Approximately 450 cartons per minute are run through eight high-speed presses. Precise temperature control is required to dry the inks instantly and prevent smudging. Ductwork at the top of each press captures the solvent-laden gases and sends them to a recuperative thermal oxidizer. A heat exchanger in the oxidizer stack recovers approximately 85 percent of the hot air needed to dry the printed paperboard. Exhaust gases from the printing presses are preheated from their incoming temperature of between 150 F and 1000 F by the heat exchanger.
Natural gas is added to bring the gases in the burner to combustion temperature.
When the VOCs are oxidized, the 1400 F oxidizer exhaust gases return to the heat exchanger where they are used to preheat incoming VOC-laden gases. This extracts energy from the clean exhaust gases to heat the thermal oil used to supply nearly all of the heat required in the process dryers. This efficiency is due to the fluid's low viscosity, which makes it easier and faster to pump through the heat transfer fluid loop. Typically, fluids are more volatile at a low viscosity. 600 F. NF has one of the lowest viscosity ratings of any high-temperature heat transfer fluid.