| Municipal Solid Waste(MSW) pyrolysis is getting more and more attention in recent years due to it not only has the advantages in volume and quantity reduction, but also it can accomplish the MSW recycling. But until now, there are many problems in MSW pyrolysis, such as the subsequent utilization of pyrolysis products, and the mechanism is not very clear. For the above problems, this paper researched on the properties of products derived from MSW pyrolysis and the elements distribution and the changes with temperature to provide the basic data for improving the pyrolysis mechanism and the theoretical guidance for the further utilization of pyrolysis products. After the experimental study, the conclusions were as follows:① The char yield decreased from 31.38% to 25.58% with the pyrolysis temperature increasing(500℃~800℃); the maximum tar yield of 28.02% was obtained at 600℃, and then decreased to minimum yield of 21.76%; the mass yield and volume yield of pyrolysis gas were all increased as the temperature rising, in which the mass yield increased from 41.70% to 52.66% and the volume yield rose from 143.50L/kg to 438L/kg.② Compared with MSW, the char and tar were relatively concentrated C, that is the carbonization degree improved significantly, and the enrichment degree of C in tar was higher than that of char.; the O/C ratio and H/C ratio which decreased with the temperature rising were all significantly lower than that of MSW. Compared with tar, the aromatic and polar degree of char were all higher.③ The MSW mainly contained aliphatic functional groups such as ethers, ketones, methyl and methylene, and structure of char was in disordered array. Compared with MSW, the number of aliphatic functional groups of char reduced significantly, and the functional groups of char were based on aromatic ring =C-H, aromatic/aliphatic methyl and methylene functional groups; With the temperature increasing, the number of aromatic functional groups increased, and the structure of char was gradually in ordered; the band of carbonate was present in chars and MSW.④ The C, O, N, Cl, Ca, Si, Na and K elements were present on the surface of chars, where the main element was C; the sp2 hybrid C(with aromatic C-H) was the main form of C; O was mainly in the form of COO- bond; Si existed on the surface of chars was in the forms of Si-N-C, Si O2 and so on; Cl was in the form of inorganic chlorine(such as Na Cl and KCl); Na Cl and Na OH were the existence form of Na. N on the surface of C500(char obtained at 500℃) was in the form of N-Si, amine-N and so on; On the surface of C500, C600 and C700, Ca were all in the form of Ca CO3, but Ca CO3、Ca O、Ca SO4 and Ca Cl2 were the existence form of Ca on the surface of char obtained at 800℃.⑤ The activity of O and N on the surface of chars was higher than that of the interior of chars; Cl was enriched on the surface of chars; S was not detected by XPS.⑥ The water content of tars was between 18.43% and 26.11%, the solid content was 0.75%~1.29%, and the LHV value was between 24.12 MJ/kg and 28.36 MJ/kg; Tar components had been detected included alkanes, alkenes, phenols, alcohols, ketones, esters, mononuclear aromatic, PAHs, etc. For the components of T500(tar obtained at 500℃), it is based on the mononuclear aromatic and PAHs; With the temperature increasing, the PAHs became the main component of tars, and the content was raised from 8.84% to 83.45%. When the temperature was less than or equal to 600℃, PAHs derived from MSW pyrolysis were primarily attributed to Diels-Alder reaction, and when the temperature was above 600℃, the main PAHs producing pathways were also included the radical reaction of phenols and its derivatives.⑦ The pyrolysis gas had been detected included alkanes, alkenes, alkynes, CO2, sulfurous gas(mainly with H2S), chlorine gas(mainly with CH3Cl) and so on. When the pyrolysis temperature was raised from 500℃ to 800℃, the gas volume increased, in which the volume of alkanes, alkenes, CO2, sulfurous gas and chlorine gas were increased 1.85, 3.46, 19.23, 2.17, 3.28 and 1.65 times. When the temperature≤600℃, the dehydrogenation reaction was dramatic. However, when the temperature>600℃, the dehydrogenation reaction improved slowly; Olefin was the main component of pyrolysis gas, and the proportion was gradually increased with the temperature rising.⑧ When the temperature ≤600℃, the char-C, tar-C and gas-C were produced by the first pyrolysis reaction of MSW-C; The maximum tar-C yield of 32.81% was obtained at 600℃; When the temperature>600℃, the secondary pyrolysis reaction was happened, the tar –C yield decreased to the minimum of 29.39% at 700℃and partial of tar-C transformed to gas-C; Char-C yield dropped from 36.39% to 29.40% with temperature increasing; Instead, gas-C yield increased from 31.95% to 40.28%;⑨ More than 50% of H and O distributed in gaseous phase, and the proportion was increased with the temperature rising; However, the yields of chare-C and tar-C decreased gradually; Char-N yield dropped from 57.73% to 30.46% with the temperature increasing, tar-N yield achieved the maximum value of 39.41% at 600℃, then decreased gradually and stabilized around 32%, gas-N got the minimum yield of 9.04% at 600℃, and increased to 37.43% gradually; More than 80% of S distributed in gaseous phase, the char-S yield was between 6.68% and 4.95%, and the char-S was in the form of sulphate at 800℃, tar-S yield achieved the maximum value of 10.41% at 600℃, then transformed to gas-S; More than 60% of Cl distributed in gaseous phase, tar-Cl yield was very low which was between 0.09% and 2.80%, char-Cl yield decreased from 38.40% to 29.96% with the temperature increasing. |
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