CN109763883B - Method, device and system for detecting ammonia gas leakage of SCR system - Google Patents

Method, device and system for detecting ammonia gas leakage of SCR system Download PDF

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CN109763883B
CN109763883B CN201910110057.XA CN201910110057A CN109763883B CN 109763883 B CN109763883 B CN 109763883B CN 201910110057 A CN201910110057 A CN 201910110057A CN 109763883 B CN109763883 B CN 109763883B
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selective catalytic
reduction device
catalytic reduction
outlet
inlet
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CN109763883A (en
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卢丰翥
刘法学
张斌
张克平
吴伟涛
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Wuxi Weifu Lida Catalytic Converter Co Ltd
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Wuxi Weifu Lida Catalytic Converter Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Abstract

The invention relates to the technical field of diesel engine post-treatment, and particularly discloses a method for detecting ammonia gas leakage of an SCR system, which comprises the following steps: calculating the urea injection quantity at the inlet of the oxidation catalyst; injecting urea to the first selective catalytic reduction device; calculating the urea injection quantity at the inlet of the second selective catalytic reduction device; judging whether the temperature of the second selective catalytic reducer meets a second reaction temperature range or not; injecting urea to the second selective catalytic reducer; making a difference between the NOx emission at the outlet of the second selective catalytic reduction device and the NOx emission at the inlet of the oxidation catalyst to obtain a difference result; judging whether the difference result is greater than or equal to a second preset threshold value or not; if so, judging that the ammonia gas at the outlet of the first selective catalytic reducer leaks. The invention also discloses a detection device for ammonia gas leakage of the SCR system and the SCR system. The method for detecting ammonia gas leakage of the SCR system can judge whether the ammonia gas leaks or not, and has the advantages of being simple to implement and convenient to operate.

Description

Method, device and system for detecting ammonia gas leakage of SCR system
Technical Field
The invention relates to the technical field of diesel engine aftertreatment, in particular to a method and a device for detecting ammonia gas leakage of an SCR system and the SCR system comprising the device.
Background
The mainstream technical route of the national six-stage Diesel engine tail gas aftertreatment is DOC (Diesel oxidation Catalyst), DPF (Diesel particulate Filter), SCR (Selective catalytic Reduction), wherein the SCR mainly functions to reduce NO in the Diesel engine tail gasXHowever, the current mainstream NOx sensors on the market have NH3And NOXCross-sensitivity of (1), indistinguishable as NH3Leak or NOXExcessive dischargeResulting in NO at the SCR outletXDuring detection, NH will appear3Misjudgment of leakage as NOXThus, the urea injection amount is increased so that the more urea is injected, the vicious circle is formed.
Disclosure of Invention
The invention aims to at least solve one of the technical problems in the prior art, and provides a detection method of ammonia gas leakage of an SCR system, a detection device of ammonia gas leakage of the SCR system and the SCR system comprising the detection device of ammonia gas leakage of the SCR system, so as to solve the problems in the prior art.
As a first aspect of the present invention, a method for detecting ammonia gas leakage from an SCR system is provided, where the SCR system includes a diesel exhaust after-treatment device, the diesel exhaust after-treatment device includes an oxidation catalyst, a diesel particulate filter, a first selective catalytic reducer, and a second selective catalytic reducer, which are connected in sequence, and the method for detecting ammonia gas leakage from the SCR system includes:
calculating the urea injection quantity at the inlet of the oxidation catalyst according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the inlet of the oxidation catalyst;
when the temperature of the first selective catalytic reduction device meets a first reaction temperature range, injecting urea to the first selective catalytic reduction device;
calculating the urea injection quantity of the inlet of the second selective catalytic reduction device according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity of the outlet of the first selective catalytic reduction device;
when the urea injection amount at the inlet of the second selective catalytic reduction device is larger than a first preset threshold value, judging whether the temperature of the second selective catalytic reduction device meets a second reaction temperature range;
if the temperature of the second selective catalytic reducer meets a second reaction temperature range, spraying urea to the second selective catalytic reducer;
acquiring the NOx emission at the outlet of the second selective catalytic reduction device, and making a difference between the NOx emission at the outlet of the second selective catalytic reduction device and the NOx emission at the inlet of the oxidation catalyst to obtain a difference result;
judging whether the difference result is greater than or equal to a second preset threshold value or not;
and if the difference result is greater than or equal to the second preset threshold, judging that the ammonia gas at the outlet of the first selective catalytic reduction device leaks.
Preferably, the method for detecting ammonia gas leakage of the SCR system further comprises:
if the difference result is smaller than the second preset threshold, judging that the NOx emission amount of the outlet of the first selective catalytic reduction device is too much;
calculating the urea injection quantity at the outlet of the second selective catalytic reduction device according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the outlet of the second selective catalytic reduction device;
calculating the total urea injection quantity according to the urea injection quantity at the inlet of the oxidation catalyst and the urea injection quantity at the outlet of the second selective catalytic reduction device;
injecting urea to the first selective catalytic reduction device according to the total urea injection amount.
Preferably, the method for detecting ammonia gas leakage of the SCR system comprises, before the step of injecting urea to the first selective catalytic reducer when the temperature of the first selective catalytic reducer satisfies the first reaction temperature range:
judging whether the temperature of the first selective catalytic reducer is in a first reaction temperature range or not;
if the temperature of the first selective catalytic reducer is within a first reaction temperature range, the temperature of the first selective catalytic reducer satisfies the first reaction temperature range.
Preferably, the first reaction temperature range includes an outlet temperature greater than the first selective catalytic reducer and an inlet temperature less than the first selective catalytic reducer.
Preferably, the method for detecting ammonia gas leakage of the SCR system comprises:
and if the temperature of the second selective catalytic reducer does not meet the second reaction temperature range, heating the second selective catalytic reducer.
Preferably, the second reaction temperature range includes an outlet temperature greater than the second selective catalytic reducer and an inlet temperature less than the second selective catalytic reducer.
As a second aspect of the present invention, there is provided a device for detecting ammonia gas leakage from an SCR system, wherein the SCR system includes a diesel exhaust gas after-treatment device, the diesel exhaust gas after-treatment device includes an oxidation catalyst, a diesel particulate filter, a first selective catalytic reducer, and a second selective catalytic reducer, which are connected in sequence, and the device for detecting ammonia gas leakage from an SCR system includes:
the first urea injection quantity calculating module is used for calculating the urea injection quantity at the inlet of the oxidation catalyst according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the inlet of the oxidation catalyst;
the first injection control module is used for injecting urea to the first selective catalytic reduction device when the temperature of the first selective catalytic reduction device meets a first reaction temperature range;
the second urea injection quantity calculating module is used for calculating the urea injection quantity at the inlet of the second selective catalytic reducer according to the engine speed, the oil consumption, the exhaust gas mass flow of the tail gas and the NOx emission quantity at the outlet of the first selective catalytic reducer;
the temperature judgment module is used for judging whether the temperature of the second selective catalytic reduction device meets a second reaction temperature range or not when the urea injection amount at the inlet of the second selective catalytic reduction device is larger than a first preset threshold;
the second injection control module is used for injecting urea to the second selective catalytic reduction device if the temperature of the second selective catalytic reduction device meets a second reaction temperature range;
the difference value calculating module is used for obtaining the NOx emission amount of the outlet of the second selective catalytic reduction device and making a difference value between the NOx emission amount of the outlet of the second selective catalytic reduction device and the NOx emission amount of the inlet of the oxidation catalytic converter to obtain a difference value result;
the difference value judging module is used for judging whether the difference value result is larger than or equal to a second preset threshold value or not;
and the ammonia gas leakage judging module is used for judging ammonia gas leakage at the outlet of the first selective catalytic reduction device if the difference result is greater than or equal to the second preset threshold value.
Preferably, the device for detecting ammonia gas leakage of the SCR system further comprises:
the excessive NOx emission determining module is used for determining that the NOx emission at the outlet of the first selective catalytic reduction device is excessive if the difference result is smaller than the second preset threshold;
the third urea injection quantity calculating module is used for calculating the urea injection quantity at the outlet of the second selective catalytic reduction device according to the engine speed, the oil consumption, the exhaust gas mass flow of the tail gas and the NOx emission quantity at the outlet of the second selective catalytic reduction device;
the total urea injection quantity calculating module is used for calculating the total urea injection quantity according to the urea injection quantity at the inlet of the oxidation catalyst and the urea injection quantity at the outlet of the second selective catalytic reduction device;
a urea injection module to inject urea to the first selective catalytic reducer based on the total urea injection amount.
As a third aspect of the present invention, an SCR system is provided, where the SCR system includes a diesel exhaust gas aftertreatment device, a control device, and the aforementioned detection device for ammonia gas leakage from the SCR system, the diesel exhaust gas aftertreatment device includes an oxidation catalyst, a diesel particulate filter, a first selective catalytic reduction device, and a second selective catalytic reduction device, which are connected in sequence, the oxidation catalyst, the diesel particulate filter, the first selective catalytic reduction device, and the second selective catalytic reduction device are all in communication connection with the detection device for ammonia gas leakage from the SCR system, the detection device for ammonia gas leakage from the SCR system is in communication connection with the control device, and the detection device for ammonia gas leakage from the SCR system is used to detect whether ammonia gas leaks from an outlet of the first selective catalytic reduction device under the control of the control device.
Preferably, the SCR system further comprises a first NOx sensor, a first urea nozzle, a second NOx sensor, a second urea nozzle, a third NOx sensor, a first temperature sensor, a second temperature sensor, a third temperature sensor, and an SCR heating module,
the first NOx sensor is arranged at the inlet of the oxidation catalyst and used for detecting the NOx discharge amount of the inlet of the oxidation catalyst;
the second NOx sensor is arranged at the outlet of the first selective catalytic reduction device and used for detecting the NOx emission amount at the outlet of the first selective catalytic reduction device;
the third NOx sensor is arranged at the outlet of the second selective catalytic reducer and used for detecting the NOx emission amount at the outlet of the second selective catalytic reducer;
the first urea nozzle is arranged at the inlet of the first selective catalytic reduction device and used for spraying urea to the first selective catalytic reduction device;
the second urea nozzle is arranged at the inlet of the second selective catalytic reduction device and used for spraying urea to the second selective catalytic reduction device;
the first temperature sensor is arranged at the inlet of the first selective catalytic reducer and used for detecting the inlet temperature of the first selective catalytic reducer;
the second temperature sensor is disposed between the first selective catalytic reducer and the second selective catalytic reducer, and is configured to detect an outlet temperature of the first selective catalytic reducer and an inlet temperature of the second selective catalytic reducer;
the third temperature sensor is arranged at the outlet of the second selective catalytic reducer and used for detecting the outlet temperature of the second selective catalytic reducer;
the SCR heating module is arranged at the inlet of the second selective catalytic reduction device and used for heating the second selective catalytic reduction device.
According to the method for detecting the ammonia gas leakage of the SCR system, the selective catalytic reducer is added on the basis of the existing diesel engine tail gas aftertreatment device, then the urea amount is sprayed to the newly added selective catalytic reducer, and whether the ammonia gas is leaked or not is judged by judging the difference result of the NOx emission amount at the outlet of the second selective catalytic reducer and the NOx emission amount at the inlet of the oxidation catalyst and the size of the second preset threshold value.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a flow chart of a method for detecting ammonia gas leakage of an SCR system provided by the invention.
Fig. 2 is a schematic structural diagram of an SCR system provided in the present invention.
Fig. 3 is a flowchart of an embodiment of a method for detecting ammonia gas leakage of an SCR system according to the present invention.
Fig. 4 is a block diagram of a structure of a device for detecting ammonia gas leakage in an SCR system according to the present invention.
Fig. 5 is a block diagram of an SCR system according to the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
As a first aspect of the present invention, there is provided a method for detecting ammonia gas leakage from an SCR system, wherein, as shown in fig. 1 and 2, the SCR system includes a diesel exhaust after-treatment device including an oxidation catalyst DOC, a diesel particulate filter DPF, a first selective catalytic reducer SCR1, and a second selective catalytic reducer SCR2, which are connected in sequence, the method for detecting ammonia gas leakage from an SCR system includes:
s110, calculating urea injection quantity of the DOC inlet of the oxidation catalyst according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity of the DOC inlet of the oxidation catalyst;
s120, when the temperature of the first selective catalytic reducer SCR1 meets a first reaction temperature range, injecting urea to the first selective catalytic reducer SCR 1;
s130, calculating urea injection quantity at the inlet of a second selective catalytic reduction device SCR2 according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the outlet of the first selective catalytic reduction device SCR 1;
s140, when the urea injection quantity of the inlet of the second selective catalytic reduction device SCR2 is larger than a first preset threshold value, judging whether the temperature of the second selective catalytic reduction device SCR2 meets a second reaction temperature range;
s150, if the temperature of the second selective catalytic reduction device SCR2 meets a second reaction temperature range, urea is injected into the second selective catalytic reduction device SCR 2;
s160, acquiring the NOx emission amount of the outlet of the second selective catalytic reducer SCR2, and making a difference between the NOx emission amount of the outlet of the second selective catalytic reducer SCR2 and the NOx emission amount of the inlet of the oxidation catalyst DOC to obtain a difference result;
s170, judging whether the difference result is larger than or equal to a second preset threshold value;
and S180, if the difference result is larger than or equal to the second preset threshold, judging that the ammonia gas at the outlet of the first selective catalytic reduction device SCR1 leaks.
According to the method for detecting the ammonia gas leakage of the SCR system, the selective catalytic reducer is added on the basis of the existing diesel engine tail gas aftertreatment device, then the urea amount is sprayed to the newly added selective catalytic reducer, and whether the ammonia gas is leaked or not is judged by judging the difference result of the NOx emission amount at the outlet of the second selective catalytic reducer and the NOx emission amount at the inlet of the oxidation catalyst and the size of the second preset threshold value.
It should be noted that both the first preset threshold and the second preset threshold may be calibrated in advance, and may be calibrated according to different SCR average temperatures and exhaust gas qualities of the engine. For example, the first predetermined threshold may be rated at 20PPM when the engine exhaust mass flow rate is 300kg/h and the average temperature of the SCR1 is 250 ℃, and may be rated at 15PPM when the engine exhaust mass flow rate is 400 kg/h and the average temperature of the SCR1 is 350 ℃. It should be understood that the first preset threshold may be considered as a map, a corresponding value is searched according to different exhaust mass flow rates and different average temperatures of the SCR, and the size of the corresponding value may be set according to requirements, that is, if it is considered that the NOx emission is within 20PPM of the whole emission cycle, it is determined how the whole map is calibrated according to the condition. Similarly, the second predetermined threshold value is also calibrated for different exhaust mass flow rates and average temperature of SCR2, and this value is compared to the difference between the two NOx sensors.
Specifically, the method for detecting ammonia gas leakage of the SCR system further includes:
if the difference result is smaller than the second preset threshold, determining that the NOx emission amount of the SCR1 outlet is too much;
calculating the urea injection quantity at the outlet of the second selective catalytic reducer SCR2 according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the outlet of the second selective catalytic reducer SCR 2;
calculating the total urea injection quantity according to the urea injection quantity at the DOC inlet of the oxidation catalyst and the urea injection quantity at the SCR2 outlet of the second selective catalytic reduction device;
injecting urea to the first selective catalytic reduction SCR1 according to the total urea injection amount.
Specifically, the method for detecting the ammonia gas leakage of the SCR system comprises the following steps of, when the temperature of the first selective catalytic reducer SCR1 meets the first reaction temperature range, injecting urea to the first selective catalytic reducer SCR 1:
determining whether the temperature of the first selective catalytic reducer SCR1 is within a first reaction temperature range;
if the temperature of the first selective catalytic reducer SCR1 is within a first reaction temperature range, the temperature of the first selective catalytic reducer satisfies the first reaction temperature range.
Preferably, the first reaction temperature range includes an outlet temperature greater than the first selective catalytic reducer and less than an inlet temperature of the first selective catalytic reducer SCR 1.
Specifically, the method for detecting ammonia gas leakage of the SCR system comprises the following steps:
heating the second SCR2 if the temperature of the second SCR2 does not meet a second reaction temperature range.
Preferably, the second reaction temperature range includes an outlet temperature greater than the second selective catalytic reducer SCR2 and less than an inlet temperature of the second selective catalytic reducer SCR 2.
The method for detecting ammonia gas leakage of the SCR system provided by the present invention is described in detail below with reference to fig. 3.
As shown in fig. 2, after the engine starts to operate, a DCU (Drive Control Unit) first calculates the urea injection amount at the inlet of the oxidation catalyst according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission amount at the inlet of the oxidation catalyst detected by the first NOx sensor 1, and when the temperature of the first selective catalytic reduction SCR1 meets the average value requirement of the first temperature sensor 7 and the second temperature sensor 8, the first correction module applies the urea injection amount to the first urea injection nozzle 2 to perform urea injection. After the injected urea passes through the SCR1, the injected urea is detected by the second NOx sensor 3, and since the characteristics of the existing NOx sensor on the market cannot distinguish NOx from NH3, there may be two situations of gas passing through the position of the second NOx sensor 3, one is NH3 leakage caused by over-injection of the first urea nozzle 2, and the other is NOx discharge caused by under-injection of the first urea nozzle 2, and in any case, as long as the detected value of the second NOx sensor 3 is too large and larger than the first preset threshold value under the working condition, the gas enters the injection delay module, and if the average temperature of the second selective catalytic reduction SCR2 (i.e. the average value of the second temperature sensor 8 and the third temperature sensor 9) is smaller than the urea injection limit, the SCR heating module 5 starts to heat the SCR 2; if the average SCR2 temperature meets the urea injection requirements, heating of the SCR2 is not required. After heating is completed, the second urea nozzle 4 starts to inject a small amount of urea, meanwhile, the injection delay module transmits a signal to the third NOx sensor 6, the first NOx sensor 1 and the third NOx sensor 6 are subjected to difference, the difference result is compared with a second preset threshold, if the difference result is larger than or equal to the second preset threshold, the gas passing through the SCR2 contains a large amount of NOx, the gas passes through the SCR2 and reacts with NH3, and the NOx value is reduced; conversely, if the difference result is less than the second predetermined threshold, indicating that the gas passing through the SCR2 is NH3, and the second urea injector 4 injects a small amount of NH3, the NH3 slip at the outlet of the SCR2 is further increased.
After detecting whether the SCR2 outlet gas is NOx or NH3 leakage, the information is fed back to a DCU (digital control unit), and the DCU controls a first urea injection quantity calculation module to perform over-injection or under-injection of urea, so that the SCR2 outlet gas has no NH3 leakage or NOx discharge, and the balance of reaction is achieved.
As a second aspect of the present invention, there is provided a device for detecting ammonia gas leakage from an SCR system, wherein the SCR system includes a diesel exhaust after-treatment device, the diesel exhaust after-treatment device includes an oxidation catalyst, a diesel particulate filter, a first selective catalytic reducer, and a second selective catalytic reducer, which are connected in sequence, and as shown in fig. 4, the device 100 for detecting ammonia gas leakage from an SCR system includes:
a first urea injection quantity calculation module 110, wherein the first urea injection quantity calculation module 110 is used for calculating the urea injection quantity at the inlet of the oxidation catalyst according to the engine speed, the oil consumption quantity, the exhaust gas mass flow and the NOx emission quantity at the inlet of the oxidation catalyst;
a first injection control module 120, the first injection control module 120 to inject urea to a first selective catalytic reducer when a temperature of the first selective catalytic reducer satisfies a first reaction temperature range;
a second urea injection quantity calculating module 130, wherein the second urea injection quantity calculating module 130 is used for calculating the urea injection quantity at the inlet of the second selective catalytic reducer according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the outlet of the first selective catalytic reducer;
the temperature judgment module 140 is used for judging whether the temperature of the second selective catalytic reduction device meets a second reaction temperature range or not when the urea injection amount at the inlet of the second selective catalytic reduction device is larger than a first preset threshold;
a second injection control module 150, wherein the second injection control module 150 is configured to inject urea to the second selective catalytic reducer if the temperature of the second selective catalytic reducer satisfies a second reaction temperature range;
a difference calculation module 160, wherein the difference calculation module 160 is configured to obtain the NOx emission at the outlet of the second selective catalytic reduction device, and make a difference between the NOx emission at the outlet of the second selective catalytic reduction device and the NOx emission at the inlet of the oxidation catalyst device to obtain a difference result;
a difference value determining module 170, where the difference value determining module 170 is configured to determine whether the difference value result is greater than or equal to a second preset threshold;
and the ammonia gas leakage judging module 180 is used for judging ammonia gas leakage at the outlet of the first selective catalytic reducer if the difference result is greater than or equal to the second preset threshold value.
The detection device for ammonia gas leakage of the SCR system provided by the invention has the advantages that whether ammonia gas leaks or not can be judged by adding the selective catalytic reducer on the basis of the existing diesel engine tail gas aftertreatment device, then spraying urea quantity to the newly added selective catalytic reducer and judging the difference result of the NOx discharge quantity at the outlet of the second selective catalytic reducer and the NOx discharge quantity at the inlet of the oxidation catalyst and the size of the second preset threshold value, and the detection device for ammonia gas leakage of the SCR system can judge whether ammonia gas leaks or not after passing through the first selective catalytic reducer, and is simple to realize and convenient to operate.
Specifically, the detection device for ammonia gas leakage of the SCR system further includes:
the excessive NOx emission determining module is used for determining that the NOx emission at the outlet of the first selective catalytic reduction device is excessive if the difference result is smaller than the second preset threshold;
the third urea injection quantity calculating module is used for calculating the urea injection quantity at the outlet of the second selective catalytic reduction device according to the engine speed, the oil consumption, the exhaust gas mass flow of the tail gas and the NOx emission quantity at the outlet of the second selective catalytic reduction device;
the total urea injection quantity calculating module is used for calculating the total urea injection quantity according to the urea injection quantity at the inlet of the oxidation catalyst and the urea injection quantity at the outlet of the second selective catalytic reduction device;
a urea injection module to inject urea to the first selective catalytic reducer based on the total urea injection amount.
It should be noted that the first injection control module 120 corresponds to a first correction module in fig. 3, and the second injection control module 150 corresponds to a second correction module in fig. 3.
The working principle of the device for detecting ammonia gas leakage from an SCR system provided by the present invention can refer to the description of the method for detecting ammonia gas leakage from an SCR system, and is not described herein again.
As a third aspect of the present invention, there is provided an SCR system in which, as shown in fig. 2 and 5, the SCR system 10 comprises a diesel exhaust after-treatment device 200, a control device 300 and the aforementioned device 100 for detecting ammonia gas leakage from the SCR system, the SCR system oil engine post-processor device 200 includes an oxidation catalyst DOC, a diesel particulate trap DPF, a first selective catalytic reduction device SCR1, and a second selective catalytic reduction device SCR2 which are sequentially connected, the oxidation catalyst DOC, the diesel particulate filter DPF, the first selective catalytic reducer SCR1 and the second selective catalytic reducer SCR2 are all in communication connection with the detection device 100 for ammonia gas leakage of the SCR system, the device 100 for detecting ammonia gas leakage of the SCR system is in communication connection with the control device 300, the device 100 for detecting ammonia gas leakage of the SCR system is used for detecting whether ammonia gas at the outlet of the first selective catalytic reducer SCR1 leaks or not under the control of the control device 300.
According to the SCR system provided by the invention, the selective catalytic reducer is added on the basis of the existing diesel engine tail gas aftertreatment device, then the urea amount is sprayed to the newly added selective catalytic reducer, and whether the ammonia gas leaks or not is judged by judging the difference result of the NOx discharge amount at the outlet of the second selective catalytic reducer and the NOx discharge amount at the inlet of the oxidation catalyst and the size of the second preset threshold value.
Specifically, as shown in FIG. 2, the SCR system further includes a first NOx sensor 1, a first urea nozzle 2, a second NOx sensor 3, a second urea nozzle 4, a third NOx sensor 6, a first temperature sensor 7, a second temperature sensor 8, a third temperature sensor 9, and an SCR heating module 5,
the first NOx sensor 1 is arranged at the inlet of the oxidation catalyst DOC and used for detecting the NOx emission amount at the inlet of the oxidation catalyst DOC;
the second NOx sensor 3 is provided at the outlet of the first selective catalytic reducer SCR1 for detecting the amount of NOx emissions at the outlet of the first selective catalytic reducer SCR 1;
the third NOx sensor 6 is provided at the outlet of the second selective catalytic reducer SCR2 for detecting the amount of NOx emissions at the outlet of the second selective catalytic reducer SCR 2;
the first urea nozzle 2 is disposed at an inlet of the first selective catalytic reduction SCR1 for injecting urea to the first selective catalytic reduction SCR 1;
the second urea nozzle 4 is disposed at an inlet of the second selective catalytic reduction SCR2 for injecting urea to the second selective catalytic reduction SCR 2;
the first temperature sensor 7 is disposed at an inlet of the first selective catalytic reducer SCR1 for detecting an inlet temperature of the first selective catalytic reducer SCR 1;
the second temperature sensor 8 is disposed between the first selective catalytic reducer SCR1 and the second selective catalytic reducer SCR2 for detecting an outlet temperature of the first selective catalytic reducer SCR1 and an inlet temperature of the second selective catalytic reducer SCR 2;
the third temperature sensor 9 is arranged at the outlet of the second SCR2 for detecting the outlet temperature of the second SCR 2;
the SCR heating module 5 is disposed at an inlet of the second SCR2 for heating the second SCR 2.
Preferably, the control means comprises a DCU.
It should be noted that the first reaction temperature range mentioned above preferably includes a temperature value greater than the average value of the first temperature sensor 7 and the second temperature sensor 8 and less than the inlet temperature of the first selective catalytic reducer SCR1, and since the first temperature sensor 7 is used for detecting the inlet temperature of the first selective catalytic reducer SCR1, the first reaction temperature range preferably includes a temperature value greater than the average value of the first temperature sensor 7 and the second temperature sensor 8 and less than the temperature value of the first temperature sensor 7.
The aforementioned second reaction temperature range preferably includes a temperature value greater than the average of the second and third temperature sensors 8 and 9 and less than the inlet temperature of the second selective catalytic reducer SCR2, and since the second temperature sensor 8 is used to detect the inlet temperature of the second selective catalytic reducer SCR2, the second reaction temperature range preferably includes a temperature value greater than the average of the second and third temperature sensors 8 and 9 and less than the second temperature sensor 8.
For the specific operation process of the SCR system provided by the present invention, reference may be made to the foregoing description of the method for detecting ammonia gas leakage of the SCR system, and details are not described herein again.
Therefore, the method, the device and the SCR system for detecting ammonia gas leakage of the SCR system can effectively distinguish whether the gas component at the outlet of the SCR2 is NOx or NH3, and feed back the result, so that the urea nozzle 1 can accurately inject urea; providing two urea nozzles, wherein the two urea nozzles are respectively arranged on a first urea nozzle at the front end of an SCR1 and a second urea nozzle at the front end of an SCR2, the first urea nozzle is a working nozzle, a certain amount of urea is injected to react NOx in exhaust gas during the operation of an engine, and the second urea nozzle is a detection nozzle and is used for injecting a small amount of urea to detect whether gas at an SCR2 outlet is NOx or NH3 leakage; the invention arranges two levels of SCR, namely SCR1 and SCR2, wherein the front end of the SCR2 is provided with an electric heating function, when the average temperature of the SCR2 is lower than a temperature limit value, a heating module is started, and when the average temperature of the SCR2 is higher than the temperature limit value, the heating module is closed. Therefore, the method has the advantages that on the basis of not changing the characteristics of the NOx sensor, the SCR outlet gas is effectively distinguished from NH3 leakage or NOx emission through control logic operation; there is no major change in post-processing configuration and so it is easier to produce and apply.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims (10)

1. The method for detecting the ammonia gas leakage of the SCR system is characterized in that the SCR system comprises a diesel engine tail gas aftertreatment device, the diesel engine tail gas aftertreatment device comprises an oxidation catalyst, a diesel particulate filter, a first selective catalytic reducer and a second selective catalytic reducer which are sequentially connected, and the method for detecting the ammonia gas leakage of the SCR system comprises the following steps:
calculating the urea injection quantity at the inlet of the oxidation catalyst according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the inlet of the oxidation catalyst;
when the temperature of the first selective catalytic reduction device meets a first reaction temperature range, injecting urea to the first selective catalytic reduction device;
calculating the urea injection quantity of the inlet of the second selective catalytic reduction device according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity of the outlet of the first selective catalytic reduction device;
when the urea injection amount at the inlet of the second selective catalytic reduction device is larger than a first preset threshold value, judging whether the temperature of the second selective catalytic reduction device meets a second reaction temperature range;
if the temperature of the second selective catalytic reducer meets a second reaction temperature range, spraying urea to the second selective catalytic reducer;
acquiring the NOx emission at the outlet of the second selective catalytic reduction device, and making a difference between the NOx emission at the outlet of the second selective catalytic reduction device and the NOx emission at the inlet of the oxidation catalyst to obtain a difference result;
judging whether the difference result is greater than or equal to a second preset threshold value or not;
and if the difference result is greater than or equal to the second preset threshold, judging that the ammonia gas at the outlet of the first selective catalytic reduction device leaks.
2. The method for detecting ammonia gas slip of an SCR system according to claim 1, further comprising:
if the difference result is smaller than the second preset threshold, judging that the NOx emission amount of the outlet of the first selective catalytic reduction device is too much;
calculating the urea injection quantity at the outlet of the second selective catalytic reduction device according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the outlet of the second selective catalytic reduction device;
calculating the total urea injection quantity according to the urea injection quantity at the inlet of the oxidation catalyst and the urea injection quantity at the outlet of the second selective catalytic reduction device;
injecting urea to the first selective catalytic reduction device according to the total urea injection amount.
3. The method of detecting ammonia slip in an SCR system of claim 1, comprising, prior to the step of injecting urea into the first SCR when the temperature of the first SCR satisfies the first reaction temperature range:
judging whether the temperature of the first selective catalytic reducer is in a first reaction temperature range or not;
if the temperature of the first selective catalytic reducer is within a first reaction temperature range, the temperature of the first selective catalytic reducer satisfies the first reaction temperature range.
4. The method of detecting ammonia slip in an SCR system of claim 1 or 3, wherein the first reaction temperature range comprises greater than an outlet temperature of the first selective catalytic reducer and less than an inlet temperature of the first selective catalytic reducer.
5. The method for detecting ammonia gas leakage from an SCR system according to claim 1, wherein the method for detecting ammonia gas leakage from an SCR system comprises:
and if the temperature of the second selective catalytic reducer does not meet the second reaction temperature range, heating the second selective catalytic reducer.
6. The method of detecting ammonia slip in an SCR system of claim 1 or 5, wherein the second reaction temperature range comprises greater than an outlet temperature of the second SCR and less than an inlet temperature of the second SCR.
7. The utility model provides a detection device that SCR system ammonia was revealed which characterized in that, the SCR system includes diesel engine tail gas aftertreatment device, diesel engine tail gas aftertreatment device is including oxidation catalyst converter, diesel particulate filter, first selective catalytic reduction ware and the second selective catalytic reduction ware that connect gradually, detection device that SCR system ammonia was revealed includes:
the first urea injection quantity calculating module is used for calculating the urea injection quantity at the inlet of the oxidation catalyst according to the engine speed, the oil consumption, the exhaust gas mass flow and the NOx emission quantity at the inlet of the oxidation catalyst;
the first injection control module is used for injecting urea to the first selective catalytic reduction device when the temperature of the first selective catalytic reduction device meets a first reaction temperature range;
the second urea injection quantity calculating module is used for calculating the urea injection quantity at the inlet of the second selective catalytic reducer according to the engine speed, the oil consumption, the exhaust gas mass flow of the tail gas and the NOx emission quantity at the outlet of the first selective catalytic reducer;
the temperature judgment module is used for judging whether the temperature of the second selective catalytic reduction device meets a second reaction temperature range or not when the urea injection amount at the inlet of the second selective catalytic reduction device is larger than a first preset threshold;
the second injection control module is used for injecting urea to the second selective catalytic reduction device if the temperature of the second selective catalytic reduction device meets a second reaction temperature range;
the difference value calculating module is used for obtaining the NOx emission amount of the outlet of the second selective catalytic reduction device and making a difference value between the NOx emission amount of the outlet of the second selective catalytic reduction device and the NOx emission amount of the inlet of the oxidation catalytic converter to obtain a difference value result;
the difference value judging module is used for judging whether the difference value result is larger than or equal to a second preset threshold value or not;
and the ammonia gas leakage judging module is used for judging ammonia gas leakage at the outlet of the first selective catalytic reduction device if the difference result is greater than or equal to the second preset threshold value.
8. The apparatus for detecting ammonia gas slip of an SCR system of claim 7, further comprising:
the excessive NOx emission determining module is used for determining that the NOx emission at the outlet of the first selective catalytic reduction device is excessive if the difference result is smaller than the second preset threshold;
the third urea injection quantity calculating module is used for calculating the urea injection quantity at the outlet of the second selective catalytic reduction device according to the engine speed, the oil consumption, the exhaust gas mass flow of the tail gas and the NOx emission quantity at the outlet of the second selective catalytic reduction device;
the total urea injection quantity calculating module is used for calculating the total urea injection quantity according to the urea injection quantity at the inlet of the oxidation catalyst and the urea injection quantity at the outlet of the second selective catalytic reduction device;
a urea injection module to inject urea to the first selective catalytic reducer based on the total urea injection amount.
9. An SCR system, characterized in that, the SCR system includes a diesel engine exhaust after-treatment device, a control device and a detection device for detecting ammonia gas leakage of the SCR system as claimed in claim 7 or 8, the diesel engine exhaust after-treatment device includes an oxidation catalyst, a diesel particulate trap, a first selective catalytic reduction device and a second selective catalytic reduction device which are connected in sequence, the oxidation catalyst, the diesel particulate trap, the first selective catalytic reduction device and the second selective catalytic reduction device are all in communication connection with the detection device for ammonia gas leakage of the SCR system, the detection device for ammonia gas leakage of the SCR system is in communication connection with the control device, and the detection device for ammonia gas leakage of the SCR system is used for detecting whether ammonia gas leakage at the outlet of the first selective catalytic reduction device is detected under the control of the control device.
10. The SCR system of claim 9, further comprising a first NOx sensor, a first urea nozzle, a second NOx sensor, a second urea nozzle, a third NOx sensor, a first temperature sensor, a second temperature sensor, a third temperature sensor, and an SCR heating module,
the first NOx sensor is arranged at the inlet of the oxidation catalyst and used for detecting the NOx discharge amount of the inlet of the oxidation catalyst;
the second NOx sensor is arranged at the outlet of the first selective catalytic reduction device and used for detecting the NOx emission amount at the outlet of the first selective catalytic reduction device;
the third NOx sensor is arranged at the outlet of the second selective catalytic reducer and used for detecting the NOx emission amount at the outlet of the second selective catalytic reducer;
the first urea nozzle is arranged at the inlet of the first selective catalytic reduction device and used for spraying urea to the first selective catalytic reduction device;
the second urea nozzle is arranged at the inlet of the second selective catalytic reduction device and used for spraying urea to the second selective catalytic reduction device;
the first temperature sensor is arranged at the inlet of the first selective catalytic reducer and used for detecting the inlet temperature of the first selective catalytic reducer;
the second temperature sensor is disposed between the first selective catalytic reducer and the second selective catalytic reducer, and is configured to detect an outlet temperature of the first selective catalytic reducer and an inlet temperature of the second selective catalytic reducer;
the third temperature sensor is arranged at the outlet of the second selective catalytic reducer and used for detecting the outlet temperature of the second selective catalytic reducer;
the SCR heating module is arranged at the inlet of the second selective catalytic reduction device and used for heating the second selective catalytic reduction device.
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