(621a) Reduction of Metal Oxide Particles with Syngas for Hydrogen Production

The understanding of the reduction mechanisms of metal oxide particles with syngas is important for the designing of the Syn Gas Redox (SGR) process. In the SGR process, composite particles of iron oxide are reduced in a moving bed reactor with syngas producing a sequestration ready CO₂ stream. Subsequently, the reduced particles are partially oxidized in a second reactor with steam to produce hydrogen. Finally, the particles are oxidized with oxygen before they are cycled back into the first reactor. In the SGR process, the heat liberated by the oxidation of the particles with steam and oxygen is used for the production of the high temperature steam. The heat integration of the SGR process leads to an estimated hydrogen production efficiency range of 70-75% (HHV).

Coal derived syngas usually contains various gases with its majority being carbon monoxide and hydrogen. To better understand the reduction of iron oxide composite particles, in this work, hydrogen gas was used as a reducing agent. Based on the kinetic data obtained, a diffusion–surface reaction kinetic model was developed. Further, a countercurrent moving bed reactor model was developed for the reduction of iron oxide with hydrogen. An industrial scale reactor was simulated and its performance was studied for various reactor lengths. It was found that, after a critical value, the increase in reactor length does not have a significant effect on the final conversion for gas and solids. This was explained by the formation of a near dead zone in the middle of the bed where the gas and solids reach a pseudo-equilibrium.