Following a national trend, a southeastern pharmaceutical manufacturer produces transdermal patches in a big way. The self adhesive patches apply directly to the skin for time-release of medicine. To meet consumer demand for them, the company recently added a second production line at a plant it recently built.

In the manufacturing process, a coating machine applies medication to the patch in layers, and then hot air cures the medicine. Needing a system to supply heat for curing, the company turned to Plymouth Michigan based Durr Environmental, a manufacturer of air pollution control systems that had previously supplied equipment for the facility.

Des Champs supplied the VariMax system, an indirect-fired recirculating gas heater. A burner in the combustion chamber generates heat, and the combustion products recirculate by means of a fan, rather than flowing straight up a stack.

Indirect firing involves transferring heat from one airstream to another while keeping them separate. As Yves Pszenica, project manager at Durr Environmental, explains, "The customer didn't want combustion byproducts in their process air." Because an air-to-air plate heat exchanger provides an ideal means of heat transfer, Durr specified two Des Champs Thermo-Z models. A larger primary heat exchanger in the recirculating box uses exhaust air at 875 degrees F to heat outside air from 40 degrees F to 410 degrees F for the curing process. A secondary heat exchanger uses bleed air from the exhaust to preheat inlet combustion air, saving fuel.

In the past, indirect heaters have suffered from low efficiency and high fuel consumption when compared to direct-fired burners. By combining the Des Champs heat exchangers with the recirculating burner yielded an efficiency of over 90%, nearly equaling that of direct-fired heaters.

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