Distillation vacuum boiling point environment feeding problem
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Production status: The vacuum of the rectifying kettle is -78~-83KPa, the outlet pressure of the magnetic pump on the first floor is 0.3~0.4MPa, and the material is pumped into the rectifying kettle. The rectifying kettle is at a height of about 10M on the third floor. The coil in the kettle is heated. The temperature of the rectifying kettle is about 70. The material is The boiling point in this vacuum state is about 55°C. The feed regulating valve and metal rotor flowmeter are on the third floor at the same height as the distillation kettle. The feed flow rate is designed to be 450~600L/H, and the feed pipe diameter is DN40. The current problem is that the flow rate display fluctuates very much. Current analysis reasons: Under vacuum, the boiling point of the feed material (about 55°C) is lower than the temperature of the material in the kettle (about 70-80°C). The feed material vaporizes instantly, and the vacuum degree difference at the feed port is transmitted to the feed pipe. The pressure difference at the feed port becomes smaller, the feed flow rate decreases, the vacuum degree at the feed port increases, and the feed flow rate increases. This forms a pulsating pressure change at the feed port, which extends to the feed pipe to form a pulsating flow. Is this analysis correct? (Faults with the feed pump and flow meter have basically been ruled out, and there are no air leaks in the pipelines. ) plan: Feed into the distillation tower still (temperature is about 60°C), so that the distillation still is equivalent to a falling film evaporator. Can this problem be solved? (The material transfer from the distillation tower to the distillation kettle is transferred by pump) Please see the picture
Replenish: The temperature of the distillation kettle is high because of the accumulation of heavy components and the discontinuity of the tower kettle.
There may be a software problem, such as the wrong algorithm for converting flow rate in the PLC program. This situation may exist
Thanks for the discussion. I don't know much about this, but both the flow counter display and the pointer display fluctuate greatly. The pointer is directly affected by the movement of the rotor, so it should have nothing to do with the PLC.
It should be two-phase mixed flow at the flow meter, and the flow meter cannot work properly. There is already gas phase flow in the distillation kettle. It is recommended to improve the working condition of the flow meter. To maintain the temperature, corresponding pressure is required, or the feed temperature must be lowered not to exceed the boiling point at the feed pressure.
Yes, the material first passes through the regulating valve and then through the flow meter
Will it be more stable if the flow meter regulating valve is adjusted down?
The regulating valve is installed incorrectly, behind the flow meter. Pipe not full after pressure surge.
If your analysis is correct, the vacuum of the distillation kettle will fluctuate.； If there is no change in the vacuum, the reason for your analysis is not valid.