CN113482751B - SCR urea metering injection system - Google Patents

SCR urea metering injection system Download PDF

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Publication number
CN113482751B
CN113482751B CN202110901024.4A CN202110901024A CN113482751B CN 113482751 B CN113482751 B CN 113482751B CN 202110901024 A CN202110901024 A CN 202110901024A CN 113482751 B CN113482751 B CN 113482751B
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urea
valve
metering
gear pump
path
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CN113482751A (en
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史有程
董庆震
曹文斌
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Lanzhou University of Technology
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Lanzhou University of Technology
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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]
    • 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]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • 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
    • F01N3/24—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 constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • 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
    • 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
    • F01N2610/1406—Storage means for substances, e.g. tanks or reservoirs
    • 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
    • F01N2610/1426—Filtration means
    • 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
    • F01N2610/1453—Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
    • F01N2610/146—Control thereof, e.g. control of injectors or injection valves
    • 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
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

The invention discloses an SCR urea metering and spraying system which comprises a supply unit, a metering and spraying unit and a control unit, wherein the supply unit comprises a driving source, a gear pump, a pressure gauge, a stop valve, an overflow valve, a one-way valve, a damping hole and the like, an inlet of the gear pump is connected with a urea box through a pipeline, an outlet of the gear pump is divided into three paths, one path is communicated with the metering and spraying unit, the other path is connected with the overflow valve, the other path is communicated with the one-way valve and the damping hole, and an outlet of the overflow valve and an outlet of the damping hole are communicated with the urea box. Compressed air is communicated with the triplet of the metering jet unit via a shut-off valve. In the spraying stage, the liquid path and the air path of the metering spraying unit are mixed at the outlet of the nozzle, and the urea solution is atomized under the traction action of the air jet. The control unit is mainly responsible for maintaining stable system pressure, adjusting urea injection quantity, switching working states and the like. The invention adopts the gear pump as the system liquid supply and adopts the gas auxiliary atomization mode, and has the advantages of difficult in-tube crystallization, good atomization effect and the like.

Description

SCR urea metering injection system
Technical Field
The invention belongs to the technical field of tail gas aftertreatment, relates to a marine or automobile tail gas aftertreatment technology, and particularly relates to an SCR urea metering and spraying system.
Background
The tail gas of diesel engine contains a large amount of particulate matters and nitrogen oxides (NOx), which is a poisonous gas and is the main source of pollution problems such as photochemical smog. To reduce environmental pollution, emission regulations in various countries further require reduction of NOx emissions from diesel engines, and SCR technology (SCR denitration) has become a mainstream technology for reducing NOx emissions from diesel engines. The urea metering system is one of the core components of the SCR system and is a device for quantitatively delivering urea solution to a urea nozzle.
The marine SCR urea metering and spraying system generally adopts an air-assisted atomized urea aqueous solution mode (air-assisted mode). Most of the existing marine SCR urea metering and spraying systems adopt a centrifugal pump as a power source of a supply unit, and the centrifugal pump has little self-absorption capacity and can not absorb liquid reversely, so that the system requires that the liquid outlet of a urea box is higher than the liquid inlet of the centrifugal pump. Because urea aqueous solution in the pipeline between the liquid outlet of the urea box and the metering valve cannot be emptied after the machine is stopped, each component is contacted with the urea aqueous solution for a long time, and the problems of short service life, poor stability and the like of the system are easily caused.
Disclosure of Invention
The invention aims to provide an SCR urea metering injection system, which solves the problems that a centrifugal pump in the prior art has little self-absorption capacity and cannot absorb liquid reversely.
In order to achieve the above object, the present invention provides the following solutions:
the invention provides an SCR urea metering and spraying system, which mainly comprises:
the feeding unit comprises a driving source and a gear pump connected with the driving source, and the inlet and/or the outlet of the gear pump is provided with a pressure gauge and a stop valve; the inlet of the gear pump is connected with the urea box through a pipeline, and the outlet of the gear pump is at least connected with a first branch, a second branch and a third branch, wherein the first branch and the second branch are both connected with the urea box, an overflow valve is arranged on the first branch, and a one-way valve and a damping hole are arranged on the second branch;
the metering and spraying unit comprises a liquid path for flowing urea aqueous solution, the liquid path comprises a metering unit, a liquid path one-way valve and a nozzle which are sequentially connected, and an inlet of the liquid path is connected with the third branch;
and the control unit is in communication connection with the supply unit and/or the metering injection unit.
Optionally, the metering injection unit further comprises a gas circuit, the gas circuit comprises a triplet, a first switch valve and a gas circuit one-way valve which are sequentially connected, an inlet of the gas circuit is connected with a compressed gas source, an outlet of the gas circuit is connected with the nozzle, and the gas circuit is used for flowing compressed air so as to realize atomization of urea aqueous solution.
Optionally, the metering jet unit further comprises a blowing path, the blowing path comprises a blowing check valve and a second switching valve which are sequentially connected, one end of the blowing path is connected with the gas path, the other end of the blowing path is connected with the liquid path, and the blowing path is used for enabling compressed air to flow so as to realize blowing of urea aqueous solution in the pipe.
The metering injection unit integrates a gas path, a liquid path and a purging path, the gas path and the liquid path are connected with the nozzle, and the purging path is connected with the nozzle in parallel. When the system works in the spraying stage, the liquid path and the gas path are mixed at the outlet of the nozzle, and urea solution is atomized under the traction action of gas jet. The control unit is mainly responsible for maintaining stable system pressure, adjusting urea injection quantity, switching working states and the like. The gear pump is adopted to supply liquid for the system, and the gas auxiliary atomization mode is adopted, so that the device has the advantages of difficult in-tube crystallization, good atomization effect and the like.
Optionally, the compressed air source is connected with the triple piece through a stop valve.
Optionally, the inlet and/or the outlet of the gear pump is provided with a filter to filter out impurities in the urea aqueous solution.
Optionally, the metering unit comprises a pressure sensor and a metering valve.
Optionally, the driving source is a servo motor. Or the driving source is a common motor, namely a non-servo motor.
Optionally, the nozzle is a gas-liquid external mixing nozzle or a gas-liquid internal mixing nozzle. The gas-liquid mixing type nozzle is mainly applied to a mode of gas-assisted urea liquid atomization.
Optionally, the air passage check valve, the liquid passage check valve and/or the purging check valve are soft sealing check valves.
Optionally, a thermometer and/or a liquid level meter are arranged in the urea box
Alternatively, when the pressure of the gear pump is more than 2MPa, the nozzle can be a non-air-assisted nozzle, and the high pressure of the urea aqueous solution can be directly utilized for atomization. The gas path may be closed or removed at least during the spraying phase.
Optionally, the invention adopts the one-way valve, the switch valve and the metering valve with soft seal, and can realize reverse reliable seal, thereby avoiding the problem of urea crystallization in the gas circuit pipeline.
Compared with the prior art, the invention has the following technical effects:
the SCR urea metering and spraying system provided by the invention has reasonable structural arrangement, adopts the gear pump as a power source of the supply unit, has strong self-priming capability, and has no special requirement on the arrangement of the urea box, and wider adaptability; the gear pump can realize forward and reverse liquid suction, and can empty the urea aqueous solution in the pipe after stopping, thereby avoiding the urea aqueous solution from freezing in the pipeline and reducing the corrosion of the urea aqueous solution to components and parts, and further reducing the running cost of the urea solution supply system. Meanwhile, the highest supply pressure of the gear pump can reach more than 2MPa, and the gear pump is supported to be upgraded into a non-air-assisted system, namely, compressed air is not adopted for auxiliary atomization, and the urea aqueous solution is directly atomized by high pressure.
The SCR urea metering and spraying system provided by the invention has long service life and strong stability, and is especially suitable for the post-treatment of tail gas in the field of ships or automobiles.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of operation of an SCR urea metering injection system according to an embodiment of the present invention when executing a pressure build-up function;
FIG. 2 is a schematic diagram of the SCR urea metering and injection system according to the embodiment of the invention when executing the injection function, wherein solid line arrows and dotted line arrows respectively indicate the flow directions of a liquid path and a gas path;
FIG. 3 is a schematic diagram illustrating operation of an SCR urea metering injection system according to an embodiment of the present disclosure when performing a purge function;
FIG. 4 is a schematic diagram illustrating operation of a non-air assisted SCR urea metering and injection system according to an embodiment of the present invention.
Wherein, the reference numerals are as follows: the device comprises a 1-urea box, a 2-supply unit, a 3-metering injection unit, a 4-compressed air source, a 5-stop valve, a 6-metering unit, a 7-non-air-assisted nozzle, a 1.1-thermometer, a 1.2-liquid level meter, a 1.3-prefilter, 2.1, 2.5-stop valves, 2.2, 2.6-pressure gauges, a 2.3-driving source, a 2.4-gear pump, a 2.7-check valve, a 2.8-damping hole, a 2.9-overflow valve, a 3.1-post filter, a 3.2-pressure sensor, a 3.3-metering valve, a 3.4-liquid path one-way valve, a 3.5-purging one-way valve, a 3.6-purging switch valve, a 3.7-nozzle, a 3.8-air path one-way valve, a 3.9-air path switch valve and a 3.10-triplet.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide an SCR urea metering injection system, which solves the problems that a centrifugal pump in the prior art has little self-absorption capacity and cannot absorb liquid reversely. According to the problem that the centrifugal pump has no self-priming capability, a measure of adopting a gear pump to act as a power source of a supply unit is provided, the gear pump has strong self-priming capability, and forward and reverse liquid suction can be realized; the SCR urea metering and spraying system has no special requirement on arrangement of a urea box, and can drain urea aqueous solution in a pipe after the shutdown, so that the service life and stability of the SCR urea metering and spraying system are effectively improved.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Example 1
As shown in fig. 1-3, the present embodiment provides an SCR urea metering injection system, which mainly includes a supply unit 2, a metering injection unit 3, and a control unit, wherein:
the supply unit 2 comprises a driving source 2.3, a gear pump 2.4, pressure gauges 2.2 and 2.6, stop valves 2.1 and 2.5, an overflow valve 2.9, a one-way valve 2.7, a damping hole 2.8 and the like, wherein an inlet of the gear pump 2.4 is connected with the urea box 1 through a pipeline, an outlet of the gear pump 2.4 is connected with three branches, one branch is communicated with the metering jet unit 3, the other branch is connected with the overflow valve 2.9, and the other branch is communicated with the one-way valve 2.7 and the damping hole 2.8, and all hydraulic elements are connected through pipelines; the outlet of the overflow valve 2.9 and the outlet of the damping hole 2.8 are communicated with the urea box 1;
the metering and spraying unit 3 is divided into a gas circuit, a liquid circuit and a blowing-sweeping circuit, wherein the gas circuit comprises a triple piece 3.10, a switching valve 3.9, a gas circuit one-way valve 3.8, a nozzle 3.7 and the like, the liquid circuit comprises a filter 3.1, a metering unit 6, a liquid circuit one-way valve 3.4, a nozzle 3.7 and the like, and the blowing-sweeping circuit comprises a blowing one-way valve 3.5, a switching valve 3.6 and the like. The air path and the liquid path are connected with the same nozzle 3.7, the purging path is connected in parallel between the air path and the liquid path, the liquid path is a urea aqueous solution flowing channel, the air path is a compressed air flowing channel, and the purging path is a compressed air flowing channel when the compressed air purges urea aqueous solution in the pipe. Wherein the metering unit 6 comprises a pressure sensor 3.2 and a metering valve 3.3.
In this embodiment, as shown in fig. 1-3, the inlet and outlet sides of the gear pump 2.4 are respectively provided with a pre-filter 1.3 and a post-filter 3.1 for filtering impurities in the urea solution to protect the gear pump 2.4, the metering valve 3.3 and the nozzle 3.7.
In this embodiment, the driving source 2.3 may be a servo motor or a general motor.
In this embodiment, the nozzle 3.7 may be a gas-liquid external mixing type nozzle or a gas-liquid internal mixing type nozzle. The gas-liquid mixing type nozzle is mainly applied to a mode of gas-assisted urea liquid atomization.
In this embodiment, the liquid path unidirectional valve 3.4, the purge unidirectional valve 3.5 and the gas path unidirectional valve 3.8 all preferably adopt a soft sealing mode, and the opening pressure is lower, so as to ensure reverse reliable sealing and smaller pressure loss.
In the embodiment, the highest supply pressure of the gear pump 2.4 can reach more than 2MPa, and the system is supported to be upgraded into a non-air-assisted system, namely, the compressed air is not adopted for auxiliary atomization, and the high pressure of the urea aqueous solution is directly used for atomization. At the moment, the system gas path is removed or closed, and the nozzle is replaced by a non-air-assisted nozzle, so that the non-air-assisted SCR urea metering and spraying system can be formed. The principle of operation is shown in fig. 4, wherein 7 is a non-air assisted nozzle.
The working process of the SCR urea metering injection system provided in this embodiment is specifically described below.
As shown in fig. 1, the schematic diagram of the urea solution supply system when executing the pressure building function is shown, when executing the pressure building function, the control unit sends an instruction, the metering valve 3.3, the purge switch valve 3.6 and the air path switch valve 3.9 lose electricity, the motor (driving source 2.3) operates in the forward direction, the gear pump 2.4 sucks liquid from the urea tank 1, the urea solution extruded by the gear pump 2.4 flows back to the urea tank 1 through the one-way valve 2.7 and the damping hole 2.8, and when the pressure sensor 3.2 detects that the system pressure reaches a set value, the system pressure building is successful. After the system is successfully pressurized, the spraying function can be executed.
The control unit calculates the required urea aqueous solution injection quantity according to the parameters of the engine speed, torque, exhaust temperature and the like, and then sends an instruction to execute an injection function.
FIG. 2 is a schematic diagram of an SCR urea metering injection system performing an injection function. When the spraying function is executed, the motor (the driving source 2.3) continues to run forward, the gear pump 2.4 presses out a part of urea solution, the urea solution flows back to the urea tank 1 through the one-way valve 2.7 and the damping hole 2.8, and the other part of urea solution is sprayed to the tail gas pipe through the metering spraying unit 3. At this time, the gas circuit switch valve 3.9 is powered on, the purge switch valve 3.6 is powered off, the flow directions of the liquid circuit and the gas circuit are respectively shown in the directions of solid lines and dotted arrows in the figure, the gas and the liquid are mixed at the outlet of the nozzle 3.7, and the urea aqueous solution is atomized under the impact and traction actions of high-speed flowing gas; the injection quantity of the urea aqueous solution is regulated by a metering valve 3.3, the metering valve 3.3 is controlled by a pulse width modulation PWM signal, and a definite relation exists between the injection quantity of the system and the PWM duty cycle of the metering valve 3.3.
After the system is shut down, the purging function is automatically executed. As shown in fig. 3, when the purging function is executed, the purging switch valve 3.6 and the gas path switch valve 3.9 are powered, the metering valve 3.3 is powered off, the motor (the driving source 2.3) runs reversely, the gear pump 2.4 sucks liquid from the pipeline and presses the liquid out to the urea box 1, compressed air is divided into two paths through the stop valve 5 and the triple piece 3.10, one path flows to a gas path runner in the nozzle 3.7 through the gas path switch valve 3.9 and the gas path check valve 3.8, and the other path purges residual urea aqueous solution in the pipeline to the tail gas pipe through the purging switch valve 3.6 and the purging check valve 3.5 and the liquid path runner of the nozzle 3.7.
When the engine is started, the control unit will start initializing internal parameters and check if the whole system is faulty. If the fault exists, a fault code is reported, and the work is stopped; if no fault exists, the pressure build-up state is entered.
Therefore, compared with the prior art, the technical scheme of the embodiment mainly has the following technical advantages:
1. the embodiment provides that the gear pump is adopted to act as a power source of the supply unit, and the gear pump has strong self-priming capability, so that the SCR urea metering and spraying system provided by the embodiment has no special requirements on the arrangement of the urea box.
2. The embodiment adopts the one-way valve, the switch valve and the metering valve with soft seal, and can realize reverse reliable seal, thereby avoiding the problem of urea crystallization in the gas circuit pipeline.
3. According to the embodiment, the gear pump is used for supplying the unit power source, the gear pump can realize forward and reverse liquid suction, and urea aqueous solution in the pipe can be emptied after the machine is stopped, so that the urea aqueous solution is prevented from freezing in the pipeline, corrosion of the urea aqueous solution to components is reduced, and the running cost of the urea solution supply system is reduced.
4. In the embodiment, the gear pump is used as a power source of the supply unit, the highest supply pressure of the gear pump can reach more than 2MPa, and the gear pump is supported to be upgraded into a non-air-assisted system, namely, compressed air is not used for assisting in atomization, and the high pressure of the urea aqueous solution is directly used for atomization.
It should be noted that it will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
The principles and embodiments of the present invention have been described in detail with reference to specific examples, which are provided to facilitate understanding of the method and core ideas of the present invention; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.

Claims (8)

1. An SCR urea metering injection system, comprising:
the feeding unit comprises a driving source and a gear pump connected with the driving source, and the inlet and the outlet of the gear pump are provided with pressure gauges and stop valves; the inlet of the gear pump is connected with the urea box through a pipeline, and the outlet of the gear pump is at least connected with a first branch, a second branch and a third branch, wherein the first branch and the second branch are both connected with the urea box, an overflow valve is arranged on the first branch, and a one-way valve and a damping hole are arranged on the second branch; when the highest supply pressure of the gear pump reaches more than 2MPa, the gear pump can directly atomize urea by the high pressure of urea aqueous solution without adopting compressed air for auxiliary atomization;
the metering and spraying unit comprises a gas circuit, a blowing-off circuit and a liquid circuit for flowing urea aqueous solution, the liquid circuit comprises a metering unit, a liquid circuit one-way valve and a nozzle which are sequentially connected, and an inlet of the liquid circuit is connected with the third branch circuit; the air channel comprises a triple piece, a first switch valve and an air channel one-way valve which are sequentially connected, an inlet of the air channel is connected with a compressed air source, an outlet of the air channel is connected with the nozzle, and the air channel is used for flowing compressed air so as to realize atomization of urea aqueous solution; the purging path comprises a purging one-way valve and a second switching valve which are sequentially connected, one end of the purging path is connected with the gas path, the other end of the purging path is connected with the liquid path, and the purging path is used for enabling compressed air to flow so as to purge urea aqueous solution in the pipe;
and the control unit is in communication connection with the supply unit and/or the metering injection unit.
2. The SCR urea dosing injection system of claim 1, wherein the compressed air source is connected to the triplet via a shut-off valve.
3. The SCR urea dosing injection system according to claim 1, wherein the inlet and/or outlet of the gear pump is provided with a filter to filter out impurities in the urea aqueous solution.
4. The SCR urea dosing injection system of claim 1, wherein the dosing unit comprises a pressure sensor and a dosing valve.
5. The SCR urea dosing injection system of claim 1, wherein the drive source is a servo motor.
6. The SCR urea metering injection system of claim 1, wherein the nozzle is a gas-liquid external mix nozzle or a gas-liquid internal mix nozzle.
7. The SCR urea dosing injection system of claim 1, wherein the gas circuit check valve, the liquid circuit check valve, and/or the purge check valve are soft seal check valves.
8. The SCR urea dosing injection system of claim 1, wherein a thermometer and/or a level gauge is disposed within the urea tank.
CN202110901024.4A 2021-08-06 2021-08-06 SCR urea metering injection system Active CN113482751B (en)

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Citations (5)

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Publication number Priority date Publication date Assignee Title
CN102297005A (en) * 2011-09-13 2011-12-28 浙江邦得利汽车环保技术有限公司 Selective catalytic reduction (SCR) urea jet device of diesel engine
EP2447490A1 (en) * 2010-10-29 2012-05-02 Hanspeter Mayer Device for selective catalytic reduction of nitrogen oxides in an exhaust gas line of a motor vehicle
EP2722505A1 (en) * 2012-10-17 2014-04-23 Wärtsilä Finland Oy Urea injection system for an internal combustion engine
CN108625940A (en) * 2017-03-20 2018-10-09 天纳克（苏州）排放系统有限公司 Integrating device, exhaust gas aftertreatment system and control method
CN208831077U (en) * 2018-09-14 2019-05-07 罗伯特·博世有限公司 Exhaust gas aftertreatment system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2447490A1 (en) * 2010-10-29 2012-05-02 Hanspeter Mayer Device for selective catalytic reduction of nitrogen oxides in an exhaust gas line of a motor vehicle
CN102297005A (en) * 2011-09-13 2011-12-28 浙江邦得利汽车环保技术有限公司 Selective catalytic reduction (SCR) urea jet device of diesel engine
EP2722505A1 (en) * 2012-10-17 2014-04-23 Wärtsilä Finland Oy Urea injection system for an internal combustion engine
CN108625940A (en) * 2017-03-20 2018-10-09 天纳克（苏州）排放系统有限公司 Integrating device, exhaust gas aftertreatment system and control method
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