Liquid heaters and vaporizers – Miscellaneous
Patent
1992-03-09
1993-01-12
Favors, Edward G.
Liquid heaters and vaporizers
Miscellaneous
110212, 110345, 422182, 422183, B09B 300, F22B 100
Patent
active
051781018
ABSTRACT:
A method and corresponding system are provided for reducing quantities of oxides of nitrogen, including N.sub.2 O, that are generated in a coal-fired fluidized bed boiler, the exhaust stream from the fluidized bed boiler being at a temperature of about 600.degree.-650.degree. F. and including from about 3 to 6% oxygen, from about 50 to 500 ppmv of NO.sub.x and from about 50 to 300 ppmv of N.sub.2 O. Pursuant to the invention, the exhaust stream is flowed through a thermal reaction zone at which fuel and air are burned, to provide a modified heated stream which includes small quantities of combustibles and of oxygen. The modified heated stream is passed over a first catalyst bed under overall reducing conditions, the quantity of oxygen in the stream being in stoichiometric excess of the amount of NO.sub.2 O and NO.sub.x, but less than the amount of said combustibles; whereby the N.sub.2 O and NO.sub.x are first oxidized to NO.sub.2, and then the NO.sub.2 is reduced by the excess combustibles. The stream from the first catalyst bed is cooled by passing it through a heat exchanger. Air is added to the resulting stream from the heat exchanger to produce a further cooled stream having a stoichiometric excess of oxygen. The further cooled stream is then passed over an oxidizing catalyst bed to oxidize remaining excess combustibles, to thereby provide an effluent stream having environmentally safe characteristics.
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Favors Edward G.
Radian Corporation
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