Lee Steam Station coal to gas upgrade/conversion complete

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By David Meade/Stan Welch

An innovative project to convert Duke Energy’s W. S. Lee Steam station near Williamston from coal to gas and retrofit a 57 year old steam turbine has recently been completed.

More than sixty years ago, Duke Power, as they were known then, built the William States Lee steam plant. The plant was named for a man who was instrumental in building the Duke Power system over the thirty one years of his career with the energy giant. Lee began as an engineer and became the company’s top man.

When the plant was placed into operation in 1951 it was one of the most modern and efficient power plants Duke Power had constructed. It was also innovative and engineered looking to the future.

The plant was constructed with three coal fired steam turbine units and designed so that it could be converted to natural gas one day. Fifty-seven years later that day has arrived.

The original Lee Steam plant began generating electricity with one steam driven turbine unit when the plant opened in 1951. A second unit was added and placed into operation the next year.

Unit 3, the newest turbine located inside the original plant, was installed and operating by 1958.

All three of the original units relied on steam which was produced in a massive boiler system fired by coal which was brought in by rail.

The upgrade project converting the Lee Steam Station from coal to gas included gutting and replacement of the coal based fuel system and refitting the plant for cleaner, more efficient natural gas.

Duke Energy spokesperson Lisa Parrish said that the upgrade to natural gas took fifty four months and 64,000 man hours were worked during the conversion.

Units 1 & 2 were kept on line until they were retired in October of last year. On Nov. 4, 2014, the facility was retired as the last coal fed plant in South Carolina.

However, with the plant now retrofitted for gas, Unit 3 continues to provide electricity to the nation’s power grid.

Lee Steam Unit 3
Lee Steam Unit 3

Parrish explained that upgrading Units 1 and 2 was considered, but issues of customer costs, fuel diversity and system flexibility led to the decision to build a new and separate plant on the 600 acre site.

The Lee Steam upgrade included new gas supply lines and other necessary equipment including digital monitoring to transform the facility from coal to natural gas. In addition to repurposing Unit 3, the upgrade project kept the existing boiler, pumps and other support equipment.

New Control Room Equipment
New Control Room Equipment

The conversion process was $75 million less expensive than replacing the remaining turbine unit with a new combustion turbine.

“This project is like converting your garage into a family room,” Parrish said. “The basic structure was already there making it less costly than building a new wing onto your house.”

Gas is supplied from a nearby supply pipeline.

Specialized gas detection systems were installed throughout the plant along the gas piping to protect the equipment when it is in operation. New LED explosive proof lighting was also installed.

Repowering the current plant to use natural gases cut greenhouse gases making it more environmentally friendly, Parrish said. By using natural gas instead of coal, all sulfur dioxide emissions have been eliminated.

The nitrogen oxide emission rate has been cut by 550 percent.

Lee Steam’s Unit 3 has a quick start up and can power on faster than traditional coal or nuclear plants, providing greater operating flexibility, Parrish said.

Total cost for the upgrade project was $22 million. A new combustion turbine plant would have cost more than $95 million.

Currently the plant provides enough electricity to power 122,000 homes in the area.

But Duke continues to look to the future, and with a nearby gas supply line and room for expansion at the existing Lee Steam site, the company is investing in a completely new combined cycle facility.

The new W. S. Lee Natural Gas Combined Cycle Facility will rely on natural gas and will be extremely efficient. The new plant facility will be a 750-megawatt natural gas-fired combined cycle plant and will employ 40 fulltime, well paying jobs.

It will house two state of the art combined cycle natural gas fired turbines.

Those units will be baseload units, operating around the clock, and generating 750 megawatts of electricity.

Retrofitted Unit 3, which generates 180 megawatts will be used during peak energy demand. Unit 3 has a life expectancy of 10 years, a spokesperson said.

More than 500 workers are expected to be involved in construction which is expected to begin in June and take approximately three years to complete.

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When the boiler is running at maximum levels, the internal temperature can reach 1400 degrees Farenheit. (Pictured above)