U.S. Nitrogen LLC reported a nitric acid vapor release on April 19 at its plant in Mosheim, Tenn. “Around 6:30 p.m., U.S. Nitrogen experienced a release of nitric acid vapors,” according to a USN statement. “The release is dissipating, and no workers were injured.” USN said it notified local authorities and would cooperate with these agencies and investigate the cause of the release to ensure that the issues are resolved.
By 8:30 p.m., local authorities reported that the leak had been contained.
“Our operations and maintenance teams responded quickly and effectively to the release, limiting its size and duration,” a USN source told Green Markets April 20. “They were ably supported by local emergency response teams from Greeneville and Greene County. Regarding the cause of the release, a preliminary assessment suggests a gasket failure on an acid heat exchanger for the ammonium nitrate solution plant. We are in the midst of an in-depth investigation this morning to develop the root cause of the failure. We expect to resume safe operation of our solution plant in short order.”
USN said the nitric acid plant has operated very well and continues to progress through the operating permit protocol as defined by the Tennessee Department of Environment and Conservation (TDEC).
Greene County Sheriff Pat Hankins, one of the first responders on the scene, likened the release to an “orange haze” similar to a cloud of pollen, according to The Greeneville Sun, which also reported that local residents complained of not being promptly or properly notified of the incident. The haze reportedly went in the direction of a nearby woodland, and residents in the area were told to shelter-in-place.
A similar release occurred at the plant in August 2016 (GM Sept. 1, 2016), when residents reported an “orange plume.” The nitric acid plant also came up and went back down again in January (GM Feb. 3, p. 18).
In recent weeks, USN has increased its intake of water from the Nolichucky River and resumed nitric acid production. While the company said it has not consistently produced nitric acid and liquid ammonium nitrate (AMSOL) due to market conditions (GM March 17, p. 13), it confirmed that it has been producing anhydrous ammonia all along. What was not needed internally was sold into the market.