Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR CONVERTING HYDROCARBON
FUEL INTO HYDROGEN GAS AND CARBON DIOXIDE
This application is a Divisional of Application Serial
No. 2,265,468, filed August 25, 1997.
Background of the invention
Fuel cells continue to play an increasingly important
role in power generation for both stationary and
transportation applications. A primary advantage of fuel
cells is their highly efficient operation which, unlike
today's heat engines, are not limited by Carnot cycle
efficiency. Furthermore, fuel cells far surpass any known
energy conversion device in their purity of operation. Fuel
cells are chemical power sources in which electrical power is
generated in a chemical reaction between a reducer (hydrogen)
and an oxidizer (oxygen) which are fed to the cells at a rate
proportional to the power load. Therefore, fuel cells need
both oxygen and a source of hydrogen to function.
There are two issues which are contributing to the
limited use of hydrogen gas today. Firstly, hydrogen gas (H2)
has a low volumetric energy density compared to conventional
hydrocarbons, meaning that an equivalent amount of energy
stored as hydrogen will take up more volume than the same
amount of energy stored as a conventional hydrocarbon.
Secondly, there is presently no widespread hydrogen
infrastructure which could support a large number of fuel cell
power systems.
An attractive source of hydrogen to power fuel cells is
contained in the molecular structure of various hydrocarbon
and alcohol fuels. A reformer is a device that breaks down
the molecules of a primary fuel to produce a hydrogen-rich gas
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stream capable of powering a fuel cell. Although the process
for reforming hydrocarbon and alcohol fuels is established on
a large industrial basis, no known analogous development has
occurred for small-scale, highly integrated units.
Therefore, a need exists for a more compact apparatus for
generating hydrogen gas from a variety of hydrocarbon fuel
sources for use in a fuel cell to power a vehicle.
Summary of the invention
The present invention relates to a reformer and method
for converting an alcohol or hydrocarbon fuel into hydrogen
gas and carbon dioxide.
The reformer includes a first vessel having a partial
oxidation reaction zone and a separate steam reforming
reaction zone that is distinct from the partial oxidation
reaction zone. The first vessel has a first vessel inlet at
the partial oxidation reaction zone and a first vessel outlet
at the steam reforming zone. The reformer also includes a
helical tube extending about the first vessel. The helical
tube has a first end connected to an oxygen-containing source
and a second end connected to the first vessel at the partial
oxidation reaction zone. Oxygen gas from an oxygen-containing
source can be directed through the helical tube to the first
vessel. A second vessel having a second vessel inlet and
second vessel outlet is annularly disposed about the first
vessel. The helical tube is disposed between the first vessel
and the second vessel and gases from the first vessel can be
directed through the second vessel.
The method includes directing oxygen-containing gas
through a helical tube which is disposed around a first
vessel. Hydrocarbon vapor and steam are directed into the
helical tube to form a mixture of oxygen gas, fuel vapor and
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steam. The mixture of oxygen gas, fuel vapor and steam are
directed into the first vessel. The fuel vapor spontaneously
partially oxidizes to form a heated reformate stream that
includes carbon monoxide and hydrogen gas. The remaining fuel
vapor is steam reformed in the heated reformate stream to form
hydrogen gas and carbon monoxide. The heated reformate stream
is directed over the exterior of the helical tube, whereby the
heated reformate stream heats the mixture in the helical tube.
A portion of the carbon monoxide gas of the reformate stream
is converted to carbon dioxide and hydrogen gas by a high
temperature shift reaction. At least a portion of the
remaining carbon monoxide gas of the reformate stream is
converted to carbon dioxide and hydrogen gas by a low
temperature shift reaction.
In another embodiment of a reformer for converting a
hydrocarbon fuel into hydrogen gas and carbon dioxide, the
apparatus includes a first tube which has a first tube inlet
for receiving a first mixture of an oxygen-containing gas and
a first fuel, which can be a hydrocarbon or an alcohol, and a
first tube outlet for conducting a first reaction reformate of
the first mixture. A second tube is annularly disposed about
the first tube, wherein the second tube has a second tube
inlet for receiving a second mixture of a second fuel, which
can be a hydrocarbon or an alcohol, and steam. A second tube
has a second tube outlet for conducting a second reaction
reformate of the second mixture. A catalyst reforming zone is
annularly disposed about the second tube. The first reaction
reformate and the second reaction reformate can be directed
through the first tube outlet and the second tube outlet,
respectively, to the catalyst reforming zone for further
reforming of the mixtures. In a preferred embodiment, a
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hydrocarbon fuel fractionator is attached at the first tube
inlet and second tube inlet. The fractionator can separate a
heavy portion from the hydrocarbon fuel for subsequent
direction to the partial oxidation zone in the first tube. A
light portion can be separated from the hydrocarbon fuel for
subsequent direction to the steam reforming zone in the second
tube.
In another embodiment of the method for converting a
hydrocarbon or alcohol fuel into hydrogen gas and carbon
dioxide, a first mixture of first hydrocarbon or alcohol fuel
and oxygen-containing gas is' directed into a first tube. The
hydrocarbon or alcohol fuel in the first mixture spontaneously
partially oxidizes to form a first heated reformate stream
that includes hydrogen gas and carbon monoxide. A second
mixture of a second hydrocarbon or alcohol fuel and steam is
directed into a second tube annularly disposed about the first
tube. The second hydrocarbon or alcohol fuel of the second
mixture partially steam reforms to form a second heated
reformate stream that includes hydrogen gas and carbon
monoxide. The first heated reformate stream and second heated
reformate stream are directed through a catalyst reforming
zone to further reform the reformate streams to hydrogen gas
and carbon dioxide. In a preferred embodiment, the
hydrocarbon fuel prior to direction into the first tube and
the second tube is fractionated into heavy portion of the
hydrocarbon fuel and a light portion of the hydrocarbon fuel.
The heavy portion is subsequently directed to the partial
oxidation zone. The light portion is directed to the steam
reforming zone.
This invention has many advantages. The apparatus can
use a variety of hydrocarbon fuels, such as gasoline, JP-8,
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methanol and ethanol. The partial oxidation reaction zone
allows the fuel to partially burn while not forming soot and
while providing heat to the steam reforming zone and the other
portions of the reactor annularly disposed around the partial
oxidation zone. Further, the apparatus is sufficiently compact
for use in an automobile. In some embodiments, the apparatus
includes a high temperature shift catalyst which allows the
apparatus to be more compact and lighter in weight than if
only a low temperature shift catalyst is used.
Brief description of the Drawings
Figure 1 is an orthogonal projection side view of one
embodiment of the apparatus of the present invention.
Figure 2 is an orthogonal projection side view of a
second embodiment of the apparatus of the present invention.
Figure 3 is an orthogonal projection side view of a third
embodiment of the apparatus of the present invention.
Detailed description of the Invention
The features and details of the method and apparatus of
the invention will now be more particularly described with
reference to the accompanying drawings and pointed out in the
claims. The same numeral present in different figures
represents the same item. It will be understood that the
particular embodiments of the invention are shown by way of
illustration and not as limitations of the invention. The
principal features of this invention can be employed in
various embodiments without departing from the scope of the
invention. All percentages and parts are by weight unless
otherwise indicated.
One embodiment of the invention is shown in Figure 1.
Reformer 10 has reformer vessel 12. Reformer vessel 12 can be
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cylindrical in shape. Reformer 10 has upper portion 14 and
lower portion 16. Disposed in the center of reformer vessel
12 is first vessel 18 which extends substantially the height
of reformer vessel 12. First vessel 18 has first vessel inlet
20 for receiving gases into first vessel 18 and can
tangentially direct the gases through the first vessel. First
vessel 18 has first vessel outlet 22 at upper portion 14 of
reformer 10 for gases to exit first vessel. Perforated plate
31 is located at first vessel outlet 22 and covers the
diameter of first vessel 18. Partial oxidation reaction zone
24 is in lower portion 16 of first vessel 18.
Partial oxidation zone 24 is suitable for partial
oxidation of a hydrocarbon or alcohol fuel with oxygen to form
a mixture including carbon monoxide, steam and hydrogen gas.
Steam reforming zone 26 is above partial oxidation zone 24 and
includes a steam reforming catalyst 28. Preferably, the steam
reforming catalyst includes nickel with amounts of a noble
metal, such as cobalt, platinum, palladium, rhodium,
ruthenium, iridium, and a support such as magnesia, magnesium
aluminate, alumina, silica, zirconia, singly or in
combination. Alternatively, steam reforming catalyst 28 can
be a single metal, such as nickel, supported on a refractory
carrier like magnesia, magnesium aluminate, alumina, silica,
or zirconia, singly or in combination, promoted by an alkali
metal like potassium. Steam reforming zone 26 can
autothermally reform steam and methane generated in partial
oxidation zone 24 to hydrogen gas and carbon monoxide. Steam
reforming catalyst 28, which can be granular, is supported
within partial oxidation zone 24 by perforated plate 30 and
perforated plate 31.
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Helical tube 32 extends about the length of first vessel
18. First end 34 of helical tube 32 is located at inlet
housing 33. Oxygen source 42 is connected to inlet housing 33
by conduit 35 with first end inlet 36 for receiving oxygen-
containing gas from oxygen gas zone 40. Second end 44 of
helical tube 32 is connected at first vessel inlet 20.
Examples of suitable oxygen-containing gas include oxygen (OZ),
air, etc. Fuel inlet 46 is joined to helical tube 32
proximate to second end 44. Conduit 50 extends from fuel
source 48 to fuel inlet 46. Examples of suitable fuels
include hydrocarbons which encompass alcohols, also. Fuels
include gasoline, kerosene, JP-8, methane, methanol and
ethanol. Steam inlet 52 is proximate to fuel inlet 46. Steam
can be directed from steam source 54 to steam tube 56 through
first steam inlet 52 into helical tube 32. In another
embodiment, fuel and steam can be directed into helical tube
32.
Second vessel 58 is annularly disposed about first vessel
18. Second vessel inlet 60 receives gaseous products from
first vessel outlet 22. Second vessel outlet 62 at lower
portion 16 of reformer 10 allows gas to exit second vessel 58.
Helical tube 32 is disposed between first vessel 18 and second
vessel 58 and gases from first vessel 18 can be directed
through second vessel 58 from second vessel inlet 60 over and
around helical tube 32 to second vessel outlet 62. Flow
distribution region 63 conducts gas from second vessel outlet
62 to high temperature shift zone 64. Additional steam or
water can be directed from a steam source into second vessel
58 through second steam inlet 53 to provide added steam to
provide added cooling and further the reformation of the
fuels.
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High temperature shift zone 64 is annularly located
between second vessel 58 and reformer vessel 12 and includes a
high temperature shift catalyst. An example of a suitable high
temperature shift catalyst are those that are operable at a
temperature in the range of between about 300°C and about
600°C. Preferably the high temperature shift catalyst
includes transition metal oxides, such as ferric oxide (Fe203)
and chromic oxide (Cr203). Other types of high temperature
shift catalysts include iron oxide and chromium oxide promoted
with copper, iron silicide, supported platinum, supported
palladium, and other supported platinum group metals, singly
and in combination. High temperature shift catalyst 66 is
held in place by perforated plate 68 and perforated plate 70.
Gas can pass through high temperature shift zone 64 through
perforated plate 70 to sulfur removal zone 71.
Above high temperature shift zone 64 is sulfur removal
zone 71. Sulfur removal zone 71 includes a catalyst which can
reduce the amount of hydrogen sulfide (HZS), which is
deleterious to a low temperature shift catalyst, in the gas
stream to a concentration of about one part per million or
less. An example of a suitable catalyst includes a zinc
oxide. Sulfur removal zone 71 is sized depending on the type
of fuel used. If a low sulfur fuel is used, a small sulfur
removal zone is needed. If a high sulfur fuel is used, a
larger sulfur removal zone is necessary. Gas can pass from
sulfur removal zone 71 through perforated plate 73 to cooling
zone 72.
Cooling zone 72 includes a plurality of vertical fins 74
which radiate from second vessel 58 to reformer vessel 12
which extends from high temperature shift zone 64 to low
temperature shift zone 76.
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Cooling tube 78 is helically disposed about second vessel
58 and is attached to vertical fins 74. Cooling tube 78 has
cooling tube inlet 80 for receiving a cooling medium, such as
water, through cooling tube 78 to cooling tube outlet 82. In
another embodiment, cooling tube 78 is wound a second series
of times around second vessel 58. The gaseous products from
high temperature catalyst zone 64 can pass between the
vertical fins 74 and pass over cooling tube 78 allowing
gaseous products to cool.
Low temperature shift zone 76 is annularly disposed above
cooling zone 72 and between second vessel 58 and reformer
vessel 12 and includes low temperature shift modifying
catalyst 84 for reducing carbon monoxide to a level of less
than about one percent, by volume, or below. An example of a
suitable low temperature modifying catalyst are those that are
operable at a temperature in a range of between about 150°C
and about 300°C. Preferably, the low temperature modifying
catalyst includes cupric oxide (Cu0) and zinc oxide (Zn0).
Other types of low temperature shift catalysts include copper
supported on other transition metal oxides like zirconia, zinc
supported on transition metal oxides or refractory supports
like silica or alumina, supported platinum, supported rhenium,
supported palladium, supported rhodium and supported gold.
Low temperature shift zone catalyst 84 is held in place by
lower perforated plate 86 and upper perforated plate 88.
Gaseous products from cooling zone 72 can pass through
perforated plate 86 through low temperature shift zone 76
through upper perforated plate 88. Exit zone 90 is above low
temperature shift zone 76 and has reformer exit 92.
In the method for converting hydrocarbon fuel into
hydrogen gas, an oxygen-containing gas, such as air, is
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directed from oxygen source 42 through conduit 35 to inlet
housing 33 to oxygen gas zone 40 into first end inlet 36 of
helical tube 32. Reformer 10 can operate at a pressure in the
range of between about 0 and 500 psig. The oxygen-containing
gas, such as air, is preheated to a temperature of about
450°C. In a preferred embodiment, air has a velocity of
greater than about 40 meters per second.
A suitable hydrocarbon or alcohol vapor is directed from
fuel source 48 through fuel tube 50 to fuel inlet 46. Examples
of suitable hydrocarbon fuels include gasoline, JP-8,
methanol, ethanol, kerosene and other suitable hydrocarbons
typically used in reformers. Gaseous hydrocarbons, such as
methane or propane, can also be used. Steam is directed from
steam source 54 through steam tube 56 to first steam inlet 52.
Steam has a temperature in the range between about 100 and
about 150°C. The air, steam and hydrocarbon fuel are fed at
rates sufficient to mix within helical tube 32 and
spontaneously partially oxidize as the mixture enters partial
oxidation zone 24 through first vessel inlet 20 to form a
heated reformate stream that includes carbon monoxide and
hydrogen gas. In a preferred embodiment, oxygen-containing
gas is tangentially directed around the interior of partial
oxidation zone 24, which is an empty chamber. In partial
oxidation zone 24, the reformate products can include methane,
hydrogen gas, water and carbon monoxide. Partial oxidation
zone 24 has a preferred temperature in the range of between
about 950°C. and about 1150°C. A heavier fuel is
preferentially run at the higher end of the temperature range
while a lighter fuel is run at a lower end of the temperature
range.
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From partial oxidation zone 24, reformate products are
directed through perforated plate 30 to steam reforming zone
26. In steam reforming zone 26, the remaining hydrocarbon
vapor in the heated reformate stream from partial oxidation
zone 24 is steam reformed in the presence of steam reforming
catalyst 28 into hydrogen gas and carbon monoxide. Steam
reforming zone 26 typically has a temperature in the range of
between about 700 and 900°C The partial oxidation reaction
provides sufficient heat to provide heat to helical tube 32 to
preheat the air and other contents of helical tube 32 and also
provide heat to the steam reforming step. The hydrocarbon
fuel is burned partly in partial oxidation zone 24 and the
remainder of the fuel with the steam is mixed with the partial
oxidation zone combustion products for steam reforming and
hydrocarbon shifting to carbon monoxide and hydrogen gas in
the presence of steam reforming catalyst 28. The heated
reformate stream exiting from steam reforming zone 26 has a
temperature of between about 700°C and about 900°C. The
heated reformate stream is directed between first vessel 18
and second vessel 58 and around the exterior of helical tube
32, whereby the heated reformate stream is cooled by heating
the contents of helical tube 32 and also the first vessel 18
and second vessel 56.
Heated reformate stream exits second vessel outlet 62 to
flow distribution zone 63, where it has been cooled to a
temperature of between about 300°C and about 600°C and is
directed through perforated plate 68 to high temperature shift
zone 64 where essentially all of the carbon monoxide is
removed or reduced by contacting the heated reformate stream
with high temperature shift catalyst 66 at a temperature in
the range of between about 300°C and 600°C. High-temperature
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shift zone 64 operates adiabatically to reduce the carbon
monoxide levels with modest temperature rise. In one
embodiment, heated reformate stream entering high temperature
shift zone 64 has about fourteen to seventeen percent carbon
monoxide, by volume, and exits high temperature shift zone 64
with about two to four percent carbon monoxide, by volume.
The high temperature shift zone treated reformate stream
is directed through sulfur removal zone 71 where the hydrogen
sulfide content of the stream is reduced to a concentration of
less than about one part per million. From sulfur removal zone
71, the reformate is directed to cooling zone 72 where the
stream contacts the vertical fins 74 and cooling tubes 78 to
lower the temperature of the stream to between about 150°C and
about 300°C because low temperature shift catalyst 84 is
temperature sensitive and could possibly sinter at a
temperature of above about 300°C. Cooling zone 72 cools high
temperature reformate gas for low temperature shift zone 76.
Cooling zone tubes 78 operate continuously flooded to allow
accurate and maximum steam side heat transfer, to reduce
fouling and corrosion to allow use of contaminated water, and
to achieve a constant wall minimum temperature.
Reformate stream is directed through perforated plate 86
to low temperature shift reaction zone 76 where the reformate
stream contacts low temperature shift catalyst 84 converting
at least a portion of the remaining carbon monoxide gas of the
reformate stream to carbon dioxide by low temperature shift
reaction to form product stream. Low temperature shift
reaction zone 76 operates adiabatically to reduce the
remainder of the carbon monoxide to trace levels with modest
catalyst temperature rise. The resulting gas product stream
exits low temperature shift reaction zone 76 through
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perforated plate 88 to exit gas zone 90 to reformer exit 92.
The exiting product stream can have a composition of about 40~
hydrogen gas and less than one percent carbon monoxide on a
wet volume basis.
A second embodiment of the invention is shown in Figure
2. Second reformer 100 has reformer shell 102. Reformer shell
102 has upper portion 104 and lower portion 106. Disposed in
the center of reformer shell 102 is first tube 108 which
extends substantially the height of reformer shell 102. First
tube 108 has a first tube inlet 110 at lower portion 106 for
receiving gases into first tube 108. First tube 108 is
configured for receiving a first mixture of oxygen and first
hydrocarbon fuel. First tube outlet 112 is configured for
directing a first reaction reformate of the first mixture to
mixing zone 114.
Second tube 116 is annularly disposed about first tube
108. Second tube 116 has second tube inlet 118 for receiving
second hydrocarbon fuel and steam. Second tube 116 also has
second tube outlet 120 for directing a second reaction
reformate of a second mixture. Second tube 116 can include a
steam reforming catalyst. An example of a suitable catalyst
includes nickel with amounts of a noble metal such as cobalt,
platinum, palladium, rhodium, ruthenium, iridium, and a
support such as magnesia, magnesium aluminate, alumina,
silica, zirconia, singly or in combination. Alternatively,
steam reforming catalyst can be a single metal, such as
nickel, supported on a refractory carrier like magnesia,
magnesium aluminate, alumina, silica, or zirconia, singly or
in combination, promoted by an alkali metal like potassium.
In another embodiment, second tube 116 can be annularly
disposed within first tube 108, wherein steam and fuel can be
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directed into the center tube and fuel and oxygen can be
directed into the tube annularly disposed around the center
tube.
Oxygen source 122 is connected by oxygen tube 124 to
first tube 108. An example of a suitable oxygen source is
oxygen gas or air. Steam source 126 is connected to second
tube 116 by steam tube 128. In one embodiment, steam source
126 can provide a source of steam at a temperature of about
150°C and a pressure of about 60 psia. Fuel source 130 is
connected by fuel tube 132 to fractionator 134. Fuel source
130 includes a suitable fuel, such as a hydrocarbon, including
gasoline, JP-8, kerosene, also alcohol including methanol and
ethanol. Fractionator 134 has light portion outlet 136 for
directing light portion from fractionator 134 and heavy
portion outlet 138 for directing heavy portion from
fractionator 134. Heavy portion can be directed from heavy
portion outlet 138 through heavy portion tube 140 to first
tube inlet 110. Light portion can be directed from light
portion outlet 138 through light portion tube 142 to second
tube inlet 118. In another embodiment, separate sources can
be used for heavy portion (first hydrocarbon fuel) and light
portion (second hydrocarbon fuel) without having a
fractionator.
Catalyst reforming zone 144 is annularly disposed about
second tube 116. First reaction reformate and second reaction
reformate can be directed through first tube outlet 112 and
second tube outlet 120, respectively, to mixing zone 114 above
catalyst reforming zone 144.
Catalyst reforming zone 144 includes a catalyst for
further reforming of the mixtures to hydrogen gas. An example
of a suitable catalyst includes nickel with amounts of a noble
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metal such as cobalt, platinum, palladium, rhodium, ruthenium,
iridium, and a support such as magnesia, magnesium aluminate,
alumina, silica, zirconia, singly or in combination.
Alternatively, the catalyst can be a single metal, such as
nickel, supported on a refractory carrier like magnesia,
magnesium aluminate, alumina, silica, or zirconia, singly or
in combination, promoted by an alkali metal like potassium.
Catalyst reforming zone 144 can have a height that is
substantially the length of first tube 108 and second tube
116. Catalyst reforming zone 144 is sufficiently porous to
allow passage of gas from exit zone 146. Catalyst 147 in
catalyst reforming zone 144 is held in place by lower
perforated plate 148 and upper perforated plate 150. Product
gases of catalyst reforming zone 144 can exit second reformer
100 from exit zone 146 through reformer shell exit 152.
In the second embodiment of the invention for converting
hydrocarbon fuel into hydrogen gas and carbon dioxide, a fuel
is directed from fuel source 130 to fractionator through fuel
tube 132. The fuel is separated into a light portion and a
heavy portion in fractionator 134. The heavy portion is
directed from heavy portion outlet 138 through heavy portion
tube 140 to first tube inlet 110. An oxygen-containing gas,
such as air, is directed from oxygen source 122 through oxygen
tube 124 to first tube inlet 110. The oxygen-containing gas
and the heavy portion of the hydrocarbon fuel form a mixture
in first tube, whereby the hydrocarbon fuel of the first
mixture spontaneously partially oxidizes to form a first
heated reformate stream that includes hydrogen gas and carbon
monoxide. First heated reformats stream can be heated to about
1525°C. The ratio of fuel to oxygen is adjusted depending
upon the type of fuel used. A heavier fuel can require a
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higher combustion temperature. The partial oxidation of the
fuel results in the fuel mixture that includes carbon
monoxide, water, hydrogen gas and methane. Excess heat from
the partial oxidation reaction allows transfer of heat from
first tube 108 to second tube 116. By burning the heavy
portion at a temperature of above about 1375°C, there is no
significant formation of carbon soot or tar in the partial
oxidation zone. If necessary, ignition can be with a hot
surface igniter or a spark plug.
The light portion of the fuel is directed from light
portion outlet 136 of fractionator 134 through light portion
tube 142 to second tube 116. Steam is directed from steam
source 126 through steam tube 128 to second tube inlet 118
into second tube 116. Also oxygen gas is directed from oxygen
source 122 through oxygen tube 124 to second tube inlet 118
into second tube 116. In another embodiment, only steam is
directed with a light portion of hydrocarbon fuel into second
tube. A second mixture of oxygen-containing gas, a light
portion of hydrocarbon fuel and steam is formed in second tube
116 annularly disposed about first tube 108. Hydrocarbon fuel
of second mixture partially reacts to form a second heated
reformats stream that includes hydrogen gas and carbon
monoxide. In the presence of steam, second mixture partially
steam reforms. The heat from the reaction in first tube 108
provides energy to help cause the reaction to progress in
second tube 116.
The first heated reformats stream from first tube 108 and
second heated reformats stream from second tube 116 are
directed through first tube outlet 112 and second tube outlet
120, respectively, into mixing zone 114. The separate tubes
allow carbon reduced operation at high fuel to oxygen ratios
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of about four to one. It also allows using distillate fuels,
such as gasoline, diesel fuel, jet fuel or kerosene, whereby
heavy portion type fuels are preferentially directed to first
tube 108 for high-temperature combustion necessary to break
heavy molecules while the light portion-type vapors are
directed to second tube 116 for partial steam reforming as a
result of thermal contact with combustion chamber. First
heated reformate stream and second heated reformate stream mix
within mixing zone 114. The mixture is directed from mixing
zone 114 through catalyst reforming zone 144 to exit zone 146.
In catalyst reforming zone 144, the remainder of the carbon
monoxide is reformed to carbon dioxide to form product stream.
The product stream exits through exit zone 146 and from second
reformer 100 through reformer shell exit 152.
Another embodiment of the invention is shown in Figure 3.
Third reformer 200 has reformer shell 202. Reformer shell 202
has upper portion 204 and lower portion 206. Disposed in the
center of reformer shell 202 is first tube 208. First tube
208 has a first tube inlet 210 at lower portion 206 for
receiving gases into first tube 208. First tube 208 has first
tube outlet 212 at upper portion 204 for gases to exit first
tube 208. First tube 208 includes steam reforming catalyst
214 for reforming a hydrocarbon in the presence of steam. An
example of a suitable steam reforming catalyst is nickel with
amounts of a noble metal such as cobalt, platinum, palladium,
rhodium, ruthenium, iridium, and a support such as magnesia,
magnesium aluminate, alumina, silica, zirconia, singly or in
combination. Alternatively, steam reforming catalyst can be a
single metal, such as nickel, supported on a refractory
carrier like magnesia, magnesium aluminate, alumina, silica,
or zirconia, singly or in combination, promoted by an alkali
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metal like potassium. First tube 208 is configured for
receiving a mixture of steam and a first hydrocarbon or
alcohol fuel. First tube outlet 212 is configured for
directing a first reaction reformate of the first mixture to
mixing zone 216. First tube 208 can be uniform in diameter, or
alternatively, the tube can be tapered such as having a
smaller diameter at first tube inlet 210 than the diameter at
first tube outlet 212.
Steam source 213 is connected to first tube 208 by steam
tube 215. Steam source 213 can provide a source of steam at a
temperature of about 150°C and a pressure of about 60 psia.
Light fuel source 217 is connected by light fuel tube 219 to
first tube 208 for directing light fuel into first tube 208.
Light fuel includes a suitable fuel such as a hydrocarbon,
including gasoline, JP-8, kerosene, also alcohol including
methanol and ethanol.
Second tube 218 is annularly disposed about first tube
208. Second tube 218 has second tube inlet 220 for receiving
a mixture of oxygen and heavy hydrocarbon fuel. Second tube
218 also has second tube outlet 222 for directing a second
reaction reformate of a second mixture. Second tube 218 can
have a uniform diameter length of second tube 218, or
alternatively second tube 218 can be tapered, such as having a
larger diameter at lower portion 206 and narrower diameter at
upper portion 204. Second tube outlet 222 is configured for
directing a second reaction reformate of the second mixture to
mixing zone 216.
Annularly disposed about second tube is third tube 224.
Third tube 224 has third tube inlet 226 proximate to mixing
zone 216 for receiving a mixture of first reaction reformate
of the first mixture and second reaction reformate of the
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second mixture. Third tube 224 has third tube outlet 228 for
directing mixture of first reaction reformats and second
reaction reformats from third tube 224. Third tube 224 can
include steam reforming catalyst 225 for further reforming the
hydrocarbon present in the mixture. An example of a suitable
steam reforming catalyst includes the same catalyst described
for steam reforming catalyst 214.
Helical tube 232 extends about the length of third tube
224, First end 234 of helical tube 232 is located at inlet
housing 233. Oxygen source 242 is connected to inlet housing
233 by conduit 235 with first end inlet 236 for receiving
oxygen-containing gas from oxygen gas zone 240. Second end
247 of helical tube 232 has helical tube outlet 244 for
directing oxygen-containing gas into second tube 218.
Examples of suitable oxygen-containing gas include oxygen (O2),
air, etc.
Heavy fuel source 241 is connected by heavy fuel tube 243
to heavy fuel inlet 246. Heavy fuel inlet 246 is joined to
helical tube 232 proximate to second end 247. Examples of
suitable heavy fuels include gasoline, kerosene, JP-8,
methanol and ethanol. In another embodiment, the same sources
of fuel can be used for heavy fuel (first hydrocarbon fuel)
and light fuel (second hydrocarbon fuel), Alternatively, a
fractionator, as described in Figure 2, can be used to supply
a heavy fuel and a light fuel. In another embodiment, the
light fuel and heavy fuel can be the same and can come from
the same source.
Vessel 252 is annularly disposed about third tube 224.
Vessel inlet 254 can direct reformats products from third tube
outlet 228 into vessel 252. Helical tube 232 is disposed
between vessel 252 and third tube 224 and gases from third
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tube 224 can be directed through vessel 252 from vessel inlet
254 over and around helical tube 232 to vessel outlet 256.
Flow distribution region 258 conducts gas from vessel outlet
256 to catalyst reforming zone 260. Additional steam can be
added through second steam inlet 257 to provide added cooling
and water for reforming.
Catalyst reforming zone 260 is annularly disposed about
vessel 252. Catalyst reforming zone 260 includes catalyst 262
for further shifting the reformate to hydrogen gas. An
example of a suitable catalyst includes ferric oxide (Fe203)
and chromic oxide (Cr203). Other types of high temperature
shift catalysts include iron oxide and chromium oxide promoted
with copper, iron silicide, supported platinum, supported
palladium, and other supported platinum group metals, singly
and in combination. The catalyst can be in powdered form and
have a height substantially the height of vessel 252.
Catalyst reforming zone 260 is sufficiently porous to allow
passage of gas from flow distribution region 258 to exit zone
268. Catalyst 262 in catalyst reforming zone 260 is held in
place by lower perforated plate 264 and upper perforated plate
266. Product gases of catalyst reforming zone 260 can exit
third reformer 200 from exit zone 268 through reformer shell
exit 270.
In a third embodiment of the invention for converting
hydrocarbon or alcohol fuel into hydrogen gas and carbon
dioxide, a fuel is directed from light fuel source 217 through
light fuel tube 219 to first tube inlet 210. Steam is
directed from steam source 213 through steam tube 215 to tube
inlet 210 into tube 208. Light fuel partially reacts with the
steam to form a first heated reformate stream that includes
hydrogen gas and carbon monoxide. First heated reformate
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stream is directed from first tube 208 through first tube
outlet 212 to mixing zone 216.
An oxygen containing gas, such as air, is directed from
oxygen source 242 through conduit 235 to inlet housing 233 to
oxygen gas zone 240 into first end inlet 236 of helical tube
232. The oxygen containing gas, such as air, is preheated to
a temperature of about 450°C. In a preferred embodiment, the
air has a velocity of greater than about 40 meters per second.
As oxygen containing gas is directed through helical tube 232,
a suitable heavy fuel vapor is directed from heavy fuel source
241 through heavy fuel tube 243. Examples of suitable heavy
fuels include JP-8, kerosene and other hydrocarbon fuels
typically used in reformers. Gaseous hydrocarbons, such as
methane and propane, can also be used. The oxygen-containing
gas and heavy fuel are fed at rates sufficient to mix within
helical tube 232 and spontaneously partially oxidize as the
mixture enters second tube 218 through second tube inlet 220
to form a heated second reformats stream that includes steam,
carbon monoxide and oxygen gas. In a preferred embodiment,
oxygen-containing gas is tangentially directed around the
interior of second tube 218. A hydrocarbon fuel of second
mixture partially reacts to form a second heated reformats
stream that includes hydrogen gas and carbon monoxide. The
heat in second tube 218 provides energy to cause the reaction
to progress in first tube 208.
The fuel that is fed into first tube 208 and second tube
218 may or may not be about equal in amount. Second tube 218,
the partial oxidation chamber, is operated at a ratio of about
two to one, fuel to oxygen gas, for example, with a
temperature of about 1375°C. Heat transfer from second tube
218 to first tube 208 can cause partial steam reforming in
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first tube 208 while the temperature is maintained at about
925°C. For liquid fuels, such as gasoline and light kerosene,
the lighter fuel ends are prevaporized for delivery to first
tube 208. Heavy fuels are burned in the partial oxidation zone
where high temperature (about 1375°C) can break down fuel with
minimal carbonization.
The first heated reformate stream from first tube 208 and
second heated reformate stream from second tube 218 are
directed to first tube outlet 212 and second tube outlet 222,
respectively, into mixing zone 216. The separate tubes allow
carbon reduced operation at high fuel to oxygen ratios of
about four or five to one, thereby reducing soot formation.
It allows using distillate fuels, such as gasoline or
kerosene, whereby heavy portion type fuels are preferentially
directed to second tube 218 for high temperature combustion
necessary to break heavy molecules while a light portion-type
vapors are directed to first tube 208 for partial steam
reforming as a result of thermal contact with the heated
combustion from second tube 218. First heated reformate
stream and second heated reformate stream mix within mixing
zone 216. The mixture is directed from mixing zone 216 through
third tube inlet 226 into third tube 224.
In third tube 224, a further portion of the fuel is
reformed to hydrogen and carbon monoxide to form third tube
reformate stream. Third tube reformate stream exits through
third tube outlet 228. Third tube reformate products are
directed through vessel inlet 254 into vessel 252 where the
reformate stream passes over and around helical tube 232 to
vessel outlet 256. Additional steam can be added to vessel
252 through steam inlet 253 to provide additional cooling and
further reform the hydrocarbon and carbon monoxide present in
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the reformate stream. The reformate stream is directed from
flow distribution region 258 through catalyst reforming zone
260 where reformate stream is directed through catalyst
reforming zone for further reforming the carbon monoxide into
hydrogen gas and carbon dioxide to form product stream having
a concentration of about 0.5 percent, by volume, carbon
monoxide. The product stream exits through exit zone 268
through shell exit 270.
Equivalents
Those skilled in the art will recognize or be able to
ascertain using no more than routine experimentation, many
equivalents to the specific embodiments of the invention
described specifically herein. Such equivalents are intended
to be encompassed in the scope of the claims.
