CN105452623B - 内燃发动机的废气净化系统 - Google Patents
内燃发动机的废气净化系统 Download PDFInfo
- Publication number
- CN105452623B CN105452623B CN201480044203.9A CN201480044203A CN105452623B CN 105452623 B CN105452623 B CN 105452623B CN 201480044203 A CN201480044203 A CN 201480044203A CN 105452623 B CN105452623 B CN 105452623B
- Authority
- CN
- China
- Prior art keywords
- exhaust gas
- catalyst
- removal methods
- hydrocarbon
- ammonia
- 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.)
- Expired - Fee Related
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 25
- 239000002912 waste gas Substances 0.000 title claims description 14
- 238000004140 cleaning Methods 0.000 title description 43
- 239000003054 catalyst Substances 0.000 claims abstract description 277
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 148
- 239000004215 Carbon black (E152) Substances 0.000 claims abstract description 131
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 126
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 124
- 238000000034 method Methods 0.000 claims abstract description 103
- 239000000446 fuel Substances 0.000 claims abstract description 80
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 78
- 238000010521 absorption reaction Methods 0.000 claims abstract description 17
- 239000007789 gas Substances 0.000 claims description 222
- 238000000746 purification Methods 0.000 claims description 28
- 230000000694 effects Effects 0.000 claims description 16
- 239000003795 chemical substances by application Substances 0.000 claims description 14
- RJIWZDNTCBHXAL-UHFFFAOYSA-N nitroxoline Chemical compound C1=CN=C2C(O)=CC=C([N+]([O-])=O)C2=C1 RJIWZDNTCBHXAL-UHFFFAOYSA-N 0.000 claims description 13
- 229910000510 noble metal Inorganic materials 0.000 claims description 12
- 238000011144 upstream manufacturing Methods 0.000 claims description 7
- 238000006555 catalytic reaction Methods 0.000 claims description 4
- 238000004364 calculation method Methods 0.000 claims description 2
- 239000010970 precious metal Substances 0.000 claims description 2
- 239000000543 intermediate Substances 0.000 description 28
- 238000002347 injection Methods 0.000 description 26
- 239000007924 injection Substances 0.000 description 26
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 19
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 18
- 229910002651 NO3 Inorganic materials 0.000 description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 14
- 229910052760 oxygen Inorganic materials 0.000 description 14
- 239000001301 oxygen Substances 0.000 description 14
- 238000003860 storage Methods 0.000 description 14
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 12
- -1 Free radical hydrocarbon Chemical class 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 9
- 229910052697 platinum Inorganic materials 0.000 description 8
- 238000001816 cooling Methods 0.000 description 7
- 230000007423 decrease Effects 0.000 description 6
- RZCJYMOBWVJQGV-UHFFFAOYSA-N 2-naphthyloxyacetic acid Chemical compound C1=CC=CC2=CC(OCC(=O)O)=CC=C21 RZCJYMOBWVJQGV-UHFFFAOYSA-N 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 230000006870 function Effects 0.000 description 4
- 239000012948 isocyanate Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 231100001143 noxa Toxicity 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 3
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 239000000498 cooling water Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 238000006479 redox reaction Methods 0.000 description 3
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 239000002283 diesel fuel Substances 0.000 description 2
- 239000002828 fuel tank Substances 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 150000002828 nitro derivatives Chemical group 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 239000010948 rhodium Substances 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 230000002457 bidirectional effect Effects 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 230000035568 catharsis Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000003502 gasoline Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 239000003863 metallic catalyst Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 150000003254 radicals Chemical class 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000002407 reforming Methods 0.000 description 1
- 230000006833 reintegration Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 230000004083 survival effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- 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
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- 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
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
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- B01D53/9404—Removing only nitrogen compounds
- B01D53/9409—Nitrogen oxides
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- B01D53/9409—Nitrogen oxides
- B01D53/9413—Processes characterised by a specific catalyst
- B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
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- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
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- B01D53/9477—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on separate bricks, e.g. exhaust systems
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Abstract
内燃发动机,其中烃进料阀(15)、废气净化催化剂(13)和NOX选择性还原催化剂(14)布置于发动机排气通道中。使用第一NOX脱除方法和第二NOX脱除方法,所述第一NOX脱除方法在预定时间范围内由烃进料阀(15)注入烃,并使用因此产生的还原性中间体以将包含在废气中的NOX还原,第二NOX脱除方法以比该预定范围更长的时间使得流入废气净化催化剂(13)中的废气的空气‑燃料比为富空气‑燃料比。当应使用第一NOX脱除方法且NOX选择性还原催化剂(14)上的吸附氨的量为大的时,停止使用第一NOX脱除方法。
Description
技术领域
本发明涉及内燃发动机的废气净化系统。
背景技术
本领域中已知这样的内燃发动机,其在发动机排气通道中布置废气净化催化剂,在发动机排气通道中的三效催化剂下游布置NOX选择性还原催化剂,在发动机排气通道中的废气净化催化剂上游布置烃进料阀。贵金属催化剂负载在废气净化催化剂的废气流动表面上且碱性层围绕贵金属催化剂形成。使用第一NOX脱除方法和第二NOX脱除方法,所述第一NOX脱除方法用于通过保持在碱性层上并由于在预定时间范围内由烃进料阀注入烃而产生的还原性中间体将包含在废气中的NOx还原,在所述第二NOx脱除方法中,通过比所述预定范围更长的时间使流入废气净化催化剂中的废气的空气-燃料比变成富空气-燃料比,以将在废气的空气-燃料比为贫空气-燃料比时储存在废气净化催化剂中的NOX释放并还原(例如参见PTL 1)。
引用目录
专利文献
PTL 1:WO2011/114498A1
发明概述
技术问题
在内燃发动机中,当流入废气净化催化剂中的废气的空气-燃料比变成富空气-燃料比时,储存在废气净化催化剂中的NOX被释放并还原。此时,一部分释放的NOX被还原并且变成由废气净化催化剂排出的氨。由废气净化催化剂排出的氨吸附在置于废气净化催化剂下游的NOX选择性还原催化剂上。吸附在NOX选择性还原催化剂上的氨具有对NOX而言的强还原力。因此,如果NOX流入吸附了氨的NOX选择性还原催化剂中,则该NOX在NOX选择性还原催化剂中很好地被还原。因此,如果在废气净化催化剂下游安置了NOX选择性还原催化剂,则未在废气净化催化剂处除去的NOX在NOX选择性还原催化剂处除去,因此,可得到高NOX净化率。
就这点而言,如果进行上述第一NOX脱除方法,则由烃进料阀供入的一部分烃滑过废气净化催化剂,流入NOX选择性还原催化剂并沉积在NOX选择性还原催化剂上。就这点而言,如果烃沉积在NOX选择性还原催化剂上,则沉积的烃阻挡吸附的氨对NOX的还原作用。因此,即使大量氨吸附在NOX选择性还原催化剂上,NOX选择性还原催化剂也不再能够很好地除去NOX。另一方面,如果NOX选择性还原催化剂吸附大量氨,只要在NOX选择性还原催化剂上未沉积大量烃,即使废气净化催化剂不除去几乎任何NOX,吸附的氨也可以在NOX选择性还原催化剂处很好地除去NOX。即,当大量氨吸附在NOX选择性还原催化剂上,即使不进行第一NOX脱除方法的NOX脱除作用,也可得到高NOX净化率。因此,当大量氨吸附在NOX选择性还原催化剂上,而不是使用第一NOX脱除方法并消耗大量烃时,可以说,优选的是停止使用第一NOX脱除方法并有效地利用了吸附在NOX选择性还原催化剂上的氨除去NOX。与此相反,当吸附在NOX选择性还原催化剂上的氨的量小时,不能预期吸附的氨的良好NOX脱除作用,所以此时可以说,优选的是使用第一NOX脱除方法除去NOX。
解决问题的方案
因此,在本发明中,提供内燃发动机的废气净化系统,其包含:布置于发动机排气通道中的废气净化催化剂,在发动机排气通道中的废气净化催化剂下游布置的NOX选择性还原催化剂,和在发动机排气通道中的废气净化催化剂上游布置的烃进料阀,贵金属催化剂负载在废气净化催化剂的废气流动表面上,围绕贵金属催化剂形成碱性层,使用第一NOX脱除方法和第二NOX脱除方法,其中第一NOX脱除方法用于通过保持在碱性层上并由于在预定时间范围内由烃进料阀注入烃而产生的还原性中间体将废气中包含的NOX还原,在所述第二NOX脱除方法中,通过比所述预定范围更长的时间使流入废气净化催化剂中的废气的空气-燃料比变成富空气-燃料比,以将在废气的空气-燃料比为贫空气-燃料比时储存在废气净化催化剂中的NOX释放并还原,其中当吸附在NOX选择性还原催化剂上的氨的量小于其中应使用第一NOX脱除方法除去NOX时的发动机操作状态时的预定量时,使用第一NOX脱除方法,并且当吸附在NOX选择性还原催化剂上的氨的量大于其中应使用第一NOX脱除方法除去NOX时的发动机操作状态时的预定量时,停止第一NOX脱除方法。
本发明的有利效果
通过当吸附在NOX选择性还原催化剂上的氨的量大于其中应使用第一NOX脱除方法除去NOX时的发动机操作状态时的预定量时停止使用第一NOX脱除方法,可降低烃的消耗量,同时有效地利用了吸附在NOX选择性还原催化剂上的氨除去NOX。
附图简述
[图1]图1为压缩点火型内燃发动机的全貌图。
[图2]图2为示意性显示催化剂载体的表面部分的视图。
[图3]图3为解释废气净化催化剂处的氧化反应的视图。
[图4]图4为显示流入废气净化催化剂中的废气的空气-燃料比的变化的视图。
[图5]图5为显示NOX净化率R1的视图。
[图6]图6A和6B为解释废气净化催化剂中的氧化还原反应的视图。
[图7]图7A和7B为解释废气净化催化剂中的氧化还原反应的视图。
[图8]图8为显示流入废气净化催化剂中的废气的空气-燃料比的变化的视图。
[图9]图9为显示NOX净化率R2的视图。
[图10]图10为显示烃浓度的变动周期ΔT与NOX净化率R1之间的关系的视图。
[图11]图11A和11B为显示烃的注入量等的图的视图。
[图12]图12为显示NOX释放控制的视图。
[图13]图13为显示排出的NOX量NOXA的图的视图。
[图14]图14为显示燃料注入时机的视图。
[图15]图15为显示额外烃进料量WR的视图。
[图16]图16A、16B和16C为解释NOX选择性还原催化剂中的氧化还原反应的视图。
[图17]图17A和17B为显示氨的生成量的视图。
[图18]图18为进行NOX净化控制的流程图。
实施方案描述
图1为压缩点火型内燃发动机的全貌图。
参考图1,1表示发动机体,2表示各个气缸的燃烧室,3表示用于将燃料注入各燃烧室2中的电子控制燃料喷射器,4表示进气歧管,5表示排气歧管。进气歧管4通过导入管6与废气涡轮增压器7的压缩机7a的出口连接,同时压缩机7a的入口通过进气量检测器8与空气清洁器9连接。在导入管6内部,布置了由致动器驱动的节流阀10。在导入管6周围布置了冷却装置11以将流过导入管6内部的进入空气冷却。在图1所示实施方案中,将发动机冷却水导向冷却装置11的内部,在那里,发动机冷却水用于将进入空气冷却。
另一方面,排气歧管5与废气涡轮增压器7的废气涡轮7b的入口连接,且废气涡轮7b的出口通过排气管12与废气净化催化剂13的入口连接。在本发明一个实施方案中,该废气净化催化剂13包含NOX储存催化剂13。废气净化催化剂13的出口与NOX选择性还原催化剂14连接,并且在排气管12内部的废气净化催化剂13上游,布置了烃进料阀15以供入用作压缩点火型内燃发动机燃料的包含柴油或其它燃料的烃。在图1所示实施方案中,柴油作为由烃进料阀15供入的烃使用。应当指出,本发明也可适用于火花点火型内燃发动机,其中燃料在贫空气-燃料比下燃烧。在这种情况下,由烃进料阀15供入用作火花点火型内燃发动机燃料的包含汽油或其它燃料的烃。
另一方面,排气歧管5和进气歧管4通过废气再循环(在下文中称为“EGR”)通道16相互连接。在EGR通道16内部布置了电子控制的EGR控制阀17。另外,在EGR通道16周围,布置冷却装置18以将流过EGR通道16内部的EGR气体冷却。在图1所示实施方案中,将发动机冷却水导向冷却装置18内部,在那里发动机冷却水用于冷却EGR气体。另一方面,各个燃料喷射器3通过燃料进料管19与共轨20连接。该共轨20通过电子控制的可变释放燃料泵21与燃料罐22连接。储存在燃料罐22内的燃料通过燃料泵21供入共轨20内部。供入共轨21内部的燃料通过各个燃料进料管19供入燃料喷射器3中。
电子控制单元30包含具有ROM(只读存储器)32、RAM(随机存取存储器)33、CPU(微处理器)34、通过双向汇流排31相互连接的输入端35和输出端36的数字计算机。在废气净化催化剂13下游,布置温度传感器23以检测从废气净化催化剂13中流出的废气的温度,将该温度传感器23和进气量检测器8的输出信号并通过各相应的AD转换器37输入至输入端35中。另外,油门踏板40具有与它连接的负载传感器41,其产生与油门踏板40的下陷量L成比例的输出电压。负载传感器41的输出电压通过相应的AD转换器37输入至输入端35。此外,在输入端35处连接有曲柄角传感器42,曲轴每次旋转例如15°时该传感器产生输出脉冲。另一方面,输出端36通过相应的驱动电路38与各燃料喷射器3、驱动节流阀10的致动器、烃进料阀15、EGR控制阀17和燃料泵21连接。
图2示意性地显示图1种所示的废气净化催化剂13的基底上负载的催化剂载体的表面部分。在该废气净化催化剂13处,如图2所示,例如提供了由氧化铝构成的催化剂载体50,在催化剂载体50上负载有包含铂Pt的贵金属催化剂51。此外,在该催化剂载体50上,形成碱性层53,其包含至少一种选自如下的元素:钾K、钠Na、铯Cs或者其它这类碱金属、钡Ba、钙Ca或者其它这类碱土金属、镧系元素或其它这类稀土元素以及银Ag、铜Cu、铁Fe、铱Ir或者能够向NOX提供电子的其它金属。在这种情况下,除铂Pt外,在废气净化催化剂13的催化剂载体50上可进一步负载铑Rh或钯Pd。应当指出,废气沿着催化剂载体50的顶部流过,因此可以说,贵金属催化剂51负载在废气净化催化剂13的废气流动表面上。另外,碱性层53的表面显示出碱度,所以碱性层53的表面被称为“废气流动碱性表面部54”。
如果烃由烃进料阀15注入废气中,则烃通过废气净化催化剂13重整。在本发明中,此时重整的烃用于在废气净化催化剂13处除去NOX。图3示意性地显示此时在废气净化催化剂13处进行的重整作用。如图3所示,由烃进料阀15注入的烃HC由于贵金属催化剂51而变成具有小碳数的自由基烃HC。
图4显示来自烃进料阀15的烃的进料时机和流入废气净化催化剂13中的废气的空气-燃料比(A/F)in的变化。应当指出,空气-燃料比(A/F)in的变化取决于流入废气净化催化剂13中的废气中的烃浓度的变化,因此可以说图4所示空气-燃料比(A/F)in的变化体现了烃浓度变化。然而,如果烃浓度变得较高,则空气-燃料比(A/F)in变得较小,所以在图4中,空气-燃料比(A/F)in变得越接近富侧,烃浓度越高。
图5显示当定期使流入废气净化催化剂13中的烃浓度改变以如图4所示定期使流入废气净化催化剂13中的废气的空气-燃料比(A/F)in为富空气-燃料比时,废气净化催化剂13的NOX净化率R1相对于废气净化催化剂13的催化剂温度TC的关系。就这点而言,根据长时间NOX净化的研究结果,获知的是如果使流入废气净化催化剂13中的烃浓度在预定幅度范围内以及在预定时间范围内变动,则如图5所示,甚至在350℃或更高的高温区中得到极高的NOX净化率R1。
此外,获知的是,此时包含氮和烃的大量还原性中间体继续保持或吸附在碱性层53的表面上,即在废气净化催化剂13的废气流动碱性表面部54上,且还原性中间体在得到高NOX净化率R1中起中心作用。接下来,将参考图6A和6B解释。应当指出,这些图6A和6B示意性地显示废气净化催化剂13的催化剂载体50的表面部分。这些图6A和6B显示当使流入废气净化催化剂13中的烃浓度在预定幅度范围内以及在预定时间范围内变动时可能发生的反应。
图6A显示当流入废气净化催化剂13中的烃浓度低时的情况,而图6B显示当烃由烃进料阀15供入并使流入废气净化催化剂13中的废气的空气-燃料比(A/F)in为富空气-燃料比,即流入废气净化催化剂13中的烃浓度变得更高时的情况。
现在,如由图4所理解,除瞬时外,流入废气净化催化剂13中的废气的空气-燃料比保持为贫空气-燃料比,所以流入废气净化催化剂13中的废气通常变成氧气过量状态。此时,包含在废气中的一部分NO沉积在废气净化催化剂13上,同时包含在废气中的一部分NO如图6A所示在铂51上被氧化并变成NO2。接着,该NO2进一步呗氧化并变成NO3。另外,一部分NO2变成NO2 -。因此,在铂Pt 51上产生NO2 -和NO3。沉积在废气净化催化剂13上的NO以及在铂Pt 51上形成的NO2 -和NO3在活性方面是强的。因此,在下文中,这些NO、NO2 -和NO3被称为“活性NOX”。
另一方面,如果烃由烃进料阀15供入并使流入废气净化催化剂13中的废气的空气-燃料比(A/F)in为富空气-燃料比,则烃接连地沉积在整个废气净化催化剂13上。大部分沉积的烃接连地与氧气反应并燃烧。一部分沉积的烃接连地重整并变成废气净化催化剂13的自由基化内部,如图3所示。因此,如图6B所示,活性NOX *周围的氢浓度变得较高。就这点而言,如果产生活性NOX *之后,活性NOX *周围的高氧气浓度状态继续恒定的时间或更久,则活性NOX *被氧化并以硝酸根离子NO3 -的形式吸收在碱性层53内部。然而,如果在该恒定时间过去以前,活性NOX *周围的烃浓度变得较高,如图6B所示,则活性NOX *在铂51上与自由基烃HC反应,由此形成还原性中间体。还原性中间体附着或吸附在碱性层53的表面上。
应当指出,此时,认为首先产生的还原性中间体为硝基化合物R-NO2。如果产生该硝基化合物R-NO2,则结果变成腈化合物R-CN,但该腈化合物R-CN在该状态下仅瞬时幸存,所以立即变成异氰酸酯化合物R-NCO。如果水解的话,该异氰酸酯化合物R-NCO变成胺化合物R-NH2。然而,在这种情况下,认为水解的是一部分异氰酸酯化合物R-NCO。因此,如图6B所示,认为保持或吸附在碱性层53的表面上的大部分还原性中间体为异氰酸酯化合物R-NCO和胺化合物R-NH2。
另一方面,如图6B所示,如果产生的还原性中间体被烃HC围绕,则还原性中间体被烃HC阻挡,反应将不能进一步进行。在这种情况下,如果流入废气净化催化剂13中的烃浓度降低,则沉积在还原性中间体周围的烃被氧化并消耗,由此围绕还原性中间体的氧气浓度变得较高,还原性中间体与废气中的NOX反应,与活性NOX *反应,与周围的氧气反应或者自己分解。因此,还原性中间体R-NCO和R-NH2转化成N2、CO2和H2O,如图6A所示,因此NOX被除去。
这样,在废气净化催化剂13中,当使流入废气净化催化剂13中的烃浓度较高时,产生还原性中间体,且在流入废气净化催化剂13中的烃浓度降低以后,当氧气浓度提高时,还原性中间体与废气中的NOX或者与活性NOX *或者氧气反应或者自己分解,由此除去NOX。即,为使废气净化催化剂13除去NOX,必须定期改变流入废气净化催化剂13中的烃浓度。
当然,在这种情况下,需要使烃浓度提高至足够高以产生还原性中间体的浓度,并且需要使烃浓度降低至足够低以使产生的还原性中间体与废气中的NOX或者活性NOX *或者氧气反应或者自己分解的浓度。即,需要使流入废气净化催化剂13中的烃浓度在预定的幅度范围变动。应当指出,在这种情况下,需要使这些还原性中间体保持在碱性层53,即废气流动碱性表面部54上,直至产生的还原性中间体R-NCO和R-NH2与废气中的NOX或者与活性NOX *或者氧气反应或者自己分解。为此,提供废气流动碱性表面部54。
另一方面,如果延长烃的进料周期,则在供入烃之后直至下一次供入烃的期间,直至氧气浓度变得较高时的时间变得更长。因此,活性NOX *以硝酸盐的形式吸收在碱性层53中而不产生还原性中间体。为避免这一点,需要使流入废气净化催化剂13中的烃浓度在预定时间范围内变动。
因此,在本发明实施方案中,为使包含在废气中的NOX和重整烃反应产生包含氮和烃的还原性中间体R-NCO和R-NH2,将贵金属催化剂51负载在废气净化催化剂13的废气流动表面上。为使产生的还原性中间体R-NCO和R-NH2保持在废气净化催化剂13内部,围绕贵金属催化剂51形成碱性层53。保持在碱性层53上的还原性中间体R-NCO和R-NH2转化成N2、CO2和H2O。烃浓度的变动周期视为继续产生还原性中间体R-NCO和R-NH2所需的变动周期。顺便提及,在图4所示实施例中,注入间隔为3秒。
如果烃浓度的变动周期,即由烃进料阀15注入烃的注入周期长于以上预定时间范围,则还原性中间体R-NCO和R-NH2从碱性层53的表面消失。此时,在铂Pt 53上产生的活性NOX *如图7A所示以硝酸根离子NO3 -的形式在碱性层53中扩散并且变成硝酸盐。即,此时废气中的NOX以硝酸盐的形式吸收在碱性层53内部。
另一方面,图7B显示,当NOX以硝酸盐的形式吸收在碱性层53内部时使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比的情况。在这种情况下,废气中的氧气浓度下降,所以反应以相反的方向(NO3 -→NO2)进行,因此吸收在碱性层53中的硝酸盐接连地变成硝酸根离子NO3 -,且如图7B所示以NO2的形式从碱性层53中释放。接着,释放的NO2被包含在废气中的烃HC和CO还原,且一部分释放的NO2变成氨NH3。这样,在本发明的该实施方案中,当使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比时,在废气净化催化剂13中产生氨。废气净化催化剂13中产生的氨流入NOX选择性还原催化剂14中并吸附在NOX选择性还原催化剂14上。
图8显示在碱性层53的NOX吸收能力变得饱和之前不久使流入废气净化催化剂13中的废气的空气-燃料比(A/F)in暂时性地为富空气-燃料比的情况。应当指出,在图8所示的实始例中,该富空气-燃料比控制的时间间隔为1分钟或更久。在这种情况下,当废气的空气-燃料比(A/F)in为贫空气-燃料比时吸收在碱性层53中的NOX在使废气的空气-燃料比(A/F)in暂时性地为富空气-燃料比时一下从碱性层53中释放并被还原。因此,在这种情况下,碱性层53起到暂时吸收NOX的吸收剂的作用。
应当指出,此时,有时碱性层53暂时性地吸收NOX。因此,如果使用术语“储存”作为包括“吸收”和“吸附”的术语,则此时碱性层53发挥暂时储存NOX的NOX储存剂的作用。即,在这种情况下,如果供入发动机进气通道、燃烧室2和废气通道中的废气净化催化剂13上游的空气与燃料(烃)的比称为“废气的空气-燃料比”,则废气净化催化剂13充当NOX储存催化剂,其在废气的空气-燃料比为贫空气-燃料比时储存NOX,并在废气中的氧气浓度下降时释放储存的NOX。
图9的实线显示当使废气净化催化剂13以此方式充当NOX储存催化剂时的NOX净化率R2。应当指出,图9的横坐标显示废气净化催化剂13的催化剂温度TC。当使废气净化催化剂13充当NOX储存催化剂时,如图9所示,当催化剂温度TC为250℃至300℃时,得到极高的NOX净化率,但当催化剂温度TC变成350℃或更高的高温时,NOX净化率R2下降。应当指出,在图9中,图5中所示的NOX净化率R1由虚线表示。
这样,当催化剂温度TC变成350℃或更大时,NOX净化率R2下降,因为如果催化剂温度TC变成350℃或更大,则NOX较不容易储存且硝酸盐由于热而分解并以NO2的形式从废气净化催化剂13中释放。即,只要NOX以硝酸盐的形式储存,当催化剂温度TC高时,难以得到高NOX净化率R2。然而,在图4至图6A和6B所示的新NOX净化方法中,以硝酸盐的形式储存的NOX的量是小的,因此如图5所示,即使催化剂温度TC高,也得到高NOX净化率R1。
在本发明实施方案中,为了能够通过使用该新NOX净化方法而将NOX净化,将用于供入烃的烃进料阀15布置于发动机排气通道中,将废气净化催化剂13置于发动机排气通道中烃进料阀15的下游,贵金属催化剂51负载在废气净化催化剂13的废气流动表面上,围绕贵金属催化剂51形成碱性层53,废气净化催化剂13具有如下性能:如果在预定时间范围内由烃进料阀15注入烃的话通过保持在碱性层53上的还原性中间体将包含在废气中的NOX还原的性能,和如果使由烃进料阀15注入烃的注入周期长于该预定范围的话提高包含在废气中的NOX的储存量的性能,并且在发动机操作时,在预定时间范围内由烃进料阀15注入烃,从而在废气净化催化剂13中将包含在废气中的NOX还原。
即,可以说,由图4至图6A和6B显示的NOX净化方法为设计用于在使用带有贵金属催化剂并形成可吸收NOX的碱性层的废气净化催化剂的情况下除去NOX而不形成太多的硝酸盐的新NOX净化方法。实际上,当使用该新NOX净化方法时,由碱性层53检测到的硝酸盐的量与使废气净化催化剂13充当NOX储存催化剂的情况相比更小。应当指出,该新NOX净化方法在下文中称为“第一NOX净化方法”。
现在,如前文所提到的,如果由烃进料阀15注入烃的注入周期ΔT变得较长,则在注入烃以后至下次注入烃时的时间周期中,活性NOX *周围的氧气浓度变得较高的时间变得较长。在这种情况下,在图1所示实施方案中,如果烃的注入周期ΔT变得长于约5秒,则活性NOX *开始以硝酸盐的形式吸收在碱性层53内部。因此,如图10所示,如果烃浓度的变动周期ΔT变得长于约5秒,NOX净化率R1下降。因此,必须使烃的注入周期ΔT为5秒或更小。
另一方面,在本发明实施方案中,如果烃的注入周期ΔT变成约0.3秒或更小,则注入的烃在废气净化催化剂13的废气流动表面上开始积聚,因此,如图10所示,如果烃的注入周期ΔT变成约0.3秒或更小,则NOX净化率R1下降。因此,在本发明实施方案中,使烃的注入周期为0.3秒至5秒。
在本发明实施方案中,预先得到为确保第一NOX净化方法的良好NOX净化作用而最佳的由烃进料阀15注入烃的注入量和注入时机。在这种情况下,在本发明实施方案中,将进行第一NOX净化方法的NOX净化作用时的最佳烃注入量WT以如图11A所示图的形式作为燃料喷射器3的注入量Q和发动机速度N的函数预先储存在ROM 32中。另外,此时烃的最佳注入周期ΔT也以如图11B所示图的形式作为燃料喷射器3的注入量Q和发动机速度N的函数预先储存在ROM 32中。
接着,参考图12至图15,具体地解释使废气净化催化剂13充当NOX储存催化剂时的NOX净化方法。以此方式使废气净化催化剂13充当NOX储存催化剂的情况下的NOX净化方法在下文中称为“第二NOX净化方法”。
在该第二NOX净化方法中,如图12所示,当储存在碱性层53中的NOX的NOX储存量ΣNOX超过预定的容许量MAX时,使流入废气净化催化剂13中的废气的空气-燃料比(A/F)in临时性地为富空气-燃料比。如果使废气的空气-燃料比(A/F)in为富空气-燃料比,则在废气的空气-燃料比(A/F)in为贫空气-燃料比时储存在碱性层53中的NOX一下从碱性层53中释放并被还原。因此,除去NOX。
储存的NOX量ΣNOX例如由从发动机中排出的NOX的量计算。在本发明这一实施方案中,每单位时间从发动机中排出的NOX的排放NOX量NOXA以如图13所示图的形式作为注入量Q和发动机速度N的函数预先储存在ROM 32中。储存的NOX量ΣNOX由该排放的NOX量NOXA计算。在这种情况下,如前文所解释的,使废气的空气-燃料比(A/F)in为富空气-燃料比的时间通常为1分钟或更久。
在该第二NOX净化方法中,如图14所示,通过将燃烧所用的燃料Q以外的额外燃料WR由燃料喷射器3注入各燃烧室2中,使流入废气净化催化剂13中的废气的空气-燃料比(A/F)in为富空气-燃料比。应当指出,在图14中,横坐标表示曲柄角。该额外燃料WR在它会燃烧但不显示为发动机输出的时机注入,即稍微在压缩上止点后ATDC90°之前。该燃料量WR以如图15所示图的形式作为注入量Q和发动机速度N的函数预先储存在ROM 32中。当然,在这种情况下,也可使来自烃进料阀15的烃的注入量提高以使废气的空气-燃料比(A/F)in为富空气-燃料比。
那么,应理解,如果将图5和图9所示第一NOX脱除方法的NOX净化率R1与图9所示第二NOX脱除方法的NOX净化率R2对比,当催化剂温度TC较低时,第二NOX脱除方法的NOX净化率R2变得较高,而当催化剂温度TC变得较高时,第一NOX脱除方法的NOX净化率R1变得较高。因此,在本发明一个实施方案中,一般而言,当催化剂温度TC低时,使用第二NOX脱除方法,而当催化剂温度TC高时,使用第一NOX脱除方法。
接着解释图1所示的NOX选择性还原催化剂14。NOX选择性还原催化剂14例如包含Fe沸石。如果废气包含氨NH3或烃,则这些氨NH3和烃吸附在NOX选择性还原催化剂14上。如果废气包含NOX,则该NOX被吸附在NOX选择性还原催化剂14上的氨NH3或烃而还原。然而,在这种情况下,当NOX选择性还原催化剂14吸附了氨NH3时,导致烃流入NOX选择性还原催化剂14中的问题。接着,参考图16A、16B和16C解释这一点。应当指出,这些图16A、16B和16C示意性地显示了NOX选择性还原催化剂14的催化剂载体55的表面部分。这些图16A、16B和16C显示了被认为在NOX选择性还原催化剂14的催化剂载体55上发生的反应。
如上文所解释的,如果使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比,则废气净化催化剂13产生氨NH3。此时产生的氨NH3流入NOX选择性还原催化剂14中,并如图16A所示吸附在NOX选择性还原催化剂14上。如图16A所示包含在废气中的NOX在氧气的存在下被吸附在NOX选择性还原催化剂14上的氨NH3而还原并被除去。因此,即使不能通过废气净化催化剂13除去的NOX由废气净化催化剂13排出,该NOX在NOX选择性还原催化剂14处除去。图16A显示大量氨NH3吸附在NOX选择性还原催化剂14上的情况。吸附在NOX选择性还原催化剂上的氨对NOX具有强还原力。因此,如图16A所示,当大量氨NH3吸附在NOX选择性还原催化剂14上时,当在废气净化催化剂13处进行NOX脱除作用时当然地,以及当在废气净化催化剂13处未进行NOX脱除作用时,包含在废气中的NOX在NOX选择性还原催化剂14中极好地被除去。
图16B显示当使用第一NOX脱除方法时的情况。当使用第一NOX脱除方法时,定期地由烃进料阀15注入烃。此时,由烃进料阀15注入的一部分烃滑过废气净化催化剂13并从废气净化催化剂13排出。从废气净化催化剂13中排出的烃流入NOX选择性还原催化剂14中并如图16B所示吸附在NOX选择性还原催化剂14上。如图16B所示,包含在废气中的NOX被吸附在NOX选择性还原催化剂14上的烃还原并除去。因此,即使不能在废气净化催化剂13处除去的NOX从废气净化催化剂13中排出,该NOX在NOX选择性还原催化剂14处除去。应当指出,吸附在NOX选择性还原催化剂14上的烃的NOX还原力弱于吸附在NOX选择性还原催化剂14上的氨NH3的NOX还原力。
另一方面,图16C显示这种情况:如图16A所示,当大量氨NH3吸附在NOX选择性还原催化剂14上时使用第一NOX脱除方法,并且此时滑过废气净化催化剂13的烃流入NOX选择性还原催化剂14中。这样,当大量氨NH3吸附在NOX选择性还原催化剂14上时,如果烃流入NOX选择性还原催化剂14中,则如图16C所示,烃沉积在NOX选择性还原催化剂14上。就这点而言,如果烃沉积在NOX选择性还原催化剂14上,则沉积的烃阻挡吸附的氨NH3的NOX还原作用。因此,如从图16C中所理解,即使大量氨吸附在NOX选择性还原催化剂14上,NOX选择性还原催化剂14也不再能够很好地除去NOX。
另一方面,如图16A所示,当大量氨NH3吸附在NOX选择性还原催化剂14上时,只要大量烃不沉积在NOX选择性还原催化剂14上,即使废气净化催化剂13没有除去几乎任何NOX,吸附的氨NH3可用于在NOX选择性还原催化剂14处除去NOX。即,当大量氨吸附在NOX选择性还原催化剂14上时,即使没有第一NOX脱除方法的NOX脱除作用,也可获得高NOX净化率。因此,当大量氨NH3吸附在NOX选择性还原催化剂14上而不是使用第一NOX脱除方法并消耗大量烃时,可以说,优选的是停止使用第一NOX脱除方法并有效地利用了吸附在NOX选择性还原催化剂14上的氨除去NOX。与此相反,当吸附在NOX选择性还原催化剂14上的氨的量小时,不能预期吸附的氨NH3的良好NOX脱除作用,因此此时可以说,优选的是使用第一NOX脱除方法除去NOX。应当指出,同样在这种情况下,如图16B所示,不能在废气净化催化剂13处除去的NOX也通过吸附在NOX选择性还原催化剂14上的烃除去。
因此,在本发明中,在包含布置于发动机排气通道中的废气净化催化剂13、布置于发动机排气通道中的废气净化催化剂13下游的NOX选择性还原催化剂14和布置于发动机排气通道中的废气净化催化剂13上游的烃进料阀15的内燃发动机废气净化系统中,贵金属催化剂51负载在废气净化催化剂13的废气流动表面上,在贵金属催化剂51周围形成碱性层53,使用第一NOX脱除方法和第二NOX脱除方法,所述第一NOX脱除方法用于通过保持在碱性层53上并由于在预定时间范围由烃进料阀15注入烃而产生的还原性中间体将包含在废气中的NOX还原,在所述第二NOX脱除方法中,通过比上述预定范围更长的时间使流入废气净化催化剂13中的废气的空气-燃料比变成富空气-燃料比,以将在废气的空气-燃料比为贫空气-燃料比时储存在废气净化催化剂13中的NOX释放并还原,
当吸附在NOX选择性还原催化剂14上的氨的量小于其中应使用第一NOX脱除方法除去NOX时的发动机操作状态时的预定量时,使用第一NOX脱除方法,并且在吸附在NOX选择性还原催化剂14上的氨的量大于其中应使用第一NOX脱除方法除去NOX时的发动机操作状态时的预定量时,停止使用第一NOX脱除方法。
这样,在本发明中,在其中应使用第一NOX脱除方法除去NOX时的发动机操作状态时,根据吸附在NOX选择性还原催化剂14上的氨的量确定是否进行第一NOX脱除方法。就这点而言,如上文所解释的,在本发明一个实施方案中,一般而言,当废气净化催化剂13的温度TC低时,使用第二NOX脱除方法,而当废气净化催化剂13的温度TC高时,使用第一NOX脱除方法。若给出一个具体实例的话,则例如如果废气净化催化剂13的温度TC超过预定温度,则NOX脱除方法从第二NOX脱除方法转换成第一NOX脱除方法。在该实例的情况下,当废气净化催化剂13的温度TC超过预定温度,并因此NOX脱除方法为第一NOX脱除方法时的状态在本发明的用法中为其中应使用第一NOX脱除方法除去NOX的发动机操作状态。
另外,在本发明中,根据吸附在NOX选择性还原催化剂14上的氨的量是否大于预定量而确定是否进行第一NOX脱除方法。在这种情况下,在本发明一个实施方案中,提供一种计算装置以计算吸附在NOX选择性还原催化剂14上的氨的量。当由该计算装置计算的氨的量小于其中应使用第一NOX脱除方法除去NOX时的发动机操作状态时的预定量时,使用第一NOX脱除方法,而当由该计算装置计算的氨的量大于其中应使用第一NOX脱除方法除去NOX时的发动机操作状态时的预定量时,停止使用第一NOX脱除方法。在这种情况下,在本发明一个实施方案中,电子控制单元30构成该计算装置。
接着参考图17A和图17B解释基于该计算装置计算吸附的氨的量的方法。如上文所解释的,如果使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比,则在废气净化催化剂13处产生氨NH3。该产生的氨NH3吸附在NOX选择性还原催化剂14上。图17A显示当使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比时在废气净化催化剂13处产生的氨的生成量与储存在废气净化催化剂13的碱性层53处的储存NOX的量ΣNOX之间的关系,而图17B显示当使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比时在废气净化催化剂13处产生的氨的生成量与此时的空气-燃料比之间的关系。
如图17A所示,当使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比时在废气净化催化剂13处产生的氨的生成量提高,储存的NOX量ΣNOX越大,而如图17B所示,当使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比时在废气净化催化剂13处产生的氨的生成量提高,此时的废气的空气-燃料比越小,即富的程度越小。在本发明一个实施方案中,当使流入废气净化催化剂13中的废气的空气-燃料比为富空气-燃料比时,氨NH3的生成量基于图17A和图17B计算,且该氨NH3的生成量为新吸附在NOX选择性还原催化剂14上的氨的量。
另外,在本发明中,对比吸附在NOX选择性还原催化剂14上的氨的量和预定量。在这种情况下,在本发明中,基于实验发现该预定量WX。该预定量WX为即使停止第一NOX脱除方法的NOX脱除作用,吸附在NOX选择性还原催化剂14上的氨NH3也足以能够将流入NOX选择性还原催化剂14中的废气中的NOX还原的量。
图18显示NOX净化控制程序。该程序通过每隔预定时间中断而执行。
参考图18,首先在步骤60中判断发动机操作状态是否是应使用第一NOX脱除方法除去NOX的状态。当判断不是应使用第一NOX脱除方法除去NOX时的发动机操作状态时,程序进行至步骤61,进行第二NOX脱除方法的NOX脱除作用。即,在步骤61,由图13所示图计算每单位时间排出的NOX的量NOXA,接着在步骤62,将每单位时间排出的NOX的量NOXA与ΣNOX相加以计算储存的NOX量ΣNOX。接着在步骤63,判断储存的NOX量ΣNOX是否超过容许值MAX。
当储存的NOX量ΣNOX不超过容许值MAX时,程序进行至步骤70,使用第二NOX脱除方法时的NOX净化率R2计算废气净化催化剂13处的NOX滑过率SR(=(100-R2)/100),所述NOX净化率R2在图9中基于废气净化催化剂13的温度TC显示。接着,在步骤71,将排出的NOX量NOXA乘以NOX滑过率SR,由此计算每单位时间流入NOX选择性还原催化剂14中的NOX的量WB。接着,在步骤72,通过将NOX量WB乘以常数C而找到每单位时间将流入NOX选择性还原催化剂14中的NOX还原所消耗的氨的量。将每单位时间消耗的该氨量C·WB从吸附的氨的量W中减去以计算吸附在NOX选择性还原催化剂14上的吸附氨的量W。
与此相反,当在步骤63中判断储存的NOX量ΣNOX超过容许值MAX时,程序进行至步骤64,由图15所示图计算额外燃料量WR,并进行由燃料喷射器3的另外燃料注入作用。此时,使流入废气净化催化剂13中的废气的空气-燃料比暂时成为富空气-燃料比。接着,在步骤65,基于图17A和图17B所示关系,计算此时在废气净化催化剂13处产生的氨的生成量WA。接着,在步骤66,将该氨生成量WA与吸附在NOX选择性还原催化剂14上的吸附氨的量W相加。接着,在步骤67,清除ΣNOX。
另一方面,当在步骤60中判断发动机操作状态为其中应使用第一NOX脱除方法除去NOX的状态时,程序进行至步骤68,在此判断吸附在NOX选择性还原催化剂14上的吸附氨的量W是否大于预定量WX。当吸附在NOX选择性还原催化剂14上的吸附氨的量W大于预定量WX时,程序进行至步骤69,尽管发动机操作状态为应使用第一NOX脱除方法除去NOX的状态,停止第一NOX脱除方法的NOX脱除作用。接着,程序进行至步骤70。与此相反,当在步骤68中判断吸附在NOX选择性还原催化剂14上的吸附氨的量W小于预定量WX时,程序进行至步骤73,进行第一NOX脱除方法的NOX脱除作用。此时,由烃进料阀15注入由图11A所示图计算的量WT的烃,注入周期ΔT由图11B所示图计算。
应当指出,作为另一实施方案,也可将用于将烃重整的氧化催化剂置于废气净化催化剂13上游的发动机排气通道内。
附图标记目录
4 进气歧管
5 排气歧管
7 废气涡轮增压器
12 排气管
13 废气净化催化剂
14 NOX选择性还原催化剂
15 烃进料阀
Claims (4)
1.净化由内燃发动机排放的废气的方法,其包括布置于发动机排气通道中的废气净化催化剂,在所述发动机排气通道中的所述废气净化催化剂下游布置的NOx选择性还原催化剂,和在所述发动机排气通道中的所述废气净化催化剂上游布置的烃进料阀,贵金属催化剂负载在所述废气净化催化剂的废气流动表面上,围绕所述贵金属催化剂形成碱性层,使用第一NOx脱除方法和第二NOx脱除方法,所述第一NOx脱除方法通过保持在碱性层上并由于在预定时间范围内由烃进料阀注入烃而产生的还原性中间体将包含在废气中的NOx还原,在所述第二NOx脱除方法中,通过比所述预定范围更长的时间使流入所述废气净化催化剂中的废气的空气-燃料比变成富空气-燃料比,以将在废气的空气-燃料比为贫空气-燃料比时储存在所述废气净化催化剂中的NOX释放并还原,其中:
通过吸附在所述NOx选择性还原催化剂上的氨将包含在废气中的NOx还原,
当所述废气净化催化剂的温度低于预定温度的状态时,使用第二NOX脱除方法,当吸附在所述NOx选择性还原催化剂上的氨的量小于所述废气净化催化剂的温度超过预定温度的状态时的预定量时,使用所述第一NOx脱除方法,并且当吸附在所述NOx选择性还原催化剂上的氨的量大于所述废气净化催化剂的温度超过预定温度的状态时的预定量时,停止使用所述第一NOx脱除方法。
2.如权利要求1所述的净化由内燃发动机排放的废气的方法,其中提供用于计算吸附在所述NOX选择性还原催化剂上的氨的量的计算装置,当通过所述计算方法计算的氨的量小于所述废气净化催化剂的温度超过预定温度的状态时的预定量时,使用所述第一NOx脱除方法,并且当通过所述计算装置计算的氨的量大于所述废气净化催化剂的温度超过预定温度的状态时的预定量时,停止使用所述第一NOx脱除方法。
3.如权利要求1所述的净化由内燃发动机排放的废气的方法,其中所述预定量为即使停止所述第一NOX脱除方法的NOX脱除作用,吸附在所述NOX选择性还原催化剂上的氨足以能够还原流入所述NOX选择性还原催化剂中的废气中的NOX的量。
4.如权利要求1所述的净化由内燃发动机排放的废气的方法,其中当使用所述第二NOx脱除方法时,在使流入所述废气净化催化剂中的废气的空气-燃料比变成富空气-燃料比时在所述废气净化催化剂上产生的氨被吸附在所述NOX选择性还原催化剂上。
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EP (1) | EP3030763B1 (zh) |
JP (1) | JP6090051B2 (zh) |
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JP2017194022A (ja) | 2016-04-21 | 2017-10-26 | トヨタ自動車株式会社 | 排気浄化装置の制御装置 |
JP6512199B2 (ja) | 2016-09-30 | 2019-05-15 | トヨタ自動車株式会社 | 内燃機関の排気浄化システム |
JP6512200B2 (ja) | 2016-09-30 | 2019-05-15 | トヨタ自動車株式会社 | 内燃機関の排気浄化システム |
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CN102713189A (zh) * | 2010-09-02 | 2012-10-03 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
CN103003539A (zh) * | 2010-08-30 | 2013-03-27 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
CN103180558A (zh) * | 2010-08-30 | 2013-06-26 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
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DE19852240A1 (de) * | 1998-11-12 | 2000-05-18 | Volkswagen Ag | Überwachungsverfahren für NOx-Speicherkatalysatoren und Abgasreinigungsvorrichtung zur Durchführung dieses Verfahrens |
DE10023439A1 (de) * | 2000-05-12 | 2001-11-22 | Dmc2 Degussa Metals Catalysts | Verfahren zur Entfernung von Stickoxiden und Rußpartikeln aus dem mageren Abgas eines Verbrennungsmotors und Abgasreinigungssystem hierfür |
US7082753B2 (en) * | 2001-12-03 | 2006-08-01 | Catalytica Energy Systems, Inc. | System and methods for improved emission control of internal combustion engines using pulsed fuel flow |
DE10300298A1 (de) * | 2003-01-02 | 2004-07-15 | Daimlerchrysler Ag | Abgasnachbehandlungseinrichtung und -verfahren |
JP4020054B2 (ja) * | 2003-09-24 | 2007-12-12 | トヨタ自動車株式会社 | 内燃機関の排気浄化システム |
JP2005226504A (ja) * | 2004-02-12 | 2005-08-25 | Hino Motors Ltd | 排気浄化装置の制御方法 |
JP4924217B2 (ja) * | 2007-06-06 | 2012-04-25 | トヨタ自動車株式会社 | 内燃機関の排気浄化装置 |
EP2239432B1 (en) | 2007-12-26 | 2013-05-29 | Toyota Jidosha Kabushiki Kaisha | Exhaust purification device for internal combustion engine |
JP4730379B2 (ja) * | 2007-12-26 | 2011-07-20 | トヨタ自動車株式会社 | 内燃機関の排気浄化装置 |
US8122712B2 (en) * | 2008-01-03 | 2012-02-28 | GM Global Technology Operations LLC | Exhaust system with improved NOX emission control |
WO2011114498A1 (ja) | 2010-03-15 | 2011-09-22 | トヨタ自動車株式会社 | 内燃機関の排気浄化装置 |
CN102933807B (zh) | 2010-05-20 | 2015-04-29 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
US9051860B2 (en) | 2010-05-20 | 2015-06-09 | Toyota Jidosha Kabushiki Kaisha | Exhaust purification system of internal combustion engine |
CN102753794B (zh) * | 2011-02-07 | 2015-05-13 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
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- 2014-06-19 WO PCT/JP2014/066917 patent/WO2015019737A1/en active Application Filing
- 2014-06-19 EP EP14741424.7A patent/EP3030763B1/en not_active Not-in-force
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CN103003539A (zh) * | 2010-08-30 | 2013-03-27 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
CN103180558A (zh) * | 2010-08-30 | 2013-06-26 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
CN102713189A (zh) * | 2010-09-02 | 2012-10-03 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
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EP3030763A1 (en) | 2016-06-15 |
CN105452623A (zh) | 2016-03-30 |
JP2015034504A (ja) | 2015-02-19 |
US9890679B2 (en) | 2018-02-13 |
US20160177798A1 (en) | 2016-06-23 |
JP6090051B2 (ja) | 2017-03-08 |
WO2015019737A1 (en) | 2015-02-12 |
EP3030763B1 (en) | 2016-11-09 |
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