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FLEXO Magazine : March 2009
TECHNOLOGIES & TECHNIQUES An air-to-air heat exchanger. tern as a whole, Plan A should consider upstream opportunities. For example, retrofits which reduce overall airflow to the oxi- dizer system and/or increase the concentration of solvents to be treated. Plan B should focus on the internal TER (Thermal Energy Recovery) of the oxidizer system itself. After airflow reduction, maximizing the internal energy recovery of an oxidizer system will almost always lead to the best project payback. Hence, it follows that energy recovery in the exhaust stack of the oxidizer is Plan C. Now calling it Plan C is by no means meant to downplay the opportunities associated with oxidizer stack energy recovery. The only intent is to fit the concept into the greater framework of energy usage in the oxidizer system as a whole. There are many reasons why Plan A and/or Plan B as de- fined above may not be attractive or even feasible-making Plan C: energy recovery in the oxidizer exhaust stack-the best overall choice for energy conservation efforts. The second reason that the letters C, D and E are a better fit for the title of this section is that those three letters represent the challenges associated with energy recovery efforts in oxidizer exhaust stacks, namely: · Capturing the energy from the stack itself. · Delivering the energy back into the plant cost-effectively. · Employing the recovered energy effectively inside the plant. Cold side and hot side air stream flowing through an air-to-air heat exchanger. CAPTURING THE ENERGY Of the three challenges, the first is usually the easiest to evalu- ate and estimate. By simply knowing the airflow and temperature of the exhaust gases in the oxidizer stack, suppliers of energy recovery equipment can quickly begin to model an appropriate device for reclaiming energy effectively. It is often during this first challenge that the overall opportunity for yearly savings is also quantified. The more information that an oxidizer end-user can provide at this juncture, the more realistic the opportunity analysis can be. At a minimum, those considering stack energy recovery should gather the following before beginning this process: . Expected airflow and average temperature in the oxidizer stack. Air to air heat exchanger plate type. www.flexography.org MARCH 2009 FLEXO -
Sustainable Winter 2009