Method for recovering dichloro-dihydro silicon from off-gas generated from the production of polycrystalline silicon

Abstract

A method for recovering dichlordihydrosilicate from tail gas generated from polysilicon production comprises the following steps: the tail gas is leached at low temperature, pressurized and cooled for gas-liquid separation; gaseous hydrogen, hydrogen chloride and the dichlordihydrosilicate pass through a liquid absorbent to cause the gaseous hydrogen chloride and the dichlordihydrosilicate to be dissolved in the liquid absorbent, and the hydrogen is separated from the hydrogen chloride and the dichlordihydrosilicate; the hydrogen chloride and the dichlordihydrosilicate dissolved in the liquid absorbent are desorbed by increasing the temperature; the gas-liquid separation is carried out on the desorbed gaseous hydrogen chloride and the dichlordihydrosilicate by controlling the pressure and / or the temperature, therefore, the hydrogen chloride becomes gaseous and the dichlordihydrosilicate becomes liquid, and then the dichlordihydrosilicate is recovered. By adopting dry processing, the dichlordihydrosilicate in the tail gas is recovered and can be reused in the polysilicon production, therefore, the method has the advantages of adequate utilization of raw materials, reducing pollutants, solving the problem of environmental pollution, improving product quality and lowering cost.

Description

technical field [0001] The invention relates to a method for recovering and treating tail gas produced by industrial production of polysilicon, more specifically, to a method for recovering dichlorodihydrogen silicon from the tail gas produced by producing polysilicon. 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 proce...

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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 rinsed with water to recover hydrogen, but it does not recycle dichlorodihydrogen silicon, etc. At the same time, due to During the water leaching process, impurity gases such as oxygen and carbon dioxide in the water will contaminate the hydrogen to be recovered, so a large amount of recovered hydrogen needs to be purified again. In addition, after the chlorosilane is hydrolyzed during the leaching process, a large amount of sewage will be generated, which needs further treatment , will also lead to environmental pollution and material consumption

Moreover, the dichlorodihydrogen silicon produced in the production has not been fully utilized, which has not only wasted energy, but also caused environmental pollution.

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