Application of Supercritical Carbon Dioxide Extraction in Petroleum Industry
Supercritical Fluid Extraction (SFE), as an environmentally friendly high-tech chemical industry, has many advantages, such as high efficiency, energy saving and practicability. It has been widely used in many fields, such as medicine, food, petrochemical industry, environmental protection and so on. This technology is a new technology developed by utilizing the characteristics of Supercritical Fluid (SCF). Supercritical fluid has the characteristics of both gas and liquid, low viscosity, high density, high diffusion coefficient, good solubility and mass transfer characteristics, and is particularly sensitive to pressure and temperature near the critical point. Since the late 1970s, supercritical fluid technology has become a key project developed by many research institutes at home and abroad. Especially, the research and development of supercritical carbon dioxide extraction technology has entered a practical stage in many aspects, and has been put into industrial application, and has achieved remarkable economic and social benefits. Benefits.
Characteristics of Supercritical Carbon Dioxide Fluids
Solvents suitable for supercritical fluid extraction are carbon dioxide, ethylene, ethane, propane, propylene, ammonia, ethanol, dichloroethane, n-heptane and toluene, among which carbon dioxide is most suitable for industrial applications.
Supercritical carbon dioxide has little intermolecular force, which is similar to gas. It has a high density and is close to liquid. It is a state of gas-liquid inseparability. It has no phase interface and no phase effect. It can improve the extraction efficiency and save energy greatly. Using carbon dioxide as supercritical fluid extraction has the following advantages:
(1) The TC (31.4 C) of CO2 is close to normal temperature, PC (7.38 MPa) is low, and the critical point is easy to reach, so the operating conditions are relatively simple, and CO2 is inert gas. Therefore, it has no degradation and metamorphism to some thermosensitive substances and substances with poor heat demand.
(2) CO2 is a non-polar solvent with high affinity for non-polar compounds, which can selectively separate and recover active components from natural substances or remove certain components.
(3) The chemical stability of CO2 is good, non-toxic, colorless, tasteless, non-polluting extracts and environment, and there is no problem of residual solvents.
(4) CO2 is inexpensive, easy to obtain, non-flammable and safe to use.
(5) CO2 can prevent oxidation and inhibit bacteria.
(6) The technology has the advantages of simple process, high efficiency and low energy consumption.
Application of Supercritical Carbon Dioxide Fluid in Oil and Gas Exploration
Surface oil and gas geochemical exploration is mainly based on near-surface soil and rock as medium, using micro and ultra-micro testing methods to detect oil and gas and its associated organisms and their derivatives in the process of migration, as indicators of whether there are oil and gas reservoirs in the deep. Therefore, in surface petroleum geochemical exploration, supercritical carbon dioxide (SCCO2) has the special properties of penetrating sample media easily near critical pressure and temperature, and achieves the purpose of rapid extraction of hydrocarbon substances from samples.
Application of Supercritical Carbon Dioxide Fluid in Oil and Gas Exploitation
The critical temperature of carbon dioxide is close to the reservoir temperature. The high-pressure carbon dioxide injected into the reservoir can partially dissolve in the oil, causing oil expansion and viscosity reduction. On the other hand, the volatile components in the oil evaporate to form enriched gas, and the advancing gas repeatedly contacts the non-functioning reservoir. It can dissolve with petroleum. Because the interfacial tension between the gas phase and the remaining liquid oil is small, the remaining oil can be replaced by gas entering the reservoir pore.
Application of Supercritical Carbon Dioxide Fluid in Petroleum Refining
Supercritical fluid extraction (SFE) technology is also widely used in heavy oil upgrading. The ROSE (Residual Oil Supercritical Extraction) process developed by kerr-Mcgee and UOP has been industrialized for many years. Shi et al. systematically separated vacuum residue into narrow fractions with carbon atoms ranging from 15 to 17 by supercritical fluid extraction under increasing pressure.
China University of Petroleum has also carried out this research and achieved some results. In the past, there are not many reports about the use of carbon dioxide as supercritical fluid for deasphalting, because the solubility of light hydrocarbons such as propane in supercritical solvent is better than that of carbon dioxide. However, recent literature studies have found that Russia and Germany have used supercritical carbon dioxide fluid for oil dehydration. Qingzhong.
Supercritical carbon dioxide fluids as environmentally friendly clean fluids have shown their superior performance in the petroleum industry. Supercritical carbon dioxide extraction technology plays an important role in both early oil and gas exploration, exploitation and later petroleum refining. Although the application of supercritical carbon dioxide chemical reaction in petroleum industry is still in the stage of laboratory research, the existing research results indicate that this technology will have a good application prospect in petroleum industry.