The Transformation Of Phosphorus And Recovery Of Municipal Sewage Sludge Gasification In Supercritical Water

With the acceleration of urbanization, increasingly stringent emissionrequirements for sewage and the growing of wastewater treatment plant and sewagetreatment capacity across the country, the amount of sewage sludge consequentsignificant increase year by year. On the one hand, a variety of toxic and hazardoussubstances in sewage sludge may produce a potential threat on human health and theenvironment. On the other hand, municipal sludge contains large amounts of organicmatter, N, P and other nutrients, organic matter content accounted for more than30%-40%of dry organic matter, sludge treatment and disposal are increasingly concernedby people around the world. Conventional sludge treatment and disposal methodshave been unable to meet environmental requirements, therefore, it is necessary tolook a new method of sludge disposal to achieve the requirements of harmless,reduction, stabilization, resource.In this experiment, we mainly studied the municipal sludge supercriticalliquefaction process in autoclave batch reactor. The research was conducted with thefollowing reaction conditions: different temperature, different sludge-based activatedcarbon prepared in different temperatures. We investigated the product of oil insludge supercritical liquefaction, and the study focused on the migration andtransformation of phosphorus in sludge supercritical liquefaction process.Phosphorus migrated into the solid residues is extracted easily by hydrochloricacid (HCl), and the some heavy metals were extracted from solid residues too. How toextract pure phosphorus become a key. this study cleverly used the high-adsorptionproperties of activated alumina and the desorption of low concentration of the sodiumhydroxide solution (NaOH), heavy metals were separated from phosphorus productssuccessfully obtained the product of a high phosphorus concentration, low heavymetal content, and activated alumina and hydrochloric acid solution can be recycled,reducing the cost recovery.The results showed that80%organic P (OP) was converted into HCl-P. The totalP (TP)(the chief ingredient of HCl-P) in solid residue increased from86.1%to95.6%with the temperature increased from350℃to400℃.97.8%of P in solid residuehad been dissolved by1mol/L HCl, and over95%of P in the leaching solution (50mg/L for P concentration) was adsorbed when2.0g of the powder Al2O3was added. 98.7%of P had been dissolved from Al2O3with0.1mol/L NaOH. Ultimately, over85%of TP in SS was recovered. Moreover, the proportion of Cu, Zn, Pb in theextracted P-products was less than5%.