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Tangential Combustion Systems (TLN1, TLN2, TLN3)
Foster Wheeler's Tangential Low NOx (TLN) Combustion Systems provide industrial and utility boiler owners with an effective solution to their NOx compliance needs. Our systems are designed to maximize NOx reduction efficiency while minimizing the impact on combustion performance and unit operation. Numerous tangential coal-fired units are equipped with Foster Wheeler's TLN systems. Fuels fired range from lignite and sub-bituminous through low and higher sulfur eastern bituminous coals to pet coke and PRB as well as numerous global coals. Foster Wheeler has retrofitted units from 45 MWG to 900 MWG.
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Staging of secondary combustion air has been well documented throughout the international boiler industry to be the single most effective technique for reducing NOx emissions from tangentially fired boilers. By redirecting a portion of the combustion air above the upper fuel elevation, fuel nitrogen conversion and thermal NOx production is reduced. Control of this staging process through proper nozzle and damper design is critical in order to maximize combustion efficiency and component longevity. Depending on the unit configuration and level of NOx reduction, FW can offer several optional arrangements, known as TLN1, TLN2 and TLN3, as shown in the figure to the right.
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Foster Wheeler's TLN1 arrangement is an "in-windbox" or "close-coupled" overfire air (CCOFA) system. It consists of lowering the upper coal elevation and reconfiguring the windbox nozzle arrangement and damper system. This creates the required "in-windbox" overfire air effect. This lower cost modification typical provides NOx reduction of approximately 0.10 lbs/MBtu.
Foster Wheeler's TLN2 system consists of adding a single level of separated overfire air (SOFA) above the main firing zone to provide the required vertical air staging effect. Due to increased spacing from the upper coal elevation, separated overfire air arrangements provide significantly higher NOx reduction efficiencies as compared with "in-windbox" arrangements.
The TLN3 system consists of adding a single level of separated overfire air to units that already have in-windbox Overfire air compartments. Both the TLN2 and TLN3 have demonstrated NOx reductions of up to 75% firing a wide range of global coals.
Each Foster Wheeler TLN retrofit includes a complete review of the existing nozzle tips and air distribution flow control. Using Foster Wheelers proprietary computer-modeling program each TLN retrofit is assured that proper airflow distribution control and air/coal mixing is maintained throughout the unit load range, thereby assuring long term post retrofit predicted performance.
Most TLN retrofits also include the numerous Foster Wheeler-unique design features, such our patented DS coal and air nozzle tip designs, lower furnace stoichiometry control, flame shaping boundary air and as well as numerous hardware upgrades. Also available as complimentary options are our ECT real time coal flow and CADM air flow distribution monitoring systems.
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Copyright
© 2008 by Foster Wheeler Ltd. All Rights Reserved.
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