Study On Modification And Application Of Semi-dry Sintering Flue Gas Desulphurization Ash

Primary air pollutants, such as oxysulfide, oxynitride, doxin and ash containing heavy metals, are discharged during the procedure of the iron and steel making. These air pollutants have a serious impact on human health and ecological habitat environment, especially, the emission of pollutants is increasing with a rapid development of China's industry. According to the statistics, the economic loss in China caused by air pollutants is around 2%~3% of China's GDP, and the acid rain caused by SO2 would inflict economic loss about 110 billion yuan every year. In 2013, the SO2 emission of the iron and steel industry is 2.00 million tons, which is 10.5% of the total industrial discharges. After the power and construction materials industries, the iron and steel industry is the third largest emission. During production process of iron and steel making, 50%~70% SO2 emission is from sintering process and this ratio keeps the increasing trend in recent years. Therefore, controlling SO2 emission of sintering process is the key point to control air pollutions and the key link to ensure the continuous development of society, economy and environment.Semi-dry sintering flue gas desulphurization(FGD) technology is the most widely used technology during Chinese sintering flue gas treatment at present. Semi-dry sintering FGD ash is a kind of solid waste which is alkaline, high CaSO3 content, self-hardening and so on. Most sintering FGD ash is stockpiling and there is no maturely comprehensive utilization method because of above characteristics.This paper aims at Chinese FGD technology of sintering plant, analyzing the chemical compositions, phase constitution, particles characteristics and thermal stability of semi-dry sintering FGD ash systematically. In order to compare the properties of FGD ash after different modifying approaches, the hypothermal catalytic oxidation experiments, hyperthermal roasted experiments and acid leaching modified experiments are adopted. Adding modified FGD ash as raw material to prepare steam-cured brick and eco-cement, the optimum condition of preparing could be acquired and the mature method of semi-dry sintering FGD ash comprehensive utilization is established.The experimental results prove that the semi-dry sintering FGD ash is stable under dry and common temperature condition. And particle shape is irregular with porous structure, the main component is CaSO3, CaSO4, CaCO3 and so on. Grain diameter distribution is 13.18?m~30.20?m, and surface area is 6.47 m2/gIn the hypothermal catalytic oxidation experiments, the most obvious modifying effect on CaSO3 of FGD ash is MnO2, Fe2O3 comes second, and V2O5 would be negative to the oxidization of CaSO3. When the calcination temperature is above 350 ?in the hyperthermal roasted experiments, there is obvious modifying effect on CaSO3 of FGD ash. After acid leaching modifying experiments, thermal stability of FGD ash gets worse and the chemical property of resultant is unstable. It's stimulative for modifying of FGD ash, and the removal rate of S reaches 97.03%.As the result of comprehensive utilization experiments shown, the optimum ratio of components to prepare steam-cured brick which can meet MU15 standards is as follow: FGD ash 30.0wt%, fly ash 44.0wt%, sand and gravel aggregate ratio the 2:3 of 25.0wt%, 1.0wt% activator(Na2SO4) and water 25%. The optimum process conditions are studied, digestion time 36 h, curing 8h at 100?. When adding FGD ash to prepare eco-cement, it's proper for ensuring the content of FGD ash from 8.0wt% to 12.0wt% under the cement setting time, strength, workability and so on.