Israeli coal ash characterization & environmental effects By Dr. Lionel Metzger,
Coal ash chemical and mineralogical properties Si, Al, Fe, Ca and Mg oxides constitute more than 95% of the ash matrix. Coal ash produced in Israel is alkaline: ph of fly ash suspension: 10-13. Mineralogical fractions Amorphous phase Glass on average ~ 70% Crystalline phase o Alumino-silicate phase on average ~ 20% Mullite 2-3(Al 2 O 3 ).1-2(SiO 2 ) Quartz SiO 2 o Iron phase on average ~ 10% Spinel, Hematite, Magnetite
Major chemical constituents in coal ash - for 2004 Concentrations given in % Component South Africa Australia Columbia Indonesia SiO 2 41.7-52.1 50.0 58.3-60.4 55.7 Al 2 O 3 26.5-33.0 36.8 20.0-23.1 24.1 Fe 2 O 3 2.9-6.0 4.6 7.9-8.3 10.0 CaO 6.0-10.9 3.5 2.4-2.6 2.0 MgO 1.8-2.3 0.8 1.1-2.2 2.1 TiO 2 1.5-1.8 1.2 1.0 1.0 K 2 O 0.5-1.0 0.8 1.6-2.3 2.2 Na 2 O 0.1-0.3 0.4 0.5-0.6 0.7 SO3 1.8-2.8 1.2 2.1-2.7 1.4 Na 2 O 1.2-2.6 1.3 0.2 0.4 % coal basket 57 5 24 14 % ash prod. 72 7 15 6
Coal ash classification All the coal burnt in Israeli power stations is bituminous, so all the fly ash produced is Class F fly ash, according to ASTM classification (pozzolanic, not cementitious ash). According to the coal sources, two kinds of ash are produced: Fly ash with high CaO content (8-11%) Fly ash with low CaO content (1-4%) There are few experimental applications for which only high Ca fly ash has been considered: Heavy soil stabilization under road basements Sewage sludge treatment with fly ash
Trace elements in Israeli coal ash Concentrations given in ppm, dry weight basis Element As Cd Cr Hg Pb Se B Mo V Bottom Ash Range 1.0 25 <0.05 0.7 80-243 <0.01 0.34 8-89 <0. 6 5.5 47-185 1.6 15.0 95-200 Average 4.9 0.22 138 0.11 24 2.4 96 5.2 142 Range 36-140 0. 8 24 75-540 8 24 Fly Ash 9 60 0.44 1.5 110-205 <0.02 0.30 130-455 Average 22 0.9 142 0.17 62 7 215 13 197 Summary of analyses performed on semi-annual ash samples during the period 7/91 12/04 Range for soils 0.1 40 0.01 7 5 3000 0.02 0.2 2-200 0.1-2 2 100 0.2 5 20 500
Trace elements in Israeli fly ash leachates Leaching test procedure: TCLP Concentrations given in ppb in leachate Element As Cd Cr Hg Pb Se B Mo V Fly Ash Israeli MOE 7/98 12/04 Criterion <2 960 0.3 26 20-610 <0.01 4 0.1-8 23 320 3350 19000 127-675 150 1550 2000 100 2000 25 150 700 20000 2000 5000 EPA Criterion 5000 1000 5000 200 5000 1000 - - -
Coal ash water pollution potential Coal ash produced in Israel is characterized by low trace element concentrations, similar with those found in soils and rocks. Trace element concentrations in fly ash produced in Israel are similar with those reported for power stations in Europe burning high quality coal. From the summary of all TCLP leachate analyses performed until now, fly ash is considered as utilizable according to the guidelines issued by the Ministry of the Environment. According to the results of the leaching tests, the potential release of trace elements from the ash is low, thus there is only a minor risk of groundwater contamination under ash use sites. Environmental specifications imposed on any source of coal proposed to ensure that the ash quality will not be impaired in the future.
Monitoring at ash storage & utilization sites Data collected from environmental monitoring performed close to ash storage and utilization sites confirmed that there is no risk of groundwater pollution as a result of ash utilization. No modification of groundwater quality was found during the monitoring programs performed in the nineties at Orot Rabin and Rutenberg power stations. According to the results of the environmental monitoring program performed near the road to Jassar A Zarka, there is no sign of any environmental damage due to ash utilization. Groundwater quality monitored after 1-3 and 6 years All data collected until now in the laboratory and the field lead to the conclusion that ash utilization in Israel is safe for the environment.