| The sludges taken from municipal and chemical industrial sewage treatment plants were taken as the research objects in this dissertation.This work focused on the impact of sludge characteristics on its pyrolysis mechanism and the properties of pyrolytic char.Thermo-Gravimetric analysis and Pyrolysis-Gas Chromatography /Mass spectrometry(Py-GC/MS)analysis were used to investigate the effects of heating rate,temperature and reaction time on pyrolysis reaction and pyrolysis products generations.By using Scanning Electron Microscopy(SEM),nitrogen adsorption(BET),Fourier Transform Infrared Spectroscopy(FT-IR)and X-ray Diffraction(XRD),the variation of pyrolytic chars was investigated,including surface morphology,pore structure,functional group distribution and crystal phase at different pyrolytic temperature.The relationship between the characteristics of pyrolytic char and sludge properties was explored.Furthermore the feasibility of using pyrolytic char as adsorption or catalytic raw material was to analyzed.The main conclusions are as follows:(1)The sludge pyrolysis process was mainly affected by temperature and could be divided into three stages,i.e.water evaporation(room temperature~250?),volatile release(250?~ 500?)and inorganic minerals and coke decomposition(500?~ 800?).The heating rate was another important factor affecting the pyrolytic characteristics of sludge.The high heating rate could significantly increase the pyrolytic reaction speed,the activation energy(E)and the frequency factor(A).In addition,the sludge with high volatile content was found to show better reactivity.The maximum weight loss rate and total weight loss were higher than sludge with low volatile content.(2)Sludge pyrolytic products mainly contained small molecules of gases,acids,aldehydes,aromatic,indoles,etc.However the products composition and the changes for these two sludges were quite different.The content of long-chain fatty acids in sludge S1 was about 50%,and decreased rapidly with the increase of pyrolysis temperature,while the proportion of CO2 increased to 55%.There was a clearly competitive relationship between acids and CO2.The molecular weight of sludge S2 was less than that of sludge S1,the content of acid was only about 20% and decreased slowly with the increase of pyrolytic temperature.While there was no obvious change of CO2 content.The product characteristics and formation regularities of the two sludge showed that the pyrolysis reaction of S2 sludge was more active than S1 sludge.The pyrolytic temperature could promote the pyrolysis process and led to more thorough reaction.(3)S1 pyrolytic char had excellent pore development,narrow pore shape,less surface functional groups and Si O2 based crystalline phase..In contrast S2 pyrolytic char had poor development of pore,more surface attachments and functional groups including O-H,N-H,C=O,C=C and others.The crystal phase was based on kalium element compounds.In addition,increasing pyrolytic temperature could promote the pore structure development of pyrolytic char,but reduce the surface functional groups content.Overall,S1 pyrolytic char adsorption was better than S2 pyrolytic char,while S2 pyrolytic char had better chemical properties and catalytic potential.It can be deduced that the properties of sludge pyrolytic char was largely affected by the metal elements contained in the sludge.Especially,K and Na elements were likely to restrict the pore development of pyrolytic char and resulted in poor adsorption performance. |
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