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Current Page: Clean Coal > Clean Coal Technologies - Examples

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Clean Coal Technologies - Examples
Clean coal technologies are a family of new technological innovations that are environmentally superior to the technologies in common use today.

Clean coal technologies can be new combustion processes - like fluidized bed combustion and low-NOx burners - that remove pollutants, or prevent them from forming, while the coal burns.

Clean coal technologies can be new pollution control devices - like advanced scrubbers - that clean pollutants from flue gases before they exit a plant's smokestack.

Still other clean coal technologies can convert coal into fuel forms that can be cleaned before being burned. For example, a clean coal plant may convert coal into a gas that has the same environmental characteristics as clean-burning natural gas.


Examples of clean coal technologies currently in operation or under development around the world include

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Advanced Pulverised Fuel (PF) Combustion
Industry has continuously striven to increase efficiencies of conventional plant; for example, the average thermal efficiency of US power stations has increased from 5% in 1900, to around 35% currently. In China, most power plants are relatively small, average efficiency is about 28% compared to an OECD average of 38%. New conventional PF power plants achieve above 40% efficiency.

Advanced modern plants use specially developed high strength alloy steels, which enable the use of supercritical and ultra-supercritical steam (pressures >248 bar and temperatures >566ฐC) and can achieve, depending on location, close to 45% efficiency.

Application of new advanced materials to PF power plant should enable efficiencies of 55% to be achieved in the future. This results in corresponding reductions in CO2 emissions as less fuel is used per unit of electricity generated.



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Fluidised Bed Combustion (FBC)
Fluidised bed combustion is a method of burning coal in a bed of heated particles suspended in a gas flow. At sufficient flow rates, the bed acts as a fluid resulting in rapid mixing of the particles. Coal is added to the bed and the continuous mixing encourages complete combustion and a lower temperature than that of PF combustion.




The advantages of fluidised beds are they produce less NOx in the outlet gas, because of lower combustion temperatures, and they produce less SOx when limestone is continuously added with the coal. They can also use a wider range of fuels than PF combustion.

Atmospheric-pressure fluidised beds are commercially available now as two types, bubbling-bed (known as Atmospheric Fluidised Bed Combustion - AFBCs) and circulating-bed (CFBCs). The efficiency of most fluidised beds used for power generation is similar to that of conventional plant. However, use of this technology has been stimulated by its better environmental performance when utilising lower grade fuels.

Pressurised fluidised beds, which can achieve efficiencies of 45%, are now in commercial operation. As with PF plants, employing higher steam conditions would further boost efficiency.

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http://www.australiancoal.com.au/cleantech.htm

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Clean coal technology นี้ บ้านเรานำมาใช้ในโรงไฟฟ้า แม่เมาะ หน่วยที่ 12-13 เป็น แห่งแรกเมื่อประมาณ 10 ปีก่อนเพื่อแก้ปัญหา ก๊าซซัลเฟอร์ใดออกไซด์ในอากาศ ที่เกิดจากการเผาไหม้ถ่านหินที่มีกำมะถันเจือปน(แหล่งแม่เมาะมีกัมมะถันเจือปนประมาณ 2 %) โดยการใช้หินปูนไปทำปฏิกริยากับก๊าซซัลเฟอร์ไดออกไซด์กลายเป็นยิปซัมออกมา(CaCO3 + SO2 --> CaSO4 + CO2) ทำให้อากาศที่ผ่านการเผ่าไหม้ ที่ปล่อยออกมามีความสะอาด ต้นทุนในการก่อสร้างประมาณ 3000 ล้านบาท(ค่าก่อสร้างโรงไฟฟ้าถ่านหินขนาด 300 MWเมื่อ 10 ปีก่อน ประมาณ 15000 ล้านบาท)