Mineral carbonation of a desulfurization residue for CO2 sequestration

Abstract

The feasibility of mineral carbonation of a desulfurization residue for sequestering CO₂ was evaluated both through theoretical and experimental approaches. The carbonation reaction, including carbonation of Ca(OH)₂ and CaSO₄, occurred through a kinetically controlled stage with an activation energy of 20.21 kJ mol⁻¹. The concentration of ammonia, CO₂ flow rate, liquid to solid ratio and temperature impacted on the carbonation ratio of the desulfurization residue through their direct and definite influence on the rate constant. Concentration of ammonia and liquid to solid ratio were the most important factors influencing the desulfurization residue carbonation in terms of both the carbonation ratio and reaction rate. Under optimized conditions the carbonation ratio could reach approximately 98% when using industry-grade CO₂. The crystalline phases of the carbonated desulfurization residue were calcite and vaterite with spherical and granular morphology. CO₂/O₂/N₂ mixed gas was also used as the simulated desulfurization fuel gas in the carbonation reaction and it had a relatively minor effect on the carbonation ratio. However, it slowed the carbonation reaction and produced a carbonation product with a smaller average particle size, which included high purity (≥99%) white calcite. The carbonated desulfurization residue reported herein showed a rapid CO₂ sequestration ratio, high CO₂ sequestration amount, low cost, and a large potential for in situ CO₂ sequestration in the electricity and steel industry.