| With high purity, safety and deposition speed, Improved Siemens process is the most mainstream production technology of polysilicon. But the downside of the traditional distillation process are more stages, numerous trays, the high operating pressure, high energy consumption and poor purification effect. In its energy consumption composition, in addition to power consumption of reduction furnace, distillation sector accounts for a considerable proportion. The distillation sector of Improved Siemens process mainly includes three aspects:trichlorosilane synthetic material distillation, silicon tetrachloride-hydrogenated material distillation and exhausted gas recycling material distillation. For these three kinds of material, there are two kinds of distillation process route of removing light components after removal of heavy components (referred to as the former process route) and removing heavy components after removal of light components (referred to as the latter process route).In order to simply the process of traditional Improved Siemens and reduce the cost of distillation section, the two kinds of distillation process route for these three kinds of material are systematically studied, the amount of public works, the annual operating costs and the annual comprehensive energy consumption of two kinds of distillation process routes are compared. A new process is presented by replacing the original process route of Improved Siemens with the lower energy consumption process route. In addition, the application of heat integrated distillation technology and heat pump technology in the modified Siemens distillation process is also studied, obtaining a series of results which can guard the actual production. Finally, combined with the actual situation of polysilicon plant, a part of the research results is applied to practical production, aiming to optimize the column operating program, improve the distillation process, reduce energy consumption and cost.The model of distillation process of removing light components after removal of heavy components for trichlorosilane synthetic material is established, in good agreement with the industrial values, verifying the reliability of the model.According to the quality requirements for electronic grade polysilicon, for three kinds of the feed, the two kinds of distillation process route for trichlorosilane synthetic material is stimulated and optimized, the amount of public works, the annual operating costs and the annual comprehensive energy consumption of the two kinds of distillation process routes are compared. The results show, in terms of the amount of public works, compared to the latter process route, amount of condensate of the former process route is larger, amount of chilled water is equal, the amount of cooling water is higher than 50%,47.1% and 39.8% for the feed 1,2,3 respectively; Compared to the latter process route, the annual operating costs of the former process route is higher than 16.16%,13.28% and 10.2% for the feed 1,2,3 respectively; Compared to the latter process route, the annual overall energy consumption of the former process route is higher than 17.6%,14.73% and 11.28% for the feed 1,2,3 respectively. In conclusion, the latter process route is better for trichlorosilane synthetic material distillation.For three kinds of the feed, the two kinds of distillation process route for silicon tetrachloride-hydrogenated material is stimulated and optimized, the amount of public works, the annual operating costs and the annual comprehensive energy consumption of the two kinds of distillation process routes are compared. The results show, in terms of the amount of public works, compared to the former process route, amount of condensate of the latter process route is larger than 32.2%,29.1% and 20.4% for the feed 1,2,3 respectively; amount of cooling water is equal, the amount of chilled water is higher than 165.1% ,88.6% and 58.8% for the feed 1,2,3 respectively; Compared to the former process route, the annual operating costs of the latter process route is higher than 29.1% ,26.8% and 20% for the feed 1,2,3 respectively; Compared to the former process route, the annual overall energy consumption of the latter process route is higher than 25.8%,24% and 16.1% for the feed 1,2,3 respectively, In conclusion, the former process route is better for silicon tetrachloride-hydrogenated material distillation.For three kinds of the feed, the two kinds of distillation process route for exhausted gas recycling material is stimulated and optimized, the amount of public works, the annual operating costs and the annual comprehensive energy consumption of the two kinds of distillation process routes are compared. The results show, in terms of the amount of public works, compared to the latter process route, amount of condensate and chilled water of the former process route is very close, the amount of cooling water is higher than 17.4%,13.3% and 10.5% for the feed 1,2,3 respectively; Compared to the latter process route, the annual operating costs and the annual overall energy consumption of the former process route is almost equal. In conclusion, the latter process route is better for exhausted gas recycling material distillation.Heat pump distillation of direct compression overhead gas and tower kettle liquid flash and reboiiing are applied to the second tower of silicon tetrachloride distillation process. Although the application of heat pump technology will bring additional investment in equipment and operating costs, The results show that the two kinds of heat pump distillation can save energy consumption up to 21.8% and 28.9% respectively, comparing to conventional distillation, because saving energy costs significantly.Heat integrated distillation technology of two towers is applied to the new process of removal of heavy components after removing light components. To facilitate the implementation of the heat exchange, there must be sufficient temperature difference between the overhead of the first tower and the bottom of the second tower. The solution of increasing operating pressure of the first tower while decreasing that of the second tower is carried out. The results showed that the new process can save energy consumption up to 50%, the coefficient of recovery for trichlorosilane is up to 98.7%. Combined with the actual situation of polysilicon plant, a part of the research results is applied to practical production. Firstly, for silicon tetrachloride-hydrogenated material distillation, the reseach results of the distillation process route of removing light components after removal of heavy components is used to practical production, improved the position of feed tray of distillation column, reduced the reflux ration,adjusted the bottoms to feed ratio. Based on the research conclusions from the third and the fifth chapters, for trichlorosilane synthetic material distillation and exhausted gas recycling material distillation, the former process route is replaced by the latter process route. The new process needs a total of six distillation column, less one than the original process. This not only reduces the tower hardware investment, but also simplifies the process, reducing the difficulty of the operation and control in the actual operation, helping improve product purity.
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