Method and system for controlling balance of dichlorosilane in production of polycrystalline silicon

Abstract

The invention discloses a method and system for controlling the balance of dichlorosilane in production of polycrystalline silicon. The method comprises the following steps: 1) analyzing tail gas of polycrystalline silicon prepared by a chemical vapor deposition reaction, then carrying out rectifying purification and separation, and carrying out rectifying purification and separation on synthesisgas which is used for synthesizing trichlorosilane by a cold hydrogenation reaction; 2) mixing a tower bottom liquid of a second tail gas condensation liquid separation tower and a tower bottom liquidof a last-stage trichlorosilane rectification tower to obtain a first mixture; 3) mixing a tower top liquid of the second tail gas condensation liquid separation tower and the first mixture to obtaina second mixture, and adjusting the flow rate to enable the mol percentage content of dichlorosilane in the second mixture to be a second preset mol percentage content of dichlorosilane; and 4) introducing the second mixture in to the chemical vapor deposition reaction in the step 1) as a raw material for continuously preparing polycrystalline silicon. According to the method, the content of dichlorosilane in the second mixture is accurately controlled, reasonable and effective treatment and utilization of dichlorosilane are ensured, and energy consumption is reduced.

Description

technical field [0001] The invention belongs to the technical field of polysilicon production, and in particular relates to a method and system for controlling the balance of dichlorosilane in polysilicon production. Background technique [0002] High-purity polysilicon production is usually prepared by the "modified Siemens (Siemens)" process, in which trichlorosilane (SiHCl 3 or TCS) gas is deposited onto the heated silicon core carrier in a hydrogen environment. In such a production process, only a small part of TCS is deposited as simple silicon, and the rest is discharged from the reactor in the form of gas, which usually contains more than 45% (mole fraction) is the TCS participating in the reaction, forming a part of 5-10% (mole fraction) dichlorosilane (SiH 2 Cl 2 or DCS), 45-50% (mol fraction) of silicon tetrachloride (SiCl 4 or STC), silicon powder (silicon or Si) and other by-products. [0003] The DCS produced in the production process has always been deeply ...

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a method and system for the balance control of dichlorosilane in polysilicon production to solve the unreasonable control of dichlorodihydrosilicon in the polysilicon production process. , resulting in increased energy consumption, abnormal increase in polysilicon products, decreased yield, fluctuations in system parameters, poor utilization, etc.

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