Study On The Technology Of FGD In An Internally Circulating Fluidized Bed

A new technology of internally circulating fluidized bed (ICFB) for flue gas desulfurization (FGD) was developed in this study. Our research aims to solve problems of wall wetting and agglomeration , high external circulating rate and low sorbent utilization under the condition of low approach to saturation temperature in the traditional CFB-FGD technologies, to enhance the mass and heat transfer, and to increase the sorbent utilization and S02 removal efficiency, therefore to push the development and application of this technology in our country.The experimental research includes two sections: cold condition section and hot condition section.In the cold condition, the fluidization phenomena in the plexiglass column of 190mm in i. d, 5. 1m in height were investigated with different top and bottom structures and different kinds of bed material. According to the fluidization states observed and the external circulating rates measured, we could select a spout-fluid or orifice distributor as bottom structure, a baffleplate-equipped and expanded column as the top structure and the 40-60 mesh or 60-80 mesh sand as the suitable bed material. Therefore, an internally circulating fluidized bed in which when the superficial gas velocity was at 2-5m/s, most of particles return to the bottom section along the column wall and just a few were entrained out was developed. In additional, the effects of superficial gas velocity and the weight of bed material on the solid holdups in axial direction of the bed were discussed. The results indicate that the solid distribution present characteristics of "c" type in theaxial direction section and a "core-annulus" structure in radial under the condition of high superficial gas velocity. In the hot condition, the experimental apparatus of 300mm in i. d and 5. 3m in height was proportionally scaled up on the basis of that used in the cold condition, we could select a orifice distributor as bottom structure, a baffleplate-equipped and expanded column of 480mm in i. d, 1. 1m in height as the top structure. Most of 60-80 mesh sand used as the main bed material internally circulated when superficial gas velocity was at 2.55 m/s. In this process, effects of the factors such as the flow rate of water sprayed, inlet gas temperature, S02 inlet concentration, Ca/S ratio, solid concentration, on the efficiency of S02 removal were discussed. The experimental results show that approach to saturation temperature is the key factor on efficiency and solid concentration is the important factor that affects the stability of system. Under the condition of Ca/S of 1. 2, solid concentration of 10100g/m3 and other optimum factors, the system can continually and stably operate in long time with S02 removal efficiency above 90%. At last, a simple model was developed to predict the efficiency of S02 removal in the study.