Fly ash as a chemical scrubber and fixation agent for acidic waste of the fertilizer industry

Fly ash is produced in Israeli power stations via bituminous coal combustion. At present 1.5 million tons of fly ash are produced annually in 4 power stations and only ∼50% of it is used as a cement additive. Regulations imply that the ash to be used will be in accordance with the CALWET or the improved EPA-TCLP1311 leaching methods. The fly ash produced in Israel is very basic due to the low sulfur content and up to 12% mineral matter in the coals imported to Israel and thus it is a good potential chemical scrubber to acidic wastes. The fertilizer industry in Israel produces mainly phosphate based products. The production methods rely heavily on dissolution of phosphate rock in strong acids. Thus large quantities of acidic wastes are produced. These wastes have to be treated before final storage. The results show that the fly ash is an excellent scrubber and also that it's large surface area serves as a very efficient absorber to the toxic heavy metals from the waste. The final product is an aggregate substitute and as it stands the CAL WET leach test it can be used as a substitute to aggregates in the concrete industry. Initial calculations show that the actual economic value of the ash is in the range of 3 to 5 times better than its present value in utilization as a cement additive or in the construction industry. Thus using two wastes (fly ash and the acidic waste) can result in a green non-polluting product with an appreciable economic value.