Experimental Study on Compact External Heat Exchanger for a 4 MWth Circulating Fluidized Bed Combustor

The characteristics of the external heat exchanger (EHE) for a 4 MWth circulation fluidized bed combustor were studied in the present paper. The length, width and height of EHE were 1.5 m, 0.8 m and 9 m, respectively. The circulating ash flow passing the heating surface bed could be controlled by adjusting the fluidizing air flow and the heating transferred from the circulating ash to the cooling water. The ash flow rate passing through the heat transfer bed was from 0.4 to 2.2 kg/s. The ash average temperature was from 500 to 750 °C. And the heat transfer rate between the ash and the cooling water was between 150 and 300 W/(m2·°C). The relationships among the circulating ash temperature, the heat transfer, heat transfer rate, the heat transfer coefficient and the circulating ash flow passing through the heating exchange cell were also presented and could be used for further commercial EHE design.