The Study On The Preparation Of Biosorbents And Their Application For Flue Gas Desulfurization Process

SO₂ emission from the combustion of fossil fuels is a major air pollutant and it has resulted in national and regional initiatives to reduce its emissions.Biosorption was introduced into flue gas desulfurization(FGD) process for the first time.R08 biomass(Bacillus licheniformis) is used to remove sulfur dioxide in simulated flue gas atmosphere.In this paper,the adsorption and desorption properties of the R08 biomass were discussed,furthermore the mechanisms between R08 and SO₂ were studied and kinetic model and isothermal adsorption equation were presented.Then two immobilized biosorbents were prepared and its desulfurization abilitites were studied.The results are as follows:1.The effect of different adsorption conditions on removal of SO₂ was investigated.The results showed that under the adsorption conditions of inlet concentration of SO₂ 1.675%,H₂O 20%,GHSV 2500 h^-1,temperature 50℃,the breakthrough time and adsorption capacity of R08 biomass were 30 min and 76.6 mg/g respectively.The biomass adsorbent has a good regeneration ability,the adsorption capacity of R08 biomass still keeps stable after several adsorptiondesorption cycles and it can be reused for many times.2.The adsorption mechanisms were studied by FTIR and XPS characterization. The results showed that only physical adsorption happened on the surface of R08 biomass in absent of H₂O,however both physical adsorption and chemical adsorption happened in the present of H₂O and three sulfur species are formed in adsorption process,(1) some SO₂ are weakly and physically adsorbed on the biomass,(2) some SO₂ react with amido functional groups forming sulfite specie,(3) some SO₂ are reduced into S^2- by reducing group of the biomass.The weakly and physically adsorbed SO₂ on the surface of the biomass can be easily desorbed by vacuum or increasing temperature.The isothermal adsorption process can be described by Freundlich Model. 3.The R08/Al₂O₃ adsorbents were prepared by immobilizing R08 solution on alumina and its desulfurization property was studied.The results showed that under the adsorption conditions of inlet concentration of SO₂ 1.041%,H₂O 20%, temperature 50℃,GHSV 5000 h^-1,biomass loading 32.4%,the adsorption capacity was 50.1 mg/g adsorbent,equal to 154.6 mg/g biomass.The adsorbent has a good regeneration ability,the adsorption capacity keeps stable and reach to 105 mg/g biomass after several regeneration cycles.The isothermal adsorption equation can be described by Freudlich Model.4.The bio-Cu adsorbent was prepared by immobilizing chemically modified R08 biomass with Cu²⁺ on alumina.FTIR and XPS results indicated that Cu²⁺ can be reduced into Cu⁺ by functional groups of biomass.Cu⁺ can also adsorb SO₂ via complexation which is favorable to weak SO₂ adsorption and regeneration of adsorbent.Furthermore,R08 can prevent Cu⁺ to be oxidized in the present of H₂O and O₂ atmosphere which can keep the adsorbent stable.