Mineral Carbonation Combined With SO₂ Disposal Of Flue Gas By Seawater Decalcification

The scaling of calcium ions has been regared as an important limiting factor during seawater desalination process.And the greenhouse gas CO₂ and poisonous SO₂ containing in flue gas have already affected our daily life.In this study,the integration of seawater decalcification,carbon fixation and desulfurization have been explored using simulated flue gas by two different methods,which are respectively achieved by chemical regents and bipolar membrane electrodialysis.Firstly,the feasibility of magnesia and seawater were chosen to deal with the simulated flue gas for realizing the integrated disposal of SO₂ and CO₂.The process was conducted by adding MgO in seawater to reinforce the absorption of SO₂ and to facilitate the mineralization of CO₂ by calcium ions.The influences of various factors,including digestion time of magnesia,reaction temperature,salinity were discussed by investigating decalcification rate,carbonation rate and desulfurization rate.And the effect of SO₂ on CO₂ fixation and mineral carbonation has been investigated by replacing SO₂ with N2 in the simulated flue gas.Experimental results show that the optimal decalcification rate is 94.43%,which is obtained under 1.5 times artificial seawater system(the reagents of seawater are 1.5 times)at 80?and without digestion of magnesia.After combing SO₂ removal process with mineral carbonation,Ca²⁺removal rate is suggested to have a certain degree of descend.The desulfurization rate is close to one hundred percent under any condition,indicating the seawater has sufficient desulfurization capacity with adding magnesia.This work proves absorption of SO₂ process could successfully combine with absorption and mineralization of CO₂.Membrane fouling has always been a limiting factor for the application of membrane technology.In this study,the investigation of membrane scaling had been explored during mineral carbonation combined with the integrated dispoal of CO₂ process.To avoid membrane scaling,different operating conditions:salt chamber ventilation with seeding,alkali chamber ventilation with seeding and alkali chamber ventilation without seeding were respectively studied.After that the principle of ion migration and induced crystallization were used to clarify membrane scaling mechanism.Experimental results show that high decalcification and carbonation rate are ontained during alkali chamber ventilation with seeding process.Meanwhile,membrane scaling could be successfully avoided with low energy consumption.Which indicates that bipolar membrane electrodialysis could be used as a reactor in the absorption of gas and liquid-solid reaction,meanwhile membrane scaling could be successfully avoided.After that,mineral carbonation combined with the integrated dispoal of CO₂ and SO₂were explored using bipolar membrane electrodialysis and crystallizer.The exploration was conducted under alkali chamber ventilation with seeding process by changing the current density,the gas flow rate and the carbon dioxide content in the flue gas with decalcification rate,carbonation rate,desulfurization rate,energy consumption and membrane fouling as the index of evaluation.The optimal condition is obtained with the decalcification rate,carbonation rate and desulfurization rate are respectively 83.26%,36.67%and 100%at90min,when the gas flow is 30 L/h,the content of CO₂ is 10%and the current density is 12.5A/m².As for the energy consumption,they are respectively 2.73 Wh/kg of raw material,3.25k Wh/kg of Ca CO3 and 1.72 k Wh/kg of CO₂.Meanwhile,membrane fouling could be successfully avoided.This work proves absorption of SO₂ process could successfully combine with absorption and mineralization of CO₂ using bipolar membrane electrodialysis.