In the industrial use of clay refining methods are diafiltration, contact method. There have been reports of continuous diafiltration (moving bed), but no promotion. Diafiltration is mainly used for gasoline, kerosene, diesel and other light oil and transformer oil refining. The process requires the preparation of granular clay in the vertical tank, the oil slowly diafiltration, when the clay activity decreased to a certain extent, switch to another tank. Waste clay can burn the adsorbed material and use it again. The shortcomings of this method is the efficiency is too low, a large investment, oil loss, it is not seen in large-scale industrial production.
At present, the more widely used clay refining method is the contact method. The method is mainly used for the final refining of various lubricants, industrial often known as clay to refine. It is the clay and oil mixed with slurry, heated by a heating furnace to a certain temperature, and to maintain a certain time, and then filter out the refined oil. The right figure is the contact method of clay refining process.
The raw material oil is heated and enters the mixer and the clay is mixed for 20 ~ 30min, then pumped into the heating furnace. With the different nature of the oil, the heating temperature is very different. After heating into the evaporation tower, the top of the tower with a vacuum equipment, the general use of jet pump vacuum. From the top of the evaporation tower in the heating furnace in the cracking of the light components and residual solvent, and then into the middle tank. And then from the middle of the first into the Shi filter, filter out the vast majority of clay. Because of this coarse filter cloth filter, some small particles can still pass, so need to filter through the box filter again to ensure that the product without solid particles exist.