NOVELTY - The method comprises producing trichlorosilane, producing monosilane by disproportionation of the produced trichlorosilane to obtain a monosilane-containing reaction mixture, which contains silicon tetrachloride as by-product, and thermally decomposing produced mono silane into silicon and hydrogen. Silicon with hydrogen chloride and silicon tetrachloride with silicon and hydrogen resulting as by-product during a conversion process is converted to a trichlorosilane-containing reaction mixture. The production of trichlorosilane comprises a purification process and a thermal separation process.    USE - Method for producing highly pure silicon, which is useful in the semiconductor industry for the production of solar cells or microchips.    ADVANTAGE - The method is capable of economically and ecologically producing highly pure silicon in an energy-efficient manner.    DETAILED DESCRIPTION - The method comprises producing trichlorosilane, producing monosilane by disproportionation of the produced trichlorosilane to obtain a monosilane-containing reaction mixture, which contains silicon tetrachloride as by-product, and thermally decomposing produced mono silane into silicon and hydrogen. Silicon with hydrogen chloride and silicon tetrachloride with silicon and hydrogen resulting as by-product during a conversion process is converted to a trichlorosilane-containing reaction mixture. The production of trichlorosilane comprises a purification process, in which the trichlorosilane-containing reaction mixture from a hydrochlorination process and/or from a conversion process is processed and released from solid by-products, and a thermal separation process. The purification process comprises a dry (101) and/or a wet (102) cleaning step. The cleaned reaction mixtures from the hydrochlorination process and the conversion process are mixed and transferred into a common collector, where the mixing ratio of the reaction mixtures is 1:10 to 10:1. The thermal separation is carried out after the purification process and in which the reaction mixture are partly separated into their components. The silicon tetrachloride separated in the thermal separation process is fed into the conversion process. The hydrochlorination process takes place with a pressure of 2-12 bar at 350-370 degrees C. The silicon converted in the hydrochlorination process is used as powder, where the silicon particles have a diameter of 0.5-1.6 mm. The conversion process takes place with a pressure of 8-15 atmospheres at 500-600 degrees C. The ferrous silicon converted in the hydrochlorination process is used as powder, where the silicon particles have a diameter of 0.5-2 mm. The disproportionation of the trichlorosilane takes place according to the principle of reactive distillation at a solid organic catalyst. The organic catalyst is a weak base, macro-porous anion exchange resin with functional groups from three and tetravalent amines. The disproportionation of trichlorosilane takes place in a reactive column of a disproportionation reactor (112) at 60-120 degrees C and a pressure of atmospheres, which is filled with the organic catalyst (75-85%). The thermal decomposition process comprises a thermal separation process, in which the reaction mixture resulting during the disproportionation is partly separated into its components. Monochloro-, dichloro- and trichlorosilane resulting during isolating the reaction mixture is injected to the disproportionation reactor for renewed conversion. The thermal decomposition of the monosilane takes place in the decomposition reactor, in which the monosilane is cyclically injected as mixture (0.5-15 mol%) with a feed gas in a cyclic manner and is contacted with carriers heated at 800-1450 degrees C (surface temperature). The cycle guidance of the mixture takes place under the conditions of a forced convection. A part of the mixture after passing through the decomposition reactor is removed and recycled in the conversion process. An INDEPENDENT CLAIM is included for plant for the production of highly pure silicon.    DESCRIPTION OF DRAWING(S) - The diagram shows a flow chart of a method for producing high-purity silicon.    Dry cleaning step (101)    Wet cleaning step (102)    Conversion reactor (105)    Collecting tank (109)    Disproportionation reactor. (112)