Also known as extraction tower, a kind of liquid-liquid mass transfer equipment commonly used in chemical industry, petroleum refining, environmental protection and other industrial sectors. Liquid-liquid extraction is a way of mass transfer, in which one or more compound components in the mixture solution are extracted with another liquid (called a solvent, which is insoluble to the solvent of the mixture solution), so that it can be separated, enriched, and purified. This process is called extraction, extraction, liquid-liquid extraction, solvent extraction process. The equipment used is called extractor, there are one and multiple extraction, there are gaps and continuous extraction process, the extractor used for continuous multiple extraction is a tower type equipment, called extraction tower. Its internal structure is to use gravity or mechanical action to break a liquid into droplets, dispersed in another continuous liquid, liquid-liquid extraction.

The functions of the extraction column are as follows: between the residual oil inlet and the main solvent inlet is the extraction area. The above part of residue oil import is the branch library area. Below the main solvent inlet is the asphalt settling area.