Host: The Society of Chemical Engineers, Japan
A coal ash-based sorbent was prepared by mixing coal ash with slaked lime for dry HCl sorption in pyrolysis gas from MSW. The HCl sorption performance of the sorbent was evaluated by the breakthrough of HCl sorption and was compared with those of slaked lime and calcined dolomite. The influence of temperature and presence of H2O in a test gas on HCl sorption characteristics were investigated. The experiment was conducted in a packed bed reactor where the sample pellets of 3mm¢ × 2mm were packed. A mixed gas of HCl (1%) - H2O (10%) - N2 was fed to the reactor in the temperature range of 723K to 1123K. Compared with slaked lime and calcined dolomite, coal ash-based sorbent showed a higher HCl sorption capacity at 823K. From a SEM-EDX observation, it was found that HCl penetrated more into inside of the sorbent. The main components of SiO2 and Al2O3 in coal ash were considered to contribute to keeping larger pore volume, so that HCl might be absorbed effectively. On the other hand, the HCl sorption capacity of the proposed sorbent was the smallest among the three sorbents at 1123K. Low temperature eutectic mixtures were detected for the sorbent subjected to HCl sorption at 1123K. It was found that HCl sorption capacities of coal ash-based sorbents employed were reduced in all the temperature range of 723K to 1123K when H2O was present. It was considered that the lower HCl sorption capacities of the sorbent were caused by the shift of reaction equilibrium from HCl sorption to HCl emission.
