Experimental and Economic Assessment of Temperature Swing Adsorption Systems for the purpose of Claus Tail Gas Clean Up

Abstract

Current regulations of SOx emissions require Sulfur Recovery Units to achieve recoveries in excess of 99.9% which falls beyond the practical limits of a conventional Claus plant. Tail gas treatment unit are commonly added to the Claus unit as to achieve the target recovery. Capital cost of existing commercial Claus Tail gas clean up technologies capable of achieving that recovery can amount to 45% of the total capital cost of the SRU. Adsorption based processes hold significant potential for achieving the targeted recovery at lower costs considering their high selectivity towards removal of ppm level contaminants. This work assesses the potential of such system in competing with commercial alternatives. We begin by identifying and assessing a suitable adsorbent for the target removal. The assessments attempt at understanding the governing mechanism of the adsorption phenomenon by using several material characterization techniques including XRD, TEM, EELS, in addition of traditional breakthrough assessment. Following the adsorption phenomenon is modelled using an appropriate partial differential equations based model which captures the adsorption mechanism and the mass transfer effects. The resulting model is then used in the design and cost optimization of a scaled up unit embedded within the a real industrial plant. A mixed integer nonlinear programing model of the net present worth of costs is formulated and subsequently solved for the minimum possible cost of the entire unit while considering realistic constraints. The resulting figures strongly suggest the potential of an adsorption based process in competing with commercial alternatives.