Regarding the change of raw materials for aromatic hydrocarbon extraction, the adjustment method of the extraction tower
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The content of non-aromatic hydrocarbons in the extraction feed increases. How to adjust the extraction tower? Aromatic hydrocarbon extraction includes SED (extractive distillation) process and liquid-liquid extraction process. The extractive distillation process is discussed here. The raw materials for extraction are benzene, toluene and non-aromatic hydrocarbons. The extractive distillation process is used (please separate it from liquid-liquid extraction), which consists of an extractive distillation tower, a non-aromatic hydrocarbon tower, a solvent recovery tower, etc. Now the non-aromatic content in the aromatic products recovered from the top of the tower has increased. How should the extractive distillation tower be adjusted? There are 3 ideas below : 1. It can be seen as the non-aromatic hydrocarbon content of the extraction feed component increases, then the amount of non-aromatic hydrocarbon gas phase in the extractive distillation tower increases. The steam volume of the extractive distillation tower should be increased to meet the rising power of the non-aromatic hydrocarbon gas phase, and the solvent ratio should be increased accordingly to dissolve the aromatic hydrocarbons in the gas phase. (This plan is provided by UOP) 2. A petrochemical company’s adjustment plan is to reduce the solvent ratio and increase the bottom temperature of the extractive distillation tower, thereby increasing the temperature of the sensitive plate of the extractive distillation tower. 3. Reduce the solvent ratio, thereby dissolving less non-aromatic hydrocarbons and reducing the non-aromatic hydrocarbons in the aromatic hydrocarbon products recovered from the top of the tower. The above adjustment plan seems a bit contradictory. The adjustment ideas are different and the methods used are opposite. The first method is to extract steam and increase the solvent ratio; the second method is to extract steam and reduce the solvent. May I ask how you handle this situation when your device encounters it?
The non-aromatic content in the recovery tower increases, indicating that the selectivity of the solvent is reduced and the volume ratio is too large. The volume ratio can be reduced while ensuring the temperature at the bottom of the tower. Of course, increasing steam is relative. As you said, if the non-aromatic content of raw materials increases, the best way is to reduce the solvent ratio. If possible, you can fine-tune the solvent temperature. This is generally not done by w adjustment method.
To add, you should also check whether the aromatic hydrocarbon content in the raffinate oil is high.
When the non-aromatic content increases and the aromatic content decreases, the temperature of the tower kettle should be increased and the solvent ratio should be reduced.
What is the non-aromatic content in the feed? Can you give specific data? How many feeds are there to the extraction tower?
In fact, there are many reasons. The poster should explain the production conditions in detail, such as whether the processing capacity is high or low, whether the wet solvent is being recycled, the raw oil components, and the reforming reaction temperature, all of which will affect extractive distillation.