Operation of a circulating fluidised bed boiler system - recovering heat at different loads by maintaining large enough flow of solid material in heat exchanger chamber

摘要

Improved method of operating a circulating fluidised bed (CFB) system including a heat exchanger chamber formed in the lower part of the return duct, having one wall section in common with the combustion chamber, comprises (a) establishing a fast fluidised bed of solid particles in the combustion chamber so that a particle suspension of flue gases and solid particles entrained therein is caused to flow upwardly in the combustion chamber and be discharged through the discharge opening; (b) sepg. solid particles from the particle suspension; (c) directing sepd. solid particles into a return duct having a heat exchange chamber in its lower portion; (d) establishing a bed of solid particles in the heat exchanger chamber; (e) reintroducing solid particles from the heat exchanger chamber into the combustion chamber through the solid particle inlet in the common wall section; and (f) introducing additional solid particles directly from the combustion chamber into the lower part of the return duct; such that (g) during high load conditions a large solid particle flow is entrained with the flue gases and recycled through the separator, return duct and heat exchanger chamber into the combustion chamber, providing the desired heat transfer capacity; whilst (h) during low load conditions solid particles are caused to flow directly from the combustion chamber into the heat exchanger chamber through a passage in the common wall between them, the direct solid flow enhancing the heat transfer capacity so that it achieves the desired level. Also claimed is a CFB reactor system.