The Research On Application And Theory Of Dividing Wall Column Distillation In Purification Of Chlorsilanes

In recent years,solar energy has caused much attention because of the outstanding advantages such as cleaner,safety,widely distribution,abundant and so on.Besides,it also has some special characters which not been owned by conventional energy such as long-period,unnecessary care so that the photovoltaic industry has been developed at the growth rate of 20%-30%.The increasing demand accelerate the speed of polysilicon industry development,which is the basis material of photovoltaic industry.There have several main production methods to polysilicon such as improved siemens process,the silane process,zinc reduction process,metallurgical process,fluidized bed process,hot wire process,and so on.The yield by improved siemens process has 80%base on all yield in the world.To overcome the problem of the high energy consumption in trichlorosilane distillation process,In this paper,Aspen Plus simulation software the has been used to simulate and optimize the trichlorosilane distillation process,which main used to purify the trichlorosilane that as the key component of reduction chlorsilane from the reduction process in improved siemens process.The RadFrac module has been used for conventional indirect distillation process and Multi Frac module for dividing wall distillation process simulate with NRTL property method.Besides,The sensitivity analysis tool also be used to optimize the operating parameters of columns and analyze the effects to energy consumption and purification of production.Through calculation,tray numbers,reflux ratio,feed stage of B3 column is respectively 40,1.6,22.And the theory trays,reflux ratio,feed stage of B4 column is 40,14.5,9 respectively.The theory trays of pro-fractionator and the main column,reflux ratio,feed stage,side draw stage,the flow rate of side draw,the flow rate of connecting vapor stream V12 and the flow rate of connecting liquid stream L12 in dividing wall column is 29,44,38,16,21,2600kg·h-1,3 700kg·h-1,2000kg·h-1 respectively.Besides,the temperature profile,pressure profile,the flow rate of vapor and liquid,each component mole fraction also has been analyzed and explained.In addition,the reboiler duty and condenser duty has been compared in both distillation process under the same condition of yield and purification.The results show that the reboiler duty and the condenser duty of dividing wall distillation process saving energy 23.9%,22.2%respectively compared to conventional indirect distillation process.Besides,a reboiler,a condenser,a column and associated pipeline and control facility also be saved by the dividing wall column distillation process to conventional distillation process,as a result,the equipment cost has been reduced.We can conclusion that,through analysis to the profile of temperature and mol fraction of each component in column,the main reason of energy saving for dividing wall distillation process compare to conventional distillation process is that it’s not only decreased the mixing entropy caused by component difference between the feed stages which connecting pre-fractionator and main column,but also avoid the backing mixing which occurred in conventional distillation column.The research results supplied theory basis for modification of existing distillation equipment and the industry application of dividing wall column.