OCR Text |
Show matter to 3 percent and sulphur to 1.2 percent: grinding and multistage flotation can reduce these levels to 1.5 percent and 0.8 percent respectively: if lower quality (less expensive) coals are used, the same process is expected to attain about 3 percent minerals and 1.5 percent sulphur, the cost difference being in the starting feedstock rather than in the process. The program will include preparation and combustion of the cleanest coal-water mixtures that can be manufactured as well as fuels containing more ash and sulphur. This range of fuels will enable an economic assessment to relate cost of production to saleability and price which is one of the major objectives. Use of coal-liquid mixtures by utilities requires a delivery and storage system, including stirring vessels where necessary, and pumps which can deal with fluctuations in diurnal and seasonal demand. The program will demonstrate methods of transportation which would be applicable to industrial users and at least one of the combustion tests will be scheduled in freezing weather so that any problems due to low temperature operations can appear and be solved. Addition of antifreeze may be necessary, this will add to the cost but may improve combustion characteristics or cause corrosion problems. The performance of utility boilers designed for oil will be significantly different when using coal-water mixtures. The problem of unit derating has already been mentioned and each unit to be converted will need a detailed individual assessment to ascertain its loss in electrical generating capacity when firing a typical coal-water mixture. Again, the derating will depend strongly on the fuel and the boiler design. One of the objectives of the current program is to provide data for the determination of the inter relationship between quality and quantity of mineral matter in the coal-water fuel, the flame and unit derating. The utility company will then determine the net loss in its system generating capacity if 12-12 |