| A large number of tannery sludge was produced in the process of leatherprocessing which could cause serious pollution to the environment. In recentyears, researchers tried to recycl use the tannery sludge by using many methods.Among them, low temperature carbonization technology as a recycling treatingmethod which was quick and efficient was attracted much attention. Moreover,there is not any relevant research in the area of tannery sludge at present.Tannery sludge came from different tannery process in different tannerycompany was used as the research object in this paper. Compared withmunicipal sludge, pyrolysis process and pyrolysis kinetics of tannery sludgewere studied by using thermogravimetric analysis method. Properties andcomposition of tannery sludge and pyrolysis production was analyzed byfluorescence spectrum, gas chromatography-mass spectrometry and elementalanalysis. And pyrolysis production was evaluated as waste water absorbent.In the range of room temperature to600℃, three kinds of tannery sludgeand one kind of municipal sludge was analyzed by elemental analysis methodand thermogravimetric analysis method after pyrolysis, and its fitting kineticswas also discussed. Different heating rate had little effect on the pyrolysisprocess of sludge. The whole pyrolysis could be divided in three stages andpyrolysis of sludge mainly reacted in the second stage (200-500℃). Allpyrolysis reactions of this stage accorded with first order chemicaldecomposition reaction mechanism function and apparent activation energy ofthree stages were all in the range of5.5～6.3kJ·mol-1. Relative weight loss ofmunicipal sludge and two kinds of tannery sludge were40.1%,63.8%and56.0%respectively. Peak temperature of the maximum rate of weight loss are285℃,400℃and315℃respectively. The pyrolysis treating equipment ofmunicipal sludge also could be used in the pyrolysis process of tannery sludgein theory and the temperature of this equipment should be enhanced in the practical application.The carbon sequestration rate, iodine value, organic matter content andother characteristics of carbonization products were used as indicators in themethod research of tannery sludge pyrolysis. The results indicated that the bestcarbonization temperature of municipal sludge was300℃and the bestcarbonization temperature of tannery sludge was400℃. In pyrolysis process,tannery sludge produced more oil than municipal and with the increase ofcarbonization temperature, the iodine value of sludge carbonization productincreased. If the tannery sludge was decomposed under the condition of400℃,the carbon sequestration rate of carbonization product would be the highest.After the low temperature carbonization pyrolysis of tannery sludge, thecomponent of pyrolysis oil and solid residue were analyzed. The resultsindicated that pyrolysis oil was mainly including light component whencomparing with the oil which was extracted directly. The organic matter contentof pyrolysis solid product was also increased obviously and this kind of producthad a definite adsorptive property.After the adsorptive property experiment of tannery sludge which wascarbonized under low temperature, it could be found that tannery sludge hadlittle effect on the absorption of chromium which was ionic state. With theincrease of carbonization temperature, the absorption rate of tannery sludgeincreased. And the absorption rate could reach27.5%in the existing experimentcondition. To chromium ion, the absorption rate of tannery sludge which wasdegreased was88.5%. Comparing with tannery sludge which was carbonizedunder low temperature, degreased tannery sludge had better effect on theabsorption of chromium which was ionic state. Extracing oil from tannerysludge and realizing the recycling use of tannery sludge was feasible. |
PDF Full Text Request