Decomposition kinetics of sodium amalgam in fixed bed of WC‐coated tubular SS‐304 packing: Modelling and validation

Abstract

AbstractErosion of graphite packing in continuously operating fixed bed sodium amalgam decomposers leads to performance degradation accompanied by clogging in the downstream process lines which not only increases the maintenance and catalyst refilling costs but also aggravates the risk of mercury vapour exposure. To overcome this drawback, the present work utilizes tubular SS‐304 packing coated with tungsten carbide (WC) on the outer surface. The coating is obtained using an indigenously developed laser‐directed energy deposition facility. Dedicated experimental setup is developed for each set of process parameters to comparatively study the fixed bed decomposition kinetics at steady state for three types of WC‐coated SS‐304 packing and a conventional spherical graphite packing. In parallel, a numerical 3D–1D model is implemented using open source computational solvers and is experimentally validated. The algorithm of this model is based on proposed drop–fill approach for WC‐coated SS‐304 packing and modified drop approach for spherical graphite packing, respectively. In terms of decomposition rates, the performance of WC‐coated SS‐304 packing surpasses that of spherical graphite packing at high amalgam flowrates; meanwhile, the average alteration in experimental steady‐state temperature profile after continuous operation of 2 years is around 2% for WC‐coated SS‐304 packing as compared to nearly 17% for spherical graphite packing.