Clean Coal Technologies (thing)
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|Coal Cleaning Technologies (CCTs) are a group of new technological innovations developed to clean coal of sulfur dioxide, nitrogen oxide, carbon dioxide, air toxins and particulates, while enabling coal-burning facilities to meet or exceed the regulated emission standards and operate in a more efficient and cost-effective manner. Coal represents 95 percent of U.S. fossil fuel reserves, and nine out of every 10 tons of coal is used to make electricity. It is understandable then, why CCTs are so important.|
Clean coal technology uses resources more efficiently and reduces the impact on the environment through reducing emissions and improving efficency. With CCTs coal gets cleaner before it ever enters the power plants. Emissions from U.S. coal-based generating plants have fallen over 20% in the past 30 years while CCTs produced electricity has more than tripled. The net effect of CCTs can result in a reduction in total emissions to the atmosphere.
The Four Categories of Clean Coal Technologies
Pre-combustion cleaning - these are technologies that are used to clean the coal before it is burned. These methods include chemical and biological cleaning to remove sulfur and ash, the coal is crushed and screened for impurities. These are known as Coal benefication technologies including; Physical cleaning, Column flotation, Aggregate flotation, and Biological cleaning.
Combustion - These are technologies that are used to clean coal inside the furnace where the coal is actually burned, removing pollutants, or preventing them from forming, while the coal burns before they reach the environment. Fluidized bed combustion, Circulating fluidized bed combustion, Atmospheric fluidized bed combustion, Multistage boilers, and Limestone injection are examples of this method.
Post-combustion cleaning - technologies are applied after the coal is burned. The gases, or emission, that are released from burning coal are cleaned before they reach the smokestack and are released into the atmosphere. Some of these methods include; Flue gas desulfurization, In-duct sorbent injection, and Scrubbing.
Conversion - technologies turn coal into a gas or liquid that can be cleaned and used as fuel. The most advanced conversion techonogy is combined-cycle coal gasification. Coal gasification centers around heating the coal to a minimum of eight hundred degrees, while adding oxygen and water, once coal is in its gaseous state, undesirable components can be removed. Hybrid combined cycles which combine the best features of both gasification and combustion technologies, using coal in a two-stage process are also under development. The initial stage gasifies the majority of the coal, while the second stage combusts the residual char to produce steam.
The Clean Coal Technology (CCT) Program was co-funded in 1986, by the government and industry, the goal of the CCT Program is to furnish more advanced and effictient coal-based technologies. President George W. Bush's National Energy Policy he announced on May 17, 2001 pledges over 10 billion to be spent on CCT over the next 10 years. The National Electricity and Environmental Technology Act spells out in detail the global importance of the CCT program:
The `National Electricity and Environmental Technology Act'...for the purpose of continued environmental improvement in coal-based generation through continued research, development, and demonstration toward an ultimate goal of near-zero emissions is important and desirable.The four main categories of CCT projects include: Advanced electrical power generation; Environmental control devices; Coal processing for clean fuels; and Industrial applications, dependent upon coal use.
In considering each CCT, key factors to consider are:Two of the most common CTTs include fluidized bed combustion and low-NOx abatement and control burners -- these remove pollutants, or prevent them from forming, while the coal burns. Pollution control devices - like advanced scrubbers clean pollutants from flue gases before they even exit a plant's smokestack. CCT-by-products are created from gases and liquids from the removal of sulfur and nitrogen from coal. The Energy Policy Act of 1992 calls for increased utilization of coal combustion solid by-products. One possible use of solid by-products is stabilization and solidification of hazardous, metal-laden solid wastes. At this time there are numerous reserach projects looking into possible uses of CCT-by-products
Technological benefits of CTT:
Low Nitrogen Oxide (NOx) Burners - now on 75% of U.S. coal-based power plants at up to 1/2 the cost of older systems.
Selective Catalytic Reduction - achieves NOx reductions of 80% or more, at half the cost of the 1980s.
Flue Gas Desulfurization - more than 400 commercial units have been deployed at 1/3rd the cost of the 1970s.
Integrated Gasification Combined Cycle - Over 1,500 megawatts of coal-based generation operating today, another 2,200 megawatts are in design.
Coal is vital to present and future U.S. economic and energy security, and Clean Coal Technologies are vital to the human race globally - to promote both the public welfare and quality of life. Giant strides are being made by nations around the world, with billions being invested by both governments and the industry to ensure the operational efficiency and environmental performance of power systems using coal.
Advanced Clean Coal Technologies and Low Value Coals Published by IEA Coal, Research 2000
Clean Coal Technologies: The New Coal Era, ISBN: 0-7881-3119-2, Diane Publishing
Bourillon C. 1994 Clean coal technologies, UNEP Industry and Environment