Monday, May 15, 2017
Heat Exchanger Rupture Caused USN Acid Release
By Walter F. Roche Jr.
Officials of US Nitrogen say that a ruptured heat exchanger caused the accidental release of some 424 pounds of nitric acid, according to a report filed with Tennessee environmental officials.
In a two-page letter filed Friday with the Tennessee Department of Environment and Conservation and state and local emergency management, the Midway company also reported that they did not believe the release caused injury to company employees or local residents.
The release of acid vapors occurred April 19 and marked the latest in a series of missteps in the startup of the acid plant, a key element in the production of ammonium nitrate.
According to the letter from US Nitrogen an estimated 59 percent of the nitric acid released was released to the atmosphere.
The incident started at 6 p.m. and lasted four minutes, the letter states, adding that local emergency management officials were notified at 6:10 p.m.
"A shelter-in-place was issued for industry and residents in the footprint of the nitric acid vapor cloud," the letter states.
US Nitrogen said the acid was minimized when the main acid feed to the heat exchanger were isolated within four minutes from when the leak started."
The company also noted that the heat exchanger is located within a containment dike and the dike area is in as asphalt paved, "so the majority of the liquid from the heat exchanger rupture was contained."
"US Nitrogen does not believe personnel at the plant or members of the public were exposed to levels of nitric acid vapor requiring medical attention," the letter states.
US Nitrogen, a subsidiary of Ohio-based Austin Powder, produces ammonium nitrate which is then shipped to other Austin facilities for use in the manufacture of explosives.