Horsehead Holding Corp. has provided an update on its efforts at restarting the operations at its Monaca, Pa., refining facility.
The Monaca plant's zinc oxide and metal refinery remains temporarily closed after an explosion at the plant on July 22 killed two employees.
Since closing, teams from the U.S. Occupational, Safety and Health Administration (OSHA), the U.S. Chemical Safety & Hazard Investigation Board (CSB) and Horsehead Holding have been conducting investigations into the cause and the circumstances that may have contributed to the explosion.
In a press release on the update, Horsehead says that it believes that the incident was caused by liquid zinc escaping into a hotter combustion chamber surrounding the distillation column. The liquid zinc vaporized and expanded rapidly, breaching a column wall and combusting upon reaching the atmosphere.
In the release, Horsehead added that it plans to implement certain preventive and protective enhancements to the Monaca refinery based on results of the investigations to date. The enhancements include changing the design of the columns and operating procedures to minimize the risk of a reoccurrence. In addition, an alarm system will be installed and barriers will be constructed around the columns to further protect employees.
Regarding zinc oxide production, Horsehead expects to restart all four Larvik furnaces by the end of September. The company expects to restart the zinc oxide and refined zinc metal columns in stages, starting in November. If the rebuilding process is completed on schedule, the company expects to bring its zinc oxide production and refined zinc metal to pre-incident levels by January, 2011.