Cleaner Coal Technologies (including carbon capture and storage) ~ Funding, Development, and Implementation
A July 4, 2010 letter to the editor, prepared by former ACC CEO, Janet Gellici, and published on Trib.com provides an excellent introduction to our section on Cleaner Coal Technologies (CCT).
Clean coal technologies have successfully helped reduce regulated emissions by 60 percent since 1970. While coal use has more than doubled over the past 40 years, emissions of SO, NOx, particulates, ozone, lead and CO have decreased. This is due, in large part, to public-private clean coal technology (CCT) programs administered by the Department of Energy (DOE) that have reduced pollution, increased energy efficiency and created American jobs.
CCT programs have produced substantial benefits for U.S. taxpayers that far exceed the federal government’s investments. Cumulative benefits to date total $6 billion vs. DOE costs of $3.5 billion -- a return on investment (ROI) of 1.7. By 2020, the cumulative benefits from the program will likely total $111 billion vs. DOE costs of $8.5 billion for an ROI of more than 13.
Building on the success of curtailing criteria pollutants, industry and government efforts are now underway to develop and deploy carbon management technologies. Billions of dollars have already been invested to reduce CO2 emissions, including projects now under construction to enhance power plant efficiency and to capture and store carbon (CCS), at both existing and new generating facilities.
Coal is the only internationally sustainable resource with the scale to meet energy demand and the technology to address our global carbon goals. As the National Research Council noted, "... by making an abundant low-cost energy resource compatible with environmental goals, CCS allows the world to continue to derive the economic and geopolitically stabilizing benefits associated with coal."
Call them what you may, clean coal technologies or advanced coal technologies, the fact remains that the U.S. has benefited greatly from clean energy investments. To ensure we meet our future energy and environmental goals, we should focus less on playing with words and more on working towards solutions.
JANET GELLICI, CEO, Washington, D.C.
Follow these links to learn more about,
Ongoing Cleaner Coal Technology Programs
Some of the cleaner coal technologies in use today include,
- Carbon Capture, Utilization, & Storage (CCUS): When coal is combusted, one of the byproducts produced is CO2. Technological advances allow us to capture that CO2 to prevent it from being released into the atmosphere. If pumped underground into oil fields, the increased pressure helps enhance oil recovery (EOR). It will also displace methane gas when pumped into deep coalbeds. It can also be stored long-term in deep saline aquifers. In one commercial operation, CO2 produced in North Dakota is being pipelined to Weyburn, Saskatchewan and pumped into old oil fields to enhance oil production.
- There are several active carbon capture and storage operations and research projects in the United States and around the world.
- MIT has undertaken a Carbon Capure and Storage Technologies research program that is aimed at studying various CCUS technologies and mapping the locations where it is being studied and/or implemented across the world.
- The American Coalition for Clean Coal Electricity (ACCCE) website has a 12-2008 database of U.S. CCS research and operations. The data in this document provides information on the name of the project, the state in which the project is being carried out, the organizations responsible, public vs. private funding, and a brief description. You can also download the pdf document here.
- ACCCE also has an CCUS information page with graphics and videos describing the process of capturing, transporting, and storing CO2 underground.
- The U.S. Department of Energy National Energy Technologies Laboratory has established a list of active and proposed Carbon Capture and Storage (CCS) projects around the world. The database is "active" as it is being regularly updated as new projects are started or proposed. The database is linked with Google Earth. However, there is also an Excel spreadsheet that lists the CCS projects.
- Washing (also called coal preparation): This method uses water
to clean coal before it is combusted in a burner. Coal is crushed and
then fed into a large water tank. The rock, sulfur, and other impurities
in the coal sink to the bottom and the coal floats to the top.
- Flue gas desulfurization ("FGDs" or "scrubbers"): any plant built after 1978 in the U.S. is required to have a scrubber; while many older plants have had FGDs added on. There are two main types of scrubbers used today, 1) wet and 2) dry. In both systems, a "reagent," such as lime is sprayed into the flue gas (or exhaust) of a power plant. That chemical reacts with acid gases in the flue gas, removing chemicals (like sulfur dioxide, SO2) and particulate matter. One benefiit of using FGDs is that the limestone-based scrubbers produce synthetic gypsum that can be used in the manufacture of drywall and other green building products. Scrubbers can also be used to lower other emissions like NOX and mercury.
- Low NOX burners: Nitrogen Oxides (NOX) are formed when heat forces nitrogen atoms apart and they recombine with oxygen atoms. Any fuel that is burned in high enough temperatures will form NOX. One of the best ways to reduce NOX is to keep it from forming in the first place, so low-NOX burners, which burn fuels at lower temperatures and in stages are used. In these burners, the fuel and oxygen combine, rather than nitrogen and oxygen.
- Fluidized bed combustion (FBC): In a FBC boiler, pulverized coal (and other fuels) is suspended on jets of pressurized air. This results in a turbulent, moving mass of fuel that mixes with air inside the boiler. FBC boilers typically allow the fuels to stay inside the boiler much longer than other boilers, which ensures more complete combustion. FBC boiler temperatures are far lower than conventional boilers (1400° F, rather than almost 3,000° F), so NOXformation is minimized. Additionally, limestone can be mixed in with the fuel and the mixing in the air makes sulfur removal very effecitive.
- Activated Carbon Injection (ACI): ACI is primarily used to remove mercury from flue gas. However, it can also capture other flue gas constituents. In these systems, powdered activated carbon (PAC) is injected into the flue gas. The PAC adsorbs the vaporized mercury in the flue gas and is collected with fly ash in the particulate collection device.
- Particulate Matter (PM): Collection of PM is primarily handled with the use of fabric filters, which capture particles much like the air filter in your home furnace or A/C. Electrostatic Precipitation, which involves using electric fields to attract charged particles in the flue gas, is also used.
- Gasification: Put coal into a large pressure vessel and blast it with superheated steam and you'll eventually break down the atomic bonds holding it together. In the right conditions, those atoms will reform into CO (carbon monoxide) and hydrogen - this process is called gasification. While you're gasifying the coal, sulfur, nitrogen, and trace metals can be removed. You can then burn the hydrogen, much like you would natural gas to make electricity. You can also use the CO and hydrogen to make a variety of products like plastics, chemicals, and transportation fuels.
- Integrated Gasification Combined Cycle (IGCC): IGCC uses gasification (described above) to produce synthetic natural gas (or syn-gas), which is then combusted in combined cycle gas turbines, much like natural gas.
- Supercritical and Ultra Supercritical pulverized coal: Just like previous models of coal-fueled boilers, (ultra) supercritical coal boilers burn coal that has been pulverized into a fine powder-like texture. However, the steam that is produced when coal is combusted in these boilers exists at much higher pressures. Newer, more durable metals and alloys allow a more efficient combustion process and higher temperatures to exist in the boiler. The more efficient process allows a utility to produce the same amount of energy, using less coal (i.e., less coal is used per megawatt hour produced). That efficiency entails less GHG and other emissions.
Cleaner Coal Technology Funding
An American Coalition for Clean Coal Electricity study (titled "Benefits of Investment in Clean Coal Technology" & published in 2009) indicated that for every $1 that was invested in clean coal technologies research, the American taxpayer would see a $13 return.