Various external heat exchangers (EHE) are widely used with largescale circulating fluidized bed(CFB) boilerThe solids mass flow rate diverted from the standpipe to the EHE or the loop seal can be controlled and the flow of hot particles into the EHE passes through all heat exchanger chambers in successionSo 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 pneumatically controlled EHE was developed in this paperThe major feature of this EHE system was that the solids flow to two heat transfer chambers could be controlledThereby the distribution of the quantity of heat transfer could 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 the visible cold EHE test rig showed that the solids mass flow rate to the EHE or the loop seal

to two heat transfer chambers

to two exports of solids could be controlled by the aeration airflow into each chamber and geometrical dimension like the height of partitionAt the same time

the flow characteristics of solids in heat transfer chambers were investigatedBy measuring the visible transport disengagement height (TDH)

the design principle of the relative height of partition of heat transfer and distributing chamber was proposed.