Breathe Easy With Environmental Controls

IN 1967, THE ENVIRONMENTAL Protection Agency (EPA) issued the Clean Air Act (CAA). Twenty-three years later, the Act was amended, requiring the EPA to set national ambient air quality standards; six Titles were added, including primary standards (to protect public health) and secondary standards (to protect public welfare). Today, most packaging plants that print, laminate, or coat with solvent-based inks and coatings are subject to various levels of these air regulations.

One potential area of concern for packagers is using hazardous air pollutants (HAPs), says Steven Rach, senior account executive at MEGTEC Systems. He explains regulations, referred to as Maximum Achievable Control Technology (MACT), were issued and in 1996, the EPA promulgated a Printing MACT, which requires a minimum of 95 percent overall control of both the capture of HAPs from the process and their destruction. According to Rach, the EPA is currently working on a very similar MACT for paper and other web coatings (POWC). “The primary difference between the two rules is the POWC MACT requires over 98 percent overall control only for new lines. Therefore, if a packaging company did not opt their coaters into the Printing MACT, they may be facing a higher level of HAP reduction for the new line [per the POWC MACT].”

The EPA has long been concerned about emission control systems’ ability to continue meeting the required compliance levels after initial tests are performed. To keep companies in check, the EPA Emission Measurement Center is developing monitoring protocol, which will require companies to verify continued compliance and record the data. This will provide authorities assurance that installed systems are working properly. Companies considered major sources of emissions (or which fall under a MACT rule) will be required to develop and maintain a compliance-monitoring schedule.

Keeping silicone under control

Whether in pressure-sensitive materials or on coating lines, silicone shows up in many printers’ press rooms. It can enhance a finished product’s attributes or help improve production characteristics. However, silicone does come with its own set of environmental challenges. Scott Shaver, product manager at Catalytic Products, states the basis for these problems stems from the oxidation process. “During operation of the production source, silicones are driven off along with the VOCs,” he says. “Since the air pollution control equipment is installed to destroy the VOCs, any system has to be designed to also process the silicone vapors. During the oxidation process, silicone will convert to silicon dioxide (SiO2). This [SiO2] is often the culprit for failing and/or under-performing air pollution control equipment.”

Shaver explains the SiO2 is a talcum powder-like substance that clings to metal surfaces, robbing the system of efficiency and putting its ability to effectively destroy VOCs at risk.

Catalytic Products collaborates with silicone coaters to design thermal (recuperative) oxidizers capable of working through the varying ranges of operations. The oxidizers employ a unique approach to facing difficulties associated with SiO2 by combining the harmful air pollutants with oxygen and heat. In a controlled environment, VOCs are converted to carbon dioxide and water vapor. These harmless byproducts are released over the shell and tube heat exchanger for energy recovery.

One particular application called for a pollution control system to destroy VOCs such as ketones, alcohols, acetates, glycols, and other organic vapor emissions. Depending on the line speed and the product width, these solvents could range from 10 percent lower explosive limit (LEL) to over 25 percent LEL. A majority of the time, the coating line is operated at 15 percent to 17 percent LEL.

When designing an oxidizer system’s thermal rate efficiency, it is important to rate the maximum efficiency of the primary heat exchanger to the solvent load thought to be encountered almost 80 percent of the time. This allows the oxidizer to use very little natural gas during normal operations. It is also important to design a system capable of working through the higher solvent loading conditions. A hot-gas bypass is a standard recommendation on all thermal oxidizers. The hot-gas bypass becomes the safety valve for the system and allows higher LELs to be safely and effectively managed, without any need for operator involvement.

In this application, the customer expected 2-5 lbs./hr. of silicone products such as SiO2 (an inorganic), hexamethylcyclotetrasiloxane, and/or octamethyl-cyclotetrasiloxane (both organic) could be found in the exhaust stream. For this reason, the system had to be engineered to withstand the rigors of a considerable amount of particulate buildup.

Catalytic Products’ solution: the QUADRANT SR-Silicone Series Thermal Oxidizer. This unit replaced two older-style, square-box-designed thermal oxidizers and exceeded the local CAA requirements by providing 99.9 percent destruction of all VOCs.

What’s new?

• Glenro has introduced a new 3000 scfm catalytic oxidation system that removes multiple solvents and odors from a process exhaust stream at the rate of 13.3 lbs./hr. Its primary energy source is a gas burner, which is fed by a complete IRI-approved safety gas train. The system measures 18´x6´x12´, including heat exchanger, ductwork, supply blower, and steel skid mounting, and is designed to maintain catalyst temperatures of 750°F-800°F.

• Anguil Environmental Controls is a supplier of VOC control systems, including catalytic recuperative and regenerative thermal/catalytic oxidizers (RTO/RCO). The company’s Permanent Total Enclosure (PTE) installations capture 100 percent VOC emissions, while exhaust recirculation on existing processes cuts capital and operating costs.

• Adwest Technologies offers the RETOX RTO Oxidizers with flameless, zero nitrogen oxide operation for VOC control projects. RETOX Twin Bed RTOs are available in shop-assembled, skid-mounted modules from 1,000 cfm to 85,000 cfm flowrates and include a 95 percent-efficient ceramic heat exchanger for fuel-free operation at 400 ppmv and greater inlet solvent loadings. The systems are designed to provide one hour cold start-ups, feature automatic PLC controls, and are available with optional AC variable speed drives for varying process and dryer flowrates.