CO2 capture of calcium based sorbents developed by sol–gel technique in the presence of steam

• Excellent sorbents CaO–MgO and CaO–MnO2 were synthesized by sol–gel technique.
• Steam in carbonation or calcination only enhanced CO2 capture capacity of CaO–MgO and CaO–MnO2.
• The greatest CO2 capture capacity was achieved with 5% steam in carbonation and 10% steam in calcination atmosphere.
• Both surface area and pore volume were increased with appropriate amount of steam presence.
• High and stable reactivity of the synthesized sorbents were detected under the severe but realistic reaction conditions.

The carbonation–calcination of CaO is considered one of the promising technologies for capturing CO2 from fossil fuel power plants. The problem of this technology is the decay in reactivity of the sorbent over multiple cycles. CaO sorbents were synthesized by the sol–gel process to improve CO2 capture capacity and sintering resistant of the sorbents. The focus of this paper is to investigate the influence of steam, which will be present in flue gases, on the reactivity of the sorbents synthesized by the sol–gel process. Steam in carbonation or calcination atmosphere only enhanced CO2 capture capacity of the synthesized sorbents, with greater influence presenting in carbonation atmosphere of 15% CO2/10% H2O/N2 balance. The further enhanced positive effect of steam on carbonation of sorbents is presented with 5% steam in carbonation and 10% steam in calcination atmosphere. The synthesized sorbents demonstrate high and relatively stable reactivity, even under the severe but more realistic conditions, enabling a conversion of 0.79 and 0.76 for CaO–MgO and CaO–MnO2 respectively after 50 cycles. Relatively stable pore volume and excellent pore size distribution of the synthesized sorbents under these conditions accounts for the high carbonation conversion.