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CITGO Refinery Hydrofluoric Acid Release and Fire

Overview

On July 19, 2009, a hydrocarbon gas release occurred in the CITGO Corpus Christi East Refinery hydrogen fluoride (HF) alkylation unit in Corpus Christi, Texas. The release ignited and caused extensive damage. The fire burned for several days. The incident involved violent shaking in process recycle piping, failure of a control valve, and release of highly flammable hydrocarbons. The ensuing fire caused multiple failures and released HF. CITGO reported that approximately 21 tons (42,000 pounds) of HF were released from alkylation unit piping and equipment and captured by the HF water mitigation system, with 30 pounds not captured. The incident nearly exhausted the stored water supply for fire suppression and HF mitigation on the first day of response.

Incident Snapshot

Field Value
Facility / Company CITGO
Location Corpus Christi, TX
Incident Date 07/19/2009
Investigation Status The CSB issued urgent recommendations on December 9, 2009, and formally closed its investigation at a public meeting on January 28, 2015.
Accident Type A fire in the alkylation unit led to a release of hydrofluoric acid (HF). One worker was critically burned.
Final Report Release Date 12/09/2009

What Happened

  • On July 19, 2009, a hydrocarbon gas release occurred in the CITGO Corpus Christi East Refinery hydrogen fluoride (HF) alkylation unit at 1802 Nueces Bay Boulevard, Corpus Christi, Texas.
  • The incident occurred when violent shaking in the process recycle piping broke two threaded connections, releasing highly flammable hydrocarbons.
  • The shaking was caused by nearly complete flow blockage, which occurred due to the sudden failure of a control valve.
  • The control valve failed when an internal plug unthreaded from the valve stem, closing the valve.
  • The only existing bypass valve was manually operated and became inaccessible following the hydrocarbon release.
  • The cloud of releasing hydrocarbons reached an adjacent unit and ignited.
  • The release ignited, causing extensive damage. The ensuing fire burned for several days.
  • The ensuing fire caused multiple failures, releasing HF.
  • 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.
  • CITGO reported 30 pounds of HF were not captured by the mitigation system.
  • During this incident, CITGO nearly exhausted its stored water supply for fire suppression and HF mitigation on the first day of the multi-day incident response.
  • About 11.5 hours after the initial release, before the water supply was completely exhausted, the Refinery Terminal Fire Company began pumping salt water from the Corpus Christi ship channel into the CITGO fire water system using a barge equipped for firefighting.
  • Multiple failures occurred during the salt water transfer, including multiple ruptures of the barge-to-shore transfer hoses and two water pump engine failures.
  • CITGO impounded the salt water used for HF mitigation and fire suppression on-site.
  • On November 1, 2009, CITGO restarted the HF alkylation unit.

Facility and Process Context

  • CITGO Corpus Christi East Refinery hydrogen fluoride (HF) alkylation unit at 1802 Nueces Bay Boulevard, Corpus Christi, Texas.
  • The alkylation unit makes high-octane blending components for gasoline.
  • CITGO operates two US refineries with HF alkylation units, one in Corpus Christi, TX and one in Lemont, IL.
  • The CITGO Alkylation Unit Process Hazard Analysis assumes that the HF mitigation system is available to minimize the consequences of an HF release.
  • The water mitigation system provides the last defense against an HF release into the surrounding community.
  • Prevailing winds during the incident carried any HF not captured by the water mitigation system toward the Corpus Christi ship channel and Nueces Bay.

Consequences

  • Fatalities: None reported.
  • Injuries: The fire critically injured one CITGO employee. One other employee was treated for possible HF exposure during emergency response activities.
  • Environmental release: Approximately 21 tons (42,000 pounds) of HF released from alkylation unit piping and equipment, but was captured by the HF water mitigation system. CITGO reported 30 pounds of HF were not captured by the mitigation system.
  • Facility damage: The release ignited causing extensive damage; the ensuing fire burned for several days. The ensuing fire caused multiple failures.
  • Operational impact: CITGO nearly exhausted its stored water supply for fire suppression and HF mitigation on the first day of the multi-day incident response. On November 1, 2009, CITGO restarted the HF alkylation unit.

Key Findings

Immediate Causes

  • violent shaking in the process recycle piping broke two threaded connections
  • nearly complete flow blockage
  • the sudden failure of a control valve
  • an internal plug unthreaded from the valve stem, closing the valve

Contributing Factors

  • The only existing bypass valve was manually operated and became inaccessible following the hydrocarbon release.
  • The cloud of releasing hydrocarbons reached an adjacent unit and ignited.
  • The ensuing fire caused multiple failures, releasing HF.
  • During this incident, CITGO nearly exhausted its stored water supply for fire suppression and HF mitigation on the first day of the multi-day incident response.
  • Multiple failures occurred during the salt water transfer, including multiple ruptures of the barge-to-shore transfer hoses and two water pump engine failures.
  • Prevailing winds during the incident carried any HF not captured by the water mitigation system toward the Corpus Christi ship channel and Nueces Bay.

Organizational and Systemic Factors

  • CITGO installed the HF water mitigation system after a release and fire in the alkylation unit had resulted in an uncontrolled release of HF from the refinery in April 1997.
  • The CITGO Alkylation Unit Process Hazard Analysis assumes that the HF mitigation system is available to minimize the consequences of an HF release.
  • CITGO’s PSM/RMP Incident Investigation Team Interim Recommendations for the July 19, 2009 HF alkylation unit release and fire did not include any recommendations addressing the HF mitigation system water supply.
  • CITGO has never conducted a safety audit of HF alkylation operations at either of its US refineries equipped with HF alkylation units pursuant to recommendations of API Recommended Practice 751, Safe Operation of Hydrofluoric Acid Alkylation Units.

Failed Safeguards or Barrier Breakdowns

  • The only existing bypass valve was manually operated and became inaccessible following the hydrocarbon release.
  • The HF water mitigation system.
  • CITGO nearly exhausted its stored water supply for fire suppression and HF mitigation on the first day of the multi-day incident response.
  • The CITGO Alkylation Unit Process Hazard Analysis assumes that the HF mitigation system is available to minimize the consequences of an HF release.

Recommendations

  1. 2009-14-I-TX-UR1 | Recipient: CITGO, Inc. | Status: Urgent safety recommendation | Within 30 days, develop and initiate actions to ensure adequate water supply to the CITGO HF mitigation system. Actions could include, but are not limited to, increasing onsite storage capacity, installing a permanent backup system, and developing procedures and training for water management in an emergency. Every 30 days, report actions planned or completed to the Refinery Terminal Fire Company and Local Emergency Planning Committee. Continue the 30-day periodic reporting until all planned actions are fully implemented.
  2. 2009-14-I-TX-UR2 | Recipient: CITGO, Inc. | Status: Urgent safety recommendation | Within 60 days, complete a third-party audit of all (Corpus Christi, TX and Lemont, IL) CITGO HF alkylation unit operations in the United States as recommended by API Recommended Practice 751, Safe Operation of Hydrofluoric Acid Alkylation Units, Third Edition June 2007. The selected lead auditor shall have extensive knowledge of HF hazards, HF alkylation units, and API 751. Consistent with the employee participation requirements of the Process Safety Management Standard for Highly Hazardous Chemicals (29 CFR 1910.119(c)), share all audit results and actions planned or completed to correct deficiencies in each refinery with all CITGO and contract employees whose work area includes that refinery’s alkylation unit.

Key Engineering Lessons

  • HF mitigation systems should not be treated as the sole last defense without assured, adequate water supply for the full duration of a credible incident.
  • Manual bypass arrangements that can become inaccessible during a release are not reliable safeguards for controlling flow blockage or isolating a failed valve.
  • Process hazard analyses that assume the availability of mitigation systems should explicitly verify the supporting utilities and water supply needed for those systems to function.
  • Emergency response water transfer arrangements should be robust enough to avoid hose ruptures and pump failures during prolonged fire and HF mitigation operations.

Source Notes

  • Priority 1 source (FINAL REPORT: Urgent Recommendation) was used to resolve conflicts and establish authoritative findings.
  • All facts are limited to the provided source extracts; no external information was added.
  • The incident involved a hydrocarbon release and fire in the HF alkylation unit, with HF released as a consequence of the fire.

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