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What is the Circulating fluidized bed technology?

What is the Circulating fluidized bed technology?

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The new buzz on clean energy and green energy has made us demand a pollution free world. Most of the nations have realized the importance of clean practices for the production of energy. Many technologies have been developed to achieve that. Some of them have been quite successful in reducing emissions and costs of operation. One such technology which has gained importance in the fossil fuel based power industries is circulating fluidized bed technology. Unlike the traditional steam generators which involves burning  fuels at high temperatures, CFB  technology burns fuels without fire or burners in the furnace but through a process of fluidization mixes the fuel particles with limestone which captures the sulfur oxides that are formed and the low temperature reduces nitrogen oxide formation. The limestone and fuel are recycles multiples times which increases both the efficiency of producing high quality steam to produce power and also reduces pollution due to its ability to burn fuel in a clean way than the conventional processes. Circulating fluidized bed technology(CFB) also offers the flexibility of using both coal as well as biomass fuels.




What is the principle behind circulating fluidized bed technology?

While burning the coal, sulfur dioxide is released and that is captured by limestone involved in the process. Since the coal is burnt at a lower temperature the formation of nitrogen oxides are reduced.  The fuels and limestone asre recycled. CFB has the flexibilty to burn both coal and other biomass fuels which makes them burn fuel in a clean way. This technology is being supported and adopted by many nations to ensure that the fossil fuel reserves are utilized in a clean way.



What is the process of Circulating fluidized bed technology?

On upward blowing jets of air fluidized beds  the solid fuels are suspended during the combustion process. Gas and solids mix turbulently. Such mixing ensures better heat transfer and chemical reactions. The fuel is not burnt at a very high temperature but it is burnt 1400 to 1700 degree F well below the temperature at which Nitrogen oxides are formed. A sulfur absorbing chemical such as dolomite or limestone is brought in contact with the flue gases while mixing and it absorbs sulfur pollutants. 95% of the sulfur pollutants are captured in this way. From coal to municipal wastes, anything can be combusted in this process to meet the emission standards.Most boiler manufacturers are nowadays offering fluidized bed boilers in their standard package. The Clean Coal technology program has influenced such positive measures.




What were the development stages of Circulating fluidized bed technology?

The global construction and engineering contractor Foster Wheeler was the first to try the circulating fluidized bed technology for the generation of steam from coal. The concept of bubbling bed technology was used by the first generation of circulating fluidized bed technology boilers. A stationary bed was made in the boiler which made use of low air velocities for the purpose of fluidizing the substance. A heat exchanger for the generation of steam was immersed in the bed. For the removal of particulate matter from the flue gas before it enters the gas turbine, cyclone separators were employed. This part was designed to just allow moderate particulate matter amount.



How different is the second generation circulating fluidized bed technology?

In the second generation, pressurized circulating fluidized bed technology, we see the use of efficiency enhancement measures. The technology has the ability to improve the operational characteristics by making use of higher air flows for moving the bed material and re-circulating the bed material with hot cyclone separators that are of higher volume. The flue gas that is relatively clean now goes to the heat exchanger. The second generation model approach can make the feed design much simpler. It also extends the contact between flue gas and the sorbent. The chances of the heat exchanger to erode are also reduced as a result of this technique. The combustion and sulfur dioxide capture are very efficient. The efficiency of the second generation steam generation is mainly due to the step of introducing the gasification of coal for the production of synthesis gas. The Clean Coal technology introduced the first generation of Circulating fluidized bed technology to the market. Nearly 1000 MW of power has been installed using this technology. This technology can help build the burning of fossil fuel based energy in a cleaner way.

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