Injection and mixing system for reducing agents

Abstract

Injection and mixing system (10) for a gaseous reducing agent, comprising: an injector (20) for injecting the gaseous reducing agent into an exhaust gas stream, wherein the injector has: an outer injection tube (24), a plurality of openings (28) defined in the outer injection tube through which the gaseous reducing agent is injected into an exhaust gas stream, an inner injection tube (26) which is concentric to and bounded by the outer injection tube, wherein the plurality of openings (28) is also defined in the inner injection tube, and a reducing agent supply tube (21) which is in fluid communication with the inner injection tube and the outer injection tube, wherein the reducing agent supply pipe extends through the outer injection pipe and the inner injection pipe, so that both the inner injection pipe and the outer injection pipe are halved, the reducing agent supply tube has reducing agent inlets (23A, 23B) arranged at opposite ends of the reducing agent supply tube to introduce reducing agent from opposite ends of the reducing agent supply tube; and The injector further comprises a mixer (30) attached to a surface of the injector and comprising a plurality of fluid diversion elements (32).

Description

AREA

[0001] The present invention relates generally to exhaust aftertreatment systems for internal combustion engines and in particular to SCR systems (SCR = selective catalytic reduction) with injection components for gaseous reducing agents. BACKGROUND

[0002] Exhaust aftertreatment systems take in and treat exhaust gas produced by an internal combustion engine. Typical exhaust aftertreatment systems include various components designed to reduce the level of harmful emissions in the exhaust gas. For example, some exhaust aftertreatment systems for diesel-powered internal combustion engines include components such as a diesel oxidation catalyst (DOC), a particulate filter or diesel particulate filter (DPF), and an SCR catalyst (SCR = selective catalytic reduction). In some exhaust aftertreatment systems, the exhaust gas first flows through the diesel oxidation catalyst, then through the diesel particulate filter, and finally through the SCR catalyst.

[0003] Each component of the DOC, DPF, and SCR catalyst is designed to perform a specific process for treating exhaust emissions in the exhaust gas flowing through it. The DOC generally reduces the amount of carbon monoxide and hydrocarbons present in the exhaust gas using oxidation techniques. The DPF filters out harmful diesel particulate matter and soot from the exhaust gas. Finally, the SCR catalyst reduces the amount of nitrogen oxides (NOx) present in the exhaust gas. X ).

[0004] The SCR catalyst is designed to reduce NO Xto convert the high-carbon dioxide (NH3) into less harmful emissions, such as N2 and H2O, in the presence of ammonia. Since ammonia is not a natural byproduct of combustion, it must be artificially added to the exhaust gas before it enters the SCR catalyst. For safety reasons related to the storage of gaseous ammonia, ammonia is generally not injected directly into the exhaust gas.

[0005] Accordingly, conventional systems are designed to inject an aqueous diesel exhaust fluid or reducing agent into the exhaust gas, whereby the fluid or reducing agent can decompose into gaseous ammonia in the presence of exhaust gas under certain conditions. The aqueous reducing agent most commonly used by conventional exhaust aftertreatment systems is a urea-water solution (hereinafter referred to as "urea").

[0006] In general, the decomposition of aqueous urea to gaseous ammonia occurs in three phases. First, the aqueous urea evaporates or mixes with the exhaust gas. Second, the temperature of the exhaust gas causes a thermolytically induced phase change in the aqueous urea, leading to its decomposition into isocyanic acid (HNCO) and NH3. Third, the isocyanic acid reacts with water in a hydrolysis process under specific pressure and temperature concentrations to decompose into ammonia and carbon dioxide (CO2). The gaseous ammonia is then introduced at the inlet face of the SCR catalyst, flows through the catalyst, and is converted to NO in the process. x -Reduction consumed. Any unused ammonia that escapes from the SCR system can be broken down to N2 and other less harmful or less polluting components using an ammonia oxidation catalyst.

[0007] SCR systems typically include a urea source and a urea injector or metering device connected to the source and located upstream of the SCR catalyst. The urea injector sprays urea into a decomposition chamber through which an exhaust gas stream flows. Upon injection into the exhaust gas stream, the injected urea spray is heated by the exhaust gas to trigger the decomposition of the urea to ammonia. As the urea-exhaust gas mixture flows through the decomposition chamber, the urea mixes further with the exhaust gas before entering the SCR catalyst. Ideally, the urea is sufficiently decomposed and mixed with the exhaust gas before entering the SCR catalyst to provide a sufficiently uniform distribution of ammonia at the inlet face of the SCR catalyst.

[0008] However, some state-of-the-art exhaust aftertreatment systems do not provide sufficient decomposition and mixing of the injected aqueous urea, which can lead to the formation of solid urea deposits on the inner walls of the decomposition chamber and the urea injector. Furthermore, insufficient mixing can result in a low ammonia vapor uniformity index, leading to uneven ammonia distribution on the SCR catalyst surface and lower NOₓ emissions. x -conversion efficiency and other deficits may result.

[0009] Further devices for mixing exhaust gases from combustion engines with additives are known from DE 20 2006 017 848 U1, US 2010 / 0 148 382 A1 and US 2010 / 0 293 931 A1. SUMMARY

[0010] The subject matter of the present application was developed in response to the current state of the art and, in particular, in response to the problems and requirements of conventional injection systems for aqueous urea that have not yet been fully resolved by currently available systems. In general, the subject matter of the present application was developed to provide an injection and mixing system for gaseous ammonia and an associated apparatus that eliminates at least some of the deficiencies of prior art systems discussed above.

[0011] An injection and mixing system for gaseous reducing agent according to the present invention is specified in claim 1. Optional embodiments are described in the dependent claims.

[0012] According to one embodiment, an injection and mixing system for a gaseous reducing agent comprises an injector for injecting a gaseous reducing agent into an exhaust gas stream and a mixer attached to the surface of the injector, comprising a plurality of fluid diverting elements. The injector has a plurality of openings defined in the outer injection tube through which the gaseous reducing agent is injected into an exhaust gas stream. The injector further comprises an inner injection tube, which is concentric with and bounded by the outer injection tube, the plurality of openings also being defined in the inner injection tube, and a reducing agent supply tube, which is in fluid communication with the inner injection tube and the outer injection tube.The reducing agent supply tube extends through the outer and inner injection tubes, thus bisecting both. The reducing agent supply tube has reducing agent inlets located at opposite ends to introduce reducing agent from opposite ends.

[0013] In some applications of the system, the multitude of openings injects the gaseous reducing agent into the exhaust gas stream in a first direction, which is generally opposite to the direction of exhaust gas flow. The injector may have an upstream-facing surface. The multitude of openings may be formed in this upstream-facing surface. The gaseous reducing agent may be gaseous ammonia or a pressurized gaseous reducing agent. An opening in the reducing agent supply tube may be defined at the geometric center of the outer injection tube and the inner injection tube.

[0014] Depending on certain system applications, the injector has a downstream-facing surface. The mixer can be attached to the downstream surface of the injector. The multiple fluid diverting elements can extend downstream at an angle to the exhaust gas flow.

[0015] The mixer can have a first annular ring to which the fluid diverting elements are connected. The first annular ring can be attached to a surface of the first annular tube. The mixer can have a second annular ring, and the fluid diverting elements can also be connected to the second annular ring. The second annular ring can be attached to a surface of the inner injection tube.

[0016] The described features, structures, advantages, and / or properties of the subject matter of this disclosure can be suitably combined in one or more embodiments and / or applications. Numerous specific details are provided in the following description to convey a thorough understanding of embodiments of the subject matter of this disclosure. A person skilled in the art will recognize that the subject matter of this disclosure can be exercised without one or more of the specific features, details, components, materials, and / or methods of a particular embodiment or application. In other cases, additional features and advantages may be recognized in certain embodiments and / or applications that may not be present in all embodiments or applications.Furthermore, in some cases well-known structures, materials, or processes are not shown or described in detail to prevent aspects of the subject matter of this disclosure from becoming unclear. The features and advantages of the subject matter of this disclosure will become even clearer from the following description and the accompanying claims, or they can be learned by implementing the invention as described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To further clarify the advantages of the subject matter, a more detailed description of the subject matter briefly described above follows, with reference to the specific embodiments illustrated in the accompanying drawings. Under the understanding that these drawings only show typical embodiments of the subject matter and are therefore not to be considered as limiting the scope of protection, the subject matter is described and explained more precisely and in greater detail using the drawings, in which: Fig. 1 a front or downstream view of an injection and mixing system for gaseous reducing agent according to an embodiment; Fig. 2 A side view of the injection and mixing system for gaseous reducing agent from Fig. 1, shown in an exhaust gas stream according to an embodiment, is; Fig. 3 A front view of an ammonia feed pipe from an injector of the gaseous reducing agent injection and mixing system of Fig. 1 according to one embodiment; Fig. 4 an upper view of the ammonia supply pipe from Fig. 3 is; Fig. 5 a cross-sectional view of the ammonia supply pipe from Fig. 3 is; Fig. 6 A front view of a section of an inner tube of the injector of the injection and mixing system for gaseous reducing agent of Fig. 1 according to one embodiment; Fig. 7 a lower view of the section of the inner tube of Fig. 6 is; Fig. 8 A front view of a section of an outer tube of the injector of the injection and mixing system for gaseous reducing agent of Fig. 1 according to one embodiment; Fig. 9 a lower view of the section of the outer tube of Fig. 8 is; Fig. 10 A front view of a mixer of the injection and mixing system for gaseous reducing agent of Fig. 1 according to one embodiment; Fig. 10A a side view of the mixer from Fig. 10 is; Fig. 10B a top view of the mixer from Fig. 10 is; and Fig. 11 A detailed front view of a fluid deflection element of the mixer from Fig. 10 is. DETAILED DESCRIPTION

[0018] Throughout the patent specification, reference to "an embodiment" or similar expressions means that a particular feature, structure, or property described in connection with the embodiment is included in at least one embodiment of the subject matter of the present disclosure. Phrases such as "in an embodiment" and similar expressions throughout the patent specification may all refer to the same embodiment, but this is not necessarily the case.Similarly, the use of the term "application form" means an application form with a particular feature, structure or property that has been described in connection with one or more embodiments of the subject matter of the present disclosure, but without an express assignment indicating otherwise, an application form may be assigned to one or more embodiments.

[0019] This document describes various embodiments of an injection and mixing system for reducing agents and associated devices and methods, which serve, among other things, to improve the concentration of gaseous ammonia in the exhaust gas stream entering the SCR catalyst of an exhaust aftertreatment system and to improve the uniform distribution of gaseous ammonia entering the SCR catalyst. In general, the injection and mixing system of the present application is designed to introduce a gaseous reducing agent, such as gaseous ammonia, into the exhaust gas stream, instead of an aqueous reducing agent, such as aqueous urea, as is the case with conventional systems. Accordingly, the system of the present invention, in contrast to conventional systems, injects gaseous ammonia directly into the exhaust gas stream and then mixes the gaseous ammonia with the exhaust gas.Since the ammonia is injected into the exhaust stream in gaseous form, the decomposition inefficiencies associated with aqueous urea are eliminated. Accordingly, the present system favors higher concentrations and a more uniform distribution of gaseous ammonia into an SCR catalyst than prior art systems. Furthermore, because the need to promote the decomposition of an aqueous reducing agent to a gaseous reducing agent is eliminated, the present system does not require an extended decomposition tube upstream of the SCR catalyst, which would allow for close coupling of the SCR catalyst to the engine.

[0020] Although not shown, the injection and mixing system for reducing agents of the present application is used together with an exhaust aftertreatment system connected to an internal combustion engine. The aftertreatment system can take in and treat exhaust gas produced by the engine. After treatment by the aftertreatment system, the exhaust gas is discharged into the atmosphere via an exhaust pipe. In certain applications, the exhaust aftertreatment system is attached to a vehicle in which the engine is housed. Conventionally, exhaust aftertreatment systems include a variety of exhaust treatment devices. For example, an exhaust aftertreatment system may include a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and an SCR system (SCR = selective catalytic reduction) with an SCR catalyst.

[0021] With reference to Fig. Figure 1 shows an embodiment of an injection and mixing system for gaseous reducing agent 10. The system 10 is arranged at least partially in an exhaust gas line 90 (e.g., duct or pipe) of an exhaust aftertreatment system upstream of an SCR catalyst. Generally, the system 10 injects gaseous ammonia into the exhaust gas flow through the exhaust gas line 90 and mixes the injected gaseous ammonia by introducing a vortex flow before it enters the SCR catalyst. The system 10 comprises an injector 20 and a mixer 30 connected to the injector.

[0022] The injector 20 has an ammonia supply tube 21 and an inner and an outer injection tube 24, 26, which are in ammonia-receiving communication with the ammonia supply tube. At least one end of the ammonia supply tube 21 is in gaseous ammonia-receiving communication with one or more of the (not shown) sources of gaseous ammonia. The ends of the ammonia supply tube 21 can form ammonia inlets 23A, 23B for connection to an ammonia supply line. In some embodiments, only one end of the ammonia supply tube 21 forms an inlet and the other has a closed or plugged end. The ammonia supply pipe 21 can be connected to a wall of the exhaust pipe 90 in order to arrange (e.g. suspend) the injector 20 and the mixer 30 of the system 10 in the exhaust pipe and consequently in the exhaust gas flow, which flows in one direction of the exhaust gas flow through the exhaust pipe.

[0023] The inner and outer injection tubes 24, 26 each form essentially circular or annular tubes and are connected to each other by means of the supply tube 21. As shown in the Fig. 6 and Fig. As shown in Figure 7, the inner tube 24 can have two semicircular tube sections 24A, 24B. Similarly, as shown in the Fig. 8 and Fig. As shown in Figure 9, the outer tube 26 has two semicircular tube sections 26A, 26B. The outer injection tube 26 has a larger diameter to effectively limit the inner injection tube 24. The ammonia supply line 21 extends through the inner and outer injection tubes 24, 26 to effectively bisect each injection tube. The inner and outer injection tubes 24, 26 each have a plurality of openings 28 formed (e.g., drilled or punched) in and around the upstream surfaces 80, 82 of the tubes. The openings 28 extend only through the upstream surfaces or sides 80, 82 of the injection tubes 24, 26. In certain applications, the ammonia supply tube 21 also has one or more openings 29 formed in and arranged along an upstream surface of the supply tube.For example, in the illustrated embodiment of . Fig. 1 an opening 29 on the upstream surface of the feed tube 21 is arranged at a geometric center of the circular injection tubes 24,26.

[0024] According to one embodiment, as in Fig. As shown in Figure 6, the openings 28 formed in the inner injection tube 24 are evenly spaced from one another around the inner injection tube. More precisely, in some embodiments, the inner tube 24 has six openings 28 spaced apart from one another at an angle Ø1. In the illustrated embodiment, the angle Ø1 is 60 degrees, but it can be any other angle, possibly associated with any number of openings. Similarly, according to one embodiment, as shown in Fig. Figure 8 shows that the openings 28 formed in the outer injection tube 26 are evenly spaced apart around the outer injection tube. More precisely, in some embodiments, the outer tube 26 has ten openings 28 spaced apart at an angle Ø2. In the illustrated embodiment, the angle Ø2 is 30 degrees, but it can be any other angle, possibly associated with any number of openings. Although the openings 28 are evenly distributed around the tubes, in some embodiments the openings need not be equidistant. For example, in some embodiments the openings 28 may be closer together at some points along the tubes than at other points along the tubes.

[0025] The mixer 30 has an inner ring 36 which is connected to an outer ring 38 by means of a crossbar 39. In some applications, the size and general shape of the inner ring 36 correspond approximately to that of the inner injection tube 24, the size and general shape of the outer ring 38 correspond approximately to that of the outer injection tube 26, and the size and general shape of the crossbar 39 correspond to that of a central section of the feed tube 21. In certain embodiments, the mixer 30 does not have a crossbar 39, so that the inner ring 36 and the outer ring 38 are each formed as a separate, unconnected element.

[0026] As in the Fig. 1 and Fig. As shown in Figure 10, both the inner and outer rings 36, 38 have a plurality of fluid diversion elements 32 spaced apart around the respective rings. Each fluid diversion element 32 has radially outward-facing diversion elements or ribs 34A and opposite radially inward-facing diversion elements or ribs 34B. The diversion elements 34A, 34B are considered radially outward-facing and radially inward-facing, respectively, because the diversion elements 34A extend from the rings in a direction away from a center or central axis of the rings, and the diversion elements 34B extend from the rings in a direction toward a center or central axis of the rings. The fluid diversion elements 32 can be spaced evenly apart from one another around the outer and inner rings 36, 38, respectively. More precisely, in some applications, such as in Fig. As shown in Figure 10, the inner ring 36 has six diverting elements 32 spaced apart from each other at an angle Ø6. In the illustrated embodiment, the angle Ø6 is 60 degrees, but it can be any other angle, possibly associated with any number of openings. Similarly, according to one embodiment, as shown in Fig. Figure 10 shows the outer ring 38 having twelve openings spaced apart from each other at an angle Ø5. In the illustrated embodiment, the angle Ø5 is 30 degrees, but it can be any other angle, possibly associated with any number of diverting elements. Although the diverting elements 32 are evenly distributed around the rings, in some embodiments the diverting elements are not evenly distributed around the rings.

[0027] As in Fig. As shown in Figure 2, the mixer 30 is attached to downstream surfaces 84, 86 of the injector 20. In the illustrated embodiment, the mixer 30 is attached to the injector 20 such that the inner ring 36 of the mixer lies above (or below) the inner injection tube 24, the outer ring 38 of the mixer lies above (or below) the outer injector 26, and the crossbar 39 lies above (or below) the supply tube 21. In this way, exhaust gas can flow radially outward around the outer injection tube 26 and the ring 38, between the outer injection tube and the ring 38, between the inner injection tube 24 and the ring 36, and between the inner injection tube and the ring 36 and the central section of the supply tube 21. The mixer 30 can be attached to the downstream surface of the injector 20 using various fastening methods known in the prior art, such as welding, bonding, anchoring, etc.In some applications, the mixer 30 is detachably attached to the injector 20. In other applications, the mixer 30 is integrally formed as a single-piece, cast assembly with the injector 20.

[0028] With reference to the Fig. 1 and Fig. 2. Gaseous ammonia is supplied from a source of gaseous ammonia (e.g., a compression vessel filled with gaseous ammonia), when in operation and located in an exhaust gas stream at a point upstream of the SCR catalyst, to the injector 20 via one of the inlets 23A, 23B of a corresponding inlet section 22A, 22B of the supply pipe 21, as indicated by the directional arrows. Although not shown, an engine control module can control the supply of gaseous ammonia to the injector according to NO. X- Control the degradation requirements as specified by the operating conditions of the engine. As further indicated by the directional arrows, the absorbed gaseous ammonia flows through the inner channels 25 formed in the feed pipe 21 and into corresponding inner channels 60, 62 of the inner and outer injection pipes 24, 26 through corresponding openings in the feed pipe (see, for example, openings 52A, 52B of Fig. 3 and Fig. 4) The gaseous ammonia is driven through the openings 28 by the inner and outer injection tubes 24, 26 and through the opening 29 by the supply tube 21.

[0029] As in Fig. As shown in Figure 2, the gaseous ammonia is injected from the openings in a direction opposite to the flow direction of the exhaust gas stream 40 because the openings 28, 29 are open in an upstream direction or point in this direction. Since the gaseous ammonia is injected into the exhaust gas against the flow of the exhaust gas, a stagnation point is created between the gaseous ammonia and the exhaust gas, which improves the mixing of the gaseous ammonia and the exhaust gas. In some embodiments, the openings 28, 29 can point in a downstream direction or in any direction between the downstream and upstream directions, as desired. For example, the openings 28, 29 can be angled sharply or slightly with respect to the exhaust gas flow direction in order to inject gaseous ammonia into the exhaust gas at the angle formed.

[0030] After the ammonia is injected into the exhaust gas stream and partially mixes with it, the mixture 44 of gaseous ammonia and exhaust gas flows around the fluid diversion elements 32 of the mixer 30. As in Fig. As shown in Figure 2, the fluid diversion elements 32, thanks to the design of the ribs 34A, 34B of the elements, promote turbulent flow and swirling of the mixture 44. With reference to the Fig. 10A and Fig. In the embodiment 10B, the ribs 34A, 34B of each of the fluid diversion elements 32 are angled in a downstream direction. In this way, the ribs 34A, 34B divert the mixture 44 of ammonia and exhaust gas radially outwards and inwards, creating low-pressure areas that cause a swirling motion of the mixture. Furthermore, the design of the ribs 34A, 34B produces an angular vortex effect on the exhaust gas (e.g., a swirling of the exhaust gas around an axis that is angled with respect to the main flow direction of the exhaust gas), resulting in improved mixing of the gaseous reducing agent with the exhaust gas. In the illustrated embodiment, the ribs 34A, 34B, which are located on both the inner and outer rings 36, 38, promote a swirling of the exhaust gas in the same direction.In other embodiments, however, the ribs can be designed differently to promote swirling of the exhaust gas in opposite directions, to facilitate an increase in turbulent flows, in order to further improve mixing.

[0031] As in Fig. As shown in Figure 10A, the ribs 34A, 34B of the elements 32 arranged around the outer ring 38 are angled at an angle Ø3 with respect to a plane perpendicular to the direction of the exhaust gas flow. This is similar to the case shown in Figure 10A. Fig. As shown in Figure 10B, the ribs 34A, 34B of the elements 32, arranged around the inner ring 36, are angled at an angle Ø4 with respect to a plane perpendicular to the direction of the exhaust flow. The angles Ø3, Ø4 can be different or the same (e.g., in one embodiment, the angles Ø3, Ø4 can each be 60 degrees). The surfaces of the ribs 34A, 34B are substantially curved. For example, the upstream surfaces of the ribs 34A, 34B are convex, and the downstream surfaces of the ribs 34A, 34B are concave.

[0032] With reference to Fig.Each fluid diversion element 32 of the mixer 30 can be formed by cutting opposing slots 70A, 70B into a stamped piece of rolled sheet (or a relatively flat sheet) that has the shape of the rings. At the ends of the slots 70A, 70B, small openings 72A, 72B can be formed (e.g., drilled) in the metal. Then, a sheet bending technique can be used to bend the ribs 34A, 34B along the slots 70A, 70B to the desired angles, as discussed above. The small openings 72A, 72B prevent a notch effect at the ends of the slots, which could lead to undesired cracking or transverse breakage of the metal. The edges of the ribs 34A, 34B can have any different shapes, as desired, such as curved, as shown, or tapered.

[0033] Although system 10 is depicted as a single assembly, in some embodiments the injector 20 for gaseous ammonia can be used without the mixer 30, and vice versa. Furthermore, system 10 can be manufactured by producing the injector 20 and the mixer 30 separately, for example, by stamping or injection molding methods, and then joining the dissimilar parts together later. Alternatively, the injector 20 and the mixer 30 of system 10 can be formed together as a single, cast assembly.

[0034] When one element is "connected" to another, this can include direct and indirect connection. Direct connection can be defined as one element being connected to another and thus in some form of contact. Indirect connection can be defined as connecting two elements that are not in direct contact with each other, but have one or more additional elements between them. Furthermore, as used herein, attaching one element to another can include both direct and indirect attachment. In addition, "adjacent," as used herein, does not necessarily imply contact. For example, one element may be adjacent to another without being in contact with it.

[0035] As used herein, the phrase "at least one of" when used with an enumeration of items means that various combinations of one or more of the enumerated items can be used, and only one of the enumerated items may be required. The item may be a specific object, thing, or category. In other words, "at least one of" means that any combination of items or any number of items from the enumeration may be used, but not all items in the enumeration may be required. For example, "at least one of item A, item B, and item C" could mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C.In some cases, “at least one of item A, item B, and item C” may, for example, but is not limited to, mean two of item A, one of item B, and ten of item C; four of item B and seven of item C; or any other suitable combination.

[0036] In the preceding description, certain terms such as "top," "bottom," "upper," "lower," "horizontal," "vertical," "left," "right," "above," "below," and the like may be used. These terms are used, where appropriate, to provide a more precise description when referring to relationships between objects. However, these terms are not intended to imply absolute relationships, positions, and / or orientations. For example, with respect to an object, an "upper" surface can become a "lower" surface simply by turning the object upside down. It is still the same object. Furthermore, the terms "including," "comprising," "exhibiting," and variations thereof mean "including, but not limited to," unless explicitly stated otherwise.A numbered list of items does not imply that all of these items exclude and / or include each other, unless explicitly stated otherwise. The terms "a," "an," "one," and "the" refer to "one or more," unless explicitly stated otherwise. Furthermore, the term "plural" can be defined as "at least two."

[0037] The described embodiments are to be regarded in every respect as merely illustrative and not as limiting.

Claims

[1] Injection and mixing system (10) for a gaseous reducing agent, comprising: an injector (20) for injecting the gaseous reducing agent into an exhaust gas stream, wherein the injector has: an outer injection tube (24), a plurality of openings (28) defined in the outer injection tube through which the gaseous reducing agent is injected into an exhaust gas stream, an inner injection tube (26) which is concentric to and bounded by the outer injection tube, wherein the plurality of openings (28) is also defined in the inner injection tube, and a reducing agent supply tube (21) which is in fluid communication with the inner injection tube and the outer injection tube, wherein the reducing agent supply pipe extends through the outer injection pipe and the inner injection pipe, so that both the inner injection pipe and the outer injection pipe are halved, the reducing agent supply tube has reducing agent inlets (23A, 23B) arranged at opposite ends of the reducing agent supply tube to introduce reducing agent from opposite ends of the reducing agent supply tube; and The injector further comprises a mixer (30) attached to a surface of the injector and comprising a plurality of fluid diversion elements (32). [2] Injection and mixing system for gaseous reducing agent according to claim 1, wherein the plurality of openings (28) injects the gaseous reducing agent into the exhaust gas stream in a first direction, the first direction generally being opposite to a flow direction of the exhaust gas stream. [3] Injection and mixing system for gaseous reducing agent according to claim 1, wherein the injector comprises an upstream-facing surface (80, 82) and wherein the plurality of openings (28) are formed in the upstream-facing surface. [4] Injection and mixing system for gaseous reducing agent according to claim 1, wherein the gaseous reducing agent comprises gaseous ammonia. [5] Injection and mixing system for gaseous reducing agent according to claim 1, wherein the gaseous reducing agent comprises a pressurized gaseous reducing agent. [6] Injection and mixing system for gaseous reducing agent according to claim 1, wherein an opening (29) in the reducing agent supply tube is defined at a geometric center between the outer injection tube and the inner injection tube. [7] Injection and mixing system for gaseous reducing agent according to claim 1, wherein the injector (20) comprises a downstream surface (84, 86) and wherein the mixer (30) is attached to the downstream surface of the injector. [8] Injection and mixing system for gaseous reducing agent according to claim 7, wherein the plurality of fluid diversion elements (32) extends in a downstream direction at an angle to the direction of flow of the exhaust gas stream. [9] Injection and mixing system for gaseous reducing agent according to claim 1, wherein the mixer (30) comprises a first annular ring (38), wherein the fluid diversion elements (32) are connected to the first annular ring and wherein the first annular ring is attached to a surface of the outer injection tube (26). [10] Injection and mixing system for gaseous reducing agent according to claim 7, wherein the mixer (30) comprises a second annular ring (36), wherein the fluid diversion elements (32) are also connected to the second annular ring and wherein the second annular ring is attached to a surface of the inner injection tube (24).

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