Control method for stably adjusting purity of trichlorosilane

Abstract

The invention provides a control method for stably adjusting the purity of trichlorosilane. Polycrystalline silicon is prepared according to vapor deposition of Siemens, crude chlorosilane is continuously introduced into a rectifying tower, and tower operating characteristics and reflux quantity are not changed. The control method is characterized in that: four temperature measuring points are respectively arranged in a rectifying section and a stripping section, two temperature difference values are calculated, and a double temperature difference value is obtained by subtracting one temperature difference value by the other temperature difference value; the aim of controlling the impurity element content of produced liquid at the bottom of the tower is fulfilled by stabilizing the double temperature difference value and adjusting a ratio of distillate quantity D to feed quantity F on the top of the tower, and the high-purity trichlorosilane is obtained; moreover, products with different purities can be obtained by adjusting different temperature difference points. By the control method, the quality of the trichlorosilane is ensured, and unnecessary loss of the trichlorosilane is reduced.

Description

technical field [0001] The invention relates to an adjustable and stable method for controlling the purity of trichlorosilane. Background technique [0002] Monocrystalline silicon is a material for manufacturing semiconductors. In industry, polycrystalline silicon is generally converted into monocrystalline silicon by the Czochralski method or the suspension zone solution method. With the rapid development of information technology and solar energy industry, the global demand for polysilicon is growing rapidly. The Siemens method to prepare polysilicon is one of the most commonly used methods at present. It is mainly to mix high-purity trichlorosilane from the rectification section with hydrogen and send it to the reduction furnace, and then precipitate polysilicon on the surface of the silicon rod heated by electricity. The product is good Bad depends on the purity of trichlorosilane in the rectification process. [0003] In the Siemens method, the purity of the raw mate...

AI Technical Summary

Problems solved by technology

That is, the control effect may have an opposite effect on different product concentrations, and it is difficult to accurately control the composition of the extreme point only by indirectly adjusting the return flow

In addition, the increase or decrease of the reflux flow will also cause changes in the pressure drop of the tray. The impact of this pressure change on the product composition will cause adverse consequences to the operation of the rectification column as the rate of rising steam and liquid changes.

More importantly, while adjusting the return flow, it is necessary to carry out a large number of multi-point sampling and testing work to feedback whether each adjustment is effective, which may require a large amount of extraction of tower top materials, resulting in a lot of waste and affecting subsequent recycle and re-use

To sum up, this manual adjustment-feedback control method brings great inconvenience to the field operation, has a certain delay and interference, and needs further optimization and improvement

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