Experimental Study On Oxidation Of Magnesium Sulfite By Microporous Aeration

Comparing with calcium flue gas desulfurization(FGD),magnesium FGD has advantages of high desulfurization efficiency,low investment,small occupied area,low operation cost,etc.Magnesium sulfite,the by-product from magnesium FGD,not only leads to corrosion,wear and clogging,but also increases the COD value of desulfurization wastewater.Meanwhile,magnesium sulfite may decompose into SO2 and magnesium oxide under certain conditions,which induces secondary pollution.Therefore,oxidizing magnesium sulfite into stable and soluble magnesium sulfate has become a research hotstop.In this thesis,microporous aeration was applied to magnesium sulfite oxidation in order to promote the application of magnesium FGD.Using a microporous aeration device,a series of clear water aeration experiments have been conducted under the condition of different water depth and air flow.With the increasing of air flow,the oxygen transfer coefficient and oxygenation capacity increase gradually.However,while the air flow is up to a certain value,the oxygen transfer coefficient and oxygenation capacity are increased slowly.Increasing the water depth can increase the total oxygen transfer coefficient and promote the oxygenation capacity,and the greater the air flow,the more effective the water deptth is.The oxygen utilization rate increases with the increase of water depth,decreases linearly with the increase of air flow,and decreases with the increase of water depth.The effects of concentration of magnesium sulfite,water depth,air flow rate,pH and temperature on uncatalyzed oxidation efficiencies of magnesium sulfite have been discussed.The oxidation reaction rate increases firstly and then decreases with the increase of magnesium sulfite concentration,and reaches the maximum at about 0.1 mol/L.The aeration water depth has little effect on the oxidation reaction.Increasing the air flow and reaction temperature are helpful to increase the oxidation reaction rate with low pH value.The oxidation reaction should be carried out under the low pH value.The optimum reaction temperature is 50?.The optimum oxidation reaction conditions of 100L of sulfite solution with 1.05m aeration depth were obtained by orthogonal test,i.e.,the concentration of magnesium sulfite is 0.15 mol/L,the air flow rate is 1.5 m3/h,and the pH value is 7.0-7.5.