Towards soot-blowing optimization in superheaters

This paper seeks the optimization of steam consumptions dedicated to ash removal in large-sized superheaters operating at coal-fired utility boilers. The methodology consists of the design of a thermal model aiming at the real-time calculation of the fouling rates, the statistical fitting of the computed rates to obtain their time evolution and the assessment of optimized soot-blowing manoeuvres. Fouling rates are estimated by means of global thermal resistances, since local deposition is not feasible from available, standard measurements. The methodology is applied to the upper superheaters of a selected 350 MWe utility boiler, where significant steam rates are actually consumed. The results from the comparison of the heat transfer gains in this case-study show that energy savings can be attained by adopting new soot-blowing schedules in the plant. The methodology can be easily implemented in other coal-fired utility boilers, without demanding special instrumentation or computation requirements.