Study On Kinetics And The Heat And Mass Transfer Characteristics Of Oily Sludge Pyrolysis

Oily sludge is one of the pollutants which have to be disposed both in oil field andrefining industry. The oily sludge pyrolysis technology can realize quantity reduction,harmless and recycle treatments. In this article, in order to study the pyrolysis process and theproducts characteristics under different temperature, several pyrolysis experiments were did.Oily sludge pyrolysis process was mainly divided into moisture volatilizes evaporation, lightoil volatilizes evaporation and heavy oil cracking, the energy consumption occured maily in thefirst and the third stage. The pyrolysis product was composed of light oil and low carbonhydrocarbons.The drying experiments of oily sludge showed, decreasing the particle diameter, orincreasing the drying temperature, could effectively enhance the drying rate of the oily sludge,and reduce the total amount of sludge. The kinetic model fitting results showed that modifiedpage model (Ⅰ) was more suitable for oily sludge than other models. The drying rate constanthas a relationship to the drying temperature and the sludge particle size, the experienceformula of the drying rate constant was obtained in this paper, which then be substituted indrying equation can make moisture distribution under different size and temperatureconditions be calculated.Pyrolysis kinetic of the light oil evaporation stage and the heavy oil cracking stage wereanalysed, the kinetic equation were fitted by the Coast-Redfern method. Ultimately, it wasshowed that, the two pyrolysis stages were both fit a first-order reaction. The reactionactivation energies and pre-exponential factors of the two pyrolysis stages were solved, andthe kinetic equation was established. The results of fitting agreed with the results ofexperiment. The kinetics equation was helpful to estimate the oily sludge pyrolysis conversionrate. According to the characteristics of oily sludge pyrolysis, physical model andmathematical model of heat and mass transfer were established. Combining drying andpyrolysis kinetics parameters, the numerical method was used to simulate. The results showedthat, under the high temperature conditions, relative to the surface temperature the centertemperature of the particle has a certain delay, the temperature influenced product distribution.Overall, the temperature and the conversion has separatly the same trend everywhere.Decreasing water content and the particle size or increasing the heating temperature wouldhelp to improve the thermal efficiency. The model can be used to estimate the oily sludgepyrolysis time, the results can provide parameters and theoretical support for the design ofpyrolysis equipment.