Methodical Testing Gains Catalytic Oxidizer's Compliance
Situation
A New Jersey pharmaceutical company purchased a thermal oxidizer to treat the heptane and hexane exhaust from its system for washing capsules. The unit's "tubular" design was modified with a catalyst bed to reduce the system's operational costs.
Unfortunately, in its catalytic mode the oxidizer failed to provide the New Jersey Department of Environmental Protection's required 95% destruction efficiency of non-methane hydrocarbons.
These odorous emissions led to neighbor's complaints, a U.S. EPA consent decree, and a US$175,000 civil penalty—despite the company's being proactive in trying to solve the emission problem.
The original equipment supplier attempted without success to rectify the problem.
Action
After meeting with several potential suppliers, the pharmaceutical company turned to Anguil Environmental Systems Inc. because its track record of successful installations and engineering strengths made it the most likely to solve the VOC problem successfully.
Solution
Anguil first examined several possible reasons for catalyst nonperformance.
The possibilities of catalyst masking or the presence of a poisoning agent (such as sulfur, phosphorous, heavy metals) within the VOC-laden stream were examined. However, no significant levels of these agents were detected.
Another possibility was that the industrial process stream was being allowed to pass through the oxidizer before it achieved proper operating temperature. This would coat the stainless steel rings with heptane and hexane hydrocarbons. Then oxidation would occur on the catalyst as the unit was achieving its proper operating temperature, leaving a carbon deposit to interfere with destruction efficiency and complete combustion products.
However, no signs of these carbon deposits, known as coking, were detected.
Anguil then conducted a laboratory performance test that indicated that the catalytic stainless steel rings lacked suitable surface area to achieve more than 50% destruction efficiency of a propane and propylene in the test stream optimum.
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 of precious metal (such as platinum, palladium, rhodium). The surface area of this replacement catalyst is more than 100 times greater than that of its stainless-steel counterpart—with a cubic foot having more surface area than does a football field.
The oxidizer was equipped 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.
Follow-up with a flame ionization detector (FID) indicated a VOC inlet concentration of 943 ppm and an oxidizer outlet concentration of less than 20 ppm. (A carbon filter was used to eliminate methane readings.)
Anguil successfully retrofitted the non-compliant system and brought the company into EPA compliance. The company's oxidizer now achieves a 97.8% destruction efficiency.
For more information: Anguil Environmental Systems Inc., 8855 N. 55th St., Milwaukee, WI 53223. Tel: 414-365-6400. Fax 414-365-6410. Email: info@anguil.com.