Simulation Investigation For Reducing Exhaust Recovery In Polysilicon Production By Aspen Plus

In recent years, the development of solar energy, making raw materials of theproduction of solar cell-polysilicon attracted wide attention. The methods ofPolysilicon production are modified Siemens process, silane, metallurgy method andso on. Improved Siemens is most widely used. But from the current productionsituation, improved Siemens core technology still in the hands of developed countries,leading to domestic polysilicon production technology fall behind, high energyconsumption, high production costs and other issues, especially the dry exhaust gasrecycling process, which have an important impact in energy consumption, recyclingand product purity as the core part of polysilicon production technology in the entireprocess. Therefore, reducing the energy consumption of separation and recyclingreduction exhaust in polysilicon production process is very meaningful.In this paper, based on a domestic company with an annual3,200tons ofpolysilicon production plant, reducing exhaust of polysilicon production as theresearch object, chlorosilane as absorbent, hydrogen chloride and hydrogen for thepurpose of product. The exhaust gas absorption process was simulated with Aspenplus software, NRTL property method and RadFrac rigorous calculation module. Themain equipments of absorption separation process including absorber tower, desorbertower and heat exchangers. Simulated result show that the absorption rate of hydrogenchloride up to99.00%. Original absorption process has achieved very satisfactoryseparation result.Secondly, sensitivity analysis tool is used to optimize operating parameters oforiginal separation process, such as: the temperature of the feed streams, operatingpressure of each device, mass flow of absorber and the number of theoretical plates, todetermine what influence various operating parameters to the absorption results andsystem energy consumption.Finally, introducing the saving-energy principle of intermediate heat exchangertechnology, feed-splitting technology and the principles related process parameters.Designing two improvement processes, one is with intermediate heat exchangertechnology in desorption tower; another is feed-splitting of desorption tower.Simulated result shows that two new methods have energy saving signs comparedwith the original process. Relatively speaking, the intermediate heat exchangertechnology is not particularly obvious saving-energy, but the use of feed-splitting technology is very obvious in energy efficiency about26.85%reduces and28.95%ofsteam savings. Based on the results of column duties, it is conclude that the newfeed-splitting process can be considered as a serious alternative candidate for therecovery of HCl process from poly-silicon exhaust gases due to its greaterperformance.In summary, the entire process of absorber-desorber process was simulated andoptimized and propose improvements process to achieve saving-energy in this paper.This research has important significance for the domestic polysilicon production.