OCR Text |
Show performance. It is felt that this problem can be eliminated by appropriate materials and equipment design considerations. Pipework was relatively unaffected by wear, essentially due to the low prevailing fluid velocities. The major problem of burner tip erosion may be solved by choice of a less abrasive coal, improved coal cleaning by ash and pyrites rejection, further reductions in coal particle size, materials selection or the use of externally atomized burners with low coal-oil mixture efflux velocities and a simple configuration. In 1980 and 1981 a pilot plant for production of coal-oil-water mixtures was constructed in Dartmouth, Nova Scotia, with assistance from the governments of Canada and Nova Scotia through their Oil Substitution and Conservation Agreement. This pilot plant is designed to produce about 5 tonnes per hour of coal-oil-water mixture containing about 60 percent coal, 25 percent oil and 15 percent water. Special proprietary features of the preparation process include a specially designed grinding mill, ultrasonic stabilization of the mixture, and spherical agglomeration to reduce mineral matter. Production and small-scale combustion of fuel (known by the proprietary name of Scotia Liquicoal) from this plant have progressed well, apart from the severe wear on burner tips which paralleled early experience at Chatham. The relative advantages of a coal-oil-water mixture over coal-water are its better ignitability and reactivity and less susceptibility to freezing: the relative disadvantages are that it requires a substantial proportion of oil and that its viscosity varies widely with temperature. In developing a marketing strategy for their product Scotia Liquicoal conducted field trials in small commercial installations to demonstrate the feasibility of burning their fuel . During these boiler evaluations, burner tip erosion remained the major problem which the company was then compelled to address as a matter of some 12-7 |