Catalytic Oxidizer Catalyst Replacement
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.
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.
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.
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