Following a national trend, a southeastern pharmaceutical manufacturer began producing transdermal patches in a big way. The self-adhesive patches contain time-released medicine and are applied directly to the skin. To meet consumer demand for them, the company recently added a second production line at a newly built plant.
In the manufacturing process, a coating machine applies medication to the patch in layers, and then hot air cures the medicine. Munters supplied a VariMax™ IFRG (indirect-fired recirculating gas) heater system to supply heat for curing. The Varimax system uses a burner in the combustion chamber to generate 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, the project manager, 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, two Munters Thermo-Z models were specified. A larger primary heat exchanger in the recirculating box uses exhaust air at 875ºF to heat outside air from 40ºF to 410ºF 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. But combining the Munters heat exchangers with the recirculating burner yielded an efficiency of over 90%, nearly equaling that of direct-fired heaters.