How to determine the reflux flow rate in distillation columns
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In the actual production process, the backflow rate has a direct impact on product quality; if the backflow rate is low, the product quality will not meet the requirements, while too high a backflow rate increases energy consumption. How to determine an appropriate return flow rate under load addition and reduction conditions? I hope all the experts can give me some advice
First, provided that the product quality is satisfactory, adjust the reflux at the top of the tower; either too high or too low a level can affect the flash point and final boiling point
It’s true to say that as well; one can only figure things out slowly. Another issue is the pressure drop across the tower. Generally, what is an appropriate level for the pressure drop in a plate tower or a packed tower? What should it not exceed?
Adjust the reflux volume according to the product quality requirements.
The original poster is well aware that backflow affects product quality. But in a distillation tower, which factor determines the quality of the reaction product? It depends on how high the quality of your products is! Under normal circumstances, controlling the temperature at the top of the tower or the temperature of a specific tray inside the tower is sufficient to ensure product quality, and controlling temperature fluctuations is achieved by adjusting the reflux rate. If it is a high-purity column and the purity requirements for the product are very high, then temperature differences are used for control, and regulating these temperature difference fluctuations is achieved by adjusting the reflux flow rate. So, it’s necessary to analyze each specific case; determine how your distillation tower is controlled, and adjust the reflux flow based on fluctuations in temperature or temperature differences within the tower.
The operation of a distillation column requires mastery of three types of equilibrium: material balance, heat balance, and gas-liquid phase equilibrium. During operation, control of the material balance is usually the primary focus, with the heat balance adjusted accordingly, in order to ultimately achieve gas-liquid phase equilibrium. The reflux ratio is generally controlled based on the design reflux ratio of the tower; in most cases, the priority is to ensure that the product meets the required standards.
Hehe, an endless question. It is recommended that, before understanding the design principles behind the process parameters, it is best to control things according to the existing design parameters first. A few people have already made it very clear.
Of course, it is adjusted based on the product specifications
The backflow rate was determined at the initial design stage, right? This is one of the important parameters in distillation; it’s best not to tamper with it. These devices and parameters work together as a set, and changing one of them could trigger a chain reaction.
When designing the reflux flow rate for a distillation column, the fluctuating impulse of the column is generally taken into account. During normal control, the setting can be reduced appropriately; adjustments should be made in small amounts multiple times, with the analysis results serving as a guide. Operators are required to operate carefully, increasing the reflux rate promptly in case of large fluctuations. Adjustments can be made in advance based on the temperature at the top of the tower or the temperature difference, in order to minimize the occurrence of defective products.
This post was last edited by goldliyang on 2017-10-24 at 13:32. Online monitoring in the chemical industry enables real-time control on the DCS, just like in the case of temperature and pressure.