Theoretical solution

Extraction is a method for separating mixtures based on the difference in solubility of the two components in the same solvent. For example, in the case of a liquefied gas mixture containing a small amount of methanol, water can be used as an extractant. The liquefied gas enters the extraction tower from the bottom, while the extractant water flows down from the top; they come into contact in a counter-current manner, with methanol dissolving into the water. Since liquefied gas is insoluble in water, it exits the tower from the top, while the methanol-water solution emerges from the bottom of the tower. Thereby achieving the separation of methanol and liquefied gas

An azeotrope refers to a mixture that, under certain pressures, forms a relatively stable compound; the boiling point of this compound is generally lower than that of the individual components of the mixture. The azeotropic distillation tower of MTBE plants can be used as a reference

Extraction: In simple terms, liquid-liquid extraction involves transferring solutes from one solution into another solvent. For example: carbon tetrachloride is insoluble in water. When carbon tetrachloride is added to iodine water and shaken, the iodine molecules move into the carbon tetrachloride layer; this is what is known as extraction. An azeotrope refers to a homogeneous solution composed of two or more different components; when these components are mixed in a specific ratio, the mixture has only one boiling point at a fixed pressure, and at this point it is called an azeotrope. Distillation makes use of the distribution of different components between the gas and liquid phases, achieving separation through multiple processes of mass and heat transfer between these phases. The distillation method also varies depending on the substances to be separated. For example, a binary system separating ethanol and water. Since ethanol and water can form an azeotrope, and the azeotrope temperature at atmospheric pressure is very close to the boiling point of ethanol, ordinary distillation methods can only yield a mixture of ethanol and water, without allowing the production of anhydrous ethanol. To this end, a third substance is added to the ethanol-water system; this substance is known as an azeotrope-forming agent. An azeotrope-forming agent has the property of being able to form a minimum azeotrope with one or several substances in the system to be separated. During the distillation process, the boiling agent will evaporate from the top of the tower in the form of an azeotrope, while anhydrous ethanol is obtained at the bottom of the tower. This method is called azeotropic distillation.