Differential Pressure in Distillation Tower
The tower differential pressure is the difference between the pressures at the bottom of the tower and the pressures at top of the tower. This difference in pressure is caused by the flow of vapor in the tower. Without vapor flow there is no different pressure. Generally if the rate which the vapor moves up the tower decreases, the differential pressure would also decrease and if the rate which the vapor moves up the tower increases the differential pressure would increase.
Changes in the differential pressure may indicate the problems exist. For example an increasing differential pressure could an indication that the feed rate is too high. Too much feed entering the tower would overload it, if this happened the differential pressure would increase and the tower would be unable to make the desired separation. In this case it might be necessary to decrease the feed rate.
Changes in the tower’s differential pressure may be caused by other problems. For example if differential pressure is increases the boil-up operate may be too high in other word the re-boiler may be returning too much vapor or vapor – liquid mixture to the tower. This problem can be corrected by reducing the boil-up operate.
Another problem that may affect the tower differential pressure is the decrease in the condenser efficiency. If the condenser’s tube is surged or plug or there is not enough cooling water flowing to the condenser, the condenser pressure would increase as a result the flow of vapor from the top tower to the condenser would decrease. This means that the tower top pressure will increase and the differential pressure will decrease. If the condenser problem is suspected, the condenser should be checked and corrective action should be taken if necessary.
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