Retention of zinc compounds in solid sorbents during hot gas cleaning processes

The development of new processes for coal-based energy production, as is the case of the integrated gasification combined cycle processes (IGCC), have made it necessary to devise new strategies to prevent trace element involvement in corrosion and environmental problems. The present study evaluates the retention capacity of zinc species present in the gas phase in different solid sorbents at temperatures typical of hot gas cleaning systems. The sorbents tested were kaolin, limestone, alumina, and fly ashes. The study was carried out in a laboratory-scale reactor, in which the sorbent was employed as a fixed bed, using synthetic gas mixtures. The influence of the solid sorbent and gas composition (with and without HCl(g)) on retention capacity (milligrams of element retained per gram of sorbent) was evaluated. It was concluded that when HCl(g) is not present in the gas atmosphere, fly ash and alumina are efficient sorbents for retaining zinc compounds in the gas phase from a coal gasification flue gas. In this case, retention capacities close to 15 mg g(-1) were achieved. When HCl(g) is present, alumina is the most effective sorbent, its retention capacities reaching 50 mg g(-1).