How to handle the situation where the Reconstituted components level at the top of the degassing tower is too high and does not meet the requirements
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Dear teachers, my workshop has a distillation packing tower: the feedstock enters the tower at the bottom for light-component removal, the light components are collected at the top of the tower, and the material from the bottom of the tower goes to the tower used for heavy-component removal (as feedstock there). The finished product is obtained at the top of the degassing tower, while the heavy components are discharged from the bottom of the tower. Currently, the finished product at the top of the tower does not meet the standards; its purity is around 99.4%, while the required level is above 99.5%. The content of the other reconstituent in the finished product is 0.4–0.5%, and their boiling points differ by about 10°C. The measures taken so far have been to keep the temperature and pressure in each section unchanged, while adding one distillation section and one stripping section (each 2.5 meters high, with the packing in each section being 1.5 meters high); however, there has been basically no change in the results. I’m a bit confused; I hope someone experienced can give me some advice.
When dealing with the issue of substandard reconstituted components at the top of the degassing tower, the following approaches can be considered: 1. **Check operating conditions**: First, verify whether the current operating conditions (such as temperature, pressure, and feed rate of raw materials) are optimal for the requirements of the existing raw materials and products. Inappropriate operating conditions may result in low separation efficiency. 2. **Adjusting the reflux ratio**: Increasing the reflux ratio at the top of the tower can help improve separation purity; especially when the number of theoretical plates is close to its maximum value, raising the reflux ratio can effectively enhance the purity of the product at the tower top. 3. **Optimize filler efficiency**: Consider whether the separation efficiency of the existing fillers is insufficient. You can try replacing it with a more efficient packing material, or check whether the existing packing is clogged or unevenly distributed. 4. **Increase the height of the trays or packing**: Although you have already tried increasing the height of the distillation section and the stripping section, it may be necessary to increase it further, or to optimize the layout and height of the packing layer, in order to ensure sufficient contact time and separation efficiency. 5. **Analysis of side-stream extraction**: If possible, consider adding side-stream extraction to the tower; by using these side streams, it is possible to control the amount of certain reconstituted components extracted, thereby allowing for more flexible adjustment of the purity of the products at the top and bottom of the tower. 6. **Simulation and Optimization**: Use process simulation software to conduct simulations and identify the optimal operating conditions. Simulation can help understand how different operating variables affect product purity and guide adjustments in actual operations. Through these adjustments, you can gradually approach the desired purity standard for the top product. If these measures still cannot resolve the issue, it is recommended to consult a more experienced chemical process engineer for in-depth analysis and on-site diagnosis. .
Thank you for the teacher’s detailed response. Previously, the target product could be obtained under the existing tower operation conditions, but later on, changes in the previous reaction steps led to slight variations in the composition of the materials. Does this mean that the operation conditions need to be adjusted? Does it have a significant impact on the purity of the target product? If the reflux ratio is too high, the yield becomes too low; moreover, testing showed that the impact isn’t significant, and it can just barely meet the requirements. Is it necessary to change the feed position of the degassing tower? Currently, feeding is done at the top of the tower; if it is changed to the middle or lower part of the tower, will this affect the proportion of the target product among the heavier components at the bottom of the tower, thereby leading to waste?
Changes in the previous reaction steps lead to slight variations in the composition of the materials, and it is indeed necessary to adjust the operating conditions to address such changes, as even minor compositional changes can have a significant impact on the separation efficiency of the tower and the purity of the final product.
1. Increasing the distillation section (adjusting the feed position to the middle or lower part) or raising the reflux ratio should be sufficient to meet the requirements. Or replace the tower internals with more efficient ones