Metallurgical coals in Canada: resources, research, and utilization

Abstract

Canada has a vast metallurgical coal base located mainly in the Provinces of British Columbia and Alberta in the west and Nova Scotia in the east. Large mines, efficient rail transportation and port facilities, and good coking coal properties at competitive prices have allowed Canada's metallurgical coal exports to double in the last 12 years to 22 million tonnes. Western Canadian and eastern Canadian coals are quite different as a result of their different geological histories. The Cretaceous western Canadian coals were formed about 100 million years ago in swamps but, unlike the Carboniferous coals from eastern North America, have generally matured in a non-marine environment. The stresses that occurred during the formation of the mountains in western Canada have brought the coals to the surface, often in faulted, folded, or steep seams. The resulting coals range from high-volatile to low-volatile bituminous in rank and generally are friable. They have more inherent ash and semifusinite, and less sulphur and alkalis than corresponding Carboniferous coals. Their unusually low Gieseler fluidity and dilatation properties make these test methods, at best, doubtful in grading Cretaceous coking coals. Individually, western Canadian coals make strong cokes with excellent coke strength after reaction (CSR) properties because of the low basicity of their ash. Removal of mineral matter and high bulk density charging of coke ovens significantly improves their coke quality. The MVB coals can be added to eastern North American binary blends to bridge the fluid temperature ranges of the component coals, to reduce coking pressures and to improve CSR properties. Weak and non-coking coals from western Canada can be used in conventional cokemaking, partial briquetting, pitch additives, or form coke processes using pitch binder. Pitch enhances the caking properties of these coals and improves coke properties. Strong formed coke can be made by carbonizing briquets made from oxidized western Canadian coals without the use of binder. Weak and non-coking coals could also be used in other metallurgical processes such as direct ironmaking and coal injection into blast furnaces. Coals from Atlantic Canada are Carboniferous and were formed 200 million years prior to the Cretaceous coals from western Canada. Coking coal from Nova Scotia has good blending properties and ideally complements the properties of the western Canadian coals to make strong cokes. It is hvA bituminous in rank, has low ash but high sulphur and vitrinite contents, and very high fluidity and dilatation properties. It can be used effectively in preheating processes. Char or petroleum coke can be incorporated into coking blends containing this coal to make strong coke. It is a very good binder coal in hot briquetting formed coke processes because of its high caking properties. Details and results of CANMET investigations of Canada's metallurgical coals are discussed.