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US 4,756,890 AGranted
Reduction of NO.sub.x in flue gas
AssigneePyropower Corporation
InventorsJohn T. Tang, Juha P. Sarkki, Asfaha Tesfai, Folke Engstrom
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AssigneePyropower Corporation
InventorsJohn T. Tang, Juha P. Sarkki, Asfaha Tesfai, Folke Engstrom
Estimating the term…
NO.sub.x reduction in a combustion product flue gas stream is greatly improved by the efficient mixing of the reducing agent, e.g., NH.sub.3 or an NH.sub.3 precursor, with the stream in the absence of a catalyst, such as CaO or CaCO.sub.3, that promotes undesirable combination of NH.sub.3 and O.sub.2 to form additional NO.sub.x. By employing a high-temperature cyclone separator of the like and by injecting the reducing agent into the stream within such hot cyclone at a location where there is a strong vortex region, extremely efficient mixing of the NO.sub.x reducing agent and the combustion product flue gas is promoted after particulates which are harmful to the reaction that promotes NH.sub.3 and NO.sub.x reduction have been separated from the flue gases. A refractory-lined cyclone separator may be employed, and a plurality of injectors used which discharge liquid or gas into the strong vortex region.
In a method for purifying gaseous combustion products by reducting the NO.sub.x content thereof by contacting a stream of hot gaseous combustion products with a reducing agent that effects a chemical reaction which reduces the NO.sub.x content by at least partial conversion to N.sub.2, said reducting agent being ammonia, a precursor of ammonia or a mixture thereof in vapor or vaporizable form, the improvement comprising routing said stream, while at a temperature of at least about 1400.degree. F., through a confined region of substantially circular cross section wherein a strong vortex is created as a result of substantially tangential entry of said stream and introducing said reducing agent into said stream immediately following entry into said confined region.
In a method for purifying gaseous combustion products by reducing the NO.sub.x content thereof by contacting a stream of hot gaseous combustion products with a reducing agent that effects a chemical reaction which reduces the NO.sub.x content by at least partial conversion to N.sub.2, said reducing agent being ammonia, a precursor of ammonia or a mixture thereof in vapor or vaporizable form, the improvement comprising routing said stream, while at a temperature of at least about 1400 F., through high-temperature cyclone separation means and injecting said reducing agent into a radially zero velocity zone within said cyclone separation means which is spaced radially inward from the outer boundary thereof, whereby said reducing agent is rapidly dispersed throughout said stream as it thereafter spirals within said cyclone separation means.
A system for purifying gaseous combustion products by reducing the NO.sub.x content thereof by contact with a reducing agent, which system comprises conduit means for carrying a stream of gaseous combustion products at a high temperature, high-temperature cyclone separation means having a tangential inlet in an upper portion thereof connected to an outlet from said conduit means for generating a vortex flow of said stream therewithin, said cyclone separation means including a body cylinder section and an interior exit duct of generally circular cross section, and injection means for introducing a reducing agent into said stream in a zone of essentially zero velocity spaced radially inward from the outer boundary of said cyclone separator, said injection means being positioned at a location between about 0.1 L and about 0.8 L, where L is the radial distance between said exit duct and said body cylinder wall, whereby the agent is rapidly dispersed throughout the stream as it thereafter spirals downward.
Dependencies are inferred from the claim text.