Research On A New Technology Of Sulphuric Acid Produced By Liquid Oxidation Of SO₂from Fuel Gas Desulphurization

In the process of flue gas desulfurization for power plant and smeltery, how couldconverse into sulphuric acid from low concentration SO₂will realize the resourceutilization of sulfur element. In the traditional double-absorption contact oxidationprocess of sulphuric acid production, energy input and operating cost for the oxidationof gas SO₂are higher because of the conversion from SO₂into SO₃requiring highertemperature and catalyst. Oxidating in liquid phase could greatly decrease thedifficulty in the conversion of SO₂, but in the acid solution SO₂is little dissolved inthe liquid phase, and it has hampered the application of sulphuric acid production byoxidating SO₂in the liquid phase. Therefore, it has important significance forexploring a new technique of sulphuric acid production by dissolving rapidly andoxidating SO₂.In this study, a new method of sulphuric acid production in the liquid wasproposed, in which ozone as the oxidant was introduced and oxidated rapidly SO₂inthe liquid into sulphuric acid by its own strong oxidative ability. The oxidation effectand oxidation mechanism of this method was investigated. Moreover, SO₂oxidatedby hydrogen peroxide combining with oxygen in the liquid phase into sulphuric acidwas primary explored.The results showed that ozone introduced in the acid solution could greatlyimprove the conversion rate of SO₂into sulphuric acid and absorptivity of gas SO₂.By analyzing the oxidation mechanism of SO₂, it was found out that the masstransmission of SO₂was improved from the gas phase to the liquid phase in thepresence of ozone, which results from the strengthen of transformation velocity ofsulfuric acid into sulphuric acid and the enhancement of oxidation rate of SO₂. Further,the oxidation-reduction potential of the solution significantly increased, it may be thekey reason of the improvement of conversion from sulfuric acid into sulphuric acid.By analyzing the oxidation of SO₂and existing forms of oxygen element in thesolution, it implied that the existence of ozone could promote the oxygen from ozonegenerator involved in the oxidation process of SO₂. Besides1mol oxygen atomproduced by ozone involving the oxidation process,0.602mol oxygen was alsopromoted to react with per mole of ozone under the condition of10.15min, sulphuric acid concentration of3%（mass concentration）, SO₂concentration of1.33%（V/V）and ozone concentration of1.31%.For low concentration gas SO₂, sulfate ion yield was up to100%at sulphuric acidsolution of3%（mass concentration）, SO₂gas concentration of0.67%（V/V）, ozoneconcentration of1.31%（V/V）. The increase of gas SO₂concentration and theaccumulation of sulfuric acid in the liquid led to the decrease of absorbing efficiencyof SO₂. For high concentration gas SO₂, the increase of gas ozone concentration couldgreatly enhance the absorptivity and conversion of SO₂in the gas phase.In addition, the sulphuric acid production through SO₂oxidated by hydrogenperoxide combining with oxygen in the liquid phase was studied. The results showedthat the amount of sulfate ion produced from half of hydrogen peroxide substituted byoxygen was equivalent to that of hydrogen peroxide alone, and the oxidation rate ofSO₂between them was close, which implied hydrogen peroxide combining withoxygen is feasible for the oxidation of SO₂in the liquid phase into sulphuric acid toremove SO₂in flue gas. However, water in hydrogen peroxide will lead to the dilutionof sulphuric acid produced and decrease the concentration of sulphuric acid.