RU144303U1 - DEVICE FOR REDUCING DIESEL ENGINE EMISSIONS - Google Patents

Abstract

1. A device for reducing emissions of a diesel engine containing a low pressure exhaust gas recirculation system, which comprises an exhaust gas recirculation loop (14, 24, 34, 44, 54, 64, 74, 84), at least one storage catalyst (12, 22, 32, 42a, 42b, 72) NОх for accumulating nitrogen oxides from the exhaust gas supplied from the diesel engine (11, 21, 31, 41, 51, 61, 71, 81), and at least one SCR catalyst ( 13, 23, 33, 43) installed after the NOx storage catalyst for selective catalytic reduction of nitrogen oxides in trabotavshem gas supplied to the SCR-katalizator.2. The device according to claim 1, characterized in that the NOx storage catalyst and the SCR catalyst are made in the form of a single device (29, 39, 49, 59, 69, 79, 89), which is located either entirely inside or outside the loop (24, 34 44, 54, 64, 74, 84) exhaust gas recirculation. 3. The device according to claim 1 or 2, characterized in that the storage catalyst (12, 22, 42a) NOx is structurally located near the engine, in the circuit (14, 24, 44) of the exhaust gas recirculation. The device according to claim 3, characterized in that the storage catalyst (12, 42a) NOx is placed on a diesel particulate filter (15, 45) .5. A device according to claim 1 or 2, characterized in that the SCR catalyst (23) is structurally located near the engine, inside the exhaust gas recirculation loop (24). The device according to claim 5, characterized in that the SCR catalyst (23) is placed on a diesel particulate filter. A device according to claim 1 or 2, characterized in that the NOx storage catalyst (32, 42b) is located outside the exhaust gas recirculation loop (34, 42). The device according to claim 1 or 2, characterized in that it further comprises a diesel oxidizing catalyst (8

Description

The technical field to which the utility model relates.

This utility model relates to a device for reducing diesel engine emissions.

State of the art

Stricter emission limits for vehicles with a diesel engine or a combination of an internal combustion engine with an exhaust gas treatment means that the emission reduction must meet even higher requirements.

As a measure to reduce emissions for internal combustion engines, low-pressure exhaust gas recirculation (LP-EGR) systems have been developed in which the exhaust gas recirculation point is shifted to the place of the exhaust system located after the diesel particulate filter, DPF (Diesel Particle Filter). A circulating exhaust gas that is accordingly clean, i.e. soot-free then transferred back into the air stream to a point in front of the compressor, and again circulated in the internal combustion engine.

With regard to the exhaust gas itself, even more stringent requirements for the NOx limit lead to the use of mainly two different exhaust gas treatment technologies, which constitute possible technical solutions for limiting the emission of NOx (nitrogen oxides) in the exhaust gases. One of these solutions is a storage catalyst, LNT (Lean NOx Trap), the principle of which is based on the fact that first, when the engine is running on a lean fuel mixture, the catalyst accumulates nitrogen oxides (NOx), and then, when a rich air-fuel mixture is established at the stage of regeneration, the catalyst neutralizes toxic oxides.

The second technology for reducing nitrogen oxides (NOx) is selective catalytic reduction, SCR (Selective Catalytic Reduction), which, for example, involves injecting an aqueous urea solution into the exhaust gas stream upstream of the SCR catalyst (urea injection catalytic neutralization system). In this case, the reaction of urea with the formation of ammonia (NH ₃ ) and water (H ₂ O) is used, while the ammonia (NH ₃ ) formed in the SCR catalyst reduces nitrogen oxides (NOx) in the exhaust gas to nitrogen (N ₂ ) .

As for the technology that was mentioned first, i.e. the catalytic neutralization of NOx (LNT), it is known that when working with a rich air-fuel mixture (ie in the “enrichment” mode), the NOx storage catalyst (LNT) instead of converting all nitrogen oxides to nitrogen (N ₂ ) also produces ammonia (NH ₃ ), and ammonia (NH ₃ ) is discharged from the storage catalyst (LNT) to the outside.

Also known in this context is a combination system constructed from an NOx storage catalyst (LNT) and an in situ SCR catalyst (also called a passive SCR system, or shortly “pSCR”) in which the SCR catalyst is located downstream of the NOx storage catalyst (LNT ), wherein said SCR catalyst serves to accumulate ammonia (NH ₃ ) discharged from the NOx storage catalyst (LNT) in enrichment modes. The ammonia accumulated in the SCR catalyst can be used to neutralize additional nitrogen oxides (NOx), which can break through the NOx storage catalyst (LNT) during operation with the lean air-fuel mixture (ie, in the “depletion operation” mode ").

In addition, the use of an SCR catalyst provides additional advantages, such as, for example, the possibility of accumulation of hydrogen sulfide (N ₂ S) and the ability to neutralize the latter at the stages of the so-called desulfurization (desulfurization) of the NOx storage catalyst (LNT), in which the NOx storage catalyst (LNT) is exposed to high temperatures during enrichment operation to remove sulfur from the NOx storage catalyst (LNT), which is deposited at the NOx storage sites in the storage catalyst (LNT).

Utility Model Disclosure

The objective of this utility model is to create a device for reducing emissions of a diesel engine, which will make it possible to achieve a more effective reduction in emissions, and the implementation of more stringent emission standards.

The solution to the problem is provided by the distinguishing features set forth in independent paragraph 1 of the attached formula.

According to a utility model, a diesel engine emission reduction device comprises:

a low pressure exhaust gas recirculation system that comprises an exhaust gas recirculation loop,

at least one NOx storage catalyst for accumulating nitrogen oxides from the exhaust gas supplied from the diesel engine, and

at least one SCR catalyst installed downstream of the NOx storage catalyst for selective catalytic reduction of nitrogen oxides in the exhaust gas supplied to the SCR catalyst.

The utility model is based, in particular, on the idea of using a low pressure EGR system with an exhaust gas recirculation circuit in combination with an exhaust gas treatment device that contains an NOx storage catalyst (LNT) and a passive SCR catalyst. By combining NOx neutralization on the engine side by means of a low pressure exhaust gas recirculation system, on the one hand, and NOx neutralization, which is realized by treating the exhaust gas by the NOx storage catalyst and the SCR catalyst, on the other hand, a more efficient emission reduction can be achieved. while optimizing cost aspects, fuel consumption and structural space. In this case, in particular, it also becomes possible to introduce the device into comparatively small vehicles or internal combustion engines. Moreover, in comparison with the use of active SCR systems, it is also possible to avoid the structural space requirements typical of SCR systems and the costs associated with providing additional tanks with liquid (for example, urea).

As will be shown in more detail below, the NOx storage catalyst (LNT) and the SCR catalyst can be placed in the exhaust system in many different ways. According to embodiments of the utility model, the NOx storage catalyst or LNT porous oxide coating included in the NOx storage catalyst can be provided on a standard catalyst support inside the low pressure exhaust gas recirculation loop or outside the exhaust gas recirculation loop. In addition, the NOx storage catalyst or LNT porous oxide coating included in the NOx storage catalyst can be provided inside the exhaust gas recirculation loop even on the diesel particulate filter itself.

According to one embodiment of the utility model, an NOx storage catalyst may be placed within the circuit of the exhaust gas recirculation system structurally near the engine (“direct connection” to the engine). According to another embodiment, the NOx storage catalyst may also be located downstream of the exhaust gas recirculation loop, in combination with a passive SCR catalyst.

Placing the NOx storage catalyst inside the exhaust gas recirculation loop near the engine may be preferable depending on the actual use of the car or driving cycle in terms of the temperature profile to initiate recovery in the NOx storage catalyst, and also to achieve a temperature window that is optimal for working with rich air -fuel mixture. Placing the NOx storage catalyst outside the exhaust gas recirculation loop may be preferable depending on the actual application of the car or driving cycle, since the NOx storage catalyst is then placed in a different temperature window, as well as a different exhaust gas flow rate (which partially passes through the recirculation loop), which are characterized by lower values, which thus sometimes, in turn, leads to more favorable conditions for neutralizing the hour eggs, present in the exhaust gas (in this case also no recycling of NH ₃ or H ₂ S from the storage NOx catalyst in an internal combustion engine).

According to one embodiment of the utility model, a passive SCR catalyst porous oxide coating (“pSCR coating”) can be placed inside the exhaust gas recirculation loop on a diesel particulate filter. This may be preferable since treatment designed to neutralize NH ₃ and H ₂ S can occur before the exhaust gas reaches the recirculation loop, and thus the negative effect of NH ₃ and H ₂ S on the respective components can be avoided.

According to one embodiment, it is envisaged to place the diesel oxidation catalyst (DOC) on the diesel particulate filter matrix (also called the Single Block Carrier System, SBS - Single Brick System) structurally near the engine in the exhaust gas recirculation loop, while outside the loop The exhaust gas recirculation houses a combination of an NOx storage catalyst (LNT) and a passive SCR catalyst. Such a scheme may be preferable, since the NOx storage catalyst (LNT) and the passive SCR catalyst are then only responsible for reducing NOx emissions (this is preferable both from the point of view of depletion of HC / CO content in the environment of the NOx storage catalyst and from the point of view of increasing accumulation of NOx in the catalyst).

According to one embodiment, the first NOx storage catalyst may also be structurally located in the vicinity of the engine in the exhaust gas recirculation loop, and outside of the exhaust gas recirculation loop, a combination of an additional NOx storage catalyst and a passive SCR catalyst may be placed. Such a scheme may be preferable since the placement of NOx storage catalysts in two different temperature windows and regions with different exhaust gas flow rates is favorable for the accumulation of NOx, and in particular with regard to nitrogen oxides, which due to adverse temperature and gas flow conditions pass through the NOx storage catalyst (LNT), absorption, accumulation and neutralization can still occur in the second NOx storage catalyst (LNT) and / or in the passive SCR Ator (which are sometimes placed in a more favorable temperature window and window flow rates).

Further refinements regarding the utility model can be found in the description of the dependent claims.

Brief Description of the Drawings

Embodiments of the present utility model will be described in more detail below with reference to the accompanying drawings, in which:

1 is a diagram illustrating a possible arrangement of components for reducing emissions of a diesel engine according to a first embodiment of the utility model.

Figure 2-8 depict schemes of other embodiments of the utility model.

Utility Model Implementation

The utility model includes, in particular, a combination of a low pressure EGR (LP-EGR) system with an exhaust gas treatment device that comprises an NOx storage catalyst (LNT) and a passive SCR catalyst, as shown in FIGS. 1-8. In this case, in FIGS. 2-8, similar and substantially functionally identical components have reference numbers increased by 10 compared to each previous figure.

1 and 2, an NOx storage catalyst 12, 22 or a porous oxide LNT coating (for example, on a standard catalyst support) can be located in the exhaust gas recirculation loop 14, 24 (“LP-EGR loop”).

The scheme selected in FIG. 1 with the location of the NOx storage catalyst near the engine inside the exhaust gas recirculation loop may be preferable depending on the actual application of the engine or driving cycle, taking into account the temperature profile for initiating recovery in the NOx storage catalyst, and also to achieve a temperature window, which is optimal for working with a rich air-fuel mixture. At the same time, the SCR catalyst (located in a different temperature window) allows the passive neutralization of NOx, in particular, even when the efficiency of the storage NOx catalyst decreases, for example, due to the fact that the operating temperatures are too high.

In this case, in particular, as shown in FIGS. 2-8, the NOx storage catalyst and the SCR catalyst can be made as a single device 29, 39, 49, 59, 69, 79, 89, which is located entirely inside or in full outside circuit 24, 34, 44, 54, 64, 74 or 84 of the exhaust gas recirculation.

In particular, according to FIG. 1, a porous oxide NOx or LNT storage catalyst 12 can be placed inside the exhaust gas recirculation circuit 14, even on the diesel particulate filter 15. In addition, according to FIG. 2, a passive SCR catalyst or SCR -coating from porous oxide can be applied, for example, in the form of a coating of a particulate filter matrix (in figure 2 such a device is indicated by index 23). 2, a schematic diagram of a passive SCR catalyst structurally placed adjacent to the engine on a particulate filter matrix may be preferred since treatment involving NH ₃ and N ₂ S may occur before the exhaust gas reaches the exhaust gas recirculation loop 24 gases, thus eliminating the negative effect of NH ₃ and H ₂ S on the corresponding components.

In subsequent embodiments, as shown in FIGS. 3-8, at least one of the devices — an NOx storage catalyst or LNT porous oxide coating — can also be located outside the exhaust gas recirculation loop.

3, in the exhaust gas recirculation loop 34, in front of the diesel particulate filter 35 or the particulate filter matrix, which is designed to be placed near the engine (“direct connection” to the engine), a diesel oxidizing catalyst 36, DOC (Diesel Oxidation Catalyst) is provided while a combination of 32 NOx storage catalyst 32 (LNT) and passive SCR catalyst 33 (block 39) is located outside the exhaust gas recirculation loop. This arrangement may be preferable because the proximity to the engine of the oxidizing catalyst 36 (DOC) and the diesel particulate filter 35 or the particulate filter matrix allows the exhaust gas to be treated with HC / CO such that the 32 NOx storage catalyst (LNT) and the passive SCR catalyst 33 were then only responsible for suppressing NOx emissions (this is preferable both from the point of view of depletion of HC / CO content in the environment of the NOx storage catalyst 32 and from the point of view of increasing the NOx accumulation in the catalyst 32).

According to FIG. 4, an NOx storage catalyst 42a (LNT) 42c may be placed in the exhaust gas recirculation loop, the structure of which is designed to be placed near the engine (“direct connection” to the engine), together with the diesel particulate filter 45, while outside The exhaust gas recirculation loop 44 is a combination of an optional NOx storage catalyst 42b (LNT) and a passive SCR catalyst 43 (block 49). This scheme may be preferable, since the placement of NOx storage catalysts 42a, 42b (LNT) in two different temperature windows and in areas with different flow rates favorably affects the absorption of NOx. In this case, in particular, with respect to nitrogen oxides, which, due to adverse temperature and gas flow conditions, pass through the NOx storage catalyst 42a (LNT), absorption, accumulation and neutralization can still occur in the second 42x NOx storage catalyst (LNT) ) and / or in a passive SCR catalyst 43 (which are sometimes located in a more favorable temperature window and a window of flow rates).

In addition, as in the case of the variants shown in FIGS. 5-8, both the NOx storage catalyst (LNT) and the passive SCR catalyst can be combined or arranged as units 59, 69, 79 or 89 outside circuit 54, 64 74 or 84 exhaust gas recirculation. Figure 5 shows a system containing one SBS carrier unit (Single Brick System), which corresponds to a diesel oxidation converter on a particulate filter matrix, the design of which is designed to be located near the engine, and which is located in the exhaust gas recirculation circuit 54, as well as the block 59 comprising an NOx storage catalyst and a passive SCR catalyst outside the exhaust gas recirculation loop 54. This scheme in the first place has advantages comparable with the advantages of the scheme shown in figure 3, but in this case, additional savings in structural space.

According to Fig.6-8, in the circuit 64, 74 and 84 exhaust gas recirculation provides a LNT coating of porous oxide on a diesel particulate filter matrix (which in Fig.6-8 indicated by the indices 68, 78 and 88).

The circuit shown in Fig.6, in the first place, has the advantages described in relation to the schemes of Fig.3 and Fig.5; in addition, the diesel particulate filter matrix functions as an NOx storage catalyst for HC / CO, and NOx control on the particulate filter matrix. According to FIG. 7, in a circuit similar to that of FIG. 6, an additional NOx storage catalyst 72 (LNT) is located in front of block 78 or in front of the NOx storage catalyst therein, which as a result helps to more effectively perform the NOx neutralization function. In the circuit of FIG. 8, similarly to FIG. 7, the NOx storage catalyst (LNT), which is present in block 88 on the diesel particulate filter matrix, eliminates the task of neutralizing HC / CO and improves the NO ₂ formation efficiency for the storage catalyst NOx (LNT), which is located in block 88 on the diesel particulate filter matrix.

Claims (8)

1. A device for reducing emissions of a diesel engine containing a low pressure exhaust gas recirculation system, which comprises an exhaust gas recirculation loop (14, 24, 34, 44, 54, 64, 74, 84), at least one storage catalyst (12, 22, 32, 42a, 42b, 72) NОх for accumulating nitrogen oxides from the exhaust gas supplied from the diesel engine (11, 21, 31, 41, 51, 61, 71, 81), and at least one SCR catalyst ( 13, 23, 33, 43) installed after the NOx storage catalyst for selective catalytic reduction of nitrogen oxides in trabotavshem gas supplied to the SCR-catalyst. 2. The device according to claim 1, characterized in that the NOx storage catalyst and the SCR catalyst are made in the form of a single device (29, 39, 49, 59, 69, 79, 89), which is located either entirely inside or outside the loop (24 , 34, 44, 54, 64, 74, 84) exhaust gas recirculation. 3. The device according to claim 1 or 2, characterized in that the storage catalyst (12, 22, 42a) NOx is structurally located near the engine, in the exhaust gas recirculation circuit (14, 24, 44). 4. The device according to claim 3, characterized in that the storage catalyst (12, 42a) NOx is placed on a diesel particulate filter (15, 45). 5. The device according to claim 1 or 2, characterized in that the SCR catalyst (23) is structurally located near the engine, inside the exhaust gas recirculation loop (24). 6. The device according to claim 5, characterized in that the SCR catalyst (23) is placed on a diesel particulate filter. 7. The device according to claim 1 or 2, characterized in that the storage catalyst (32, 42b) NOx is located outside the circuit (34, 42) for exhaust gas recirculation. 8. The device according to claim 1 or 2, characterized in that it further comprises a diesel oxidizing catalyst (86).