Problem
A New Jersey pharmaceutical company purchased a thermal
incinerator to treat the heptane and hexane exhaust from their
capsule wash system. The thermal incinerator's "tubular" design was
modified with a catalyst bed in order to reduce the system's
operational costs. Unfortunately, when operating in the catalytic
mode, the oxidizer failed to provide the required 95% destruction
efficiency of non-methane hydrocarbons required by the New Jersey
Department of Environmental Protection. These odorous emissions led
to neighbor complaints and an EPA consent decree, complete with a
$175,000 civil penalty. Although the company was proactive in
trying to solve the emission problem, the EPA stipulated penalties
of $2500 for every day the violation existed. The original
equipment supplier attempted to rectify the problem to no avail and
the pharmaceutical company remained in violation of their New
Jersey air permit.
Action
After meeting with several potential suppliers, the company
selected was Anguil Environmental Systems, Inc. Anguil's track
record with catalytic systems, knowledge of catalyst and
engineering strength made them the most likely candidate to tackle
the VOC problem successfully.
Solution
Anguil successfully retrofitted the non-compliant system and
brought the company into EPA compliance. The first step in Anguil's
approach was to examine the reason for catalyst nonperformance.
There were several potential reasons for catalyst failure. The
possibility of catalyst masking or the presence of a poisoning
agent (i.e. sulfur, phosphorous, heavy metals) within the VOC-laden
stream was examined; however, no significant levels of any of these
agents were detected.
The second possibility was that the
industrial process stream was being allowed to pass through the
oxidizer before it was brought to proper operating temperature.
This would result in the coating of the stainless steel rings with
the heptane and hexane hydrocarbons. If this was the case, when the
unit was brought to the proper operating temperature, oxidation
would occur on the catalyst, leaving a carbon deposit. This type of
carbon deposit would result in decreased destruction efficiency and
the formation of incomplete combustion products. No signs of these
carbon deposits, known as coking, were detected.
Having eliminated these suspects, Anguil conducted a laboratory
performance test that indicated the reason for catalyst failure:
the catalytic stainless steel rings lacked the proper surface area
to achieve the quoted destruction efficiency. This performance test
revealed that there was less than 50% destruction efficiency of a
propane and propylene test stream. This is an excellent indicator
of catalyst failure or inactivity.
Anguil modified the system design to accommodate a honeycomb
catalyst. The monolithic catalyst Anguil chose was a 300
cell-per-square-inch ceramic substrate. An alumina washout was used
to deposit large quantities if precious metal (i.e. platinum,
palladium, rhodium). The surface area of this replacement catalyst
is more than 100 times greater than that of its stainless steel
counterpart. (Note: a cubic foot of this monolithic catalyst
contains more surface area than that of a football field.) The
oxidizer was equipped to with a new reactor section to house the
nine cubic feet of monolithic catalyst. A 95% destruction
efficiency guarantee was provided along with the system
retrofit.
A follow-up Flame Ionization Detector (FID) was also performed
on this retrofit and a carbon filter was added to eliminate methane
readings. The FID test results indicated a VOC inlet concentration
of 943 ppm and an oxidizer outlet concentration of less than 20
ppm. The company is now EPA-compliant 97.8% destruction efficiency.
Anguil is well-known for providing VOC control systems but in this
case, they demonstrated their ability to provide answers where
others had failed.