Solvent deasphalting is a pretreatment process for inferior residual oil. A petroleum product refining process for removing petroleum oil and bitumen oil from the vacuum residue obtained by distillation of crude oil (sometimes also from atmospheric residue) to obtain deasphalted oil and simultaneously producing petroleum pitch.
- Raw materials: heavy oil such as vacuum residue or atmospheric residue
- Product: Deasphalted oil, etc.
- Basic concepts
Solvent deasphalting is a petroleum refining process for processing heavy oil. The process uses heavy oil such as vacuum residue as raw material, and extracts hydrocarbons such as propane and butane as solvent. The extract is deasphalted oil. It can be used as a heavy lubricating oil raw material or a cracking raw material, and the raffinate deoiled asphalt can be used for road asphalt or other purposes.
- Production process
Includes extraction and solvent recovery. The extraction section generally takes an extraction process or a two-stage extraction process.
Asphalt and re-de-asphalt oil solution contain less propane, use one evaporation and stripping to recover propane, light de-asphalt oil solution contains more propane, use multi-effect evaporation and stripping or critical recovery and stripping to recover propane to reduce Energy consumption.
The critical recovery process is based on the fact that propane is close to the critical temperature and slightly above the critical pressure (the critical temperature of propane is 96.8 ° C, the critical pressure is 4.2 MPa), the solubility of the oil is close to the minimum and the density is also close to the minimum. The light deasphalted oil and most of the propane are settled and separated in the critical tower, thereby avoiding the evaporation condensation process of the propane, thereby reducing the energy consumption more.
The domestic solvent deasphalting process mainly includes the second-stage deasphalting process, the critical recovery deasphalting process, and the supercritical extraction solvent deasphalting process.
(1) Two-stage deasphalting process for sedimentation method
The two-stage deasphalting of the sedimentation method was developed on the basis of a conventional one-stage deasphalting. On the basis of studying the peculiar nature of Daqing vacuum residue, it is noted that the conventional propane deasphalting can not make full use of this resource, and a new deasphalting process has been developed.
(2) Critical recovery deasphalting process
The solvent’s ability to dissolve oil decreases with increasing temperature. When the temperature and pressure are close to critical conditions, the solvent’s ability to dissolve oil has been reduced to a low level. At this time, the propane solvent can be directly recycled after being cooled. It does not have to be recovered by evaporation.
(3) Supercritical extraction solvent deasphalting process
Supercritical fluid extraction is an extraction system with abnormal phase equilibrium characteristics and abnormal thermodynamic properties in the vicinity of the critical region. By changing parameters such as temperature and pressure, the mutual solubility between the components in the system changes drastically. Separation technique
- Production equipment
- extraction tower
The function of the extraction tower is: a stripping zone between the residue inlet and the main solvent inlet, a fractionation zone above the residue inlet, and a bitumen settling zone below the main solvent inlet.
- Solvent critical / supercritical recovery tower
The deasphalted oil solution separator, also known as a supercritical tower or a critical tower, is actually a liquid-liquid separator that can be operated above the critical pressure of the solvent to recover the solvent in the deasphalted oil solution.
- booster pump
The deasphalted oil solution booster pump is the key equipment to realize the supercritical solvent recovery process. It needs to have a lift of 1.5Mpa or more. The inlet can withstand high pressure and temperature, and the pump can ensure the circulation of solvent in the system.
