| Air caps and air distributors are the important components in circulating fluidized bed (CFB) boilers. Their resistance characteristics and anti-slag-leakage performance directly affect the operation of CFB boiler. The design of caps and air distributors in large scale CFB boilers is critical to distribute air uniformity and avoid slag leakage.Cold resistance experiments of single cap were carried out to investigate the influence of structural factors on the resistance characteristics of caps. The resistance coefficient was derived, providing some reference for the engineering design of cap resistance.The influence of opening rate in air distributor and the arrangement of caps on the resistance of air distributor was studied by means of cold resistance experiments of multiple caps.The experiments were conducted to study the anti-slag-leakage characteristics of caps. Water was used as bed material. Air chamber was artificially divided, resulting in imbalanced pressure in order to make some specific air caps leak at different water levels and air flows. The pressure characteristics of air chamber were studied under the condition of water leakage of air caps. When the water is leaking, the pressure of the air chamber fluctuates sharply. There is a critical relation between pressure in the normal air chamber and the minimum pressure in the specific air chamber. The critical pressure drop increases linearly with the increase in cap resistance. And in the same stream of air flow, the critical pressure drop decreases with the increase in bed pressure. All these relations are in line with the operation experience of CFB boilers, indicating that critical pressure drop can be used to represent the difficult degree of slag leakage of air caps. Through these experiments, the mechanism of air cap leakage in air distributor of CFB boilers is analyzed, providing some reference for increasing anti-slag-leakage performance.
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