THE CHALLENGE

Tekra, a custom coater of plastic films in Wisconsin, has always had an eye for energy conservation. State regulations in Wisconsin require an over 98% destruction rate of volatile organic compounds (VOCs). While many companies simply abide by that regulation, Tekra takes it steps further in their exhaust process.

While considering their first oxidizer system, Tekra’s Engineers did their research and selected an early model regenerative thermal oxidizer (RTO). While RTOs were an investment, Tekra knew that long-term, it was their best choice for reliable air pollution control, lower operating costs, and a smaller carbon footprint. “We have always tried to be a green company,” said Zachary Gernetz, Project Engineer for Tekra.

In 2003 it was time for Tekra to replace their aging RTO system, and they turned to Anguil Environmental Systems. The equipment of choice was again an RTO, although Anguil’s RTO had significant advantages over the previous model including: 95% thermal energy recovery (TER), lower horsepower and operating temperatures, as well as better options for turndown and idle modes.

“Tekra went so far as to have us install a small odometer-style meter right on the front of the control panel for the Anguil RTO, showing exactly how many BTUs, they were saving over their previous unit,” says Greg Blando, former Service Manager for Anguil.

THE SOLUTION

Thermal efficiency of an RTO relates to the ceramic media inside the oxidizer which captures and then releases energy to pre-heat the incoming, untreated airstream.

Tekra’s focus on achieving energy efficiency did not stop in 2003. With a reinvigorated nationwide focus on green business practices, and energy costs on the rise, they again challenged Anguil to perform even better in 2009. Anguil studied the temperature charts of the RTO system and took air samples during peak VOC loading production runs. Using that data, it was determined that the 95% TER of the system could be pushed closer to 97% without creating any adverse high-temperature conditions in the RTO.

“A two percent improvement in TER may not sound all that impressive,” says Mike Scholz, Project Engineer for Anguil. “But most RTOs out there today were designed to achieve about 95% TER. The natural gas required by those systems is directly tied to five percent of energy lost. Getting back two of the lost five percent is a 40% reduction in energy lost. In practical terms, that two percent improvement in TER can translate into 40% less on your RTO natural gas bill.” In addition, the enhanced performance at Tekra put their oxidizer into a self-sustaining mode more often, meaning the fuel value in the VOC-laden exhaust gases are enough to operate the RTO and no auxiliary fuel is needed, hence fewer greenhouse gases are emitted.

THE RESULT

As advances in RTO ceramic heat recovery media happen, Anguil is routinely able to provide RTO operators like Tekra with a performance upgrade. The upgrade is achieved by either adding to the top of existing media beds or at times replacing the top layers of existing beds with new extruded ceramic media blocks.

“With this type of project, payback is king,” comments Lee Kottke, a manufacturer’s rep for Anguil closely involved in the Tekra relationship. “That’s why it is exciting that Anguil can achieve this level of success with only partial media change-outs. That keeps the project cost down and payback periods very reasonable.”

There are other possible influences to consider. Deeper media beds may require the relocation of chamber instrumentation – like thermocouples. Also, higher efficiency media styles can come with increased back pressure and electrical horsepower cost. Often, however, as in the case of Tekra’s RTO, the electrical use is minor compared to the natural gas savings.

Tekra confirmed that with two coaters running a variety of coating weights and line speeds, it is difficult to get an exact dollar savings. However, prior to the media replacement, their RTO often required natural gas to maintain temperature when only treating the exhaust from one coating line. Post retrofit, “the RTO rarely requires natural gas even when only one coater is operating and never when both are on,” says Gernetz. Zach added, “Jobs that were never self-sustaining before are now. So, I know that the media retrofit is saving us money.” He estimates a two year payback for this retrofit.

Considering some enhancements to your RTO?  Think about this:

  • Up until recently, most RTOs were designed with 95% thermal energy recovery (TER) or less.
  • Rule of Thumb for self-check: If the average RTO outlet temperature is more than 100°F higher than the RTO inlet temperature, your actual TER is probably less than 95%.
  • Even a small increase in TER can have a dramatic effect on RTO fuel usage. In some cases, a bump in TER could eliminate RTO fuel use entirely.
  • Advances in ceramic media have allowed Anguil to improve TER in RTOs by only replacing a portion of the existing ceramic media beds, improving payback periods.
  • Anguil has performed this retrofit on numerous RTOs, regardless of original manufacturer, and offer free savings analysis for those interested.

According to Chris Anguil, President of Anguil Environmental Systems, Inc, “When I reflect on the relationship between Anguil and Tekra, it strikes me how RTOs, while such a huge leap forward in energy efficiency over previous oxidizer styles, are continuing to evolve. Advances in media and controls mean there is still room for efficiency improvements on any RTO system out there, regardless of age. Anyone who owns an RTO should follow Tekra’s lead and continue to ask if they can do even better energy efficiency-wise. We applaud Tekra’s commitment to environmental compliance and energy efficiency and thank them for challenging us with this opportunity.”