ABSTRACT
Furnace slagging is often regarded as one of the major problems in the operation of pf-fired boilers. Ash deposits on furnace walls not only affect boiler efficiency but can also lead to unscheduled outages if the problem is severe. Previous attempts to relate the slagging tendency of coal to the chemical composition of the ash have been found to be unsatisfactory. Besides, these characterisation based models are not capable to simulate the effects of operating conditions, burner configurations and furnace geometry on ash deposition behaviour. Because of the importance to control slagging problems, a collaborative research programme has been put together to address all aspects of slagging in pf-fired boilers. The project is supported by DTI, with contributions from National Power Plc, PowerGen Plc, Babcock Energy Ltd., British Coal Corporation, Diamond Power Speciality Ltd., Imperial College of Science, Technology and Medicine and the University of Bristol. The objective of the programme is to investigate and understand the processes involved in coal ash deposition and removal in pf-fired furnaces, so as to minimise losses in both plant efficiency and availability. The project is also aiming to develop a set of guidelines for the design and operation of plant at optimum efficiency with respect to slagging performance. This paper describes the fly ash trajectory and deposition models that are being developed by National Power Plc as part of the above mentioned project. Different modes of ash deposition have been considered and incorporated into a deposition rate post-processor. Preliminary studies on the effect of ash size distribution, starting locations and burner swirl on ash deposition have been carried out and the results are discussed.
