| Sewage sludge is the solid residue produced by sewage treatment plant in each stage of sewage treatment.Huge sewage treatment capacity leads to huge sludge output.The sewage sludge without treatment will seriously harm the environment,at the same time,the sludge itself has the use value,so it is urgent to develop a scientific way of sludge treatment and disposal.Microwave can solve the problem of uneven heating and high energy consumption.The addition of corn straw can improve and promote the pyrolysis process.In this paper,the pyrolysis characteristics of sewage sludge(SS)and sewage sludge-corn straw(CT)mixture were studied by using a self-designed microwave heating mobile screw reactor.The three-phase products were collected and characterized,and the synergistic effect of SS-CT copyrolysis was studied.The main results are as follows:(1)The experiments of SS pyrolysis and SS-CT co yrolysis were carried out separately.The effects of temperature and CT addition on product yield were studied.With the increase of temperature,the yield of solid-phase product(PC)decreased,while that of gas-phase product(PG)increased,while that of liquid-phase product increased first and then decreased,reaching the highest at 450?.The more corn straw is added,the lower the yield of PC is,and the faster the rate of decline is.When the mass ratio of CT is 30wt.%the reaction temperature is 750?,the lowest is 57.55wt%.At this time,the highest yield of PG is 34.15wt.%.At a lower mixing ratio,the yield of liquid products increased with the increase of straw addition.When the mixing ratio increased to 30wt.%,the yield of liquid products decreased.When the mass ratio of CT was 15wt.%,and the reaction temperature was 550?,the highest yield of liquid products was 13.85wt%.(2)With the increase of temperature,the color of PC changes from brown black to black and its pH shows an increasing trend.The content of C,H,N,Fe,Ca,P,K,Cl elements in PC decreases,while the content of Si,Al,Mg elements increases.CT is conducive to the enrichment of Fe and P,and accelerates the decomposition of macromolecules.More CT addition makes the content of H,elements in PC decrease,and N,Si,Fe,P elements increase.XRD analysis shows that the main components of PC include quartz,calcium phosphate,block phosphorite,compounds containing N,P and S elements,feldspar,dolomite and their decomposition products,muscovite and silicate.The enrichment of alkaline earth metals and the increase of pH in solid phase products are related to Altisite(Na3K6Ti2[Al2Si8O26]C13).The addition of CT can transform dolomite into ferruginous dolomite and promote the decomposition of N-containing compounds.FTIR analysis showed that the increase of temperature and the addition of CT promoted the transformation of amines,alkenes,organic compounds containing Cl into small molecules.(3)The pH value of the liquid product is not affected by the pyrolysis conditions,and its water content is at a very high level(>85wt.%).The change rule of PO yield with temperature is consistent with that of liquid phase product.The higher the amount of CT is,the higher the Po yield is.When the amount of CT is 30wt.%at 550?,the highest PO yeild is 1.65w.t%.GC-MS analysis showed that the main components of Po were N-Heterocycle,phenol and hydrocarbons with high unsaturation.Temperature will promote the increase of N-heterocyclic compounds and decrease of oxygen-containing compounds.(4)PG mainly includes CO2,CO,CH4 and H2.At each pyrolysis temperature,the order of gas content in pyrolysis gas is CO2>CO>CH4>H2.The yield of CO,CH4 and H2 increased with the increase of temperature.When the amount of corn straw was 5wt.%and 15wt%,the content of CO2 under 650?increased with the increase of temperature,but decreased when the temperature reached 750 ?.More straw means more CO2 and CO,and more H2 is produced at high temperature(750 ?). |
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