Liquid Surge Volume
Unless surge volume has been specified elsewhere, provide liquid volume between the maximum and minimum liquid levels to give the following residence times for each product stream. This is for control purposes:
Stream Time, Minutes
Distillation Column Reflux 6
Net Product to Storage 4
Net Product to Onplot Column or Heater 10
Net Product to Offplot Processing 20
These volume requirements are additive. Thus, 100 gpm of reflux and 200 gpm of net product to storage would require 1400 gallons of surge.
For continuous water drawoff, size the water drawoff leg for a minimum of 10 minutes residence time. For manual, intermittent drawoff, size the leg to require drawoff no more than once per shift (usually 8 hours).
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