Fractionator operation

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This post was last edited by Guan Gongyu on 2017-10-10 at 15:23. Operation adjustments of the distillation column: Previously, basic knowledge about distillation columns was covered, including the establishment of initial equilibrium in such columns; now we will discuss the operation adjustments for distillation columns. First, we need to understand the function and principle of a distillation tower: 1. The function of a distillation tower is to separate different components ； 2. The principle of a distillation tower is to utilize the difference in boiling points of various substances under certain pressure to achieve separation. Once we understand the function and principles of distillation columns, we can operate them by applying those principles: 1. Temperature (bottom temperature of the column, top temperature of the column): The level of the bottom temperature determines, to a certain extent, the top temperature; it also determines the components that are involved in the distillation process. For example, a bottom temperature of 180°C means that only those components that can boil at temperatures below 180°C under that pressure will be separated ； The top temperature determines the dry point of the product at the tower top ； The distillation effect is best when the tower top temperature and the temperature difference at the tower top are minimal. (Rationale: The number of trays is generally fixed; the smaller the temperature difference, the higher the distillation precision of the trays, that is, the smaller the difference in boiling points of the materials on the trays.) 2. Pressure (top pressure): The pressure in the distillation column is adjusted by controlling the emission of non-condensable gases from the top of the column. The higher the pressure, the higher the boiling points of the components, and the boiling points of different components will vary accordingly. 3. Number of trays: As mentioned in the basics, multiple heat exchanges of the material and changes in its properties occur on the trays. The more trays there are, the more times such changes take place, and the purer the material on the trays becomes. 4. Rejection ratio: From the outside of the tower, the amount of vapor rising from the bottom of the tower equals the rejection volume plus the amount of product at the top of the tower. When the rejection ratio is high, the amount of material involved in the exchange on the tray becomes closer to the amount of vapor, resulting in better performance; however, increasing the rejection ratio excessively leads to significant increases in energy consumption. 5. Material difference: The greater the difference in boiling points of the materials, the better the distillation effect. 6. Material feed temperature and location: The material feed temperature determines the changes that occur as the material enters the distillation tower. If the feed temperature is high and the feed location is high, it will cause the material to be carried directly into the top product of the tower before it can be separated; if the feed location is low, it will result in increased energy consumption, which is not worthwhile. Personal understanding: The material feed temperature and location should be similar to the temperature of the tray at the feed inlet of the current distillation tower. Recommended reading: Basics of fractional distillation towers http://bbs.hcbbs.com/thread-1726383-1-1.html (Source: Haichuan Chemical Industry Forum)