Recycling of high-boiling compounds within an integrated chlorosilane system

An integrated plant process for the production of trichlorosilane, comprising the following steps:

• A) feeding hydrogen chloride to a fluidized bed reactor (1) charged with metallurgical grade silicon and reacting the hydrogen chloride with the metallurgical grade silicon in the fluidized bed reactor (1) at a temperature of 290° C. to 400° C. to form a gaseous chlorosilane product stream containing trichlorosilane;
• B) introducing a high boiler fraction containing high boilers, derived from a) the chlorosilane product stream of a plant process for production of trichlorosilane, b) the offgas of polycrystalline silicon production, or c) high boilers from both a) and b), into a saturator together with at least a portion of the hydrogen chloride fed to the fluidized bed reactor (1) in step A) to form a high boiler- and hydrogen chloride-containing mixture, and
• C) feeding the high boiler- and hydrogen chloride-containing mixture from the saturator in step B) to the fluidized bed reactor (1) and recovering a chlorosilane product stream with a greater amount of trichlorosilane than is recovered in the absence of feeding high boilers to the fluidized bed reactor (1),
• wherein when the high boiler- and hydrogen chloride-containing mixture contains high boilers from a gaseous chlorosilane product stream from a fluidized bed reactor for preparing trichlorosilane, the gaseous chlorosilane product stream is filtered to remove silicon dust such that the high boiler- and hydrogen chloride-containing mixture is free of silicon dust, and wherein the high boilers have a boiling point at standard pressure greater than the boiling point of silicon tetrachloride, and are composed of silicon, chlorine and optionally hydrogen, oxygen, and carbon.