It takes arresting design and lively colors to move consumer goods packaged in paperboard boxes from supermarket shelves to shopping carts.  The Jefferson Smurfit plant in Stone Mountain, Ga., should know.  It prints tons of eye-catching, high consumer appeal paperboard annually. 
The paperboard is run through eight different presses, each with a different ink or coating.  Approximately 450 cartons are converted every minute on 55-in.-wide web presses.  To avoid smudging, the inks and coatings printed on each pass must be dried almost instantly. 
A year ago, the plant redesigned and improved the process whereby the solvent-laden exhaust gases from its printing presses provide the energy required to heat the dryers. 
A heat recovery process designed by Thermo Wisconsin using Paratherm heat-transfer fluid generates about 85 percent of the hot air needed to dry the printed paperboard. 
Using practical and economic sense 
Organic solvents facilitate the high-speed drying of the inks and coatings used by JSC, but federal and state regulations limit the release of VOCs to the environment.  The best solution for JSC is to burn them. 
The system starts with the duct-work at the top of the eight printing units designed to capture the VOC-laden gases and send them to a Thermo Wisconsin Titan recuperative thermal oxidizer (Model 2270).  The 150 deg F incoming gases are preheated to 1,000 deg F by the primary heat exchanger.  At the point, they pass through the burner where processed VOCs and natural gas are used to increase the temperature of the gases to the desired combustion temperature.  Once VOC oxidation is complete, the gases are returned to the primary heat exhanger at 1,400 deg F to preheat newly arriving VOC-laden gases. 
The clean air then leaves the oxidizer and enters an air-to-oil heat recovery coil, which extracts energy from the clean oxidizer exhaust gases and uses it to heat thermal oil.  The thermal oil is then returned to the process dryers, supplying nearly all of the heat required. 
JSC selected Paratherm NF as the heat-transfer fluid for the new system because of its environmental and safety characteristics.  "We did not want a big clean-up problem if there was a leak or spill," says Melvin Johnson, plant engineer. 
When the VOC capture system was designed by Thermo Wisconsin, the physical properties of the NF fluid were used to calculate heater size, pressure drop and other system design considerations.  The ink drying application required heat-transfer fluid heated to 400 deg.  The NF fluid is "nonfouling" and will not cause hard carbon formation to build on heated surfaces - even when overheated.  Moreover, it reportedly has one of the lowest viscosity ratings of any high-temperature heat-transfer fluid.  This becomes increasingly important when the primary heat-transfer fluid loop is a long one - such as at JSC. 
Johnson says the Paratherm NF fluid is performing well and passed the company's regularly scheduled testing and evaluation with consistently high marks. 
A Thermo Wisconsin oil economizer is installed in the stack of the thermal oxidizer.  When supply temperatures fall below required levels, reserve is provided by a fully modulating 6 MM Btu/hr thermal fluid heating system manufactured by GTS Energy (Model DH-V-15/40).  In addition to the heater, GTS provided the pump skid and expansion tank. 
All temperatures are controlled and monitored at each press by CNC controls outside the pressroom.  The air heated for the drying operation is drawn from ambient air in the plant.