Low-NOx Technologies for Gas Turbine Applications

1 Low-NOx Technologies for Gas Turbine Applications - The existing methods for NOx control in gas turbines may be broadly divided into primary measures to control the combustion and secondary measures to clean up the flue gas containing NOx. Primary measures include, beside catalytic combustion, water or steam injection, lean-premixed combustion and staged combustion. To 

The most important secondary measures include the effective selective catalytic reduction (SCR) and the less effective selective non-catalytic reduction (SNCR). The major drawbacks with SCR are the high capital and operating costs, the large bulky catalytic reactor, NOx/NH3 analytical equipment as well as an ammonia or urea storage and distribution system. SNCR on the other hand has a lower capital cost, but is less effective in NOx reduction. 

The catalytic combustor is basically a lean-premixed combustor, in which the combustion is stabilized by a catalyst. Here, the combustion can be ultra-lean, since the catalyst can operate below the limits of homogeneous flammability. Hence the thermal-NOx emission can be even lower than for lean-premixed combustors. Clearly, catalytic combustion is one of the most promising alternatives for ultra-low emission gas turbines. It has been shown that catalytic combustion should be the lowest-cost and preferred technology for applications that require emission levels below 5 ppm.  

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