Catalytic/non-catalytic combination process for nitrogen oxides reduction

Claim 2

A process for the reduction of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel, the process comprising; a) introducing a nitrogenous treatment agent comprising urea, one or more of the hydrolysis products of urea, ammonia, compounds which produce ammonia as a by-product, ammonium salts of organic acids, 5- or 6-membered heterocyclic hydrocarbons having at least one cyclic nitrogen, hydroxy amino hydrocarbons, or mixtures thereof into the effluent at an effluent temperature between about 1200° F. and about 2100° F. to create a treated effluent having reduced nitrogen oxide concentration, wherein said nitrogenous treatment agent is introduced such that ammonia is present in the treated effluent; and b) contacting the treated effluent under conditions effective to reduce the nitrogen oxides in the effluent with a catalyst effective for the reduction of nitrogen oxides in the presence of ammonia.

Claim 3

The process of claim 1 wherein said nitrogenous treatment agent comprises urea.

Claim 4

The process of claim 2 wherein said nitrogenous treatment agent is introduced at an effluent temperature of about 1700° F. to about 2100° F.

Claim 5

The process of claim 2 wherein said first treatment agent further comprises an enhancer selected from the group consisting of an oxygenated hydrocarbon, a heterocyclic hydrocarbon having at least one cyclic oxygen, sugar, molasses and mixtures thereof.

Claim 6

The process of claim 4 wherein said nitrogenous treatment agent is introduced at an effluent temperature of about 1350° F. to about 1750° F.

Claim 7

The process of claim 2 wherein said nitrogenous treatment agent is introduced at a molar ratio of treatment agent nitrogen to effluent baseline nitrogen oxides level of about 1:10 to about 10:1.

Claim 8

The process of claim 6 wherein said nitrogenous treatment agent is introduced at molar ratio and a temperature wherein the molar ratio of ammonia in the treated effluent to nitrogen oxides in the treated effluent is about 1:10 to about 10:1.

Claim 9

The process of claim 7 wherein the conditions under which said nitrogenous treatment agent is introduced comprise introducing said nitrogenous treatment agent at a temperature wherein substantial nitrogen oxides reduction are achieved yet ammonia is generated for said catalyst.

Claim 10

The process of claim 8 wherein said nitrogenous treatment agent is introduced on the left side of the plateau of the nitrogen oxides reduction versus effluent temperature curve of said nitrogenous treatment agent.

Claim 11

The process of claim 1 wherein said nitrogen oxides-reducing catalyst comprises a metal compound selected from the group consisting of platinum, palladium, rhodium, iridium, vanadium, titanium, iron, copper, manganese and oxides and mixtures thereof, on a support.

Claim 12

The process of claim 10 wherein the effluent, when contacted with said catalyst, is at a temperature of about 400° F. to about 1000° F.

Claim 13

The process of claim 1 which further comprises contacting the treated effluent with a catalyst effective for the reduction of carbon monoxide in the effluent.

Claim 14

A process for the reduction of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel to a predetermined level, the process comprising: a. selecting a desired level of nitrogen oxides in the effluent; b. introducing a nitrogenous treatment agent comprising urea, one or more of the hydrolysis products of urea, ammonia, compounds which produce ammonia as a by-product, ammonium salts of organic acids, 5- or 6-membered heterocyclic hydrocarbons having at least one cyclic nitrogen, hydroxy amino hydrocarbons, or mixtures thereof into the effluent at an effluent temperature between about 1200° F. and about 2100° F. to at least partially reduce the nitrogen oxides level in the effluent to said desired level, wherein said nitrogenous treatment agent is also effective to cause ammonia to be present in the effluent; c. contacting the ammonia-containing effluent with a catalyst effective for the reduction of nitrogen oxides in the effluent in the presence of ammonia to said desired level.

Claim 15

A process for the reduction of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel to a predetermined level, the process comprising: a. selecting a desired level of nitrogen oxides in the effluent; b. introducing a nitrogenous treatment agent comprising urea, one or more of the hydrolysis products of urea, ammonia, compounds which produce ammonia as a by-product, ammonium salts of organic acids, 5- or 6-membered heterocyclic hydrocarbons having at least one cyclic nitrogen, hydroxy amino hydrocarbons, or mixtures thereof into the effluent at an effluent temperature between about 1200° F. and about 2100° F. to at least partially reduce the nitrogen oxides level in the effluent to said desired level, wherein said nitrogenous treatment agent is also effective to cause ammonia to be present in the effluent; c. contacting the ammonia-containing effluent with a catalyst effective for the reduction of nitrogen oxides in the effluent in the presence of ammonia to said desired level.

Claim 16

The process of claim 13 wherein said nitrogenous treatment agent comprises urea.

Claim 17

The process of claim 14 wherein said nitrogenous treatment agent is introduced at an effluent temperature of about 1700° F. to about 2100° F.

Claim 18

The process of claim 15 wherein said nitrogenous treatment agent further comprises an enhancer selected from the group consisting of an oxygenated hydrocarbon, a heterocyclic hydrocarbon having at least one cyclic oxygen, sugar, molasses and mixtures thereof.

Claim 19

The process of claim 16 wherein said nitrogenous treatment agent is introduced at an effluent temperature of about 1350° F. to about 1750° F.

Claim 20

The process of claim 14 wherein said nitrogenous treatment agent is introduced at a molar ratio of treatment agent nitrogen to effluent baseline nitrogen oxides level of about 1:10 to about 10:1.

Claim 21

The process of claim 18 wherein said nitrogenous treatment agent is introduced at molar ratio and a temperature wherein the molar ratio of ammonia in the treated effluent to nitrogen oxides in the treated effluent is about 1:10 to about 10:1.

Claim 22

The process of claim 13 wherein the conditions under which said nitrogenous treatment agent is introduced are effective to generate sufficient ammonia for said catalyst.

Claim 23

The process of claim 13 wherein the conditions under which said nitrogenous treatment agent is introduced comprise introducing said nitrogenous treatment agent at a temperature wherein substantial nitrogen oxides reductions are achieved yet ammonia is generated for said catalyst.

Claim 24

The process of claim 21 wherein said nitrogenous treatment agent is introduced on the left side of the plateau of the nitrogen oxides reduction versus effluent temperature curve of said nitrogenous treatment agent.

Claim 25

The process of claim 13 wherein said nitrogen oxides-reducing catalyst comprises a metal compound selected from the group consisting of platinum, palladium, rhodium, iridium, vandium, titanium, copper, iron and manganese and oxides and mixtures thereof, on a support.

Claim 26

The process of claim 23 wherein the effluent, when contacted with said catalyst, is at a temperature of about 400° F. to about 1000° F.

Claim 27

The process of claim 13 which further comprises contacting the treated effluent with a catalyst effective for the reduction of carbon monoxide in the effluent.