Evaluation of selected chemical processes for production of low-cost silicon (Phase III). Fifteenth quarterly progress report, April 1-June 30, 1979

Progress has been made during this quarter on the assembly of the Process Development Unit (PDU) consisting of four of the critical components of the 50 MT/year Experimental Process System Development Unit (EPSDU) for the production of granular semiconductor-grade silicon by the zinc vapor reduction of silicon tetrachloride in a fluidized bed of seed particles. The target operation date of October 1, 1979, still appears attainable. An experimental wetted-wall condenser, about 1/10 the size of the PDU/EPSDU design was operated to demonstrate that recirculated liquid zinc chloride can indeed be used to wash down the condensed by-product of the fluidized-bed reactor containing finely divided solid zinc and some silicon dust. The temperature distribution proved to be more critical than anticipated but the condenser now appears to be operable. Some improvement in condensation efficiency is desirable, however. Procedures were established for safe handling of SiCl/sub 4/ leaks and spills from the EPSDU and PDU. Preparations are being made to conduct zinc vaporization experiments in that portion of the PDU before operation of the entire PDU is initiated.