Research On Simulation,Energy Saving And Process Of Electronic Grade Silicon Tetrachloride Distillation System

Electronic grade silicon tetrachloride is the main raw material for the production of silicon epitaxial wafers and fiber mats.With the rapid development of semiconductors,integrated circuits and optical fiber communication industry,the demand for electronic grade silicon tetrachloride is very large.In addition,there is huge overcapacity in the domestic polysilicon industry,so a large number of silicon tetrachloride waste need to be treated urgently.In this paper,thr-ough the distillation process,we deal with polysilicon waste and produce electronic grade silicon tetrachloride,which has a very good economic prospects and environmental significance.According to the characteristics of silicon tetrachloride distillation process,the process program of four-differential pressure was determined,and four towers(T1101,T1102,T1103 and T1104)were simulated.Firstly,according to product requirements,using the Aspen Plus steady-state simulation,parameters are optimized.Adjust the differential pressure distillation parameters to achieve energy matching,and to analyze the economic benefits.Finally,using the Aspen Dynamics dynamic simulation,the appropriate control program was designed.The main conclusions are as follows:The main physical system of this distillation process is silicon tetrachloride(STC)-trichlorosilane(TCS).Firstly,the thermodynamic consistency test of STC-TCS vapor-liquid equilibrium experiment data which obtained from related references is carried out.According to the selection method,three thermodynamic models suitable for the system was identified,which named PENG-ROB,RK-SOAVE and NRTL-RK.Using the Data Regression model in Aspen Plus,the binary interaction parameters of the three physical methods were fitted to analyze and contrast the deviation of experimental data and calculated data.Four towers were simulated by the PENG-ROB property method with smallest deviation.According to the requirements of cooling medium,heating medium and heat transfer temperature difference,the pressure of each tower in four-tower four-pressure distillation process was determined.The parameters of the four towers(T1101,T1102,T1103 and T1104)are optimized by sensitivity analysis and orthogonal test.The reflux ratio R is 9.9,11.2,10.1,10.8,the feed position NF is 5,52,6,63,the yield ratio is 0.11(D/F),0.16(B/F),0.11(D/F),0.16(B/F).In the product,the mass fraction of low boiling impurities is 0.011ppt;the mass fraction of high boiling impurities is 2.03ppt,in line with industry requirements.For the problem of high energy consumption in this distillation process,analyze the heat transfer situation of four-tower four-pressure distillation process.Energy matching and recycling were achieved by adjusting the operating parameters which affected energy consumption.Adjust T1103 reflux ratio of 16.8,T1104 reflux ratio of 15,T1104 yield ratio of 0.07.Contrast the energy-saving process with original process from three aspects of energy consumption,utility consumption and cost of equipment.The results were as follows:the new process saved energy of 48.75%,cooling medium of 2.4926 million tons/year(by 57.84%),heating medium of 29900 tons/year(by 56.63%),and reduced two heat transfer equipment.Considering the instability of the distillation operation,the appropriate control scheme was selected by the dynamic simulation of each tower.Firstly,through the analysis,the sensitive plates of rectifying section and stripping section were determined:T1101 of the 2nd and 29th plates,T1102 of the 2nd and 59th plates,T1103 of the 2nd and 21st plates,T1104 of the 53rd and 74th plates.In this paper,two kinds of control schemes were proposed for each tower.In the face of the disturbances of feed quantity and feed component,the dynamic responses of the two schemes were compared in three aspects of the energy consumption,material consumption and product quality.T1101 adopted material balance control,T1102 adopted double temperature control,T1103 adopted constant recovery and feed ratio control,and T1104 adopted proportional control.Through parameter optimization,process optimization and control design,the energy-saving process program and control structure of the electronic grade silicon tetrachloride purification process are obtained,which achieved the purpose of saving costs,stabilizing production and increasing economic benefits.