Method and device for efficiently producing polycrystalline silicon

Abstract

The invention discloses a method for efficiently producing polycrystalline silicon. A raw material mixed gas consisting of trichlorosilane and hydrogen in a volume ratio of 1 to 2-15 is firstly delivered into a shell and tube heat exchanger to be heated, then delivered into a plate heat exchanger to exchange heat and delivered into a polycrystalline silicon reduction reactor to perform reaction, and the inlet temperature of the feed gas in the reduction reactor is kept between 200 and 500 DEG C; in the shell and tube heat exchanger, the feed gas exchanges heat with the tail gas produced in the polycrystalline silicon production process; in the plate heat exchanger, the feed gas exchanges heat with water vapor; and the reaction is controlled by adjusting the pressure, temperature and hydrogen flow till the reduction reactor is shut down. The method of the invention effectively improves the disposable yield of silicon, is favorable for reducing production cycle and energy consumption in the production process, is simple and feasible, greatly saves the production cost, and reduces the difficulty of treating the tail gas.

Description

technical field [0001] The invention relates to the production of polysilicon, in particular to a method and device for improving the one-time yield of silicon in polysilicon production. Background technique [0002] The production of polysilicon by the Siemens method is a process in which hydrogen and trichlorosilane are mixed into the reduction furnace to react and precipitate and grow on silicon rods. The production of polysilicon by the improved Siemens method is currently the main production method of polysilicon in the world. The one-time yield of silicon is about About 12%, the process is carried out in a bell-type reactor, the silicon core is pre-installed in the bell, and the silicon core is heated by high-voltage electricity, H 2 and TCS (SiHCl 3 ) reacts on the surface of the silicon core at about 1080°C, and grows continuously to finally become the product polysilicon rod. The reaction equation involved is as shown in (1) formula below: [0003] SiHCl 3 +H 2...

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Problems solved by technology

[0008] The side reaction mainly occurs in the gas phase, which reduces the concentration of TCS during the reaction process. At the same time, most of the Si generated does not adhere to the surface of the silicon rod and enters the exhaust system with the gas. This not only causes waste of raw materials, but also increases the exhaust gas treatment. difficulty

[0009] In the prior art, in order to reduce the occurrence of side reactions, the usual treatment method is to increase the H 2 The ratio of TCS and TCS, but after increasing the ratio of raw materials, the reaction speed decreases significantly, and the output decreases, which makes the profit of the factory decrease

[0010] In order to save energy consumption, the high-temperature exhaust gas after the reaction is used to heat the intake air. Although this method heats the intake air mixture, since the intake air volume and the temperature of the exhaust gas are not fixed during the entire reaction process, the temperature of the exhaust gas is not fixed during the entire process. The temperature of the air is also changing

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