The biggest advance in technology at the Valdez Marine Terminal was installation of a vapor control system at the oil loading berths in 1998, according to Alyeska Pipeline Service Co. officials.
Before Alyeska installed its vapor control system, an estimated 45,000 tons of crude oil fumes escaped annually from oil tankers in the Port of Valdez into the air as a result of loading operations. That made the Valdez terminal one of the largest emitters of such fumes in North America, and responsible for nearly half of all such emissions nationwide, according to the Prince William Sound Regional Citizens Advisory Council.
The problem was one of basic chemistry. During storage, light hydrocarbons previously dissolved in the crude tend to vaporize. These gases can collect in empty spaces either below a tank roof or onboard an empty oil tanker.
Most often methane, other gases such as propane, butane, ethane, nitrogen, and carbon dioxide may be present in the mixture. The vapors also can contain potentially hazardous substances such as the BTEX compounds (benzene, toluene, ethylbenzene and xylene).
The vapor control system reduced emissions of these vapors from the tankers while they load. It uses vapor compressors and special vapor recovery arms to collect the gases that accumulate in empty spaces of shipboard oil tanks during the tanker-loading process. The vapors must be kept in an oxygen-deficient atmosphere because they become explosive when mixed with oxygen. The vapors are stored onshore and then burned to generate power, which is used to operate the terminal.
The RCAC lobbied aggressively for Alyeska to install vapor controls and the difference the system made in the atmosphere in and near the terminal was immediate and dramatic.
“Our people and the people on board the tankers had to wear respirators in the vicinity of the loading and generally a substantial amount of emissions was going into the atmosphere,” said Greg Jones, senior vice president of operations at Alyeska Pipeline Service Co.
“This was a big event. It reduced total emissions from the terminal by 90 percent,” he said. “And our employees like it because they don’t have to wear respirators anymore.”
Solutions for ballast waterAnother big project currently under way at the terminal is designed to control vapors escaping from the ballast water treatment system. Ballast water is kept in three huge 430,000-gallon tanks that also have vents to allow vapors to escape into the atmosphere.
Alyeska is tying the three ballast water tanks into its vapor control system. The move will reduce remaining emissions from the terminal by 60 percent, Jones said.
“Closed systems are the way of the future,” said Alyeska spokesman Mike Heatwole.
The company will spread blanket gas inside the tanks to keep the contents inert and prevent an explosive atmosphere from developing. The work is due for completion by year’s end.
“This is a big deal. The terminal will be much more environmentally friendly,” Jones said.
Meanwhile, the ballast water treatment system is undergoing a modernizing process after three years of study and design review. Built to handle the ballast of virtually nonstop oil loading when 77 tankers would pony up to the berths regularly to take on up to 2.15 million barrels of crude per day, the system now routinely accommodates 18 tankers loading oil at a rate of 750,000 bpd.
Technology testsThe ballast water treatment system is based on having microbes that eat the oil in the water.
“It’s hard to keep the bugs alive when you don’t have ballast water coming in,” Jones said. “It’s becoming obsolete, so we’re making changes.”
One tank will be removed from the system, and Alyeska is considering installing an inert gas flotation system in the other two tanks to remove potentially harmful emissions. A pilot project is under way to test off-the-shelf technology considered some of the best in the world.
Jones said the changes should be complete by 2009.
Alyeska, meanwhile, is also working to improve boom performance to contain oil better at the terminal. When heavy winds undermine the performance of boom placed around the tankers while they are loading crude at the terminal’s berths, the company has been forced to shut down the loading until the winds subside.
Now, Alyeska is conducting a search for better boom technology.
“We’re working on R&D and some other companies are looking at it,” Jones said. “Within the next year, we’ll probably try out some things on a pilot basis and see if they work.”