CN113931723A - Device and method for reducing urea crystallization of SCR system - Google Patents
Device and method for reducing urea crystallization of SCR system Download PDFInfo
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- CN113931723A CN113931723A CN202111185570.9A CN202111185570A CN113931723A CN 113931723 A CN113931723 A CN 113931723A CN 202111185570 A CN202111185570 A CN 202111185570A CN 113931723 A CN113931723 A CN 113931723A
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- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 title claims abstract description 49
- 239000004202 carbamide Substances 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000002425 crystallisation Methods 0.000 title claims abstract description 15
- 230000008025 crystallization Effects 0.000 title claims abstract description 15
- 239000007789 gas Substances 0.000 claims abstract description 173
- 239000002912 waste gas Substances 0.000 claims abstract description 46
- 238000010248 power generation Methods 0.000 claims abstract description 34
- 238000005485 electric heating Methods 0.000 claims abstract description 30
- 230000001105 regulatory effect Effects 0.000 claims abstract description 24
- 238000010438 heat treatment Methods 0.000 claims abstract description 22
- 230000001965 increasing effect Effects 0.000 claims abstract description 11
- 230000003134 recirculating effect Effects 0.000 claims description 26
- 238000002156 mixing Methods 0.000 claims description 21
- 238000002347 injection Methods 0.000 claims description 12
- 239000007924 injection Substances 0.000 claims description 12
- 238000009529 body temperature measurement Methods 0.000 claims description 6
- 238000009530 blood pressure measurement Methods 0.000 claims description 5
- 238000006555 catalytic reaction Methods 0.000 claims description 5
- 238000010586 diagram Methods 0.000 claims description 4
- 239000000243 solution Substances 0.000 claims description 4
- 238000004891 communication Methods 0.000 claims description 3
- WTHDKMILWLGDKL-UHFFFAOYSA-N urea;hydrate Chemical compound O.NC(N)=O WTHDKMILWLGDKL-UHFFFAOYSA-N 0.000 claims description 3
- 230000003197 catalytic effect Effects 0.000 claims description 2
- 239000007864 aqueous solution Substances 0.000 abstract description 13
- 238000006243 chemical reaction Methods 0.000 abstract description 11
- 239000007788 liquid Substances 0.000 abstract description 6
- 239000013078 crystal Substances 0.000 abstract description 5
- 238000005516 engineering process Methods 0.000 abstract description 3
- 238000004134 energy conservation Methods 0.000 abstract description 2
- 238000004064 recycling Methods 0.000 abstract description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 20
- 239000003054 catalyst Substances 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- 239000006227 byproduct Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
- F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
- F01N3/2013—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using electric or magnetic heating means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N9/00—Electrical control of exhaust gas treating apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/14—Arrangements for the supply of substances, e.g. conduits
- F01N2610/148—Arrangement of sensors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/14—Arrangements for the supply of substances, e.g. conduits
- F01N2610/1486—Means to prevent the substance from freezing
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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
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
The invention discloses a device and a method for reducing urea crystallization of an SCR system. The device comprises a temperature sensor, a pressure sensor, a heating and pressurizing gas nozzle, a pressurizing device, an electric heating device, an electronic regulating valve, a pump machine, a waste gas temperature difference power generation device, a storage battery, a recycling waste gas pipe and an electronic control unit. Aiming at the low-temperature working condition, the exhaust gas reduced by the SCR system is heated, recirculated and injected into the SCR system, so that the reaction temperature of NOx and urea aqueous solution is increased. The reaction temperature is increased, the probability of forming a liquid film is reduced, and the generation of urea crystals is reduced. Meanwhile, the urea aqueous solution and the heated recirculated exhaust gas are relatively sprayed in the SCR system, so that the airflow disturbance in the pipe is increased, the probability of forming a liquid film is reduced, and the urea aqueous solution and the recirculated exhaust gas are fully mixed and fully reacted. Meanwhile, the waste gas temperature difference power generation technology is adopted to generate power by using heat in the waste gas, so that power is supplied to electrical appliances in the device, and energy conservation and emission reduction are realized.
Description
Technical Field
The invention belongs to the field of emission control of internal combustion engines, and particularly relates to a device and a method for reducing urea crystallization of an SCR system.
Background
Currently, Selective Catalytic Reduction (SCR) technology is the most effective solution to the problem of reducing emissions from internal combustion engines. In an SCR system, after a urea aqueous solution (UWS) is contacted with high-temperature tail gas, urea is subjected to hydrolysis and pyrolysis reaction at high temperature to generate ammonia gas, and the ammonia gas is used as a reducing agent under the action of a catalyst to reduce nitrogen oxides (NOx) in the tail gas into nitrogen gas and water.
However, at low temperatures, i.e. when the engine is operated at low load and the exhaust temperature is low, the urea decomposition process is accompanied by the formation of a large amount of by-products. The by-products can be crystallized on the catalyst part of the SCR system and the inner wall of the pipeline, and a large amount of deposits are formed to cause blockage, thereby influencing the proceeding of catalytic reaction. And in the process of impacting the inner wall of the SCR system by urea aqueous solution droplets, the wall surface is further cooled by the urea aqueous solution droplets, and when the temperature is lower than the moisture evaporation temperature, moisture in the droplets cannot be evaporated, so that a wall surface liquid film is formed, which further causes the generation of crystals. The accumulation of crystals can cause problems such as increased backpressure in the SCR system, reduced NOx conversion efficiency, failure of the aftertreatment system to function properly, and increased fuel consumption.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a device and a method for reducing urea crystallization of an SCR system.
The invention provides a device for reducing urea crystallization of an SCR system, which is characterized by comprising a temperature sensor, a pressure sensor, a heating and pressurizing gas nozzle, a pressurizing device, an electric heating device, an electronic regulating valve, a pump, an exhaust gas temperature difference power generation device, a storage battery, a recirculating exhaust gas pipe and an electronic control unit, wherein the temperature sensor is connected with the pressure sensor;
the tail end of an air outlet pipe of the SCR system is connected with the waste gas temperature difference power generation device, and waste gas treated by the SCR system enters the waste gas temperature difference power generation device to convert heat energy into electric energy; the temperature sensor is arranged on an air inlet pipe of the SCR system and used for measuring the inlet air temperature of the exhaust gas entering the SCR system; the pressure sensor is arranged on the air inlet pipe and used for measuring the inlet pressure of the exhaust gas entering the SCR system; one end of the recirculating exhaust gas pipe is communicated with the side opening of the gas outlet pipe of the SCR system or the outlet of the catalytic converter, and the other end of the recirculating exhaust gas pipe is provided with a heating and pressurizing gas nozzle; the recirculating exhaust gas pipe is sequentially provided with an electronic regulating valve, a pump machine, an electric heating device and a pressurizing device according to the gas flow direction; the tail end of the heating and pressurizing gas nozzle is positioned in the gas mixing chamber and corresponds to the position of a urea nozzle of the SCR system, and the heating and pressurizing gas nozzle is used for increasing the airflow disturbance in the gas mixing chamber of the SCR system;
the waste gas temperature difference power generation device is electrically connected with the storage battery, and the electric energy generated by the waste gas temperature difference power generation device is stored in the storage battery to charge the storage battery; the storage battery supplies power for the temperature sensor, the pressure sensor, the pressurizing device, the electric heating device, the electronic regulating valve, the pump and the electronic control unit;
the electronic control unit is respectively in communication connection with the temperature sensor, the pressure sensor, the pressurizing device, the electric heating device, the electronic regulating valve, the pump and the storage battery.
The invention provides a method for reducing urea crystallization of an SCR system based on the device, which is characterized by comprising the following steps:
step 1, in the normal running process of an engine, waste gas enters an SCR system, a temperature sensor measures the inlet gas temperature of the waste gas entering the SCR system to obtain a waste gas temperature measured value, a pressure sensor measures the inlet gas pressure of the waste gas entering the SCR system to obtain a waste gas pressure measured value, and the waste gas temperature measured value and the waste gas pressure measured value are transmitted to an electronic control unit;
step 2, the electronic control unit judges the size relation between the temperature measurement value and the starting threshold value of the device according to the received exhaust gas temperature measurement value and the received exhaust gas pressure measurement value; the starting threshold of the device is determined according to the analysis result of the early test;
when the measured value of the temperature of the exhaust gas is not higher than the starting threshold value of the device, the electronic control unit opens the electronic regulating valve, the pump machine, the electric heating device and the pressurizing device according to a pre-calibrated MAP (MAP) diagram, and controls the heating intensity of the electric heating device, the power of the pump machine, the opening degree of the electronic regulating valve and the pressurizing degree of the pressurizing device, so that the injection temperature and the injection speed of the recirculated exhaust gas are in proper ranges; part of the waste gas treated by the SCR system enters a waste gas temperature difference power generation device through an air outlet pipe, and the electric quantity generated by the waste gas temperature difference power generation device is stored in a storage battery; the other part of the exhaust gas treated by the SCR system is pumped into a recirculating exhaust gas pipe through a pump and is conveyed by the pump to flow into an electric heating device; the electric heating device heats the recirculated exhaust gas to a corresponding degree according to the MAP graph, so that the temperature of the recirculated exhaust gas meets the requirement, and high-temperature recirculated exhaust gas is formed; the high-temperature recirculating exhaust gas is pressurized by a pressurizing device, so that the pressure value of the pressurized high-temperature recirculating exhaust gas is higher than the pressure measurement value of the exhaust gas, and finally the pressurized high-temperature recirculating exhaust gas is injected into a gas mixing chamber through a heating and pressurizing gas nozzle, mixed with the urea water solution sprayed out of the urea nozzle and the exhaust gas entering an SCR system, and then enters the SCR system for treatment;
when the measured value of the temperature of the waste gas is higher than the starting threshold value of the device, the whole device is closed, the waste gas treated by the SCR system completely enters the waste gas temperature difference power generation device through the gas outlet pipe, and the electric quantity generated by the waste gas temperature difference power generation device is stored in the storage battery and used for supplying power to an electric appliance when the device is started;
and 3, repeating the step 1 and the step 2, so that the temperature of the mixed exhaust gas in the gas mixing chamber is kept within the proper temperature range of the catalytic reaction.
Compared with the prior art, the invention has the beneficial effects that:
(1) aiming at the low-temperature working condition, the exhaust gas reduced by the SCR system is heated, recirculated and injected into the SCR system, so that the reaction temperature of NOx and urea aqueous solution is increased. The reaction temperature is increased, the probability of forming a liquid film is reduced, and the generation of urea crystals is reduced. Meanwhile, the urea aqueous solution and the heated recirculated exhaust gas are relatively sprayed in the SCR system, so that the airflow disturbance in the gas mixing chamber is increased, the probability of forming a liquid film is reduced, the generation of urea crystals is reduced, the back pressure is reduced, the urea aqueous solution liquid drops and the recirculated exhaust gas are fully mixed, the flow uniformity of urea and the temperature uniformity of a reaction area are promoted, the reaction is more sufficient, and the high conversion efficiency of the SCR system is ensured.
(2) The invention adopts the waste gas temperature difference power generation technology to generate power by utilizing heat in the waste gas, supplies power to electrical appliances in the device and achieves the purposes of energy conservation and emission reduction.
(3) The invention makes full use of the heat of the tail gas by the way of exhaust gas recirculation. Meanwhile, the recycling can also enable the unreacted nitrogen oxides to react again, thereby achieving the purpose of reducing the nitrogen oxides and the ammonia gas. At the same time, no other substances are introduced into the SCR system by exhaust gas recirculation, which increases other side reactions.
(4) The invention does not directly heat the urea aqueous solution or the air inlet pipe orifice, but heats the recirculated exhaust gas to achieve the purpose of heating the urea aqueous solution, and the energy is fully utilized.
(5) On the premise of ensuring the reliability of the SCR system, the conversion efficiency of the SCR system is improved, the discharge amount of NOx is reduced, and the problem of environmental pollution caused by leakage of redundant ammonia gas is solved.
Drawings
FIG. 1 is a schematic diagram of the connection of the apparatus of the present invention;
FIG. 2 is a schematic diagram of the overall power supply of the present invention;
FIG. 3 is a control flow chart of the present invention.
In the figure, 101, a urea tank; 102. a temperature sensor; 103. a urea nozzle; 104. a mixer; 105. a catalyst; 106. an air outlet pipe; 107. an exhaust gas temperature difference power generation device; 108. an air inlet pipe; 109. a heated pressurized gas nozzle; 110. a pressurizing device; 111. an electric heating device; 112. an electronic control unit; 113. an electronic regulating valve; 114. a pump machine; 115. a storage battery; 116. a gas mixing chamber; 117. a recirculating exhaust pipe; 118. a pressure sensor.
Detailed Description
Specific examples of the present invention are given below. The specific examples are only intended to illustrate the invention in further detail and do not limit the scope of protection of the claims of the present application.
The invention provides a device (short for device) for reducing urea crystallization of an SCR system, wherein the SCR system comprises a urea tank 101, a urea nozzle 103, a mixer 104, a catalyst 105, an air outlet pipe 106, an air inlet pipe 108 and a gas mixing chamber 116; a gas mixing chamber 116, a mixer 104 and a catalyst 105 are sequentially arranged between the gas inlet pipe 108 and the gas outlet pipe 106 according to the gas flow direction; the beginning end of the air inlet pipe 108 is connected with the DPF system and is used for enabling the exhaust gas treated by the DPF system to enter the SCR system; the urea tank 101 is connected with the urea nozzle 103 through a pipeline; the tail end of the urea nozzle 103 is positioned in the gas mixing chamber 116 and is used for spraying urea aqueous solution into the SCR system, and the spraying angle is 30 degrees with the horizontal plane, so that the urea crystallization phenomenon is not easy to occur at the angle;
the device is characterized by comprising a temperature sensor 102, a pressure sensor 118, a heating and pressurizing gas nozzle 109, a pressurizing device 110, an electric heating device 111, an electronic regulating valve 113, a pump 114, an exhaust gas temperature difference power generation device 107, a storage battery 115, a recirculating exhaust gas pipe 117 and an electronic control unit 112;
the tail end of an air outlet pipe 106 of the SCR system is connected with an exhaust gas temperature difference power generation device 107, and exhaust gas treated by the SCR system enters the exhaust gas temperature difference power generation device 107 to convert heat energy into electric energy; a temperature sensor 102 is mounted on the intake pipe 108 for measuring the temperature of the exhaust gas intake entering the SCR system; a pressure sensor 118 is mounted on the intake pipe 108 for measuring the intake pressure of the exhaust gas entering the SCR system; one end of the recirculating exhaust pipe 117 is communicated with the side opening of the outlet pipe 106 of the SCR system or the outlet of the catalyst 105, and the other end is provided with a heating and pressurizing gas nozzle 109; an electronic regulating valve 113, a pump 114, an electric heating device 111 and a pressurizing device 110 are sequentially arranged on the recirculating exhaust gas pipe 117 according to the gas flow direction; the tail end of the heating and pressurizing gas nozzle 109 is positioned in the gas mixing chamber 116 and corresponds to the position of the urea nozzle 103, and is used for increasing the gas flow disturbance in the gas mixing chamber 116;
the waste gas temperature difference power generation device 107 is electrically connected with the storage battery 115, and the electric energy generated by the waste gas temperature difference power generation device 107 is stored in the storage battery 115 to charge the storage battery 115; the storage battery 115 supplies power to the temperature sensor 102, the pressure sensor 118, the pressurizing device 110, the electric heating device 111, the electronic regulating valve 113, the pump 114 and the electronic control unit 112;
the electronic control unit 112 is respectively connected with the temperature sensor 102, the pressure sensor 118, the pressurizing device 110, the electric heating device 111, the electronic regulating valve 113, the pump 114 and the storage battery 115 in a communication manner, and is used for receiving a temperature signal transmitted by the temperature sensor 102, receiving a pressure signal transmitted by the pressure sensor 118, controlling the starting, stopping and pressurizing degrees of the pressurizing device 110, the starting, stopping and heating intensity of the electric heating device 111, the starting, stopping and power of the pump 114, the opening degree of the electronic regulating valve 113 and controlling the discharging function of the storage battery 115.
Preferably, the exhaust gas temperature difference power generation device 107 generates power through the temperature difference between the exhaust gas and the external cold source. The battery 115 is used to store the surplus power generated by the thermoelectric power generation device 107 and provide sufficient power for the electrical equipment when the thermoelectric power generation device 107 cannot provide sufficient power for the electrical equipment in the device. The electric heating device 111 is used for heating through a resistance wire to raise the temperature of the recirculated exhaust gas. The pressurizing device 110 is used for pressurizing the high-temperature recirculated exhaust gas to meet the injection requirement. The electronic regulating valve 113 is used to regulate the flow rate of the recirculated exhaust gas in the recirculated exhaust gas pipe 117. The pump 114 is used to pump the exhaust gas treated by the SCR system out of the outlet pipe 106 into the recirculating exhaust pipe 117 as recirculating exhaust gas, and to feed the recirculating exhaust gas to the electric heating device 111. The pressure sensor 118 is used to measure the exhaust gas intake pressure entering the SCR system, facilitating the electronic control unit 112 to adjust the degree of pressurization of the pressurization device 110 accordingly.
Preferably, the injection angle of the heated and pressurized gas nozzle 109 is 30 ° from the horizontal plane and is axisymmetric to the injection angle of the urea nozzle 103, the symmetry axis is the central axis of the SCR system, and the two nozzles will be mixed in the middle of the gas mixing chamber 116 by opposite injection, which has the effect of enhancing turbulence.
Preferably, the temperature sensor 102 is mounted on the end of the intake pipe 108 to facilitate more accurate measurement of the exhaust gas intake temperature after DPF system treatment entering the plenum 116. A pressure sensor 118 is mounted on the end of the intake pipe 108 to facilitate a more accurate measurement of the exhaust gas intake pressure after DPF system treatment entering the plenum 116.
Preferably, the electronic control unit 112 employs an ECU.
The invention also provides a method (short for method) for reducing the urea crystallization of the SCR system based on the device, which is characterized by comprising the following steps:
step 1, in the normal operation process of the engine, the exhaust gas enters the SCR system, the temperature sensor 102 measures the inlet temperature of the exhaust gas entering the SCR system to obtain an exhaust gas temperature measured value, meanwhile, the pressure sensor 118 measures the inlet pressure of the exhaust gas entering the SCR system to obtain an exhaust gas pressure measured value, and the exhaust gas temperature measured value and the exhaust gas pressure measured value are transmitted to the electronic control unit 112;
step 2, the electronic control unit 112 judges the size relationship between the temperature measurement value and the starting threshold value of the device according to the received exhaust gas temperature measurement value and the exhaust gas pressure measurement value; the starting threshold of the device is determined according to the analysis result of the early test;
when the measured value of the exhaust gas temperature is not higher than the starting threshold value of the device, the electronic control unit 112 opens the electronic regulating valve 113, the pump 114, the electric heating device 111 and the pressurizing device 110 according to a pre-calibrated MAP, controls the heating intensity of the electric heating device 111, the power of the pump 114, adjusts the opening degree of the electronic regulating valve 113 to control the flow rate of the recirculated exhaust gas, and adjusts the pressurizing degree of the pressurizing device 110 according to the received measured value of the exhaust gas pressure, so that the injection temperature and the injection speed of the recirculated exhaust gas are in proper ranges; a part of the exhaust gas treated by the SCR system enters the exhaust gas temperature difference power generation device 107 through the outlet pipe 106, and the electric quantity generated by the exhaust gas temperature difference power generation device 107 is stored in the storage battery 115; another portion of the SCR system treated exhaust gas (i.e., recirculated exhaust gas) is pumped by pump 114 into recirculated exhaust gas line 117, and is delivered by pump 114 into electric heater 111; the electric heating device 111 heats the recirculated exhaust gas to a corresponding degree according to the signal transmitted by the electronic control unit 112 and the MAP, so that the temperature of the recirculated exhaust gas meets the requirement, and high-temperature recirculated exhaust gas is formed; the high-temperature recirculating exhaust gas is pressurized by a pressurizing device 110, so that the pressure value of the pressurized high-temperature recirculating exhaust gas is 0.5-1 MPa higher than the measured value of the exhaust gas pressure, and finally the pressurized high-temperature recirculating exhaust gas is injected into a gas mixing chamber 116 through a heating and pressurizing gas nozzle 109, mixed with the urea water solution sprayed out of a urea nozzle 103 and the exhaust gas entering an SCR system, and then enters the SCR system for treatment;
in the process of using the electric heating device 111, the temperature of the recirculated exhaust gas is regulated and controlled through the preset relationship between the heating intensity of the electric heating device 111 and the temperature of the recirculated exhaust gas, and the temperature in the gas mixing chamber 116 is in a proper temperature range by combining the real-time exhaust gas temperature measured value measured by the temperature sensor 102, so that the subsequent reaction of nitrogen oxides and the urea aqueous solution is facilitated;
when the measured value of the exhaust gas temperature is higher than the starting threshold of the device, the electronic control unit 112 shuts down the device to prevent the SCR system from being damaged to a certain extent due to overhigh temperature, the exhaust gas treated by the SCR system completely enters the exhaust gas temperature difference power generation device 107 through the gas outlet pipe 106, and the electric quantity generated by the exhaust gas temperature difference power generation device 107 is stored in the storage battery 115 and used for supplying power to electrical appliances when the device is started;
and 3, repeating the step 1 and the step 2, so that the temperature of the mixed exhaust gas in the gas mixing chamber 116 is kept in a proper temperature range of the catalytic reaction, and the catalytic reaction efficiency is higher.
Nothing in this specification is said to apply to the prior art.
Claims (8)
1. A device for reducing urea crystallization of an SCR system is characterized by comprising a temperature sensor, a pressure sensor, a heating and pressurizing gas nozzle, a pressurizing device, an electric heating device, an electronic regulating valve, a pump, an exhaust gas temperature difference power generation device, a storage battery, a recirculating exhaust gas pipe and an electronic control unit;
the tail end of an air outlet pipe of the SCR system is connected with the waste gas temperature difference power generation device, and waste gas treated by the SCR system enters the waste gas temperature difference power generation device to convert heat energy into electric energy; the temperature sensor is arranged on an air inlet pipe of the SCR system and used for measuring the inlet air temperature of the exhaust gas entering the SCR system; the pressure sensor is arranged on the air inlet pipe and used for measuring the inlet pressure of the exhaust gas entering the SCR system; one end of the recirculating exhaust gas pipe is communicated with the side opening of the gas outlet pipe of the SCR system or the outlet of the catalytic converter, and the other end of the recirculating exhaust gas pipe is provided with a heating and pressurizing gas nozzle; the recirculating exhaust gas pipe is sequentially provided with an electronic regulating valve, a pump machine, an electric heating device and a pressurizing device according to the gas flow direction; the tail end of the heating and pressurizing gas nozzle is positioned in the gas mixing chamber and corresponds to the position of a urea nozzle of the SCR system, and the heating and pressurizing gas nozzle is used for increasing the airflow disturbance in the gas mixing chamber of the SCR system;
the waste gas temperature difference power generation device is electrically connected with the storage battery, and the electric energy generated by the waste gas temperature difference power generation device is stored in the storage battery to charge the storage battery; the storage battery supplies power for the temperature sensor, the pressure sensor, the pressurizing device, the electric heating device, the electronic regulating valve, the pump and the electronic control unit;
the electronic control unit is respectively in communication connection with the temperature sensor, the pressure sensor, the pressurizing device, the electric heating device, the electronic regulating valve, the pump and the storage battery.
2. The apparatus of claim 1, wherein the heated and pressurized gas nozzles have an injection angle of 30 ° from horizontal and are axisymmetric with respect to an injection angle of the urea nozzles.
3. The apparatus of claim 1, wherein a temperature sensor is mounted at the end of the inlet pipe to measure the inlet temperature of the exhaust gas after treatment by the DPF system entering the mixing chamber.
4. The apparatus of claim 1, wherein a pressure sensor is mounted at the end of the inlet pipe to measure the inlet pressure of the exhaust gas after treatment by the DPF system entering the mixing chamber.
5. The apparatus for reducing urea crystallization in an SCR system of claim 1, wherein the electronic control unit employs an ECU.
6. The apparatus for reducing urea crystallization in an SCR system of claim 1, wherein an electronic regulating valve is used to regulate the flow of recirculated exhaust gas in the recirculated exhaust gas conduit; the pressure sensor is used for measuring the pressure of the exhaust gas entering the SCR system, so that the electronic control unit can conveniently adjust the pressurization degree of the pressurization device.
7. A method for reducing urea crystallization in an SCR system based on the apparatus of any of claims 1-6, comprising the steps of:
step 1, in the normal running process of an engine, waste gas enters an SCR system, a temperature sensor measures the inlet gas temperature of the waste gas entering the SCR system to obtain a waste gas temperature measured value, a pressure sensor measures the inlet gas pressure of the waste gas entering the SCR system to obtain a waste gas pressure measured value, and the waste gas temperature measured value and the waste gas pressure measured value are transmitted to an electronic control unit;
step 2, the electronic control unit judges the size relation between the temperature measurement value and the starting threshold value of the device according to the received exhaust gas temperature measurement value and the received exhaust gas pressure measurement value; the starting threshold of the device is determined according to the analysis result of the early test;
when the measured value of the temperature of the exhaust gas is not higher than the starting threshold value of the device, the electronic control unit opens the electronic regulating valve, the pump machine, the electric heating device and the pressurizing device according to a pre-calibrated MAP (MAP) diagram, and controls the heating intensity of the electric heating device, the power of the pump machine, the opening degree of the electronic regulating valve and the pressurizing degree of the pressurizing device, so that the injection temperature and the injection speed of the recirculated exhaust gas are in proper ranges; part of the waste gas treated by the SCR system enters a waste gas temperature difference power generation device through an air outlet pipe, and the electric quantity generated by the waste gas temperature difference power generation device is stored in a storage battery; the other part of the exhaust gas treated by the SCR system is pumped into a recirculating exhaust gas pipe through a pump and is conveyed by the pump to flow into an electric heating device; the electric heating device heats the recirculated exhaust gas to a corresponding degree according to the MAP graph, so that the temperature of the recirculated exhaust gas meets the requirement, and high-temperature recirculated exhaust gas is formed; the high-temperature recirculating exhaust gas is pressurized by a pressurizing device, so that the pressure value of the pressurized high-temperature recirculating exhaust gas is higher than the pressure measurement value of the exhaust gas, and finally the pressurized high-temperature recirculating exhaust gas is injected into a gas mixing chamber through a heating and pressurizing gas nozzle, mixed with the urea water solution sprayed out of the urea nozzle and the exhaust gas entering an SCR system, and then enters the SCR system for treatment;
when the measured value of the temperature of the waste gas is higher than the starting threshold value of the device, the whole device is closed, the waste gas treated by the SCR system completely enters the waste gas temperature difference power generation device through the gas outlet pipe, and the electric quantity generated by the waste gas temperature difference power generation device is stored in the storage battery and used for supplying power to an electric appliance when the device is started;
and 3, repeating the step 1 and the step 2, so that the temperature of the mixed exhaust gas in the gas mixing chamber is kept within the proper temperature range of the catalytic reaction.
8. The method for reducing urea crystallization of the SCR system according to claim 7, wherein the pressure value of the pressurized high-temperature recirculated exhaust gas is 0.5-1 MPa higher than the measured value of the exhaust gas pressure.
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