For over 30 years the EPA has developed rules that require capture and control of air pollutants such as volatile organic compounds (VOC’s) generated by the printing industry. The first generation of pollution control equipment was a catalytic oxidizer, which is very similar to those found in cars.
These oxidizers use platinum as a catalyst and when heated up to 650° F (343° C) or more the catalyst destroys the VOC’s, making the exhausts free from any hazardous components. These oxidizers typically destroy more than 98 percent of the exhausted solvents from a printing press, but they use large quantities of natural gas in order to reach proper destruction temperatures. Regenerative thermal oxidizers (RTO’s) are designed to do the same thing, but in an entirely different way. An RTO works with significantly higher temperatures—about 1650° F (900° C). At this heat the VOC’s break down in the same way as they do in a catalytic converter. Interestingly enough however, there is no additional energy needed.
Generally, the RTO heat exchanger consists of two compartments referred to as “beds” fabricated from carbon steel and insulated with high temperature insulation. Within each “bed” is a high-temperature heat adsorbing ceramic media. The purpose of this ceramic media is to capture the heat of combustion from the RTO exhaust as it passes through the “bed” of heat adsorbing media. A valve system directs the “hot” exhaust through one media “bed” at a time by alternating and reversing the intake and exhaust through each compartment, working in sequence. Thus, allowing the incoming ambient VOC-laden air stream to pass through a heated media “bed” prior to entering the RTO combustion chamber for oxidation, significantly raising the VOC-laden air stream temperature.
Due to the highly efficient heat exchange technology used by an RTO, many VOC’s emission streams (solvent-laden air) will have sufficient heat (BTU’s) value to operate the RTO on “auto-therm”. This means that little, or no natural gas, is required to maintain oxidation temperature after start-up (heat up to preset operating temperature).
The new RTO at Multifilm has reduced our natural gas consumption by more than 90 percent. This allows for a significant reduction in our environmental footprint as well as a nice cost reduction for our company.