The Impact of Sorbent Geometry on the Sulphur Adsorption under Supercritical Water Conditions: a Numerical Study

A numerical model to show the impact of the adsorption bed geometry on the desulfurization process of wet biomass under supercritical water (SCW) gasification process has been developed. Three different geometries, straight channels (pipe), sharp-edged channels (sharp) and packed bed of particles (pebbles) have been considered for the sorbent bed. The influence of the flow patterns on the sulphur distribution inside the bed and on the saturation of the sorbent has been analysed. The results show that, when the flow is unidirectional with a parabolic profile, as in the pipe geometry, the adsorption process can be explained based on the 1D plug-flow model. In the case of more complex flow structures, when torus-shaped vortices appeared in the sharp or pebbles geometries, the 3D flow effects should be considered. The present work might provide useful information for the evaluation of sulphur sorption under SCW conditions. The models obtained by computational fluid dynamic, which are under experimental validation using neutron imaging, will help for the sorbent design and production by 3D printing techniques, which represent an advanced engineered tool to improve the process efficiency and sorbent material selection.