Investigation Of Phosphorus On Bed Agglomeration/defluidization And The Pattern Of Heavy Metals Fraction During Fluidized Bed Sewage Sludge Co-combustion

The fluidized bed sludge co-combustion technique was considered as one of the most effective methods to the treatment of municipal waste sewage sludge.However,phosphorus from sewage sludge would influence not only behavior of bed agglomeration/defluidization,but also change the pattern of heavy metals fraction.The effects of the intereaction among phosphorus,particle agglomeration,and the pattern of heavy metals fraction are not clearly understoo.Therefore,this study aims the effect of phosphorus on bed agglomeration/defluidization induced by Na-based alkalis.The pattern of heavy metals fraction during processes is also in consideration.Experiments are conducted by laboratory scale fluidized bed incinerator,the eutectics examed by chemical sequential extraction and characterization analysis?XPS and SEM/EDS?.Thermodynamic equilibrium calculation model?HSC Chemistry?is also used.The results can be seen as below:?1?The reaction model g???at volatiles of exhalation stage was satisfied with two-dimensional equation,Jander equationand Zhuralev,Lesokin and TemPelmanfan equation?ZLT?.Reaction model g???at combustion of fixed carbon combustion was satisfied with ZLT and second order chemical reaction in the tests of MSW sample with alkali metals.Additionally,the reaction models at volatiles of exhalation stage and fixed carbon combustion are not changed with the phosphorus presentation.?2?The concentration of heavy metal in particle agglomerates increased sharply after the system formed defluidization.In addition,the present of phosphorus would benefit for the solification of heavy metal in solid phase.?3?The effect of phosphorus on the agglomeration/defluidization as the function of inhibition and promotion.In other word,at the lower ratio of P/Na,phosphorus and alkali metals would form the higher melt-point compound like Na₃PO₄,which inhibit defluidization significantly.However,when the ratio of P/Na exceeds 1/2,the formation of compounds like NaPO₃ would promote the phenomenon of agglomeration appear.?4?Distribution of heavy metals?Pb,Cd and Cr?show the similar pattern with the presence of a lower ratio of P/Na:the relative concentration of heavy metals in solid phase rise with the increased of phosphorus.Additionally,in the condition of the higher ratio of P/Na,the relative concentration of Pb and Cd increased with the presence of phosphorus.While,the distribution of Cr is on the contrary.?5?Due to the formation of the lower-melting-point compounds like NaPO₃,the proportion of Pb and Cr residual form increased.While the percentage of Cd residual form reduced with the increasing of the amount of phosphorus.