Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02686097 2009-11-20
GAS FIRED CATALYTIC HEATER
FIELD OF INVENTION
The present invention relates to catalytic heaters and more specifically to
gas fired
explosion-proof and non-explosion proof catalytic heaters.
BACKGROUND
Non-explosion proof, gas fired, catalytic heaters are typically used for
camping or
indoors to provide heat to a room as well as for industrial applications for
curing paint,
powder, glue, etc.
Explosion proof, gas fired, catalytic heaters are typically used for freeze-up
protection in
areas where hazardous compounds may be present. They are widely used in the
oil
and gas industry for providing heat to a room or equipment (e.g. pressure
regulators) as
well as in various industrial processes such as curing solvent based paint.
Explosion
proof, gas fired, catalytic heaters are designed to work in atmospheres of
petroleum
products including oil vapours, natural gas, ethane, propane, butane,
methanol, ethanol,
and other compounds without igniting those vapours or liquids. Catalytic
heaters
typically comprise of a catalyst pad, a heat source for activating the
catalyst pad and a
fuel source for combustion on the activated catalyst pad.
Existing explosion proof, gas fired, catalytic heaters typically require the
use of electrical
elements as the heat source to provide the necessary activation energy for the
catalyst
pad. Once the catalyst pad is preheated to its activation temperature (minimum
temperature requirement), catalytic combustion is initiated upon the
introduction of fuels
such as natural gas, methane, propane and/or other suitable hydrocarbons. This
catalytic reaction then self propagates across the surface of the pad. This
process
usually takes from 10 to 30 minutes.
One drawback with existing explosion proof, gas fired, catalytic heaters is
that the
current technology for start-up of the heater is dependent on an outside
electric power
source such as power grids or automotive batteries to provide the energy flux
for the
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electrical elements used to initiate start-up. The development of a heater
that is
independent of these power systems is particularly attractive.
Another drawback with the existing explosion proof, gas fired, catalytic
heaters is that
the start-up time is too long, particularly in low temperatures.
One method to reduce start-up time is the use of a blow torch (open fire) in
certain
instances to initialize catalytic reaction. However, this method increases the
risk of
injury or danger and is not allowed in hazardous locations. As such, catalytic
gas fired
heaters are primarily initiated with imbedded electrical element technology.
A need therefore exists to provide a catalytic gas fired heater which
overcomes or
mitigates at least one of the drawbacks outlined above or recognized in the
industry.
SUMMARY OF INVENTION
A gas fired, explosion or non-explosion proof, catalytic heater is provided
that foregoes
the need for an electrical heating element to provide the activation energy
for the
hydrocarbon catalyst pad. An alcohol self-igniting catalyst pad is used in
conjunction
with a suitable alcohol to provide the necessary activation energy to the
hydrocarbon
catalyst pad thereby removing dependence of the heater on an outside
electrical energy
source to initiate start-up of the heater.
In one embodiment there is provided a gas fired catalytic heater comprising:
a hydrocarbon catalyst pad for igniting a hydrocarbon fuel;
an alcohol injection device; and
an alcohol self-igniting catalyst pad in communication with the alcohol
injection
device, the alcohol self-igniting catalyst pad adapted for exothermic reaction
with
alcohol to provide activation energy to activate the hydrocarbon catalyst pad
and initiate
catalytic combustion of the hydrocarbon fuel when injected thereacross.
In another embodiment, there is provided an alcohol injector syringe for
injecting alcohol
into a catalytic heater, the alcohol injector syringe comprising:
a body comprising an alcohol compartment and a molecular sieve compartment
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CA 02686097 2009-11-20
separated by a membrane;
an outlet for communication with an alcohol injection device of the catalytic
heater, the outlet in fluid communication with the molecular sieve
compartment;
a plunger for forcing alcohol from the alcohol compartment through the
molecular
sieve compartment and out the outlet.
In another embodiment there is provided an alcohol injector syringe for
injecting alcohol
into a catalytic heater, the alcohol injector syringe comprising:
an alcohol injector unit comprising:
an alcohol compartment;
an outlet; and
a plunger in communication with the alcohol compartment for forcing
alcohol through the outlet upon depression; and
a molecular sieve unit comprising:
an alcohol input for communication with the outlet of the alcohol injector
unit;
a molecular sieve compartment containing molecular sieves; and
an activated alcohol outlet for communication with a alcohol injection device
of the
catalytic heater, the activated alcohol outlet in fluid communication with the
molecular
sieve compartment.
In another embodiment there is provided an alcohol self-igniting catalyst pad
for
insertion in or behind a hydrocarbon catalyst pad of a gas fired catalytic
heater, the
alcohol self-igniting catalyst pad adapted for exothermic reaction with
alcohol to provide
activation energy to activate the hydrocarbon catalyst pad and initiate
catalytic
combustion.
In another embodiment there is provided a method of igniting a gas fired
catalytic
heater, the method comprising:
i) initiating an exothermic reaction between an alcohol self-igniting catalyst
pad
and alcohol for providing activation energy to a hydrocarbon catalyst pad,
ii) contacting the hydrocarbon catalyst pad with a hydrocarbon fuel once the
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CA 02686097 2009-11-20
necessary activation energy has been imparted to the hydrocarbon catalyst pad
from
the exothermic reaction to initiate combustion of the hydrocarbon fuel across
the
hydrocarbon catalyst pad.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an exploded view of one illustrative embodiment of a catalytic
heater;
Figure 2 is a cross-sectional view of one illustrative embodiment of an
alcohol injector
syringe; and
Figure 3 is a cross-sectional view of another illustrative embodiment of an
alcohol
injector syringe.
DETAILED DESCRIPTION
Gas Fired Catalytic Heater
One illustrative embodiment of a gas fired catalytic heater is shown in Figure
1 wherein
the heater 10 is shown in exploded view. The gas fired catalytic heater 10
includes a
heater box 120. The gas catalytic heater 10 uses an alcohol self-igniting
catalyst pad
20 in place of an electrical heating element to provide sufficient activation
energy to a
hydrocarbon catalyst pad 30, such as a WX catalyst pad from CCI, such that
once
activation temperature is achieved, catalytic combustion is initiated upon the
introduction of a suitable hydrocarbon fuel such as natural gas, methane or
propane. It
should be noted that the gas fired catalytic heater 10 may be a non-explosion
(regular)
or an explosion proof, gas fired, catalytic heater thereby providing increased
safety and
decrease risk of fire, especially in a hazardous location. Non-explosion proof
heaters
i.e. used for camping, curing paint or domestic heaters can use the same start-
up
procedure, an example of which is outlined below. Other manufacturers of gas
fired,
explosion proof heaters can adopt this method for their own products. This
eliminates
the need for matches, piezoelectric or electrical elements.
The alcohol self-igniting catalyst pad 20 comprises a catalyst component that
reacts
with alcohol in an exothermic reaction which generates sufficient heat to
provide
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CA 02686097 2009-11-20
activation energy to the hydrocarbon catalyst pad 30. Typically, the alcohol
catalyst pad
20 reacts with an alcohol such as methanol, ethanol, propanol, or isopropanol.
In one
embodiment, the alcohol is methanol and the alcohol self-igniting catalyst pad
20 reacts
on contact with methanol in an exothermic reaction to provide the necessary
activation
energy to the hydrocarbon catalyst pad 30.
In one illustrative embodiment, the catalyst component of the alcohol self-
igniting
catalyst pad 20 comprises a noble metal dispersed on a cloth-like flexible
wash coat
saturated with anti-sintering elements and a catalyst promoter.
The noble metal may be an oxidation catalyst composed of metals selected from
Rh,
Ru, Pd, Pt, Ir or Au or mixtures thereof. Typical metal content may be from 1%-
30% by
weight.
The wash coat composition may comprise of at least one compound selected from
A1203, SiO2, TiO2 or mixtures thereof. Typical content may be from 70%-99% by
weight.
An anti-sintering element is optional and may be composed of metals selected
from Ni,
Sb, Zr, La or Y or mixtures thereof. Typical metal content may be from 0%-5%
by
weight.
A promoter element is also optional and may be composed of metals selected
from Al,
Si, Ce, or Zr or mixtures thereof. Typical metal content may be from 0%-5% by
weight.
By using the alcohol self-igniting catalyst pad 20 to provide the activation
energy to the
hydrocarbon catalyst pad 30, the need for an electric element to provide the
necessary
activation energy is eliminated. The alcohol self-igniting catalyst pad 20
requires
minimal activation energy and as a result, spontaneously combusts when
alcohol, such
as methanol, comes into contact with it. The catalytic combustion occurs at
room
temperature and can occur from -40 C to 30 C thereby providing for usability
in most
outdoor and indoor applications. The initiation of start-up of the catalytic
heater 10 is
controlled by the alcohol injection and the alcohol sensitive catalyst that
spontaneously
combusts the alcohol in an exothermic reaction thereby initiating catalytic
combustion of
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CA 02686097 2009-11-20
hydrocarbon fuel, such as natural gas, once in contact with the hydrocarbon
catalyst
pad 30. Once the heater 10 is fired and the alcohol is exhausted, there is no
need for
the alcohol self-igniting catalyst pad 20 to be operational until the heater
has to be re-
started.
The alcohol self-igniting catalyst pad 20 is typically housed between a top
screen 40
and a bottom screen 45, optionally in a 20 gauge stainless steel screen
housing. The
housing is of similar dimension to the pad 20 and may be appended to a side of
the
heater box 120 using any suitable means such as with rivets or a swage-lock
system.
The housing is perforated to allow for the percolation of alcohol and air to
the alcohol
self-igniting catalyst pad 20. The housing may be sandwiched between an
insulation
pad 70 and the hydrocarbon catalyst pad 30. A further insulation pad 60,
optionally a
superwool insulation pad, with a void cut out substantially in the shape of
the alcohol
catalyst pad housing may be used and provides a plane for the alcohol catalyst
pad
housing to sit in.
Alcohol may be delivered to the alcohol self igniting catalyst pad 20 through
the use of
an alcohol injector device 50. The device 50 may be made of stainless steel or
other
suitable metallic material. One non-limiting embodiment of a device 50
provides for a
wand having an outside diameter of 0.125 inches and an interior diameter of
0.078
inches. However, it will be appreciated that other suitable sizes may be used
for the
wand. The device 50 includes a delivery section which may comprise a series of
holes
(not shown), optionally evenly spaced, situated such that alcohol is sprayed
onto the
surface of the alcohol self igniting catalyst pad 20 upon alcohol injection
into the device
50. The delivery section of the device 50 may be affixed diagonally across the
surface
of the alcohol self igniting catalyst pad 20, however it will be appreciated
that this is not
a required conformation for utility and other formats, such as for example,
the device 50
situated on top of the alcohol catalyst top screen 40 may be used.
The device 50 may be held in place by the use of a bulkhead connector 160. In
such a
setup, the device 50 may be swage-locked into the bulkhead connector 160 and
bolted
onto the heater box 120. The device 50 serves as the port of entry for alcohol
that is
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CA 02686097 2009-11-20
injected to initiate catalytic reaction. This entrance port is typically
closed with a screw-
on cap or the like. The entire system should be sealed as known in the art.
The remaining heater components may be provided as in a typical heater or
explosion
proof heater to provide for suitable insulation, valving, piping, safety
features, etc.
These components may include for example, a bezel 90, a screen 80, a spud
nozzle
110, gaskets 200, washers 190 and 150, connector nut 170, brackets 210, rivets
160
and 220, connectors 240, lockwashers 230, a thermocouple 140 and thermocouple
gasket 130, a safety shut off valve 180 and baffle plate 100. It will be
appreciated that
any suitable gas fired catalytic heater construction and components may be
used as
known in the art to complete the heater as necessary or desired for a given
application
and/or use. Additional components known to those in the art may be used and
the
exploded illustrative representation of the heater 10 of Figure 1 is merely
illustrative of
one construction of a heater and is not limiting other than the use of the
alcohol self-
igniting catalyst pad 20.
In contrast to prior systems which take up to 30 minutes to complete ignition,
typical
ignition times of a heater of the present invention range from 1 to 5 minutes
depending
on the ambient temperature, the amount of alcohol injected, the hydrocarbon
fuel
activation energy required, sensitivity of the thermocouple 140 and the safety
shut off
valve (SSOV) 180. If the thermocouple 140 and SSOV 180 are not used, the start-
up
time is reduced and would be substantially instantaneous. While when they are
used as
required for hazardous locations, there is a small time delay needed for the
thermocouple 140 to warm up in order to generate enough current that the
electromagnet inside the SSOV 180 remains open and allows the fuel to enter
the
heater 10. At lower ambient temperatures the catalytic alcohol combustion
reaction
may take longer to provide sufficient activation energy to initiate catalytic
combustion of
the fuel when in contact with the hydrocarbon catalyst pad 30.
One issue involved with the use of the alcohol catalyst pad 20 is that over
time the
alcohol active pad 20 may become dormant. This arises as a result of the
adsorption of
moisture onto the active catalytic sites of the alcohol self-igniting catalyst
pad 20. The
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adsorbed water molecules inhibit the adsorption of the alcohol species onto
the active
catalytic sites thereby preventing the exothermic catalytic combustion of the
alcohol
from propagating. As such, enough energy is not generated to initiate the
spontaneous
combustion reaction and the heater 10 does not fire. The alcohol species are
not able
to displace the adsorbed water molecules, resulting in the pad 20 becoming
dormant.
One embodiment of the heater 10 at least partially overcomes this issue
thereby
extending the operational life of the alcohol self-igniting catalyst pad 20 by
incorporating
a module 47 containing desiccants within the alcohol self-igniting catalyst
pad 20 to
serve as a sacrificial agent. The desiccants attract moisture thereby reducing
the
quantity adsorbed on the active catalytic sites. When the heater 10 is in use,
i.e. fired,
the desiccant module 47 is regenerated rendering it active for re-start of the
heater 10.
A further or alternative solution to the issue of moisture adsorption is to
inject activated
alcohol onto the alcohol self-igniting catalyst pad 20. For the purposes of
this
disclosure, activated alcohol can be considered to be alcohol having an
elevated
temperature suitable for displacing the water molecules from the active
catalytic sites.
Typically, the activated alcohol has an elevated temperature of about 20 C -
60 C to
displace the water molecules from the active catalytic sites. An alcohol
injector syringe
for injecting activated alcohol into the heater 10 will be outlined in detail
further below.
Alcohol, and especially methanol, is a suitable chemical for use in catalytic
heaters and
explosion proof catalytic heaters as the Canadian Standards Associations in
Canada
and Factory Mutual in the United States have deemed methanol to be permitted
in
Class 1, Division 1, Group D locations. This is important as heaters of this
type are
generally used in these locations as flammable petroleum products such as
natural gas,
propane as well as alcohols, including methanol, and organic solvents may be
present
in these locations. As a result the use of alcohol is a viable and useful
solution for use
with a alcohol sensitive catalyst for producing sufficient energy from alcohol
combustion
capable of activating combustion in the hydrocarbon catalytic pad and/or an
explosion
proof catalytic heater.
To ensure that the heater 10 may be considered to be an explosion proof heater
certain
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fabrication steps should be taken. The alcohol self-igniting catalyst pad 20
may not be
explosion proof while the hydrocarbon catalyst pad 30 is. To provide an
explosion proof
heater, the alcohol self-igniting catalyst pad 20 is placed inside the gas
fired heater 10
so that excessive heat coming from the alcohol combustion is contained inside
the
explosion proof unit.
Thus, accidental ignition of petroleum product before injection into the
heater is reduced
or even eliminated. By placing the alcohol self-igniting catalyst pad 20 on
the opposite
side of the hydrocarbon catalyst pad 30, only the hydrocarbon catalyst pad 30
is
exposed to the environment and the hydrocarbon fuel. Excess alcohol, if any,
is
adsorbed by the hydrocarbon catalyst pad 30, considered to be explosion proof,
that is
not sensitive to the alcohol at ambient temperature and would consume any
excess
alcohol at elevated temperature, maintaining its explosion-proof
characteristic. After the
hydrocarbon catalyst pad 30 is operational, it consumes all combustion oxygen,
which is
diffusing from the front of the hydrocarbon catalyst pad 30, and therefore,
the imbedded
alcohol pad 20 does not produce any additional heat. The lack of oxygen
deactivates
the alcohol catalyst pad 20, as it may be active at elevated temperatures in
the
presence of hydrocarbon based fuel and oxygen from the air. This feature is
important
in hazardous locations where no need for any additional heat is required but
for that
generated from the hydrocarbon catalyst pad 30.
A further benefit of the heater 10 is that the ignition mechanism including
the alcohol
self-igniting catalyst pad 20 and the hydrocarbon catalyst pad 30 may be used
for
activation of gas fired heaters, furnaces, barbeques, including camping,
furnished with a
regular or/and explosion proof units. This avoids the need for spark initiated
systems or
electric element dependent systems.
It will be appreciated that the Canadian Electrical Code Definition of
"explosion-proof'
means enclosed in a case which is capable of withstanding, without damage, an
explosion, which may occur within it, of a specified gas or vapour and capable
of
preventing the ignition of a specified gas or vapours surrounding the
enclosure from
sparks, flashes, or explosion of the specified gas or vapour within the
enclosure.
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CA 02686097 2009-11-20
In a further embodiment, it will also be appreciated that for the purposes of
this
disclosure, the term "explosion-proof' includes explosion proof heater
certified in Class I
Division 1 and Group D, will not ignite gases or vapours that are in group D
when they
are present 24 hours a day. Canadian Standard Associations and Factory Mutual
list
those substances in Groups A-G. Heater's case (metal) temperature is below the
auto-
ignition temperature of gases/vapours from group D, while the explosion proof
catalyst
pad (burner) consumes those gases/vapours without igniting them, e.g. if you
take a
glass full of gasoline and pour on the explosion proof burner the gasoline is
not ignited.
Evaporation would likely occur as well as associated odours.
Alcohol Infection Syringe
Figures 2 and 3 illustrate separate embodiments of an alcohol injection
syringe useful
for injecting alcohol or activated alcohol into an alcohol receiver such as an
alcohol
injection wand as described above with reference to Figure 1.
An alcohol injection syringe is shown generally at 300 in Figure 2. The
syringe 300,
also referred to as a cartridge, includes an upper alcohol compartment 320 for
containing alcohol, such as methanol, and a lower molecular sieve compartment
330 for
containing molecular sieves 335. The two compartments 320 and 330 are
separated by
a non-permeable membrane 310, for example a thin polyethylene membrane. A
plunger 350, when depressed, forces alcohol to break the membrane 310 and flow
from
the alcohol compartment 320 across the molecular sieves 335 in the molecular
sieve
compartment 330 and become activated. Activated alcohol may then be released
and
injected into a suitable inlet on the heater, such as the device 50 described
above,
through the outlet 340. The molecular sieves 335 adsorb a certain amount of
alcohol
and release heat through adsorption. The excess alcohol adsorbs this heat and
in turn
is heated up and activated. Upon injection into the heater 10, the activated
alcohol is
able to initiate catalytic reaction faster and at lower temperatures.
In one embodiment, the outlet 340 is sized to fit with and inject alcohol into
the device
50 of the heater described above.
CA 02686097 2009-11-20
The injection syringe 300 may be sealed at the top around the plunger 350 with
a press
seal 360.
The alcohol injection syringe 300 is convenient for use in camping or similar
applications as it is easy to store, flameless and because it is sealed,
minimizes
environmental impact due to spillage. The syringe 300 may be refilled with
alcohol after
use and the molecular sieves may be either recharged for use again or simply
replaced.
Alternatively, a user may simply purchase multiple syringes for repeated start-
up of the
heater. Risk of fire or explosion is reduced or even eliminated as the syringe
300 may
be adapted to fit tightly or even sealingly with a alcohol input in the heater
thereby
further minimizing spillage and exposure of the alcohol to an exterior heat
source or
spark.
Figure 3 shows an illustrative embodiment of a variant of an alcohol injector
syringe
shown generally at 400. The syringe 400 includes two units, namely an alcohol
injector
unit 405 and a molecular sieve unit 450. The alcohol injector unit 405
includes an
alcohol compartment 430 and a plunger 420 for forcing the alcohol through an
output
410. The alcohol compartment 430 may be sealed as described above with a press
seal 440. The molecular sieve unit 450 includes an alcohol input 460 for
connection
with the output 410, a molecular sieve compartment 480 containing molecular
sieves
485 and an output 470 suitable for connection with an alcohol input of a
heater such as
that described above with reference to Figure 1. To activate the alcohol, the
alcohol
injector unit 405 is connected to the molecular sieve unit 450 via the output
410 and the
input 460 and the plunger 420 is depressed. Alcohol is injected into the
molecular sieve
compartment 480 and flows over the molecular sieves 485 where, as outlined
above,
the molecular sieves 485 adsorb a certain amount of alcohol and release heat
through
adsorption. The excess alcohol adsorbs this heat and in turn is heated up and
activated. Upon injection into the heater 10, the activated alcohol is able to
initiate
catalytic reaction faster and at lower temperatures.
By having a separate unit for alcohol and for molecular sieves, a user need
only replace
the molecular sieve unit 450 and refill the alcohol in the alcohol unit 405 in
order to have
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CA 02686097 2009-11-20
a syringe useful for starting the heater. Unit 450 may contain a screw cap for
re-
charging molecular sieves 485. It should be noted however, that if the alcohol
catalyst
pad 20 is active or non-dormant, the alcohol injector unit 405 may be used to
initiate
alcohol combustion without the need for the molecular sieve unit 450. However,
if the
alcohol active pad 20 becomes dormant this method may not be able to initiate
alcohol
combustion, while the presence of molecular sieve unit 450, allows for prompt
initiation
process.
The cartridges 300 and 450 should be stored in a sealed container such as a
plastic
bag (e.g. zip lock) and/or with caps on their inlet 460 and outlet 340, 470
ports in order
not to adsorb moisture from the air.
Molecular sieve 13X was chosen for this application as it produced the highest
amount
of heat per unit of mass, however, other molecular sieves such as 4A, 5A,
other
chemicals including activated alumina and other types of desiccants may be
used.
Start-up Operation of Alcohol Activated Heater
The following is a non-limiting example of a suitable start-up procedure for
firing a
heater such as that described with reference to Figure 1.
Remove the threaded cap from the bulkhead adapter 160 and attach the alcohol
input,
for example the input 340 or 410/ 470 of the alcohol injector syringe as
described with
reference to Figure 2 or 3, respectively. Gently inject about 30-40 ml of
methanol into
the methanol injection device 50. Remove the methanol injector from the
bulkhead
adapter 160 and attach the threaded cap to avoid gas leakage when the heater
is
operational. The methanol catalytic combustion reaction should be
substantially
instantaneous and depending on the environment ambient temperature, the user
should
be able to feel heat being generated from the methanol combustion within
seconds of
injection. After injecting the methanol, the user may confirm the initiation
of the catalytic
reaction by placing their hand over the methanol catalyst pad 20 and observing
the
generation of heat. The catalytic combustion of methanol is highly exothermic
and
provides the activation energy required for the activation of the hydrocarbon
catalyst
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pad 30. After approximately 3-5 minutes has elapsed, depress the safety shut-
off valve
180. The valve 180 should open allowing hydrocarbon fuel such as natural gas
to flow
to the heater 10. At this stage, the initial burst of heat energy should be
sufficient to
initiate the catalytic combustion of the hydrocarbon fuel. The catalytic
reaction self
propagates across the entire hydrocarbon catalyst pad 30.
Alternatively an alcohol injection unit 405 can be used by itself. However,
alcohol
catalytic combustion reaction may not be initiated particularly at low ambient
temperature. At temperatures above 0 C that could be a more convenient, less
cumbersome method for startup.
The present invention has been described with regard to a plurality of
illustrative
embodiments. However, it will be apparent to persons skilled in the art that a
number of
variations and modifications can be made without departing from the scope of
the
invention as defined in the claims.
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