Clean coal technology

Refers than traditional coal burning process can reduce the sulfur dioxide (SO2), nitrogen oxides (of NOX) techniques and more coal dust pollution, but also specifically refers cleaner coal fired power plants, more efficient advanced coal technology. It includes four aspects, namely pre-combustion, combustion, post-combustion and conversion technology.

Clean pre-combustion technology

Mainly refers to the selection of coal. It is an important measure to improve coal quality, rational use of coal resources, reduce inefficient transportation, and reduce pollution.

Physical coal preparation separates objects that are different from the physical properties of coal by the difference in density and surface properties, such as vermiculite and iron sulfide. Usually 30% to 50% of sulfur compounds and 60% of ash can be removed, but organic sulfur and nitride cannot be separated.

Chemical coal preparation removes organic sulfur from coal by chemical methods, and generally obtains low-ash, low-sulfur clean coal by molten alkali leaching.

Biological coal preparation is a technology that removes sulfur from coal by bacteria, enzymes and microorganisms, and can remove 90% to 100% of sulfur. It is still in the experimental stage.

2. Clean technology in combustion

Fluidized bed boilers with reduced combustion temperatures and slagging boilers with increased combustion temperatures are used to reduce SO2 and NOx emissions or increase heat exchange rates.

In a fluidized bed boiler, pulverized coal and lime powder are suspended together in a gas stream to form a bed, and sulfur and lime released during combustion are chemically reacted or adsorbed to form sulfur-containing lime powder as a dry waste.

The slag-type boiler is produced by a swirling burner to burn coal in a combustion chamber outside the boiler, and then introduced into a boiler for heat exchange to prevent ash from accumulating in the boiler pipe, thereby increasing the heat exchange rate.

3. Clean technology after combustion

The focus is on the removal of SO2 and NOX produced after combustion.

The use of selective catalyst nitrogen removal technology (SCR) to remove NOx from flue gas can reduce nitrogen emissions by 50% to 80%. Another technique, known as natural gas reburning, injects a small amount of natural gas over the combustion zone, creating an anoxic zone that prevents it from forming NOx.

The limestone is sprayed into the center of the flue pipe, and the sulfur-containing particles are generated by the linear jet adsorption method, and collected at the downwind port to remove 50% to 70% of the SO2.

4. Conversion clean technology

That is, gasification, liquefaction and coking of coal.

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