New Technology for Control of N2O Emissions from Fluid Bed Combustors

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This program is aimed at development of a novel method of controlling N2O emissions from fluidized bed coal combustors, involving injection of sodium vapor at very low levels into the flue gas leaving the fluidized bed. The objectives of the Phase I effort are: (1) Demonstrate that sodium injection can cause substantially complete decomposition of N2O at conditions relevant to coal-fired fluid bed combustors; (2) Obtain chemical kinetic data for comparison with predictions of kinetic calculations; and, (3) Complete that comparison. Laboratory experiments will be carried out in a system consisting of four subsystems, a system for blending fixed gases and vaporized liquids, a sodium vaporizer, a reactor, and an analytical train. The reactor to be employed consists of a quartz tube into which a length of steel tubing projects, with the main flow gas going through the resulting annular space and the nitrogen-sodium mixture through the steel tubing. The analytical system will be centered around an NDIR instrument for N2O, with the analytical train also including a CO analyzer, a Pulsed Fluorescent SO2 analyzer, and a Chemiluminescent NOx analyzer. Successful completion of the Phase I studies will provide a lab-scale demonstration of the process and provide a clear understanding of the chemistry involved. Considerable effort has been expended on development of fluid bed combustion technology for burning of coal with low SOx and NOx emissions. Unfortunately, this technology approach leads to production of copious amounts of N2O emissions, an unacceptably serious drawback since N2O is both a greenhouse gas and a major contributor to depletion of the ozone layer. Accordingly, development of a means of dealing with this problem is of major importance to the viability of fluidized bed combustors for burning of coal.