Efficient Biological Desulfurization Technologies For VB₁₂ Wastewater Anaerobic Methane

Biogas from the anaerobic treatment of VB₁₂2 wastewater contains highly concentrated hydrogen sulfide,which corrodes the pipelines and equipments,produces during combustion tail gas with a SOx level that is much higher than the emission standard.Therefore,the biogas must be removed of hydrogen sulfide.By taking use of sulfide oxidizing bacteria,biodesulfurizaiton and sulfur recovery for biogas oxidizes sulfide into element sulfur.Compared with traditional chemical and physical methods,the biological one has many advantages such as simple process,little alkali consumption,high sulfur purity and no-secondary-pollution,and has been considered as a novel next-generation desulfurization technology.However,existing biodesulfurization technology aims to removing hydrogen sulfide in accordance with the requirements for gas purifying,with the requirements of sulfur recovery having not been taken into full account.It has faults in terms of combining biodesulfurization and sulfur recovery,which has seriously restricted the industrial application of this technology.This study focused on the key technical bottlenecks which restrict the biodesulfurization and sulfur recovery for biogas from VB₁₂2 wastewater anaerobic treatment,with an aim to resolve several key problems,including improving the efficiency of biodesulfurization and the yield of element sulfur,and proposing corresponding control strategy.It determined the size distribution of sulfur particles,and tested two sulfur recovery methods-centrifugation and coagulant-sedimentation.On the basis of analyzing lab experiment results,the process of biodesulfurization and sulfur recovery for biogas had been built up and verified on site.The results showed that the raise of alkalinity could increase the element sulfur yield of bio-oxidation,and reduce carbon dioxide absorption.Meanwhile,the salinity should be controlled below 120 mmol/L,in order to avoid inhibition of the growth of sulfide oxidizing bacteria.The ratio of hydrogen sulfide to ventilation could be taken as a control parameter for improving yield of sulfur.When this ratio was 1.5,the yield of sulfur reached its maximum.The optimum loading of hydrogen sulfide was 3.0 mmol/?h·L?,and the maximum one was 4.0 mmol/?h·L?.The range of size distribution of biosulfur particles was 2³0?m.Particles with a diameter beyond 10?m could be recovered at centrifugation of 4000 rpm and 6 minutes.All of three common coagulants-polymerization aluminum chloride,ferric sulfate,and polyacrylamide could accelerate the sediment of sulfur.The sequence of capability was polymerization aluminum chloride>polyacrylamide>ferric sulfate.Among which,ferric sulfate would cause acidity of the solution,which is disadvantageous to biodesulfurization.Though the coagulant reagents could accelerate sulfur sediment,they reduced sulfur purity too and made the purifying process more difficult.Therefore,the physical methods,such as centrifugation and sediment,should be preferentially selected.According to the optimum conditions acquired from lab experiments,an on-site experiment of biodesulfurization and sulfur recovery for biogas was built up,and the system had been stably working for 30consecutive days.After treatment,the hydrogen sulfide concentration of biogas reduced to5¹0 mg/m³,reaching the national standard for Level-2 pipeline natural gas.The removing rate of sulfides was above 99%,and the sulfur yield was 86.7⁹2.5%.The small amount of wastewater from biodesulfurization was treated through filtration,with the COD value reducing to 120²40 mg/L.The treated wastewater could be pumped to aerobic section without causing secondary pollution.