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August explosion at Unocal Alaska Nitrogen Products Kenai plant injures three Plant down for three weeks from Aug. 20; ammonia plants running again Sept. 12, first urea plant up Sept. 14 Kristen Nelson PNA News Editor
An explosion occurred at 1:31 a.m. Aug. 20 at the Unocal Alaska Nitrogen Products Kenai plant, injuring three workers and taking the plant down for more than three weeks. Unocal spokeswoman Roxanne Sinz said Aug. 20 that the three were treated and released from the hospital that same day and all are back at work. One of the employees suffered first degree burns and bruises, a second suffered from smoke inhalation and a third sprained his knee while responding to the incident.
The two ammonia plants were started up the morning of Sept. 12 and that the first of the two urea plants was expected to start up Sept. 14, Sinz told PNA that day.
Apologies to community Unocal apologized to the Nikiski community for the incident and expressed regret for the employee injuries. The company said this incident is the only one of its magnitude to occur in the plant’s 30-year operating history.
“We are committed to continuing our tradition of safe operations and are thoroughly investigating the incident and improving operations to ensure that it does not happen again,” Unocal said in a statement.
The explosion occurred while Unocal was in the process of shutting down ammonia plant No. 1 to repair a leak in the plant’s carbon dioxide removal system, Sinz said.
Unocal said hydrogen passing through a valve caused the explosion in an empty tank; the force of the initial explosion blew the tank from its pad and into other process equipment.
MDEA spill The impact of the tank caused a second explosion which ruptured a system containing Methyldiethanolamine, called MDEA. The plant utility system was also damaged by these events, Unocal said, causing the remainder of the plant to lose power and shut down.
Original estimates were that 30,000 gallons of MDEA were spilled, most into containment areas.
Sinz said Aug. 24 that 30,000 gallons would have been the worst case. Unocal now estimates, she said, that 10,000-15,000 gallons were spilled, of which 8,600 gallons have been recovered.
The balance, at least 1,400 gallons, was spilled on to soil and the soil has been excavated and gravel cleaned up to the satisfaction of the state and the U.S. Environmental Protection Agency, Sinz said.
The MDEA, used to remove carbon dioxide from the ammonia process solution, will be recycled back to the plant, she said.
Sinz also noted that the Alaska Department of Environmental Conservation had reported that the MDEA contained 7 percent arsenic.
The arsenic, she said, was a residual of what had been in the tank and is not measured in percentage points, as originally reported by DEC, but in parts per million, making the correct figure 7 parts per million not 7 percent.
Start up under way Sinz said Aug. 24 that Unocal was working on starting up the plant, which was completely shut down following the explosion. Start up is time consuming, Sinz said, because integrity has to be carefully checked since the plant came down ‘hard’ — with no warning — rather than in a controlled fashion. Production will be phased in once start-up is achieved.
The urea plants, she said, can’t be started until they’re about half way through bringing up the ammonia plants because ammonia is used in the manufacture of urea.
Unocal said Aug. 23 that it has initiated a corporate-led investigation into the explosion, including events leading up to the incident, analysis of physical evidence and an evaluation of Unocal’s response. Unocal said an investigation as to the cause is still in progress.
“During this episode, the community was not in any danger,” Mike Nugent, plant manger, said in a statement. “Unocal has systems in place to alert the community of any immediate danger from hazardous emissions.”
Only nitrogen producer in region The Unocal Alaska Nitrogen Products Kenai plant manufactures and distributes nitrogen-based fertilizers to agricultural and industrial markets throughout the Pacific Rim and the western United States.
Unocal said the Kenai plant is the only nitrogen producer in the region, and “one of the largest and most modern plants of its type in the world.”
The first plant was built in 1967 by Collier Carbon and Chemical, a subsidiary of Union Oil of California, now known as Unocal.
In 1974, construction of additional plants was authorized, greatly expanding the facility. In 1998 Unocal formed Alaska Nitrogen Products LLC to own these assets.
Plant capacity is 1.3 million tons a year of ammonia and 1.1 million tons a year of urea.
The plant operates 24 hours a day, seven days a week and includes two ammonia plants, two urea plants and utility plants for steam, air and electricity.
The plant has 287 employees and an annual payroll of $30 million.
The majority of the plant’s ammonia and urea are transported by barge or ship. The plant’s top markets are Unocal’s West Coast operations and international markets in Korea, Thailand and Mexico.
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