Patent EP-2463021-A1 (EP)
Inventor: ACKER JOERG PROF DR
IPC: B01J8/02
Filed: 2011-12-02
Abstract: Increasing the purity of silicon by a chemical cleaning process, comprises: (a) subjecting the silicon to a liquid cleaning chemical; (b) subjecting the chemical reaction mixture to an atmospheric pressure of 1 bar or to a pressure higher than atmospheric pressure during the cleaning process; (c) exposing the chemical reaction mixture to an elevated temperature above room temperature during the cleaning process; and (d) removing the purified silicon from the chemical reaction mixture comprising the purified silicon and partially spent cleaning chemical. Increasing the purity of silicon having a content of more than 90 wt.% of silicon, in finely divided form and particle sizes of less than 500 mu m, preferably less than 250 mu m, by a chemical cleaning process, comprises: (a) subjecting the silicon to a liquid cleaning chemical, where the silicon and the cleaning chemical form a chemical reaction mixture in which the chemical cleaning process takes place with or without energy supply, and the metallic and/or non-metallic impurities are removed in large part from the silicon, such that a chemical reaction mixture comprising purified silicon and the partially spent cleaning chemical is present; (b) subjecting the chemical reaction mixture to an atmospheric pressure of 1 bar or to a pressure higher than atmospheric pressure during the cleaning process; (c) exposing the chemical reaction mixture to an elevated temperature above room temperature during the cleaning process; and (d) removing the purified silicon from the chemical reaction mixture comprising the purified silicon and partially spent cleaning chemical. An independent claim is also included for a device for carrying out the above mentioned method, comprising: a pressure vessel (2) or a receiving container for receiving the chemical reaction mixture from the finely-grained silicon and the liquid cleaning chemical, where the pressure vessel and receiving container exhibit a filling device (12); a device for discharging; an externally arranged energy source (10) for generating the elevated temperature in the reaction mixture, which is located in the respective pipeline; an ambient pressure resistant container arranged on the receiving container, in which a predetermined ambient pressure of 1 bar upright is obtainable; a pipeline (18) for flow of the chemical reaction mixture from the finely-grained silicon and the liquid cleaning chemical; a pressure source for maintaining a pressure of >= 1 bar in the pipeline and in a container-like portion (28); a pressure-tight stop valve for blocking a pipe segment and the container-like portion and to interrupt the flow of the chemical reaction mixture and for the development of a pressure of greater than 1 bar in the pipe segment and in the container-like portion through the energy source acting on the pipe segment and container-like portion; a conveying device of the chemical reaction mixture comprising metallurgical silicon in a liquid cleaning chemical, and an additional conveying device of the chemical reaction mixture comprising purified silicon and partially spent cleaning chemical; a container-like portion, which receives the chemical cleaning mixture containing the cleaning chemical and the finely-grained silicon; an externally arranged energy source on the container-like portion for generating the elevated temperature in the reaction mixture, which is located precisely in the container-like portion; and a conduit for receiving the chemical reaction mixture, where the cleaning chemical is stationary in the pipeline and the grains of silicon move by settling or sedimentation under the action of gravity.