The U.S. Chemical Safety and Hazard Investigation Board (CSB) penned a letter of support for the Environmental Protection Agency’s (EPA) National Enforcement and Compliance Initiative (NECI): Reducing Risks of Accidental Releases at Industrial and Chemical Facilities.
The letter urges the EPA to retain the initiative for 2024, and in particular, to prioritize inspections of fluid catalytic cracking (FCC) units in refineries that operate hydrofluoric acid (HF) alkylation units.
The CSB pointed to its investigations of near-miss HF releases -- the 2019 fire and explosions at the Philadelphia Energy Solutions (PES) refinery, and both the 2015 ExxonMobil Torrance refinery explosion and the 2018 Husky Energy superior refinery explosion and fire.
As a result of these incidents, the CSB issued two recommendations to the EPA. From the Philadelphia Energy Solutions investigation:
Develop a program that prioritizes and emphasizes inspections of refinery HF alkylation units, for example under EPA’s National Compliance Initiative called Reducing Risks of Accidental Releases at Industrial and Chemical Facilities. As part of this program, verify that HF alkylation units are complying with API RP 751 Safe Operation of Hydrofluoric Acid Alkylation Units, including but not limited to the implementation of a special emphasis inspection program to inspect all individual carbon steel piping components and welds to identify areas of accelerated corrosion; the protection of safety-critical safeguards and associated control system components, including but not limited to wiring and cabling for control systems and primary and backup power supplies, from fire and explosion hazards including radiant heat and flying projectiles (per recommendation 2019-04-I-PA-R4); and the installation of remotely operated emergency isolation valves on the inlet(s) and outlet(s) of all hydrofluoric acid-containing vessels, and hydrocarbon-containing vessels meeting defined threshold quantities (per recommendation 2019-04-I-PA-R4).
From the Husky Energy Superior investigation:
Develop a program that prioritizes and emphasizes inspections of FCC units in refineries that operate HF alkylation units (for example, under EPA’s National Compliance Initiative called Reducing Risks of Accidental Releases at Industrial and Chemical Facilities). As part of this program, verify FCC unit safeguards that prevent explosions during transient operation (including startup, shutdown, standby, and emergency procedures). At a minimum, the program will verify the following specific safeguards:
a) Implementation of the reactor steam barrier, or a similar inert gas flow, to maintain an inert barrier at an elevated pressure between the main column (containing hydrocarbon) and the regenerator (containing air);
b) Purging the main column with a non-condensable gas as needed to prevent a dangerous accumulation of oxygen in the main column overhead receiver; U.S. Chemical Safety and Hazard Investigation Board
c) Monitoring to ensure that there is a sufficient non-condensable gas purge of the main column to prevent a dangerous accumulation of oxygen in the main column overhead receiver (either through direct measurement of the oxygen concentration and/or through engineering calculation);
d) Monitoring of critical operating parameters for flows, pressures, pressure differences, and catalyst levels;
e) Documentation of consequences of deviating from the transient operation safe operating parameters and of predetermined corrective actions; and
f) Inclusion of the above items in the appropriate FCC operator training curricula. This recommendation is in addition to the recommendations to EPA relating to hydrofluoric acid outlined in the CSB’s report on the 2019 fire and explosions at the Philadelphia Energy Solutions refinery. In that report, the CSB recommended (1) that the EPA prioritize inspections of refinery HF alkylation units to ensure units are complying with API good practice guidance, (2) to require petroleum refineries with HF alkylation units to evaluate inherently safer technology, and (3) to initiate prioritization and, as applicable, risk evaluation of HF under the Toxic Substances Control Act.
