Will ceramics be oxidized?
2021 01/21
The ceramic oxide flashed from the second reactor to a pressure of 0.14MPa. The unreacted ethylene, ethane in the effluent and 2% cyclohexane diluent were compressed and cooled to 2.5MPa after two times. The stripping tower recovers the ethane for recycling. The slurry remaining after flash evaporation is centrifuged to recover most of the diluent, and the solid filter cake is sent to the dryer to reduce the volatile content to about 5% (mass fraction). The dryer is operated with nitrogen protection as a closed cycle. The dried polymer powder is sent to a fluidized bed for drying to remove all hydrocarbon diluents. After drying, the polymer particles are sent to the mixing section to add various additives, and then granulated. (2) Loop tube reactor technology The typical Silicon Carbide Ceramics representatives of loop tube reactor technology are Phillips technology of Phillips company and Innovene S technology of INEOS company. The Phillips process uses isobutane as the diluent and uses a chromium catalyst. The catalyst must be activated before use. The activated catalyst powder forms a catalyst slurry with high-purity isobutane under the protection of nitrogen, and then enters the loop reactor After the raw material ethylene monomer is refined, it is premixed with hydrogen and comonomer hexene-1 and then injected into the loop reactor. The ethylene generates polyethylene under the action of the catalyst. The axial flow pump maintains the high-speed flow and very uniform mixing of the materials in the reactor, and the reaction heat is evenly withdrawn by the jacket cooling water. The MI range produced by this process is 0.15-100, and the density is 0.936-0.972 g/cm3. The characteristics of the loop reactor process are: less equipment, short process, low investment cost; no wax and oligomers, no sticking to the wall; good shape of the powder, easy to transport; reaction heat is taken out by the cooling water of the reactor jacket It is easy to withdraw heat and convenient to adjust; raw materials are required to be purified; hexene is used as comonomer; and isobutane is used as solvent, which is easy to remove residual solvent. The technological process is as follows: after drying fresh polymer grade ethylene, the molecular weight regulator hydrogen, antifreeze and circulating diluent isobutane are mixed and then sent to the multi-loop continuous process reactor, and the catalyst is supplemented with isobutane. Into the reactor. The reaction temperature was 106.7°C and the pressure was 3.9 MPa. The polymer and diluent slurry passed through the loop reactor at a speed of 6m/s by means of an axial flow pump. The water cooling in the reactor jacket controls the reaction temperature, and the polymer solids are discharged from the vertical settling port in the loop reactor. So that the slurry concentration can reach 55%, and the conversion rate is 98%-99%. After the polymer is discharged, flash evaporation will discharge isobutane and residual monomers to the diluent recovery device. Other solid polymers are mixed with additives and pelletized. 2. Gas-phase polymerization method: typical representatives of the gas-phase polymerization method (gas-phase fluidized bed method) are the univation technology of DOW Chemical Company and the Innovene technology of INNOS. The univation technology process adopts low pressure gas phase fluidized bed reactor, adopts ZN catalyst and chromium system The catalyst and the purified raw materials are injected into the reactor to produce polymerization reaction under the action of the catalyst storage. The reaction is carried out under the conditions of 85~110℃ and 2.41 MPa. The single-pass conversion rate of ethylene is about 1%~2%, and the reaction heat is removed. Mainly through the cooling of circulating logistics, the MI range of the production product is 0.01 ~ 150, and Silicon Carbide Ceramics the density range is 0.915 ~ 0.970 g/cm3. The characteristics of the gas phase fluidized bed polymerization process are: low operating pressure and low temperature; it can produce full-density polyethylene; the catalyst system includes titanium series, chromium series; metallocene catalyst; high raw material purity requirements, all raw materials must be refined; No solvent is needed, energy consumption is low, maintenance and operation costs are low. The production process is: dry monomer and hydrogen are added to the reactor system together, the raw materials are added to a large circulating steam flow loop, and through the gas distribution to enter the bottom of the large fluidized bed reactor, according to the design of the reactor raw materials are 69.57 % Ethylene (99.9% ethylene content, 0.1% ethane), 10.43% hydrogen, 7.56% ethane and 12.44% nitrogen. This raw gas composition produces a product with a melt index of 8g/10min and a density of 0.964g/cm3. The catalyst is a magnesium dioxide mixture with titanium trichloride and tetrahydrofuran as promoters, and the co-catalyst is triethyl aluminum. The catalyst enters the reactor from the painless reactor part in solid form together with nitrogen. The operating temperature is 105℃, and the Silicon Carbide Ceramics specific temperature is determined according to the product brand. The operating pressure of the reactor is 2.0 MPa, and the reaction gas from the top of the reaction is separated from the catalyst containing solids by a cyclone and sent back to the reactor. Then the gas from the cyclone is compressed and circulated to the bottom of the reactor after being compressed and recirculated to the cooler. The reactor discharge passes through an air lock system to intermittently deliver product particles to the tank. Part of the gas entering the discharge tank enters the compressor circulation system through the upper buffer tank, filter, gas cooler, and separation tank. The polymer comes out of the lower part of the discharge tank and enters the purge tank and post-processing system. The post-processing system includes adding various additives to the polymer, melting, pelletizing and packaging.