Reason why the pressure in the atmospheric distillation column for methanol is lower than that in the atmospheric reflux tank
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In methanol distillation, the pressure at the top of the atmospheric tower and the pressure in the reflux tank fluctuate regularly, with an inversion of pressures – the pressure in the atmospheric reflux tank being higher than that at the top of the tower. What causes this phenomenon, and how should it be addressed? This phenomenon has been occurring frequently lately. I seek advice from all the experts out there. The pressure trend is as shown in the figure below
First, inspect all control valves and instrument controls. For example, issues such as liquid in the positive pressure tube of the level gauge can be addressed by trying to change the reflux ratio or reducing the load; once the distillation conditions stabilize, the load can be increased back to normal levels to identify the cause. It would be best to include a flowchart of the process for easier discussion and reference.
Does it affect operation and quality? If it doesn’t cause any problems, then it’s not a big issue. This is likely due to an increased load, resulting in more condensation. As a result, the gravity of the condensate increases, and if there is a vapor equilibrium line from the top of the tower to the reflux tank, pressure can be balanced, preventing pressure fluctuations caused by the increase in the gravity of the condensate.
Consider whether there is liquid accumulation in the balance line at the top of the reflux drum; such accumulation can easily lead to an inversion between the pressure in the drum and the pressure at the top of the tower.