U.S. patent application number 12/538453 was filed with the patent office on 2010-03-04 for apparatus for storing nox reductant on a vehicle.
This patent application is currently assigned to DELPHI TECHNOLOGIES, INC.. Invention is credited to Bob Xiaobin Li, Michael James Seino.
Application Number | 20100050603 12/538453 |
Document ID | / |
Family ID | 40227556 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100050603 |
Kind Code |
A1 |
Seino; Michael James ; et
al. |
March 4, 2010 |
APPARATUS FOR STORING NOx REDUCTANT ON A VEHICLE
Abstract
Apparatus is disclosed for storing a liquid NO.sub.x reductant
on a vehicle. The apparatus comprises a container for containing
the liquid NO.sub.x reductant, a first heating device located in
the container and adapted to heat the NO.sub.x reductant in use,
and a tube that has a first end adapted to be submerged in the
liquid NO.sub.x reductant in the container in use. The tube is
adapted to extract liquid NO.sub.x reductant from the container and
the tube includes a second heating device extending along at least
a portion of the length of the tube that is located within the
container.
Inventors: |
Seino; Michael James;
(Flushing, MI) ; Li; Bob Xiaobin; (Grand Blanc,
MI) |
Correspondence
Address: |
Delphi Technologies, Inc.
M/C 480-410-202, PO BOX 5052
Troy
MI
48007
US
|
Assignee: |
DELPHI TECHNOLOGIES, INC.
Troy
MI
|
Family ID: |
40227556 |
Appl. No.: |
12/538453 |
Filed: |
August 10, 2009 |
Current U.S.
Class: |
60/282 ;
219/202 |
Current CPC
Class: |
F01N 2610/10 20130101;
F01N 3/36 20130101; F01N 2610/1406 20130101; Y02A 50/2325 20180101;
F01N 2610/02 20130101; F01N 3/2066 20130101; F01N 2610/14 20130101;
Y02A 50/20 20180101; Y02T 10/24 20130101; Y02T 10/12 20130101 |
Class at
Publication: |
60/282 ;
219/202 |
International
Class: |
F01N 3/10 20060101
F01N003/10; F01N 7/00 20060101 F01N007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 2008 |
EP |
08163622.7 |
Claims
1. Apparatus for storing a liquid NO.sub.x reductant on a vehicle,
the apparatus comprising: a container for containing the liquid
NO.sub.x reductant; a first heating device located in the container
and adapted to heat the NO.sub.x reductant in use; a tube assembly
having a first end adapted to be submerged in liquid NO.sub.x
reductant in the container in use, and being adapted to extract
liquid NO.sub.x reductant from the container, the tube assembly
comprising a tube and a second heating device extending along at
least a portion of the length of the tube that is located within
the container; and a plate member mechanically coupled to the first
heating device and the first end of the tube assembly.
2. Apparatus according to claim 1, wherein the container includes a
removable closure and the first and second heating devices are
electrically coupled to electrical apparatus outside the container
through the removable closure and the tube assembly is fluidly
coupled to further apparatus outside the container through the
removable closure when the container is closed by the closure.
3. Apparatus according to claim 2, wherein the first heating device
and the first end of the tube assembly are mechanically coupled to
a plate member that is adapted to be located adjacent the bottom of
the container when the container is closed by the closure.
4. Apparatus according to claim 1, wherein the second heating
device comprises a helical resistive wire heating device encircling
the tube.
5. Apparatus according to claim 1, wherein the second heating
device comprises a ribbon heater.
6. Apparatus according to claim 1, wherein the second heating
device comprises a flexible resistive heater.
7. Apparatus according to claim 1, wherein the second heating
device comprises a film heater circuit.
8. Apparatus according to claim 7, wherein the film heater circuit
is printed on the outside surface of the tube.
9. Apparatus according to claim 1, wherein the tube comprises a
flexible tube.
10. Apparatus according to claim 9, wherein the second heating
device is embedded within the walls of the flexible tube
11. Apparatus according to claim 1, wherein the tube comprises a
first substantially rigid tube.
12. Apparatus according to claim 11, wherein the first
substantially rigid tube comprises a metal tube and the second
heating device is in contact with the external surface of the first
substantially rigid tube, so that heat from the second heating
device is conducted through the sidewall of the first substantially
rigid tube.
13. Apparatus according to claim 1, wherein the tube assembly
comprises an outer sheath, and wherein the portion of the tube
along which the second heating device (11; 21; 46; 40) extends is
enclosed in the outer sheath.
14. Apparatus according to claim 13, wherein the tube and the outer
sheath define a space between the outer surface of the tube and the
inner surface of the outer sheath, and the space is plugged at both
ends to isolate the second heating device from NO.sub.x reductant
in the container, in use.
15. Apparatus according to claim 1, wherein the tube assembly
further comprises a temperature sensor and/or a liquid level
sensor.
16. Apparatus according to claim 1, wherein the tube has an
internal wall defining a channel for extracting liquid NO.sub.x
reductant from the container and an external wall, and the second
heating device is adapted to heat both the internal wall and the
external wall of the tube.
17. Apparatus according to claim 1, wherein the first and second
heating devices are independently operable.
18. An NO.sub.x reductant storage apparatus for a vehicle, the
apparatus comprising: a container for containing the NO.sub.x
reductant; a first heating device located in the container; a tube
assembly adapted to extract liquid NO.sub.x reductant from the
container, the tube assembly comprising a flexible tube and a
second heating device extending along at least a portion of the
length of the tube; and a plate member mechanically coupled to the
first heating device and the tube assembly and adapted to locate
the first heating device within the container at a predetermined
position relative to the tube assembly.
19. The NO.sub.x reductant storage apparatus of claim 18, wherein
the first heating device is a resistive element coiled heater which
is thermally coupled to the plate member.
20. The NO.sub.x reductant storage apparatus of claim 18, wherein
the first and second heating devices are independently operable.
Description
TECHNICAL FIELD
[0001] The invention relates to apparatus for storing NO.sub.x
reductant on a vehicle.
BACKGROUND OF THE INVENTION
[0002] Diesel engines are typically more efficient than gasoline
engines, with regard to fuel economy and emit less greenhouse
gasses. However, diesel engines typically produce emissions
containing higher concentrations of nitrogen oxides (NO.sub.x)
compared to gasoline engines fitted with three-way catalysts.
SUMMARY OF THE INVENTION
[0003] One method that has been employed to remove NO.sub.x from
diesel exhaust utilizes selective catalytic reduction (SCR) of
NO.sub.x with a liquid nitrogen containing reductant, such as
aqueous urea. NO.sub.x and the liquid reductant are brought into
contact with a selective catalyst and catalytically converted into
environmentally safe nitrogen and water. When a liquid reductant is
used, the liquid reductant is typically injected directly into the
exhaust pipe in front of a catalyst to effect reduction of NO.sub.x
on the surface of the catalyst or in the catalyst itself.
[0004] However, one major disadvantage of liquid reductants is that
freezing of the reductant may occur. The freezing temperature
varies relative to the composition and concentration of the
dissolved reductant. For example, solutions having a urea content
of about 32.5% in water (eutectic), typically freeze at about
12.degree. F., (-11.degree. C.). As can be readily expected, liquid
reductant freezing is particularly a problem for the use of diesel
vehicles in cold-weather climates when a liquid reductant is
employed to help meet emission standards for NO.sub.x.
[0005] Therefore, a thermal heating system is required to melt the
solidified urea solution to enable an on-board-vehicle pump to draw
the liquid urea solution from its container and to deliver it into
the exhaust pipe for the SCR.
[0006] In accordance with a first aspect of the present invention,
there is provided apparatus for storing a liquid NO.sub.x reductant
on a vehicle, the apparatus comprising a container for containing
the liquid NO.sub.x reductant, a first heating device located in
the container and adapted to heat the NO.sub.x reductant in use,
and a tube having a first end adapt to be submerged in liquid
NO.sub.x reductant in the container in use, and the tube being
adapted to extract liquid NO.sub.x reductant from the container,
the tube including a second heating device extending along at least
a portion of the length of the tube that is located within the
container. The container may be a NO.sub.x reductant tank used to
store the NO.sub.x reductant (e.g. urea) for use in a catalytic
emission reduction system on a vehicle.
[0007] In accordance with a second aspect of the invention, there
is provided an NO.sub.x reductant storage apparatus for a vehicle,
the apparatus comprising: a container for containing the NO.sub.x
reductant; a first heating device located in the container; a tube
assembly adapted to extract liquid NO.sub.x reductant from the
container, the tube assembly comprising a flexible tube and a
second heating device extending along at least a portion of the
length of the tube; and a plate member mechanically coupled to the
first heating device and the tube assembly and adapted to locate
the first heating device within the container at a predetermined
position relative to the tube assembly.
[0008] Beneficially, at least a section of the portion of the
length of the tube along which the second heating device extends
and any length of tube between the section and the first end are
adapted to be submerged in NO.sub.x reductant in the container, in
use.
[0009] Typically, the portion of the length of the tube along which
the second heating device extends is at least substantially the
length of the tube that is located within the container.
[0010] In one example of the invention, the second heating device
comprises a helical resistive wire heating device encircling the
tube. In another example of the invention, the second heating
device comprises a ribbon heater, which may be, for example, made
from carbon fibre materials. Alternatively, the second heater may
be a flexible resistive heater, for example, made of carbon or
silicon rubber materials.
[0011] In a further example of the invention, the second heater may
comprise a thick film heater circuit, which may be printed on the
outside surface of the tube.
[0012] In one example of the invention, the tube may be a flexible
tube and in this case, the second heating device may be integrally
formed within the material of the tube. A flexible tube can be
advantageous it that it allows for ease of manufacture and assembly
of the apparatus.
[0013] In another example of the invention, the tube may be a
substantially rigid tube, for example, a metal tube, such as
stainless steel and the second heating device is in contact with
the external surface of the tube so that heat from the heating
device is conducted through the side wall of the tube to the
interior of the tube.
[0014] Typically, the portion of the tube along which the second
heating device extends, may be enclosed in an outer tube, which,
for example, may be a metal tube, such as a stainless steel tube.
Typically, the outer tube is plugged at both ends and for example,
could be filled with a filler material, such as a resin or
elastomeric material that is preferably compatible with the
NO.sub.x reductant.
[0015] Suitably, where an outer tube surrounds the second heating
device and the portion of the tube along which the second heating
device extends, a temperature sensor and/or a liquid level sensor
may be housed within an annular gap between the tube and the outer
tube to sense the temperature and the level of the NO.sub.x
reductant within the container, in use.
[0016] Generally, the liquid NO.sub.x reductant is a urea solution,
typically having a urea content of between 25% and 40% and
suitably, between 30% and 35% and most preferably, substantially
32.5%.
[0017] In one example of the invention, the tube extends through a
sidewall of the container so that a second end of the tube is
outside the container. For example, it is possible that the tube
could extend to a dispensing device, such as an injector, for
dispensing the NO.sub.x reductant into the exhaust flow. However,
alternatively, the second end of the tube could terminate inside
the container at a connector mounted on a sidewall of the
container. The term "sidewall" in this context means any wall of
the container, including the top, bottom or sides of the
container.
[0018] Advantageously, the container includes a removable closure
and the first and second heating devices are electrically coupled
and the tube is fluidly coupled to further apparatus outside the
container through the removable closure when the container is
closed by the closure. Conveniently, the closure is adapted to
removably mount to the top of the container.
[0019] Typically, the first heating device and the first end of the
tube are mechanically coupled to a plate member that is located
adjacent the bottom of the container when the container is closed
by the closure. In this way the location of the first end of the
tube can be fixed at a position relative to the plate member and to
the first heating device. This allows a beneficial predetermined
separation of the first end of the tube and the heater to optimise
the performance of the apparatus and maximise the usable urea. This
arrangement is convenient for allowing the withdrawal of liquid
NO.sub.x reductant rapidly after activation of the first heating
device, and is particularly beneficial when a flexible pickup tube
is used as the first end of the tube will remain in the optimal
predetermined location relative to the first heating device, even
when the apparatus is moving or not positioned in its intended
orientation.
[0020] The mechanical coupling between the first heating device and
the plate member also acts as thermal coupling between the
respective components so that the base plate provides additional
surface area for more rapidly heating the NO.sub.x reductant.
[0021] The first heating device may be a resistive heating element,
typically located at or adjacent to the bottom of the container.
For example, the resistive heating element may be in the form of a
helical coil.
[0022] Alternatively, the first heating device may comprise a
positive temperature coefficient (PTC) heater element. Typically,
where the first heating device comprises a PTC heater element, the
PTC heater element is located at or adjacent to the bottom of the
container. Typically, a number of PTC heater elements form the
first heating device. For example, the first heating device may
include three PTC heater elements. However, any number of PTC
heater elements may be used. The number of PTC elements that are
used may depend, for example, on the shape and configuration of the
container, the type of NO.sub.x reductant used and the maximum
volume of NOx reductant that can be held in the container.
Suitably, the PTC heater elements are encased in a NO.sub.x
reductant compatible material. For example, the PTC heater elements
could be encapsulated in a suitable material that is resistant to
the NO.sub.x reductant. The encapsulation could be performed by a
moulding technique, such as injection moulding.
[0023] In a particularly suitable embodiment the first heating
device is a resistive element coiled heater that is mechanically
(and thermally) coupled to a plate member. A pickup tube is further
connected to the plate member. Conveniently the pickup tube is a
flexible tube containing a second heating device.
[0024] Where the tube is a flexible tube, the tube may comprise a
multilayer tube and for example, may include at least a sealing
layer and a thermoplastic elastomeric layer and the second heating
device is integrally formed in at least one of the layers. The tube
may also preferably include an insulating layer.
[0025] Typically, the second heating device is located in or close
to the innermost layers of the tube so that it is relatively close
to the internal surface of the tube. Alternatively or in addition,
the second heating device may be located in or close to the
outermost layers of the tube. Beneficially, the second heating
device extends between the innermost and the outermost layers of
the tube. This has the advantage that the second heating device can
be used to both heat the interior of the tube and the exterior of
the tube. Heating the exterior of the tube as well as the interior
of the tube has the advantage of helping to create a liquid flow
path along the outside surface of the tube when the NO.sub.x
reductant is frozen in the container, in use.
[0026] Advantageously, the first and second heating devices can be
controlled independently of each other, as desired.
[0027] The invention also encompasses apparatus for extracting
liquid NO.sub.x reductant from a container on a vehicle. Thus, is
another aspect the invention provides apparatus for extracting a
liquid NO.sub.x reductant from a container on a vehicle, the
apparatus comprising a tube having a first end for submersion in a
liquid NO.sub.x reductant and a heating device extending along at
least a portion of the length of the tube.
[0028] It will be appreciated that while features of the invention
may be described in relation to particular aspects, embodiments or
examples, these features may be applicable to any other aspect,
embodiment or example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Examples of apparatus for storing an NO.sub.x reductant in
accordance with the invention will now be described with reference
to the accompanying drawings, in which:
[0030] FIG. 1A is a perspective view of a first example of
apparatus for storing a urea solution on a vehicle and including
three PTC heater elements and a heated flexible pickup tube;
[0031] FIG. 1B is a perspective view from below of a cover for the
apparatus shown in FIG. 1A
[0032] FIG. 2 is a perspective view of a second example of
apparatus for storing a urea solution on a vehicle and including a
resistive heater element and a heated flexible pickup tube;
[0033] FIG. 3 is an enlarged view of a bottom of the apparatus
shown in FIG. 2;
[0034] FIG. 4 is a cross-sectional view of the heated flexible
pickup tube shown in FIGS. 1A, 1B, 2 and 3;
[0035] FIGS. 5A and 5B are cross sectional views of a first example
of a heated rigid pickup tube;
[0036] FIGS. 6A and 6B are cross sectional views of a second
example of a heated rigid pickup tube; and
[0037] FIGS. 7A and 7B are cross sectional views of a third example
of a heated rigid pickup tube.
BEST MODE FOR CARRYING OUT THE INVENTION
[0038] All references cited herein are incorporated by reference in
their entirety. Unless otherwise defined, all technical and
scientific terms used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs.
[0039] FIGS. 1A and 1B show a urea solution storage system for
light duty vehicles that is mounted in an appropriate location on
the vehicle. The storage system consists of a container (or tank)
1, a cover 2, a combined liquid level and temperature sensor 3, a
pickup tube 5 with a filter (not shown) at its lower end and a
heater 4. The heater 4 consists of three positive temperature
coefficient (PTC) heating elements 61 that are located near the
bottom 6 of the container 1. The PTC heating elements 61 are
encased in a urea resistant protective shell and are mechanically
mounted on a base plate 8 and electrically coupled by wires 62 to a
connector 7 on the other side of the cover 2. Generally, the base
plate 8 also supports lower end of the pickup tube 5. The base
plate 8 is mounted inside the container 1 near the base 6 of the
container 1. This helps to prevent movement of the heater elements
61 and the pickup tube 5 within the container 1 during movement of
the vehicle and also spaces the heater and the lower end of the
pickup tube 5 from the bottom 6 so that liquid urea solution can
easily enter the lower end of the pickup tube 5 and to permit a
pool of liquid urea solution to form under the pickup tube 5 and
the heater 4 during melting of frozen urea solution within the
container 1.
[0040] FIGS. 2 and 3 show a urea solution storage system similar to
that shown in FIGS. 1A and 1B, except that the PTC heating elements
61 of the heater 4 are replaced with a coiled resistive heating
element 65 mechanically mounted on the base plate 8 and which is
electrically coupled to a connector 66 on the cover 2 by means of a
heater shaft 67. In this example, the resistive heating element is
in the form of a resistive heating wire mounted inside a coiled
metal tube to form the coiled resistive heating element 65.
However, any suitable type of resistive heating element could be
used. Also, in the example shown in FIGS. 2 and 3, the heater shaft
67 is not heated. This helps to avoid the problem of the urea
solution being overheated by the heater shaft.
[0041] FIG. 3 shows a filter connector 60 that is connected to a
connector 16 on the lower end of the pick-up tube 5. The filter
connector 60 attaches to a filter (not shown) located below the
base plate 8.
[0042] FIG. 4 is a cross sectional view of the pickup tube 5 shown
in FIGS. 1 and 2. The pickup tube 5 comprises a flexible hose 10.
Typically, the flexible hose is a multilayered hose that includes
at least a thermoplastic elastomeric layer, a heating element, a
sealing layer and insulating layer. Typically, the sealing layer is
the inner most layer and the next inner layer is the thermoplastic
elastomeric layer and the heating element is preferably
incorporated into the thermoplastic elastomeric layer. The outer
layer is typically the insulating layer. As shown in FIG. 4, the
heating element 11 is a resistive wire heater that is helically
formed along the length of the flexible hose 10 and is an integral
part of the hose 10. However, other heating devices could be used,
such as a ribbon heater made of carbon fibre materials or an etched
resistive pattern ribbon heater. At end 12 of the pickup tube 5 is
an end connector 13 that connects the pickup tube 5 to a tubing
connector 14 in the cover 2. At the opposite end 15 of the pickup
tube 5 is another connector 16 which permits the pickup tube 5 to
be coupled to the filter 60. As shown in FIG. 1B, the electrical
connections for the heating element 11 are provided by wires 17
that extend from the sidewall of the pickup tube 5 through a sealed
opening 18 in the cover to terminate in a connector 19. However, an
alternative option would be to have the wires 17 extend from the
sidewall of the pickup tube 5 on the other side of the cover 2.
This would have the advantage of not requiring the opening 18 in
the cover 2.
[0043] FIGS. 5A to 7B show three further examples of the pickup
tube 5 in which the pickup tube 5 comprises a rigid stainless steel
tube 20 through which the urea solution is extended from the
container 1.
[0044] FIGS. 5A and 5B show a first example of a rigid pickup tube
35 using the rigid stainless steel tube 20. In this example a
flexible heater 21 is in intimate contact with the outside surface
of the stainless steel tube 20 and partially encircles the
stainless steel tube 20. An outer protective stainless steel tube
22 encloses the flexible heater 21 and the length of the stainless
steel tube 20 along which the flexible heater 21 extends. At both
the upper end 23 and the lower end 24 of the outer stainless steel
tube 22 is an elastomeric end plug 25, 26 respectively. The rubber
end plugs 25, 26 are compatible with the NO.sub.x reductant and
seal the ends of the annular gap between the outer stainless steel
tube 22 and the inner stainless steel tube 20 to prevent the
ingress of urea solution into the annular gap between the tubes 20,
22 and so isolate the flexible heater 21 from the urea
solution.
[0045] The upper plug 25 also provides a connection to permit the
plug 25 to be inserted into a boss 50 in the cover 2 and the lower
plug 26 provides for connection of the pickup tube 35 to a filter
(not shown).
[0046] As shown in FIG. 5B, the outer stainless steel tubing 22 can
also house a printed circuit board (PCB 27) in the annular gap. The
PCB 27 includes a temperature sensor and a liquid level sensor to
enable monitoring of the temperature of the urea solution in the
container 1 and the level of the urea solution in the container 1.
The wiring for the sensors and the heater 21 are also contained
within the annular gap between the inner and outer tubes 20, 22 but
are not shown in FIGS. 5A and 5B.
[0047] FIGS. 6A and 6B show a second example of a rigid pickup tube
45 incorporating an inner stainless steel tube 20. In this example,
a thick film heater 46 is printed onto the outside surface of the
stainless steel tube 20. As in the first example described above
and shown in FIGS. 5A and 5B, the inner stainless steel tube 20 and
printed heater 46 are enclosed in an outer protective stainless
steel tube 22 that has plugs 25, 26 at its upper 23 and lower ends
23, 24 to seal the annular gap between the inner tube 20 and the
outer tube 22 to prevent the ingress of urea solution into the
annular gap between the tubes 20, 22.
[0048] As in the first example of the pickup tube 35 described
above and shown in FIGS. 5A and 5B, the annular gap between the
inner tube 20 and the outer tube 22 in the second example shown in
FIGS. 6A and 6B can also accommodate a PCB 27. The PCB 27 can
include a temperature sensor and a liquid level sensor to permit
the temperature of the urea solution in the container 1 to be
monitored and the level of the urea solution in the container 1 to
be monitored.
[0049] FIGS. 7A and 7B show a third example of a rigid pickup tube
55 incorporating an inner stainless steel tube 20. In this example,
the heating element is provided by an electrically insulated
resistive wire wound heater 40 that is wound helically around the
inner tube 20 along the length of the inner tube 20, as shown in
FIG. 7A. As with the first and second examples shown in FIGS. 5A to
6B, an outer protective stainless steel tube 22 is located around
the resistive wire heater element 40 and the inner tube 20 and
plugs 25, 26 are provided at the upper and lower ends 23, 24 of the
outer tube 22, respectively. As in the first and second examples of
the pickup tubes 35, 45, the pickup tube 55 is mounted on a boss 50
of the cover 2 by means of the upper plug 25 and the lower plug 26
provides a connection to a filter (not shown). The plugs 25, 26
also seal the annular gap between the outer tube 22 and the inner
tube 20 to prevent the ingress of urea solution into the annular
gap between the tubes 20, 22.
[0050] Furthermore, a PCB 27 with a temperature sensor and liquid
level sensor may also be mounted in the outer protective tube 22,
in a similar manner to that described above for the pickup tubes
35, 45.
[0051] In use, the apparatus is mounted on a diesel fuel powered
vehicle and contains a urea solution for injection into the exhaust
of the vehicle upstream of a catalyst so that the urea solution
mixes with the exhaust gases and on contact with the catalyst
reduces any NO.sub.x in the gases to nitrogen and water.
[0052] If the vehicle is in a cold climate and the urea solution
has frozen in the container 1, the temperature sensor 3 detects
that the urea solution may be frozen and switches on the heater 4
to start to melt the urea solution in the container 1.
[0053] A certain amount of urea solution around the pickup tube 5
also needs to melted to so that it creates a fluid path from the
top of the container 1 to below the base plate 8 where the urea
pickup occurs through the filter 60 attached to the lower end of
the pickup tube 5. This path creates a fluid communication channel
to prevent vacuum locking beneath the frozen urea solution as
melted urea solution is extracted from the container 1. Therefore,
the heating device 11, 21, 46, 40 in the pickup tube 5 is also used
to melt frozen urea solution surrounding the tube 5 to create this
communication path around the outside of the pickup tube 5, as well
as heating the interior of the tube 5 to reduce the risk of melted
urea solution within the pickup tube 5 refreezing in the pickup
tube 5.
[0054] An advantage of the invention is that it enables independent
heating control of the pickup tubes 5, 35, 45, 55 and the urea
liquid within the container 1 which is heated by the separately
controlled heater 4. This enables optimum heating of both the
pickup tube 5 and the mass of urea solution within the container
1.
[0055] In addition, the use of a heated pickup tube 5, 35, 45, 55
mitigates the risk of the urea solution freezing at the cover
interconnection 14.
[0056] Another advantage of the invention is its ease of
manufacture and assembly. For example, it does not require a
separate thawing container (including one or more heating elements)
within the NO.sub.x reductant container/tank in order to operate
efficiently and rapidly.
[0057] Although particular embodiments of the invention have been
disclosed herein in detail, this has been done by way of example
and for the purposes of illustration only. The aforementioned
embodiments are not intended to be limiting with respect to the
scope of the appended claims, which follow. It is proposed by the
inventors that various substitutions, alterations, and
modifications may be made to the invention without departing from
the spirit and scope of the invention as defined by the claims.
* * * * *