PARALLEL REFORMING IN CHEMICAL PLANT

Abstract

A chemical plant including: a reforming section arranged to receive a feed gas comprising hydrocarbons and provide a combined synthesis gas stream, wherein the reforming section includes: an electrically heated reforming reactor housing a first catalyst, an autothermal reforming reactor in parallel with the electrically heated reforming reactor, wherein the reforming section is arranged to output a combined synthesis gas stream including at least part of the first and/or second synthesis gas streams, an optional post processing unit downstream the reforming section, a gas separation unit arranged to separate a synthesis gas stream into a water condensate and an intermediate synthesis gas, and a downstream section arranged to receive the intermediate synthesis gas and to process the intermediate synthesis gas to a chemical product and an off-gas. Also, a process for producing a chemical product from a feed gas comprising hydrocarbons.

Claims

1. A chemical plant comprising: a reforming section arranged to receive a feed gas comprising hydrocarbons and provide a combined synthesis gas stream, wherein said reforming section comprises: an electrically heated reforming reactor housing a first catalyst, said electrically heated reforming reactor being arranged for receiving a first part of said feed gas and generating a first synthesis gas stream, an autothermal reforming reactor in parallel with said electrically heated reforming reactor, said autothermal reforming reactor housing a second catalyst, said autothermal reforming reactor being arranged for receiving a second part of said feed gas and outputting a second synthesis gas stream, wherein said reforming section is arranged to output a combined synthesis gas stream comprising at least part of said first and/or second synthesis gas streams, an optional post processing unit downstream the reforming section, where said optional post processing unit is arranged to receive the combined synthesis gas stream and provide a post processed synthesis gas stream, a water separation unit arranged to separate said combined synthesis gas stream or said post processed synthesis gas stream into a water condensate and an intermediate synthesis gas, and a downstream section arranged to receive the intermediate synthesis gas and to process the intermediate synthesis gas to a chemical product and an off-gas.

2. The chemical plant according to claim 1, wherein said electrically heated reforming reactor comprises: a pressure shell housing an electrical heating unit arranged to heat said first catalyst, where said first catalyst comprises catalytically active material operable to catalyzing steam reforming of said first part of said feed gas, wherein said pressure shell has a design pressure of between 5 and 45 bar, a heat insulation layer adjacent to at least part of the inside of said pressure shell, and at least two conductors electrically connected to said electrical heating unit and to an electrical power supply placed outside said pressure shell, wherein said electrical power supply is dimensioned to heat at least part of said first catalyst to a temperature of at least 800° C. by passing an electrical current through said electrical heating unit.

3. The chemical plant according to claim 2, wherein said electrical heating unit comprises a macroscopic structure of electrically conductive material, where said macroscopic structure supports a ceramic coating and said ceramic coating supports said catalytically active material.

4. The chemical plant according to claim 1, further comprising: a fired heater unit upstream said autothermal reforming reactor, the fired heater unit being arranged to preheat said second part of said feed gas, and means for recycling at least part of said off-gas from said downstream section as fuel to the fired heater unit.

5. The chemical plant according to claim 1, wherein said reforming section furthermore comprises a fired steam methane reforming reactor upstream said autothermal reforming reactor, wherein said fired steam methane reforming reactor comprises one or more tubes housing a third catalyst, wherein said fired steam methane reforming reactor comprises one or more burners for providing heat for the steam methane reforming reaction within said one or more tubes, and wherein said chemical plant comprises means for recycling at least part of said off-gas from said downstream section as fuel to the one or more burners of the fired steam methane reforming reactor, where the fired steam methane reforming reactor is arranged to receive said second part of said feed gas and to provide a partially reformed second feed gas, and wherein the partially reformed second feed gas is led to the autothermal reforming reactor.

6. The chemical plant according to claim 1, wherein said reforming section furthermore comprises a gas heated steam methane reforming reactor in parallel to the combination of said electrically heated steam methane reforming reactor and the autothermal reforming reactor, wherein said gas heated steam methane reforming reactor comprises a fourth catalyst and being operable to receive a third part of said feed gas and to utilize at least part of said first and/or second synthesis gas streams as heating media in heat exchange within said gas heated steam methane reforming reactor, said gas heated steam methane reforming reactor being arranged for generating a third synthesis gas stream and outputting said third synthesis gas stream from said reforming section as at least part of said combined synthesis gas stream.

7. The chemical plant according to claim 1, wherein said reforming section furthermore comprises a gas heated steam methane reforming reactor upstream of said autothermal reforming reactor, wherein said gas heated steam methane reforming reactor comprises a fourth catalyst and being operable to utilize at least part of said second synthesis gas stream as heating media in heat exchange within said gas heated steam methane reforming reactor, said gas heated steam methane reforming reactor being arranged to receive said second part of said feed gas and to provide a partially reformed second feed gas, and wherein the partially reformed second feed gas is led to the autothermal reforming reactor.

8. The chemical plant of claim 7, wherein said gas heated steam methane reforming reactor is further operable to utilize at least part of said first synthesis gas stream as heating media in heat exchange within said gas heated steam methane reforming reactor.

9. The chemical plant according to claim 1, wherein said post processing unit is a post conversion unit having an inlet for allowing addition of heated CO.sub.2 to the combined synthesis gas stream upstream the post conversion unit and housing a fifth catalyst active for catalyzing steam methane reforming, methanation and reverse water gas shift.

10. The chemical plant according to claim 1, wherein said post processing unit is a water gas shift unit arranged to carry out the water gas shift reaction.

11. The chemical plant according to claim 1, wherein said downstream section comprises gas separation unit(s) arranged to separate a stream of substantially pure CO.sub.2, H.sub.2, and/or CO from said intermediate synthesis gas, thereby providing a refined synthesis gas.

12. The chemical plant according to claim 1, wherein said downstream section comprises an ammonia reactor to convert said intermediate synthesis gas or said refined synthesis gas to ammonia, a methanol reactor to convert said intermediate synthesis gas or said refined synthesis gas to methanol, or a Fischer-Tropsch reactor to convert said intermediate synthesis gas or said refined synthesis gas to a mixture of higher hydrocarbons.

13. A process for producing a chemical product from a feed gas comprising hydrocarbons, in a chemical plant comprising a reforming section, said reforming section comprising an electrically heated reforming reactor housing a first catalyst, an autothermal reforming reactor in parallel with said electrically heated reforming reactor, said autothermal reforming reactor housing a second catalyst, said process comprising the steps of: inletting a first part of said feed gas to said electrically heated reforming reactor and carrying out steam methane reforming to provide a first synthesis gas stream, inletting a second part of said feed gas to said autothermal reforming reactor, and carrying out reforming to provide a second synthesis gas stream, outputting a combined synthesis gas stream comprising at least part of said first and/or second synthesis gas streams from said reforming section, optionally, in a post processing unit downstream said electrically heated reforming reactor and said autothermal reforming reactor, post processing said combined synthesis gas stream to provide a post processed synthesis gas stream, separating said combined synthesis gas stream or said post processed synthesis gas stream into a water condensate and an intermediate synthesis gas in a water separation unit downstream said post processing unit, and providing said intermediate synthesis gas to a downstream section arranged to receive the intermediate synthesis gas and to process the intermediate synthesis gas to a chemical product and an off-gas.

14. The process according to claim 12, wherein said electrically heated reforming reactor comprises a pressure shell housing an electrical heating unit arranged to heat said first catalyst, wherein said first catalyst comprises a catalytically active material operable to catalyze steam reforming of said first part of said feed gas, wherein said pressure shell has a design pressure of between 5 and 45 bar, a heat insulation layer adjacent to at least part of the inside of said pressure shell, and at least two conductors electrically connected to said electrical heating unit and to an electrical power supply placed outside said pressure shell, wherein said process further comprises the steps of: pressurizing said first part of said feed gas to a pressure of between 5 and 45 bar, upstream said electrically heated reforming reactor, passing an electrical current through said electrical heating unit thereby heating at least part of said first catalyst to a temperature of at least 800° C.

15. The process according to claim 13, further comprising: providing fuel to a fired heater unit upstream said autothermal reforming reactor, thus preheating said second part of said feed gas, and recycling at least part of said off-gas from said downstream section as fuel to the fired heater unit.

16. The process according to claim 13, wherein said reforming section furthermore comprises a fired steam methane reforming reactor upstream said autothermal reforming reactor, wherein said steam methane reforming reactor comprises one or more tubes housing a third catalyst, wherein said fired steam methane reforming reactor comprises one or more burners for providing heat for the steam methane reforming reaction within said one or more tubes, said process furthermore comprising the steps of: inletting said second part of the feed gas into said fired steam methane reforming reactor, and carrying out steam methane reforming within tubes of said fired reforming reactor to provide a partially reformed second feed gas, providing said partially reformed second feed gas to said autothermal reforming reactor, and recycling at least part of said off-gas from said downstream section as fuel to the one or more burners of the fired steam methane reforming reactor.

17. The process according to claim 13, wherein said reforming section furthermore comprises a gas heated steam methane reforming reactor in parallel to the combination of said electrically heated reforming reactor and said autothermal reforming reactor, wherein said gas heated steam methane reforming reactor comprises a fourth catalyst, said process furthermore comprising the steps of: inletting a third part of said feed gas into said gas heated steam methane reforming reactor, utilizing at least part of said first and/or second synthesis gas streams as heating media in heat exchange within said gas heated steam methane reforming reactor, generating a third synthesis gas stream over the fourth catalyst within the gas heated steam methane reforming reactor, and outputting said third synthesis gas stream from said reforming section as at least part of said combined synthesis gas.

18. The process according to claim 13, wherein said reforming section furthermore comprises a gas heated steam methane reforming reactor upstream of said autothermal reforming reactor, wherein said gas heated steam methane reforming reactor comprises a fourth catalyst, said process further comprising the steps of: inletting said second part of the feed gas into said gas heated steam methane reforming reactor, and carrying out steam methane reforming within said fired reforming reactor to provide a partially reformed second feed gas, providing said partially reformed second feed gas to said autothermal reforming reactor, and utilizing at least part of said second synthesis gas streams as heating media in heat exchange within said gas heated steam methane reforming reactor.

19. The process according to claim 18 further comprising the step of: utilizing at least part of said first synthesis gas stream as heating media in heat exchange within said gas heated steam methane reforming reactor.

20. The process according to claim 13, wherein said post processing unit is a post conversion unit housing a fifth catalyst active for catalyzing steam methane reforming, methanation and reverse water gas shift reactions, wherein said process furthermore comprises the step of inletting heated CO.sub.2 to the combined synthesis gas stream upstream post conversion unit.

21. The process according to claim 13, wherein said post processing unit is a water gas shift unit and the step of post processing said combined synthesis gas stream comprises carrying out the water gas shift reaction.

22. The process according to claim 13, wherein said process comprises separating a stream of substantially pure CO.sub.2, H.sub.2, and/or CO from said intermediate synthesis gas, thereby providing a refined synthesis gas, in one or more gas separation unit(s) of said downstream section.

23. The process according to claim 13, wherein the first part of the feed gas is about 5-20 vol % of the feed gas.

24. The process according to claim 17, wherein the first part of the feed gas is about 5-10 vol % of the feed gas and the third part of the feed gas is about 5-10 vol % of the feed gas.

25. The process according to claim 13, wherein said process further comprises: converting said intermediate synthesis gas to ammonia in an ammonia reactor of said downstream section, to convert said intermediate synthesis gas to methanol in a methanol reactor of said downstream section, or to convert said intermediate synthesis gas to a mixture of higher hydrocarbons in a Fischer-Tropsch reactor.

Description

SHORT DESCRIPTION OF THE FIGURES

[0126] FIG. 1 shows a chemical plant according to an embodiment of the invention, where the reforming section comprises an autothermal reforming reactor and an electrically heated reforming reactor in parallel;

[0127] FIG. 2 shows a chemical gas plant according to an embodiment of the invention, where the reforming section also comprises a fired steam methane reforming reactor upstream the autothermal reforming reactor; and

[0128] FIG. 3 shows a chemical plant according to an embodiment of the invention, where the reforming section comprises four reforming reactors.

[0129] FIG. 4 shows a chemical gas plant according to an embodiment of the invention, where the reforming section also comprises a gas heated steam methane reforming reactor upstream the autothermal reforming reactor.

DETAILED DESCRIPTION OF THE FIGURES

[0130] FIG. 1 shows a chemical plant 100 according to an embodiment of the invention. The chemical plant 100 comprises a reforming section 110 with an autothermal reforming reactor 109 and an electrically heated reforming reactor 108 in parallel.

[0131] The electrically heated reforming reactor 108 houses a first catalyst and the autothermal reforming reactor 109 houses a second catalyst. The electrically heated reforming reactor 108 is heated by means of an electrical power supply 107.

[0132] The electrically heated reforming reactor 108 and autothermal reforming reactor 109 are arranged in parallel. The electrically heated reforming reactor 108 is heated by means of an electrical power supply 107. The electrically heated reforming reactor 108 and autothermal reforming reactor 109 are arranged to receiving a first part 25a and a second part 25b of a feed gas 25 and to generate a first and second synthesis gas 30a, 30b, respectively.

[0133] During operation of the chemical plant 100, a feed gas 21 comprising hydrocarbons undergoes feed purification in a desulfurization unit 101 and becomes a desulfurized gas 22. The feed gas 21 comprising hydrocarbons is e.g. natural gas or town gas. The desulfurized gas 22 is preheated in a fired heating unit 105 and steam 23 is added to the desulfurized gas 22, resulting in a gas stream 24. The gas stream 24 is led to a prereforming unit 102 housing steam reforming catalyst. Typically, the prereforming unit 102 is an adiabatic prereforming unit, wherein higher hydrocarbons are reacted so that the prereformed gas 25 exiting the prereforming unit 102 contains no or very small amounts of higher hydrocarbons. The prereformed gas 25 is divided into a first part 25a of the feed gas which is led to the electrically heated reforming reactor 108 and a second part 25b of the feed gas which is led to the autothermal reforming reactor 109. Additional steam may be added to the first part 25a of the feed gas (not shown in FIG. 1). The first catalyst in the electrically heated reforming reactor 108 is a steam methane reforming catalyst arranged to catalyze the steam methane reforming reaction in the electrically heated reforming reactor 108. The autothermal reforming reactor 109 also comprises a steam methane reforming catalyst arranged to carry out steam methane reforming reaction. Air or oxygen 26 is also added to the autothermal reforming reactor 26 in order to carry out partial combustion of the second part of the feed gas 25b upstream the second catalyst within the autothermal reforming reactor 109. A first and second synthesis gas stream 30a, 30b exit the electrically heated reforming reactor 108 and the autothermal reforming reactor 109, respectively, and are combined to a combined synthesis gas stream 30 exiting the reforming section 110. The combined synthesis gas stream 30 is cooled in a heat exchanger 111 to a cooled combined synthesis gas stream 30′. The cooled combined synthesis gas stream 30′ enters a post processing unit 112, viz. a water gas shift unit, and a water gas shifted synthesis gas 32 exits the water gas shift unit 112. The water gas shifted synthesis gas 32 is cooled in a second heat exchanger 113 to a cooled water gas shifted synthesis gas 32′, which enters the water separation unit 115, such as e.g. a flash separation unit 115 arranged to separate the cooled water gas shifted synthesis gas 32′ into a condensate 27 and an intermediate synthesis gas 34. The intermediate synthesis gas 34 is a dry synthesis gas and enters the downstream section 116 arranged to process the intermediate synthesis gas 34 to a chemical product 40 and an off-gas 45. The downstream section 116 comprises e.g. an ammonia reactor to convert the intermediate synthesis gas 34 to ammonia, a methanol reactor to convert the intermediate synthesis 34 gas to methanol, or a Fischer-Tropsch reactor to convert the intermediate synthesis gas 34 to a mixture of higher hydrocarbons.

[0134] The off-gas 45 from the downstream section 116 is recycled as fuel to one or more burners of the fired heating unit 105. The off-gas 45 is combined with a small amount of natural gas 46 to form the fuel gas 47 sent to the one or more burners of the fired heating unit 105. The fired heating unit is arranged to provide heat for preheating the feed gas 21, the desulfurized feed gas 22, and the first and/or second part 25a, 25b of the feed gas 25. In FIG. 1, only the second part 25b of the feed gas 25 is heated in the fired heating unit 105 prior to entering into the autothermal reforming reactor 109. However, it is also conceivable that the first part 25a of the feed gas 25 is preheated in the fired heating unit 105.

[0135] A heat exchange fluid 20, such as water, is used for heat exchange in the heat exchanger 111 and a heated heat exchange fluid, such as steam, is exported as stream 20′. A part of the steam is used as addition of steam 23 to the desulfurized gas 22.

[0136] It should be noted, that the chemical plant 100 typically comprises further equipment, such as compressors, heat exchangers etc.; however, such further equipment is not shown in FIG. 1.

[0137] FIG. 2 shows a chemical gas plant 200 according to an embodiment of the invention, where the reforming section 210 also comprises a fired steam methane reforming reactor 104 upstream the autothermal reforming reactor 109.

[0138] The chemical plant 200 comprises a reforming section 210 with an electrically heated reforming reactor 208 housing a first catalyst, an autothermal reforming reactor 109 housing a second catalyst and a fired steam methane reforming reactor 104 housing a third catalyst. The fired reforming reactor 104 is a side fired tubular steam methane reforming reactor 104. Thus, the side fired tubular steam methane reforming reactor 104 comprises a number of tubes 106 housing the third catalyst and a number of burners 103 arranged to heat the tubes 106. For the sake of clarity, only one tube 106 is shown in FIG. 2. Fuel is fed to the burners 103 and is burned to provide the heat for the tubes 106. Hot flue gas from the burners 103 is directed to a preheating section 205 of the steam methane reforming reactor 104 and is used for preheating feed gas and steam. The electrically heated reforming reactor 108 is arranged in parallel to the combination of the fired steam methane reforming reactor 104 and the autothermal reforming reactor 109. The electrically heated reforming reactor 108 is heated by means of an electrical power supply 107.

[0139] The electrically heated reforming reactor 108 and side fired steam reforming reactor 104 are arranged to receive a first and second feed gas 25a, 25b, respectively, and to generate a first synthesis gas 30a and a pre-reformed feed gas 25b. The pre-reformed feed gas 25b exits the fired reforming reactor at a temperature of between 700° C. and 900° C. and therefore needs no further preheating prior to entering the autothermal reforming reactor 109. A stream 26 of air or oxygen is added to the autothermal reforming reactor 109. The autothermal reforming reactor 109 outputs a second synthesis gas 30b.

[0140] During operation of the chemical plant 200, a feed gas 21 comprising hydrocarbons undergoes feed purification in a desulfurization unit 101 and becomes a desulfurized gas 22. The feed gas 21 comprising hydrocarbons is e.g. natural gas or town gas. The desulfurized gas 22 is preheated in the preheating section 205 of the steam methane reformer 104 and steam 23 is added, resulting in a gas stream 24. The gas stream 24 is led to a prereforming unit 102 housing steam reforming catalyst. Typically, the prereforming unit 102 is an adiabatic prereforming unit, wherein higher hydrocarbons are reacted so that the prereformed gas 25 exiting the prereformer contains no or very small amounts of higher hydrocarbons. The prereformed gas 25 is divided into a first part 25a of the feed gas which is led to the electrically heated reforming reactor 208, and a second part 25b of the feed gas which is led to the steam methane reformer 104. The first catalyst in the electrically heated reforming reactor 108, the second catalyst in the autothermal reforming reactor 109 and the third catalyst in the steam methane reformer 104 are steam methane reforming catalysts arranged to catalyze the steam methane reforming reaction in the electrically heated reforming reactor 108, the steam methane reformer 104 and autothermal heated reforming reactor 109.

[0141] The electrically heated reforming reactor 108 generates a first synthesis gas 30a, and the steam methane reformer 104 generates a partially reformed synthesis gas 25b and the autothermal reforming reactor 109 provides a second synthesis gas 30b. The first and second synthesis gas 30a, 30b are combined to a synthesis gas stream 30 which is outlet from the reforming section 210 as a combined gas synthesis stream 30.

[0142] The combined synthesis gas stream 30 is cooled in a heat exchanger 111 to a cooled combined synthesis gas stream 30′. The cooled combined synthesis gas stream 30′ enters a post processing unit 112, viz. a water gas shift unit, and a water gas shifted synthesis gas 32 exits the water gas shift unit 212. The water gas shifted synthesis gas 32 is cooled in a second heat exchanger 113 to a cooled water gas shifted synthesis gas 32′, which enters the water separation unit 114, e.g. a flash separation unit 115. The cooled water gas shifted synthesis gas 32′ is separated into a condensate 27 and an intermediate synthesis gas 34. The intermediate synthesis gas 34 is a dry synthesis gas which is led to the downstream section 116 arranged to process the intermediate synthesis gas 34 to a chemical product 40 and an off-gas 45.

[0143] The downstream section 116 comprises e.g. an ammonia reactor to convert the intermediate synthesis gas 34 to ammonia, a methanol reactor to convert the intermediate synthesis gas 34 to methanol, or a Fischer-Tropsch reactor to convert the intermediate synthesis gas 34 to a mixture of higher hydrocarbons.

[0144] An off-gas 45 from the downstream section 116 is recycled as fuel to the burners 103 of the steam methane reformer 104. The off-gas 45 is combined with a small amount of natural gas 46 to form the fuel gas 47 sent to the burners 103 of the steam methane reformer 104. The fuel gas 47 is burnt off in the burners 103, thus heating the tubes 106 with third catalyst. In the preheating section 205, the flue gas from the burners 103 provides heat for preheating the feed gasses and exits as flue gas 48 from the preheating section 205. A heat exchange fluid 20, such as water, is used for heat exchange in the heat exchanger 211 and a heated heat exchange fluid, such as steam, is exported as stream 20′. A part of the steam is used as addition of steam 23 to the pre-sulfurized gas 22.

[0145] It should be noted, that the chemical plant 200 typically comprises further equipment, such as compressors, heat exchangers etc.; however, such further equipment is not shown in FIG. 2.

[0146] FIG. 3 shows a chemical plant 300 according to an embodiment of the invention, where the reforming section comprises four reforming reactors, namely an electrically heated reforming reactor 108 housing a first catalyst in parallel with the combination of a fired steam reforming reactor 104 housing a third catalyst and an autothermal reactor 109, housing a second catalyst, in addition to a gas heated reactor 112 housing a fourth catalyst.

[0147] The fired steam reforming reactor 104 is a side fired, tubular steam methane reforming reactor 104 comprising a number of tubes 106 housing the third catalyst and a number of burners 103 arranged to heat the tubes 106. For the sake of clarity, only one tube is shown in FIG. 3. Fuel is fed to the burners 103 and is burned to provide the heat for the tubes 106. Hot flue gas from the burners 103 is directed to a preheating section 205 of the steam methane reforming reactor 104 and is used for preheating feed gas and steam. The electrically heated reforming reactor 108 is arranged in parallel to the combination of an upstream fired steam reforming reactor 104 and the autothermal reforming reactor 109. The electrically heated reforming reactor 108 is heated by means of an electrical power supply 107.

[0148] A first part 25a of the feed gas 25 comprising hydrocarbons is led to the electrically heated reforming reactor 108 and a second part 25b of the feed gas 25 comprising hydrocarbons is led to the side fired steam reforming reactor 104. In the side fired steam reforming reactor 104 the second part 25b of the feed gas 25 is partially reformed to a partially reformed second feed gas 25b, which is fed to the autothermal reforming reactor 109 together with a stream of oxidant gas 26, such as oxygen or air.

[0149] During operation of the chemical plant 300, a feed gas 21 comprising hydrocarbons undergoes feed purification in a desulfurization unit 101 and becomes a desulfurized gas 22. The feed gas 21 comprising hydrocarbons is e.g. natural gas or town gas. The desulfurized gas 22 is preheated in the preheating section 205 of the steam methane reforming reactor 104 and steam 23 is added, resulting in a gas stream 24. The gas stream 24 is led to a prereforming unit 102 housing steam reforming catalyst. Typically, the prereforming unit 102 is an adiabatic prereforming unit, wherein higher hydrocarbons are reacted so that the prereformed gas 25 exiting the prereformer contains no or very small amounts of higher hydrocarbons. The prereformed gas 25 is divided into a first part 25a of the feed gas, which is led to the electrically heated reforming reactor 108, a second part 25b of the feed gas which is led to the fired steam methane reforming reactor 104 and a third part 25c of the feed gas which is led to the gas heated steam methane reforming reactor 112.

[0150] The first catalyst in the electrically heated reforming reactor 308, the second catalyst in the autothermal reformer 109, the third catalyst in the steam methane reforming reactor 104 and the fourth catalyst in the gas heated steam methane reforming reactor 112 are steam methane reforming catalysts arranged to catalyze the steam methane reforming reaction in the electrically heated reforming reactor 108, the autothermal reformer 109, the steam methane reforming reactor 104 and the gas heated steam methane reforming reactor 112.

[0151] The first, second and third part 25a, 25b, 25c, of the feed gas 25, respectively, undergo steam methane reforming in the electrically heated reforming reactor 108, the steam methane reforming reactor 104, the autothermal reforming reactor 109 and the gas heated steam methane reforming reactor 106, respectively. The electrically heated reforming reactor 108 generates a first synthesis gas 30a, whilst the steam methane reforming reactor 104 generates a partially reformed second feed gas 25b′ which is further reformed in the autothermal reforming reactor 109 to provide a second synthesis gas 30b. The first and second synthesis gas 30a, 30b are combined to a synthesis gas stream 31 which is inlet to the gas heated steam methane reforming reactor 112 in order to provide heat for the steam methane reforming reaction of the third part 25c of the feed gas entering the gas heated steam methane reforming reactor 112 from another side.

[0152] A synthesis gas steam 30 is outlet from the gas heated steam methane reforming reactor 112 and thereby from the reforming section 310 as a combined gas synthesis stream 30. The combined synthesis gas stream 30 is cooled in a heat exchanger 113 to a cooled combined synthesis gas stream 30′.

[0153] The cooled combined synthesis gas stream 30′ enters a water separation unit 114, such as a flash separation unit 115 arranged to separate the cooled combined synthesis gas 30′ into a condensate 27 and an intermediate synthesis gas 34 in the form of a dry synthesis gas. The dry synthesis gas 34 enters the downstream section 116 arranged to process the dry synthesis gas 34 gas to a chemical product 40 and an off-gas 45. The downstream section 116 comprises e.g. an ammonia reactor to convert the intermediate synthesis gas 34 to ammonia, a methanol reactor to convert the intermediate synthesis gas 34 to methanol, or a Fischer-Tropsch reactor to convert the intermediate synthesis gas 34 to a mixture of higher hydrocarbons.

[0154] The off-gas 45 from the downstream section 116 is recycled as fuel to the burners 103 of the fired steam methane reforming reactor 104. The off-gas 45 is combined with a small amount of natural gas 46 to form the fuel gas 47 sent to the burners 103 of the steam methane reforming reactor 104. The fuel gas 47 is burnt off in the burners 103, thus heating the tubes 106 with third catalyst. In the preheating section 305, the flue gas from the burners 303 provides heat for preheating the feed gasses and exits as flue gas 48 from the preheating section 305. A heat exchange fluid 20, such as water, is used for heat exchange in the heat exchanger 113 and a heated heat exchange fluid, such as steam, is exported as stream 20′.

[0155] It should be noted, that the chemical plant 300 typically comprises further equipment, such as compressors, heat exchangers etc.; however, such further equipment is not shown in FIG. 3.

[0156] FIG. 4 shows a chemical gas plant 400 according to an embodiment of the invention, where the reforming section 410 also comprises a gas steam methane reforming reactor 420 upstream the autothermal reforming reactor 109.

[0157] The second part of the feed gas 25b is heated and prereformed in the gas steam methane reforming reactor 420 to provide a partially reformed second feed gas 25c, and the partially reformed second feed gas 25c is led to the autothermal reforming reactor 109. The second synthesis gas 30b is utilized as heating media in heat exchange within said gas heated steam methane reforming reactor 420 to heat the second part of the feed gas 25b thereby providing a partially cooled second synthesis gas 30c. The partially cooled second synthesis gas 30c is combined with the first synthesis gas 30a to form a combined synthesis gas 30 exiting the reforming section 410.

EXAMPLE 1

[0158] Table 1 shows an example of how an ATR and an electric reformer is integrated for production of a combined synthesis gas. Firstly, by coupling the electric reformer in parallel to the ATR, the production capacity of synthesis gas is increased without additional requirements for oxygen. Secondly, the module of the synthesis gas can be changed, as the H.sub.2/CO ratio out of the ATR is 2.3, which is increased to 2.6 in the combined synthesis gas in the given case.

TABLE-US-00001 TABLE 1 Stream 25a to Synthesis gas 30 a Second Synthesis Electrically from electrically Combined Stream 25b Oxygen 26 gas 30b from ATR heated Reform- heated reforming synthesis gas to ATR 109 to ATR 109 109 ing reactor 108 reactor 108 30 T [° C.] 625 240 1050 420 950 1015 P [kg/cm.sup.2g] 39.5 39.7 38 40 39.5 38 CH.sub.4 25027 0 1291 10726 2702 3993 [Nm.sup.3/h] CO 830 0 21508 356 6908 28416 [Nm.sup.3/h] CO.sub.2 616 0 3675 264 1736 5410 [Nm.sup.3/h] H.sub.2 [Nm.sup.3/h] 1527 0 48482 654 74680 74680 N.sub.2 [Nm.sup.3/h] 0 279 279 0 0 279 O.sub.2 [Nm.sup.3/h] 0 13655 0 0 0 0 H.sub.2O 15016 132 15663 19306 9811 25474 [Nm.sup.3/h] H.sub.2/CO 2.3 10.8 2.6