Novel Regenerable Magnesium Hydroxide Sorbents for CO2 Capture at Warm Gas Temperatures

A novel sorbent consisting of Mg(OH)(2) was developed for carbon dioxide (CO2) capture at 200-315 degrees C suitable for CO2 capture applications such as coal gasification systems. Thermodynamic analysis conducted with the FactSage software package indicated that the Mg(OH)(2) sorbent system is highly favorable for CO2 capture up to 400 degrees C at 30 atm. MgCO3 formed during sorption decomposes to release CO2 at temperatures as low as 375 degrees C up to 20 atm. MgO rehydroxylation to form Mg(OH)(2) is possible at temperatures up to 300 degrees C at 20 atm. The experimental data show that the sorbent is regenerable at 375 degrees C at high pressure and that steam does not affect the sorbent performance. A multicycle test conducted in a high-pressure fixed-bed flow reactor at 200 degrees C with 28% CO2 showed stable reactivity during the cyclic tests. The capture capacity also increased with increasing pressure. The sorbent is unique because it exhibits a high CO2 capture capacity of more than 3 mol/kg at 200 degrees C and also is regenerable at a low temperature of 375 degrees C and high pressure. High-pressure regeneration is advantageous because the CO2 compression costs required for sequestration can be reduced.