Migration and transformation of phosphorus during pyrolysis process of sewage sludge
(2.College of Environmental Science & Engineering, Kunming University of Science and Technology, Kunming, Yunnan, China 650093)
【Abstract】The migration and transformation of phosphorus in sewage sludge during the pyrolysis process were studied based on standard measurement testing (SMT), analyzing the phosphorus in the treated sludge samples using nuclear magnetic spectrum and X-ray diffraction, and also the occurrence and distribution of phosphorus in the residue of the sewage sludge sample after pyrolysis. From the results obtained, with increasing heat treatment temperature, the organic phosphorus continuously transformed to inorganic phosphorus. Phosphorus was concentrated in the residue of the sludge after pyrolysis when the pyrolysis temperature was below 800 °C. With increasing pyrolysis temperature, the contents of total phosphorus (TP), inorganic phosphorus (IP), apatite phosphorus (AP) in the sludge showed a trend of gradual increase, while the non-apatite inorganic phosphorus (NAIP) content indicated a trend of fluctuation with an increase and then decrease. The increase of pyrolysis temperature led NAIP transform into AP, and the AP content reached the maximum at 800 °C. The XRD results showed that the main forms of NAIP in the sludge were aluminum phosphate and ferric phosphate. The content of calcium phosphate in the sludge sample increased with increasing temperature. From the results of 31P NMR, the orthophosphoric acid monoester was converted to orthophosphate after heating, and orthophosphate was the most stable form of phosphorus. After the heat treatment, phosphorus was mainly in the form of orthophosphate. The new understanding on phosphorus migration and transformation in the process of sludge pyrolysis was discovered, and the theoretical support for the harmless, resource utilization and phosphorus pollution control technology of sludge was provided.
【Keywords】 sewage sludge; pyrolysis; phosphorus; migration of phosphorus;
(Translated by WANG YX)
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