(67g) Calcium Looping Process for Clean Coal Conversion

The rising energy demand coupled with the depleting global oil reserves and the environmental degradation due to emissions has led to extensive research in the field of clean energy production. The Calcium Looping Process (CLP) is one of the clean coal technologies being developed for the production of hydrogen (H2), electricity and liquid fuels and is based on the syngas obtained from 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 WGS catalyst and reducing the overall foot print of the hydrogen production process. The CLP comprises of two reactors; the carbonation reactor where the thermodynamic constraint of the WGS reaction is overcome by the incessant removal of the CO2 product and high-purity H2 is produced with contaminant removal and the calciner where the calcium sorbent is regenerated and a sequestration-ready CO2 stream is produced. The purity of H2 is increased by a large extent when the carbonation reaction is integrated with the WGS reaction. The steam addition for the WGS reaction is also reduced to stoichiometric quantities which aids in reducing the parasitic energy consumption of the process. The integration of the calcium looping process results in an increase in the energy efficiency by about 7% when compared to the state of the art coal to hydrogen process. In this paper, the reaction chemistry occurring in the calcium looping process, thermodynamics, lab and bench scale experimental studies, process intensification strategies and energy conversion efficiencies will be discussed.