| This paper selects the pulp sludge(ZJ)from Yuanjiang paper factory and the waste paper pulp sludge(FZ)from a waste paper factory in Qinhuangdao as the research object.Using the acid washing method to removing the alkali metal minerals in the sludge and use tube furnace at different pyrolysis temperatures(300?900?)to get coke.Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD)and Raman spectroscopy(Raman)were used to analyze the evolution about microstructure and mineral of coke with the pyrolysis temperature changing.Pyrolysis,combustion and kinetics of papermaking sludge were studied by thermogravimetric analyzer(TGA).The results of thermogravimetric experiments show that the presence of alkali metal minerals has a certain catalytic effect on the pyrolysis of paper sludge.The secondary pyrolysis stage of the paper sludge after acid washing is obviously weakened or even disappeared,indicating that the weight loss process of secondary pyrolysis is mainly caused by the decomposition of minerals such as calcite.Compared with waste paper sludge,pickling has a great influence on the pyrolysis characteristics of pulp sludge.The pyrolysis start temperature and termination temperature of unpicked pulp sludge are lower than that of pulp sludge after pickling,indicating pulp fouling.The minerals in the mud have a certain catalytic effect on the pyrolysis of pulp sludge.FTIR results show that due to the high content of calcite and kaolinite in paper sludge,the mineral absorption peaks in paper sludge and coke mask the organic functional groups.The pyrolysis temperature significantly affects the microstructure and mineral composition of paper sludge.The absorption peaks of calcite and kaolinite begin to weaken at 500?,calcite completely decomposes at 800?900?,and kaolinite begins at 500 0C.It is converted into metakaolin and reacts with calcium oxide at 800?900? to form anorthite and acacia.The results of XRD are basically consistent with the results of FTIR analysis.The results of Raman spectroscopy indicate that the structural characteristic parameters of paper sludge coke show opposite trends in the high temperature zone and the low temperature zone.In the low temperature region,the increase of pyrolysis temperature will increase the characteristic parameters such as ID1/IG and ID3/IG,and decrease IG/IAll.In the high temperature region,the increase of pyrolysis temperature will lead to ID1/IG,ID3/IG.When the characteristic parameters are reduced,IG//IA11 is increased.In the low temperature zone,the increase of pyrolysis temperature causes the polycondensation reaction of the macromolecular structure inside the paper sludge coke,and the volatilization analysis,the deposition of small molecular compounds on the coke surface,resulting in the formation of a large number of defective structures and amorphous structures;With the increase of temperature,the internal polycondensation reaction of paper sludge coke is basically completed,the amorphous structure and the defect structure are continuously transformed into order,the carbon microcrystal structure grows,and the graphitization process takes place.The results of temperature-programmed combustion experiments show that the combustion process of paper sludge undergoes combustion of volatile matter and coke(300?600?)and thermal decomposition of minerals(600?1000 ?).Combustion kinetic analysis showed that as the pyrolysis temperature increased(300?700?),the sample released more highly reactive organic volatiles,which led to an increase in the activation energy required for coke combustion after pyrolysis.For paper sludge coke with pyrolysis temperature of 800?900 ?,because the minerals have been decomposed in a large amount during pyrolysis,and high temperature pyrolysis generates a large amount of hybrid carbon atoms,the ignition temperature and activation energy decrease. |
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