Staged Combustion with Nitrogen-Enriched Air (SCNEA)

Lawrence Livermore National Lab (LLNL) recently announced they’re developing a unique combustion method that results in lower power plant pollutant emissions, without efficiency penalties, by combining staged-combustion with nitrogen-enriched air.

The SCNEA combustion method burns fuels in two or more stages, where the fuel is combusted fuel-rich with nitrogen-enriched air in the first stage, and the fuel remaining after the first stage is combusted in the remaining stage(s) with air or nitrogen-enriched air. This method substantially reduces the oxidant and pollutant loading in the effluent gas and is applicable to many types of combustion equipment including: boilers, burners, turbines, internal combustion engines and many types of fuel including coal, oil and natural gas.

Results to date are from computer models. The next stage (Phase 1), to be completed in October ’02, is to do a small scale-pilot program involving experimental measurements at a bench scale (10-50 kw) to confirm predictions. Thereafter, Phase 2 will be conducted using commercial boilers and burners with an industry partner.

Provisional patents have been filed for the coal applications, and are in the process of filing on others.

To date, the work has been funded internally by the lab, and they are seeking additional funds (e.g. DOE, industry matching, etc.) to continue. LLNL is in the process of forming a consortium that includes the EPA, DOE, utilities, suppliers to the industry (e.g. boiler and burner manufacturers), engineering design firms, and suppliers of nitrogen enriched air. They are actively encouraging participation from industry.

Here is the abstract of a recent 8-page unpublished white paper prepared by LLNL. (I can send the pdf on request).

“A new primary control process for stationary combustion processes is predicted to significantly reduce NOx emissions, reduce corrosion in equipment, and enhance energy efficiency. This combustion method combines the technologies of stage-combustion with nitrogen-enriched air for the oxidant stream in one or more of the combustion stages, and is termed Staged Combustion with Nitrogen-Enriched Air (SCNEA). … SCNEA can replace or enhance currently employed NOx control technologies, such as low-NOx burners, overfire, reburning, and advanced flue gas treatment. SCNEA offers the ability to achieve NOx emission levels lower than levels attained using secondary control methods (e.g. SCR and SNCR) without the use of a catalyst.”

[another excerpt]
“SCNEA utilizes two stages. The first combustion stage is operated fuel-rich so that enough fuel remains for a second combustion stage. Nitrogen-enriched air is used as the oxidant stream in the first combustion stage, which allows precise control of the combustion temperature while producing effluent gases that have a very low oxidant and pollutant loading. The fuel remaining after the first combustion stage (along with the other effluent gases) is mixed with a stoichiometric amount of air and burned in the second stage. The temperature of the second combustion stage is maintained at or below the temperature of the first combustion stage by: (1) controlling the amount of fuel remaining after the first combustion stage (the equivalence ratio of the first combustion stage), (2) using nitrogen-enriched air as the oxidant stream for the second stage, and/or (3) controlling the minimum temperature between the two combustion stages.
NOx levels are significantly lower (1.40×10-2 lb NOx/MBTU) than either of the other single stage methods. Oxidant levels are also significantly reduced (3.30×10-2 lb O2/MBTU, and 6.45×10-6 lb O/MBTU). These advantages are coupled with an improvement in the amount of heat released per scf, i.e. 75.2 BTU/scf. ”

For more information, contact:
Kevin O’Brien, New Business Development
LLNL, Livermore, CA

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