Kinetics of reduction of nickel chloride with hydrogen
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22,240 2.303RT' K is in min-
The activation energy for the reduction was found to be 22,240 cal/mol (or 93,050 J / m o l ) in the chemical kinetic regime.
THE smelting-reduction
of metallic oxides constitutes the principal mode of producing a wide variety of metals from their respective ores. For some important metals such as copper, nickel and cobalt, alternative techniques involving the production and reduction of chloride intermediates hold considerable promise. In the Cyprus copper process, ~a cuprous chloride intermediate is produced by leaching chalcopyrite concentrates with a ferric chloride-cupric chloride solution. Copper is produced by the hydrogen reduction of cuprous chloride. In the Falconbridge matte leach process for nickel, 2 nickel chloride tetra-hydrate (NiC12.4H20) is produced from a finely-divided nickelcopper matte by leaching it with a strong solution of hydrochloric acid. In that process the chloride product is hydrolyzed and the resulting oxide is reduced to the metallic state. The direct reduction of nickel chloride to metallic nickel remains unexplored. In fact very little work has been done on the reduction of metal chlorides with hydrogen gas. The objective of the present research was to investigate the hydrogen reduction of nickel chloride. The temperatures employed were purposely kept in the low to moderate range in order to minimize the diffusion effects. The equilibria involved in the reduction of nickel chloride (NiC12) with hydrogen have been investigated and data on the equilibrium constants have been published? Figure 1 shows the partial pressures of gaseous species partaking in the reduction process. The vapor pressure of NiC12 does not become appreciable until about a temperature of 1000 K. Thus at low to moderate temperatures used in this research the gasphase over NiCl2-solid essentially consists of hydrogen and hydrogen chloride. The present research is part of an overall research program aimed at determining the intrinsic kinetics of heterogeneous reactions. To date the study of the D. T. WILLIAMS is Undergraduate Research Assistant, S. K. E1-RAHAIBYis Graduate Research Assistant and Y. K. RAO is Professor, Division of Metallurgical Engineering, University of Washington, Seattle, WA 98195. Manuscript submitted July 7, 1980.
kinetics of hydrogen reduction of cuprous chloride and also that of the nickel chloride have been completed. The results of the study on cuprous chloride are reported separately. 4,5
EXPERIMENTAL The kinetics of reduction of nickel chloride with hydrogen were investigated in the temperature range of 533 (260 ~ to 788 K (515 ~ by means of the weight loss measurement technique. Materials Anhydrous nickel chloride of reagent grade was obtained from PCR Chemicals, Inc. of Gainsville, Florida. This nickel chloride was in the form of porous granules. This material was screened to different size fractions using Tyler standard sieves. Two fractions, one - 8 + 10 mesh (average size: 2.03 mm) and the other - 20 + 28 mesh (average size: 0.715 mm) were chosen f
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