Hydrogen Fluoride Usage a Catalyst for Controversy

For the last two years, fire, safety and air quality officials in Los Angeles County, as well as City Council members and environmental activists, have been studying and debating whether bulk use of hazardous hydrogen fluoride should be banned.

The debate is drawing to a head. The staff of the South Coast Air Quality Management District is prepared to recommend a ban. But a task force appointed by the AQMD two years ago appears ready to recommend the continued use of the chemical.

The substance is used in substantial quantities by four refineries--Mobil in Torrance, Ultramar in Wilmington, and Powerine and Golden West, both in Santa Fe Springs--as well as by an Allied Signal refrigerant manufacturing plant in El Segundo. Each plant typically has on hand thousands of gallons of hydrofluoric acid--the liquid form of hydrogen fluoride.

Refineries that use hydrofluoric acid to boost the octane of unleaded gasoline could make an expensive conversion to sulfuric acid. There is no substitute for it in the manufacture of refrigerants.

The chief argument against hydrofluoric acid cites its danger.

Opponents argue that it could precipitate a large-scale disaster because the substance turns to a heavier-than-air gas at room temperature. They say a large release might form a dense, ground-hugging cloud that would sweep through neighborhoods and harm thousands of people.

Opponents cite industry-sponsored tests that showed an uncontrolled two-minute release of 500 gallons per minute could prove lethal up to five miles downwind. They see no adequate way of controlling releases that might be caused by earthquakes, sabotage or human error.

The opponents favor sulfuric acid because it would remain liquid in a spill.

Refineries that use the substance oppose any change, arguing that sulfuric acid poses its own dangers and that a conversion would be costly.

They add that they have learned how to better control releases and that the chance of a fatal release is extremely low.

Both sulfuric and hydrofluoric acid may be used as catalysts in a refinery process known as the alkylation reaction, which combines hydrocarbons too volatile to use for gasoline into a high-grade unleaded gasoline.

Although the chemical reactions are similar, there are key differences.

Alkylation using hydrofluoric acid requires far less acid--100 to 200 times less--than alkylation using sulfuric acid.

Refineries making the switch would either have to build a plant on site to make fresh acid or would import what they need in trucks or tank cars. Their officials say hauling sulfuric acid would dramatically increase the risk of a spill during transportation.

In addition to requiring much more acid, the sulfuric acid alkylation reaction generates more heat.

Instead of the water cooling system used in hydrofluoric acid units, a more powerful ammonia refrigeration system would be needed, said refinery manager Marshall A. (Bud) Bell of Ultramar. But that would entail additional risks of breakdowns and the possibility of a release of poisonous ammonia vapors.

Although refinery officials acknowledge the danger of an uncontrolled hydrofluoric acid spill, they point to later test results that say up to 90% of a spill could be washed from the atmosphere if water drenches the fumes at a ratio of 40-1.

The four refineries and Allied Signal have all increased their water spray systems--or are planning to do so--to be able to handle a release of 100 gallons per minute. It would take a water system that could spray 4,000 gallons per minute--in the right place--to contain such a spill.

In addition, they have installed or are planning to install tanks and remote control equipment that would shunt acid from a leaking tank to an intact one.

Mobil and Ultramar officials say the dangers of using hydrofluoric acid have been overstated. They cite risk assessment reports done by each refinery under a new state law. Mobil’s report was released last year; Ultramar made its report public Thursday.

The reports analyze the probabilities of various accident scenarios and say that one death in 100 years is likely to result from their use of hydrofluoric acid.

Mobil has put the cost of conversion to sulfuric acid at $100 million, and Ultramar says the conversion cost at its plant, which is smaller, would be about $45 million. According to AQMD estimates, it would cost Mobil $13 million annually to convert to sulfuric acid. The cost for Ultramar would be about $9 million a year.