Reaction system for producing polycrystalline silicon by using multiple polycrystalline silicon reduction furnaces and operating method of reaction system

Abstract

The invention relates to a reaction system for producing polycrystalline silicon by using multiple polycrystalline silicon reduction furnaces and an operating method of the reaction system. The system comprises multiple polycrystalline silicon reduction furnaces and a heat exchanger, wherein the multiple polycrystalline silicon reduction furnaces are connected in series; except the first reduction furnace, a feeding hole of each of the other reduction furnaces is connected with a discharging hole of the adjacent previous reduction furnace; a hydrogen supply pipeline is connected between the feeding hole and the discharging hole which are connected with each other; the two inlets of the heat exchanger in the system are connected with a feed pipe and a discharging hole of the last reduction furnace respectively; and the two outlets of the heat exchanger are connected with a feeding hole and a final tail gas exhaust outlet of the first reduction furnace. By adopting the reaction system, the retention time of a reaction material in the reduction furnaces is remarkably prolonged, the once-through conversion of trichlorosilane can be increased by 30-40 percent, the steps for separating and purifying tail gas of each reduction furnace are eliminated, the production cost is saved, the energy consumption on material heating of each reduction furnace is lowered, and the energy consumption of polycrystalline silicon production is lowered.

Description

technical field [0001] The invention belongs to the technical field of polysilicon production, in particular a reaction system and an operation method for producing polysilicon by a plurality of polysilicon reduction furnaces proposed for the reduction section of trichlorosilane in the "improved Siemens method". Background technique [0002] At present, the main process technology for polysilicon production at home and abroad is the improved Siemens method. The core step of this process technology - the reduction reaction of trichlorosilane is carried out in the polysilicon reduction furnace: firstly, high-purity trichlorosilane and hydrogen are mixed in proportion and then passed into the polysilicon reduction furnace, and then at a certain temperature (1080°C ~ 1150°C) and under pressure, the deposition reaction is carried out on the energized high-temperature silicon core to generate polysilicon; among them, the single furnace (single polysilicon reduction furnace) conver...

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Problems solved by technology

Careful analysis of the above process shows that: First, since the reactants need to be heated in the reduction furnace, in order to prevent the heated gas from leaving the reduction furnace without reacting, the feed flow rate of the reactants is generally low, resulting in the reaction of the reactants in the furnace. The turbulence is very weak and the mixing is very uneven, which affects the rate and conversion rate of the reaction; secondly, because the reaction is a vapor deposition reaction, the reaction product is solid, and the single-pass conversion rate of the reaction is very low, so there is no need for reaction. After the remaining gas is separated and purified and then returned to the reduction furnace, such a process will inevitably increase the cost of production; third, in this production process, the heat of the reaction tail gas has not been fully and effectively utilized, and the waste of this part of heat is essentially It is equivalent to increasing the energy consumption in the polysilicon production process

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