U.S. patent application number 13/156825 was filed with the patent office on 2011-09-29 for compositions containing sulfur hexafluoride and uses thereof.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. Invention is credited to Matthew H. Luly, Robert G. Richard, Rajiv R. Singh.
Application Number | 20110232939 13/156825 |
Document ID | / |
Family ID | 40533173 |
Filed Date | 2011-09-29 |
United States Patent
Application |
20110232939 |
Kind Code |
A1 |
Luly; Matthew H. ; et
al. |
September 29, 2011 |
COMPOSITIONS CONTAINING SULFUR HEXAFLUORIDE AND USES THEREOF
Abstract
A method for suppressing an electric arc or corona discharge
includes providing a device capable of storing, transmitting, or
generating an electrical current or field; and enveloping at least
a portion of said device with a dielectric gas consisting
essentially of: sulfur hexafluoride; a second component selected
from the group consisting of nitrous oxide; carbon dioxide;
trifluoromethane (R32); trifluoroiodomethane; octafluoropropane
(R218); 1,1,1,2,2-pentafluoroethane (R125); propane (R290);
1,1,1,2-tetrafluoropropene (HFO-1234yf);
1,2,3,3-tetrafluoro-2-propene (HFO-1234yc);
1,1,3,3-tetrafluoro-2-propene (HFO-1234zc);
1,1,1,3-tetrafluoro-2-propene (HFO-1234ze);
1,1,2,3-tetrafluoro-2-propene (HFO-1234ye);
1,1,1,2,3-pentafluoropropene (HFO-1225ye);
1,1,2,3,3-pentafluoropropene (HFO-1225yc);
1,1,1,3,3-pentafluoropropene (HFO-1225zc);
(Z)1,1,1,3-tetrafluoropropene (HFO-1234zeZ);
(Z)1,1,2,3-tetrafluoro-2-propene (HFO-1234yeZ);
(E)1,1,1,3-tetrafluoropropene (HFO-1234zeE);
(E)1,1,2,3-tetrafluoro-2-propene (HFO-1234yeE);
(Z)1,1,1,2,3-pentafluoropropene (HFO-1225yeZ);
(E)1,1,1,2,3-pentafluoropropene (HFO-1225yeE) and combinations of
two or more of these; and optionally, an additive selected from the
group consisting of stabilizers, metal passivators, corrosion
inhibitors, and lubricants.
Inventors: |
Luly; Matthew H.; (Hamburg,
NY) ; Singh; Rajiv R.; (Getzville, NY) ;
Richard; Robert G.; (Hamburg, NY) |
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morristown
NJ
|
Family ID: |
40533173 |
Appl. No.: |
13/156825 |
Filed: |
June 9, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12728371 |
Mar 22, 2010 |
7985355 |
|
|
13156825 |
|
|
|
|
11871729 |
Oct 12, 2007 |
7736529 |
|
|
12728371 |
|
|
|
|
Current U.S.
Class: |
174/17GF |
Current CPC
Class: |
H01H 2033/566 20130101;
H01B 3/16 20130101; A62C 99/0018 20130101 |
Class at
Publication: |
174/17GF |
International
Class: |
H05K 5/00 20060101
H05K005/00 |
Claims
1. A gas insulated electrical device comprising: at least one
component capable of generating, storing, and/or transmitting an
electrical current and/or field, and a dielectric gas consisting
essentially of: sulfur hexafluoride; and a second component
selected from the group consisting of nitrous oxide; carbon
dioxide; trifluoromethane (R32); trifluoroiodomethane;
octafluoropropane (R218); 1,1,1,2,2-pentafluoroethane (R125);
propane (R290); 1,1,1,2-tetrafluoropropene (HFO-1234yf);
1,2,3,3-tetrafluoro-2-propene (HFO-1234yc);
1,1,3,3-tetrafluoro-2-propene (HFO-1234zc);
1,1,1,3-tetrafluoro-2-propene (HFO-1234ze);
1,1,2,3-tetrafluoro-2-propene (HFO-1234ye);
1,1,1,2,3-pentafluoropropene (HFO-1225ye);
1,1,2,3,3-pentafluoropropene (HFO-1225yc);
1,1,1,3,3-pentafluoropropene (HFO-1225zc);
(Z)1,1,1,3-tetrafluoropropene (HFO-1234zeZ);
(Z)1,1,2,3-tetrafluoro-2-propene (HFO-1234yeZ);
(E)1,1,1,3-tetrafluoropropene (HFO-1234zeE);
(E)1,1,2,3-tetrafluoro-2-propene (HFO-1234yeE);
(Z)1,1,1,2,3-pentafluoropropene (HFO-1225yeZ);
(E)1,1,1,2,3-pentafluoropropene (HFO-1225yeE) and combinations of
two or more of these, wherein at least a portion of said one or
more components is enveloped by said dielectric gas.
2. The gas insulated electrical device of claim 1 wherein said
sulfur hexafluoride and said second component are present in said
dielectric gas in amounts sufficient to form an azeotrope-like
composition.
3. The gas insulated electrical device of claim 2 wherein said one
or more components comprises a high voltage electrical network
and/or circuit.
4. The gas insulated electrical device of claim 2 wherein said
component is selected from the group consisting of resistor,
inductor, capacitor, transformer, transistor, inductor, rectifier,
transmission line, motor, generator, voltage source, circuit
breaker, and electrical switchgear.
Description
RELATED APPLICATION
[0001] This application is a divisional of U.S. Ser. No.
12/728,371, filed Mar. 22, 2010, currently pending, which is a
divisional of U.S. Pat. No. 7,736,529, issued on Jun. 15, 2010, the
disclosures of which are hereby incorporated by reference in their
entirety.
BACKGROUND
[0002] 1. Field of Invention
[0003] The present invention relates to compositions containing
sulfur hexafluoride, methods of using the same, and devices and
articles of manufacture comprising the compositions.
[0004] 2. Description of Related Art
[0005] Perfluorocarbon compounds (PFC's), hydrofluorocarbon
compounds (HFC's), chlorofluorocarbons (CFC's),
hydrochlorofluorocarbon compounds (HCFC's), and sulfur hexafluoride
(SF.sub.6) are widely used in a variety of industrial, commercial,
consumer and public use applications and uses. However, several of
these compounds have been identified as particularly problematic to
the environment in that they contribute to the greenhouse gas
effect, i.e., they have relatively high global warming potentials
(GWP). For example, SF.sub.6 possesses one of the highest GWP
values of known compounds.
[0006] Due to its relatively high GWP, SF.sub.6 is being phased out
of several applications for which low-GWP substitutes are
available. However, presently there is no adequate substitute for
SF.sub.6 when used as a gaseous dielectric medium in high voltage
(.gtoreq.1 kV) applications, such as circuit breakers, switchgear,
and other electrical equipment. In such devices, pressurized
SF.sub.6 is used as a gas-phase insulator because it has much
higher dielectric strength compared to several other available
compounds such as air or dry nitrogen. Although the electrical
industry has taken steps to reduce the leak rates of SF.sub.6 from
high voltage equipment, monitor SF.sub.6 usage, increase recycling
of equipment utilizing SF.sub.6, and generally reduce SF.sub.6
emissions to the atmosphere, it would still be advantageous to find
a SF.sub.6 substitute for electrical applications utilizing a
dielectric gas.
[0007] In addition to electrical applications, relatively low GWP
substitutes for SF.sub.6 are desirable for other applications such
as refrigeration, closed cell foam production, propellants for
sprayable compositions, magnesium cover gases, and the like. There
is particularly a need for such new compositions that are
essentially non-flammable, that do not have a deleterious effect on
the atmosphere, that are chemically stable, and that have high
dielectric strength. For example, new low GWP compositions designed
for use as refrigerants or blowing agents should preferably have
similar stability as existing refrigerants or blowing agents, be
non-flammable, and have a normal boiling point within a reasonable
range as existing refrigerants or blowing agents.
[0008] While a number of compositions have been proposed as
suitable substitutes for high GPW compositions, compounds were
heretofore unknown that have an acceptable combination of boiling
point, chemical stability, low GWP, non-flammability, and
acceptable performance as a refrigerant, blowing agent, and/or
high-voltage dielectric gas. For example, carbon dioxide is a
refrigerant that is stable and has a relatively low GWP, but the
vapor pressure of this compound are significantly higher than most
refrigerants now in use. This deficiency generates significant
problems in attempting to implement its use in the refrigeration
industry because existing refrigeration equipment would have to be
extensively modified, redesigned, or replaced to utilize CO.sub.2
as a refrigerant. Thus, there is still a significant need to
develop a composition or mixture of compositions that have an
acceptable combination of boiling point, chemical stability, low
GWP, non-flammability and dielectric performance.
SUMMARY OF THE INVENTION
[0009] Applicants have found novel azeotrope-like mixtures of
sulfur hexafluoride (SF.sub.6) and nitrous oxide (N.sub.2O). In
addition to the unpredictable nature of azeotrope formation, these
azeotrope-like compositions unexpectedly possess dielectric
strengths that are not proportionate to their molar ratios. That
is, the combination of sulfur hexafluoride and nitrous oxide in
azeotrope-like amounts produces a synergistic effect with respect
to the composition's dielectric strength. Applicants have also
found that these compositions are essentially non-flammable (e.g.,
according to ASHRAE Standard 34 (2004)), have relatively low GWP,
have good chemical stability, and have normal boiling points
comparable to common refrigerants, foam blowing agents, and
propellants for sprayable compositions. These azeotrope-like
compositions are, therefore, ideally suited for applications that
are flammable and/or can benefit from an electrically-insulating
gas and that are subject to leaking of the composition into the
ambient environment.
[0010] Applicants have also found that known azeotrope-like
mixtures of SF.sub.6 and a second component, such as carbon dioxide
(CO.sub.2), trifluoromethane (R23), trifluoroiodomethane
(CF.sub.3I), octafluoropropane (R218), 1,1,1,2,2-pentafluoroethane
(R125), and propane (R290) also unexpectedly possess dielectric
strength that is not proportionate to their molar ratios. These
azeotrope-like compositions are also essentially non-flammable
(e.g., according to ASHRAE Standard 34 (2004)), have relatively low
GWP, have good chemical stability, and have normal boiling points
comparable to common refrigerants, foam blowing agents, and
propellants for sprayable compositions. Thus, these compositions
are also ideally suited for applications that are flammable and/or
can benefit from an electrically-insulating gas and that are
subject to leaking of the composition into the ambient
environment.
[0011] Applicants have further found that mixtures of SF.sub.6 and
certain hydrofluoroolefins, such as tetrafluoropropene and
pentafluoropropene, produce a synergistic effect with respect to
the composition's dielectric strength, are essentially
non-flammable (e.g., according to ASHRAE Standard 34 (2004)), have
relatively low GWP, have good chemical stability, and have normal
boiling points comparable to common refrigerants, foam blowing
agents, and propellants for sprayable compositions. Examples of
suitable tetrafluoropropenes include 1,1,1,2-tetrafluoropropene
(HFO-1234yf); 1,2,3,3-tetrafluoro-2-propene (HFO-1234yc);
1,1,3,3-tetrafluoro-2-propene (HFO-1234zc);
1,1,1,3-tetrafluoro-2-propene (HFO-1234ze);
1,1,2,3-tetrafluoro-2-propene (HFO-1234ye); and related
stereoisomers such as (Z)1,1,1,3-tetrafluoropropene (HFO-1234zeZ);
(Z)1,1,2,3-tetrafluoro-2-propene (HFO-1234yeZ); and
(E)1,1,1,3-tetrafluoropropene (HFO-1234zeE). Suitable
pentafluoropropenes include 1,1,1,2,3-pentafluoropropene
(HFO-1225ye); 1,1,2,3,3pentafluoropropene (HFO-1225yc);
1,1,1,3,3-pentafluoropropene (HFO-1225zc); and related
stereoisomers such as (E)1,1,2,3-tetrafluoro-2-propene
(HFO-1234yeE); (Z)1,1,1,2,3-pentafluoropropene (HFO-1225yeZ); and
(E)1,1,1,2,3-pentafluoropropene (HFO-1225yeE). Thus, these
compositions are also ideally suited for applications that are
flammable and/or can benefit from an electrically-insulating gas
and that are subject to leaking of the composition into the ambient
environment.
[0012] Accordingly, provided is a binary azeotrope-like composition
consisting essentially of SF.sub.6, N.sub.2O, and optionally, an
additive selected from the group consisting of stabilizers, metal
passivators, corrosion inhibitors, and lubricants.
[0013] Also provided is a method for suppressing an electrical arc
or corona discharge comprising (a) providing a device capable of
storing, transmitting, or generating an electrical current or
field; and (b) enveloping at least a portion of said device with a
dielectric gas, preferably as an azeotrope-like mixture, consisting
essentially of SF.sub.6; a second component selected from the group
consisting of N.sub.2O, CO.sub.2, R32, CF.sub.3I, R218, R125, R290,
HFO-1234 isomers including HFO-1234yf, HFO-1234ze, HFO-1234zc,
HFO-1234yc, HFO-1234ye, as well as stereoisomers thereof, HFO-1225
isomers including HFO-1225ye, HFO-1225yc, HFO-1225zc, as well as
stereoisomers thereof, and combinations two or more of these; and
optionally, an additive selected from the group consisting of
stabilizers, metal passivators, corrosion inhibitors, and
lubricants.
[0014] Further provided is a gas insulated electrical device
comprising a device capable of generating, storing, and/or
transmitting an electrical current or field, and a dielectric gas,
preferably as an azeotrope-like mixture, consisting essentially of
SF.sub.6; a second component selected from the group consisting of
N.sub.2O, CO.sub.2, R32, CF.sub.3I, R218, R125, R290, HFO-1234
isomers including HFO-1234yf, HFO-1234ze, HFO-1234zc, HFO-1234yc,
HFO-1234ye, as well as stereoisomers thereof, HFO-1225 isomers
including HFO-1225ye, HFO-1225yc, HFO-1225zc, as well as
stereoisomers thereof, and combinations two or more of these;
wherein at least a portion of said device is enveloped by said
dielectric gas.
[0015] Further provided is a method for flame suppression
comprising (a) providing a contained environment comprising one or
more flammable materials; and (b) introducing a fluid composition,
preferably as an azeotrope-like mixture, into the environment,
wherein the fluid composition consists essentially of SF.sub.6; a
second component selected from the group consisting of N.sub.2O,
CO.sub.2, R32, CF.sub.3I, R218, R125, R290, HFO-1234 isomers
including HFO-1234yf, HFO-1234ze, HFO-1234zc, HFO-1234yc,
HFO-1234ye, as well as stereoisomers thereof, HFO-1225 isomers
including HFO-1225ye, HFO-1225yc, HFO-1225zc, as well as
stereoisomers thereof, and combinations two or more of these; and
optionally, an additive selected from the group consisting of
stabilizers, metal passivators, corrosion inhibitors, and
lubricants; wherein said gaseous mixture is present in an amount
effective to reduce the flammability of said environment.
[0016] Still further provided is a rigid closed cell foam
comprising a dielectric gas, preferably as an azeotrope-like
mixture, consisting essentially of SF.sub.6; a second component
selected from the group consisting of N.sub.2O, CO.sub.2, R32,
CF.sub.3I, R218, R125, R290, HFO-1234 isomers including HFO-1234yf,
HFO-1234ze, HFO-1234zc, HFO-1234yc, HFO-1234ye, as well as
stereoisomers thereof, HFO-1225 isomers including HFO-1225ye,
HFO-1225yc, HFO-1225zc, as well as stereoisomers thereof, and
combinations two or more of these, wherein said dielectric gas is
disposed within cells of said foam.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] In certain preferred embodiments, provided are novel
azeotrope-like compositions consisting essentially of SF.sub.6 and
N.sub.2O.
[0018] As used herein, the term "azeotrope-like" is intended in its
broad sense to include both compositions that are strictly
azeotropic as well as compositions that generally behave like
azeotropic mixtures. Fundamental thermodynamic principles define
the state of a fluid by its pressure, temperature, liquid
composition, and vapor composition. An azeotropic mixture is a
system of two or more components in which the liquid composition
and vapor composition are equal at the stated pressure and
temperature. In practice, this means that the components of an
azeotropic mixture are constant-boiling and generally cannot be
separated during a phase change.
[0019] According to the present invention, the azeotrope-like
compositions that consist essentially of two components are binary
azeotrope-like compositions although such compositions may include
additional components, provided that the additional components do
not form new azeotrope-like systems (e.g., ternary azeotropes or
azeotropes wherein one or more of the azeotropic components is
other than the named components), and/or are not in a first
distillation cut. The first distillation cut is the first cut taken
after the distillation column displays steady state operation under
total reflux conditions. One way to determine whether the addition
of a component forms a new azeotrope-like system so as to be
outside of this invention is to distill a sample of the composition
with the component under conditions that would be expected to
separate a non-azeotropic mixture into its separate components. If
the mixture containing the additional component is
non-azeotrope-like, the additional component will fractionate from
the azeotrope-like components. If the mixture is azeotrope-like,
some finite amount of a first distillation cut will be obtained
that contains all of the mixture components that is constant
boiling or behaves as a single substance.
[0020] Another characteristic generally possessed by azeotrope-like
compositions is that there is a range of compositions containing
the same components in varying proportions that are azeotrope-like
or approximately constant boiling. All such compositions are
intended to be covered by the terms "azeotrope-like" and "constant
boiling". As an example, it is well known that azeotropes possess
the same vapor pressure at a given temperature for at least two
different ratios of components (thus a deviation from Raoult's
law). Azeotrope-like compositions, by corollary, possess vapor
pressures that vary only slightly at the same temperature for two
or more ratios of components, but generally deviate significantly
from the vapor pressure as predicted by Raoult's law. All such
compositions are intended to be covered by the term azeotrope-like
as used herein.
[0021] It is well-recognized in the art that it is not possible to
predict the formation of azeotropes. Applicants have discovered
unexpectedly that sulfur hexafluoride forms azeotrope-like
compositions when mixed N.sub.2O.
[0022] Preferably, the SF.sub.6/N.sub.2O azeotrope-like
compositions consists essentially of from greater than about 0 to
about 55 weight percent sulfur hexafluoride and from about 45 to
less than about 100 weight percent nitrous oxide, more preferably
from about 1 to about 54.9 weight percent sulfur hexafluoride and
from about 45.1 to less than about 99 weight percent nitrous oxide,
and even more preferably from about 33 to about 34 weight percent
sulfur hexafluoride and from about 66 to less than about 67 weight
percent nitrous oxide.
[0023] The azeotrope-like compositions of the present invention may
further include any of a variety of optional additives including
stabilizers, metal passivators, corrosion inhibitors, and the like,
provided that the additive does not affect the binary
azeotrope-like nature of the composition.
[0024] Any of a variety of compounds suitable for stabilizing a
composition of the present invention may be used as a stabilizer.
Examples of certain preferred stabilizers include stabilizer
compositions comprising at least one phenol, compositions
comprising at least one epoxide selected from the group consisting
of aromatic epoxides, alkyl epoxides, alkenyl epoxides, and
combinations of two or more of these composition.
[0025] Preferably, the amount of stabilizer present in the
composition is an effective stabilizing amount. As used herein, the
term "effective stabilizing amount" refers to an amount of
stabilizer that when added to a composition, results in a
composition that degrades (e.g., chemical, thermal, electrical,
and/or radiation degradation) more slowly and/or to a lesser degree
relative to the original composition, under the same or similar
conditions. In certain preferred embodiments, an "effective
stabilizing amount" of stabilizer comprises an amount which, when
added to a composition results in a stabilized composition under
the conditions of at least one, and preferably both, of the
standards tests SAE J1662 (issued June 1993) and ASHRAE 97-1983R.
Certain preferred effective amounts of stabilizer for use in the
present invention include those present in an amount from about
0.001 to about 10, more preferably from about 0.01 to about 5, even
more preferably from about 0.3 to about 4 weight percent, and even
more preferably from about 0.3 to about 1 weight percent based on
the total weight of the composition of the present invention.
[0026] In certain preferred embodiments, the compositions of the
present invention further comprise a lubricant. Any type of
conventional lubricant may be used in the present compositions,
provided that they do not have an adverse effect on the
application. For refrigeration systems, it is preferred that the
composition comprise a lubricate that can be returned to the
compressor of the system in an amount sufficient to lubricate the
compressor. Thus, suitability of a lubricant for any given system
is determined partly by the physical and chemical characteristics
of the lubricant itself and partly by the characteristics of the
system in which it is intended to be used. Examples of suitable
lubricants, particularly for heat transfer systems, include mineral
oil, alkyl benzenes, polyol esters, including polyalkylene glycols,
PAG oil, and the like. Mineral oil, which comprises paraffin oil or
naphthenic oil, is commercially available as, for example,
Witco.RTM. LP 250 from Witco, Zerol.RTM. 300 from Shrieve Chemical,
Sunisco.RTM. 3GS from Witco, and Calumet.RTM. R015 from Calumet.
Commercially available alkyl benzene lubricants include Zerol.RTM.
150. Commercially available esters include neopentyl glycol
dipelargonate which is available as Emery.RTM. 2917 and Hatcol.RTM.
2370. Other useful esters include phosphate esters, dibasic acid
esters, and fluoroesters. Preferred lubricants include polyalkylene
glycols and esters. Certain more preferred lubricants include
polyalkylene glycols.
[0027] In certain other embodiments of the invention, provided is a
method for suppressing an electric arc or corona discharge
comprising the steps of (a) providing a device capable of storing,
transmitting, or generating an electrical current or field; and (b)
enveloping at least a portion of said device with a dielectric gas
comprising (i) a novel SF.sub.6/N.sub.2O azeotrope-like composition
as described herein, (ii) a known azeotrope-like mixture consisting
essentially of SF.sub.6 and a second component, such as a compound
selected from the group consisting of CO.sub.2, R32, CF.sub.3I,
R218, R125, and R290, or (iii) a mixture of SF.sub.6 and a
hydrofluoroolefin, such as HFO-1225yeZ, HFO-1234yf, HFO-1234ze, and
stereo-isomers thereof.
[0028] As used herein, the term "electric arc" means an undesired
or unintended electrical breakdown of gas which produces an ongoing
or momentary plasma discharge or other electrostatic discharge,
whereas the term "corona discharge" means the ionization of a fluid
surrounding a conductor which occurs when the strength of the
electric field exceeds a minimum threshold, but under conditions
insufficient to cause complete electrical breakdown. Arc and corona
discharges can be mitigated via the presence of a dielectric medium
because when two electric charges move through a dielectric medium,
the interaction energies and forces between them are reduced.
[0029] SF.sub.6 is used by the electrical industry as a pressurized
gaseous dielectric medium for high-voltage (e.g., about 1 kV or
greater) circuit breakers, switchgear, and other electrical
equipment. However, according to the Intergovernmental Panel on
Climate Change, SF.sub.6 is the most potent greenhouse gas that it
has evaluated, with a global warming potential of 22,200 times that
of CO.sub.2 over a 100 year period. Thus the leakage of SF.sub.6
from the electrical device into the atmosphere is undesirable. The
presence of N.sub.2O, CO.sub.2, R32, CF.sub.3I, R218, R125, R290,
an isomer of HFO-1225, or an isomer of HFO-1234 in the SF.sub.6
compositions mitigates this effect by proportionately reducing the
overall GWP of the composition--i.e., a portion of the relatively
high GWP SF.sub.6 is substituted with a relatively lower GWP
compound.
[0030] It is expected that the presence of SF.sub.6 proportionately
increases the dielectric strength of the overall composition based
upon the molar concentration of the SF.sub.6. However, the SF.sub.6
compositions described herein have a synergistic effect in that
their combination produces unexpectedly high dielectric strength.
That is, blending SF.sub.6 with N.sub.2O, CO.sub.2, R32, CF.sub.3I,
R218, R125, R290, HFO-1234 isomers including HFO-1234yf,
HFO-1234ze, HFO-1234zc, HFO-1234yc, HFO-1234ye, as well as
stereoisomers thereof, HFO-1225 isomers including HFO-1225ye,
HFO-1225yc, HFO-1225zc, preferably at concentrations necessary to
form an azeotrope-like mixture, produces a synergistic effect with
respect to the composition's dielectric strength.
[0031] For compositions having two or more components, the term
"synergistic effect" means a property or quality of a composition
achieved via the co-action of the components in combination which
would not be achieved merely from the proportionate amount of the
individual components alone. For example, the dielectric strength
of the compositions of the present invention is higher than would
be expected based upon the molar concentrations of the individual
components in the composition.
[0032] Accordingly, the SF.sub.6 compositions described herein can
be used to advantageously reduce global warming while providing a
high dielectric medium for suppressing electric arcs and corona
discharges. In preferred embodiments of this method, the dielectric
gas are azeotrope-like in nature. Azeotrope-like compositions are
preferred in some applications because the dielectric gas
inadvertently or unintentionally lost from an electrical system
will have a compositional ratio similar to the original
composition. Thus, the loss of dielectric gas does not
significantly change the relative concentration of components
remaining in the system thereby maintain the system's chemical and
physical properties.
[0033] Particularly preferred dielectric gases for this method
include: a dielectric gas consisting essentially of from greater
than about 0 to about 55 weight percent sulfur hexafluoride and
from about 45 to less than about 100 weight percent nitrous oxide;
a dielectric gas consisting essentially of from greater than about
0 to about 43 weight percent sulfur hexafluoride and from about 57
to less than about 100 weight percent carbon dioxide; a dielectric
gas consisting essentially of from greater than about 0 to about 53
weight percent sulfur hexafluoride and from about 47 to less than
about 100 weight percent trifluoromethane; and a dielectric gas
consisting essentially of from greater than about 0 to about 64
weight percent sulfur hexafluoride and from about 36 to less than
about 100 weight percent octafluoropropane.
[0034] In certain other embodiments of the invention, provided is a
gas insulated electrical device comprising one or more components
capable of generating, storing, and/or transmitting an electrical
current and/or field, and a dielectric gas consisting essentially
of SF.sub.6 and a second component selected from the group
consisting of N.sub.2O, CO.sub.2, R32, CF.sub.3I, R218, R125, R290,
HFO-1234 isomers including HFO-1234yf, HFO-1234ze, HFO-1234zc,
HFO-1234yc, HFO-1234ye, as well as stereoisomers thereof, HFO-1225
isomers including HFO-1225ye, HFO-1225yc, HFO-1225zc, as well as
stereoisomers thereof, and combinations two or more of these;
wherein at least a portion of said one or more components is
enveloped by said dielectric gas. Due to its high dielectric
strength, the dielectric gas is highly resistant to the flow of
electrical current and, thus, can serve as an electrical insulator.
Preferably, the dielectric gas of this embodiment has a much higher
dielectric strength than air or dry nitrogen. This property makes
it possible to significantly reduce the size of an electrical
device (compared to devices using air or nitrogen as a gas
insulator) because a smaller volume of the SF6 dielectric gas
provides the same insulative capacity as a larger void of air or
nitrogen.
[0035] Preferably, the SF.sub.6 and said second component are
present in said dielectric gas in amounts sufficient to form an
azeotrope-like composition.
[0036] In preferred embodiments, the one or more electrical
components comprise a high voltage (i.e., .gtoreq.about 1 kV)
electrical network and/or circuit. Particularly preferred
components include resistors, inductors, capacitors, transformers,
transistors, inductors, rectifiers, transmission lines, motors,
generators, voltage sources, circuit breakers, and electrical
switchgears.
[0037] In certain embodiments, the invention provides a method for
flame suppression comprising (a) providing a contained environment
having, or adapted to receive, one or more flammable materials; and
(b) introducing into at least a portion of said environment a fluid
composition, preferably as an azeotrope-like mixture, consisting
essentially of SF.sub.6; a second component selected from the group
consisting of N.sub.2O, CO.sub.2, R32, CF.sub.3I, R218, R125, R290,
HFO-1234 isomers including HFO-1234yf, HFO-1234ze, HFO-1234zc,
HFO-1234yc, HFO-1234ye, as well as stereoisomers thereof, HFO-1225
isomers including HFO-1225ye, HFO-1225yc, HFO-1225zc, as well as
stereoisomers thereof, and combinations two or more of these; and
optionally, one or more additives selected from the group
consisting of stabilizers, metal passivators, corrosion inhibitors,
and lubricants; wherein said gaseous mixture is present in an
amount effective to reduce the flammability of said
environment.
[0038] The fluid composition, and the contents of the nonflammable
environment having the fluid composition, are preferably
nonflammable according to ASHRAE Standard 34 (2004) and/or other
standards. Flame suppression is achieved by the fluid, in part,
from the physical and chemical properties of SF.sub.6, including
its relatively high heat capacity, reactive inertness (e.g., low
oxidation potential), and its ability to displace other, more
oxidizable gases from the closed environment. Since the
compositions have a relatively low GWP which is desirable in
several application, particularly applications from which the fluid
is susceptible to leaking into the ambient environment. Moreover,
the fluids have normal boiling points that are comparable to the
boiling points of several common refrigerants and, thus, can be
used as a low-GWP, nonflammable refrigerant substitutes for known
refrigerants that are either flammable or have a relatively higher
GWP. Such fluids can also ideally be used as a cover gas in the
production of non-ferrous metal, such as magnesium.
[0039] In certain other embodiments, provided is a rigid closed
cell foam comprising a dielectric gas, preferably as an
azeotrope-like mixture, consisting essentially of SF.sub.6; a
second component selected from the group consisting of N.sub.2O,
CO.sub.2, R32, CF.sub.3I, R218, R125, R290, HFO-1234 isomers
including HFO-1234yf, HFO-1234ze, HFO-1234zc, HFO-1234yc,
HFO-1234ye, as well as stereoisomers thereof, HFO-1225 isomers
including HFO-1225ye, HFO-1225yc, HFO-1225zc, as well as
stereoisomers thereof, and combinations two or more of these,
wherein said dielectric gas is disposed within cells of the foam.
Such closed cell foams can be produced from known polyol premixes,
but using the dielectric gas as a blowing agent. Advantageously,
these dielectric gases have normal boiling points comparable to
common blowing agents. In addition to a high thermal insulative
value, the resulting foams also are highly electrically
insulative.
EXAMPLES
[0040] The invention is illustrated by, but not limited to, the
following examples which are intended to be illustrative, but not
limiting in any manner.
Example 1
[0041] Two vessels, each having a pressure gage and a platinum
resistance thermometer are disposed in an isothermic environment
(i.e., a water bath) at 2.0.degree. C. The first vessel is charged
with about 16 g nitrous oxide and the second vessel is charged with
SF.sub.6. The SF.sub.6 is added in small, measured increments from
the second vessel to the first vessel while recording the first
vessel's pressure. No significant pressure change (i.e., pressure
change is within about 1 psi of starting pressure) is observed when
SF.sub.6 is added to nitrous oxide, from greater than about 0 to
about 56 weight percent SF.sub.6 indicating a binary minimum
boiling azeotrope-like composition formed. The properties of binary
mixtures are shown in Table 1.
[0042] The pressure of the blend did not drop with the addition of
the sulfur hexafluoride. It would be expected to drop since sulfur
hexafluoride has a lower vapor pressure than nitrous oxide. This
demonstrates a constant boiling mixture and azeotrope-like behavior
of the composition over this range.
TABLE-US-00001 TABLE 1 SF6/nitrous oxide compositions at
2.0.degree. C. SF6 Raoult's excess liquid phase Pressure law
pressure (mole fraction) (psia) (psia) (psi) 0.000 477.6 477.6 0.0
0.005 477.6 476.1 1.5 0.011 476.6 474.4 2.1 0.016 477.6 473.1 4.5
0.028 477.6 469.7 7.9 0.036 477.6 467.4 10.2 1.000 197.8 197.8
0.0
Prophetic Example
[0043] An ASTM-E681 apparatus can be used to measure the
flammability of the mixtures of sulfur hexafluoride and nitrous
oxide. The procedure described in the ASHRAE-34 can be used to
judge the flammability of the mixtures at 60.degree. C. and at
100.degree. C. Accordingly it will be found that at about
60.degree. C. and at about 100.degree. C., the blend is
nonflammable.
[0044] Having thus described a few particular embodiments of the
invention, it will be apparent to those skilled in the art, in view
of the teachings contained herein, that various alterations,
modifications, and improvements not specifically described are
available and within the scope of the present invention. Such
alterations, modifications, and improvements, as are made obvious
by this disclosure, are intended to be part of this description
though not expressly stated herein, and are intended to be within
the spirit and scope of the invention. Accordingly, the foregoing
description is by way of example only, and not limiting. The
invention is limited only as defined in the following claims and
equivalents thereto.
* * * * *