Investigation Into Calcium-based Oxygen Carrier For Chemical-looping Of Flue Gas Desulfurization Technology

Due to the wide use of fossil fuels such as oil and coal, sulfur dioxide (SO2) hasbecome one of the most serious hazards of air pollutants. Significant emissions of SO2is the main cause of acid rain which bring increasingly serious harm to human andecological environment. Therefore reducing SO2emissions has become one importantproblem of our country to be solved. Reducing the flue gas SO2to high purity andrecovery elemental sulfur is the crucial problem to deal with SO2pollution.This issue based on chemical-looping technology taking calcium sulfide (CaS) asthe desulfurization agent, reducing the flue gas SO2to elemental sulfur to realize fluegas desulfurization in a fixed-bed reactor. The reaction between CaSO4and CO, H2may facilitate the achievement of CaS sorbent regeneration, and forming chemicallooping reaction circulation system. The main research contents and results are asfollows：1Based on the principle of freedom of Gibbs energy minimization, using theHSC software equilibrium (Equilibrium Composition) modules, analog Fe-SO2,FeS-SO2, NiS-SO2and CaS-SO2reaction system. According to the variouscomponents of the system under different temperatures, elect the most efficientdesulfurization sorbent. Compare desulfurizer CaS with Fe, FeS, NiS desulfurization,CaS having high elemental sulfur production rate, fewer side effects, and can berecycled, etc. When the molar ratio of reactants CaS: SO2: N2=2:1:3, the reactiontemperature is lower than600℃desulfurization rate as high as100%. So use CaS asa desulfurization agent for further experiments.2The effects of SO2removal CaS process results showed that the optimumconditions in a fixed bed: SO2concentration was0.0592%at a reaction temperature of 650℃, when the reaction space velocity was1600h-1, SO2removal rate can reach99.5%in the first30minutes and decreased to91%after180minutes. In the SO2concentration was4.44%, the reaction temperature was700℃, when the reactionspace velocity was1600h-1, the reaction SO2removal rate was90.5%within20minutes and after180minutes the desulfurization rate reduced to75%. Elementalsulfur yield of more than70%, the reaction is mainly generated steam S2, after coolingthe final form of the elemental sulfur is rhombic sulfur (α-S8).3Detailed analysis of the system under different concentrations, such as reactiontemperature, gas space velocity, particle size and other factors on the SO2removalefficiency and yield of elemental sulfur. Through a variety of characterization methodsessentially in-depth analysis and compare equilibrium conversion of SO2andexperimental SO2removal efficiency and concluded that the reaction is most obviousthan in a fixed bed and a space velocity of the reaction temperature by effect. Due tothe desulfurization experiments were performed in a small reactor, the reaction ofmany factors, such as particle size, the wall effect and the gas residence time resultingreaction deviates from the actual chemical equilibrium, drawn desulfurization reactiontemperature was controlled at600℃-700℃within the optimal range.4The CaS for fixed bed desulfurization mechanism for removing SO2reactionkinetics and preliminary studies, results of the kinetic equation as follows:r=0.3526.CSO20.0285.Sv0.00529.exp(-11900/RT), and based on quantum chemical theory,using the Gaussian software based on HF (Hartree-Fock) theory, set b31yp/6-31G (d, p)level of writing calculated that the total energy of the reactants CaS and SO2is2172.94au and the total energy is greater than the product of CaSO4and S2is2172.67au.