CN114810285A - Exhaust gas post-treatment system - Google Patents

Abstract

The application discloses exhaust gas aftertreatment system for promoting NOx and PM's desorption efficiency in the waste gas. The application includes: the system comprises an engine, a supercharger, a diesel particulate filter (SCRF) loaded with a selective catalytic reduction catalyst, a Selective Catalytic Reduction (SCR) catalyst, an Ammonia Slip Catalyst (ASC), a first urea injection device and a second urea injection device; the intercooler is mounted on an air inlet pipeline between the engine and the supercharger; the SCRF is mounted on an exhaust conduit between the engine and the supercharger; the SCR catalyst is arranged on an exhaust pipeline at the rear end of the supercharger; the ASC is arranged on an exhaust pipeline at the rear end of the SCR catalyst; the first urea injection device is mounted on an exhaust conduit between the engine and the SCRF; the second urea injection device is mounted on an exhaust pipe between the supercharger and the SCR catalyst.

Description

An exhaust gas aftertreatment system

technical field

The present application relates to the technical field of diesel engine exhaust gas treatment, and in particular, to an exhaust gas aftertreatment system.

Background technique

A diesel engine is an engine that releases energy by burning diesel, and has excellent characteristics such as large torque and good economic performance. The working process of a diesel engine is the same as that of a gasoline engine. Each working cycle needs to go through strokes such as intake, compression, work, and exhaust. In terms of exhaust emissions, the HC and CO emissions of diesel engines are lower than those of gasoline engines, but the emissions of NOx and particulate matter (PM, Particulate Matter) are much higher than those of gasoline engines. Therefore, how to reduce NOx in exhaust gas And PM content has become the key research object of diesel engine in the field of exhaust gas purification.

At present, in order to reduce pollutants in the exhaust gas, most diesel engines are equipped with an aftertreatment system. The aftertreatment system is sequentially arranged with a diesel oxidation catalyst (DOC, Diesel Oxidation Catalyst), a diesel particulate filter (DPF, Diesel Particulate Filter) and a selective catalytic reduction (SCR, Selective Catalytic Reduction) catalyst in the flow direction of the exhaust gas, wherein DPF can effectively filter PM, and SCR catalyst can effectively remove NOx. However, the aftertreatment system is all arranged on the chassis of the vehicle, and its installation position is relatively far from the diesel engine body. This results in a lower temperature of the exhaust gas flowing into the DPF and the SCR catalyst, thereby reducing the regeneration efficiency of the DPF and the conversion efficiency of the SCR catalyst.

SUMMARY OF THE INVENTION

The present application provides an exhaust gas after-treatment system, which can improve the removal efficiency of NOx and PM in exhaust gas.

The application provides an exhaust gas aftertreatment system, including: an engine, a supercharger, a diesel particulate filter SCRF loaded with a selective catalytic reduction catalyst, a selective catalytic reduction SCR catalyst, an ammonia slip catalyst ASC, a first urea an injection device and a second urea injection device;

The intercooler is installed on the intake duct between the engine and the supercharger;

the SCRF is installed on the exhaust pipe between the engine and the supercharger;

the SCR catalyst is installed on the exhaust pipe at the rear end of the supercharger;

The ASC is installed on the exhaust pipe at the rear end of the SCR catalyst;

the first urea injection device is installed on the exhaust pipe between the engine and the SCRF;

The second urea injection device is installed on the exhaust pipe between the supercharger and the SCR catalyst.

Optionally, the exhaust gas aftertreatment system further includes: a diesel oxidation catalyst DOC;

The DOC is installed on the exhaust pipe between the engine and the first urea injection device, and the DOC is used for oxidizing nitric oxide, hydrocarbons and carbon monoxide.

Optionally, the exhaust gas after-treatment system further includes: a first temperature sensor, a second temperature sensor and a third temperature sensor;

the first temperature sensor is installed on the exhaust pipe between the first urea injection device and the DOC;

the second temperature sensor is installed on the exhaust pipe between the supercharger and the second urea injection device;

The third temperature sensor is installed on the exhaust pipe at the rear end of the ASC.

Optionally, the exhaust gas after-treatment system further includes: an intercooler;

The intercooler is installed on the intake duct between the engine and the supercharger.

Optionally, the exhaust gas aftertreatment system further includes: an exhaust gas recirculation device EGR;

The EGR is installed between the intake duct and the exhaust duct of the engine, and the EGR is used for introducing the exhaust gas discharged from the exhaust duct into the intake duct for secondary combustion.

Optionally, the exhaust gas after-treatment system further includes: a differential pressure sensor;

Two ends of the differential pressure sensor are respectively installed on both sides of the SCRF, and the differential pressure sensor is used to detect the load state of the SCRF.

Optionally, the differential pressure sensor is a semiconductor piezoresistive sensor.

Optionally, the exhaust gas after-treatment system further includes: a first NOx sensor and a second NOx sensor;

the first NOx sensor is installed on the exhaust pipe between the supercharger and the SCR catalyst;

The second NOx sensor is mounted on the exhaust pipe at the rear end of the ASC.

Optionally, the exhaust gas after-treatment system further includes: an exhaust throttle valve;

The exhaust throttle valve is installed on the exhaust pipe between the supercharger and the SCR catalyst, and the exhaust throttle valve is used to control the exhaust gas flowing into the SCR catalyst in the exhaust pipe flow.

Optionally, the exhaust throttle valve is a sliding sleeve type exhaust throttle valve.

As can be seen from the above technical solutions, the application has the following effects:

The intercooler is installed on the intake pipe between the engine and the supercharger; the DPF (SCRF, SCR catalysts coated DPF) loaded with the SCR catalyst is installed on the exhaust pipe between the engine and the supercharger; the SCR catalyst Installed on the exhaust pipe at the rear end of the supercharger; Ammonia slip catalyst (ASC, Ammonia Slip Catalyst) is installed on the exhaust pipe at the rear end of the SCR catalyst; The first urea injection device is installed in the exhaust between the engine and SCRF On the pipeline; the second urea injection device is installed on the exhaust pipeline between the supercharger and the SCR catalyst. SCRF is a DPF loaded with SCR catalyst, which can treat NOx and PM at the same time, and the SCRF is installed on the body of the engine, and the temperature of the exhaust gas flowing into the SCRF is relatively high. When the engine is cold started, NOx and PM can be removed by SCRF. When the exhaust gas temperature increases to a specified temperature, NOx can be removed by the rear-stage SCR catalyst and ASC. In this way, the front-stage SCRF can be used for low-temperature treatment, and the rear-stage SCR catalyst and ASC are used for high-temperature treatment, which reduces the reduction of the regeneration efficiency of DPF and the conversion efficiency of SCR catalyst due to the low exhaust gas temperature. Therefore, the removal efficiency of NOx and PM in the exhaust gas can be improved.

Description of drawings

FIG. 1 is a schematic structural diagram of the exhaust gas after-treatment system in the application.

Detailed ways

In this application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", The orientation or positional relationship indicated by "vertical", "horizontal", "horizontal", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only used to illustrate the relative positional relationship between each component or component , and does not specifically limit the specific installation orientation of each component or component.

In addition, some of the above-mentioned terms may be used to express other meanings besides orientation or positional relationship. For example, the term "on" may also be used to express a certain attachment or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present application can be understood according to specific situations.

Furthermore, the terms "installed", "arranged", "provided", "connected", "connected" should be construed broadly. For example, it may be a fixed connection, a detachable connection, or a unitary structure; it may be a mechanical connection, or an electrical connection; it may be directly connected, or indirectly connected through an intermediary, or between two devices, elements, or components. internal communication. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

In addition, the structures, proportions, sizes, etc. drawn in the drawings in this application are only used to cooperate with the contents disclosed in the description, so as to be understood and read by those skilled in the art, and are not used to limit the implementation of this application. Therefore, it does not have technical substantive significance. Any modification of structure, change of proportional relationship or adjustment of size shall still fall within this within the scope of the technical content disclosed in the application.

The present application provides an exhaust gas after-treatment system for improving the removal efficiency of NOx and PM in exhaust gas.

The exhaust gas after-treatment system described in this application is applied in the field of diesel engines, and can filter and purify the exhaust gas emitted by the diesel engine.

Referring to FIG. 1 , the exhaust gas after-treatment system in this embodiment includes: an engine 1, a supercharger 2, an SCRF3, an SCR catalyst 4, an ASC5, a first urea injection device 6 and a second urea injection device 7; The cooler 12 is installed on the intake pipe between the engine 1 and the supercharger 2; the SCRF3 is installed on the exhaust pipe between the engine 1 and the supercharger 2; the SCR catalyst 4 is installed at the rear end of the supercharger 2. On the exhaust pipe; ASC5 is installed on the exhaust pipe at the rear end of the SCR catalyst 4; the first urea injection device 6 is installed on the exhaust pipe between the engine 1 and SCRF3; the second urea injection device 7 is installed on the supercharger 2 and the exhaust pipe between the SCR catalyst 4.

In this embodiment, the supercharger 2 includes a turbine and a compressor, and the supercharger 2 is used to increase the intake air volume of the engine 1 , so that the pressure and density of the air entering the engine 1 are increased, and the output power of the engine 1 is improved. The working principle of the supercharger 2 is as follows: the exhaust gas discharged from the engine 1 is introduced into the turbine, and the energy of the exhaust gas is used to drive the turbine to rotate, thereby driving the compressor coaxial with the turbine to achieve supercharging.

SCRF3 is a DPF covered with SCR coating. Since SCRF3 is installed on the body of engine 1, the temperature of exhaust gas entering SCRF3 will be higher. Filtration and removal of NOx from exhaust gas. The SCR coating in the front-stage SCRF3 is used to deal with NOx in low temperature conditions, and the rear-stage SCR catalyst 4 is used to deal with NOx in high temperature conditions, which can reduce the temperature of the exhaust gas entering the SCR catalyst 4 when the engine 1 is cold started. If it is too low, the removal efficiency of NOx will decrease.

The first urea injection device 6 and the second urea injection device 7 respectively inject urea solution to the SCR coating in the SCRF3 and the SCR catalyst 4, and the urea solution is decomposed into ammonia and carbon dioxide under the action of high temperature, and the urea solution is decomposed into ammonia gas and carbon dioxide in the exhaust pipe. After the exhaust gas is mixed, it enters the SCR coating in the SCRF3 and the SCR catalyst 4 respectively. Under the catalysis of the SCR, the carbon monoxide, nitrogen monoxide and nitrogen dioxide in the exhaust gas react with the ammonia gas to generate gas that can be directly discharged into the atmosphere. Nitrogen, carbon dioxide and water. However, part of the ammonia gas will be directly discharged into the atmosphere through the SCR. ASC5 reacts the unreacted ammonia gas with oxygen to generate nitrogen and water that can be discharged into the atmosphere, thereby reducing the amount of gas in the exhaust gas at the rear end of the SCR catalyst 4. Ammonia gas leaking out.

In this embodiment, the SCRF3 is a DPF loaded with an SCR catalyst, which can treat NOx and PM at the same time, and the SCRF3 is installed on the body of the engine 1, and the temperature of the exhaust gas flowing into the SCRF3 is relatively high. When the engine 1 is cold started, NOx and PM can be removed by SCRF3, and when the exhaust gas temperature increases to a specified temperature, NOx can be removed by the rear-stage SCR catalyst 4 and ASC5. In this way, the front-stage SCRF3 can be used for low-temperature treatment, and the rear-stage SCR catalyst 4 and ASC5 are used for high-temperature treatment, which reduces the regeneration efficiency of DPF and the conversion efficiency of SCR catalyst 4 due to low exhaust gas temperature. Therefore, the removal efficiency of NOx and PM in the exhaust gas can be improved.

Optionally, as shown in FIG. 1 , the exhaust gas after-treatment system in this embodiment further includes: a diesel oxidation catalyst DOC8; DOC8 is installed on the exhaust pipe between the engine 1 and the first urea injection device 6, and the DOC8 is used to oxidize nitric oxide, hydrocarbons and carbon monoxide.

In this embodiment, the exhaust gas discharged from the engine 1 can be first flowed through the DOC 8 for oxidation treatment before entering the SCRF 3. The DOC 8 can oxidize nitrogen monoxide, hydrocarbons and carbon monoxide to generate nitrogen dioxide, carbon dioxide and water, and During the reaction, a large amount of thermal energy is released to provide a high temperature environment for DPF in SCRF3, which can promote the passive regeneration of DPF.

Optionally, as shown in FIG. 1 , the exhaust gas after-treatment system in this embodiment further includes: a first temperature sensor 9 , a second temperature sensor 10 and a third temperature sensor 11 ; the first temperature sensor 9 is installed in the first temperature sensor 9 . On the exhaust pipe between the urea injection device 6 and the DOC8; the second temperature sensor 10 is installed on the exhaust pipe between the supercharger 2 and the second urea injection device 7; the third temperature sensor 11 is installed at the rear end of the ASC5. on the exhaust duct.

In this embodiment, the first temperature sensor 9 can be used to monitor the temperature of the exhaust gas before entering the SCRF 3 , and control the start and stop of the first urea injection device 6 according to the exhaust gas temperature. In addition, the first temperature sensor 9 can also be used to monitor the regeneration temperature of the DPF in the SCRF3, and adjust the heat released by the DOC 8 according to the detected regeneration temperature, so that the regeneration temperature of the DPF can always be within a reasonable range. The second temperature sensor 10 can be used to monitor the temperature of the exhaust gas before entering the SCR catalyst 4, and control the start and stop of the second urea injection device 7 according to the exhaust gas temperature. The third temperature sensor 11 can be used to monitor the temperature of the exhaust gas flowing out of the rear end of the ASC5, and judge the reaction state of the SCR catalyst 4 and the ASC5 according to the exhaust gas temperature.

Optionally, as shown in FIG. 1 , the exhaust gas after-treatment system in this embodiment further includes: an intercooler 12 ; the intercooler 12 is installed on the intake pipe between the engine 1 and the supercharger 2 .

In this embodiment, since the temperature of the exhaust gas discharged from the engine 1 is relatively high, the heat conduction through the supercharger 2 will increase the temperature of the intake air. During the process of being compressed, the density of the air will increase, and at the same time, the temperature of the air discharged from the supercharger 2 will increase, but the oxygen density will decrease accordingly, thereby affecting the effective charging efficiency of the engine 1 . In order to improve the charging efficiency, an intercooler 12 may be provided on the intake duct between the engine 1 and the supercharger 2 . The intercooler 12 can reduce the intake air temperature and reduce the adverse effects caused by the temperature rise of the supercharged air, thereby improving the effective charging efficiency of the engine 1 .

Optionally, as shown in FIG. 1 , the exhaust gas aftertreatment system in this embodiment further includes: an exhaust gas recirculation device (EGR13, Exhaust Gas Recirculation); the EGR13 is installed between the intake pipe and the exhaust pipe of the engine 1 During this time, the EGR13 is used to guide the exhaust gas discharged from the exhaust duct into the intake duct for secondary combustion.

In this embodiment, since the exhaust gas discharged from the engine 1 contains a large amount of polyatomic gas such as carbon dioxide, the polyatomic gas with high specific heat capacity cannot participate in combustion and can absorb a large amount of heat. Therefore, part of the exhaust gas discharged from the engine 1 can be re-introduced In the intake pipe, the exhaust gas is mixed with the air in the intake pipe and then enters the engine 1 for secondary combustion, thereby reducing the maximum combustion temperature of the engine 1 and reducing the generation of NOx in the exhaust gas.

Optionally, as shown in FIG. 1 , the exhaust gas aftertreatment system in this embodiment further includes: a differential pressure sensor 14 ; two ends of the differential pressure sensor 14 are respectively installed on both sides of the SCRF3 , and the differential pressure sensor 14 is used to detect Load status of SCRF3.

Optionally, as shown in FIG. 1 , the differential pressure sensor 14 in this embodiment is a semiconductor piezoresistive sensor.

In this embodiment, the differential pressure sensor 14 can be used to detect the air pressure difference between the front end air pressure and the rear end air pressure of the DPF in SCRF3, and judge the load state of the DPF according to the air pressure difference. When the load state of the DPF reaches a preset value, start the Passive regeneration of DPF. The differential pressure sensor 14 can be a semiconductor piezoresistive sensor, and its working principle is: according to the principle of the piezoresistive effect of the semiconductor, the pressure difference between the front end and the rear end of the DPF will act on the diaphragm, thereby causing the resistance value of the silicon chip on the diaphragm When there is a change, the change of the resistance value will be converted into a differential pressure electrical signal. When the pressure difference is larger, the differential pressure electrical signal will be higher, the more serious the blockage of the DPF, and the greater the load of the DPF.

Optionally, as shown in FIG. 1 , the exhaust gas aftertreatment system in this embodiment further includes: a first NOx sensor 15 and a second NOx sensor 16 ; the first NOx sensor 15 is installed on the supercharger 2 and the SCR catalyst 4 on the exhaust pipe; the second NOx sensor 16 is installed on the exhaust pipe at the rear end of ASC5.

In this embodiment, the first NOx sensor 15 may be used to detect the first NOx content at the front end of the SCR catalyst 4 , and the second NOx sensor 16 may be used to detect the second NOx content at the rear end of the SCR catalyst 4 . The difference between the content and the second NOx content adjusts the urea pan injection amount of the second urea injection device 7 .

Optionally, as shown in FIG. 1 , the exhaust gas aftertreatment system in this embodiment further includes: an exhaust throttle valve 17 ; the exhaust throttle valve 17 is installed between the supercharger 2 and the SCR catalyst 4 . On the exhaust pipe, the exhaust throttle valve 17 is used to control the flow of exhaust gas flowing into the SCR catalyst 4 in the exhaust pipe.

Optionally, as shown in FIG. 1 , the exhaust throttle valve 17 in this embodiment is a sliding sleeve type exhaust throttle valve.

In this embodiment, the exhaust throttle valve 17 may be used to control the flow rate of exhaust gas entering the SCR catalyst 4 , so as to make the SCR catalyst 4 more stable and efficient. The exhaust throttle valve 17 can be a sliding sleeve type exhaust throttle valve. The valve core of the exhaust throttle valve 17 adopts a low-noise balanced structure, which is easy to open. The surface of the valve core is covered with tungsten carbide, which has a long service life and a flow rate The adjustment precision is high.

It should be stated that the above-mentioned content of the invention and the specific embodiments are intended to prove the practical application of the technical solutions provided in the present application, and should not be construed as limiting the protection scope of the present application. Those skilled in the art can make various modifications, equivalent replacements or improvements within the spirit and principles of the present application. The scope of protection of this application is subject to the appended claims.

Claims (10)

1. An exhaust gas aftertreatment system is characterized in that, comprising: engine, supercharger, diesel particulate filter SCRF loaded with selective catalytic reduction catalyst, selective catalytic reduction SCR catalyst, ammonia slip catalyst ASC, A urea injection device and a second urea injection device; The intercooler is installed on the intake duct between the engine and the supercharger; the SCRF is installed on the exhaust pipe between the engine and the supercharger; the SCR catalyst is installed on the exhaust pipe at the rear end of the supercharger; The ASC is installed on the exhaust pipe at the rear end of the SCR catalyst; the first urea injection device is installed on the exhaust pipe between the engine and the SCRF; The second urea injection device is installed on the exhaust pipe between the supercharger and the SCR catalyst. 2. The exhaust gas aftertreatment system according to claim 1, wherein the exhaust gas aftertreatment system further comprises: a diesel oxidation catalyst DOC; The DOC is installed on the exhaust pipe between the engine and the first urea injection device, and the DOC is used for oxidizing nitric oxide, hydrocarbons and carbon monoxide. 3. The exhaust gas after-treatment system according to claim 2, wherein the exhaust gas after-treatment system further comprises: a first temperature sensor, a second temperature sensor and a third temperature sensor; the first temperature sensor is installed on the exhaust pipe between the first urea injection device and the DOC; the second temperature sensor is installed on the exhaust pipe between the supercharger and the second urea injection device; The third temperature sensor is installed on the exhaust pipe at the rear end of the ASC. 4. The exhaust gas after-treatment system according to claim 1, wherein the exhaust gas after-treatment system further comprises: an intercooler; The intercooler is installed on the intake duct between the engine and the supercharger. 5. The exhaust gas aftertreatment system according to claim 1, wherein the exhaust gas aftertreatment system further comprises: an exhaust gas recirculation device EGR; The EGR is installed between the intake duct and the exhaust duct of the engine, and the EGR is used for introducing the exhaust gas discharged from the exhaust duct into the intake duct for secondary combustion. 6. The exhaust gas after-treatment system according to claim 1, wherein the exhaust gas after-treatment system further comprises: a differential pressure sensor; Two ends of the differential pressure sensor are respectively installed on both sides of the SCRF, and the differential pressure sensor is used to detect the load state of the SCRF. 7 . The exhaust gas aftertreatment system according to claim 6 , wherein the differential pressure sensor is a semiconductor piezoresistive sensor. 8 . 8. The exhaust gas aftertreatment system according to claim 1, wherein the exhaust gas aftertreatment system further comprises: a first NOx sensor and a second NOx sensor; the first NOx sensor is installed on the exhaust pipe between the supercharger and the SCR catalyst; The second NOx sensor is mounted on the exhaust pipe at the rear end of the ASC. 9 . The exhaust gas aftertreatment system according to claim 1 , wherein the exhaust gas aftertreatment system further comprises: an exhaust gas throttle valve; 10 . The exhaust throttle valve is installed on the exhaust pipe between the supercharger and the SCR catalyst, and the exhaust throttle valve is used to control the exhaust gas flowing into the SCR catalyst in the exhaust pipe flow. 10 . The exhaust gas aftertreatment system according to claim 9 , wherein the exhaust throttle valve is a sliding sleeve type exhaust throttle valve. 11 .

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