Coal is one of the world's fastest growing energy sources. It fuels almost 40% of electricity worldwide, with even higher percentages in several countries. However, coal is also the most unclean energy source in the world. Upon burning, coal releases a number of problem pollutants such as mercury, sulfur, nitrogen, and carbon dioxide. These pollutants are not only harmful to breathe in, but are also avid greenhouse gases and contribute significantly to global warming.
Clean coal is a term used to refer to many different processes and technologies. Clean coal can be better defined with the goal in mind – the objective of clean coal is to ensure that the total amount of greenhouse gases and other pollutants into the atmosphere through the use of coal is minimized.
The objective of “clean coal” can be achieved through the following:
- By making power plants more efficient, thereby releasing less CO2 for the same amount of power produced,
- Turning coal into oil through thermochemical means, thereby removing impurities such as SO2 along the way
- Gasifying coal (into a gas called syngas) and using this syngas to run a turbine, and
- Using methods such as carbon capture and storage (CCS) by which the CO2 emitted by power plants is absorbed and stored under geological formations.
An array of clean coal technologies have been, and continue to be, developed to address environmental concerns surrounding coal utilisation. Increasing the combustion efficiency of both conventional and advanced new power systems has taken precedence. Advanced technologies such as integrated gasification combined-cycle (IGCC), ultra-supercritical pulverised coal (USC PC), circulating fluidized-bed combustion (CFBC), and oxygen (rather than air) combustion for pulvarised coal (PC) and CFBC units are the prime drivers for this innovation. The application of innovative techniques such as carbon capture and sequestration will lead to a near zero emissions future for coal.
Technologies deployed today
Examples of technologies that are deployed today and continue to be improved upon include:
Fluidized-bed combustion –Limestone and dolomite are added during the combustion process to mitigate sulfur dioxide formation. There are 170 of these units deployed in the U.S. and 400 throughout the world.
Integrated Gasification Combined Cycle (IGCC) – Heat and pressure are used to convert coal into a gas or liquid that can be further refined and used cleanly. The heat energy from the gas turbine also powers a steam turbine. IGCC has the potential to improve coal’s fuel efficiency rate to 50 percent. Two IGCC electricity generation plants are in operation in the U.S.
Flue Gas Desulfurization – Also called “scrubbers,” and removes large quantities of sulfur, other impurities and particulate matter from emissions to prevent their release into the atmosphere.
Low Nitrogen Oxide (NOx) Burners – Reduce the creation of NOx, a cause of ground-level ozone, by restricting oxygen and manipulating the combustion process. Low NOx burners are now on 75 percent of existing coal power plants.
Selective Catalytic Reduction (SCR) – Achieves NOx reductions of 80-90 percent or more and is deployed on approximately 30 percent of U.S. coal plants.
Electrostatic Precipitators – Remove particulates from emissions by electrically charging particles and then capturing them on collection plates.
Clean coal technologies on the horizon
New federal programs, such as the Clean Coal Power Initiative (CCPI), focus on eliminating emissions of pollutants, including particulates and mercury; improving technologies to increase efficiency and thereby reduce carbon dioxide and other emissions; and reducing carbon dioxide emissions through carbon capture and storage. Other technologies such as coal liquefaction and gasification are being pursued to produce low cost, secure alternatives to oil and natural gas for use in electricity generation and transportation. Focus areas for new technology R&D include:
Efficiency Improvements – To raise plant efficiency and reduce carbon dioxide (CO2) and other emissions. While some efficiency technologies are commercially available, others, such as Ultra Supercritical Pulverized Coal (USPC) and IGCC require continued research, development and demonstration. Improved efficiency at an existing plant can reduce CO2 emissions by 10-16 percent, and by 2025, new units could reduce CO2 emissions by as much as 30 percent.
High-efficiency fuel cells – To operate on a range of domestic fuels with virtually emissions-free performance at unsurpassed efficiencies.
Advanced high-efficiency combustion - For generating systems with increased operating temperatures, new computerized controls, improved burner designs and higher performance turbines.
Hydrogen production – A clean energy carrier—via gasification
Carbon Capture and Storage (CCS) – Captures and stores CO2 emissions in geologic formations or deep in the ocean where it dissolves under pressure. CCS technologies under development include:
Post-combustion capture from flue gas using an amine solvent and chilled ammonia
Pre-combustion capture using IGCC to isolate and capture CO2 before it is released
Oxy-Coal combustion using pure oxygen in the boiler to significantly reduce the dilution of CO2 in the exhaust gas stream
US exports of clean coal technology
The United States is a world leader in technology that allows coal to be burned for electricity production without excessive emissions of sulfurdioxide, nitrogen oxide, mercury, and particulate matter. To reduce overall emissions, the U.S. coal industry is developing specific technology that can be incorporated into coal-fired power plants. That technology will allow coal to be burned with lower emissions of carbon dioxide. The U.S. technological preeminence in this field presents an opportunity to export the equipment and to license the technology to countries such as China and India, where coal-fired electricity production is rising quickly. U.S. exports of CCT to Australia, Brazil, China, India, Mexico, New Zealand, South Africa, South Korea, and the European Union (EU) 251 could amount to US$36 billion between now and 2030.
Specifically, China, India, and South Korea present the greatest value of U.S. CCT exports, representing approximately $26 billion, $3.5 billion, and $3.2 billion, respectively. Australia, Brazil, Mexico, New Zealand, South Africa, and the EU 25 account for an additional $2.9 billion of growth.
Clean coal is an important part of governments and nations worldwide, and is widely discussed and debated at critical international forums such as the Copenhagen and Cancun summits.
- Clean coal provides us with an opportunity to utilize the proven and cost effective fossil fuels while significantly lowering the ecological harm associated with their usage
- By providing an avenue to convert coal into oil or syngas, clean coal also provides an opportunities for oil-poor but coal rich countries such as USA, China and India to become more self-reliant for oil.
- Many environmental activists argue that clean coal will just ensure that we continue with our bad habit of relying on fossil fuels
- Many technologies that comprise clean coal (CCS for instance) are not fully proven economically and technologically.
- The total costs of many clean coal technologies are not fully clear.
- Clean Technology Verticals
- Energy Generation
- Solar Energy
- Wind Energy
- Hydro Energy
- Bio-based Energy
- Geothermal Energy
- Ocean Energy
- Hydrogen Energy
- Waste to Energyl
- Natural Gas
- Nuclear Energy
- Coal Energy
- Energy Efficiency
- Energy Infrastructure and Carriers
- Energy Storage
- Air & Environment Management
- Water and Waste water Management
- Sustainable Materials
- Sustainability Production/Manufacturing
- Sustainable Agriculture
- Sustainable Transportation
- Recycling Waste Management
- Sustainable Life Style