EP1794083A1 - Integrated process for hydrocarbon synthesis - Google Patents

Integrated process for hydrocarbon synthesis

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Publication number
EP1794083A1
EP1794083A1 EP05789543A EP05789543A EP1794083A1 EP 1794083 A1 EP1794083 A1 EP 1794083A1 EP 05789543 A EP05789543 A EP 05789543A EP 05789543 A EP05789543 A EP 05789543A EP 1794083 A1 EP1794083 A1 EP 1794083A1
Authority
EP
European Patent Office
Prior art keywords
reforming
partial oxidation
zone
stream
carbon dioxide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05789543A
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German (de)
French (fr)
Inventor
Wilhelmus Johannes Franciscus Scholten
Thian Hoey Tio
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shell Internationale Research Maatschappij BV
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Shell Internationale Research Maatschappij BV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Priority to EP05789543A priority Critical patent/EP1794083A1/en
Publication of EP1794083A1 publication Critical patent/EP1794083A1/en
Withdrawn legal-status Critical Current

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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
    • C01B3/382—Multi-step processes
    • 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
    • C01B3/36—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 oxygen or mixtures containing oxygen as gasifying agents
    • 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
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
    • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
    • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
    • 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
    • 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
    • C01B2203/0244—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step the reforming step being an autothermal reforming step, e.g. secondary reforming processes
    • 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
    • C01B2203/025—Processes for making hydrogen or synthesis gas containing a partial oxidation step
    • C01B2203/0255—Processes for making hydrogen or synthesis gas containing a partial oxidation step containing a non-catalytic partial oxidation 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
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/025—Processes for making hydrogen or synthesis gas containing a partial oxidation step
    • C01B2203/0261—Processes for making hydrogen or synthesis gas containing a partial oxidation step containing a catalytic partial oxidation step [CPO]
    • 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
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C01B2203/0475—Composition of the impurity the impurity being carbon dioxide
    • 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
    • C01B2203/062—Hydrocarbon production, e.g. Fischer-Tropsch process
    • 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
    • C01B2203/0838—Methods of heating the process for making hydrogen or synthesis gas by heat exchange with exothermic reactions, other than by combustion of fuel
    • C01B2203/0844—Methods of heating the process for making hydrogen or synthesis gas by heat exchange with exothermic reactions, other than by combustion of fuel the non-combustive exothermic reaction being another reforming reaction as defined in groups C01B2203/02 - C01B2203/0294
    • 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
    • C01B2203/14—Details of the flowsheet
    • C01B2203/141—At least two reforming, decomposition or partial oxidation steps in parallel
    • 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
    • C01B2203/14—Details of the flowsheet
    • C01B2203/142—At least two reforming, decomposition or partial oxidation steps in series
    • 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
    • C01B2203/14—Details of the flowsheet
    • C01B2203/148—Details of the flowsheet involving a recycle stream to the feed of the process for making hydrogen or synthesis gas
    • 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
    • C01B2203/80—Aspect of integrated processes for the production of hydrogen or synthesis gas not covered by groups C01B2203/02 - C01B2203/1695
    • C01B2203/82—Several process steps of C01B2203/02 - C01B2203/08 integrated into a single apparatus
    • 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 an improved process for the preparation of liquid and/or solid hydrocarbons from a hydrocarbonaceous feedstock, especially a gaseous hydrocarbon feedstock such as methane from a natural source, preferably natural gas.
  • the invention further relates to a process for preparation of syngas for use in the preparation of liquid and/or solid hydrocarbons.
  • the Fischer Tropsch process is often used for the conversion of hydrocarbonaceous feed stocks into liquid and/or solid hydrocarbons.
  • the feed stock for example natural gas, associated gas and/or coal-bed methane
  • the syngas is then converted in a second step over a suitable catalyst at elevated temperature and pressure into paraffinic compounds ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances, even more.
  • GB 2183672 discloses one such process where a mixture of products from catalytic reforming and partial oxidation steps are used in a Fischer Tropsch type synthesis having first had carbon dioxide removed from the syngas, wherein the separated carbon dioxide is combined with the hydrocarbonaceous feedstock used in at least one of the catalytic reforming and partial oxidation steps.
  • WO 03/000627 discloses a process for producing liquid hydrocarbons comprising catalytic reforming and partial oxidation steps which involves recycling at least part of a carbon dioxide feed obtained from a heating gas and/or from a light hydrocarbon product stream to the hydrocarbonaceous feedstock fed utilised in the reforming step. In this process the reforming product is fed directly into the partial oxidation zone to produce the heating gas.
  • the present invention provides a process for the preparation of syngas from a hydrocarbonaceous feedstock comprising the steps of: (i) splitting the hydrocarbonaceous feedstock into a first feedstock stream and a second feedstock stream; (ii) catalytically reforming the first feedstock stream in at least one reforming zone to produce a reforming product;
  • step (v) is carried out without passing the reforming product produced according to step (ii) through the partial oxidation zones, i.e. an indirect heat exchange.
  • the mixing is carried out in a mixing zone which is separated, i.e. not directly connected and not within the same reactor, from the reforming zone and the partial oxidation zone.
  • two separate syngas streams are obtained, which are transported via a transportation zone to an independent mixing zone, from which mixing zone the mixed syngas stream is transported via a further transportation zone to the reforming zone for indirect heating purposes.
  • the independent zones give the possibility to mix all synthesis gas from both sources or only part of it. It also gives the possibility to treat the two streams in different ways.
  • the partial oxidation stream may contain trace impurities which are not present in the reformed syngas stream (e.g. sulphur compounds used to prevent metal dusting of the burner, nitrogen compounds as ammonia and/or hydrogen cyanide due to the presence of residual nitrogen in the oxygen etc.) .
  • the two synthesis gas streams can each be optimally treated without the unnecessary treatment of the other stream.
  • the mixed stream may be treated in one way or another before use as heating gas.
  • an adiabatic reforming may be applied, reducing the temperature and adjusting the H2/CO ratio to a desired ratio.
  • carbon dioxide and/or steam may be introduced in the adiabatic reforming zone to further adjust the desired H2/CO ratio.
  • the independent mixing zone also opens the possibility to use part of any of the two synthesis gas stream and/or part of the mixed stream for other purposes, e.g. the manufacturing of hydrogen, methanol synthesis etc. If desired a certain amount of heat may be extracted from one or more of the separate streams, especially the mixed stream after further reforming (to further reduce the temperature, the heat being available at a relatively high level) .
  • Suitable transportation zones are for instance pipes of certain diameter and a certain length.
  • the diameter may be in the same range of the diameter of the pipe of natural gas feed-stream (e.g. two or three times the diameter of the natural gas pipe may be used (in view of the chemical conversion and the temperature increase) .
  • the length may be from 1 in till several hundreds of meters or even more, depending on the distance between the different zones and the options to treat the streams.
  • the mixing zone may very well be a connection between two pipes, or, if desired, a reactor, either empty or provided with gas-mixing internals. In the case of direct connection between two pipes, (static) mixtures may be present in the combined stream.
  • the oxidation step, step (iii) may suitably be carried out using known techniques such as for example the Shell Gasification Process (a comprehensive survey of this process can be found in the Oil and Gas Journal, September 6, 1971, pp 86-90), auto thermal reforming or catalytic partial oxidation.
  • Shell Gasification Process a comprehensive survey of this process can be found in the Oil and Gas Journal, September 6, 1971, pp 86-90
  • auto thermal reforming or catalytic partial oxidation.
  • step (vi) may be provided in which carbon dioxide from the cooled heating gas is removed to produce a carbon dioxide depleted syngas stream.
  • the process may additionally comprise the further step (via) of recycling the carbon dioxide produced according to step (vi) back to the partial oxidation zone(s) and/or reforming zone(s), preferably to the partial oxidation zone(s) .
  • a post reforming step, (iia) may be included, wherein the heating gas produced from step (iv) is fed to at least one post reforming zone prior to step (v) .
  • step (vi) The recycling of carbon dioxide removed in step (vi) back to the partial oxidation zones has the advantages of facilitating milder operating conditions for the POX (for example lower temperature and lower oxygen use) and reducing soot formation in the POX (for a given temperature compared to operation of the POX without carbon dioxide recycling) .
  • step (iv) all of the reforming product and all of the partial oxidation product are mixed in step (iv) .
  • step (i) is adapted to balance the effects of steps (ii) and (iii) and thus to provide for energy balancing between the reforming and partial oxidation processes.
  • step (i) will be carried out by passing from about 1 to about 60% by volume, preferably from about 10 to about 45% by volume, more preferably from 20 to 40% by volume of the hydrocarbonaceous feedstock to the at least one reforming zone and from about 40 to about 99% by volume of the hydrocarbonaceous feed stock to the at least one partial oxidation zone preferably from 55 to 90% by volume, more preferably from 60 to 80% by volume.
  • the present invention provides a process for the preparation of hydrocarbonaceous products comprising catalytically converting synthesis gas produced as herein described to produce a hydrocarbonaceous product stream This step is hereinafter also termed "step (vii)".
  • the catalytic conversion (step (vii) ) is a Fischer Tropsch conversion.
  • the process for the preparation of hydrocarbonaceous products may comprise the additional steps of (viii) separating the product stream into a light product stream; comprising unconverted syngas, carbon dioxide, inerts and light hydrocarbons; and a heavy product stream; comprising liquid and solid hydrocarbons; and (ix) separating carbon dioxide from the light product stream.
  • the process may comprise a further step of (x) recycling at least part of the carbon dioxide depleted light product stream from step (ix) directly to at least one reforming zone. This may be used to establish an optimum energy balance for the total process .
  • a further option is to use the carbon dioxide depleted light product stream as fuel.
  • the process may comprise a further step (xi) of recycling the carbon dioxide from steps (vi) and/or (ix) to at least one partial oxidation zone.
  • the process may comprise a further step (xii) of recycling carbon dioxide produced according to steps (vi) and/or (ix) to the reforming zones.
  • the process may comprise a further step (xiii) of mixing hydrogen with the carbon dioxide depleted syngas stream produced according to step (vi) .
  • the fractions of hydrocarbonaceous feedstock passed to the reforming zones and the partial oxidation zones respectively may be adapted to produce a carbon dioxide depleted syngas stream having a H2/CO ratio of from about 1.3 to about 5, preferably of from 1.6 to 3.0 and more preferably from 1.7 to 2.3.
  • the present invention thus provides an integrated process for syngas production and conversion of carbonaceous feedstocks to hydrocarbonaceous products (including for example light and heavy paraffins, methanol and the like) .
  • One of the advantages of such an integrated process is the ability to balance the energy requirements/output of various steps and thus improve the overall efficiency (in terms of carbon efficiency and thermal efficiency) of the process as a whole. Further advantages of the invention will be apparent from the following description.
  • Figure 1 is a schematic flow diagram of an integrated hydrocarbon synthesis process according to the invention.
  • the preparation of synthesis gas by means of a reforming reaction requires a relatively large energy input.
  • the partial oxidation step, step (iii) may suitably be carried out using known techniques such as for example the Shell gasification process, auto thermal reforming or catalytic partial oxidation.
  • the partial oxidation process is in this context defined as a generic term including partial oxidation carried out with or without a catalyst, with or without a flame and with or without steam and/or carbon dioxide injection.
  • partial oxidation step suitably results in a synthesis gas having a temperature between 900 and 1800 0 C, preferably between 1000 and 1700 C. In the case of natural gas as feedstock in a pure partial oxidation reaction the temperature is suitably between 1150 and 1450 0 C.
  • Synthesis gas produced by reforming in the absence of CC>2 or off-gas from the Fischer Tropsch reaction (for example, off-gas from heavy paraffin synthesis typically comprises unconverted synthesis gas, light C1-C4 hydrocarbons, some CO2 and usually inerts, and is sometimes referred to as HPS off-gas) recycle, typically has a relatively high H2/CO ratio, usually between 4 and 7.
  • the reforming process suitably results in a synthesis gas having a temperature between 300 and 1050 0 C, preferably between 400 and 950 °C.
  • the user ratio of Fischer Tropsch hydrocarbon synthesis using a cobalt catalyst and producing large amounts of heavy wax is about 2.
  • hydrogen is needed for hydrocracking the heavy wax into lighter products boiling especially in the kerosene/gasoil range. In some cases additional hydrogen is needed for desulphurisation of the hydrocarbonaceous feed.
  • the off-gas of the Fischer Tropsch reaction (comprising unconverted synthesis gas, C]_-C4 hydrocarbons, CO2 and usually inerts) may be used to generate energy and/or synthesis gas/hydrogen.
  • Carbon dioxide generated in the production of especially energy/hydrogen/hydrocarbons, may be used as additional feedstream in the reforming and/or partial oxidation. Carbon dioxide produced may also be used for other purposes such as for example enhanced oil recovery or C02 sequestration. Many variations of the overall process are possible, each having its own advantages/ disadvantages.
  • the combination of reforming and partial oxidation results in an optimum energy efficiency.
  • This combination in which the heat required in the reforming reaction is produced by the partial oxidation reaction, together with a number of carbon dioxide recycles, the preparation of hydrogen by means of extraction from one of the process streams and the optional recycle of Fischer Tropsch off-gas results in a very high thermal and carbon efficiency.
  • the combination of reforming and partial oxidation requires less oxygen when compared with partial oxidation alone. A saving of between 15 and 40% of oxygen intake can be obtained.
  • the temperature of the heating gas has gone down usually for at least 50 0 C, preferably even more, making the condition in the reformer/heat exchanger less severe, which results in a more reliable process, and makes the choice of the heat exchanger materials more easy. This is especially the case when pure (catalytic) partial oxidation is used, due to the very high temperature of the synthesis gas, and the very strong reducing nature of the gas in the absence of water. - li ⁇ lt is observed that especially partial recycle of depleted light product stream (including C1-C4 products) to the reforming zones is advantageous for the efficiency of the total process.
  • the recycle of carbon dioxide extracted from the Fischer Tropsch hydrocarbon synthesis product to the partial oxidation process and/or the reforming process provides a means of controlling the H2/CO ratio of the syngas .
  • the reforming zone(s) and partial oxidation zone(s) are fed separately by splitting the hydrocarbonaceous feed stock.
  • the reforming product and partial oxidation product arising from each of the respective processing steps are then combined downstream to produce a heating gas which is used, through heat exchange means, in heating the reforming zones.
  • the cooled heating gas is then optionally treated to remove carbon dioxide before being fed to a Fischer Tropsch reactor.
  • the hydrocarbon products produced according to the Fischer Tropsch synthesis may then be separated into a light product stream, comprising unconverted syngas, CO2, inerts and light hydrocarbons, and a heavy product stream, comprising liquid and solid hydrocarbons.
  • the heavy product stream may be drawn off in a suitable manner with the light product stream undergoing further processing to remove carbon dioxide before, optionally, being recycled directly to the reforming zone(s) .
  • Carbon dioxide removed from the cooled heating gas and/or the light FT product stream may optionally be recycled to either the reforming process and/or the partial oxidation process.
  • the process of the invention does not require the reforming product or the light product stream (derived from the FT synthesis) to be fed through the partial oxidation zone(s) .
  • step (ii) of the process according to the invention various reforming catalysts can suitably be used, for instance catalysts comprising one or more metals from Group VIII of the Periodic Table of Elements, such as nickel, platinum, palladium, rhodium, iridium and the like on a support (for example, as a carrier material, alumina, silica, titania, zirconia and/or combinations thereof) .
  • Step (ii) is suitably carried out at a temperature from 350 to 1100 0 C, preferably 450 to 1000 0 C more preferably between 600 and 950 0 C, and a pressure from 10 to 100 bar, preferably 30 to 70 bar.
  • the space velocity of the gaseous hydrocarbonaceous feed and steam combined is suitably from 1000 to 10000 1 (STP) /1 catalyst/hour, preferably from 4000 to 7000 1 (STP) /1 catalyst/hour.
  • the percentage of the first feedstock stream (i.e. that portion of the hydrocarbonaceous feed fed to the reforming (s) ) which is converted in step (ii) is suitably between about 50 and about 98 %wt.
  • the H2O/C ratio in step (ii) will be in the order of about
  • step (iii) 0.5-7 mol steam/mol carbon, preferably about 1-5 and more preferably 1.5-4; where the carbon fraction is calculated on the basis of all hydrocarbonaceous carbon (i.e. does not include non-organic carbon such as CO2) .
  • the remaining 50 to 100 %wt, preferably of hydrocarbonaceous feed is fed to the partial oxidation zone(s) for the purposes of step (iii) .
  • the catalytic reforming step (ii) may be carried out in a fixed-, moving-, or fluidized bed of catalyst particles; fixed beds.
  • the reforming reactor is suitably a heat exchange hydrocarbon reforming reactor.
  • oxygen containing gas for use in step (iii) air can be employed.
  • an enriched oxygen gas is used, more preferably substantially pure oxygen, i.e. oxygen gas which contains less than 2 %vol of contaminants as nitrogen and argon, preferably less than 1 %vol of contaminants.
  • oxygen gas which contains less than 2 %vol of contaminants as nitrogen and argon, preferably less than 1 %vol of contaminants.
  • the presence of such contaminants is undesirable because in the case of off-gas recycle it can lead to a gradual build up of such gases (known as inerts) in the system and it may result in enhanced formation of undesired compounds in the gasification process as HCN or NH3.
  • Step (iii) of the process of the present invention is preferably carried out non-catalytically at substantially the same pressure of step (ii) .
  • catalyst especially metal catalysts of Group VIII of the Periodic Table are used, such as nickel, rhodium, iridium, platinum and/or palladium.
  • the temperature of the heating gas produced in step (iv) is higher than the temperature inside the reforming zone(s) which are to be heated; suitably the heating gas temperatures ranges from 700 to 1350 0 C, preferably from 800 to 1300 0 C.
  • Step (ii) may optionally be combined with an adiabatic post reforming step (iia) employing one or more adiabatic zones, using a reforming catalyst such as those described for step (ii) in respect of catalytic partial oxidation or auto thermal reforming for example.
  • a reforming catalyst such as those described for step (ii) in respect of catalytic partial oxidation or auto thermal reforming for example.
  • the temperature of the product stream obtained in (iii) is at least 150 0 C higher than the temperature of the product stream obtained in step (ii), more preferably at least 250 0 C, Still more preferably between 300 and 600 0 C.
  • the hydrocarbonaceous feed for the process according to the invention is usually gaseous and if liquid is a product different from the liquid hydrocarbons produced, for example condensate (mainly C3-C5 hydrocarbons) or heavy hydrocarbons (residual oils as short residue) .
  • the hydrocarbonaceous feed comprises large amounts of methane, for example in the form of natural or associated gas.
  • the feed is at least partly desulphurized, preferably with hydrogen extracted from one of the product streams.
  • At least part, and preferably substantially all (i.e. more than 70%, especially more than 90%), of the carbon dioxide present in the heating gas with which the reforming zone(s) have been heated in step (v) is removed in step (vi) by means of for example liquid absorption (with for example methanol or organic amines), adsorption on molecular sieves or using membranes.
  • Steam is suitably removed simultaneously with carbon dioxide and may be re ⁇ used after any treatment which may be necessary or desirable.
  • Preferably at least 50% more preferably all the carbon dioxide thus removed is combined with the hydrocarbonaceous feedstream fed to the partial oxidation process (step iii) .
  • additional amounts of carbon dioxide from extraneous sources can be used.
  • a hydrogen- and carbon monoxide-containing gas (syngas) obtained in step (vi) is converted in one or more steps at least partly into liquid hydrocarbons in the presence of a Fischer Tropsch type catalyst which preferably comprises at least one metal (compound) selected from Group VIII of the Periodic Table.
  • Preferred catalytic metals are iron and cobalt, especially cobalt. It is preferred to produce a very heavy product in step (vii) . This results in a relatively low amount of light hydrocarbons, for example C1-C4 hydrocarbons, resulting in a higher carbon efficiency.
  • step (vii) boiling above the middle distillate boiling range may be converted into middle distillates by means of hydrocracking. Such a step will also result in the hydrogenation of the product as well as in (partial) isomerization of the product.
  • the Fischer Tropsch synthesis is, as indicated above, preferably carried out with a catalyst producing large amounts of unbranched paraffinic hydrocarbons boiling above the middle distillate range. Relatively small amounts of oxygen containing compounds are produced.
  • the process is suitably carried out at a temperature of 150 to 300 0 C, preferably 190 to 260 0 C, and a pressure from 20 to 100 bar, preferably from 30 to 70 bar.
  • at least the fraction boiling above the middle distillate boiling range is hydrocracked into middle distillate.
  • all C5+, especially all C]_Q+ hydrocarbons are hydrocracked in view of the improved pour point of the middle distillates obtained in such a process.
  • the temperature in the second stage is preferably from 250 to 400 0 C, in particular 300 to 350 0 C.
  • a catalyst which contains at least one noble metal from Group 8 (in particular platinum and/or palladium) on a carrier (in particular silica, alumina or silica/ alumina, more particularly amorphous silica alumina) .
  • a carrier in particular silica, alumina or silica/ alumina, more particularly amorphous silica alumina.
  • such catalysts contain 0.1 to 2 %wt of noble metal catalyst.
  • methane and carbon monoxide in the Fischer Tropsch off-gas may be converted to hydrogen, for example, using a methane steam reformer plus shift combination.
  • Hydrogen-containing gas is preferably recovered from product gas obtained in at least one of the steps of the process according to the invention in order to provide hydrogen needed in any stage of the overall process.
  • the hydrogen is recovered from the carbon dioxide depleted gas obtained in step (vi) .
  • Another option is to use a part of the product stream produced in step (ii), in view of its high hydrogen content.
  • hydrogen is recovered by means of semi-permeable membranes wherein hydrogen with a relatively high purity is recovered at a low pressure and the remainder of the stream has a pressure substantially equal to the feed pressure.
  • Hydrogen may also be recovered by means of "pressure swing adsorption", using molecular sieves wherein components other than hydrogen are selectively adsorbed at a higher pressure and desorbed at a lower pressure, thereby producing the hydrogen at a pressure substantially the same as the feed pressure.
  • the main component of the other components is carbon monoxide, it is preferred after re- pressurisation to reintroduce the carbon monoxide into the main stream.
  • the product stream obtained in step (vii) may be separated into a relatively light stream and a relatively heavy stream (step viii) .
  • the relatively light stream (off gas) comprises mainly unconverted synthesis gas, inerts, carbon dioxide and the C1-C4 hydrocarbons.
  • At least part, and preferably substantially all (i.e. more than 70%, especially more than 95%), of the carbon dioxide present in the off gas of step (viii) may be removed by means of for example liquid absorption (with for example methanol or organic amines) , absorption on molecular sieves or using membranes. Optionally all the carbon dioxide thus removed is combined with the total hydrocarbonaceous feed.
  • a hydrocarbonaceous feedstock 1 is split into first and second feedstock streams 2,3 to which steam is added as required 4,4a.
  • the first feedstock stream 2 undergoes reforming in at least one reforming zone 5, while the second feedstock stream 3 undergoes partial oxidation in at least one partial oxidation zone 6.
  • the reforming product stream 7 is combined with the partial oxidation product stream 8 to produce a hot gas stream 9.
  • the combination of the reforming product stream 7 and the partial oxidation product stream 8 takes place downstream of the partial oxidation zone(s) 6 such that the reforming product stream 7 does not pass through the partial oxidation zone(s) .
  • an adiabatic steam reforming zone 5a may be provided downstream of the point at which the reforming product stream 7 and the partial oxidation product stream 8 are combined.
  • Said hot gas stream 9 is used to heat the reforming zone(s) 5, typically by means of a heat exchange arrangement (not shown) .
  • the cooled heating gas 10 is then treated by suitable means 11 to remove carbon dioxide. At least some of the carbon dioxide thus obtained may be recycled 12 to the feedstock stream 3 feeding the partial oxidation process. Optionally some of the carbon dioxide removed from the cooled heating gas 10 may be recycled (not shown) to the feedstock stream feeding the reforming zone(s) 5.
  • the carbon dioxide depleted gas stream 13 represents a carbon dioxide depleted syngas stream which may subsequently be used in Fischer Tropsch or other similar type reactions, such as for example the production of methanol.
  • the carbon dioxide depleted gas stream 13 (syngas) is fed to a reactor 14 for the purposes of conversion to hydrocarbon products.
  • reactor 14 will be a Fischer Tropsch reactor.
  • the syngas undergoes catalytic conversion to produce a product stream (substantially made up of light and heavy hydrocarbon products) . Additional hydrogen may be added to the Fischer Tropsch reactor in order to adjust the H2/CO ratio if desired.
  • a heavy product stream 15 is drawn off for further use or processing.
  • the light product stream 16 also known as offgas, hydrocarbon synthesis offgas
  • the carbon dioxide depleted offgas 18 is preferably at least partly recycled to the reforming process (as shown in Figure 1.
  • the remaining fraction, including inerts may be removed from the process and used as fuel for utilities and/or as a hydrogen source.
  • the carbon dioxide 19 separated from the light product stream 16 may be recycled to the partial oxidation process (as shown in Figure 1) and/or the reforming process (not illustrated) .
  • the present invention provides an integrated process for the production of hydrocarbon products from a hydrocarbonaceous feedstock. Operation of the reforming step and the partial oxidation step in parallel as opposed to in series (as is the situation in WO 03/000627) provides an effective means for balancing the energy characteristics of the two steps.
  • the process of the invention also facilitates flexible operation in that the H2/CO ratio can be readily tuned in a number of ways.
  • the hydrocarbon synthesis process of the present invention provides improvements and flexibility in terms of overall energy balance and carbon efficiency.

Abstract

A process for the preparation of syngas from a hydrocarbonaceous feedstock is described. It comprises the steps of: (i) splitting the hydrocarbonaceous feedstock into a first feedstock stream and a second feedstock stream; (ii) catalytically reforming the first feedstock stream in at least one reforming zone to produce a reforming product; (iii) oxidising the second feedstock stream in at least one partial oxidation zone to produce a partial oxidation product; (iv) mixing some or all of the reforming product and some or all of the partial oxidation product to produce a heating gas (syngas) in a mixing zone which is separated from the reforming zone and the partial oxidation zone; (v) heating the reforming zone(s) by means of the heating gas; and (vi) optionally separating carbon dioxide from the cooled heating gas to produce a carbon dioxide depleted syngas stream. The syngas can be used to produce hydrocarboneous products, e.g. by the Fischer Tropsch process. The invention provides an integrated process for the production of hydrocarbon products from a hydrocarboneous feedstock. Operation of the reforming step and the partial oxidation step in parallel as opposed to in series provides an effective means for balancing the energy characteristics of the two steps. The process of the invention also facilitates flexible operation in that the H2/CO ratio can be readily tuned in a number of ways.

Description

INTEGRATED PROCESS FOR HYDROCARBON SYNTHESIS
The present invention relates to an improved process for the preparation of liquid and/or solid hydrocarbons from a hydrocarbonaceous feedstock, especially a gaseous hydrocarbon feedstock such as methane from a natural source, preferably natural gas. The invention further relates to a process for preparation of syngas for use in the preparation of liquid and/or solid hydrocarbons.
Various processes are known for the conversion of gaseous hydrocarbonaceous feedstocks, especially methane from natural sources, for example natural gas, associated gas and/or coalbed methane, into liquid products, especially methanol and liquid hydrocarbons, particularly paraffinic hydrocarbons. At ambient temperature and pressure these hydrocarbons may be gaseous, liquid and (often) solid. Such processes are often required to be carried out in remote and/or offshore locations, where no direct use of the gas is possible. Transportation of gas, for example through a pipeline or in the form of liquefied natural gas, requires extremely high capital expenditure or is simply not practical. This holds true even more in the case of relatively small gas production rates and/or fields. Reinjection of gas will add to the costs of oil production, and may, in the case of associated gas, result in undesired effects on crude oil production. Burning of associated gas has become an undesirable option in view of depletion of hydrocarbon sources and air pollution. A process often used for the conversion of carbonaceous feedstocks into liquid and/or solid hydrocarbons is the well-known Fischer-Tropsch process.
The Fischer Tropsch process is often used for the conversion of hydrocarbonaceous feed stocks into liquid and/or solid hydrocarbons. The feed stock (for example natural gas, associated gas and/or coal-bed methane) is converted in a first step into a mixture of hydrogen and carbon monoxide (this mixture is referred to as synthesis gas or syngas) . The syngas is then converted in a second step over a suitable catalyst at elevated temperature and pressure into paraffinic compounds ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances, even more.
GB 2183672 discloses one such process where a mixture of products from catalytic reforming and partial oxidation steps are used in a Fischer Tropsch type synthesis having first had carbon dioxide removed from the syngas, wherein the separated carbon dioxide is combined with the hydrocarbonaceous feedstock used in at least one of the catalytic reforming and partial oxidation steps.
WO 03/000627 discloses a process for producing liquid hydrocarbons comprising catalytic reforming and partial oxidation steps which involves recycling at least part of a carbon dioxide feed obtained from a heating gas and/or from a light hydrocarbon product stream to the hydrocarbonaceous feedstock fed utilised in the reforming step. In this process the reforming product is fed directly into the partial oxidation zone to produce the heating gas.
It is an object of the present invention to provide an efficient, process- and energy- integrated scheme for the production of especially (easily manageable) normally liquid hydrocarbonaceous products (STP) and normally solid hydrocarbonaceous products (STP) from hydrocarbonaceous feedstock.
According to one aspect, the present invention provides a process for the preparation of syngas from a hydrocarbonaceous feedstock comprising the steps of: (i) splitting the hydrocarbonaceous feedstock into a first feedstock stream and a second feedstock stream; (ii) catalytically reforming the first feedstock stream in at least one reforming zone to produce a reforming product;
(iii) oxidising the second feedstock stream in at least one partial oxidation zone to produce a partial oxidation product;
(iv) mixing some or all of the reforming product and some or all of the partial oxidation product to produce a heating gas (syngas) in a mixing zone which is separated from the reforming zone and the partial oxidation zone; (v) heating the reforming zones by means of the heating gas; and
(vi) optionally separating carbon dioxide from the cooled heating gas to produce a carbon dioxide depleted syngas stream.
In essence step (v) is carried out without passing the reforming product produced according to step (ii) through the partial oxidation zones, i.e. an indirect heat exchange. The mixing is carried out in a mixing zone which is separated, i.e. not directly connected and not within the same reactor, from the reforming zone and the partial oxidation zone. Thus, two separate syngas streams are obtained, which are transported via a transportation zone to an independent mixing zone, from which mixing zone the mixed syngas stream is transported via a further transportation zone to the reforming zone for indirect heating purposes. The independent zones give the possibility to mix all synthesis gas from both sources or only part of it. It also gives the possibility to treat the two streams in different ways. For instance, the partial oxidation stream may contain trace impurities which are not present in the reformed syngas stream (e.g. sulphur compounds used to prevent metal dusting of the burner, nitrogen compounds as ammonia and/or hydrogen cyanide due to the presence of residual nitrogen in the oxygen etc.) . Thus, the two synthesis gas streams can each be optimally treated without the unnecessary treatment of the other stream. Further, the mixed stream may be treated in one way or another before use as heating gas. Very suitably an adiabatic reforming may be applied, reducing the temperature and adjusting the H2/CO ratio to a desired ratio. Optionally carbon dioxide and/or steam may be introduced in the adiabatic reforming zone to further adjust the desired H2/CO ratio. The independent mixing zone also opens the possibility to use part of any of the two synthesis gas stream and/or part of the mixed stream for other purposes, e.g. the manufacturing of hydrogen, methanol synthesis etc. If desired a certain amount of heat may be extracted from one or more of the separate streams, especially the mixed stream after further reforming (to further reduce the temperature, the heat being available at a relatively high level) .
It is observed that processes for the preparation of syngas are known in which the reformed syngas is directly introduced into a mixing zone together with partial oxidation steam, where after the mixture is directly used for heating of the reforming reaction. See for instance WO 2004/083115. Such a process, in which the reforming zone and the mixing zone are directly connected (and are situated in the same reactor) is much less flexiable than the process according to the present invention. It is clear that all reforming synthesis gas is introduced in the mixing zone, and that separate treatments of the several syngas streams are not possible.
Suitable transportation zones are for instance pipes of certain diameter and a certain length. The diameter may be in the same range of the diameter of the pipe of natural gas feed-stream (e.g. two or three times the diameter of the natural gas pipe may be used (in view of the chemical conversion and the temperature increase) . The length may be from 1 in till several hundreds of meters or even more, depending on the distance between the different zones and the options to treat the streams. The mixing zone may very well be a connection between two pipes, or, if desired, a reactor, either empty or provided with gas-mixing internals. In the case of direct connection between two pipes, (static) mixtures may be present in the combined stream.
The oxidation step, step (iii), may suitably be carried out using known techniques such as for example the Shell Gasification Process (a comprehensive survey of this process can be found in the Oil and Gas Journal, September 6, 1971, pp 86-90), auto thermal reforming or catalytic partial oxidation.
Optionally a further step, step (vi) may be provided in which carbon dioxide from the cooled heating gas is removed to produce a carbon dioxide depleted syngas stream. The process may additionally comprise the further step (via) of recycling the carbon dioxide produced according to step (vi) back to the partial oxidation zone(s) and/or reforming zone(s), preferably to the partial oxidation zone(s) .
Optionally a post reforming step, (iia) , may be included, wherein the heating gas produced from step (iv) is fed to at least one post reforming zone prior to step (v) .
The recycling of carbon dioxide removed in step (vi) back to the partial oxidation zones has the advantages of facilitating milder operating conditions for the POX (for example lower temperature and lower oxygen use) and reducing soot formation in the POX (for a given temperature compared to operation of the POX without carbon dioxide recycling) .
Preferably, all of the reforming product and all of the partial oxidation product are mixed in step (iv) .
Preferably, step (i) is adapted to balance the effects of steps (ii) and (iii) and thus to provide for energy balancing between the reforming and partial oxidation processes.
Typically step (i) will be carried out by passing from about 1 to about 60% by volume, preferably from about 10 to about 45% by volume, more preferably from 20 to 40% by volume of the hydrocarbonaceous feedstock to the at least one reforming zone and from about 40 to about 99% by volume of the hydrocarbonaceous feed stock to the at least one partial oxidation zone preferably from 55 to 90% by volume, more preferably from 60 to 80% by volume.
According to a second aspect, the present invention provides a process for the preparation of hydrocarbonaceous products comprising catalytically converting synthesis gas produced as herein described to produce a hydrocarbonaceous product stream This step is hereinafter also termed "step (vii)".
Preferably the catalytic conversion (step (vii) ) is a Fischer Tropsch conversion.
The process for the preparation of hydrocarbonaceous products may comprise the additional steps of (viii) separating the product stream into a light product stream; comprising unconverted syngas, carbon dioxide, inerts and light hydrocarbons; and a heavy product stream; comprising liquid and solid hydrocarbons; and (ix) separating carbon dioxide from the light product stream.
Optionally the process may comprise a further step of (x) recycling at least part of the carbon dioxide depleted light product stream from step (ix) directly to at least one reforming zone. This may be used to establish an optimum energy balance for the total process .
A further option is to use the carbon dioxide depleted light product stream as fuel. Preferably at least part of the carbon dioxide depleted light product stream, especially up to 50% by volume, preferably between 5 and 40% by volume, is used as fuel to reduce or avoid build up of inerts.
Optionally, the process may comprise a further step (xi) of recycling the carbon dioxide from steps (vi) and/or (ix) to at least one partial oxidation zone.
As a further option, the process may comprise a further step (xii) of recycling carbon dioxide produced according to steps (vi) and/or (ix) to the reforming zones. As another option, the process may comprise a further step (xiii) of mixing hydrogen with the carbon dioxide depleted syngas stream produced according to step (vi) .
Bearing in mind the process as a whole, and in particular the carbon dioxide recycles, the fractions of hydrocarbonaceous feedstock passed to the reforming zones and the partial oxidation zones respectively may be adapted to produce a carbon dioxide depleted syngas stream having a H2/CO ratio of from about 1.3 to about 5, preferably of from 1.6 to 3.0 and more preferably from 1.7 to 2.3.
The present invention thus provides an integrated process for syngas production and conversion of carbonaceous feedstocks to hydrocarbonaceous products (including for example light and heavy paraffins, methanol and the like) . One of the advantages of such an integrated process is the ability to balance the energy requirements/output of various steps and thus improve the overall efficiency (in terms of carbon efficiency and thermal efficiency) of the process as a whole. Further advantages of the invention will be apparent from the following description.
The invention is described in more detail below with reference to the accompanying drawings in which:
Figure 1 is a schematic flow diagram of an integrated hydrocarbon synthesis process according to the invention.
The preparation of synthesis gas by means of a reforming reaction requires a relatively large energy input. The partial oxidation step, step (iii) may suitably be carried out using known techniques such as for example the Shell gasification process, auto thermal reforming or catalytic partial oxidation. The partial oxidation process is in this context defined as a generic term including partial oxidation carried out with or without a catalyst, with or without a flame and with or without steam and/or carbon dioxide injection. When partial oxidation is used, a relatively large amount of energy is produced. The partial oxidation step suitably results in a synthesis gas having a temperature between 900 and 1800 0C, preferably between 1000 and 1700 C. In the case of natural gas as feedstock in a pure partial oxidation reaction the temperature is suitably between 1150 and 1450 0C.
Synthesis gas produced by reforming, in the absence of CC>2 or off-gas from the Fischer Tropsch reaction (for example, off-gas from heavy paraffin synthesis typically comprises unconverted synthesis gas, light C1-C4 hydrocarbons, some CO2 and usually inerts, and is sometimes referred to as HPS off-gas) recycle, typically has a relatively high H2/CO ratio, usually between 4 and 7. The reforming process suitably results in a synthesis gas having a temperature between 300 and 1050 0C, preferably between 400 and 950 °C.
Synthesis gas produced by means of partial oxidation, in the absence of CO2 recycle, typically has an H2/CO ratio of about 1.5 to 1.8 where natural gas is used as the feed. The user ratio of Fischer Tropsch hydrocarbon synthesis using a cobalt catalyst and producing large amounts of heavy wax is about 2. Further, in the case that heavy wax is produced, hydrogen is needed for hydrocracking the heavy wax into lighter products boiling especially in the kerosene/gasoil range. In some cases additional hydrogen is needed for desulphurisation of the hydrocarbonaceous feed. The off-gas of the Fischer Tropsch reaction (comprising unconverted synthesis gas, C]_-C4 hydrocarbons, CO2 and usually inerts) may be used to generate energy and/or synthesis gas/hydrogen.
Carbon dioxide, generated in the production of especially energy/hydrogen/hydrocarbons, may be used as additional feedstream in the reforming and/or partial oxidation. Carbon dioxide produced may also be used for other purposes such as for example enhanced oil recovery or C02 sequestration. Many variations of the overall process are possible, each having its own advantages/ disadvantages.
The combination of reforming and partial oxidation results in an optimum energy efficiency. This combination, in which the heat required in the reforming reaction is produced by the partial oxidation reaction, together with a number of carbon dioxide recycles, the preparation of hydrogen by means of extraction from one of the process streams and the optional recycle of Fischer Tropsch off-gas results in a very high thermal and carbon efficiency. In addition, the combination of reforming and partial oxidation requires less oxygen when compared with partial oxidation alone. A saving of between 15 and 40% of oxygen intake can be obtained. Further, by mixing the very hot partial oxidation synthesis gas with the hot reforming gas, the temperature of the heating gas has gone down usually for at least 500C, preferably even more, making the condition in the reformer/heat exchanger less severe, which results in a more reliable process, and makes the choice of the heat exchanger materials more easy. This is especially the case when pure (catalytic) partial oxidation is used, due to the very high temperature of the synthesis gas, and the very strong reducing nature of the gas in the absence of water. - li ¬ lt is observed that especially partial recycle of depleted light product stream (including C1-C4 products) to the reforming zones is advantageous for the efficiency of the total process.
The recycle of carbon dioxide extracted from the Fischer Tropsch hydrocarbon synthesis product to the partial oxidation process and/or the reforming process provides a means of controlling the H2/CO ratio of the syngas .
According to the process of the present invention the reforming zone(s) and partial oxidation zone(s) are fed separately by splitting the hydrocarbonaceous feed stock. The reforming product and partial oxidation product arising from each of the respective processing steps are then combined downstream to produce a heating gas which is used, through heat exchange means, in heating the reforming zones. Following heat exchange and usually further heat exchange to produce steam as well as a synthesis gas having a temperature between 50 and 300 °C, the cooled heating gas is then optionally treated to remove carbon dioxide before being fed to a Fischer Tropsch reactor.
The hydrocarbon products produced according to the Fischer Tropsch synthesis may then be separated into a light product stream, comprising unconverted syngas, CO2, inerts and light hydrocarbons, and a heavy product stream, comprising liquid and solid hydrocarbons. The heavy product stream may be drawn off in a suitable manner with the light product stream undergoing further processing to remove carbon dioxide before, optionally, being recycled directly to the reforming zone(s) . Carbon dioxide removed from the cooled heating gas and/or the light FT product stream may optionally be recycled to either the reforming process and/or the partial oxidation process.
In any event, the process of the invention does not require the reforming product or the light product stream (derived from the FT synthesis) to be fed through the partial oxidation zone(s) . This results in significant advantages in terms of the partial oxidation process in that the partial oxidation zone(s) can comprise units having a lower capacity and may be operated under milder conditions (i.e. lower temperatures) .
In step (ii) of the process according to the invention various reforming catalysts can suitably be used, for instance catalysts comprising one or more metals from Group VIII of the Periodic Table of Elements, such as nickel, platinum, palladium, rhodium, iridium and the like on a support (for example, as a carrier material, alumina, silica, titania, zirconia and/or combinations thereof) . Step (ii) is suitably carried out at a temperature from 350 to 1100 0C, preferably 450 to 1000 0C more preferably between 600 and 950 0C, and a pressure from 10 to 100 bar, preferably 30 to 70 bar. The space velocity of the gaseous hydrocarbonaceous feed and steam combined is suitably from 1000 to 10000 1 (STP) /1 catalyst/hour, preferably from 4000 to 7000 1 (STP) /1 catalyst/hour.
The percentage of the first feedstock stream (i.e. that portion of the hydrocarbonaceous feed fed to the reforming (s) ) which is converted in step (ii) is suitably between about 50 and about 98 %wt. Typically the H2O/C ratio in step (ii) will be in the order of about
0.5-7 mol steam/mol carbon, preferably about 1-5 and more preferably 1.5-4; where the carbon fraction is calculated on the basis of all hydrocarbonaceous carbon (i.e. does not include non-organic carbon such as CO2) . The remaining 50 to 100 %wt, preferably of hydrocarbonaceous feed is fed to the partial oxidation zone(s) for the purposes of step (iii) .
The catalytic reforming step (ii) may be carried out in a fixed-, moving-, or fluidized bed of catalyst particles; fixed beds. The reforming reactor is suitably a heat exchange hydrocarbon reforming reactor.
As oxygen containing gas for use in step (iii) air can be employed. Preferably an enriched oxygen gas is used, more preferably substantially pure oxygen, i.e. oxygen gas which contains less than 2 %vol of contaminants as nitrogen and argon, preferably less than 1 %vol of contaminants. The presence of such contaminants is undesirable because in the case of off-gas recycle it can lead to a gradual build up of such gases (known as inerts) in the system and it may result in enhanced formation of undesired compounds in the gasification process as HCN or NH3.
Step (iii) of the process of the present invention is preferably carried out non-catalytically at substantially the same pressure of step (ii) . When catalyst are used especially metal catalysts of Group VIII of the Periodic Table are used, such as nickel, rhodium, iridium, platinum and/or palladium. The temperature of the heating gas produced in step (iv) is higher than the temperature inside the reforming zone(s) which are to be heated; suitably the heating gas temperatures ranges from 700 to 1350 0C, preferably from 800 to 1300 0C. Step (ii) may optionally be combined with an adiabatic post reforming step (iia) employing one or more adiabatic zones, using a reforming catalyst such as those described for step (ii) in respect of catalytic partial oxidation or auto thermal reforming for example. Preferably the temperature of the product stream obtained in (iii) is at least 150 0C higher than the temperature of the product stream obtained in step (ii), more preferably at least 250 0C, Still more preferably between 300 and 600 0C.
The hydrocarbonaceous feed for the process according to the invention is usually gaseous and if liquid is a product different from the liquid hydrocarbons produced, for example condensate (mainly C3-C5 hydrocarbons) or heavy hydrocarbons (residual oils as short residue) . Preferably the hydrocarbonaceous feed comprises large amounts of methane, for example in the form of natural or associated gas. In the case of a feed with a relatively high sulphur content, the feed is at least partly desulphurized, preferably with hydrogen extracted from one of the product streams.
At least part, and preferably substantially all (i.e. more than 70%, especially more than 90%), of the carbon dioxide present in the heating gas with which the reforming zone(s) have been heated in step (v) is removed in step (vi) by means of for example liquid absorption (with for example methanol or organic amines), adsorption on molecular sieves or using membranes. Steam is suitably removed simultaneously with carbon dioxide and may be re¬ used after any treatment which may be necessary or desirable. Preferably at least 50% more preferably all the carbon dioxide thus removed is combined with the hydrocarbonaceous feedstream fed to the partial oxidation process (step iii) . Furthermore, additional amounts of carbon dioxide from extraneous sources can be used.
In the catalytic conversion of the syngas produced (step (vii) of the process) according to the present invention a hydrogen- and carbon monoxide-containing gas (syngas) obtained in step (vi) is converted in one or more steps at least partly into liquid hydrocarbons in the presence of a Fischer Tropsch type catalyst which preferably comprises at least one metal (compound) selected from Group VIII of the Periodic Table. Preferred catalytic metals are iron and cobalt, especially cobalt. It is preferred to produce a very heavy product in step (vii) . This results in a relatively low amount of light hydrocarbons, for example C1-C4 hydrocarbons, resulting in a higher carbon efficiency. Large amounts of heavy products may be produced by catalysts which are known in the literature (for example vanadium or manganese promoted cobalt catalysts) under suitable conditions. Any hydrocarbons produced in step (vii) boiling above the middle distillate boiling range may be converted into middle distillates by means of hydrocracking. Such a step will also result in the hydrogenation of the product as well as in (partial) isomerization of the product.
The Fischer Tropsch synthesis is, as indicated above, preferably carried out with a catalyst producing large amounts of unbranched paraffinic hydrocarbons boiling above the middle distillate range. Relatively small amounts of oxygen containing compounds are produced. The process is suitably carried out at a temperature of 150 to 300 0C, preferably 190 to 260 0C, and a pressure from 20 to 100 bar, preferably from 30 to 70 bar. In the hydrocracking process preferably at least the fraction boiling above the middle distillate boiling range is hydrocracked into middle distillate. Preferably all C5+, especially all C]_Q+ hydrocarbons are hydrocracked in view of the improved pour point of the middle distillates obtained in such a process. The temperature in the second stage is preferably from 250 to 400 0C, in particular 300 to 350 0C. In the hydrocracking reaction preferably a catalyst is used which contains at least one noble metal from Group 8 (in particular platinum and/or palladium) on a carrier (in particular silica, alumina or silica/ alumina, more particularly amorphous silica alumina) . Preferably such catalysts contain 0.1 to 2 %wt of noble metal catalyst.
Optionally methane and carbon monoxide in the Fischer Tropsch off-gas may be converted to hydrogen, for example, using a methane steam reformer plus shift combination.
Hydrogen-containing gas is preferably recovered from product gas obtained in at least one of the steps of the process according to the invention in order to provide hydrogen needed in any stage of the overall process. Optionally the hydrogen is recovered from the carbon dioxide depleted gas obtained in step (vi) . Another option is to use a part of the product stream produced in step (ii), in view of its high hydrogen content.
Alternatively, hydrogen is recovered by means of semi-permeable membranes wherein hydrogen with a relatively high purity is recovered at a low pressure and the remainder of the stream has a pressure substantially equal to the feed pressure. Hydrogen may also be recovered by means of "pressure swing adsorption", using molecular sieves wherein components other than hydrogen are selectively adsorbed at a higher pressure and desorbed at a lower pressure, thereby producing the hydrogen at a pressure substantially the same as the feed pressure. As the main component of the other components is carbon monoxide, it is preferred after re- pressurisation to reintroduce the carbon monoxide into the main stream.
It is observed that such an integrated process, which not only converts the hydrocarbonaceous feedstock into synthesis gas followed by conversion into Fischer Tropsch hydrocarbons but also produces hydrogen, may have advantages over the use of a dedicated hydrogen unit.
The product stream obtained in step (vii) may be separated into a relatively light stream and a relatively heavy stream (step viii) . The relatively light stream (off gas) comprises mainly unconverted synthesis gas, inerts, carbon dioxide and the C1-C4 hydrocarbons.
At least part, and preferably substantially all (i.e. more than 70%, especially more than 95%), of the carbon dioxide present in the off gas of step (viii) may be removed by means of for example liquid absorption (with for example methanol or organic amines) , absorption on molecular sieves or using membranes. Optionally all the carbon dioxide thus removed is combined with the total hydrocarbonaceous feed.
Turning now to Figure 1, a hydrocarbonaceous feedstock 1 is split into first and second feedstock streams 2,3 to which steam is added as required 4,4a. The first feedstock stream 2 undergoes reforming in at least one reforming zone 5, while the second feedstock stream 3 undergoes partial oxidation in at least one partial oxidation zone 6. The reforming product stream 7 is combined with the partial oxidation product stream 8 to produce a hot gas stream 9. The combination of the reforming product stream 7 and the partial oxidation product stream 8 takes place downstream of the partial oxidation zone(s) 6 such that the reforming product stream 7 does not pass through the partial oxidation zone(s) . Optionally, an adiabatic steam reforming zone 5a may be provided downstream of the point at which the reforming product stream 7 and the partial oxidation product stream 8 are combined.
Said hot gas stream 9 is used to heat the reforming zone(s) 5, typically by means of a heat exchange arrangement (not shown) . The cooled heating gas 10 is then treated by suitable means 11 to remove carbon dioxide. At least some of the carbon dioxide thus obtained may be recycled 12 to the feedstock stream 3 feeding the partial oxidation process. Optionally some of the carbon dioxide removed from the cooled heating gas 10 may be recycled (not shown) to the feedstock stream feeding the reforming zone(s) 5. The carbon dioxide depleted gas stream 13 represents a carbon dioxide depleted syngas stream which may subsequently be used in Fischer Tropsch or other similar type reactions, such as for example the production of methanol.
In Figure 1 the carbon dioxide depleted gas stream 13 (syngas) is fed to a reactor 14 for the purposes of conversion to hydrocarbon products. Typically said reactor 14 will be a Fischer Tropsch reactor. The syngas undergoes catalytic conversion to produce a product stream (substantially made up of light and heavy hydrocarbon products) . Additional hydrogen may be added to the Fischer Tropsch reactor in order to adjust the H2/CO ratio if desired. A heavy product stream 15 is drawn off for further use or processing. The light product stream 16 (also known as offgas, hydrocarbon synthesis offgas ) may be treated using suitable means 17 to remove carbon dioxide. The carbon dioxide depleted offgas 18 is preferably at least partly recycled to the reforming process (as shown in Figure 1. The remaining fraction, including inerts may be removed from the process and used as fuel for utilities and/or as a hydrogen source. Similarly, the carbon dioxide 19 separated from the light product stream 16 may be recycled to the partial oxidation process (as shown in Figure 1) and/or the reforming process (not illustrated) .
Thus it can be seen that the present invention provides an integrated process for the production of hydrocarbon products from a hydrocarbonaceous feedstock. Operation of the reforming step and the partial oxidation step in parallel as opposed to in series (as is the situation in WO 03/000627) provides an effective means for balancing the energy characteristics of the two steps. The process of the invention also facilitates flexible operation in that the H2/CO ratio can be readily tuned in a number of ways.
When compared with known processes, the hydrocarbon synthesis process of the present invention provides improvements and flexibility in terms of overall energy balance and carbon efficiency.

Claims

C L A I M S
1. A process for the preparation of syngas from a hydrocarbonaceous feedstock comprising the steps of:
(i) splitting the hydrocarbonaceous feedstock into a first feedstock stream and a second feedstock stream;
(ii) catalytically reforming the first feedstock stream in at least one reforming zone to produce a reforming product;
(iii) oxidising the second feedstock stream in at least one partial oxidation zone to produce a partial oxidation product;
(iv) mixing some or all of the reforming product and some or all of the partial oxidation product to produce a heating gas (syngas) in a mixing zone which is separated from the reforming zone and the partial oxidation zone;
(v) heating the reforming zone(s) by means of the heating gas; and
(vi) optionally separating carbon dioxide from the cooled heating gas to produce a carbon dioxide depleted syngas stream.
2. A process according to Claim 1 comprising the further step (iia) of feeding the heating gas produced from step (iv) to at least one post reforming zone prior to step (v) .
3. A process according to either of Claims 1 and 2 which is adapted to control energy integration of the reforming and oxidation steps.
4. A process according to any preceding Claim wherein step (i) is carried out by passing from about 1 to about 60% by volume, preferably about 10 to about 45 vol%, of the hydrocarbonaceous feedstock to the at least one reforming zone and from about 40 to about 99% by volume of the hydrocarbonaceous feedstock to the at least one partial oxidation zone.
5. A process according to any preceding Claim further comprising the step (via) of recycling the carbon dioxide produced according to step (vi) back to the partial oxidation zone(s) and/or the reforming zone(s), preferably to the partial oxidation zone(s) .
6. A process according to any preceding Claim wherein step (ii) is carried out at a temperature from 350 to 1100 0C, preferably 400 to 1000 0C, and a pressure from 10 to 100 bar, preferably 30 to 70 bar and wherein the H2O/C ratio in step (ii) is about 0.5-7 mol steam/mol carbon, preferably about 1-5 mol steam/mol carbon and more preferably 1.5-4 mol steam/mol carbon.
7. A process according to any preceding Claim wherein step (iii) is carried out by non-catalytic partial oxidation, auto thermal reforming or catalytic partial oxidation, preferably wherein step (iii) is carried out non-catalytically at substantially the same pressure of step (ii) .
8. A process according to any preceding Claim wherein step (iii) uses an oxygen containing gas selected from the group consisting of air, an enriched oxygen gas and substantially pure oxygen, preferably substantially pure oxygen.
9. A process according to any preceding Claim wherein the temperature of the heating gas produced in step (iv) ranges from 600 to 1300 0C, preferably from 700 to
1200 0C.
10. A process for the preparation of hydrocarbonaceous products comprising preparing syngas according to any one of claims 1 to 9, followed by the step of:
(vii) catalytically converting the syngas to produce a product stream, preferably wherein the catalytic conversion is a Fischer Tropsch conversion to produce preferably 50 wt%, and more preferably 80 wt% C5+ products.
11. A process according to claim 10 further comprising the steps of:
(viii) separating the product stream into a light product stream; and a heavy product stream; and
(ix) separating carbon dioxide from the light product stream.
12. A process according to claim 11 further comprising the step of:
(viii) (recycling at least a part of the carbon dioxide depleted light product stream from step (ix) directly to at least one reforming zone, preferably further comprising the step of:
(viii) recycling at least a part of the carbon dioxide from steps (vi) and/or (ix) to at least one partial oxidation zone, more preferably further comprising the step of:
(viii) recycling at least a part of the carbon dioxide produced according to steps (vi) and/or (ix) to at least one reforming zones.
CS/TS1400FF
EP05789543A 2004-10-04 2005-10-04 Integrated process for hydrocarbon synthesis Withdrawn EP1794083A1 (en)

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EP05789543A EP1794083A1 (en) 2004-10-04 2005-10-04 Integrated process for hydrocarbon synthesis
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WO2016016251A1 (en) * 2014-07-29 2016-02-04 Eni S.P.A. Integrated sct-cpo/sr process for producing synthesis gas
WO2016016257A1 (en) * 2014-07-29 2016-02-04 Eni S.P.A. Integrated sct-cpo/pox process for producing synthesis gas
WO2016016256A1 (en) * 2014-07-29 2016-02-04 Eni S.P.A. Integrated sct-cpo/atr process for the production of synthesis gas
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MY139324A (en) * 2001-06-25 2009-09-30 Shell Int Research Integrated process for hydrocarbon synthesis
US7138001B2 (en) * 2003-03-16 2006-11-21 Kellogg Brown & Root Llc Partial oxidation reformer-reforming exchanger arrangement for hydrogen production
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