Study On Desorption Mechanism And Oil Removal Characteristics Of Oily Sludge In Ultrasonic Field

A large amount of oily sludge can be produced during oil exploitation,storage and transportation,which not only harms human health but also pollutes the environment.Ultrasound is an emerging method for sludge disintegration that can penetrate gaps and blind holes of oily sludge that cannot be reached by other methods,achieving significant recovery of petroleum hydrocarbons.This paper reveals the oil desorption process of oily sludge in ultrasonic field from a microscopic point of view,and macroscopic experiments are subsequently carried out to study the oil removal characteristics of oily sludge in ultrasonic field.On that basis,the methods for parameter optimization of oily sludge treatment with different physical properties are proposed,which provides theoretical foundation for the development of ultrasonic treatment technology of oily sludge.The main research contents and conclusions are as follows:The oil desorption characteristics in ultrasonic field are studied by microscopic experiments.The radial dissipation of the acoustic field is found in the parallel cross-sectional direction by measuring the acoustic pressure distribution in the acoustic chamber.The acoustic field presents the standing wave distribution in the propagation direction.The acoustic pressure amplitude at the nodes is not 0 due to the standing wave damping,and the acoustic field dissipation in the emission and reflection surfaces is serious.In addition,the dynamic behaviors of cavitation bubbles and desorption of oil on quartz substrates in ultrasonic field are studied.The results show that the cavitation bubbles implode during transient cavitation,releasing high temperature and high pressure,leading to the desorption of oil from the surface of substrates.The oil removal characteristics and disintegration mechanism of oily sludge in ultrasonic field are studied.The results show that lower frequency ultrasound results in larger and more energetic cavitation bubbles that are more effective in the desorption of oil from solid particles.Moreover,acoustic intensity and treatment time that correspond to maximal oil recovery are found.Increasing the ratio of water to sludge and p H can reduce the slurry viscosity and facilitate the formation of HSi O₃^-,respectively,which improves the oil recovery efficiency.Moreover,nonionic surfactants have better oil solubilizing effects than ionic surfactants.Asphaltenes are more stable on solid particle surfaces than other components.The reason is that heteroatoms such as S,N,and O in asphaltenes form hydrogen bonds with hydroxyl groups on the surface of the particles,impeding the desorption of oil.Mechanical effects such as shock waves and micro jets due to acoustic cavitation can break the hydrogen bonds between asphaltenes and solid particles,thereby facilitating disintegration and oil recovery of oily sludge.The ultrasonic desorption characteristics of oily sludge with different oil/solid components are studied.The characteristic properties of different oil phases（functional group and element content）and different solid phases（particle size distribution,morphology and Zeta potential）are measured.The effects of the ratio of polar/non-polar component in the oil phase and the ratio of kaolin/quartz in the solid phase on the adsorption characteristics of oily sludge are obtained.The results show that the composition of the oil phase and solid phase affect the adsorption location and type（hydrogen bond and electrostatic force）.For oily sludge with strong adsorption,high acoustic intensity-short time treatment can improve oil removal efficiency.In addition,the strong adsorption between the polar component in oil phase and the kaolin is the dominant factor that hinders the ultrasonic desorption.