|Engineered Coal Fuels|
Engineered coal fuel technologies
Currently U.S. energy policy and the public debate over clean coal technologies primarily focus on next generation power plants and transportation fuels. They focus on the effect that energy production, generation, and use will have on greenhouse gases. While these are important considerations, there are also opportunities that exist to generate economically viable and environmentally attractive electricity from coal, using engineered coal fuels technologies.
There are a number of processes either in operation or under development, which treat coal prior to combustion making it a cleaner, more efficient fuel. These engineered clean coal fuel technologies produce enhanced fuels that result in lower sulfur dioxide (SO2), nitrogen oxides (NOX), mercury (Hg) and carbon dioxide (CO2) air emissions at plants that burn them.
The environmental benefits of pre-combustion technologies can be enhanced if other combustion (oxy-coal combustion) or post-combustion technologies (fabric filters, electrostatic precipitation, scrubbers, etc.) are also used.
There are three coal preparation technologies used to improve coal prior to combustion
Coal preparation is the most widely used engineered coal fuels technology. It involves cleaning the coal, to remove ash, before combustion. Lower ash levels result in decreased SO2 and Hg emissions. Washing also allows coal-fueled boilers to operate more efficiently as there are fewer impurities and other chemicals that can decrease heat and combustion rates. More efficient combustion reduces NOX and CO2 emissions.
Cleaning technologies also encourage the use and recycling of other "waste” coals that might have been previously abandoned because of lower Btu values and higher levels of impurities, rock, or dirt.
Coal upgrading technologies increase the Btu content of lower-ranked coals by removing water (dewatering or drying). Dewatering uses four different technologies – three thermal and one non-thermal.
Dewatering and upgrading help to reduce emissions. Sulfur and Hg are reduced with water removal. NOX emissions are reduced as higher Btu values result in more complete combustion. Increased fuel and boiler efficiency 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 Hg in solid byproducts from the generating process rather than allowing them to be emitted in power plant exhaust gases. In addition, combustion efficiency improvements result in lower NOX and CO2 emissions per kilowatt hour generated.
Recent studies conducted by EPRI (Electric Power Research Institute) and CURC (Coal Utilization Research Council) indicate that for each 1% increase in combustion efficiency there is a 2.5% reduction in CO2 emissions from power plants. By applying these technologies other emissions can also be reduced. Depending on the specific technology employed and the coal being used, emissions of mercury can be reduced from 15-90%; nitrogen oxides (NOX) can be reduced from 10-50%, and sulfur dioxide (SO2) can be reduced 10-80%.
When improvements in efficiency and reductions in emissions from engineered coal fuels technologies are combined with other clean coal technologies (combustion and postcombustion), the environmental and cost benefits are manifold.
Engineered coal fuels technologies represent an excellent opportunity to use coal – our most abundant/secure and affordable energy resource – in an environmentally sound manner. By applying these technologies along with combustion and post-combustion stage technologies our coal use will help to power us well into the future.
Objective: The ACC’s Coal 2.0 Alliance is focused on advancing the development and utilization of engineered coal fuels technologies and coal preparation technologies through enhancing awareness of their environmental and efficiency performance benefits.
Download our Engineered Coal Fuels Technologies fact sheet (pdf format) for information on pre-combustion technologies and a list of the Coal 2.0 member companies.