High Purity Hydrogen Production with in-situ CO2 and Sulfur Capture

Enhancement in the production of high purity hydrogen (H2) from synthesis gas, obtained by coal gasification, is limited by the thermodynamics of the water-gas shift reaction (WGSR). However, this constraint can be overcome by concurrent WGSR and carbonation (of calcium oxide) reaction to enhance H2 production. The carbonation of calcium oxide forming calcium carbonate incessantly drives the equilibrium-limited WGSR forward by removing the carbon dioxide (CO2) product from the reaction mixture. Calcium carbonate can be separately calcined to yield a pure CO2 stream for its subsequent sequestration and the calcium oxide recycled back. This calcium looping scheme not only improves the hydrogen yield and purity but also integrates a CO2 management scheme in the hydrogen production process while achieving near complete conversion of the carbon monoxide reactant. This process developed at the Ohio State University can effectively and economically produce a pure H2 stream, at high temperature and pressure, by coal gasification with integrated capture of CO2 emissions, for its subsequent sequestration. We have identified a high reactivity patented, mesoporous calcium oxide sorbent for the in-situ CO2 capture as well as H2S removal. The morphological properties of our patented precipitated calcium carbonate sorbent (PCC) can be tailored using surface modifiers to demonstrate a high CO2 capture capacity of about 70% by weight (~700g of CO2/kgsorbent), yield a high calcium conversion of above 80% while removing H2S at high temperatures (700-900 C). Experimental evidence clearly shows that this proprietary calcium sorbent (PCC) performance dominates over that of commercial limestone sorbents. This integrated “one box” process depicts the potential to achieve higher system efficiencies with lower overall footprint by combining different process units in one stage. This process removes the need for hydrogen separation membranes with integrated CO2 and sulfur capture.