U.S. patent application number 12/696347 was filed with the patent office on 2011-08-04 for method of producing an insulated exhaust gas device.
Invention is credited to Steven Freis, Ruth Latham, Benedikt Mercker, Keith Olivier.
Application Number | 20110185575 12/696347 |
Document ID | / |
Family ID | 44319653 |
Filed Date | 2011-08-04 |
United States Patent
Application |
20110185575 |
Kind Code |
A1 |
Olivier; Keith ; et
al. |
August 4, 2011 |
Method of Producing an Insulated Exhaust Gas Device
Abstract
A method is provided for producing an exhaust gas aftertreatment
or acoustic device (18) having a maximum operating temperature
Tmax. The method includes the steps of providing a blanket (28) of
silica fiber insulation material having a weight percentage of
SiO.sub.2 of greater than 65%; heating the blanket (28) so that all
of silica fiber insulation material is raised to a temperature T
greater than Tmax; and installing the blanket (28) in the device
(18) after the heating step.
Inventors: |
Olivier; Keith; (Jackson,
MI) ; Freis; Steven; (Ann Arbor, MI) ;
Mercker; Benedikt; (Edenkoben, DE) ; Latham;
Ruth; (Ann Arbor, MI) |
Family ID: |
44319653 |
Appl. No.: |
12/696347 |
Filed: |
January 29, 2010 |
Current U.S.
Class: |
29/890.08 |
Current CPC
Class: |
Y10T 29/49345 20150115;
F01N 2310/02 20130101; F01N 3/2835 20130101; F01N 1/24 20130101;
F01N 13/148 20130101; Y10T 29/49398 20150115; F01N 13/14
20130101 |
Class at
Publication: |
29/890.08 |
International
Class: |
B21D 51/16 20060101
B21D051/16 |
Claims
1. A method of producing an exhaust gas aftertreatment or acoustic
device having a maximum operating temperature Tmax, the method
comprising the steps of: providing a blanket of silica fiber
insulation material having a weight percentage of SiO.sub.2 of
greater than 65%; heating the blanket so that all of silica fiber
insulation material is raised to a temperature T greater than Tmax;
and installing the blanket in the device after the heating
step.
2. The method of claim 1 wherein T is at least 1.05.times.Tmax.
3. The method of claim 1 wherein the installing step comprises
installing the blanket so that the blanket is compressed between
two adjacent surfaces of the device to achieve an average installed
density of 0.18 grams/cubic centimeter to 0.30 grams/cubic
centimeter of the insulation material in the blanket.
4. The method of claim 1 wherein during the heating step the
blanket is an uncompressed state.
5. The method of claim 1 wherein during the heating step the
blanket is heated in a rolled state wherein the blanket has been
formed into a roll having a central axis.
6. The method of claim 5 wherein during the heating step the
blanket is rotated about the central axis.
7. The method of claim 1 wherein during the heating step the
blanket is planar.
8. The method of claim 1 wherein Tmax is within the range of
300.degree. C. to 1100.degree. C.
9. The method of claim 1 wherein the installing step comprises
installing the blanket so that the blanket encircles a core of the
device through which the exhaust gas passes.
10. The method of claim 1 wherein the silica fiber insulation
material has a weight percentage of SiO.sub.2 of greater than
95%.
11. A method of producing an exhaust gas aftertreatment or acoustic
device having a maximum operating temperature Tmax, the method
comprising the steps of: providing a blanket of silica fiber
insulation material having a weight percentage of SiO.sub.2 of
greater than 65%; heating the blanket so that all of silica fiber
insulation material is raised to a temperature T greater than Tmax;
and installing the blanket in the device after the heating step so
that the blanket encircles a core of the device through which the
exhaust gas passes and the blanket is compressed between two
adjacent surfaces of the device to achieve an average installed
density of 0.18 grams/cubic centimeter to 0.30 grams/cubic
centimeter of the insulation material in the blanket.
12. The method of claim 11 wherein T is at least
1.05.times.Tmax.
13. The method of claim 11 wherein during the heating step the
blanket is an uncompressed state.
14. The method of claim 11 wherein during the heating step the
blanket is heated in a rolled state wherein the blanket has been
formed into a roll having a central axis.
15. The method of claim 14 wherein during the heating step the
blanket is rotated about the central axis.
16. The method of claim 11 wherein during the heating step the
blanket is planar.
17. The method of claim 11 wherein Tmax is within the range of
300.degree. C. to 1100.degree. C.
18. The method of claim 11 wherein the silica fiber insulation
material has a weight percentage of SiO.sub.2 of greater than
95%.
19. The method of claim 11 wherein the two adjacent surfaces are
cylindrical surfaces.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
MICROFICHE/COPYRIGHT REFERENCE
[0003] Not Applicable.
FIELD OF THE INVENTION
[0004] This invention relates to exhaust gas aftertreatment and/or
acoustic systems and the devices used therein that utilize
insulation blankets or batts.
BACKGROUND OF THE INVENTION
[0005] Heat insulating batts and blankets are utilized in exhaust
gas systems in order to provide heat insulation for acoustic and
aftertreatment devices of the system to control the heat exchange
to and from the devices. It is known to place such heat insulating
blankets between adjacent wall surfaces of such device with the
material of the heat insulation blanket being compressed to provide
a desired installed density for the material to help maintain the
heat insulating blanket in its mounted position via frictional
forces between the blanket and the adjacent wall surfaces. Cost is
typically a concern in any commercial system and one cost efficient
heat insulation blanket material is made from silica fiber
insulation material having a weight percentage of SiO.sub.2 of
greater than 65%. Unfortunately, when such a material was utilized
in an exhaust gas aftertreatment device, the material failed after
a period of time because the heat insulation blanket could not
maintain adequate frictional engagement with the adjacent sidewalls
in order to prevent destructive movement of the insulation blanket
within the component.
SUMMARY OF THE INVENTION
[0006] In accordance with one feature of the invention, a method is
provided for producing an exhaust gas aftertreatment or acoustic
device having a maximum operating temperature Tmax. The method
includes the steps of: providing a blanket of silica fiber
insulation material having a weight percentage of SiO.sub.2 of
greater than 65%; heating the blanket so that all of silica fiber
insulation material is raised to a temperature T greater than Tmax;
and installing the blanket in the device after the heating
step.
[0007] As one feature, T is at least 1.05.times.Tmax.
[0008] According to one feature, the installing step includes
installing the blanket so that the blanket is compressed between
two adjacent surfaces of the device to achieve an average installed
density of 0.18 grams/cubic centimeter to 0.30 grams/cubic
centimeter of the insulation material in the blanket.
[0009] In one feature, during the heating step the blanket is an
uncompressed state.
[0010] As one feature, during the heating step the blanket is
heated in a rolled state wherein the blanket has been formed into a
roll having a central axis. In a further feature, during the
heating step the blanket is rotated about the central axis.
[0011] According to one feature, during the heating step the
blanket is planar.
[0012] In one feature, Tmax is within the range of 300.degree. C.
to 1100.degree. C.
[0013] As one feature, the installing step includes installing the
blanket so that the blanket encircles a core of the device through
which the exhaust gas passes.
[0014] In one feature, the silica fiber insulation material has a
weight percentage of SiO.sub.2 of greater than 95%.
[0015] In accordance with one feature of the invention, a method is
provided for producing an exhaust gas aftertreatment or acoustic
device having a maximum operating temperature Tmax. The method
includes the steps of: providing a blanket of silica fiber
insulation material having a weight percentage of SiO.sub.2 of
greater than 65%; heating the blanket so that all of silica fiber
insulation material is raised to a temperature T greater than Tmax;
and installing the blanket in the device after the heating step so
that the blanket encircles a core of the device through which the
exhaust gas passes and the blanket is compressed between two
adjacent surfaces of the device to achieve an average installed
density of 0.18 grams/cubic centimeter to 0.30 grams/cubic
centimeter of the insulation material in the blanket.
[0016] Other objects, features, and advantages of the invention
will become apparent from a review of the entire specification,
including the appended claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a diagrammatic representation of an exhaust gas
system employing the invention;
[0018] FIG. 2 is a section view of an exhaust system component
employing the invention of FIG. 1 taken from line 2-2 in FIG.
1;
[0019] FIG. 3 is a side elevational diagrammatic representation of
a heat treatment process employed in the invention;
[0020] FIG. 4 is a perspective view diagrammatic representation of
an alternative heat treatment process employed in the invention;
and
[0021] FIG. 5 is a top plan view of yet another diagrammatic
representation showing another alternate embodiment of a heat
treatment process employed in the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] An exhaust gas system 10 is shown in FIG. 1 in the form of a
diesel exhaust gas aftertreatment system to treat the exhaust 12
from a diesel combustion process 14, such as a diesel compression
engine 16. The exhaust 12 will typically contain oxides of nitrogen
(NO.sub.x) such as nitric oxide (NO) and nitrogen dioxide
(NO.sub.2) among others, particulate matter (PM), hydrocarbons,
carbon monoxide (CO), and other combustion by-products. The system
10 includes one or more exhaust gas acoustic and/or aftertreatment
devices or components 18, with each device having a corresponding
maximum operating temperature Tmax that can be achieved during
operation of the system 10. Examples of such devices 18 include
catalytic converters, diesel oxidation catalysts, diesel
particulate filters, gas particulate filters, lean NO.sub.x traps,
selective catalytic reduction monoliths, burners, manifolds,
connecting pipes, mufflers, resonators, tail pipes, emission
control system enclosure boxes, insulation rings, insulated end
cones, insulated end caps, insulated inlet pipes, and insulated
outlet pipes, all of any cross-sectional geometry, many of which
are known. As those skilled in the art will appreciate, some of the
foregoing devices 18 are strictly metallic components with a
central core 19 through which the exhaust 12 flows, and other of
the devices 18 can include a core 19 in the form of a ceramic
monolithic structure and/or a woven metal structure through which
the exhaust 12 flows. These devices 18 are conventionally used in
motor vehicles (diesel or gasoline), construction equipment,
locomotive engine applications (diesel or gasoline), marine engine
applications (diesel or gasoline), small internal combustion
engines (diesel or gasoline), and stationary power generation
(diesel or gasoline).
[0023] FIG. 2 shows one example of such a device 18 for use in the
system 10 in the form of a catalytic unit 20 having a catalytic
core 22, a mount mat 24, a cylindrical inner housing or can 26, and
heat insulating blanket or batt 28, and a cylindrical outer housing
or jacket 30. The core 22 will typically be a ceramic substrate 32
having a monolithic structure with a catalyst coated thereon and
will typically have an oval or circular cross section. The mounting
mat 24 is sandwiched between the core 22 and the can 26 to help
protect the core 22 from shock and vibrational forces that can be
transmitted from the can 26 to the core 22. Typically the mounting
mat 24 is made of a heat resistant and shock absorbing-type
material, such as a mat of glass fibers or rock wool and is
compressed between the can and the carrier in order to generate a
desired holding force.
[0024] The heat insulating blanket 28 is made of a silica fiber
insulation material having a weight percentage of SiO.sub.2 of
greater than 65%, and in preferred embodiments greater than 95%,
and in highly preferred embodiments greater than 98%. Such material
is known and commercially available, with one suitable example
being supplied by BGF Industries, Inc. under the trade name
SilcoSoft.RTM., and another suitable example being supplied by
ASGLAWO technofibre GmbH under the trade name Asglasil.RTM.. Such
material is typically supplied in rolls, with the individual
blankets 28 being die cut to the appropriate length and width for
the corresponding device 18 after the material has been taken from
the roll. Preferably, the blanket 28 is sandwiched or compressed in
the annular gap 34 between the outer surface 36 of the can 26 and
the inner surface 38 of the housing 30 to achieve an average
installed density of 0.18 grams/cubic centimeter to 0.30
grams/cubic centimeter of the silica fiber insulation material of
the blanket 28. This provides sufficient frictional engagement
between the blanket 28 and the surfaces 36 and 38 to suitably
maintain the blanket in its desired location. It should be
appreciated that while the blanket 28 is shown being compressed in
the annular gap 34 between the cylindrical can 26 and housing 30,
the blanket 28 could be compressed between other adjacent surfaces
of a device, including for example, a pair of planar adjacent
surfaces, a pair of non-planar adjacent surfaces, a pair of conical
adjacent surfaces, or any other pair of adjacent surfaces that can
be found in acoustic or aftertreatment devices for exhaust
systems.
[0025] According to the invention, before the blanket 28 is
installed into the device 18, the blanket 28 is heat treated to
achieve calcination of the silica fiber insulation material. In
this regard, the blanket 28 is heated so that all of the silica
fiber insulation material in the blanket 28 is raised to a
temperature T greater than the maximum operating temperature Tmax
of the device 18. This heat treatment improves the resiliency and
erosion resistance of the silica fiber insulation material and also
eliminates the potential for a "thermoset" failure mode that can
result if the silica fiber material were calcinated in-situ in the
device 18 during operation of the system 10. Preferably, this heat
treatment takes place with the blanket 28 in an uncompressed or
free state wherein there are no compressive forces being applied to
the silica fiber insulation material of the blanket 28. The
temperature T preferably has some margin of safety above the
maximum operating temperature Tmax of the device 18, with one
preferred margin of safety being 1.05.times.Tmax.
[0026] As shown in FIG. 3, it is also preferred that the heat
treatment take place using an in-line oven 40 wherein the silica
fiber heat insulation material is unrolled from a supply roll 42 of
the material and passed flat through the oven 40 on conveyor 43 so
that the blanket 28 is planar during the heat treatment to reduce
or prevent differential heating of the material of the blanket 28
and variation in thickness of the material in the blanket 28. After
heat treatment, the individual blankets 28 can be die cut to the
desired length and width before installing in the device 18. As an
alternative, the complete supply roll 42 of the silica fiber heat
insulation material can be heat treated, with or without rotation
of the roll 42 about its center axis 44 in an oven 46, as shown in
FIG. 4. In this regard, it is believed that rotating the roll 42
about its axis 44 will serve to prevent a differential heating in
the roll. Again, the individual blankets 28 can be die cut to the
desired length and width after heat treatment and before installing
in the device 18. As yet an another alternative, the silica fiber
insulation material can be die cut before heat treatment, with the
blanket 28 being slightly oversized in length and width to account
for shrinkage during heat treatment. The die cut blankets 28 can
then be heat treated in an oven 40 or 44 while laying flat on a
planar surface, as shown in FIG. 5.
[0027] It has been found that by heat treating the silica fiber
heat insulation material to the temperature T greater than Tmax
before the blanket 28 is installed in the device 18, the heat
treated blanket 28 can be installed in a device 18 so that the
blanket 28 is compressed between two adjacent surfaces of the
device 18 and can maintain suitable frictional engagement with the
surfaces over the desired life of the device 18 because the silica
fiber insulation material of the blanket 28 maintains its
resiliency and does not take on a "thermoset" from the max
operation temperature Tmax of the device 18.
[0028] It should be appreciated that while the invention has been
described herein in connection with a diesel combustion process in
the form of a diesel compression engine 16, the invention may find
use in devices that are utilized in exhaust gas systems for other
types of combustion processes, including other types of internal
combustion engines, including, for example, internal combustion
engines that use gasoline or other alternative fuels.
* * * * *