Research On Modification Of Municipal Sludge And Burning Ceramsite

Common disposal methods of urban sludge include incineration,sanitary landfill,agricultural composting etc,but there are still many problems,especially the drying modification has a great impact on its subsequent resource utilization.This paper takes the dewatered municipal sludge from a sewage treatment plant in Zhengzhou City,Henan Province as the research object.From the perspective of waste management,the uniform design of the mixture is adopted,and the slag,fly ash and quicklime are used as raw materials to prepare high-performance sewage.Sludge modifier,after modifying the sludge,the effect of the modifier on the moisture content of the sludge under different conditions is studied,and the influence of different dosage and curing time on the leaching effect of heavy metals in the sludge and the form of heavy metals Variety.The phase diagram is used to guide the optimal ratio of the ceramsite for firing sludge,and the orthogonal experiment is used to analyze the performance indicators of the ceramsite.At the same time,the modified sludge and sludge ceramsite are micro-analyzed by XRD,SEM and other technologies.The mineral composition and microstructure of the sludge ceramsite.Provide a certain theoretical basis and technical basis for the future realization of the resource utilization of industrial waste residue and urban sludge.The main conclusions obtained through the above research:(1)Using DPS software to design the experiment,when the ratio of slag:fly ash:quicklime is=0.5430:0.0542:0.4028,the modification effect of sludge is the best.Under the same modifier content,the sludge moisture content decreases with the extension of the curing time,and under the same curing time,the sludge moisture content decreases with the increase of the modifier content.The content of Zn in the original sludge is the highest.The content of three heavy metals of Cr,Cu and Pb exceeds the national average of the content of heavy metals in the sludge.The content of As and Cd in the sludge is low,but its content exceeds the standard.The contents are all lower than the specified value.The determination of the leaching concentration of heavy metals in the original sludge is found to meet the specified value in the"Identification Standard for Hazardous Waste-Identification of Leaching Toxicity".Six kinds of heavy metals,Cr and As are mainly in the form of residues,Cu and Pb are mainly in the form of reducible state,and Zn and Cd are mainly in the form of extractable state.(2)With the same amount of modifier,the stabilization efficiency of the six heavy metals increases with the increase of curing time.The stabilization efficiency of Cu is the highest,and the stabilization efficiency of Cr is the lowest.At the same modifier content,Under the circumstances,extending the curing time has a certain effect on the solidification of heavy metals in the sludge.Under the same curing time,the stabilization efficiency of the six heavy metals increases with the increase of the modifier content;under the same curing time,with the increase of the modifier content,the growth rate of the six heavy metals starts to slow down,and the sludge After the modification,the solidification effect of heavy metals is good,and the stabilization efficiency is high.(3)At the same content of the six heavy metals,Pb and As mainly exist in the residue state.With the extension of the curing time,the two heavy metal residues account for the largest proportion.Cr mainly exists in the residue state,and Cu mainly exist in an oxidizable state,the two heavy metals Zn and Cd exist in three forms:extractable state,reducible state,and oxidizable state,and the proportion of extractable state decreases with the extension of curing time.For the six heavy metals under the same curing time,the oxidizable state and residue state of Cr and Cu account for a relatively large proportion.Most of Cr exists in the form of residue.With the increase of curing time,the proportion of residue is increasing,while Cu is mainly in the form of residue.The oxidized state exists.With the increase of the content of the modifier,the proportion of the residual state shows an increasing trend.The three forms of Zn and Cd in the extractable state,reducible state and oxidizable state have a larger proportion,and the residual state accounts for the least proportion,of which the extractable state The proportion of Pb and As is mainly in the form of residue.Under the same curing time,the proportion of residue increases with the increase of the content of modifier.(4)According to the ternary phase diagram,the range of fired ceramsite is obtained:modified sludge is 60%～82%,clay is 0～17%,and bentonite is 0%～24%.Through the orthogonal experiment scheme,the bulk density,cylinder compression strength,and 1hr water absorption rate of ceramsite were analyzed to determine the optimal conditions for firing ceramsite.The bulk density and cylinder compressive strength reach the maximum at 1250℃.With the increase of temperature,the bulk density and cylinder compressive strength begin to decrease,while the water absorption rate of ceramsite has a single change trend,which has been decreasing with the increase of the firing temperature.The bulk density and cylinder compressive strength increase with the increase of clay content,and the bulk density and cylinder compressive strength increase with the increase of bentonite content.(5)With the increase of the curing age,the mayemite and magnesia molite in the modified sludge will decrease.The mayemite and free water undergo hydration reaction to generate SiO32-and Ca2+,which play a role in the modification of the sludge.effect.The structure of the ceramsite blank is mainly aluminosilicate crystals,and the phase composition mainly includes anorthite(CaAl2Si2O8),albite(Na(AlSi3O8)),quartz(SiO2)etc.The sludge is being modified in the process Flocculent crystal products are formed.The products are wollastonite and sludge particles.In the process of firing ceramsite,the decomposition of minerals produces gas,the combustion of organic matter,and the volatilization of water,so that the surface of the ceramsite forms many different shapes.Pore structure,these interconnected pores may have an impact on the dissolution of heavy metals.