Characterization of coal fly ash from Israel

Abstract

The use of coal in electric power plants in Israel is relatively recent (1982). However, already in 1996, the Hadera and Ashqelon power plants had produced about 850 000 tons of fly ash. Most of it was used as an additive to clinker (cement). Nevertheless, because of the increase in electricity production, the amount of ash produced will increase proportionally. It is predicted that 1.2 million tons of coal ash will be produced by the year 2000. Since 800 000 tons of ash is the maximum that can be added to clinker under present legislation, this means that considerable quantities of ash (some 400 000 tons per year) will have to be used (apart from cement production) or disposed off without polluting the environment. As a consequence, a large national program was carried out in Israel to characterize coal ash produced in Israel and study the potential toxic effect of coal ash leachates on groundwater and soils. In particular, two compliance tests were studied: the European CEN/TC192 and the US TCLP 1311 methods. The results show that the TCLP 1311 method is more appropriate for testing the alkaline fly coal ash produced in Israel. The fine particles and particularly the very fine particles (<1 μm) in coal ash play an important role above their weight concentration because of their large active surface area. This is significant both for leaching and physical properties. We used computerized scanning electron microscope feature analysis to characterize these particles and to determine their distribution among the different small grain sizes in two industrial fly coal ashes. While the results are not quantitative, they add considerable knowledge to coal fly ash characterization.