Study On Macro-thermogravimetry Kinetics Of Pyrolysis Of Oil Sludge

Oil sludge, the mixture of mud, sand, water, petroleum and other organics, is the byproduct of the oil field production activities, which comes from the processes of crude oil exploitation, refining, collection and transportation. The stabilization, reduction and reclamation of oil sludge have attracted more and more attention in petroleum chemical industry. Pyrolysis has the benefit of high efficiency of energy recovery, low secondary pollution in the process of treatment and disposal of oil sludge. This study focused on the investigation of themal kinetics of pyrolysis of oil sludge. The kinetics parameters of oil sludge pyrolysis are basis of pyrolysis reactor design.Thermogravimetric(TG) analysis was used to obtain the parameters of kinetics. The results of micro-TG pyrolysis showed that the pyrolysis process of oil sludge was divided into two stages201.7-355.8℃and355.8-488.7℃according to derivative thermogravimetry curves. With the increasing of heating rates, degradation steps shifted to higher temperatures. Coats Redfern model was used to obtain activation energy. The activation energy was in the range of37.9-45.21kJ/mol for the first stage and93.47-103.38kJ/mol for the second stage.The micro-thermogravimetry had the shortage of overlooking mass diffusion and calorific delivery, which is important in engineer process. The pyrolysis of oil sludge tests were carried out on a self-designed laboratory scale macro-thermogtavimetry. The effects of particle size and heating rate on weight loss were carried out. The results indicated that large particles have a pyrolysis reaction retardancy compared to fine one. With the increasing of heating rate and the particle size, the process of weight loss moved towards higher tempeature range. The activation energy of pyrolysis of oil sludge by macro-TG was obtained by distributed activation energy model. The activation energy was in the range of14.4-35.81kJ/mol. However, The activation energy of micro-TG was in the range of27.22-249.65kJ/mol.In order to further investigate the heat transfer behavior of the granule under the condition of large particles, relative tests was carried out with regard to the variation of interior temperature gradient of the granule. The result showed larger granule lead to fluctuation of interior temperature. An empirical formula for interior temperature of oil sludge particle was derived.Oil sludge cracking process was simulated by software RMG(reaction mechanism generator). The simulation results showed that the gas composition of hexane cracking approached oil sludge cracking.