ClCH₂Cl+H₂O △H＝-251kJ/mo1

according to the metering relation of the ethylene oxychlorination reaction equation,C₂H₄:HC1:O₂1:2:0.5 (mol). Under normal operating conditions, C₂H₄Slight excess of O₂About 50% excess to complete conversion of HC 1. The actual raw material ratio is C₂H₄:HC1:O₂(1.05: 2: 0.75-0.85 (mol)). If HC1 is excessive, the excessive HCl will be adsorbed on the surface of the catalyst, so that the catalyst particles will swell and the density will decrease; if a fluidized bed reactor is adopted, the bed layer can be sharply raised, and even a slugging phenomenon can occur, so that the normal operation can not be realized. C₂H₄Slight excess can ensure complete conversion of HC1, but too much excess, CO and CO in the exhaust₂The content of (a) increases, so that the selectivity decreases. If the amount of oxygen is too large, the above phenomenon may occur.

The oxidant air or oxygen, the ethylene and the hydrogen chloride are mixed in a distributor and then enter a catalytic bed layer to generate oxychlorination reaction. The heat evolved is removed by vaporization of the hot water in the cooling tubes. The reaction temperature is controlled by adjusting the pressure of the steam-water separator. Catalyst needs to be continuously supplemented into the oxychlorination device M11 in the reaction process so as to compensate the loss of the catalyst. The cooling pipe is the pipe pass of the oxychlorination device M11, and the reaction heat released in the reaction process is removed by vaporization of hot water in the pipe pass; the steam-water separator is connected with a tube pass outlet of the oxychlorination reaction tower in series, and the steam-water ratio is controlled by adjusting the pressure of the steam-water separator, so that the purpose of controlling the reaction temperature is achieved.

The polyvinyl chloride device M12 adopts a suspension method to prepare the polyvinyl chloride, and the preparation process is as follows: the vinyl chloride monomer synthesized by the oxychlorination device M11 is used as a raw material, the vinyl chloride monomer is subjected to suspension polymerization in the polyvinyl chloride device M12 to generate polyvinyl chloride resin, and the polymerization slurry is subjected to steam stripping and centrifugal drying to prepare a finished product. And conveying the finished product of the polyvinyl chloride S-PVC powder to a product bin and a packaging bin.

As shown in fig. 3, according to one embodiment of a clean closed loop polyolefin production system of the present invention, the system further comprises,

a first air separation unit M13, the first air separation unit M13 being connected to the gasification unit M1 for separating oxygen from air and supplying to the gasification unit M1;

a limestone tanker M14, said limestone tanker M14 being connected to said gasification unit M1 for providing said limestone to said gasification unit M1;

a raw coal silo M15, the raw coal silo M15 being connected to the gasification unit M1 for storing and transporting the coal for supply to the gasification unit M1;

a sulfur recovery unit M16, said sulfur recovery unit M16 being connected to said purification unit M2 for recovering hydrogen sulfide-rich acid gas from the by-products produced by said purification unit M2;

a caustic soda device M17, wherein the caustic soda device M17 is connected behind the caustic soda device M4 and is used for receiving the sodium hydroxide solution produced by the caustic soda device M4 and preparing a solid caustic soda finished product or a caustic soda finished product through evaporation and concentration.

The gasification device M1 adopts a Colin pulverized coal pressurized gasification process for reaction, and carbon dioxide is generated in the gasification reaction process; the granularity of the coal is less than 10mm, and the coal is stored in a raw coal bin M15; the oxygen is generated by separating air by a first air separation unit M13; the limestone is transported by a limestone tank wagon M14;

the purification device M2 adopts a low-temperature methanol washing process to purify the synthesis gas, carbon dioxide is released, and the acidic gas rich in hydrogen sulfide in the by-products is recovered by a sulfur recovery device M16;

the reaction of the methanol device M3 takes purified gas as a raw material, adopts a David process, and produces MTO-grade methanol by pressure synthesis;

and the sodium hydroxide solution produced by the caustic soda device M4 is evaporated and concentrated to prepare a solid caustic soda finished product or a flake caustic soda finished product. Further, the reaction of the caustic soda device M4 adopts an ionic membrane electrolysis technology, and the sodium hydroxide solution may be a 32% sodium hydroxide solution.

The gasification device M1 takes raw material coal, oxygen and limestone as raw materials, and adopts the Kolin powdered coal pressure gasification technology to produce synthesis gas. Raw material coal from outside the battery limits, the granularity of which is less than 10mm, is continuously sent into the raw coal bin M15 through a belt, limestone from the limestone tank wagon M14 and oxygen from the first air separation unit M13 enter a gasification furnace together to be pressurized to generate synthesis gas to synthesize methanol.

The air separation device is a set of industrial equipment for separating the component gases in the air and producing oxygen and nitrogen. The specific principle is as follows: after the impurities such as moisture, carbon dioxide, hydrocarbon and the like are removed from the compressed air from the air compressor through the molecular sieve, one part of the air is directly sent to the upper tower of the rectifying tower, and the other part of the air enters the expansion machine to be subjected to expansion refrigeration and then is sent to the lower tower. In the rectifying tower, after heat exchange between ascending steam and falling liquid, nitrogen with high purity can be obtained at the top of the upper tower, and oxygen with high purity can be obtained at the bottom of the upper tower. The first air separation unit M13 supplies oxygen of high purity obtained by separating air to the gasification unit M1.

The sulfur recovery unit M16 is a unit for hydrolyzing COS in the syngas to H by injecting a small amount of water from a scrubber into the syngas₂And S. Then, the residue was passed through a desulfurizing tank of the sulfur recovery apparatus M16 to remove residual H₂S, which otherwise would poison the methanol synthesis catalyst.

The Davy technology is characterized in that an SRC radial steam-producing methanol synthesis tower is adopted by Davy corporation to synthesize MTO-grade methanol, the SRC radial steam-producing methanol synthesis tower is an isothermal in-pipe water-cooling radial tower, a catalyst is filled on the shell side of a reactor, and medium-pressure steam is generated in a pipe. The purified gas passes through the shell side provided with the catalyst bed layer from top to bottom in the radial direction, and the bed layer temperature of the catalyst is controlled by controlling the steam pressure to achieve the temperature distribution close to the isothermal temperature. The advantages of the David process are: the bed temperature of the catalyst is controlled by controlling the steam pressure by using a radial flow reactor, and the catalyst has a temperature distribution close to isothermal temperature; the gas passes through the catalyst bed layer from inside to outside along the radial direction, and the pressure drop is small; the catalyst has high efficiency and is simple and convenient to fill; noble metals are not needed, the requirements on materials are relatively low, and the cost of the reaction synthesizer is low.

The caustic soda device M17 can make the sodium hydroxide solution into solid caustic soda or caustic soda flakes. Evaporating and concentrating the sodium hydroxide solution to prepare a solid caustic soda finished product; the sodium hydroxide solution can be used for producing the caustic soda flakes by adopting a multi-effect countercurrent falling film evaporation technology and a solid caustic soda evaporation technology. The sodium hydroxide solution may be a 32% sodium hydroxide solution

As shown in fig. 4, the olefin production apparatus M6 is a DMTO apparatus, and the DMTO apparatus employs DMTO technology to produce the ethylene and the propylene meeting the polymer grade from the methanol.

The DMTO device takes the methanol synthesized by the methanol device M3 and the synthesis conversion device M5 as raw materials, firstly enters a methanol buffer tank, is subjected to pressure rise by a methanol feed pump, then is subjected to heat exchange to 100 ℃ by a heater, a methanol-purified water heat exchanger and a methanol-condensed water heat exchanger in a reactor, and then is divided into three paths: the first path exchanges heat through a methanol-stripping gas heat exchanger; the second path exchanges heat through a methanol-steam heat exchanger to gasify the methanol, the third path is boosted by a methanol booster pump and atomized by an atomizing nozzle, the atomized methanol is mixed with the methanol gasified in the front of the methanol-reaction gas heat exchanger and then enters the methanol-reaction gas heat exchanger to exchange heat with the high-temperature reaction gas from the reactor sufficiently to recover high-temperature heat, and the methanol exchanges heat to about 250 ℃ and enters a reactor feeding distributor. The methanol in the reactor is directly contacted with the high-temperature regenerated catalyst from the regenerator, the exothermic reaction is rapidly carried out under the action of the catalyst, the reaction gas is discharged after most of the carried catalyst is removed by a two-stage cyclone separator, the carried catalyst is removed by a three-stage cyclone separator of the reactor and a four-stage cyclone separator of the reactor, and the reaction gas is subjected to heat exchange by a methanol-reaction gas heat exchanger

And then sent to a rear quenching tower. The catalyst recovered from the third cyclone separator enters the fourth cyclone separator and the reverse reaction is discharged from the topThe reaction gas enters an outlet at the top of the quenching tower.

After heat recovery, reaction gas rich in ethylene and propylene enters the lower part of the quenching tower, the reaction gas is in countercurrent contact with cooling water at the top of the quenching tower from bottom to top to wash a small amount of catalyst carried in the reaction gas, simultaneously reducing the temperature of reaction gas, pumping out quench water from the bottom of the tower in two paths, pumping one path of the quench water through a quench tower bottom pump, dividing the other path of the quench water into two paths, sending the other path of the quench water to an olefin separation and C4 comprehensive utilization device as a low-temperature heat source, the steam consumption of the olefin separation and C4 comprehensive utilization device is reduced, the other stream of quenching water enters a quenching water hydrocyclone after being boosted by a quenching water rotary pump, the reaction gas is in countercurrent contact with the washing water from bottom to top, the temperature of the reaction gas is reduced, the bottom water of the washing tower is pumped out and then is boosted by a washing tower bottom pump to be divided into two paths, and one path of the reaction gas is mixed with the first-section condensate of the gas compressor, the second-section condensate of the gas compressor and the third-section condensate of the gas compressor from the olefin separation and C4 comprehensive utilization device and the washing water of the olefin separation device and then enters a settling tank. And the other path of water washing water is sent to a propylene rectifying tower bottom reboiler of the olefin separation and C4 comprehensive utilization device as a heat source and is sent to an olefin separation and C4 comprehensive utilization device. And (3) sending the reaction gas at the top of the water washing tower to an olefin separation and C4 comprehensive utilization device gas compressor inlet under the normal working condition for olefin separation, and preparing the ethylene and the propylene meeting the polymerization grade.

As shown in fig. 5, the present invention provides a clean closed-loop polyolefin production system further comprising,

a polyethylene product receiving bin M18, wherein the polyethylene product receiving bin M18 is connected to the rear part of the polyethylene device M9 and is used for receiving and storing the polyethylene finished product generated by the reaction;

a polypropylene product receiving bin M19, wherein the polypropylene product receiving bin M19 is connected to the rear part of the polypropylene device M10 and is used for receiving and storing the polypropylene finished product generated by reaction.

The preparation of polyethylene takes the ethylene as raw material, the reaction is carried out by adopting a low-pressure gas-phase polymerization process, and the polyethylene generated by the reaction is sent to the polyethylene product receiving bin M18 after being granulated.

The preparation of the polypropylene takes the propylene as a raw material, the propylene is refined and then carries out polymerization reaction under the action of a catalyst, the polypropylene generated by the reaction is conveyed to the polypropylene product receiving bin M19 from a product blanking system in a dense phase through an airflow conveying system and is degassed, the degassed powder and additives are simultaneously conveyed to an extrusion granulator for granulation, and the powder and additives are conveyed to a blending bin through the pneumatic conveying system after granulation and then conveyed to a packaging and stacking system for packaging and stacking and then conveyed to a finished product warehouse.

As shown in fig. 6, the present invention provides a clean closed-loop polyolefin production system further comprising:

a second air separation unit M20, said second air separation unit M20 being connected to said oxychlorination unit M11 for separating said oxygen from the air to be supplied to said oxychlorination unit M11;

a polyvinyl chloride product bin M21, the polyvinyl chloride product bin M21 being connected behind the polyvinyl chloride unit M12 for receiving and storing the polyvinyl chloride.

The oxygen is generated by separating air by a second air separation unit M20; and the polyvinyl chloride generated by the reaction of the polyvinyl chloride device M12 is sent to a polyvinyl chloride product bin M21.

The air separation device is a set of industrial equipment for separating the component gases in the air and producing oxygen and nitrogen. The specific principle is as follows: after the impurities such as moisture, carbon dioxide, hydrocarbon and the like are removed from the compressed air from the air compressor through the molecular sieve, one part of the air is directly sent to the upper tower of the rectifying tower, and the other part of the air enters the expansion machine to be subjected to expansion refrigeration and then is sent to the lower tower. In the rectifying tower, after heat exchange between ascending steam and falling liquid, nitrogen with high purity can be obtained at the top of the upper tower, and oxygen with high purity can be obtained at the bottom of the upper tower. The second air separation unit M20 supplies oxygen of high purity obtained by separating air as an oxidizing agent to the oxychlorination unit M11.

The second air separation unit M20 may also be an air compressor, which compresses air to be fed to the oxychlorination unit M11, and the air may also participate in the oxychlorination reaction of the oxychlorination unit M11 as an oxidant.

The polyvinyl chloride device M12 produces polyvinyl chloride resin through suspension polymerization, the polymerization slurry is prepared into polyvinyl chloride S-PVC powder through steam stripping and centrifugal drying, and the polyvinyl chloride S-PVC powder is sent to the polyvinyl chloride product bin M21 and further sent to a packaging bin.

As shown in fig. 7, the present invention provides a clean closed-loop polyolefin production system further comprising,

the cracking furnace M22 is connected with the oxychlorination device M11, and is used for cracking a part of dichloroethane generated by the oxychlorination device M11 to generate vinyl chloride and hydrogen chloride, the hydrogen chloride is sent to the oxychlorination device M11 to continue reacting to generate vinyl chloride, and the vinyl chloride is sent to the polyvinyl chloride device M12 to synthesize polyvinyl chloride.

The reaction in the oxychlorination unit M11 also produces a portion of dichloroethane; the dichloroethane enters a cracking furnace M22 for cracking to generate chloroethylene and hydrogen chloride; the hydrogen chloride is sent to the oxychlorination device M11 to continue the reaction; the vinyl chloride generated by the cracking of the cracking furnace M22 is sent to the polyvinyl chloride device M12 to synthesize polyvinyl chloride.

The chlorine CL from the caustic soda device M4₂As the raw material of the oxychlorination device M11, and the ethylene and oxidant produced by the olefin preparation device M6 directly perform oxychlorination reaction, wherein one part of the oxychlorination reaction can be directly chlorinated into vinyl chloride, and the other part of the oxychlorination reaction can be chlorinated into dichloroethane EDC, the dichloroethane EDC can be cracked by the cracking furnace M22 to generate vinyl chloride, and then the vinyl chloride is sent to the polyvinyl chloride device M12 for polymerization; dichloroethane EDC is cracked by the cracking furnace M22 to generate hydrogen chloride, and the hydrogen chloride continuously enters the oxychlorination device M11 participate in the oxychlorination reaction. Thus, the small circulation of industrial production is formed, the clean production and the cyclic utilization of resources can be realized, and the zero emission of waste gas is realized.

The product of the oxychlorination unit M11 coming out of the top of the oxychlorination reactor contains, in addition to the vinyl chloride, dichloroethane formed by the reaction and CO as by-product₂CO and other chlorinated derivatives in small amounts, unconverted ethylene, oxygen, hydrogen chloride and inert gases, and also water formed by the main and secondary reactions. The reaction mixture gas enters a quenching tower, is sprayed with water and quenched to 90 ℃, absorbs hydrogen chloride in the gas, and removes entrained catalyst powder. The product dichloroethane and other chlorinated derivatives still remain in the gas phase and escape from the top of the quenching tower, and flow into a delayer after being condensed in a cooling condenser, and crude dichloroethane is obtained after being separated from water layer by layer. The separated water is recycled to the quench tower. And condensing the gas from the delayer through a low-temperature condenser, recovering dichloroethane and other chlorinated derivatives, introducing the non-condensable gas into an absorption tower, absorbing the dichloroethane and the like still existing in the absorption tower by using a solvent, and discharging tail gas containing about 1% of ethylene out of the system. The absorption liquid dissolved with dichloroethane and other components is desorbed in a desorption tower. The dichloroethane recovered in the low-temperature condenser and the desorber is sent to the delayer together. The crude dichloroethane from the delaminator enters a storage tank after being subjected to alkaline washing by an alkaline washing tank and water washing by a water washing tank, and then is separated and refined in 3 rectifying towers. The first tower is a light component removing tower to separate light components; the second tower is a dichloroethane tower, and a finished product of dichloroethane is mainly obtained; the third column is a heavies removal column operating at reduced pressure to distill the high boilers at reduced pressure and recover a portion of the dichloroethane therefrom. The refined dichloroethane was sent to a cracking furnace M22.

The water absorption liquid discharged from the bottom of the quenching tower contains hydrochloric acid and a small amount of chlorinated derivatives such as dichloroethane, and the like, and enters a stripping tower for steam stripping after alkali neutralization, the chlorinated derivatives such as dichloroethane and the like are recovered, and the condensed chlorinated derivatives enter an analyzer.

Hydrogen chloride obtained by cracking dichloroethane in the cracking furnace M22 is preheated to about 170 ℃ and is reacted with H₂Together into a hydrogenation reactor, and is catalyzed by palladium on aluminaIn the presence of a catalyst, the catalyst is hydrorefined to selectively hydrogenate the harmful acetylene impurity contained in the catalyst to ethylene. The ethylene feed is also overhead heated to a certain temperature and then mixed with hydrogen chloride and fed into the oxychlorination unit M11.

This cracking furnace M22 was supplied by Western American chemistry and was designed by the French Hull corporation. And (3) feeding the refined dichloroethane EDC into a cracking furnace M22, cracking at high temperature to obtain vinyl chloride VCM and hydrogen chloride HCL, wherein the cracking reaction is carried out in a fuel gas or fuel oil box-type furnace at the temperature of 490-510 ℃ and the pressure of 1Mpa, and the hydrogen chloride HCL is dried and then continuously fed into the oxychlorination device M11 for reaction.

As shown in fig. 8, the present invention provides a clean closed-loop polyolefin production system further comprising,

a rectifying apparatus M23 connected to the cracking furnace M22, and configured to purify the vinyl chloride produced by the cracking furnace M22;

and a vinyl chloride monomer ball tank M24 respectively connected with the rectifying device M23 and the polyvinyl chloride device M12 and used for receiving and storing the vinyl chloride refined by the rectifying device M23 and conveying the vinyl chloride to the polyvinyl chloride device M12.

And the chloroethylene generated after cracking in the cracking furnace M22 is refined by a rectifying device M23 and then sent to the chloroethylene monomer ball tank M24 for storage, and then sent to the polyvinyl chloride device M12 to synthesize polyvinyl chloride.

And a vinyl chloride finished product generated after cracking in the cracking furnace M22 is refined by a rectifying device M23 and then is stored in the vinyl chloride monomer spherical tank M24, and then is sent to the polyvinyl chloride device M12 for polymerization.

The invention aims at the defects of the existing polyolefin engineering project and forms a clean closed-loop production method and a system for polyolefin, wherein the method comprises the steps of resource → production → product → consumption → waste recycling → production → product → consumption. The production method and the system pay attention to the circulating combination among industries, and realize the large circulation of simultaneously preparing a series of products such as methanol preparation, olefin preparation, polyolefin preparation, polyvinyl chloride preparation, solid caustic soda or flake caustic soda and the like in one system through the large circulation of an industrial chain, for example, the polyolefin clean closed-loop production method and the system, and fully utilize byproducts and waste gas, realize the zero emission of waste, and fundamentally realize the comprehensive utilization of resources.

Meanwhile, small circulation in the industry is strengthened, clean production and recycling of resources are implemented, for example, carbon dioxide in a gasification device M1 and a purification device M2 is recovered as raw materials of a synthesis conversion device M5 to further synthesize methanol, and the methanol is sent to the next olefin preparation step, so that the small circulation is formed; and through the arrangement of the cracking furnace M22, the dichloroethane generated by the oxychlorination device M11 is fully utilized for cracking, the internal small circulation from the chloroethylene preparation to the polyvinyl chloride preparation is formed, and the hydrogen chloride generated by the cracking of the cracking furnace M22 is continuously fed into the oxychlorination device M11 to participate in the oxychlorination reaction, so that the small circulation from the cracking of the cracking furnace to the oxychlorination reaction is formed, and the zero emission of waste gas is really realized.

The invention utilizes the comprehensive utilization of coal resources to drive the comprehensive development of various resources such as chlorine, sodium and the like, and constructs a complete circular economy industrial chain. The fusion development among multiple industries of salt chemical industry, coal chemical industry, chlor-alkali chemical industry and petrochemical industry is realized; on one hand, the zero emission of waste gas in the process of preparing methanol from coal is realized, and the discharged waste gas CO is₂All the components are recovered and used as raw material gas of a synthesis conversion device M5; on the other hand, the method realizes the mercury-free production of the polyvinyl chloride and realizes the requirement of Water guarantee convention. China is one of the contracting countries of the Water guarantee convention, and according to terms of the convention, the contracting countries forbid the production, import and export of mercury products in 2020. Mercury chloride is used as a catalyst in the production of PVC by a calcium carbide method, and the method is an industry with the largest mercury consumption in China. The convention will reverse the transformation and upgrade of the industry, and the enterprises of the calcium carbide method will be forced to turn to the ethylene method. The production and sales of PVC by calcium carbide method are reduced, the total mercury consumption is reduced, and the production process of PVC by calcium carbide method is eliminated.

In addition, the control of the whole polyolefin clean closed-loop production system process adopts an advanced DCS control technology, and has higher automation level and operability. The construction of the industrial chain conforms to the scientific development and national industrial policies, and conforms to the development planning and development strategy of the circular economy industry; the method is favorable for further promoting the comprehensive and effective utilization of resources, fully exerts the advantages of the resources, accelerates the resource conversion process, and has great significance for promoting the circular economy of salt lakes and the economic, fast and sustainable development of Qinghai provinces.

The invention realizes the organic combination and mutual circulation of chlor-alkali chemical industry and coal chemical industry, and realizes zero emission through the clean production and the cyclic utilization of resources. The construction of the industrial chain can relieve the contradiction between the polyolefin market supply and the shortage of energy and resources, environmental pollution and ecological protection, and can also drive the reasonable development and utilization of local upstream and downstream products such as coal mines, polyolefin profiles and pipes, polyvinyl chloride profiles and various chlorine products, thereby forming an upstream and downstream integrated green industrial chain. Meanwhile, the method can drive the comprehensive utilization of local commerce, transportation industry and byproducts, accelerate the construction of energy and heavy chemical industry bases in project construction areas, promote economic development, improve the unbalanced pattern of industrial distribution in China, reduce the dependence of national economic development on petroleum, and has very positive significance for improving the energy and chemical raw material structures.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims

1. A clean closed-loop production method of polyolefin, comprising the following steps:

methanol production step (S1):

purifying the synthesis gas by a purification device to obtain purified gas;

the purified gas enters a methanol device to synthesize methanol;

the solid raw salt is subjected to electrolytic reaction in a caustic soda device by adopting an ion membrane electrolysis technology to produce hydrogen, chlorine and a sodium hydroxide solution, and the sodium hydroxide solution is evaporated and concentrated to prepare a solid caustic soda finished product;

polyolefin production step (S2):

the ethylene enters a polyethylene device to react to generate polyethylene;

the propylene enters a polypropylene device to react to generate polypropylene;

polyvinyl chloride production step (S3):

the ethylene, the oxygen and the chlorine produced by the caustic soda device enter an oxychlorination device to carry out oxychlorination reaction, and C₂H₄:HC1:O₂The method comprises the following steps that (1.05: 2: 0.75-0.85 (mol)), generated chloroethylene enters a polyvinyl chloride device to synthesize polyvinyl chloride, dichloroethane is generated through reaction in an oxychlorination device, the dichloroethane enters a cracking furnace to be cracked to generate chloroethylene and hydrogen chloride, the hydrogen chloride is sent to the oxychlorination device to continue reacting, and the chloroethylene generated after cracking in the cracking furnace is refined through a rectifying device and then sent to a chloroethylene monomer spherical tank to be stored, and then the chloroethylene is sent to the polyvinyl chloride device to synthesize polyvinyl chloride.

2. The production method according to claim 1, wherein, in the step (S1),

3. The production method according to claim 1, wherein, in the step (S2),

4. The production method according to claim 1, wherein, in the step (S2),

5. The production method according to claim 1, wherein the step (S3), further comprises,

the oxygen is generated by separating air by a second air separation unit;

6. A clean closed-loop polyolefin production system comprising:

an oxychlorination device respectively connected with the ethylene storage tank and the caustic soda device, and using the ethylene, the chlorine and the oxygen as raw materials, C₂H₄:HC1:O₂Generating oxychlorination reaction to generate chloroethylene, wherein the molar ratio of the chloroethylene to the chloroethylene is 1.05:2: 0.75-0.85 (mol);

the polyvinyl chloride device is connected behind the oxychlorination device and takes the chloroethylene generated by the oxychlorination device as a raw material to synthesize polyvinyl chloride;

the cracking furnace is connected with the oxychlorination device and is used for cracking a part of dichloroethane generated by the oxychlorination device to generate vinyl chloride and hydrogen chloride;

7. The production system of claim 6, further comprising:

8. The production system according to claim 6,

the olefin preparation device is a DMTO device, the DMTO device adopts DMTO technology, and the methanol is used as a raw material to prepare the ethylene and the propylene which meet the polymer grade.

9. The production system of claim 6, further comprising,

10. The production system of claim 6, further comprising: