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Faulty coking process blamed for February fire at Billings refinery

Posted at 6:51 AM, Mar 22, 2024

BILLINGS - Officials with Phillips 66 refinery in Billings have reported the cause and initial investigation that led to a series of fires with black smoke that belched into the skies on Feb. 9.

In reports submitted to the Montana Department of Environmental Quality and obtained through a public information request, senior environmental consultant Matt Evans of Phillips 66 said hydrocarbons that should have been cleared during the “coking process” — to remove a solid residue — accidentally remained in the refining process too long and the volatile fluids caught a coke pit on fire, not once, but twice, reports the Daily Montanan.

Billings residents saw black smoke pouring into a Friday afternoon sky in February, but likely did not notice a second fire later that evening because it happened during the night, against the backdrop of an already dark sky.

The second fire started sometime shortly after 6:30 p.m., and wasn’t contained until 8 p.m. The original fire began around 2 p.m. and was contained by 2:54 p.m.

Refineries are required to keep exhaust from coking units at less than 20% opacity. The higher the opacity, the harder it is to see through the smoke or gases. During both fires, opacity levels reached 100%.

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In its initial report to the Montana DEQ, Evans reports that air quality standards were exceeded for a total of 138 minutes during the day, or a little more than two hours.

While Evans said the initial root cause of the investigation is still being conducted as of March 6 when the refinery issued its report, the preliminary explanation was that liquid hydrocarbons, or oil-based liquids, somehow were not extracted after the “cracking process.” Crude oil is processed by high temperatures and high pressures to “crack” the long, complex hydrocarbon molecules into smaller molecular components where they can be refined into multiple products from fuel oil to lighter fluid.

The coking process then leaves behind a solid residue called “coke” which is used in other industrial applications. However, that left-behind coke has to be removed from the coking drums, a process which is done with water-cutting torches.

Evans’ reports indicate that not all the hydrocarbons were removed by the coking process and as the refinery started to remove the coke from the drums, the hydrocarbons, which are incredibly volatile, caught fire.

“The preliminary investigation indicates that liquid hydrocarbon reached the tank that supplies the quench/cutting water and inadequate removal of hydrocarbon in the tank occurred,” Evans said.