Equipment for exhaust aftertreatment

Abstract

The present invention relates to an exhaust aftertreatment device for an internal combustion engine (1), having an exhaust pipe configured to deliver exhaust gas blown from the internal combustion engine (1) to at least one component for exhaust aftertreatment, wherein at least an adsorber (3) for temporarily storing hydrocarbons contained in the exhaust gas, a catalytic converter (5) for catalytic aftertreatment of the exhaust gas, an electrically heated catalytic converter (4), and a cracking catalytic converter (2) for cracking long-chain hydrocarbons into short-chain hydrocarbons are arranged in the exhaust pipe.

Description

Technical Field

[0001] The present invention relates to an exhaust aftertreatment apparatus for an internal combustion engine, comprising an exhaust pipe configured to: deliver exhaust gas blown from the internal combustion engine to at least one component for exhaust aftertreatment, wherein at least an adsorber for temporarily storing hydrocarbons contained in the exhaust gas, a catalytic converter for catalytic aftertreatment of the exhaust gas, an electrically heated catalytic converter, and a cracking catalytic converter for cracking long-chain hydrocarbons into short-chain hydrocarbons are arranged in the exhaust pipe. Background Technology

[0002] To achieve exhaust aftertreatment for internal combustion engines, so-called hydrocarbon adsorbers (HC adsorbers) are used in exhaust systems. These adsorbers are used to temporarily store hydrocarbons at low exhaust temperatures, such as during the cold start phase, thereby preventing hydrocarbons from escaping into the environment. Hydrocarbons—especially unburned residues of fuel—typically undergo chemical reactions in exhaust systems within catalytic converters designed for this purpose, producing environmentally harmless byproducts. These catalytic converters operate reliably only from a certain minimum temperature, the so-called ignition temperature.

[0003] To prevent hydrocarbons in exhaust gas from being released uncontrollably into the environment from the exhaust system, the purpose is to temporarily store hydrocarbons until they reach the ignition temperature, so that the hydrocarbons can then react on a suitable catalytic converter.

[0004] The hydrocarbons contained in the exhaust gas are both short-chain and long-chain hydrocarbons. Short-chain hydrocarbons are weakly adsorbed by known hydrocarbon adsorbers and are therefore desorbed at lower temperatures. Long-chain hydrocarbons, on the other hand, are more strongly bound and are desorbed only at higher temperatures. Furthermore, the adsorber may not be completely emptied depending on the chain length of the hydrocarbons and the chemical composition of the adsorber's reservoir. This results in a higher hydrocarbon concentration downstream of the adsorber at the next engine start compared to upstream of the adsorber.

[0005] This results in the following: as the temperature of the loaded adsorber gradually increases, short-chain hydrocarbons are desorbed first, followed by long-chain hydrocarbons as the temperature continues to rise. This can lead to a preferential retention of long-chain hydrocarbons in the adsorber, which is unfavorable because long-chain hydrocarbons tend to aggregate and coke within the pores of the adsorber. This causes a decrease in the storage capacity of the HC adsorber over its service life. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide an apparatus for exhaust gas aftertreatment that enables the cracking of long-chain hydrocarbons, thereby improving adsorption and desorption on hydrocarbon adsorbers.

[0007] The objective in terms of the device is achieved by the device having the features of claim 1.

[0008] One embodiment of the present invention relates to an exhaust aftertreatment apparatus for an internal combustion engine, having an exhaust pipe configured to deliver exhaust gas blown from the internal combustion engine to at least one component for exhaust aftertreatment, wherein at least an adsorber for temporarily storing hydrocarbons contained in the exhaust gas, a catalytic converter for catalytic aftertreatment of the exhaust gas, an electrically heated catalytic converter, and a cracking catalytic converter for cracking long-chain hydrocarbons into short-chain hydrocarbons are arranged in the exhaust pipe.

[0009] Catalytic cracking converters are essentially used to crack long-chain hydrocarbons contained in exhaust gas, for example, as unburned fuel residues. Hydrocarbons, or hydrocarbon molecules, are chains of carbon atoms of varying lengths, in which the carbon atoms are linked to each other and the individual free chemical bonds of the carbon atoms are occupied by hydrogen atoms or other molecular clusters.

[0010] The longer the hydrocarbon chain, the more difficult it is for the adsorber to adsorb. Furthermore, higher temperatures are required in the adsorber to desorb long-chain hydrocarbons. Short-chain hydrocarbons are adsorbed more quickly and desorbed again at lower temperature levels. This makes the adsorber more effective overall because it operates more quickly after engine startup, such as after a cold start, and simultaneously reduces the risk of long-chain hydrocarbons remaining in the adsorber and clogging it.

[0011] Especially when the internal combustion engine runs for a short period, the temperature level on the adsorber may not reach a sufficiently high level, causing all the adsorbed hydrocarbons to desorb. In this case, some hydrocarbons remain in the adsorber. When the internal combustion engine is restarted, the concentration of hydrocarbons downstream of the adsorber along the flow direction may be higher than that upstream of the adsorber. This is because newly added hydrocarbons and hydrocarbons already present in the adsorber, which additionally flow into the exhaust pipe when the desorption temperature is reached, are located downstream of the adsorber.

[0012] The cracking catalytic converter is located upstream of the adsorber in the direction of exhaust flow. Preferably, the cracking catalytic converter is the first component that the exhaust flows through, so that cracking occurs as early as possible.

[0013] Of particular advantage is that the reaction surfaces of the cracking catalytic converter are coated with active aluminosilicate. Aluminosilicate, or so-called zeolite, is particularly suitable for cracking hydrocarbons in reactions occurring on the reaction surfaces of the catalytic converter. Here, these reaction surfaces are the surfaces through which exhaust gas overflows. If the cracking catalytic converter is formed, for example, by a flow-through honeycomb structure, the walls defining the flow channels form the reaction surfaces.

[0014] Aluminum silicate, for example, is chromium oxide (Cr2O3). Other aluminum silicates may also be used advantageously.

[0015] Another advantage is that the exhaust pipe has a bypass channel, which branches off downstream of the electrically heated catalytic converter and includes a cracking catalytic converter, cooling elements, and an adsorber, while opening into the exhaust pipe upstream of the electrically heated catalytic converter. This bypass allows exhaust gas to recirculate through the cracking catalytic converter and the remaining exhaust aftertreatment components arranged in the bypass channel, thereby improving exhaust purification. Furthermore, it allows other uncracked long-chain hydrocarbons to be cracked in the cracking catalytic converter. By branching off the bypass channel directly downstream of the electrically heated catalytic converter, sufficiently high temperature levels can be reached in the bypass channel as early as possible, thereby enabling carbon monoxide to react very early, particularly in the cracking catalytic converter.

[0016] Devices, such as valves / hinges or valves, can be installed to control the exhaust flow, thereby distributing the exhaust flow between the main channel and the bypass channel.

[0017] A preferred embodiment is characterized in that the cracking catalytic converter is configured to crack long-chain hydrocarbons in the exhaust gas having a corresponding number of 8 to 12 carbon atoms into hydrocarbons having a maximum of 7 carbon atoms. The reduction in the average length of the hydrocarbons contributes to improved adsorption and thus improved temporary storage. Furthermore, the risk of adsorber coking is significantly reduced due to the presence of particularly short-chain hydrocarbons having seven or fewer carbon atoms arranged together, as these short-chain hydrocarbons are already desorbed again at lower temperatures.

[0018] Also preferably, the desorption temperature of the adsorber is in the range of 150°C to 200°C. A desorption temperature in the range of 150°C to 200°C is advantageous because this temperature range is reached more quickly and therefore desorption can be carried out more rapidly.

[0019] The desorption of uncracked long-chain hydrocarbons, especially those with seven or more carbon atoms linked together, typically occurs at high temperatures, such as up to 400 degrees Celsius. Reaching such high temperatures requires significantly more time. Furthermore, under certain operating conditions, these temperatures may not be reached at all, and therefore complete desorption may not occur.

[0020] The cracked hydrocarbons are thus released from the adsorber earlier, and the adsorber is completely unloaded more quickly. This effectively prevents charring of the adsorber and thus improves the durability of the system.

[0021] Furthermore, it is advantageous that the ignition temperature at which the hydrocarbons begin to crack is 100 degrees Celsius. Preferably, this temperature is as low as possible to allow the hydrocarbons to crack as early as possible.

[0022] Furthermore, it is advantageous to have a cooling element in the exhaust pipe downstream of the cracking catalytic converter, which cools the exhaust gas flowing out of the cracking catalytic converter. Heat is generated through the cracking or breaking of carbon chains. This heat is also output to the exhaust pipe. To avoid affecting adsorption and desorption on the adsorber, active cooling can be implemented to compensate for the additional heat input caused by the chemical reaction of carbon chain cracking.

[0023] Another advantage is that the cracking catalytic converter is designed as a tubular reactor, through which a coolant can flow. Tubular reactors offer the particular advantage of allowing active cooling in addition to the actual chemical reaction, by allowing a cooling medium to flow through the circumference of the reactor or through the gaps between flowable channels. This enables a particularly compact structural form with a functional combination.

[0024] Advantageous improvements of the invention are described in the dependent claims and the following description of the drawings. Attached Figure Description

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. In the drawings:

[0026] Figure 1 This is a schematic diagram of the exhaust system of an internal combustion engine, showing the different components used for exhaust aftertreatment.

[0027] Figure 2 This illustrates an alternative design for the exhaust system.

[0028] Figure 3 This illustrates an alternative design for the exhaust system. Detailed Implementation

[0029] Figure 1A possible design for the exhaust system is shown. The internal combustion engine is indicated by reference numeral 1, from which exhaust gas flows through the exhaust manifold and into the tubular exhaust pipe from each cylinder. The first component for exhaust aftertreatment is a cracking catalytic converter 2, suitable for breaking down / fragmenting long-chain hydrocarbons. In the flow direction, an adsorber 3 for adsorbing hydrocarbons present in the exhaust gas is located downstream of the cracking catalytic converter 2. Figure 1 In this embodiment, an electrically heated catalytic converter 4 and a three-way catalytic converter 5 follow, and they can be arranged in any order. Then, after flowing through the various components for exhaust aftertreatment, the exhaust gas flows into the environment through the exhaust valve.

[0030] Figure 2 Different arrangements of components used for exhaust aftertreatment are shown. Due to the use of... Figure 1 The components in the figures are the same, so the same components are represented by the same reference numerals.

[0031] Downstream of the internal combustion engine 1, an electrically heated catalytic converter 4 and / or a three-way catalytic converter 5 are arranged. Following this, a cracking catalytic converter 2 and an adsorber 3 are arranged. Downstream of the adsorber 3, an electrically heated catalytic converter 4 and / or a three-way catalytic converter 5 may also be arranged.

[0032] Figure 3 Another alternative arrangement is shown, in which the exhaust pipe has a main channel in which an electrically heated catalytic converter 4 and a three-way catalytic converter 5 are arranged. A bypass channel is also shown, in which a cracking catalytic converter 2, a cooler 6, and an adsorber 3, such as an HC adsorber, are arranged. The bypass channel branches downstream of the electrically heated catalytic converter 4 and rejoins the main channel upstream of the electrically heated catalytic converter 4. The adsorber 3 and the cracking catalytic converter 2 form additional heat capacity. Because the carbon monoxide on the cracking catalytic converter 2 should be reacted / converted as early and completely as possible, the bypass channel branches downstream of the electrically heated catalytic converter 4.

[0033] The adsorber is used to store as many hydrocarbons as possible during the cold start phase. To do this, the temperature in the adsorber should be kept low so that desorption does not occur too quickly. Therefore, the adsorber is strategically positioned further downstream. After the cold start phase, because the exhaust temperature is already very high, the adsorber, cracking catalytic converter, and cooler no longer function (they only become additional, undesirable heat capacity for CO and HC). In this case, only the main (gas) flow continues.

[0034] Different features of the various embodiments can also be combined with each other.

[0035] Figures 1 to 3 The embodiments described are, in particular, non-limiting and are used to illustrate the ideas of the invention.

[0036] List of reference numerals in the attached diagram:

[0037] 01 Internal Combustion Engine

[0038] 02 Cracking Catalytic Converter

[0039] 03 Adsorber

[0040] 04 Electrically heated catalytic converter

[0041] 05 Three-way catalytic converter

[0042] 06 Cooling Components

Claims

1. An apparatus for exhaust aftertreatment of an internal combustion engine (1), comprising an exhaust conduit configured to deliver exhaust gas discharged from the internal combustion engine (1) to at least one component for exhaust aftertreatment, wherein, The exhaust pipeline is equipped with at least an adsorber (3) for temporary storage of hydrocarbons contained in the exhaust, a catalytic converter (5) for catalytic aftertreatment of the exhaust, an electrically heated catalytic converter (4), and a cracking catalytic converter (2) for cracking long-chain hydrocarbons into short-chain hydrocarbons. Among them, the cracking catalytic converter (2) is located upstream of the adsorber (3) in the direction of exhaust flow, and The exhaust pipe has a bypass passage that branches off from the exhaust pipe downstream of the electrically heated catalytic converter (4) and has a cracking catalytic converter (2), a cooling element (6) and an adsorber (3), and enters the exhaust pipe upstream of the electrically heated catalytic converter (4).

2. The device according to claim 1, characterized in that, The reaction surface of the cracking catalytic converter (2) is coated with active aluminum silicate.

3. The device according to claim 1 or 2, characterized in that, The cracking catalytic converter (2) is configured to: crack long-chain hydrocarbons in the exhaust gas having a corresponding 8 to 12 carbon atoms into hydrocarbons having a maximum of 7 carbon atoms.

4. The device according to claim 1 or 2, characterized in that, The desorption temperature of the adsorber (3) is in the range of 150 degrees Celsius to 200 degrees Celsius.

5. The device according to claim 1 or 2, characterized in that, The ignition temperature at which hydrocarbons in the cracking catalytic converter (2) begin to crack is 100 degrees Celsius.

6. The device according to claim 1 or 2, characterized in that, The exhaust pipe downstream of the cracking catalytic converter (2) has a cooling element (6) that can cool the exhaust gas flowing out of the cracking catalytic converter (2).

7. The device according to claim 1 or 2, characterized in that, The cracking catalytic converter (2) is designed as a tubular reactor through which a coolant can flow.

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