Could the experts help analyze why the heat exchanger at the bottom of the tower is not performing its heat exchange function?
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Our plant has a flash tower, which is heated at its bottom using heat transfer oil. Everything was normal at the beginning of operation, but as the processing capacity was increased, the temperature at the bottom of the tower started to drop and wouldn’t rise again (the increase in processing capacity was only about 10%); the temperature there remained around 50 degrees, whereas it needs to be raised to around 130 degrees. The current temperature of the heat transfer oil is 180 degrees. Can you analyze the reasons? The heat exchanger shouldn’t be clogged; it was just serviced. Could everyone please provide some ideas?
The low heat transfer efficiency of the heat exchanger at the bottom of the tower may be caused by the following reasons: 1. **Insufficient flow rate of the heat transfer oil**: Even if the temperature of the heat transfer oil is sufficient, an insufficient flow rate will result in inadequate heat transfer. Check whether the flow rate of the heat transfer oil meets the design requirements. 2. **Air or gas leakage within the system**: The presence of air or other gases in the system can affect the efficiency of heat exchange. Check whether the system is properly sealed and free of leaks. 3. **Insufficient heat exchange area**: As the processing capacity increases, the existing heat exchange area may not be sufficient to meet the increased heat exchange requirements. It is necessary to consider increasing the heat exchange area. 4. **Control system issues**: Check whether the control system is functioning properly, such as whether the flow rate of the heat transfer oil and temperature control are accurate. 5. **Increased thermal resistance**: Although it has just been serviced, it is still necessary to check whether there is dirt or carbon buildup inside that could lead to an increase in thermal resistance. 6. **Issue of matching the heat exchanger configuration to actual operating conditions**: If the design of the heat exchanger is not well-suited to handle an increased processing capacity, it will also affect the efficiency of heat exchange. By examining the above aspects, it should be possible to identify the problem and make the necessary adjustments or repairs. .
Could you provide a flowchart? Try lowering the pressure in the tower slowly
Thank you for your reply. I’m taking a break; I don’t have any diagrams handy. It’s just a normal hydrogenation unit followed by a distillation unit, with a flash tower coming after the low-pressure section. The pressure is already very low; it’s basically at slightly positive pressure. I’m wondering if it’s because the pressure is too low, causing the liquid to vaporize easily and thus creating air blockages in the heat exchanger; I think I’ll try increasing the pressure
Thank you for your reply. The heat exchange area you mentioned could indeed be the cause; I increased the temperature of the heat transfer oil by 10 degrees, and as a result, the low-temperature value rose from 50 degrees to 110 degrees!
If it has already been used and is a heat exchanger that has passed the design checks, check whether there is any air blockage between the two layers of the heat exchanger.