Studies on Hydrochlorination of Silicon in a Fluidised Bed Reactor

Abstract

The present work aims to study the reaction between silicon and hydrogen chloride (HCl) gas to produce, primarily, trichlorosilane in fluidised bed condition. The experimental data were obtained first in fixed bed and then in fluidised bed to determine reaction rate constants for the reaction of HCl gas on metallurgical grade silicon. The reactor used for the purpose was a laboratory reactor of ID 26.6 mm and height 470 mm made up of stainless steel 316L. The reaction products were condensed at – 78°C after coming out from the outlet of the fluidised bed reactor. Uncondensed trichlorosilane vapours, if any, from the condenser were trapped in caustic soda solution forming silica that was washed and weighed to calculate the amount of uncondensed trichlorosilane. The experiments were carried out in temperature range 316–326°C, using the average silicon particle sizes of 88–208 μ and flow rates of HCl gas of 1.6–3.2 lpm at 1.0 atmospheric pressure. Experimental conversions of HCl were evaluated. Fluidised bed models of Kunii and Levenspiel, and Kato and Wen were analysed utilising the experimental data to determine overall rate constant and conversions. The experimental conversions of HCl were compared with the estimated values from the Kunii and Levenspiel model as well as from the Kato and Wen model.