Ash reactivation technology using the Szego MillTM for grinding ashes with water, previously presented** at the Clearwater Clean Energy Conference in Florida, USA, June 2018, is now being applied to the activation of ashes from oil shale combustion. For coal ashes, typically from fluidized bed combustion (FBC), limestone has been added as a source of calcium. In typical oil shales, there is a great deal of calcium carbonate present naturally. In an FBC boiler, there is enough time for sulfur adsorption, but with pulverized firing, that is not the case. Thus, it is necessary to remove the sulfur dioxide from the flue gases. At the Eesti Power Plant in Narva, Estonia, the Alstom-developed Novel Integrated Desulfurization (NID) reactor system is used and some additional lime is added since much of the original calcium has been encapsulated at the high combustion temperature in the furnaces. Several tests using cyclone ash from that plant, activated with the Szego Mill, have been carried out with good results. The initial publication has compared the characteristics of activated ash and commercial lime and established their importance for sulfur capture. The performance results indicate that, per unit free CaO, well-activated ash is at least as good as the purchased lime, but three times more is needed due to the lower CaO content. Further testing is planned, both in the laboratory and, it is hoped, also at the Power Plant in Narva. As use of oil shale is increasing in various countries, the results anticipated should find broader utilization.
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