Investigation Major Factors Of Semi-Dry Desulfurization

In 2003, The amount of SO2 emission goes up to 22.2 million tons, much more than 2002 by 2.93 million tons. It is very urgent to control SO2 emission in China. Flue Gas Desulfurization(FGD) process is effective for the reduction of SO2 emission. The semidry and semiwet flue gas desulfurization is a kind of semidry desulfurization technology. This technology is different from other semidry process because of the conveyance by steam. on desulfurization efficiency. This paper presents the relationship between desulfurization efficiency and the parameters of temperature, absolute humidity , fly ash , SO2 contentration, reacting time, etc. The study of reaction between the sorbents and SO2 has been performed from 65℃ to 110℃, and the humidity is changed by adjusting the flow rate of the steam from 0 to 10%. In addition, the fly ash is added to simulate the recycle of fly ash, the ratio of calcium to fly ash are 1:3, 1:5, 1:8 respectively. The experiment results indicate that temperature doesn't have an strong effect upon desulfurizatin efficiency without water vapor, and the highest efficiency 74.5% is achieved when temperature of flue gas is 68℃ or so with water vapor when absolute humidity is 7.3%; absolute humidity has a significant effect on SO2 removal, the best removal efficiency is 59.7% when absolute humidity is 7.3% and Ca/S is 1.2; as for the influence of fly ash, when T=68℃, Ca/S=1.2, comparing with calcium, the efficiency increases 12.8% by the sorbent of 1:8 (calcium to fly ash). The results of study the effect of SO2 concentration and reacting time is subtle. In order to demonstrate the physical and chemical changes of the sorbent with a ration of 1:8 (CaO/fly ash) during steam conveyance, we determined the specific surface area and found the specific area increasing from 7.8688m2/g to 10.0715m2/g. XRD (X-Ray Diffraction) results indicated that the content of CaO increased to 9.1% and the content of Ca(OH)2 reached 16.9% from 4% after reactivation in sorbent. The pictures of SEM (Scanning Electron Microscopy) also illuminated that there happened some changes on the surface of the sorbent, having shapes of foil. This probably was the results of the formation of calcium silicate hydrates. The results of our investigation provided the semidry and semiwet desulfurization theory to practical engineering. But the reactive and kinetic meachnism of desulfurization need to be studied further.