The 11 major polyethylene production technologies worldwide

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　　According to the Chemical Engineering 707 News Network: There are many companies in the world that possess polyethylene production technology; 7 companies have LDPE technology, 10 companies have LLDPE and high-density polyethylene technologies, and 12 companies have HDPE technology. In terms of technological development, the high-pressure method for producing LDPE is the most technologically mature method in PE resin production. Both the batch process and the tubular process technologies have reached maturity; currently, these two production technologies coexist. Developed countries **generally use the tubular process for production. 　　Furthermore, foreign companies generally use low-temperature, high-activity catalysts to initiate the polymerization process, which allows for lower reaction temperatures and pressures. The production of LDPE by high-pressure methods will evolve toward larger scale and tubular formats. In the low-pressure process for producing HDPE and LLDPE, titanium-based and chromium-based catalysts are primarily used. In Europe and Japan, Ziegler-type titanium-based catalysts are commonly employed, while in the United States, chromium-based catalysts are more frequently used. 　　Currently, 11 production technologies for polyethylene are widely used in the world, which are briefly introduced as follows: (1) Basell’s Spherilene process via gas phase method – this process can produce linear PE ranging from ultra-low density PE (ULDPE) to LLDPE, as well as HDPE. A Ziegler-Natta-type titanium-based catalyst and the Spherilene vapor-phase process are employed. In the presence of light inert hydrocarbons, the catalyst and feed undergo bulk pre-polymerization first, with bulk polymerization taking place under mild conditions. The slurry enters the first gas-phase reactor, where it is cooled by a circulating gas loop cooler, before proceeding to the two subsequent gas-phase reactors. 　　The density of the produced products ranges from ULDPE (less than 900 kg/m3) to HDPE (greater than 960 kg/m3), while the melt flow rate (MFR) ranges from 0.01 to 100. Thanks to the use of two gas-phase reactors, bimodal-grade and specialty polymers can be produced. Since the Spherilene process was introduced to the market in 1992, its production capacity has now reached 1.8 million tons per year. Six production units (1 in the United States, 2 in South Korea, 2 in Brazil, and 1 in India) are already in operation, with another two (one in India and one in Iran) under construction. The annual production capacity per unit ranges from 100,000 tons to 300,000 tons. At present, China does not have production facilities for such technology. 　　(2) Bastar process of Nordic Chemicals The Bastar PE process can produce bimodal and unimodal LLDPE, MDPE (medium-density PE), and HDPE. A series-connected loop and a low-pressure gas-phase reactor are used. The PE density is 918–970 kg/m3, with a melt index of 0.1–100. Z-N catalysts or SSC (single active center) catalysts are used. 　　The catalyst and propane diluent are mixed and fed into a compact prepolymerization reactor, along with the co-catalyst, ethylene, comonomer, and hydrogen. The pre-polymerized slurry then enters a second, larger slurry loop reactor, which operates under supercritical conditions (75–100°C, 5.5–6.5 MPa). Bimodal-grade products can be produced. The polymer after flash evaporation is further fed into a fluidized-bed gas-phase reactor; without the need to add new catalyst, a homopolymer can be obtained. The operating conditions for the gas-phase reaction are: 75–100°C and 2.0 MPa. The first industrial-scale plant was put into operation in Finland in 1995; the two production lines built in Abu Dhabi (with a capacity of 450,000 tons per year for bimodal-grade products) were commissioned in the second half of 2001. The fifth 250,000-ton/year unit (the second bimodal-grade unit) has also been commissioned at Shanghai Petrochemical Company in China, making it the largest PE plant in the country. The maximum designed capacity of this process on a single line can reach 300,000 tons/year. 　　(3) BP’s gas-phase Innovene process: capable of producing LLDPE and HDPE products, using Z-N titanium-based, chromium-based, or metallocene catalysts. Chromium catalysts can produce products with a wide molecular weight distribution, while Ziegler-Natta (Z-N) catalysts produce products with a narrow molecular weight distribution. The operating conditions of the bed reactor are mild, at 75–100°C and 2.0 MPa. Butene or hexene can be used as comonomers. 30 production lines are already in operation, under design, or under construction. The capacity range is 50,000 to 350,000 tons per year. 　　Technip, in partnership with BP, operates BP’s Innovene process for producing polyethylene in Europe, the former Soviet Union, South America, China, and Malaysia. BP’s Innovene PE capacity now exceeds 8 million tons per year, including PE plants in Bandar Imam, Iran; Grangemouth, Scotland; Merak, Indonesia; and Kerteh, Malaysia. The secondary expansion of the LLDPE/HDPE plant at China’s Dushanzi Petrochemical Company also employed the Innovene process, increasing production capacity from 120,000 tons per year to 200,000 tons per year. Sinopec’s newly built 600,000-ton polyethylene plant will use this technology. 　　(4) ExxonMobil’s tubular and batch reaction processes: High-pressure free-radical processes are used to produce LDPE homopolymers and EVA (ethylene vinyl acetate) copolymers. Large-scale tubular reactors (capacity of 130,000–350,000 tons per year) and stirred-tank reactors (capacity of about 100,000 tons per year) are used. The operating pressure of tubular reactors can reach up to 300 MPa, while that of batch reactors is below 200 MPa. The advantage of high-pressure processes is reduced residence time, allowing the same reactor to switch from producing homopolymers to copolymers. The density of the homopolymer is 912–935 kg/m3, and its melt index ranges from 0.2 to 150. The vinyl acetate content can be as high as 30%. The material and energy consumption per ton of polymer produced is as follows: 1.008 tons of ethylene, 800 kwh of electricity, 0.35 tons of steam, and 5 m3 of nitrogen. 23 high-pressure reactor units have been put into operation, with an annual production capacity of 1.7 million tons. Produces homopolymers and various copolymers. The newly built 200,000 tons/year LDPE plant in Yanshan currently utilizes this company’s tubular process technology. 　　(5) Mitsui Chemicals’ low-pressure slurry process CX – This process is used to produce HDPE and MDPE, and it relies on the low-pressure slurry process CX technique. Products with a bimodal molecular weight distribution can be produced. Ethylene, hydrogen, comonomers, and an ultra-highly active catalyst enter the reactor where polymerization occurs in a slurry state. An automatic control system for polymer properties enables effective control of product quality, and there is no need to remove the ultra-highly active catalyst from the product. 90% of the solvent separated from the slurry can be directly recycled to the reactor without any treatment. Products with a narrow or wide molecular weight distribution can be produced, with a density of 930–970 kg/m3 and a melt index of 0.01–50. The material and energy consumption per ton of product produced is as follows: 1010 kg of ethylene and comonomers, 305 kwh of electricity, 340 kg of steam, 190 tons of cooling water, and 30 m3 of nitrogen. 35 production lines have been put into operation or are under construction, with a total capacity of 3.6 million tons per year. Currently in China, the main enterprises utilizing this technology include a 220,000-ton plant in Daqing, 140,000-ton plants in Yangzi and Yanshan, and a 70,000-ton plant in Lanzhou. 　　(6) Chevron-Phillips’ two-loop reactor LPE process Linear polyethylene (LPE) is produced using Phillips Petroleum Company’s LPE process. Polymerization is carried out in a loop reactor and isobutane slurry using a highly active catalyst. The product melt index and molecular weight distribution can be adjusted and controlled by the catalyst, operating conditions, and hydrogen. Possible comonomers include butene-1, hexene-1, octene-1, etc. The highly active catalyst eliminates the need for catalyst removal, and no paraffin or other by-products are generated during polymerization, **reducing environmental pollution from emissions. Ethylene, isobutane, comonomers, and catalyst are continuously fed into the loop reactor, where they react at temperatures below 100°C and pressures of about 4.0 MPa, with a residence time of approximately 1 hour. The single-pass conversion rate of ethylene exceeds 97%. The material and energy consumption per ton of product produced is as follows: 1.007 tons of ethylene, 2–10 dollars for catalysts and chemicals (varies depending on the product), 350 kwh of electricity, 0.25 tons of steam, 185 tons of cooling water, and 30 m3 of nitrogen. A total of 82 production lines have been put into operation or are under construction, accounting for 34% of the world’s PE capacity. The 135,000-ton facility of Shanghai Jinfei Company utilizes this technology. The newly built 350,000 tons per year plant in Maoming may also adopt this technology. 　　(7) Univation Technologies’ low-pressure gas-phase Unipol process
The low-pressure, gas-phase Unipol PE process is used to produce LLDPE-HDPE. Slurry catalysts and gas-phase, fluidized-bed reactors are used. Conventional metallocene catalysts can be used without a catalyst removal step. The investment and operating costs are low, and it causes less environmental pollution. Ethylene, comonomers, and catalyst are fed into the fluidized bed reactor under operating conditions of about 100°C and 2.5 MPa. The product density is 915–970 kg/m3, with a melt index of 0.1–200. Depending on the catalyst type, a narrow or broad molecular weight distribution can be adjusted. A total of 89 production lines have been put into operation or are under construction. The single-line capacity can range from 40,000 to 450,000 tons per year. Currently, there are many facilities in China that use this technology, mainly in Maoming, Jihua, Yangzi, Tianjin, Zhongyuan, Guangzhou, Daqing, Qilu, and other places. 　　(8) Stamicarbon’s COMPACT process: This process utilizes advanced Z-N catalysts along with the COMPACT Solution technology to produce PE with a density of 900–970 kg/m3. A stirred-tank reactor is used, with a polymerization temperature of 200°C. Hydrogen is used to control the polymer molecular weight. There is no need for a catalyst removal step. The material and energy consumption per ton of product produced is as follows: 1.016 tons of ethylene and comonomers, 500 kwh of electricity, 400 kg of steam, 230 m3 of cooling water, and 330 kg of low-pressure steam (as a by-product). 5 sets of units are in operation, with a total capacity of 650,000 tons per year. 　　(9) Basel Polyolefins Hostalen process HDPE is produced using the Hostalen process in a stirred-tank reactor. Slurry polymerization is carried out using two reactors in parallel or in series. The material and energy consumption per ton of product produced is as follows: 1.015 t of ethylene and comonomers, 400 kg of steam, 350 kwh of electricity, and 165 m3 of cooling water. Currently, 31 production lines are in operation or under construction, with a production capacity of nearly 3.4 million tons per year. Currently, the only domestic enterprise applying this technology is Liaohua Company, whose production capacity is merely 40,000 tons. Currently, the maximum production capacity of this technology on a single line can reach 350,000 tons per year. It can produce almost all products, including bimodal ones. Its films, hollow products, and pipes have gained a certain reputation worldwide. 　　(10) Eni Chemical’s high-pressure process: LDPE and EVA are produced using high-pressure batch or tubular processes. The density of LDPE is 918–935 kg/m3, and the VAM (vinyl acetate monomer) content in EVA can range from 3% to 40%. There are currently 24 production lines in operation or under construction, with each line having a capacity of up to 200,000 tons per year. Currently, the investment cost and energy consumption of this equipment are relatively high; therefore, this technology is generally not used in newly built facilities. 　　(11) Stamicarbon’s high-pressure process – Uses high-pressure tubular reactors to produce LDPE and EVA copolymers. The material and energy consumption per ton of output is as follows: 1.005 tons of ethylene, 800 kwh of electricity, 230 kg of high-pressure steam, 120 m3 of cooling water, and 650 kg of low-pressure steam (as output). Since 1996, multiple units with a single-line capacity of 150,000–300,000 tons per year have been put into operation, resulting in a total capacity of over 1.8 million tons per year.