CO2 capture by double metal modified CaO-based sorbents from pyrolysis gases

Abstract

High-temperature pyrolysis technology can effectively solve the problem of municipal solid waste pollution. However, the pyrolysis gas contains a large amount of CO2, which would adversely affect the subsequent utilization. To address this problem, a novel method of co-precipitation modification with Ca, Mg and Zr metals was proposed to improve the CO2 capture performance. X-ray diffraction (XRD) patterns and energy dispersive X-ray spectroscopy analysis showed that the two inert supports MgO and CaZrO3 were uniformly distributed in the modified calcium-based sorbents. In addition, the XRD results indicated that CaZrO3 was produced by the reaction of ZrO2 and CaO at high temperatures. The effects of doping ratios, adsorption temperature, calcination temperature, CO2 concentration and calcination atmosphere on the adsorption capacity and cycle stability of the modified calcium-based sorbent were studied. The modified calcium-based sorbent achieved the best CO2 capture performance when the doping ratio was 10:1:1 with carbonation at 700 °C under 20% CO2/80% N2 atmosphere and calcination at 900 °C under 100% N2 atmosphere. After ten cycles, the average carbonation conversion rate of Ca-10 sorbent was 72%. Finally, the modified calcium-based sorbents successfully reduced the CO2 concentration of the pyrolysis gas from 37% to 5%.