| With the urbanization standards improving, the production of municipal sewage increase steeply. At the same time, as a by-product of wastewater treatment, the amount of sewage sludge growed rapidly. If haven't been treated properly and timely, the sludge will cause serious environmental pollution for the human. So, sludge treatment and disposal has been a burning question.In fact, sludge is a resource which is put in a mistake place. Because of containing a large number of organic matters which are available, such as protein, polysaccharide, fat and so on, sludge has a large amount of energy. If the energy is recycled and utilized, sludge will be alternate energy sources. It is receiving more and more attention as an economic efficient and environmental friendly route to waste treatment. Pyrolysis of sewage sludge is a promising thermal conversion technology aiming at sludge reduction, stabilization, detoxification and recycle. The sludge of complicated compositions bring about bio-oil from pyrolysis rich in various materials. So, crude bio-oil are hard to be used as liquid fuels due to the poor fuel properties, and also difficult for chemical recovery owing to the complex chemical composition. Based on this background, the work performed in this thesis includes:1) using alkaline thermal extract EPS from sludge, then pyrolyze sludge at low-temperature and gather the bio-oil, at last analysis the compositions of the oil. At the same time, examine pH, temperature and heating time how to impact the extraction percent of EPS by acid thermal and alkaline thermal; 2) dispart and abstract the crude protein and crude polysaccharide from sludge, then examine the compounds of protein and polysaccharide by Py/GC-MS seperately; 3) do some research on the pre-treatment sludge to discover the use.Using the waste activated sludge which is from Songjiang wastewater treatment plant as raw sludge (RS), the results of the proximate analysis, elements analysis and testing calorie are found that RS is a high volatile (51.28%), low Ash (38.42%), higher calorie (13.83MJ/kg) matter and the potential of using as fuel resource is great. The pyrolytic characteristics of EPS, crude protein, crude polysaccharide, RS and pretreatment sludges by TGA and obtain the result:pyrolysis processes of EPS, crude protein, crude polysaccharide have three stages less than RS which had four stages. Decomposition of organic matter of all the samples happen mainly at the temperature which is less than 500℃. It indicates that the pyrolysis experiments can be done at the low temperature of 500℃. The kinetic parameters of RS and two pretreatment sludges are found out by Coats-Redfern integration methods.Crude protein and polysaccharide could be directly injected in the py/GC-MS and detected. Other samples need to pyrolysis in tubular furnace at first, then collect the bio-oil and finally use GC-MS to anaylze the compositions of those oil. The results show that the pyrolysis constituent parts of EPS, crude protein, crude polysaccharide indeed are simpler than RS. The bio-oil of EPS contains more low carbon compounds, at the same time, aliphatic hydrocarbon (including alkyl group and alpha olefin) has 6.8% more than RS's, which show that the quality of bio-oil from EPS pyrolysis is better than RS's. Crude protein and crude polysaccharide's pyrolysis products not only contain those compoundswhich are representative, but also include a certain amount of alkyl group, alpha olefin, ester, benzenes and so on. However, compounds in the bio-oils of RS are more complicted, and high content oxygen containing compounds and low content aliphatic hydrocarbon are found which due to reduce the fuel value.
|
PDF Full Text Request