Study On Product Characteristics And Process Conditions Of Municipal Sludge Pyro Lysis

Municipal sewage sludge is a kind of the solid、semisolid and liquid floccule sludge with high moisture and organic substances, and it can also be a potential biomass energy. With the improving of capacity in treating wastewater, sludge production has been enhancing sharply,the disposal sludge with safety have become a major problem in environmental fields. The sludge pyrolysis is an ideal way of sludge disposal because it can implement sludge reuse. However, there exist great differences between product characteristics and process conditions of sludge pyrolysis due to the complex composition of the sludge.In this paper, We take it for the object of study that the municipal sludge (moisture content of the sludge less than sixty percent) which is dried by oxidation disintegration-membrance. Calorific value of sludge was measured by using oxygen bomb under different conditions; three-phase products of the sludge pyrolysis were obtained under the low temperature and pressure, and product characteristics was studied by means of thermogravimetric analysis(TGA)、scanning electron microscope (SEM) and gas chromatograph-mass spectrometer-computer (GC-MS); At the same time, Selecting the best catalyst、particle size of sludge and heating rate in the process of sludge pyrolysis by using TGA. These datas obtained provides the experimental basis to pyrolysis recycling disposal in industry for this kind of municipal sludge. The experimental results showed that:(1) Type of sludge have a greater influence on the physical and chemical properties to sludge, sludge calorific value in winter is higher than summer, The calorific value of municipal sludge is higher than textile dyeing sludge. There are suitable methods of sludge pretreatment for the determination of calorific value:The optimum time is2h by heating drying;The best storage time is8d by room temperature drying; Freeze-drying is the best way of the room temperature and CaO drying; Adding high proportion oxidizer can more accurately determinate the calorific value of sludge with the high moisture content.(2) The pyrolysis productivity of liquid、gas and solid respectively is25.17%、9.25%、65.58%. Pyrolysis oil pyrolysis is divided into three stages, Volatile spilled out most happened in the second stage (130℃-350℃), in while weightlessness rate is64.04%; Combustion is divided into two stages, The weight loss maximumly in the second stage (130℃-700℃), while during130℃to600℃, high speed of weightlessness existed in the process. Its composition is mainly composed of alkanes, monocyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbon compounds, nitrogen compounds and fatty acid composition. The alkane content is24.3%, and aromatic hydrocarbons content is22%, these two take over the highest contents in pyrolysis oil. Among the pyrolysis gas, productivity of CO2, CH4and CO are increased in first, then decreased with the extension of heating time, the CO2reach to peak at primarily, and the overall yield is the most, but CO arrives its peak finally. Residue can be developed as adsorbent and raw material to product rich hydrogen for developed pore and high carbon content.(3) The residue of textile dyeing sludge catalytic effect is better than of municipal sludge for municipal sludge pyrolysis, Catalytic effect is similar to Fe2O3. The sludge at the different particle size has tiny effect for total loss weight of sludge pyrolysis, The best particle size is among0.154mm<d<0.180mm. There is a greater influence for sludge pyrolysis under the different heating rate, and20℃·min-1is the best heating rate.