Preparation Of A Flue Gas Desulfurization Sorbent With Fly Ash And Its Performance Research

The main chemical components of fly ash with pozzolanic effect and adsorptiveproperty include SiO2and Al2O3, so it can be used as a kind of flue gas desulfurizationsorbent, denoted as FGD sorbent. The desulfurization efficiency of fly ash is ratherishlow when used directly, energizing the potential activity of fly ash by a series ofmethods that can overcome the disadvantages.A FGD sorbent was prepared with high calcium fly ash produced fromcirculating fluid bed. The microstructure, mineral constituent as well as physical andchemical properties have been characterized and analyzed by some modern testingmeans, i.e., scanning electron microscopy (SEM), X-ray diffraction analysis (XRD)and laser particle size analysis etc. The potential activity has been energized byphysical mechanical milling, chemical hydration reaction and adding exciting agent tofind out the best energization method. Then FGD sorbent was thus prepared.⑴The main chemical components of material were SiO2and Al2O3, while theCaO made up about7.3%, the fly ash was consequently classified as high calcium flyash. The density of material was2.38g/cm3, the loss-on-ignition was9.6%, and theaverage grain diameter was2.10μm. Additionally, the specific surface area was2.78m2/g with4.44nm in average pore diameter. There were sparse orifices on theirregularities surface of material. The mineral constituent was made up with quartz,mullite, hematite and CaO.⑵The activity of fly ash could be increased by physical mechanical milling, theactivity increased rapidly in the first0.5hours and slew down bewteen0.5hours and3hours, finally it almost remained in a certain state after3hours.⑶The chemical hydration reaction was better than the physical mechanicalmilling. Four effect factors on the fly ash activity in sequence included temperature,time, fly ash-Ca ratio and water-solid ratio. The activity of fly ash was the highest andthe specific surface area was64.16m2/g under the following optimum conditions, i.e.,12hours of reaction time in90℃system,5of the fly ash-Ca ratio and15of thewater-solid ratio.⑷With appropriate ratios, all the six exciting agent could enhance the activity of fly ash. However, the Na2SiO3·9H2O was the best one, the specific surface area of theproduct was105.84m2/g as the weight of Na2SiO3·9H2O was1.5times as Ca(OH)2.⑸The activity of fly ash could be increased by physical mechanical millingbecause the fly ash particle size became small and well-distributed. The appearance ofhydration products was the main reason for the activity of fly ash increasing inchemical hydration reaction. Exciting agent could enhance the chemical activation,and made the network configuration of hydration products more markedness.⑹The desulfurization performance of the flue gas desulfurization sorbenttransmuted from fly ash was proved to be excellent in fixed simulator ofdesulfurization. The accumulative removal amount of SO2reached29mg/g while theinitial concentration of SO2was2000mg/m3, the temperature was60℃, the Ca/S was0.8, the humidifying ratio of flue gas was5%and the humidifying ratio of flue gasdesulfurization sorbent was20%.