Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2002-12-04
2004-08-17
Tran, Diem (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
C060S286000, C060S295000
Reexamination Certificate
active
06775973
ABSTRACT:
TECHNICAL FIELD
This invention relates to a NOx-reducing adsorption unit having an adsorption bed, in which the engine exhaust and the stream of regeneration gas, including hydrogen and carbon monoxide, both flow continuously, the adsorption bed and a gas inlet distributor having continuous relative rotation, portions of the adsorption bed being in fluid communication with engine exhaust inlet manifold for a first fraction of each cycle and then being in fluid communication with the regeneration gas for another fraction of each cycle, whereby successive portions of the filter first adsorb engine exhaust and then are regenerated, continuously.
BACKGROUND ART
The Environmental Protection Agency (EPA) has set, for 2007 and beyond, vehicle internal combustion engine emission requirements; one exemplary requirement for diesel engines, is NOx and non-methane hydrocarbons below 0.20 grams bhp-hr and 0.14 grams/bhp-hr, respectively. This contrasts with current standards of 4.0 grams/bhp-hr and 1.3 grams/bhp-hr, respectively. Thus, the catalytic converters must accomplish a significant reduction in NOx.
Apparatus that oxidizes engine fuel to provide a mix that enhances NOx reduction is disclosed in U.S. Pat. No. 5,412,946, in PCT published application WO 01/34950, and U.S. patent application Publication 2001/41153.
In commonly owned U.S. patent application Ser. No. 10/159,369, filed May 31, 2002, moisture and possibly oxygen, derived from the exhaust of a hydrocarbon-fueled, internal combustion engine are processed along with fuel from the engine's fuel tank in a fuel processor, which may be a catalytic partial oxidation reformer, a non-catalytic (homogeneous) partial oxidation reformer, or an auto thermal reformer, to generate a stream of hydrogen and carbon monoxide which is used to regenerate NOx traps following the formation of nitrogen-containing compounds by reaction of the exhaust with adsorbent in the NOx traps.
In
FIG. 1
, an engine
9
has a conventional turbo compressor
10
feeding an air inlet line
11
, a hydrocarbon fuel tank
12
, and a fuel pump
13
. The fuel may be diesel fuel, gasoline, natural gas, liquid petroleum gas, or propane. The fuel is fed by a first line
17
to the engine for combustion with the air, and is fed by a second line
18
through a heat exchanger
50
, to a mixer
19
in a pipe
20
that feeds a small amount of exhaust from an exhaust pipe
21
to a hydrogen generator
22
.
The hydrogen generator
22
may be a catalytic partial oxidizer (CPOx), a non-catalytic (homogeneous) partial oxidizer, or an auto thermal reformer (ATR). Within the hydrogen generator, if it is a CPOx, foam monolith or other form of catalyst, which may comprise a group VIII metal, preferably nickel, cobalt, rhodium, iridium or platinum, convert fuel along with hydrocarbons, water and oxygen into a mix of hydrogen, CO and CO
2
, which is regeneration gas, commonly called “syngas”. This is provided through a conduit
26
to a pair of NOx adsorbent traps
35
,
36
which are alternatively connected by corresponding valves
40
-
43
to either the conduit
26
with hydrogen-containing gas from the generator
22
, or to a pipe
48
containing engine exhaust.
The valves are controlled so that engine exhaust is allowed to flow in one of the traps
35
,
36
for a period of time which is less than the time necessary to saturate it with NOx, and then the valves are switched so that exhaust flows in the other NOx trap, while the first NOx trap is regenerated by the hydrogen and carbon monoxide from the generator
22
. In one regeneration cycle, the valves
41
and
42
will be closed and the valves
40
,
43
will be open so that engine exhaust is adsorbed in the trap
35
, and the trap
36
is regenerated; in the next regeneration cycle, valves
40
and
43
will be closed and the valves
41
and
42
will be open so that engine exhaust is adsorbed in the trap
36
, and the trap
35
is regenerated, and so forth.
Although various adsorbents may be used, the NOx traps may, for example, contain barium carbonate (BaCO
3
) as the adsorbent. Typically, a catalyst, such as platinum, may be wash-coated on the adsorbent material to catalyze the reaction. When the diesel exhaust is adsorbed by the barium carbonate, a reaction generates barium nitrate.
2NOx+BaCO
3
→Ba(NO
3
)
2
+CO
2
Then, during the regeneration cycle, the barium nitrate is converted back to barium carbonate, as follows:
3H
2
+2CO+Ba(NO
3
)
2
→BaCO
3
+N
2
+3H
2
O+CO
2
The heat exchanger
50
causes heat of the engine exhaust to vaporize the fuel in the line
18
before applying it to the hydrogen generator, which is particularly useful in the case of a CPOx reformer being used as the hydrogen generator.
A CPOx reformer is preferred in one sense because it is very small and can run with low steam carbon ratios and high turndown ratios without soot or carbon formation. However, diesel engine exhaust contains particulates (soot) and oxides of sulfur (SOx), which may deactivate the CPOx catalyst over a period of time. Therefore, a non-catalytic (homogeneous) partial oxidizer may alternatively be selected as the hydrogen generator
22
. The percentage of hydrogen produced is only slightly less than that produced by a CPOx. It is easily started by employing a simple spark plug, as is known. Additionally, POX is cheaper than CPOx; control of the O
2
/C ratio is known (similar to engine O
2
/fuel ratio), and simpler; SOx and soot do not affect it; and there is no steam/C ratio problem.
However, the alternating adsorption and regeneration cycles require large, high temperature valves for the engine exhaust. Switching of the exhaust from one adsorption bed to the other, at high exhaust temperature, is a difficult operation.
Furthermore, the engine exhaust valves leak: typically on the order of 5% of the total engine exhaust will flow through the wrong adsorption bed during regeneration thereof. Because there may be up to 15% oxygen in the engine exhaust, which oxygen will react with the hydrogen and carbon monoxide in the regeneration gas, a significant amount of regeneration gas is consumed (wasted) by being combined with oxygen due to the leaks in the valves. The reaction of O
2
with H
2
and CO will cause a rise in temperature which could deactivate the NOx adsorption bed catalyst.
DISCLOSURE OF INVENTION
Objects of the invention include: eliminating high temperature valves in regenerating adsorption beds; improvement in the reduction of NOx to nitrogen and other harmless gases in internal combustion engine exhaust; providing a continuous process for regenerating NOx adsorbents; reducing the size and complexity of NOx-reducing equipment for engine exhaust; simplified equipment for meeting EPA 2007 NOx emission requirements; and avoiding waste of regeneration gas that occurs due to valve leakage in alternating NOx-adsorption systems.
This invention is predicated in part on the discovery that the amount of time that it takes to regenerate an NOx adsorption bed when exposed to regeneration gas is much less than the amount of time that the same size of adsorption bed may take to become saturated with NOx, when in the flow of engine exhaust.
According to the present invention, a relatively rotating inlet gas distributor and NOx adsorption bed having a plurality of flow paths lined with adsorption catalyst, causes a flow of internal combustion engine exhaust in each path during a first fraction of a revolution, and a flow of regeneration gas in each path during the remainder of a revolution. The exhaust gas and regeneration gas are both flowed continuously through the bed.
According to the invention, the flow of gases into the bed is controlled by a distributor having a baffle therein to keep the exhaust gas and regeneration gas separate, and to determine which paths receive one or the other of the gas flows at any point in time. Either the bed (in one embodiment) or the distributor (in another embodiment) may be rotated to cause the gas flows to alternate in the flow paths.
According to
Foley Peter F.
Liu Ke
Rohrbach Eric A.
Wnuck Wayne G.
HydrogenSource LLC
Tran Diem
Williams M. P.
LandOfFree
Continuous flow, NOx-reduction adsorption unit for internal... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Continuous flow, NOx-reduction adsorption unit for internal..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Continuous flow, NOx-reduction adsorption unit for internal... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3358610