Chemical Processing - August 2007 - (Page 37) < > be the case. The new cooling tower has been trouble-free for over three years. We still have normal maintenance. We clean in the spring and make sure the filters are clean. But there has been no repair work on the tower, no leaks at all.” Olin Brass in East Alton, Ill., is another company pleased with its switch to plastic. “The decision was to replace our galvanized-steel cooling towers with the newer moldedplastic cooling tower design,” explains Matt Niemeyer, staff engineer. “They were 10-or-12-years-old and had already rusted completely through in several areas. All of that was in terrible shape and had to be repaired several times.” “The cooling tower was a straight splash bar design,” continues Niemeyer, “and because the tower would fill with all the heavy junk that collected as the dirty water was cooled, the grid and fill within the tower eventually collapsed.” Last year Olin changed its contact cooling method to a closed-loop clean water configuration. “We converted to a Delta Cooling Tower to overcome the inefficient open-loop system that had collapsed the fill under the weight of dirt and scale in the water,” he notes. “The closed-loop clean water system made it possible to go with the different cooling tower design. Instead of having a splash bar fill, which is about the best you can do for dirty water, we were able to go with a PVC film fill — what’s in the Delta tower. That also allowed us to change from a crossflow tower to a counterflow tower, which gives us greater cooling capacity for its size. We had a limited footprint for the tower, so that has worked out great.” “The new plastic tower is corrosion proof, and so we don’t have to worry about rust,” Niemeyer adds. “It was also the most economical price, and we were very pleased about that.” Environmental testing of equipment for oil drilling and production operations poses special demands, notes test engineer Burroughs. “I needed a cooling tower with waterdistribution power that is far from normal operating conditions… Secondly, I hate doing maintenance.” The cooling tower supports electrodynamic shakers that check whether the equipment is tough enough. “These shakers emit a great deal of heat and they’re cooled by a closed distilled water system because distilled water doesn’t conduct electricity,” he explains. “Once heated, the distilled water flows through heat exchangers that are cooled by a chill water loop. A three–year-old, 100-ton Delta plastic tower is on the other end of the chill water loop. Another similar unit was also used to reject the heat created by two 1,000-hp drilling mud pumps. It has been working fine for over 13 years.” Electricity costs to drive cooling tower fans may seem minor, but add up. increasing size and efficiency In the past, plastic cooling towers were considered “too small” for many plants and galvanized-steel cooling towers were generally chosen for packaged applications above 250 tons. However, factory-assembled plastic towers such as Delta’s TM Series can now be combined to provide up to 2,000 cooling tons in a single modularized unit. The modular design makes it easy to provide an extra margin of capacity to handle heat-load or outflow changes, or to upgrade to meet future requirements. The modular design also introduces new flexibility for conserving valuable real estate. By molding towers in a rectangular shape, some manufacturers enable users to cluster cooling towers in a group that occupies a much smaller footprint. “With the new Delta system we actually got more cooling with less tower,” says Richer. “Our old 45 × 20 × 18 metal cooling tower was replaced by a lightweight plastic model that is only half that size, yet has slightly greater cooling capacity.” While the cost of electricity to drive cooling tower fans may seem minor compared to process costs, it adds up. Direct-drive motors are more efficient and hence deliver substantial energy savings as well as more horsepower. “The two motors installed on the old tower were each 40hp, 3-phase, 480-volts. On the new tower there are four 10-hp motors,” Richer says. “So we now have only half the power requirement. Plus the new motors are more efficient than the old ones. We have not measured the energy saving, but it’s there.” August 2007 • 37 >> Taming scale Figure 1. Scale can deposit on metal surfaces (left), but not on engineered plastics, where removal only requires a washdown. www.chemicalprocessing.com http://www.chemicalprocessing.com
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