Research On Process Control And Consumption-reducing Technological Design For Off-gas Recovery Plant In Polysilicon Production

Polysilicon,a form of high purity silicon,is widely used as a raw material in solar photovoltaic and semiconductor-electronic industry.Siemens method is currently the most mature process route used for preparation of polysilicon with the advantages of high purity production and energy saving as well as environmental protection.However,a large quantity of by-product reducing exhaust rich in H₂,HCl and silane will be produced in the polysilicon production process as well.Because there is no a large-scale industrial application for the reducing exhaust,so it is necessary to further separate and recover this part of exhaust gas in order to achieve a recycled material feed.Nevertheless,the flow rate and composition of the captured reducing exhaust will not reach a steady state due to the inherent discontinuous and periodic characteristics in the upstream CVD reactors,which will in turn affect the stability,safety and economy of recovery unit in the downstream.Exhaust gas recovery by a dry process is a widely used waste gas treatment technology,which has an important impact on the energy consumption cost and safety for the entire process operation.Therefore,it is of great theoretical and practical value to study the process design of safe and energy-saving process for the exhaust recovery of polysilicon production.Firstly,based on a 10000 tons/year of industrial polysilicon production installation,our paper has developed a plant-scale supervisory controller system based on a centralized model predictive control?MPC?,and then tested the effectiveness and robustness of the proposed control scheme.The control results showed that the control strategy designed in this paper had a better regulation performance for the periodic perturbations from the batch-continuous process in polysilicon production and exhaust recovery.Furthermore,based on a 6000 tons/year of industrial polysilicon production installation,we have designed a new process with a dividing-wall distillation column?DWC?for the recovery of the exhaust gas and simulated this process in the PRO//II on a plant scale.And we also examined and verified the high separation effect and energy-saving effect of the new process.Finally,in this paper,the process research on the process control and energy saving as well as consumption reduction process design for reducing exhaust recovery in polysilicon production is capable of providing key theoretical and technical guidance for the process safety design,control and energy optimization.