Research On Droplets Coalescing And Demulsification Mechanism During Electrocoalescence Process

With exploitation of oil fields having entered later period and polymer flooding method been widely used, the inferior and emulsification of crude oil become more and more seriously, as a result, the pretreatment difficulty of crude oil has been greatly increased. To meet the demand of conserving energy and reducing pollution, how to raise the demulsification effect of crude oil becomes the problem for oil chemistry enterprise to solve. This paper mainly deals with the newly developing high-voltage and high-frequency technology. Based on theory analysis, microscopic tests are carried on to investigate droplets’deformation, breaking up, coalescence and moving principles in pulse electric field, and the mechanism of droplet coalescing and demulsification is thoroughly investigated.Firstly, the polarization deformation theory of droplet in electric field is analyzed, and it is found that Maxwell tensor component of oil-water interface is the directly reason for deformation. Microscopic experiment results indicate that, electrical parameters (electric field intensity, voltage amplitude, frequency and duty ratio), physical parameters (granularity of disperse phase, surfactant concentration, kind and concentration of mineral salt, pH value of disperse phase, oil phase character, aging time, et al.) and operating parameters (water content, emulsification strength, operating temperature, et al.) greatly affect the polarization deformation, critical electric intensity, critical deformability, approaching and moving velocity and electrostatic demulsification process of droplets. The interaction among electric field intensity, frequency and duty ratio cannot be neglected for the polarization deformation and breaking up behaviors of droplets.Breaking up tests show that, polarization effect is more obvious with the increase of electric field, polarization deformation, one bottom break up, two bottoms break up and middle part break up of droplets take place in succession. Based on the phenomenon and combined with theory analysis, the mathematical model of droplet break up criteria has been obtained. Coalescence tests indicate that, droplets will line along in accordance with the direction of electric field during approach together if the initial intersection angle between droplets and electric field is not zero. Coalescing time of droplets rising with initial intersection angle and distance between droplets increasing. With the distance between droplets increasing, approaching velocity of intersection angle decreasing and turn to negative value, droplets will line against the direction of electric field in different initial intersection angle conditions.Following, in this paper, mechanism analysis of droplets over polarized is carried on,“oil phase breakthrough theory”and“polarization stretch theory”are proposed, the mathematical model of droplet coalescing and demulsification criteria is obtained, and equilibrium state of separated droplets is thoroughly discussed. Finally, based on the research above, microscopic tests are carried on to investigate the principle of droplets moving, coalescing and chain formation in W/O emulsion, a further discussion is made to illustrate droplets coalescing and demulsification mechanism.The experimental research and theory analysis work above lays a good foundation for further research on demulsification mechanism of W/O emulsion during electrostatic coalescence process, and provides theoretical principle for further development of effective and compact electrostatic coalescence equipment.