Analysis of Sustainable Technologies for Acid Gas Removal

Acid gases, such as sulphur dioxide and hydrogen halides and – in a broad sense – carbon dioxide, are typical pollutants generated by combustion processes. Their removal by means of solid sorbents represent an efficient and cost-effective approach in dry acid gas treatment systems for waste incineration flue gas, while for CO2 capture the process is exploratively studied as a promising alternative to amine scrubbing. The present study addressed both aspects. In waste incineration flue gas cleaning, acid gas removal by sorbent injection is a well-established process. Nonetheless, a thorough understanding of the gas-solid reactions involved in the process has not been reached yet and, thus, the operation of dry treatment systems is still highly empirical. In the present study, the process was analysed using different levels of detail: from the microscopic level of a lab-scale experimental campaign and phenomenological description of the kinetic and mass transfer phenomena governing the gas-solid reaction to the macroscopic level of techno-economic and environmental assessment of alternative full-scale dry treatment systems. With respect to CO2 capture technologies, the process is still in the development stage and research is focused on the identification of highly-efficient sorbents. The present study analysed the enhancement of CO2 uptake potential of magnesium oxide, a promising sorbent for intermediate-temperature carbon capture, by means of coating with alkali metal molten salts. The joint analysis of gas-solid reaction for flue gas cleaning in two diverse contexts allowed the identification of common issues and of possible shared solutions.