Control of air emissions has become an important issue that flexible packaging converters must consider when changing or upgrading equipment. Robbie Manufacturing of Lenexa, KS, a producer of printed shrink films, bags and pouches for a diverse range of applications, addressed its emissions in 1991 and 1996 by investing in two catalytic oxidizers to control the EPA-regulated air emissions generated in their various processes.
But when the company recently decided to purchase a new 10-color gearless press to increase capacity and capability, management knew they also needed to analyze the condition and operating costs of their two catalytic oxidizers.
Robbie contacted the supplier of the catalytic units, Anguil Environmental Systems, Inc. of Milwaukee, WI to analyze the most cost-effective and compliant way to replace the two aged systems. After an analysis, Anguil recommended replacement of the existing equipment with a single 25,000 Regenerative Thermal Oxidizer (RTO).
RTOs Replace Catalytic Oxidizers
Though the catalytic units were a logical choice at he time of purchase technological advances in the ensuing years had caused the RTO to become a viable alternative. Particularly important was the improvement in RTO cost-effectiveness generated in part by significant reduction in cost of ceramic energy recovery media, along with improvements in hear transfer capability.
Robbie and Anguil’s objectives were to achieve destruction of 98 percent of the Volatile Organic Compounds (VOCs) in the air stream, to fit the system into the space occupied by the two catalytic systems and to accomplish the tear-out and subsequent installation in just six days.
The operation of the RTO is considerably different than the existing catalytic units. The oxidizer consists of two reinforced, insulated chambers filled with high temperature structured ceramic energy recovery media. The oxidizer utilizes two burners to maintain the oxidizer above the oxidation temperature. Located beside the energy recovery chambers are diverter valves and air duct plenum passages, which allow the process airglow to diverted into and out of the oxidizer in either a clockwise or counter clockwise mode. The directional mode is controlled by a PLC, which changes the direction of airflow at regular intervals to optimize system efficiency. Typical operational cycles range from two to four minutes.
The RTO in Action
In operation, solvent laden air (SLA) enters the oxidizer via an energy recovery chamber where the high temperature ceramic heat transfer media preheats the SLA prior to introduction into the oxidation chamber. As the SLA passes up through the bed, its temperature rapidly increases. After the chemical oxidation purification reaction occurs, the hot, clean, outgoing gas heats the exit energy recovery bed. In order to maintain optimum heat recovery efficiency of the bed, the SLA flow direction is switched at regular intervals by the automatic diverter valves on demand from the PLC control system. This periodic flow direction shift provided a uniform temperature distribution throughout the entire oxidizer.
With sufficient concentration of hydrocarbons in the process air stream, the heat energy content of the hydrocarbons will self-sustain the oxidation process, and no additional heat energy will be required.
Features that are specific to the RTO include:
- High volumetric turn-down capability, enabling the control of multiple sources and the reduction of operating cost.
- Thermal energy recovery of 95 percent or higher, allowing self-sustaining at levels as low as 3 percent while reducing operating costs.
- Customized thermal energy recovery media, providing low-pressure drop and low electrical cost.
Customized thermal energy recovery media, providing low-pressure drop and low electrical cost.
Anguil’s vast experience, gained after supplying more than 1,500 successful systems around the world, provided the confidence necessary for Robbie’s management to choose Anguil as their continued VOC control supplier. Robbie’s decision to work with the supplier of the original catalytic units to analyze the most best, most-effective way to replace the two aged systems was they key to the success of this project.
Anguil was able to modify its standard RTO design to fit into the space Robbie provided and to execute tear-out and new installation within the agreed-upon six days. The result was a system that exceeded the 98 percent destruction efficiency objective while lowering Robbie’s operating cost by more than 60 percent.