Chemical Engineering & Technology, Vol.35, No.3, 525-531, 2012
Mg-Silicate Carbonation Based on an HCl- and NH3-Recyclable Process: Effect of Carbonation Temperature
A new indirect mineral carbonation process is studied which could mitigate anthropogenic CO2 emissions. In this process, magnesium silicate is dissolved in HCl and the resulting MgCl2 solution is subsequently reacted with CO2 in NH3. HCl and NH3 are recovered from NH4Cl in a two-step thermal decomposition. Carbonation is investigated from 30 degrees C to 180 degrees C at 4?MPa CO2 pressure and Mg-carbonate morphology transformations with increasing temperature are identified. Nesquehonite (MgCO3 center dot 3H2O) is obtained below 70 degrees C, hydromagnesite (Mg5(CO3)4(OH)2 center dot 4H2O) is formed at 100 degrees C, and further temperature increase to 180 degrees C leads to magnesite (MgCO3) precipitation. Nesquehonite and magnesite can fix more CO2 per mole Mg than hydromagnesite.