| Calcium-based sorbents are used universally because they exist widely and they are is cheap. Influencing factors and evaluating methods of calcium-based sorbent's sperformance are analysed and summarized in this paper. Through comparision of several kinds of desulfurization sorbents, it is found that Ca(0H)2 is very suitable for flue gas desulfurization(FGD).FGD technologies with calcium-based powdery sorbents and humidificating water injection, inherit the advantages of semi-dry FGD technologies, overcome the disadvantages of pipeline and nozzle blocking, and have a bright applying prospect. The preparation of the powdery sorbent is an important respect for this kind of FGD technology, and hydrated lime is preferred. Powdery hydrated lime can be produced by lime slaking, and its parameters such as component, Patical Size and Specific Surface Area should be considered comprehensively as desulfurization sorbent. After systematical research of themodynamics, kinetics character of lime slaking and its craft classification, comparison, it is found that there are many researches focusing on wet lime slaking area, but few deal with dry lime slaking. So it is essential to do more about this.Basic parameters of dry lime slaking under different mole ratio of H2O to CaO and different slaking water temperature are tested in this paper. In the experiment it is found that these reactions are exothermic violently. The temperature would rise to 100 ℃ within 2.5 minutes and the highest temperature can reach to 160℃. The reaction would finish in 6.5 minutes when the mole ratio of H2O to CaO is 1.0, and slaking time may decrease to 5 minutes when the mole ratio of H2O to CaO is up to 1.6. In experiment of thermogravometric analyser incorporated with X-ray diffractometer, it is found that Ca(OH)2 is decomposed during 380 to 450℃ and CaCO3 is decomposed during 550 to 650℃ as well as a little Ca(OH)2. With the mole ratio of H2O to CaO increasing, the proportion of hydrated lime in which particle size is less than 154μm increases and then decreases because of particle conglutination. Different water temperature has no obvious influence on particle size of hydrated lime. Under the experimental conditionmentioned in this paper, more than 73 percent of Ca(OH)2 is contained in hydrate lime. An experimental equipment which uses fluid-bed and mixing mechanism with spiral blades is designed for lime slaking in this paper. In order to have a good fluidization condition and purify hydrated lime, fluid-bed is designed with Venturi tube and cinder outlet. With the reasonable setting and slope angle choice of lamina, lime can stay in slaker for about 8 to 10 minutes and it is slaked well with sufficient mixing. In the operation condition of 45kg/h lime feeding and 1.0 m/s fluidizing velocity, we find that much heat gives off and makes the slaking time shorter. By using fluid-bed equipment, impurity or less active lime can be discharged form the outlet at the middle of distributor. With the mole ratio of H2O to CaO being 1.0 and 7 minutes for lime staying in slaker, more than 71 percent of Ca(OH)2 is contained in hydrated product and the BET Specific Surface Area is 15.29m2/g. |
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