U.S. patent application number 11/067815 was filed with the patent office on 2005-09-08 for oxygen-enriched feedgas for reformer in emissions control system.
This patent application is currently assigned to Southwest Research Institute. Invention is credited to Anthony, Joseph W., Webb, Cynthia C..
Application Number | 20050193724 11/067815 |
Document ID | / |
Family ID | 34915001 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050193724 |
Kind Code |
A1 |
Webb, Cynthia C. ; et
al. |
September 8, 2005 |
Oxygen-enriched feedgas for reformer in emissions control
system
Abstract
A method and systems for supplying oxygen-enriched feedgas to a
reformer. The reformer is placed on an exhaust bypass line, which
has a valve upstream the reformer, for opening and closing the flow
of exhaust gas into the bypass line. The bypass line receives
atmospheric air at a venturi, and this air is mixed with the
exhaust gas to supply feedgas to the reformer. The output of the
reformer is directed via the bypass line to a point on a main
exhaust line upstream an emissions control device, such as a
NAC.
Inventors: |
Webb, Cynthia C.; (San
Antonio, TX) ; Anthony, Joseph W.; (Lytle,
TX) |
Correspondence
Address: |
BAKER BOTTS L.L.P.
PATENT DEPARTMENT
98 SAN JACINTO BLVD., SUITE 1500
AUSTIN
TX
78701-4039
US
|
Assignee: |
Southwest Research
Institute
San Antonio
TX
|
Family ID: |
34915001 |
Appl. No.: |
11/067815 |
Filed: |
February 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60548354 |
Feb 27, 2004 |
|
|
|
Current U.S.
Class: |
60/289 ; 60/286;
60/287; 60/295; 60/301 |
Current CPC
Class: |
F01N 13/107 20130101;
F01N 3/22 20130101; Y02T 10/40 20130101; Y02T 10/144 20130101; F01N
9/00 20130101; F01N 3/0878 20130101; F01N 2240/30 20130101; Y02T
10/47 20130101; F01N 3/0842 20130101; F01N 2560/025 20130101; Y02T
10/12 20130101; F02B 37/00 20130101; F01N 3/021 20130101; F01N 3/30
20130101 |
Class at
Publication: |
060/289 ;
060/287; 060/286; 060/295; 060/301 |
International
Class: |
F01N 003/10; F01N
003/00 |
Claims
What is claimed is:
1. A method, for use in a diesel engine having an air-charging
device, of providing a reformate to an emissions control device on
an exhaust line, comprising: using a bypass line to carry exhaust
gas from the engine to a point on the exhaust line upstream the
emissions control device; opening a valve on the bypass line
upstream the reformer; directing atmospheric air to a venturi in
the bypass line, upstream the reformer; receiving the air and
exhaust into the reformer; using the reformer to generate the
reductant; and routing the reductant, via the bypass line, to the
point on the exhaust line upstream the emissions control
device.
2. The method of claim 1, further comprising the step of closing
the exhaust flow from the air-charging device.
3. The method of claim 1, further comprising the step of using a
valve to decrease or stop the flow of exhaust through the exhaust
line.
4. The method of claim 1, further comprising the step of using
backpressure of the air-charging device to boost flow to the
reformer.
5. The method of claim 1, wherein the emissions control device is a
NOx adsorption catalyst (NAC), and wherein the method operates
during regeneration of the NAC.
6. The method of claim 1, further providing the step of using a
sensor to detect the oxygen provided to the reformer.
7. The method of claim 1, wherein the method is used with closed
loop control hardware for control of oxygen to the reformer.
8. The method of claim 1, wherein the bypass line begins at a point
between the exhaust manifold and the air-charging device.
9. The method of claim 1, wherein the atmospheric air is routed
from the air output side of the air-charging device.
10. The method of claim 1, wherein the atmospheric air is routed
directed directly from atmosphere.
11. An exhaust system for a diesel engine having an air-charging
device, comprising: an exhaust line for carrying exhaust gas from
the engine to atmosphere; at least one emissions control device on
the exhaust line; a bypass line to carry exhaust gas from the
engine to a point on the exhaust line upstream the emissions
control device; a reformer on the bypass line; a valve on the
bypass line upstream the reformer, for opening and closing the flow
of exhaust gas from the engine into the bypass line; a venturi in
the bypass line, upstream the reformer; and an air inlet for
receiving air into the bypass line at the venturi; wherein the air
inlet receives air from the air-charging device.
12. The system of claim 11, further comprising a valve for closing
the flow of exhaust into the exhaust line.
13. A method, for use in a diesel engine, of providing a reformate
to an emissions control device on an exhaust line, comprising:
using a bypass line to carry exhaust gas from the exhaust manifold
of the engine to a point on the exhaust line upstream the emissions
control device; opening a valve on the bypass line upstream the
reformer; directing atmospheric air to a venturi in the bypass
line, upstream the reformer; receiving the air and exhaust into the
reformer; using the reformer to generate the reformate; and routing
the reformate, via the bypass line, to the point on the exhaust
line upstream the emissions control device.
14. The method of claim 13, further comprising the step of using a
valve to decrease or stop the flow of exhaust through the exhaust
line.
15. The method of claim 13, wherein the emissions control device is
a NOx adsorption catalyst (NAC), and wherein the method operates
during regeneration of the NAC.
16. The method of claim 13, further providing the step of using a
sensor to detect the oxygen provided to the reformer.
17. The method of claim 13, wherein the method is used with closed
loop control hardware for control of oxygen to the reformer.
18. An exhaust system for a diesel engine, comprising: an exhaust
line for carrying exhaust gas from the engine to atmosphere; at
least one emissions control device on the exhaust line; a bypass
line to carry exhaust gas from the engine to a point on the exhaust
line upstream the emissions control device; a reformer on the
bypass line; a valve on the bypass line upstream the reformer for
opening and closing the flow of exhaust gas from the engine into
the bypass line; a venturi in the bypass line, upstream the
reformer; and an air inlet for receiving air into the bypass line
at the venturi.
19. The system of claim 18, wherein the emissions control device is
a NOx adsorber catalyst (NAC).
20. The system of claim 18, further comprising a valve for closing
the flow of exhaust into the exhaust line.
Description
RELATED PATENT APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/548,354, filed Feb. 27, 2004 and entitled
"Oxygen-Enriched Feedgas for Reformer in NOx Adsorber Emissions
System".
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates to reducing exhaust emissions from
internal combustion engines, and more particularly to providing
oxygen-enriched feedgas for an exhaust gas reformer used upstream
of an emissions control device, such as a lean NO.sub.x
catalyst.
BACKGROUND OF THE INVENTION
[0003] Internal combustion engines are a major contributor to
harmful emissions. Internal combustion engines dominate land
transportation propulsion--cars, trucks, off-highway vehicles,
railroad, marine, motorcycles--as well as provide mechanical and
electrical power for a wide range of large and small applications.
The two dominant types of internal combustion engines are
spark-ignition and diesel. The amount and composition of the
emissions exhausted from these engines depend on the details of the
processes that occur within the engine during operation, the
characteristics of the fuel used, and the type of emissions control
system used.
[0004] For diesel engines, the main pollutants of concern are
nitrogen oxides (NOx) and particulate matter (PM). The latter is
composed of black smoke (soot), sulfates generated by the sulfur in
fuel, and organic components of unburned fuel and lubricating
oil.
[0005] In-cylinder design changes have had some success in reducing
emissions, but have fallen short of allowing diesel engines to meet
today's emissions limits. Post-combustion treatment systems often
include catalysts and particulate filters for reducing NOx and PM
respectively. Technology advances in the catalyst field have made
it possible for integrated systems of engine and exhaust treatment
to achieve extremely low emissions. Yet, more emission reduction
efficiencies are sought from existing systems and new catalytic
reduction solutions are needed to achieve even lower emissions.
[0006] Indications are that diesel oxidation catalyst performance
improves with increased engine speed, airflow, and hence oxygen
content. For particulate filters, both oxygen content and exhaust
gas temperature their regeneration.
[0007] On the other hand, for regeneration of modern NO.sub.x
reduction catalysts such as the lean NO.sub.x trap (NO.sub.x
adsorber catalyst), reduced oxygen content in the exhaust is
desirable. Normally in diesel exhaust, attempts are made to reduce
oxygen to regenerate the system from its stored nitrogen compounds.
Attempts to reduce exhaust oxygen content are usually combined with
increasing exhaust hydrocarbon to obtain the rich mixture needed
for the NO.sub.x regeneration process.
[0008] It is customary in diesel NO.sub.x adsorber technology to
place a diesel oxidation catalyst upstream from the lean NO.sub.x
trap. Its purpose is to condition the exhaust hydrocarbon or reform
it to obtain the ideal reductant for the lean NO.sub.x trap
regeneration.
[0009] Having established the need for controlling the composition
of the reductant, some companies have announced plans for using
onboard fuel reformers to accomplish their needs. Onboard fuel
reformers involve some kind of catalyst that is provided with a
supply of fuel and a supply of air. Providing a continuous but
controllable supply of fuel has not been a significant obstacle.
However, providing a suitable supply of air to the reformer has
been challenging.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A more complete understanding of the present embodiments and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings, in
which like reference numbers indicate like features, and
wherein:
[0011] FIG. 1 illustrates a first embodiment of the invention;
and
[0012] FIG. 2 illustrates a second embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The following description is directed to an engine-based
means and method, used in conjunction with a diesel emissions
control system, for supplying an exhaust reformer with a source of
air. The air enriches the feedgas to the reformer, which generates
a reformate. In the example of this description, the enriched
feedgas is used by the reformer to provide a reductant during
regeneration of a NO.sub.x adsorbtion catalyst (NAC).
[0014] FIG. 1 illustrates a method and system for supplying air to
a reformer 101 in accordance with the invention. Reformer 101 is
part of an emissions control system 100, which also has at least
one emissions control device 102 that has cause to use feedgas from
reformer 101. In the example of this description, the emissions
control device 102 is a NAC (NO.sub.x adsorber catalyst) sometimes
also referred to as an LNT (lean NO.sub.x trap).
[0015] Engine 103 is a diesel engine, and in the example of this
description, is a dual bank engine. It is equipped with an
air-charging device 104, such as a turbocharger. In the example of
this description, turbocharger 104 is a VNT (variable nozzle
turbocharger).
[0016] The method is particularly useful for supplying
oxygen-enriched feedgas to reformer 101 under low flow and/or low
load engine operating conditions. Under such conditions, fresh air
from a boosted source (such as turbocharger 104) is low or
unavailable.
[0017] As illustrated, NAC 102 is mounted along the engine exhaust
pipe. NAC 102 is essentially a storage device for NO.sub.x
contained in the exhaust gas. It has two principal elements: a
NO.sub.x adsorbent and a three-way conversion catalyst. NAC 102 has
three primary functions: conversion of NO to NO.sub.2, adsorption
of NO.sub.2, and release and reduction of NO.sub.2 during
regeneration of the NAC 102.
[0018] As stated in the Background, regeneration of NAC 102 is
performed under rich exhaust gas conditions. Under such conditions,
the stored NO.sub.x is released from the adsorbent and
simultaneously reduced to N.sub.2 (and/or N.sub.2O or NH.sub.3)
over precious metal sites.
[0019] Reformer 101 is placed on an exhaust bypass 105. As
explained below, the purpose of reformer 101 is to supply reductant
for regeneration of the NAC 102. Reformer 101 typically has a
catalyst, and is provided with a supply of fuel and a supply of
air. A supply line (not shown) may be used to supply fuel or any
other liquid or gas consumed by the reformer.
[0020] In the example of this description, where engine 103 is a
dual-bank engine, exhaust bypass 105 is routed off one side of the
exhaust manifold, prior to turbocharger 104. For an in-line engine,
the bypass would be installed upstream of the turbocharger. Bypass
105 joins the main exhaust pipe upstream the NAC 102
[0021] Exhaust bypass 105 is normally closed, using valve 107. When
flow through reformer 101 is desired, and exhaust flow conditions
are low, valve 107 blocking the exhaust bypass 105 is opened.
[0022] At the same time, the turbocharger 104 is operated to as to
obstruct exhaust flow from the turbocharger. For example, the
turbine vanes may be closed. Essentially, while exhaust gas is
flowing through bypass 105, turbocharger 104 is used to put
backpressure on the exhaust flow. If the turbocharger 104 does not
sufficiently obstruct exhaust flow, an optional exhaust valve 106
may be closed to increase the flow through the exhaust bypass
105.
[0023] Flow through exhaust bypass 105 may be metered by using a
metering valve for valve 107. An example of a suitable valve is an
EGR (exhaust gas recirculation) metering valve. A venturi 108 is
placed downstream valve 107.
[0024] A fresh air line 109 is plumbed to the center of venturi
108, which pulls air in. During low flow conditions, the air into
venturi 108 is not necessarily charged; charged air is not required
for operation of the invention. However, in various embodiments of
the invention, charged air may be available and used.
[0025] In the example of FIG. 1, fresh air line 109 is routed
through the compressor side of turbocharger 104. This permits fresh
air line 109 to receive charged air from turbocharger 104 if
available and desired. As explained below in connection with FIG.
2, in other embodiments, fresh air line 109 may be routed directly
from atmosphere.
[0026] The fresh air entering exhaust bypass 105 at venturi 108
provides oxygen-enrichment of the exhaust, which already has a high
oxygen content at low load and idle. Under these conditions, the
exhaust prior to enrichment already typically has more than 15%
oxygen.
[0027] The oxygen-enriched gas mixture is then supplied to reformer
101. An example of a suitable reformer 101, is a fuel-based
reformer, which burns diesel fuel, and makes the exhaust gas
fuel-rich, to be used for regeneration of NAC 102.
[0028] Optionally, a small diesel particulate filter 110 can be
placed at the entrance to exhaust bypass 105, to clean the exhaust
gas. The filter 110 may be placed anywhere upstream reformer
101.
[0029] Various sensors, such as mass airflow (MAF) sensor 111
and/or an oxygen sensor 112 can be used to determine an oxygen mass
flow rate. This measurement is especially useful for closed-loop
control of fuel to the reformer 101. A metering valve 113 may be
used to control the amount of oxygen received at venturi 108.
[0030] A controller 120 can be used to receive measurements from
various sensors, such as sensors 111 and 112. Controller 120 would
deliver control signals to various valves, such as valves 107, 106,
and 113. Controller 120 would be programmed to perform the method
described above, and wherein the emissions control device 102 is a
NAC, would be programmed to provide oxygen-enriched feedgas via the
bypass line 105 during regeneration of NAC.
[0031] FIG. 2 illustrates a second embodiment of the invention, in
which fresh air line 209 is routed directly to atmosphere, rather
than being routed through the compressor side of turbocharger 204.
The embodiment of FIG. 2 operates in the same manner as the
embodiment of FIG. 1, being particularly designed for use during
low-flow/low-load conditions. It is conceivable that engine 203 may
lack a turbocharger or other air-charging device, in which case the
above-described method is operable independently of such
devices.
* * * * *