Distillation deserves a high profile

What symbolizes the chemical industry? To many, undoubtedly it’s a plantscape full of fractionating columns. While a reactor certainly conveys chemical synthesis, it doesn’t offer the towering presence of a distillation unit.

Going beyond visual impact, distillation columns stand out in another way — they typically represent a large part of the energy consumption at many sites. So, columns really deserve particular attention. CP has recently published a number of articles to help you make the most of your columns.

Efforts of course should begin at the very earliest stage of a project. As Ray Sowiak and the late John Kunesh stressed (in "Distill your quote request") a lot of details require careful scrutiny before any request for proposals. For instance, don’t base design loads on simulations alone, they warn, and do your own preliminary column sizing. They also point out a number of other details that can allow you to get adequate and comparable proposals from vendors of tower internals.

In a follow-up article ("Determining the best hardware quote"), Sowiak and Kunesh give some hard-nosed guidance for assessing the proposals you get. Always verify that the devices offered actually will meet capacity, efficiency and pressure-drop criteria, as well as turndown, mechanical-strength and other requirements. Be realistic about the value of process guarantees. And don’t forget to consider factors such as delivery schedules and possible material surcharges.

Achieving trouble-free startups and optimum performance depends upon proper installation of tower internals. Frank Rukovena provides some practical insights gleaned from experts at Fractionation Research Inc., the non-profit research and testing organization ("Properly install column"). Checks should start well before installation — both at the fabrication shop, confirming dimensions, component location, levelness and even for removal of scale and dirt, and then on the tower shell once erected, for roundness, vertical-ness, etc. Rukovena also includes specific real-world tips for the installation of key components such as support plates, packing and trays. (By the way, he handles distillation questions on the Ask the Experts feature.)

This issue adds to the arsenal of useful information about distillation.

First, Andrew Sloley poses seven key questions that you should ask about your columns to get a realistic handle on their energy efficiency. For instance, is your control measurement in the right place? And have you checked basic heat integration? Sloley, who also writes our monthly Plant InSites column, stresses that simple steps such as operating changes and minor projects that don’t involve much process risk or capital often can save significant amounts of energy. He cites cases where savings paid for the investments after only a few months.

Meanwhile Mike Spear, our editor at large, provides an update on gamma scanning. This established technique can pinpoint problems in columns such as damaged trays and packing, liquid maldistribution, weeping, entrainment, fouling and foaming. Yet, far too few young engineers at operating companies are really familiar with it. That’s not surprising because most of the companies don’t have in-house resources to do the scans. However, as Spear reports, some vendors would like to see more of role for dedicated specialists permanently on-site.

Rest assured, we will continue to give distillation a high profile.