U.S. patent application number 13/082733 was filed with the patent office on 2011-10-13 for demisting flame arrestor for an electrolytic hydrogen generator.
Invention is credited to Stuart I. Smedley.
Application Number | 20110250554 13/082733 |
Document ID | / |
Family ID | 44761168 |
Filed Date | 2011-10-13 |
United States Patent
Application |
20110250554 |
Kind Code |
A1 |
Smedley; Stuart I. |
October 13, 2011 |
Demisting Flame Arrestor for an Electrolytic Hydrogen Generator
Abstract
A demisting flame arrestor provides a border between an
electrolytic reaction vessel and an intake manifold of an engine,
and includes a composite material having hydrophilic zones and
hydrophobic zones constructed to form multiple pathways for
permitting gaseous flow. The hydrophilic zones promote trapping and
condensation of water vapor and in the event of fire disperse flame
into the multiple pathways to arrest the flame front. The
hydrophobic zones repel condensed water to return the water to the
reaction vessel through force of gravity.
Inventors: |
Smedley; Stuart I.;
(Oceanside, CA) |
Family ID: |
44761168 |
Appl. No.: |
13/082733 |
Filed: |
April 8, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61322252 |
Apr 8, 2010 |
|
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Current U.S.
Class: |
431/346 ;
29/592 |
Current CPC
Class: |
Y10T 29/49 20150115;
F23D 14/82 20130101 |
Class at
Publication: |
431/346 ;
29/592 |
International
Class: |
F23D 14/82 20060101
F23D014/82 |
Claims
1. A demisting flame arrestor, comprising: a composite material
having hydrophilic zones and hydrophobic zones; multiple pathways
constructed through the hydrophilic zones and hydrophobic zones for
permitting gaseous flow; and the hydrophilic zones configured to
disperse flame into the multiple pathways and to promote trapping
and condensation of water vapor.
2. The demisting flame arrestor of claim 1 wherein the hydrophilic
zones and hydrophobic zones are evenly distributed throughout the
composite material.
3. The demisting flame arrestor of claim 1 wherein the hydrophilic
zones comprise a structural base containing the hydrophobic
zones.
4. The demisting flame arrestor of claim 1 wherein the hydrophobic
zones comprise a structural base containing the hydrophilic
zones.
5. The demisting flame arrestor of claim 1 wherein the composite
material has a gradual distribution of hydrophobic zones from one
end of the demisting flame arrestor to an opposite end of the
demisting flame arrestor.
6. The demisting flame arrestor of claim 1 wherein the hydrophilic
zones comprise metal and the hydrophobic zones comprise a
polymer.
7. The demisting flame arrestor of claim 6 wherein the metal
comprises nickel and the polymer comprises Teflon.
8. The demisting flame arrestor of claim 1 wherein the hydrophilic
zones comprise nickel mesh and the hydrophobic zones comprise
Teflon particles.
9. A method for manufacturing a demisting flame arrestor,
comprising: preparing an emulsion of polymer; soaking a metal mesh
in the emulsion; removing the metal mesh from the emulsion;
draining the metal mesh; applying heat to the metal mesh to sinter
the polymer onto the metal mesh; and compressing the sintered metal
mesh into a desired form.
10. The method of claim 9 wherein the metal mesh comprises nickel
and the polymer comprises Teflon.
Description
BACKGROUND OF THE INVENTION
[0001] This application claims priority to U.S. Provisional
Application No. 61/322,252, which was filed Apr. 8, 2010, and which
is fully incorporated herein by reference.
1. Field of the Invention
[0002] The present invention relates generally to flame arrestors
and demisters used in reaction cells, and more specifically to a
device that functions as both a flame arrestor and a demister for
use in an electrolytic hydrogen generator.
[0003] 2. Description of Related Art
[0004] Water electrolyzers have been used for the purpose
generating and supplying a small stream of hydrogen and oxygen gas
to internal combustion engines. The hydrogen/oxygen gas stream is
usually only a fraction of a percent of the intake combustion air
flow but evidence has been presented to show that this small stream
can reduce emissions of particulates from diesel engines and in
some cases also reduce emissions of NOx and provide small increases
in engine fuel efficiency. Typically these electrolyzers are
powered by electrical current from the vehicle battery or
alternator and are fitted to the back of the cab compartment of a
truck or under the hood of a car. To further improve the
effectiveness of these devices it is necessary to minimize their
volume and mass and maximize their energy efficiency for a given
intended hydrogen output. Furthermore it is important to operate an
electrolyzer that can function reliably for thousands of hours in
extremes of temperature, the presence of continuous shock and
vibration and road grime and grit.
[0005] The science and engineering principles behind the design and
operation of water electrolyzers are well known and understood.
Electrolysis of water is the decomposition of water (H.sub.2O) into
oxygen (O.sub.2) and hydrogen gas (H.sub.2) due to an electric
current being passed through the water. An electrical power source
is connected to two electrodes, or two plates, (typically made from
some inert metal such as platinum or stainless steel) which are
placed in the water. Hydrogen will appear at the cathode (the
negatively charged electrode, where electrons are transferred to
water molecules), and oxygen will appear at the anode (the
positively charged electrode where electrons are transferred from
water molecules to the electrode). The generated amount of hydrogen
is twice the amount of oxygen, and both are proportional to the
total electrical charge that was sent through the water. Electrons
carry the current in the circuit external to the electrolysis cell
and in the electrodes, while charged ions carry electric current
through the water or electrolyte solution.
[0006] In the water at the negatively charged cathode, a reduction
reaction takes place, with electrons (e.sup.-) from the cathode
being given to water molecules to form hydrogen gas: [0007] Cathode
(reduction):
2H.sub.2O(1)+2e.sup.-.fwdarw.H.sub.2(g)+2OH.sup.-(aq)
[0008] At the positively charged anode, an oxidation reaction
occurs, where water is oxidized to generate oxygen gas and giving
electrons to the anode. [0009] Anode (oxidation): H.sub.2O(1)
.fwdarw.1/2O.sub.2(g)+2H.sup.+(aq)+2e.sup.-
[0010] Combining these two reactions with [0011]
H.sub.2O(1).fwdarw.2H.sup.+(aq)+2OH.sup.-(aq) yields the overall
decomposition of water into oxygen and hydrogen: [0012] Overall
reaction: 2H.sub.2O(1).fwdarw.2H.sub.2(g)+O.sub.2(g)
[0013] For every two electrons the number of hydrogen molecules
produced is twice the number of oxygen molecules. Assuming equal
temperature and pressure for both gases, the produced hydrogen gas
has therefore twice the volume of the produced oxygen gas.
[0014] In acid solution the reactions and standard electrode
potentials are [0015] 2H.sup.+(aq)+2e.sup.-.fwdarw.H.sub.2(g)
E.sup.0=0.00V [0016]
1/2O.sub.2(g)+2H.sup.+(aq)+2e.sup.-.fwdarw.H.sub.2O(1)
E.sup.0=1.23V giving a Standard EMF of 1.23 V.
[0017] In base solution the reactions and standard electrode
potentials are [0018]
2H.sub.2O(1)+2e.sup.-.fwdarw.H.sub.2(g)+2OH.sup.-(aq)
E.sup.0=-0.83V [0019] 1/2O.sub.2(g)+2H.sub.2O(1)+2e.sup.-
2OH.sup.-(aq) E.sup.0=0.40V giving a Standard EMF of 1.23 V.
[0020] Electric current is carried through the electrolyte solution
by way of movement of ions such as H.sup.+(aq) or OH.sup.-(aq) .
However in pure water these ions are in very low concentration so
an additional electrolyte must be added to allow practical values
of current to flow. Typically an alkalis such as Sodium Hydroxide
(Na0H) or Potassium Hydroxide (KOH) is added in quite high
concentrations. A typical value for KOH would be about 30 wt%, the
concentration at which the electrical conductivity reaches a
maximum.
[0021] Faraday's Law provides the relationship between the current
and the rate of electrolysis, where N the number of moles of gas
released by a current I in time t is given by [0022] N=I*t/(n*F)
(1)
[0023] N is the number of electrons required to deliver one mole of
gas, for hydrogen n=2 for oxygen n=4. Thus the rate of hydrogen
production is given by [0024] .DELTA.I/.DELTA.t=I/(2*F) (2)
[0025] The minimum voltage required to electrolyze water is 1.23 V
but higher voltages must be applied in order to increase the
current. Voltage drops occur at the electrodes due to overpotential
and across the electrolyte gap between to two electrodes.
[0026] Overpotential (.eta.) refers to the difference between the
applied potential necessary to produce a current i and the
equilibrium potential E.sub.0 at zero current, [0027]
.eta.=E-E.sub.0 (3)
[0028] For the anode where oxygen is produced the Overpotential is
related to the current density by [0029] i=i.sub.0exp(-b .eta.)(4)
[0030] where b=.alpha.nF/RT and i=I/A (5) and where i.sub.0 is a
constant relating to the particular electrode reaction and the
surface on which it occurs say platinum in KOH, a is a constant
usually with a value of 0.5. F is the Faraday constant, R the gas
constant and T temperature in K. A is the active area of the
electrode and I is the actual measured current. A similar equation
exists for the cathode but with different values of i.sub.0 and a.
These equations can also be expressed in .sub.terms of the
overvoltage as [0031] .eta.=Bln i.sub.0-Blni=Bln i.sub.0/I (6)
[0032] where B=1/b.
[0033] The gap between to two electrodes is filled with conducting
electrolyte but does incurred a potential drop. This potential drop
is given by [0034] V.sub.electrolyte=I*R (7)
[0035] where I is the current and R the resistance of the
electrolyte, given by: [0036] R=A/d*.kappa.(8)
[0037] A is the effective electrode area and d the electrode
separation, .kappa. is the conductivity of the electrolyte which is
a function of the electrolyte composition and concentration and
temperature.
[0038] The Current Voltage Characteristic for a single cell is
therefore given by [0039] V=E.sub.0
=.eta..sub.anode-.eta..sub.cathode+IR (9) [0040] V=E.sub.0
B.sub.anodeln i.sub.0/i-B.sub.cathodeln i.sub.0/i+IR (10)
[0041] It can be seen that for a given current the voltage can be
reduced by increasing the effective surface area of the electrodes,
reducing the electrode separation, increasing the concentration and
temperature of the electrolyte and by catalyzing the electrodes
which has the effect of increasing the value of i.sub.0.
[0042] The maximum efficiency of an Electrolyzer c, is given by,
[0043] .epsilon.=.DELTA.H.sup.0/.DELTA.G.sup.0
[0044] where .DELTA.G.sup.0 and .DELTA.H.sup.0 are the standard
Cibbs Energy Change and standard Enthalpy change for the
electrolysis reaction. For water electrolysis the maximum
efficiency is 120% this is greater than 100 because in principle
the reaction can extract heat from the surroundings, in practice
however the efficiency is below 100% because the driving voltage is
always greater than 1.23 V.
[0045] The actual efficiency is given by [0046]
.epsilon.=.DELTA.H.sup.0/(nFV) where V is the cell operating
voltage at a given current. V is given by equation (10).
[0047] At a practical current density of about 2 A cm.sup.-2 the
cell voltage is about 2 V, this would give an efficiency of
74%.
[0048] Electrolyzer Design
[0049] From the above descriptions and equations it can be shown
that the most energy efficient electrolyzer is one that minimizes
the overall cell impedance. For an electrolyzer supplied with
current from a vehicle alternator operating at a constant voltage
if .about.13 V and with a current draw limited to 20-30 A, the
impedance of the electrolyzer is minimized by reducing the
electrode gap, increasing the electrolyte conductivity and
increasing the number of cells in series, usually to six. Under
these circumstances the electrode area is optimized to reduce cell
impedance but to remain within the chosen current draw the
alternator.
[0050] If the electrolyte is potassium hydroxide the maximum
conductivity occurs at about 28% by weight potassium hydroxide.
[0051] An electrolyzer with 6 cells in series with stainless steel
electrodes of 200 cm.sup.2 and a spacing of 1 cm immersed in 28%
KOH will operate at 12 V and about 30 A and produce about 1.3 L/min
of hydrogen. This electrolyzer would require a minimum volume of
about 1.5 L of electrolyte or about 1 L of water. This amount of
water would be consumed in 16.5 hours.
[0052] During electrolyzer operation, water vapor or tiny droplets
of water can become entrained in the flow of gasses out of the
electrolyzer. This process leads to an undesirable loss of water
volume from the electrolyzer vessel, and an unwanted introduction
of water into the engine manifold. To minimize these problems, a
water trap or other means for separating water from the gasses
generated by the electrolyzer may be incorporated into the
electrolyzer design.
[0053] The production of a volatile gas such as hydrogen raises
safety concerns, especially if the hydrogen is allowed to
accumulate under pressure during equipment malfunction or under
some other accident scenario. To mitigate damage in the event that
the hydrogen ignites, it is prudent to incorporate safety measures
such as a flame arrestor or other means for flame suppression in
some part of the system. Ideally, the flame suppression should
prevent a flame that originates in the engine from propagating into
the electrolysis vessel, and vice-versa.
[0054] For the present inventors, a design objective for an
on-board hydrogen/oxygen generator is the minimization of cost and
complexity through the use of passive controls. The problem being
solved by the present invention is how to design a filtration
device between the electrolytic reactor and the intake manifold of
the engine, so that the device acts as both a flame arrestor and a
demister.
SUMMARY OF THE INVENTION
[0055] The present invention provides an engineering design for a
demisting flame arrestor that may be installed, for example, in an
on-board electrolytic hydrogen generator. The demisting flame
arrestor provides a border between a reaction vessel of the
generator and an intake manifold of an internal combustion
engine.
[0056] In one embodiment, the demisting flame arrestor includes a
composite material having hydrophilic zones and hydrophobic zones
constructed to form multiple pathways for permitting gaseous flow.
The hydrophilic zones may be configured to promote trapping and
condensation of water vapor during normal operation, and to
disperse flame into the multiple pathways to arrest the flame front
in the event of an accidental explosion. The hydrophobic zones may
be configured to repel condensed water to return the water to the
reaction vessel through force of gravity. The hydrophilic zones and
hydrophobic zones may be evenly distributed throughout the
composite material, or they may be distributed in a graduated,
layered, or random arrangement. The composite material may be
constructed so that the hydrophilic material forms a structural
base for hydrophobic material, or so that the hydrophobic material
forms a structural base for hydrophilic material, or so that both
materials contribute to the structural integrity of the composite.
In one implementation, the hydrophilic zones comprise a metal such
as nickel and the hydrophobic zones comprise a polymer such as
Teflon.
[0057] Another embodiment of the invention provides a method for
manufacturing a demisting flame arrestor. The method prescribes
salient steps for preparing an emulsion of polymer, soaking a metal
mesh in the emulsion, removing the metal mesh from the emulsion,
draining the metal mesh, applying heat to the metal mesh to sinter
the polymer onto the metal mesh, and compressing the sintered metal
mesh into a desired form. The metal mesh may be nickel mesh and the
polymer may be Teflon particles. In another embodiment, a method
for forming a demisting flame arrestor may include steps for
soaking sintered metal particles within a polymer emulsion,
removing and drying the particles, then heating and compressing
them into a desired form. In another embodiment, a method for
forming a demisting flame arrestor may include steps for mixing
polymer particles such as Teflon particles with a metallic powder
such as nickel powder, then applying heat and compression to
achieve a desired form.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] Other systems, methods, features and advantages of the
invention will be or will become apparent to one with skill in the
art upon examination of the following figures and detailed
description. It is intended that all such additional systems,
methods, features and advantages be included within this
description, be within the scope of the invention, and be protected
by the accompanying claims. Component parts shown in the drawings
are not necessarily to scale, and may be exaggerated to better
illustrate the important features of the invention. Dimensions
shown are exemplary only. In the drawings, like reference numerals
may designate like parts throughout the different views,
wherein:
[0059] FIG. 1 is a cross sectional diagram of a reaction cell
incorporating one embodiment of a demisting flame arrestor
according to the invention.
[0060] FIGS. 2 through 9 each show a cross sectional diagram of a
design for a demisting flame arrestor having both hydrophobic and
hydrophilic properties according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0061] The following disclosure presents an exemplary embodiment of
the invention for a demisting flame arrestor for use in a reaction
cell. In one application, the demisting flame arrestor is designed
for installation in an on-board electrolytic hydrogen generating
system to form a boundary in the gaseous flow path between a
reactor such as an electrolysis vessel and an outflow conduit such
as an engine manifold.
[0062] FIG. 1 shows cross sectional view of a reaction cell 10
equipped with an exemplary embodiment of a demisting flame arrestor
12 of the present invention. Reaction cell 10 may be an
electrolysis vessel containing a volume of an electrolyte 14, such
as KOH. An anode 16 and a cathode 18 may be suspended at least
partially within the electrolyte 14, and each of these electrodes
may be conductively connected, respectively, to positive and
negative terminals 20 and 22. Terminals 20 and 22 are preferably
located outside of the vessel 10 at any location that is convenient
for connection to an external source of electrical power, such as a
vehicle battery, battery charging system, or other DC source.
Energization of terminals 20 and 22 creates an electric field
between anode 16 and cathode 18 to cause electrolysis of the
electrolyte. For an aqueous electrolyte 14, hydrogen and oxygen gas
will be produced according to the oxidation and reduction reactions
presented above.
[0063] The hydrogen and oxygen gases will form initially on the
electrodes 16 and 18 and rise, along with some amount of water
vapor, through the surface of the electrolyte 14 and into the air
gap 24. Under the proper operating conditions, a pressure
differential will occur across the demisting flame arrestor 12,
that is, between the air gap 24 and a conduit 26. For example, in
an application where conduit 26 is connected to an intake manifold
of an internal combustion engine, a vacuum in the manifold will
draw the gases and water vapor through the demisting flame arrestor
12 and into the manifold.
[0064] The demisting flame arrestor 12 is shown at a location
directly above the surface of electrolyte 14. In other embodiments,
the demisting flame arrestor may be located a greater distance
above the electrolyte, or a considerable distance away from
reaction cell 10, such as further within conduit 26, or at an
interface between conduit 16 and the intake manifold of an engine
or other apparatus. In any case, it may be desirable to locate the
demisting flame arrestor out of range of electrolyte "slop",
particularly in on-board applications where one would expect the
electrolyte surface to rise and fall as a result of the
acceleration or travel of a vehicle.
[0065] According to the invention, the demisting flame arrestor 12
has both hydrophilic and hydrophobic properties, so that the
collection of water vapor may be promoted by the hydrophilic
property, and the repulsion of water droplets may be promoted by
the hydrophobic property. Generally speaking, hydrophilic and
hydrophobic properties are mutually exclusive properties within any
homogeneous material. It is therefore an object of the invention to
construct the flame arresting demister as a composite material, or
as an assembly of hydrophilic and hydrophobic materials, in such a
way that hydrophilic and hydrophobic zones are distributed
throughout the composition.
[0066] In one embodiment, a demisting flame arrestor 12 comprises a
composite material that is between about 10% and about 90%
hydrophilic, with the balance of the composite being hydrophobic.
The hydrophilic material may be a metal that is readily wettable by
the electrolyte but not corrodible. Metals such as nickel,
stainless steel, noble metals, and plated metals--such as iron or
steel plated with nickel or chromium--are examples of hydrophilic
materials that are suitable for use in the demisting flame
arrestor. The hydrophobic material may be a thermoplastic polymer
such as Teflon or polypropylene, or some other material that is
stable in the electrolyte and that possesses the desired water
repulsion properties.
[0067] In one embodiment, as shown in the figure, demisting flame
arrestor 12 comprises a composite having a structural base composed
of a hydrophilic material 28 that contains a regular or irregular
distribution of hydrophobic materials 30 throughout the structure.
In another embodiment, the hydrophobic material may serve as the
structural base, and the hydrophilic material may be distributed
throughout the hydrophobic material. In another embodiment, the two
materials may be assembled so that both materials provide
structural support to maintain the integrity of the assembly. The
distribution of one material within the other material may be an
even distribution (homogeneous) or an uneven distribution (random,
graduated, or layered).
[0068] Operating as a demister (during normal operation), the
demisting flame arrestor 12 works as a filter that ideally traps
water vapor while passing hydrogen and oxygen (or other) gases. The
arrangement of hydrophilic and hydrophobic zones create tiny
circuitous pathways through the demisting flame arrestor. The gases
compelled by the pressure differential will easily work their way
through these pathways and around the hydrophilic zones. The water
vapor however, when contacting a hydrophilic zone, will tend to
agglomerate there and condense to form a water droplet on the
hydrophilic zone. As the droplet grows and becomes heavier, it will
fall through the demisting flame arrestor under force of gravity,
encountering hydrophobic zones along the way. The hydrophobic zones
will repel the droplet, helping to accelerate its passage downward
until it eventually drops back into the volume of electrolyte 14.
In this way, the combination of hydrophilic and hydrophobic
materials according to the invention discourages the accumulation
of water droplets that would otherwise clog the demisting flame
arrestor and obstruct the passage of the electrolysis gases.
[0069] Operating as a flame arrestor (during an accident), the
demisting flame arrestor 12 works by absorbing heat and directing a
flame front through multiple pathways that are too narrow to permit
the continuance of the flame. The multiple pathways may be the same
circuitous pathways that allow the passage of gases through the
demisting flame arrestor. The multiple pathways are bordered, in
part, by the metal construction of the hydrophilic zones, which
provide a corresponding multiplicity of surface areas that are
ideal for sinking heat. In the event of an explosion or fire
originating on either side of the demisting flame arrestor, the
metal material suppresses the flames by dispersing the flame front
and by absorbing the heat.
[0070] In one embodiment, the demisting flame arrestor may be
formed from a combination of metal wool and small particles of
polymer, such as Teflon balls. For example, the wool may be spread
flat, the polymer balls may be arranged on the wool, and the wool
may be rolled into a cylindrical or "jelly roll" form.
[0071] In another embodiment, the demisting flame arrestor may be
formed as a sintered metal disk or perforated filter, and partially
filled with hydrophobic particles.
[0072] A method of manufacturing a demisting flame arrestor
according to the invention may include the following salient steps:
A polymer emulsion may be prepared, for example, using 5 nm Teflon
particles and water. A metal or wire mesh, such as nickel mesh, may
then be soaked in the Teflon emulsion, then removed and drained.
Heat and compression may then be applied to the wire mesh to sinter
the polymer onto the metal. A temperature of about 350 degrees C.
may be suitable for this purpose. The compression may be used to
mold the mesh into a desired form.
[0073] Alternatively, one may start with sintered metal particles
and soak them within a polymer emulsion. The particles may then be
removed and dried, then heated and compressed into a desired form,
again using a temperature around 350 degrees C. Alternatively, one
may start with polymer particles such as Teflon particles, mix them
with a metallic powder such as nickel powder, then apply heat and
compression to achieve a desired form.
[0074] FIGS. 2 through 9 show different exemplary embodiments of
demisting flame arrestors according to the invention. Each may be
characterized by its distribution of hydrophobic and hydrophilic
materials, each material being complimentary to the other. FIGS. 2
through 5 show embodiments wherein hydrophilic material 28 provides
a structural base within which a plurality of hydrophobic zones 30
may be distributed. FIGS. 6 through 9 show embodiments wherein the
hydrophobic material 30 provides a structural base within which a
plurality of hydrophilic zones 28 may be distributed. Round and
triangular zones are shown for purposes of illustration only. Many
geometries for zones 28 or 30 other than round and triangular may
be employed in various embodiments of the invention.
[0075] FIGS. 2 and 6 correspond to the general design of demisting
flame arrestor 12 of reaction cell 10. FIG. 2 consists of a
hydrophilic base material 28 within which a plurality of round or
spherical hydrophobic zones 30 are embedded. FIG. 6 consists of a
hydrophobic base material 30 within which a plurality of round or
spherical hydrophilic zones 28 are embedded.
[0076] FIGS. 3 and 7 show embodiments of the demisting flame
arrestor 12 in which either the hydrophobic zones 30 or hydrophilic
zones 28 are more or less randomly distributed within the
complimentary base material. The random placement of the plural
zones 30 or 28 may result from the exploitation of randomness
introduced by a manufacturing process, such as mixing.
[0077] FIGS. 4 and 8 show an embodiment of the demisting flame
arrestor 12 that includes a graduated distribution of hydrophobic
or hydrophilic zones, 30 or 28, within a complimentary structure.
The graduated distribution may occur in the direction of gas flow
or flame propagation, i.e. vertically with respect to the figures.
For example, as shown in FIG. 4, a greater percentage of
hydrophobic zones 30 may be arranged nearer to the bottom portion
of the demisting flame arrestor to promote the rejection of water
back into the reaction cell. The triangular shape of the zones 30
will promote such flow. The density of the zones 30 gradually
decreases as we move toward the top of the device. However, in the
embodiment shown in FIG. 8, a greater percentage of hydrophilic
zones could be arranged nearer the top portion of the demisting
flame arrestor to discourage flame propagation into the reaction
cell from an explosion originating somewhere outside the reaction
cell, such as in an engine. In this embodiment, the base of each
triangular zone 28 faces toward the top surface of the demisting
flame arrestor to increase flame resistance. The density of the
zones 28 gradually decreases as we move toward the lower surface of
the device.
[0078] For the embodiments illustrated in FIGS. 4 and 8, the
distribution of hydrophilic or hydrophobic zones could be gradual,
so that the density of zones at any elevation within the demisting
flame arrestor satisfies a desired distribution formula, such as a
linear, polynomial, non-linear, or transcendental formula, or some
other formula for statistical distribution.
[0079] Alternatively, the distribution of zones throughout the
demisting flame arrestor could be organized according to layers.
This concept is illustrated in FIGS. 5 and 9, each of which shows a
demisting flame arrestor 12 comprising multiple layers 31, 32, 33.
In these examples, the density of hydrophilic or hydrophobic zones
could be made greatest only at a top-most or bottom-most layer of
the demisting flame arrestor, with a corresponding lesser
distribution used in the remaining layers to achieve one or more
lower densities.
[0080] Exemplary embodiments of the invention have been disclosed
in an illustrative style. Accordingly, the terminology employed
throughout should be read in a non-limiting manner. Although minor
modifications to the teachings herein will occur to those well
versed in the art, it shall be understood that what is intended to
be circumscribed within the scope of the patent warranted hereon
are all such embodiments that reasonably fall within the scope of
the advancement to the art hereby contributed, and that that scope
shall not be restricted, except in light of the appended claims and
their equivalents.
* * * * *