The Calcium Looping Process is one of the clean coal technologies being developed for the production of hydrogen, electricity and liquid fuels from syngas obtained via coal gasification. It integrates the water gas shift (WGS) reaction with in-situ carbon dioxide (CO2), sulfur and halide removal at high temperatures in a single reactor while eliminating the need for a water gas shift catalyst thus reducing the overall foot print of the hydrogen production process. The calcium looping process comprises of two reactors: the carbonation reactor where the thermodynamic constraint of the water–gas-shift reaction is overcome by the incessant removal of the CO2 product from the reaction mixture and high-purity hydrogen is produced with contaminant removal and the calciner where the calcium sorbent is regenerated and a sequestration-ready CO2 stream is produced.

Process evaluation and optimization of the calcium looping system for the production of hydrogen from coal has been conducted using the commercial ASPEN Plus® process simulation software. The over all efficiency of this process for the production of 99.999% pure hydrogen from coal is 63% (HHV) when compared to the state-of-the-art, hydrogen from coal process which has an efficiency of 57% (HHV). The purity of hydrogen is increased by a large extent when the carbonation reaction is integrated with the WGSR. The steam addition for the WGSR can also be reduced to near-stoichiometric quantities which aids in reducing the parasitic energy consumption of the process. In addition, the extent of H2S removal by the CaO sorbent is also enhanced by operating at lower steam concentrations. High purity hydrogen of 99.7% with less that 1 ppm sulfur impurity has been obtained in a bench scale fixed bed reactor system. Experiments conducted in a bench scale system have revealed the superior performance of the OSU patented PCC based calcium oxide sorbent for the production of hydrogen.