Abstract:

With the development of economy and accelerated urbanization, the increasing production of municipal solid wastes brings great impact on people’s daily life and health. How to recycle, reduce and harmlessly treat solid wastes has become an urgent problem. The pyrolysis of municipal solid wastes is an effective way to solve the current “garbage siege” and resource shortage, but the high content of CO₂ in the pyrolysis gas will affect its subsequent combustion and utilization. Calcium-based sorbents are considered as one of the most promising CO₂ capture materials due to their wide source, low cost and high adsorption capacity. However, the adsorption performance of conventional calcium-based sorbents decays rapidly as the number of cycles increases. To address this problem, this study prepared modified calcium-based sorbents doped with metal Zr and Mg by co-precipitation method. The effects of doping ratios of Zr and Mg, carbonation temperature and calcination temperature on the modified calcium-based sorbents were obtained by fixed bed reactor. The experimental results show that the doping ratios of metal Mg and Zr should not be too high or too low, and the optimal doping ratio (the molar ratios of Ca, Mg and Zr) is 10∶1∶0.5. Because too low doping ratio will retard the sintering of the sorbent, while too high doping ratio will lead to the reduction of CaO content and active reaction sites on the surface of the sorbent. The sorbent with the doping ratio of 10∶1∶0.5 has the best adsorption performance when adsorbed at 700 °C and calcined at 900 °C, respectively, with an average carbonation conversion of 76.3% after ten cycles.When applying on product gas, the capture ratio of CO₂ reaches 83.8% with 10∶1∶0.5 doping ratio under 700 °C carbonation temperature.

Key words: pyrolysis gas, calcium-based sorbents, CO₂ capture, metal doping, carbonation conversion rate