Refinery's sulfur removers are blamed for tainted gas

A pair of units designed to remove sulfur from gasoline during the refining process paradoxically were to blame for creating a batch of sulfur-tainted gasoline at a Norco refinery in May, one of the refinery's owners said this week.

The bad gasoline damaged more than 80,000 fuel gauges in cars and trucks in Louisiana and Florida.

The sulfur-removing units began operating at the Motiva Norco Refining plant on May 4 and 6, about two weeks before motorists in the New Orleans area started reporting fuel gauge problems, said Shawn Frederick, a spokesman for Shell Oil Products, the refinery's U.S. owner.

In addition to the elemental sulfur that previously had been detected in the bad gas, Shell now says the tainted fuel also contained hydrogen sulfide, an extremely corrosive compound that occurs naturally in "sour" crude oil.

More than 200 gas stations mostly operating under the Shell, Texaco and Chevron brands sold the tainted fuel in the New Orleans area in May.

The gas was a problem in some vehicles with silver electrical contacts in their fuel-gauge sensor units that sit in gas tanks. The elemental sulfur and hydrogen sulfide can corrode the silver contacts and cause a false reading in the dashboard fuel gauge. Some motorists ran out of gas while driving, even though their gas gauge indicated they had plenty of fuel.

Shell has processed about 53,000 broken fuel gauge claims in Louisiana and about 28,000 in Florida, totaling 81,000, Frederick said.

He couldn't say how much money the company has paid out in claims.

Considering that each broken gauge can cost from $200 to $1,000 to fix depending on the car model, Shell's cost for the repairs thus far could be in the tens of millions of dollars.

Though the company has traced the problem to the new refining units, the exact reason why the units malfunctioned remains a mystery, Frederick said.

"The precise technical reasons for the appearance of minute amounts of elemental sulfur and hydrogen sulfide continue to be investigated," he said.

One of the units has been modified and returned to operation, while the other remains off-line awaiting repairs, Frederick said.

The units were installed at Motiva to meet new federal environmental regulations that limit sulfur levels in gas to 30 parts per million. The new rules go into effect Jan. 1.

Current rules limit sulfur levels in gas to 300 parts per million.

The new sulfur-removing units process about 60,000 barrels of gas per day, about 25 percent of the refinery's total capacity.

Though questions remain about the tainted fuel problem, Frederick said, Motiva has added safety measures to prevent the mishap from recurring.

"We do know how to prevent a similar reoccurrence, and our customers can be confident that our gasoline manufactured at the Motiva Norco Refinery will not interact with silver gas gauge sensors," he said.

One precautionary measure involved subjecting samples of gas to a so-called silver strip test, a rarely used test that can detect tiny levels of corrosive sulfur.

Motiva and other U.S. refineries commonly use copper strip tests to detect corrosive material in fuel, but that test is less precise, Frederick said.

Copper strip tests were performed on the batch of tainted gas before the fuel left the Norco refinery but they gave no indication of corrosive sulfur.

When the fuel was retested with copper strips several days later, after the fuel gauge problem surfaced, the results indicated the presence of a corrosive substance.

Several theories could explain the conflicting copper strip test results. The initial tests at the refinery might have been flawed. The gas might have picked up trace amounts of sulfur in transit to the Kenner fuel terminal where it was stored before being trucked to stations. Or something else might have caused benign sulfur compounds in the fuel to undergo a chemical change.

Frederick said the explanation remains elusive.

"We continue to investigate the reason for the discrepancy between the tests," he said.