Leachate treatment technique utilizing fly ash as a low cost sorbent
Department of Civil and Environmental Engineering
Master of Science
Liskowitz, John W.
Perna, Angelo J.
Trattner, Richard B.
This study was 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 coal fired 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 elemental analysis consisting of Ti, Cd, Sn, Ni, Pb, Mo, Cu, Cr. Zn, Mn, Ba, and V in the twelve coals and their respective fly and bottom ashes. In addition, the leaching characteristics of the fly ashes with respect to pH, Cd, B, Sn, Ni, Pb, Mo, Cu, Cr, Zn, Mn and Fe have been defined.
The results indicate that in the combustion of low ash fusion coals, the Sn, Ni, Mo, Cu, Cr and Mn tend to concentrate in the bottom ash, whereas the Ti, Zn and Ba tend to concentrate in the fly ash. For the high fusion coal, Sn, Cd, Pb, Mo, Cu, Cr, Ba and V in the parent coal concentrate in the bottom ash and Ti, Ni, Zn and Mn in the fly ash.
An increase in boiler temperatures were observed to favor lower concentrations of the above trace elements in fly ash particles produced from low ash fusion coals. Also, smaller fly ash particles were found to contain higher concentrations of the above trace elements when compared to that present in larger fly ash particles produced from the same coal.
The addition of the additive LPA-40 (which contains sulfur compounds to alter the sensitivity of the fly ash) to the combustion gases appears partially responsible for the amount of sulfur found on the surface of the fly ash particles.
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 in the fly ash, (2) decrease in pH, (3) decreases in boiler temperatures and (4) increases in ash fusion temperatures. Fly ash particles which in general leached the least amount of the above elements exhibited the best sorbate characteristics.
njit-etd1982-003 (162 pages ~ 5,968 KB pdf)
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Created September 17, 2007