U.S. patent application number 13/528698 was filed with the patent office on 2012-12-06 for nanoporous articles and methods of making same.
This patent application is currently assigned to ADVANCED TECHNOLOGY MATERIALS, INC.. Invention is credited to Brian Bobita, J. Donald Carruthers, Frank Dimeo, JR..
Application Number | 20120305450 13/528698 |
Document ID | / |
Family ID | 38328129 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120305450 |
Kind Code |
A1 |
Carruthers; J. Donald ; et
al. |
December 6, 2012 |
NANOPOROUS ARTICLES AND METHODS OF MAKING SAME
Abstract
A method is provided for producing an ultra-low sulfur
hydrocarbon product from a hydrocarbon feedstock containing
refractory sulfur compounds utilizing a carbon adsorbent. Also
described is a hydrocarbon processing system configured to produce
an ultra-low sulfur hydrocarbon product from hydrocarbon feedstock
containing refractory sulfur compounds. The hydrocarbon processing
system also utilizes a carbon adsorbent.
Inventors: |
Carruthers; J. Donald;
(Fairfield, CT) ; Dimeo, JR.; Frank; (Falls
Church, VA) ; Bobita; Brian; (Northampton,
CT) |
Assignee: |
ADVANCED TECHNOLOGY MATERIALS,
INC.
Danbury
CT
|
Family ID: |
38328129 |
Appl. No.: |
13/528698 |
Filed: |
June 20, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12984216 |
Jan 4, 2011 |
8221532 |
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13528698 |
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12182880 |
Jul 30, 2008 |
7862646 |
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12984216 |
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PCT/US07/61255 |
Jan 29, 2007 |
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12182880 |
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PCT/US07/61256 |
Jan 29, 2007 |
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PCT/US07/61255 |
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60763258 |
Jan 30, 2006 |
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60763258 |
Jan 30, 2006 |
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Current U.S.
Class: |
208/213 ;
196/46 |
Current CPC
Class: |
C10G 2300/202 20130101;
Y10T 428/249957 20150401; F17C 11/007 20130101; C10G 45/02
20130101; F17C 11/00 20130101; B01D 53/0446 20130101; B01J 20/2808
20130101; Y02E 60/321 20130101; C10G 25/003 20130101; Y10T
428/249956 20150401; B01D 2253/202 20130101; B01D 2258/0216
20130101; B01D 2259/455 20130101; B01D 2253/342 20130101; B01J
2220/66 20130101; C10G 2300/1033 20130101; B01J 20/28052 20130101;
B01J 20/28097 20130101; Y02E 60/32 20130101; B01D 2259/4146
20130101; C01B 13/0251 20130101; Y02E 60/325 20130101; Y10S 95/903
20130101; B01D 2259/40096 20130101; C10G 67/06 20130101; B01J
20/28023 20130101; B01D 2253/102 20130101; C01B 3/0021 20130101;
B01D 2253/311 20130101; B01D 2253/308 20130101; B01J 20/28014
20130101; B82Y 30/00 20130101; B01D 2259/4525 20130101; B01D
53/0415 20130101; B01J 20/20 20130101; B01D 2257/30 20130101; B01J
20/28042 20130101; B01J 20/28033 20130101; C10G 2300/1051 20130101;
B01J 20/28011 20130101; C10G 2300/1055 20130101; B01D 2256/24
20130101; C10G 2300/1044 20130101; C10G 2300/207 20130101; B01D
2253/1122 20130101 |
Class at
Publication: |
208/213 ;
196/46 |
International
Class: |
C10G 45/00 20060101
C10G045/00; C10G 53/04 20060101 C10G053/04 |
Claims
1. A method of producing an ultra-low sulfur hydrocarbon product
from a hydrocarbon feedstock containing refractory sulfur
compounds, comprising: contacting the hydrocarbon feedstock with a
carbon adsorbent effective for sorptive removal of said refractory
sulfur compounds, to yield desulfurized hydrocarbon; desorbing from
said carbon adsorbent a desorbate comprising said refractory sulfur
compounds; evaporation processing of said desorbate to recover a
high sulfur bottoms material therefrom; hydrodesulfurizing the high
sulfur bottoms material to yield hydrodesulfurized hydrocarbon; and
blending the desulfurized hydrocarbon and hydrodesulfurized
hydrocarbon to yield said ultra-low sulfur hydrocarbon product.
2. The method of claim 1, wherein said hydrocarbon feedstock
comprises feedstock selected from the group consisting of gasoline,
jet fuel, diesel fuel, crude oil, and petroleum.
3. The method of claim 1, wherein said hydrocarbon feedstock
comprises feedstock selected from the group consisting of gasoline,
jet fuel, and diesel fuel.
4. The method of claim 1, wherein the refractory sulfur compounds
comprise at least one of dibenzothiophene,
4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene.
5. The method of claim 1, further comprising recovering a
sulfur-depleted overhead from said evaporation processing, and
recycling the sulfur-depleted overhead to said contacting.
6. The method of claim 1, wherein the carbon adsorbent comprises
nanoporous carbon.
7. The method of claim 1, wherein the carbon adsorbent comprises a
PVDC-derived carbon.
8. The method of claim 7, wherein said PVDC-derived carbon has at
least 30% of overall porosity constituted by slit-shaped pores
having a size in a range of from 0.3 to 0.72 nm, and at least 20%
of the overall porosity comprising pores of diameter <2 nm, with
a bulk density of from 0.80 to 2.0 g per cubic centimeter.
9. The method of claim 1, wherein said carbon adsorbent is provided
in a bed of said adsorbent for said contacting.
10. The method of claim 9, wherein the bed of carbon adsorbent
comprises carbon adsorbent particles.
11. The method of claim 9, wherein the bed of carbon adsorbent
comprises monolithic carbon.
12. The method of claim 1, wherein said contacting is conducted by
flow of the hydrocarbon feedstock through one of multiple
adsorbers, wherein each of the adsorbers includes a vessel having a
bed of the carbon adsorbent therein, and wherein the adsorbers are
operated with one of the multiple adsorbers engaged in said
contacting, while another is offstream during an offstream duration
in which it is subjected to purging with a purge medium to carry
out said desorbing.
13. The method of claim 1, wherein the hydrocarbon feedstock
contains at least one of the sulfur compounds dibenzothiophene,
4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene, and the
ultra-low sulfur hydrocarbon product contains less than 1 ppm of
each such compound that is present in the hydrocarbon
feedstock.
14. A hydrocarbon processing system configured to produce an
ultra-low sulfur hydrocarbon product from a hydrocarbon feedstock
containing refractory sulfur compounds, said system comprising: at
least one adsorber, wherein each said adsorber comprises a vessel
containing carbon adsorbent, and the vessel is arranged for (i)
flow of hydrocarbon feedstock to contact the carbon adsorbent to
sorptively remove the refractory sulfur compounds, to yield
desulfurized hydrocarbon, and (ii) subsequent desorption from said
carbon adsorbent of desorbate comprising said refractory sulfur
compounds; an evaporator arranged in fluid flow communication with
the at least one adsorber, for flow of the desorbate from the
adsorber to the evaporator, wherein the evaporator is configured to
process the sorbate to produce a high sulfur bottoms material and a
sulfur-depleted overhead; a hydrodesulfurization reactor arranged
in fluid flow communication with the evaporator, for flow of the
high sulfur bottoms material to the hydrodesulfurization reactor,
wherein the hydrodesulfurization reactor is configured to
hydrodesulfurize the high sulfur bottoms material to yield
hydrodesulfurized hydrocarbon; and a blender arranged in fluid flow
communication with (i) the at least one adsorber, to receive
therefrom the desulfurized hydrocarbon, and (ii) the
hydrodesulfurization reactor, to receive therefrom the
hydrodesulfurized hydrocarbon, wherein the blender is configured to
blend the desulfurized hydrocarbon and hydrodesulfurized
hydrocarbon to yield the ultra-low sulfur hydrocarbon product.
15. The hydrocarbon processing system of claim 14, further
comprising a source of said hydrocarbon feedstock, arranged in feed
relationship to the at least one adsorber.
16. The hydrocarbon processing system of claim 15, wherein said
source comprises feedstock selected from the group consisting of
gasoline, jet fuel, diesel fuel, crude oil, and petroleum.
17. The hydrocarbon processing system of claim 15, wherein said
source comprises feedstock selected from the group consisting of
gasoline, jet fuel, and diesel fuel.
18. The hydrocarbon processing system of claim 15, wherein the
hydrocarbon feedstock comprises refractory sulfur compounds
including at least one of dibenzothiophene,
4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene.
19. The hydrocarbon processing system of claim 14, further
comprising a recycle line arranged to flow the sulfur-depleted
overhead from the evaporator to the at least one adsorber.
20. The hydrocarbon processing system of claim 14, wherein the
carbon adsorbent comprises nanoporous carbon.
21. The hydrocarbon processing system of claim 14, wherein the
carbon adsorbent comprises a PVDC-derived carbon.
22. The hydrocarbon processing system of claim 21, wherein said
PVDC-derived carbon has at least 30% of overall porosity
constituted by slit-shaped pores having a size in a range of from
0.3 to 0.72 nm, and at least 20% of the overall porosity comprising
pores of diameter <2 nm, with a bulk density of from 0.80 to 2.0
g per cubic centimeter.
23. The hydrocarbon processing system of claim 14, wherein said
carbon adsorbent is provided in a bed of said adsorbent in said
vessel.
24. The hydrocarbon processing system of claim 23, wherein the bed
of carbon adsorbent comprises carbon adsorbent particles.
25. The hydrocarbon processing system of claim 23, wherein the bed
of carbon adsorbent comprises monolithic carbon.
26. The hydrocarbon processing system of claim 14, wherein said at
least one adsorber comprises multiple adsorbers, configured for
flow of the hydrocarbon feedstock through one of multiple adsorbers
for contacting the carbon adsorbent thereof, wherein the adsorbers
are operated with one of the multiple adsorbers engaged in
contacting the hydrocarbon feedstock, while another is offstream
during an offstream duration in which it is subjected to purging
with a purge medium to carry out said desorbing.
27. The hydrocarbon processing system of claim 14, configured so
that when the hydrocarbon feedstock contains at least one of the
sulfur compounds dibenzothiophene, 4-methyldibenzothiophene, and
4,6-dimethyldibenzothiophene, the ultra-low sulfur hydrocarbon
product contains less than 1 ppm of each such compound that is
present in the hydrocarbon feedstock.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/984,216 filed Jan. 4, 2011, which is a
continuation of U.S. patent application Ser. No. 12/182,880 filed
Jul. 30, 2008, issued Jan. 4, 2011 as U.S. Pat. No. 7,862,646,
which is a continuation-in-part under 35 USC .sctn.120 of
International Patent Application No. PCT/US07/61255 filed Jan. 29,
2007 and International Patent Application No. PCT/US07/61256 filed
Jan. 29, 2007, each in turn claiming the benefit of priority under
35 USC .sctn.119 of U.S. Provisional Patent Application No.
60/763,258 filed Jan. 30, 2006, the benefit of priority of which is
also hereby claimed. The disclosures of all such applications
and/or patents are hereby incorporated herein by reference, in
their respective entireties, for all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to nanoporous articles, e.g.,
carbonaceous materials having utility for fluid storage/dispensing
and desulfurization and other applications, and to apparatus and
methods utilizing same. The present invention also relates to
nanoporous carbon materials having utility for fluid
storage/dispensing applications, and to systems and methods
utilizing same, as well as impregnated nanoporous carbon materials
useful in tribological applications and as ultra-tough structural
materials.
DESCRIPTION OF THE RELATED ART
[0003] Carbonaceous materials are used as fluid adsorbent media in
many applications, including fluid purification, fluid storage and
dispensing, and fluid filtration.
[0004] One specific application of commercial significance is fluid
storage and dispensing systems, wherein a carbonaceous adsorbent
material is deployed to sorptively retain a fluid in an adsorbed
state, and to release such fluid for dispensing under appropriate
dispensing conditions, such as application of heat to effect
thermal desorption of the fluid, application of reduced pressure
conditions to effect desorption of the fluid, and/or application of
a concentration gradient such as by flowing a carrier gas in
contact with the adsorbent having the fluid adsorbed thereon to
cause the desorption of the fluid and entrainment thereof in the
carrier fluid.
[0005] A fluid storage and dispensing system is disclosed in U.S.
Pat. No. 6,743,278 issued Jun. 1, 2004 in the name of J. Donald
Carruthers for "Gas storage and dispensing system with monolithic
carbon adsorbent," the disclosure of which is hereby incorporated
herein by reference in its entirety, for all purposes. This patent
describes a monolithic carbon physical adsorbent that is
characterized by at least one of the following characteristics: (a)
a fill density measured for arsine gas at 25.degree. C. and
pressure of 650 ton that is greater than 400 grams arsine per liter
of adsorbent; (b) at least 30% of overall porosity of the adsorbent
including slit-shaped pores having a size in a range of from about
0.3 to about 0.72 nanometer, and at least 20% of the overall
porosity including micropores of diameter <2 nanometers; and (c)
having been formed by pyrolysis and optional activation, at
temperature(s) below 1000.degree. C., and having a bulk density of
from about 0.80 to about 2.0 grams per cubic centimeter.
[0006] In one embodiment, the monolithic carbon adsorbent is
utilized in a puck or disc form, with a multiplicity of such
articles being arranged in a stack in a containment vessel that is
enclosed by valve head or other closure assembly. The stack of
disc- or puck-form blocks of the carbon adsorbent material is
efficient as a sorptive matrix for a variety of fluids, e.g.,
fluids used for semiconductor device manufacturing, but suffers the
disadvantage that individual blocks in the stack can shift
positionally, and impact or rub against the interior wall surfaces
of the containment vessel and/or against one another, in response
to movement of the vessel or shocks or impacts thereon, e.g.,
during transport of the vessel from a manufacturing facility to a
fluid filling or end use facility.
[0007] In addition to causing unwanted noise, such impact and/or
rubbing of the monolithic blocks can damage the blocks as well as
cause them to generate carbon dust or fines. Such dust or fines are
carried in the dispensed fluid stream, and adversely affect
downstream pumps, compressors, valves and fluid-utilizing process
equipment.
[0008] Another problem associated with the use of low-pressure
adsorbent-based fluid storage and dispensing vessels that dispense
fluid to vacuum or low pressure environments is that it becomes
disproportionately more difficult to desorb and dispense the fluid
as the inventory of fluid in the vessel drops to residual levels.
The pressure drop from the vessel to a downstream tool or flow
circuitry may in fact become too low to support dispensing, with
the result that a substantial amount of fluid remains as so-called
"heels" on the adsorbent in the vessel when dispensing can no
longer take place. This heels portion then is lost as
"non-removable" fluid.
[0009] Thus, the fluid storage and dispensing vessel may be taken
out of service with a significant quantity of fluid still in the
vessel. This circumstance results in reduced gas utilization
efficiency. To improve fluid utilization, the vessel can be
externally heated to drive off more fluid from the adsorbent. This
approach, however, is not practical in many fluid dispensing
applications, since the associated process facility is not
adaptable to such external heating.
[0010] An improved approach therefore is desired to maximize fluid
utilization in the use of low-pressure adsorbent-based fluid
storage and dispensing vessels, for dispensing fluid to low
pressure applications.
[0011] In addition to the issues described above related to fluid
storage and dispensing systems, carbon is conventionally used as a
component in high-strength composites, as a reinforcing medium. In
addition, carbon is used in composite materials applications as a
continuous medium in vitreous carbon composites, which are useful
in a variety of tribological applications, but suffer the inherent
disadvantage of being highly brittle and therefore subject to
cracking and loss of physical integrity.
SUMMARY OF THE INVENTION
[0012] The present invention relates to nanoporous materials, and
to apparatus and methods utilizing same.
[0013] In one aspect, the invention relates to an adsorbent having
porosity expanded by contact with a first agent effecting such
expansion and a pressurized second agent effecting transport of the
first agent into said porosity, wherein the adsorbent subsequent to
removal of said first and second agents retains expanded
porosity.
[0014] Another aspect of the invention relates to a method of
increasing loading capacity of an adsorbent for a fluid, said
method comprising (i) contacting the adsorbent with a first agent
effecting expansion of porosity of said adsorbent, (ii) contacting
the adsorbent contacted with the first agent, with a second agent
under superatmospheric pressure conditions effecting transport of
the first and second agents into said porosity, and (iii) removing
said first and second agents from said adsorbent.
[0015] Still another aspect of the invention relates to a
nanoporous carbon composite including nanoporous carbon having
porosity that is at least partially filled with material imparting
to the composite an enhanced character with respect to
characteristics selected from the group consisting of hardness,
wear-resistance and toughness, as compared with the nanoporous
carbon alone.
[0016] Additional aspects, features and embodiments of the
invention will be more fully apparent from the ensuing disclosure
and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic exploded elevation view, in partial
cross-section, of a fluid storage and dispensing apparatus
according to one embodiment of the invention.
[0018] FIG. 2 is a schematic elevation view, in partial
cross-section, of the fluid storage and dispensing apparatus of
FIG. 1, as assembled.
[0019] FIG. 3 is a schematic elevation view, in partial
cross-section, of a fluid storage and dispensing apparatus
according to another embodiment of the invention.
[0020] FIG. 4 is a schematic elevation view, in partial
cross-section, of a fluid storage and dispensing apparatus
according to yet another embodiment of the invention.
[0021] FIG. 5 is a schematic representation of an adsorbent-based
process system for deep desulfurization of sulfur-containing
hydrocarbon feedstocks.
[0022] FIG. 6 is a cross-sectional elevational view of a fluid
storage and dispensing apparatus incorporating a adsorbent article
fixturing assembly, according to one embodiment of the present
invention.
[0023] FIG. 7 is a schematic representation of an infrared emitter
device according to another embodiment of the present
invention.
[0024] FIG. 8 is a schematic representation of a fluid storage and
dispensing system, according to yet another embodiment of the
invention.
[0025] FIG. 9 is a schematic representation of a fluid storage and
dispensing system, according to a further embodiment of the
invention.
[0026] FIG. 10 is a schematic representation of a Wheatstone Bridge
circuit in which one of the resistive elements is constituted by a
carbon adsorbent bed.
[0027] FIG. 11 is a schematic representation of a fluid storage and
dispensing system according to another embodiment of the
invention.
[0028] FIG. 12 is a schematic cross-section elevation view of a
fluid storage and dispensing system, according to a further
embodiment of the invention.
[0029] FIG. 13 is a schematic cross-sectional elevation view of a
fluid storage and dispensing system, in accordance with another
embodiment of the invention.
[0030] FIG. 14 is a perspective view of an impregnated carbon
structural member according to one embodiment of the invention.
[0031] FIG. 15 is a schematic elevation view of a fluid storage and
dispensing apparatus according to one embodiment of the invention,
as arranged for supplying fluid to a fluid-utilizing facility.
DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS
THEREOF
[0032] The present invention in various aspects thereof relates to
carbonaceous materials having utility for fluid storage/dispensing
and desulfurization applications, and to apparatus and methods
utilizing same.
[0033] In one aspect, the invention relates to provision of porous
carbon as an adsorbent medium in a fluid storage and dispensing
container, in monolithic form. Such monolithic form may include
blocks, bricks, rods, etc., each formed of porous carbon, which may
be aggregated to form an array or assembly for adsorption of fluid
thereon and desorption of the fluid therefrom under dispensing
conditions. The porous carbon in such respect may comprise an
assembly of multiple porous carbon articles, or its may comprise a
single monolithic block, cylinder, or other form of the porous
carbon adsorbent.
[0034] In one preferred embodiment, the monolithic form of the
porous carbon is cylindrical discs, which are assembled in a
stacked array, so that the successive porous carbon discs are
coaxial with one another, being of a same diameter. By this
arrangement, the vertically extending stack can be inserted into a
containment vessel and sealed, permitting adsorbable fluid to be
charged to the containment vessel for adsorption on the porous
carbon discs, and subsequent storage thereon. Thereafter, the
vessel can be deployed at a fluid-utilizing site for dispensing of
the adsorbate fluid, involving desorption of the adsorbed fluid
from the porous carbon discs.
[0035] Such gas packaging involving a stacked array of porous
carbon articles may be fabricated as more specifically described in
U.S. Pat. No. 6,743,278 issued Jun. 1, 2004 in the name of J.
Donald Carruthers for "Gas storage and dispensing system with
monolithic carbon adsorbent," the disclosure of which is hereby
incorporated herein by reference in its entirety, for all
purposes.
[0036] In some applications of such gas packaging involving
provision of a stacked or otherwise aggregated array of porous
carbon discs or other porous carbon shapes, the individual porous
carbon articles are susceptible to movement, producing an audible
rattling in the vessel. If the vessel is being transported and
subject to movement, e.g., in a trailer of a tractor-trailer
vehicle, movement of the monolithic carbon articles allows them to
develop momentum in relation to the containment vessel, and when
the containment vessel motion is terminated, the monolithic carbon
articles collide with the interior wall surface of the containment
vessel, causing excessive noise as well as damage to the monolithic
carbon articles.
[0037] To address such issues, the invention in another aspect
provides positional stabilization structure in the containment
vessel to retain the monolithic adsorbent articles in position and
restrain their movement in relation to one another and in relation
to the vessel. Such positional stabilization structure can be of
any suitable type that is effective to fix and maintain the
monolithic adsorbent articles in position in the vessel. The
positional stabilization structure can for example include
packings, fixture plates, resilient compression elements, screens,
bags, adsorbent article configurations (e.g., with individual
adsorbent articles being molded or otherwise formed to interlock or
otherwise engage with one another, to positionally fix them in the
array), vessel interior wall conformations (for example,
longitudinal ribs on interior wall surfaces of the vessel that
engage channels in the cylindrical side surfaces of successive
adsorbent discs in a vertically stacked disc array), etc., as may
be appropriate in a given fluid storage and dispensing apparatus
employing the array of monolithic adsorbent articles.
[0038] The positional stabilization structure is advantageously
formed of materials such as non-reactive metal and metal alloys,
ceramics, polymers, and combinations thereof. Specific examples of
materials of construction that may be used in various embodiments
of the invention include stainless steel, aluminum, nickel and
carbon.
[0039] In one embodiment, plate and spring assemblies are employed
in the positional stabilization structure, to fix the position of
the monolithic adsorbent articles in the multi-article array.
[0040] FIG. 1 is a schematic exploded elevation view, in partial
cross-section, of a fluid storage and dispensing apparatus 10
illustrating such approach.
[0041] The fluid storage and dispensing apparatus 10 includes a
vessel formed by cylindrical sidewall 12 and floor 14 which
together with the circular top wall closure 40 encloses an interior
volume 18. In the interior volume 18 is disposed a vertically
stacked array 20 of monolithic porous carbon discs 22, 24, 26, 28,
30, 32, 34, 36 and 38. The topmost disc has a central opening 44
therein, to accommodate insertion thereinto of a particle filter 58
of the valve head assembly 46.
[0042] The monolithic porous carbon discs 22, 24, 26, 28, 30, 32,
34, 36 and 38 are each coaxial with one another and each is of a
same diameter, with cylindrical side surfaces of the respective
discs being vertically aligned with one another.
[0043] The floor 14 of the vessel may optionally include a central
dimpled portion 16, as illustrated. The circular top wall closure
40 may be secured to the cylindrical sidewall 12 of the vessel in
any suitable manner, e.g., by welding, brazing, mechanical
fastening, etc. Additionally, the cylindrical sidewall may be
threaded at an upper portion of its interior surface, whereby a
complementarily threaded top wall closure can be threadably engaged
with the cylindrical sidewall. The top wall closure has a central
opening 42 therein, circumscribed by a threaded surface that is
threadably engageable with a complementarily threaded tubular
portion 56 of the valve head assembly 46.
[0044] The valve head assembly 46 includes a main valve body 48
having a valve element therein that is translatable between a fully
opened and a fully closed position. Such valve element is coupled
via valve stem 52 to handwheel 54. The valve element in the main
valve body 48 is disposed in a valve cavity, or working volume,
that communicates with a dispensing port of the outlet 50 secured
to the main valve body 48. The valve cavity communicates with a
passage in the threaded tubular portion 56 of the valve head
assembly, and such threaded tubular portion in turn is coupled with
particle filter 58.
[0045] The positional stabilization structure in the FIG. 1
embodiment includes a coil spring 60 that is reposed in the central
opening 42 of the top wall closure 40, and an upper distribution
plate 62 reposed on the top surface of the uppermost adsorbent disc
22. As shown, the upper distribution plate 62 is generally
coextensive in diameter with the discs in the stacked disc array,
and has a central opening that accommodates passage of the particle
filter 58 therethrough into the central opening 44 of the uppermost
adsorbent disc 22. In other embodiments, the upper distribution
plate may be of greater or lesser diameter than the discs in the
stacked array. When the valve head assembly 46 is threadably
engaged with the threading in central opening 42, the coil spring
is compressed to bear on the distribution plate, which in turn
exerts compressive bearing pressure on the vertically stacked array
20 of porous carbon discs.
[0046] The positional stabilization structure in the FIG. 1
embodiment optionally further includes a lower distribution plate
64 arranged to engage the dimple 16 forming a protruberant bearing
surface in the interior volume 18 of the fluid storage and
dispensing vessel. Thus, the lower distribution plate 64 is reposed
on the bearing surface of the dimple 16, and the vertically stacked
array 20 of porous carbon discs in turn is reposed on the main top
surface of such distribution plate. By this arrangement, the
vertically stacked array 20 of porous carbon discs is compressively
held between the upper and lower distribution plates, thereby
securing the array against movement of the stack, or individual
discs thereof against one another. The lower distribution plate may
additionally be secured in position in the lower part of the vessel
interior volume, by brackets, shelf elements, or other securement
structure, as necessary or desirable in specific embodiments.
[0047] FIG. 2 is a schematic elevation view, in partial
cross-section, of the fluid storage and dispensing apparatus 10 of
FIG. 1 as assembled, with the valve ahead 46 threadably engaged in
the circular top wall closure 40 at the threaded tubular portion
56, and with the upper distribution plate 62 and lower distribution
plate 64 compressively retaining the vertically stacked array 20 of
porous carbon discs in position against movement and impact with
the interior wall surfaces of the vessel. The parts and elements of
the fluid storage and dispensing apparatus 10 in FIG. 2 are
numbered correspondingly with respect to the same elements in FIG.
1.
[0048] FIG. 3 is a schematic elevation view, in partial
cross-section, of a fluid storage and dispensing apparatus 110
according to another embodiment of the invention. In the FIG. 3
embodiment, the parts and elements corresponding to those of the
FIGS. 1-2 embodiment are correspondingly numbered, by addition of
100 to the number of the corresponding part or element in FIGS. 1
and 2.
[0049] The FIG. 3 embodiment differs from the embodiment of FIGS. 1
and 2, in the provision of a helical compression element at the
lower portion of the vessel, in the form of coil spring 180. The
coil spring 180 rests on the floor 114 of the vessel and exerts
upward compressive force on the distribution plate 164, which in
turn spreads the compressive force over the entire bottom face of
the lowermost porous carbon disc in the vertically stacked array
120. Such dual-spring arrangement enhances the load bearing
character of the lower distribution plate 164.
[0050] FIG. 4 is a schematic elevation view, in partial
cross-section, of a fluid storage and dispensing apparatus to 10
according to yet another embodiment of the invention, wherein
corresponding parts and elements to the embodiment of FIGS. 1 and 2
are correspondingly numbered, by addition of 200 to the reference
numeral of the corresponding part or element of FIGS. 1-2.
[0051] In the FIG. 4 embodiment, the positional stabilization
structure includes a packing of mesh material 290, which may be
provided in the form of a batting or sheet material that is wrapped
about the vertical stacked array 220 of porous carbon discs.
Additional mesh material is provided at the upper portion of the
interior volume 218, overlying the main top surface of the
uppermost porous carbon disc in the array 220, as well as at the
lower portion of the interior volume 218, beneath the main bottom
surface of the lowermost porous carbon disc in the array 220.
[0052] The springs used in the above-described embodiments can be
formed of any suitable materials of construction that are
compatible with the chemistry that is being used, and compatible
with the process in which the dispensed fluid is to be employed.
The upper spring is placed in the threaded cylinder opening (e.g.,
the central opening 42 in the top wall closure 40 as shown in FIG.
1) prior to the "valving in" of the container, i.e., rotationally
engaging the threading of the threaded tubular portion 56 with the
threading circumscribing the opening 42 in the top wall
closure.
[0053] The upper spring is sized such that the valving process
compresses the spring between the bottom of the valve (bottom face
of the tubular threaded portion 56) and the distribution plate
overlying the uppermost porous carbon article in the vertically
stacked array of porous carbon articles. It will be recognized that
the distribution plate overlying the uppermost porous carbon
article may in some instances not be required and is generally an
optional additional component of the stabilization structure, but
such plate is typically preferred to spread the compressive force
exerted by the spring over the full facial area of the face of the
adjacent porous carbon article in the stacked array.
[0054] The force applied by the compressed upper spring is selected
to be sufficiently large to effect friction between the monolithic
porous carbon particles, between the porous carbon articles and the
containment vessel, and between the uppermost porous carbon article
and the spring, which will restrain, and preferably eliminate,
movement of the porous carbon articles incident to handling,
transport or other translation of the vessel, as well as
susceptibility to movement due to shock, vibration, and impact. The
positional stabilization structure therefore damps the force of any
contact between any of the porous carbon articles, and the interior
of the containment vessel, minimizing the likelihood of damage of
the porous carbon articles as a result of such contact, and
minimizing or eliminating noise resulting from such contact.
[0055] An alternative approach for deployment of a spring
contacting the uppermost porous carbon article in the array
involves inserting the spring prior to welding of the cylinder, so
that the spring is in contact with the interior face of the top
wall closure of the containment vessel at an upper end of the
spring, and in contact with the uppermost porous carbon article (or
a distribution plate thereover) at a lower end of the spring.
[0056] The provision of a second, lower spring in the containment
vessel, beneath the stacked array of porous carbon articles (as in
FIG. 3), allows the suspension of the stacked array between the
respective upper and lower springs, and minimizes or eliminates the
contact of the porous carbon articles with interior surfaces of the
containment vessel. Such approach also serves to damp the force of
any contact between the porous carbon articles and the interior
surfaces of the containment vessel, to minimize the incidence of
damage to the porous carbon articles by such contact, and
minimizing or eliminating noise resulting from such contact.
[0057] As indicated, the provision of pressure distribution plates
serves to distribute compressive forces exerted by the spring
across the full facial area of the porous carbon article(s) that
is/are in contact with the distribution plate. Such distribution of
force reduces the potential for fragmentation of the porous carbon
articles due to sudden impacts.
[0058] The springs generally may be of any suitable type,
including, without limitation, coil type springs, wave type
springs, o-rings, polymer cushions, multiple coil type springs,
multiple wave type springs, and multiple polymer cushions.
[0059] Packing materials utilized in the positional stabilization
structure, as illustratively shown in FIG. 4, can be used to
restrain or cushion movement of the porous carbon articles inside
the containment vessel. The packing material can be of any suitable
composition, and can be in the form of a cloth or mesh
material.
[0060] In one preferred embodiment, the porous carbon articles are
wrapped in a cloth made of carbon fiber (preferably formed of
activated carbon) prior to insertion of the porous carbon articles
into the interior volume of the containment vessel. Such wrapping
of the porous carbon articles serves to dampen all contacts between
the stacked array of porous carbon articles and the interior
surface of the containment vessel, and may provide significant
independent gas storage capacity, to augment that of the porous
carbon articles wrapped in the carbon fiber cloth. The mesh size of
the wrapping can be readily optimized, by the expedient of simple
empirical determination, to allow gas flow across the wrap that
satisfies the process requirements of the end-use application of
the dispensed fluid, while enabling effective dampening of shock,
concurrent protection of the porous carbon articles, and
minimization of the volume requirement for the wrapped stacked
array in the interior volume of the containment vessel.
[0061] Excess wrapping medium from the packing operation can be
left in the upper and lower portions of the interior volume in the
containment vessel, to function as a cushion for the stacked array,
as shown in FIG. 4. The wrapping medium can simply be wrapped
around the porous carbon articles before their insertion into the
interior volume of the containment vessel, with the excess wrapping
material at the respective ends being folded or twisted to
constitute additional cushioning masses above and below the stacked
array.
[0062] Alternatively, the wrapping medium may be preformed into a
sealed tube, through an open end thereof, prior to placement of the
porous carbon articles into the tube and sealing of such open end
thereof.
[0063] If a very fine mesh wrapping medium is employed, such medium
also serves as a particle filter to prevent particulates, such as
may reside on the porous carbon articles, from migrating out of the
containment vessel during the dispensing of fluid therefrom.
[0064] In general, the wrapping medium may be of any suitable type,
formed of any appropriate material construction, such as carbon,
fiberglass, metal, polymer, etc., depending on material
compatibility considerations, with respect to the materials
utilized in the fluid storage and dispensing apparatus and
materials used in the fluid-utilizing apparatus or process that
receives the dispensed fluid from the fluid storage and dispensing
containment vessel.
[0065] It will be recognized that the positional stabilization
structure utilized to maintain the array of monolithic porous
carbon articles in a fixed position, can be varied widely in the
broad practice of the present invention, utilizing various
structural elements and approaches to minimize or eliminate
movement of the porous carbon articles in the interior volume of
the container in which they are disposed.
[0066] In another aspect of the invention, porous carbon adsorbent
is utilized for removal of highly refractory, difficult-to-remove
(by standard catalytic desulfurization techniques) aromatic
sulfur-containing molecules from hydrocarbon feedstocks such as
gasoline, jet or diesel fuel, or crude oil, petroleum or other
precursors or source materials therefor.
[0067] There is currently a movement in worldwide environmental
legislation toward requiring improved emission controls from
gasoline- and diesel-fueled vehicles. Sulfur-containing molecules
in the feedstocks for such fuels must be removed in order for
catalytic controls to be effective at the levels of emission
control necessary to meet new legislative constraints (e.g., in the
U.S., sulfur levels in gasoline must be reduced from the current
300 ppm sulfur limit to 30 ppm by 2006 and sulfur in diesel fuels
must be reduced from the current maximum of 500 ppm to 15 ppm by
2006; concurrently, Japan is requiring sulfur in diesel fuels to be
reduced to 10 ppm by 2007; the European Union is requiring sulfur
content of gasoline to be reduced to 50 ppm in 2005; and Germany is
requiring sulfur content of diesel fuels to be reduced to 10 ppm by
2006).
[0068] Newly developing fuel-cell engines for vehicular
applications, operating with on-board fuel processors, require even
greater levels of desulfurization than is required by conventional
internal combustion engine power systems. For example, polymer
electrolyte membrane (PEM) fuel cell engines require sulfur levels
that typically are below 1 ppm.
[0069] Current catalytic hydrodesulfurization techniques can
achieve sulfur levels close to these required limits, particularly
for diesel fuels, but there remain very refractory sulfur molecules
that defy conversion. These residual refractory sulfur molecules
tend to be sterically-hindered molecules, such as dibenzothiophene,
4-methyldibenzothiophene and the most refractory,
4,6-dimethyldibenzothiophene.
[0070] In gasoline production, the sulfur molecules in the naphtha
fraction of the distillate do not include all of the aforementioned
refractory molecules, but there is another complication.
Hydrodesulfurization of this fraction could be very effective in
principle, but the operating conditions of conventional
hydrodesulfurization units convert many of the `high octane`
olefinic molecules into `low octane` saturates, with consequent
downgarding of the quality of the fuel (olefins can be present in
amounts of up to 40% of the gasoline fraction).
[0071] The present invention overcomes this deficiency by effecting
adsorptive removal of refractory sulfur molecules such as
dibenzothiophene, 4-methyldibenzothiophene and
4,6-dimethyldibenzothiophene, utilizing nanoporous carbon having
porosity predominantly constituted by pores of less than 1 nm
diameter.
[0072] The invention therefore contemplates the use of a nanoporous
carbon of such type for removing refractory, flat-conformation
molecules that otherwise constitute an obstacle to achieving
ultra-low sulfur fuels.
[0073] In one embodiment of the invention, the nanoporous carbon is
constituted by a polyvinylidene chloride (PVDC)-derived carbon that
provides a highly effective adsorbent medium for removing
refractory sulfur-containing molecules from liquid phase
transportation fuels (gasoline, diesel, jet fuels) to achieve the
levels of deep desulfurization necessary to meet environmental
legislative constraints.
[0074] The nanoporous PVDC carbon is suitably formed as more fully
described in U.S. Pat. No. 6,743,278 issued Jun. 1, 2004 in the
name of J. Donald Carruthers for "Gas Storage and Dispensing System
with Monolithic Carbon Adsorbent," the disclosure of which hereby
is incorporated herein by reference, in its entirety.
[0075] FIG. 5 is a schematic representation of an adsorbent-based
process system 300 for deep desulfurization of sulfur-containing
hydrocarbon feedstocks.
[0076] As illustrated in FIG. 5, the process system includes two
adsorbers 302 and 304, manifolded together to allow flow of fluid
therethrough. Each of the adsorbers includes a vessel having a bed
of the nanoporous carbon therein. The bed may be a fixed bed or a
fluidized bed, as necessary or desired in a given application of
the process system technology of the invention. The bed can be
formed of monolithic (bulk form) nanoporous carbon articles in the
case of a fixed bed, and in the case of a fluidized bed is
constituted by finely divided particles, e.g., in the form of
cylindrical pellets, spherical particles, rings, cruciform shaped
articles, etc., or any other shape or form appropriate to
fluidization and effective for removal of highly refractory sulfur
compounds from hydrocarbon raw material containing same.
[0077] The two adsorbers 302 and 304 are manifolded to one another
by an inlet manifold 306 joined to respective feed lines 308 and
312 containing flow control valves 310 and 314 therein,
respectively. The feed lines 308 and 312 are additionally connected
to a purge line 320, which includes a distal portion of the purge
line containing flow control valve 322 therein, and joined to feed
line 12, with a branch line 324 containing flow control valve 326
therein, joined to feed line 308. The purge line 320 is joined in
flow communication with a source of purge gas (not shown in FIG.
5).
[0078] The two adsorbers 302 and 304 are also manifolded to one
another at their outlet ends, by an outlet manifold assembly
including discharge manifold line 322, joined to discharge line 328
from adsorber 302 containing flow control valve 346 therein, and
joined to discharge line 330 from adsorber 304, containing flow
control valve 344 therein. The discharge manifold line 322 is
joined to product line 348 for flow of the desulfurized hydrocarbon
to blender 350 for mixing therein with hydrodesulfurized
hydrocarbon from the hydrodesulfurization reactor 374, as
hereinafter more fully described, to yield an ultralow sulfur
product hydrocarbon stream, discharge from the blender in discharge
line 352.
[0079] The outlet manifold assembly also includes a desorbate
discharge line 336 containing flow control valve 338 therein for
discharging desorbate from adsorber 304, and desorbate discharge
line 340 containing flow control valve 342 therein, for discharge
of sulfur-containing desorbate from adsorber 302. The respective
desorbate discharge lines 336 and 340 are joined in turn to
desorbate feed line 362, which feeds the sulfur-containing
desorbate to the evaporator 360.
[0080] Evaporator 360 produces a high sulfur fraction bottoms that
is flowed in line 372 to the hydrodesulfurization reactor 374 for
reaction with hydrogen, introduced to the reactor in hydrogen feed
line 373. The hydrodesulfurized hydrocarbon from the
hydrodesulfurization reactor then is flowed in line 376 to the
separator, from which hydrogen sulfide and hydrogen gas are
separated as overhead discharged in line 382, and desulfurized
hydrocarbon bottoms flowed in line 384 to the blender 350.
[0081] The evaporator 360 produces a sulfur-depleted overhead, that
is flowed in recycle line 364 through the heat exchange passage 368
in cooler 366 to condense the sulfur-depleted overhead. The
sulfur-depleted overhead then is flowed from the condenser in line
370 to the purge gas feed line 320, for recycle to the on-stream
adsorber. By the condensation and recycle of the sulfur-depleted
overhead from the evaporator to the on-stream adsorber, the overall
yield of the purified hydrocarbon ultimately discharged as product
in line 352 is enhanced.
[0082] In operation, one of the adsorbers 302 and 304 is on stream
actively processing the feedstock hydrocarbon that is flowed into
such adsorber in the inlet manifold, to produce a reduced sulfur
hydrocarbon stream. The reduced sulfur hydrocarbon stream is
discharged from such adsorber by the discharge manifold, and passes
to the blender.
[0083] While the on-stream adsorber is processing hydrocarbon, the
off-stream adsorber during a portion of its off-stream duration is
subjected to purging with a suitable purge medium introduced in
purge feed line 320 to such off-stream adsorber. The purging
operation effects desorption of the highly refractory sulfur
compounds from the nanoporous carbon adsorbent, and the desorbed
compounds are conveyed in the carrier purge gas stream to the
evaporator 360.
[0084] The process system 300 shown in FIG. 5 utilizing nanoporous
PVDC adsorbent in adsorbers 302 and 304 is capable of producing
desulfurized product hydrocarbon having less than ppm of each of
dibenzothiophene, 4-methyldibenzothiophene and
4,6-dimethyldibenzothiophene therein.
[0085] A particularly preferred nanoporous carbon adsorbent for
such desulfurization process is a PVDC char material having at
least 30% of overall porosity constituted by slit-shaped pores
having a size in a range of from about 0.3 to about 0.72 nanometer,
and at least 20% of the overall porosity comprising pores of
diameter <2 nanometers, with a bulk density of from about 0.80
to about 2.0 grams per cubic centimeter.
[0086] The invention in another aspect contemplates an
adsorbent-based storage and dispensing apparatus, including a
container having an interior volume in which is disposed a
plurality of individual adsorbent articles, with a coupling
structure adapted to couple the individual adsorbent articles with
one another so that they are positionally stabilized against
movement in relation to one another, with the coupling structure
being secured to the container.
[0087] The coupling structure in one embodiment includes at least
one rod passing through the individual adsorbent articles, wherein
the rod has a first end that is secured to the container and a
second end that is coupled with a mechanical fastener, such as by a
threaded coupling. The rod at its first end may be threadably
engaged with the container.
[0088] The container can be constructed to include a closure member
to which the coupling structure is secured.
[0089] The individual adsorbent articles in a preferred embodiment
are coupled to one another to form an assembly of such individual
adsorbent articles that does not contact the interior surface of
the container. Each of the individual adsorbent articles can be
disk-shaped, and the disk-shaped articles can be coupled by the
coupling structure to form a positionally fixed stack of the
adsorbent articles. The disk-shaped articles can be of any suitable
size. Preferably, all of such disk-shaped articles are the same
size, so that when stacked, the stack of disk-shaped articles is
cylindrical in form.
[0090] The coupling structure can be of any suitable type. As
mentioned, the coupling structure can include a rod and when the
adsorbent articles form is that, each of the individual adsorbent
articles can include an opening therethrough, so that the rod
extends through the opening in each of the stacked articles. When
the stack is cylindrical in form, the rod may extend through the
stack in a direction parallel to a central axis of the stack.
[0091] A lowermost adsorbent article in the stack can have a cavity
formed therein, to accommodate attachment of a fastener to the rod.
The apparatus may include two or more rods, e.g., two rods that are
in spaced-apart relation to one another. An uppermost adsorbent
article in the stack likewise can have a cavity formed therein, in
which is at least partially disposed a particle filter. The
particle filter can be coupled with a valve assembly for dispensing
fluid from the container. The valve assembly can be threadably
engaged with the container, and can include a flow control member,
and that is coupled with a valve element in a valve cavity in the
valve assembly, such that the valve element is translatable between
a fully closed position and a fully open position.
[0092] Thus, the invention contemplates an adsorbent-based storage
and dispensing apparatus, which may be embodied as a container
having an interior volume, with a mounting member in the interior
volume and secured to the container, and a plurality of individual
adsorbent articles mounted on the mounting member in the interior
volume, so that the individual adsorbent articles are positionally
stabilized against movement in relation to one another.
[0093] The adsorbent in a preferred embodiment comprises carbon,
but more generally may comprise any suitable sorbent material
having sorptive affinity to the fluid that is to be stored in and
dispensed from the container holding the adsorbent. The adsorbent
in use has a fluid stored thereon, that is selectively dispensed
from the vessel, e.g., for flow to a microelectronic device
manufacturing tool or other fluid utilizing device.
[0094] The adsorbed fluid can be of any suitable type, e.g., a
fluid useful in semiconductor manufacturing, such as organometallic
precursors, hydrides, halides, acid gases, etc., or a fluid useful
in operation of a solar cell, fuel cell, etc.
[0095] The container holding the adsorbent articles can have a
dispensing assembly coupled with the container, for dispensing of
fluid from the container to downstream flow circuitry or other
locus of use or transport.
[0096] In the container, a gasket or cushioning element, or a
pressure distribution plate, can be provided to contact at least
one individual adsorbent article in the plurality of individual
adsorbent articles that are fixedly positioned by the
above-described rod and mechanical fastener assembly, or other
positional fixturing structure. The purpose of such elements is to
increase the resistance of the assemblage of adsorbent articles to
damage in the event of shock or impact, and to further reduce any
incidence of relative movement of the individual adsorbent articles
that could result in generation of fines or particles.
[0097] FIG. 6 is a cross-sectional elevational view of a fluid
storage and dispensing apparatus 400 incorporating an adsorbent
fixturing assembly, according to one embodiment of the present
invention.
[0098] The fluid storage and dispensing apparatus 400 includes a
fluid storage and dispensing vessel 401 having a vessel side wall
402 and floor 403 having a central cavity (dimple) 404 therein. The
apparatus includes a top closure member 408 having central opening
490 therein to accommodate passage therethrough of the threaded
stem 436 of a valve head assembly. The threaded stem 436 has a
particle filter 438 joined to its lower end, which serves to filter
the dispensed fluid to remove fines and particulates therefrom. The
particle filter 438 is accommodated at its lower end by a central
opening 422 in the uppermost physical adsorbent article.
[0099] The valve head assembly includes a valve body 430 containing
a valve cavity therein (not shown in FIG. 6) communicating with a
discharge passage. The valve cavity contains a translatable valve
element that is movable between a fully open and a fully closed
position, with the valve element being coupled to the valve hand
wheel 432 for manual actuation of the valve.
[0100] The vessel 401 and top closure member 408 together enclose
an interior volume of the vessel in which is disposed a vertically
stacked array of physical adsorbent articles, or pucks, that are
each of cylindrical disk shape, and that when stacked with side
surfaces in register with one another forms a columnar monolithic
adsorbent article 406.
[0101] The top closure member 408 also contains openings 460 and
462 therein in which rods 412 and 414 are threaded, welded, press
fit or otherwise coupled with the top closure member. The rods 412
and 414 extend vertically downwardly through the stack of physical
adsorbent pucks and at their lower ends are secured by locking
assemblies 415. Specifically, the rods at their lower ends of the
rods 412 and 414 are threaded, and the threaded ends are engaged
with nuts 416 and 418. The nuts 416 and 418 are reposed in
associated openings in the lowermost puck in the stacked array.
[0102] By tightening the nuts on the threaded rods until the nuts
are in bearing contact with the floors of the cavities, the
vertically stacked puck array is held in a fixed position. Washers,
rings, lock-nuts and gaskets may be employed in securing the
stacked puck array with the rods, as a fixturing assembly. The
fixturing assembly permits the stacked puck array to be
positionally secured in the interior volume of the vessel 401, so
that the stacked puck array does not impact the interior wall
surface of the vessel, and so that individual pucks in the array do
not rub against one another to generate fines or dust, and so that
the pucks do not translate in relation to one another to generate
unwanted noise.
[0103] In the stacked assembly as secured by the rod assembly, the
rods can be secured to the closure member, as illustrated, or may
alternatively be secured to the floor of the vessel, with the rods
passing through openings in the pucks. The rods, as mentioned, may
be secured at one end (to the closure member or to the floor of the
vessel) by threadable engagement with threaded receiving openings
in the closure member or the floor, or by welds, gluing, press
fitting, or any other method or means of securement. The pucks are
secured onto the rods by nuts or other fastening techniques such as
peening, gluing, press fitting, or the like.
[0104] The contact surfaces between the pucks, or between the
fasteners and the pucks, or between the closure member and the
pucks, can be gasketed to prevent pointed contact between the pucks
and hard surfaces to minimize the occurrence of excess pressure on
small areas of the pucks that could otherwise cause fracture of the
pucks. The gasketing thereby acts as a cushion for the pucks.
Springs and lock washers may be incorporated into the design to
provide cushioning as well, either with or without other gasketing
or cushioning type materials. The fasteners can be combined with
pressure distributing techniques such as a pressure distribution
plate or washers to displace pressure over a greater surface area
to minimize the potential for damage to the pucks.
[0105] The number of rods used in the fixturing assembly can be
determined by the diameter and the length of the rods, the height
of the stacked array of pucks, the mechanical characteristics of
the pucks, the mechanical characteristics of the rods and the
service-handling requirements of the intended use application of
the fluid storage and dispensing apparatus.
[0106] The materials of construction of the gaskets, rods,
fasteners, distribution plates and springs used in the fluid
storage and dispensing apparatus will be determined by the diameter
and length of the rods, the height of the stacked puck array, the
mechanical characteristics of the pucks, the mechanical
characteristics of the rods and the service-handling-chemical
requirements of the intended use application of the fluid storage
and dispensing apparatus.
[0107] The stacked puck array fixturing assembly of the invention
overcomes the problems incident to movements of the component pucks
in the stacked array in the vessel, and prevents such problems from
adversely impacting the fluid storage and dispensing apparatus
service life, performance, or adverse user impressions associated
with noise generation. This fixtured stacked array provides a
greater degree of stability for the pucks, since the pucks are
positionally secured in the interior volume of the vessel to such
extent that there is little or no independent motion of the pucks
themselves.
[0108] The invention in another aspect relates to an infrared
emitter device, including a container having an interior volume
holding silane gas in an adsorbed state. The container includes an
oxygen-selective permeation element allowing selective ingress of
oxygen from an ambient environment of the container into the
interior volume, and an insulative medium is disposed in the
interior volume of the container adapted to enhance infrared
emissivity of the device.
[0109] The silane gas in the container in a preferred embodiment is
held in an adsorbed state on a carbon adsorbent, e.g., an adsorbent
in a monolithic form, such as a cylindrical or rectangular block or
brick, or an adsorbent in a finely divided or other form. The
silane gas can be held in the interior volume of the container at
any suitable pressure, e.g., a subatmospheric pressure.
[0110] The insulative medium can by way of example include a
silica-based aerogel thermal insulation, and the oxygen-selective
permeation element can comprise an oxygen perm-selective membrane
of suitable type. The container can be formed of any suitable
material, such as a plastic material or glass material. Optionally,
the container can include reflective elements in the interior
volume, with the reflective elements being adapted to reduce
thermal conductivity heat losses from the container, and to control
emissivity consistent with the requirements of providing an
extended duration infrared radiation signature from the device.
[0111] In preferred practice, the device is designed to hold
sufficient silane gas and to allow ingress of oxygen sufficient to
generate an infrared radiation signature for a period of at least
five days, more preferably for a period of at least 10 days, and
most preferably for a period of at least 15 days. Such extended
duration IR signature achieves a substantial advance in the art,
relative to chemical lighting markers utilized in the prior art,
whose signature duration is at best only a fraction of a day.
[0112] The invention correspondingly provides a method of
generating an extended infrared radiation signature, by permeating
oxygen through an oxygen-selective permeation element, and reacting
the permeated oxygen with silane held in an adsorbed state, thereby
generating the radiation signature.
[0113] In carrying out such method in preferred practice, thereof,
the permeated oxygen and silane are reacted in a container holding
a carbon adsorbent having silane adsorbed thereon, preferably with
an insulative medium in the container that is arranged to enhance
infrared emissivity deriving from the reaction of silane and
permeated oxygen, and the carbon adsorbent preferably is of a
monolithic form, as previously described. The term "enhance" in
reference to the emissivity deriving from the reaction of silane
and oxygen, means that the infrared emissivity deriving from such
reaction is greater than is achievable in a corresponding reaction
in which the insulative medium is not employed.
[0114] The invention in a specific aspect contemplates infrared
emitting marker sticks that produce a signature detectable by
infrared detection apparatus. The infrared marker sticks overcome
the problems associated with currently used chemiluminescence
sticks relating to their limited lifetimes. Chemiluminescent sticks
typically have an illumination lifetime of 3-8 hours. The infrared
marker sticks of the invention provides a longer lasting emitter
device that reduces the number of sticks needed for a given end use
application, and enable long emitter life applications that
heretofore have been unattainable by chemiluminescent marker
sticks.
[0115] The infrared emitting marker stick of the invention utilizes
slow controlled combustion of silane gas to maintain a constant
elevated temperature. Normally considered as a hazardous gas,
silane is used in the infrared emitting marker stick in an
inherently safe and energy efficient device.
[0116] The infrared emitting marker stick of the invention
comprises four primary components: (i) silane gas, a readily
available commodity gas, (ii) a nanoporous carbon adsorbent in
monolithic form, commercially available from ATMI, Inc. (Danbury,
Conn., USA) under the trademark "Mblock;" (iii) silica-based
aerogel thermal insulation, commercially available from Aspen
Aerogels, Inc. under the trademark "Spaceloft," and (iv) an
oxygen-selective flow rate limiting membrane medium, e.g., of a
type commercially available from Mott Metalurgical.
[0117] In the infrared emitting marker stick of the invention,
silane is stored on the nanoporous carbon adsorbent in an
appropriate amount and at an appropriate pressure for the desired
marker application.
[0118] For example, in a given embodiment, 0.75 mole of silane may
be stored on the nanoporous carbon adsorbent at a pressure of 380
torr. Oxygen is leaked through the oxygen-selective flow rate
limiting membrane medium at a suitable rate, e.g., 1.3 sccm in the
illustrative example. The silane in the presence of oxygen is
combusted to form SiO.sub.2 and H.sub.2O, releasing 1.5 Megajoules
per mole of silane. At a permeation rate of 1.3 sccm of O.sub.2,
0.73 watt of energy is produced. The aerogel insulation may be used
in combination with metal reflectors to minimize losses due to
thermal conductivity effects and to control the emissivity
aperture, resulting in an internal temperature rise, with
negligible external increase in temperature. The 0.73 watt energy
production then is dissipated by IR radiation, creating the IR
signature. The SiO.sub.2 based insulation is essentially IR
transparent. As a result, at a radiation rate of 0.73 watt, 0.75
moles of SiH4 will last approximately 17 days.
[0119] The advantages of the infrared emitter marker device of the
invention include (i) production of a high specific energy density,
e.g., 6.5 times the energy density of corresponding iron oxidation
on a per gram of starting material basis, (ii) provision of long
life service as compared to 3-8 hour chemiluminescent light sticks
and up to 20 hours for iron-based heat packs, (iii) the use of only
low-cost components (SiO.sub.2 insulation, SiH.sub.4 gas, carbon,
aluminum shields), without the need for expensive precious metal
catalysts, (iv) the production of non-toxic end products (charcoal,
sand and water), unlike butane-based heaters, and (v) the
achievement of sub-atmospheric pressure safety as a result of the
silane gas being contained at sub-atmospheric pressure.
[0120] FIG. 7 is a schematic representation of an infrared emitter
device 500 according to another embodiment of the present
invention.
[0121] The emitter device includes a container 502 fabricated of
plastic or glass material in which is disposed a block or other
preferably bulk form of an adsorbent 506. This adsorbent body holds
adsorbed silane 508 thereon and is wrapped or otherwise surrounded
with infrared transparent thermal insulation 512. The container is
capped with a porous oxygen separator and flow restrictor element
504, which is permselective to allow oxygen to enter the container
for reaction therein with the adsorbed silane on the adsorbent. The
container on interior wall surface thereof has mounted an array of
reflectors 516.
[0122] The IR emitter device of the invention may be readily
designed to provide a desired IR signature for a predetermined
period of time, based on selection of silane storage capacity,
geometric ratio (size vs. lifetime considerations), type and
characteristics of the separator/restrictor element, combustion
rate of the silane/oxygen reaction, and consequent thermal
increase, the nature of the container material of construction, and
the fill pressure for silane gas in the container. Accordingly,
such design variables may be empirically selected, and modeled
and/or experimentally varied, to determine an IR emitter device
that is appropriate for a given application, to provide an IR
signal for an extended length of time.
[0123] The IR emitter device of the invention may be utilized for a
wide variety of end uses, including, without limitation, surveying,
mapping, geographic marking, target marking, deployment as
emergency rescue beacons, tracking of wildlife, orienteering and
other recreational uses, etc., in connection with IR detectors and
sensors of various suitable types.
[0124] The carbon adsorbent utilized in the IR emitter device, as
well as in other embodiments of the present invention, can be of
any suitable type, and may for example include carbon nanotubes in
a supported or consolidated state, such as the aerogel monolith
having carbon nanotubes grown within it, as described in U.S. Pat.
No. 6,906,003 issued Jun. 14, 2005 to Struthers et al., or the
nanoporous structures formed using nanofibers and "gluing" agents
described in U.S. Pat. No. 6,432,866 issued Aug. 13, 2002 to
Tennent et al., the disclosures of which hereby are incorporated
herein by reference in their respective entireties.
[0125] The invention in another aspect takes advantage of the
electrical properties of carbon as a conductor having significant
resistivity, which enables carbon adsorbent to be electrically
energized to effect resistive and/or inductive heating for
desorption of residual adsorbed fluid. By inputting electrical
energy to the carbon adsorbent, heels fluid can be removed from the
carbon adsorbent, to achieve higher fluid utilization than
heretofore has been possible in low pressure carbon adsorbent-based
fluid storage and dispensing operations, without external heating
of vessels in which the carbon adsorbent is contained.
[0126] The invention in one embodiment relates to a fluid storage
and dispensing apparatus, comprising a fluid storage and dispensing
vessel holding carbon adsorbent, a dispensing assembly for
dispensing of fluid from the vessel under dispensing conditions,
and an electrical power assembly adapted to input electrical energy
to the carbon adsorbent for resistive and/or inductive heating
thereof to effect desorption of fluid from the carbon
adsorbent.
[0127] The electrical power assembly can be configured in any
suitable manner. In one embodiment, the electrical power assembly
includes at least one electrode adapted to transmit electrical
energy to the carbon adsorbent, e.g., an electrode arranged in
contact with carbon adsorbent articles. The carbon adsorbent
articles can be provided in a stacked array in a vessel, and the
electrical power assembly can include an electrical transmission
wire coupled with the vessel, when the vessel includes a conductive
material of construction. The conductive material can be a metal,
such as steel, ferrous alloys, aluminum, titanium, etc. The fluid
storage and dispensing system can also be configured to include
multiple electrodes in contact with the carbon adsorbent.
[0128] In one embodiment, the carbon adsorbent may be provided in
an extended length conformation, as hereinafter more fully
described. For example, the extended length conformation may
include a helical conformation carbon adsorbent that is coupled at
respective ends thereof with the electrical power assembly.
[0129] The electrical power assembly can include a power supply of
any suitable type, including radio frequency power supplies, DC
power supplies, AC power supplies, etc. The carbon adsorbent can be
coupled with the power supply by electrical power supply wires, and
the power supply can be arranged to be detachably coupled to the
carbon adsorbent.
[0130] In one embodiment, the electrical power assembly includes a
Wheatstone bridge circuit in which the carbon adsorbent is a
resistive element of the circuit.
[0131] In various other embodiments, the carbon adsorbent is
inductively resistively heated, such as by use of a coil arranged
to non-contacting surround at least a portion of a fluid storage
and dispensing vessel containing the carbon adsorbent. In one such
embodiment, the fluid storage and dispensing vessel contains a
first transformer winding adapted to input to electrical energy to
the carbon adsorbent for induction of eddy currents therein.
Inductively coupled with the first transformer winding in the
vessel is a second transformer winding exterior of the vessel.
Second transformer winding is suitably coupled to an alternating
current power supply, by wires constituting a circuit arrangement
with the second transformer winding.
[0132] In another embodiment, the electrical power assembly
includes an electrode disposed in the fluid storage and dispensing
vessel and extending exteriorly thereof, and then the electrical
connection in contact with the vessel, with the vessel comprising a
metal material of construction. In such embodiment, the electrical
connection and exterior portion of the electrode are coupled with a
power supply. The power supply is adapted to be selectively
actuated at the end of the dispensing operation, when fluid
inventory in the vessel has declined to a predetermined low level,
so that electrical energy is transmitted to the carbon adsorbent
for heating thereof, to drive off the residual fluid from the
adsorbent.
[0133] The invention correspondingly contemplates a method of
dispensing fluid from a carbon adsorbent involving desorption of
fluid therefrom, which includes inputting electrical energy to said
carbon adsorbent to effect resistive and/or inductive heating
thereof. The adsorbent in such method can be contained in a vessel
adapted to selectively dispense fluid under dispensing conditions.
The inputting of electrical energy to the carbon adsorbent can be
carried out in apparatus arrangements of the type described above,
e.g., involving inputting electrical energy to effect resistive
heating by at least one electrode in contact with the carbon
adsorbent.
[0134] The inputting of electrical energy to the carbon adsorbent
to effect the resistive and/or inductive heating thereof can be
controllably modulated to effect desorption of residual fluid from
the carbon adsorbent, as appropriate to achieve a predetermined
extent of fluid utilization. The modulation may be carried out in
response to monitoring of a condition of the carbon adsorbent or
fluid desorbed therefrom, such as temperature of the carbon
adsorbent, desorbed fluid pressure, etc.
[0135] The aforementioned method may involve inductive heating in
which eddy currents are induced in the carbon adsorbent from a
first transformer winding that is inductively coupled with a second
transformer winding coupled with an alternating current power
supply, such as a radio frequency AC power supply. Alternatively,
the input of electrical energy can include passage of alternating
current through a coil surrounding the carbon adsorbent, e.g.,
wherein the carbon adsorbent is contained in a vessel positioned
within said coil.
[0136] As indicated, the inputting of electrical energy may involve
resistive heating of the carbon adsorbent, wherein the carbon
adsorbent comprises a resistance of a Wheatstone Bridge
assembly.
[0137] The invention in another method aspect relates to a method
of reducing heels of adsorbed fluid in a vessel containing carbon
adsorbent having such fluid adsorbed thereon, in which the method
includes inputting electrical energy to the carbon adsorbent for
resistive heating and/or inductive heating of the carbon adsorbent
to effect desorption of heels fluid therefrom. The desorb heels
fluid then can be used in a fluid-utilizing process, such as a
microelectronic device manufacturing process, e.g., involving ion
implantation.
[0138] The carbon adsorbent used in the practice of the present
invention for heels fluid recovery can be of any suitable type,
including activated carbon, carbon impregnated with metal
particles, fibers, etc., or any other form of or composition of
carbon adsorbent that is responsive to input of electrical energy
to become heated and thereby release an increased amount of an
adsorbed fluid therefrom, in relation to a corresponding carbon
adsorbent that is not heated by input of electrical energy.
[0139] The invention in another aspect contemplates a method of
fluid delivery, including providing fluid in an absorbed state on
activated carbon; selectively dispensing fluid from the activated
carbon; and when a predetermined residual amount of fluid remains
adsorbed on the carbon adsorbent, electrically heating the
adsorbent to effect removal of the residual fluid, by resistive
heating and/or inductive heating of the carbon adsorbent. In a
specific embodiment, the carbon adsorbent is contained in a fluid
storage and dispensing vessel, and the removed residual fluid is
used to manufacture a microelectronic device.
[0140] The invention also contemplates a semiconductor
manufacturing facility comprising a fluid storage and dispensing
system as previously described. The semiconductor manufacturing
facility may for example include an ion implanter arranged to
receive fluid desorbed from the carbon adsorbent. More generally, a
fluid-utilizing process system can be provided, comprising a fluid
source and dispensing system as previously described and a
fluid-utilizing apparatus adapted to receive fluid desorbed from
the carbon adsorbent.
[0141] The carbon adsorbent can be utilized to store and
selectively dispense any suitable fluid for which the carbon
adsorbent has appropriate sorptive affinity. The fluid can for
example comprise a microelectronic device manufacturing fluid, such
as a deposition reagent, etchant, cleaning fluid, polishing
reagent, photoresist, etc. Specific fluids that may be stored on
and dispensed from the carbon adsorbent include, without
limitation, arsine, phosphine, ammonia, boron trifluoride, boron
trichloride, diborane, organometallic species, nitrogen
trifluoride, and hydrogen chloride.
[0142] Referring now to the drawings, FIG. 8 is a schematic
representation of a fluid storage and dispensing system 600,
according to one embodiment of the invention.
[0143] As illustrated, the storage and dispensing system 600
includes a vessel 602 defining an interior volume 604 therein. In
the interior volume 604 is disposed a stack 606 of monolithic
carbon adsorbent articles, which are generally coextensive in
diameter with the vessel, so that the carbon adsorbent articles are
in contact with the interior surface of the vessel wall.
[0144] The carbon adsorbent articles in the stack 606 are of
generally cylindrical form, being stacked in face-to-face contact,
to extend in the vertical direction from a lower portion of the
vessel to an upper portion thereof. The adsorbent articles have
sorptive affinity for a fluid of interest, e.g., a gas or liquid.
Such fluid may for example comprise a semiconductor manufacturing
chemical reagent, such as arsine, phosphine, ammonia, boron
trifluoride, boron trichloride, diborane, organometallic species,
nitrogen trifluoride, hydrogen chloride, etc.
[0145] The vessel 602 can be formed of steel or other ferrous alloy
or other metal such as aluminum, titanium, etc. The vessel at its
upper end is joined to a valve head assembly 630, having a valve
passage therein containing a valve element that is translatable
between a fully open and a fully closed position, by rotation of
the handwheel 632. The valve head assembly 630 includes a discharge
port 636, to which may be joined a dispensing line or other
coupling, instrumentation or flow circuitry.
[0146] In this embodiment, electrode 608 is mounted centrally in
the interior volume 604 of the vessel 602, extending downwardly
through central openings in the carbon adsorbent articles in the
stack 606. The upper end of the electrode is mounted in an
insulated bushing in the valve head, being connected to the central
processing unit and power supply module 612, by power supply line
610. The central processing unit and power supply module 612 also
is connected by a second power supply line 616 to a contact collar
614 mounted in electrical contact with the exterior surface of the
vessel 602, as shown.
[0147] By the arrangement shown in FIG. 8, the fluid sorptively
retained on the carbon adsorbent articles in the stack 606 is
desorbed from the adsorbent under dispensing conditions, and
discharged after flow through the valve head 630 to discharge port
636. After a sustained period in operation, the amount of the fluid
held on the carbon adsorbent declines to a low level, at which it
is difficult to effect desorption and continued discharge of fluid
from the vessel.
[0148] At that point, the CPU and power supply module 612 is
actuated, for example by a pressure transducer (not shown in FIG.
8) in the flow circuitry downstream from the vessel, or other
process monitoring system, and delivers electrical energy to the
electrode 608 and the contact collar 614. By this action, current
flows through the electrode 608 and the conductive carbon adsorbent
to the vessel wall, to complete the circuit with the power supply
lines 610 and 616.
[0149] The carbon adsorbent in the stack 606 is thereby
electrically resistively heated, to produce elevated temperature in
the adsorbent, effecting desorption of the fluid from the carbon
adsorbent and discharge of the desorbed fluid from the vessel
through discharge port 636.
[0150] In this arrangement, the enclosing wall of the vessel 60
acts as a second electrode and the carbon adsorbent acts in the
manner of an electrolyte medium having sufficient resistivity to
effect heating of the adsorbent and thereby drive off residual
fluid from the adsorbent. This arrangement thereby enables a very
high utilization of the adsorbed fluid to be achieved, with
percentage dispensed fluid values (i.e., the percent of originally
charged fluid in the vessel that is subsequently dispensed from the
vessel) approaching 100%.
[0151] Temperature sensing of the resistively heated adsorbent
material can be conducted, and the extent of electrical energy
input modulated in response to the sensed temperature, to achieve a
necessary or desired level of desorption of the fluid. In other
embodiments, various other sensors and sensing arrangements can be
employed to monitor the electrical energy input to the carbon
adsorbent, and to generate sensing/monitoring signals that can be
employed to control the input and duration of electrical energy to
the adsorbent.
[0152] In the specific arrangement shown in FIG. 8, a thermocouple
620 is positioned in the stack 606 of adsorbent articles, to
monitor the stack temperature. The thermocouple generates a
temperature sensing signal that is transmitted in temperature
signal transmission line 622 to the CPU and power supply module
612. The CPU and power supply module 612 in response modulates the
power transmitted to the adsorbent stack, to achieve a
predetermined temperature and desorption of fluid from the
adsorbent material.
[0153] As another variation of the specific embodiment shown in
FIG. 8, a second electrode 618 can be deployed in the interior
volume 604 of vessel 602, extending through the stack of adsorbent
articles, and joined at an upper end thereof to the power supply
line 616. The power supply line 616 in such variation extends
through the wall of the vessel, e.g., by an insulated collar
positioned in the wall of the vessel through which the power supply
line 616 passes to connect with the second electrode. In such
variation, the contact collar 614 optionally may be employed, or
alternatively absent from the arrangement.
[0154] The fluid storage and dispensing system shown in FIG. 8
enables resistive heating of the carbon adsorbent medium, to effect
a high level of utilization of the sorbate fluid initially charged
to the vessel. It will be recognized that the supply of electrical
power to the adsorbent may be effected in a wide variety of
alternative ways, and that such power may be modulated during the
resistive heating phase of operation in any suitable manner, to
achieve the desired level of desorption of fluid from the sorbent
medium in the vessel.
[0155] FIG. 9 is a schematic representation of a fluid storage and
dispensing system 700, according to a further embodiment of the
invention.
[0156] The fluid storage and dispensing system 700 includes a
vessel 702 enclosing an interior volume 680 in which is disposed a
helically shaped adsorbent body 682 formed of carbon, e.g.,
activated carbon. The carbon body 682 is joined at an upper end
thereof to electrical supply wire 692 which passes through
insulated bushing 694 and is coupled to electrical feed line 696.
The electrical feed line 696 is in turn connected to power supply
690.
[0157] At its lower end, the carbon body 682 is joined to
electrical supply wire 684 which passes through insulated bushing
686 and is coupled to electrical feed line 688, connected in turn
to power supply 690.
[0158] The bushings 686 and 694 are mounted on the vessel in
association with respective openings in the vessel wall. At its
upper end, the vessel 702 is joined to valve head assembly 698,
including a discharge port 706 and a handwheel 708 arranged for
manual opening or closure of the valve in the valve head 698. In
lieu of such handwheel, an automatic valve actuator can be
employed.
[0159] By the arrangement shown in FIG. 9, the adsorbent body 682
can be selectively heated by action of the power supply 690
delivering electrical energy in feed lines 696 and 688 to
electrical supply wires 692 and 684, respectively. Since the
adsorbent body has a length that is substantially greater than the
height of the vessel 702, current flowing into the adsorbent body
at one end and passing to the other end of such body travels a
distance much greater than the linear distance from the lower
portion to the upper portion of the vessel. This "extended length"
conformation of the adsorbent body increases the resistivity
significantly, over a linear conformation of the adsorbent body, so
that less current is required to heat the carbon body than in a
linear conformation.
[0160] In lieu of the helical conformation of the adsorbent body
shown in FIG. 9, the adsorbent body can be in any other suitable
"extended length" conformation, to provide a tortuous or elongated
path for current flow through the body. As used herein, the term
"extended length conformation" refers to a physical form of the
adsorbent body in which the current path for electrical energy
through the body is substantially greater than the linear extent,
e.g., length dimension, of the body. The carbon adsorbent body may
therefore have a pleated, zigzag, spiral, wool or porous matrix
form, or any other suitable physical or morphological form that
provides the extended length conformation.
[0161] FIG. 10 is a schematic representation of a Wheatstone Bridge
circuit in which one of the resistive elements is constituted by a
carbon adsorbent bed, according to another embodiment of the
invention.
[0162] The bridge circuit includes a power supply 720 connected as
shown to the Wheatstone Bridge 730 including fixed resistors 736,
738 and 740 and variable resistor 742. Between the resistor legs of
the bridge is disposed a voltage detector 760. The voltage detector
760 is joined in series with an operational amplifier 732, to
provide inputs to the amplifier as shown. The amplifier output is
coupled with NPN transistor 734, to transmit the output to the gate
structure of the transistor. The source and drain of the transistor
are coupled with the power supply 720 and Wheatstone Bridge 730,
respectively.
[0163] The Wheatstone Bridge circuit of FIG. 10 is constituted with
one of the fixed resistors being the resistance of the carbon
adsorbent in a fluid storage and dispensing system of a type as
previously described. By this arrangement, the Wheatstone Bridge
can be balanced by the variable resistance of the variable resistor
742 to achieve zero current flow through the carbon adsorbent
during normal dispensing operation or when the system is in a
non-dispensing state.
[0164] When dispensing operation has continued for sufficient
duration to reduce the inventory of the fluid in the system to a
low level at which dispensing becomes disproportionately more
difficult, the resistance of the variable resistor 742 can be
adjusted to unbalance the Wheatstone Bridge, and cause current to
flow to the carbon adsorbent for electrical resistance heating
thereof. In such manner, the carbon adsorbent can be used as a
temperature sensing element, thereby self-regulating at a desired
temperature. Alternatively, a simple current limit device could be
implemented, or alternatively, an embedded temperature sensor could
be employed, in the manner of the arrangement shown in FIG. 8.
[0165] FIG. 11 is a schematic representation of a fluid storage and
dispensing system 800 according to another embodiment of the
invention.
[0166] In the FIG. 11 arrangement, a vessel holding in its interior
volume a bed of carbon adsorbent 804 is joined to a valve head
assembly 808, including a fluid discharge port 810 and a handwheel
812 for manual opening or closing of the valve in the valve head
assembly. In lieu of a manual handwheel, the valve in the valve
head assembly 808 may be connected to a valve actuator, e.g., a
pneumatic, electrical, or other actuator, which is operatively
arranged to open or close the valve in the valve head assembly.
[0167] The FIG. 11 arrangement includes an RF power supply 814,
operatively coupled with an induction coil 816, with the induction
coil being appropriately sized to permit the vessel 802 to reside
within the loops of the coil.
[0168] In use, fluid is dispensed from the vessel 802 under
dispensing conditions, which may include a reduced pressure in a
fluid-utilizing tool or downstream portion of the flow circuitry
resulting in pressure gradient-induced desorption, or passage of a
carrier gas through the interior volume of the vessel 802, to
create a mass transfer gradient effecting desorption from the
adsorbent and entrainment in the carrier gas being flowed through
the vessel, or in other manner effecting release of fluid from the
adsorbent.
[0169] When the inventory of fluid in the vessel has been
sufficiently depleted, the RF power supply 814 is activated, to
send alternating current through the coil 816, thereby generating a
magnetic field producing eddy currents in the carbon adsorbent. As
a result, heat is produced in the adsorbent, to produce an enhanced
desorption of fluid from the adsorbent, relative to a corresponding
adsorbent in which no such inductive heating takes place.
[0170] The inductive heating described with reference to the FIG.
11 arrangement effects removal of residual fluid from the vessel
802 in a simple and non-invasive manner, so that substantially
complete dispensing of the fluid from the vessel is achieved.
[0171] It will be appreciated that the frequency of the alternating
current provided by the RF power supply 814 in the FIG. 11 system
can be selected to achieve optimum coupling efficiency in effecting
desorption of residual fluid from the adsorbent material in
container 802.
[0172] The FIG. 11 system can employ a control scheme of any
suitable type, to modulate the RF power supply 814 in providing
alternating current to the induction coil 816. For example,
pressure of the dispensed gas can be monitored, and a suitable
feedback control assembly can be employed to maintain a fixed
operating pressure of the dispensed gas.
[0173] More generally, the fluid storage and dispensing systems of
FIGS. 8, 9 and 11 can employ a wide variety of monitoring and
feedback control components and sub-systems to ensure that the
residual fluid in the vessel at the final stage of dispensing
operation (as the vessel is approaching exhaustion) is extracted,
to minimize the heels in the vessel.
[0174] Such monitoring and control apparatus can include power
monitoring of the electrical power input to the carbon adsorbent,
thermal monitoring of the adsorbent during such power input,
pressure monitoring of the dispensed gas, flow monitoring of the
dispensed fluid, use of blending systems (e.g., for combining the
fluid from a vessel approaching exhaustion that is being submitted
to electrical power inputting for resistive and/or inductive
heating of the adsorbent therein, and fluid from a second fresh
vessel containing a full or substantial charge of fluid), etc.
[0175] FIG. 12 is a schematic cross-sectional elevation view of a
fluid storage and dispensing system 860 according to a further
embodiment of the invention.
[0176] The fluid storage and dispensing system 860 includes a
vessel 862 joined to a fluid dispensing assembly 866 at its upper
end. The vessel 862 encloses an interior volume 864, in which is
disposed a vertical stack 870 of carbon adsorbent discs 872, 874,
876, 878, 880, 882 and 884, as illustrated.
[0177] The stack 870 of carbon adsorbent articles is arranged with
an electrode 886 extending through a glass or ceramic seal 888
upwardly into the interior volume 864, through central openings in
each of the carbon adsorbent particles 872, 874, 876, 878, 880, 882
and 884.
[0178] The vessel 862 is provided with an electrical connection
890, in contact with the metal wall of the vessel 862, such wall
being formed of steel, aluminum, or other conductive material. The
electrical connection 890 may be integrally formed on the vessel,
or such connection may be coupled with the vessel in any suitable
manner, such as by provision on the exterior surface of the vessel
of a coupling structure or a fitting for such purpose.
[0179] The electrode 886 and connection 890 are coupled with a
suitable power supply (not shown) in a circuit arrangement, whereby
electrical energy is inputted into the stack 870, to effect
resistive heating thereof.
[0180] FIG. 13 is a schematic elevation view, in cross-section, of
a fluid storage and dispensing system 820, according to a further
embodiment of the invention.
[0181] The fluid storage and dispensing system 820 includes a
vessel 822 defining an enclosed interior volume 826 in which is
disposed a stack 828 of adsorbent articles 830, 832, 834, 836, 838,
840 and 842.
[0182] The vessel 822 in this embodiment contains a transformer
winding 850 in the lower portion of the vessel, beneath the stack
828 of carbon adsorbent articles.
[0183] The vessel is positioned above a second transformer winding
852, for inductive coupling of the respective transformer windings
850 and 852.
[0184] The vessel 822 is joined at its upper end to a dispensing
assembly 824, which may include a valve structure and dispensing
port, for egress of desorbed fluid from the vessel, under
dispensing conditions, e.g., when the valve is open to flow, and a
pressure differential, mass transfer gradient, or other transport
condition causes efflux of fluid from the vessel to a downstream
flow circuitry, process tool, or other end use location for the
dispensed fluid.
[0185] The transformer winding 850 and 852 as indicated above are
inductively coupled with one another, and the exterior transformer
winding 852 is suitably coupled with a power supply (not shown) in
circuit relationship therewith, so that the energization of
transformer winding 852 correspondingly energizes transformer
winding 850 and produces a field in the interior volume 828 of
vessel 822, thereby electrically energizing and resistively heating
the carbon adsorbent articles in the stack 828.
[0186] By this arrangement, the resistive heating is carried out in
a non-invasive manner as regards the vessel 822. By avoiding the
need for any openings in the vessel, other than that associated
with the dispensing assembly 824, a vessel can be provided of a
highly reliable character, having only a single seam at the
juncture of the dispensing assembly and the top of the vessel.
[0187] The invention thus contemplates a wide variety of specific
arrangements and embodiments for inputting of electrical energy to
a carbon adsorbent for removal of heels fluid therefrom, which may
be correspondingly embodied and implemented to achieve high fluid
utilization in the use of carbon adsorbent-based fluid storage and
dispensing systems for low pressure dispensing of fluid.
[0188] In another aspect, the invention contemplates a method of
increasing fill capacity of a nanoporous carbon adsorbent, e.g., in
the form of porous carbon discs in a stacked array, such as are
disposed in a fluid storage and dispensing package including a
vessel containing such fluid, in which the stored fluid comprises a
small molecule fluid species. The fill capacity of the porous
carbon adsorbent is the amount of adsorbate that can be taken up by
the adsorbent, i.e., the loading of the adsorbate species on the
adsorbent.
[0189] In this aspect of increasing the loading capacity of the
porous carbon adsorbent, the adsorbent is contacted with a swelling
agent, followed by contacting of the carbon adsorbent with a
pressurized gaseous penetration agent, followed by removal of the
swelling agent and penetration agent, e.g., by vacuum extraction
and heating of the porous carbon to volatilize any residual
swelling agent and penetration agent therein.
[0190] As used herein, the term "swelling agent" refers to an agent
that in contact with the microstructure of the porous carbon
material effects an expansion of the porosity and void structure of
such material. The swelling agent may be of any suitable type, and
may for example include agents such as water, ethers, alcohols or
other organic or inorganic solvent media that effects such
expansion of the porous carbon.
[0191] The term "penetration agent" as used herein refers to an
agent that (1) in a pressurized form is contacted with the porous
carbon material containing the swelling agent to effect transport
of the swelling agent into the porosity and void structure for
enhancement of the loading capacity of the porous carbon material
upon its being subsequently contacted by an adsorbate and (2) is
compatible with the swelling agent to permit the swelling agent and
penetration agent to be volatilized and removed from the porosity
and void structure without loss of the swelling effect of the
swelling agent on such porosity and void structure. The penetration
agent may be of any suitable type, and may for example include
inert gases such as helium, argon, krypton, neon, etc.
[0192] In the one preferred embodiment, the swelling agent
comprises water vapor, and the penetration agent comprises
helium.
[0193] In the removal of the residual swelling agent and
penetration agent from the porosity and void structure of the
porous carbon, after swelling has been effected, it is important
that the removal not involve heating to temperatures of 350.degree.
C. or higher, since temperatures of 350.degree. C. or higher result
in loss of the increased loading capability that is otherwise
obtained when the removal of the swelling agent and penetration
agent is effected at temperatures below 350.degree. C.
[0194] In such aspect of the invention, the carbon adsorbent is
pretreated by exposure to water vapor so that the carbon adsorbent
takes up the water vapor. This water vapor exposure is followed by
contact with helium (or other inert gas, e.g. argon, krypton,
nitrogen, xenon) at elevated pressure, such as pressure in a range
of from 100 to 500 psi. The helium is then removed from the carbon
adsorbent under vacuum, followed by a bake-out at elevated
temperature, e.g., temperature in a range of from 100.degree. C. to
300.degree. C. This yields a pretreated carbon adsorbent having
enhanced adsorptive capacity for the small molecule fluid
species.
[0195] Such pretreatment method can be advantageously employed for
any of a variety of fluid species, and is most beneficially applied
for enhancing activated carbon, e.g., in the form of beads,
granules, tablets, pellets, powders, extrudates, particulates,
cloth or web form articles, monolithic forms, composites of the
porous carbon with other materials, comminuted forms of the
foregoing, and crushed forms of the foregoing, for storage and
dispensing of a gas whose molecules have a relatively flat steric
molecular conformation, as opposed to a spherical conformation. In
one embodiment, the fluid species comprises a halide gas. Examples
of illustrative halide gases include boron trifluoride, diborane,
boron trichloride, phosphorus trifluoride, arsenic pentafluoride,
silicon tetrachloride, germanium tetrafluoride. Boron trifluoride
is a particularly useful gas for storage on and dispensing from
carbon adsorbent that has been treated by such methodology.
[0196] By way of specific example, the carbon adsorbent
pretreatment method of the invention has been demonstrated to
increase the capacity of the carbon adsorbent for boron trifluoride
by levels of 35-50% in relation to corresponding carbon adsorbent
that has not been pretreated in such manner. It will be recognized
that the specific process conditions for the pretreatment method of
the invention can be readily experimentally determined for a given
fluid species, by the simple expedient of varying the process
conditions for the adsorbate gas of interest, and measuring the
loading of adsorbate fluid species that is achievable on the
adsorbent, to determine the adsorbent capacity for such fluid
species.
[0197] The invention correspondingly contemplates a fluid storage
and dispensing apparatus comprising a vessel containing carbon
adsorbent that has been pretreated by the aforementioned
pretreatment method of the invention, prior to the vessel being
charged with fluid to be adsorbed on and subsequently dispensed
from the adsorbent in the vessel.
[0198] The features and advantages of the carbon adsorbent
pretreatment method of the invention are more fully shown by the
following examples. Such examples are intended to be illustrative
of the practice of the carbon pretreatment method in specific
embodiments, and are not intended to be limitingly construed, as
regards the general character and applicability of the carbon
pretreatment method of the invention.
Example 1
[0199] In a standard fill procedure for boron trifluoride gas
storage and dispensing packages, a cylindrical gas vessel is filled
with a stack of activated carbon pucks, and a headpiece is welded
to the gas cylinder. The cylinder fabrication then is completed by
installation of a valve head assembly on the headpiece.
[0200] The resulting gas supply package with the valve in the valve
assembly in an open position, is charged with helium gas at 300 psi
pressure through the valve head assembly, and the valve then is
closed. The helium-containing package next is placed in a vacuum
chamber. The vacuum chamber is subjected to high vacuum, with a
helium gas detector monitoring any leakage of the helium that may
occur from the vessel.
[0201] If the vessel by such testing is determined to be leak-tight
in character, then the helium is removed from the vessel by
applying a high vacuum to the system, followed by a bake-out at
elevated temperature. This procedure drives off residual volatile
components and contaminants from the adsorbent. After cooling to
ambient temperature, the vessel is charged with the boron
trifluoride gas. Once charged, the vessel is sealed by closure of a
fill port or a valve in the valve head assembly, with the adsorbed
boron trifluoride gas stored on the carbon adsorbent. Such stored
boron trifluoride gas can thereafter be desorbed from the carbon
adsorbent under dispensing conditions, such as may include a
pressure differential between the interior volume of the vessel and
a downstream dispensing location exterior of the vessel, and/or
heating of the vessel to effect desorption of the boron trifluoride
from the carbon adsorbent, and/or flowing of a carrier gas through
the interior volume of the vessel to create a concentration
gradient for effecting a desorption of the boron trifluoride gas
from the carbon adsorbent.
Example 2
[0202] A gas supply package is fabricated as in Example 1, but
prior to contacting with helium gas, the carbon adsorbent is
exposed to water vapor so that water vapor is taken up by the
adsorbent. The amount of water vapor taken up by the adsorbent can
be in a range of from 5% to 40% by weight, or more, based on the
weight of carbon adsorbent.
[0203] The gas supply package then is pressurized with helium at
300 psi, as described in Example 1. The vessel after removal of
helium is then subjected to bake-out of the adsorbent, cooling of
the vessel to ambient temperature and is then charged with boron
trifluoride gas.
[0204] Results of Comparative Testing
[0205] A comparative test was carried out to determine the efficacy
of the pretreatment method of Example 2 over the standard method of
Example 1.
[0206] Two series of comparative tests were conducted.
[0207] In the first series, each of four gas cylinder vessels was
loaded with 2550 grams of carbon adsorbent, in the form of a stack
of puck articles of such sorbent. The vessels were then charged
with helium gas. After removal of helium, the vessel was baked out
to remove residual gas and contaminants from the carbon adsorbent
and then charged with boron trifluoride gas.
[0208] The carbon adsorbent in the first vessel (Sample 1) was not
exposed to any water vapor prior to helium charging and bake-out;
the bake-out was conducted at 180.degree. C. The carbon adsorbent
in the second vessel (Sample 2) was exposed to water vapor
resulting in a moisture content of 24.5% by weight on the carbon
adsorbent, based on the weight of the carbon adsorbent, and was
charged with helium prior to bake-out at 180.degree. C. The carbon
adsorbent in the third vessel (Sample 3) was exposed to water vapor
resulting in a moisture content of 25.6% by weight on the carbon
adsorbent, based on the weight of the carbon adsorbent prior to
helium charging and bake-out at 350.degree. C. The carbon adsorbent
in the fourth vessel (Sample 4) was exposed to water vapor
resulting in a moisture content out of 25.3% by weight on the
carbon adsorbent, based on the weight of the carbon adsorbent,
prior to helium charging.
[0209] After helium charging, subsequent removal of the helium gas
and bake-out at 180.degree. C., boron trifluoride was charged to
the vessel and the amount of such boron trifluoride gas taken up by
the adsorbent was measured.
[0210] The results of the first test series are set out in Table 1
below. Samples 2-4 were subjected to moisture exposure prior to
helium pressurization and bake-out, and Sample 1 was not exposed to
moisture prior to such helium pressurization and bake-out.
TABLE-US-00001 TABLE 1 Amount of Boron Trifluoride Taken up by 2550
Grams of Carbon Adsorbent Moisture Pretreatment Amount of Boron
Loading on Bake-Out Trifluoride on Carbon Sample No. Adsorbent
Temperature, .degree. C. Adsorbent, Grams 1 None 180.degree. C.
601.8 2 24.5% 180.degree. C. 841.5 3 25.6% 350.degree. C. 573.8 4
25.3% 180.degree. C. 785.4
[0211] The data in Table 1 showed that the standard pretreatment of
the carbon adsorbent (Sample 1), without moisture exposure before
the helium pressurization and bake-out, produced a boron
trifluoride loading on the carbon adsorbent of 23.6% (=601.8 g of
boron trifluoride/2550 g of carbon adsorbent).
[0212] Sample 2, with moisture pretreatment producing 24.5%
moisture loading on the adsorbent, helium pressurization and a
bake-out temperature of 180.degree. C., produced a boron
trifluoride loading on the carbon adsorbent of 33%.
[0213] Sample 3, with moisture pretreatment producing 25.6%
moisture loading on the adsorbent, helium pressurization and
bake-out temperature of 350.degree. C., produced a boron
trifluoride loading on the carbon adsorbent of 22.5%.
[0214] Sample 4, with moisture pretreatment producing a 25.3%
moisture loading on the adsorbent, helium pressurization and
bake-out temperature of 180.degree. C., produced a boron
trifluoride loading on the carbon adsorbent of 34%.
[0215] In the second test series, all conditions were maintained
the same as in the first test series, but the amount of activated
carbon adsorbent was 2525 grams instead of 2550 grams.
[0216] Data for the second test series are set out in the Table 2
below.
TABLE-US-00002 TABLE 2 Amount of Boron Trifluoride Taken up by 2525
Grams of Carbon Adsorbent Moisture Pretreatment Amount of Boron
Loading on Bake-Out Trifluoride on Carbon Sample No. Adsorbent
Temperature, .degree. C. Adsorbent, Grams 5 None 180.degree. C.
518.6 6 24.5% 180.degree. C. 833.3 7 25.6% 350.degree. C. 568.1 8
25.3% 180.degree. C. 777.7
[0217] The data in Table 2 showed that the standard pretreatment of
the carbon adsorbent (Sample 5), without moisture exposure before
the helium pressurization and bake-out, produced a boron
trifluoride loading on the carbon adsorbent of 20.5% (=518.6 g of
boron trifluoride/2525 g of carbon adsorbent).
[0218] Sample 6, with moisture pretreatment producing 24.5%
moisture loading on the adsorbent, helium pressurization and a
bake-out temperature of 180.degree. C., produced a boron
trifluoride loading on the carbon adsorbent of 33%.
[0219] Sample 7, with moisture pretreatment producing 25.6%
moisture loading on the adsorbent, helium pressurization and
bake-out temperature of 350.degree. C., produced a boron
trifluoride loading on the carbon adsorbent of 22.4%.
[0220] Sample 8, with moisture pretreatment producing a 25.3%
moisture loading on the adsorbent, helium pressurization and
bake-out temperature of 180.degree. C., produced a boron
trifluoride loading on the carbon adsorbent of 30.8%.
[0221] Accordingly, the data in Tables 1 and 2 showed that the
moisture exposure/helium exposure and bake-out pretreatment method
of the invention produced a loading of boron trifluoride that was
approximately 50% higher than the boron trifluoride loading
achievable with the corresponding pretreatment method of the prior
art lacking such moisture exposure.
[0222] The present invention in various additional aspects relates
to nanoporous carbon materials suitable for tribological and
ultra-tough structural materials applications, as well having
utility in fluid storage/dispensing applications. The invention
also relates to systems and methods utilizing such nanoporous
carbon materials.
[0223] The invention in one aspect relates to nanoimpregnated
carbon composite materials that are impregnated with complimentary
materials to yield composites that are useful for a variety of
purposes, e.g., as tribological materials of high wear-resistant
character, as ballistically tough materials, and as armor and
armor-piercing materials.
[0224] The impregnant can be of any suitable type, as introduced
into the porosity of the carbon material to yield a composite
having desired properties for a given use application. For such
purpose, the carbon material suitably has a porosity comprising
pores that are sufficiently deep and extensive throughout the
material to enable impregnation to be effected in a simple and
efficient manner. For example, the carbon may have nanoporosity
including pores having an average pore diameter of less than 10 nm,
it being recognized that the specific pore size, pore size
distribution, pore tortuosity, etc., may be varied widely in the
general practice of the present invention.
[0225] Illustrative techniques that may be employed to impregnate
the porosity of the carbon material include, without limitation,
solution deposition, vapor deposition, ion implantation, etc.
[0226] In one embodiment, the impregnant material includes
polymers. As an example of an application of such polymer
impregnation, a nanoporous carbon material may be impregnated with
a polymer such as high molecular weight silicone or polyethylene
glycol to produce a super-tough ballistic armor. In the use of such
impregnated material, increasing impact of the material will result
in the polymer forming long-range linkages between graphitic
plates, so that a high degree of fracture toughness is
achieved.
[0227] Alternatively, polymeric fibers such as long chain aramid
fibers, or fibers commercially available under the trademarks
Kevlar, PBO, Zorlon and Spectra can be employed as the impregnant.
The objective in such impregnation is to attain polymeric
penetration of the nanopores to provide multiple anchor points and
a three-dimensional array of high-strength fibers, yielding a high
fracture toughness material. Such impregnated materials afford the
advantages of decreased weight, increased strength, and the ability
to form molded structures in a green state that permits uniquely
shaped ballistically tough materials to be obtained.
[0228] In another embodiment, the impregnant material is selected
from among hard materials, the term "hard" denoting materials that
have intrinsic hardness and toughness characteristics that
distinguish them from "soft" materials such as the polymers and
fibers described above.
[0229] The impregnant in such applications can be a precursor
material that reacts in situ with the carbon to form carbides
and/or other reaction products providing the desired properties. As
an example, tungsten can be impregnated into nanoporosity of the
carbon material by suitable vapor phase deposition techniques, such
as by volatilization of an organotungsten precursor so that
tungsten vapor permeates the pores of the carbon material, and is
converted during the deposition and/or by subsequent heat treating
of the material to tungsten carbide.
[0230] Tungsten carbide is a highly dense material, and one of the
hardest materials known. Its use has heretofore been limited due to
its difficult-to-machine character. Such difficulty can be
surmounted by a provision of a shaped porous carbon article of the
ultimate desired conformation, which subsequent to formation of
tungsten carbide in porosity thereof provides the finished article
having the desired dimensions and configuration. The carbon
porosity could for example be penetrated using chemical vapor
deposition techniques employing tungsten carbonyl or tungsten
hexafluoride to provide tungsten deposits in the pores that then
react under elevated temperature conditions to form tungsten
carbide in situ.
[0231] Such carbon/tungsten carbide composites can be manufactured
to provide a replacement material for depleted uranium, e.g., in
projectiles for use as armor piercing weapons. Currently, depleted
uranium is used for such armor piercing applications, but depleted
uranium is a toxic material that is the focus of international
efforts to eliminate same from use in weaponry.
[0232] More generally, such carbon porosity impregnation can be
employed to form structurally graded materials, in which porosity
is impregnated to a certain depth or dimension of the porous
carbon, or in which diffusional characteristics are employed to
provide a concentration gradient of the impregnant over a depth or
dimension of the porous carbon material.
[0233] Other hard impregnants that may be useful in specific
embodiments of the invention include, without limitation, lead,
titanium, aluminum, aluminum oxide, silicon, silicon oxide and the
like.
[0234] The use of an impregnant to at least partially fill porosity
of porous carbon material enables the creation of new composite
materials, with the ability to create a wide variety of
conformations and structural forms in a green state that then can
be converted to materials of a desired shape and/or functional
character, e.g., ultra-hard and/or densified materials useful in
armor piercing bullets and the corresponding dense armor.
[0235] In other embodiments of the invention, porous carbon is
incorporated with boron to provide a hydrogen storage medium of
high hydrogen loading capacity. The boronated porous carbon then
can be loaded with hydrogen, so that hydrogen is stored by the
porous carbon and released therefrom under dispensing conditions to
provide hydrogen, e.g., for a hydrogen fuel cell or other
hydrogen-utilizing apparatus or process. In this way, the
boron-containing porous carbon provides a hydrogen storage medium
having high loading capacity as useful for applications such as
hydrogen-powered vehicles.
[0236] The boron can be incorporated in the porous carbon material
in any suitable manner and by any suitable technique. In one
preferred embodiment, boron is at least partially introduced into
the porous carbon material by ion implantation, and combinations of
ion implantation of boron and vapor deposition or solution
deposition techniques can be employed to create boron-containing
carbon materials of desired properties.
[0237] Another aspect of the invention relates to the use of porous
carbon as a chlorine storage medium at subatmospheric storage
conditions. Although porous carbon has heretofore been employed as
a storage medium for a wide variety of fluids and gases that are
adsorbable on such material, chlorine has not been considered for
such storage applications, since liquids typically occupy many
orders of magnitude less volume than gases, and since chlorine is
normally stored and transported in pressurized liquid form.
[0238] Such pressurized liquid form of chlorine, however, presents
issues of safety and toxicity, particularly when the amount of
chlorine involved is large. For example, on Jan. 6, 2005, a Norfolk
Southern Corp. freight train carrying chemicals hit a parked train
near the Avondale Mills Plant in Graniteville, S.C., USA. The
chemicals being transported by the freight train included
pressurized liquid-form chlorine. As a result of the collision,
toxic chlorine gas was released into the air surrounding the crash
site, which caused the deaths of 10 individuals and required the
evacuation of 5000 people from nearby residences.
[0239] The storage of chlorine in gaseous form as an adsorbate on
porous carbon would on initial consideration not appear to be
economically viable or practical as a mode of packaging chlorine,
but it has surprisingly been found that when comparing the loading
capacity of a confined volume holding pressurized liquid chlorine,
with the capacity of an equal volume of porous carbon having
chlorine gas adsorbed thereon at subatmospheric pressure, the
actual capacity of the porous carbon exceeds the capacity of the
high-pressure liquid containment volume by approximately 30%.
[0240] As applied to the catastrophic release of chlorine at the
Graniteville, S.C., USA crash site, the transport of the same
amount of chlorine gas (as carried by the Norfolk Southern Corp.
freight train) in tube-trailer type rail cars containing porous
carbon adsorbent at less than atmospheric pressure, would have
resulted in the rate of the release of chlorine being reduced by
approximately 1/100,000th compared to the high pressure release
that caused the death and damage that occurred.
[0241] The surprising capacity improvement in chlorine storage that
is achievable by gaseous chlorine storage on porous carbon, as
compared to capacity of a corresponding confinement volume of
pressurized chlorine liquid, is due to the fact that the
confinement volume is limited in the amount of pressurized chlorine
liquid that can be stored, since changes in ambient temperature of
the confinement volume can cause evaporation, gas expansion and
rupture of the containment structure. Accordingly, the confinement
volume holding pressurized chlorine liquid must be designed and
employed to accommodate increases in temperature of the environment
in which the confinement volume resides, as well as evaporation and
gas expansion deriving from the liquid chlorine.
[0242] In the storage of gaseous chlorine on porous carbon at
subatmospheric pressure, however, the chlorine gas is held on the
porous carbon adsorbent by physical adsorption forces, enabling the
volume containing the porous carbon adsorbent to be much more
effectively used at subatmospheric pressure than is achievable by
the corresponding volume in which pressurized chlorine liquid is
held. As a result, a surprising and unexpected improvement in
chlorine storage capacity is achieved, with an accompanying high
level of safety improvement, as a result of the subatmospheric gas
storage condition of the chlorine gas adsorbed on the porous
carbon.
[0243] Thus, chlorine gas can be efficiently stored in an adsorbed
state at subatmospheric pressure, to obviate the hazards associated
with prior art storage and transport of pressurized liquid
chlorine, with markedly improved capacity of chlorine per unit of
storage volume. At the point of use, the chlorine gas is readily
dispensed from the porous carbon adsorbent, by any of suitable
thermally-mediated desorption, pressure gradient-mediated
desorption, and/or concentration gradient-mediated desorption
techniques. For example, a vacuum pump may be employed to effect
desorption of chlorine from the porous carbon in the dispensing
operation.
[0244] In addition to chlorine, such sorbent-based storage and
dispensing approach may be applied to ammonia, or to phosgene, or
to other industrial gases.
[0245] Referring now to the drawings, FIG. 14 is a perspective view
of an impregnated carbon structural member 10 according to one
embodiment of the invention. The impregnated carbon structural
member 10 is constituted by a main body portion 12 having a front
surface 14 in the view shown.
[0246] The impregnated carbon structural member 10 can be a
constituent portion of an article of widely varying type. Such
member can for example be fabricated from a porous carbon that is
impregnated with long chain aramid fibers, or fibers commercially
available under the trademarks Kevlar, PBO, Zorlon and Spectra, or
with long chain silicone or polyethylene glycol polymers, or with
tungsten carbide or other metal carbide. The porous carbon for such
application can be formed or provided with porosity of any suitable
pore size and pore size distribution, as appropriate to the end use
of the structural member.
[0247] The structural member itself can be employed for any of a
variety of applications, such as ultra-tough composite body armor,
vehicular armor, bumper member or impact element, or as a densified
material for construction or coating of munitions articles, as a
casing material for rugged notebook computers, personal digital
assistants, extreme sport watches, and deep sea sensor assemblies,
etc.
[0248] The impregnant component may be deposited in the porosity of
the porous carbon material in any suitable manner, such as vapor
deposition (chemical vapor deposition, plasma contacting, etc.),
solution deposition, vacuum evacuation and high pressure
impregnation of the pores, or any other technique or methodology
that is effective to introduce the reinforcement component or a
precursor thereof into the porosity of the porous carbon.
[0249] FIG. 15 is a schematic elevation view of a fluid storage and
dispensing apparatus 42 according to one embodiment of the
invention, as arranged for supplying fluid to a fluid-utilizing
facility 56 in a process system 40.
[0250] The fluid storage and dispensing apparatus 42 as shown
includes a fluid storage and dispensing vessel 44 containing a
sorbent medium 48, which may be formed of a porous carbon material,
in a discontinuous (e.g., bead or pellet) form, or alternatively in
a monolithic bulk form, such as one or more porous carbon sorbent
articles, each of which may be in the form of a brick, block, disc,
sheet or other conformation for use in storing and dispensing
fluids such as gases for fluid-utilizing applications.
[0251] The vessel 44 is joined at its upper neck region to a valve
head assembly 46 including a flow control valve element (not shown)
in the valve body that is translatable between fully open and fully
closed positions under the controlling action of the handwheel 50,
to effect discharge of the fluid from the vessel 44. By opening the
valve, to expose the interior volume of the vessel 44 to the lower
pressure in the line 52 coupled to the discharge port of the valve
head assembly, fluid adsorbed on the porous carbon sorbent medium
in the vessel is caused to desorb and to flow through the valve in
the valve head and through the discharge port to the fluid
discharge line 52 for dispensing.
[0252] The fluid can be dispensed from the vessel 44 in any
suitable manner, e.g., in which the dispensing comprises at least
one dispensing modality selected from the group consisting of
thermally-mediated desorption, pressure gradient-mediated
desorption, and concentration gradient-mediated desorption
[0253] The dispensed fluid in line 52 flows through flow control
unit 54 to the fluid-utilizing facility 56. The flow control unit
may include any suitable flow control devices or flow modulating
elements, such as for example, regulators, mass flow controllers,
restricted flow orifices, flow control valves, pumps, compressors,
venturis, eductors, flow-smoothing surge vessels, etc. The flow
control unit may for example include a vacuum pump for extraction
of the fluid from the vessel.
[0254] The fluid-utilizing facility 56 may be of any suitable type,
as appropriate to the specific fluid that is being delivered. The
facility may for example be a manufacturing process facility, a
chemical reactor, distribution or blending facility, or the
like.
[0255] In one embodiment of the invention, the porous carbon 48 in
the vessel 44 has boron impregnated in the porosity of the carbon
medium, e.g., by ion implantation of boron in the porosity from a
precursor such as diborane, borohydride or other boron source
material, and functions as a hydrogen gas storage medium. Under
dispensing conditions, hydrogen is desorbed from the sorbent medium
and flows into the dispensing line 52 to the hydrogen-utilizing
facility 56, which may be constituted by a hydrogen fuel cell unit
wherein the hydrogen fuel is used to generate a power output, e.g.,
for vehicular propulsion.
[0256] In another embodiment of the invention, the porous carbon 48
in the vessel 44 has chlorine gas adsorbed thereon, for storage of
chlorine and selective dispensing thereof from the vessel. The
vessel in lieu of the gas supply cylinder shown, may be configured
as a tube trailer vessel, or a railcar vessel, for motive transport
of chlorine. By such sorptive holding of the chlorine in an
adsorbed state on the porous carbon adsorbent medium, the chlorine
is maintained in an inherently safer state than high pressure gas
vessels of the prior art.
[0257] As indicated earlier herein, such sorbent-based storage and
dispensing arrangement may be applied to phosgene, ammonia or other
industrial gases, to store and transport such gases in an
inherently safer form that the high pressure containment structures
of the prior art.
[0258] While the invention has been described herein in reference
to specific aspects, features and illustrative embodiments of the
invention, it will be appreciated that the utility of the invention
is not thus limited, but rather extends to and encompasses numerous
other variations, modifications and alternative embodiments, as
will suggest themselves to those of ordinary skill in the field of
the present invention, based on the disclosure herein.
Correspondingly, the invention as hereinafter claimed is intended
to be broadly construed and interpreted, as including all such
variations, modifications and alternative embodiments, within its
spirit and scope.
* * * * *