Clean coal technology
Coal, the dirtiest of all fossil fuels, when burned produces emissions that contribute to global warming, create acid rain and pollute water. But coal is a vital fuel in most parts of the world. Almost 92 percent of the coal in the U.S. goes into power production.  The most promising "clean coal" technology involves using the coal to make hydrogen from water, then burying the resultant carbon dioxide by-product and burning the hydrogen.
Why should I be aware of this?
Burning coal without adding to global carbon dioxide levels is a major technological challenge. The greatest challenge is bringing down the cost of this technology for ‘clean coal’ to compete with nuclear power on the basis of near-zero emissions for base-load power.
Since CO2 contributes to global warming, reducing its release into the atmosphere has become a major international concern. In order to discover the most efficient and economical means of carbon capture, researchers have developed several technologies.
All about clean coal technology
Burning of coal releases carbon dioxide and other emissions in flue gas. Some clean coal technologies purify the coal before it burns. One type of coal preparation, coal washing, removes unwanted minerals by mixing crushed coal with a liquid and allowing the impurities to separate and settle.
The technology also minimizes emissions of sulfur dioxide, nitrogen oxides and particulates through other control systems. Sulfur dioxide, a major cause of acid rain, is removed by spraying flue gas with limestone and water.
Creation of nitrogen oxides, a cause of ground-level ozone, is reduced by Low-NOx (nitrogen oxide) burners by restricting oxygen and manipulating the combustion process. Electrostatic precipitators remove particulates that aggravate asthma and cause respiratory ailments by charging particles with an electrical field and then capturing them on collection plates.
Because of gasification burning of coal is avoided altogether. With integrated gasification combined cycle (IGCC) systems, steam and hot pressurized air or oxygen combine with coal. This forms a reaction that forces carbon molecules apart. The resulting syngas, a mixture of carbon monoxide and hydrogen, is then cleaned and burned in a gas turbine to make electricity.
- Flue-gas separation
With this technology carbon dioxide is stripped off with steam, and the steam is condensed into a concentrated stream. Another process, oxy-fuel combustion, burns the fuel in pure or enriched oxygen to create a flue gas composed primarily of CO2 and water. This eliminates the energy-intensive process of separating the CO2 from other flue gasses. A third technology, pre-combustion capture, removes the CO2 before it's burned as a part of a gasification process.
- Carbon capture and storage
This is perhaps the most promising clean coal technology as it catches and sequesters carbon dioxide (CO2) emissions from stationary sources like power plants.
Coal is still remains the cheapest and most plentiful source of energy. Since alternative forms of energy cannot yet replace coal, clean coal technology promises to mitigate the increasingly severe climactic effects ¬of coal emissions. However, the technology must first make economic sense for utility companies and businesses to adopt them. They are unlikely to use this technology purely for the sake of the environment .
- Some 23% of primary energy needs are met by coal and 39% of electricity is generated from coal.
- About 70% of world steel production depends on coal feedstock.
- However, burning coal produces about 9 billion tons of carbon dioxide each year which is released to the atmosphere, about 70% of this being from power generation.
- Other estimates put carbon dioxide emissions from power generation at one third of the world total of over 25 billion tons of CO2 emissions.