A Novel strategy to produce ultrapure hydrogen from coal with pre-combustion carbon capture

Integrated Gasification Combined Cycles (IGCCs) are one of the emerging clean coal technologies which paves the way for producing power from coal with a higher net power efficiency than conventional PC-fired boiler power plants. It is also advantageous that in an IGCC power plant a carbon capture unit can be applied to a stream having a very high CO₂ partial pressure upstream of gas combustion that would not be available in case of a PC-fired boiler power plant, leading to less energy penalty involved in the carbon capture. In this study it is aimed to design a cogeneration process where a Hydrogen Pressure Swing Adsorption (H₂ PSA) unit is retrofitted to an IGCC power plant with pre-combustion capture for producing ultrapure hydrogen (99.99+ vol%). The ultrapure hydrogen is commonly utilised as feedstock for deep desulphurisation and hydrocracking units at refineries as well as H₂ fuel cells. It is found that, at the same H₂ purity of 99.99+%, the hydrogen recovery could be improved up to 93% with the increasing number of columns. Improving the H₂ recovery at the H₂ PSA to its maximum can contribute to reducing the power consumption for compressing the H₂ PSA tail gas by minimizing the yield of the H₂ PSA tail gas by-product. Furthermore, it is demonstrated that the H₂ PSA can also be designed to achieve 90% H₂ recovery even when a portion of the tail gas is recycled to the shift reactors in order to improve the overall advanced IGCC performance by increasing the H₂ yield and by reducing the auxiliary power consumption at carbon capture unit.