A novel CO_2-water leaching method for AAEM removal from Zhundong coal

摘要

Zhundong coal has caused serious fouling and slagging problems during combustion due to its high contents of AAEM. This work proposed a CO2-water leaching method to remove AAEM in Zhundong coal. The results show that CO2-water leaching can effectively remove Na, Mg, Ca etc, especially for the organic metals removal. The removal efficiencies of Na and Ca, which are the key elements causing fouling and slagging during Zhundong coal combustion, were as high as 90.5% and 31.1%, respectively by CO2-water leaching. They were much higher than those of pure water leaching which were as low as 71.4% and 19.6%, respectively. Na removal efficiency increased largely with leaching time and temperature, while the Ca removal efficiency appeared fluctuating changes. The removal mechanism includes two steps. The first step is the dissolution of CO2 into water to form radical hydrogen (H+). The second step is the removal of organic AAEM by H+ through ion exchange. The results also indicated that the removal efficiency can be further promoted by using flow water. And the flue gas from coal fired power plant can be a good CO2 source. Thus, this study proved that the CO2 -water leaching was an effective and promising method for AAEM removal from Zhundong coal.