April 14, 2012:

HollyFrontier Corp. officials still refuse to talk about the cause of a fire atop Tank 13 at its west Tulsa refinery nearly one year ago, but the company's communications with state regulators blamed a bad valve allowing hydrocarbons to slip into the wrong tank, officials confirmed this week. The April 22, 2011, blaze gained a tremendous amount of media and neighbors' attention but caused no injuries nor significant damage to the refinery, according to reports. Photos show flames shooting up around the top rim of the tank.

Some observers initially wondered whether the cause was lightning on a stormy night, but that was later ruled out. HollyFrontier - then called Holly Corp. before its summer merger with Frontier Oil Corp. - investigated but announced in June it would not release findings to the public. The company is keeping that stance this week. "Things that are material to us we are required publicly to note," HollyFrontier spokesman Neale Hickerson said. "It was an incident which did occur, but there was little loss of property and no injuries." State Department of Environmental Quality spokeswoman Skylar McElhaney confirmed that HollyFrontier officials revealed the fire's cause. McElhaney sent the Tulsa World an email quoting from the company's report about Tank 13's ignition source.

The report indicated that "a malfunctioning valve at the unifiner boot prevented the boot from holding a liquid level and allowed hydrocarbon to pass into the sour water system." Sour water has hydrogen sulfide present, and refineries remove sulfur from refined products to meet federal standards. A sour water degassing slop pump, as HollyFrontier called it, would normally remove hydrocarbon which gets past the protective boots. "The combination of these two mechanical failures at the unifiner and the SWS (sour water stripper) allowed some hydrocarbon from the unifiner that is normally stored in a cooled tank to be routed to a heated tank (13)," the company informed regulators.

HollyFrontier also reported details of unrelated, more recent flare gas recovery unit compressor shutdowns on April 5 and 10. The first shutdown was due to flare volume exceeding compressor capacity, while the April 10 event was likely due to malfunction of a pressure control valve, according to the DEQ.  The flareups lasted several hours and were both reported from HollyFrontier's "Tulsa East" facility, formerly known as the Sinclair refinery. HollyFrontier bought the two Tulsa refineries from Sunoco and Sinclair in 2009 and connects the two units via a series of pipelines. The company will stay publicly mum about both incidents since they did not threaten the public or cause damage. "We think we go the distance with regard to public relations," Hickerson said. The company allowed the Tulsa World in on an exclusive, four-hour tour of the two sites in August 2011. At the time, HollyFrontier noted some $70 million worth of improvement projects were under way at that time.

The Tulsa refinery can process 125,000 barrels per day. HollyFrontier produces gasoline, diesel, solvents, lubricants, asphalt and other products.

By Tulsaworld.com