Chemical Looping Reforming – an Efficient Process for the Production of Hydrogen from Coal

A novel Chemical Looping Reforming (CLR) process is proposed in which a highly recyclable iron oxide composite particle is reduced with coal and then oxidized back with steam to generate hydrogen. The reduction of iron oxide with coal results in a mixture of CO2 and H2O in the exhaust stream which after water condensation provides a ready to sequester relatively pure CO2 stream. This eliminates the need for energy intensive CO2 separation process which will be required in traditional air fired coal combustion processes. In oxidation part of the process, the reduced particle is oxidized with steam in a second reactor producing hydrogen and regenerating the iron oxide. This paper describes the contacting pattern necessary for achieving high coal conversions in the first reactor. Detailed ASPEN simulations were carried out to simulate the workings of the reactor. It was found that a high H2 production rate (0.183kg H2/kg coal) is possible with complete conversion of carbon. The material balances and concentrations for various gaseous and solid streams are reported. The exit flue gas contained mainly CO2. The sulfur in the coal was captured by introducing lime into the reactor which prevented FeS formation. FeS formation may potentially decrease the recyclability of the Fe2O3 containing particles as well as lead to contamination of the hydrogen produced by H2S. The simulations showed that NOx will be produced at below detectable limits. Chlorine was found to form HCl and exit along with the CO2 gas. It was found that a high Fe2O3 flow rate and temperature and a low oxygen demand are ideal for achieving high H2 production rates, high carbon conversions and high CO2 exit purity. Combining with a low cost of hydrogen production of $0.83/kg, which is very competitive with respect to the $1.2/kg H2 as obtained from SMR of natural gas ($7/M BTU) the CLR process is at the leading edge of clean coal conversion technologies. * Corresponding Author, Ph 614-688-3262, [email protected]