Study On A New Desulfurization Technology Using Liquid Film Containing H₂O₂

According to the relevant national policy,it is required that for large coal fired boilers flue gas desulfurization is compulsory.For lots of small and middle coal fired boilers with capacity lower than 200 MW there is no technique supporting and policy requirement.Due to wide distribution and large amount of small and middle coal fired boilers which also cause serious air pollution it is impossible to install complicated desulfurization system for them.A new desulfurization method using H₂O₂ is put forward in this paper for small and middle coal fired boilers.Device is simple and desulfurization efficiency is high.By-product H₂SO₄ could be recycled and reused,so there is no second pollution.Experimental studies on H₂O₂ characteristics showed that temperature,H₂O₂ initial concentration,pH value and content of coal ash which exists in flue gas have little effect on decomposition ratio of H₂O₂. Under the influences of reactor structure and air flow,decomposition ratio of H₂O₂ could reach more than 10%.It is indicated that using H₂O₂,desulfurization efficiency could be above 95%.If the bulk concentration of H₂O₂ is high enough, desulfurization efficiency is independent on variation of inlet SO₂ concentration and H₂O₂ initiation concentration.As concentration of H₂SO₄ increases to 2mol/L,desulfurization efficiency decreases to 92%. With the rising of temperature from 20℃to 80℃,desulfurization efficiency increases form 95.98%to 97.25%.When gas-liquid ratio is 12.5 and 100,desulfurization efficiency are separately 95.57%and 82.47%.When height of packing layer is 3.5 cm,desulfurization efficiency is 95.57%.With the increase of height,desulfurization efficiency increases very slowly.Absorption of SO₂ with H₂O₂ is mass transfer process with chemical reaction.When solvent is H₂SO₄ with concentration of 20%,second-order reaction rate constant k₂ is 3334.3 L·mol^-1·s^-1.Liquid-phase mass transfer coefficient k_L is 2.23×10^-5ms^-1and gas-phase mass transfer coefficient k_G is 0.0735 mol/m²Ã‚·s·atm.Enhancement factor E is 27,so it is an instantaneous reaction.By-product H₂SO₄ is mixed with coal ash containing Al₂O₃ to make aluminum sulfate flocculants which could be used to treat waste water. Self-made flocculants is used to treat simulated active red and disperse blue wastewater.Decoloration efficiencies are separately 93%and 88%.Compared with calcium-based desulphurization method,this new method using H₂O₂ solution as absorbent does not have the problems such as secondary pollution,corrosion and fouling.It is potential to develop to a new desulphurization method which is suitable for small and middle coal fired boilers.