CN110848004B - Multi-stage parallel SCR system - Google Patents
Multi-stage parallel SCR system Download PDFInfo
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- CN110848004B CN110848004B CN201911314994.3A CN201911314994A CN110848004B CN 110848004 B CN110848004 B CN 110848004B CN 201911314994 A CN201911314994 A CN 201911314994A CN 110848004 B CN110848004 B CN 110848004B
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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
- F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
- 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
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features
- F01N13/011—Exhaust or silencing apparatus characterised by constructional features having two or more purifying devices arranged in parallel
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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
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features
- F01N13/14—Exhaust or silencing apparatus characterised by constructional features having thermal insulation
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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
- F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
- F01N3/208—Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent
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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
- F01N3/24—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
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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
- F01N3/24—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
- F01N3/2892—Exhaust flow directors or the like, e.g. upstream of catalytic device
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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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- 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
本发明公开了一种多级并联SCR系统，依次串联设置进气单元、反应单元及出气单元，反应单元内设置有若干个反应通道，进气单元上对应若干个反应通道设置若干个分流支管，若干个分流支管连通至进气单元的同一个进气口上；出气单元对应若干个反应通道设置若干个汇流支管，若干个汇流支管连通至出气单元的同一个出气口上。本发明通过进气单元的若干个分流支管将大流量的尾气气流分流至若干个反应通道内，单个反应通道内的尾气气流流量相应减小，因而单个反应通道的筒体横截面尺寸可以相应减小，尾气气流的速度均匀性更容易控制，其他流速分布均匀性高，降低尿素结晶的风险，确保后处理系统的性能，提高氮氧化物的转化效率。
The present invention discloses a multi-stage parallel SCR system, in which an air intake unit, a reaction unit and an air outlet unit are sequentially arranged in series, a plurality of reaction channels are arranged in the reaction unit, a plurality of branch pipes are arranged on the air intake unit corresponding to the plurality of reaction channels, and the plurality of branch pipes are connected to the same air intake port of the air intake unit; a plurality of converging branches are arranged on the air outlet unit corresponding to the plurality of reaction channels, and the plurality of converging branches are connected to the same air outlet port of the air outlet unit. The present invention diverts a large amount of tail gas flow to a plurality of reaction channels through a plurality of branch pipes of the air intake unit, and the tail gas flow in a single reaction channel is reduced accordingly, so that the cross-sectional size of the cylinder of a single reaction channel can be reduced accordingly, the speed uniformity of the tail gas flow is easier to control, and the uniformity of other flow rate distribution is high, thereby reducing the risk of urea crystallization, ensuring the performance of the post-treatment system, and improving the conversion efficiency of nitrogen oxides.
Description
Technical Field
The invention relates to the technical field of marine engine tail gas aftertreatment, in particular to a marine multistage parallel SCR system.
Background
The flourishing development of the shipping industry is a powerful motive force for promoting the economic development of China, but at the same time, the pressure and challenges brought by the concomitant atmospheric pollution emission of ships on the air quality are not quite as great. The marine engine mainly uses a diesel engine, along with the continuous development of the shipping industry, the pollution of tail gas discharged by the marine diesel engine to the atmosphere is increasingly serious, nitrogen oxide (NO X) discharged by the marine diesel engine is one of main pollution sources causing the atmosphere pollution, and in order to reduce the pollution of diesel emission to the atmosphere, the tail gas discharge of the marine diesel engine needs to be treated. Marine diesel engines usually adopt a Selective Catalytic Reduction (SCR) technology to post-treat exhaust emissions, urea aqueous solution is decomposed into ammonia (NH 3) at the temperature of diesel engine exhaust, and under the action of a catalyst, nitrogen oxides (NO X) in diesel engine exhaust are reduced into harmless nitrogen (N 2) and water (H 2 O) by ammonia (NH 3), and finally discharged into the atmosphere, so that the purpose of reducing emissions is achieved.
At present, marine diesel engines generally adopt a single-channel and single-nozzle SCR system for post-treatment of tail gas, and the single-channel and single-nozzle SCR system has the following problems: (1) In order to meet the requirement of large displacement of a marine diesel engine, the cross section size of a cylinder body of an SCR system is generally larger, namely the cylinder body is thicker, an air flow channel in the cylinder body is wider, tail gas air flow is easy to be mixed in the air flow channel in the cylinder body, the speed uniformity of the tail gas air flow is difficult to control, and the distribution uniformity of the gas flow velocity is poor. Poor uniformity of gas flow velocity distribution can lead to uneven catalyst aging on the one hand; on the other hand, because the gas flow velocity distribution is uneven, the temperature of the inner wall surface in the area with smaller gas flow velocity is lower in the tail gas aftertreatment mixing device, when urea liquid drops contact the inner wall surface of the part, a part of heat can be taken away, so that the temperature of the inner wall surface of the part is further reduced, urea liquid drops falling on the inner wall surface with too low temperature are easy to form urea crystals due to insufficient endothermic decomposition, the performance of an aftertreatment system is further influenced, and even the exhaust is out of standard or the aftertreatment system is blocked, so that the power is insufficient. Furthermore, due to poor uniformity of gas flow velocity distribution in the cylinder, after the urea aqueous solution is decomposed into NH 3, the uniformity of mixing the urea aqueous solution with the tail gas flow in the cylinder is poor, so that the conversion efficiency of nitrogen oxides is reduced, and part of ammonia is escaped, thereby influencing the overall performance of the catalyst. Poor air flow uniformity can also lead to carrier temperature gradient, which affects carrier service life. (2) Because the discharge capacity of the marine diesel engine is large, the injection efficiency of a single nozzle is limited, and the aqueous urea solution injected by the single nozzle is difficult to meet the requirement of high-flow exhaust gas flow on NH 3, the conversion efficiency of the single-nozzle SCR system on nitrogen oxides in the exhaust gas flow of the marine diesel engine is lower. Further, even if the spraying amount of the urea aqueous solution of the single nozzle can be increased enough to meet the requirement of the exhaust gas flow with large flow rate on NH 3, the too large spraying amount can be intensively sprayed into the cylinder, the too concentrated large-flow urea aqueous solution is difficult to be quickly decomposed in a short time, the decomposition effect is poor, and the urea crystal is easily formed by falling the urea liquid drops which are not decomposed in the concentrated urea aqueous solution on the inner wall surface of the cylinder.
Disclosure of Invention
The application provides a marine multistage parallel SCR system with reasonable structure, which aims at the defects of poor gas flow velocity distribution uniformity, easiness in forming urea crystals, poor mixing uniformity of air flow, low conversion efficiency of nitrogen oxides and the like of the conventional marine single-channel and single-nozzle SCR system.
The technical scheme adopted by the invention is as follows:
The multistage parallel SCR system is sequentially provided with an air inlet unit, a reaction unit and an air outlet unit in series, wherein a plurality of reaction channels are arranged in the reaction unit, a plurality of branch pipes are arranged on the air inlet unit corresponding to the plurality of reaction channels, and the plurality of branch pipes are communicated to the same air inlet of the air inlet unit; the gas outlet unit is provided with a plurality of converging branch pipes corresponding to the plurality of reaction channels, and the plurality of converging branch pipes are communicated to the same gas outlet of the gas outlet unit.
According to the invention, the high-flow tail gas flow is split into the reaction channels through the split branch pipes of the air inlet unit, and the flow rate of the tail gas flow in the single reaction channel is correspondingly reduced, so that the cross section size of the barrel of the single reaction channel can be correspondingly reduced, the speed uniformity of the tail gas flow is easier to control, the other flow velocity distribution uniformity is high, the risk of urea crystallization is reduced, the performance of a post-treatment system is ensured, and the conversion efficiency of nitrogen oxides is improved.
As a further improvement of the above technical scheme:
The reaction channel is sequentially connected with a flow calculation unit, a decomposition mixing unit and an SCR unit from left to right through flanges; the flow calculation unit adopts a venturi flowmeter and is sequentially provided with a contraction section, a throat and a diffusion section, wherein the contraction section is provided with a temperature sensor and a high-pressure end of a differential pressure sensor, and the throat is provided with a low-pressure end of the differential pressure sensor; the decomposing and mixing unit is provided with a plurality of mixers and a nozzle seat, and the urea nozzle is arranged in the nozzle seat; the SCR unit is internally packaged with a plurality of carriers.
The flow calculation unit adopts a venturi flowmeter, accurately calculates the flow of the tail gas air flow in a single reaction channel through a temperature sensor, a high-pressure end of a differential pressure sensor and a low-pressure end of the differential pressure sensor, feeds back calculation results to a corresponding control system, and guides the injection quantity of the urea aqueous solution in the reaction channel corresponding to the nozzle according to the calculation results to ensure that the injection quantity of the urea aqueous solution meets the demand quantity of the tail gas air flow in the reaction channel for NH 3. The SCR unit is internally packaged with a plurality of carriers, and the carriers can purify pollutants in the tail gas flow in a chemical catalysis mode.
A plurality of V-shaped plates are arranged on the cylinder body of the decomposing and mixing unit, and the V-shaped plates are recessed towards the inside of the cylinder body; a plurality of mixers can be respectively arranged at the front side and the rear side of the V-shaped plate in the cylinder body, and the internal cavity of the cylinder body is divided into an accelerating cavity, a decomposing cavity and a mixing cavity; the accelerating cavity is positioned between the front baffle plate of the V-shaped plate and the mixer at the front side of the V-shaped plate; the decomposing cavity is positioned between the rear baffle of the V-shaped plate and the first mixer at the rear side of the V-shaped plate; the mixing chamber is located between a plurality of mixers at the rear side of the V-shaped plate.
A cylinder body of the decomposing and mixing unit is provided with a plurality of V-shaped plates, and the V-shaped plates are recessed towards the inside of the cylinder body; the inside of the cylinder is provided with a plurality of mixers, and the front side and the rear side of the V-shaped plate can be respectively provided with a plurality of mixers to divide the internal cavity of the cylinder into an accelerating cavity, a decomposing cavity and a mixing cavity. Under the action of a plurality of mixers of a plurality of reaction channels, the tail gas flow is decomposed and mixed for a plurality of times, urea dropping liquid is fully decomposed, the gas flow velocity distribution uniformity is good, the urea crystallization risk is low, the mixing uniformity of the gas flow is good, and the NO X conversion efficiency is high.
The decomposing and mixing unit is uniformly provided with a plurality of nozzle seats along the circumferential direction, and the nozzle seats are respectively arranged on the rear baffle plates of the V-shaped plates.
The included angle between the spraying line of urea water solution sprayed by the urea nozzle on the nozzle seat and the central axis of the cylinder body is 35-65 degrees.
According to the invention, a plurality of V-shaped plates are uniformly arranged on each decomposition mixing unit along the circumferential direction, a nozzle seat is arranged on a rear baffle plate of each V-shaped plate, a urea nozzle is arranged in the nozzle seat, and the urea nozzle can spray urea aqueous solution into a cylinder; the included angle between the spraying line of the urea aqueous solution and the central shaft of the cylinder body is 35-65 degrees, the urea aqueous solution is favorable for fully contacting with the tail gas air flow, the urea aqueous solution can fully absorb heat and accelerate volatilization, the volatilization rate of urea dropping liquid is improved, and the conversion efficiency of NO X is further improved. The urea nozzles are arranged on the rear baffles of the symmetrical V-shaped plates, so that single-channel multi-stage urea aqueous solution injection can be realized, and the requirement of high-flow tail gas flow on injection quantity is met; and a plurality of nozzles spray simultaneously, can spray the urea aqueous solution comparatively dispersedly into the barrel, and the urea aqueous solution of dispersion can decompose rapidly, and decomposition effect is good, and urea liquid drop is decomposed rapidly, is difficult for dropping on the internal face of barrel and forms urea crystallization, and urea crystallization risk is little.
The mixer is provided with a plurality of blade holes which are arranged in an array way, blades are inwards arranged on the blade holes towards the direction of exhaust gas flow and air outlet, and openings of two adjacent rows of blades are staggered.
The openings of the blades of the first mixer positioned on the front side of the V-shaped plate are opposite to the front baffle plates of the V-shaped plate.
The mixer is provided with a plurality of blade holes which are arranged in an array, blades are inwards arranged on the blade holes towards the direction of exhaust gas flow and air outlet, and openings of the blades in two adjacent rows are staggered. The openings of the blades of the first mixer at the front side of the V-shaped plates are opposite to the front baffles of the two V-shaped plates respectively, on one hand, the tail gas flow is dispersed into the accelerating cavity in the directions of the blades, the distribution in the accelerating cavity is more uniform, and the uniformity of the flow velocity of the gas flow is higher; on the other hand, the tail gas air flow is guided to collide towards the front baffle and then turns to, and is accelerated and converged towards the center of the cylinder along the front baffle, so that the flow speed of the tail gas air flow is improved, the accelerated tail gas air flow enters the decomposition cavity along the rear baffle, NH 3 which is decomposed by the urea aqueous solution in the decomposition cavity is more fully mixed, the mixing effect is better, and the mixing uniformity is higher. The tail gas flow is mixed with urea aqueous solution and NH 3 in the decomposition cavity to form mixed gas flow, the mixed gas flow enters the mixing cavity through the second mixer and then enters the SCR unit from the mixing cavity through the third mixer, on one hand, the unverified urea liquid drops in the tail gas flow are impacted on the blades and broken into smaller liquid drops, the volatilization of the urea liquid drops is easier, the decomposition rate of the urea liquid drops is higher, and the risk of urea crystallization on the blades is reduced; on the other hand, the mixed air flows collide with the blades with different directions to turn, and the adjacent two rows of turned air flows are converged, collided and mixed in the directions close to each other, so that the mixing uniformity is higher.
The blade opening directions of the plurality of mixers are arranged around the central axis of the cylinder body at different included angles.
According to the invention, the opening directions of the blades of the plurality of mixers are arranged at different included angles around the central axis of the cylinder, the direction of the airflow is continuously changed after the airflow passes through each mixer, and the airflow is continuously collided and accelerated to be mixed, so that the uniform distribution of airflow velocity is facilitated, the mixing effect is better, and the mixing uniformity is higher.
A plurality of through holes are uniformly formed in the mixer, close to the periphery, along the circumferential direction, and the through holes are positioned on the outer sides of the blade holes.
The mixer is provided with the through holes, so that the flow rate of the tail gas flowing through the through holes is high, on one hand, the back pressure of the gas flow can be reduced, on the other hand, the tail gas flow passing through the mixer can preheat the inner wall surface of the cylinder and the inner wall surface of the front baffle of the V-shaped plate, and the risk of urea crystallization on the inner wall surface of the cylinder and the inner wall surface of the front baffle of the V-shaped plate is reduced.
The periphery of the flow calculating unit and the decomposing and mixing unit is fixedly sleeved with a heat shield.
The heat shield is fixedly sleeved on the periphery of the flow calculating unit and the decomposing and mixing unit, and can play a role in heat preservation of the flow calculating unit and the decomposing and mixing unit, so that heat loss in the flow calculating unit and the decomposing and mixing unit is prevented, the heat of tail gas air flow is fully utilized in the decomposing and mixing unit, urea aqueous solution can fully absorb heat and volatilize, the volatilization rate of urea drops is improved, and the conversion efficiency of NO X is further improved.
The beneficial effects of the invention are as follows:
According to the invention, the high-flow tail gas flow is split into the reaction channels through the split branch pipes of the air inlet unit, and the flow rate of the tail gas flow in the single reaction channel is correspondingly reduced, so that the cross section size of the barrel of the single reaction channel can be correspondingly reduced, the speed uniformity of the tail gas flow is easier to control, the other flow velocity distribution uniformity is high, the risk of urea crystallization is reduced, the performance of a post-treatment system is ensured, and the conversion efficiency of nitrogen oxides is improved.
The flow calculation unit adopts a venturi flowmeter, accurately calculates the flow of the tail gas air flow in a single reaction channel through a temperature sensor, a high-pressure end of a differential pressure sensor and a low-pressure end of the differential pressure sensor, feeds back calculation results to a corresponding control system, and guides the injection quantity of the urea aqueous solution in the reaction channel corresponding to the nozzle according to the calculation results to ensure that the injection quantity of the urea aqueous solution meets the demand quantity of the tail gas air flow in the reaction channel for NH 3. The SCR unit is internally packaged with a plurality of carriers, and the carriers can purify pollutants in the tail gas flow in a chemical catalysis mode.
A cylinder body of the decomposing and mixing unit is provided with a plurality of V-shaped plates, and the V-shaped plates are recessed towards the inside of the cylinder body; the inside of the cylinder is provided with a plurality of mixers, and the front side and the rear side of the V-shaped plate can be respectively provided with a plurality of mixers to divide the internal cavity of the cylinder into an accelerating cavity, a decomposing cavity and a mixing cavity. Under the action of a plurality of mixers of a plurality of reaction channels, the tail gas flow is decomposed and mixed for a plurality of times, urea dropping liquid is fully decomposed, the gas flow velocity distribution uniformity is good, the urea crystallization risk is low, the mixing uniformity of the gas flow is good, and the NO X conversion efficiency is high.
According to the invention, a plurality of V-shaped plates are uniformly arranged on each decomposition mixing unit along the circumferential direction, a nozzle seat is arranged on a rear baffle plate of each V-shaped plate, a urea nozzle is arranged in the nozzle seat, and the urea nozzle can spray urea aqueous solution into a cylinder; the included angle between the spraying line of the urea aqueous solution and the central shaft of the cylinder body is 35-65 degrees, the urea aqueous solution is favorable for fully contacting with the tail gas air flow, the urea aqueous solution can fully absorb heat and accelerate volatilization, the volatilization rate of urea dropping liquid is improved, and the conversion efficiency of NO X is further improved. The urea nozzles are arranged on the rear baffles of the symmetrical V-shaped plates, so that single-channel multi-stage urea aqueous solution injection can be realized, and the requirement of high-flow tail gas flow on injection quantity is met; and a plurality of nozzles spray simultaneously, can spray the urea aqueous solution comparatively dispersedly into the barrel, and the urea aqueous solution of dispersion can decompose rapidly, and decomposition effect is good, and urea liquid drop is decomposed rapidly, is difficult for dropping on the internal face of barrel and forms urea crystallization, and urea crystallization risk is little.
The mixer is provided with a plurality of blade holes which are arranged in an array, blades are inwards arranged on the blade holes towards the direction of exhaust gas flow and air outlet, and openings of the blades in two adjacent rows are staggered. The openings of the blades of the first mixer at the front side of the V-shaped plates are opposite to the front baffles of the two V-shaped plates respectively, on one hand, the tail gas flow is dispersed into the accelerating cavity in the directions of the blades, the distribution in the accelerating cavity is more uniform, and the uniformity of the flow velocity of the gas flow is higher; on the other hand, the tail gas air flow is guided to collide towards the front baffle and then turns to, and is accelerated and converged towards the center of the cylinder along the front baffle, so that the flow speed of the tail gas air flow is improved, the accelerated tail gas air flow enters the decomposition cavity along the rear baffle, NH 3 which is decomposed by the urea aqueous solution in the decomposition cavity is more fully mixed, the mixing effect is better, and the mixing uniformity is higher. The tail gas flow is mixed with urea aqueous solution and NH 3 in the decomposition cavity to form mixed gas flow, the mixed gas flow enters the mixing cavity through the second mixer and then enters the SCR unit from the mixing cavity through the third mixer, on one hand, the unverified urea liquid drops in the tail gas flow are impacted on the blades and broken into smaller liquid drops, the volatilization of the urea liquid drops is easier, the decomposition rate of the urea liquid drops is higher, and the risk of urea crystallization on the blades is reduced; on the other hand, the mixed air flows collide with the blades with different directions to turn, and the adjacent two rows of turned air flows are converged, collided and mixed in the directions close to each other, so that the mixing uniformity is higher.
According to the invention, the opening directions of the blades of the plurality of mixers are arranged at different included angles around the central axis of the cylinder, the direction of the airflow is continuously changed after the airflow passes through each mixer, and the airflow is continuously collided and accelerated to be mixed, so that the uniform distribution of airflow velocity is facilitated, the mixing effect is better, and the mixing uniformity is higher.
The mixer is provided with the through holes, so that the flow rate of the tail gas flowing through the through holes is high, on one hand, the back pressure of the gas flow can be reduced, on the other hand, the tail gas flow passing through the mixer can preheat the inner wall surface of the cylinder and the inner wall surface of the front baffle of the V-shaped plate, and the risk of urea crystallization on the inner wall surface of the cylinder and the inner wall surface of the front baffle of the V-shaped plate is reduced.
The heat shield is fixedly sleeved on the periphery of the flow calculating unit and the decomposing and mixing unit, and can play a role in heat preservation of the flow calculating unit and the decomposing and mixing unit, so that heat loss in the flow calculating unit and the decomposing and mixing unit is prevented, the heat of tail gas air flow is fully utilized in the decomposing and mixing unit, urea aqueous solution can fully absorb heat and volatilize, the volatilization rate of urea drops is improved, and the conversion efficiency of NO X is further improved.
Drawings
Fig. 1 is a perspective view of the present invention.
Fig. 2 is an exploded top view of the present invention.
Fig. 3 is a front view of fig. 1.
Fig. 4 is a cross-sectional view A-A in fig. 3.
Fig. 5 is a schematic diagram of a flow calculation unit.
Fig. 6 is a cross-sectional view of an exploded mixing unit.
Fig. 7 is a schematic diagram of a mixer.
In the figure: 1. an air intake unit; 2. a reaction unit; 3. an air outlet unit; 5. a reaction channel; 6. a branch pipe; 7. an air inlet; 8. a confluence branch pipe; 9. an air outlet; 10. a flow rate calculation unit; 11. a decomposition mixing unit; 12. an SCR unit; 13. a heat shield; 14. a carrier; 15. a constriction section; 16. a throat; 17. a diffusion section; 18. a temperature sensor; 19. a differential pressure sensor high pressure end; 20. a low pressure end of the differential pressure sensor; 21. a cylinder; 22. a mixer; 221. a through hole; 222. a blade hole; 223. a blade; 23. v-shaped plates; 231. a front baffle; 232. a rear baffle; 24. a nozzle holder; 25. an acceleration chamber; 26. a decomposition chamber; 27. a mixing chamber; 28. and (5) spraying rays.
Detailed Description
The following describes specific embodiments of the present invention with reference to the drawings.
As shown in fig. 1, 2 and 3, the invention is provided with an air inlet unit 1, a reaction unit 2 and an air outlet unit 3 in series from left to right, wherein the air inlet unit 1, the reaction unit 2 and the air outlet unit 3 are respectively connected through flanges, so that the disassembly and the assembly are convenient, and the maintenance is convenient. As shown in fig. 2, according to the displacement of the marine diesel engine, a plurality of reaction channels 5 are arranged in the reaction unit 2, a plurality of branch pipes 6 are arranged on the air inlet unit 1 corresponding to the plurality of reaction channels 5, and the plurality of branch pipes 6 are integrally formed and simultaneously communicated to the same air inlet 7 of the air inlet unit 1; the gas outlet unit 3 is provided with a plurality of confluence branch pipes 8 corresponding to the plurality of reaction channels 5, and the plurality of confluence branch pipes 8 are integrally formed and are simultaneously communicated to the same gas outlet 9 of the gas outlet unit 3; in this embodiment, the reaction unit 2 is provided with two reaction channels 5, two branch pipes 6 are correspondingly disposed on the air inlet unit 1, and two converging branch pipes 8 are correspondingly disposed on the air outlet unit 3. The tail gas flow exhausted by the diesel engine is input from the air inlet 7 of the air inlet unit 1, is split into each reaction channel 5 of the reaction unit 2 through a plurality of split branch pipes 6 for corresponding treatment, and is converged to the air outlet 9 through a plurality of converging branch pipes 8 of the air outlet unit 3 for output. According to the invention, the high-flow tail gas flow is split into the reaction channels 5 through the split branch pipes 6 of the air inlet unit 1, and the flow rate of the tail gas flow in the single reaction channel 5 is correspondingly reduced, so that the cross section size of the barrel body of the single reaction channel 5 can be correspondingly reduced, the speed uniformity of the tail gas flow is easier to control, the other flow velocity distribution uniformity is high, the risk of urea crystallization is reduced, the performance of a post-treatment system is ensured, and the conversion efficiency of nitrogen oxides is improved.
As shown in fig. 4, each reaction channel 5 is sequentially flange-connected with a flow calculation unit 10, a decomposition mixing unit 11 and an SCR unit 12 from left to right; the heat shield 13 is fixedly sleeved on the peripheries of the flow computing unit 10 and the decomposition mixing unit 11, the heat shield 13 can play a role in preserving heat of the flow computing unit 10 and the decomposition mixing unit 11, heat loss inside the flow computing unit 10 and the decomposition mixing unit 11 is prevented, the heat of tail gas flow is fully utilized in the decomposition mixing unit 11, urea aqueous solution can fully absorb heat and volatilize, the volatilization rate of urea drops is improved, and then the conversion efficiency of NO X is improved. The SCR unit 12 has a plurality of carriers 14 enclosed therein, and the carriers 14 are capable of purifying pollutants in the exhaust gas stream by means of chemical catalysis.
As shown in fig. 5, the flow calculation unit 10 adopts a venturi flowmeter, and sequentially sets a contraction section 15, a throat 16 and a diffusion section 17 from front to back, a temperature sensor 18 and a differential pressure sensor high-pressure end 19 are arranged on the contraction section 15, a differential pressure sensor low-pressure end 20 is arranged on the throat 16, the flow of the tail gas air in the single reaction channel 5 is accurately calculated through the temperature sensor 18, the differential pressure sensor high-pressure end 19 and the differential pressure sensor low-pressure end 20, the calculation result is fed back to a corresponding control system, and the control system guides the injection quantity of the urea aqueous solution of a corresponding nozzle in the reaction channel 5 according to the calculation result, so that the injection quantity of the urea aqueous solution is ensured to meet the demand quantity of the tail gas air in the reaction channel 5 for NH 3.
As shown in fig. 6, two V-shaped plates 23 are symmetrically arranged on the outer peripheral surfaces of the two opposite sides of the front end portion of the cylinder 21 of the decomposing and mixing unit 11, the V-shaped plates 23 are recessed toward the inside of the cylinder 21, one side of the V-shaped plates 23, which is close to the flow rate calculating unit 10, is provided with a front baffle 231, and the other side is provided with a rear baffle 232; the rear baffle 232 of each V-shaped plate 23 is provided with a nozzle seat 24, a urea nozzle is arranged in the nozzle seat 24, a nozzle injection opening is arranged in the center of the nozzle seat 24 (the urea nozzle is not shown in the figure), and the urea nozzle can inject urea aqueous solution into the cylinder 21; the included angle between the spraying line 28 of the urea aqueous solution and the central shaft of the cylinder 21 is 35-65 degrees, so that the urea aqueous solution is in full contact with the tail gas flow, the urea aqueous solution can absorb heat fully and volatilize rapidly, the volatilization rate of urea drops is improved, and the conversion efficiency of NO X is further improved. The urea nozzles are arranged on the rear baffles 232 of the two symmetrical V-shaped plates 23, so that single-channel multi-stage urea aqueous solution injection can be realized, and the requirement of high-flow tail gas flow on injection quantity is met; and two nozzles spray simultaneously, can spray the urea aqueous solution comparatively dispersedly into barrel 21, and the urea aqueous solution of dispersion can decompose rapidly, and decomposition effect is good, and the urea liquid drop is decomposed rapidly, is difficult for dropping on the internal face of barrel 21 and forms urea crystallization, and urea crystallization risk is little. The inside of the cylinder 21 is sequentially provided with a plurality of mixers 22 from front to back, three mixers 22 are arranged in this embodiment, one mixer 22 is located at the front side of the V-shaped plate 23, the other two mixers 22 are located at the rear side of the V-shaped plate 23, and the internal cavity of the cylinder 21 is divided from front to back into an accelerating cavity 25 located between the first mixer 22 and the front baffle 231 of the V-shaped plate 23, a decomposing cavity 26 located between the rear baffle 232 of the V-shaped plate 23 and the second mixer 22, and a mixing cavity 27 located between the second mixer 22 and the third mixer 22.
As shown in fig. 7, the mixer 22 is a circular plate, a plurality of elongated through holes 221 are uniformly formed in the circular plate near the periphery along the circumferential direction, and the flow rate of the tail gas flowing through the elongated through holes 221 is relatively large, so that on one hand, the back pressure of the gas flow can be reduced, and on the other hand, the tail gas flow passing through the through holes can preheat the inner wall surface of the cylinder 21 and the inner wall surface of the front baffle 231 of the V-shaped plate 23, thereby reducing the risk of urea crystallization on the inner wall surface of the cylinder 21 and the inner wall surface of the front baffle 231 of the V-shaped plate 23. A plurality of blade holes 222 which are arranged in an array are formed in the inner side of the plurality of through holes 221 on the circular plate, blades 223 are inwards arranged in the direction of the exhaust gas flow and the air outlet direction on the blade holes 222, and openings of the blades 223 of two adjacent rows are staggered. The opening directions of the blades 223 of the three mixers 22 are arranged around the central axis of the cylinder 21 at different angles, and the range of the included angles between the openings of the blades 223 of the two adjacent mixers 22 is 60-120 degrees. After the first mixer 22 is installed, the openings of a plurality of blades 223 are opposite to the front baffles 231 of the two V-shaped plates 23 respectively, on one hand, the tail gas flow is dispersed into the accelerating cavity 25 in two directions of the blades 223, the tail gas flow is distributed more uniformly in the accelerating cavity 25, and the uniformity of the flow velocity of the tail gas flow is higher; on the other hand, the tail gas flow is guided to collide towards the front baffle 231 and then turns to be accelerated and collected towards the center of the cylinder 21 along the front baffle 231, so that the flow speed of the tail gas flow is improved, the accelerated tail gas flow enters the decomposition cavity 26 along the rear baffle 232, NH 3 decomposed by the urea aqueous solution in the decomposition cavity 26 is more fully mixed, the mixing effect is better, and the mixing uniformity is higher. The tail gas flow is mixed with urea aqueous solution and NH 3 in the decomposition cavity 26 to form mixed gas flow, the mixed gas flow enters the mixing cavity 27 through the second mixer 22, and then enters the SCR unit 12 from the mixing cavity 27 through the third mixer 22, on one hand, the unverified urea liquid drops in the tail gas flow impact on the blades 223 and are broken into smaller liquid drops, the volatilization of the urea liquid drops is easier, the decomposition rate of the urea liquid drops is higher, and the risk of urea crystallization on the blades 223 is reduced; on the other hand, the mixed air flows collide with the blades 223 with different directions to turn, and the adjacent two rows of turned air flows are converged, collided and mixed in the directions close to each other, so that the mixing uniformity is higher. In addition, because the opening directions of the blades 223 of the three mixers 22 have included angles, the airflow continuously changes direction after passing through each mixer 22, and the airflow is continuously collided and accelerated to be mixed, so that the uniform distribution of airflow velocity is facilitated, the mixing effect is better, and the mixing uniformity is higher.
When the invention actually works, the tail gas flow exhausted by the diesel engine is input from the air inlet 7 of the air inlet unit 1 and then is split into each reaction channel 5 of the reaction unit 2 through a plurality of split branch pipes 6; a urea nozzle in the nozzle holder 24 of each reaction channel 5 injects a predetermined amount of urea aqueous solution into the decomposition chamber 26 based on the calculation result of the flow rate calculation means 10 in the reaction channel 5; the tail gas flow in each reaction channel 5 enters the decomposition mixing unit 11 after passing through the flow calculating unit 10, and the urea aqueous solution sprayed by the urea nozzle absorbs the heat of the tail gas flow in the decomposition cavity 26 of the decomposition mixing unit 11 to complete the first decomposition of urea liquid drops and form mixed gas flow; the mixed gas flows through the second mixer 22, and the urea liquid drops which are not decomposed in the mixed gas impact on the blades 223 of the second mixer 22, are broken into urea liquid drops with smaller particles, are further volatilized into the mixed gas after absorbing heat, flow into the mixing cavity 27 along with the mixed gas, and complete the second decomposition and mixing of the urea liquid drops; the mixed gas flow in the mixing cavity 27 flows through the third mixer 22, and the urea liquid drops which are not decomposed in the mixed gas flow impact on the blades 223 of the third mixer 22, are broken into urea liquid drops with smaller particles, are volatilized further into the mixed gas flow after absorbing heat, flow into the SCR unit 12 along with the mixed gas flow, and complete the third decomposition and mixing of the urea liquid drops; the mixed gas flows through the carrier 14 of the SCR unit 12, is purified and enters the confluence branch pipe 8 of the air outlet unit 3; the gas flows in the reaction channels 5 are collected by a plurality of collecting branch pipes 8 and then output from the gas outlet 9. Under the action of the mixers 22 of the reaction channels 5, the tail gas flow is decomposed and mixed for many times, urea drops are decomposed sufficiently, the gas flow velocity distribution uniformity is good, the urea crystallization risk is low, the mixing uniformity of the gas flow is good, and the NO X conversion efficiency is high.
The above description is illustrative of the invention and is not intended to be limiting, and the invention may be modified in any form without departing from the spirit of the invention. For example, according to the flow requirement in each reaction channel 5, each decomposition mixing unit 11 may also be uniformly provided with a plurality of V-shaped plates 23 along the circumferential direction, and each V-shaped plate 23 is provided with a nozzle seat 24, so that the urea aqueous solution is more dispersed and injected into the cylinder 21, and the decomposition of urea droplets is more facilitated. The front side and the rear side of the V-shaped plate 23 in the cylinder 21 can be respectively provided with a plurality of mixers 22, and the opening directions of the blades 223 of the plurality of mixers 22 are arranged at different included angles around the central axis of the cylinder 21, so that the flow velocity distribution of the tail gas air flow is more uniform, and the air flow mixing effect is better.
Claims (8)
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| DE102020106882A1 (en) * | 2020-03-13 | 2021-09-16 | Purem GmbH | Exhaust gas treatment system for an exhaust system of an internal combustion engine and method for operating such an exhaust gas treatment system |
| CN112228195A (en) * | 2020-09-21 | 2021-01-15 | 江苏大学 | A variable combination control system and exhaust gas collection device for engine exhaust aftertreatment |
| WO2022087279A1 (en) * | 2020-10-22 | 2022-04-28 | Cummins Emission Solutions Inc. | Exhaust gas aftertreatment system |
| CN112814770B (en) * | 2020-12-31 | 2022-04-05 | 潍柴动力股份有限公司 | Uniformity evaluation method and device of parallel SCR system |
| CN112763222A (en) * | 2021-01-07 | 2021-05-07 | 无锡亿利环保科技有限公司 | Post-treatment mixer crystallization monitoring rack |
| CN113931723A (en) * | 2021-10-12 | 2022-01-14 | 河北工业大学 | A device and method for reducing urea crystallization in SCR system |
| CN114810293B (en) * | 2022-04-21 | 2023-04-07 | 无锡威孚力达催化净化器有限责任公司 | Device and method for controlling and eliminating SCR system mixer crystallization |
| CN115030803B (en) * | 2022-06-28 | 2023-12-15 | 潍柴动力股份有限公司 | Mixer and diesel engine |
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