Note: Descriptions are shown in the official language in which they were submitted.
CA 02403694 2002-09-27
Description
Title
o Flow-Through Aamnonia Photodissociation Device
Technical Field
o This invention relates to photodissociation devices, more particularly
to a flow-through ammonia photodissociation device.
Background Art
o There are many instances where it would be desirable to be able to
provide a flow-through device which dissociates ammonia (NH3) into
nitrogen (N2) and hydrogen (H2).
o Compared to other candidate fuels for fuel-cell vehicles, such as pure
hydrogen (H2) and methanol (CH30H), ammonia (NH3) has advantages in
energy density (high) and fire safety (non-flammable), among others. In
addition, an ammonia fuel-cell system has superior environmental
performance to a methanol fuel cell system because the exhaust contains
not C02 (greenhouse gas) or CO (toxic gas) but NZ (inert gas). What is
more, ammonia is naturally found (e. g., urine), and is a household
cleaning product (e.g., Windex (Trade Mark)). Moreover, ammonia is a
liquid at modest pressures, not unlike propane. Therefore, high
hydrogen content is possible in a relatively small volume. As for
toxicity, the smell of ammonia will prevent people from drinking it.
o Because ammonia (NH3) can be decomposed easily to yield hydrogen (H2),
it is a convenient portable source of atomic hydrogen for welding. If
an atom or molecule absorbs energy from a beam of light (E = hv), it
gains far more energy than it ever could by other methods (e. g., from
ordinary heating).
o A large number of patents disclose photodissociation devices.
o U. S. Patent 3 933 432 discloses "Photoionization" .
o U.S. Patent 4 995 955 discloses "Optically-assisted gas
decontamination process".
o These prior art arrangements do not provide a flow-through device which
uses photodissociation to crack ammonia (NH3) into nitrogen (N2) and
hydrogen (H2).
Description of the Invention
o It is a primary object of the invention to provide a flow-through
device which dissociates ammonia (NH3) into nitrogen (N2) and hydrogen
H2 ) .
o It is another object of the invention to provide a flow-through device
which uses photodissociation with ultraviolet light to crack ammonia
NH3 ) .
o It is another object of the invention to provide a flow-through device
CA 02403694 2002-09-27
which uses a catalyst in a porous membrane.
o An ammonia photodissociation device comprises a flow-through fluid
channel, a porous membrane, a catalyst, and an ultraviolet light
source. The flow-through fluid channel has an inlet port for inflow of
gaseous ammonia (NH3), and an outlet port for outflow of a mixture of
gaseous nitrogen (N2) and gaseous hydrogen (H2). The porous membrane
separates the flow-through fluid channel into a first chamber and a
second chamber. The catalyst is disposed on the porous membrane in
order to increase the rate of chemical reactions. The ultraviolet light
source generates electromagnetic radiation in the ultraviolet (W)
region of the spectrum, and is capable of dissociating gaseous ammonia
(NH3) into a mixture of gaseous nitrogen (N2) and gaseous hydrogen (H2)
according to formula: 2 NH3 -> N2 + 3 HZ.
Brief Description of the Figures in the Drawings
o In drawings which illustrate embodiments of the invention:
o Figure 1 is a sectional side view of one embodiment of a
flow-through ammonia ghotodissociation device according to the
invention;
o Figure 2 is a sectional top view of the invention of Figure 1;
o Figure 3 is a sectional side view of another embodiment of a
flow-through ammonia photodissociation device according to the
invention; and
o Figure 4 is a sectional top view of the invention of Figure 3.
Modes for Carrying Out the Invention
o According to the present invention shown in one embodiment in Figure 1
and Figure 2 , and in another embodiment in Figure 3 and Figure 4 , an
ammonia photodissociation device comprises a flow-through fluid channel
1-1/2-l, a porous membrane 1-4/2-4, a catalyst, and an ultraviolet
light source 1-5/2-5.
o The flow-through fluid channel 1-1/2-1 has a middle portion, an inner
surface, an inlet port 1-2/2-2 for inflow of gaseous ammonia (NH3),
and an outlet port 1-3/2-3 for outflow of a mixture of gaseous
nitrogen (N2) and gaseous hydrogen (H2).
o The porous membrane 1-4/2-4 separates the flow-through fluid channel
into a first chamber which is adjacent to the inlet port 1-2/2-2 and a
second chamber which is adjacent to the outlet port 1-3/2-3. The
porous membrane 1-4/2-4 is securely attached to the middle portion of
the flow-through fluid channel 1-1/2-1. The porous membrane 1-4/2-4
has pores in order to provide fluid communication between the first
chamber of the flow-through fluid channel 1-1/2-1 and the second
chamber of the flow-through fluid channel 1-1/2-1.
o The catalyst is disposed on the porous membrane 1-4/2-4 in order to
increase the rate of chemical reactions.
o The ultraviolet light source 1-5/2-5 generates electromagnetic
radiation in the ultraviolet (W) region of the spectrum. The
ultraviolet light source 1-5/2-5 is mounted inside the flow-through
fluid channel 1-1/2-1.
CA 02403694 2002-09-27
o The electromagnetic radiation from the ultraviolet light source
1-5/2-5 is capable of irradiating inside the flow-through fluid
channel 1-1/2-1 in order to dissociate gaseous ammonia (NH3) into a
mixture of gaseous nitrogen (N2) and gaseous hydrogen (H2) according to
formula: 2 NH3 -> N2 + 3 H~.
o The ultraviolet light source 1-5/2-5 may irradiate either the first
chamber of the flow-through fluid channel 1-1/2-1 or the second
chamber of the flow-through fluid channel 1-1/2-1.
o The ammonia photodissociation device may further comprise a heating
element embedded in the porous membrane 1-4/2-4 in order to increase
the rate of dissociation of gaseous ammonia (NH3) by means of thermal
energy. The heating element may be heated by combustion. Alternatively,
the heating element may be heated by resistive heating.
o The ammonia photodissociation device may further comprise an ultrasonic
transducer acoustically connected to the porous membrane 1-4/2-4 in
order to increase the rate of dissociation of gaseous ammonia (NH3) by
means of acoustical energy. The ultrasonic transducer may be made of a
magnetostrictive material such as Terfenol.-D alloy. Alternatively, the
ultrasonic transducer may be made of a piezoelectric material such as
Lead Zirconate Titanate (PZT).
o The catalyst may be additionally disposed on the inner surface of the
flow-through fluid channel 1-1/2-1.
o The flow-through fluid channel 1-1/2-1 may be cylindrical. The porous
membrane 1-4/2-4 may be circular, as shown in Figure 1 and Figure 2.
Alternatively, the porous membrane 1-4/2-4 may be cylindrical, as
shown in Figure 3 and Figure 4.
o The porous membrane 1-4/2-4 may be a mesh or a honeycomb. The porous
membrane 1-4/2-4 may be corrugated.
o The catalyst may be either a photocatalyst, a thermocatalyst, or a
mixture of photocatalyst and thermocatalyst. The catalyst may be an
inorganic oxide semiconductor, a noble metal, a transition metal, or an
alloy.
o The catalyst may comprise titanium dioxide (Ti02), indium tantalum
oxide (InTaO), nickel (Ni), molibdenum (Mo), a mixture of indium (In),
nickel (Ni) and tantalum (Ta), or a mixture of titanium dioxide (Ti02)
and platinum (Pt).
o Preferably, the ultraviolet light source 1-5/2-5 generates
electromagnetic radiation in the vacuum ultraviolet (~) region of the
spectrum, at wavelengths shorter than 254 nm.
o The ultraviolet light source 1-5/2-5 may be a dielectric barrier
discharge (DBD) lamp with a noble gas such as xenon (Xe), krypton (Kr)
or argon (Ar). The ultraviolet light source 1-5/2-5 may be an excimer
lamp with a noble gas such as xenon (Xe), krypton (Kr) or argon (Ar).
