(Certified Best Practice by BMPCOE)
Polaroid Corporation - Waltham, MA
To meet air pollution standards levied in 1984, Polaroid
had to either revise its air emissions or face a shutdown. At the time,
Polaroid had been releasing more than 2,500 tons of VOC emissions into the air
annually. Emissions were generated from the drying ovens associated with film
coating equipment. Direct-fired, continuous-burn incineration was a possible
solution, but its associated high-energy consumption cost was a drawback.
Polaroid needed a way to eliminate VOCs at a reduced energy cost. In response,
Polaroid designed the specifications of the VOC Abatement system. The system's
(Figure 2-4) cost was $5 million and went on-line in January 1985.
Built by Regenerative Environmental Equipment Company (REECO), the VOC Abatement system was a high-efficiency regenerative cycling incineration system which abated the hydrocarbons contained in solvent laden process exhaust. Contaminated fumes enter the system through an upper ring-shaped manifold where inlet flow control valves direct the air from the manifold to the energy recovery stoneware beds. Fumes, progressively heated as they pass through the hot stoneware bed, move toward the incineration chamber. Upon leaving the stoneware beds, the fumes are very close to the incineration temperature. Oxidation is completed in the gas-fired central chamber which is maintained at 1500°F. VOCs, present in the fumes, autoignite while still in the stoneware beds which reduces auxiliary fuel requirements. When the incoming air contains enough VOCs, the energy released will provide enough heat to support the inner chamber ignition, allowing the burner to switch automatically to pilot mode. The purified air is then pulled from the central chamber through the stoneware beds and exits through the outlet control valves. The stoneware beds absorb the heat. The cooled air then exits to the exhaust fan at a temperature only slightly higher than that of the incoming air. Subsequently, the direction of flow reverses, the energy stored in the stoneware now preheats the incoming batch of air, and the inlet stoneware bed becomes the outlet stoneware bed.
The VOC Abatement system's action is continuous cycling by taking advantage of the use and reuse of the heat energy stored in ceramic stoneware beds. With its high surface area for heat transfer and mass for energy retention, the stoneware beds' size and shape assure excellent air flow around, over, and under every element.
Polaroid's VOC Abatement system is virtually indestructible and has required minimal upkeep maintenance since its installation (only the valves have been redesigned). The system can receive more than 75,000 standard cubic feet of process exhaust streams per minute destroy 2,800 tons of VOCs per year produce a destruction efficiency greater than 98% achieve a thermal efficiency greater than 95% and operate in temperatures up to 1800°F. The 1996 annual operating cost of the VOC Abatement system was $500,000, including $45,000 for natural gas.