Study On The Desulfurization Of Flue Gas With A Ferric-Microbial Solution

As the environment gets worse, developing new desulfurization technologies is more and more urgent to fit the Chinese pollution control policy. The desulfurization with a ferric-microbial solution was studied by combining the principle of both inorganic chemistry and microbiology. This new method was shown to be effective to control the air pollution.Comparative experiments for SO2 removal from flue gas stream was carried out with dilute sulfuric acid solutions, acidic ferric solutions or microbial solutions. In the dilute sulfuric acid solution, SO2 is removed from the flue gas by physical absorption even if O2 is excessive. The desulfurization rate was greatly enhanced by introducing ferric ion in to the acidic solution. The Fe3+ serves as a catalyst to convert to SO2 to SO3. As the result, it increases the driving force of mass transfer for SO2 from gas to liquid. The concentration of ferric and pH significantly influence the ability of desulfurization. The desulfurization degree is up to 85% when the concentration of ferric ion is 1.5g/L and pH is 2.0 in 170min. In the microbial solution, both ferric ion and Thiobacillus ferrooxidans were used, while the rate of desulfurization increase 10~20%. Thiobacillus ferrooxidans can oxidize to ferric ion to accelerate the redox cycle. The optimal reaction condition for the bio-desufurization locates at pH=1.5. A high desulfurization degree(>90%) was obtained at the concentration of Thiobacillus ferrooxidans 107 cells/mL, ferric ion 1.5g/L and pH 1.5-2.0.Kinetics of desulfurization in ferric-microbial solution was conducted at pH 1.5-2.0 and temperature 10~40@. It shows that ferric ion is a dominant factor affecting the reaction rate. The relationship can be expressed following,Here the activation energy E is 80.15kJ/mol and the frequency factor ko is 3.74 X 1015 L-mol-1-min-1. The oxidation of Fe2+ is suggested to be the rate-limited step of the rate-limited step of the desulfurization reaction. Thiobacillus ferrooxidans affect the reaction rate by enhancing the oxidation of Fe2+. The concentration of Fe3+ can be calculated with the following equation:Here k4 and ks are reaction rate constants relying on the concentration of Thiobacillus ferrooxidans.