Experimental Research On Ash Regulating And External Heat Exchanger Of Circulating Fluidized Bed

With increasing capacity of circulating fluidized bed (CFB) boilers, the arrangement of heating surface is more difficult resulting from the imbalance between heat income and heat outcome. In order to address the issue, external heat exchanger (EHE) is often installed to the CFB circulating loop. A stable ash-controlling valve is crucial for the realization of EHE’s various functions. It will facilitate the development of our country’s CFB boiler that EHE theory is further studied and an EHE is designed which is stable and has a simple ash-controlling method.In this paper, a new assumption is proposed in which a new type gate valve is utilized to control the material’s split-flow. Early in the experiment, a simplified experimental rig is designed to test the feasibility and regulating characteristics of the gate valve, and then the EHE is introduced into the experimental system. ECT method which is the latest technology to measure particle consistence is applied on the cold experiment rig with an EHE, where research on kinetic characteristics and distribution homogeneity of material in EHE is done. The main conclusions are at follows:1. Regulating characteristics of the gate valve:Experimental results show that the regulating characteristics of this kind of gate valve is good and under the condition of valve opening from0to80%, split-flow rate increase linearly with the augment of valve opening. The larger the solid circulation is, the more split-flow rate will be, while the split-flow quotient has just an opposite tendency. There is no apparent influence on the split-flow rate from material-returning or aeration air velocity.2. Ash-flow characteristics and material’s distribution homogeneity of EHE: The experimental results show that the airflow increase from320m3/h to480m3/h in the chamber with heating surface will promote to transport the material to the risers, leading to0.16kPa reduction of average pressure drop in this chamber and103%increase of average particle consistency in split-flow pipe. The airflow increase from70m3/h to140m3/h in the chamber without heating surface will promote to transport the material to the chamber with heating surface, leading to0.83kPa reduction of average pressure drop in the chamber without heating surface, 0.13kPa increase of that in the chamber with heating surface and3.8%decrease of average particle consistency in returning pipe. Distribution mechanism and the influence of air quantity in pipe laying bed on material’s flow are also obtained via experimental research.