The U.S. Chemical Safety Board on Wednesday called a July explosion at Citgo Petroleum Corp.’s Corpus Christi, Texas, refinery “a significant near-miss” for a widespread release of highly toxic hydrogen fluoride (HF) into a community.
“It’s a significant near-miss of an HF release into the refinery and into the community,” said CSB Investigations Supervisor Robert Hall at a Houston news conference.
On Wednesday, the CSB warned of a potential hazard from HF vapor releases at Citgo’s Corpus Christi refinery.
The board, which is investigating the cause of and response to the July explosion at an alkylation unit that uses HF, urged Citgo to develop and implement plans to ensure an adequate water supply to prevent toxic HF vapor releases.
The CSB also called on Citgo to have a third party audit operations on hydrogen fluoride alkylation units at its 163,000 barrels per day (bpd) Corpus Christi and 167,000 bpd Lemont, Illinois, refineries to see if they conform with practices recommended by the American Petroleum Institute.
Citgo has never performed such an audit. The API issued the recommendation in 1992. The audits are to be performed every three years.
The company said it had taken action on the CSB’s recommendations.
“We hold nothing in higher regard than the safety of our employees and members of the local community,” Citgo said in a statement.
Citgo is an indirect subsidiary of Venezuela’s state-owned oil company PDVSA.
In the fire following the July explosion, only steady winds blowing HF vapor out over a nearby bay and a water cannon system that was able to keep functioning despite several breakdowns in back-up water supply prevented a widespread disaster, Hall said.
Hydrogen fluoride is a highly toxic substance that can spread long distances as a vapor. It can cause burns to skin and eyes as well as damage heart, lungs and bones in humans.
The release of hydrocarbon vapor containing HF began when a control valve on the alkylation unit broke leading to violent shaking in piping and then a break in a connection on that piping.
One type of alkylation units uses HF to make octane boosting additives for gasoline. Another type uses sulfuric acid.
Citgo’s emergency water supply at the Corpus Christi refinery was nearly exhausted as water cannons sprayed the burning alkylation unit to prevent HF vapor from spreading.
A system to replenish the firefighting water supply with sea water from the Corpus Christi ship channel had multiple failures including hose ruptures and pump engine fires, Hall said.
About 42,000 pounds of HF was released in the fire. An estimated 4,000 pounds was not absorbed by the water spray from the cannons and escaped into the atmosphere and blew out to sea, Hall said.
One worker at the refinery, Gabriel Alvarado, remains in a San Antonio hospital undergoing treatment for burns and HF during the fire. Alvarado has had a portion of one arm amputated.
After the Citgo blast, the United Steelworkers union, which represents 30,000 U.S. refinery workers launched a campaign to replace HF alkylation units.
The union, which also represents workers at the Citgo refinery criticized the board for not pushing harder for testing alternatives to using HF as the catalyst in alkylation.
“We would have liked to have heard an urgent recommendation to have a test slip stream done to compare the HF process to the solid-acid catalyst,” the union said. “A slip stream allows for an alternative catalyst to be run at the same time as the HF system and is affordable. The inherently safer technology is here; it just has to be used.”
CSB Chairman John Bresland called Citgo’s cooperation with the probe “marginal,” saying the company has refused document requests and attempted to stop the release of security camera video of the explosion and fire on grounds of national security.
Citgo’s attempt to “to block release of information to the public was unrelated to national security,” Bresland said.
The board also verified with the U.S. Homeland Security Department that it could release the tapes.
Citgo said it was “simply acting in good faith to maintain and preserve the security of our refinery.”
As part of its investigation, the CSB is also looking at other HF alkylation unit mishaps and how vapor releases are prevented at the 51 U.S. refineries with such units.
The U.S. Chemical Safety Board investigates chemical plant accidents. It has not regulatory or enforcement powers.
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