CN118110586A - Method for improving reaction capacity of two-stage DeNOx system through periodic ammonia storage state control - Google Patents
Method for improving reaction capacity of two-stage DeNOx system through periodic ammonia storage state control Download PDFInfo
- Publication number
- CN118110586A CN118110586A CN202410229272.2A CN202410229272A CN118110586A CN 118110586 A CN118110586 A CN 118110586A CN 202410229272 A CN202410229272 A CN 202410229272A CN 118110586 A CN118110586 A CN 118110586A
- Authority
- CN
- China
- Prior art keywords
- ammonia storage
- state
- carrier
- cat2
- urea nozzle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 221
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 110
- 238000003860 storage Methods 0.000 title claims abstract description 110
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 68
- 230000000737 periodic effect Effects 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000002347 injection Methods 0.000 claims abstract description 63
- 239000007924 injection Substances 0.000 claims abstract description 63
- 101100208039 Rattus norvegicus Trpv5 gene Proteins 0.000 claims abstract description 55
- 101100494773 Caenorhabditis elegans ctl-2 gene Proteins 0.000 claims abstract description 41
- 101100112369 Fasciola hepatica Cat-1 gene Proteins 0.000 claims abstract description 41
- 101100005271 Neurospora crassa (strain ATCC 24698 / 74-OR23-1A / CBS 708.71 / DSM 1257 / FGSC 987) cat-1 gene Proteins 0.000 claims abstract description 41
- 238000011217 control strategy Methods 0.000 claims abstract description 12
- 230000007423 decrease Effects 0.000 claims abstract description 7
- 239000007921 spray Substances 0.000 claims abstract description 6
- 238000012544 monitoring process Methods 0.000 claims abstract description 5
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 80
- 239000004202 carbamide Substances 0.000 claims description 80
- 239000003054 catalyst Substances 0.000 claims description 19
- 238000001179 sorption measurement Methods 0.000 claims description 8
- 238000003795 desorption Methods 0.000 claims description 7
- 238000007254 oxidation reaction Methods 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 238000012360 testing method Methods 0.000 claims description 3
- 230000009977 dual effect Effects 0.000 claims description 2
- 238000011065 in-situ storage Methods 0.000 claims description 2
- 239000003638 chemical reducing agent Substances 0.000 abstract description 17
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 85
- 239000007789 gas Substances 0.000 description 9
- 230000006872 improvement Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 238000011144 upstream manufacturing Methods 0.000 description 5
- 101150116295 CAT2 gene Proteins 0.000 description 4
- 101100326920 Caenorhabditis elegans ctl-1 gene Proteins 0.000 description 4
- 101100126846 Neurospora crassa (strain ATCC 24698 / 74-OR23-1A / CBS 708.71 / DSM 1257 / FGSC 987) katG gene Proteins 0.000 description 4
- 238000010531 catalytic reduction reaction Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000003745 diagnosis Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000006722 reduction reaction Methods 0.000 description 3
- 230000008929 regeneration Effects 0.000 description 3
- 238000011069 regeneration method Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000003631 expected effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
The invention provides a method for improving the reaction capacity of a two-stage DeNOx system through the control of a periodic ammonia storage state, which comprises the following steps: s1, continuously monitoring temperatures, exhaust temperatures and mass flow rates of Cat1 and Cat2, and judging whether working conditions are suitable for implementing an ammonia storage periodic control strategy; s2, judging whether the actual ammonia storage amount of Cat1 exceeds the upper limit value of an ammonia storage target, and if so, enabling the No.1 nozzle to enter a blowout reducing state; s3.1# nozzle enters a spray reducing state and 2# nozzle enters a spray state; s4, when the actual ammonia storage amount of Cat2 exceeds the upper limit value of the ammonia storage target, the No. 2 nozzle enters a blowout reducing state; s5, after the conversion efficiency of Cat2 is monitored to start to decrease, the No.1 nozzle enters an injection state; s6, when the actual ammonia storage amount of Cat1 exceeds the upper limit value of the ammonia storage target, repeating S2, switching the No.1 nozzle to a reduced-injection state, and starting a new ammonia storage periodic control. By using the method, the aftertreatment system under the same hardware performance condition can realize higher overall conversion efficiency and reductant energy efficiency ratio.
Description
Technical Field
The invention relates to the field of exhaust emission, in particular to a method for improving the reaction capacity of a two-stage DeNOx system through periodical ammonia storage state control.
Background
The exhaust gas of the diesel engine contains more nitrogen oxides (NOx) and Particulate Matters (PM), the existing emission regulations limit the emission amount of the NOx and the PM, limit values of different degrees are regulated, and as the emission regulations are further tightened, the weighting factors of the corresponding emission limit values on the emission of the cold start working condition are obviously increased, and the aftertreatment system is promoted to develop in the direction of tight coupling of the size and the function.
NOx is a reaction product of N 2 and O 2 in air in the cylinder that the engine draws in at high temperature, and its main components are NO and NO 2. Urea selective catalytic reduction (Urea-SCR) technology is the primary technology for engine control of NOx emissions, the most common form of which is: the ammonia (NH 3) is generated by decomposing urea aqueous solution, and under the action of the SCR catalyst, the ammonia and NOx are subjected to selective catalytic reduction reaction, nitrogen and water are generated and then discharged into the atmosphere, and different urea amounts are sprayed into the exhaust gas of the diesel engine to effectively control the emission amount of the NOx. Hydrolysis and pyrolysis reactions of urea do not take place sufficiently at temperatures below 187 c, while the reaction rate of SCR reactions at temperatures below 250 c is significantly affected by the NO 2/NOx ratio, real-time ammonia storage, temperature and space velocity.
Currently, the main DeNOx system is a two-stage DeNOx system, and the front stage is as close to the engine outlet as possible to reach the high-efficiency reaction temperature more quickly. There are many technical routes for a two-stage DeNOx system, in which the arrangement space and cost of the technical route of oxidation catalyst (DOC) +particulate trap coated with SCR catalyst (SDPF) +selective catalytic reduction catalyst (SCR) +ammonia oxidation catalyst (ASC) are significantly advantageous and widely used. But the application of this technical line has the following problems. Because the oxidation catalyst is not selective, NH 3 will be directly oxidized, SDPF is usually only coated with SCR catalyst, and the SCR reaction will preferentially consume NO 2 in the exhaust gas, so that the passive regeneration capability of SDPF is seriously weakened, the active regeneration interval is shortened, and the fuel consumption and the service life of the aftertreatment system are affected.
Meanwhile, the urea distribution strategy of the two-stage injection system of the traditional SDPF+SCR is mainly based on the upstream SDPF, the downstream SCR is used as a supplement for the condition of insufficient reaction capacity of the upstream SDPF, a large amount of reducing agent reacts on the SDPF at the moment, NO 2 almost does not exist, and therefore the condition of short regeneration interval of the aftertreatment system can occur. In addition, the traditional distribution strategy of the two-stage urea distribution system is characterized in that the urea injection quantity is concentrated at an SDPF inlet with higher temperature under the high-temperature working condition, so that the injected urea is oxidized to a greater extent, and the energy efficiency of the reducing agent is poor.
Therefore, the current main stream SCR system urea injection control strategy adopts a strategy based on a relatively constant Ammonia Nitrogen Ratio (ANR) as feedforward control and assisted by a downstream NOx concentration or a catalyst carrier ammonia storage quantity feedback value as closed-loop control, and basically controls the urea injection quantity in a relatively stable state with the upstream NOx emission. However, the results of the performance study on the selective catalytic conversion system show that: the constant injection quantity cannot exert the performance of the catalyst and the energy efficiency of the reducing agent to the maximum degree at the same time under the condition of stable inlet condition, and only when the reducing agent supply quantity is changed along with the optimal change curve of the dynamic parameters under the current working condition, namely a periodical reducing agent supply strategy is adopted, the relevant parameters of the catalyst can be ensured to be always maintained at a higher activity level within a controllable range, so that higher conversion efficiency and energy efficiency ratio are realized. When the unipolar DeNOx system adopts a periodic reductant supply strategy, the actual ammonia storage capacity of the carrier is limited, a long storage time is required for the carrier to reach a higher NH 3 storage level or a NOx storage level, and a relatively short NOx conversion efficiency peak window cannot cover the NOx conversion efficiency reduction caused in the storage process, so that the overall application effect is poor.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for improving the reaction capacity of a two-stage DeNOx system through periodical ammonia storage state control, and the NOx conversion efficiency and the reducing agent energy efficiency ratio of the aftertreatment system are effectively improved under the same performance condition of aftertreatment hardware.
In order to achieve the technical effects, the invention adopts the following technical scheme:
A method for improving the reaction capacity of a two-stage DeNOx system through the control of a periodic ammonia storage state specifically comprises the following steps:
S1, continuously monitoring the Cat1 carrier temperature, the Cat2 carrier temperature, the exhaust temperature and the exhaust mass flow rate, and judging whether the current working condition is suitable for implementing an ammonia storage periodic control strategy;
S2, when judging that the condition is met, the system enters an ammonia storage periodic control state, firstly judging whether the actual ammonia storage amount of the Cat1 carrier exceeds the upper limit value of an ammonia storage target of the ammonia storage periodic control state, and if the actual ammonia storage amount does not exceed the upper limit value, adjusting the urea injection amount of the No. 1 urea nozzle to promote the ammonia storage level on the Cat1 carrier to be rapidly increased; when the actual ammonia storage exceeds the limit value, the No. 1 urea nozzle enters a blowout reducing state;
S3.1# urea nozzle enters an injection state and 2# urea nozzle enters an injection state at the same time of entering a spray reducing state, and the injection quantity of the 2# urea nozzle is controlled;
s4, when the actual ammonia storage amount of the Cat2 carrier exceeds the upper limit value of the ammonia storage target, the 2# urea nozzle enters a blowout reducing state;
S5, after the real-time DeNOx conversion efficiency of the Cat2 carrier is monitored to start to decrease, the 1# urea nozzle enters an injection state and sets an injection quantity control target of the 1# urea nozzle as follows: the NH 3 leakage concentration at the outlet of the Cat1 carrier is controlled within a calibrated limit value while the ammonia storage rate of the Cat1 carrier is maximized; control target of the supply amount of the 1# urea nozzle NH 3 in this state=nh 3 theoretical reaction consumption rate calculated by the in-situ NOx sensor+maximum ammonia storage rate of Cat1 carrier+ammonia slip rate limit;
S6, when the actual ammonia storage amount of the Cat1 carrier exceeds the upper limit value of the ammonia storage target, repeating the step S2, switching the No. 1 urea nozzle to a blowout reducing state, and starting a new round of ammonia storage periodic control;
s7, in the ammonia storage periodic control process, if the temperature and the exhaust conditions no longer meet the conditions for implementing the ammonia storage periodic control strategy, exiting the ammonia storage periodic control mode.
Preferably, the control strategy implementation conditions require the determination of the appropriate temperature window and space velocity window by conducting a catalyst strip test.
Preferably, in step S2, the specific injection control target of the injection reducing state of the # 1 urea nozzle needs to be determined according to the real-time reaction capability of the Cat2 carrier, and when the real-time reaction capability of the Cat2 carrier is weak, the injection amount of the # 1 urea nozzle needs to be increased appropriately to control the NOx level entering the Cat2 carrier to be within the convertible range thereof; when the real-time reaction capability of the Cat2 carrier is sufficient, the injection amount of the 1# urea nozzle may be set to 0.
Preferably, in step S3, the injection amount of the # 2 urea nozzle after entering the injection state needs to be calculated through a chemical reaction kinetic model and an adsorption and desorption rate model of the Cat2 carrier: NH 3 target supply to urea nozzle # 2 = NH 3 theoretical reaction consumption rate calculated from Cat2 carrier inlet NOx sensor measurements + maximum ammonia storage rate in current state calculated from Cat2 carrier adsorption and desorption rate model + maximum NH 3 oxidation reaction rate calculated from ASC reaction kinetics model.
Compared with the prior art, the invention has the following beneficial effects:
The invention provides an ammonia storage periodic control method for a two-stage DeNOx system, which can realize the great improvement of the reaction capacity of the 3-stage system in one injection control period by carrying out periodic full-load and no-load control on the ammonia storage levels of front and rear-stage DeNOx catalyst carriers. By using the method, the aftertreatment system under the same hardware performance condition can realize higher overall conversion efficiency and reductant energy efficiency ratio. The wide-range ANR environment provided by the method can provide better diagnosis basic conditions for the realization of functions such as signal diagnosis of the NOx sensor, catalyst performance diagnosis and the like, and is convenient for helping an aftertreatment system to realize a more comprehensive and accurate on-line monitoring (OBM) function.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a schematic illustration of a vehicle aftertreatment system suitable for use with a dual stage DeNOx system as described in example 2;
FIG. 2 is a flow chart showing the implementation of the method for improving the reaction capacity of a dual-stage DeNOx system by periodic ammonia storage state control as described in example 1;
fig. 3 is a schematic diagram showing a system state change during the ammonia storage periodic control described in example 1.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The description herein of "first," "second," etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated.
Example 1
As shown in fig. 2, the present embodiment provides a method for improving the reaction capacity of a dual-stage DeNOx system through the periodic ammonia storage state control, which includes the following steps:
1) The control system judges whether the implementation condition of the ammonia storage periodic control strategy is met or not by continuously monitoring the Cat1 carrier temperature, the Cat2 carrier temperature, the exhaust temperature and the exhaust mass flow; under the condition of lower temperature, the adsorption and desorption rate of ammonia and the SCR reaction rate are lower, so that the period for obtaining the primary conversion efficiency gain is prolonged, and when the time of the whole period is long and the primary conversion efficiency gain is insufficient to compensate the conversion efficiency reduction of other periods in the period, the periodic ammonia storage control strategy is selected to be developed under the working condition, so that the expected effect cannot be obtained; meanwhile, when the temperature is too high, the ammonia storage capacity of the carrier is very limited, the implementation significance of the periodic ammonia storage control strategy is not great, and the control difficulty of the system can be increased. The control strategy implementation conditions require the determination of the appropriate temperature window and space velocity window by conducting a catalyst strip test.
When judging that the condition is met, entering an ammonia storage periodic control state, wherein the reducing agent supply strategy before entering the state is generally closed-loop controlled based on the target ammonia storage amount under normal conditions, so that Cat1 is generally in a higher ammonia storage level, firstly comparing the calculated value of the actual ammonia storage amount of Cat1 with the target upper limit value in the ammonia storage periodic control state, and once the actual ammonia storage exceeds the limit value, entering a spray reducing state by a No. 1 urea nozzle to obtain a short-time reaction capacity improvement, and entering an injection state by a No. 2 urea nozzle to enable Cat2 to quickly reach the ammonia storage target upper limit value; after the No. 1 urea nozzle enters a spray reducing state, as the proportion of NOx/(NH 3 +NOx) in exhaust gas at the inlet of Cat1 is very high and active sites of the Cat1 carrier are occupied by NH 3 mostly, the collision probability of NH 3 molecules and NOx molecules at the active sites is increased under the condition, and the reaction capacity of the Cat1 for a short time is improved. The decrease in injection quantity of urea nozzle #1 can quickly empty the ammonia storage on Cat1, and the duration of this state allows for continued storage of NOx on the Cat1 carrier.
The specific injection control target of the injection reducing state of the No. 1 urea nozzle needs to be determined according to the real-time reaction capacity of Cat2, and when the real-time reaction capacity of Cat2 is weak, the injection quantity of the No. 1 urea nozzle needs to be properly increased to control the NOx level entering the Cat2 to be in the convertible range; when the real-time reaction capability of Cat2 is sufficient, the injection amount of the urea nozzle # 1 may be set to 0.
The injection quantity of the No. 2 urea nozzle after entering an injection state needs to be calculated through a chemical reaction kinetic model and an adsorption and desorption rate model of Cat 2: NH 3 target supply amount of urea nozzle #2 = NH 3 theoretical reaction consumption rate calculated by Cat2 inlet NOx sensor measurement value + maximum ammonia storage rate under current state calculated by Cat2 adsorption and desorption rate model + maximum NH 3 oxidation reaction rate calculated by ASC reaction kinetics model, the purpose of this target supply amount is to quickly establish Chu Anshui flat of Cat2 to the target value to ensure that DeNOx efficiency of the system as a whole is always at a higher level while controlling ammonia slip within conversion capability of ASC.
2) Before the calculated value of the actual ammonia storage amount of Cat2 does not exceed the ammonia storage target upper limit value, the 1# urea nozzle and the 2# urea nozzle maintain the current injection control state, once the calculated value of the actual ammonia storage amount of Cat2 is monitored to exceed the ammonia storage target upper limit value, the 2# urea nozzle enters the injection reducing state to obtain a short-time reaction capacity improvement, and the actual conversion efficiency of Cat2 can be rapidly reduced after the short-term efficiency peak value is still in the injection reducing state at the moment, and the 1# urea nozzle enters the injection state before the actual conversion efficiency of Cat2 starts to be reduced.
The time interval from the state of injection reduction of the 2# urea nozzle to the start of injection of the 1# urea nozzle is a key parameter for improving the direct overall conversion efficiency, and if the time interval is set to be too short, the ratio of the NOx at the Cat2 inlet to the NH 3 is not obviously improved, so that the efficiency improvement of the 2# urea nozzle is difficult to obtain; if this time interval is set too long, the decrease in conversion efficiency of Cat2 in the state where no injection is performed by the urea nozzle # 1 will directly result in a decrease in overall DeNOx efficiency; thus, there is an optimum value for the time interval from the 2# urea nozzle entering the reduced injection state to the 1# urea nozzle beginning injection, which can be obtained by looking up the optimum injection interval calibration table for the inlet NOx mass flow and real-time ammonia storage amount Cat 2. In order to avoid emission risk brought to the system by the calibration deviation of the optimal injection interval, the real-time DeNOx efficiency of the Cat2 carrier needs to be monitored at the same time, and once the real-time DeNOx efficiency of the Cat2 carrier is monitored to be obviously reduced in a short period of time, the 1# urea nozzle is immediately opened to supply the reducing agent.
3) After the # 1 urea nozzle is opened, cat1 will achieve a short reaction capacity boost due to the high NOx storage level. When the ammonia storage amount of Cat1 is monitored to reach the target value, a new cycle of periodic ammonia storage control is started.
4) After entering the ammonia storage periodic control state, the control system still monitors the Cat1 carrier temperature, the Cat2 carrier temperature, the exhaust temperature and the exhaust mass flow, and once the state entering condition is not met for more than a certain time, the ammonia storage periodic control state can be exited, and the normal reducing agent supply control state is entered.
The system state change during the ammonia storage periodic control is shown in fig. 3, and the ammonia storage periodic control is performed under appropriate temperature and exhaust conditions. After entering an ammonia storage periodic control state, the system firstly confirms whether the actual ammonia storage amount of Cat1 reaches the upper limit value of an ammonia storage target in the control state, and if the actual ammonia storage amount reaches the upper limit value, the 1# urea nozzle enters a blowout reducing control state to obtain the improvement of primary conversion efficiency; the injection of the No. 1 urea nozzle is reduced, and the injection of the No.2 urea nozzle is started, and the injection control aim is to enable Cat2 to reach the upper limit value of the ammonia storage aim as soon as possible, so that the NH 3 maximum adsorption rate of Cat2, the NOx mass flow of the Cat2 inlet and the real-time ammonia storage quantity under the working condition need to be continuously calculated.
As this condition continues, the ammonia storage level of Cat1 will continue to drop, and after a certain level, the NOx storage amount will begin to rise because insufficient NH 3 has reacted with NOx in the exhaust. At this point Cat2 has its NOx storage level approaching 0 due to the presence of continuous urea injection at the inlet.
When the actual ammonia storage amount of Cat2 reaches the target upper limit value of ammonia storage under the control state, the 2# urea nozzle enters the injection reducing control state to obtain the improvement of primary conversion efficiency, at the moment, the 1# urea nozzle is still in the injection stopping state, the NOx concentration at the inlet of Cat2 is high, and the actual ammonia storage level of Cat2 is rapidly reduced.
After the efficiency peak of Cat2 is generated, once the efficiency of Cat2 is detected to start to decline, the 1# urea nozzle is opened immediately, at this time, a great amount of NOx is adsorbed on the Cat1 carrier, and at this moment, the adsorbed active NOx molecules and NH 3 molecules generated by the injection of the 1# urea nozzle have higher collision probability, so that a conversion efficiency peak will be generated. As the reaction occurs, NOx stored on Cat1 is rapidly reacted away and the remaining NH 3 begins to be stored on Cat1, causing the ammonia level stored by Cat1 to rise gradually. And after the actual ammonia storage amount of Cat1 is monitored to reach the upper limit value of the ammonia storage target in the control state, starting a new round of ammonia storage periodic control.
Example 2
As shown in fig. 1, the present embodiment provides a post-treatment system for a motor vehicle, which is adapted to match a two-stage DeNOx system, wherein exhaust gas of an engine sequentially passes through DOC, cat1, cat2 and then enters the atmosphere, wherein the DOC oxidizes reducing gases such as CO, HC and the like in the exhaust gas, and the Cat1 and Cat2 consume NOx in the exhaust gas through SCR reaction. When the carrier temperature of Cat1 exceeds the urea start-injection critical temperature, the urea nozzle # 1 starts to inject urea, the injected urea is subjected to pyrolysis and hydrolysis reaction under the heating effect of exhaust gas, NH 3,NH3 is generated to react with NOx rapidly under the effect of an SCR catalyst on Cat1, N 2 and H 2 O are generated, if the urea injection amount is insufficient, the rest of NOx continuously flows to the downstream, and if the urea injection amount is excessive, the rest of NH 3 flows to the downstream; cat2 as a redundant DeNOx system assumes the remaining NOx conversion work, to which the # 2 urea nozzle supplies the required reductant. The reductant supply system of the entire aftertreatment system uses an aqueous urea solution with a mass concentration of 32.5% as reductant. The ECU and the DCU can be mutually independent hardware structures, and can also be combined into a complete control unit. The ECU and the DCU collect signals sent by an engine rotating speed, an engine fuel injection quantity, an air inlet temperature, an air inlet pressure, an air inlet mass flow, an EGR valve opening, a cooling water temperature, a DOC catalyst upstream temperature sensor, a Cat1 inlet temperature sensor, a Cat2 inlet temperature sensor, an SCR catalyst downstream temperature sensor, a DOC catalyst upstream NOx concentration sensor, a Cat2 inlet NOx concentration sensor, a Cat2 outlet NOx concentration sensor, a urea liquid level sensor and the like, and based on periodic control targets of Cat1 and Cat2 ammonia storage levels, the accurate calculation of the reducing agent supply quantity of the two-stage injection system is completed through the calculation of corresponding control function modules, so that the overall conversion efficiency and the improving target of the reducing agent energy efficiency ratio of the two-stage DeNOx system are realized.
While the present invention has been described with reference to the above embodiments, it is apparent to those skilled in the art from this disclosure that various changes and modifications can be made without departing from the spirit of the invention.
Claims (4)
1. A method for improving the reaction capacity of a two-stage DeNOx system through the control of a periodic ammonia storage state, which is characterized by comprising the following steps:
S1, continuously monitoring the Cat1 carrier temperature, the Cat2 carrier temperature, the exhaust temperature and the exhaust mass flow rate, and judging whether the current working condition is suitable for implementing an ammonia storage periodic control strategy;
S2, when judging that the condition is met, the system enters an ammonia storage periodic control state, firstly judging whether the actual ammonia storage amount of the Cat1 carrier exceeds the upper limit value of an ammonia storage target of the ammonia storage periodic control state, and if the actual ammonia storage amount does not exceed the upper limit value, adjusting the urea injection amount of the No. 1 urea nozzle to promote the ammonia storage level on the Cat1 carrier to be rapidly increased; when the actual ammonia storage exceeds the limit value, the No. 1 urea nozzle enters a blowout reducing state;
S3.1# urea nozzle enters an injection state and 2# urea nozzle enters an injection state at the same time of entering a spray reducing state, and the injection quantity of the 2# urea nozzle is controlled;
s4, when the actual ammonia storage amount of the Cat2 carrier exceeds the upper limit value of the ammonia storage target, the 2# urea nozzle enters a blowout reducing state;
S5, after the real-time DeNOx conversion efficiency of the Cat2 carrier is monitored to start to decrease, the 1# urea nozzle enters an injection state and sets an injection quantity control target of the 1# urea nozzle as follows: the NH 3 leakage concentration at the outlet of the Cat1 carrier is controlled within a calibrated limit value while the ammonia storage rate of the Cat1 carrier is maximized; control target of the supply amount of the 1# urea nozzle NH 3 in this state=nh 3 theoretical reaction consumption rate calculated by the in-situ NOx sensor+maximum ammonia storage rate of Cat1 carrier+ammonia slip rate limit;
S6, when the actual ammonia storage amount of the Cat1 carrier exceeds the upper limit value of the ammonia storage target, repeating the step S2, switching the No. 1 urea nozzle to a blowout reducing state, and starting a new round of ammonia storage periodic control;
s7, in the ammonia storage periodic control process, if the temperature and the exhaust conditions no longer meet the conditions for implementing the ammonia storage periodic control strategy, exiting the ammonia storage periodic control mode.
2. The method for increasing the reactive capacity of a dual stage DeNOx system by periodic ammonia storage state control according to claim 1, wherein the control strategy implementation conditions require determination of the appropriate temperature window and space velocity window by performing a catalyst strip test.
3. The method for improving the reaction capacity of a two-stage DeNOx system through the periodic ammonia storage state control according to claim 1, wherein in step S2, the specific injection control target of the injection reducing state of the # 1 urea nozzle is determined according to the real-time reaction capacity of the Cat2 carrier, and when the real-time reaction capacity of the Cat2 carrier is weak, the injection quantity of the # 1 urea nozzle is required to be increased appropriately to control the NOx level entering the Cat2 carrier to be within the convertible range thereof; when the real-time reaction capability of the Cat2 carrier is sufficient, the injection amount of the 1# urea nozzle may be set to 0.
4. The method for improving the reaction capacity of a two-stage DeNOx system through the periodic ammonia storage state control according to claim 1, wherein in the step S3, the injection quantity of the 2# urea nozzle after entering the injection state is calculated through a chemical reaction kinetics model and an adsorption and desorption rate model of the Cat2 carrier: NH 3 target supply to urea nozzle # 2 = NH 3 theoretical reaction consumption rate calculated from Cat2 carrier inlet NOx sensor measurements + maximum ammonia storage rate in current state calculated from Cat2 carrier adsorption and desorption rate model + maximum NH 3 oxidation reaction rate calculated from ASC reaction kinetics model.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410229272.2A CN118110586A (en) | 2024-02-29 | 2024-02-29 | Method for improving reaction capacity of two-stage DeNOx system through periodic ammonia storage state control |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410229272.2A CN118110586A (en) | 2024-02-29 | 2024-02-29 | Method for improving reaction capacity of two-stage DeNOx system through periodic ammonia storage state control |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN118110586A true CN118110586A (en) | 2024-05-31 |
Family
ID=91217605
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202410229272.2A Pending CN118110586A (en) | 2024-02-29 | 2024-02-29 | Method for improving reaction capacity of two-stage DeNOx system through periodic ammonia storage state control |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN118110586A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118934174A (en) * | 2024-07-31 | 2024-11-12 | 广西玉柴机器股份有限公司 | A NOx and N2O emission suppression control method based on ammonia storage synergy |
-
2024
- 2024-02-29 CN CN202410229272.2A patent/CN118110586A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118934174A (en) * | 2024-07-31 | 2024-11-12 | 广西玉柴机器股份有限公司 | A NOx and N2O emission suppression control method based on ammonia storage synergy |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7861516B2 (en) | Methods of controlling reductant addition | |
| Schär et al. | Control of a urea SCR catalytic converter system for a mobile heavy duty diesel engine | |
| CN115506874B (en) | Aftertreatment device for two-stage-active-passive SCR (selective catalytic reduction) coupled hydrogen fuel internal combustion engine and control method thereof | |
| CN106837497A (en) | Diesel catalyst based on storage ammonia amount management in real time reduces method for urea injection control | |
| US11346266B2 (en) | Engine exhaust aftertreatment device and method | |
| CN116576004B (en) | Reducing agent cooperative efficient distribution method and system for two-stage urea injection system | |
| CN119412209B (en) | Composite double-stage SCR system, control method, post-processing system and vehicle | |
| US11047282B2 (en) | Exhaust gas purification device | |
| CN113513392A (en) | Active hot patching type aftertreatment system | |
| CN116291819A (en) | Aftertreatment system regeneration control method and device and vehicle | |
| CN118110586A (en) | Method for improving reaction capacity of two-stage DeNOx system through periodic ammonia storage state control | |
| Zhao et al. | Experimental study on pollutant emission characteristics of diesel urea-based selective catalytic reduction system based on corrugated substrate | |
| CN118088296A (en) | Diesel engine aftertreatment system N2Active control method and system for O emission | |
| CN117703570A (en) | Tail gas aftertreatment device for hydrogen internal combustion engine and control method thereof | |
| CN116877240A (en) | A diesel exhaust after-treatment system that meets non-road stage 5 emissions | |
| CN114575969A (en) | Vehicle exhaust gas treatment system and vehicle | |
| EP4043707B1 (en) | Exhaust gas after-treatment system | |
| CN216342391U (en) | Tail gas post-treatment device for non-road diesel engine by using liquid ammonia as SDPF reducing agent | |
| CN118896017B (en) | An exhaust gas treatment device and an exhaust gas treatment method for an ammonia diesel engine | |
| US10704442B2 (en) | Method for optimizing the consumption of reducing agent in a motor vehicle exhaust line | |
| CN112943418B (en) | A lean-burn engine high-efficiency denitrification tail gas post-treatment system and control method | |
| CN120273804A (en) | Urea injection control method and device and vehicle | |
| CN116717354B (en) | Emission treatment system suitable for lean-burn methanol engine and control method | |
| Erçek et al. | A study on the effect of injection amount on NOx emissions in the selective catalytic reduction (SCR) system in a single cylinder Diesel engine | |
| EP4198272B1 (en) | A method for controlling the operation of an exhaust aftertreatment system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |