The Performance of a Compact Oil-Designed Utility Boiler When Firing Coal-Water Fuel

The Canadian coal-water fuel technology development program has been in progress since 1980. This phase of the work is the final stage in the demonstration of practicability of burning coal-water fuel in a boiler designed to burn oil. Early tests in small coal-capable front-wall and tangentially fired utility boilers have shown that two of the major problems to be addressed are both burner related: atomizer durability and poor carbon conversion performance. The present paper describes tests that were conducted in a 20 MWe compact, oil-designed boiler. Five burners were modified to burn coal-water fuel and oil with minimum changeover time. No changes were made to the boiler heat transfer tubes or to the flat furnace bottom to facilitate ash removal. The addition of a fabric filter bag house to contain fly ash emissions is the subject of another paper at this conference. The performance of the unit on coal-water fuel and oil is compared and evidence given that the derating was not as severe as had been predicted. The commercial burner supplied did show some atomizer wear, part of which could be attributed to manufacturing deficiences. It is suggested that the performance of this small unit should be applicable to larger units in the 100 MWe range.