A seven-person investigation team from the U.S. Chemical Safety Board (CSB) has arrived at the site of an accident reportedly involving the release of hydrofluoric acid (HF) at the CITGO Corpus Christi, Texas alkylation unit.
According to media reports, no injuries were reported as detectors sensing the HF set off water cannons to contain the acid release.
The alkylation unit in the 163,000 barrel a day refinery utilizes HF to make high-octane blending components for gasoline. HF is highly corrosive and toxic. Absorption through the skin can produce fatal cardiac arrest and inhalation causes damage to the linings of the lungs.
On July 19, 2009, hydrocarbons and hydrogen fluoride were suddenly released from the same unit. The hydrocarbons ignited, leading to a fire that burned for several days. The fire critically injured one employee and another was treated for possible hydrogen fluoride exposure.
CITGO reported to the Texas Commission on Environmental Quality that approximately 21 tons (42,000 pounds) of HF released from alkylation unit piping and equipment, but was captured by the HF water mitigation system.
The CSB’s investigation into this accident is continuing. Investigators early on determined that during the first day of response efforts, CITGO nearly exhausted the stored water supply for the water mitigation system, causing the refinery to begin pumping salt water as a backup. Multiple failures occurred during the salt water transfer including ruptures of the barge-to-shore transfer hoses and water pump engine failures.
In December 2009, the CSB issued urgent safety recommendations calling on CITGO to immediately improve its emergency water mitigation system in the event of another release hydrogen fluoride. The Board also called on CITGO to perform third-party audits to ensure the safety of its hydrogen fluoride units at its Corpus Christi, Texas, and Lemont, Illinois, refineries. CITGO met the requirements of the recommendations and the Board closed them as “Acceptable Action” in 2011.
CSB Chair Rafael Moure-Eraso said, “We are launching an investigation into this accident as we continue our investigation of the 2009 HF release event, because of the toxic nature of hydrofluoric acid and the need to keep it contained, or to mitigate the consequences of a release. Approximately fifty of the nation’s refineries still use HF in their alkylation units, requiring great care in its handling.”