Progress in the development of CWF burners for boiler and process combustor applications

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The Canadian program of coal-water fuel (CWF) technology development has been in progress since 1980. The main emphasis has been on CWF manufacturing technology and burner development. In the latter area, the commercial burner manufacturers have been involved in the program, but have not been too successful in achieving reliable wear resistant atomizers that were durable and burners which gave good combustion. For this reason, a research program was undertaken by the Energy Research Laboratories, Canada Centre for Mineral and Energy Technology (CANMET) in collaboration with the National Research Council to design and develop a dual oil/CWF burner based on the basic principles of atomization and combustion air mixing. The burner has been scaled up from a pilot-scale (5 GJ/h) to a commercial scale (55 GJ/h) prototype and has been tested on a 20 MWe compact oildesigned utility boiler in Charlottetown, Prince Edward Island. In a similar development, durable burners were developed for a cement kiln which enabled a cement manufacturing company in Richmond, B.C., to convert its operations economically from natural gas to CWF. Details are given of the respective programs, the development of burners and their impact on operation, since it is clear that oil-replacement combustion technologies will be in great demand when the price of oil escalates again as it has done in the past. Furthermore, the Canadian experience indicates that this is a new coal burning technology that gives compact flames, a benign ash behaviour with reduced erosion and deposition on heat transfer surfaces, more rapid char combustion due to differences in morphology which combined with the ease of handling a liquid fuel will eventually enable it to compete with oil and pulverized coal firing technology.