OCR Text |
Show This paper wi 11 present the resul ts of work performed to determine composition and adhesive strength of ash particle that form deposits on superheater tubes, under the strictly controlled combustion, fluid dynamic and heat transfer parameters of test furnace. 1. INTRODUCTION The quanti tative assessment of coal properties, especially with reference to the fly ash behaviour on superheater tubes is part of the combustion research programme being carried out by the Department of Mechanical Engineering at Cagliari Uni versi ty. In 1987, the Italian electrici ty board ENEL financed a research programme to assess the "fouling" process of a few coals commonly used in Italian power stations. ENEL recognized that this problem warranted scientific investigation because of the incidence of the phenomenon and its influence on operating costs. Indeed, the accumulation of deposi ted material coming from the ash co ,ponents of coal can give rise to bridges between tubes, reduction in heat transfer coefficient, higher pressure losses and the need to clean frequently with expensive soot-blowing. The idea of the research was to collect data on deposi ts produced by the coals on a laboratory test facility and later, during a field test campaign, compare these measurements wi th observation made by utili ty-boiler operators who have fired coal from the same sources in order to propose a tentative interpretation of measured fireside behaviour. As part of this fouling research programme we had to modify a combustion test facility built in 1985 to develop small-scale burners for pulverized coal and pet coke combustion. We added to the rig an exhaust gas duct which had to have the following characteristics: a) easy access for insertion and retrieval of deposition probes |