Effect of Morphology of Sulfurized Materials in the Retention of Mercury from Gas Streams

Abstract

The retention of mercury vapor by sulfur supported on sepiolite has been studied, and the utility of sepiolite as a dispersant for the active phase, sulfur, has been thoroughly ascertained. Samples with 10% S supported on sepiolite of varying size and shape have been prepared from powders sulfurized by reaction/deposit, and their efficiency in depurating air streams with 95 ppm mercury has been tested in a dynamic system using a fixed-bed glass reactor and fluid velocities ranging from 3.1 to 18.9 cm s-1. From breakthrough curves under various sets of conditions, the importance of mass transfer under the process conditions has been proven. The progress of the reaction is limited by the resistance to reactant diffusion inside the solid through the layer of product formed. Sulfur reaction to HgS is reduced to an external zone of the solid, giving rise to an egg-shell deposit whose extension is related to sulfur dispersion and porosity of the adsorbent. Then, conversion and capacity of the samples are related to their porosity and S/V ratio. The use of SEM helps to confirm those statements. The 10% S samples compare well with the more conventional S/activated carbon, with their use being advantageous for the low price and abundance of the substrate.