In-situ CO2 capture in a pilot-scale fluidized-bed membrane reformer for ultra-pure hydrogen production

A novel pilot fluidized-bed membrane reformer (FBMR) with permselective palladium membranes was operated with a limestone sorbent to remove CO₂in-situ, thereby shifting the thermodynamic equilibrium to enhance pure hydrogen production. The reactor was fed with methane to fluidize a mixture of calcium oxide (CaO)/limestone (CaCO₃) and a Ni-alumina catalyst. Experimental tests investigated the influence of limestone loading, total membrane area and natural gas feed rates. Hydrogen-permeate to feed methane molar ratios in excess of 1.9 were measured. This value could increase further if additional membrane area were installed or by purifying the reformer off-gas given its high hydrogen content, especially during the carbonation stages. A maximum of 0.19 mol of CO₂ were adsorbed per mole of CaO during carbonation. For the conditions studied, the maximum carbon capture efficiency was 87%. The reformer operated for up to 30 min without releasing CO₂ and for up to 240 min with some degree of CO₂ capture. It was demonstrated that CO₂ adsorption can significantly improve the productivity of the reforming process. In-situ CO₂ capture enhanced the production of hydrogen whose purity exceeded 99.99%.