Catalytic Oxidation Of SO₂ Via Vanadium-based Catalysts In Simulated Preheater Environment And Consequent Effect On SO₂ Capture By Calcium-based Desulfurizer

Cement industry is the third largest SO₂ source in China With the improvement of environmental awareness in the society,the state and provincial government have issued stricter emission standards to reduce industrial SO₂ emission.The present wet flue gas desulfurization technology is not suitable for the cement industry with low SO₂ emission concentration because of its high cost and producing waste water and waste residue.Although calcium-based dry flue gas desulfurization technology is more compatible with the cement production process,but the desulfurization efficiency is very low and cannot meet the stricter emission standards.The calcium-based desulfurizers'?Ca CO₃,Ca O,Ca?OH?₂?desulfurization efficiency is very low.The main reason is that the reactivity and the reaction rate of SO₂ is very low.The desulfurization product,Ca SO₃ is easily decomposed to re-release SO₂,resulting efficiency of flue gas desulfurization is very low.Adopting catalyst oxidize SO₂ into more active SO₃,then react with the calcium-based desulfurizers,the reaction rate is greatly increased.In this thesis,a series of vanadium-based catalysts were designed and prepared.Their catalytic oxidation of SO₂ activity was evaluated under preheater environment.Combined catalyst and calcium-based desulfurizer to improve the efficiency of different calcium-based desulfurization catalysts in a simulated preheater environment.The research significances are summarized in detail as follows:A series of vanadium-based catalysts were designed and prepared.The performance of catalysts of catalytic oxidation of SO₂ in low O₂ and high CO₂ environments was studied.Since a large amount of active components(V⁵⁺)are reduced during the catalytic reaction,the activity of V₂O₅ catalyst is low,the efficiency of the V₂O₅ catalysts?The V₂O₅ load is 5%?is only 38%;The addition of Ti O₂ can't significantly improve the activity of catalyst for the oxidation of SO₂;After loading Ce O₂,e catalyst activity is obviously improved?SO₂ conversion rate is up to56.1%?;After the V₂O₅catalyst is loaded with Mn O₂,the activity is obviously improved?SO₂conversion rate is up to 54.5%?,Benefitting from the Mn⁴⁺binding electrons preferentially,protecting the active component V⁵⁺from being reduced.The effects of O₂ concentration,SO₂ concentration,CO₂ concentration and H₂O on the performance of vanadium-based catalysts for the oxidation of SO₂ were studied.The change of O2 concentration has no significant effect on the activity of the catalyst;As the SO₂concentration increases,the efficiency of various catalysts to catalyze the oxidation of SO₂decreases slightly,but the total amount of catalytic oxidation of SO₂ increases;when the CO₂concentration gradually increases from 0%to 35%,the conversion rate of SO₂ decreased by about 3%;After introducing H₂O,it can be adsorbed and activated by the active sites on the surface of the catalyst,then generate hydroxyl and oxygen radicals,which significantly improves the activity of the catalyst?The conversion rate is increased by about 10%?.In the simulated preheater environment,the catalytic desulfurization performance of three calcium-based desulfurizers?Ca CO₃,Ca O,and Ca?OH?₂?were studied respectively.The vanadium-based catalyst oxidizes SO₂ to form SO₃,SO₃ can react with H₂O to form H₂SO₄ and then react with calcium-based desulfurizer.And SO₃ can also directly react with calcium-based desulfurization reaction.The rate and efficiency of the desulfurization reaction are greatly improved.The maximum desulfurization efficiency of the three calcium-based desulfurization agents is 65.6%,69.5%,75.5%respectively.In this study,the performance of vanadium-based catalysts for the oxidation of SO₂ in the simulated preheater environment was investigated,as well as the effects of temperature,gas composition and humidity on the activity of vanadium-based catalysts.Using calcium-based desulfurization agent with vanadium-based catalyst to remove SO₂in flue gas,the desulfurization efficiency improves greatly.The results laid a firmly theoretical foundation and technical support for the development of catalytic flue gas desulfurization technology suitable for the new suspension preheater cement kiln system.Resulting in an important environmental,social,and economic benefits for the cement industry.