Mechanism Of Magnetic Nanoparticles Enhancing Microwave Pyrolysis Of Oily Sludge

With the increasing demand for crude oil in China,the output of oily sludge has also increased year by year,but it will seriously affect the ecological environment and oilfield production.Therefore,realizing the reduction,harmlessness,and resource treatment of oily sludge has become a current research hotspot.By studying the pyrolysis of oily sludge by microwave,it is found that the addition of microwave absorbent can improve the efficiency of microwave pyrolysis,but traditional absorbents have problems such as low pyrolysis efficiency,high treatment cost,and so on.Magnetic nanoparticles with high coercivity,low Curie temperature,superparamagnetism and high magnetic susceptibility are used as new microwave absorbers to explore the mechanism of microwave-enhanced pyrolysis of oily sludge.Taking the oil sludge of Changqing Oilfield as the research object,the independent design and construction of the microwave heat treatment system was first completed,which consists of a continuous collection device,a thermogravimetric device and a stage collection device.The continuous collection experiment device explored the influence of microwave action time and the type and concentration of magnetic nanoparticles on the pyrolysis of oil sludge.Then,the thermogravimetric experiment of the presence or absence of magnetic nanoparticles was compared with the thermogravimetric device,and two sets of thermogravimetric curves were obtained and the pyrolysis process with or without particles was divided into stages respectively.The two sets of pyrolysis products were collected by stage collection device and analyzed by gas chromatography.Finally,according to Arrhenius formula,the kinetics of pyrolysis process was simulated by integral method,and the kinetic equations of each reaction stage of pyrolysis of oil sludge were obtained,and the apparent activation energy and pre-exponential factor were calculated.Experimental and theoretical studies show that:by adding different types and different concentrations of magnetic nanoparticles to oily sludge,when the mass concentration of nano-Zn Fe2O4 is 5mg/g as a microwave absorber,its pyrolysis effect is the best.The final pyrolysis temperature reaches 284℃in 20 minutes,the gas production volume is 405 ml,and the liquid production volume is 10.6 ml.According to the thermogravimetric curve,the pyrolysis of oil sludge can be divided into three stages:rapid heating and water evaporation（room temperature～150℃）,evaporation of light components（150～24℃）,and preliminary pyrolysis of heavy components（240～300℃）.The addition of nano-Zn Fe₂O₄ as absorbent increased the final pyrolysis temperature,heating rate and weight loss rate of oil sludge,and the microwave radiation time was greatly shortened when the pyrolysis temperature was the same.The volume fraction of H₂ and light components in the pyrolysis products is larger,resulting in more oil production.By establishing the kinetic equation of each reaction stage,it is found that the addition of magnetic particles can reduce the apparent activation energy required for the reaction,making the pyrolysis reaction easier to occur.