Evaluation of selected chemical processes for production of low-cost silicon (Phase III). Silicon material task Low-Cost Solar Array Project. Nineteenth quarterly progress report, April 1-June 30, 1980

Early in this report period, the PDU was operated for a short time (one-half hour) before downstream constrictions prompted termination. The problem was traced to malfunction of the wetted-wall by-product condenser owing to the zinc chloride having a higher-than-anticipated viscosity near its melting point. Since then, a number of problems, minor in origin but major in effect, have hampered operation of the PDU. Steps are being taken to correct these deficiencies of design or mode of operation as they are revealed. Mathematical models were developed for testing against the data on the removal of zinc from silicon granules by vacuum heat treatment. With a suitable model confirmed, it will be possible to extrapolate the results to the larger particle size and different zinc content expected in the eventual product.