Dakota Gas’ Great Plains Synfuels Plant completes ‘brown plant’ turnaround

The new BD5712 damper valve prior to installation. This damper provides isolation of the flue gas at the inlet to the flue gas desulfurization unit.

Dakota Gas’ Great Plains Synfuels Plant recently completed a “brown plant” turnaround and is in the process of going through the multi-step process of startup. Turnarounds improve reliability, safety, and productivity and help to maintain equipment and efficiency.

“The first train of the gas path was shut down on Sept. 3 and the second train of the gas path was shut down on Sept. 9. The ammonia and urea units were shut down on Sept. 7,” said Dale Johnson, Basin Electric senior vice president and plant manager at Dakota Gas. 

There were over 4,000 tasks completed during the turnaround. “Going into this turnaround, I think we were all concerned about the boiler duct replacement project. That was probably the most complex project for this outage, and it went very well,” Johnson said. “The spray cooler replacement was another large complex project that went well.”


Installation of the flue gas duct exiting A-Riley boiler.

There were some projects that had quality and timing issues, which was a significant factor in the overall length of the turnaround. There were two contractor welding tasks that took longer than expected to complete, which resulted in the outage being extended by two weeks. In both cases, the contractor welds failed, and Dakota Gas welders completed the jobs.

Another setback during the turnaround was the failure of the 25,000-horsepower motor for the main air compressor for the oxygen plant. “We planned to run this during the outage to provide nitrogen for the plant. This motor failed one week into the turnaround. Fortunately, we had a contingency plan in place to utilize purchased nitrogen, but this added significant cost and we certainly didn’t plan to rebuild the motor at this time,” Johnson said.

Every turnaround provides an opportunity to make repairs and complete inspections. “The outage allowed us to perform work on common systems like the steam and cooling piping throughout the plant that are rarely out of service,” Johnson said. “For example, there was a large chunk of plastic, weighing about 3,000 pounds, that was created in a cooling tower fire. This chunk was floating in the cooling tower sump and was damaging the screens on the inlet to the cooling water pumps. This chunk of plastic, plus a bunch of smaller material, was removed from the sump, and this work could only be done during a brown plant outage.”

“I feel really good about our planning effort,” Johnson said. “We were able to complete virtually all of the planned work, plus some work that was identified as we started to open up the equipment; however, there were also a few items that were discovered during the outage that will require action at a later date.”

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