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Clean coal technology

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Clean coal technology is a collection of technologies being developed in attempts to lessen the negative environmental impact of coal energy generation and to mitigate worldwide climate change. When coal is used as a fuel source, the gaseous emissions generated by the thermal decomposition of the coal include sulfur dioxide (SO2), nitrogen oxides (NOx), mercury, and other chemical byproducts that vary depending on the type of the coal being used. These emissions have been established to have a negative impact on the environment and human health, contributing to acid rain, lung cancer and cardiovascular disease. As a result, clean coal technologies are being developed to remove or reduce pollutant emissions to the atmosphere. Some of the techniques that would be used to accomplish this include chemically washing minerals and impurities from the coal, gasification (see also IGCC), improved technology for treating flue gases to remove pollutants to increasingly stringent levels and at higher efficiency, carbon capture and storage technologies to capture the carbon dioxide from the flue gas and dewatering lower rank coals (brown coals) to improve the calorific value, and thus the efficiency of the conversion into electricity. Concerns exist regarding the economic viability of these technologies and the timeframe of delivery, potentially high hidden economic costs in terms of social and environmental damage, and the costs and viability of disposing of removed carbon and other toxic matter.

In its original usage, the term "Clean Coal" was used to refer to technologies that were designed to reduce emission of pollutants associated with burning coal, such as washing coal at the mine. This step removes some of the sulfur and other contaminants, including rocks and soil. This makes coal cleaner and cheaper to transport. More recently, the definition of clean coal has been expanded to include carbon capture and storage. Clean coal technology usually addresses atmospheric problems resulting from burning coal. Historically, the primary focus was on SO2 and NOx, the most important gases in causation of acid rain, and particulates which cause visible air pollution and have deleterious effects on human health.

Technology

Several different technological methods are available for the purpose of carbon capture as demanded by the clean coal concept:

  • Pre-combustion capture – This involves gasification of a feedstock (such as coal) to form synthesis gas, which may be shifted to produce a H2 and CO2-rich gas mixture, from which the CO2 can be efficiently captured and separated, transported, and ultimately sequestered, This technology is usually associated with Integrated Gasification Combined Cycle process configurations.
  • Post-combustion capture – This refers to capture of CO2 from exhaust gases of combustion processes.
  • Oxy-fuel combustion – Fossil fuels such as coal are burned in a mixture of recirculated flue gas and oxygen, rather than in air, which largely eliminates nitrogen from the flue gas enabling efficient, low-cost CO2 capture.

The Kemper County IGCC Project, a proposed 582 MW coal gasification-based power plant, was expected to use pre-combustion capture of CO2 to capture 65% of the CO2 the plant produces, which would have been utilized and geologically sequestered in enhanced oil recovery operations. However, after many delays and a cost runup to $7.5 billion (triple the initial budget), the coal gasification project was abandoned and as of late 2017, Kemper is under construction as a cheaper natural gas power plant.

The Saskatchewan Government's Boundary Dam Integrated Carbon Capture and Sequestration Demonstration Project will use post-combustion, amine-based scrubber technology to capture 90% of the CO2 emitted by Unit 3 of the power plant; this CO2 will be pipelined to and utilized for enhanced oil recovery in the Weyburn oil fields.

An oxyfuel CCS power plant operation processes the exhaust gases so as to separate the CO2 so that it may be stored or sequestered

An early example of a coal-based plant using (oxy-fuel) carbon-capture technology is Swedish company Vattenfall’s Schwarze Pumpe power station located in Spremberg, Germany, built by German firm Siemens, which went on-line in September 2008. The facility captures CO2 and acid rain producing pollutants, separates them, and compresses the CO2 into a liquid. Plans are to inject the CO2 into depleted natural gas fields or other geological formations. Vattenfall opines that this technology is considered not to be a final solution for CO2 reduction in the atmosphere, but provides an achievable solution in the near term while more desirable alternative solutions to power generation can be made economically practical.

Other examples of oxy-combustion carbon capture are in progress. Callide Power Station has retrofitted a 30-MWth existing PC-fired power plant to operate in oxy-fuel mode; in Ciuden, Spain, Endesa has a newly built 30-MWth oxy-fuel plant using circulating fluidized bed combustion (CFBC) technology. Babcock-ThermoEnergy's Zero Emission Boiler System (ZEBS) is oxy-combustion-based; this system features near 100% carbon-capture and according to company information virtually no air-emissions.

Other carbon capture and storage technologies include those that dewater low-rank coals. Low-rank coals often contain a higher level of moisture content which contains a lower energy content per tonne. This causes a reduced burning efficiency and an increased emissions output. Reduction of moisture from the coal prior to combustion can reduce emissions by up to 50 percent.

The UK government is working towards a clean energy future and supported clean coal projects across the country. In August 2010, UK-based company B9 Coal announced a clean coal project with 90% carbon capture to be put forward to DECC. This proposed project was to create pure streams of hydrogen and carbon dioxide. The hydrogen was then to be used as an emissions-free fuel to run an alkaline fuel cell whilst the carbon dioxide was to be captured.

Demonstration projects in the United States

In the late 1980s and early 1990s, the U.S. Department of Energy (DOE) began conducting a joint program with the industry and State agencies to demonstrate clean coal technologies large enough for commercial use. The program, called the Clean Coal Technology & Clean Coal Power Initiative (CCPI), has had a number of successes that have reduced emissions and waste from coal-based electricity generation. The National Energy Technology Laboratory has administered three rounds of CCPI funding and the following projects were selected during each round:

  • Round 1 CCPI Projects
    • Advanced Multi-Product Coal Utilization By-Product Processing Plant
    • Demonstration of Integrated Optimization Software at the Baldwin Energy Complex
    • Gilberton Coal-to-Clean Fuels and Power Co-Production Project
    • Increasing Power Plant Efficiency: Lignite Fuel Enhancement
    • TOXECON Retrofit for Mercury and Multi-Pollutant Control on Three 90-MW Coal-Fired Boilers
    • Western Greenbrier Co-Production Demonstration Project
    • Commercial Demonstration of the Airborne Process
    • Integration of Advanced Emission Controls to Produce Next-Generation Circulating Fluid Bed Coal Generating Unit
  • Round 2 CCPI Projects
    • Airborne Process Commercial Scale Demonstration Program
    • Demonstration of a Coal-Based Transport Gasifier
    • Mercury Species and Multi-Pollutant Control Project
    • Mesaba Energy Project
  • Round 3 CCPI Projects

These programs have helped to meet regulatory challenges by incorporating pollution control technologies into a portfolio of cost-effective regulatory compliance options for conventional and developmental coal-fired power plants. This portfolio has positioned the U.S. as a top exporter of clean coal technologies such as those used for SOx, NOx and mercury, and more recently for carbon capture, consistent with a goal of deploying advanced coal-based power systems in commercial service with improved efficiency and environmental performance to meet increasingly stringent environmental regulations and market demands, leading to widespread, global deployment which will contribute to significant reductions in greenhouse gas emissions. The DOE continues its programs and initiatives through regional sequestration partnerships, a carbon sequestration leadership forum and the Carbon Sequestration Core Program, a CCS research and development program.

According to a report by the assistant secretary for fossil energy at the U.S. Department of Energy, clean coal technology has paid measurable dividends. Technological innovation introduced through the CCT Program now provides consumers cost-effective, clean, coal-based energy.

Clean coal and the environment

Further information: Environmental effects of coal

According to United Nations Intergovernmental Panel on Climate Change, the burning of coal, a fossil fuel, is a major contributor to global warming. (See the UN IPCC Fourth Assessment Report). As 26% of the world's electrical generation in 2004 was from coal-fired generation (see World energy resources and consumption), reaching the carbon dioxide reduction targets of the Kyoto Protocol will require modifications to how coal is utilized.

Coal, which is primarily used for the generation of electricity, is the second largest domestic contributor to carbon dioxide emissions in the US. The public has become more concerned about global warming which has led to new legislation. The coal industry has responded by running advertising touting clean coal in an effort to counter negative perceptions and claiming more than $50 billion towards the development and deployment of "traditional" clean coal technologies over the past 30 years; and promising $500 million towards carbon capture and storage research and development. There is still concern about clean coal technology being perceived as more environmentally friendly than it is, and the term "Clean Coal" has been used as an example of "greenwashing". According to the Sierra Club, "Despite the industry's hype, there's no such thing as 'clean coal.' But new technologies and policies can help reduce coal plants' deadly emissions."

Conjunction with enhanced oil recovery and other applications; commercial-scale CCS is currently being tested in the U.S. and other countries. Proposed CCS sites are subjected to extensive investigation and monitoring to avoid potential hazards, which could include leakage of sequestered CO2 to the atmosphere, induced geological instability, or contamination of water sources such as oceans and aquifers used for drinking water supplies.

The Great Plains Synfuels plant supports the technical feasibility of carbon dioxide sequestration. Carbon dioxide from the coal gasification is shipped to Canada where it is injected into the ground to aid in oil recovery. A drawback of the carbon sequestration process is that it is expensive compared to traditional processes.

Clean coal and health

Both traditional coal technology and clean coal technologies result in a release of hazardous air pollutants and many of them have an adverse effect on human health. According to Alan H. Lockwood, MD, coal is linked to diseases of the Respiratory System, Cardiovascular System, and Nervous System. A key point that Dr. Lockwood brings up is that “the most obvious threats to health posed by the carbon capture and storage strategies… would occur in the event of the release of large amounts of CO2. The potential releases could occur at any of the stages: at the site of CO2 capture, during transport, or transfer… or escape during or after storage.” Dr. Lockwood goes on to explain that this can lead to “symptoms of death by displacing oxygen from inhaled air, leading to hypoxia and asphyxiation, or by causing symptomatic or fatal acidification of the blood and body fluids after inhalation”

See also

References

  1. "Coal vs. Wind". Union of Concerned Scientists. Retrieved 2008-12-30.
  2. Pearce, Fred (2008-10-30). "Time to bury the 'clean coal' myth". London: The Guardian. Retrieved 2008-12-23.
  3. "The True Cost of Coal" (PDF). Greenpeace. Retrieved 2008-12-23.
  4. "Carbon Capture and Storage". University of Edinburgh, School of Geosciences. Archived from the original on 2007-02-19. Retrieved 2008-12-23.
  5. "Carbon Capture Plans get Reality Check". Discovery Channel. Retrieved 2008-12-23.
  6. ^ Lockwood, Alan (2012). The Silent Epidemic: Coal and the Hidden Threat to Health. Cambridge, Massachusetts: The MIT Press. pp. 2–5. ISBN 9780262017893.
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  9. "R&D Facts - Oxy-Fuel Combustion" (PDF). National Energy Technology Laboratory, U.S. Department of Energy. Archived from the original (PDF) on 31 October 2014. Retrieved 22 July 2014.
  10. "IGCC Project Examples - Kemper County IGCC Project". Gasifipedia. National Energy Technology Laboratory, U.S. Department of Energy. Retrieved 22 July 2014.
  11. Geuss, Megan (2017-06-29). "$7.5 billion Kemper power plant suspends coal gasification". Ars Technica. Retrieved 2017-07-01.
  12. "Boundary Dam Integrated Carbon Capture and Sequestration Demonstration Project". Global CCS Institute. Archived from the original on 10 August 2014. Retrieved 22 July 2014.
  13. "Vattenfall's Project on CSS". Vattenfall. Archived from the original on 2010-10-26.
  14. ^ http://discovermagazine.com/2009/feb/25-can-clean-coal-actually-work/?searchterm=clean%20coal "Can Clean Coal Actually Work?" article in Feb. 2009 issue, p. 18, Retrieved 2009-05-11
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  19. "Carbon Sequestration". U.S. Department of Energy.
  20. "Clean Coal Technology: The Investment Pays Off" (PDF). U.S. Department of Energy.
  21. "CRS Issue Brief for Congress - IB89005: Global Climate Change". National Council for Science and the Environment. August 13, 2001. Archived from the original on December 26, 2008. Retrieved 2008-09-13.
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  24. "ACCCE Details More than 80 CO2 Capture and Storage Projects". America's Power. Archived from the original on 2008-12-28. Retrieved 2009-01-12.
  25. Morris, Louise (2008-12-01). "Greenwashing Coal". Chain Reaction. 104: 25.
  26. Snell, Marilyn (January–February 2007). "Can Coal Be Clean". Sierra Club.
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  29. "What is clean coal technology?". HowStuffWorks. 2007-07-18. Retrieved 2018-05-10.
  30. "Carbonomics: How to Fix the Climate and Charge it to OPEC". SSRN. SSRN 1300126. {{cite web}}: Missing or empty |url= (help)

Further reading

External links

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