SOx CAPTURE USING CARBONATE ABSORBENT

A process for removing CO2 from a gas comprising at least water vapor, CO2 and SOx, where x is equal to 2 and/or 3, the gas having an initial gas temperature, the process comprising a pre-treatment loop for desulfurizing the gas and recovering a SOx-depleted gas, and an absorption loop for removing CO2 from the SOx depleted gas, wherein the process comprises cooling an alkaline aqueous solution comprising water and a carbonate and bicarbonate of an alkali metal to obtain a cooled alkaline aqueous solution having a temperature lower than the initial gas temperature;

• contacting the gas with the cooled alkaline aqueous solution in a desulfurization unit of the pre-treatment loop, thereby causing cooling of the gas, condensation of some water vapor and absorption of the Sox in the cooled alkaline aqueous solution, and producing the SOx depleted gas and an acidic aqueous solution comprising sulfate and/or sulfite ions;
• purging a first portion of the acidic aqueous solution exiting the desulfurization unit;
• supplying the SOx depleted gas which contains CO2 from the desulfurization unit to a CO2 capture unit of the absorption loop;
• in the CO2 capture unit, contacting the SOx depleted gas with an absorption solution comprising water and carbonate of the alkali metal, thereby causing absorption of the CO2 in the absorption solution and producing a CO2-depleted gas and a carbonate and bicarbonate-rich absorption solution;
• treating the carbonate and bicarbonate-rich absorption solution in a stripping unit to generate a purified CO2 gas and recover a carbonate and bicarbonate-lean absorption solution;
• bleeding a fraction of an absorption solution circulating in the absorption loop (e.g., from the carbonate and bicarbonate-lean absorption solution or from the carbonate and bicarbonate-rich absorption solution) as an absorption solution bleed;
• and mixing the absorption solution bleed with a second portion of the acidic aqueous solution exiting the desulfurization unit of the pre-treatment loop to produce the alkaline aqueous solution.