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The Phase Rule in Distillation

This is perhaps an idea you remember from high school, but never quite understood. The phase rule corresponds to determining how many independent variables we can fix in a process before all the other variables become dependent variables. In a … Continue reading

05. March 2020 by Jack
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Loss of Once-Through Thermosyphon Circulation

There are several common causes of loss of circulation. The common symptoms of this problem are • Inability to achieve normal reboiler duty. • Low reflux drum level, accompanied by low tower pressure, even at a low reflux rate. • … Continue reading

04. March 2020 by Jack
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Heat-Balance Calculations

If you have read this far, and understood what you have read, you will readily understand the following calculation. It is simply a repetition, with numbers, of the discussion previously presented. However, you will require the following values to perform … Continue reading

26. February 2020 by Jack
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Internal Reflux Evaporation

The tray temperatures in our preflash tower, shown in Fig. 6.4, drop as the gas flows up the tower. Most of the reduced sensible-heat content of the flowing gas is converted to latent heat of evaporation of the downflowing reflux. … Continue reading

24. February 2020 by Jack
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Causes of Tray Inefficiency : Loss of Downcomer Seal

We stated that the top edge of the outlet weir is maintained about 0.5 in above the bottom edge of the inlet downcomer to prevent vapor from flowing up the downcomer. This is called a 0.5-in positive downcomer seal. But … Continue reading

12. February 2020 by Jack
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Conversion of Sensible Heat to Latent Heat

When we raise the top reflux rate to our preflash tower, the tower-top temperature goes down. This is a sign that we are washing out from the upflowing vapors more of the heavier or higher-molecular-weight components in the overhead product. … Continue reading

24. January 2020 by Jack
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Tower Internal Manways

Contract maintenance workers often will not replace the tray manways unless the tray manway is adjacent to a tower external manway. They reason that once the tray manways that are visible from the tower manway are closed, there is no … Continue reading

30. April 2011 by Jack
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Tower Final Inspection

At a Gulf Coast refinery, the reboiler thermosyphon circulation could not be reestablished after a turnaround. The tower was reopened and a lessthan-alive contract employee was found stuck in the reboiler draw-off nozzle. At the Good Hope Refinery (when I … Continue reading

30. April 2011 by Jack
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Shear Clips

If a tower has a history of tray deck damage due to pressure surge or high liquid level, the mechanical integrity of the trays should be upgraded. This is done by the use of shear clips, as shown in Fig. … Continue reading

30. April 2011 by Jack
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Seal Pans Downcomer

The downcomer from the bottom tray is submerged in a seal pan (see Fig. 8.3), to preserve its downcomer seal. I always set the horizontal dimension between the over-flow lip of the seal pan, (dimension y) the downcomer at four … Continue reading

30. April 2011 by Jack
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