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Tale of 2 coal plants: Turk tackles emissions with cutting-edge controls

S&P Global MarketIntelligence recently visited two of American Electric Power's coal-fired powerplants. One was the 609-MW John W. Turk Jr. UPC plant in Arkansas, a modernultra-supercritical advanced coal plant that started operating about four yearsago. The other is the massive 2,900-MW John E. Amos plant that went online in1971 — more than four decades before Turk.

Both plants, in verydifferent ways, continue to convert coal into electricity while navigating thecomplexities of state and federal clean-air regulations.

This article focuseson the Turk plant. To read the companion article about the Amos plant,click here.

A train stops at the John W. Turk Jr. UPC coal complex in rural southwestArkansas, where it surrenders its black load to conveyor belts in the yard,where a smokestack belches steam, where turbines noisily spin the generator andwhere plant operators monitor what most assume is an age-old process common tothe industry.

However, here at this 3,100-acre coal complex, newtechnology with advanced efficiency and emissions control measures set this609-MW ultra-supercritical plant apart from its peers.

A tour of this sprawling plant, as well as the much olderJohn E. Amosfacility, both operated by American Electric Power Co. Inc., revealed the steps theindustry is taking to abide by stringent emissions standards while cuttingcosts and increasing efficiency at a time when the economics of coal generationis increasingly under pressure.

"We have more invested in efficiency controls thanprobably the power plant [itself]," plant manager Tim Gross said during amid-August tour of the site.

Turk was brought online in December 2012 for about $1.8billion. AEP subsidiary Southwestern Electric Power Co. owns 73% of the facilityand operates the plant.

Gross noted that when visiting a power plant site, he alwayspays attention to the distance from the boiler or steam generator to the coalstack. The longer the distance, the more efficiency and emissions controls usedby the facility, he said.

Emissions controls at Turk begin with the simple fact thatthe plant — which Gross said has one of the strictest air permits in the UnitedStates — sources its fuel from the Powder River Basin in Wyoming, whichproduces coal with some of the lowest sulfur and ash content in the nation.

Special water filtration systems at the Turk coal plant remove suspended solids and dissolved
solvents in order to make "pure water" for use in the energy conversion process.

Photo credit: Darren Sweeney

Turk uses a spray dry-absorber process involving thecontinuous spray of a slurry of lime and recycled ash to control SO2 emissions.The power plant also uses selective catalytic reduction technology involvingthe injection of anhydrous ammonia into flue gas to remove NOx emissions andinjects activated carbon to capture mercury emissions. A pulse jet fabricfilter collects and removes the leftover ash created by the process.

"It's just a big catalytic converter," DavidRoberts, operations superintendent at Turk, explained.

The air quality control systems at Turk are supplied byBabcock & Wilcox Co.

The combination of emissions controls and low-sulfur PowderRiver Basin coal enables Turk to have significantly lower emissions rates thana plant like AEP's supercritical coal-fired Amos station, a 2,900 MW behemothin West Virginia.

In 2015, Turk emitted SO2 and NOx at rates of 0.059 lb/MMBtuand 0.041 lb/MMBtu, respectively, according to SNL Energy data. Amos, which wasbuilt in 1971 and burns primarily higher-sulfur coal sourced from Appalachia,emitted NOx at a rate more than twice as high as Turk — 0.089 lb/MMBtu in 2015,and SO2 at a rate of 0.078 lb/MMBtu, 32% higher than Turk.

Efficiency

Roberts said Turk's energy conversion process is what makesit much more efficient than a typical coal plant.

"To be efficient, the hotter you can get the waterbefore it gets to the boiler, the less energy or the less fuel you need to heatthe water," Roberts said. "If you can have it 1,000 degrees before itgets there, you take less fuel.

"Fuel costs more than anything else, essentially."

The control room at the Turk plant includes a digital control system that involves 15,000 control
units monitoring power plant activity.

Photo credit: Darren Sweeney

Roberts said the plant uses feedwater heaters to preheatwater on its way to the boiler using excess steam from the turbine.

"At Turk, we have an extra heater that makes us evenmore efficient," Roberts added.

However, what makes the plant ultra-supercritical is thatthe water temperature can be heated to approximately 1,115 degrees on mainsteam and reheated to approximately 1,125 degrees, Gross noted.

At this point, steam and water are essentially "actingthe same," Gross said, adding that the steam temperature in a subcriticalcoal plant may reach 1,000 degrees.

Turk's higher steam temperature enables it to operate at alower heat rate, allowing it to burn less coal and therefore produce lessemissions than a standard coal-fired plant. In 2015, Turk operated at anaverage heat rate of 9,145 Btu/kWh, according to SNL Energy data. In contrast,the Amos plant operated at an average heat rate of 10,053 Btu/kWh in 2015.

AEP's top executive lauded the plant's heat rate shortlyafter it came online.

"We originally anticipated that it would be one of thelowest heat rate coal units in the country. It is. But in fact, it's even lowerthan we anticipated," AEP President and CEO Nicholas Akins said in aFebruary 2013 earnings call.

Apart from its environmental and efficiency controls, plantoperators contend that technology also plays a significant role in ensuringTurk runs successfully.

Roberts noted that the company used high-fidelity simulationbefore the unit was brought online. He credits this technology, which isdesigned to simulate real-life scenarios, with uncovering design problems atthe plant and helping the company to commission the facility in about fourmonths. Southwestern Electric Power Co. operators continually undergo trainingusing this simulation technology.

The coal yard at the John W. Turk Jr. plant in Hempstead County, Ark.

Photo credit: Darren Sweeney

Another critically important piece to the technology behindTurk is a digital control system that involves 15,000 control units monitoringpower plant activity. There are also 12,000 alarms attached to this system tohelp alert operators when there is a problem, Roberts said.

Coal

While there are operational and technological differencesthat help Turk stand out, the plant also has some of the same fundamentalequipment and fuel supply needs of other coal plants.

There are six pulverizers on-site that grind chunks of coalinto a fine powder that is then blown into the boiler by industrial-sized fans.Turk receives two or three trainloads of coal per week, with each traincarrying more than 16,000 tons of coal, according to plant officials.

Each train supplies about three days of coal supply, and theplant had roughly 48 to 50 days of stored coal at the time of the tour.

SNL Energy data shows that Turk received approximately 1.8million tons of subbituminous coal in 2015 from 's Antelope coalmine in Converse County, Wyo., as well as Peabody Energy Corp.'s North Antelope Rochelle andArch Coal Inc.'sBlack Thunder mines in Campbell County, Wyo.

"We don't make it long without coal," Gross said.

SNL Energy is anoffering of S&P Global Market Intelligence.