Method for preparing polysilicon

Abstract

An improved method for producing polycrystalline silicon is characterized in that industrial silicon and hydrogen chloride are taken as raw materials and react to obtain trichlorosilane; the trichlorosilane is purified, put into a reducing furnace and reacts with hydrogen for reduction to obtain the polycrystalline silicon; and the tail gas is collected, wherein, the tail gas mainly comprises hydrogen, hydrogen chloride, dichlordihydrosilicate, trichlorosilane and silicon tetrachloride. The method comprises the following steps: the tail gas is pressurized and cooled; gas-liquid separation is carried out for separating the hydrogen, the hydrogen chloride and the dichlordihydrosilicate that are in gaseity from the trichlorosilane and the silicon tetrachloride which are in liquid state; the hydrogen is separated from the hydrogen chloride and the dichlordihydrosilicate by the liquid silicon tetrachloride. The method can recover and recycle the hydrogen which is reused for the polycrystalline silicon production. The method has the advantages of sufficiently using the raw materials, reducing pollutants, solving the environmental pollution problem, improving the product quality and reducing the cost.

Description

technical field [0001] The invention relates to a method for producing polysilicon, more specifically, to an improved method for producing polysilicon that can recycle and recover hydrogen in tail gas. Background technique [0002] Polycrystalline silicon is the raw material for preparing monocrystalline silicon, which is ultimately used in the production of integrated circuits and electronic devices. It is one of the basic raw materials with the largest consumption and the highest purity requirements in the information industry. It is also a product and industry that the country encourages the development of. [0003] The world's advanced polysilicon production technology has always been monopolized by companies from the United States, Japan, and Germany. Each company has its own technical secrets and technical characteristics. After continuous research and development, it has formed its own production process. Set out, strictly control technology transfer and monopolize th...

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Problems solved by technology

[0004] my country's polysilicon industry started in the 1950s, realized industrialization in the mid-1960s, and developed blindly in the early 1970s. There were more than 20 production plants, all using traditional Siemens technology, backward technology, serious environmental pollution, and material consumption. Large, high production costs, most enterprises lose money and stop production or change production one after another

[0005] The outstanding feature of the traditional polysilicon production process is the tail gas wet recovery technology, that is, the tail gas in the reduction furnace is initially pressurized to separate chlorosilane and then washed with water to recover hydrogen. Due to the process of water washing, impurity gases such as oxygen and carbon dioxide in the water will be released. Contamination of hydrogen, so a large amount of recovered hydrogen needs to be purified again. During the leaching process, chlorosilane is hydrolyzed to produce sewage, which needs further treatment, resulting in environmental pollution and large material consumption.

At the same time, the hydrogen generated in the production has not been fully utilized, which not only wastes energy, but also causes environmental pollution

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