IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0788597
(2010-05-27)
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등록번호 |
US-8225600
(2012-07-24)
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발명자
/ 주소 |
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
61 인용 특허 :
8 |
초록
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A method for remediating a NOx-containing lean diesel emission includes providing a LNT/SCR catalyst system including a SCR catalyst and a first and second LNT. The SCR catalyst is disposed downstream of the second LNT which is disposed downstream of the first LNT. The lean NOx-containing diesel emi
A method for remediating a NOx-containing lean diesel emission includes providing a LNT/SCR catalyst system including a SCR catalyst and a first and second LNT. The SCR catalyst is disposed downstream of the second LNT which is disposed downstream of the first LNT. The lean NOx-containing diesel emission is introduced to the first LNT with the NOx being absorbed on to the first LNT forming a substantially NOx-free lean diesel emission. An exotherm generating agent is introduced to the substantially NOx-free diesel emission between the first LNT and the second LNT to form a reactive lean diesel emission. The reactive lean diesel emission is introduced to the second LNT generating a quantity of heat effective for desorbing absorbed NOx. A reducing agent is introduced into the desorbed NOx between the second LNT and SCR catalyst. The desorbed NOx diesel emission is remediated in the SCR catalyst.
대표청구항
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1. A method for remediating a NOx-containing lean diesel emission having a direction of flow, the method comprising the steps of: (a) providing a LNT/SCR catalyst system including a SCR catalyst, a first LNT having a first NOx storage capacity, and a second LNT having a second NOx storage capacity,
1. A method for remediating a NOx-containing lean diesel emission having a direction of flow, the method comprising the steps of: (a) providing a LNT/SCR catalyst system including a SCR catalyst, a first LNT having a first NOx storage capacity, and a second LNT having a second NOx storage capacity, the second LNT being disposed downstream of the first LNT relative to the direction of flow of the NOx-containing lean diesel emission, having a downstream exit from the second LNT, and fluidly communicating with the first LNT, the SCR catalyst being disposed downstream of and fluidly communicating with the second LNT, the SCR catalyst being capable of communicating with the first LNT, the second LNT having a portion of absorbed NOx;(b) introducing the lean NOx-containing diesel emission to the first LNT;(c) absorbing at least a portion of the NOx from the NOx-containing lean diesel emission on the first LNT to form a substantially NOx-free, lean diesel emission exiting downstream from the first LNT;(d) introducing an exotherm generating agent (EGA) for an EGA introduction time period into the substantially NOx-free lean diesel emission between the first LNT and the second LNT to form a reactive lean diesel emission;(e) introducing the reactive lean diesel emission to the second LNT generating a quantity of heat effective for desorbing a portion of absorbed NOx from the second LNT to form a lean, desorbed NOx emission;(f) streaming the lean, desorbed NOx emission downstream from the exit of the second LNT;(g) introducing a reducing agent (RA) for an RA introduction time period into the lean, desorbed NOx diesel emission between the second LNT and the SCR catalyst; and(h) remediating the lean, desorbed NOx diesel emission in the SCR catalyst to obtain the remediated diesel emission. 2. The method of claim 1, further comprising the steps of (i) providing an engine control strategy to a controller;(j) providing at least one sensor signal to the controller from at least one sensor for at least one of an emission temperature, an LNT bed temperature, a rate of emission flow, an emission air-to-fuel ratio, or a NOx concentration in at least one of the lean NOx-containing diesel emission, the substantially NOx-free, lean diesel emission, the reactive lean diesel emission, or the lean, desorbed NOx diesel emission;(k) combining the sensor signal and the control strategy; and(l) signaling to introduce at least one of EGA or RA when remediating NOx concentrations during acceleration and deceleration transient operations. 3. The method of claim 1, further comprising the step of preconditioning the SCR catalyst, wherein the step of preconditioning the SCR catalyst includes introducing the RA between the second LNT and the SCR catalyst for a preconditioning time period occurring after step (b) begins and before step (f) begins. 4. The method of claim 1, wherein the step of introducing the RA in step (g) ceases during a delay time period after the EGA introduction time period ends. 5. The method of claim 4, wherein the delay time period ranges from 5 to 15 seconds. 6. The method of claim 1, wherein introducing the EGA in step (d) occurs after a preconditioning time period starts, wherein the preconditioning time period starts after step (b) begins and before step (f) begins. 7. The method of claim 1, wherein introducing the EGA in step (d) occurs when the second LNT has a remaining absorbable capacity less than or equal to 50% of the second NOx storage capacity. 8. The method of claim 1, wherein introducing the EGA in step (d) when the second LNT has a remaining absorbable capacity in the range from 10% to 30% of the second NOx storage capacity. 9. The method of claim 1, further comprising the step of (h) reversing the direction of the flow of the NOx-containing lean diesel emission, when the direction of flow is reversed, the first LNT is disposed downstream of the second LNT relative to the direction of flow of the NOx-containing lean diesel emission and fluidly communicating with the second LNT, the SCR catalyst is disposed downstream of and fluidly communicating with the first LNT, and the SCR catalyst is capable of fluidly communicating with the second LNT. 10. The method of claim 9, further comprising the steps of (i) introducing the NOx-containing lean diesel emission to the second LNT;(j) absorbing at least a portion of the NOx on the second LNT from the NOx-containing lean diesel emission to form a substantially NOx-free lean diesel emission exiting downstream from the second LNT;(k) introducing the EGA into the substantially NOx-free lean diesel emission between the first LNT and the second LNT to form the reactive lean diesel emission;(l) introducing the reactive lean diesel emission to the first LNT to react the EGA with the first LNT generating the quantity of heat effective for desorbing a portion of absorbed NOx from the first LNT to form the lean, desorbed NOx emission exiting downstream from the first LNT;(m) introducing the RA into the lean, desorbed NOx emission between the first LNT and the SCR catalyst; and(n) remediating the lean, desorbed NOx emission in the SCR catalyst to obtain the remediated diesel emission. 11. A method for remediating a NOx-containing lean diesel emission, the method comprising: (a) directing the NOx-containing lean diesel emission into a dual-LNT, reversible-flow emission remediation system including absorbed NOx, wherein the system includes a first LNT, a second LNT disposed serially relative to the first LNT, a SCR catalyst disposed downstream of the second LNT, relative to a direction of flow of the NOx-containing lean diesel emission, and a switching valve disposed between the first LNT, the second LNT, and the SCR catalyst;(b) maintaining an average lean air-to-fuel ratio throughout the dual-LNT, reversible-flow emission system during all steps of the method;(c) absorbing substantially all of the NOx from the lean diesel emission in the dual-LNT, reversible-flow emission remediation system to form a substantially NOx-free, lean diesel emission;(d) introducing an exotherm generating agent (EGA) into the substantially NOx-free, lean diesel emission between the first and second LNTs to form a reactive lean diesel emission;(e) reacting the reactive lean diesel emission with the dual-LNT, reversible-flow emission remediation system to form a lean, desorbed NOx emission;(f) introducing a reducing agent (RA) into the lean, desorbed NOx emission between the SCR catalyst and at least one of the first LNT or the second LNT to form a lean, SCR catalyst-reactive emission; and(g) remediating the lean, SCR catalyst-reactive emission to form a lean, remediated diesel emission. 12. The method of claim 11, further comprising the steps of (h) providing an engine control strategy to a controller;(i) providing at least one sensor signal in the controller from at least one sensor disposed in dual-LNT, reversible-flow emission remediation system;(j) combining the sensor signal and the control strategy; and(k) communicating a signal from the controller to operate the switch or to introduce at least one of EGA or RA. 13. The method of claim 12, wherein controlling the quantity of EGA introduced in step (d) comprises steps of (l) receiving at least one sensor signal proportional to an average air to fuel ratio in the quantity of NOx-free, lean diesel emission disposed between the first LNT and the second LNT; and(m) controlling the introduction of EGA to the NOx-free, lean diesel emission such that the NOx-free, lean diesel emission has a lean average air to fuel ratio during an EGA introduction time period. 14. The method of claim 12, wherein controlling the quantity of RA introduced in step (f) comprises steps of (l) receiving at least one sensor signal proportional to a residual quantity of NOx disposed between the second LNT and the SCR catalyst; and(m) decreasing the introduction of RA to match stoichiometrically the residual quantity of NOx. 15. The method of claim 11, further comprising the step of (h) preconditioning a portion of the SCR catalyst of the dual-LNT, reversible-flow emission system by introducing the RA into the NOx-free, lean diesel emission for a preconditioning time period occurring after step (a) and preceding step (d). 16. The method of claim 15, wherein introducing the RA continues after step (d) for a continuation time period ranging from 5 to 15 seconds. 17. The method of claim 15, further comprising the steps of (i) providing an engine control strategy capable of receiving a sensor signal, the engine control strategy communicating with a controller;(j) receiving at least one sensor signal in the controller from a timed signal or at least one sensor for at least one of an emission temperature, an LNT bed temperature, a rate of emission flow, an emission air-to-fuel ratio, or a NOx concentration in at least one of the lean NOx-containing diesel emission, the substantially NOx-free, lean diesel emission, the reactive lean diesel emission, or the lean, desorbed NOx diesel emission;(k) combining the sensor signal with the control strategy; and(l) communicating from the controller to the switch to reverse the flow direction of the NOx-containing lean diesel emission. 18. The method of claim 15, further comprising the steps of (i) providing an engine control strategy capable of receiving a sensor signal, the engine control strategy communicating with a controller;(j) receiving at least one sensor signal in the controller from a timed signal or at least one sensor for at least one of an emission temperature, an LNT bed temperature, a rate of emission flow, an emission air-to-fuel ratio, or a NOx concentration in at least one of the lean NOx-containing diesel emission, the substantially NOx-free, lean diesel emission, the reactive lean diesel emission, or the lean, desorbed NOx diesel emission;(k) combining the sensor signal with the control strategy; and(l) flowing the NOx-containing lean diesel emission to flow over both the first LNT and the second LNT when the NOx-containing lean diesel emission temperature ranges from 150° C. to 400° C. 19. A LNT/SCR catalyst control system for use remediating a NOx-containing lean diesel emission having a direction of flow and an inlet temperature sensor, the LNT/SCR catalyst control system comprising: a first LNT having a NOx storage component (NSC);a SCR catalyst disposed downstream of first LNT with respect to the direction of the flow of the NOx-containing lean diesel emission;an exotherm generating agent (EGA) introduction port disposed upstream of the first LNT, the port being capable of introducing an EGA adjacent to an inlet to the first LNT;a reducing agent (RA) introduction port disposed between the first LNT and the SCR catalyst;a signaling device capable responding to a timed signal or at least one sensor for at least one of an emission temperature, an inlet temperature, an LNT bed temperature, a rate of emission flow, an emission air-to-fuel ratio, or a NOx concentration; andan electrical controller and an engine model, said electrical controller communicating with the EGA introduction port and the RA introduction port, wherein the controller combines one or more signals with the engine model such that either(a) an effective quantity of EGA is introduced at the EGA introduction port in order to release NOx from the NSC when remediating an over-introduction of RA, or(b) an effective amount of RA is introduced at the RA introduction port when controlling a transient NOx concentration increase. 20. The LNT/SCR catalyst control system of claim 19, wherein the electrical controller has a first control plan including storing RA on the SCR catalyst, the first control plan being for use substantially in a first temperature band ranging from 150° C. to 400° C., further, the electrical controller has a second control plan including storing NOx on the first LNT for use substantially in a second temperature band ranging from 400° C. to 550° C. 21. The LNT/SCR catalyst control system of claim 19, further comprising: a second LNT having a second NSC and being disposed upstream of the SCR catalyst, the second LNT also being disposed upstream of the first LNT and the EGA introduction port, the first LNT and second LNT comprising independently at least one of a layered LNT/SCR catalyst configuration, a zoned LNT/SCR catalyst configuration, a combined layered and zoned LNT/SCR catalyst configuration, or a separated LNT and SCR catalyst configuration; anda valve disposed upstream of and communicating with both the first LNT and the second LNT and being in communication with the signaling device, wherein the engine model signals the valve to direct the NOx-containing lean diesel emission to either the first LNT or the second LNT, the engine model signals introduction of EGA through the EGA introduction port for a time period sufficient to introduce an effective amount of EGA to purge NOx from the LNT to which the valve has not directed the NOx-containing lean diesel emission. 22. The LNT/SCR catalyst control system of claim 19, wherein the electrical controller signals introduction of RA for a portion of a RA introduction time period before introduction of EGA during an EGA introduction period when preconditioning the SCR catalyst. 23. The LNT/SCR catalyst control system of claim 22, wherein the RA introduction time period includes a continuation period continuing RA introduction after the end of the EGA introduction period.
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