OCR Text |
Show attain the maximum generating capacity for which it was designed when firing oil. The extent of this loss of electrical output will depend on the coal, its rank and reactivity, (volatile matter, inert macerals content, degree of oxidation) as well as the ash content and composition and the slagging/fouling propensity of the ash. A coal-liquid mixture which burns well is not necessarily ideal for transportation or storage. The mixture should ideally have a low viscosity which does not vary with temperature and should be readily pumpable after long periods of storage. It should not freeze in anticipated weather conditions. It should contain a ininimum of inert components to minimize transportation and storage costs. At the present stage of the program, transportation of coal-liquid mixtures will be by road, rail or barge, therefore the ultimate requirement for very low viscosity, which is needed for pipeline transportation, can be waived but the need for maximum concentration of combustibles remains. Removal of mineral matter from coal is important for boiler performance, for economy of distribution, for ash disposal, and for environmental protection. Conventional coal beneficiation removes much of the adventitious mineral matter but cannot extract minerals that are very finely interspersed or are part of the molecular structure of the coal. In the case of sulphur, the occurrence may be in pyritic, sulphatic or organic form. Very finely divided pyritic sulphur is often reported as organic because it is so difficult to remove by physical means. In Canada most beneficiation is currently applied to coarser coking coals, however, where coals will be burned as a slurry and fine grinding is essential, advantage can be taken of this grinding to liberate sulphur compounds and other minerals. Therefore in the preparation of coal-liquid mixtures, conventional washing is followed by milling and separation on the basis of surface characteristics: froth flotation for coal-water mixtures and oil agglomeration for coal-oil-water mixtures. Coal from the Sydney 12-10 |