Experimental study on the pyrolysis of sewage sludge

In this paper,the effect of final pyrolysis temperature on the yield of products from the pyrolysis of sewage sludge was studied. The light fraction from sludge pyrolysis oil was analyzed.The fundamental properties of the pyrolysis residues were also investigated briefly.The results showed that when the final pyrolysis temperature was between 450℃ to 500℃,the yield of liquid product was favorable. With the increase of final pyrolysis temperature,the decreasing trend of pyrolysis residue was similar to the increasing trend of liquid product.Both of them were steep when the temperature was under 450℃ and mild when the temperature was higher than 450℃. Meanwhile the uncondensed gas increased smoothly with the increase of final pyrolysis temperature.The light fractions of pyrolysis oil obtained at 450℃ was mainly consisted of alkanes,alkenes,nitriles and nitrogen-containing heterocyclic compounds as well as MAHs etc. Among them,the concentration of toluene,4-methyl-phenol,1 _ methyl-2,5 _ pyrrolidinedione,pyridine,1-dodecene and pentadecane etc.were significant.The pyroysis residues of sewage sludge contained low carbon and high ash.However,they still possessed some volatile content.With the increase of final pyrolysis temperature, the surface of pyrolysis residue became more and more looser and rougher.The residue obtained at 450℃ exhibited highest pore volume.Nevertheless,the residue obtained at 500℃ owned maximum specific surface area in respect that it possessed highest number of micropores.