The Study On Removing The Salts In Crude Oil Via Solvent Extraction

Crude oil containing NaCl, CaCl2, MgCl2 and other inorganic salts has significant detrimental consequence on subsequent processing equipment and technology. At present, the main methods to desalt from crude oil emulsion is using the electric desalting equipments associated with demulsifying agents, but with the viscosity and density of crude oil continues to increase, it becomes more and more difficult for crude oil desalting even the entry of secondary oil recovery.Based on the characteristics that ethylene glycol (EG) has strong solubility of inorganic salts and ethylene glycol and water are soluble, the new process was proposed that glycol was taken as solvent for extraction to separate the salts in crude oil in order to achieve the high efficient removal of salt from crude oil. This paper investigated the main factors on desalting process of glycol extraction, including the mixing intensity, mixing time, extraction temperature, sedimentation time and other factors. The results showed that when glycol/oil ratio (EG/crude oil)= 1:9, mixing intensity was 8 kr/min, mixing time was 8min, the extraction temperature was 110℃and the settling time was 180 min, the salt content of the first extraction was 7.14 mgNaCl/L and the salt content of the secondary extraction is 2.61 mgNaCl/L. The total desalination rate is 94%. The high density crude oil results showed that when glycol/oil ratio (EG/crude oil)=1:7, mixing intensity was 6 kr/min, mixing time was 5 min, the extraction temperature was 120℃and the settling time was 200 min, the salt content of the first extraction was about 15 mgNaCl/L and the desalination rate is 94%. When glycerol was taken as extraction, the salt content of thirdly extraction is 3.72 mgNaCl/L, the total desalination rate is 94.28%.Salt balance was also studies in the paper. It found that less solvent injection rate leads to the higher salt content in crude oil. The reason is that the droplets between ethylene glycol and oil are emulsified, so it cann’t reach full settlement. It was also found that the full contact of ethylene glycol and crude oil could promote the desalting process by using microscopic analysis. But the increased mix intensity leads to crude oil emulsified. Additionally, based on the study of experimental data and the mechanism of ethylene glycol extraction desalting process deduce the mass transfer rate equation (N=0.03801(y*-y)) of EG extraction. Ethylene glycol extraction desalting technology provides a new method for refining process with economic way.