Panelists get into nitty-gritty of clean coal

During the Appalachian Regional Commission conference in Athens this week, members of the energy industry met to talk about the controversial role of coal in clean-energy production.

Panelists discussed recent developments and future prospects for new technologies that reduce carbon emissions from coal-burning power plants, including co-firing with biomass, integrated gasification combined cycle (IGCC), and carbon capture and sequestration technologies.

The forum was held as protesters to the coal industry aired their concerns (see related story).

Mark Gray, vice president of engineering services for American Electric Power, spoke about what the utility giant is doing in the way of clean-coal technologies with regard to carbon capture and sequestration.

According to the Energy Information Administration, coal typically fuels about nine-tenths of net electricity generation in Ohio. AEP serves all or part of 61 counties in Ohio, including Athens.

Gray spoke about what the company is researching and doing as far as carbon-capture technologies, as well as sequestration methods.

"The reality is that every technology has a carbon footprint," Gray said, making his point that the key is to find the most efficient ways to capture carbon and sequester it.

He went on to say that in order to get to the CO2 emission targets that have been set in national policy, just switching to natural gas for energy production does not fix the problem.

"It will get you part of the way down the slope, but once you get past a 2025 or 2030 timeframe, gas doesn't keep you going down the trajectory," Gray said.

On existing power-generating units or plants, or potentially new units, post-combustion capture is what AEP is looking into right now, Gray said. Pre-combustion capture, he continued, is the focus of the IGCC technologies.

"That's taking the CO2 out of the process before you actually burn the fuel for power generation," he said. "You take [synthetic gas], you take it through what's called a water-shift reaction to produce high hydrogen-content fuel and you burn that in the gas turbine in the combined cycle system. So you've pulled the CO2 out."

The big advantage of this, Gray said, is that it's being done under pressure with smaller volumes, making it the most cost-effective way to capture carbon.

Another big cost to the energy consumer, Gray added, is the compression of the CO2.

"Once you capture it, you have to do something with it," he said. This can include putting it in the ground, in storage, or using it to enhance oil recovery, he said, but first it must be compressed. "That is a very significant energy-consumption piece of this puzzle," he said.

He said AEP is looking at an advanced supersonic compression cycle that may "dramatically improve both the cost... and the energy associated with it." The energy would come from a high-temperature fluid created as a byproduct that could be used in the recovery process, he said.

"Compression is going to be a key technology piece going forward," he said.

As far as putting CO2 in the ground, Gray said what he's learned the most is the complexity of the well system required to accomplish this.

"These wells, because of the nature of what you're doing, have to have a very high fault tolerance to deal with any problems, so there are multiple casings going down through the ground," he said. These wells, dug to around 9,000 feet, include seven or eight casings, he added.

"You have multiple casings to protect groundwater or any leakage," he said. "So this is a very conservative design base. We dealt with multiple environmental and state organizations to review this as part of our permit process."

To capture 90 percent of the CO2 from a 1,300-megawatt unit, the company would need somewhere between 12 and 18 wells scattered over about 200 square miles, Gray said.

"That unit creates 8 million tons of CO2 a year," he said. "Over 30 or 40 years of operation, that's the type of well-field configuration you would need to deal with that much CO2."

The approval process includes an underground injection control permit, a monitoring-the-well work permit and land-use permits, among several others, he said.

"You have lots and lots of permits and lots and lots of people looking at that," Gray said.

He continued that community involvement is critical to this process.

"The operation of capturing and injecting CO2 is going to be a national debate, I don't doubt that," Gray said. "And it's going to have local ramifications, regional ramifications and national ramifications."