Problem
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.
Action
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).
Solution
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.
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.