Conversion of urea to reactants for NOx reduction

Abstract

The invention provides a system for converting urea into reactants useful for removing NOX from industrial emissions. The system includes a urea inlet, a steam inlet, and a reactor in fluid communication with the urea inlet and the steam inlet. The reactor is configured and adapted to inject urea from the urea inlet into a steam flow from the steam inlet to convert the urea into at least one reactant for NOX reduction within a substantially gaseous mixture. The invention also provides a method of converting urea into reactants for reducing NOX out of industrial emissions. The method includes injecting urea into a steam flow to convert the urea into at least one reactant for NOX reduction within a substantially gaseous mixture.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application claims priority to U.S. Patent Application Ser. No. 60 / 914,598, filed Apr. 27, 2007. This application is incorporated by reference herein in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a system for NOX reduction. Particularly, the present invention is directed to a system for converting urea into reactants for removing NOX from industrial emissions.[0004]2. Description of Related Art[0005]A variety of urea conversion devices are known in the art for converting urea into reactants, such as ammonia, which are useful in reducing NOX emissions in industrial settings. Of such devices, many are directed to systems that utilize hydrolysis to convert urea into ammonia and other reactants for NOX reduction.[0006]Combustion of fossil fuels, such as in power plants and other industrial settings, leads to a release of pollutants. NO2 and NO (referred to as NOX) ...

AI Technical Summary

Benefits of technology

[0027]In further accordance with the invention, the method can further include a step of controlling conversion of urea within the substantially gaseous mixture in a reactor. The controlling step can include controlling with a first control loop operatively connected to the reactor to control urea injection rate based on demand for NOX reduction. The controlling step can further include a second control loop operatively connected to the reactor to control temperature of the substantially gaseous mixture upstream from a reducer. Further, the controlling step can in...

Problems solved by technology

Combustion of fossil fuels, such as in power plants and other industrial settings, leads to a release of pollutants.

NO2 and NO (referred to as NOX) are particularly problematic pollutants arising from fossil fuel combustion.

The ammonia typically used in SCR and SNCR presents problems of its own, however.

The most economical form of ammonia for use in SCR and SNCR is anhydrous ammonia, but classification of this reactant as a hazardous chemical may restrict its use in some locations.

But the costs of transportation, storage, and processing of aqueous ammonia are great, especially considering the fact that most of what is shipped, stored, and processed is the water, which can be in excess of about 70% by volume.

This cost may restrict the use of aqueous ammonia.

However, the state of the art urea hydrolysis reactors have large pressure vessels holding standing liquid.

Thus they take up valuable space and controlling their reaction rates can be difficult.

Typical hydrolysis reactors are heavy and operate at high pressures, which raises safety concerns.

Known hydrolysis reactors have significant reactant volumes, which can lead to complications during start up and shut down.

Moreover, the bubbling of ammonia and other gases out of the liquid state of the known urea hydrolysis reactors can cause a foam layer to build up.

This, along with the build up of additives commonly used in solid urea, can lead to an accumulation of contaminants within the reactor, requiring frequent down time for cleaning and maintenance of the reactor.

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