Evaluation of selected chemical processes for production of low-cost silocon. (Phases I and II. ) Final report, October 9, 1975--July 9, 1978. Silicon Material Task, Low-Cost Solar Array Project

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The zinc reduction of silicon tetrachloride in a fluidized bed of seed particles to yield a granular product was studied along with several modifications of the thermal decomposition or hydrogen reduction of silicon tetraiodide. Although all contenders were believed to be capable of meeting the quality requirements of the LSA Project, it was concluded that only the zinc reduction of the chloride could be made economically feasible at a cost below $10/kg silicon (1975 dollars). Accordingly, subsequent effort was limited to evaluating that process. A miniplant, consisting of a 5-cm-diameter fluidized-bed reactor and associated equipment was used to study the ... continued below

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Pages: 124

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Blocher, J.M. Jr. & Browning, M.F. July 9, 1978.

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The zinc reduction of silicon tetrachloride in a fluidized bed of seed particles to yield a granular product was studied along with several modifications of the thermal decomposition or hydrogen reduction of silicon tetraiodide. Although all contenders were believed to be capable of meeting the quality requirements of the LSA Project, it was concluded that only the zinc reduction of the chloride could be made economically feasible at a cost below $10/kg silicon (1975 dollars). Accordingly, subsequent effort was limited to evaluating that process. A miniplant, consisting of a 5-cm-diameter fluidized-bed reactor and associated equipment was used to study the deposition parameters, temperature, reactant composition, seed particle size, bed depth, reactant throughput, and methods of reactant introduction. It was confirmed that the permissible range of fluidized-bed temperature was limited at the lower end by zinc condensation (918 C) and at higher temperatures by rapidly decreasing conversion efficiency (by 0.1 percent per degree C from 72 percent (thermodynamic) at 927 for a stoichiometric mixture). Use of a graded bed temperature was shown to increase the conversion efficiency over that obtained in an isothermal bed. Other aspects of the process such as the condensation and fused-salt electrolysis of the ZnCl/sub 2/ by-product for recycle of zinc and chlorine were studied to provide information required for design of a 50 MT/year experimental facility, visualized as the next stage in the development. Projected silicon costs of $7.35 and $8.71 per kg (1975 dollars) for a 1000 MT/year facilitywere obtained, depending upon the number and size of the fluidized-bed reactors and ZnCl/sub 2/ electrolytic cells used. An energy payback time of 5.9 months was calculated for the product silicon.

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Pages: 124

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Dep. NTIS, PC A06/MF A01.

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  • Report No.: DOE/JPL/954339-11
  • Grant Number: NAS-7-100-954339
  • DOI: 10.2172/6051388 | External Link
  • Office of Scientific & Technical Information Report Number: 6051388
  • Archival Resource Key: ark:/67531/metadc1112713

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  • July 9, 1978

Added to The UNT Digital Library

  • Feb. 22, 2018, 7:45 p.m.

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  • March 23, 2018, 2:17 p.m.

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Blocher, J.M. Jr. & Browning, M.F. Evaluation of selected chemical processes for production of low-cost silocon. (Phases I and II. ) Final report, October 9, 1975--July 9, 1978. Silicon Material Task, Low-Cost Solar Array Project, report, July 9, 1978; United States. (digital.library.unt.edu/ark:/67531/metadc1112713/: accessed November 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.