Coagglomeration of coal and limestone to reduce sulphur emissions during combustion

The beneficiation of fine coal using the oil agglomeration technique (spherical or liquid phase agglomeration) has been developed at the National Research Council of Canada over a number of years. In this present study the separation of pyrite and other non-carbonaceous materials from the coal particles by selective agglomeration with fuel oil and/or bitumen has been investigated. The oil agglomeration characteristics of freshly mined and agglomerated aged coals were also compared and found to depend on their relative hydrophobicity. An improved response for weakly hydrophobic coals was achieved by treatment with conditioning agents such as sodium oleate. Even after beneficiation, the Nova Scotia coal studied still contained up to 3 wt% of sulphur, and therefore sulphur emission control on combustion is likely to be necessary. It has been demonstrated that SO 2 adsorbents can be incorporated directly into coal or coke agglomerates during liquid phase agglomeration, using bitumen or heavy oil as the binder. Static combustion tests at 850 °C were carried out in a muffle furnace and compared with results found for a bench scale fluidized bed unit at the same temperature. In both cases, sulphur capture of over 60% was obtained at a calcium to sulphur molar ratio of 1:1.