Clean Production Technology for Coal Fired Boiler Flue Gas Treatment
Coal combustion generates large amounts of pollutants and constitutes a major threat to environment and human health. Coal fired boilers installed in industrial and commercial premises need to be equipped with flue gas treatment systems to comply with national standards of pollution control. Clean production technologies are available to reduce and treat pollutants generated from coal fired boilers.
Flue gas treatment is a key component for treating and controlling harmful pollutants. A number of processes exist to remove pollutants from coal fired boiler flue gas including exhaust gas recirculation, wet scrubbing and dry scrubbing.
Exhaust gas recirculation is an advanced technology which involves re-circulation of exhaust gasses to the front of the boiler. This technology reduces the amount of exhaust emitted to the atmosphere by 50%. It is applied to control NOx emissions by keeping the temperature of the combustion process low, thus maintaining better combustion conditions and increasing combustion efficiency.
Wet scrubbing is a process of controlling pollutants in fuel combustion flue gases. The process involves spraying water and other absorbents on the smoke to remove water soluble components like ash and particulate. The mixture of water and particulates is then separated by filtration or sedimentation, thus reducing the amounts of air pollution.
Dry scrubbing is another process of controlling pollutants from coal fired boilers. This technology involves passing the contaminated flue gas through a reaction chamber filled with an absorbent powder, like lime or calcium. The absorbent reacts with and traps the pollutants, which are then collected in a separate container.
The most commonly applied combination of clean production technologies for particular types of boilers is a combination of exhaust gas recirculation, wet scrubbing and dry scrubbing. This combination together with other techniques like design and operational optimization, fuel blending and fuel switching can result in significant reduction of pollutants from coal fired boilers.
For example, this combination can result in as much as 90% reduction in emission of nitrogen oxides (NOx). In addition, it can also reduce sulfur dioxide (SO2), particulate matter (PM) and carbon monoxide (CO) emissions by more than 50%. Other, more advanced technologies like low-NOx burners and selective catalytic reduction (SCR) systems can be used for even higher levels of pollutant reduction.
In summary, numerous clean production technologies are available to reduce emission from coal fired boilers. These technologies can be combined to achieve even higher levels of pollutant reduction. The combination of exhaust gas recirculation, wet scrubbing and dry scrubbing can result in up to 90% reduction in nitrogen oxides emission. Besides these three, additional advanced technologies such as low-NOx burners and SCR systems can be used to further reduce emission levels.
