Production of high-concentration CO2 from electrified limestone calcination for carbon capture applications

Operating electrically heated kilns under high-CO 2 atmospheres can increase CO 2 capture efficiency but creates reducing conditions that drive CO formation. In this work, CO generation during limestone calcination in a 280 kW electrically heated rotary kiln at 75 vol-% CO 2 and low O 2 concentration is investigated. Equilibrium calculations indicate that sulphide and sulphite phases in limestone decompose, releasing SO 2 and promoting CO formation. Complementary packed-bed experiments confirm that sulphur species are a major CO promoter and reveal a synergistic interaction between sulphur compounds and elevated CO 2 levels. Using low-sulphur limestone could suppress CO emissions. Where low-sulphur feedstocks are unavailable, targeted electrolytic O 2 or air injection coupled with indirect limestone preheating is proposed to strip sulphur and preserve the high-purity CO 2 stream which will improve the efficiency of electrified kilns integrated with a carbon capture process. • CO formation is promoted in electric kiln when CO 2 concentration is high and O 2 concentration low. • Sulphur compounds in limestone are responsible for CO formation. • Sulphur release and CO formation can be isolated to the preheating of limestone. • A concept for indirect preheating of limestone and O 2 injection is proposed to attain high-concentration CO 2 streams from electric lime kilns.