A tail gas purification system for trichlorosilane synthesis

Abstract

The invention provides a trichlorosilane synthesis exhaust gas purification system. The system comprises a washing tower and a crude distillation tower. The washing tower is used for leaching treatment on synthetic tail gas by a chlorosilane washing liquid. Silica powder in synthesis exhaust gas and a part of high boiling components are output into a residual liquid absorption system through a liquid discharge port of the washing tower along with a chlorosilane washing solution, and a low boiling point component, the rest of the high boiling components and a low boiling component in the chlorosilane washing liquid as synthesis exhaust gas subjected to preliminary purification are output to a crude distillation tower through a gas outlet of the washing tower. Through the chlorosilane washing liquid, the crude distillation tower is used for leaching treatment on the synthesis exhaust gas subjected to preliminary purification, other high boiling components in the synthesis exhaust gas subjected to preliminary purification are output into a waste chlorosilane storage tank through a liquid discharge port of the crude distillation tower along with the chlorosilane washing liquid, and the synthesis exhaust gas subjected to preliminary purification and a low boiling component in the chlorosilane washing liquid are output to a chlorosilane cooling and purification system through a gas outlet of the crude distillation tower. The purification system has good purification effects and small maintenance work load.

Description

technical field The invention relates to the technical field of trichlorosilane production, in particular to a tail gas purification system for trichlorosilane synthesis. Background technique In the prior art, trichlorosilane is mainly produced by the gas-solid heterogeneous reaction of metallurgical grade silicon powder and hydrogen chloride gas in a fluidized bed synthesis furnace, and the synthesis tail gas discharged from the synthesis furnace not only contains chlorosilane (three Chlorosilane, silicon tetrachloride and dichlorodihydrosilane), hydrogen and hydrogen chloride, and also contain metal chlorides and chlorosilane polymers, etc., while carrying a small amount of solid silicon powder particles. The synthesis tail gas discharged from the synthesis furnace needs to go through the dry dust removal system to remove the larger particles of silicon powder, and then through the wet dust removal system to remove the fine silicon powder, metal chlorides and chlorosilane...

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Problems solved by technology

Among them, the forced reflux type washing tower using a siphon reboiler, due to the high solid content of metal chlorides, silicon powder and chlorosilane polymers in the tower liquid, the heat transfer efficiency is reduced, and the temperature of the washing tower is high. At the same time, due to the low flow rate of the chlorosilane liquid in the siphon reboiler, the solid impurities in the chlorosilane liquid adhere to the heat exchange tubes of the siphon reboiler, resulting in frequent blockage of the heat exchange tubes of the reboiler and a large maintenance workload , and the maintenance cost is high; while the silicon powder and metal chlorides washed in the forced reflux scrubber using a horizontal reboiler are scattered in the tower kettle, and only a small area around the drain port can be drained during the draining process. The silicon powder and metal chloride are discharged, and most of the silicon powder and metal chloride accumulate in the tower kettle and adhere to the heat exchange tube of the reboiler, resulting in a decrease in heat transfer efficiency and a high temperature in the washing tower kettle. The drain port is frequently blocked, resulting in frequent maintenance of the scrubber, serious corrosion of the heat exchange tubes of the reboiler, heavy maintenance workload, and high maintenance costs

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