What is the reason for overlapping products in fractionation towers?
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What is the reason for the high final boiling point of the top product and the low initial boiling point of the bottom product? There are also solutions. Thank you. This post was last edited by leisure929 on 2009-4-26 17:43 ]
The fractionation effect of the fractionating tower is poor, and the products are mixed.
This problem is a simple and complex problem, and there are certain differences between normal pressure and catalytic treatment. The so-called overlap is caused by unclear separation of offline products when they arrive online. This is related to temperature and circulation volume. Please be more specific in your explanation.
The main reason is that the separation effect is poor and overlap occurs. It is generally adjusted by adjusting the circulation volume of each section and the return temperature to the tower.
Overlap of adjacent fractions: If the final boiling point of one fraction is higher than the initial boiling point of the next fraction, the intersection of the two points is called the overlap of adjacent fractions. 1. The feed temperature is high, the gas phase load is large, the line speed is large, and mist is entrained. 2. The small stripping steam also causes overlap. 3. Excessive reflux at the fractionation top also affects the efficiency. 4. The equipment load is too large. In particular, the stripping tower is small, the distillation stop time is short, the diameter of the volatilization line at the top of the tower is small, and the light components cannot get out.
The efficiency of fractionation tower trays is also the main reason. The fractionation tower trays of our factory are divided into two parts. One part is a serpentine tray with high-efficiency float valve trays on layers 1-8 and 9-28, which has better separation effect. Secondly, the extraction amount and return amount at each point are also important indicators to prevent overlap. Then there is the phenomenon of overlap in the effects of pressure and temperature changes in the fractionation tower on the separation. Therefore, controlling the process operation of the fractionation tower is the main means to solve the overlap.
It is normal for the products of the fractionating tower to have a certain overlap, because it is not a distillation tower but only a rough separation, and it does not need to be too precise. If the overlap is serious, it is necessary to consider whether the fractionation tower has salt formation.
There are many cases of overlap. A slight overlap is okay, it is normal, but a large overlap cannot be adjusted for a long time, indicating that 1. there may be a problem with the tray. 2. Fluctuations in feed components, pressure fluctuations, feed volume fluctuations, and temperature fluctuations will all cause overlap, but these are only temporary. Another situation is that the operating parameters and process indicators are unreasonable. For example, under the premise of increasing tower pressure, the dispatch order is to increase gasoline production, which may cause overlap.
If it's a catalytic fractionation tower, I want to know what lz means. Haha, I still don't quite understand this overlap.: Is it the crude gasoline entering the diesel, or is it that other oil slurries contain more light components? Please explain in detail.
Overlap of adjacent fractions: If the final boiling point of one fraction is higher than the initial boiling point of the next fraction, the intersection of the two points is called the overlap of adjacent fractions. Reasons for overlap: 1. The gas and liquid phase load in the tower is too large ； 2. The tray structure is not good ； 3. The tray is damaged due to long-term operation ； 4. Salt formation on the tray ； 5. The return flow is too large in order to control product quality during long-term and small-volume production. ； 6. Tower operation fluctuates too much.
The fractionation effect is poor and the gas-liquid phase contact time is short. solution: First, we should analyze whether the overlapping part is the product at the bottom of the tower or the product at the top of the tower. If it is the product at the top of the tower, it means that the gas phase load is too large and the liquid phase load is too small. The liquid phase load should be increased, that is, the reflux ratio is increased, and the gas phase load is reduced, that is, the temperature at the bottom of the tower is lowered. ； vice versa.
1. Overlap indicates poor separation effect. 2. Increase the temperature of the reboiler or reboiler, or increase the amount of superheated steam. 3. Increase the feed temperature. 4. Reduce the top pressure of the fractionation tower.
The overlap is due to the unstable operation of the tower caused by excessive load on the gas and liquid phases of the tower, unstable pressure, unstable temperature, unstable liquid level, unstable feed volume, unstable feed temperature, and unstable components.