Syngas Redox (SGR) Process to Produce Hydrogen from Coal Derived Syngas

The syngas redox (SGR) process to produce hydrogen from coal derived syngas is described. The process involves reduction of a metal oxide to metallic form with syngas and subsequent regeneration with steam to generate hydrogen in a cyclic operation. Metal oxides of Ni, Cu, Cd, Co, Mn, Sn, and Fe were evaluated for this process based upon thermodynamic equilibrium limitations. It was found that Fe2O3 provided the best conversion of syngas to combustion products CO2 and H2O along with a high conversion of steam to hydrogen. Other oxides provide high conversion of syngas but were found lacking in producing hydrogen from steam. Composite particles with Fe2O3 as the key ingredient were developed that undergo multiple redox cycles without loss of activity. Analysis of process economics with respect to particle recyclability showed that the particles should undergo at least a 100 redox cycles without diminishing its activity. Process modifications to address carbon formation on reaction of syngas with iron oxide are discussed. Detailed process simulation showed that the SGR process is capable of converting 74% of the coal energy into hydrogen energy (higher heating value (HHV) basis) while delivering a pure CO2 stream without the need for costly separation technology.