Coke Making In Eastern Canada

The history of coke-making in Canada dates back to the early 19th century. It probably had its inception in eastern Canada with the development of the steel industry in the province of Nova Scotia when, in 1849, a furnace and related works were built at Londonderry to utilize iron ore from the Cobequid Mountains. The extent of the deposit was smaller than was anticipated and the plant was dismantled in 1908. There is no record of the source of carbon for this early operation. In 1890, the New Glasgow Iron, Coal and Railway Company (NGICR Co.) was organized to build a furnace at Ferrona in Pictou County, as well as a coal washery and coke ovens. The blast furnace, using ore from a deposit near New Glasgow, was blown in on August 6, 1892, and was the first of its kind in Canada. The coal washing plant, which went into operation in May 1892, was the first of its kind in Canada. It treated coal from Stellarton which averaged 17 to 25 percent ash and 2 percent sulphur.      The coke ovens were the first top-charged pusher-type coke ovens to be set up on this continent. The NGICR Co. obtained possession of part of Wabana deposit on Bell Island in 1894, and commenced operations in Ferrona in late 1895. On January 1, 1895, the NGICR Co. united with the Nova Scotia Steel and Forge Company under the name of the Nova Scotia Steel Company. At some time during this period, the company acquired mineral rights to part of the Cape Breton coal field and, with the excellent harbour available there and the proximity to Wabana, erected a steel plant in 1902 at Sydney Mines to replace the original Pictou works. A blast furnace was built, as well as four batteries of coke ovens. Also built at the colliery was a 50-ton per hour coal washery, comprising two sets of Luhrig jigs.      The Dominion Iron and Steel Company commenced operation at Sydney, Nova Scotia, on July 1, 1899. The first coke oven battery began operating on November 23, 1900, and consisted of four hundred Otto-Hoffman beehive ovens. Coal was purchased from the Dominion Coal Company and cleaned in a washery at the Sydney Plant that had two Baum jigs.      However, by 1903, the sulphur in the unwashed coal reached 2.75 percent and, with the opening of No. 6 Colliery, increased to 6 percent with a corresponding high ash content. A breach of contract suit ensued and was settled in 1907 with the Dominion Iron and Steel Company acquiring control of the coal company. This resulted in the formation of the Dominion Steel Corporation in 1910, as a holding company for both industries.      The first battery of Koppers ovens was commissioned on October 12, 1918, and the second battery in March 1919. The old Otto-Hoffman ovens were dismantled during 1920, and a third battery of Koppers ovens was completed in November 1923. Each of the three batteries contained 60 ovens (17-inch width). The expanded steel industry in this period carbonized about 4,000 tons of coal per day and had, at that time, the finest coke plant on the continent.      The two batteries, which are still in use today, were put into service in 1949 (53 ovens) and 1953 (61 ovens) and are now operated by the Sydney Steel Corporation. The ovens are Koppers Becker underjet, low differential-type, 17-inch ovens, with a 12-foot coal line and a capacity of 684 cubic feet, or 17.2 tons, at 50 pounds per cubic foot coal bulk density.      The coking coals of Eastern Canada available for the manufacture of coke are high-volatile gas coals and pseudo gas coals by rank classification. Prime quality coals of this type have excellent coking propensity but shrink excessively upon carbonization, thus producing coke with weak strength properties. Normally, excellent quality coke is obtained by blending such coals with coals of low and medium volatile matter content.      Until recent years, coke was manufactured at Sydney coke ovens from 100 percent high-volatile coking coals available in the Cape Breton area, due to the remoteness of the plant from low-volatile coal sources. As coal from the Phalen Seam has slightly better coking properties than Harbour Seam coal, it was used in as high a percentage as practicable, a 60:40 Phalen Harbour mixture being the objective. The mines chosen from these seams were those with the lowest relative sulphur and ash contents, Phalen Seam coal in general has a higher sulphur content than Harbour Seam coal. In 1961, it became necessary to import low-volatile coal from the Appalachian coal fields of the United States to blend with the Cape Breton coals for the production of the high-strength coke demanded for increased blast furnace efficiency. A blend comprising approximately 20 percent low-volatile coal produced coke of excellent strength qualities.      It is of interest to note that, during the past year, the low-volatile imported coal has been replaced by low-volatile coal from western Canada. The Sysco coke plant is the only conventional plant in Canada now producing coke from all-Canadian coal sources. A further improvement may be achieved in a three-way blend including a medium volatile coal.      Although there are no indications of the availability of low-volatile coals in eastern Canada for blending purposes, some interest has been expressed in the Pictou coal fields which contain coals of higher rank than the Cape Breton coals. Experimental coke-oven tests were carried out by the Mines Branch (now Canada Centre for Mineral and Energy Technology - CANMET) in 1951 and 1959 with coals from several seams supplied by the Intercolonial Coal Company Limited and the Acadia Coal Company Limited. The Pictou coals were blended with a blend of Harbour and Phalen Seams and carbonized in a 12-inch, Koppers-type, moveable-wall coke oven. An improvement in the coke strength was obtained with a reduction in sulphur content but with increased ash content. It may not be possible, however, to increase the strength level to that required by present coke quality standards.      Recent samples of coal, obtained from the new Lingan mine (Harbour seam) and tested by CANMET, have shown an increase in coal rank with depth of cover from 90 to 1,000 feet. The coking propensity, as determined by thermal rheology properties, has also indicated a progressive increase with depth of cover. It is postulated that, beyond 1,000 feet of cover, the properties of coal from Lingan mine will be similar to those properties of coal from the old coal workings of No. 26 Colliery. The new coal washery will clean all the coal rather than part of it as has been the practice in the past. The plant should reduce the sulphur and ash contents to levels lower than previously obtained for metallurgical coal from the Harbour Seam, as well as providing a coal with more uniform coking properties. CONCLUSION      The high-volatile coals of eastern Canada have good potential as the major component for the manufacture of good quality coke. Admixtures of low- or low/medium-volatile coals will be required to reduce their excessive shrinkage characteristics. New innovations to coke-making, such as; preheating, use of agglomerates, selective pulverization , or use of formed coke, may have additional advantages. The ash contents are quite attractive and the high sulphur content may not be as detrimental as in the past, due to improved cleaning facilities and the practice of external desulphurization of the iron.

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