Study On Supercritical CO₂ Extraction Of Oily Sludge

Oily sludge is solid waste rich in mineral oils which is discharged during the process of petroleum exploitation, transportation and refinering. Shengli Oil Field generates at least 300,000 tons of oily sludge every year. Such sludge is not only difficult to deal with or break down but also cause serious pollution to circumjacent environment. Near critical region, subtle changes of pressure and temperature can leade to tremendous change of the supercritical CO₂ solubility which is characterized by the low viscosity, large thermal diffusivity and strong salvation. By means of this property, petroleum hydrocarbon can be extracted from oily sludge, thus realize the recovery of petroleum hydrocarbon. In contrast with other techniques, this technology has such advantages such as protecting environment, energy-saving, and economy. So studying the extraction law of supercritical CO₂ extraction oily sludge has great significance for realizing reduction, resource utilization and harmlessness of oily sludge.In this paper, based on the knowing of the physical property of oily sludge in GuDong 6th joint station, the extraction law of oily sludge extraction by supercritical CO₂ is studying thoroughly through experiments, and the effect of all process parameters to the extractability of oily sludge is also analyzed. The results show that pressure, temperature and time are the key factors to affect the extractability when using supercritical CO₂. Near critical region, the extractability enhanced rapidly with increasing pressure. The effect of temperature on the extractability is comparatively complex, with the increasing of temperature the extractability will emerges a lowest value. The extractability rises with extracted time increase, and the extracting efficiency gets to the best results at 40h, than the extractability no longer rises. The optimized parameters within the range of experimental condition are given bellow:pressure is 20MPa, temperature is 55℃and time is 40 hours. The extractability is 33.15% under the best condition. Finally, based upon the results of experiments, the author demonstrates the solubilization characteristic theory of supercritical CO₂, and believes that density is the main factor to decide the solubility of supercritical CO₂. The shortcoming of the present theory and its further directions and key area of research are pointed out.