Incident investigation of hydrogen explosion and fire in a residue desulfurization process

A large hydrogen explosion and fire occurred on October 27, 2022 in a residue desulfurization (RDS) process in a refinery in Kaohsiung, Taiwan. RDS is an important process that use hydrogen to convert the sulfur in the fuel into hydrogen sulfide for producing low sulfur fuel. The incident occurred during pressurization of the RDS reactors and downstream coolers by hydrogen. The incident led to significant damages to the downstream coolers and some part of the RDS reactors. Detailed incident investigation was carried out. A reactor effluent air cooler (REAC) in the downstream of RDS reactors was found to be ruptured in the rectangular header box. With security videos, process DCS data, leak and dispersion modelling, and actual damage on the process, it is possible to reproduce the leak rate, size of the initial fireball and damages done to the process. It is also found that the hydrogen leak was accompanied by prompt ignition which is commonly encountered in high-pressure hydrogen services. Recommendations are made to prevent and mitigate any future incident from the RDS process.