Experimental Study On Pneumatic Control Of Circulation Solid Flow In Cold Model Of Circulating Fluidized Bed

External Heat Exchanger (EHE) is applied to large scale Circulating Fluidized Bed (CFB) boiler to meet the needs of heat transfer surface arrangement and bed/steam temperature control. EHE is also used in CFB incinerator to avoid high temperature corrosion due to chloride. There is a pyrolysis chamber in CFB co-generation system. In these cases, circulation solids comes out from the main circulating loop to enter EHE or pyrolysis chamber, then returns to the furnace. So the solid flow rate to enter EHE or pyrolysis chamber should be controlled. The methods and devices to control the circulation solid flow pneumatically are studied in this paper.Based on a review of the existing research works, a new type of Pneumatic Control Valve (PCV) is studied to get its adjusting characteristics under different conditions, and its applications in CFB boiler with EHE and CFB co-generation system are discussed.The PCV is located at the entrance of EHE and controls the solid flow rate in this paper. A series of experiments in a cold model are carried out under the different operation conditions of pneumatic control and the working ranges of the PCV. The relationship between the circulation solid flow rate and the controlling air velocity is given. And the affecting mechanism of the key structural parameters of the PCV on the control performance is given also.The experiment results demonstrate that this type of PCV has the capability of transporting solids and regulates the solid flow rate in a wide working range. The controlling airs can regulate the solids flow rate with different control characteristics. Increasing the height of the clapboard at the exit of the PCV lets the control characteristic from regulating to switching. The horizontal extending channel inside the PCV and the inclined segment of the entrance tube let the control performance have a change for the worse.Based on the experiments, the controlling mechanism of PCV is given. After analyzing the control performance of two existing PCVs, three application schemes of the PCV in CFB co-generation system is obtained, and one of them is proposed to investigate further.