DEVICE AND METHOD FOR CONTAINING A GAS AT LOW PRESSURE IN
VESSELS USING ABSORBENT TECHNOLOGY
FIELD
This invention relates to composite pressure vessels for containing gases, in
particular natural gas (NG, predominantly methane), at low pressure using
absorbent technology.
BACKGROUND
Nearly 3 billion people each day cook on open fires or rudimentary cookstoves
fueled by coal or solid biomass such as wood. The detrimental effects of burning
solid fuels on the environment and human health are staggering. The Global Burden
of Disease Study 2010 estimates that exposure to smoke from the simple act of
cooking using coal or solid biomass is the fourth worst risk factor for disease in
developing countries, and causes four million premature deaths per year, which
exceeds the number of deaths attributable to malaria or tuberculosis. In addition,
tens of millions more fall sick with illnesses that could readily be prevented using
clean and efficient cooking solutions. In addition, reliance on polluting cookstoves
and fuels leads to a wide variety of environmental problems. For example, using
solid biomass as fuel depletes forests, which may weaken the soil causing mudslides
and destroying agricultural land. The Global Alliance for Clean Cook Stoves
(GACC.org ) is leading the effort to provide clean fuel alternatives. It its mission
statement, the GACC notes that:
cookstove smoke-impacted households are often located
in rural and remote locations, which present challenges
for reaching those customers with clean cookstoves and
fuel in the so-called 'last mile' before the product reaches
the consumers' door. The size, weight, and fragility of
clean cookstoves often provide distribution and logistical
challenges. Other factors such as consumer price
sensitivity, deeply ingrained cultural preferences, gender
bias, and the need for both scalability and customization
must be considered when developing mechanisms for
reaching the end user.
The problem then is to develop a technology directed to an economical
readily distributable and transportable by human or animal effort only, safe and easy
to use, low-polluting source of energy for use in numerous individual tasks such as
cooking. The technology should be readily adaptable for use virtually anywhere on
earth but particularly in developing nations where the need is most urgent. The
present invention provides a unique solution to the problem.
SUMMARY
Thus, an aspect of this invention comprises a man- or animal- portable
low-pressure natural gas storage and transport vessel, comprising:
a polymeric liner that defines an interior vessel volume;
a polymeric composite outer shell that substantially completely encloses the
polymeric liner;
an absorbent that substantially fills the interior vessel volume; and
a port that connects the interior vessel volume with the external environment.
In an aspect of this invention, the polymeric liner is selected from the group
consisting of high density polyethylene and polydicyclopentadiene.
In an aspect of this invention, the polymeric composite comprises a
filamentous material impregnated with or embedded in or both impregnated with
and embedded in a polymeric matrix.
In an aspect of this invention, the filamentous material is selected from the
group consisting of a natural fiber, a metal, a glass, a ceramic, a synthetic
polymer and combinations thereof.
In an aspect of this invention, the filamentous material is selected from the
group consisting of fiberglass, carbon fibers, aramid fibers and ultra-high
molecular weight polyethylene.
In an aspect of this invention, the polymeric matrix is selected from the
group consisting of a thermoplastic polymer, a thermoplastic elastomer, a
thermoset polymer and combinations thereof.
In an aspect of this invention, the thermoset polymer is selected from the
group consisting of an epoxy polymer, a polyester polymer, a vinyl ester polymer,
a polyimide and dicyclopentadiene.
In an aspect of this invention, the thermoset polymer is dicyclopentadiene.
In an aspect of this invention, the absorbent is selected form the group
consisting of a pellet absorbent, a granular absorbent, a powder absorbent and
any combination thereof.
In an aspect of this invention, the pellet absorbent, the granular absorbent
and the powder absorbent are porous.
In an aspect of this invention, the absorbent comprises a pellet absorbent,
a granular absorbent, a powder absorbent, a porous pellet absorbent, a porous
granular absorbent, a porous powder absorbent or any combination of the
foregoing.
In an aspect of this invention, the absorbent comprises an absorbent
selected from the group consisting of a pellet absorbent, a granular absorbent, a
porous pellet absorbent, a granular absorbent and any combination of these
together with a powder absorbent, a porous powder absorbent or a combination
of these.
In an aspect of this invention, the absorbent is selected from the group
consisting of an activated carbon absorbent, a zeolite absorbent, a molecular
sieve absorbent, a metal organic framework absorbent and combinations thereof.
In an aspect of this invention, the storage and transport vessel is spherical
in shape.
In an aspect of this invention, the vessel is used as an energy source for
indoor or outdoor cooking, barbequing, heating or motorized transportation.
An aspect of this invention comprises a low-pressure composite natural
gas or hydrogen storage and transport vessel for use with a motorized
transportation vehicle, comprising:
a polymeric liner that defines an interior vessel volume;
a polymeric composite outer shell that substantially completely encloses the
polymeric liner;
an absorbent that substantially fills the interior vessel volume; and
a port that connects the interior vessel volume with the external environment.
DETAILED DESCRIPTION
The current GACC-preferred alternative to coal and biomass fuel is LPG,
liquefied petroleum gas, sometimes referred to simply as propane. On the other
hand, natural gas (NG), i.e., predominantly methane, is the cleanest burning of all
fossil fuels, is energy-efficient, is substantially less expensive than other fossil fuels
including propane and, importantly, is readily locally available in most developing
nations where the need is most critical. The present invention, thus, is directed to a
relatively light-weight, high capacity, man- or animal- portable, NG storage and
transportation system that uses absorbent technology. Such systems, often referred
to with regard to NG as ANG or absorbed natural gas systems, in addition to the
foregoing beneficial characteristics, will operate at pressures approved for operation
of coupling/ uncoupling devices by untrained personnel.
The discussion that follows is directed to ANG-powered cooking systems
although it is understood that the technology disclosed will find use in numerous
other applications such as, without limitation, heating systems, power generation
and, in particular as a fuel source for natural gas powered vehicles such as, again
without limitation, automobiles (the NGV market), marine engines including outboard
motors and small personal vehicles such as, without limitation, motorcycles, threewheeled
vehicles and mopeds. Using the information disclosed in this specification,
those skilled in the art will be able to modify the configuration of a composite,
absorbent-containing storage and transport vessel of this invention for the
preceding and many other uses. With regard to vehicles for transportation, the
present invention is directed to refillable permanently installed containment vessels
such as may be found in cars, trucks, etc. as well as "swap and go" systems
wherein small composite, absorbent-containing vessels are used and then, when
exhausted, simply removed and replaced with a full vessel.
A fundamental feature of the systems of the present invention is the use of a
composite pressure vessel containing an NG absorbent. As mentioned previously,
absorbed NG is generally referred to as "ANG." A composite pressure vessel
provides a relatively light weight containment vessel for ANG which will be make
cooking equipment easy to carry and set up using human or animal power alone.
The absorbent provides a means for loading NG into a vessel in quantities equivalent
to that loaded into a vessel without absorbent, but at a fraction of the pressure. That
is, when a vessel with a selected absorbent is used, the NG near the absorbent
particle surface undergoes a phase change from the gaseous state to an absorbed
state causing fluid densities to approach that of NG in a liquid state. The resulting
reduction in pressure of the same amount of gas in the same size vessel is
exceptional: NG is commonly supplied as compressed NG, termed CNG, at
approximately 3600 psi and the containment vessels for CNG reflect the high
pressure in that they are generally heavy, relatively thick-walled metal vessels. On
the other hand, an equivalent amount of NG supplied as ANG would require a
vessel capable of withstanding only about 600 psi. Thus, the ANG vessel would be
expected to be substantially less expensive and, ultimately, safer than current LPG
and CNG vessels. Under certain circumstances such as, without limitation,
compared to a metal vessel of the same volume containing an absorbent, the vessel
of the current invention may also be significantly lighter. Households that are
currently using LPG could be easily converted to ANG. The current cost of LPG is
several times the cost of NG. Households using LPG generally employ 3Kg and 6Kg
containers that are exchanged at a local filling station. The same approach could be
used for ANG containers. Some developing countries subsidize the cost of LPG to
make it affordable for the population. Examples of countries that would greatly
benefit from this technology include Indonesia, Bangladesh, India and China. Much
of the LPG is imported to these countries. On the other hand these countries have
large underutilized NG reserves. Thus, it is expected that the technology herein
might be well accepted in those nations currently reliant on LPG and
governmental participation may render the technology even more available and
affordable.
As used herein, the term "low pressure" refers to a storage and transportation
pressure vessel of this invention that, when loaded with a gas, which is absorbed
onto an absorbent, for example, without limitation, ANG, will exhibit a substantially
lower pressure than a pressure vessel of the same volume loaded with an
equivalent amount of the same gas but not containing an absorbent.
An embodiment of this invention is a relatively small capacity pressure
vessel, for example, without limitation, a 15 liter NG storage and transportation
system for use with stoves such as, again without limitation, indoor cook stoves,
outdoor camp stoves, BBQs and any other devices currently reliant on biomass,
kerosene and LPG as a fuel.
Current ANG technology in commercial operations has focused on
proprietary adsorbents as exemplified by Energtek and repurposing existing steel
pressure vessels such as the G-Tec system. The system herein, on the other hand
uses polymeric composite pressure vessels as storage and transport vessels for
ANG wherein the system is optimized for adsorbent characteristics while being
customized to the intended market.
In an embodiment of this invention, the system will comprise a polymer-lined
polymeric composite pressure vessel filled with an absorbent designed for optimal
absorption of methane or other gas such as hydrogen. The vessel could be
containerized to allow ease of handling, such as a barbeque grill LPG container.
A pressure vessel of this invention will in general comprise a pre-formed
polymeric liner around which a polymeric composite is wrapped to form the
completed vessel.
As used herein, to "wrap" a polymeric liner refers to the winding of a
filamentous material around a liner fabricated in the desired shape of the end
product vessel, which may be, without limitation, cylindrical, geodesic, toroidal,
spherical or oblate spheroidal. Presently preferred is a spherical liner which, at
present reduces cost of material and manufacturing. The filamentous material may
be wound around the construct in a dry state and left as such or it may subsequently
be impregnated with a polymeric matrix or covered with a polymeric protective layer.
Alternatively, the filamentous material may be impregnated with a polymeric matrix
prior to being wound onto a liner construct and thereby becomes embedded in
excess matrix material.
The polymeric liner around which the polymeric composite is wrapped can be
any polymer that can be formed into the appropriate shape and that is inert to the
gas to be contained in the vessel. Examples of suitable polymers for use as liners
for ANG vessels are, without limitation, high density polyethylene and
polyd icyclopentad iene .
As used herein, a "polymeric composite" has the meaning that would be
ascribed to it by those skilled in the art. In brief, it refers to a fibrous or filamentous
material that is impregnated with, embedded in or both impregnated with and
embedded in or enveloped by a polymer matrix material.
In general, any type of fibrous or filamentous material may be used to
create the polymeric composites of this invention. Such materials include, without
limitation, natural fibers such as, without limitation, silk, hemp, flax, etc., metals,
ceramics, basalt and synthetic polymer fibers and filaments. Examples of such
materials include, without limitation, glass fibers, commonly known as fiberglass,
carbon fibers, aramid fibers, which go mostly notably under the trade name
Kevlar® and ultra-high molecular weight polyethylene, such as Spectra®
(Honeywell Corporation) and Dyneeva® (Royal DSM N.V.).
The matrix in which the filamentous or fibrous material is impregnated or
enveloped or both impregnated and enveloped can comprise thermoplastic
polymers, thermoplastic elastomers, thermoset polymers and combinations
thereof. Of particular note are thermoset polymers, which can exhibit significantly
better mechanical properties, chemical resistance, thermal stability and overall
durability than the other types of polymers.
A particular advantage of most thermoset plastics or resins is that their
precursor monomers or prepolymers generally tend to have relatively low viscosities
under ambient conditions of pressure and temperature and therefore can be
introduced into or combined with fibers and filaments quite easily.
Another advantage of thermoset polymers is that they can usually be
chemically cured isothermally, that is, at the same temperature at which they are
combined with the fibers/filaments, which can be room temperature.
Suitable thermoset polymers include, without limitation, epoxy polymers,
polyester polymers, vinyl ester polymers, polyimide polymers,
dicyclopentadiene (DCPD) polymers and combinations thereof.
The polymeric composite may be wrapped around the liner in a relatively
straight forward manner referred by those skilled in the art as "hoop-wrapping." On
the other hand, to assure a vessel has the requisite strength to contain the NG, the
liner may be wrapped in addition to hoop-wrapping, sometimes in lieu of hoopwrapping,
in a manner called "isotensoidal wrapping," which is likewise well-known in
the art. Briefly, "isotensoidal wrapping" refers to the property of the fully wound
vessel in which each filament of the wrap experiences a constant pressure at all
points in its path. This is currently considered a desirable design for a polymeric
composite wrapped pressure vessel because, in this configuration, virtually the entire
stress imposed on the vessel by a compressed gas is assumed by the filaments of
the composite with very little of the stress being assumed by the polymeric matrix or
the liner.
The absorbent for the NG may be in pellet or granular form, a porous pellet
or porous granular form, a powder and any combination of the foregoing. A mixture
of a pellet, a granular, a porous pellet or a porous granular absorbent or any
combination of the foregoing together with a powder form absorbent is presently
preferred. It is believed that this combination of absorbent particle forms will result
in a more efficient packing in the pressure vessel. Absorbents such as, without
limitation, commercially available activated carbons, zeolites, molecular sieves, etc.
may be used. Suitable absorbents are currently commercially available from,
without limitation, the Cabot Corporation, Boston, MA.
The invention herein will additionally comprise, without limitation, features
such sensors to monitor temperature, pressure, cycle life, fill rate and location
(GPS) of the vessels. Such devices will include, without limitation, pressure
regulators, control valves, etc. These devices and others like them are wellknown
in the art and need no further description or discussion. The additional
features of a system of this invention will be coupled to the primary composite
ANG vessel by means of a port that couples the interior volume of the vessel with
the external environment. The port can include any of the multitude of devices for
coupling the port, and thence the interior volume of the pressure vessel, with any
of the foregoing features.
In addition, methods of loading the ANG pressure vessels will be an
aspect of this invention. Such methods may include manual loading or automated
method as such are available in modern packaging plants.
It is understood that, with regard to this description and the appended claims,
reference to any aspect of this invention made in the singular includes the plural and
vice versa unless it is expressly stated or unambiguously clear from the context that
such is not intended.
As used herein, any term of approximation such as, without limitation, near,
about, approximately, substantially, essentially and the like, mean that the word or
phrase modified by the term of approximation need not be exactly that which is
written but may vary from that written description to some extent. The extent to
which the description may vary will depend on how great a change can be instituted
and have one of ordinary skill in the art recognize the modified version as still having
the properties, characteristics and capabilities of the word or phrase unmodified by
the term of approximation. In general, but with the preceding discussion in mind, a
numerical value herein that is modified by a word of approximation may vary from
the stated value by ±10%, unless expressly stated otherwise. In particular, when
referring to a liner of this invention being "substantially completely" enclosed by a
composite outer shell, the use of "substantially" means that, while it is presently
preferred that the liner in fact be completely enclosed by the composite shell, either
hoop-wrapped, isotensoidally-wrapped or a combination of the two methods of
wrapping, it is possible that some portion of the shell may be left exposed to the
external environment but such constructs are still within the scope of this invention.
Likewise, to be "substantially filled" with an absorbent means that it is presently
preferred that the interior volume a vessel of this invention be filled with a pelletized,
granular or powdered absorbent such that there is minimal free volume space in the
vessel. In fact, it is presently most preferred that a combination of a pelletized or
granular absorbent or a combination of a pelletized and a granular absorbent be
mixed with a powered absorbent to fill in the free volume between the pellets, the
granules or the pellets and the granules to limit the free space as much as possible.
It is, however, within the scope of this invention that the interior volume contains any
combination of pellets, granules and powder absorbent which may leave free
volume open. In addition, it is possible that some head space may occur in a vessel
and such is still within the scope of this invention as indicated by the use of the word
"substantially.
As used herein, the use of "preferred," "preferably," or "more preferred,"
and the like refers to preferences as they existed at the time of filing of this patent
application.

WHAT IS CLAIMED:
1. A man- or animal- portable low-pressure natural gas storage and transport
vessel, comprising:
a polymeric liner that defines an interior vessel volume;
a polymeric composite outer shell that substantially completely encloses the
polymeric liner;
an absorbent that substantially fills the interior vessel volume; and
a port that connects the interior vessel volume with the external environment.
2. The storage and transport vessel of claim 1, wherein the polymeric liner is
selected from the group consisting of high density polyethylene and
polydicyclopentadiene.
3. The storage and transport vessel of claim 1, wherein the polymeric
composite comprises a filamentous material impregnated with or embedded in or
both impregnated with and embedded in a polymeric matrix.
4. The storage and transport vessel of claim 3, wherein the filamentous
material is selected from the group consisting of a natural fiber, a metal, a glass,
a ceramic, a synthetic polymer and combinations thereof.
5. The storage and transport vessel of claim 4, wherein the filamentous
material is selected from the group consisting of fiberglass, carbon fibers, aramid
fibers and ultra-high molecular weight polyethylene.
6. The storage and transport vessel of claim 3, wherein the polymeric matrix
is selected from the group consisting of a thermoplastic polymer, a thermoplastic
elastomer, a thermoset polymer and combinations thereof.
7. The storage and transport vessel of claim 6, wherein the thermoset
polymer is selected from the group consisting of an epoxy polymer, a polyester
polymer, a vinyl ester polymer, a polyimide and dicyclopentadiene.
8. The storage and transport vessel of claim 7, wherein the thermoset
polymer is dicyclopentadiene.
9. The storage and transport vessel of claim 1, wherein the absorbent is
selected form the group consisting of a pellet absorbent, a granular absorbent, a
powder absorbent and any combination thereof.
10. The storage and transport vessel of claim 9, wherein the pellet absorbent,
the granular absorbent and the powder absorbent are porous.
11. The storage and transport vessel of claim 1, wherein the absorbent
comprises a pellet absorbent, a granular absorbent, a powder absorbent, a
porous pellet absorbent, a porous granular absorbent, a porous powder
absorbent or any combination of the foregoing.
12. The storage and transport vessel of claim 11, wherein the absorbent
comprises an absorbent selected from the group consisting of a pellet absorbent,
a granular absorbent, a porous pellet absorbent, a granular absorbent or any
combination of these together with a powder absorbent or a porous powder
absorbent.
13. The storage and transport vessel of claim 11, wherein the absorbent is
selected from the group consisting of an activated carbon absorbent, a zeolite
absorbent, a molecular sieve absorbent, a metal organic framework absorbent
and combinations thereof.
14. The storage and transport vessel of claim 1, wherein the vessel is used as
an energy source for indoor or outdoor cooking, barbequing, heating or motorized
transportation.
15. The storage and transport vessel of claim 1, wherein the storage and
transport vessel is spherical in shape.