The Research In Dry Quicklime Slaking Process And Mechanism

Dry slaking of quick lime impacts greatly on the conversion rate of lime, solid particle size, specific surface area and porosity, and determines the quality of the prepared desulfurization agent. The optimum conditions of the dry slaking can be obtained by the research of the influences of dry slaking technology on the structure and desulfurized property of desulfurization agent. And then, it can help to enhance desulfurization ratio during flue gas desulfurization.This paper investigated the influences of factors, such as water/solid ratio, initial temperature of hydrating-water, agitation rate, and hydration time, on the structure and desulfurized property of dusulfurization agent by the methods of orthogonal experimental design and single factor experimental design. Thermodynamics and kinetics of this process were studied by methods of mass balance and enthalpy balance. The dry slaking velocity of quick lime and chemical-physical properties of desulfurization agent were studied on by adding additives such as silicon dioxide, ferric oxide, alumina, and magnesia, into the process with different species and amounts of additives.In this research, specific surface area and porosity were used as characteristic parameters of white lime. Experimental results indicated that the influence of these factors arranged in a decreasing order is hydration time, water/solid ratio, agitation rate and initial temperature of hydrating-water. Accordingly, the optimal values of the procedure factors obtained from this system are 5 min¹0 min of slaking time, 1.3:1¹.6:1 of water/solid ratio, 300 r/min⁴00 r/min of agitation rate, and 25℃⁴5℃of initial temperature of hydration water. Thermodynamic calculations show that in the range of the optimum water-cement ratio, the equilibrium constant of lime digestion was large, lime water content was moderate, with the best physical and chemical properties and consistent with the experimental results. Dynamics calculations show that the dry lime diffusion controlled the digestion process, lime carter equation could basically describe the reaction mechanism of dry digestion process. Different amounts of impurities added in lime had different effect on the digestive process. Impurities in a certain range were contribute to digestion. They can improve the structural performance of desulfurization agent, and improve the desulfurization performance. When SiO₂ content was in the 6.0 %⁸.0 %, MgO was about 1.0 %, Fe₂O₃ was 2.0 %³.0 % and Al₂O₃ was 1.0 %, the digestion products obtained better performance of the physical structure.