I. Trichlorosilane powder dryer - equipment overview

In the production process of trichlorosilane, the raw material silicon powder often contains impurities such as aluminum, iron and calcium, and forms a metal chloride such as aluminum chloride, ferric chloride or calcium chloride when reacted with hydrogen chloride gas at a high temperature, and trichlorosilane. The waste slag treatment system includes a vacuum sputum dryer, a condenser, a vacuum pump, a collection tank, an acid circulation pump, an acid absorption tank and a synthetic liquid storage tank, and the vacuum venting outlet of the vacuum sputum dryer is sequentially connected to the water condenser and condensed. The liquid outlet is connected to the collection tank, the liquid phase outlet and the condensate outlet of the water condenser are connected to the synthetic liquid storage tank, the evaporation gas phase outlet of the vacuum rake dryer is connected to the acid absorption tank, and the liquid phase outlet of the acid absorption tank is connected by the acid circulation pump respectively. Acid absorption tank liquid inlet and rinse. Fully recover useful materials from waste residue, improve economic efficiency and reduce environmental pollution.

(I) Vacuum squeezing dryer is a horizontal intermittent conduction drying device. With the rakes on the central shaft, the timing interval rotates in the forward and reverse directions. When the material is in contact with the cylinder wall under the constant stirring of the rakes, the surface is continuously updated. And indirectly heated by the heat transfer oil, so that the moisture in the material is continuously vaporized, and at the same time is extracted by the vacuum pump in time. Under the action of the degree of vacuum, the boiling point of the moisture fraction is lowered, and the moisture vapor pressure on the surface of the material is much larger than the moisture vapor pressure in the evaporation space of the machine, which is favorable for the evaporation of the internal moisture and promotes drying, thereby achieving the purpose of drying.

(2) Due to the special properties of the metal oxide AlCl3, it is sublimed at 177.8 ° C under standard atmospheric pressure. In the vacuum state, as the saturated vapor pressure of AlCl3 decreases, there is a possibility of sublimation at a lower temperature, which easily leads to solidification of AlCl3 gas in the subsequent pipeline and blockage of the pipeline. In order to meet the process requirements, a certain amount of complexing agent is often added during the early feeding, and the complexing agent makes the metal aluminum chloride difficult to be distilled out when the material is vacuumed, and the chlorosilane is distilled out under vacuum. After that, the aluminum chloride is distilled off again to reduce environmental pollution.