Study On The Humidified Sorbent FGD In An Internally Circulating Fluidized Bed

This thesis covers the experimental research on a new semidry FGD technology, which was carried out after surveying foreign technology and was designed to develop a novel FGD process with small place requirement, low cost, stable operation and effective SO2 removal. In this process, slurry system and atomizer were cancelled and particulate sorbent was humidified and activated outside the scrubbing column, which resolved the frequently occurring problems of wall-wetting and agglomeration in existing semidry processes and greatly simplified the process. At the same time, a newly developed internally circulating fluidized bed was employed as SO2 scrubber, which exhibited an excellent SO2 removal function.A circulating fluidized bed of 200mm in i.d. made by plexiglass was set up to carry out the experiments under cold conditions. The fluidization phenomena of sands and fly ash in the bed with different top and bottom structures were studied, through which the best fluidized bed structure that could realize internally circulating of large amount of solid particles was singled out, which was characterized by a spout-fluid bottom and an expanded and baffleplate-equipped top structure. The experimental results show that gas-solid two-phase flow in the bed presents a typical "core-annular " structure, which includes a rapid upward particulate flow at the core area of the bed and a relatively slow downward particulate flow near the wall.In the hot simulating experiments, factors affecting SO2 removal, such as the approach to saturation temperature (â–³T) , inlet gas temperature Ti, , molar ratio of Ca to S (Ca /S), inlet SO2 concentration Ci and superficial gas velocity u were determined. The results indicate that AT and Ca /S exhibit the most significant effects on SO2 removal efficiency, while other parameters' effects are less distinct.As a theoretic basis of the process, desulfurization fundamental of sorbent activated by humidification was discussed, which holds that the sulfation of the humidified sorbent particulates goes according to Shrinking Core Model and mainly controlled by the rates of the surface water evaporation and chemical reaction. When water content in the particle surpasses the critical moisture, the activating effect is very distinct.