Temperature adjustment range at the bottom of the distillation column
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The distillation unit controls the bottom temperature through hot and cold circuits. The main purpose is to control the bottom of tower liquid level and the amount of oil slurry discharged, but the adjustment range is very large; often, the temperature at the bottom of the tower drops by 10 degrees within just a few seconds. The fluctuation range can reach up to 30 degrees, which has a significant impact on stable heating. I’m worried that such handling might affect the equipment and product quality. Please advise me on how to proceed.
The circulation of the bottom slurry in our distillation column remains essentially unchanged, with the bottom temperature staying around 340 degrees. Additionally, the reboiler at the bottom of our stabilizer uses fractional distillation as its heat source, and the adjustment range is usually not large. I’m not sure what your specific procedures are, but based on what you’ve described, large fluctuations in the temperature of the slurry system can cause leaks in the equipment; it would be best to adjust the operations to maintain stability as much as possible. In particular, the slurry system has a significant impact on the long-term operation of the plant.
I agree with the view from the first floor: by maintaining a constant feed rate and reaction temperature, stabilizing the circulation rate of the slurry can help keep the temperature in its cooling circuit stable.
Is there a problem with the control valve? There shouldn’t be such large fluctuations.
What you’re referring to is the effect of human intervention – when the opening and closing range of the control valve is too large, it can easily lead to instability in the quality of the products produced. This approach is not advisable as it has an impact on the equipment. The temperature needs to be kept stable. Stable heat supply relies on the middle section; however, unstable bottom temperatures cause fluctuations in the temperature of that middle section, thereby affecting the stability of the heat source. :)
It seems you are working in a position related to stable operations; therefore, carrying out distillation processes in this manner is not advisable. There is also a heat exchanger for the slurry and the intermediate products, so fluctuations in the slurry’s temperature will certainly affect the steady heat supply provided by the stabilization system. I suggest you communicate more with the personnel responsible for distillation tasks, and you could also discuss this matter with the team leader. Hehe
The amplitude is too large; is it in automatic mode? Adjust the PID again. Frequent large adjustments up and down the tower are not advisable – could this cause blockages in the washing section?
Switch the hot and cold streams to manual control and adjust them gradually; use oil slurry to be fed back into the tower in order to control the temperature at the bottom of the tower. This is how we have always done it, and it works very well.