CN116877240A - A diesel exhaust after-treatment system that meets non-road stage 5 emissions - Google Patents

Abstract

The invention discloses a diesel engine exhaust aftertreatment system meeting the non-road fifth-stage emission, which relates to the technical field of diesel engine exhaust aftertreatment and comprises a ccSCR system, a DOC system, a CDPF system, an SCR system and an ASC system which are sequentially arranged on a diesel engine exhaust pipe along the exhaust direction of the diesel engine exhaust, wherein the ccSCR system carries out catalytic reduction on NOx in the diesel engine exhaust, the DOC system carries out catalytic oxidation on HC, CO and NO in the first treated exhaust, the CDPF system captures PM in the second treated exhaust, the SCR system carries out catalytic reduction on NOx in the third treated exhaust, the ASC system captures ammonia in the fourth treated exhaust, and the front-stage ccSCR system and the rear-stage SCR system are adopted to improve NOx conversion efficiency so as to meet the non-road fifth-stage emission requirement.

Description

A diesel exhaust after-treatment system that meets non-road stage 5 emissions

Technical field

The present invention relates to the technical field of diesel exhaust gas after-treatment, and in particular to a diesel exhaust gas after-treatment system that meets the fifth stage of off-road emissions.

Background technique

With the development of increasingly stringent emission regulations for diesel engine pollutant emissions, the EU's fifth-stage emission standard for non-road mobile machinery is about to be put into use. The EU's fifth-stage emission standard for non-road mobile machinery requires nitrogen oxides (NOx) in diesel engine exhaust. The emission limit should be close to zero.

Currently, in order to meet the fourth stage of non-road emissions of diesel engines, the diesel engine exhaust after-treatment system uses a single-stage SCR system. The SCR system is installed after the CDPF system. Since the SCR system is installed at the rear, the temperature and heat loss in the diesel exhaust pipe are The resulting reduction in the catalytic conversion efficiency of the SCR system is relatively obvious. When running under cold starts, warm-up and long-term low-load conditions, due to the low exhaust temperature at the SCR system (especially below 200°C) ), the low-temperature range of the exhaust temperature cannot meet the temperature range where the catalyst in the SCR system works efficiently. As a result, the injected urea cannot be fully hydrolyzed, and the NOx conversion efficiency is low, which cannot meet the requirements of the fifth stage of non-road diesel engine emissions in the future. . To improve the NOx conversion efficiency of diesel engines, it is necessary to continuously reduce the starting temperature of urea injection so that urea can be fully hydrolyzed in the low temperature range, and at the same time, the crystallization problem of urea under low temperature conditions must be avoided.

Based on this, there is an urgent need for a diesel exhaust after-treatment system that meets the fifth stage of non-road emissions, improves the NOx conversion efficiency, and solves the problem that the traditional single-stage SCR system cannot meet the fifth stage of non-road emission requirements.

Contents of the invention

The purpose of this invention is to provide a diesel engine exhaust after-treatment system that meets the fifth stage of non-road emissions. It adopts a front-stage ccSCR system and a rear-stage SCR system to comprehensively solve the problem that urea cannot be fully hydrolyzed and urea is easy to crystallize, and improves the NOx conversion efficiency. Able to meet non-road Stage 5 emission requirements.

In order to achieve the above objects, the present invention provides the following solutions:

A diesel exhaust after-treatment system that meets the fifth stage of non-road emissions. The diesel exhaust after-treatment system includes a ccSCR system, a DOC system, a CDPF system, and an SCR that are sequentially installed on the diesel exhaust pipe along the direction of the diesel exhaust. systems and ASC systems;

The ccSCR system is used to catalytically reduce NOx in the diesel engine exhaust gas to obtain the first treated exhaust gas;

The DOC system is used to catalytically oxidize HC, CO and NO in the first treated exhaust gas to obtain the second treated exhaust gas;

The CDPF system is used to capture PM in the second treated exhaust gas to obtain a third treated exhaust gas;

The SCR system is used to catalytically reduce NOx in the third treated exhaust gas to obtain the fourth treated exhaust gas;

The ASC system is used to capture the ammonia gas in the exhaust gas after the fourth treatment to obtain the treated exhaust gas.

In some embodiments, the diesel exhaust after-treatment system also includes an after-treatment controller and a NOx sensor installed on the diesel exhaust pipe; the after-treatment controller is connected to the NOx sensor and the ccSCR respectively. The system is connected to the SCR system;

The NOx sensor is located between the diesel engine and the ccSCR system, and the NOx sensor is used to collect the NOx emission concentration value in the exhaust gas of the diesel engine;

The post-treatment controller is used to determine the first urea injection amount of the ccSCR system and the SCR system based on the NOx emission concentration value, the exhaust flow value of the diesel engine exhaust gas and the current working condition of the diesel engine. the second urea injection volume.

In some embodiments, the ccSCR system includes a ccSCR front exhaust temperature sensor and a ccSCR catalyst installed on the diesel engine exhaust pipe, and the ccSCR front exhaust temperature sensor is located between the diesel engine and the ccSCR catalyst. The DOC system includes a DOC front exhaust temperature sensor and a DOC catalytic converter installed on the diesel engine exhaust pipe, and the DOC front exhaust temperature sensor is located between the ccSCR catalytic converter and the DOC catalytic converter;

The ccSCR front row temperature sensor and the DOC front row temperature sensor are both communicatively connected with the post-processing controller; the post-processing controller is used to measure the temperature collected by the ccSCR front row temperature sensor and the DOC front row temperature sensor. The temperature collected by the temperature sensor constructs the temperature field of the ccSCR catalyst, and the first urea injection amount is corrected according to the temperature field of the ccSCR catalyst to obtain the first corrected urea injection amount.

In some embodiments, the post-processing controller is further configured to determine whether the ccSCR system is working based on the temperature collected by the ccSCR front exhaust temperature sensor.

In some embodiments, the SCR system includes an SCR front exhaust temperature sensor and an SCR catalytic converter installed on the diesel engine exhaust pipe, and the SCR front exhaust temperature sensor is located in the CDPF system and the SCR catalytic converter. between; the ASC system includes an ASC catalytic converter and an ASC rear exhaust temperature sensor installed on the diesel engine exhaust pipe, the ASC catalytic converter is located between the SCR catalytic converter and the ASC rear exhaust temperature sensor ;

The SCR front exhaust temperature sensor and the ASC rear exhaust temperature sensor are both communicatively connected with the post-processing controller; the post-processing controller is used to measure the temperature collected by the SCR front exhaust temperature sensor and the ASC rear exhaust temperature sensor. The temperature collected by the temperature sensor constructs the temperature field of the SCR catalyst, and the second urea injection amount is corrected according to the temperature field of the SCR catalyst to obtain the second corrected urea injection amount.

In some embodiments, the post-processing controller is further configured to determine whether the SCR system is working based on the temperature collected by the SCR front row temperature sensor.

In some embodiments, the ccSCR system further includes a ccSCR pre-injection nozzle installed on the diesel engine exhaust pipe, the ccSCR pre-injection nozzle is located between the diesel engine and the ccSCR catalyst; the ccSCR The front-stage nozzle is controlled and connected with the after-treatment controller; the ccSCR front-stage nozzle is used to inject the first corrected urea into the diesel engine exhaust pipe under the control of the after-treatment controller. Injection volume of urea;

The SCR system also includes an SCR rear-stage nozzle installed on the diesel engine exhaust pipe. The SCR rear-stage nozzle is located between the CDPF system and the SCR catalytic converter; the SCR rear-stage nozzle is connected to the SCR catalytic converter. The after-treatment controller controls the connection; the SCR rear-stage nozzle is used to inject the second corrected urea injection amount of urea into the diesel engine exhaust pipe under the control of the after-treatment controller.

In some embodiments, the diesel exhaust after-treatment system further includes a urea injection device, which is connected to the ccSCR front-stage nozzle and the SCR rear-stage nozzle respectively; the urea injection device is used to The ccSCR front-stage nozzle and the SCR rear-stage nozzle provide urea.

In some embodiments, the urea injection device includes a urea tank and a urea pump; the urea tank is used to store urea; and the urea pump is connected to the urea tank, the ccSCR pre-stage nozzle and the SCR post-stage respectively. The nozzles are connected, and the urea pump is used to extract urea from the urea tank and provide urea to the ccSCR front-stage nozzle and the SCR rear-stage nozzle.

In some embodiments, the CDPF system includes a CDPF differential pressure sensor and a CDPF front exhaust temperature sensor, a CDPF catalytic converter and a CDPF rear exhaust temperature sensor installed on the diesel engine exhaust pipe; the CDPF front exhaust temperature sensor Located between the DOC catalytic converter and the CDPF catalytic converter, the CDPF differential pressure sensor is connected to the CDPF catalytic converter, and the CDPF rear exhaust temperature sensor is located between the CDPF catalytic converter and the SCR system ;

The CDPF front exhaust temperature sensor, the CDPF differential pressure sensor and the CDPF rear exhaust temperature sensor are all communicatively connected with the post-processing controller; the post-processing controller is used to collect the data according to the DOC front exhaust temperature sensor. temperature, the temperature collected by the CDPF front exhaust temperature sensor, the temperature collected by the CDPF rear exhaust temperature sensor and the pressure difference collected by the CDPF differential pressure sensor determine the amount of water injected into the DOC catalytic converter to achieve the CDPF catalysis The amount of HC injection for carrier regeneration in the device.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

The invention is used to provide a diesel engine exhaust after-treatment system that meets the fifth stage of off-road emissions, including a ccSCR system, a DOC system, a CDPF system, an SCR system, and a ccSCR system, a DOC system, a CDPF system, an SCR system, and a ASC system, ccSCR system catalytically reduces NOx in the diesel exhaust gas, DOC system catalytically oxidizes HC, CO and NO in the exhaust gas after the first treatment, CDPF system captures PM in the exhaust gas after the second treatment, SCR The system catalytically reduces NOx in the exhaust gas after the third treatment, and the ASC system captures ammonia in the exhaust gas after the fourth treatment to obtain the treated exhaust gas. By setting up the ccSCR system before the DOC system, the ccSCR system The exhaust temperature of the treated diesel engine exhaust is high, and the exhaust temperature range can meet the temperature range where the catalyst in the ccSCR system works efficiently, allowing the injected urea to be fully hydrolyzed, and at the same time, it can further reduce the urea injection starting temperature, and can To avoid urea crystallization, the present invention adopts the front-stage ccSCR system and the back-stage SCR system to comprehensively solve the problem that urea cannot be fully hydrolyzed and urea is easy to crystallize, improves the NOx conversion efficiency, and can meet the non-road fifth stage emission requirements.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the drawings of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of a diesel engine exhaust after-treatment system provided in Embodiment 1 of the present invention.

Symbol Description:

1-Diesel engine exhaust after-treatment system; 2-Urea tank; 3-Urea pump; 4-ccSCR system; 5-DOC system; 6-CDPF system; 7-SCR system; 8-ASC system; 9-Diesel engine; 10-DOC Front exhaust temperature sensor; 11-DPF front exhaust temperature sensor; 12-DPF differential pressure sensor; 13-DPF rear exhaust temperature sensor; 14-SCR rear stage nozzle; 15-SCR front temperature; 16-ASC rear temperature; 17-NOx Sensor; 18-PM sensor; 19-ccSCR front exhaust temperature sensor; 20-NOx sensor; 21-ccSCR front nozzle; 22-post-processing controller; 23-diagnostic display.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

The purpose of this invention is to provide a diesel engine exhaust after-treatment system that meets the fifth stage of non-road emissions. It adopts a front-stage ccSCR system and a rear-stage SCR system to comprehensively solve the problem that urea cannot be fully hydrolyzed and urea is easy to crystallize, and improves the NOx conversion efficiency. Able to meet non-road Stage 5 emission requirements.

In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Example 1:

This embodiment is used to provide a diesel engine exhaust after-treatment system that meets the fifth stage of non-road emissions. As shown in Figure 1, the diesel engine exhaust after-treatment system includes installations on the diesel engine exhaust exhaust pipe in sequence along the direction of the diesel engine exhaust. ccSCR system 4, DOC system, CDPF system 6, SCR system 7 and ASC system 8. At this time, the diesel engine 9 exhaust gas is processed through ccSCR system 4, DOC system 5, CDPF system 6, SCR system 7 and ASC system 8 in sequence, and we get Exhaust gas after treatment.

The ccSCR system 4 can also be called a close-coupled selective catalytic conversion device. The ccSCR system 4 is used to catalytically reduce NOx in the diesel exhaust gas to obtain the first treated exhaust gas. Specifically, urea is injected into the exhaust pipe of the diesel engine 9. After the urea is decomposed into ammonia, the ammonia reacts with the NOx in the diesel engine exhaust to generate harmless nitrogen and water, achieving low-temperature and low-load operation. NOx emission control.

The DOC system 5 can also be called a diesel catalytic oxidation system. The DOC system 5 is used to catalytically oxidize HC, CO and NO in the first treated exhaust gas to obtain the second treated exhaust gas. Specifically, the DOC system 5 combines HC (hydrocarbons) in the diesel exhaust gas with O ₂ to generate harmless H ₂ O and CO ₂ , oxidizes the CO in the diesel exhaust gas into CO ₂ , and oxidizes NO in the diesel exhaust gas. Oxidized to NO ₂ , the emission control of part of HC and CO in the diesel engine exhaust is realized, and a certain amount of NO ₂ is generated. NO ₂ can be further transmitted to the subsequent CDPF system 6, where it can directly interact with PM (carbon particulate matter) Carry out sufficient chemical reactions to achieve PM capture.

The CDPF system 6 is used to capture PM in the second treated exhaust gas to obtain the third treated exhaust gas, and the collection efficiency can reach more than 99%.

The SCR system 7 is used to catalytically reduce NOx in the third treated exhaust gas to obtain the fourth treated exhaust gas. Specifically, urea is injected into the exhaust pipe of the diesel engine. After the urea is decomposed into ammonia, the ammonia reacts with the NOx in the diesel engine exhaust to generate harmless nitrogen and water to achieve NOx reduction under high temperature and high load conditions. Emissions Control.

The ASC system 8 is used to capture the ammonia gas in the exhaust gas after the fourth treatment to obtain the treated exhaust gas. Specifically, the ASC system 8 performs an NH ₃ ammonia leakage oxidation reaction on the NH 3 generated by the SCR system 7 to reduce the NH ₃ emission leakage, realize the capture of _{NH 3 ,} and reduce the leakage in the SCR rear-end exhaust based on catalytic oxidation. ammonia released.

The diesel exhaust after-treatment system of this embodiment achieves efficient conversion of NOx in the diesel exhaust through the optimized arrangement and combination of the ccSCR+DOC+CDPF+SCR+ASC systems and meets the limit requirements of the fifth stage of non-road emissions. By setting the ccSCR system 4 before the DOC system, the ccSCR system 4 is close to the outlet of the diesel engine exhaust gas, that is, close to the exhaust outlet of the diesel engine turbocharger. At this time, the exhaust temperature of the diesel engine exhaust gas processed by the ccSCR system 4 is high, and the exhaust temperature is The range at can meet the temperature range where the catalyst in the ccSCR system 4 can work efficiently. The urea hydrolysis efficiency is high, which can fully hydrolyze the injected urea and improve the NOx conversion efficiency. At the same time, due to the high exhaust temperature of the diesel exhaust gas processed by the ccSCR system 4, the urea injection initiation temperature can be further reduced and urea crystallization can be avoided, thereby achieving efficient conversion of NOx in the diesel exhaust gas and meeting the fifth stage of off-road emissions. limit requirements.

In this embodiment, in order to meet the fifth stage of non-road emissions, the technical route used by the diesel exhaust after-treatment system 1 is ccSCR+DOC+CDPF+SCR+ASC. A urea nozzle is arranged in each of the ccSCR system 4 and the SCR system 7 to form a double nozzle. In the urea injection structure, compared with the single SCR urea injection method, since the ccSCR system 4 is located close to the diesel engine exhaust, the comprehensive conversion efficiency of NOx emissions using the dual urea nozzle injection method can be greatly improved. On this basis, this embodiment Further consider the proportional relationship between the injection amounts of the two nozzles, so that the ccSCR system 4 and the SCR system 7 can work better together to further improve the NOx conversion efficiency.

Specifically, the diesel exhaust after-treatment system of this embodiment also includes an after-treatment controller 22 and a NOx sensor installed on the exhaust pipe of the diesel engine. The NOx sensor is located between the diesel engine 9 and the ccSCR system 4. The NOx sensor is used to collect data from the diesel engine. The NOx emission concentration value in the exhaust gas is collected, and the collected NOx emission concentration value is transmitted to the aftertreatment controller 22 . The post-processing controller 22 is connected to the NOx sensor, the ccSCR system and the SCR system 7 respectively. The post-processing controller 22 is used to report the NOx emission concentration value and the exhaust flow value of the diesel engine exhaust gas through the CAN bus. The message data is sent from the high-voltage common rail electronic control unit to the post-processing electronic control unit, and then the message is parsed to obtain (no need to install a flow sensor) and the current working condition of the diesel engine 9 to determine the first urea injection amount of the ccSCR system 4 and The second urea injection amount of the SCR system 7 and the two urea injection amounts are specifically determined as follows: the post-processing controller 22 calculates the urea injection amount based on the NOx emission concentration value and the exhaust flow value of the diesel exhaust gas to obtain the total urea injection amount. quantity, and then according to the working characteristics of the diesel engine 9 under different working conditions, the working conditions include temperature, speed, load and other information. When the current working conditions of the diesel engine 9 only meet the urea injection conditions of the ccSCR system 4, the post-processing controller 22 determines that the first urea injection amount of the ccSCR system 4 is the total urea injection amount, and the second urea injection amount of the SCR system 7 is 0; when the current working condition of the diesel engine 9 satisfies both the urea injection conditions of the ccSCR system 4 and the urea injection conditions of the SCR system 7, the post-processing controller 22 reasonably allocates the total urea injection amount, and performs pre- and post-processing through calibration means. The optimal proportional control factor of the urea injection amount to achieve the best emission effect control is to determine the first urea injection amount of the ccSCR system 4 and the second urea injection amount of the SCR system 7; when the current working condition of the diesel engine 9 only satisfies the SCR When the urea injection condition of the system 7 is determined, the post-processing controller 22 determines that the first urea injection amount of the ccSCR system 4 is 0, the second urea injection amount of the SCR system 7 is the total urea injection amount, and the second urea injection amount depends on the current work. Ammonia storage set amount, temperature, exhaust flow and other information under normal conditions. The injection volume of the front and rear two-stage urea nozzles is divided according to the temperature range of the exhaust pipeline under different working conditions. It is divided into the injection temperature range of the front-stage urea injection, the injection temperature range of the front-stage and rear-stage urea injection, and the injection temperature of the rear-stage urea injection. interval, and the specific temperature threshold is obtained through specific calibration through experiments.

This embodiment determines the first urea injection amount of the ccSCR system 4 and the second urea injection amount of the SCR system 7 based on the NOx emission concentration value of the diesel engine exhaust gas, the exhaust flow rate value and the current working condition of the diesel engine 9 to determine the first urea injection amount of the SCR system 7 according to the specific work. The condition point controls the urea injection amount to achieve optimal control of the urea injection amount of the ccSCR system 4 and SCR system 7, which can make the ccSCR system 4 and the SCR system work better together to further improve the NOx conversion efficiency in the diesel engine exhaust. Through the cooperation of the front and rear two-stage SCR systems (i.e., the front-stage ccSCR system and the rear-stage SCR system), precise control of urea under all operating conditions of the diesel engine is achieved, efficient catalytic conversion of NOx emissions is achieved, and the requirements for non-road stage 5 emission control are met.

The ccSCR system 4 of this embodiment includes a ccSCR front exhaust temperature sensor 19 and a ccSCR catalyst installed on the diesel engine exhaust pipe. The ccSCR front exhaust temperature sensor 19 is located between the diesel engine 9 and the ccSCR catalyst. The ccSCR front exhaust temperature sensor 19 Used to collect the exhaust gas temperature at the location where it is installed, the ccSCR catalytic converter is used to react ammonia gas with NOx in the diesel engine exhaust gas to generate harmless nitrogen and water.

The DOC system 5 of this embodiment includes a DOC front exhaust temperature sensor 10 and a DOC catalytic converter installed on the diesel engine exhaust pipe. The DOC front exhaust temperature sensor 10 is located between the ccSCR catalytic converter and the DOC catalytic converter. The DOC front exhaust temperature sensor 10 is used to collect the exhaust gas temperature at its installation location, and the DOC catalytic converter is used to catalytically oxidize HC, CO and NO in the first treated exhaust gas. The ccSCR catalytic converter in this embodiment is installed upstream of the DOC catalytic converter, that is, the ccSCR catalytic converter is closer to the diesel engine 9 and can eliminate part of the poisoning chemical components in the exhaust gas of the diesel engine 9 .

Preferably, the ccSCR front exhaust temperature sensor 19 and the DOC front exhaust temperature sensor 10 of this embodiment are both communicatively connected with the post-processing controller 22 . The post-processing controller 22 is configured to construct a temperature field of the ccSCR catalytic converter based on the temperature collected by the ccSCR front exhaust temperature sensor 19 and the temperature collected by the DOC front exhaust temperature sensor 10 , and perform the first urea injection amount according to the temperature field of the ccSCR catalytic converter. After correction, the first corrected urea injection amount is obtained, so that the urea injection amount of the ccSCR system 4 can be determined more accurately, and the conversion efficiency of NOx in the exhaust gas of the diesel engine 9 can be further improved. Temperature field model of the ccSCR catalytic converter: According to the principle of heat transfer, the internal temperature distribution of the ccSCR carrier is obtained, and the temperature value of each carrier section is calculated. The temperature values of all carriers constitute the temperature field. After obtaining the temperature field model of the ccSCR catalytic converter, the corrected NOx conversion efficiency is obtained according to the temperature field model of the ccSCR catalytic converter, and the correction amount of the urea injection amount is calculated based on the corrected NOx conversion efficiency.

The SCR system 7 of this embodiment includes an SCR front exhaust temperature sensor and an SCR catalytic converter installed on the diesel engine exhaust pipe. The SCR front exhaust temperature sensor is located between the CDPF system 6 and the SCR catalytic converter. The SCR front exhaust temperature sensor is used to Collecting the exhaust gas temperature at its installation location, the SCR catalytic converter is used to react ammonia with NOx in the diesel engine exhaust to generate harmless nitrogen and water, that is, to perform a selective catalytic reduction reaction of NOx to achieve efficient NOx emissions. Catalytic conversion.

The ASC system 8 of this embodiment includes an ASC catalytic converter and an ASC rear exhaust temperature sensor installed on the diesel engine exhaust pipe. The ASC catalytic converter is located between the SCR catalytic converter and the ASC rear exhaust temperature sensor. The ASC catalytic converter is used to detect ammonia gas. To collect, the ASC rear exhaust temperature sensor is used to collect the exhaust gas temperature at the location where it is installed.

Preferably, both the SCR front exhaust temperature sensor and the ASC rear exhaust temperature sensor of this embodiment are communicatively connected with the post-processing controller 22 . The post-processing controller 22 is configured to construct a temperature field of the SCR catalyst based on the temperature collected by the SCR front exhaust temperature sensor and the temperature collected by the ASC rear exhaust temperature sensor, and correct the second urea injection amount based on the temperature field of the SCR catalyst, The second corrected urea injection amount is obtained, so that the urea injection amount of the SCR system 7 can be determined more accurately, and the conversion efficiency of NOx in the diesel engine exhaust can be further improved. Temperature field model of SCR catalytic converter: According to the principle of heat transfer, the internal temperature distribution of the SCR carrier is obtained, and the temperature value of each carrier section is calculated. The temperature values of all carriers constitute the temperature field of the SCR catalytic converter. After obtaining the temperature field model of the SCR catalytic converter, the corrected NOx conversion efficiency is obtained according to the temperature field model of the SCR catalytic converter, and the correction amount of the urea injection amount is calculated based on the corrected NOx conversion efficiency.

In this embodiment, after initially determining the first urea injection amount of the ccSCR system 4 and the second urea injection amount of the SCR system 7 , the first urea injection amount is further corrected in real time based on the temperature field of the ccSCR system 4 . Based on the SCR system 7 The temperature field of the second urea injection amount is corrected in real time to realize real-time correction of the urea injection amount of the ccSCR system and SCR system 7, which can achieve full hydrolysis of urea, avoid the crystallization problem of urea, and further improve the conversion efficiency of NOx in the diesel engine exhaust. .

Preferably, the post-processing controller 22 of this embodiment is also used to determine whether the ccSCR system 4 is working based on the temperature collected by the ccSCR front row temperature sensor 19. Specifically, it is determined based on the temperature collected by the ccSCR front row temperature sensor 19 whether it meets the requirements of the ccSCR system 4. Urea injection temperature. The urea injection temperature is obtained based on the ignition temperature characteristics of the ccSCR catalyst. The specific value is obtained through catalyst sample experiments. When the temperature collected by the ccSCR front exhaust temperature sensor 19 is greater than the urea injection starting temperature of the ccSCR system 4, the ccSCR system 4 is made to work, that is, the ccSCR system is made to inject the first corrected urea injection amount of urea. When the ccSCR system 4 is working, the ccSCR system 4 does not inject urea to avoid the crystallization problem of urea.

The post-processing controller 22 of this embodiment is also used to determine whether the SCR system 7 is working based on the temperature collected by the SCR front exhaust temperature sensor. Specifically, based on the temperature collected by the SCR front exhaust temperature sensor, it is determined whether the urea injection temperature of the SCR system 7 is met. The urea injection temperature is obtained based on the ignition temperature characteristics of the SCR catalyst, and the specific value is obtained through catalyst sample experiments. When the temperature collected by the SCR front exhaust temperature sensor is greater than the urea injection temperature of the SCR system, the SCR system 7 is made to work, that is, the SCR system is made to inject the second corrected urea injection amount of urea. When it is not satisfied, the SCR system is not made. 7 works, even if the SCR system 7 does not inject urea, it can avoid the crystallization problem of urea.

This embodiment can further realize the judgment of the urea injection temperature of the ccSCR system 4 and the SCR system 7, avoid injecting urea when the urea injection temperature is not met, and avoid the crystallization problem of urea.

In this embodiment, the ccSCR front row temperature sensor 19, the DOC front row temperature sensor 10 and the post-processing controller 22 cooperate with each other. The ccSCR front row temperature sensor 19 and the DOC front row temperature sensor 10 collect relevant temperature information and transmit the temperature information to The post-processing controller 22 determines the urea injection temperature based on the temperature information and estimates the temperature field of the ccSCR catalyst to perform real-time correction control of the first urea injection amount based on the estimated temperature field data. , to realize the judgment of the urea injection temperature of the ccSCR system 4, the estimation of the temperature field of the ccSCR catalyst, and the correction of the urea injection amount. The SCR front exhaust temperature sensor, the ASC rear exhaust temperature sensor and the post-processing controller 22 cooperate with each other. The SCR front exhaust temperature sensor and the ASC rear exhaust temperature sensor collect relevant temperature information and transmit the temperature information to the post-processing controller 22. Post-processing The controller 22 determines the urea injection temperature according to the temperature information, estimates the temperature field of the SCR catalyst, and performs real-time correction control on the second urea injection amount according to the estimated temperature field data to realize the urea injection of the SCR system 7 Judgment of injection temperature, estimation of temperature field of SCR catalyst and correction of urea injection amount.

The ccSCR system 4 of this embodiment also includes a ccSCR front-end nozzle 21 installed on the diesel engine exhaust pipe. The ccSCR front-end nozzle 21 is located between the diesel engine 9 and the ccSCR catalyst. In particular, the ccSCR front-end nozzle 21 and the ccSCR front-end nozzle 21 The positional relationship of the exhaust temperature sensor 19 can be customized. For example, the ccSCR front nozzle 21 can be located in front of the ccSCR front exhaust temperature sensor 19, or the ccSCR front exhaust temperature sensor 19 can be located in front of the ccSCR front nozzle 21. The ccSCR front-end nozzle 21 is controllably connected to the after-treatment controller 22. The ccSCR front-end nozzle 21 is used to inject the first corrected urea injection amount of urea into the diesel engine exhaust pipe under the control of the after-treatment controller 22. Specifically, the post-processing controller 22 generates a driving duty cycle control signal of the ccSCR front-stage nozzle 21 according to the first corrected urea injection amount, and applies the control signal to the ccSCR front-stage nozzle 21 to drive the ccSCR front-stage nozzle 21 Control to cause the ccSCR front-end nozzle 21 to inject the first corrected urea injection amount of urea into the diesel engine exhaust pipe.

The SCR system 7 of this embodiment also includes an SCR rear-stage nozzle installed on the diesel engine exhaust pipe. The SCR rear-stage nozzle is located between the CDPF system 6 and the SCR catalytic converter. It is particularly pointed out that the SCR rear-stage nozzle and the SCR front exhaust temperature The position relationship of the sensor can be customized. For example, the SCR rear-stage nozzle can be located in front of the SCR front-stage temperature sensor, or the SCR front-stage temperature sensor can be located in front of the SCR rear-stage nozzle. The SCR rear-stage nozzle is controlled and connected with the after-treatment controller 22. The SCR rear-stage nozzle is used to inject the second corrected urea injection amount of urea into the diesel engine exhaust pipe under the control of the after-treatment controller 22. Specifically, , the post-processing controller 22 generates a drive duty cycle control signal of the SCR rear-stage nozzle according to the second corrected urea injection amount, and applies the control signal to the SCR rear-stage nozzle to drive and control the SCR rear-stage nozzle, so that the SCR rear-stage nozzle The stage nozzle injects the second corrected urea injection amount of urea into the exhaust pipe of the diesel engine.

The diesel exhaust after-treatment system 1 of this embodiment also includes a urea injection device. The urea injection device is connected to the ccSCR front-stage nozzle 21 and the SCR rear-stage nozzle respectively. The urea injection device is used to inject the ccSCR front-stage nozzle 21 and the SCR rear-stage nozzle. Urea is provided. After receiving the urea provided by the urea injection device, the ccSCR front-stage nozzle 21 and the SCR rear-stage nozzle respectively inject the first corrected urea injection amount into the diesel engine exhaust pipe under the control of the after-treatment controller 22 of urea and the second corrected urea injection amount of urea. Specifically, the control signal of this embodiment can be used to control the injection time of the ccSCR front-stage nozzle 21 and the injection time of the SCR rear-stage nozzle. By controlling the injection time, the urea injection amount of the ccSCR front-stage nozzle 21 and the SCR rear-stage can be accurately controlled. The amount of urea injected from the nozzle.

The urea injection device of this embodiment includes a urea tank 2 and a urea pump 3. The urea tank 2 is used to store urea to realize the storage of urea aqueous solution and the quality measurement of urea aqueous solution. The quality of urea aqueous solution is measured by a urea quality sensor and is measured through the CAN bus. sent to the post-processing electronic control unit. The urea pump 3 is connected to the urea tank 2, the ccSCR front-stage nozzle 21 and the SCR rear-stage nozzle respectively. One end of the urea pump 3 is connected to the urea tank 2, and the other end is connected to the ccSCR front-stage nozzle 21 and the SCR rear-stage nozzle respectively. The urea pump 3 is used from Urea is extracted from the urea tank 2 and provided to the ccSCR front-stage nozzle 21 and the SCR rear-stage nozzle. The urea pump 3 can also be called a urea metering pump. It realizes the pressure building and stabilizing process of the urea aqueous solution. The pressure building process of the urea aqueous solution is to drive the diaphragm through the motor inside the urea pump 3 to achieve the establishment of the pressure of the urea aqueous solution. The urea aqueous solution The pressure stabilization is achieved through closed-loop control to achieve stability control of urea injection pressure.

This embodiment can also realize the passive regeneration function of the CDPF catalytic converter. Specifically, the CDPF system 6 includes a CDPF differential pressure sensor, a CDPF front exhaust temperature sensor, a CDPF catalytic converter, and a CDPF rear exhaust temperature sensor installed on the diesel engine exhaust pipe. The CDPF front exhaust temperature sensor is located between the DOC catalytic converter and the CDPF catalytic converter, the CDPF differential pressure sensor is connected to the CDPF catalytic converter, and the CDPF rear exhaust temperature sensor is located between the CDPF catalytic converter and the SCR system 7. The CDPF front exhaust temperature sensor, CDPF differential pressure sensor and CDPF rear exhaust temperature sensor are all communicatively connected with the post-processing controller 22. The post-processing controller 22 is used to collect the temperature collected by the DOC front exhaust temperature sensor 10 and the CDPF front exhaust temperature sensor. The temperature, the temperature collected by the CDPF rear exhaust temperature sensor and the pressure difference collected by the CDPF differential pressure sensor determine the amount of HC injected into the DOC catalytic converter to achieve carrier regeneration in the CDPF catalytic converter. Specifically, the CDPF differential pressure sensor is used The pressure difference between the front and rear ends of the CDPF catalytic converter is collected, and the carbon load borne by the DPF carrier is obtained based on the map relationship between the pressure difference and the carbon load. The post-treatment controller 22 is used to estimate the carbon load of the CDPF catalytic converter based on the pressure difference. The degree of carrier overload of the CDPF is determined based on setting different overload carbon load limits. The specific value of the carrier carbon load is subsequently used for closed-loop control of the CDPF regeneration temperature. The post-processing controller 22 then uses the temperature collected by the DOC front exhaust temperature sensor 10, the temperature collected by the CDPF front exhaust temperature sensor and the temperature collected by the CDPF rear exhaust temperature sensor. The specific value of HC injection (HC injection quantity) is calculated based on the numerical model of converting fuel injection quantity into heat. Fuel injection quantity is determined by a map between pressure differential and carbon load. The calculated HC injection amount is directly injected into the DOC catalytic converter for oxidation exothermic reaction, so as to provide heat to the CDPF catalytic converter with the help of the oxidation reaction in the DOC catalytic converter, so that the CDPF catalytic converter reaches the regeneration temperature and realizes the carrier in the CDPF catalytic converter. Regeneration to perform closed-loop control of regeneration temperature to achieve optimal regeneration temperature control of particulate matter.

The NOx sensor after the SCR catalytic converter in this embodiment is used to measure the NOx emissions at the rear end of the SCR catalytic converter, and the NOx conversion efficiency under actual road conditions is calculated through the two front and rear NOx sensors (ie, the NOx sensor 17 and the NOx sensor 20 ). Closed-loop correction of urea injection volume in real time. The PM sensor 18 after the SCR catalytic converter is used to measure the concentration of particulate matter at the exhaust rear end outlet and is used for a fault alarm function.

This embodiment provides a high-efficiency exhaust gas after-treatment system for diesel engines that meets the fifth stage of non-road emissions, including ccSCR system 4, DOC system 5, CDPF system 6, SCR system 7 and ASC system 8, which can realize the non-road stage 5 emission of diesel engines. The efficient control of five-stage emissions expands the NOx conversion efficiency temperature window toward low temperatures. The front-stage ccSCR system is used for urea injection under low-speed and low-load conditions of the diesel engine, and the rear-stage ccSCR system is used for high-speed and high-load diesel engine conditions. The SCR system performs urea injection. Through the optimal matching of urea injection in the front and rear two-stage SCR systems, optimal emission control of NOx under all operating conditions of the diesel engine is achieved, thereby achieving higher conversion efficiency of NOx and meeting the requirements of the fifth stage of off-road emissions. .

The post-processing controller 22 of this embodiment can adopt the Freescale high-performance 16-bit microcontroller MC9S12XEP100. The hardware, software and control strategy of the post-processing controller 22 are further designed to make it capable of controlling the ccSCR system 4, DOC system 5, CDPF system 6, SCR system 7 and ASC system 8 play a comprehensive control function to realize the control function of efficient catalytic conversion of diesel exhaust after-treatment system 1 and realize efficient catalytic conversion of NOx emissions, thereby meeting the fifth stage of non-road emissions. Control requirements.

The diesel exhaust after-treatment system 1 of this embodiment also includes a diagnostic LCD screen (diagnostic display screen 23), which is communicatively connected with the after-treatment controller 22 and can be used to display the sensor data received by the after-treatment controller 22 and the after-treatment data. The calculation data calculated by the controller 22 is processed.

This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and the core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the present invention There will be changes in the specific implementation methods and application scope of the ideas. In summary, the contents of this description should not be construed as limitations of the present invention.

Claims (10)

1. A diesel exhaust after-treatment system that meets the fifth stage of non-road emissions, characterized in that the diesel exhaust after-treatment system includes a ccSCR system and a DOC installed on the diesel exhaust pipe in sequence along the direction of the diesel exhaust. system, CDPF system, SCR system and ASC system; The ccSCR system is used to catalytically reduce NOx in the diesel engine exhaust gas to obtain the first treated exhaust gas; The DOC system is used to catalytically oxidize HC, CO and NO in the first treated exhaust gas to obtain the second treated exhaust gas; The CDPF system is used to capture PM in the second treated exhaust gas to obtain a third treated exhaust gas; The SCR system is used to catalytically reduce NOx in the third treated exhaust gas to obtain the fourth treated exhaust gas; The ASC system is used to capture the ammonia gas in the exhaust gas after the fourth treatment to obtain the treated exhaust gas. 2. The diesel exhaust after-treatment system according to claim 1, characterized in that the diesel exhaust after-treatment system further includes an after-treatment controller and a NOx sensor installed on the diesel exhaust pipe; The processing controller is respectively connected to the NOx sensor, the ccSCR system and the SCR system; The NOx sensor is located between the diesel engine and the ccSCR system, and the NOx sensor is used to collect the NOx emission concentration value in the exhaust gas of the diesel engine; The post-treatment controller is used to determine the first urea injection amount of the ccSCR system and the SCR system based on the NOx emission concentration value, the exhaust flow value of the diesel engine exhaust gas and the current working condition of the diesel engine. the second urea injection volume. 3. The diesel exhaust after-treatment system according to claim 2, characterized in that the ccSCR system includes a ccSCR front exhaust temperature sensor and a ccSCR catalyst installed on the diesel exhaust pipe, and the ccSCR front exhaust The temperature sensor is located between the diesel engine and the ccSCR catalytic converter; the DOC system includes a DOC front exhaust temperature sensor and a DOC catalytic converter installed on the diesel engine exhaust pipe, and the DOC front exhaust temperature sensor is located at the between the ccSCR catalytic converter and the DOC catalytic converter; The ccSCR front row temperature sensor and the DOC front row temperature sensor are both communicatively connected with the post-processing controller; the post-processing controller is used to measure the temperature collected by the ccSCR front row temperature sensor and the DOC front row temperature sensor. The temperature collected by the temperature sensor constructs the temperature field of the ccSCR catalyst, and the first urea injection amount is corrected according to the temperature field of the ccSCR catalyst to obtain the first corrected urea injection amount. 4. The diesel exhaust after-treatment system according to claim 3, wherein the after-treatment controller is further used to determine whether the ccSCR system is working based on the temperature collected by the ccSCR front exhaust temperature sensor. 5. The diesel exhaust after-treatment system according to claim 3, wherein the SCR system includes an SCR front exhaust temperature sensor and an SCR catalytic converter installed on the diesel exhaust pipe. The temperature sensor is located between the CDPF system and the SCR catalytic converter; the ASC system includes an ASC catalytic converter installed on the diesel exhaust pipe and an ASC rear exhaust temperature sensor, and the ASC catalytic converter is located on the Between the SCR catalytic converter and the ASC rear exhaust temperature sensor; The SCR front exhaust temperature sensor and the ASC rear exhaust temperature sensor are both communicatively connected with the post-processing controller; the post-processing controller is used to measure the temperature collected by the SCR front exhaust temperature sensor and the ASC rear exhaust temperature sensor. The temperature collected by the temperature sensor constructs the temperature field of the SCR catalyst, and the second urea injection amount is corrected according to the temperature field of the SCR catalyst to obtain the second corrected urea injection amount. 6. The diesel exhaust after-treatment system according to claim 5, characterized in that the after-treatment controller is also used to determine whether the SCR system is working based on the temperature collected by the SCR front exhaust temperature sensor. 7. The diesel exhaust after-treatment system according to claim 5, wherein the ccSCR system further includes a ccSCR front-stage nozzle installed on the diesel engine exhaust pipe, and the ccSCR front-stage nozzle is located on the between the diesel engine and the ccSCR catalytic converter; the ccSCR front-end nozzle is controllably connected to the after-treatment controller; the ccSCR front-end nozzle is used to inject exhaust gas into the diesel engine under the control of the after-treatment controller. Inject the first corrected urea injection amount of urea into the exhaust pipe; The SCR system also includes an SCR rear-stage nozzle installed on the diesel engine exhaust pipe. The SCR rear-stage nozzle is located between the CDPF system and the SCR catalytic converter; the SCR rear-stage nozzle is connected to the SCR catalytic converter. The after-treatment controller controls the connection; the SCR rear-stage nozzle is used to inject the second corrected urea injection amount of urea into the diesel engine exhaust pipe under the control of the after-treatment controller. 8. The diesel exhaust after-treatment system according to claim 7, characterized in that the diesel exhaust after-treatment system further includes a urea injection device, and the urea injection device is connected to the ccSCR front-stage nozzle and the SCR rear-stage nozzle respectively. The first-stage nozzles are connected; the urea injection device is used to provide urea to the ccSCR front-stage nozzle and the SCR rear-stage nozzle. 9. The diesel exhaust after-treatment system according to claim 8, wherein the urea injection device includes a urea tank and a urea pump; the urea tank is used to store urea; and the urea pump is connected to the urea tank respectively. The ccSCR front-stage nozzle and the SCR rear-stage nozzle are connected, and the urea pump is used to extract urea from the urea tank and provide urea to the ccSCR front-stage nozzle and the SCR rear-stage nozzle. 10. The diesel exhaust after-treatment system according to claim 3, wherein the CDPF system includes a CDPF differential pressure sensor, a CDPF front exhaust temperature sensor, a CDPF catalytic converter and a CDPF front exhaust temperature sensor installed on the diesel exhaust pipe. CDPF rear exhaust temperature sensor; the CDPF front exhaust temperature sensor is located between the DOC catalytic converter and the CDPF catalytic converter, the CDPF differential pressure sensor is connected to the CDPF catalytic converter, and the CDPF rear exhaust temperature sensor Located between the CDPF catalyst and the SCR system; The CDPF front exhaust temperature sensor, the CDPF differential pressure sensor and the CDPF rear exhaust temperature sensor are all communicatively connected with the post-processing controller; the post-processing controller is used to collect the data according to the DOC front exhaust temperature sensor. temperature, the temperature collected by the CDPF front exhaust temperature sensor, the temperature collected by the CDPF rear exhaust temperature sensor and the pressure difference collected by the CDPF differential pressure sensor determine the amount of water injected into the DOC catalytic converter to achieve the CDPF catalysis The amount of HC injection for carrier regeneration in the device.