Distillation is a separation process that uses the different volatility of each component in the mixture to separate each component. Commonly used equipment includes a plate rectification tower and a packed rectification tower. The principle and equipment flow of rectification are the same as ordinary rectification, except that the relative volatility between the components in the system to be separated is small (<1.05~1.10), so packing is used to realize the separation and purification of the components to be separated. There are often isomers coexisting in natural essential oils, the raw material for the production of isolated fragrances. For example, citronellol and roseol that co-exist in natural essential oils such as geraniol oil, rose oil and palmarosa oil are optical isomers. body.
Working principle: Distillation is usually carried out in a rectification tower, and the gas and liquid phases are contacted by countercurrent to conduct heat and mass transfer between phases. The volatile components in the liquid phase enter the gas phase, and the hardly volatile components in the gas phase transfer to the liquid phase, so that almost pure volatile components can be obtained at the top of the tower, and almost pure hardly volatile components can be obtained at the bottom of the tower. The feed liquid is added from the middle of the tower. The tower section above the feed port further enriches the volatile components in the rising vapor, which is called the rectification section; the tower section below the feed port extracts the volatile components from the descending liquid Divide, called the stripping section. The vapor drawn from the top of the tower is condensed, a part of the condensate is returned to the rectification tower from the top of the tower as reflux, and the remaining distillate is the top product. The liquid drawn from the bottom of the tower is partially vaporized by the reboiler, the vapor rises along the tower, and the remaining liquid is used as the bottom product of the tower. The ratio of the amount of liquid flowing back into the tower from the top of the tower to the amount of product at the top of the tower is called the reflux ratio, and its size will affect the separation effect and energy consumption of the rectification operation.