METHOD AND APPARTUS FOR TREATING ORGANIC WASTE

Abstract: A method and apparatus are disclosed for treating an organic waste containing hydrogen and carbon in molten metal to form enriched hydrogen and carbon oxide gas streams. In one embodiment, the organic waste is introduced into a molten metal contained in a carbonization reactor without the addition of a separate oxidizing agent and under conditions sufficient to decompose the organic waste to generate hydrogen gas and carbonize the molten metal. Carbonized molten metal is directed 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 said molten metal and generating an enriched stream of carbon oxide gas.

Description: METHOD AND APPARATUS FOR TREATING ORGANIC WASTE Background of the Invention Disposal of organic wastes in landfills and by incineration has become an increasingly difficult problem because of diminishing availability of disposal space, strengthened governmental regulations, and the growing public awareness of the impact of hazardous 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, useful substances. In response to this need, there has been a substantial investment in the development of alternate methods for suitably treating hazardous 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 hydrogen and carbon in molten metal to form enriched hydrogen and carbon oxide gas streams. 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 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 metal contained in a carbonization reactor without the addition 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 monoxide to form carbon dioxide. The free energies of 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 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 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. 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 desulfurization processes. Hydrogen is also an excellent "clean" or "greenhouse gas free" fuel. Brief Description 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. Figure 4 is a schematic 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 5 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 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 organic waste source 24 and organic inlet tube 18. Pump 26 is disposed in line 22 for directing organic 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 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 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 carbonization 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 etal 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 1,300°C to about 1,700°C. Suitable metals must also have a carbon solubility sufficient to allow significant amounts of hydrogen to 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 is 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 suitable for conducting an enriched carbon oxide off- 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 agent source 50. It is to be understood, however, that more than one oxidizing agent tube can be disposed at 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 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 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 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 decomposition, to its constituents including hydrogen and carbon. Generally, a temperature in the range of between about 1,300° and about 1,700°C is suitable. Optionally, molten metal 36 can have vitreous or slag layer 64. Vitreous layer 64, which is disposed on molten metal 36, is substantially immiscible with molten metal 36. Vitreous layer 64 can have a lower thermal conductivity than that of molten metal 36. Radiant heat loss from molten metal can thereby be reduced to significantly below the radiant heat loss 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 prevent formation of hydrogen halide gases, such as hydrogen chloride. A wide variety of organic waste is suitable for treatment by this invention. An example of a suitable organic waste is a hydrogen-containing carbonaceous material, such as oil or a waste which 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 waste does not need to be anhydrous. However, significant amounts of water in the organic waste can cause the water to act as an oxidizing agent, thereby interfering with the formation of enriched hydrogen gas. For the production of enriched hydrogen gas, a 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 fluid 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 hydrogen in decarbonizing reactor 12. Molten metal 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. 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 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 the 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 4,574,714 and 4,602,574 for the simultaneous, combined decomposition and oxidation of an organic waste. The 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 carbonized molten metal 36 is preferably limited to an amount below the saturation point for carbon at the temperature of molten metal 36. For molten iron, the concentration of atomic carbon preferably is limited to a concentration of less than about five percent, by weight, at l,800°C. Where molten metal 36 is cobalt, the saturation point of carbon is in the range of between about three percent at 1,400°C and about 4.3 percent, by weight, at 1,800°C. Similarly for manganese, the saturation point of carbon is in the range of between about eight percent at 1,400°C and about 8.5 percent, by weight, at 1,800°C. For chromium the saturation point of carbon is in the range of between about eleven percent at 1,800°C and about fifteen percent, by weight, at 2,000°C. If carbon contained in the molten metal becomes 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 oxidizing agent tube 44 into carbonized molten metal 56 in decarbonization reactor 14. Examples of suitable oxidizing agents include oxygen, air, iron oxide, etc., with the preferred oxidizing agent being oxygen gas. Introduction of a separate oxidizing agent 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, 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 oxide gas contained in a gas stream to the sum of the moles of hydrogen and moles of carbon oxide gases contained in the gas stream. Enriched carbon oxide gas stream is removed from decarbonization reactor 14 through carbon oxide off-gas outlet 40. It can be collected 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 carbonized 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 of molten metal. System 10 is preferably run at atmospheric pressure or under vacuum to facilitate off-gas removal. The ratio of carbon monoxide to carbon dioxide in the carbon oxide off-gas in reactor 14 can be adjusted by a number of techniques. One involves 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 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 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 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, 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 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 metal. 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 carbonization reactor inlet 114 through carbonization reactor 106 to carbonization reactor outlet 116 and 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 metal contained in reactor 102. Injection means 136 includes 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 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 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. 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. Inlet tube 238 and outlet tube 240 are of sufficient 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 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 varying 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 metal 304 to define carbonization reactor region 312 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 reactor region 314 and whereby essentially all of the carbon oxide gas is formed in decarbonization reactor region 314 while not allowing a substantial loss of carbon oxide gas to carbonization reactor region 312. Carbonization reactor region 312 has hydrogen gas region 316, and decarbonization reactor region has 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 carbonization reactor region 312, and carbon oxide off-gas outlet 322 is above the surface of molten metal 304 in decarbonization region 314. Organic waste tube 324 includes organic waste inlet 326 and is located at the lower portion of carbonization reactor region 312 for injection 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 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 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 a substantial loss of carbon oxide gas to carbonization reactor region 312. Second oxidizing agent tube 335 is disposed at the lower portion of decarbonization reactor region 314 for an additional injection site for 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. Bottom tapping spout 342 extends from the lower 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 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 dissolved carbon throughout molten metal 304. The enriched hydrogen gas is removed from carbonization 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 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 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 1. The molten metal in the system is iron at a temperature of 1,800°C. 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 removed from reactor through the hydrogen off-gas outlet. Carbonized molten iron is directed to a decarbonization reactor where, an oxidizing agent, oxygen gas, is then added to carbonized molten iron in the system. The reaction of carbon with the oxidizing 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 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 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 1,800°C. 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 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 (Curve 4) at the temperature of molten nickel. Carbon forms a mixture of carbon monoxide and carbon dioxide because the free energies of oxidation to form carbon dioxide (Curve 3) and to form carbon monoxide (Curve l) are both less than the free energy of oxidation of nickel. Oxygen gas is added continuously to the carbonized molten metal to decarbonize it. The carbon oxide gases are separated from the molten metal through a carbon oxide off-gas outlet which can then be directed to a carbon oxide collection 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.

Claims: CLAIMS 1. A method for treating an organic waste containing hydrogen and carbon in molten metal to form enriched hydrogen and carbon oxide gas streams, comprising the steps of: a) introducing the organic waste into molten metal contained in a carbonization reactor without the addition of a separate oxidizing agent and under conditions sufficient to decompose the organic waste and to generate hydrogen gas and carbonize the molten metal; b) directing the carbonized molten metal from the carbonization reactor to a decarbonization reactor; c) introducing an oxidizing agent into the carbonized molten metal in the decarbonization reactor to oxidize carbon contained therein thereby decarbonizing said molten metal and generating an enriched stream of carbon oxide gas; and d) directing the decarbonized molten metal from the decarbonization reactor to the carbonization reactor. 2. A method of Claim 1 wherein the enriched carbon oxide gas stream comprises carbon monoxide. 3. A method of Claim 2 wherein the molten metal comprises iron. 4. A method of Claim 3 wherein the separate oxidizing agent comprises oxygen gas. 5. A method of Claim 1 wherein the molten metal is selected to provide a significantly increased molar ratio of carbon dioxide/carbon monoxide compared to that produced in molten iron under the same conditions. 6. A method of Claim 5 wherein the molten metal comprises manganese. 7. A method of Claim 5 wherein the molten metal comprises two immiscible metals wherein, at the operating conditions, 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 for oxidation of carbon monoxide to form carbon dioxide. 8. A method of Claim 7 wherein the first molten metal comprises iron and the second molten metal comprises copper. 9. A method for treating an organic waste containing hydrogen and carbon in molten metal to form enriched hydrogen and carbon oxide gas streams, said carbon oxide gas having a significantly increased molar ratio of carbon dioxide/carbon monoxide compared to that produced in molten iron under the same conditions, comprising the steps of: . a) introducing the organic waste into molten metal contained in a carbonization reactor without the addition of a separate oxidizing agent and under conditions sufficient to decompose the organic waste and to generate hydrogen gas and carbonize the molten metal, said molten metal comprising two immiscible metals wherein, at the operating conditions, the first immiscible metal has a free energy of oxidation greater than that of oxidation of atomic carbon to form carbon monoxide and a second immiscible metal having a free energy of oxidation, at the conditions of molten metal, greater than that of oxidation of carbon monoxide to form carbon dioxide; b) directing the carbonized molten metal from the carbonization reactor to a decarbonization reactor; c) introducing an oxidizing agent into the carbonized molten metal in the decarbonization reactor to oxidize carbon contained therein thereby decarbonizing said molten metal and forming an enriched stream of carbon oxide gas having a significantly increased molar ratio of carbon dioxide/carbon monoxide compared to that produced in molten iron under the same conditions; and d) directing the decarbonized molten metal from the decarbonization reactor to the carbonization reactor. 10. A method for treating an organic waste containing hydrogen and carbon in molten metal to form enriched hydrogen and carbon oxide gas streams, comprising the steps of: a) introducing the organic waste into molten iron contained in a carbonization reactor without the addition of a separate oxidizing agent and under conditions sufficient to decompose the organic waste and to generate hydrogen gas and carbonize the molten iron; b) directing the carbonized molten iron from the carbonization reactor to a decarbonization reactor; c) introducing oxygen gas into the carbonized molten iron in the decarbonization reactor to oxidize carbon contained therein thereby decarbonizing said molten metal and generating an enriched stream of carbon monoxide gas; and d) directing the decarbonized molten iron from the decarbonization reactor to the carbonization reactor. 11. A method for treating an organic waste containing hydrogen and carbon in molten metal to simultaneously form enriched hydrogen and carbon oxide gas streams, comprising the steps of: a) introducing the organic waste into molten metal contained in a carbonization reactor without the addition of a separate oxidizing agent and under conditions sufficient to decompose the organic waste and to generate hydrogen gas and carbonize the molten metal; b) directing carbonized molten metal from the carbonization reactor to a decarbonization reactor; and while continuing step (a) , c) introducing an oxidizing agent into the carbonized molten metal in the decarbonization reactor to oxidize carbon contained therein thereby decarbonizing said molten metal and generating an enriched stream of carbon oxide gas; d) directing decarbonized molten metal from the decarbonization reactor to a carbonization reactor; and while continuing step (c) . 12. A method of Claim 11 wherein the enriched carbon oxide gas stream comprises carbon monoxide. 13. A method of Claim 12 wherein the molten metal comprises iron. 14. A method of Claim 13 wherein the separate oxidizing agent comprises oxygen gas. 15. A method of Claim 11 wherein the molten metal is selected to provide a significantly increased molar ratio of carbon dioxide/carbon monoxide compared to that produced in molten iron under the same conditions. 16. A method of Claim 15 wherein the molten metal comprises manganese. 17. A method of Claim 15 wherein the molten metal comprises two immiscible metals wherein, at the operating conditions, 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 for oxidation of carbon monoxide to form carbon dioxide. 18. A method of Claim 17 wherein the first molten metal comprises iron and the second molten metal comprises copper. 19. A method for treating an organic waste containing hydrogen and carbon in molten metal to simultaneously form enriched hydrogen and carbon oxide gas streams, comprising the steps of: a) introducing the organic waste into molten metal contained in a carbonization reactor without the addition of a separate oxidizing agent and under conditions sufficient to decompose the organic waste and to generate hydrogen gas and carbonize the molten metal, said molten metal having a carbon solubility at the operating conditions for said carbonization reactor of at least about 0.5 percent, by weight; b) directing carbonized molten metal from the carbonization reactor to a decarbonization reactor; c) introducing an oxidizing agent into the carbonized molten metal in the decarbonization reactor to oxidize carbon contained therein thereby decarbonizing said molten metal and generating an enriched stream of carbon oxide gas; and d) directing decarbonized molten metal from the decarbonization reactor to a decarbonization reactor. 20. A method for treating an organic waste containing hydrogen and carbon in molten metal to simultaneously form enriched hydrogen and carbon oxide gas streams, comprising the steps of: a) introducing the organic waste in a substantially vertical direction into molten metal contained in a reactor vessel under conditions sufficient to decompose the organic waste and to generate hydrogen gas and carbonize the molten metal, wherein said vessel has a baffle disposed within said reactor which extends sufficiently into the molten metal to separate the internal space within said reactor into a carbonization zone and a decarbonization zone, said baffle allows essentially all of the hydrogen gas to form in the carbonization zone while not allowing a substantial loss of hydrogen into the decarbonization zone and allows essentially all of the carbon oxide gas to form in the decarbonization zone while not allowing a substantial loss of carbon oxide gas to the carbonization zone; and b) directing the carbonized molten metal from the carbonization zone to the decarbonization zone; c) introducing the oxidizing agent in a substantially vertical direction into molten metal contained in said decarbonization zone to oxidize carbon contained therein thereby decarbonizing said molten metal and generating an enriched stream of carbon oxide gas. 21. An apparatus for treating an organic waste containing hydrogen and carbon in molten metal for the formation of an enriched hydrogen gas stream and an enriched carbon oxide gas stream, comprising: a) a carbonization reactor having a molten metal inlet, a molten metal outlet and a hydrogen off-gas outlet; b) organic waste injection means for directing organic waste into the molten metal contained in said carbonization reactor; c) a decarbonization reactor having a molten metal inlet, a molten metal outlet and a carbon oxide off-gas outlet; d) oxidizing agent injection means for injecting an oxidizing agent into the decarbonization reactor; e) means for directing the carbonized molten metal from said carbonization reactor to said decarbonization reactor; and f) means for returning the molten metal from said decarbonization reactor to said carbonization reactor. 22. An apparatus of Claim 21 wherein the carbonization reactor is substantially disposed within the decarbonization reactor. 23. An apparatus of Claim 21 wherein the carbonization reactor and decarbonization reactor are substantially disposed within a molten metal vessel for having a molten metal bath. 24. An apparatus of Claim 23 wherein the carbonization reactor has means for receiving molten metal from the molten metal vessel and means for conducting molten metal to the molten metal vessel. 25. An apparatus of Claim 24 wherein the decarbonization reactor has means for receiving molten metal from the molten metal vessel and means for conducting molten metal to the molten metal vessel. 26. An apparatus of Claim 25 wherein organic waste injection means is substantially vertical. 27. An . apparatus of Claim 26 wherein oxidizing agent injection means is substantially vertical. 28. An apparatus for treating an organic waste containing hydrogen and carbon in molten metal for the simultaneous formation of an enriched hydrogen gas stream and an enriched carbon oxide gas stream, comprising: a) a reactor vessel suitable for containing molten metal; b) a baffle disposed within said reactor which extends sufficiently into the molten metal to separate the internal space within said reactor into a carbonization zone and a decarbonization zone, said baffle allows essentially all of the hydrogen gas to form in the carbonization zone while not allowing a substantial loss of hydrogen into the decarbonization zone and allows essentially all of the carbon oxide gas to form in the decarbonization zone while not allowing a substantial loss of carbon oxide gas to the carbonization zone; c) means for injecting organic waste in a substantially vertical direction into molten metal contained in said carbonization zone, whereby the field of flow of the organic waste remains essentially in the carbonization zone; and d) means for injecting oxidizing agent in a substantially vertical direction into molten metal contained in said decarbonization zone, whereby the field of flow of the oxidizing agent remains essentially in the decarbonization zone.

Inventors: MCGEEVER CASEY E, NAGEL CHRISTOPHER J, SPARKS KEVIN A, MCGEEVER, CASEY, E., NAGEL, CHRISTOPHER, J., SPARKS, KEVIN, A.
Applicants: MCGEEVER CASEY E, MOLTEN METAL TECH INC, NAGEL CHRISTOPHER J, SPARKS KEVIN A, MOLTEN METAL TECHNOLOGY, INC.
Application year: 1993
Main classification: A62D3
IPC codes: A62D3, A62D101, C10J3