U.S. patent application number 12/261498 was filed with the patent office on 2010-02-04 for continuous production of carbon nanomaterials using a high temperature inductively coupled plasma.
This patent application is currently assigned to Plasmet Corporation. Invention is credited to Andreas Blutke, Robert Ferguson, Mark Henderson, John Vavruska.
Application Number | 20100025225 12/261498 |
Document ID | / |
Family ID | 34079040 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100025225 |
Kind Code |
A1 |
Henderson; Mark ; et
al. |
February 4, 2010 |
CONTINUOUS PRODUCTION OF CARBON NANOMATERIALS USING A HIGH
TEMPERATURE INDUCTIVELY COUPLED PLASMA
Abstract
High-power inductively coupled plasma technology is used for
thermal cracking and vaporization of continuously fed carbonaceous
materials into elemental carbon, for reaction with separate and
continuously fed metal catalysts inside a gas-phase
high-temperature reactor system operating at or slightly below
atmospheric pressures. In one particularly preferred embodiment,
in-flight growth of carbon nanomaterials is initiated, continued,
and controlled at high flow rates, enabling continuous collection
and product removal via gas/solid filtration and separation
methods, and/or liquid spray filtration and solid collection
methods suitable for producing industrial-scale production
quantities. In another embodiment, the reaction chamber and/or
filtration/separation media include non-catalytic or catalytic
metals to simultaneously or separately induce on-substrate
synthesis and growth of carbon nanomaterials. The on-substrate
grown carbon nanomaterials are produced in secondary chambers that
are selectively isolated for periodic removal of the product.
Inventors: |
Henderson; Mark; (Pasco,
WA) ; Vavruska; John; (Santa Fe, NM) ; Blutke;
Andreas; (Richland, WA) ; Ferguson; Robert;
(Richland, WA) |
Correspondence
Address: |
LAW OFFICES OF RONALD M ANDERSON
600 108TH AVE, NE, SUITE 507
BELLEVUE
WA
98004
US
|
Assignee: |
Plasmet Corporation
Walla Walla
WA
|
Family ID: |
34079040 |
Appl. No.: |
12/261498 |
Filed: |
October 30, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10865677 |
Jun 10, 2004 |
|
|
|
12261498 |
|
|
|
|
60477710 |
Jun 10, 2003 |
|
|
|
Current U.S.
Class: |
204/157.47 ;
422/186; 977/742; 977/842; 977/845 |
Current CPC
Class: |
D01F 9/12 20130101; B82Y
30/00 20130101; B01J 2219/0886 20130101; Y10S 977/844 20130101;
B01J 19/088 20130101; B01J 2219/0894 20130101; B01J 2219/0871
20130101; B82Y 40/00 20130101; C01B 32/05 20170801; B01J 2219/0807
20130101; C01B 2202/02 20130101; C01B 2202/06 20130101; B01J
2219/0869 20130101; B01J 2219/0892 20130101; C01B 32/162
20170801 |
Class at
Publication: |
204/157.47 ;
422/186; 977/742; 977/845; 977/842 |
International
Class: |
C01B 31/02 20060101
C01B031/02; B01J 19/08 20060101 B01J019/08 |
Claims
1. A method for producing carbon nanomaterials (CNMs) in-flight
within a gas flow in a reactor using an inductively coupled plasma
(ICP), comprising the steps of: (a) establishing a gas flow within
the reactor, the reactor being configured to inhibit growth of CNMs
on internal surfaces of the reactor; (b) introducing the ICP into
the reactor; (c) introducing a carbonaceous material into the
reactor, such that the ICP heats and reacts with the carbonaceous
material to produce free carbon; (d) introducing a catalyst into
the gas flow within the reactor, the catalyst having been selected
to enhance the production of CNMs from the free carbon within the
gas flow, such that the CNMs thus produced are entrained within the
gas flow; (e) directing the gas flow and entrained CNMs out of the
reactor; and (f) separating the CNMs from the gas flow outside of
the reactor.
2. The method of claim 1, wherein the step of separating the CNMs
from the gas stream outside of the reactor comprises the step of
sorting the CNMs into different groups of CNMs based on size.
3. The method of claim 1, further comprising the step of producing
the CNMs continuously, continuous production being facilitated by
separating the CNMs from the gas stream outside of the reactor, as
the reactor need not be shut down periodically to remove CNMs
accumulated within the reactor.
4. The method of claim 1, wherein the step of introducing the ICP
into the reactor comprises the step of using an inert gas to
generate the ICP.
5. The method of claim 1, wherein the step of introducing the ICP
into the reactor comprises the step of using carbon monoxide to
generate the ICP.
6. The method of claim 1, wherein the step of introducing the
catalyst into the reactor comprises one step selected from the
group consisting of: (a) introducing the catalyst into the reactor
such that relatively smaller catalytic particles are achieved,
thereby favoring the production of single wall carbon nanotubes;
(b) introducing the catalyst into the reactor such that relatively
larger catalytic particles are achieved, thereby favoring the
production of multi-walled carbon nanotubes; (c) introducing a
metal powder; and (d) introducing a metal salt.
7. The method of claim 1, further comprising the step of filtering
the gas flow exiting the reactor to recover the catalyst, and
recycling the catalyst by reintroducing the catalyst into the
reactor.
8. The method of claim 1, further comprising the step of directing
the gas flow exiting the reactor into a secondary chamber, before
separating the CNMs from the gas flow, the secondary chamber
providing additional residence time to promote the growth of longer
CNMs.
9. The method of claim 8, further comprising at least one step
selected from the group consisting of: (a) using supplemental heat
to maintain the temperature conditions in the secondary chamber
above a threshold value required to facilitate the additional
growth of the CNMs; (b) introducing additional carbonaceous
materials into the secondary chamber to provide additional carbon
to facilitate the additional growth of the CNMs; and (c) directing
the gas flow over a substrate in the secondary chamber, such that
CNMs are formed on the substrate, as well as being formed in-flight
in the gas flow.
10. The method of claim 1, further comprising at least one step
selected from a group consisting of: (a) providing a reactor that
does not include structures that would inhibit a free flow of gas
within the reactor, such that a deposition of CNMs on internal
surfaces of the reactor is minimized; and (b) providing a reactor
whose internal surfaces are non-metallic, such that a deposition of
CNMs on internal surfaces of the reactor is minimized.
11. The method of claim 1, further comprising the step of
establishing a negative pressure condition within the reactor, such
that the gas flow is pulled through the reactor.
12. The method of claim 1, wherein the step of introducing the
carbonaceous material into the reactor comprises the step of
introducing the carbonaceous material into the reactor at more than
one location, in order to prevent carbon concentrations in any one
part of the reactor to favor the formation of soot.
13. A method for producing carbon nanomaterials (CNMs) both
in-flight and on a substrate, using an inductively coupled plasma,
comprising the steps of: (a) using the ICP to establish a gas flow
in a reactor, the reactor being configured to inhibit growth of
CNMs on surfaces within the reactor; (b) introducing a carbonaceous
material into the reactor, such that the ICP reacts with the
carbonaceous material to produce free carbon in the reactor; (c)
introducing a catalyst into the gas flow, such that the catalyst
stimulates the combination of free carbon to form CNMs in-flight
within the gas flow in the reactor; and (d) directing the gas flow
from the reactor into a secondary chamber including a substrate
configured to encourage growth of CNMs on the substrate, such that
CNMs are formed on the substrate in the secondary chamber.
14. The method of claim 13, further comprising the steps of: (a)
collecting a process gas including CNMs entrained in the process
gas from at least one of the reactor and the secondary chamber; and
(b) separating the CNMs from the process gas, such that the CNMs
are sorted into different groups of CNMs based on size.
15. The method of claim 13, wherein the step of introducing the
catalyst into the reactor comprises one step selected from the
group consisting of: (a) introducing the catalyst into the reactor
such that relatively smaller catalytic particles are achieved,
thereby favoring the production of single wall carbon nanotubes;
and (b) introducing the catalyst into the reactor such that
relatively larger catalytic particles are achieved, thereby
favoring the production of multi-walled carbon nanotubes.
16. The method of claim 13, further comprising at least one step
selected from the group consisting of: (a) using supplemental heat
to maintain the temperature conditions in the secondary chamber
above a threshold value required to facilitate the additional
growth of the CNMs; and (b) introducing additional carbonaceous
materials into the secondary chamber to provide additional carbon
to facilitate the additional growth of the CNMs.
17. The method of claim 13, wherein the step of introducing the
carbonaceous material into the reactor comprises the step of
introducing the carbonaceous material into the reactor at more than
one location, in order to prevent carbon concentrations in any one
part of the reactor to favor the formation of soot.
18. A system for using an inductively coupled plasma (ICP) to
generate carbon nanomaterials (CNMs), comprising: (a) a plasma
generator capable of a sustained production of the ICP, the plasma
generator being coupled to a source of electrical power; (b) a
reactor configured to receive the ICP and a carbonaceous material,
the carbonaceous material being reformed in a gas stream in the
reactor into free carbon, which in the presence of a suitable
catalyst that is provided in the reactor, combine to produce CNMs
in-flight; and (c) a filter unit configured to remove the CNMs from
the gas stream exiting the reactor.
19. The system of claim 18, wherein the reactor is configured to
operate under at least one set of conditions selected from a group
consisting of: (a) substantially atmospheric pressure; and (b) a
pressure that is sufficiently negative such that the gas stream is
pulled through the reactor.
20. The system of claim 18, wherein internal surfaces of the
reactor are configured to inhibit the formation of CNMs on the
internal surfaces, the internal surfaces comprising at least one
element selected from a group consisting of: (a) substantially
smooth surfaces that do not inhibit gas flow through the reactor;
(b) substantially non-metallic surfaces; (c) glass surfaces; (d)
ceramic surfaces; and (e) quartz surfaces.
21. The system of claim 18, wherein the filter unit is configured
to separate the CNMs into different products according to size.
22. The system of claim 18, further comprising at least one
additional process unit selected from a group consisting of: (a) a
secondary reaction unit having an inlet and an outlet, and
configured to receive the gas stream exiting the reactor, the
secondary reaction unit being disposed between the reactor and the
filter unit, the secondary reaction unit increasing a residence
time of the gas stream and thereby providing additional time for
formation of the CNMs; (b) a catalyst recovery unit configured to
remove a catalyst entrained within the gas stream; and (c) a
product integration unit configured to receive CNMs from the filter
unit and to incorporate the CNMs into a product.
23. The system of claim 22, wherein the secondary reaction chamber
comprises at least one member selected from the group consisting
of: (a) a substantially tubular chamber such that the gas stream is
not required to change direction while traversing the secondary
reaction chamber; (b) a substantially tubular chamber including a
plurality of bends, such that the gas stream is required to change
direction while traversing the secondary reaction chamber; (c) a
plurality of ports, the plurality of ports enabling at least one of
an introduction of additional process materials, and a collection
of a product; and (d) a substrate configured to encourage formation
of CNMs on the substrate.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of a copending patent
application Ser. No. 10/865,677, filed on Jun. 10, 2004, the
benefit of the filing date of which is hereby claimed under 35
U.S.C. .sctn.120. Copending patent application Ser. No. 10/865,677
is based on prior provisional application Ser. No. 60/477,710,
filed on Jun. 10, 2003, the benefit of the filing date of which is
hereby claimed under 35 U.S.C. .sctn.119(e).
FIELD OF THE INVENTION
[0002] The present invention relates to method and apparatus for
utilizing an inductively coupled plasma torch to produce carbon
nanomaterials, and more specifically, relates to a method and
apparatus for producing graphitic single-wall carbon nanotubes,
graphitic multi-walled carbon nanotubes, graphitic carbon
nanofibers, and amorphous carbon nanowires in a continuous-flow,
in-flight production process.
BACKGROUND
[0003] Carbon nanotubes are seamless tubes of graphite sheets with
complete fullerene caps and were first discovered as multi-layer
concentric tubes or multi-walled carbon nanotubes, and
subsequently, as single-wall carbon nanotubes. Nanotubes are
typically formed in the presence of transition metal catalysts.
Carbon nanotubes have shown promise in applications such as
nanoscale electronic devices, high strength materials, thermally
and electrically conducting materials, electron field emission
devices, tips for scanning probe microscopy, gas filtration, and
gas storage.
[0004] For a number of applications, single-wall carbon nanotubes
(SWCNTs) are preferred over multi-walled carbon nanotubes, because
they have fewer defects and are therefore stronger and more
conductive than multi-walled carbon nanotubes (MWCNTs) of similar
length. Defects are less likely to occur in SWCNTs. MWCNTs can
survive occasional defects by forming bridges between unsaturated
carbon valances, while SWCNTs have no neighboring walls to
compensate for such defects.
[0005] The availability of carbon nanotubes in quantities necessary
for practical technology development and application is
problematic. The development of efficient processes for producing
carbon nanotubes of consistent high quality in quantity is the key
to the commercialization of specialty carbon nanomaterials
(CNMs).
[0006] Conventional carbon fiber materials and fiberglass are used
as additives in composite polymeric materials, for structural
reinforcement. Conventional carbon fibers and metal fibers are used
as additives in polymers to provide electrical conductive
properties required to dissipate static electricity, to provide
electromagnetic shielding, and to increase thermal conductivity.
Graphite carbon nanofibers have been utilized as a replacement
additive for conventional carbon fibers, resulting in improvements
in the mechanical and electrical properties of numerous polymer
blends. Significant reduction in weight and production costs of
finished products has been demonstrated. Although several companies
in the conductive plastic industry are starting to incorporate
carbon nanofibers in their products, they cite price, product
consistency, and supply reliability as major issues. It would
therefore be desirable to develop a method and apparatus for cost
effectively producing commercial quantities of CNMs.
[0007] It is recognized that amorphous carbon nanowires have lower
mechanical strength and electrical conduction than carbon
nanotubes. However, carbon nanowires have large active surface
areas that appear to be beneficial for applications such as
ultra-filtration and hydrogen storage. The suitability of carbon
nanowires for such applications is currently under
investigation.
[0008] Presently, there are three main approaches for synthesis of
carbon nanotubes. These include the laser ablation of carbon
(Thess, A. et al., Science 273:483 (1996)), the electric arc
discharge of a graphite rod (Journet, C. et al., Nature 388:756
(1997)), and the chemical vapor deposition (CVD) of hydrocarbons
(Qin, L. et al., Appl. Phys. Lett. 72:26 (1998)).
[0009] SWCNTs are reported to have been produced at a rate of 10
grams per day by CVD in a high-pressure (30 to 50 atm),
high-temperature (900.degree. C. to 1,100.degree. C.) process
(HiPco Process), using carbon monoxide (CO) as the carbonaceous
precursor material and a liquid catalyst in a small continuous-flow
reactor (Bronikowski, M. et al., J. Vac. Sci. Technol. A 19(4),
(2001)). Such a technique suffers from the disadvantages of
requiring high pressure systems (which significantly increases
operating costs), having a production rate that is insufficient to
meet the anticipated demand for CNMs, and for being able to utilize
only a single feedstock (CO). It would therefore be desirable to
provide a method and apparatus for producing CNMs that does not
require high pressure systems, that can produce larger quantities
of CNMs, and which can use various different feed stocks.
[0010] The production of MWCNTs by catalytic hydrocarbon cracking
is now being achieved on a commercial scale (see U.S. Pat. No.
5,578,543), while the production of SWCNTs is still only achievable
in gram scale quantities by the laser ablation technique
(Smiljanic, O. et al., INRS Energie et Materiaux, Canada,
Sa-PS2-Sy27, Log No. P109, (2002)) and arc discharge technique.
Both the laser ablation method and the arc discharge method suffer
from being difficult to implement as large quantity production
processes (Zheng, B. et al., Appl. Phys. A74:345-348 (2002)). New
and refined techniques for SWCNTs production are in the
introduction phase (Resasco et al., U.S. Pat. No. 6,333,016).
[0011] CVD over transition metal catalysts (on-substrate method)
has produced both MWCNTs and SWCNTs. The catalyst selection and
surface preparation strongly influence the CNM morphology. Laser
ablation, arc techniques, and the catalytic hydrocarbon cracking
process can be used for the production of SWCNTs. Dai, et al.
demonstrated web-like SWCNTs resulting from the disproportionation
of carbon monoxide (CO) with a molybdenum (Mo) catalyst supported
on alumina, heated to 1200.degree. C. From the reported electron
microscope images, the Mo metal apparently attaches to the
nanotubes at their tips. The reported diameter of SWCNTs generally
varies from 1 nm to 5 nm, and seems to be controlled by the
particle size of the Mo catalyst. Catalysts containing iron,
cobalt, or nickel have been used at temperatures between
850.degree. C. to 1200.degree. C., to form MWCNTs (U.S. Pat. No.
4,663,230). Rope-like bundles of SWCNTs have been generated during
the thermal cracking of benzene with an iron catalyst and sulfur
additives, at temperatures between 1100.degree. C.-1200.degree. C.
The synthesized SWCNTs are roughly aligned in bundles and woven
together like those obtained from the laser ablation and electric
arc methods.
[0012] Vaporizing targets, including one or more Group VI or Group
VIII transition metals, and graphite using lasers to form SWCNTs
have been proposed. The use of metal catalysts, including iron and
at least one element selected from Groups V (V, Nb, and Ta), VI
(Cr, Mo, and W), VII (Mn, Tc, and Re), or the lanthanides, has also
been proposed (see U.S. Pat. No. 5,707,916). Recently, new methods
have been proposed that use catalysts to produce quantities of
nanotubes having a high ratio of SWCNTs to MWCNTs (Resasco et al.,
U.S. Pat. No. 6,333,016).
[0013] As applications for graphite carbon nanotubes, carbon
nanofibers, and amorphous carbon nanowires develop, the demand for
these products will grow. Market introduction of CNM for producing
products and in other applications is highly dependent on the
availability of cost effective production methods.
[0014] The majority of the processes described above involve
growing the CNM on a substrate. On-substrate growth rates of up to
145 nm per second are reported by Portland State University, for
the synthesis of multiple-wall carbon nanotubes, with tube lengths
of tens of micrometers, suggesting growth durations of more than
one minute. However, these on-substrate growth processes are batch
mode processes, and as such, are restricted to relatively low
production rates. Substrate preparation is labor intensive and time
consuming, as is product collection and refinement. It would be
desirable to develop a method and apparatus for producing
commercial quantities of such CNMs in a less labor intensive and
more efficient manner.
[0015] Of the above-described processes, the only continuous
production process (the HiPco Process introduced by M. Bronikowski
et al.) appears to be limited to a production of 10 g/day (or less
than 5 kg/year) of SWCNTs. Such nanotubes are rather short in
length compared to other CNMs, which translates to relatively short
durations in a temperature-controlled annealing reactor.
Continuous-flow methods at production rates of many hundreds of
tons per year of product are required to enable large scale
introduction of CNMs, and to reduce unit product costs.
[0016] It is noted that the purification and separation of mixed
CNMs significantly increases the costs of carbon nanotube
production. Continuous processing of materials versus batch mode
processing (such as the substrate-based CVD process) offers
significant cost reduction potential, due to significant increases
in production rates, which requires continuous product collection,
product removal, separation, and purification (if needed). It would
therefore be desirable to develop a method and apparatus for
product collection, product removal, and product separation of
different CNMs. It would further be desirable to develop a method
and apparatus adapted to produce CNMs that do not require a high
level of separation and purification.
[0017] Inductively coupled plasma (ICP) systems are used in a wide
range of applications, including gas spectroscopy, plasma spraying,
materials synthesis, waste destruction and waste-to-energy
applications (e.g., Vavruska, J. et al., entitled "Induction Steam
Plasma Torch For Generating a Steam Plasma For Treating a Feed
Slurry" (U.S. Pat. No. 5,611,947), and Blutke, A. et. al., entitled
"Use of a Chemically Reactive Plasma For Thermal-Chemical
Processes" (U.S. Pat. No. 6,153,852)).
[0018] Knight, R. et al. have reported isolating carbon nanotubes
from residues produced and collected in a reactor energized using
an ICP, entitled "Thermal Plasma Process For Recovering Monomers
and High Value Carbons From Polymeric Materials" (U.S. Pat. No.
6,444,864). Withers, J. et al., report using a variety of heating
devices in the formation of free carbon and fullerene collection in
soot particulate in "Methods and Apparati For Producing Fullerenes"
(U.S. Pat. No. 5,876,684). This patent emphasizes the use of arc
plasma technology, but ICP technology, laser beams, and microwave
plasmas are listed as potential heat sources. Neither of these
methods discloses in-flight synthesis or continuous product
collection and removal. It would be desirable to incorporate such
features in an ICP based CNM production process and related
apparatus.
[0019] A substrate-based method using ICP has been published by
NASA Ames Research Center (Delzeit, L. et al., Journal of Appl.
Phys., 91:9, (2002)), describing the production of MWCNTs grown on
silicon substrates with multilayered Al/Fe catalysts. The authors
recognize the benefits of ICP technology for its high ionization
efficiency compared to direct current (DC) or radio frequency (RF)
capacitive discharges. The process disclosed by NASA operates at
very strong vacuum (10.sup.-5 Torr) at about 800.degree. C. and at
power levels about 500 to 1000 times smaller than is achievable in
ICP torches. It would be desirable to develop a process operating
at standard atmospheric pressures, which employs a more energetic
plasma.
[0020] Clearly, new and improved methods that are capable of
economically producing large quantities of CNMs are desirable. Such
methods should provide consistent product qualities, and be
sufficiently flexible so as to be capable of meeting the demands of
the marketplace.
SUMMARY
[0021] This application specifically incorporates by reference the
disclosures and drawings of each patent application and issued
patent identified above as a related application.
[0022] One aspect of the present invention is directed to an
economical method for producing CNMs in flight, at high production
rates, by continuously injecting carbonaceous and catalytic
materials into a plasma field produced by an ICP torch, and by
controlling reactor chamber conditions to provide a suitable
environment for the formation and growth of CNMs. The present
method is suitable for the production of various CNMs, including,
but not limited to, graphitic SWCNTs, MWCNTs, graphitic carbon
nanofibers, and amorphous carbon nanowires.
[0023] An ICP torch (or multiple ICP torches) is used to thermally
crack carbonaceous materials to form elemental carbon, by
introduction of the carbonaceous material into the ICP jet. It
should be understood that carbonaceous feed materials can also be
introduced into a process reactor through the torch (i.e., along
with the plasma gas), as well as into portions of the process
reactor that are not adjacent to the plasma jet. However,
introducing at least some of the carbonaceous material into the ICP
jet is preferred. This carbonaceous material reacts with catalytic
metals to initiate the formation and growth of CNMs in a flowing
gas stream. The catalytic metals are continuously introduced into
the reaction chamber either separately or with the carbonaceous
material. The process is conducted in a high-temperature reaction
chamber designed for operation at or below atmospheric pressure,
and control of high continuous flow rates.
[0024] The reaction chamber is configured to support the in-flight
production of CNMs and includes either minimal or none of the
baffles commonly found in other gas phase reaction chambers. Such
baffles would likely inhibit the free flow that is desired to
optimize the in-flight production of CNMs. The walls of the
reaction chamber are preferably smooth, to minimize the amount of
free carbon or CNMs deposited there. Preferably, the CNMs remain
entrained within the gas flow until separated by filtration for
recovery. The walls of the reaction chamber do not include any
metals known to act as catalysts for the production of CNMs, to
avoid deposition of CNMs on the walls. Non metallic, smooth
reaction chamber walls are thus preferred. Quartz, glass, and
ceramics are preferred materials for the walls of the reaction
chamber.
[0025] The longer the residence time of the gas stream within the
system, the longer (and larger) the CNMs that will be produced.
Note that increasing the velocity of the gas flow within the
reactor will reduce the likelihood of CNMs being deposited on the
walls of the reaction chamber, but will also minimize the residence
time. Reaction chamber size and gas flow rates can be adjusted
based on the target size of the CNMs to be produced.
[0026] In a main process for configuring a system to produce CNMs,
the process conditions are established and controlled using the
high-temperature gas phase environment provided by the ICP torch to
enable continuous vaporization and mixture of the precursors for
CNM formation and in-flight growth of CNMs entrained in the gas
phase reactor. Due to the continuous-flow operation throughout the
entire production process, the on-line production times of the ICP
production process are expected to be comparable or higher than
conventional carbon black production methods.
[0027] In addition, the reaction chamber and/or
filtration/separation media optionally includes non-catalytic or
catalytic surfaces to simultaneously or separately establish
on-substrate growth of CNMs.
[0028] Because the catalyst and CNMs are entrained in the gas
stream exiting the reactor, the gas stream can be filtered to
selectively recover the CNMs and the catalyst. Since by their
nature catalysts are not consumed in a reaction, the catalyst can
be recovered from the gas stream exiting the reactor and reused.
Filtering the gas stream exiting the reactor to recover the CNMs is
significantly more efficient than recovering CNMs from surfaces
within a reactor, or from carbon deposits within a reactor. The
moving gas stream is easily directed into a filter unit, where the
CNMs are removed from the gas stream. In at least one embodiment,
the filter unit simply removes particles entrained in the gas
stream; such particles may include particles of the catalyst, and
larger-sized, less valuable carbon materials (such as soot). The
particles from the filter unit can optionally be purified to
separate the catalysts from the carbon material. Further, the
carbon materials can optionally be purified to separate the CNMs
from the less valuable carbon materials. The filter unit is
configurable to separate the CNMs into different fractions. Several
techniques, including the use of centrifugal forces (or more
precisely, centripetal forces) and electrostatic forces are
employed to segregate CNMS by size. The less valuable carbon
materials are then reintroduced into the reactor, to be reformed
into free carbon by the ICP, to enable more CNMs to be
produced.
[0029] During the production process, the CNMs can be integrated
into a product, to enhance the value of the product. For example,
CNMs can be added to a fuel, to increase its energy density. CNMs
can also be added to a polymer to provide improved structural,
electrical conductivity, and thermal conductivity properties.
[0030] This Summary has been provided to introduce a few concepts
in a simplified form that are further described in detail below in
the Description. However, this Summary is not intended to identify
key or essential features of the claimed subject matter, nor is it
intended to be used as an aid in determining the scope of the
claimed subject matter.
DRAWINGS
[0031] Various aspects and attendant advantages of one or more
exemplary embodiments and modifications thereto will become more
readily appreciated as the same becomes better understood by
reference to the following detailed description, when taken in
conjunction with the accompanying drawings, wherein:
[0032] FIG. 1 is a process flow diagram for the in-flight
production of CNMs using an ICP, in accord with the present
invention;
[0033] FIG. 2A is a process flow diagram for the in-flight
production of CNMs using an ICP, including the sorting of CNMs by
size, in accord with another aspect of the present invention;
[0034] FIG. 2B schematically illustrates a differential mobility
analyzer that can be employed to sort CNMs by size, as indicated in
the process flow diagram of FIG. 2A;
[0035] FIG. 3 is a process flow diagram for the in-flight
production of CNMs using an ICP, including product integration of
CNMs, in accord with another aspect of the present invention;
[0036] FIG. 4 is a process flow diagram for the in-flight
production of CNMs using an ICP, including purification of CNMs in
accord with yet another aspect of the present invention;
[0037] FIG. 5 is a process flow diagram for a combined process,
including both the in-flight production and substrate-based
production of CNMs using an ICP, in accord with still another
aspect of the present invention;
[0038] FIGS. 6A and 6B schematically illustrate secondary reaction
chambers for use in any of the processes of FIGS. 1-5;
[0039] FIG. 7 is a process flow diagram of a test system employed
to generate empirical data related to the present invention;
[0040] FIG. 8 is a transmission electron microscopy (TEM) image of
multi-wall carbon nanotubes grown on a substrate;
[0041] FIG. 9 is a scanning electron microscopy (SEM) image of
multi-wall carbon nanotubes grown in-flight and collected on a
front face of a process gas heat exchanger;
[0042] FIGS. 10-12 are SEM images of carbon nanowires grown on
stainless steel reactor walls at temperatures of 700.degree. C.;
and
[0043] FIGS. 13-15 are SEM images of carbon nanomaterials grown on
stainless steel sheet metal at temperatures of about 1,000.degree.
C.
DESCRIPTION
Figures and Disclosed Embodiments are Not Limiting
[0044] Exemplary embodiments are illustrated in referenced Figures
of the drawings. It is intended that the embodiments and Figures
disclosed herein are to be considered illustrative rather than
restrictive. No limitation on the scope of the technology and of
the claims that follow is to be imputed to the examples shown in
the drawings and discussed herein.
[0045] A method discussed below is used to produce CNMs in a gas
phase reaction using the high temperature gas emitted from an ICP
torch to crack carbonaceous materials in a flowing gas stream,
where the carbon is mixed with suitable catalytic materials in the
presence of other gaseous elements that promote the formation of
the CNMs. This method offers flexibility in the production of
various CNMs, including but not limited to, graphitic SWCNTs,
graphitic MWCNTs, graphitic carbon nanofibers, and amorphous carbon
nanowires.
[0046] The continuously operated and controlled gas-phase reaction
process uses a high-power ICP torch as the main source of heat for
continuous thermal cracking of carbonaceous materials to provide
free carbon, and for heating nano-scale metal-based catalysts (the
generation of nano-scale catalyst particles is discussed in greater
detail below). The heated carbon and catalyst serve as precursors
for the formation of CNMs downstream of the ICP torch. An initial
nano-sized carbon-metal product continues to react with additional
free carbon or carbon clusters and grows into larger CNMs, as long
as suitable growth conditions are maintained. Thus, it will be
apparent that increasing residence times of the process will lead
to the production of larger CNMs.
[0047] FIGS. 1-5 are process diagrams for different ICP based
systems used for producing CNMs. The following comments relating to
feed stocks, production techniques and process conditions apply to
each of the systems in FIGS. 1-5. Characteristics of each
individual system are discussed in detail below, following a
discussion of the common characteristics.
[0048] The overall reactor gas phase environment required to
optimize the formation and growth of CNMs is a function of a number
of different factors, including the composition of the carbonaceous
materials, the metal catalyst (or precursor) used, the plasma gas
mixture, the bulk gas-phase density, the degree of mixing between
the carbon and the catalyst, any additional process materials input
into the reactor vessel, the relative purities of the input
streams, the reactor surfaces, and process parameters. The process
parameters include the reactor temperature, temperature gradient
within the reactor chamber, and reactor pressures. Manipulating
these parameters enables changes to be made in the quality,
quantity, and types of the CNMs produced.
[0049] Many different types of plasma gases can be employed. Single
gases or mixtures of gases may be used. In particular, inert gases,
such as argon and helium, are expected to be useful. Nitrogen,
while useful in this process, is less desirable because monatomic
nitrogen and monatomic carbon bond to form cyanide molecules
(CN.sup.-), which aside from being toxic, uses the carbon that
would otherwise be available for the formation of CNMs. A larger
amount of free carbon in the process results in larger quantities
of CNMs being formed. Oxidizing gases are not favored, because they
tend to result in the formation of carbon monoxide (CO) or carbon
dioxide (CO.sub.2), which again undesirably consumes carbon that
could otherwise form CNMs. More reactive gases, such as hydrogen
and carbon monoxide, can also be employed. The plasma gas that is
selected contributes to the gas phase environment under which the
growth of CNMs is promoted, so that manipulation of the plasma gas
enables changes in the CNMs produced to be effected. Mixtures of
different gases (such as helium and argon) are expected to be
useful in achieving specific desired results.
[0050] Carbonaceous materials can include carbon-containing powder
(e.g., carbon graphite powder or carbon black), hydrocarbon gases
(e.g., CH.sub.4, C.sub.2H.sub.6, etc.), non-hydrocarbon gases (CO),
carbonaceous liquids and hydrocarbons, or combinations thereof.
Carbonaceous process gases not converted to CNMs can be recycled
within the process. Cracking of the carbonaceous feed using ICP
technology produces large amounts of free carbon, a principal
building block in the formation and growth of CNMs.
[0051] All or part of the carbonaceous materials can be fed into
the process environment in several different ways. For example, the
carbonaceous materials can be fed directly through the ICP torch,
or into the high-temperature plasma jet exiting the ICP torch, or
both. The carbonaceous materials can be fed into the process
environment along with the catalytic materials, or can be fed into
the process environment separately from the catalytic materials, or
both. It is preferable to introduce the carbonaceous material into
the plasma jet, rather than through the ICP torch. Additional feed
ports can be included in the reaction chamber to inject additional
carbonaceous materials.
[0052] Catalytic metals provide nucleation sites for the initiation
of the CNM growth and can be introduced in the form of powders
(small particulate sizes are beneficial), liquids (e.g., metal
carbonyls), or as gases. Metallic salts can also be employed. If
metallic salts are employed, care should be exercised to ensure
that the anionic portion of the salt does not introduce undesired
compounds into the reaction chamber. Like the carbonaceous
materials, catalytic materials can be introduced via the ICP torch,
into the high-temperature plasma jet exiting the ICP torch, and/or
along the reaction chamber system, downstream of the ICP torch.
[0053] One aspect of the present invention that facilitates the
in-flight production of CNMs is the introduction of catalytic
material into the gas flow within the reactor. Most other CNM
production methods rely on directing free carbon onto a substrate
impregnated with a catalyst, such that the CNM is produced on the
surface of the substrate. While substrate-based CNM growth is
effective, the process of harvesting the CNMs from the substrate is
less efficient than separating CNMs from a gas flow in which they
are entrained. Further, substrate growth-based methods are
inherently batch processes, in that the substrates need to be
regularly removed from a reactor to harvest the CNMs, and the
catalytic substrate must then be returned to the reactor. In
contrast, in-flight production of CNM can be achieved in a
continuous process, because production continues for as long as raw
materials (carbon and catalyst) are introduced into the reactor
vessel at an appropriate temperature. As will be described in
detail below, the gas exiting the reactor includes CNMs entrained
in the gas flow, which can be continuously removed from the gas
stream using conventional filtration methods.
[0054] A distinction can be made between chemical processing
systems that are operated continuously, and those operated
discontinuously. Discontinuous processing is generally referred to
as batch processing. As used herein and in the claims that follow,
the term "continuous processing" refers to a processing environment
in which a continuous stream of material is processed without
interruption to remove product or to replenish or replace materials
used in the process. The continuous process might run without
interruption for relatively long periods of time, e.g., for days or
weeks, while producing a product and without the need for
interrupting the process to add more reactant or catalyst, but may
be interrupted from time-to-time, e.g., for maintaining the
processing equipment, and not because the supply of material being
treated or consumed has been exhausted. In contrast, the term
"batch processing" as used herein refers to a processing
environment in which a finite volume of material is processed
without interruption, but only until the supply of material is
exhausted or there is a need to harvest the product of the process,
and in which the processing continues only for a period that is
relatively short. For example, a batch process might be completed
in terms of minutes or hours. Batch processing, rather than
continuous flow processing, is advantageous when a limited volume
of material is to be processed or because the nature of the process
requires replenishment of input materials or harvesting of the
output materials. An advantage of continuous processing is higher
production rates and greater efficiency in producing larger
quantities of product.
[0055] All materials fed into the gas-phase environment should
promote the formation and growth of specific CNMs. High purity
material streams (e.g., gases) are favorable to avoid unwanted
secondary reactions. Favorable conditions for the growth of CNMs
include, but are not limited to, the use of mixtures of helium and
argon with quantities of hydrogen for generating the gas phase
environment. The gas phase environment is generated by introducing
plasma gases, carbonaceous feeds, and catalytic metals into the ICP
system.
[0056] Further, the high-temperature gas phase environment can be
adjusted or enhanced by introducing additional process streams,
such as inert gases, carbon monoxide, hydrogen, and/or other
inputs, at any location within the reaction chamber and process
system. These process streams can also facilitate the reduction of
the operating temperatures for the CNM synthesis.
[0057] It should be noted that the material streams fed into the
ICP system and reaction chamber may be preheated (e.g., using heat
recovery devices) to minimize overall energy consumption in the
production process.
[0058] The ICP system uses electric energy to produce a thermally
energetic and chemically reactive plasma gas by ionizing an input
gas and any other materials fed through the ICP torch. The plasma
jet exiting the ICP torch is at very high gas temperatures, which,
depending on the type of plasma gas mixture employed, can exceed
10,000.degree. C. (e.g., these high temperature can be achieved by
ionizing argon gas). At controlled flow rates, an ICP torch
provides a stable, continuous heat source for the process
reactants.
[0059] Due to the endothermic nature of the cracking reaction, the
bulk gas phase temperature is reduced in a primary section of the
reaction chamber system where most of the CNM initiation occurs.
The temperature is controlled by adjusting the power level of the
ICP torch and feed rate of the reactants to achieve the desired
bulk operating temperature. The primary reaction chamber
temperatures are preferably controlled to be within a range from
about 400.degree. C. to about 1,300.degree. C., depending on the
catalyst and carbonaceous feed materials used, and the type of CNMs
desired (i.e., SWCNTs versus MWCNTs). For the production of carbon
nanotubes in particular, the temperature preferably ranges from
about 800.degree. C. to about 1,300.degree. C. A single ICP torch
can be employed, or if desired, multiple ICP torches can be
used.
[0060] External heating can also be applied to the reaction chamber
to extend the high temperature region, to promote continued CNM
formation, and to control growth conditions. Suitable external
heating devices or methods include resistive electric heating,
combustion of carbonaceous materials, and/or process heat recovery
devices (e.g., heat exchangers transferring heat from steam,
process gas, etc.). Reaction temperatures are preferably maintained
between about 400.degree. C. and about 1000.degree. C., and most
preferably above about 500.degree. C., to facilitate continued
growth of the CNMs.
[0061] The high-temperature process chamber system preferably
includes a primary and secondary reaction chamber. The primary
chamber is designed to facilitate the plasma gas operating
conditions, to initiate the formation of the CNM product, and for
introduction of the main process material streams. The primary
reaction chamber uses the ICP to reform a carbonaceous material
into free carbon, and to vaporize the catalyst. Atoms of vaporized
catalyst will combine to form nano-sized metal catalyst particles.
Free carbon will be attracted to the nano-sized catalyst particles,
and CNMs will begin to form on the nano-sized catalyst particles.
The introduction of the catalyst into the primary reaction chamber
can be manipulated to favor certain sizes of CNMs. Larger catalyst
particles will favor lager sized CNMs. In general, the longer the
catalyst feed is exposed to the ICP, the smaller the average size
of the nano-sized catalyst particles will be. Empirical evidence
suggests that nano-sized catalyst particles under 5 nanometers will
favor the growth of SWCNT, while nano-sized catalyst particles over
5 nanometers will favor the growth of MWCNT. Where the metal
catalyst is introduced as a metal carbonyl or a liquid solution of
a metal salt, less energy (to be supplied by the ICP) will be
required to generate nano-sized catalyst particles under 5
nanometers in size. Where the metal catalyst is introduced as a
metal powder (i.e. a conventional metal powder where the average
particle size is larger than nanometer sized), more energy (to be
supplied by the ICP) will be required to generate nano-sized
catalyst particles under 5 nanometers in size. The longer the
catalyst feed is exposed to the ICP, the more energy is available
to vaporize the catalyst. Thus, the average size of the nano-sized
catalyst particles available in the primary reaction chamber can be
influenced by controlling how long the catalyst feed is exposed to
the ICP (by controlling the location of the catalyst feed relative
to the ICP), controlling the type of catalyst introduced (i.e., a
metal powder versus a solution of metal salts or a metal carbonyl),
and combinations thereof. Empirical testing in specific processing
systems will enable processing conditions favoring the production
of SWCNT over MWCNT (and vice versa) to be determined. The catalyst
can be directed into the reactor as a separate feed, or the
catalyst can be introduced into the reactor along with the plasma
gas used to generate the ICP. For example, introducing a metal
powder into the feed gas used to generate the ICP can be used to
generate nano-sized catalyst particles.
[0062] The secondary reaction chamber is employed for controlling
and maintaining optimal reaction temperatures for continued CNM
growth (a process referred to as annealing), with the integration
of external heating, and to provide the residence time required for
desired CNM growth (measured, e.g., in nanotubes length or fiber
length). The supplemental heating for the secondary reaction
chamber is used to ensure that the process gases in the secondary
reaction chamber do not cool below a threshold value (which is
based on the specific catalyst employed). As long as the secondary
chamber is kept above the threshold value, CNM formation will
continue to occur in the secondary reaction chamber. Additional
carbonaceous material can be introduced into the secondary reaction
chamber, to provide sufficient free carbon to maintain the growth
of the CNMs. Introducing excess carbonaceous materials into any one
portion of the system (i.e. into either the primary reaction
chamber or the secondary reaction chamber) can lead to conditions
favoring the formation of soot over CNMs, thus the introduction of
carbonaceous material should be managed to avoid conditions
favoring the formation of soot. Carbon or carbonaceous materials
not used in the process or resulting from unused CNM product can be
recycled as part of the carbon source in the CNM production
process. The high-temperature reaction chambers operate at or below
atmospheric pressures to enable stable plasma operation and are
designed for high, continuous gas flow rates.
[0063] Reaction chamber sizes and designs depend on the desired
residence times at specific temperatures and gas/solid flow and
mixture. As discussed above, residence time is dependent on gas
(material) flow rates, temperatures, and chamber volume (as a
function of, e.g., chamber internal diameter and chamber
length).
[0064] The secondary reaction chamber can be configured as an
elongate, straight chamber (FIG. 6A) or as a serpentine design
(FIG. 6B) and can be arranged horizontally or vertically to
accommodate thermal growth and available facility space and
services. See FIGS. 6A and 6B and the related discussion provided
below for more details. As noted above, supplemental heating for
the secondary reaction chamber can be employed to ensure that the
temperatures in the secondary reaction chamber do not fall below a
threshold value required to support the growth of CNMs. While the
threshold value is a function of the catalyst employed, in general
the threshold values vary from about 300.degree. C. to over
500.degree. C.
[0065] Table 1 (which is included below, near the end of the
Description of the Preferred Embodiment) includes a listing of the
components referenced in the Figures. As noted above, FIGS. 1-5 are
process flow diagrams providing details for different embodiments
that can be employed to produce CNMs using an ICP torch. Each
process uses the ICP torch to produce free carbon from a
carbonaceous stream, and to heat the free carbon and the catalytic
metals to a required reaction temperature selected to enhance the
formation of CNMs. The differences among the process flow diagrams
in FIGS. 1-5 relate to the variation of the basic system, to
achieve specific goals. Such goals include emphasizing the
production of certain CNM types, qualities, and/or providing an
overall method for direct integration of the raw CNMs into a CNM
product ready for use, transportation, or further processing.
[0066] Each process (as shown in FIGS. 1-5) requires a number of
individual process elements, including a high power source 3 (e.g.,
an RF power supply/oscillator) that feeds electric power 5 to one
or more ICP torches 4, each of which is configured to direct a
plasma jet into a primary reaction chamber 1. High temperature
chemical reactions are initiated in the primary reaction chamber
and maintained or altered as required in a secondary reaction
chamber 2, which is in fluid communication with primary reaction
chamber 1. Both primary reaction chamber 1 and secondary reaction
chamber 2 are configured for in-flight production and growth of
CNMs. Bulk process gas temperatures are selected and controlled
between about 400.degree. C. and about 1,300.degree. C., but mostly
above about 800.degree. C. in primary reaction chamber 1, and
between about 400.degree. C. and about 1000.degree. C., but mostly
above about 500.degree. C. in secondary reaction chamber 2.
[0067] Each reaction chamber is configured to support the in-flight
production of CNMs. Preferably, the reaction chambers each include
minimal baffles or obstructions, to enhance free flow within the
reaction chambers. The walls of the reaction chambers should be
smooth, to minimize the amount of free carbon or CNMs that will be
deposited on the walls of the reaction chamber. Smooth chamber
walls, combined with sufficiently high flow rates, will reduce the
amount of CNMs dropping out of the gas flow due to deposition on
the walls. The walls of the reaction chamber should not include any
metals known to act as catalysts for the production of CNMs. Nickel
alloyed in stainless steel has been shown to function as a catalyst
that drives CNM growth, and stainless steel is therefore not a
preferred material (unless coated with a non-metallic material).
Non-metallic, smooth reaction chamber walls, such as those achieved
using quartz, glass, ceramics (or coatings of these materials) are
thus preferred.
[0068] The size of the reaction chamber (as well as gas flow rates)
will have an effect on residence time. The longer the residence
time of the gas stream within the system, the longer (and larger)
will be the CNMs produced. Thus, both reaction chamber size (and
shape) and gas flow rates can be adjusted, based on the desired
target size of the CNMs to be produced.
[0069] Each chamber is preferably maintained at or below
atmospheric pressure. The purpose of using a negative pressure is
to "pull" gas through the system, rather than "pushing" gas through
the system. While either approach will work, using a sufficient
amount of negative pressure to cause the desired gas flow through
the system is more efficient. The purpose of using the negative
pressure relates only to achieving desired flow rates, and not to a
requirement that CNM formation occur at low pressure.
[0070] The process gas, including the entrained (and growing)
in-flight CNM product, is preferably moved through the reaction
system due to the negative pressure generated by an induced draft
(ID) fan 40. The in-flight product is separated and/or altered in
solids separation systems 50a-50d, each of which is described in
greater detail below. Systems 50a-50d control solid/gas separation.
System 50a is integrated into the process flow diagrams of FIGS. 1
and 5; system 50b is integrated into the process flow diagram of
FIG. 2A; system 50c is integrated into the process flow diagram of
FIG. 3; and, system 50d is integrated into the process flow diagram
of FIG. 4.
[0071] Separated process gas 35 can be recycled in part or in full,
back into the process, as indicated by a fluid line 37. The balance
of process gas 36 is passed through ID fan 40, and if necessary to
meet emission requirements, can be oxidized in an oxidation unit
42, cooled by a heat recovery unit 44, and filtered by a filter 46,
prior to passing through an off gas stack 48 for exhaust to the
atmosphere, as indicated by process arrow 49.
[0072] Process input streams include carbonaceous materials 8,
catalytic metals 7, plasma gases 6, and if desired, additional
process gases 9. Carbonaceous materials 8 can be in gaseous,
liquid, slurry, and/or solid form, and can include hydrocarbon
gases (e.g., CH.sub.4, C.sub.2H.sub.6, or other C.sub.xH.sub.y's),
carbon monoxide, various carbonyls, carbon powder, and other
material streams that will be apparent as suitable for the process.
Certain carbonaceous materials (e.g., carbon powder) collected in
systems 50a-50d (i.e., non CNMs, or low value CNMs) may be recycled
or added to carbonaceous materials 8 to enhance the formation of
more desired CNMs in the process. A return/recycle stream 34 from
systems 50a-50d including recycled carbonaceous materials 8a can be
combined with carbonaceous materials 8 before being fed into the
ICP torch (or into the ICP jet, or into the primary reactor),
depending on the injection method selected.
[0073] Catalytic metals 7 can be in gaseous, liquid, slurry, and/or
solid form and can include metals such as nickel, cobalt, iron,
other Group VI or Group VII transition metals, and combinations
thereof. Other metals, including metals from Group III and Group
VIII have demonstrated catalytic activity promoting the growth of
CNMs. Catalytic materials may be separated in systems 50a-50d and
recycled as a stream 32 (as shown in FIGS. 3 and 4). Recycled
metals (i.e., metals collected from within the system for reuse)
can be combined with catalytic metals 7. Catalytic metals 7a is a
combination of catalytic metals 7 and stream 32. As discussed
above, metal catalysts can be introduced in the form of metal
powders, metal salts, and solutions of metal salts or metal
carbonyls.
[0074] Plasma gases can include pure gases or mixtures of argon,
helium, and/or other inert gases, carbon monoxide, hydrogen, and
other feed gases suitable for the operation of high-power ICP torch
4. A flow control valve 10 is used to control the input of plasma
gas 6. Additional process gases 9 can include all listed plasma
gases, as well as other materials suitable for enhancing the
production of CNMs. Additional process gases 9 can be combined with
recycled process gases 9a. The recycled process gases are supplied
using fluid line 37, a pump 38, and a check valve 39.
[0075] In process operation, carbonaceous materials 8 and recycled
carbonaceous materials 8a are preferably fed via a flow control
valve 16 into primary reaction chamber 1 at an entry point in the
vicinity of a plasma jet 60 exiting each ICP torch 4. Optional or
additional feed locations in the process system can be selectively
activated using feed flow control valves 15, 17, 18, and 19, to
enable, enhance, and/or increase the formation and growth of
CNMs.
[0076] Catalytic metals 7 (including recycled metal catalysts, as
desired) are preferably fed via control valves 11 and 12. Optional
or additional feed locations in the process system can be
selectively activated using feed flow control valves 13 and 14 to
enable, enhance, and/or increase the formation and growth of
CNMs.
[0077] Additional process gas materials 9 (and/or recycled process
gases 9a) are preferably fed via a control valve 20. Optional or
additional feed locations in the process system can be selectively
activated using control valves 21, 22, 23, and 24 for increased
process control and to enable, enhance, and/or increase the
formation and growth of CNMs. Flow control valves 20, 22, and 23
can be temperature controlled to react to process temperatures
measured at various locations in one or more of primary reaction
chamber 1, secondary reaction chamber 2, a process stream 27
exiting primary reaction chamber 1, and a process stream 28 exiting
secondary reaction chamber 2. Process heat for process temperature
control (in addition to and independent of the primary process heat
provided by ICP torch 4) can be selectively added to primary
reaction chamber 1 and secondary reaction chamber 2 with
supplemental heating devices 30 and 31.
[0078] It should be noted that the entire reaction chamber system
can be designed to enable the extraction of various CNM products as
a function of the in-flight duration, at various ports 33. This
material may be further sorted, filtered, or treated as shown and
described in conjunction with FIGS. 2A-5, providing more
flexibility in the selection and production of a large variety of
CNM product grades in the same overall process system.
[0079] The above discussion generally describes the processes and
systems shown in FIGS. 1-5. Specific comments relating to the
various embodiments of FIGS. 1-5 are provided below. Referring now
to the main process configuration illustrated in FIG. 1, the
process conditions are selected to promote continuous in-flight
synthesis and growth of CNMs by keeping the precursors for CNM
formation and growth entrained within the gas phase. The in-flight
duration (residence time) of the growing particulate is determined
and can be controlled and adjusted as a function of reaction
chamber volume (e.g., diameter, length), total gas flow rates,
reaction temperatures, temperature profiles, reaction chamber
pressures, material introduction locations and orientations, and
gas and materials flow patterns. In-flight durations (bulk gas
residence times) of a few seconds to several minutes are possible.
Multiple outlet ports 33 along the length of the primary and
secondary reaction chambers enable extraction of product with
various in-flight growth durations for sampling, process control,
further treatment, and/or collection of commercial quantities of
the product. In this manner, CNMs having various properties (e.g.,
different lengths and diameters) can be produced in a continuous
operation. In the baseline configuration shown in FIG. 1, the CNM
product is collected in solids separation system 50a, enabling the
process to be operated without interruption (i.e., continuously).
Sorting system 50a (solid/gas separation) includes a filtration
system 51 (preferably including a plurality of individual filter
elements), which provides an unsorted, untreated CNM product stream
52.
[0080] The separation of solid particulates from a gas flow is a
mature art. While the small size of CNMs does pose a technical
challenge, those of ordinary skill in the art will recognize that a
plurality of different filtration systems can be employed to
separate CNMs from a gas flow. Such filtration systems can be based
on electrostatic charge, or pore-based filters (such as
high-efficiency particulate arresting (HEPA) filters), and/or
cascades or sprays of fluids. Such techniques are to be considered
exemplary, and not limiting of the present invention. Preferred
filtration systems will provide for recovery of the CNMs without
the need to shut down the overall system (i.e., the ICP torch and
the reaction chambers), thereby facilitating continuous processing,
as opposed to batch processing. This goal can be achieved by
providing a single filtration system, including multiple elements,
or multiple filtration systems such that one system can be taken
offline (to enable the recovery of the CNMs), while the other
filtration system remains online.
[0081] Due to the varying sizes of the CNMs that will be produced,
stage filters may be useful. Stage filters include multiple filter
elements (or systems), such that particulates not captured by a
"coarse" stage are subsequently captured by a later, "finer" stage.
When sufficient size differences between the CNMs being produced
exist, stage filters are useful because they enable some separation
of CNMs by size. However, due to the small size of CNMs, stage
filters are unlikely to be able to achieve a high degree of
sorting.
[0082] Variations of the baseline configuration are shown in FIGS.
2A-5. Whereas FIG. 1 shows an embodiment in which the CNM product
is untreated and unsorted, FIG. 2A illustrates a CNM process flow
that produces an untreated, but sorted CNM product. CNM solids
separation system 50b provides for the continuous, in-flight
sorting or separation of CNM. Solids separation system 50b can be
based on electrostatic, centrifugal, size distribution, or other
separation principles, and can be directly applied prior to
solid/gas separation in high-temperature or reduced temperature
filtration mechanisms. Solids separation system 50b includes a CNM
sorting system 56, and filtration systems 57, 58, and 59. CNM
sorting system 56 enables the separation and sorting of the CNMs
entrained in a main stream process stream 28 into various different
CNM fractions based on selectable separation criteria and
mechanisms. Centrifugal based processes are expected to be
particularly useful. Astute readers will recognize that centrifugal
force is a "fictitious" force, and that centrifuges actually work
based on centripetal force. Thus, stream 28 will be separated into
a plurality of different gas phase streams, each of which will be
filtered in a designated filter system, such as filtration systems
57, 58, and 59. Preferably the number of filtration systems will
correspond to the number of different streams provided by CNM
sorting system 56. Each of filtration systems 57-59 can be
implemented using the filters noted above. Since CNM sorter 56 has
separated the gas flow into different streams based on particle
sizes, each filter 57-59 can be implemented using a filtration
system optimized for a specific size of particulate. Each
filtration system will output its own specific CNM product
(products 53, 54, and 55). CNM sorter 56 can also produce a flow of
process gas, including carbonaceous matter to be reintroduced into
the system, as indicated by process arrow 34a.
[0083] The sorting of nanoparticles of varying sizes into groups of
nanoparticles of similar sizes is a growing field. As noted above,
technologies based on a variety of different mechanisms are likely
to be further developed. One technology that has been developed is
referred to as a differential mobility analyzer (DMA). This
technique has been employed by the Discovery Research Institute at
the Wako Nanomaterial Processing Laboratory, as reported by Chief
Scientist, Dr. Kazuo Takeuchizer (Riken News, Research Highlights,
No. 253, July 2002).
[0084] A DMA includes a pair of cylindrical electrodes (FIG. 2B). A
stable vertical flow of a gas (i.e., a sheath gas) flows from top
to bottom in the volume between the inner and outer cylinders. A
sample of charged nanoparticles is released into the airflow and a
voltage is applied between the cylinders. The nanoparticles are
attracted to the inner cylinder as they are carried downward by the
sheath gas. Because smaller particles move faster, they reach the
inner cylinder at a higher point. A slit located on the inner
cylinder allows particles of only a certain size range to exit
through the slit. The size of the particles to be extracted can be
controlled by varying the intensity of the applied electric
voltage.
[0085] The DMA described above functions best at low pressures.
While not specifically shown in the process flow diagram of FIG.
2A, it should be understood that CNM sorter 56 may require pressure
reduction elements, as well as the DMA of FIG. 2B. It will also be
appreciated that the DMA of FIG. 2B is merely exemplary of known
techniques that can be employed to sort nanomaterials by size.
Because additional techniques, which may be even more suitable for
incorporation into the system of FIG. 2A, are currently under
development, the invention is clearly not limited to the use of the
DMA of FIG. 2B.
[0086] FIG. 3 integrates either unsorted or sorted CNMs into a
final CNM product using solids separation system 50c, which
includes CNM sorting system 56, one or more filtrations systems 57,
and a product integration unit 61. System 50c in FIG. 3 presents a
variation of system 50b of FIG. 2 in which either sorted CNMs 53 or
unsorted CNMs 52 can be directly processed and/or upgraded in
product integration unit 61, resulting in an integrated CNM product
65. Sorted CNMs 53 can be produced as described above, using CNM
sorting system 56 with filtration systems 57-59. One implementation
of product integration unit 61 comprises a liquid spray quench
collection system, followed by filtration using a filter 62 to
produce CNM product 65. Preferably, product 65 is upgraded so that
it can be supplied for further processing, or ready for end usage,
and/or be provided in a form suitable for safe and practical
storage, transportation, and handling. An example of such a product
is CNMs containing petrochemical liquids (e.g., carbon-enriched
fuels) or chemicals used to manufacture various polymer components.
Product integration unit 61 may require various chemical materials
63 to be input to achieve such value-added characteristics.
Material exiting product integration unit 61 may be re-circulated
back into product integration unit 61 for additional processing,
e.g., to build up the concentration of CNM to a desired level.
Filter 62 provides both product 65, and a process emission stream
64.
[0087] The integration of CNMs into value-added products will be
beneficial for handling, shipping, and transportation. Such
products can be suitable for direct use in a follow-on process,
and/or be ready for final use with enhanced product value. One
application may involve production of CNM-containing petrochemical
fuels for the increase of energy released in combustion engines.
Another application may involve the capture of raw CNMs in a liquid
solution or slurry for beneficial further processing in the
production of conductive polymers or other composite materials. A
specific gravity measurement system or other techniques known in
the art of slurry production can be used to monitor and control the
collection process. Parallel collection/holding tank systems can be
used to provide continuous collection and isolation/product removal
capabilities. Furthermore, the liquid used for the quench spray can
perform post-production treatment of the CNM, by removal of the
catalytic metal through leaching or dissolving the catalyst from
the carbon structure. The catalytic metal(s) can then be recovered
and recycled.
[0088] FIG. 4 shows the production of a thermally and/or chemically
purified/upgraded CNM product, which can be either sorted or
unsorted. This purification step can include the removal of
catalytic metals through leaching or dissolving catalyst from the
carbon structure. The catalytic metal(s) can then be recovered and
recycled as described above. Solids separation system 50d combines
the options for solids separation system 50a (FIG. 1) and solids
separation system 50b (FIG. 2) with a chemical/thermal purification
system 66 that ultimately generates either an unsorted or a sorted
and purified CNM product. Purification can include the extraction
of catalytic compounds contained within untreated/unsorted CNMs 52
or sorted CNMs 53, and/or the select removal of unwanted forms of
carbon 34b, such as amorphous carbon and polyhedral carbon
particles. Purification system 66 may require various chemicals
and/or process streams 68 (e.g., water, solvent, acid, oxygen,
etc.) and/or heat 67. Extracted catalytic compounds (see stream 32)
and rejected carbonaceous materials (unwanted carbon 34b) can be
recycled into the main production process (i.e., injected into
primary reaction chamber 1). Solids separation system 50d thus
includes CNM sorting system 56, filtration systems 57, and a
thermal/chemical purification unit 66, and can be used to produce a
purified CNM product 69.
[0089] Oxidation techniques have also been reported to remove
unwanted carbon material. For example, the "Temperature Programmed
Oxidation Technique," reported by Krishnankutty, et. al., Catalysis
Today, 37, 295 (1997) provides a method to treat CNMs through
controlled oxidation at various temperatures. Amorphous carbon is
removed under partial oxidation conditions at approximately
330.degree. C. Such a method can be beneficially incorporated into
the present invention to further process CNMs.
[0090] Note that the main process configuration (See FIG. 1)
emphasizes the in-flight growth of CNMs, in contrast to
conventional CNM production methods, which emphasize
substrate-based production methods. A variation to the main process
configuration of the present invention involves the combination of
the in-flight growth and production process with vapor deposition
of the ICP-produced carbon onto designated surfaces exposed to the
in-flight growing product (i.e., the use of substrate-based CNM
production). FIG. 5 demonstrates this concept of simultaneous
in-flight CNM production with on-substrate CNM production. These
substrate surfaces can be high-temperature filtration surfaces
(with a mechanism of semi-continuous or periodic product removal)
or other non-catalytic or catalytic surfaces either introduced into
the reaction chamber as substrates or as an integral part of the
reaction chamber (with periodic removal of product materials, for
example, by controllably changing the flow of reactants between
chambers to enable production to continue in one chamber while
harvesting is done in another chamber). The catalytic surfaces
could also be located in separate high-temperature chambers
designated for on-substrate growth. These variations are likely to
only be economically viable if the overall high production rates of
the in-flight growth and production process is not significantly
affected and if the additional on-surface/on-substrate growth
product yields a high market value. One variation of the in-flight
growth and production process is the minimization of in-flight
duration, resulting primarily in on-surface/on-substrate growth,
with just enough in-flight time to start the growth process of the
free carbon.
[0091] Such a process requires modifications to the earlier
described systems, and the incorporation of additional process
equipment, generally as in system 80. The first group of
modifications involves changes to secondary reaction chamber 2 (as
shown in FIGS. 1-4) to achieve secondary reaction chamber 2a as
shown in FIG. 5. Ports 33b and 33c (additional ports can also be
employed) are required to extract in-flight grown CNMs entrained in
the process gas within secondary reaction chamber 2a. The extracted
process gas is directed into a CVD chamber 74, containing
continuous or multiple individual substrates 77, each with
catalytic metal(s). Chamber 74 can also be charged with CNM
entrained process gas via ports 33a and 33d to provide the highest
degree of process flexibility. Port 33a receives process gas
exiting primary reaction chamber 1, which due to a relatively short
residence time, is expected to include relatively shorter and
smaller CNMs. In contrast, port 33d receives process gas exiting
secondary reaction chamber 2a, which due to a relatively longer
residence time, is expected to include relatively longer and larger
CNMs.
[0092] Additional modifications to secondary reaction chamber 2a
involve the integration of continuous or multiple individual
substrates 75 (each with catalytic metal(s)) within the secondary
reaction chamber. Thus, secondary reaction chamber 2a enables
simultaneous on-substrate growth of CNMs (on substrates 75) and
in-flight CNM growth (entrained within the process gas stream in
the chamber) in a single equipment component. Production of CNMs on
substrates 75 is continuous and ongoing, since process gas flows
through the secondary reaction chamber whenever the overall system
in running. In contrast, the feed inputs into CVD chamber 74 can be
individually controlled, enabling CVD chamber 74 to produce CNMs in
a batch-like process, by closing off the CVD chamber for product
removal. Furthermore, ports 33a, 33b, 33c, and 33d provide greater
flexibility in the relative sizes of the CNMs entrained within the
process gas inputs, which ultimately effects the types of CNMs
produced on the substrates in CVD chamber 74 (because ports 33a,
33b, 33c, and 33d receive process gas from different points in the
continuous in-flight production of CNMs in the first and second
primary reaction chambers). Substrate-based CNMs 76 from within
secondary reaction chamber 2a can be combined with substrate based
CNMs 78 from within CVD chamber 74 to achieve a combined
substrate-based CNM product stream 79, in addition to
untreated/unsorted CNMs 52 that are generated in-flight. Of course,
combined substrate-based CNM product stream 79 can then be treated
either in purification system 66 of FIG. 4, or in product
integration unit 61 of FIG. 3. When beneficial or practical,
carbonaceous materials 34c from secondary reaction chamber 2a
and/or carbonaceous materials 34d from CVD chamber 74 can be
introduced back into primary reaction chamber 1. Also shown are a
process stream 81 and a process stream 82. Process stream 81 leaves
secondary reaction chamber 2a. Process stream 82 enters system 50a
and is equal to process stream 81 reduced by port 33d.
[0093] FIGS. 6A and 6B show two alternative optional secondary
reaction chamber configurations. Uniform growth of in-flight CNMs
requires laminar flow patterns achievable in long tubular reaction
chambers 2b and 2c, having smooth, non-metal internal surfaces 85.
The overall secondary reaction chamber can be formed either with
straight (see chamber 2b in FIG. 6A) or serpentine-like elements
(see chamber 2c in FIG. 6B), which can provide long in-flight
durations of up to several minutes. Continuous or multiple
individual supplemental heating elements 31a are preferred to
evenly select, hold, and control the chamber temperature profile.
Multiple ports 33a along the reaction chamber can be installed to
permit extraction of in-flight CNMs for sampling and/or product
extraction, or to introduce further process inputs.
[0094] All process equipment components for the ICP-driven CNM
production processes in accord with the present invention are
commercially available. However, the ICP torch systems described in
commonly-assigned U.S. Pat. No. 5,611,947, entitled "Induction
Steam Plasma Torch for Generating A Steam Plasma for Treating A
Feed Slurry," and U.S. Pat. No. 6,153,852, entitled "Use of A
Chemically Reactive Plasma for Thermal-Chemical Processes," are
particularly useful. The disclosure and drawings of these two
patents are hereby specifically incorporated herein by reference.
Such ICP torches are capable of the high output power levels (up to
200 KW thermal energy) required to achieve commercially viable CNM
production rates. These ICP torch systems can crack sufficient
carbonaceous materials to produce as much as 100 to 150 metric tons
of CNM per year (based on a single ICP system).
[0095] Unlike arc plasma systems, ICP technology-based systems do
not contain any integral system parts that are consumed during
operation. Compared to the ICP technology, electrodes consumed in
arc plasma systems require more maintenance and can frequently
require temporary process shut-downs, leading to lower overall
on-line production times.
Testing Experience with CNM Production Using an ICP Production
Process
[0096] FIG. 7 shows the layout of a test configuration used for a
proof-of-concept demonstration of the ICP production process for
producing CNMs. A 50 KW Lepel power supply/oscillator system 3' was
used to provide high frequency (2-3 MHz) induction power to an ICP
torch 4'. The ICP torch was mounted on top of a high-temperature
primary reaction chamber 1', enabling a bulk gas temperature in
excess of about 1,200.degree. C. to be achieved. Plasma gases 6,
such as argon (at 24% by volume in the empirical tests) and helium
(at 76% by volume in the empirical tests), a carbonaceous feed gas
8 (methane in the empirical tests), and a cooling/quench gas 9'
(helium in the empirical tests) were pressure-controlled and
flow-regulated via control valves 10, 15, 16, and 20'. Carbonaceous
feed gas 8 was either introduced via ICP torch 4 and/or in the
vicinity of the plasma jet and was rapidly heated by the plasma
jet, resulting in free reactive carbon, hydrogen, and smaller
amounts of lower hydro-carbonaceous gases.
[0097] In this simple test configuration, the process gas passes
through primary reaction chamber 1', secondary reaction chamber 2''
that includes a supplemental heater 30', and a water-to-gas heat
exchanger 44' at sub-atmospheric pressures provided by an induced
draft fan 40', which is controlled by a control valve 25' and onto
stack 48'. For safety purposes, a pressure relief system 41' and an
automatic purge gas 9'', with an energized-to-close control valve
21' were installed. Atmosphere 49' is also shown. An overall
process control system and data acquisition system (not shown)
employed BridgeView and FieldPoint instrumentation for monitoring
and recording temperatures T1-T6, pressures P and DP, and other
process parameters. On-substrate CNM growth was demonstrated by
sample collection from several characterizing locations on
catalytic metal (substrate) surfaces 75' that were placed within
each reaction chamber system 1' and 2''. Electron microscopy
analysis, both TEM and SEM, verified CNM formation, including
multi-wall carbon nanotubes, amorphous nanowires, and amorphous
carbon.
[0098] Preparatory tests were conducted to establish new torch
operating parameters for a He/Ar plasma. On-substrate production
tests were conducted at bulk gas temperatures up to about
800.degree. C., using CH.sub.4 as the carbonaceous feed. Test
operations were conducted at -20'' water column pressure (i.e.,
slightly below atmospheric pressure), at power levels of 50 KW
(plate). The catalytic material used in the experiments included
surface substrate areas inside the primary and secondary reaction
chamber.
[0099] In a limited number of tests conducted without gas-phase
injection of catalyst materials, carbon deposits and growth were
collected from substrate surfaces after reactor cool-down. Carbon
samples were analyzed using SEM and TEM.
[0100] SEM and TEM scanning analysis confirmed that (primarily)
nickel catalyst materials were extracted from (stainless steel)
substrate reactor surfaces (and seen in the tip of CNMs, mainly in
carbon nanowires). Overall, SEM and TEM imagery showed amorphous
carbon nanowires, multi-wall carbon nanotubes, polyhedral carbon
particulates, amorphous carbon nanoflakes, and other carbon forms.
The MWCNTs were believed to have formed in flight and deposited on
the walls of the process vessel.
[0101] FIGS. 8-15 are SEM or TEM images of products resulting from
CNM production testing. FIG. 8 is a TEM image of multi-wall carbon
nanotubes grown on-substrate. FIG. 9 is a SEM image of what is
believed to be multi-wall carbon nanotubes grown in-flight and
collected on the front face of the process gas heat exchanger.
Additional materials in the image are graphite flakes and
polyhedral carbon particulates.
[0102] FIGS. 10-12 are SEM images of carbon nanowires grown on
stainless steel reactor walls at temperatures of 700.degree. C. The
nickel from the stainless steel is seen on the tips of the
nanowires in FIG. 12.
[0103] FIGS. 13-15 are SEM images showing additional CNMs grown on
stainless steel sheet metal at temperatures of about 1,000.degree.
C. The carbon product was "peeled" from the sheet metal in 5-10
cm.sup.2 patches. The SEM images reveal very long nanowires of
15-25 nm in diameter, along with carbon polyhedral particles and
flakes. Accordingly, these images clearly indicate the success of
these tests in efficiently forming CNMs.
[0104] Although the present invention has been described in
connection with the preferred form of practicing it and
modifications thereto, those of ordinary skill in the art will
understand that many other modifications can be made to the present
invention within the scope of the claims that follow. Accordingly,
it is not intended that the scope of the invention in any way be
limited by the above description, but instead be determined
entirely by reference to the claims that follow.
TABLE-US-00001 TABLE 1 COMPONENTS IN FIGURES No. Explanation
Comment Qualifier 1 Primary Rx Chamber T = 400 to 1,300 C.; P = sub
atm. to atm. Equipment 1' Primary Rx Chamber as used in empirical
testing Equipment 2 Secondary Rx T = 400 to 1,300 C.; P = sub atm.
to atm. Equipment Chamber 2'' Secondary Rx as used in empirical
testing Equipment Chamber 2a Secondary Reaction T = 400-1,300 C.; P
= sub atm. to atm.; Equipment Chamber (modified) similar to 2, but
w/catalytic substrates 75 2b Secondary Reaction straight tubular
design (horizontal or Equipment Chamber vertical, with or w/o
external heating 2c Secondary Reaction serpentine-like, tubular
design, Equipment Chamber horizontal or vertical, with or w/o
external heating 3 High Power Source RF Power Supply/Oscillator; 50
kW Equipment and higher; one PS/OSC per ICP torch 3' High Power
Source empirical testing unit [50 kW Lepel unit] Equipment 4 ICP
Torch one or multiple units, mounted to Equipment Primary Reaction
Chamber 4' ICP Torch empirical testing unit [TAFA model 66,
Equipment modified] 5 Electric Power to 3 Consumable 6 Plasma Gas
Supply Argon, Helium, other inert gases, CO, Materials and/or
H.sub.2 Stream 7 Catalytic Metals Gaseous, liquid, slurry, and/or
solid Materials Form Stream 7a Catalytic Metals Sum of 7 and 32
Materials (combined) Stream 8 Carbonaceous Gaseous, liquid, slurry,
and/or solid Materials Materials (Feed) Form; CH.sub.4,
C.sub.2H.sub.6, other hydrocarbons Stream (C.sub.xH.sub.y's), CO,
Carbon Powder, Carbonyls, etc. 8a Carbonaceous Sum of 8 and 34 and
34a Materials Materials (combined Stream Feed) 9 Additional Process
Argon, Helium, other inert gases, CO, Materials Streams and/or
H.sub.2 Stream 9a Additional Process combination of 9 and 37
Materials Streams (combined) Stream 9' cooling/quench gas 9''
Automatic Purge Gas 10 Flow Control Valve one or multiple valves
controlling the Control flow rate for No. 6 Component 11 Flow
Control Valve one or multiple valves controlling the Control flow
rate for No. 7 entering in the Component vicinity of the plasma jet
12 Flow Control Valve one or multiple valves controlling the
Control flow rate for No. 7 to 4 (optional) Component 13 Flow
Control Valve one or multiple valves controlling the Control flow
rate for No. 7 to 1 (optional) Component 14 Flow Control Valve one
or multiple valves controlling the Control flow rate for No. 7 to 2
(optional) Component 15 Flow Control Valve one or multiple valves
controlling the Control flow rate for No. 8 to 4 (optional)
Component 16 Flow Control Valve one or multiple valves controlling
the Control flow rate for No. 8 to 1 Component 17 Flow Control
Valve one or multiple valves controlling the Control flow rate for
No. 8 to 1 (optional) Component 18 Flow Control Valve one or
multiple valves controlling the Control flow rate for No. 8 to 2
(optional) Component 19 Flow Control Valve one or multiple valves
controlling the Control flow rate for No. 8 to System 50 Component
(optional) 20 Flow Control Valve one or multiple (temperature
regulated) Control valves controlling the flow rate for No. 9
Component to 1 (optional); 20' Flow Control Valve as used for
empirical testing Control Component 21 Flow Control Valve one or
multiple valves controlling the Control flow rate for No. 9 to 1
(optional) Component 21' Flow Control Valve as used for empirical
testing Control Component 22 Flow Control Valve one or multiple
(temperature regulated) Control valves controlling the flow rate
for No. 9 Component to 2 (optional); 23 Flow Control Valve one or
multiple valves controlling the Control flow rate for No. 9 to 2
(optional) Component 24 Flow Control Valve one or multiple
(temperature regulated) Control valves controlling the flow rate
for No. 9 Component to 28 (optional); 25' Flow Control Valve as
used in empirical testing Control Component 26 Not used N/A N/A 27
Process Stream leaving (1) and entering (2) Process Stream 28
Process Stream leaving 2 and entering 50 Process Stream 29 Not used
N/A N/A 30 Supplemental Heating for 1 (optional) Equipment 30'
Supplemental Heating as used in empirical testing Equipment 31
Supplemental Heating for 2 Equipment 31a Supplemental Heating for
secondary reaction chamber; Equipment continuous or multiple
individual sections 32 Catalyst Recycle optional, back to combine
with 7 to 7a 33 Outlet Ports one or multiple outlet ports along 2
for Equipment sampling or product extraction (Detail) 33a-33d
Outlet Ports one or multiple outlet ports along Equipment secondary
reaction chamber for (Detail) sampling or product extraction 34
Carbon Recycle from filtration system(s) 51, 57, 58, 58, Materials
etc.; to be added to 8, resulting in 8a Stream 34a Carbon Recycle
from CNM sorting system 56; to be Materials added to 8, resulting
in 8a Stream 34b Carbon Recycle from CNM purification system 66; to
be Materials added to 8, resulting in 8a Stream 34c Carbon Recycle
from CNM purification system 2a; to be Materials added to 8,
resulting in 8a Stream 34d Carbon Recycle from CNM purification
system 74; to be Materials added to 8, resulting in 8a Stream 35
Process Off gas leaving system 50; cleaned of CNMs Materials Stream
36 Process Off gas Balance of stream 35 minus 37 Materials Stream
37 Gas Recycle Stream optional, leading to 38 Materials Stream 38
Process Gas Recycle moves stream 38 Equipment Pump 39 Check Valve
supplied by 38 with 37, adding to 9 Control Component 40 ID Fan
carrying stream 35 Equipment 40' ID Fan as used in empirical
testing Equipment 41' Pressure Relieve as used in empirical testing
Equipment System 42 Oxidation Chamber for residual combustibles in
35 Equipment 43 Not used N/A N/A 44 Heat recovery system for
steam/other heat production Equipment (optional) 44' Heat exchanger
as used in empirical testing Equipment 45 Not used N/A N/A 46
Filtration of entrained particulate (optional) Equipment 47 Not
used N/A N/A 48 Stack for process exhaust 49 Equipment 48' Stack as
used in empirical testing Equipment 49 Process Exhaust gas, mostly
CO.sub.2 and H.sub.2O, no particulates 49' Atmosphere 50a System
50a Separation system for Baseline concept System in FIG. 1
(unsorted, untreated CNMs) 50b System 50b Separation system for
FIG. 2, for sorted, System untreated CNM products 50c System 50c
Separation system for FIG. 3, for System integrated
(sorted/unsorted, untreated) CNM product 50d System 50d Separation
system (see FIG. 4), leading to System sorted/unsorted and
chemically/thermally treated CNM product 51 Filtration Systems one
or multiple units for collection of 52 Equipment 52 CNM Product
unsorted and untreated In-flight CNM Product (unsorted/untreated)
product; to be collected/stored Stream 53 CNM Product Type 1 sorted
and untreated In-flight CNM Product Product; to be collected/stored
Stream 54 CNM Product Type 2 sorted and untreated In-flight CNM
Product Product; to be collected/stored Stream 55 CNM Product Type
3 sorted and untreated In-flight CNM Product Product; to be
collected/stored Stream 56 CNM Sorting System CNM Sorter based on
centrifugal, sizing, Equipment or other sorting principles 57
Filtration System 1 one or multiple filter designed for Equipment
collection of 53 58 Filtration System 2 one or multiple filter
designed for Equipment collection of 54 59 Filtration System 3 one
or multiple filter designed for Equipment collection of 55 60
Plasma Jet at/near exit of (4), inside (1) Materials Stream 61
Product Integration to integrate raw CNMs into a final CNM System
System Product ready for direct usage, further processing, storage,
or transportation. 62 Filtration/Separation to separate or
recirculate product or a Equipment process stream during operating
cycle 63 Chemicals chemicals required for processing in 61
Materials Stream 64 Emission Stream from 62. optional: for
materials recycle Materials Stream 65 Integrated CNM sorted or
unsorted CNM product, Product Product possibly reacted in 61 Stream
66 Chemical/Thermal Equipment/ Treatment Process 67 Heat Input
Consumable 68 Process Chemicals several, including liquids, solids,
gases Materials Stream 69 CNM Product sorted or unsorted CNM
product, Product (purified) purified (chemically/thermally treated)
in Stream 66 74 CVD Chamber Chemical vapor deposition chamber
Equipment including substrates w/catalytic metal(s) 77; T = 400 to
900 C.; P = sub atmospheric 75 Substrate w/catalytic single
continuous or multiple substrates Equipment Metal(s) with catalytic
metal(s) selected for CNM (Detail) on-substrate growth in 2a 75'
Substrate w/catalytic as used in empirical testing Metal(s) 76 CNM
Product Stream On-substrate product stream from 2a; Product Stream
77 Substrate w/catalytic single continuous or multiple substrates
Equipment Metal(s) with catalytic metal(s) selected for CNM
(Detail) on-substrate growth in 74 78 CNM Product Stream
On-substrate product stream from 74; Product Stream 79 CNM Product
Stream On-substrate product stream resulting Product from 76 and 78
Stream 80 System 80 System variation to combine in-flight System
CNM production (FIG. 1) with on-substrate CNM growth capability
within 2 or external CVD chamber 74 81 Process Stream leaving (2a)
Process Stream 82 Process Stream entering 50a; equals 81 reduced by
33d Process Stream 83 Not used N/A N/A 84 Not used N/A N/A 85
Feature Materials for internal reactor surfaces: Equipment quartz
or other non-metal composition (Detail) (for in-flight growth CNM
production)
* * * * *