Cold Experiment On Regulating Characteristics Of Pneumatic Distribution Valve With Dual-side Solids Returning

It is difficult to distribute high temperature ash effectively in a circulating fluidized bed (CFB) with dual loops, such as in the system of sewage sludge drying and incineration using CFB, which will directly affect the stability. Pneumatic Distribution Valve (PDV) is a new type of solid material distribution device. Due to its simple structure and versatility, PDV can be applied to promote the development of dual-loop technology.Based on a review of the existing research works, a new PDV was designed. There are two different operational requirements for PDV:distribution according to proportion and solids flow rate. In order to find the optimal Regulation scheme of each requirement, the effects of the aeration, the solids flow rates in standpipe and the shunt board height on regulating characteristics were investigated respectively on a cold test rig. The effect of PDV structure on regulating characteristics was also studied at the state of on non-self balance.The cold test rig of PDV was a unit rig. The experimental results demonstrate that it can meet different requirements by adjusting the aeration when the solids flow rate in standpipe is fixed. The solids flow rate in standpipe has great impact on distribution according to solids flow rate, but less impact on distribution according to proportion. The solids recirculation rate of each side increases linearly with the increase in the solids supplying rate in standpipe. The shunt board height has a little influence on both operational modes. Regression relationship between distribution ratio and aeration is analyzed, resulting in good empirical correlation.The results show that the maximum solids recirculation rate of single-side is strongly influenced by the diameter of solids returning pipe and the height of rising part in recycle chamber, but relates little with the area of rising part and the height of slipping part. The regulating characteristics under different structure sizes are basically identical. Empirical relationships between the maximum solids recirculation rate and the structure size, the solids recirculation rate and aeration, are established. According to the experimental results, the regulating region of the aeration is subdivided into cut-off part, adjusting part, approximate saturation part and saturation part.