Demulsification Performance And Mechanism Of Polyether Polyquaternium And Supported Reverse Demulsifers

Chemical demulsification is a popular method which can effectively change the oil-water interface property and achieves the purpose of emulsion breaking.ASP flooding produced water is characterized as highly degree of emulsification and stable.In view of this,demulsification is a prerequisite for its disposal.When conventional chemical demulsifier was used for demulsification,it was difficult to produce fine oil droplets in the water.Competitive adsorption of demulsifier and oil-displacement surfactant on the surface of oil droplets led to secondary emulsification.Demulsification of micro-particle oil droplets was the key link of ASP flooding produced water treatment.In this paper,the group member synthized a novel polyether polyquaternium-grafted demulsifier which integrates the functions of demulsification and adsorption.This paper focuses on the demulsification performance and mechanism of PPA and PPA@SiO₂ in ternary composite flooding produced water.These researches include three parts:demulsification performance,substitution demulsification mechanism and neutralization emulsification mechanism investigation.The main contents are summarized as follows:?1?Study on the demulsification performance of PPA and PPA@SiO₂ demulsifier in ternary composite flooding produced water.The simulated produced water was prepared according to the water quality analysis results of the Daqing Oilfield ternary composite flooding.The chemical stability of the supported demulsifier was analyzed by FTIR.The supported demulsifier perfromances a good stability in the range of pH=2¹0.Solvent stability experiments shows that the supported demulsifier has better stability to petroleum ether.Demulsification performance evaluation was conducted by comparing the oil concentration,interfacial tension,oil droplets size distribution of raw and S-01,PPA or PPA@SiO₂ treated wastewater.The increased demulsifer dosage,demulsifying temperature and demulsifying time resulted in the oil content decrease,interfacial tension decrease and oil droplet size increase.At the PPA dosage of 110mg/L,the oil content of the system decreased to 97.2 mg/L,the interfacial tension decreased to 22.45 mN/m and the average size of oil droplet reached 365?m.As the demulsifying temperature increases,the oil content and interfacial tension of the ASP flooding simulated water decreases;the oil droplet size first rises and then decreases.As the pH increases,the oil content of the ASP flooding simulated water and the interfacial tension decreases first and then increases;the oil droplet size first rises and then decreases.With the increase of the inorganic salt,the oil content of the simulated water decreases,the interfacial tension decreases,and the Zeta potential value decreases.?2?Study on the mechanism of substitution demulsification of PPA and PPA@SiO₂ demulsifiers.The substitution demulsification mechanism was investigated from the aspects of oil/water interfacial behavior,competitive adsorption therodynamics of demulsifier and demulsifier molecular structure regulation.The effects of demulsifier dosage,demulsifying temperature and system pH on the rupture rate constant and the thinning rate of the oil-water interface film were investigated using high speed microscopic imaging technology.With the increase of demulsifier dosage,demulsifying temperature and acidic pH value of the system,the thinning rate of the oil/water boundary mask will be increased which is beneficial to reduce the strength of the interface film and accelerate the rupture of the oil/water interfacial film.The rupture rate constant is up to 0.0173 1/s,and the interfacial film thinning rate is up to 0.0078mm/s.The morphology of the oil/water interface film before and after demulsification was analyzed by AFM,the Image Rq value was increased.The demulsifier molecules were adsorbed to the oil/water interfacial film,resulted in displacement replacement with the original emulsifier.The elastic modulus of the oil/water interfacial film after demulsification was analyzed through the shape of the droplet.As the elastic modulus decreases the elastic deformation resistance of the interface film reduces,and the oil droplets were easy to aggregate.The competitive adsorption effect and variation law of demulsifier and surfactant for oil displacement were assessed by microcalorimeter.It was an endothermic process that the demulsifier with higher interfacial activity diffused to the oil/water interface film and arranged loosely,replacing the originally dense emulsifier molecules to form a weak-strength film.The molecular structure changes of the grafted demulsifier before and after demulsification were analyzed by FTIR and XPS.The stretching vibration peak of S=O group appeared in the molecular structure after demulsification,which proved the demulsifier molecule replaced the emulsifier molecule on the interface film.The results of XPS analysis indicates that the two peaks of S element after demulsification represented two sulfur functional groups,and further indicated the substitution demulsification.?3?Study on the mechanism of electric neutralization demulsification of PPA and PPA@SiO₂ demulsifiers.Revealing the mechanism of electric neutralization demulsification by analyzing the effect of demulsifier dosage,demulsifying temperature and pH value on Zeta potential and electrical conductivity of simulated water sample produced by ternary compound flooding.The Zeta potential absolute value of ASP flooding produced water system decreased,indicating the positive charge of demulsifier quaternary ammonium salt nitrogen ion was neutralized with the negative charge on the surface of oil droplets.The droplets coalescence efficiently due to the compression in the double layers of oil/water interface film and the decreased repulsive effect between the droplets.In addition,the electrical conductivity of the produced water system of ASP flooding increased and oil-water separation occurred after electric neutralization demulsification.The increasing slope of the conductivity curve means the demulsification and separation speed were accelerated.This article contains 59 figures,7 tables and 136 references.