Scribbling device

Abstract

The application provides an SCR aftertreatment device and method for reducing instantaneous ammonia leakage, wherein the SCR aftertreatment device comprises an exhaust gas passage, a treatment gas passage, a first SCR conversion chamber, a second SCR conversion chamber and a urea nozzle; the gas inlet of the first SCR conversion chamber is communicated with the exhaust gas passage, the gas outlet of the first SCR conversion chamber is communicated with the treatment gas passage in an electrically controllable and stoppable manner, the gas inlet of the second SCR conversion chamber is communicated with the gas outlet side of the first SCR conversion chamber in an electrically controllable and stoppable manner, the gas outlet of the second SCR conversion chamber is communicated with the treatment gas passage in an electrically controllable and stoppable manner; and the urea nozzle is arranged at the gas inlet of the first SCR conversion chamber. The ammonia gas escaped in the temperature jump instant can be used again, and ammonia gas over discharge is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of diesel engine exhaust aftertreatment technology, and particularly relates to an SCR aftertreatment device and method for reducing instantaneous ammonia leakage. BACKGROUND

[0002] The diesel engine has the characteristics of large power and good economic performance, and is widely used in the field of engineering machinery, but the problems caused by its high emission also need to be paid attention to. The SCR technology is one of the technical routes of engine aftertreatment, which refers to a method of spraying ammonia or urea as a reducing agent into the exhaust gas under the action of a catalyst, so as to reduce NOx in the exhaust gas into N2 and H2O. The SCR has the advantages of reducing fuel consumption and emission, without the need to make too many changes to the engine structure, and the SCR aftertreatment device is less sensitive to the sulfur content in the fuel, so it is the most reliable device among all aftertreatment systems. X

[0003] The catalyst of the SCR has a certain storage capacity for ammonia, and the storage capacity decreases with the increase of the catalyst temperature. The desorbed ammonia cannot react with NOx, and leaks into the atmosphere. Ammonia has a pungent odor, and its leakage into the atmosphere will pollute the environment and harm human health, and can easily cause the emission of diesel engines to exceed the standard (the existing standard stipulates that the average value of ammonia emission shall not exceed 25 ppm).

[0004] In the SCR technology, if the urea injection amount is too small, NOx is not completely reacted, resulting in NOx over-emission; if the urea injection amount is too large, ammonia over-emission occurs. Therefore, the research on SCR aftertreatment mainly focuses on the establishment of various feedback models for adjusting the urea injection. In order to reduce the leakage of ammonia due to the saturation of the catalyst and the escape of ammonia caused by the increase of temperature, the existing technology reduces the urea injection amount when the temperature is detected to be increased. This method can alleviate the subsequent ammonia escape to a certain extent, but it cannot reduce the amount of ammonia escaped in the temperature jump moment. When the catalyst adsorbs ammonia to saturation at low temperature, the load suddenly increases, the exhaust temperature rises rapidly, the amount of ammonia that can be stored by the catalyst decreases, ammonia escapes, and the desorbed ammonia cannot be consumed by reacting with NOx, resulting in the engine monitoring excessive NOx and judging that the SCR aftertreatment device fails, which causes the engine to have limited torque and other conditions. X X X

[0005] Therefore, it is urgent to treat the ammonia escaped in the temperature jump moment of the SCR aftertreatment device to prevent the emission average value from exceeding the standard caused by the instantaneous emission fluctuation. SUMMARY

[0006] (1) Technical problem to be solved ​​​​

[0007] In view of the problems in the prior art, the present application at least solves the problems to some extent. To this end, a first object of the present application is to provide an SCR aftertreatment device for reducing instantaneous ammonia leakage, which can reuse ammonia gas escaping in the temperature jump moment, and avoid ammonia gas over discharge.

[0008] A second object of the present application is to provide an SCR aftertreatment method based on the above-mentioned SCR aftertreatment device for reducing instantaneous ammonia leakage.

[0009] (II) Technical solutions

[0010] To achieve the above objects, the main technical solutions adopted by the present application include:

[0011] In a first aspect, the present application provides an SCR aftertreatment device for reducing instantaneous ammonia leakage, comprising an exhaust gas passage, a treated gas passage, a first SCR conversion chamber, a second SCR conversion chamber and a urea nozzle; the gas inlet of the first SCR conversion chamber is in communication with the exhaust gas passage, the gas outlet of the first SCR conversion chamber is in electrically controllable communication with the treated gas passage, the gas inlet of the second SCR conversion chamber is in electrically controllable communication with the gas outlet side of the first SCR conversion chamber, and the gas outlet of the second SCR conversion chamber is in electrically controllable communication with the treated gas passage; the urea nozzle is arranged at the gas inlet of the first SCR conversion chamber.

[0012] Optionally, the first SCR conversion chamber and the second SCR conversion chamber are arranged in sequence along the left-right direction, the first SCR conversion chamber has a first left end wall, a first right end wall and a first side wall for connecting the first left end wall and the first right end wall, and the second SCR conversion chamber has a second left end wall, a second right end wall and a second side wall for connecting the second left end wall and the second right end wall; the first left end wall is provided with a first gas inlet in communication with the exhaust gas passage, the first right end wall is provided with a first gas outlet in communication with the treated gas passage, the first right end wall has a common wall serving as the second left end wall, the common wall is provided with a through hole for electrically controllable opening and closing as a second gas inlet for the communication between the second SCR conversion chamber and the gas outlet side of the first SCR conversion chamber, the second side wall is provided with a second gas outlet in communication with the treated gas passage at a portion close to the first gas outlet, and the common wall has an end portion serving as the edge of the first gas outlet and the second gas outlet, and the end portion of the common wall is rotatably provided with a closable plate capable of being electrically controlled to rotate; the closable plate can rotate between a first position and a second position, when the closable plate rotates to the first position, the closable plate closes the first gas outlet and the second gas outlet is in communication with the treated gas passage, and when the closable plate rotates to the second position, the closable plate closes the second gas outlet and the first gas outlet is in communication with the treated gas passage.

[0013] Optionally, a plurality of through holes are provided on the common wall, and each through hole is covered with a cover plate for controlling the opening and closing of the through hole.

[0014] Optionally, the closing plate is rotatably connected to the end of the common wall by an electric hinge.

[0015] In a second aspect, the present application provides an SCR aftertreatment method for reducing instantaneous ammonia leakage, which is realized based on the above-mentioned SCR aftertreatment device for reducing instantaneous ammonia leakage and comprises the following steps:

[0016] S1. During the operation of the engine, the exhaust gas temperature T and the urea injection amount P of the urea injector are collected in real time, and the accelerator opening rate O and the exhaust gas temperature change rate AT are monitored in real time.

[0017] S2. According to the exhaust gas temperature T and the pre-acquired relationship between the urea injection amount and the catalyst temperature, the urea injection amount P required for the catalyst in the first SCR conversion chamber to be saturated with ammonia at the T temperature is acquired. e According to the pre-acquired exhaust gas temperature threshold T max , the pre-set accelerator opening rate threshold O set , and the pre-set exhaust gas temperature change rate threshold AT set , it is judged whether the current time satisfies O>O set , AT>AT set , T max , and P>P e .

[0018] S3. If yes, the outlet of the first SCR conversion chamber is controlled to be cut off from the treatment gas passage, the inlet of the second SCR conversion chamber is controlled to be communicated with the outlet side of the first SCR conversion chamber, and the outlet of the second SCR conversion chamber is controlled to be communicated with the treatment gas passage.

[0019] S4. When it is detected that the exhaust gas temperature T is higher than the exhaust gas temperature threshold T max , the outlet of the first SCR conversion chamber is controlled to be communicated with the treatment gas passage, the inlet of the second SCR conversion chamber is controlled to be cut off from the outlet side of the first SCR conversion chamber, and the outlet of the second SCR conversion chamber is controlled to be cut off from the treatment gas passage.

[0020] When the exhaust gas temperature T is higher than the exhaust gas temperature threshold T max , the ammonia saturated and escaped from the catalyst in the SCR aftertreatment device is lower than the pre-set threshold.

[0021] Optionally, before S1, it further comprises the following steps: at different catalyst temperatures, urea is injected into the first SCR conversion chamber, the ammonia content at the outlet of the first SCR conversion chamber is detected, and the urea injection amount at which the ammonia in the first SCR conversion chamber is saturated at each catalyst temperature is acquired; and according to the urea injection amount at which the ammonia in the first SCR conversion chamber is saturated at each catalyst temperature, the relationship between the urea injection amount and the catalyst temperature is fitted.

[0022] Optionally, the throttle opening rate threshold O set is 60%-80%, the exhaust gas temperature rate threshold ΔT set is 1.8%-2.2%, the exhaust gas temperature threshold T max is 310-330℃.

[0023] Optionally, in S3, the through hole on the common wall is controlled to be opened to realize the communication of the gas inlet of the second SCR conversion chamber with the gas outlet side of the first SCR conversion chamber; the closing plate is controlled to rotate from the second position to the first position to realize the communication of the gas outlet of the first SCR conversion chamber with the treatment gas passage and the communication of the gas outlet of the second SCR conversion chamber with the treatment gas passage.

[0024] Optionally, in S4, the gas outlet of the second SCR conversion chamber is first controlled to be cut off from the treatment gas passage, the gas outlet of the first SCR conversion chamber is controlled to be communicated with the treatment gas passage, and then the gas inlet of the second SCR conversion chamber is controlled to be cut off from the gas outlet side of the first SCR conversion chamber after a preset time.

[0025] Optionally, in S4, the gas outlet of the second SCR conversion chamber is first controlled to be cut off from the treatment gas passage, the gas outlet of the first SCR conversion chamber is controlled to be communicated with the treatment gas passage, and then the gas inlet of the second SCR conversion chamber is controlled to be cut off from the gas outlet side of the first SCR conversion chamber at a set rate.

[0026] (III) Beneficial effects

[0027] The beneficial effects of the present application are:

[0028] The SCR aftertreatment device for reducing instantaneous ammonia leakage provided by the present application is characterized in that, under normal conditions, the gas inlet of the first SCR conversion chamber is communicated with the exhaust gas passage, the gas outlet of the first SCR conversion chamber is communicated with the treatment gas passage, the gas inlet of the second SCR conversion chamber is cut off from the gas outlet side of the first SCR conversion chamber, and the gas outlet of the second SCR conversion chamber is cut off from the treatment gas passage, that is, under normal conditions, the exhaust gas is treated by the first SCR conversion chamber, and the ammonia gas adsorbed by the catalyst in the first SCR conversion chamber is supplemented by the urea sprayed by the urea nozzle. When it is detected that the temperature jump will cause the ammonia gas adsorbed by the catalyst in the first SCR conversion chamber to be saturated and escape (that is, O>O set , ΔT>ΔT set , T<T max , and P>P e), the gas inlet of the first SCR conversion chamber is communicated with the tail gas passage, the gas outlet of the electrically-controlled first SCR conversion chamber is communicated with the treatment gas passage in a cut-off mode, the gas inlet of the electrically-controlled second SCR conversion chamber is communicated with the gas outlet side of the first SCR conversion chamber, and the gas outlet of the electrically-controlled second SCR conversion chamber is communicated with the treatment gas passage, so that the tail gas flows through the first SCR conversion chamber and the second SCR conversion chamber in sequence, the urea sprayed by the urea injector replenishes the ammonia gas adsorbed by the catalyst in the first SCR conversion chamber, and the ammonia gas saturated and released by the catalyst in the first SCR conversion chamber due to temperature jump enters the second SCR conversion chamber, is adsorbed by the catalyst in the second SCR conversion chamber and is used for treating the tail gas flowing through the second SCR conversion chamber. BRIEF DESCRIPTION OF DRAWINGS

[0029] The present application is described by means of the following drawings:

[0030] Figure 1 Structure schematic view of the SCR aftertreatment device according to Embodiment 1 of the present application in a first state;

[0031] Figure 2 Structure schematic view of the SCR aftertreatment device according to Embodiment 1 of the present application in a first state;

[0032] Figure 3 Structure schematic view of the SCR aftertreatment device according to Embodiment 1 of the present application in a first state;

[0033] Figure 4 Structure schematic view of the SCR aftertreatment device according to Embodiment 1 of the present application in a first state;

[0034] Figure 5 Structure schematic view of the SCR aftertreatment device according to Embodiment 1 of the present application in a first state;

[0035] Figure 6 Relationship curve diagram of urea injection amount and catalyst temperature according to Embodiment 2 of the present application.

[0036] LEGEND OF THE DRAWINGS

[0037] 1: tail gas passage;

[0038] 2: treatment gas passage;

[0039] 3: first SCR conversion chamber; 31: first left end wall; 32: common wall; 33: first side wall; 34: first gas inlet; 35: first gas outlet; 36: through hole; 37: cover plate;

[0040] 4: second SCR conversion chamber; 41: second right end wall; 42: second side wall; 43: second gas outlet; 45: closure plate; 46: electric hinge. Detailed Implementation

[0041] To better explain and facilitate understanding of the present invention, a detailed description of the invention is provided below with reference to the accompanying drawings and specific embodiments. The directional terms such as "up," "down," "left," and "right" mentioned herein are used in conjunction with... Figure 1 The orientation is used as a reference.

[0042] Example 1

[0043] like Figures 1 to 4 As shown, this embodiment provides an SCR aftertreatment device for reducing instantaneous ammonia leakage. The SCR aftertreatment device includes an exhaust gas channel 1, a treated gas channel 2, a first SCR conversion chamber 3, a second SCR conversion chamber 4, and a urea nozzle (not shown in the figure). The inlet of the first SCR conversion chamber 3 is connected to the exhaust gas channel 1, and the outlet of the first SCR conversion chamber 3 is electrically controlled to be shut off from the treated gas channel 2. The inlet of the second SCR conversion chamber 4 is electrically controlled to be shut off from the outlet of the first SCR conversion chamber 3, and the outlet of the second SCR conversion chamber 4 is electrically controlled to be shut off from the treated gas channel 2. The urea nozzle is located at the inlet of the first SCR conversion chamber 3. Both the first SCR conversion chamber 3 and the second SCR conversion chamber 4 are coated with a catalyst to adsorb ammonia and react with NO in the exhaust gas. X The reaction will proceed.

[0044] The SCR aftertreatment device for reducing instantaneous ammonia leakage as set forth above, in normal state, the gas inlet of the first SCR conversion chamber 3 is communicated with the tail gas passage 1, the gas outlet of the first SCR conversion chamber 3 is communicated with the treated gas passage 2, the gas inlet of the second SCR conversion chamber 4 is communicated with the gas outlet side of the first SCR conversion chamber 3, and the gas outlet of the second SCR conversion chamber 4 is communicated with the treated gas passage 2, that is, in normal state, the tail gas is treated by the first SCR conversion chamber 3, and the ammonia gas adsorbed by the catalyst in the first SCR conversion chamber 3 is supplemented by the urea sprayed by the urea injector. When it is detected that the temperature jump will cause the ammonia gas adsorbed by the catalyst in the first SCR conversion chamber 3 to be saturated and to escape, the gas inlet of the first SCR conversion chamber 3 is communicated with the tail gas passage 1, the gas outlet of the first SCR conversion chamber 3 is controlled to be communicated with the treated gas passage 2, the gas inlet of the second SCR conversion chamber 4 is controlled to be communicated with the gas outlet side of the first SCR conversion chamber 3, and the gas outlet of the second SCR conversion chamber 4 is controlled to be communicated with the treated gas passage 2, so that the tail gas flows through the first SCR conversion chamber 3 and the second SCR conversion chamber 4 in turn, the ammonia gas adsorbed by the catalyst in the first SCR conversion chamber 3 is supplemented by the urea sprayed by the urea injector, the ammonia gas saturated and escaped from the catalyst in the first SCR conversion chamber 3 due to the temperature jump enters the second SCR conversion chamber 4, and the catalyst in the second SCR conversion chamber 4 adsorbs the ammonia gas and treats the tail gas flowing through the second SCR conversion chamber 4. As can be seen, the SCR aftertreatment device provided in the embodiment can make secondary use of the ammonia gas escaped instantaneously due to the temperature jump, avoid ammonia gas over-discharge, and prevent environmental pollution.

[0045] Preferably, the volume of the first SCR conversion chamber 3 is greater than the volume of the second SCR conversion chamber 4. Further preferably, the volume ratio of the first SCR conversion chamber 3 to the second SCR conversion chamber 4 is (9-11):1. In this way, while ensuring the treatment effect of the second SCR conversion chamber 4 on the saturated and escaped ammonia gas in the first SCR conversion chamber 3, the overall volume of the SCR aftertreatment device is small. As an example, the volume ratio of the first SCR conversion chamber 3 to the second SCR conversion chamber 4 is 10:1.

[0046] Preferably, the first SCR conversion chamber 3 and the second SCR conversion chamber 4 are arranged in sequence along the left-right direction, the first SCR conversion chamber 3 has a first left end wall 31, a first right end wall and a first side wall 33 connecting the first left end wall 31 and the first right end wall, and the second SCR conversion chamber 4 has a second left end wall, a second right end wall 41 and a second side wall 42 connecting the second left end wall and the second right end wall 41; the first left end wall 31 is provided with a first gas inlet 34 communicating with the exhaust gas passage 1, the first right end wall is provided with a first gas outlet 35 communicating with the treated gas passage 2, the first right end wall has a common wall 32 serving as the second left end wall, the common wall 32 is provided with a through hole 36 capable of being electrically controlled to be opened and closed, serving as a second gas inlet for the second SCR conversion chamber 4 to communicate with the first SCR conversion chamber 3 on the gas outlet side, the second side wall 42 is provided with a second gas outlet 43 communicating with the treated gas passage 2 at a portion close to the first gas outlet 35, the common wall 32 has an end portion serving as the edge of the first gas outlet 35 and the second gas outlet 43, and the end portion of the common wall 32 is rotatably provided with a closure plate 45 capable of being electrically controlled to rotate; the closure plate 45 is capable of rotating between a first position and a second position, when the closure plate 45 rotates to the first position, the closure plate 45 closes the first gas outlet 35 and the second gas outlet 43 communicates with the treated gas passage 2, and when the closure plate 45 rotates to the second position, the closure plate 45 closes the second gas outlet 43 and the first gas outlet 35 communicates with the treated gas passage 2.

[0047] The first SCR conversion chamber 3 and the second SCR conversion chamber 4 thus arranged have compact and simple structures, the through hole 36 is electrically controlled to be opened and closed to realize the cut-off or communication between the first SCR conversion chamber 3 and the second SCR conversion chamber 4, and the closure plate 45 is rotated to realize the communication between the first gas outlet 35 or the second gas outlet 43 and the treated gas passage 2.

[0048] Further, in the embodiment, the first gas inlet 34 is arranged at the lower portion of the first left end wall 31, the first gas outlet 35 is arranged at the lower portion of the first right end wall, and the second gas outlet 43 is arranged at the lower portion of the second side wall 42; the upper portion of the first side wall 33 is flush with the upper portion of the second side wall 42, the first left end wall 31 is inclined leftward along the up-down direction, and the common wall 32 and the second right end wall 41 are inclined rightward along the up-down direction. In this way, the gas is facilitated to flow in the first SCR conversion chamber 3 and the second SCR conversion chamber 4.

[0049] Preferably, the common wall 32 is provided with a plurality of through holes 36, and each through hole 36 is covered with a cover plate 37 for controlling the opening and closing of the through hole 36. Specifically, as shown in Figure 5 in the embodiment, each through hole 36 is covered with a rotating cover plate 37 for controlling the opening and closing of the through hole 36.

[0050] Preferably, as shown in Figure 6As shown, in the present embodiment, the closing plate 45 is rotatably connected to the end of the common wall 32 by an electric hinge 46. In this way, electrically controlled rotation of the closing plate 45 is achieved.

[0051] Embodiment 2

[0052] Based on the SCR aftertreatment device for reducing instantaneous ammonia leakage proposed in Embodiment 1, the present embodiment proposes an SCR aftertreatment method for reducing instantaneous ammonia leakage, comprising the following steps:

[0053] Step S1, during engine operation, the SCR aftertreatment device works in the state shown, real-time acquisition of exhaust gas temperature T and urea injection amount P of the urea injector, and real-time monitoring of throttle opening rate O and exhaust gas temperature rate ΔT. Figure 1 As shown, in the present embodiment, the closing plate 45 is rotatably connected to the end of the common wall 32 by an electric hinge 46. In this way, electrically controlled rotation of the closing plate 45 is achieved.

[0054] Step S2, according to the exhaust gas temperature T and the pre-acquired relationship between the urea injection amount and the catalyst temperature, the urea injection amount P required for the catalyst in the first SCR conversion chamber to be saturated with ammonia at T temperature is acquired e ; according to the pre-acquired exhaust gas temperature threshold T max , and the pre-set throttle opening rate threshold O set and exhaust gas temperature rate threshold ΔT set , it is judged whether the current time satisfies O>O set , ΔT>ΔT set , T<T max , and P>P e .

[0055] Specifically, at different catalyst temperatures (i.e. at different exhaust gas temperatures T), urea is slowly injected into the first SCR conversion chamber, and by detecting the ammonia content at the outlet of the first SCR conversion chamber, the urea injection amount at which the first SCR conversion chamber is saturated with ammonia at the catalyst temperature is obtained, and then according to the urea injection amount at which the first SCR conversion chamber is saturated with ammonia at different catalyst temperatures, the relationship between the urea injection amount and the catalyst temperature P(NH3·H2O)=g(T e ) is fitted.

[0056] Specifically, a cycle test is performed on the SCR aftertreatment device, and T max , when the exhaust gas temperature T is above the exhaust gas temperature threshold T max , the ammonia saturated escape amount of the catalyst in the SCR aftertreatment device is lower than the pre-set threshold. Further, the pre-set threshold is less than 10 ppm, i.e. when the exhaust gas temperature T is above the exhaust gas temperature threshold T max , even if ammonia is saturated and leaked, the leakage amount is far lower than the regulatory requirement of 25 ppm.

[0057] Specifically, the throttle opening degree reflects the engine load condition. In actual operation, increasing or decreasing the throttle opening degree can reflect the current change of the engine load, and the degree of change of the throttle opening degree (i.e., the speed of change of the throttle opening degree) can reflect the degree of change of the load, and further can reflect whether the tail gas instantaneous temperature rise situation caused by the degree of change of the load will occur. The tail gas temperature will affect the temperature of the catalyst in the SCR aftertreatment device. By monitoring the tail gas temperature, the temperature change in the SCR aftertreatment device can be understood, and the tail gas temperature change rate can directly reflect the tail gas instantaneous temperature rise situation. The tail gas temperature threshold T max Generally higher than 300°C (see Figure 6 ), when the tail gas temperature is higher than T max , the catalyst saturation ammonia gas escape amount caused by the tail gas temperature instantaneous temperature rise is very small and will not affect the average emission value. In this way, by the criteria O>O set , ΔT>ΔT set , T<T max , the moment of temperature jump can be accurately identified, and by the criterion P>P e , whether the temperature jump will cause the catalyst in the first SCR conversion bin to adsorb saturated ammonia gas and escape can be accurately predicted.

[0058] As an example, the throttle opening degree change rate threshold O set is 60%-80%, the tail gas temperature change rate threshold ΔT set is 1.8%-2.2%, and the tail gas temperature threshold T max is 310-330°C.

[0059] Step S3, if satisfied, the exhaust port of the first SCR conversion bin is controlled to be cut off from the treatment gas passage, the inlet of the second SCR conversion bin is controlled to be communicated with the exhaust side of the first SCR conversion bin, and the exhaust port of the second SCR conversion bin is controlled to be communicated with the treatment gas passage.

[0060] Specifically, the through hole on the common wall is controlled to be opened to realize the communication between the inlet of the second SCR conversion bin and the exhaust side of the first SCR conversion bin, the closing plate is controlled to be rotated from the second position to the first position to realize the cut-off communication between the exhaust port of the first SCR conversion bin and the treatment gas passage, and the exhaust port of the second SCR conversion bin is communicated with the treatment gas passage, as shown in Figure 2 and Figure 3 .

[0061] Step S4, when it is detected that the tail gas temperature T is above the tail gas temperature threshold T max , the exhaust port of the first SCR conversion bin is controlled to be communicated with the treatment gas passage, the inlet of the second SCR conversion bin is controlled to be cut off from the exhaust side of the first SCR conversion bin, and the exhaust port of the second SCR conversion bin is controlled to be cut off from the treatment gas passage.

[0062] Preferably, in step S4, the outlet of the second SCR conversion chamber is first disconnected from the treated gas channel, while the outlet of the first SCR conversion chamber is connected to the treated gas channel. After a preset time, the inlet of the second SCR conversion chamber is then disconnected from the outlet of the first SCR conversion chamber. Because the outlet of the first SCR conversion chamber is connected to the treated gas channel, the resistance to gas flow through the second SCR conversion chamber increases, and subsequent gas will flow out from the outlet of the first SCR conversion chamber and the treated gas channel. Thus, even after the outlet of the second SCR conversion chamber is disconnected from the treated gas channel, the ammonia adsorbed by the catalyst in the second SCR conversion chamber continues to react with the tail gas until the ammonia adsorbed by the catalyst is completely reacted, facilitating the catalyst in the second SCR conversion chamber to continue adsorbing ammonia from the first SCR conversion chamber.

[0063] Specifically, in step S4, the closing plate is first rotated to the second position, and after a preset time, the through hole on the common wall is closed. As an example, the preset time is the time between the maximum ammonia adsorption capacity and the maximum NO adsorption capacity of the catalyst in the second SCR conversion chamber. X The time required for a complete reaction.

[0064] Optionally, such as Figure 4 As shown, in step S4, firstly, the outlet of the second SCR conversion chamber is controlled to be disconnected from the treated gas channel, and the outlet of the first SCR conversion chamber is connected to the treated gas channel. Then, the inlet of the second SCR conversion chamber is controlled to be disconnected from the outlet of the first SCR conversion chamber at a set rate. In this way, controlling the inlet of the second SCR conversion chamber to be disconnected from the outlet of the first SCR conversion chamber at a low rate allows the ammonia adsorbed by the catalyst in the second SCR conversion chamber to continue reacting with the tail gas until the ammonia adsorbed by the catalyst is completely reacted, facilitating the subsequent adsorption of ammonia by the catalyst from the first SCR conversion chamber.

[0065] Specifically, in step S4, the closing plate is first rotated to the second position, and then the through-holes on the common wall are closed at a set rate. As an example, the time required for the through-holes on the common wall to close at the set rate is equal to the maximum ammonia adsorption capacity and NO adsorption capacity of the catalyst in the second SCR conversion chamber. X The time required for a complete reaction.

[0066] It should be understood that the above description of specific embodiments of the present invention is only for illustrating the technical approach and features of the present invention, and is intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. However, the present invention is not limited to the specific embodiments described above. All changes or modifications made within the scope of the claims of the present invention should be covered within the protection scope of the present invention.

Claims

1. An SCR aftertreatment device for reducing instantaneous ammonia leakage, characterized in that, It includes an exhaust gas passage (1), a treated gas passage (2), a first SCR conversion chamber (3), a second SCR conversion chamber (4), and a urea nozzle; The air inlet of the first SCR conversion chamber (3) is connected to the exhaust gas channel (1), and the air outlet of the first SCR conversion chamber (3) is electrically connected to the treatment gas channel (2). The air inlet of the second SCR conversion chamber (4) is electrically connected to the air outlet of the first SCR conversion chamber (3), and the air outlet of the second SCR conversion chamber (4) is electrically connected to the treatment gas channel (2). The urea nozzle is located at the air inlet of the first SCR conversion chamber (3). The first SCR conversion chamber (3) and the second SCR conversion chamber (4) are arranged in sequence along the left and right directions. The first SCR conversion chamber (3) has a first left end wall (31), a first right end wall and a first side wall (33) for connecting the first left end wall (31) and the first right end wall. The second SCR conversion chamber (4) has a second left end wall, a second right end wall (41) and a second side wall (42) for connecting the second left end wall and the second right end wall (41). The first left end wall (31) is provided with a first air inlet (34) communicating with the exhaust gas passage (1), and the first right end wall is provided with a first air outlet (35) communicating with the treatment gas passage (2). The first right end wall has a common wall (32) serving as the second left end wall. The common wall (32) is provided with an electrically controllable through hole (36) serving as a second air inlet communicating with the exhaust side of the second SCR conversion chamber (4) and the first SCR conversion chamber (3). The second side wall (42) near the first air outlet (35) is provided with a second air outlet (43) communicating with the treatment gas passage (2). The common wall (32) has an end that serves as the edge of the first air outlet (35) and the second air outlet (43). The end of the common wall (32) is rotatably mounted with an electrically controllable rotatable closing plate (45). The closing plate (45) can rotate between the first position and the second position. When the closing plate (45) rotates to the first position, the closing plate (45) closes the first air outlet (35) and the second air outlet (43) is connected to the processing air channel (2). When the closing plate (45) rotates to the second position, the closing plate (45) closes the second air outlet (43) and the first air outlet (35) is connected to the processing air channel (2).

2. The SCR aftertreatment device for reducing instantaneous ammonia leakage according to claim 1, characterized in that, The common wall (32) has multiple through holes (36), each of which is covered by a cover plate (37) for controlling the opening and closing of the through hole (36).

3. The SCR aftertreatment device for reducing instantaneous ammonia leakage according to claim 1, characterized in that, The closing plate (45) is rotatably connected to the end of the common wall (32) via an electric hinge (46).

4. A method for SCR aftertreatment to reduce instantaneous ammonia leakage, characterized in that, Based on the SCR aftertreatment device for reducing instantaneous ammonia leakage as described in any one of claims 1 to 3, the method includes the following steps: S1. During engine operation, the exhaust gas temperature T and the urea injection quantity P of the urea nozzle are collected in real time, and the throttle opening change rate O and the exhaust gas temperature change rate ΔT are monitored in real time. S2. Based on the exhaust gas temperature T and the pre-obtained relationship between the urea injection rate and the catalyst temperature, determine the urea injection rate P required for the catalyst in the first SCR conversion chamber to become saturated with ammonia at temperature T. e Based on the pre-obtained exhaust gas temperature threshold T max And the pre-set threshold for the rate of change of throttle opening O set and the threshold of exhaust gas temperature change rate ΔT set Determine whether O > O at the current time. set ΔT>ΔT set T <T max And P>P e ; S3. If satisfied, control the air outlet of the first SCR conversion chamber to be disconnected from the processing gas channel, control the air inlet of the second SCR conversion chamber to be connected to the air outlet of the first SCR conversion chamber, and control the air outlet of the second SCR conversion chamber to be connected to the processing gas channel. S4. When the exhaust gas temperature T is detected to be within the exhaust gas temperature threshold T max When the above conditions are met, the air outlet of the first SCR conversion chamber is connected to the processing gas channel, the air inlet of the second SCR conversion chamber is disconnected from the air outlet of the first SCR conversion chamber, and the air outlet of the second SCR conversion chamber is disconnected from the processing gas channel. Among them, when the exhaust gas temperature T is within the exhaust gas temperature threshold T max When the above conditions are met, the amount of ammonia gas saturated and released from the catalyst in the SCR aftertreatment unit is lower than the preset threshold.

5. The SCR aftertreatment method for reducing instantaneous ammonia leakage according to claim 4, characterized in that, Before S1, it also includes: Urea was injected into the first SCR conversion chamber at different catalyst temperatures. The amount of urea injected into the first SCR conversion chamber at each catalyst temperature when ammonia adsorption was saturated was obtained by detecting the ammonia content at the outlet of the first SCR conversion chamber. Based on the urea injection rate when ammonia adsorption in the first SCR conversion chamber is saturated at different catalytic temperatures, the relationship between urea injection rate and catalyst temperature is fitted.

6. The SCR aftertreatment method for reducing instantaneous ammonia leakage according to claim 4, characterized in that, Threshold O for throttle opening change rate set The threshold value for the rate of change of exhaust gas temperature is 60%-80%. set The range is 1.8%-2.2%, and the exhaust gas temperature threshold T max The temperature ranges from 310 to 330℃.

7. The SCR aftertreatment method for reducing instantaneous ammonia leakage according to claim 4, characterized in that, In S3 The through holes on the shared wall are opened to connect the air inlet of the second SCR conversion chamber with the air outlet of the first SCR conversion chamber; the closing plate is rotated from the second position to the first position to cut off the air outlet of the first SCR conversion chamber from the processing gas channel, and connect the air outlet of the second SCR conversion chamber with the processing gas channel.

8. The SCR post-treatment method for reducing instantaneous ammonia leakage according to claim 4, characterized in that, In S4, First, control the air outlet of the second SCR conversion chamber to be disconnected from the processing gas channel, and connect the air outlet of the first SCR conversion chamber to the processing gas channel. After a preset time, control the air inlet of the second SCR conversion chamber to be disconnected from the air outlet of the first SCR conversion chamber.

9. The SCR aftertreatment method for reducing instantaneous ammonia leakage according to claim 4, characterized in that, In S4, First, control the air outlet of the second SCR conversion chamber to be disconnected from the processing gas channel, and connect the air outlet of the first SCR conversion chamber to the processing gas channel. Then, control the air inlet of the second SCR conversion chamber to be disconnected from the air outlet of the first SCR conversion chamber at a set rate.

Images