Selective catalytic NO_xreduction process and apparatus providing improved gassification of urea to form ammonia-containing gas

摘要

Disclosed are methods and apparatus enabling the efficient utilization of urea for purposes such as selective catalytic reduction (SCR) of NOx, which enable feeding urea to a chamber designed to efficiently and completely gasify the urea to enable ammonia feed. Preferably, aqueous urea is fed to a gasification chamber, which is also fed with heated gases. An injector means, capable of distributing the aqueous urea as fine droplets, is positioned centrally of a gas distribution plate in the chamber. An arrangement of spaced holes in the gas distribution plate provides higher gas velocity in the vicinity of the injector means than near the walls of the chamber. Uniform gas distribution without equipment fouling is achieved.

主权项

1. A process for gasifying urea for reducing the concentration of nitrogen oxides in combustion gases, comprising:
a. feeding aqueous urea to a vertical gasification chamber having a top wall, a bottom wall and a side wall, b. feeding heated gases into the gasification chamber above the point for introducing the urea by urea injector means for distributing the aqueous urea as fine droplets, c. providing a horizontal gas distribution plate in the vertical gasification chamber, wherein the gas distribution plate has a central hole and arrays of smaller holes, and the injector means is juxtaposed with the plate and centrally located with the central opening in the plate and has an injector opening below or at the elevation of the plate to allow gas flow through the central hole and between the injector means and the plate, d. providing an arrangement and spacing of the smaller holes in the gas distribution plate to provide higher gas velocity in the vicinity of the injector means than near the walls of the chamber, and e. adjusting the feed rates of the aqueous urea and the heated gases effectively to gasify the urea prior to exit from the chamber.