| The sludge pyrolysis technology is a kind of thermo-chemistry treatment technology with advantages of high rate of energy recycling and low secondary pollution. But the pyrolysis oil generated from sludge pyrolysis can’t satisfy the quality demands of the fuel oil because of some complex impurity ingredients. Polycyclic aromatic hydrocarbons (PAHs) is one of the ignorable pollutant of one-off fuels, which influences calorific value impacts natural environment. In decades years, PAHs distribution characteristic in sewage sludge and its pyrolysis products are causing people’s attention. Studying the generation mechanism and release characteristics of PAHs in pyrolysis oil will be useful for the optimization of pyrolysis technology and improvement of the pyrolytic oil fuel quality.This thesis mainly investigates a series of experimental research about detection method, the distribution characteristics and forming mechanism content of PAHs’in municipal wastewater sewage sludge pyrolysic oil; First of all, according to the thermogravimetric characteristic of the sludge under different pyrolysis reaction conditions,8groups pyrolysic oil samples were colleccted. Then, according to the critical pyrolysis conditions obtained from thermal gravimetric analysis, a small test-bed of sludge pyrolysis oil was set up and eight oil samples were separated, concentrated, purified, detected by solid phase extraction and gas chromatography mass spectrometry. A new method for the detection of PAHs in sludge pyrolysis oil was set up to fill the blank of the domestic research in this area.Pyrolysis oil pretreatment methods and GC-MS analysis conditions are verified through Precision calculation and recovery test of PAHs standard solution.Finally, PAHs distribution characteristic and the pyrolysis process of PAHs formation mechanism were studied and analyzed. The main results obtained are as the follows. Based on the existing test standards of PAHs in water quality and gasoline regarding to water and sludge pyrolysis oil properties of existing, physical and chemical characteristics of PAHs to determine the serious of "separation+extraction purification+purification enrichment" as one of the pyrolytic oil pretreatment method, through the accurate calculation and PAHs standard liquid recovery rate, tests were made to verify the established pyrolysis oil pretreatment method and GC-MS analysis conditions. The detection limit was found using30mg/L of PAH standard solution for dilution test of GC-MS that if the amount of PAHs in the pyrolysis oil pretreated is less than0.3ng, benzene and (k) fluoranthene, benzo(a)pyrene, acenaphthene, naphthalene, flexion, indene benzene (1,2,3-CD) pyrene, benzene and (ghi) north and diphenyl and [a, h] anthracene can not be detected, if it is less than0.06ng, then all PAH ions would not be detected. Through the GC-MS quantitative analysis, the contents of PAH in the testing8group pyrolysis oil were obtained; The heating rate and ending temperature have important influences on PAHs generation’s and their contents; Through analyzing the impact of different heating rate and ending temperature on the distribution of PAHs, it can be found that the generation of PAHs varied with the ending temperature rise. The most suitable final temperature for the PAHs formation is750℃. Under the heating rate of15℃, the final PAHs of naphthalene, acenaphthylene, acenaphthene are diminishing and then increasing and at last diminishing with the rise of the final temperature, the middle ring and long ring of PAHs are increase firstly, then diminish to the low ebb and then increase before the final diminishment.There are three main production pathway of PAHs in the process of sludge pyrolysis:the sludge itself contains some PAHs of stable chemical properties; the big ring of PAHs are cracked into small rings of PAHs because of heating to high temperatures; PAHs resulted from volatile matter radicals were found through polymerization and reform in the pyrolysis. |
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