Note: Descriptions are shown in the official language in which they were submitted.
W093/2~27~ 2 1 ~ 6 ~ 7 3 PCT/US93/05445 '~'
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i.~
METHOD AND APPARATUS FOR TREATING ORGANIC WASTE :`
Backqround of the Invention
Disposal of organic wastes in landfills and by
incineration has become an increaslngly difficult
problem because of diminishing availability of disposal
space, strengthened governmental regulations, and the r,~i
growing public awareness of the impact of hazardous `'~ 'f
substance contamination upon the environment. Release
of hazardous organic wastes to the environment can
contaminate air and water supplies thereby diminishing
the quality of life in the affected populations.
To minimize the environmental effects of the
disposal of organic wastes, methods must be developed
to convert these wastes into benign, and preferably, ~ ~ 15 useful substances. In response to this need, there has
~been a substantial investment in the development of
alternate methods for suitably treating hazardous i`
organic wastes. One of the most promising new methods
is described in U.S. Patents 4,574,714 and~4,602,574,
issued to Bach and Nagel. The Bach/Nagel method for
destroying~organic material, including toxic wastes,
involves decomposition of the organic material to its `;
atomic constituents in a molten metal and reformation ;~
of these atomic constituents into environmentally
acceptable products, including hydrogen, carbon
monoxide and/or carbon dioxide gases.
Summary of the Invention
The present invention relates to a method and a `~
system for treating an organic waste containing `
~ ~ '
,.
W093/25278 PCT/US93/05~5 ~`
36o~
-2-
hydrogen and carbon in molten metal to form enriched
hydrogen and carbon oxide gas ctreams.
In one embodiment, organic waste containing
hydrogen and carbon is introduced into molten metal
contained in a carbonization reactor without the
addition of a separate oxidizing agent and~under i`
conditions sufficient to decompose the organic waste `~
and to generate hydrogen gas and carbonize the molten
metal. Carbonized molten metal is transferred from the
carbonization reactor to a decarbonization reactor. An
oxidizing agent is introduced into the carbonized
molten metal in the decarbonization reactor to oxidize
carbon contained therein thereby decarbonizing the
molten metal and generating an enriched stream of `~
carbon oxide gas. The decarbonized molten metal is
then~directed from the decarbonization reactor to the
carbonization reactor.
In another embodiment of the invention employed to
increase significantly the amount of carbon dioxide to
carbon monoxide in the enriched carbon oxide gas
stream~, the organic waste is introduced into molten
meta~l~ contained in a carbonization reactor without the
add`ition of a separate oxidizing agent and under ;
conditions sufficient to decompose the organic waste `
and to generate hydrogen gas and carbonize the molten
metal. In this embodiment, the molten metal includes `
two immiscible metals wherein the first immiscible `~
metal has`a free energy of oxidation greater than that
for oxidation of atomic carbon to form carbon monoxide `
and the second immiscible metal has a free energy Of
~-~ oxidation greater than that of oxidation of carbon
:,
: '
,
~ ~ ,
`
W093/2527~ 2 1 3 6 o 7 ~ PCT/US93/0544~
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monoxide to form carbon dioxide. The free energies of ~t
the aforementioned first and second immiscible metals
are taken at the operating conditions. The carbonized
molten metal is transferred from the carbonization --`
reactor to a decarbonization reactor and an oxidizing
agent is introduced into the carbonized molten metal in
the decarbonization reactor to oxidize carbon contained
therein thereby decarbonizing the molten metal and
generating an enriched stream of carbon oxide gas j`
10 having an increased molar ratio of carbon -
dioxide/carbon monoxide. The decarbonized molten metal -~
is then directed from the decarbonization reactor to -
the carbonization reactor.
An apparatus for carrying out the invention
includes a carbonization reactor having a molten metal
inlet, a molten metal outlet and a hydrogen off-gas
outlet and organic waste injection means for directing
organic waste into molten metal contained in the `
carbonization reactor. The apparatus further includes I~s
20 a decarbonization reactor having a molten metal inlet, ``
a molten metal outlet and a carbon oxide off-gas
outlet, means for directing the carbonized molten metal
from the carbonization reactor to the decarbonization
- reactor and then returning molten metal from the
decarbonization reactor to the carbonization reactor,
and oxidizing agent injection means for injecting an
oxidizing agent into the decarbonization reactor.
This invention has the advantage of treating
organic waste to form an enriched stream of hydrogen
gas and a separate enriched stream of carbon oxide gas,
such as carbon monoxide or carbon dioxide or both.
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W093/2~278 PCT/US93~05~5
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--4--
Enriched hydrogen and/or carbon oxide gas streams~are
often desired. For example, an enriched stream of
hydrogen gas is particularly useful in the synthesis of
ammonia or oxoalcohol and in hydrogenation or
S desulfurization processes. Hydrogen is also an
excellent "clean" or "greenhouse gas free" fuel.
":~
Brief Descri~tion of the Drawings
Figure 1 is a schematic representation of a system
for forming enriched hydrogen and carbon oxide gas
streams from an organic waste in molten metal according
to this invention.
Figure 2 is a schematic representation of second
system for forming enriched hydrogen and carbon oxide !,':'
gas streams from an organic waste in molten metal
according to this invention.
Figure 3 is a schematic representation of a third
system for simultaneously forming enriched hydrogen and
carbon oxide gas streams from an organic waste in ;~
molten metal according to this invention.
~20 Figure 4 is a schema.ic representation of a fourth ~
system for simultaneously forming enriched hydrogen and` ``
carbon oxide gas streams from an organic waste in
molten metal according to this invention. -
Figure S is a plot of the free energies, at
varying temperatures, for the oxidation of nickel, iron
and carbon.
Detailed Description of the Invention
The features and other details of the method and
apparatus of the invention will now be more
W093~25278 2 1 3 6 0 7 3 PCT/~S93/05~
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particularly described with reference to the ;~
accompanying drawings and pointed out in the claims.
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 principle
features of this invention can be employed in various
embodiments without departing from the scope of the ~
invention. -
The present invention generally relates to a
method and apparatus for treating an organic waste
containing hydrogen and carbon in molten metal to form
separately enriched hydrogen and carbon oxide gas -~
streams. This invention is an improvement of the
Bach/Nagel method disclosed in U.S. Patents 4,574,714 ,~
and 4,602,574, the teachings of which are hereby -~
incorporated by reference.
One embodiment of the invention is illustrated in -~
Figure 1. Therein, system 10 includes carbonization
reactor 12 and decarbonization reactor 14. Examples of
suitable reactors include appropriately modified
steelmaking vessels known in the art as argon-oxygen '`~
decarbonization furnaces (AOD), BOF, RH degassers, etc.
Hydrogen off-gas outlet 16, which extends from the
upper portion of carbonization reactor 12, is suitable !`~
for conducting an enriched hydrogen off-gas composition
out of carbonization reactor 12.
Organic waste inlet tube 18 includes organic waste `
inlet 20 and extends from the lower portion of `~
carbonization reactor 12. Line 22 extends between
30 organic waste source 24 and organic inlet tube 18. ,`-
Pump 26 is disposed in line 22 for directing organic `;
.
W093/2~278 PCT/US93/05~5 ~:
c~,6~3
-6- ~
waste from organic waste source 24 through organic :~;
waste inlet tube 18 and into molten metal contained in
carbonization reactor 12.
It is to be understood, however, that more than
5 one organic waste tube can be disposed at the lower ~-.
portion of carbonization reactor 12 for introduction of ~-
organic waste into carbonization reactor 12.
Additionally, organic waste can be introduced into the .
top of carbonization reactor 12 through port 28, or
10 through line 30. Other means, such as an injection `~
lance (not shown) can also be employed to introduce ~.
organic waste into molten metal in carbonization
reactor 12. . ` --
Bottom tapping spout 32 extends from the lower
portion of carbonization reactor 12 and is suitable for
removal of molten metal from carbonization reactor 12. ~
Material in carbonization reactor 12 can be removed by
; other methods, such as are known in the art.
Induction coil 34 is disposed at the lower portion
of carbonization reactor 12 for heating metal in
carbonization reactor 12. It is to be understood that, `~
alternatively, carbonization reactor 12 can be heated .
- by other suitable means, such as by oxyfuel burners,
electric arcs, etc.
Molten metal 36 is disposed within carbonization ;~
reactor 12. In one embodiment, molten metal 36 ~-
comprises a metal having a free energy of oxidation, at
operating conditions of carbonizat:ion reactor 12, which
is greater than the free energy for conversion of `
atomic carbon to carbon monoxide. Examples of suitable
metals include iron, chromium and manganese. Molten
i'~'
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W093/25278 PCT/US93/05~5 -
2136073 ~:~
metal 36 also can include more than one metal. For
example, molten metal 36 can include a solution of
miscible metals, such as iron and chromium. ~
Suitable metals are those with melting points
below the operating conditions of the system. It is
preferred, for example, to run carbonization reactor 12
in a temperature range of from about 1,300C to about
1,700C.
Suitable metals must also have a carbon solubility
10 sufficient to allow significant amounts of hydrogen to ~1
be generated from the metal as organic waste is
decomposed and the molten metal becomes carbonized.
Thus, metals with a carbon solubility of greater than
about 0.5 percent, by weight, are preferred, and those
with a carbon solubility of greater than about two
percent, by weight`, are particularly preferred. In the
cases where more than one metal is employed, at least
one of the metals should have the aforementioned carbon
solubility.
In many cases, it is also preferred to have the
viscosity of the molten metal in carbonization reactor ;
12 and decarbonization reactor 14 at less than about `
ten centipoise at the operating conditions of the
reactors. ~-
Molten metal 36 i5 formed by at least partially
filling carbonization reactor 12 with a suitable metal.
The metal is then heated to a suitable temperature by
induction coil 34 or by other suitable heating means
(not shown).
Carbon oxide off-gas outlet 40 extends from the ``
upper portion of decarbonization reactor 14 and is
W093/25278 PCT/US93/05~ ~
6~'l`3 - ` ~
-8- `
suitable for conducting an enriched carbon oxide o~f-
gas composition generated in decarbonization reactor 14
to a collection means (not shown) or to means for
venting the gas. .` -
Tuyere 42 is disposed at the lower portion of -~
decarbonization reactor 14. Tuyere 42 includes ~-
oxidizing agent tube 44 for injection of a separate
oxidizing agent at oxidizing agent inlet 46. Line 48
extends between oxidizing agent tube 44 and oxidizing `
10 agent source 50. It is to be understood, hawever, that `--
more than one oxidizing agent tube can be disposed at 1`
the lower portion of decarbonization reactor 14 for
introduction of oxidizing agent into decarbonization
reactor 14. Other means for introducing the separate
oxidizing agent can, of course, also be employed alone
or in combination with tuyere 42.
Bottom tapping spout 52 extends from the lower
portion of decarbonization reactor 14 and is suitable
for the removal of molten metal from decarbonization ~
20 reactor 14. `-
Induction coil 54 is disposed at the lower portion ;`
of decarbonization reactor 14 for heating carbonized
metal in reactor 14. Decarbonization reactor 14 can
be, of course, heated by other suitable means, such as
by oxyfuel burners, electric arcs, etc.
Molten metal 56 in decarbonization reactor 14 is ~`
the carbonized molten metal that was formed in
carbonization reactor 12 before it was directed to
decarbonization reactor 14. Conduit 60, disposed
between carbonization reactor 12 and decarbonization
reactor 14, is employed to transfer carbonized molten
W093/25278 2 i 3 6 0 7 3 PCT/US93/05~5
_9_ :
metal from carbonization reactor 12 to decarbonization
reactor 14. Conduit 62, disposed between
decarbonization reactor 14 and carbonization reactor
12, is employed to transfer decarbonized molten metal `
5 from decarbonization reactor 14 to carbonization
reactor 12.
Suitable operating conditions for carbonization
reactor 12 include a temperature sufficient to at least
partially convert organic waste, such as by
10 decomposition, to its constituents including hydrogen
and carbon. Generally, a temperature in the range of ?
between about 1,300 and about 1,700C is suitable.
Optionally, molten metal 36 can have vitreous or
slag Iayer 64. Vitreous layer 64, which is disposed on
15 molten metal 36, is substantially immiscible with ~.
molten metal 36. Vitreous layer 64 can have a lower
thermal conductivity than that of molten me~tal 36.
Radiant heat loss from molten metal can thereby be `
reduced to significantly below the radiant heat loss `~
20 from molten metal where no vitreous layer is present. `~
Decarbonization reactor 14 can have a similar vitreous `--~'
phase, decarbonization vitreous layer 66.
Typically, a vitreous layer 64 or 66 includes at `
least one metal oxide having a free energy of `
oxidation, at the operating conditions, which is less
than that of conversion of atomic carbon to carbon
monoxide. An example is calcium oxide (CaO). Vitreous
layer 64 can also contain a suitable compound for `
scrubbing halogens, such as chlorine or fluorine, to
30 prevent formation of hydrogen halide gases, such as
hydrogen chloride.
W0~3/~278 PCT/US93/05~5
21360~3 ~
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A wide variety of organic waste is suitable or
treatment by this invention. An example of a suitable `~
organic waste is a hydrogen-containl~g carbonaceous P-
material, such as oil or a waste wh`Ich includes organic -
compounds containing nitrogen, sulfur, oxygen, etc. It
is to be understood that the organic waste can include
inorganic compounds. In addition to carbon and
hydrogen, the organic waste can include other atomic
constituents, such as halogens, metals, etc. Organic
10 waste does not need to be anhydrous. However, -~-
significant amounts of water in the organic waste can `
cause the water to act as an oxidizin~ agent, thereby ;~
interfering with the formation of enriched hydrogen
gas. For the production of enriched hydrogen gas, a
15 preferred organic waste is containing carbonaceous `~
waste having a relatively high hydrogen content, such
as propane, butane, etc. For the production of
enriched carbon oxide gas, a preferred organic waste
includes a carbonaceous waste with a relatively low
hydrogen content, such as tars, oils, olefins, etc.
Organic waste is directed from organic waste
source 24 through line 22 by pump 26 and is injected
into molten metal 36 in carbonization reactor 12 ~
through organic waste tube 18. The organic waste can `
be solid or a fluld which can include solid organic
waste components dissolved or suspended within a
liquid. Alternatively, solid particles of organic
waste can be suspended in an inert gas, such as argon.
The organic waste directed into molten metal 36 is
converted to carbon, hydrogen, and other atomic
constituents. Atomic hydrogen combines to generate
W093/25278 PCT/US93/0~5
- ~i36073
11 ,
hydrogen in decarbonizing reactor 12. Molten meta~ 36
contained therein is concurrently carbonized. The term
"carbonize", as used herein, means the addition of
atomic carbon to molten metal to increase the overall
quantity of carbon contained in the molten metal
without any substantial losses of carbon from the ;~
molten metal due to oxidation by a separately added
oxidizing agent. It is understood, of course, that the
organic waste may contain one or more oxidizing agents ;``
but these are not considered separately added oxidizing
agents. v~
Hydrogen gas generated migrates through molten `
metal 36, such as by diffusion, bubbling or other
means. At least a portion of the hydrogen gas migrates
to a portion of molten metal 36 proximate to hydrogen
off-gas outlet 16 to form an enriched hydrogen gas l~
stream. An enriched hydrogen gas stream, as that term ---
is used herein, means a gas stream wherein the molar ,-
fraction of hydrogen contained in the gas stream, based ~`
upon thP total hydrogen and carbon oxide in the gas
stream, is greater than that generally produced in a ~;~
typical process disclosed by Bach/Nagel in U.S. Patents li`
4,574,714 and 4,602,574 for the simultaneous, combined
decomposition and ~oxidation of an organic waste. The
25 molar fraction of hydrogen is the ratio of the moles of ~-~
hydrogen contained in a gas stream to the sum of the
moles of hydrogen and moles of carbon oxide gases `
contained in the gas stream. -~
The concentration of dissolved carbon in
30 carbonized molten metal 36 is~preferably limited to an l;
amount below the saturation point for carbon at the
'
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W093/25278 PCT/US93/05~5
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-12-
temperature of molten metal 36. For molten iron,~the -
concentration of atomic carbon preferably is limited to
a concentration of less than àbout five percent, by ~.:
weight, at l,800C. Where molten metal 36~is cobalt, -
5 the saturation point of carbon is in the range of -
between about three percent at 1,400C and about 4.3
percent, by weight, at 1,800C. Similarly for -
manganese, the saturation point of carbon is in the -~
range of between about eight percent at 1,400C and ~-
about 8.5 percent, by weight, at 1,800C. For chromium `
the saturation point of carbon is in the range of
between about eleven percent at 1,800C and about
f`ifteen percent, by weight, at 2,000C.
If carbon contained in the molten metal becomes
15 insoluble because the molten metal is saturated with ::
carbon, the insoluble portion of the carbon may become
entrained in the enriched hydrogen gas stream and
thereby be removed from the molten metal through
hydrogen off-gas outlet 16. If this happens, suitable
apparatus known in the art can be used to separate the
entrained carbon dust from the hydrogen gas stream.
Examples of suitable apparatus include a cyclone
separator or baghouse filter.
Carbonized molten metal 36 is transferred from
carbonization reactor 12 through conduit 60 to
decarbonization reactor 14. A separate oxidizing agent
is directed from oxidizing agent source 50 through line
48 and is injected through oxidizi:ng agent tube 44 into
carbonized molten metal 56 in decarbonization reactor
30 14. Examples of suitable oxidizing agents include :
W093/25278 ~ l ~ b ~ ~ ~ PCT/US93/0544~ ~
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-13-
oxygen, air, iron oxide, etc., with the preferred
oxidizing agent being oxygen gas.
Introduction of a separate oxidizing ag~ent into ~;
carbonized molten metal 56 results in the generation of
an enriched carbon oxide gas stream, as molten metal 56
is decarbonized. An enriched carbon oxide gas stream, l;
as that term is used herein, means a gas stream wherein
the molar fraction of carbon oxide gas contained in the
gas stream based upon the total hydrogen and carbon
oxide gas, is greater than that generally produced in a
typical process disclosed by Bach/Nagel in U.S. Patents
4,574,714 and 4,602,574 for the simultaneous, combined
decomposition and oxidation of an organic waste. The
; molar fraction of carbon oxide~gas is the ratio of the
moles of carbon oxlde gas contained in a gas stream to
the sum of the moles of hydrogen and moles of carbon
oxid~e`gases contained in the gas stream.
Enriched carbon oxide gas stream is removed from
decarbonization reactor 14 through carbon oxide off-gas
20 outlet 40. It can be coIlected or vented. !,,,`,
Decarbonized molten metal 56 is returned to
carbonization reactor 12 via conduit 62. Decarbonized
- molten metal 56 returned to carbonization reactor 12 is
carbo~ized in reactor 12, as previously discussed, as ~`
additional organic waste is added to reactor 12 without
addition of a separate oxidizing agent to Continue the
process. Although not shown, pumps can be employed to
attain the desirable circulation o~ molten metal.
System 10 is preferably run at atmospheric `~
pressure or ùnder vacuum to facilitate off-gas removal.
The ratio of carbon monoxide to carbon dioxide in
. `.,
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W093/2s278 PCT/US93/05~5 ~
36~rl 3
-14~
the carbon oxide off-gas in reactor 14 can be adju~sted ''~
by a number of techniques. One i~volves the selection -~
of the metal or metals. For example, iron tends to '-
produce carbon monoxide whereas metals such as nickel
or manganese tend to produce increased amounts of
carbon dioxide.
U.S. Patent 5,177,304, issued to Nagel (January 5,
1993), discloses a method and system for increasing the -'
formation of carbon dioxide from carbonaceous material ,~
10 in a molten bath of immiscible metals. The teachings ~,
of this Patent are incorporated hereby by reference.
As taught therein, an increased amount of carbon ,'
dioxide can be produced from a molten bath which has ~'
two immiscible molten metals wherein the first has a ~,
15 free energy of oxidation greater than that for '~
oxidation of atomic carbon to carbon monoxide and the
second has a free energy of oxidation greater than that
for oxidation of carbon monoxide to carbon dioxide.
The molar ratio of carbon monoxide to carbon '
20 dioxide in off-gas from reactor 14 can also be affected ~,
by other operating conditions for reactor 14. For ~
example, the rate of introduction of oxidizing agent, ;
temperature, degree of carbonization of molten metal
56, etc. can be expected to affect this ratio. ,."-
An alternative embodiment of an apparatus for
carrying out this invention is illustrated in Figure 2.
Therein, system 100 has molten metal reactor 102 with ;
molten metal 104 disposed therein., Carbonization
reactor 106 is disposed in molten metal reactor 102.
Molten metal reactor 102 has oxidizing agent inlet 108,
, . .
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W O 93/25278 ~ 1 3 6 0 7 3 PC~r/US93/05445
~'~
bottom tapping spout 110 and carbon oxide off-gas ~
outlet 112. ,-
Carbonization reactor 106 has carbonization `-
reactor inlet 114, carbonization reactor outlet 116 and
hydrogen off-gas outlet 118. Carbonization reactor
inlet 114 and carbonization reactor outlet 116 are
connected to carbonization reactor inlet tube 120 and
carbonization reactor outlet tube 122, respectively.
Carbonization reactor inlet tube 120 and carbonization
reactor outlet tube 122 are of sufficient length
whereby portions of inlet tube 120 and outlet tube 122
are submerged beneath the surface of molten metal 104
in molten metal reactor 102. -
Organic waste having carbon and hydrogen is
15 introduced by injection means 124 which is disposed at ~`
carbonization reactor inlet tube 120 for introducing ;~
organic waste into molten metal 115 contained within
carbonization reactor 106. Injection means 124 include
-- organic waste source 126, line 128 and inlet tube 130. ;~`
As organic waste is introduced through inlet tube 130,
it is decomposed to generate hydrogen gas, thereby
forming a separate stream of enriched hydrogen gas
which can then be directed through hydrogen off-gas
outlet 118 contained in carbonization reactor 106.
Carbon is dissolved in molten metal 115 to form
carbonized molten metaI. As hydrogen gas migrates to ,~
hydrogen off-gas outlet 118, the movement of the -
hydrogen gas through molten metal 115 causes it to
circulate. Molten metal 115 circulates from
30 carbonization reactor inlet 114 through carbonization `
reactor 106 to carbonization reactor outlet 116 and -
W093/2527X PCT/US~3/05~5
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passes through outlet tube 122 back to the molten metal
contained in reactor 102.
An oxidizing agent is introduced by injection
means 136 into carbonized molten m.e-tal contained in
reactor 102. Injection means 136-1ncludes oxidizing .-.`
agent source 140, line 142 and oxidizing agent tube ..
144. Carbon oxide gas is formed, and the molten metal
in reactor 102 is decarbonized, as oxidizing agent is
introduced through inlet 108. :.
As the carbon oxide gas generated migrates through
molten metal 104 to carbon oxide off-gas outlet 112,
the movement of the carbon oxide gas causes the molten ~.
metal to circulate from carbonization reactor outlet
116 through molten metal 104 to carbonization reactor
inlet 114 thereby returning the decarbonized molten
metal to carbonization reactor 106. ~:
System 100 can operate at varying pressures in .. -
order to cause the desirable circulation of molten
metal. Generally, the pressure in carbonization
- 20 reactor 106 is less than the pressure in molten metal `
reactor 102 to promote the desirable circulation of ;.
molten metal. .`
Another alternative embodiment of the invention is ...
illustrated in Figure 3. Therein,~ system 200 has .
molten metal vessel 202 with molten metal 204 disposed .
therein. Carbonization reactor 206 and decarbonization
reactor 208 are disposed within molten metal vessel
202.
Carbonization reactor 206 has carbonization ;.
reactor inlet 210, carbonization reactor outlet 212 and .
hydrogen off-gas outlet 214. Carbonization reactor
.
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W093/25278 PCT/US93/05445
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inlet 210 and carbonization reactor outlet 212 are
connected to carbonization reactor inlet tube 216 and
carbonization reactor outlet tube 218, respectively.
Carbonization reactor inlet tube 216 and carbonization
reactor outlet tube 218 are of sufficient length
whereby portions of inlet tube 216 and outlet tube 218
are submerged beneath the surface of molten metal 204 `~
in molten metal vessel 202. ~-
Organic waste containing carbon and hydrogen is
introduced by injection means 220, which is disposed at
carbonization reactor inlet tube 216, for introducing
organic waste into molten metal 211 contained within
carbonization reactor 206. Injection means 220 include
organic waste source 222, line 224 and inlet tube 226.
As organic waste is introduced through inlet tube 226,
it is decomposed to generate hydrogen gas, thereby
forming an enriched hydrogen gas stream which can then
be directed through hydrogen off-gas outlet 214. l~
Carbon is simultaneously dissolved in molten metal 211
to form carbonized molten metal. The movement of
hydrogen gas through molten metal 211 causes
circulation from carbonization reactor inlet 210
through carbonization reactor 206 to carbonization ~`
reactor outlet 212. Thus, molten metal flows from
vessel 202 into reactor 206, where it is carbonized,
and back to vessel 202.
Decarbonization reactor 208 has molten metal inlet
232, outlet 234 and carbon oxide off-gas outlet 236. `~-`
Inlet 232 and outlet 234 are connected to
decarbonization reactor inlet tube 238 and
decarbonization reactor outlet tube 240, respectively. ,~-
W093/25278 PCT/US93/05~5
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Inlet tube 238 and outlet tube 2~0 are of sufficie~t
length, so that portions of inlet tube 238 and outlet
tube 240 are submerged beneath the surface of molten
metal 204 in molten metal vessel 202.
An oxidizing agent is introduced by injection
means 242, including oxidizing agent source 244, line
-246 and oxidizing agent tube 248. As oxidizing agent
is injected carbon oxide gas is formed and molten metal `-
233 causes the molten metal to circulate from
10 decarbonization reactor inlet 232 through ~`
decarbonization reactor 208 to decarbonization reactor ;~
outlet 234 and back to molten metal 204 in vessel 202. ~:
System 200 can operate at varylng pressures to
cause the desirable circulation of molten metal.
Preferably, the pressure in carbonization reactor 206
and decarbonization reactor 208 is less than the `,
pressure in molten metal vessel 202 to promote the
: desirable circulation.
A still further alternative embodiment of the
invention is illustrated in Figure 4. Therein, system
300 has molten metal vessel 302 containing molten metal !",",
304 and vitreous layer 308.
Baffle 310 is disposed within molten metal vessel
302. Baffle 310 extends substantially into molten ~-~
: 25 metal 304 to define carbonization reactor region 312 i`-.
and decarbonization reactor region 314, whereby
essentially all of the hydrogen gas is formed in ~`
carbonization reactor region 312 while not allowing a ;-
substantial loss of hydrogen gas to decarbonization
30 reactor region 314 and whereby essentially all of the ~-
: carbon oxide gas is formed in decarbonization reactor
. ~
. .
,
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~W093/25278 %1 3 6 ~ 7 3 PCT/US93/05~5
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-19- ~:
region 314 while not allowing a substantial loss o~
carbon oxide gas to carbonization reactor region 312. ;~
Carbonization reactor region 312 has hydrogen gas :~
region 316, and decarbonization reactor region has
5 carbon oxide gas region 318. There is no communication ;
between hydrogen gas region 316 and carbon oxide gas ~`;'
region 318 except through molten metal 304. Hydrogen
off-gas outlet 320 is above the surface of molten metal :
304 in carbonizatlon reactor region 312, and carbon ~`
sxide off-gas outlet 322 is above the surface of molten
metal 304 in decarbonization region 314. ,.-
Organic waste tube 324 includes organic waste
inlet 325 and is located at the lower portion of ~.
carbonization reactor region 312 for iniection of the
organic waste at organic waste inlet 326 in a
- substantially vertical direction into molten metal 304. ~.~
The injected organic waste forms a field of flow, which `-
remains substantially in carbonization reactor region ;
312, while not allowing a substantial loss of hydrogen ..
gas to decarbonization reactor region 314. Line 328 f'`
extends between organic waste source 330 and organic
waste tube 324. Pump 332 is disposed in line 328 for
directing organic feed from organic waste source 330 to f:``.
organic material inlet 326.
Oxidizing agent tube 334 is disposed at the upper
portion of decarbonization reactor region 314 for .~-~
injection of the separate oxidizing agent at oxidizing
agent inlet 336 in a substantially vertical direction ..
into molten metal 304. The oxidizing agent forms a `~
field of flow, which remains essentially in
decarbonization reactor region 314, while not allowing ~,i
. `. '
:
W093/25~78 PCT/US93/05~5
2~60~ ~
-20-
a substantial loss of carbon oxide..gas to carbonization
reactor region 312. Second oxid1zlng agent tube 335 is
disposed at the lower portion of decarbonization
reactor region 314 for an additional injection site for
5 injecting the oxidizing agent in a substantially ~
vertical direction, thereby forming a field of flow .. `
from the bottom of molten metal vessel 302, which also ~-~
remains essentially in decarbonization reactor region
314, while not allowing a substantial loss of carbon
oxide gas to carbonization reactor region 312. Line
338 extends between separate oxidizing agent tube 334
and oxidizing agent source 340. One or both locations
for introduction of the separate oxidizing agent can be
employed.
lS Bottom tapping spout 342 extends from the lower j`:
- portion of molten metal vessel 302 and is suitable for ..
removal of molten metal from molten metal vessel 302. ~.
Organic waste is introduced into molten metal 304
in carbonization reactor region 312 under conditions ...
20 sufficient to decompose the organic waste. Hydrogen ~.
gas is generated while the molten metal is carbonized
in region 312. Baffle 310 extends sufficiently into
molten metal 304 to allow the decomposition of organic
waste into hydrogen and carbon while not allowing .
substantial loss of hydrogen into decarbonization
: reactor region 314. Carbon dissolves concurrently in .`~
molten metal 304. The injection of organic waste into .
carbonization reactor region 312 can cause sufficient
circulation in molten metal 304 to distribute the `
30 dissolved carbon throughout molten metal 304. The ;
enriched hydrogen gas is removed from carbonization
W093/25278 PCT/US93/05~5
2136073 `:
-21- .
reactor region 312 through hydrogen gas region 316 to
hydrogen gas off-gas outlet 320.
Oxidizing agent is introduced into molten metal
304 in decarbonization reactor region 314 under
5 conditions to oxidize carbon contained therein, thereby `
forming an enriched stream of carbon oxide gas. Baffle ~`
310 also extends sufficiently into molten metal 304 to ;
allow the oxidation of dissolved carbon into carbon
oxide gases while not allowing substantial loss of
10 oxidizing agent into carbonization reactor region 312. ~
Dissolved carbon is oxidized, thereby decarbonizing the ~-
molten metal and forming an enriched carbon oxide gas
stream. The enriched carbon oxide gas stream is
removed from decarbonization reactor region 314 through
carbon oxide off-gas outlet. The ~evolving carbon oxide
gas causes sufficient circulation of molten bath 304 to
return decarbonized molten metal to carbonization
reactor region 312.
Illustration I
An organic waste containing an organic compound
having hydrogen and carbon, such as butane, is fed into `~
a carbonization reactor of a system, as shown in Figure
l. The molten metal in the system is iron at a
temperature of I,800C. The organic waste forms the
atomic constituents of carbon and hydrogen in the
molten metal causing separation of hydrogen from carbon
by the decomposition of hydrogen to form an enriched
hydrogen gas stream and to carbonize the molten iron.
The hydrogen gas is r`emoved from reactor through the
hydroqen off-gas outlet.
, ,,~
W093/2527~ PCT/US9~/05~5
-
'2~ 360~3
.
Carbonized molten iron is directed to a
decarbonization reactor where, an oxidizing agent,
oxygen gas, is then added t.o carbonized molten iron in
the system. The reaction of carbon with the oxidizing
5 agent occurs preferentially to the oxidation of the `
iron in the molten metal, because, as can be seen in -~`
Figure 5, the free energy of oxidation of carbon (Curve ~-
1) is lower than that for oxidation of iron (Curve 2) -
at the operating temperature. Carbon preferentially
forms carbon monoxide to iron oxide or carbon dioxide
because the free energy of oxidation of carbon to `~
carbon dioxide (Curve 3) is greater than the free
energy of oxidation of iron (Curve 2) which is greater
than the free energy of oxidation for carbon to form `~
15 carbon monoxide (Curve 1). Oxygen gas is added ~
continuously to the molten metal. The carbon monoxide `~;
is separated from molten metal through the carbon oxide
off-gas outlet decarbonization reactor which can then
be directed to a carbon oxide collection tank, not ~-j
shown, or vented to the atmosphere. The decarbonized
metal is returned to the carbonization reactor
continuously.
;,
Illustration II ;.:
In a reactor configuration similar to Illustration `
I, organic waste containing an organic compound having
hydrogen and carbon, such as butane, is fed into the
molten metal of carbonization reactor. However, the
molten metal is nickel at a temperature of l,800C.
The organic waste forms the atomic constituents of
carbon and hydrogen in the molten metal causing
:~;
~'.`
W093/25278 ~1 3 6 0 7 3 PCT/US93/OS~S ,~
23
separation of hydrogen from carbon by the decomposition
of hydrogen to form an enriched hydrogen gas stream and -
to carbonize the molten nickel. The hydrogen gas is
remove from reactor through the hydrogen off-gas
outlet.
Carbonized molten nickel is directed to a
decarbonization reactor where, oxidizing agent, oxygen !~
gas, is then added to the carbonized nickel. The ~
reaction of carbon with the oxidizing agent occurs ~`
preferentially to the oxidation of the nickel in the
molten metal, because, as can be seen in Figure 5, the
free energy of oxidation of carbon (Curve 1) is lower
than that of the nickel tCurve 4) at the temperature of
; molten nickel. Carbon forms a mixture of carbon
15~ monoxide and carbon dioxide because the free energies
of oxldation to form carbon dioxide (Curve;3) and to
form c~arbon monoxide (Curve 1) are both less than the
fre~e energy of oxidation of nickel. Oxygen gas is
added continuo~sly to the carbonized molten metal to
decarbonize it. The carbon oxide gases are separated
from~-the`mo~lten metal through a carbon oxlde off-gas
outlet which can then be directed to a carbon oxide
collècti~on tank, not shown, or vented to the
atmosphere~. The decarbonized metal is returned to the
carbonization reactor continuously.
The methods~and apparatus described herein allow `
for the simultaneous generation of enriched hydrogen ~
and carbon oxide gas streams. However, in some `
embodiments, simultaneous generation is not necessary
and sequential generation may be preferred in some
instances.
'
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