WO2014176020A1 - Procédé et système pour produire un gaz de synthèse au moyen d'un système de reformage à base de membrane de transport d'oxygène - Google Patents

Procédé et système pour produire un gaz de synthèse au moyen d'un système de reformage à base de membrane de transport d'oxygène Download PDF

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Publication number
WO2014176020A1
WO2014176020A1 PCT/US2014/033160 US2014033160W WO2014176020A1 WO 2014176020 A1 WO2014176020 A1 WO 2014176020A1 US 2014033160 W US2014033160 W US 2014033160W WO 2014176020 A1 WO2014176020 A1 WO 2014176020A1
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WIPO (PCT)
Prior art keywords
stream
oxygen
synthesis gas
transport membrane
oxygen transport
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PCT/US2014/033160
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English (en)
Inventor
Shrikar Chakravarti
Raymond F. Drnevich
Kenneth L. Burgers
Minish M. SHAH
Brian R. KROMER
Keith A. CRAIGIE
Sean M. Kelly
Juan Li
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Praxair Technology, Inc.
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Publication date
Priority claimed from US14/090,194 external-priority patent/US20140319425A1/en
Priority claimed from US14/090,289 external-priority patent/US9611144B2/en
Priority claimed from US14/098,731 external-priority patent/US9365422B2/en
Application filed by Praxair Technology, Inc. filed Critical Praxair Technology, Inc.
Priority to CA2909974A priority Critical patent/CA2909974C/fr
Priority to CN201480035848.6A priority patent/CN105377750A/zh
Publication of WO2014176020A1 publication Critical patent/WO2014176020A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/32—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air
    • C01B3/34—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents
    • C01B3/38—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using catalysts
    • C01B3/384—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using catalysts the catalyst being continuously externally heated
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0205—Processes for making hydrogen or synthesis gas containing a reforming step
    • C01B2203/0227—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step
    • C01B2203/0233—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step the reforming step being a steam reforming step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/06—Integration with other chemical processes
    • C01B2203/061—Methanol production
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/08—Methods of heating or cooling
    • C01B2203/0805—Methods of heating the process for making hydrogen or synthesis gas
    • C01B2203/0811—Methods of heating the process for making hydrogen or synthesis gas by combustion of fuel
    • C01B2203/0822—Methods of heating the process for making hydrogen or synthesis gas by combustion of fuel the fuel containing hydrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/08—Methods of heating or cooling
    • C01B2203/0805—Methods of heating the process for making hydrogen or synthesis gas
    • C01B2203/0811—Methods of heating the process for making hydrogen or synthesis gas by combustion of fuel
    • C01B2203/0827—Methods of heating the process for making hydrogen or synthesis gas by combustion of fuel at least part of the fuel being a recycle stream
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/12—Feeding the process for making hydrogen or synthesis gas
    • C01B2203/1205—Composition of the feed
    • C01B2203/1211—Organic compounds or organic mixtures used in the process for making hydrogen or synthesis gas
    • C01B2203/1235—Hydrocarbons
    • C01B2203/1241—Natural gas or methane
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/12—Feeding the process for making hydrogen or synthesis gas
    • C01B2203/1258—Pre-treatment of the feed
    • C01B2203/1264—Catalytic pre-treatment of the feed
    • C01B2203/127—Catalytic desulfurisation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency

Definitions

  • the present invention relates to a method and system for producing a synthesis gas in an oxygen transport membrane based reforming system, and more particularly, a method and system for producing a synthesis gas in an oxygen transport membrane based reforming system that utilizes a combined feed stream having a steam to carbon ratio between about 1.6 and 3.0 and a temperature between about 500 °C and 750 °C wherein the oxygen transport membrane based reforming system and associated synthesis production process equipment are substantially free of carbon formation and metal dusting corrosion.
  • the combined feed stream may comprise a pre-reformed hydrocarbon feed, superheated steam, and a reaction product stream created by the reaction of a hydrogen containing stream reacted with the permeated oxygen at the permeate side of oxygen transport membrane elements, wherein the hydrogen containing stream is a recycled portion of the synthesis gas.
  • Synthesis gas containing hydrogen and carbon monoxide is used for a variety of industrial applications, for example, the production of hydrogen, chemicals and synthetic fuel production.
  • the synthesis gas is produced in a fired reformer in which natural gas and steam is reformed in nickel catalyst containing reformer tubes at high temperatures (e.g., 850 °C to 1000 °C) and moderate pressures (e.g., 16 to 30 bar) to produce the synthesis gas.
  • high temperatures e.g., 850 °C to 1000 °C
  • moderate pressures e.g., 16 to 30 bar
  • the synthesis gas can be subjected to water-gas shift reactions to react residual steam in the synthesis gas with the carbon monoxide.
  • a well established alternative to steam methane reforming is the non-catalytic partial oxidation process (POx) whereby a substoichiometric amount of oxygen is allowed to react with the natural gas feed creating steam and carbon dioxide at high temperatures. The high temperature residual methane is reformed through reactions with the high temperature steam and carbon dioxide.
  • ATR autothermal reformer
  • ASU air separation units
  • Pre -reforming is a catalyst based process for converting higher hydrocarbons to methane, hydrogen, carbon monoxide and carbon dioxide.
  • the reactions involved in pre-reforming are endothermic.
  • Most pre- reformers operate adiabaticaliy, and thus the pre-reformed feedstock leaves at a much lower temperature than the feedstock entering the pre-reformer.
  • Another process that will be discussed in this invention is the secondary reforming process, which is essentially an autothermal process that is fed the product from a steam methane reforming process.
  • the feed to a secondary reforming process is primarily synthesis gas from steam methane reforming.
  • the SMR may operate at a lower temperature, e.g. 650°C to 825°C versus 850°C to 1000°C.
  • a typical oxygen transport membrane has a dense layer that, while being impervious to air or other oxygen containing gas, will transport oxygen ions when subjected to an elevated operational temperature and a difference in oxygen partial pressure across the membrane.
  • the present invention addresses the aforementioned problems by providing an improved process for making synthesis gas using a reactively-driven oxygen transport membrane based reforming system that comprises an oxidation process occurring at the permeate side of the oxygen transport membranes and a reforming process facilitated by a reformer catalyst in close proximity to the reactively-driven oxygen transport membranes.
  • the oxidation process which is exothermic
  • the reforming process which is endothermic, both occur within the oxygen transport membrane based reforming system and thus have a high degree of thermal integration so that heat released in the oxidation process supplies the heat absorbed by the reforming process.
  • the improvements to the reactively-driven oxygen transport membrane based reforming system include modifications to the steam and hydrocarbon feed stream to increase steam to carbon ratio thereby reducing methane slip, mitigating carbon formation issues within the system and reducing the hydrocarbon feed requirements to the reformers. It has been found that conditioning the steam and hydrocarbon feed stream feed stream to a particular temperature range and steam to carbon ratio translates into an optimum operating regime with noticeably less reliability problems in the oxygen transport membrane based reforming system due to carbon formation.
  • Additional improvements to the reactively-driven oxygen transport membrane based reforming system include modifications to the heat recovery train and synthesis gas recycle loop to mitigate metal dusting and carbon formation issues that adversely impact system performance, reliability and durability.
  • modifications to the heat recovery train and synthesis gas recycle loop to mitigate metal dusting and carbon formation issues that adversely impact system performance, reliability and durability.
  • the present invention may be characterized as a method for producing a synthesis gas in an oxygen transport membrane based reforming system, which comprises two reactors, including a reforming catalyst containing reformer reactor and an oxidation catalyst containing oxygen transport membrane reactor preferably in the form of tubes, the method comprising the steps of: (i) separating an oxygen containing stream into an oxygen permeate and an oxygen depleted retentate stream using a plurality of oxygen transport membrane elements disposed in the oxygen transport membrane based reforming system; (ii) reacting a hydrogen containing stream fed to a permeate side of the oxygen transport membrane elements with the oxygen permeate to generate a reaction product stream and heat; (iii) transferring the heat via convection to the oxygen depleted retentate stream and via radiation to at least one catalyst containing reforming reactor configured to produce a synthesis gas stream; (iv) pre-treating a hydrocarbon containing feed stream by adding steam to form a pre- treated reformer feed stream; (v) combining the pre
  • the present invention may also be characterized as an oxygen transport membrane based reforming system for producing synthesis gas comprising: (a) a reactor housing; (b) at least one catalyst containing reforming reactor disposed in the reactor housing and configured to produce a synthesis gas stream by reacting a combined feed stream in the presence of the catalyst and heat; (c) a reactively driven oxygen transport membrane reactor disposed in the reactor housing proximate the at least one catalyst containing reforming reactor, the reactively driven oxygen transport membrane reactor comprising a plurality of oxygen transport membrane elements configured to separate oxygen from an oxygen containing feed stream and produce an oxygen permeate at a permeate side of the oxygen transport membrane elements and an oxygen depleted retentate stream at a retentate side of the oxygen transport membrane elements; and (d) a hydrogen containing stream fed to the permeate side of the plurality of oxygen transport membrane elements, wherein the permeated oxygen reacts with the hydrogen containing stream to reactively drive the separation of oxygen from the oxygen containing feed stream and to generate a reaction
  • the combined feed stream comprises a pre-treated reformer feed and the reaction product stream and has a steam to carbon ratio between 1.6 and 3.0 and a temperature between 500 °C and 750 °C wherein the pre-treated reformer comprises a mixture of a hydrocarbon feed stream and steam, preferably at 20 bar or less.
  • pre-treating the hydrocarbon containing feed stream generally includes steps such as combining the hydrocarbon containing feed stream and superheated steam to form the pre-treated reformer feed stream and optionally one or more of the following: feeding the pre-treated reformer feed stream to a pre- reformer to produce a pre-reformed feed stream comprising methane, hydrogen, and carbon monoxide; combining a source of hydrogen to the hydrocarbon containing feed stream; removing sulfur from the hydrocarbon containing feed stream, etc.
  • the superheated steam is preferably at a pressure of between about 15 bar to 80 bar and a temperature of between about 300°C and 600 °C.
  • the superheated steam may be produced in a heat exchange network by further heating a source of the steam via indirect heat exchange with the oxygen depleted retentate stream.
  • the hydrocarbon containing feed stream and/or the pre-treated reformer feed may be heated in the heat exchange network or via indirect heat exchange with the oxygen depleted retentate stream.
  • the characteristics of the various input streams within the system include preferably maintaining the steam to carbon ratio of the pre-treated reformer feed stream is greater than about 0.8 and a steam to carbon ratio of the combined feed stream has between about 2.0 and 2.8.
  • the produced synthesis gas stream preferably has a module of between about 1.5 and 2.0 and a methane slip of less than about 4 percent by volume, and more preferably, a methane slip less than about 2 percent by volume.
  • a portion of the synthesis gas stream is recycled or recirculated to form all or a part of the hydrogen containing stream.
  • the present invention may also be characterized as a method for producing synthesis gas in an oxygen transport membrane based reforming system, which comprises two reactors, including a reforming catalyst containing reformer reactor and an oxidation catalyst containing oxygen transport membrane reactor preferably in the form of tubes, the method comprising the steps of: (i) separating an oxygen containing stream into an oxygen permeate and an oxygen depleted retentate stream using a plurality of oxygen transport membrane elements disposed in the oxygen transport membrane based reforming system; (ii) reacting a hydrogen containing stream contacting a permeate side of the oxygen transport membrane elements with the oxygen permeate to generate a reaction product stream and heat; (iii) pre-heating a hydrocarbon containing feed stream and combining the pre-heated hydrocarbon containing feed stream with a portion of the reaction product stream and steam to produce a combined feed stream having a temperature between about 500 °C and 750 °C; (iv) reforming the combined feed steam in the at least one catalyst containing reforming
  • the present invention may further be characterized as an oxygen transport membrane based reforming system for producing synthesis gas that is substantially free of carbon formation and metal dusting corrosion.
  • the oxygen transport membrane based reforming system comprises: (a) a reactor housing; (b) at least one catalyst containing reforming reactor disposed in the reactor housing and configured to produce a synthesis gas stream by reacting a combined feed stream in the presence of the catalyst and heat; (c) a reactively driven oxygen transport membrane reactor disposed in the reactor housing proximate the at least one catalyst containing reforming reactor, the reactively driven oxygen transport membrane reactor comprising a plurality of oxygen transport membrane elements configured to separate oxygen from an oxygen containing feed stream and produce an oxygen permeate at a permeate side of the oxygen transport membrane elements and an oxygen depleted retentate stream at a retentate side of the oxygen transport membrane elements; (d) a hydrogen containing stream in contact with the permeate side of the plurality of oxygen transport membrane elements, wherein the permeated oxygen reacts with the hydrogen containing stream
  • the preheated hydrocarbon feed and steam are mixed with the reaction product stream upstream of the at least one catalyst containing reforming reactor to produce the combined feed stream having a temperature wherein the combined feed stream has a steam to carbon ratio between about 1.6 and 3.0 and a temperature between about 500 °C and 750 °C.
  • This characterization of the present system may further include a synthesis gas recycle circuit between the heat exchange network and the oxygen transport membrane reactor to recirculate a portion of the cooled synthesis gas to the permeate side of the oxygen transport membrane elements to form all or a portion of the hydrogen containing stream. Since the recycled synthesis gas is maintained at a temperature of less than about 400 °C, the present oxygen transport membrane based reforming system and associated synthesis production process equipment will be substantially free of carbon formation and metal dusting corrosion.
  • the heat exchange network preferably comprises a first heat exchanger configured to cool the synthesis gas stream via indirect heat exchange with a process gas boiler feed stream and wherein the steam is produce from the indirect heat exchange between the synthesis gas stream and the process gas boiler feed water stream and a second heat exchanger configured to pre-heat the hydrocarbon containing feed stream via indirect heat exchange with the cooled synthesis gas stream.
  • the heat exchange network further comprises one or more coils disposed in an oxygen depleted retentate stream duct and wherein the steam is superheated to a pressure of between about 15 bar to 80 bar and a temperature of between about 300 °C and 600 °C via indirect heat exchange with the oxygen depleted retentate stream as the steam is directed through the one or more coils disposed in the oxygen depleted retentate stream duct.
  • the hydrocarbon containing feed stream or a combination of the hydrocarbon feed stream and steam are also pre-heated via indirect heat exchange with the oxygen depleted retentate stream as the stream is directed through the one or more coils disposed in the oxygen depleted retentate stream duct.
  • the present invention may be characterized as a method for producing a synthesis gas in an oxygen transport membrane based reforming system, which comprises two reactors, a reforming catalyst containing reformer reactor and an oxidation catalyst containing oxygen transport membrane reactor preferably in the form of tubes, the method comprising the steps of: (i) separating an oxygen containing stream into an oxygen permeate and an oxygen depleted retentate stream using a plurality of oxygen transport membrane elements disposed in the oxygen transport membrane based reforming system; (ii) reacting a hydrogen containing stream contacting a permeate side of the oxygen transport membrane elements with the oxygen permeate to generate a reaction product stream and heat; (iii) pre-heating a hydrocarbon containing feed stream and combining the pre-heated hydrocarbon containing feed stream with steam and then with a portion of the reaction product stream to produce a combined feed stream having a steam to carbon ratio between about 1.6 and 3.0 and a temperature between about 500 °C and 750 °C; (i)
  • FIG. 1 is a schematic illustration of an embodiment of an oxygen transport membrane based reforming system in accordance with the present invention
  • FIG. 2 is a schematic illustration of an alternate embodiment of an oxygen transport membrane based reforming system in accordance with the present invention
  • FIG. 3 is a schematic illustration of an alternate embodiment of an oxygen transport membrane based reforming system in accordance with the present invention for a methanol production facility, where the oxygen transport membrane based reforming system is the only or primary source of synthesis gas supply;
  • Fig. 4 is a graph of the temperature of a feed stream versus steam to carbon ratio of the feed stream and depicting various performance regimes of an oxygen transport membrane based reforming system.
  • FIG. 1 there is shown a schematic illustration of an embodiment of an oxygen transport membrane based reforming system 101 and assembly 100 in accordance with the present invention.
  • an oxygen containing stream 1 10 such as air
  • Heat exchanger 113 is preferably a high efficiency, cyclic and continuously rotating regenerator disposed in operative association with the oxygen containing stream 110 and the heated retentate stream 124.
  • the heated and oxygen depleted retentate stream 124 can optionally be introduced into a duct burner region containing duct burner 126 and used to support combustion of a supplemental fuel stream 128 to produce supplemental heat introduced into the continuously rotating regenerator 113 to preheat the oxygen containing stream 1 10.
  • the duct burner may also be disposed directly in the duct leaving heat exchanger 113 to pre-heat the oxygen containing stream 1 10. Exhaust stream 132 from heat exchanger 113 is discharged.
  • the heated oxygen containing stream 115 is then directed via the intake duct to the oxygen transport membrane elements 120 incorporated into the oxygen transport membrane based reforming system 101.
  • Each of the oxygen transport membrane elements 120 are preferably configured as a multilayered ceramic tube capable of conducting oxygen ions at an elevated operational temperature, wherein the retentate side of the oxygen transport membrane elements 120 is the exterior surface of the ceramic tubes exposed to the oxygen containing stream and the permeate side is the interior surface of the ceramic tubes.
  • a hydrogen containing stream is also introduced into the permeate side of the oxygen transport membrane elements 120 and is oxidized though reaction with the permeated oxygen to produce a reaction product stream 198 and heat.
  • the hydrogen containing stream is preferably a recycled portion of the produced synthesis gas 163.
  • the heated retentate stream 124 exits the oxygen transport membrane based reforming system 101, it also heats a reformer feed stream 138 to a temperature between about 450 °C and 650 °C via indirect heat transfer using one or more coils 191 disposed in the retentate duct such that the oxygen depleted retentate stream 124 heats the feed streams passing through the coils 191.
  • the hydrocarbon containing feed stream 182 to be reformed is preferably natural gas.
  • the natural gas is compressed or let down to the desired pressure via a compressor or valve arrangement (not shown) and then preheated in heat exchanger 150 that serves as a feed preheater.
  • the natural gas feed stream 182 undergoes a sulfur removal process such as hydro-treating, via device 190, to reduce the sulfur species to H 2 S, which is subsequently removed in a guard bed using material like ZnO and/or CuO.
  • a small amount of hydrogen or hydrogen-rich gas (not shown) is added to stream 182 before heat exchanger 150.
  • the hydro-treating step also saturates any alkenes present in the hydrocarbon containing feed stream.
  • the natural gas feed stream 182 is preferably pre-reformed in an adiabatic pre-reformer 192, which converts higher hydrocarbons to methane, hydrogen, carbon monoxide, and carbon dioxide.
  • Pre-reformers are typically catalyst-based systems.
  • this pre-reformed reformer feed stream 195 may be further heated via indirect heat exchange with heated retentate stream 124.
  • the pre-reformer is a heated pre-reformer that is thermally coupled with oxygen transport membrane based reforming system.
  • the above-described heated reaction product stream 198 is combined with the heated pre-reformed reformer feed stream 195 to produce a combined feed stream 200 that contains steam and hydrocarbons.
  • This combined feed stream is introduced into the catalytic reactor tubes 140 where the combined feed stream 200 is subjected to steam methane reforming to produce a synthesis gas stream 142.
  • the temperature of the combined feed stream 200 is between about 500 °C and 750 °C, and more preferably between about 600 °C and 750 °C.
  • Additional steam 180 may also be added to the natural gas feed stream 182, or the preheated pre-reformed reformer feed stream 195, as required, to adjust the temperature of stream 200 as well as the steam to carbon ratio of the final combined feed stream 200 to between about 1.6 and 3.0, and more preferably to steam to carbon ratio between about 2.0 and 2.8.
  • the steam is preferably superheated steam 180 between about 15 bar to 80 bar and between about 300 °C and 600 °C and heated by means of indirect heat exchange with the heated retentate stream 124 using steam coils 179 disposed in the retentate duct.
  • the superheated steam 180 is preferably added to the hydrocarbon containing feed stream 182 upstream of the pre- reformer 192 to adjust the steam to carbon ratio and final temperature of the combined feed stream 200.
  • the methane slip should be less than 4% by volume and preferably less than 2% by volume.
  • the synthesis gas stream 142 produced by the oxygen transport membrane based reforming system 101 generally contains hydrogen, carbon monoxide, unconverted methane, steam, carbon dioxide and other constituents.
  • Heat exchange section 104 is designed to cool the produced synthesis gas stream 142 and recycle a portion of the synthesis gas stream 162A to form all or a part of the hydrogen containing stream 163.
  • the synthesis gas stream 142 is preferably cooled before recycling such stream using a synthesis gas recycle compressor 177 or other blower means.
  • the heat exchange section 104 is also designed such that in cooling the synthesis gas stream 142, various feed streams are preheated and process steam is also generated.
  • the initial cooling of synthesis gas stream 142 is accomplished with steam generation in a process gas boiler (PG boiler) 149 coupled to steam drum 157 and designed to reduce the temperature of the cooled synthesis gas 144 to about 400 °C or less.
  • PG boiler process gas boiler
  • the initially cooled synthesis gas stream 144 is successively further cooled in a heat exchange network that includes hydrocarbon feed preheater 150, economizer 156, feed water heaters 158A and 158B, synthesis gas cooler 161 and water cooled heat exchanger 164.
  • the initially cooled synthesis gas stream 144 is directed to the feed preheater 150 to heat the natural gas feed stream 182 and then is directed to the economizer 156 to heat boiler feed water 188.
  • the boiler feed water stream 188 is preferably pumped using a feed water pump (not shown), heated in economizer 156 and sent to steam drum 157.
  • the cooled synthesis gas stream 146 is then divided into a first portion 160 and a second or recycled portion 162A.
  • First portion 160 is further cooled in a series of steps including a feed water heater 158A, used to heat feed water stream 159, followed by a synthesis gas cooler 161 and a subsequent water cooled heat exchanger 164 cooled via a separate cooling water stream 166.
  • the heated feed water 159 is directed to a de-aerator (not shown) that provides boiler feed water 188.
  • the resulting fully cooled synthesis gas stream 148 is then introduced into a knock-out drum 168 from which a condensate stream 170 is drained to produce a fully cooled synthesis gas stream 172.
  • the fully cooled synthesis gas stream 172 is optionally compressed in a synthesis gas compressor 174 to produce a synthesis gas product 176.
  • the second or recycle portion 162A of the initially cooled synthesis gas stream 144 is directed to a second feed water heater 158B, used to heat feed water stream 159, and this cooled recycle synthesis gas stream 163 is recirculated back to the permeate side of the oxygen transport membrane element 120 by means of a recycle compressor 177. Also note that any superheated steam not added or used in the natural gas feed 182 or recycle synthesis gas stream 163 is exported steam 181 that may be used for power generation.
  • the oxygen transport membrane produced synthesis gas should have a module of between about 1.5 and 2.0.
  • such produced synthesis gas stream ideally has a methane slip of less than about 4.5 percent by volume and more preferably, a methane slip of less than about 2.5 percent by volume.
  • FIG. 2 there is shown a schematic illustration of an alternate embodiment of an oxygen transport membrane based reforming system.
  • this embodiment is similar to the embodiment of Fig. 1 and, for sake of brevity, the description of the common aspects of the two embodiments will not be repeated here, rather, the following discussion shall focus on the differences between Fig. 1 and Fig. 2.
  • the primary difference between the embodiments in Fig. 1 and Fig. 2 is the use of a hot synthesis gas recycle 162B in Fig. 2 embodiment in lieu of the cold gas recycle 162A in the embodiment of Fig. 1.
  • the hot synthesis gas recycle involves recycling a portion of the heated synthesis gas stream 142 exiting the catalyst containing reforming tubes or reactor 140 and directing the hot recycled synthesis gas 162B to the permeate side of the oxygen transport membrane elements 120 to react the portion of heated synthesis gas stream 162B with the oxygen permeate stream to generate the heated reaction product stream and radiant heat.
  • the temperature of the hot synthesis recycled gas is preferably above 800 °C so as to avoid problems associated with metal dusting corrosion.
  • the hot synthesis gas stream 162B is driven or pulled to the permeate side of the oxygen transport membrane elements 120 by means of an ejector, eductor or venturi based device 199 operatively coupled to the permeate side of the oxygen transport membrane elements 120.
  • an ejector, eductor or venturi based device 199 By suctioning the streams at the permeate side of the oxygen transport membrane elements 120 into the ejector, eductor or venturi based device 199 with a motive fluid comprising the pre-reformed reformer feed stream 195, the reaction product stream 198 mixes with the pre-reformed reformer feed stream 195 to produce the combined feed stream 200, preferably having a steam to carbon ratio between about 1.6 and 3.0 and a temperature between about 500 °C and 750 °C.
  • device 199 moves lower pressure reaction product 198 to higher pressure combined feed stream 200.
  • FIG. 3 there is shown a schematic illustration of yet another alternate embodiment of an oxygen transport membrane based reforming system.
  • this illustrated embodiment is similar to the embodiments shown in Fig. 1 and Fig. 2.
  • the primary difference between the embodiments in Fig. 2 and Fig. 3 is the addition of downstream processing of the initially cooled synthesis gas in the embodiment of Fig. 3.
  • a portion of the cooled synthesis gas 350 is diverted to a synthesis gas conditioning system. This diverted portion of the cooled synthesis gas stream 350 is roughly between 5% and 25% of the synthesis gas stream 142.
  • the diverted portion of the cooled synthesis gas stream 350 is subjected to a water shift reaction 352 and subsequently cooled in heat exchanger 354 using cooling water or boiler feed water and then compressed in a synthesis gas compressor 360.
  • the compressed gas feed stream 362 is directed to a hydrogen pressure swing adsorption (PSA) unit 370 which takes the compressed feed stream 362 and produces a higher purity hydrogen stream 372 at or near the feed pressure while the carbon oxides, methane and other impurities are rejected at lower pressure tail gas stream 374.
  • PSA hydrogen pressure swing adsorption
  • Stream 374 may be recycled to use with the duct burners 126 while the higher pressure and higher purity hydrogen stream 372 is recombined with the non-diverted portion of the synthesis gas stream 172, preferably at some point mid-stage point within the synthesis gas compressor 174.
  • the higher purity hydrogen stream 372 By re-combining the higher purity hydrogen stream 372 with the non-diverted portion of the synthesis gas stream 172, one can adjust the module of the final synthesis gas product to about 2.0 to 2.2, the preferable range for methanol production or other synthesis gas characteristics such as hydrogen to carbon monoxide ratio, etc.
  • Metal dusting is a severe form of corrosion that occurs when surfaces of certain metal and metal alloy components and piping are exposed to severe gas environments with a high carbon activity or content.
  • the metal dusting corrosion is manifested by a disintegration of bulk metals, such as iron, nickel and cobalt to metal powders.
  • the typical metal dusting process results from a series of sequential steps, including (i) rapid uptake of carbon into the metallic phase leading to saturation of the alloy matrix with carbon; (ii) formation of metastable carbides; and (iii) decomposition of these carbides into a loose film of carbon and metallic particles, which acts as catalyst for further carbon deposition.
  • the exact mechanism may vary depending on the type of metal being used.
  • the temperatures normally associated with metal dusting are about 400 °C to 800 °C (i.e., about 760°F to about 1500 °F). At temperatures generally below 400°C the rate of reaction to form the metastable carbide species is too low to be significant, while at temperatures above 800 °C the carbon formation is minimal.
  • the system should be designed to avoid contact of any synthesis gas with metal surfaces having temperatures between about 400 °C to 800 °C. While it is possible to provide corrosion resistant coatings on all high temperature metal surfaces exposed to synthesis gas, such solution would be cost prohibitive.
  • the alternative corrosion prevention technique employed in the present embodiments is to manage the temperatures of the synthesis gas so as to avoid contacting bare metal surfaces with synthesis gas in the deleterious temperature range where metal dusting corrosion occurs.
  • the oxygen based transport membrane based reforming system preferably recycles the synthesis gas in a high temperature state, generally above 800 °C where the non-recycled portion of the synthesis gas is cooled in the PG boiler until the synthesis gas is cooled below 400 °C.
  • the metal surfaces of the synthesis gas piping exiting the reactor are either maintained at a temperature above 800 °C or have refractory surfaces.
  • the metal surfaces in the PG boiler and other elements of the heat recovery system that are exposed to the synthesis gas are generally maintained at temperatures below about 400 °C.
  • the cooled recycled synthesis gas stream is maintained at temperatures below about 400 °C.
  • the recycled synthesis gas stream 163 can be preheated against steam or any other stream as long as the wall temperature is less than about 400°C. For this reason, the addition of superheated steam to the recycled synthesis gas stream should be avoided unless the addition of superheated steam maintains the temperatures below about 400 °C
  • region 310 on the feed temperature versus feed steam to carbon ratio graph generally corresponds to a combined feed stream feed at a temperature near or below about 500 °C and having a steam to carbon ratio of between 1.5 and 2.4. Because the present combined feed stream contains carbon monoxide produced in the pre-reformer, a combined feed stream having characteristics of region 310, may undergo unwanted Boudouard reactions thereby depositing excessive amounts of soot on the oxygen transport membrane based reforming system as well as associated components and piping.
  • the Boudouard reaction is a redox reaction of a mixture of carbon monoxide and carbon dioxide at a given temperature and involves the disproportionation of carbon monoxide into carbon dioxide and carbon (i.e. soot).
  • region 330 generally corresponds to a region of high temperature and low steam to carbon ratios where the combined feed stream is subject to carbon lay down in the reforming catalysts.
  • Region 330 is generally depicted as the region to the right of the curve or plot line on the feed temperature versus steam to carbon ratio defined by two points, namely a feed temperature of near 500 °C with a steam to carbon ratio of about 1.5 and a feed temperature of about 700 °C with a steam to carbon ratio of about 2.4 (See Fig. 4).

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  • Engineering & Computer Science (AREA)
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Abstract

L'invention concerne un procédé et un système permettant de produire un gaz de synthèse dans un système de reformage à base de membrane de transport d'oxygène, qui utilise un flux d'alimentation combiné (200) ayant un rapport vapeur/carbone compris entre environ 1,6 et 3,0 et une température située entre environ 500 et 750 °C, ledit système de reformage à base de membrane de transport d'oxygène et l'équipement du processus de production de synthèse associé étant sensiblement exempts de formation de carbone et de corrosion due aux poussières métalliques. Le flux d'alimentation combiné se compose d'une charge hydrocarbure pré-reformée (195), de vapeur surchauffée (180) et d'un flux de produit de réaction (198) généré par la réaction d'un flux contenant de l'hydrogène (163) mis à réagir avec l'oxygène soumis à perméation côté perméat des éléments de la membrane de transport d'oxygène (120) .
PCT/US2014/033160 2013-04-26 2014-04-07 Procédé et système pour produire un gaz de synthèse au moyen d'un système de reformage à base de membrane de transport d'oxygène WO2014176020A1 (fr)

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CN201480035848.6A CN105377750A (zh) 2013-04-26 2014-04-07 在基于氧气输送膜的转化***内生产合成气的方法和***

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US61/816,297 2013-04-26
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US14/090,194 US20140319425A1 (en) 2013-04-26 2013-11-26 Method and system for producing a synthesis gas in an oxygen transport membrane based reforming system using a combined feed stream
US14/090,289 2013-11-26
US14/090,289 US9611144B2 (en) 2013-04-26 2013-11-26 Method and system for producing a synthesis gas in an oxygen transport membrane based reforming system that is free of metal dusting corrosion
US14/090,194 2013-11-26
US14/098,731 2013-12-06
US14/098,731 US9365422B2 (en) 2013-04-26 2013-12-06 Method and system for producing a synthesis gas in an oxygen transport membrane based reforming system with recycling of the produced synthesis gas

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