Frequently Asked Questions
On Dec. 24, 2018, at approximately 4:15 a.m., U. S. Steel’s Clairton Plant experienced a significant fire which required the immediate shutdown of the No. 2 control room and No. 5 control room, which house the equipment and controls necessary to clean the coke oven gases. The fire was successfully extinguished by plant and external fire departments by approximately 9:30 a.m. and no injuries were reported.
Our coking facilities convert coal into coke which is used in the making of liquid iron for the steelmaking process. The coking process produces coke oven gas (COG) as a by-product. No. 2 control room is the facility where clean coke oven gas is separated from the other gases that are generated during the coking process. After this separation, the other gases go through the remaining processes of No. 2 control room and No. 5 control room for additional gas cleaning steps.
However, the fire caused significant damage to the No. 2 control room building roof structure, and the related equipment used to clean coke oven gases, known as vacuum machines. This prevented us from restarting those processes.
The part of No. 2 control room that was affected by the fire is about the size of a football field. Portions of the building’s roof and supporting structure were significantly damaged and presented a safety risk. After a complete and thorough review of the structural safety of the building and as soon as the area was cleared for entry on Tuesday, Jan. 8, a comprehensive safety and fire investigation team that included an independent fire investigator began their work. It has been determined that the fire originated from a mechanical failure in the C-521 vacuum machine area; however, what caused that failure and the mechanism of the fire has not yet been determined and is still under investigation.
Because of the fire and damage to equipment, we are unable to perform desulfurization of the coke oven gas that is generated during the coke making process. This is the process that removes sulfur from the coke oven gas. After processing the coke oven gas, we recycle the coke oven gas to fuel our processes at our Clairton, Edgar Thomson and Irvin plants. To reduce the SO2 emissions, U. S. Steel is utilizing a fuel blend where we are limiting the use of coke oven gas and using natural gas in our process units. Mitigation techniques are also being used to minimize the environmental impact of the No. 2 and No. 5 control rooms being down, including flaring the coke oven gas to maximize dispersion and extending coking times to reduce coke oven gas produced. We will continue to explore additional techniques to further mitigate emissions. Our mitigation plan that was sent to the Allegheny County Health Department on Jan. 7 is available here. Our weekly updates to the Department are found here.
The Liberty Borough monitor, located at South Allegheny High School, tracks PM2.5 daily National Ambient Air Quality Standards (NAAQS) and hourly SO2 NAAQS. While the data is subject to verification, there have been no recorded exceedances of the PM2.5 daily NAAQS at the Liberty Borough monitor since the fire.
Since the incident, the Liberty Borough monitor has recorded exceedances during seven individual hours over five days during the first 16 days immediately following the fire that were above the 1-Hr SO2 standard of 75 ppb. The exceedances over the 75 ppb occurred on:
12/26/2018 – 10 a.m. – 79 ppb
12/26/2018 – 11 a.m. – 80 pp
12/28/2018 – 10 a.m. – 145 ppb
1/2/2019 – 9 p.m. – 81 ppb
1/3/2019 – 11 p.m. – 85 ppb
1/8/2019 – 12 midnight – 80 ppb
1/8/2019 – 4 a.m. – 76 ppb
There have been no reported exceedances of the 1-Hr SO2 NAAQS at the Liberty Borough monitor since 4 a.m. on Jan. 8.
Clairton maintains a by-product recovery plant, where we recover the various by-products from the coke oven gas stream during the gas cleaning process.
Nos. 1, 2 and 5 control rooms are part of the by-product recovery process.
No. 1 control room pulls the coke oven gas away from the coke oven batteries and compresses it to push it through the rest of the gas cleaning process. Ammonia is removed from the coke oven gas at the No. 1 control room.
No. 2 control room separates the coke oven gas into two gas streams. One is a clean gas stream that is used as fuel to the coke oven batteries, boilers, and other sources of energy at our facilities. The second gas stream is then processed for additional by-product removal. This gas stream contains the sulfur compounds that are removed in the No. 5 control room.
U. S. Steel is employing all available resources around the clock to make the necessary repairs to the impacted areas and equipment. Although we are expediting every possible repair required, many of these repairs are intricate and require additional specially fabricated parts that have long lead times to make. We anticipate that it will take approximately four months to restart these operations. We are targeting on or before May 15.
We are committed to our community, our shared environment and our role as a good corporate citizen.
Upon extinguishing the fire, we devoted all available resources and personnel toward mitigation efforts that could be implemented immediately. Hot idling means to shut down and stop operating coke making, and it is not possible to shut down a coke making facility rapidly as hot idling is a deliberate and lengthy process (due to the extreme temperatures of the ovens and need to safely control explosive gas). In this instance, diverting resources to begin a hot idle would have redirected efforts away from remedying the problem and created additional environmental and economic impacts.
Long-term, a hot idle at Clairton could mean the permanent closure of some of the impacted batteries, and other batteries would sustain damage that would adversely impact the facility’s operation and environmental performance for several years. Such a hot idle action would likely have an adverse impact on the operating levels of all of our Mon Valley facilities and could result in workforce reductions.