A polysilicon reduction furnace in which the tail gas outlet is connected to an inner extension pipe and its connection method

Abstract

The invention relates to a polycrystalline silicon reduction furnace with an exhaust outlet connected with an inner stretching tube and a connecting method. The top tray of the reduction furnace is an imporous semi-sphere, the exhaust outlet at the center is connected with the inner stretching tube and vertically stretches into the furnace, the inner stretching tube is higher than a silicon rod, a regular hexagon silicon block sheathes outside the inner stretching tube, a layer of electrodes are distributed on the bottom tray of the reduction furnace in regular hexagon, the inner diameter of the regular hexagon silicon block is slightly greater than the outer diameter of the inner stretching tube, so that the regular hexagon silicon block sheathes onto the inner stretching tube conveniently, and the side length of the regular hexagon is 1.05-1.2 times of the outer diameter of the inner stretching tube. The inner stretching tube connected with the exhaust outlet prevents mixed gas in the furnace from going into a short line, thus prolonging the staying time of the mixed gas in the reduction furnace so as to improve the conversion rate of the mixed gas; the inner stretching tube forces the mixed gas to pass through the upper space of the furnace, thus effectively avoiding generating a backflow dead area at the top of the reduction furnace; the regular hexagon nut-shaped silicon block sheathed outside the inner stretching tube also can play a role in depositing polycrystalline silicon, and has a positive role in increasing the yield of polycrystalline silicon.

Description

technical field [0001] The invention belongs to the technical field of polysilicon production, in particular to an energy-saving large-scale polysilicon reduction furnace for producing polysilicon by the Siemens method; it relates to a specific structure and connection method of a novel polysilicon reduction furnace with an exhaust gas outlet connected to an inner extension pipe. Background technique [0002] At present, polysilicon production enterprises at home and abroad mainly adopt the "improved Siemens method". The production process of this method is to synthesize trichlorosilane with hydrogen chloride and silicon powder at a certain temperature, then rectify and purify the trichlorosilane, and mix the purified high-purity trichlorosilane with hydrogen in a certain proportion It enters the polysilicon reduction furnace under temperature and pressure, and performs vapor deposition reaction on the energized high-temperature silicon core to generate polysilicon. The unre...

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Problems solved by technology

[0005] First, it is easy to cause part of the feed mixed gas to be short-circuited and directly discharged from the exhaust gas outlet with low pressure, which reduces the conversion rate of polysilicon

[0006] Second, due to the high speed and low temperature of the feed gas at the gas inlet, a concentration gradient and a temperature gradient must be generated in the vertical direction of the reduction furnace, resulting in a low deposition reaction rate of polysilicon at the root of the electrode, and at the same time Since the upward flow of gas also tends to drive the polysilicon on the surface of the electrode to move upwards, the combined effect of the two makes the growth rate of the lower part of the silicon core slower, resulting in a thicker upper part of the silicon core and a thinner root, which is not conducive to the safe and stable production of polysilicon.

[0007] Third, this structure leads to high gas velocity at the inlet of the reduction furnace, while the gas velocity at the top of the reduction furnace is low, resulting in a backflow dead zone at the top of the reduction furnace, which reduces the output of polysilicon

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