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Condenser accumulator arrangements

Q: I am in charge of overseeing the operation of several distillation/fractionation towers in my refinery. I have noticed that in some towers the overhead condensers are at ground level, while the accumulators are at a higher altitude. I know that this configuration is acceptable and even recommended where total condensing is required. In fact, some towers have no accumulators at all and the condensers are big enough to maintain a level and adequate volume for both product and reflux. However, in the towers in question, the condensing is partial. The accumulators have a vapor product (which control the accumulator/tower pressure) and a distillate product (on level control). Shouldn't the condensers be at a higher altitude than the accumulator? What is the importance of the location/configuration?

A: I am not very familiar with the pros and cons of the various possible condenser accumulator arrangements. Usually the accumulator is below the level of the condenser. The arrangement you describe is discussed in a book by Henry Z. Kister, titled Distillation Operations, and uses a hot vapor bypass to control the column pressure but is sensitive to piping arrangements and complicated interactions. This book also discusses other arrangements, see pages around 530 for more in depth discussion. A second book by Kister, Distillation Troubleshooting, discusses the same examples in somewhat greater detail, see pages 382 and 637. Both books give a lot of good references.