An important element of distillation column operation and control is to maintain an overall mass balance so that the reboiler contains an appropriate amount of liquid and does not get flooded or dried out. This is also important for operational safety and continuity of the entire plant, in which the distillation column is one downstream unit operation process. Typical operation of the reboiler keeps all the heating tubes submerged in the liquid. This not only ensures the efficient use of the condensation heat but also avoids some safety hazards associated with higher temperatures in exposed heating tubes.
Control of the reboiler liquid level is typically achieved by using a level controller, as seen in this equipment. A differential pressure transducer measures the liquid level in the reboiler. This signal is used as an input for the level controller, which adjusts the bottom product flow rate to achieve the desired liquid level. This approach causes the overall mass balance for the operation to be maintained automatically. The dynamic flow rate of the bottom product is monitored by an online flow meter.
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