Research On Movement Law And Charge Properties Of Petroleum Asphaltene Under Electric Field

The asphaltene is of great significance to the storage,transportation,and processing of petroleum.The deposition of asphaltene can cause blockage in conveying pipes and coking of equipment,so it is necessary to develop efficient de-asphaltene technology for improving the quality of heavy oil.As a strategy of de-asphaltene based on the charged properties of asphaltene,the electrodeposition method has gradually attracted the attention of researchers in recent years for its higher removal rate and lower energy consumption in theory.In this paper,a type of model oil(toluene/alkane)was selected to simulate the composition of crude oil.The law of movement and deposition of asphaltene in electric field was studied,and the change of charge property of asphaltene was analyzed.Then,the asphaltene removal of different real oil products under the electric field is explored.The specific work is as follows:1.The distinct deposition of asphaltene by the direct current electric field is determined.Asphaltene in the unstable model oil can be precipitated as flocculants,forming loose sediments after a long time of placement.The applied electric field can make the asphaltene aggregates migrate oriented and overcome the repulsive force when further polymerization repulsion.Asphaltene can form stable deposits on the plate and the model oil is clarified quickly.2.The effect of electric field on the removal of asphaltene under different experimental factors was investigated.When the plate area is sufficient,asphaltene existing as an adsorption layer,there is a positive linear relationship between time and adsorption value.When the plate area is limited,the asphaltene in high concentration model oil forms an accumulation layer that is easy to fall off from the plate.The adsorption process of asphaltene on the plate can be further described by the n-order adsorption equation.The aromatic hydrocarbon(toluene)in model oil can improve the solubility of asphaltene,while the non-asphaltene component enables the asphaltene to disperse effectively in the model oil.Both of these effects increase the stability of asphaltene-containing system and decrease the adsorption effect.The increase of electric field strength is beneficial to the precipitation of asphaltene in the stable system,which accelerates the directional migration of asphaltene in the model oil,and enhances the plate adsorption effect dramatically.3.The influence mechanism of electrification of asphaltene is revealed.charge and charge alteration of asphaltene are mainly affected by electric field strength.The resin can be adsorbed on the asphaltene surface.On the one hand,the charge of asphaltene is reduced through electrostatic shielding,which reduces the migration and deposition effect of asphaltene under electric field.On the other hand,resin blocks the charge transition of asphaltene by occupying ion adsorption sites.4.The phenomenon of charge alteration of asphaltene is explained.After infrared characterization,elemental analysis,and repeated electrical experiments of the anode and cathode asphaltene,the mechanism of charge and charge alteration of asphaltene was proposed.At low electric field strength,asphaltene is positively charged due to metal polarization.With the electric field strength increased,the metal polarization continues to be enhanced,and the adsorption effect is improved.At the same time,the ion dissociation degree of partial asphaltenes is improved.The adsorption of anions on the asphaltene surface prompted the charge alteration,resulting in adsorption on both plates.Experiments show that the minimum electric field strength of charge alteration is 6k V/cm.5.The deposition of unsteady real oil by electric field is determined.The deasphalting process of different raw oils with electric field is explored.It is found that the asphaltene and other components are relatively balanced in stable crude oil system,and the effect of electric field is not obvious.The colloid equilibrium system in real oil is broken by hydrogenation or adding a small amount of solvent.At this time,the application of electric field can accelerate the precipitation and deposition of asphaltene,and achieve a better effect of asphaltene and metal removal.The above results show that the process conditions for applying electric field to asphalt removal should be selected according to the composition difference of raw materials.For the stable system,higher electric field strength should be applied.At the same time,it is also necessary to consider the charge change of asphaltene under the condition of applying electric field,to prevent the reduction of charge of asphaltene,resulting in poor deposition results.