Polyethylene is the most important downstream product of ethylene, polyethylene (PE) accounted for 70% of the world's consumption of polyolefins, accounted for 44% of the total thermoplastic general-purpose plastics consumption, and consumed 52% of the world's ethylene production. Polyethylene is basically categorized into three main types, namely high-pressure low-density polyethylene (LDPE), high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). Film is its main processed product, followed by sheets and coatings, hollow containers such as bottles, cans, drums and other various injection and blow molded products, pipes and insulation and sheathing for wires and cables. Mainly used in packaging, agriculture and transportation sectors. Compared with other countries in the world, China is used for agricultural film LDPE and LLDPE amount is more. China is the world's largest production of agricultural films, which is determined by the characteristics of China's large agricultural country.2. Production capacity and output By the end of 1998, China has built 26 sets of polyethylene units, with a total capacity of 2.51 million tons.3. Brief description of the production method HP-LDPE is produced by two kinds of high-pressure liquid-phase method process, i.e., kettle method and tube method. The polymer produced by kettle process has narrow molecular weight distribution and more branched chains, while the product of tube process has wider molecular weight distribution and less branched chains. The process steps of the kettle and tube methods are similar except for the polymerization reactor. The maximum single-line reactor capacity of tubular method is 200,000 tons/year (such as Exxon's plant in Belgium and DSM's plant in the Netherlands), while the maximum single-line reactor capacity of kettle method is 180,000 tons/year (with the possibility of reaching 200,000 tons/year), which is the plant built in Qatar by QGPC with Orchem (CdF) technology. The kettle process and tube process have their own merits, generally speaking, large-scale device tends to use the tube method; production of specialized grades of the device is more inclined to use the kettle method. 1998 November put into operation in Qilu Petrochemical Company's LDPE plant, the use of the Netherlands DSM company's high-pressure tube method process, is the most similar devices in China's current product grades, the largest production capacity of a single line of the largest device. Yanshan Petrochemical Company will also build a set of 200,000 tons / year of LDPE plant, using Exxon technology, the contract has been signed. Linear polyethylene (HDPE/LLDPE) is produced by low-pressure liquid-phase method and gas-phase method. The two current liquid phase processes in the world, the slurry process and the solution process, are still dominant in terms of total production. Important solution-phase processes are the medium-pressure process of DuPont (now Novacor) in Canada, the low-pressure cooled process of Dow and the Dutch Mining Company (DSM) process. Each of these plants can alternately produce HDPE and LLDPE (industrially known as convertible plants, domestically known as full density polyethylene). The two most widely used slurry processes are the ring tube reactor process with light diluents (Phillips and Solvay) and the stirred tank process with heavy diluents (Hoechst, Nissan, Mitsui). The primary product of the slurry process is HDPE, but some MDPE can be produced as a secondary product. UCC and BP are the major holders of line-type polyethylene vapor phase process technology. Gas phase process units are generally convertible units that can produce LLDPE and HDPE alternately, subject to certain limitations in the patent agreements. Units licensed to produce both products are also typically required to prioritize the production of one product for an extended period of time. Even for convertible units, frequent interchanges between HDPE and LLDPE products are uneconomical and are not practiced. The world's peaceful capacity for polyethylene in 1997 was about 50.7 million tons per year, with North America and Western Europe accounting for more than half of the world's total capacity. Asian countries (including Japan) accounted for about 1/4 of the world's total capacity. in terms of process, high-pressure polyethylene accounted for about 38% of the total, with the tube method and kettle method each accounting for almost half of the total. The slurry process accounts for about half of the 62% share held by bus type polyethylene. In China, the proportions of kettle method, tube method, slurry method, vapor phase method and solution method in the total polyethylene production capacity in 1998 were 9%, 18%, 26%, 43% and 3.2% respectively. Compared with the world average proportion of production capacity of various process methods (19%, 19%, 30%, 24% and 8), the gas-phase method is high, the tubular method is similar, and other methods are low. In recent years, China's polyethylene industry has also made promising achievements in catalyst development, process equipment localization and new product development. Significant progress in catalyst localization 30 tons / year localized HDPE catalyst production unit has been built in Yanshan Petrochemical Company, the production of catalyst has been used in large-scale industrialized devices. At present, the recapitulation rate of domestic catalyst applied on slurry method HDPE plant has exceeded 80%. The research of metallocene catalyst in China has made good progress, by the middle of 1996, ****developed five model test or patented technology, has obtained five Chinese patent application number, Beijing Petrochemical Science and Technology Research Institute, Lanzhou Chemical Industry Company and the Shanghai Research Institute of Chemical Technology has been in the gas-phase fluidized bed model test device with a bimodal molecular weight distribution of metallocene - LLDPE, Shiyan Institute of Science and Technology also synthesized the production of high-density, low-density, ultra-low-density, ultra-low-density, ultra-low-density HDPE plant, the catalysts have been used in large-scale industrial plants. The Institute has also synthesized metallocene catalysts for the production of high-density, low-density, ultra-low-density and long-chain branched polyethylene resins, and the loaded bridged zirconium catalysts developed by the Institute have been validated in different scales of medium-sized tests. The metallocene catalyst APE-1S developed by the institute has successfully passed the pilot test in Liaohua, and has completed the pilot evaluation test in the continuous reactor of ring tube slurry method in cooperation with Phillips Company of the U.S.A. The test shows that the catalyst has higher activity and better catalytic ability for 1-hexene*** polymerization, and the polymerized products have better particle size distribution and higher stack density. In March 1999, the catalyst passed the appraisal organized by China Petroleum & Chemical Corporation and China National Petroleum Corporation. Process development has achieved fruitful results, Shanghai Research Institute of Pharmaceutical Industry, Yangzi Petrochemical Company Design Institute and Yanshan Petrochemical Company have developed slurry HDPE process. The 140,000 tons/year HDPE plant of Yanshan Petrochemical Company was designed and constructed by our country, and it took only 27 months and 25 days from June 1, 1992, when the plan was determined, to September 26, 1994, when the plant was put into operation, saving 47.43 million yuan of foreign exchange compared with the introduction of technology and equipment construction. After that, 70,000 tons/year production line was built in Lanzhou Chemical Industry Company by this process. Yangzi Petrochemical Company has completed the "200,000 tons/year slurry high-density low-pressure polyethylene technology package", which has an advanced level in the same kind of plant, and has passed the appraisal of SINOPEC Corporation in 1997. The adoption of this technology can greatly reduce the project cost of the new polyethylene plant and effectively guide the expansion and transformation of the existing plant. Shanghai Pharmaceutical Industry Design Institute and Yanshan Petrochemical Company have jointly developed a new process of full-density polyethylene production by slurry method and horizontal gas-phase kettle tandem, which has been applied for Chinese patent and is ready to be implemented in Yanshan's industrialized plant. The development of new products has made certain achievements. Qilu Petrochemical Company's production of high-strength film, pipe and large hollow containers has become the company's fist product, HDPE wrapped pipe special material following the national key project Shaan-Beijing natural gas gathering and transmission projects in the successful application of the recent international bidding to beat a number of well-known foreign companies, to achieve the pipeline anticorrosive plant in Egypt's exports to break the Europe and the United States completely control the situation of the Middle East synthetic resins special materials. The situation is broken. Yanshan Petrochemical Company trial production of high molecular weight, wide molecular weight distribution, ESCR performance of the pipe material 6000 M. Beijing Research Institute of Chemical Technology successfully developed for automotive fuel tanks HDPE material, the Institute simulated two kettle tandem method of two kettle polymerization of ethylene in 2-liter polymerization kettle, the preparation of molecular weight distribution of high molecular weight bimodal molecular weight butene *** polymerization of HDPE resins, performance indexes with the foreign single layer of the base resin for automotive fuel tanks. The performance index is comparable with the performance of the base resin of the special material for automobile fuel tank. 4. demand in 1998 China's polyethylene production of 2.3 million tons, of which 740,000 tons of HDPE, LDPE 591,000 tons, LLDPE (including full-density polyethylene device in the production of HDPE) 971,000 tons. 1998 China's net imports of polyethylene 2.42 million tons, apparent consumption of 4.72 million tons. 1998 China's polyethylene production capacity of about the world's production capacity (55.23 million tons), the production capacity of the world's polyethylene production capacity (55.23 million tons). In 1998, China's polyethylene production capacity was about 4.5% of the world's production capacity (55.23 million tons), and the apparent consumption was 10.8% of the world's consumption (43.7 million tons). Because a considerable part of the imported polyethylene in China is processed from incoming materials, but half of the resin processed from incoming materials often stays in the country. When calculating the demand, 60% of the imported resin is imported for incoming processing, and half of the incoming processed polyethylene stays in the country, i.e. 70% of the imported volume is calculated to meet the domestic demand. 5. growth rate 1983-1998 China's average annual growth rate of polyethylene consumption of 15.2%, for the GDP growth rate (10.3%) of 1.5 times. 1993-1997 China's polyethylene plant average operating rate of 90.5%. 6. Application Distribution The largest amount of LDPE is used for film and sheet, followed by extrusion coating, injection molding, wire and cable. These four applications total*** 90% of LDPE applications. Film is the largest market for LDPE, with packaging and non-packaging applications accounting for roughly 50% each. Extrusion coating is the world's second largest market for LDPE, is the fast-growing application of LDPE, mainly due to the development of packaging technology and packaging styles continue to renovate. Film and sheet applications account for 75% of world LLDPE consumption. Injection molding and wire and cable are the second and third largest applications of LLDPE respectively, but only accounted for 7%~15% of the total LLDPE consumption. Stretch film is the world's fastest-growing market for LLDPE in the packaging field, is replacing packing tape, corrugated board, wrapping paper and shrink wrap. Packaging accounted for 75% of the amount of HDPE resin, construction accounted for 10% to 15%, while the remaining 10% to 15% for a variety of other consumer and industrial supplies. The United States and Western Europe blow molding and injection molding is the most important application areas, accounting for about 60% of the total consumption of ~ 50%, but in Japan and other countries in Asia, HDPE in these sectors of consumption is only 1 / 3 of the total consumption, according to the proportion of consumption, the proportion of Asian countries, the proportion of the film used in the United States and Western Europe, 2 times. To the U.S. market, for example, HDPE consumption of the largest sectors are all kinds of bottles, barrels, cans and bags, followed by sheet, pipe, boxes, trays and wires, cables, etc., but is expected to grow at the highest annual rate of application of automotive fuel tanks, barrels and tanks, followed by lining boards, water supply and irrigation water pipes and geotextile film. Films account for almost 60% of China's polyethylene consumption (see table), of which agricultural films account for 20.4%. in 1998, China consumed more than 700,000 tons of polyethylene resin for agricultural films. China has the highest production of agricultural films in the world, which is determined by the characteristics of China as a large agricultural country. Other applications of polyethylene include pipes, sheets, hollow containers, monofilaments, woven products, injection molded parts, wires and cables. Domestic consumption of agricultural pipes, followed by drinking water pipes and gas pipes; hollow containers are mainly used for beverages, cosmetics, edible oils and pharmaceutical packaging. 1997 more than 100 liters of containers with resin consumption of about 60,000 tons; monofilament and woven products are mainly used for ropes, fishing nets, and colorful fabrics; cable materials are mainly used for insulation, cross-linked cable materials and sheathing materials; injection molded plastics are mainly used for the production of crates, plastic trays, plastic bottles and caps. Plastic injection molding is mainly used for the production of crates, plastic trays, plastic bottle caps and other products; others include polyethylene coating and chlorinated polyethylene and so on. 7. development prospects for many years China's polyethylene production has not been able to meet market demand, imports accounted for about half of the apparent demand. 1983-1997 China's average apparent demand for polyethylene to meet the rate of 46%, the average rate of satisfaction is 54%. If all of China's large and medium-sized ethylene can complete the transformation in 2002, it is expected that the capacity of polyethylene can be up to 3.7 million tons, with an output of 3.3 million tons based on 90% of the start-up rate. According to the historical changes in demand, according to the development of China's national economy is predicted, it is predicted that China's polyethylene demand in 2002 for 5.86 million tons (apparent demand of 7 million tons), in 2005 for 7.9 (9.5) million tons, in 2010 for 12.2 (14.8) million tons. The fulfillment rate and apparent fulfillment rate of polyethylene in China in 2002 are projected to be 56% and 47% respectively. It is comparable to the average level of 1983-1997. Polyethylene in China has considerable market potential, is very promising petrochemical products.