Characteristics Study On Sludge After Reclaimed Water Treament Reuse To Wet Flue Gas Desulfurization

The reutilization of urban sewage,the reuse of medium water,has opened up a new way to solve the shortage of water resources.In order to make the water quality of the middle water meet the reuse standard,most of the technology used for lime softening treatment.This method will produce a lot of sludge discharge.If we can recycle these sludge,we can achieve the purpose of reusing waste,reducing initial investment,reducing operation cost and saving energy and reducing emissions,which is in line with the strategic requirement of national sustainable development.In this paper,the feasibility of wet reuse of sludge after reclaimed water treatment is first analyzed,and the physicochemical properties of sludge and limestone,including composition,particle size,microstructure and reactivity,are studied and compared.It is found that the sludge purity is basically maintained at80-85%,but contains a certain amount of impurities such as organic matter,Al,Fe and Si.Moreover,the sludge has large particle size and low reactivity,so it can not completely replace limestone desulfurization.In laboratory static experiments,NaHSO₃ instead of SO₂ in flue gas is used to simulate wet desulphurization process.After measuring and comparing sedimentation performance,particle size,dehydration time and microstructure of gypsum,it is determined that the best laboratory static test time is 8 hours.Under this reaction time,the sludge mixing ratio experiment was carried out.The results showed that the quality of slurry and gypsum would be significantly reduced when the mixing ratio of sludge reached 30%.Foaming and defoaming experiments showed that when the mixing ratio of sludge reached over 20%,there would be more serious blistering phenomena.Adding defoamers would have a certain inhibitory effect on blistering,but could not completely eliminate foam.Considering the factors of operation stability and cost,it is suggested that the mixing ratio of sludge in dynamic experiment is not more than 20%.This paper is based on the static experimental results,also discusses the sludge back for the dynamic experiment of wet flue gas desulfurization process,the effects of10%,20%,30%and three gradient mixed ratio of the operation of desulfurization system,24 hours for the period of the experiment,the study found that with the passage of time,by adding mixed slurry can basically maintain the tower of grout pH stable,the desulfurization efficiency reached the standard,the slurry density increased gradually.The test of the performance of defoaming agent again shows that the antifoaming effect of 821 defoamer is the most ideal.