AQMD Report Cites Danger of Chemical Used by Mobil : Safety: A report based on computer simulations says the hydrogen fluoride used at Mobil’s Torrance refinery is more dangerous to the public if spilled than the sulfuric acid used at most other refineries.

Hydrogen fluoride, used by four Los Angeles County refineries to make unleaded gasoline, poses a significantly greater risk to public safety than a chemical used by other refineries, says a South Coast Air Quality Management District staff report released Wednesday.

The report--which used computer modeling to study hypothetical spills of hydrogen fluoride--found that in a worst-case, uncontrolled spill, the highly toxic chemical would endanger human life and health over an area six times as large as its alternative, sulfuric acid.

In a spill that was 90% controlled, the report said, hydrogen fluoride would still endanger life and health outside the refinery, while a similar spill of sulfuric acid would not even pose an immediate health threat within the plant’s boundaries.

The study would appear to support the arguments of those recommending that refineries be prohibited from using hydrogen fluoride.

The AQMD board is scheduled to consider such a ban March 2. Torrance residents, meanwhile, will vote March 6 on a ballot initiative that would in effect prevent Mobil Oil Corp. from using hydrogen fluoride at its Torrance refinery.

“The bottom line is that the use of hydrogen fluoride presents a hazard to the community to a greater extent than the use of sulfuric acid,” said Edward Camarena, the AQMD’s deputy executive officer for operations.

The AQMD staff plans to propose a ban on hydrogen fluoride. “Our recommendation to the board will be in part based on this information,” Camarena said.

Wyman Robb, manager of Mobil’s Torrance refinery, declined Wednesday to comment in detail on the AQMD report, saying it had became available only that afternoon. However, Robb said the methodology of the computer modeling used in the study appeared “a little bit strange” to him at first glance.

“All they’ve done here is make a comparison of a couple of release situations,” Robb said.

Officials at the other refineries that use the chemical could not be reached for comment.

Four Los Angeles area refineries use hydrogen fluoride in its liquid form--hydrofluoric acid--as a catalyst in the alkylation process, which boosts the octane of unleaded gasoline.

They are Mobil’s Torrance facility, Ultramar’s Wilmington plant, and the Powerine and Golden West refineries in Santa Fe Springs. The chemical is also used in bulk by Allied Signal’s El Segundo plant to make refrigerants.

There is no substitute for hydrogen fluoride in the manufacture of refrigerants. But according to Camarena of the AQMD, nine of the 13 California refineries with alkylation units rely on sulfuric acid as a catalyst--five in Los Angeles County and four in Northern California.

Sulfuric acid has its own disadvantages--primarily that it has to be used in far greater amounts than hydrofluoric acid.

Robb said Mobil’s Torrance plant would require 1,500 truckloads of sulfuric acid a year compared to 25 to 28 truckloads a year of hydrofluoric acid.

Such a demand, he said, would probably require the construction of a sulfuric acid plant at or near the Torrance refinery. “That also comes with some risks and dangers,” Robb said.

The AQMD study underscores what has often been cited as the major drawback of hydrogen fluoride: It represents a greater threat to public safety than sulfuric acid. Mobil typically has on hand 29,000 gallons of hydrofluoric acid.

The study said an uncontrolled storage-tank spill of sulfuric acid would not cause an “immediate danger to health and life,” which it defined as a concentration that would make a person lose consciousness within half an hour.

The reason is that sulfuric acid is heavy and oily and would not cause a toxic cloud unless released under pressure, Camarena said. By contrast, hydrogen fluoride turns into a heavier-than-air gas at room temperature, which means that a release into the air could create a dense, ground-hugging cloud.

The computer study attempted to estimate the effects of controlled and uncontrolled spills of hydrogen fluoride and sulfuric acid at all four refineries that use hydrogen fluoride. The variables included wind patterns and the amount of acid stored at each plant.

In the case of hydrogen fluoride, the study found that an uncontrolled spill would present an immediate danger to life and health within a radius of 3.4 to 4.5 kilometers (2.1 to 2.8 miles), depending on the refinery.

For sulfuric acid, an uncontrolled release under pressure--the worst-case scenario--would affect areas only one-sixth as large, the study said.

Though AQMD staff members did not release their report until Wednesday, they say it influenced their recent decision to recommend to the AQMD board that the bulk use of hydrogen fluoride be banned.

At its March 2 meeting, the board will consider not only that recommendation but also a report on hydrogen fluoride being prepared by a 45-member task force that the agency appointed two years ago to study the issue.

A draft report being considered by the task force stops short of endorsing a ban on bulk hydrogen fluoride use. Instead, it calls for the imposition of additional safety requirements on companies that use the chemical.

The task force is scheduled to consider its final recommendations in a meeting Friday, AQMD spokesman Bill Kelly said.