Leachate-Treatment Technique Utilizing Fly Ash as Low-Cost Sorbent. Quarterly Progress Report

摘要

A two year investigation is being carried out to design a system for the inexpensive treatment of ash pond effluent or leachate. Twelve different coals were burned in three different types of boilers to determine the influence of coal composition, ash fusion temperatures, boiler additives, combustion conditions and co-firing of natural gas or oil with the coal, on the composition of the fly ash and bottom ash as well as the leaching and sorbate characteristics of the fly ash produced. The trace element analysis in the twelve coals and their respective fly and bottom ashes as well as surface analysis of a selected number of fly ashes using ESCA is reported. The leaching characteristics of the fly ashes with respect to pH have been defined for several trace elements. For low ash fusion coals, Sn, Ni, Mo, Cu, Cr and Mn tend to concentrate in the bottom ash, whereas Ti, Zn and Ba tend to concentrate in the fly ash. Cd, Pb and V did not show a preference. For high ash fusion coal, Sn, Sd, Pb, Mo, Cu, Cr, Ba and V concentrate in the bottom ash and Ti, Ni, Zn and Mn in the fly ash. An increase in boiler temperature favored lower concentrations of the above trace elements in the fly ash from low ash fusion coals. Smaller fly ash particles contained higher concentrations of the above trace elements than larger fly ash particles produced from the same coal. Leaching of Cd, B, Sn, Ni, Pb, Mo, Cu, Cr, Zn, Mu and Fe from the fly ash was found to be directly proportional to (1) the amount of these trace elements present, (2) decreases in pH, (3) decreases in boiler temperatures and (4) increases in ash fusion temperatures. In general fly ash particles which leached the least amount of the above elements exhibited the best sorbate characteristics.