Rotary Air Preheaters for Circulating Fluidized Bed Boilers

摘要

CFB boilers continue to increase in output with unit sizes of up to 350MWe underconstruction. For unit sizes above 100MWe generating capacity, the size and cost of rotaryregenerative air preheaters becomes increasingly attractive compared that of the tubular airpreheaters that were often used for smaller sized units.However, CFB boilers operate at much higher inlet air pressures than conventional balanceddraughtboilers firing pulverized coal. As this produces both increased pressure loadings andthe potential for higher levels of air leakage, the heaters must be specifically designed to meetthese more rigorous duties. In addition, they must be designed for high-cleanability inapplications in the presence of either limestone by-products or ammonia slip from upstreamSO2 or NOx reduction.This paper describes the main design features and early operating experience of a rotaryregenerative air preheater installed on a 240MWe unit in Finland that uses fossil fuel with cofiringof biomass and waste. Such installations are becoming prototypes for future units to beinstalled in the United States and elsewhere. The installation of specially designed rotaryregenerative air preheaters as described in this paper will play an important part in theirsuccess.