Method for reducing NOx with an activated catalyst

Details Method for reducing NOx with an activated catalyst Method for reducing NOx with an activated catalyst

1999-08-10

2001-07-31

Griffin, Steven P. (Department: 1754)

Chemistry of inorganic compounds

Modifying or removing component of normally gaseous mixture

Nitrogen or nitrogenous component

C502S005000, C502S522000

Reexamination Certificate

active

06267940

ABSTRACT:

BRIEF DESCRIPTION OF THE INVENTION
This invention relates generally to the control of pollutants from combustion processes. More particularly, this invention relates to a technique for enhancing NO
X
reducing catalyst activity and thereby efficiently removing NO
X
from a combustion process gas stream.
BACKGROUND OF THE INVENTION
The 1990 Clean Air Act Amendments require major sources of air emissions to limit the discharge of NO
X
. NO
X
is present in the flue gas emitted from combustion processes. Therefore, cost-effective methods for controlling NO
X
are of significant interest.
Selective Catalytic Reduction (SCR) catalysts for NO
X
removal are known in the art. Conventional NO
X
SCR catalysts require large amounts of catalyst and the flue gas stream to be at relatively high temperatures (between approximately 300 to 400° C.) in order to have sufficient activity for effective NO
X
reduction. In such schemes, ammonia is also added as a reducing agent.
There are ongoing efforts to develop low temperature catalysts for applications between approximately 100 to 250° C. Unfortunately, these low temperature catalysts are sensitive to high SO
X
, concentrations in the flue gas. There are also NO
X
SCR catalysts being developed that are reagentless, so, for instance, ammonia is not required as a reducing agent. These catalyst systems can benefit from the imposition of additional and alternative activating agents to the catalyst so that they can operate at lower temperatures, be less sensitive to poisoning agents, and more reactive without the addition of chemical agents.
In view of the foregoing, it would be highly desirable to provide an approach to enhance NO
X
removal. Ideally, the technique would reduce the amount of catalyst needed, or would operate at relatively low temperatures, or reduce the amount of required chemical reducing agents.
SUMMARY OF THE INVENTION
A method of reducing NO
X
within a gas stream includes the step of placing a NO
X
reducing catalyst within a flue gas stream that is further activated to enhance NO
X
reduction in the flue gas stream. The NO
X
reducing catalyst may be a stationary NO
X
reducing catalyst structure positioned in the flue gas stream. Alternately, the NO
X
reducing catalyst may be injected into the flue gas stream as a NO
X
reducing catalyst powder. The NO
X
reducing catalyst powder may be subsequently gathered in a particulate collection device. The NO
X
reducing catalyst may be further activated in the particulate collection device. The operation of enhancing the activity of the NO
X
reducing catalyst may be implemented by applying electromagnetic energy to the NO
X
reducing catalyst, by applying an electric field to the NO
X
reducing catalyst, by applying electric current through the NO
X
reducing catalyst, or by applying a magnetic field to the NO
X
reducing catalyst.
The invention provides a technique for promoting catalytic activity in various NO
X
SCR catalysts so that the catalysts can be operated and installed under conditions where they are less active and therefore otherwise not effective for NO
X
reduction in gases. The invention facilitates the use of catalysts at lower temperatures. The invention renders the catalysts less sensitive to poisoning agents, and otherwise more reactive, even without the addition of chemical agents. The enhanced catalytic activity reduces the amount and size of the catalyst needed to reduce NO
X
effectively. The NO
X
reduction technique of the invention is cost-effective, thereby minimizing the overall cost of generating electricity in fossil-fired power plants.


REFERENCES:
patent: 6153159 (2000-11-01), Engeler et al.
patent: 1212179A (1999-03-01), None

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