OCR Text |
Show several units are to be converted to coal-water fuel. It must be noted that a significant requirement of the coal-water mixture program is that the slurry burners be also able to utilize fuel oil, thereby retaining the capability to attain full generating capacity during peak demand periods. Assuming successful demonstrations at Chatham, the next step will be to design systems for burning coal-water fuel in larger utility units. In eastern Canada there is a 100 MW(e) front-wall fired unit which originally used coal but was converted to oil in 1969 to minimize particulate emissions; there is also a 50 MW(e) tangentially fired unit designed for oil-burning. The current program embraces the design of coal-water systems for these two units. Details of Present Program The present program comprises several elements which will combine to achieve the objectives set out above. These are construction of a 5 tonne per hour pilot plant at Sydney, Nova Scotia, for preparation of a coal-water mixture containing about 70 percent coal, the design of burners suitable for reliable combustion of this fuel, the demonstration of the use of fuel and burners at Chatham and the design of coal-water burner systems for larger units. The fuel preparation pilot plant will treat clean coal (- 3 mm) from an adjacent conventional dense medium coal preparation plant which reduces the mineral matter content from about 8 percent to 3 percent. The pilot plant will comprise two stages of grinding, particle size control, two stages of froth flotation (further reducing the mineral matter to about 1.5 percent) and the mixing to add a stabilizer. The process is based on the proprietary CARBOGEL process. The target solids content is 75 percent with viscosity in the 800-1000 centipoise range. Attempts will be made to use different coals with higher mineral matter and sulphur contents, and 12-13 |