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  • 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
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  • 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
  • C01B3/38—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
  • C01B2203/02—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
  • C01B2203/06—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
  • C01B2203/0816—Heating by flames
• • 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
• • 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
  • C01B2203/142—At least two reforming, decomposition or partial oxidation steps in series
  • C01B2203/143—Three or more reforming, decomposition or partial oxidation steps in series

Definitions

• This invention relates to a process for the conversion of hydrocarbon feed to synthesis gas which can be further con- verted and/or purified as required for production of hydro ⁇ gen, carbon monoxide, mixtures of hydrogen and carbon monoxide, as well as for the production of methanol, dimethyl ether (DME) , and liquid hydrocarbons.
• the invention relates to a combined reforming process for the preparation of synthesis gas suitable for conversion of a hydrocarbon feed stock to such products in plants of large capacity capable of converting hydrocarbon feed to more than 8000 metric tons per day of such products.
• the synthesis gas section is the most expensive section of a plant for conversion of hydrocarbon feed to end products, both in terms of energy requirements and capital costs. Therefore, major efforts have been focusing on finding alternative process schemes for synthesis gas production which are less expensive and/or more energy efficient than hitherto known.
• Synthesis gas technology includes steam reforming (tubular or primary reforming) and pure oxygen autothermal reforming (ATR) , enriched air ATR and air ATR (secondary reforming) .
• Steam reforming can be divided into adiabatic prereforming (APR) , tubular reforming with external firing (SMR) and heat exchange reforming (HTER) .
• APR adiabatic prereforming
• SMR tubular reforming with external firing
• HTER heat exchange reforming
• the reactions 1-3 are carried out in an externally heated reactor, hereinafter referred as a primary reformer (SMR) .
• the feed to the primary reformer may be desulphurised hydrocarbon feed mixed with steam or the partly converted product gas from a previous prereform- ing step.
• the primary reformer is often a fired tubular reformer consisting of catalyst filled tubes placed in a fur ⁇ nace heated by one or several burners and which operates at conditions where the outlet temperature from the catalyst filled tubes is relatively high, usually in the range 650 to 950°C.
• Autothermal reforming is a technology used for the production of synthesis gas in which the conversion of a hydrocarbon feedstock or the conversion of a partly converted gas from a prereforming step into synthesis gas is completed in a single reactor by the combination of partial combustion and adiabatic steam reforming. Combustion of hydrocarbon feed is carried out with substoichiometric amounts of air, enriched air or oxygen by flame reactions in a burner combustion zone. Steam reforming of the partially combusted hydrocarbon feedstock is subsequently con- ducted in a fixed bed of steam reforming catalyst.
• Secondary reforming is a process in which partly converted (partly reformed) feed from a primary reforming step is further converted by the combination of partial combustion and adiabatic steam reforming.
• the secondary reformer in ammonia plants is usually air-blown while in methanol, DME and hydrocarbon synthesis plants it is oxygen blown.
• reaction (4) In autothermal reforming and secondary reforming the steam reforming reactions 1-3 are supplemented by partial combus- tion, which may be represented by reaction (4) :
• synthesis gas It is conventional to produce synthesis gas by first pass- ing a hydrocarbon feedstock mixed with steam through a steam reforming step, which comprises passing the feedstock through a prereformer, then a primary reformer, and finally through a secondary reformer fired with air, enriched air or oxygen.
• a steam reforming step which comprises passing the feedstock through a prereformer, then a primary reformer, and finally through a secondary reformer fired with air, enriched air or oxygen.
• This combination of steam reforming followed by secondary reforming is often referred to as two-step re ⁇ forming and is particularly suitable for the preparation of synthesis gas suitable for methanol, dimethyl ether and am ⁇ monia production.
• a synthesis gas having the correct stoichiometry for methanol synthesis or a synthesis gas having the correct hydrogen-to-nitrogen ra ⁇ tio for ammonia synthesis or any other application can be prepared .
• reactions 1-3 are carried out in adiabatic reactors, also called adiabatic prereformers (APR), at relatively low temperatures, usually 350° to 650°C.
• An adiabatic reactor is a reactor in which no heat is transferred to or from the reacting stream (except for heat loss to the surroundings) . Frequently the above reforming techniques are combined ei ⁇ ther in series or in parallel.
• Typical reforming combinations are: - SMR
• US patent 6,444,712 discloses a method for the production of methanol and hydrocarbons from synthesis gas being ob- tained from two parallel single lines steam reforming.
• a methane containing gas is subjected to primary steam reforming in an SMR and the other single line, a methane containing gas is directed a partial oxida ⁇ tion reformer.
• the synthesis gas produced in both single lines is introduced into the methanol synthesis step.
• the partial oxidation reactor may be an ATR.
• US 6,444,712 is silent about the steam to carbon ratio in the feed gas to the parallel single lines steam reforming.
• the required steam-to-carbon ratio (S/C-ratio), defined as the molar ratio between the total amount of steam added to the process in the steam reforming step and the carbon contained in the hydrocarbon feed, depends on the particular steam reforming technique, as further explained in the fol ⁇ lowing description.
• the steam required for the process can be added as one stream before a prereforming step and another supplementary stream after the prereforming step; if no prereforming step is present the steam is added before the steam reforming step .
• the optimum synthesis gas composition depends on the prod ⁇ uct to be produced.
• One way of characterising a synthesis gas composition is by means of the molar ratio of (3 ⁇ 4- C0 2 ) / (CO+C02) (Ml) and the molar ratio of H 2 /CO (M2).
• Table 1 lists typi ⁇ cal values/ranges of steam-to-carbon ratio, Ml, M2 and ap- proximate single line synthesis gas production capacity for various reforming reactors. Table 1
• the maximum capacity in a plant is related to the amount of product such as methanol, gasoline, and hydrocarbons which can be produced in a process scheme for synthesis gas production consuming a given amount of oxygen and usually involving a steam reforming step with a given transferred duty.
• the maximum capacity may be determined by the maximum allowable pressure drop in the adiabatic oxidative reactor (ATR or secondary reformer) of the maxi- mum practical size.
• the pressure drop in a given ATR reac ⁇ tor or secondary reformer depends on the total volumetric flow of product gas from the adiabatic oxidative reactor, i.e. its exit flow, so that the maximum achievable capacity with good approximation is defined by a maximum allowable volumetric flow of wet product gas from the adiabatic oxi- dative reactor.
• one of either the size of the steam reformers, the supply of oxygen from an air separation unit to the ATR reactor or the exit flow of the ATR represents the bottleneck for the capacity in terms of for instance methanol produc ⁇ tion from the produced synthesis gas. It is desirable to obtain an increased plant capacity for the same steam re ⁇ former size or duty when for instance the duty of the steam reformer represents the bottleneck for the capacity. Simi- larly, it is desirable to obtain an increased plant capac ⁇ ity for the same exit flow from the adiabatic oxidative re ⁇ actor when the duty of the steam represents the bottleneck for the capacity. Furthermore, low steam-to-carbon ratios increase the possi ⁇ ble maximum size and decrease the investment and operating costs.
• An SMR requires a steam-to-carbon ratio above 1.4 whereas an ATR can operate at steam to carbon ratios down to 0.4. This means that for capacities larger than the achievable single line capacity it is an advantage to main ⁇ tain a single line design and thereby to achieve optimum synthesis gas composition for example for methanol produc ⁇ tion by mixing synthesis gas from individual optimized re ⁇ forming sections.
• the main object of this invention is to provide a process for the preparation of synthesis gas producing a maximum amount of synthesis gas with a specific Ml and M2,said production exceeding the maximum production capacity of a single line process as defined in Table 1. Accordingly, the invention provides a process for the pro ⁇ duction of synthesis gas in two single line steam reforming steps comprising:
• M2 is the molar ratio of 3 ⁇ 4/CO.
• steam-to-carbon ratio is de- fined by the molar ratio between the amount of steam added to the process gas in a given single line of steam reform ⁇ ing and the carbon contained in the hydrocarbon feed to said reforming step.
• process parameters such as steam-to- carbon ratio, amount of the hydrocarbon feedstock, reformer duty in a heated steam reformer, and amount of oxygen added in the adiabatic oxidative reactor for the conversion of the second hydrocarbons stream into synthesis gas, can be expediently adjusted so as to obtain a maximum amount of combined synthesis gas from the two single line reforming steps with predetermined H 2 /CO/CO 2 molar ratios which are suitable for the production of large amounts (several thou ⁇ sand metric tons per day (MTPD) ) of products in any given downstream application, such as methanol and/or DME synthesis, ammonia synthesis and synthesis of liquid hydrocar ⁇ bons, e.g. gasoline.
• MTPD metric tons per day
• the process further comprises prereforming of the first and/or second hydrocarbon stream.
• prereforming is conducted adiabatically .
• the prereforming step provides the possibility of heating the first and/or the second stream to higher temperatures than in processes operating without the prereforming step
• the reforming in steps (c) and (d) may be performed by passing the hydrocarbon streams through a series of one or more reforming steps in each single line.
• the steam reforming may thus be conducted in one or more heated steam re ⁇ forming stages in series and/or in one or more autothermal reforming stages in series, respectively.
• the heat required for the reforming in step (c) is preferably provided by indirect heat ex ⁇ change with flue gas from the SMR and/or produced synthesis gas withdrawn from the ATR in step (d) .
• step (c) it is advantageous to further reform the synthesis gas from the primary reforming in step (c) passing the primary reformed gas through an auto thermal reforming step.
• the steam reforming in step (c) further comprises autothermal steam reforming downstream the primary reforming.
• At least part of the carbon dioxide is removed from the second syn ⁇ thesis gas product and directed to the heated primary re- forming in step in step (c) .
• the invention also encompasses a process accord ⁇ ing to claim 1 further comprising converting the synthesis gas from step (e) into ammonia, methanol, DME, liquid hy ⁇ drocarbons, or combinations thereof.
• Fig.l is a sim ⁇ plified flow sheet of a particular embodiment of the inven ⁇ tion for the production of synthesis gas employed in the preparation of methanol.
• synthesis gas is produced according to two single lines 1 and 2, arranged in parallel.
• Single line 1 includes in series an adiabatic prereformer 6 and a pri ⁇ mary reformer 8.
• Desulphurized hydrocarbon feed stock is introduced into the single line 1 together with steam 5.
• the amount of steam is adjusted to provide an S/C ratio of
• Prereformed gas is directed via line 7 to a primary reformer 8.
• the operating conditions in reformer 8 are adjusted to provide a final synthesis gas 10 according to single line 1 with a module Ml of 3.0.
• the single line 2 includes an adiabatic prereformer 11 and an autothermal reformer 12.
• Line 2 is fed with hydrocarbon feed stock 13 and steam 14.
• the amount of steam passed into single line 2 is adjusted to provide an S/C ratio of 0.6.
• the steam hydrocarbon mixture is prereformed in reformer
• reactor 12 is operated with pure oxygen (>99.5) .
• the operation conditions of reactor 12 are ad ⁇ justed to result in module Ml of 1.9 in the final synthesis gas 18 according to single line 2 after an optional removal of carbon dioxide in the reformed gas by means of CO 2 wash 17.
• the ratio between the amounts of hydrocarbon feed 3 and 13 is adjusted to result in a module Ml in the combined syn ⁇ thesis gas of 2.1.
• the synthesis gases 10 and 18 are mixed in a synthesis gas header 19 and the combined synthesis gas 20 with a module Ml of 2.1 is passed to methanol synthesis 21.
• carbon dioxide resulting from the CO 2 removal in the stripper 17 is passed via line 22 to the prereformed gas in line 7 of the single line 1 when higher amounts of carbon monoxide in the primary reformed gas 10 are re ⁇ quired .
• a further option is to recycle part of the tail gas from the methanol reactor 21 consisting mainly of unconverted synthesis gas to single line 1 via line 23 and/or to single line 22 via line 24, as shown in Fig. 1.
• the optimum design for a 10000 MTPD MeOH plant is a synthesis gas section consisting of a single line with APR-SMR units corresponding to 2500 MTPD and a single line with APR-ATR units corresponding to 7500 MTPD.
• This solution is compared with two APR, SMR, ATR units (two step reforming) each unit presenting a capacity of 5000 MTPD.
• the calculations show that for similar/identical con- sumption figures a considerable saving in investment costs can be achieved by the invention.

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• 2012
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