Distillation is bubbling up

By Seán Ottewell

ChemicalProcessing.com

High capacity utilization is prompting significant efforts to optimize column performance

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Hopes that fallout from the subprime lending fiasco would mainly impact the U.S. and Western European economies seem largely misplaced now as its malaise spreads ever wider around the globe. The ongoing tribulations of the world economy are making even the modest growth predictions made late last year by the American Chemistry Council (ACC), Arlington, Va., seem quite optimistic. ACC did warn, though, that ongoing financial problems and an oil price shock could take a toll.

Other problems are emerging, too. Even before subprime problem surfaced, China was always going to be the economic driving force for global development over the next few years. Now, however, that country is suffering its worst winter in decades. Food costs have climbed 18% as a result of snow-related supply problems. Inflation has hit an 11-year high in January, an annualized 7.1% — up by more than ½% compared to the previous month.

On the other hand, however, a low dollar is good for U.S. exports, particularly if overseas growth remains robust. If this is the case, last year’s $154 billion export figure could rise to $169 billion this year and $180 billion in 2009, says ACC.

Latest data from ACC show shipments of chemicals rising and capacity utilization hovering just below 80%. So, continuing strong demand for exports should edge U.S. capacity utilization to 80% in 2008.

It’s not just the mainstream chemical producers that are enjoying high capacity utilization. In August, the American Petroleum Institute (API), Washington, D.C., reported 90.8% refinery utilization rates, the highest level since September 2006. Production of gasoline hit 9.325 million bbl/d, another new record. By November, refinery activity was the highest in three years.

API’s annual statistical report published in late January noted that overall capacity utilization averaged 88.1% for all of 2007, up slightly from a year before.

Meanwhile, the International Energy Agency (IAE), Vienna, Austria, predicts that global refinery crude runs will average 74.3 million bbl/d for the first quarter of 2008, a year-on-year increase of 1 million bbl/d.

While it remains to be seen how much further damage the subprime fiasco can do to the world economy — there are rumors of major investments in the Far East being postponed by many years — high capacity utilization is spurring companies to place even more emphasis on asset optimization. And, because at many plants, distillation plays a crucial role, demand for mass transfer products and services is booming. Operating companies are looking to gain improvements through everything from better packings and trays to improved control systems and simulators.

“The biggest trend at the moment is the massive number of projects. There’s a huge uptake after the lull in the late 1990s,” says Gary Sturtevant, industry segment leader in UOP’s Refining Business Unit, Des Plaines, Ill. UOP also is building up a healthy stream of business for its new Ecofining technology. This converts raw materials such as vegetable oils into biodiesel. “The challenge here is that we are not dealing with traditional hydrocarbon feedstocks, so we are having to do a lot of development work associated with their [the biofeedstocks] handling and processing,” he notes.

Improvements in internals

UOP is seeing continuing strong demand for its high performance distillation trays, notes Sturtevant, particularly for its high capacity MD ones (Figure 1).

They typically are used for large liquid loads, especially when the volumetric ratio between vapor and liquid rates is low — common conditions in medium- to high-pressure services. Because MD trays can be used at close spacings, they can reduce both the height and diameter of a new column compared to one fitted with conventional multipass trays, says the company, thus significantly cutting vessel shell costs. The closer spacing means that retrofitted towers can contain far more trays, increasing product purity and recovery while reducing reflux ratio and therefore energy consumption.

“The point here is that we are able to get more out of existing columns and make new columns smaller to achieve the same throughput,” Sturtevant says.

It’s a similar story with Koch-Glitsch, Wichita, Kan., another major player in the mass transfer equipment and services market. Like UOP, the company has a long tradition of manufacturing trays and in pioneering specialty high capacity designs.

For instance, Superfrac trays, which are the culmination of 10 years of development work, are designed to produce the maximum capacity and maximum vapor/liquid contact efficiency achievable with crossflow distillation trays. They have provided the highest combined capacity and efficiency of any crossflow tray tested so far at Fractionation Research Inc. (FRI), Bartlesville, Okla., boasts Koch-Glitsch.