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1. (WO2009085641) APPAREIL CATALYTIQUE MUNI D'UN MÉLANGEUR EN LIGNE À TOILE MÉTALLIQUE SE TROUVANT EN AMONT
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique
What is claimed is:
1. A method for reducing NOx pollutants in an exhaust stream originating from combustion in the presence of air, said exhaust stream being conducted in an exhaust pipe, said method comprising in order:
(a) spraying a reductant into the exhaust stream from an injector;
(b) conducting the stream containing the reductant through a mixer which is attached to the exhaust pipe and is effective to disperse the reductant substantially throughout the stream, said mixer comprising a crimped, knitted wire mesh having the following properties:
(i) a density that is less than or equal to 5%; and
(ii) a circumferential contact area that is less than or equal to 50%; and
(c) subjecting the exhaust stream to selective catalytic reduction.
2. The method of Claim 1 wherein the circumferential contact area is less than or equal to 25%.
3. The method of Claim 1 wherein the mixer produces a back pressure that is less than or equal to 2 kilopascals for an exhaust gas flow rate of 1200 kg/hour and an exhaust gas temperature of 55O0C.
4. The method of Claim 1 wherein the injector produces a spray pattern within the exhaust pipe and the spacing between the mixer's upstream face and the injector is sufficiently short so that the injector's spray pattern does not contact the inner surface of the exhaust pipe before contacting the upstream face of the mixer.
5. The method of Claim 1 wherein the mixer has upstream and downstream sections, the upstream section being proximal to the injector and the downstream section being proximal to the location at which the selective catalytic reduction occurs.
6. An exhaust system for a combustion device comprising: a conduit directing exhaust from said combustion device to a selective catalytic reduction unit; an injector supplied with a reductant solution for dispensing said solution into the conduit; and a crimped, knitted wire mesh mixer disposed between the injector and the unit, wherein the crimped, knitted wire mesh of the mixer is characterized by:
(i) a density that is less than or equal to 5%; and
(ii) a circumferential contact area that is less than or equal to 50%.

7. The exhaust system of Claim 6 wherein the circumferential contact area is less than or equal to 25%.
8. The exhaust system of Claim 6 wherein the system has at least one of the following characteristics:
(a) the mixer has a flat face;
(b) the mixer has a slanted face;
(c) the mixer has a face that is not flat;
(d) the mixer has a stepped face;
(e) the mixer has a curved face;
(f) the mixer has a concave face;
(g) the mixer has a non-uniform density;
(h) the mixer has a portion which is coated with a ceramic material;
(i) the mixer has first and second sections separated by a gap;
(J) the mixer has first and second sections separated by a gap and the sections
have different densities;
(k) the mixer is brazed;
(1) the mixer is brazed and shaped by compression molding;
(m) the mixer is brazed to the conduit,
(n) the mixer is sintered;
(o) the mixer's knitted wire mesh has a herringbone crimp;
(p) the mixer is disposed in the conduit;
(q) the mixer is disposed in the unit; and
(r) the mixer is disposed in both the conduit and the unit;
9. The exhaust system of Claim 6 further comprising said combustion device, wherein said combustion device is an internal combustion engine.
10. The exhaust system of Claim 6 further comprising said combustion device, wherein said combustion device is a boiler, a furnace, or a gas turbine.
11. An exhaust system comprising:
(a) a pipe having an internal wall;
(b) a reductant injector within the pipe, said reductant injector producing a spray pattern; and (c) a knitted wire mesh mixer within the pipe, said mixer being located downstream of the reductant injector;
wherein the mixer is positioned relative to the reductant injector so that the spray pattern contacts the mixer without contacting the internal wall of the pipe.
12. The exhaust system of Claim 11 wherein the pipe has a centerline and the mixer is oriented at an angle to the centerline.
13. A mixer for use in an exhaust system, said mixer comprising knitted wire mesh having a first portion and a second portion, the first portion being downstream from the second portion when the mixer is installed in the exhaust system, wherein the wire mesh of the first portion is coated with a ceramic material capable of facilitating conversion of isocyanic acid to ammonia and the wire mesh of the second portion is free of the coating.
14. The mixer of Claim 13 wherein the ceramic material comprises TiO2.
15. A method of making a wire mesh mixer comprising:
(a) making at least one wire mesh tube;
(b) flattening the at least one wire mesh tube;
(c) crimping each side of the at least one wire mesh tube;
(d) forming a roll from the at least one crimped, flattened tube with the peaks of adjacent crimp patterns substantially sitting on one another;
(e) inserting the roll into a pipe; and
(f) brazing the resulting structure.
16. The method of Claim 15 wherein the brazing is between portions of the wire mesh which contact:
(i) other portions of the wire mesh;
(ii) portions of the wall of the pipe; or
(iii) both other portions of the wire mesh and portions of the wall of the pipe.
17. The method of Claim 15 wherein the roll is mounted in a retaining ring prior to step (f) and in step (f), the brazing is between the retaining ring and the wall of the pipe and between portions of the wire mesh which contact:
(i) other portions of the wire mesh;
(ii) portions of the retaining ring; or
(iii) both other portions of the wire mesh and portions of the retaining ring.

18. The method of Claim 15 wherein the crimping produces a herringbone crimp pattern.
19. The method of Claim 15 wherein the crimping produces an angled crimp pattern.