The dozen or so member companies of a group calling itself Coal 2.0 have been working collectively and individually on developing and promoting the use of coal-cleaning methods that can potentially improve the thermal efficiency of coal-fueled power plants while substantially reducing emissions. The members of Coal 2.0 are among the nearly 160 members of the American Coal Council, an organization comprised of companies representing all facets of the coal market. The members of Coal 2.0, which was formed about a year ago, largely specialize in coal preparation and handling. The group’s name denotes the capability inherent in these technologies to take coal to the next level, improving its environmental performance. We spoke with Michael Ferguson, vice president for Taggart Global LLC, a company that focuses on the design and construction of coal handling and preparation facilities.

Pathfinder: Coal 2.0 focuses on treating coal ahead of combustion in order to increase the efficiency of the combustion process and reduce the emitted pollutants. Why treat it beforehand? What's the advantage over just making generation more efficient?

Coal preparation is the most widely used method of pre-combustion treatment available today. Cleaning the coal removes ash, resulting in decreased sulfur dioxide and mercury emissions. Coal-fueled boilers can operate more efficiently due to the reduction of impurities that decrease heat and combustion rates. Cleaning technologies also encourage the use and recycling of so-called waste coals that are generally abandoned because of lower Btu values and higher levels of impurities, rock, or dirt. Advancement of cleaning technologies has produced more efficient cleaning of ultra fine coal.

Coal upgrading technologies increase the Btu content of lower-ranked coals by removing water through dewatering or drying processes. Moisture removal is accomplished through the use of four different technologies, three thermal and one non-thermal. Dewatering and upgrading help reduce emissions as some of the Coal 2.0 technologies remove impurities such as sulfur, mercury and other minerals with the water. NOx emissions are reduced as higher Btu-ranked fuel can result in a more complete combustion. The increased fuel and boiler efficiency realized when burning upgraded coal leads to lower CO2 emissions per kilowatt-hour generated.

Coal treatment technologies use additives to alter the coal’s combustion characteristics. These technologies generally use latex, metallic or mineral reagents or sorbents to change the way the coal burns. These technologies can capture sulfur and mercury in solid by-products during the generating process rather than allowing them to be emitted in the exhaust gas. In addition, combustion efficiency improvements result in lower NOx and CO2 emissions per kilowatt-hour.

Pathfinder: What kind of coal would you treat and does that coal account for any significant portion of the coal burned to produce electricity?

Ferguson: Approximately 50% of the coals consumed in the United States are lower rank coals such as lignite and sub-bituminous. These coals are prime candidates for the coal upgrading technologies. By treating the coal, consumers can realize substantial gains in transportation efficiency, product storage, mill efficiency, boiler efficiency and gains in most areas of emission controls.

As an example, the Powder River Basin mines produce and ship more than 1 million tons of coal per day with moisture content generally greater than 25%. That’s equivalent to 16 unit trains of water each day. If coal upgrading technologies were deployed, the mines would ship fewer trainloads, the utilities would handle fewer tons and we would see a significant increase in boiler efficiency.

Pathfinder: What does the process do to the coal? How much does the process increase efficiency?  How much does it increase the cost of coal?

Preparation and upgrading technologies concentrate the coal. Removing the non-coal portion of the fuel provides utilities with a purer carbon product. Treatment can result in a reduction of ash that can be as much as 40% in some coals; a reduction of moisture through upgrading can be as much as 20%.

The spontaneous combustion of dried coal has been a concern with some technologies, but recent advances in the stabilization of the lower rank coals has allowed for safer transportation and long-term storage of the products.

Costs vary and are dependent on the individual technologies. While each technology will increase the initial cost of the coal, improvements in transportation costs and gains in generation and environmental efficiency can provide positive economic results.

Pathfinder: Would pre-combustion treatment affect emissions of carbon dioxide?

Ferguson: Treatment does affect the emission of carbon dioxide. By increasing boiler efficiency using treated coal and improving the heat rate of the boilers themselves, carbon dioxide emissions can be reduced.

• Lignite heat value increase by 900 Btu/lb.
• Reduction of fuel input by 14%.
• Increase in overall power plant efficiency by 2%.
• Reduced stack emissions yield:
  –Sulfur dioxide cut by more than 40%.
  –Mercury reduced by more than 40%.
  –Nitrogen oxide cut by more than 20%.
  –Carbon dioxide cut by 4%.

The diagram illustrates the benefits of pre-combustion technologies: (The blue text represents the effect of reduced moisture, brown is reduced mineral matter, and green is the combined benefit.)

Pathfinder: The government will spend large sums to support research on technologies that will reduce carbon dioxide emissions at the power station itself.  Does the government support pre-combustion research as well?

Ferguson: The government has supported pre-combustion technologies in the past and we expect that it will continue to do so in the future. Both Congress and the administration have stated their interest in pursuing development and commercial deployment of clean coal technologies to further out nation’s environmental objectives. The technologies represented by the Coal 2.0 Alliance certainly fit the bill.

Pathfinder: When can you start to employ pre-combustion processes on a commercial scale?

Ferguson: Coal preparation is widely used today and can be deployed to clean finer grades of coal. Several of the Coal 2.0 members involved with coal upgrading have moved their technologies from the laboratory to the pilot stage and are ready to deploy now. Chemical treatment is starting to be accepted at utilities and is having an expanded role in efficiency of the boiler.

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