Original Title Dry Goods Sharing │ Detailed Interpretation of High Pressure Low Density Polyethylene Production Process Technology Low density polyethylene (LDPE) is a thermoplastic resin obtained by free radical polymerization with polymerization grade ethylene as polymerization monomer and peroxide as initiator Its molecular weight is generally between 100000 and 500000 and its density is 091 ~ 093 G/cm3 It is the lightest variety of polyethylene resin It has good softness extensibility electrical insulation transparency easy processing and certain air permeability It has good chemical stability alkali resistance and general organic solvent resistance and has a wide range of applications including extrusion coating blown film wire and cable coating injection molding and blow molding As the service cbd centrifugal extractor life of the free radicals generated by the initiator is relatively short the ethylene is highly compressed by increasing the reaction pressure (110-350MPa) so that the density of the ethylene is increased to 05g/cm3 which is similar to a liquid that can not be compressed any more so as to shorten the distance between ethylene molecules and increase the collision probability between free radicals or active propagation chains and ethylene molecules for free radical polymerization Low density polyethylene is produced so low density polyethylene is also called high pressure low density polyethylene Low density polyethylene production proces The production process of low density polyethylene mainly includes ethylene two-stage compression initiator and regulator injection polymerization system high and low pressure separation and recovery system extrusion granulation and post-treatment system According to the different types of reactors it can be divided into high-pressure tube method and autoclave method The tubular process and the autoclave process have their own characteristics The tubular reactor is simple in structure easy to manufacture and maintain and can withstand higher pressure The structure of kettle reactor is complex and it is relatively difficult to maintain and instal
The pulse operation improves the mixing effect in the reactor has good reaction stability and high conversion rate reduces the wall sticking of the reactor improves the heat transfer coefficient and has better heat removal effect of jacket water; (2) peroxide is taken as an initiator and is inject into different areas of a reactor at four point to form four sections of reaction areas; (3) propylene and propionaldehyde are use as molecular weight regulators and are introduce from that inlet of a primary compressor and enter the reactor along with ethylene and the product range is wide; (4) The high-pressure circulating gas system can realize the self-cleaning dissolution dewaxing operation through sequential control to reduce the impact on the normal production operation; (5) Set up hot water hemp extraction centrifuge station system to reduce cooling water consumption and recover the heat of polymerization reaction and high-pressure circulating gas system for other devices 02 Exxon Mobil Tube Test Process Under The conditions of reaction pressure 250 ~ 310 MPa reaction temperature 215 ~ 310 ℃ conversion rate up to 40% product density 0918 ~ 0934 G/cm 3 melt index 02 ~ 50 G/ (10 min) and productivity of 50 × 10 4 t/a per line The process has six technical characteristics (1) a plug-flow tubular reactor is adopted the diameter of the reactor is gradually enlarged along the axial direction and the gas flow rate and the pressure drop of the reactor are optimized The reaction stability is increased the decomposition reaction is reduced the scaling inside the reactor is reduced and the heat transfer efficiency of the reactor is improved;
propylene is generally used as a regulator to control the melt index propionaldehyde is used as a regulator in the production of medium density grade products the regulator is injected to the inlet of the secondary compressor through a high-pressure diaphragm pump and then enters the reactor along with ethylene; And (4) a mode of combining the forward feeding of hot ethylene and the multi-point lateral feeding of cold ethylene in the tubular reactor is adopted so that the reaction heat is uniformly released and can be removed the cooling load of a reactor jacket is optimized jacketed glass reactor the length of the reactor is reduced the temperature distribution of the reactor is stable and the ethylene conversion rate is improved At the same time because of multi-point lateral feeding the forward hot ethylene feeding amount of the reactor is reduced the heat load of the preheater at the inlet of the reactor is reduced and the consumption of high-pressure and medium-pressure steam is reduced; (5) a closed temperature regulate water system is adopt to supply water for that reactor jacket reaction heat is removed the heat transfer efficiency is improved the length of the reactor is shorten and the conversion rate is improved by optimizing the water supply temperature of the jacket water;
The melt index and density of LDPE/EVA products can be well controlled by APC control system and uniform products can be obtained Sierbang Petrochemical Company Yangzi Petrochemical Company and Shanghai Petrochemical Company have introduced this process in China and the capacity of their plants is 10 × 104t/a 02 Exxon Mobil kettle proces The Exxon Mobil autoclave process uses a 15m3 multi-zone autoclave reactor designed by ourselves The reactor has a larger aspect ratio longer residence time higher initiator efficiency and narrower molecular weight distribution of the product which is conducive to the production of film products with quality similar to the tubular process Different from the Exxon Mobil tubular process the regulator uses isobutylene or n-butane which is boosted to 25 ~ 30 MPa by a high-pressure diaphragm pump injected from the inlet of the secondary compressor and enters the reactor together with ethylene The pressure range of the reactor is wide the maximum reaction pressure is 200 MPa and the LDPE homopolymer with low melt index and the EVA copolymer with high vinyl acetate content can be produced LDPE homopolymerized products with melt index of 02 ~ 150 G/ (10 min) and density of 0910 ~ 0935 G/cm3 can be produced by Exxon Mobil autoclave process An ethylene-vinyl acetate copolymer (EVA) product with a melt index of 02 to 450 G/ (10min) and a vinyl acetate content of 35% In China Levima Group (formerly Shandong Haoda) with a plant capacity of 10 × 104t/a and Zhongtian Co-founder with a plant capacity of 12 × 104t/a are the main ones to introduce this process Return to Sohu to see more Responsible Editor toptiontech.com