Improvement On The Production Capacity Of Vinyl Chloride Suspension Polymerization Autoclave

The development of PVC industry is restricted by the higher cost and lower efficiency in our country for a long time. The polymerization process is the main influencing factor. To optimize the producing process and to improve the production efficiency have became the main approach to improve the production capacity of PVC for companies in foreign countries. Juhua Electric-chemical Factory has produced suspension PVC resin for more than 30 years and possess matured production technology and 7 LF-II type 30m3 polymerization reactors. The production capacity of each reactor is about 5000t/a or 167t/a m3. The significant difference is existed between Juhua's devices and foreign advanced devices in production capacity. Base on the production practices of Juhua Electric-chemcial Company and aiming to improve the production capacity of 30 m3, the factors affecting the production capacity was analyzed and it was proposed to shorten the polymerization time by using of composite initiator system, to shorten the auxiliary production time by setting up of close feeding technology, to prolong the reactor cleaning period by using of new anti-scale agent and to improve the production by increasing the feeding weigh of VC. The industry experimental production showed good results and it exhibits good application prospect.The initiator is the key to increase the reaction rate and to shorten the polymerization time. According to the rule for choosing initiator and applying the kinetics model of VC suspension polymerization initiated by the composite initiator system, the initiator recipe was designed to shorten polymerization time to be 5h. The kinetics was predicted for VC suspension polymerization carried out at 51,57 and 62. The model values were fitted well with experimental values. It showed that the polymerization time could be shorten to be 4~4.5h by using the composite of EHP and TX99 at 51 , the composite of EHP,TX23 and TX36 at 57掳C, and the composite of TX23 and TX36 at 62 , respectively.The balance between the maximum reaction rate and the heat transfer capacity of the reactor was the key factor for shortening of polymerization time and improving the production capacity. The theoretical calculation, cold reactor measurement and polymerization examination showed that the average heat transfer coefficient with no polymerization (993kcal/m2 hr) and the average heat transfer coefficient during the polymerization (800kcal/m2 hr) of No.8 (LF-IV type, with semi-circle tubejacket) reactor were greater, and it could be satisfied the requirement for shortening of polymerization time to be 4.5~5h. Although No.3 reactor was equipped with helix baffle jacket and had used for more than 12 years, it still exhibited higher heat transfer capacity (750kcal/m2 hr and 650kcaJ/m2 hr in cases of with no polymerization and during polymerization) and could be satisfied the need of shorting polymerization time if the incrustation was removed. The agitation dynamic property (0.90~0.9SKW/m3) and circular number (6.1~8.9/min) could be satisfied the requirement of PVC production.Combining with the kinetics of VC polymerization initiated by the composite initiator system and the heat transfer capacity of 30m3 reactor, three optimized initiator recipes were obtained and applied in 30m3 reactor polymerizations. The polymerization kinetics, heat transfer capacity and the quality of the resulting PVC resins were examined. Comparing with the original polymerization recipe, the polymerization time could be shortened 40-~45min by applying No.l and No.3 recipes, and shortened 80min by applying No.2 recipe. The quality of the obtained PVC resins was all satisfied the corresponding national standard.It was also important to shorten the auxiliary production time. By setting up of the close, continuous and automatic feeding technology after perfecting the DSC control system and using of the new anti-scale agent, the auxiliary time of VC polymerization was shorten 2h.Combining with the shortening of polymerization time and auxili...