Investigation on the Integrated External Heat Exchanger for a New Type CFB Boiler Arrangement

Abstract

Various external heat exchangers (EHE) are widely used with large-scale CFB boiler. The solid mass flow rate diverted from the standpipe to the EHE or the loop seal can usually be controlled well and the flow of hot particles into the EHE passes through all heat exchanger chambers in succession. However, it is not feasible to control the quantity of heat transfer of different and multilevel heat transfer surfaces in the EHE. A new type of EHE in which the solid flow was controlled by pneumatic is developed in this paper. The major feature of this EHE system is that the solid flow can be introduced to one heat transfer chamber or another. Thereby the distribution of the quantity of heat transfer can be easily adjusted. Simultaneously, the EHE and recycle device were connected in order to recycle the solid back to the furnace steadily. Experiments completed in a visible cold EHE test rig showed that the solid mass flow rate to the EHE or the loop seal, to two heat transfer chambers, to two exports of solid could be controlled well by the aeration airflows into each chamber. In addition, the integrated EHE has been used in a new designed CFB boiler successfully.