Method and system for synthesizing methanol

Abstract

The present invention relates to a method for synthesizing methanol (1), wherein: a carbon-containing fuel stream (11) is supplied to a synthesis gas reactor component (13) to obtain a synthesis gas stream (2) containing hydrogen and carbon oxides, the synthesis gas stream (2) is supplied to a first reactor stage (21a) of a methanol reactor component (4) to be partially converted into methanol (1), the generation pressure when the synthesis gas stream (2) is obtained in the synthesis gas reactor component (13) is higher than the synthesis pressure when the synthesis gas stream (2) is partially converted into methanol (1) in the first reactor stage (21a), a residual gas stream (15) containing unreacted carbon oxides is obtained from the methanol reactor component (4), and the residual gas stream (15) is supplied to a circulation compressor (14) to provide The method comprises the steps of: raising the pressure of a residual gas stream (15), supplying the pressure-raised residual gas stream (15) to a methanol reactor assembly (4) for partial conversion into methanol (1), supplying the synthesis gas stream (2) to a heat recovery device (10) before supplying it to a first reactor stage (21a) to recover heat from the synthesis gas stream (2), supplying a recovery stream (6) with unreacted hydrogen from unreacted residual gas (16a) from the first reactor stage (21a) to a hydrogen recovery assembly (5) to obtain an H recovery stream (7) containing unreacted hydrogen from the recovery stream (6), and resupplying the unreacted hydrogen of the recovery stream (6) to the first reactor stage (21a) for at least partial conversion into methanol (1). The method is characterized in that the unreacted hydrogen of the recovery stream (6) is only lifted once by a recycle compressor (14) with unreacted carbon oxides from the first reactor stage (21a) before being resupplied to the first reactor stage (21a). The invention also relates to a corresponding system for the synthesis of methanol (1).

Description

[0001] The invention relates to a method for synthesizing methanol according to the preamble of claim 1 and to a system for synthesizing methanol according to the preamble of claim 15 .

[0002] In general, methanol is produced in a reactor of a system for synthesizing methanol, to which a synthesis gas stream comprising hydrogen and carbon oxides is supplied and in which an exothermic reaction for producing methanol takes place.

[0003] In principle, it is advisable to carry out the methanol synthesis at high pressure. Therefore, a synthesis gas compressor is usually provided in the system, which compresses the synthesis gas flow to the desired pressure. However, such synthesis gas compressors are particularly energy-intensive and therefore represent a significant cost factor in the methanol synthesis process.

[0004] In the prior art, there are attempts to dispense with such a synthesis gas compressor. US Pat. No. 6,881,758 B2 describes a system for producing methanol which does not require a synthesis gas compressor. Specifically, the synthesis gas is provided in a corresponding reactor at a pressure of 60 bar, for example by autothermal reforming with the addition of oxygen at elevated pressure, so that the synthesis gas can be supplied to the methanol synthesis without the need for pressure increase.

[0005] A disadvantage of this prior art is that the preferred stoichiometry for methanol synthesis cannot be achieved when the synthesis gas is produced by autothermal reforming.

[0006] Patent application WO 2005 / 108336 A1 of the prior art also describes a system for synthesizing methanol, in which no synthesis gas compressor is provided either. In the system shown in WO 2005 / 108336 A1, the synthesis gas is obtained by non-catalytic partial oxidation. Indeed, the hydrogen obtained by PSA of the residual gas from the methanol reactor is recycled to the methanol reactor, which hydrogen is not compressed at all or is compressed using its own compressor. However, on the other hand, the compression of the pure hydrogen stream is complicated and, on the other hand, it is also expensive to provide another compressor.

[0007] The prior art EP2011564A1 is the basis of the present invention, which not only does not use a synthesis gas compressor, but also provides a solution, which supplies the hydrogen gas stream obtained from the unreacted residual gas by PSA back to the recycle compressor. However, the disadvantage of the solution shown here is that the stream supplied to the PSA has been pressurized by the recycle compressor. Since the reflux from the recycle compressor outlet to the recycle compressor inlet occurs in a separate cycle, the size of the recycle compressor needs to be larger, larger than the size necessary by itself.

[0008] Based on this prior art, the object of the present invention is therefore to improve and further develop the method known from the prior art for synthesizing methanol without a synthesis gas compressor and the system known from the prior art for synthesizing methanol without a synthesis gas compressor, wherein the recirculation of hydrogen does not require a separate compressor and the size of the circulation compressor can be smaller.

[0009] With regard to the method for synthesizing methanol according to the preamble of claim 1, this object is achieved by the technical features of the characterizing portion of claim 1. With regard to the system for synthesizing methanol according to the preamble of claim 15, this object is achieved by the technical features of the characterizing portion of claim 15.

[0010] The invention is based on the discovery that the extraction of hydrogen from the hydrogen recovery can be carried out in such a way that it undergoes only one pressure increase by the circulation compressor between its discharge from the first reactor stage of the methanol synthesis and its resupply to the first reactor stage of the methanol synthesis. This avoids repeated and substantially unnecessary increases in the hydrogen pressure. As a result, the size of the circulation compressor can be reduced.

[0011] The method of the present invention is used to synthesize methanol. In the method of the present invention, a carbonaceous fuel stream is supplied to a synthesis gas reactor assembly to obtain a synthesis gas stream comprising hydrogen and carbon oxides. Therefore, the synthesis gas stream comprises hydrogen, carbon monoxide and carbon dioxide, and may also contain other components, such as nitrogen and rare gases. The synthesis gas stream may also be referred to as a fresh gas stream.

[0012] Likewise, in the method according to the invention, the synthesis gas stream is supplied to the first reactor stage of the methanol reactor assembly for partial conversion into methanol. The feature of partial conversion into methanol is based on the fact that the unconverted residue of the starting material is discharged from the methanol reactor assembly, so that the conversion is not completely carried out. The methanol reactor assembly can have multiple reactor stages, or only a single reactor stage. If the methanol reactor assembly has only a single reactor stage, the first reactor stage is the single reactor stage of the methanol reactor assembly. The first reactor stage of the methanol reactor assembly is the reactor stage of the methanol reactor assembly to which the synthesis gas stream is supplied before it or the remaining residual gas stream is supplied to other reactor stages. In this regard, in terms of process technology, the first reactor stage is the reactor stage of the methanol reactor assembly that is the most forward. This fact coincides with the fact that the synthesis gas stream can be called a fresh gas stream. In terms of process technology, each individual reactor stage of the methanol reactor assembly can have multiple individual reactors for methanol synthesis, which are connected in parallel with each other.

[0013] According to the method of the invention, a synthesis gas stream is obtained in the synthesis gas reactor assembly, the generation pressure of which is higher than the synthesis pressure when the synthesis gas stream is partially converted into methanol in the first reactor stage. In other words, the synthesis gas stream and the synthesis gas do not experience any pressure increase from the time of their generation to their arrival at the methanol reactor assembly for methanol synthesis. In particular, the synthesis gas stream does not experience any pressure increase after it is generated by a compressor located upstream of the methanol synthesis, i.e. downstream of the synthesis gas preparation. It can also be the case that the residual gas remaining after passing through the methanol reactor assembly is subjected to a pressure increase. This is explained below.

[0014] The method of the invention provides that a residual gas stream comprising unreacted carbon oxides is obtained from the methanol reactor assembly, and the residual gas stream is supplied to a circulation compressor to increase the pressure of the residual gas stream. The residual gas stream also comprises unreacted hydrogen. If the methanol reactor assembly has more than one reactor stage, the residual gas stream can be obtained after any reactor stage.

[0015] The process according to the invention further provides that the elevated pressure residual gas stream is supplied to a methanol reactor component for partial conversion into methanol.The elevated pressure residual gas stream is now recirculated to the methanol reactor component, where the residual gas stream was obtained.

[0016] The method of the present invention also provides that, before being supplied to the first reactor stage, the synthesis gas stream is supplied to a heat recovery device to recover heat from the synthesis gas stream. In other words, in terms of process technology, the heat recovery device is located between the synthesis gas reactor assembly and the methanol reactor assembly. It should be noted that the heat recovery device herein generally only represents one stage of a heat recovery assembly with multiple heat recovery devices. In other words, the situation may be that, before being supplied to the methanol reactor assembly, the synthesis gas stream is supplied to only one heat recovery device among multiple interconnected heat recovery devices.

[0017] The method of the present invention further provides that a recovery stream with unreacted hydrogen from the unreacted residual gas of the first reactor stage is supplied to a hydrogen recovery component to obtain a H recovery stream containing the unreacted hydrogen of the recovery stream. As a result, the hydrogen of the H recovery stream corresponds at least partially and preferably completely to the unreacted hydrogen of the recovery stream. The unreacted residual gas can be only a portion of the total unreacted gas from the first reactor stage. It can also be the case that the unreacted hydrogen is only a portion of the total unreacted hydrogen in the first reactor stage.

[0018] The method of the present invention provides that the unreacted hydrogen of the recovery stream is resupplied to the first reactor stage to be at least partially converted into methanol. The unreacted hydrogen of the recovery stream can be resupplied to the first reactor stage directly or indirectly. In the case of indirect supply, the unreacted hydrogen is first supplied to other devices.

[0019] The method of the present invention is characterized in that, before being resupplied to the first reactor stage, the pressure of the unreacted hydrogen of the recovery flow is only (exactly) promoted once by the recycle compressor with the unreacted carbon oxide from the first reactor stage. In other words, between the discharge of unreacted hydrogen from the first reactor stage and the resupplied of the unreacted hydrogen to the first reactor stage, boosting particularly occurs only once by the recycle compressor. As has been confirmed, because the recycle compressor promotes the pressure of the residual gas stream containing unreacted carbon oxide, the recycle compressor is boosted with unreacted carbon oxide. Similarly, the unreacted hydrogen from the first reactor stage that is not supplied to the hydrogen recovery assembly is boosted by the recycle compressor.

[0020] Therefore, unnecessary repeated pressure increases per se are avoided. It should be noted that this requirement for only one pressure increase by the circulation compressor affects only the unreacted hydrogen from the first reactor stage, which is also included in the recovery stream. If, as is usually the case, the unreacted hydrogen from the first reactor stage is not included in the recovery stream, it is not necessary for this unreacted hydrogen to undergo only one pressure increase by the circulation compressor outside the recovery stream. On the contrary, multiple pressure increases and no pressure increase at all are possible.

[0021] As described below, this resupply of unreacted hydrogen to the first reactor stage may occur indirectly such that hydrogen is supplied to the methanol reactor assembly as part of a series of other streams.

[0022] In principle, the boost of the above-mentioned unreacted hydrogen can be any amount of boost. Preferably, before at least part of the conversion into methanol, the unreacted hydrogen is boosted to a pressure higher than the H recovery stream from the hydrogen recovery assembly. It may also be the case that before being resupplied to the first reactor stage, the unreacted hydrogen is boosted to a pressure higher than the recovery stream when it is supplied to the hydrogen recovery assembly.

[0023] On the other hand, the pressurization of unreacted hydrogen can occur before it is supplied to the hydrogen recovery component. The pressure of the recovery stream may be generally improved. However, the pressurization of unreacted hydrogen can also occur after it is supplied to the hydrogen recovery component. Therefore, the pressure of the unreacted hydrogen of the H recovery stream can be improved by improving the overall pressure of the H recovery stream.

[0024] A syngas reactor assembly, a methanol reactor assembly, a heat recovery device, a recycle compressor, and a hydrogen recovery assembly may be included in a system for methanol synthesis.

[0025] The generation pressure is preferably greater than 60 bar or greater than 70 bar or greater than 80 bar. The generation pressure can also be greater than 90 bar and in particular greater than 100 bar.

[0026] In principle, the residual gas stream supplied to the recycle compressor can have any composition as long as the residual gas stream contains any proportion of unreacted carbon oxides and unreacted hydrogen of the recycle stream. However, it is preferred that the molar hydrogen content of the residual gas stream supplied to the recycle compressor is less than 90%, in particular less than 85% and further in particular less than 80%. Alternatively or additionally, the molar hydrogen content of the residual gas stream supplied to the recycle compressor can be greater than 50%, in particular greater than 60% and further in particular greater than 70%. The molar proportion of hydrogen is related to the total molar proportion of hydrogen in the residual gas stream. Therefore, this includes not only hydrogen from the recycle stream, but also other hydrogen in the residual gas stream.

[0027] The methanol reactor assembly preferably comprises a methanol separation device to obtain the unreacted residual gas of the first reactor stage and the crude methanol stream of the first reactor stage. In principle, the methanol separation device can be operated in any manner. In particular, the methanol separation device can comprise a condensing device to obtain the unreacted residual gas of the first reactor stage and the crude methanol stream of the first reactor stage by condensation.

[0028] Only a portion of the elevated pressure residual gas stream may be supplied to the methanol reactor assembly. In particular, it is preferred that a portion of the elevated pressure residual gas stream is diverted and supplied to the synthesis gas reactor assembly. In particular, it may be provided that the diverted portion of the elevated pressure residual gas stream is supplied to the fuel stream.

[0029] As already established, the methanol reactor assembly can contain only a single methanol reactor stage. A more preferred embodiment of the method is characterized in that, in terms of process technology, the methanol reactor assembly has a plurality of reactor stages for methanol synthesis, which are connected in series. Each individual reactor stage has one or more reactors. In terms of process technology, the reactors of the reactor stages can in particular be arranged in parallel. In addition, corresponding unreacted residual gas can be obtained from each of the plurality of reactor stages by means of a methanol separation device.

[0030] In terms of process technology, the fact that the reactor stages are connected in series means that the residual gas from one reactor stage (as long as it is not the last reactor stage in the series of reactor stages) is supplied directly or indirectly to the subsequent reactor stage. In principle, the above-mentioned circulation compressor can be arranged according to the needs of multiple reactor stages. In terms of process technology, a variant is to arrange the circulation compressor between two reactor stages. This means that at least a part of the unreacted residual gas from the reactor stage is supplied to the circulation compressor as a residual gas stream, and the residual gas stream with increased pressure is then supplied to the reactor stage located downstream of this reactor stage.

[0031] In principle, the H recovery stream can be directed as required, as long as at least a portion of its hydrogen is converted into methanol. According to a more preferred embodiment of the method, it is preferred in this respect from a process technology point of view that the H recovery stream is supplied to the unreacted residual gas in a reactor stage downstream of the first reactor stage. In other words, after the supply, the unreacted hydrogen of the H recovery stream is treated together with at least a portion of the unreacted residual gas from reactor stages other than the first reactor stage.

[0032] Preferably, the H2 recovery stream is supplied to a recycle compressor, thereby raising the pressure with the residual gas stream.

[0033] According to a preferred embodiment of the method, in terms of process technology, the residual gas stream is obtained by a reactor stage located downstream of the first reactor stage. In other words, the residual gas stream supplied to the circulation compressor does not come from the first reactor stage (i.e. the reactor stage to which the synthesis gas stream is directly supplied), but from a downstream reactor stage. The circulation compressor can also supply the residual gas stream with increased pressure to the first reactor stage. However, in principle, the residual gas stream with increased pressure can also be supplied to other reactor stages of a plurality of reactor stages.

[0034] A further preferred embodiment of the process according to the invention is characterized in that the residual gas stream is obtained from the last reactor stage of the plurality of reactor stages in terms of process technology.

[0035] In principle, the recovery stream can be obtained at any point in the methanol reactor assembly and from any source. It only needs to contain unreacted hydrogen from the unreacted residual gas from the first reactor stage. A first preferred variant provides that the recovery stream is at least partially shunted from the unreacted residual gas from the first reactor stage. In terms of process technology, the recovery stream can be at least partially shunted upstream of the recycle compressor.

[0036] However, the recycle stream may also have been pressurized by a recycle compressor. Therefore, a more preferred embodiment of the method is characterized in that the supply pressure of the recycle stream when it is supplied to the hydrogen recovery component is higher than the residual gas pressure when the residual gas stream is obtained from the methanol reactor component. A preferred option for increasing the pressure of the recycle stream is to compress the recycle stream in advance by a recycle compressor. Therefore, in terms of process technology, it is preferred that the recycle stream is diverted from the residual gas stream downstream of the recycle compressor.

[0037] However, the hydrogen recovery assembly can also be supplied with more than one stream (hydrogen is obtained therefrom). According to a preferred embodiment of the method, at least a portion of the synthesis gas stream is shunted to supply to the water-gas shift reaction device. The synthesis gas stream can also be supplied to the water-gas shift reaction device as a whole. It is also preferred to at least partially obtain another recovery stream from the water-gas shift reaction device, and supply it to the hydrogen recovery assembly to obtain the H recovery stream. In other words, at least a portion of the hydrogen of the H recovery stream is obtained by the other recovery stream. The water-gas shift reaction device can be included in a system for methanol synthesis.

[0038] Specifically, at least part of the carbon oxides in the synthesis gas stream can be reacted by a water-gas shift reaction in a water-gas shift reactor to form carbon dioxide and hydrogen. The stoichiometry of methanol synthesis can be improved by increasing the hydrogen content.

[0039] It may also be the case that the H recovery stream is not first supplied to the first reactor stage. According to a more preferred embodiment of the method, the H recovery stream is supplied to the synthesis gas stream. In particular, in terms of process technology, this means that the H recovery stream is supplied downstream of the synthesis gas stream of the synthesis gas reactor assembly. In other words, in terms of process technology, the H recovery stream is supplied upstream of the synthesis gas stream of the first reactor stage. However, by supplying the synthesis gas stream to the reactor stage of the first methanol reactor assembly, the hydrogen of the H recovery stream is ultimately supplied back to the first reactor stage.

[0040] In addition to the reactor for producing synthesis gas, the synthesis gas reactor assembly may have further devices. Thus, in terms of process technology, the synthesis gas reactor assembly may have devices for desulfurizing the carbon-containing combustion stream upstream of the reactor, a saturation stage for saturating the carbon-containing fuel stream with water, a pre-reformer for pre-reforming the carbon-containing stream, and / or devices for heating the carbon-containing fuel stream.

[0041] In principle, the synthesis gas stream can be obtained from the fuel stream by any means. Preferably, the oxygen-containing stream is supplied to the synthesis gas reactor assembly to obtain the synthesis gas stream. In principle, the oxygen-containing stream may also contain other components in addition to oxygen. The oxygen-containing stream may also be ambient air.

[0042] In principle, the synthesis gas stream can be obtained, for example, by steam reforming a carbonaceous stream. A more preferred embodiment of the method is characterized in that, in the synthesis gas reactor assembly, the synthesis gas stream is obtained from a carbonaceous fuel stream by autothermal reforming. In this autothermal reforming, catalytic partial oxidation provides the heat required for the endothermic reforming reaction. Compared with pure steam reforming, the advantage of autothermal reforming is that the synthesis gas stream can be provided at a higher pressure. Alternatively or additionally, the synthesis gas stream can be obtained from a carbonaceous fuel stream by partial oxidation in the synthesis gas reactor assembly.

[0043] In principle, autothermal reforming can also be carried out with ambient air. However, it is preferred that the oxygen-containing stream is obtained by an air separation unit for obtaining an oxygen stream from ambient air. The air separation unit can be further configured to obtain a nitrogen stream. In particular, the oxygen-containing stream can consist essentially of oxygen. In this way, the proportion of inert gases in the methanol synthesis is reduced, so that the size of the various devices of the system can be reduced.

[0044] According to a preferred embodiment of the method, the H recovery stream is supplied to the fuel stream. Specifically, in terms of process technology, the H recovery stream can be supplied to the fuel stream upstream of the synthesis gas reactor component.

[0045] In addition to the H recovery stream, the hydrogen recovery assembly can also output other streams. The hydrogen recovery assembly preferably outputs a purge stream. Specifically, the purge stream can be discharged for combustion.

[0046] In principle, the H recovery stream can have any composition as long as it contains unreacted hydrogen. According to a more preferred embodiment of the method, the H recovery stream has a higher molar ratio of hydrogen than the recovery stream. In other words, relative to the recovery stream, the hydrogen in the H recovery stream is enriched. It is also preferred that the H recovery stream comprises a higher molar ratio of hydrogen than the purge stream.

[0047] In principle, the hydrogen recovery assembly can work according to any desired principle, for example based on a membrane or a refrigeration unit. A preferred embodiment of the method is characterized in that the hydrogen recovery assembly has a pressure swing adsorption device (PSA) for obtaining a H recovery stream from the recovery stream. In this way, a high degree of hydrogen recovery can be achieved in the H recovery stream. Similarly, the pressure loss in this pressure swing adsorption device is still acceptable. In this case, high hydrogen purity is basically not required, but can be achieved. Therefore, the H recovery stream can be basically composed of hydrogen.

[0048] The system of the present invention is used for synthesizing methanol and comprises a syngas reactor assembly for obtaining a syngas stream containing hydrogen and carbon oxides from a carbon-containing fuel stream, a methanol reactor assembly having a first reactor stage, a heat recovery device for recovering heat from the syngas stream, a hydrogen recovery assembly and a circulating compressor.

[0049] In the system of the invention, the synthesis gas stream is supplied to the first reactor stage for partial conversion into methanol, which is obtained in the synthesis gas reactor assembly at a production pressure higher than the synthesis pressure when the synthesis gas stream is partially converted into methanol in the first reactor stage.

[0050] Furthermore, in the system of the present invention, a residual gas stream containing unreacted carbon oxides is obtained from the methanol reactor component, and the residual gas stream is supplied to a circulating compressor to increase the pressure of the residual gas stream, wherein the residual gas stream with increased pressure is supplied to the methanol reactor component to be partially converted into methanol, wherein the synthesis gas stream is supplied to a heat recovery device before being supplied to the first reactor stage, wherein a recovery stream of unreacted hydrogen from the unreacted residual gas of the first reactor stage is supplied to a hydrogen recovery device to obtain an H recovery stream containing unreacted hydrogen of the recovery stream, and the unreacted hydrogen of the recovery stream is resupplied to the first reactor stage to be at least partially converted into methanol.

[0051] The process according to the invention is characterized in that the pressure of the unreacted hydrogen of the recovery stream is raised only once by means of a recycle compressor with unreacted carbon oxides from the first reactor stage before being fed back to the first reactor stage.

[0052] The features, advantages, and properties of the system of the present invention correspond to the features, advantages, and properties of the method of the present invention, and vice versa.

[0053] Further details, features, objects and advantages of the invention are described below with reference to the accompanying drawings, which show only an embodiment.

[0054] Figure 1 FIG. 1 is a schematic flow chart of a system for implementing the method of the present invention according to a first embodiment.

[0055] Figure 2 FIG. 2 is a schematic flow chart of a system for implementing the method of the present invention according to a second embodiment.

[0056] Figure 3 FIG. 1 is a schematic flow chart of a system for implementing the method of the present invention according to a third embodiment.

[0057] Figure 4 FIG. 4 is a schematic flow chart of a system for implementing the method of the present invention according to a fourth embodiment, and FIG.

[0058] Figure 5 Shown is a schematic flow chart of a system for implementing the method of the present invention according to a fifth embodiment.

[0059] Figure 1 The system shown in the first embodiment of the system according to the invention is for synthesizing methanol 1 and can be operated according to the method according to the invention.

[0060] A synthesis gas stream 2 consisting essentially of hydrogen, carbon monoxide and carbon dioxide is obtained from a fuel stream 11 formed from natural gas (i.e. containing carbon), which is supplied to a synthesis gas reactor assembly 13. Autothermal reforming takes place in the synthesis gas reactor assembly 13 to obtain the synthesis gas stream 2. An oxygen-containing stream 22 is supplied to the autothermal reforming, where the oxygen-containing stream 22 is obtained from an air separation unit 23 and consists essentially of oxygen. The air separation unit 23 is configured to obtain an oxygen stream, in this case the oxygen-containing stream 22, from ambient air. The synthesis gas stream 2 is obtained at a generation pressure of essentially 80 bar.

[0061] The synthesis gas stream 2 is first supplied to a heat recovery device, in which the synthesis gas stream 2 is cooled, in this way recovering part of the heat generated in the autothermal reforming. The synthesis gas stream 2 of the first reactor stage 21a is supplied to the methanol reactor assembly 4, in which methanol synthesis occurs, and at least part of the synthesis gas stream 2 is converted into methanol 1. The methanol synthesis occurs at a synthesis pressure of more than 70 bar. Therefore, no synthesis gas compressor is required to increase the pressure of the synthesis gas stream 2.

[0062] The system has a pressure swing adsorption system 24 (which may also be referred to as PSA), a designed hydrogen recovery assembly 5, which obtains a H recovery stream 7 from a recovery stream 6, the H recovery stream 7 being substantially composed of hydrogen. Likewise, residual gas is output from the hydrogen recovery assembly 5 as a purge stream, and then burned in a combustion heating device of the system (not shown). The H recovery stream 7 is supplied to the synthesis gas stream 2.

[0063] like Figure 1 As shown, the system of the first embodiment also has a circulation compressor 14, which compresses a residual gas stream 15. The residual gas stream 15 contains unreacted residual gas 16b, which then essentially contains those components of the synthesis gas that have not been converted into methanol 1 in the methanol reactor component 4. Accordingly, the residual gas stream 15 specifically contains unreacted carbon oxides. The residual gas stream 15 with increased pressure is resupplied to the methanol reactor component 4 of the first part.

[0064] Unreacted residual gas 16a, b is obtained from the methanol separation device 17 of the methanol reactor assembly 4, which here comprises two condensation devices 18a, b. Unreacted residual gas 16a, b on the one hand and corresponding crude methanol stream 19a, b on the other hand are obtained by condensation in each of them. The crude methanol stream 19a, b is then supplied to the distiller 20 of the system to obtain methanol 1 from the crude methanol stream 19a, b.

[0065] exist Figure 1In the system of the embodiment shown, in terms of process technology, the methanol reactor assembly 4 has two reactor stages 21a, b connected in series for methanol synthesis. In this embodiment, the first reactor stage 21a has two adiabatic reactors arranged in parallel with each other, while the second reactor stage 21b has a single adiabatic reactor. The product streams from each reactor stage 21a, b are supplied to two condensing devices 18a, b, respectively. The reactor stage 21a to which the synthesis gas stream 2 is directly supplied is called the first reactor stage 21a. In terms of process technology, the reactor stage 21b is located downstream of the first reactor stage 21a, and is supplied with the unreacted residual gas 16a from the first reactor stage 21a to be converted into methanol 1.

[0066] exist Figure 1 In the embodiment shown, a recovery stream 6 is branched off from a residual gas stream 15, the pressure of which is increased by means of a recycle compressor. In terms of process technology, this residual gas stream 15 supplied to the recycle compressor 14 is obtained not from the unreacted residual gas 16a of the first reactor stage 21a, but from the unreacted residual gas 16b of the reactor stage located downstream of the first reactor stage 21a, i.e. the second reactor stage 21b.

[0067] Nevertheless, in addition to the unreacted carbon oxides already mentioned, the residual gas stream 15 also contains unreacted hydrogen from the first reactor stage 21a. Any unreacted hydrogen from the residual gas 16a of the first reactor stage 21a is supplied to the second reactor stage 21b. Since the hydrogen in the second reactor stage 21b is also not completely reacted, the unreacted residual gas 16b from the second reactor stage 21b also contains unreacted hydrogen from the first reactor stage 21a.

[0068] Because the recovery stream 6 is separated from the residual gas stream 15 at increased pressure, the H recovery stream 7 also contains unreacted hydrogen from the residual gas 16a of the first reactor stage 21a. Specifically, the second part of the residual gas stream 15 at increased pressure is diverted as the recovery stream 6. Because the H recovery stream 7 is supplied to the synthesis gas stream 2, the unreacted hydrogen from the residual gas 16a of the first reactor stage 21a is supplied back to the recovery stream 6 of the first reactor stage 21 to be converted into methanol. However, between leaving the first reactor stage 21a and being resupplied to the first reactor stage 21a, the unreacted hydrogen from the recovery stream 6 as a component of the residual gas stream 15 is subjected to only one pressure increase through the circulation compressor 14 together with the unreacted carbon oxides in the residual gas 15. Afterwards, the residual gas stream 15 compressed by the circulation compressor 14 is then directly supplied to the first reactor stage 21a of the first part mentioned above.

[0069] Figure 2A second embodiment of the system of the present invention is shown, which is Figure 1 The embodiment shown differs in that, in terms of process technology, the recycle compressor 14 is arranged between the first reactor stage 21a and the reactor stage 21b downstream thereof. Therefore, the residual gas stream 15 supplied to the recycle compressor 14 is obtained from the unreacted residual gas 16a of the first reactor stage 21a. The residual gas stream 15 containing unreacted carbon oxides compressed by the recycle compressor 14 is supplied to the reactor stage 21b downstream of the first reactor stage 21a. The unreacted residual gas 16b from the reactor stage 21b is supplied back to the first reactor stage 21a without further compression. In contrast to the first embodiment, in terms of process technology, the recycle stream 6 is obtained from the unreacted residual gas 16a of the first reactor stage 21a, wherein, similar to the first embodiment, the recycle stream 6 is split downstream of the recycle compressor 14. Therefore, in the second embodiment, likewise, before the unreacted hydrogen is supplied back to the first reactor stage 21a, the unreacted hydrogen from the residual gas 16a of the first reactor stage 21a in the recycle stream 6 containing unreacted carbon oxides is pressurized only once by the recycle compressor 14.

[0070] exist Figure 3 In the third embodiment shown, the recycle stream 6 is obtained from the residual gas 16a of the first reactor stage 21a in a similar manner to the second embodiment. However, in contrast to the second embodiment, there is no circulation compressor 14 arranged between the first reactor stage 21a and the second reactor stage 21b. Instead, as in the first embodiment, the circulation compressor 14 is arranged downstream of the second reactor stage 21b in terms of process technology.

[0071] In contrast to the first and second embodiments, in the third embodiment, the H recovery stream 7 is supplied to the residual gas 16b of the second reactor stage 21b downstream of the first reactor stage 21a. Specifically, the supply is before the pressure increase of the circulation compressor 14. The hydrogen in the H recovery stream 7 corresponds to the unreacted hydrogen from the residual gas 16a of the first reactor stage 21a in the recovery stream 6, which is pressurized by the circulation compressor 14 with other unreacted residual gas 16b of the second reactor stage 21b, in particular with unreacted carbon oxides. This pressure increase only occurs once before the unreacted hydrogen is resupplied to the first reactor stage 21a, which compensates for the lack of pressure increase due to the lack of a synthesis gas compressor.

[0072] Furthermore, the third embodiment provides that part of the increased-pressure residual gas flow 15 is branched off and supplied to the fuel flow 11. However, this branching off of part of the increased-pressure residual gas flow 15 can also be omitted.

[0073] Figure 4 The system according to the fourth embodiment shown corresponds to Figure 3 The third embodiment shown. However, it has a water-gas shift reaction device 9, to which part of the synthesis gas flow 2 is supplied after being supplied to the heat recovery device 10. The water-gas shift reaction occurring in the water-gas shift reaction device 9 increases the hydrogen content in the diverted part of the synthesis gas flow 2. Part of the synthesis gas flow 2 from the water-gas shift reaction device 9 is diverted in this way and subjected to a water-gas shift reaction, where another recovery flow is formed, which is supplied to the hydrogen recovery component 5 together with the recovery flow 6. Similarly, as Figure 3 As in the embodiment shown, the H recovery stream 7 is fed to the residual gas 16b of the second reactor stage 21b downstream of the first reactor stage 21a, so that in this embodiment too, a pressure increase with unreacted carbon oxides occurs via the recycle compressor 14.

[0074] Figure 5 The fifth embodiment shown provides for the arrangement of a recycle compressor 14 between the reactor stages 21a, b of the methanol reactor assembly 4, as in the second embodiment on which the fifth embodiment is based. In contrast to the second embodiment, a recycle stream 6 is obtained from the residual gas 16b of the second reactor stage 21b. The hydrogen in this recycle stream 6 undergoes a pressure increase by a recycle compressor, in particular before it is supplied to the second reactor stage 21b.

Claims

1. A method for synthesizing methanol (1), wherein: A carbon-containing fuel stream (11) is supplied to a synthesis gas reactor assembly (13) to obtain a synthesis gas stream (2) containing hydrogen and carbon oxides, the synthesis gas stream (2) is supplied to a first reactor stage (21a) of a methanol reactor assembly (4) to be partially converted into methanol (1), the generation pressure when the synthesis gas stream (2) is obtained in the synthesis gas reactor assembly (13) is higher than the synthesis pressure when the synthesis gas stream (2) is partially converted into methanol (1) in the first reactor stage (21a), a residual gas stream (15) containing unreacted carbon oxides is obtained from the methanol reactor assembly (4), the residual gas stream (15) is supplied to a circulation compressor (14) to increase the pressure of the residual gas stream (15), and the residual gas stream (15) with increased pressure is supplied to the methanol reactor assembly (4) to be partially converted into methanol (1), Before being supplied to the first reactor stage (21a), the synthesis gas stream (2) is supplied to a heat recovery device (10) to recover heat from the synthesis gas stream (2), a recovery stream (6) of unreacted hydrogen with unreacted residual gas (16a) from the first reactor stage (21a) is supplied to a hydrogen recovery component (5) to obtain an H recovery stream (7) containing unreacted hydrogen from the recovery stream (6), and the unreacted hydrogen of the recovery stream (6) is resupplied to the first reactor stage (21a) to be at least partially converted into methanol (1), characterized in that before being resupplied to the first reactor stage (21a), the unreacted hydrogen of the recovery stream (6) is only lifted once with unreacted carbon oxides from the first reactor stage (21a) by a recycle compressor (14).

2. The method according to claim 1, characterized in that The methanol reactor component (4) comprises a methanol separation device (17) to obtain unreacted residual gas (16a) from the first reactor stage (21a) and a crude methanol stream (19a) from the first reactor stage (21a), wherein the methanol separation device (17) comprises a condensation device (18a) to obtain unreacted residual gas (16a) from the first reactor stage (21a) and a crude methanol stream (19a) from the first reactor stage (21a) by condensation.

3. The method according to claim 2, characterized in that A portion of the elevated pressure residual gas stream (15) is branched off and supplied to a synthesis gas reactor assembly (13), wherein the branched portion of the elevated pressure residual gas stream (15) is supplied to a fuel stream (11).

4. The method according to any one of claims 1 to 3, characterized in that From a process technology perspective, a methanol reactor assembly (4) has two reactor stages (21a, b) for methanol synthesis, which are connected in series, wherein, from a process technology perspective, a circulation compressor (14) is located between the two reactor stages (21a, b), and wherein corresponding unreacted residual gases (16a, b) are obtained from each of the two reactor stages (21a, b) via a methanol separation device (17).

5. The method according to claim 4, characterized in that In terms of process technology, the H recovery stream (7) is fed to the unreacted residual gas (16b) of a reactor stage (21b) located downstream of the first reactor stage (21a), wherein the H recovery stream (7) is fed together with the residual gas stream (15) to a circulation compressor (14) to increase the pressure.

6. The method according to claim 4, characterized in that In terms of process technology, a residual gas stream (15) is obtained from a reactor stage (21b) located downstream of a first reactor stage (21a), wherein a circulation compressor (14) supplies the residual gas stream (15) at increased pressure to the first reactor stage (21a).

7. The method according to claim 6, characterized in that The residual gas stream ( 15 ) is obtained from the reactor stage ( 21 b ) of the two reactor stages ( 21 a , b ) which is located last in terms of process technology.

8. The method according to claim 1, characterized in that In terms of process technology, the recovery stream (6) is at least partially branched off from the unreacted residual gas (16a) of the first reactor stage (21a).

9. The method according to claim 8, characterized in that In terms of process technology, the supply pressure of the recovery stream (6) when it is supplied to the hydrogen recovery component (5) is higher than the residual gas pressure when the residual gas stream (15) is obtained from the methanol reactor component, wherein the recovery stream (6) is at least partially diverted from the residual gas stream (15) downstream of the recycle compressor (14).

10. The method according to claim 1, characterized in that The H recovery stream (7) is supplied to the synthesis gas stream (2).

11. The method according to claim 1, characterized in that In order to obtain a synthesis gas stream (2), an oxygen-containing stream (22) is supplied to a synthesis gas reactor component (13), wherein, in the synthesis gas reactor component (13), the synthesis gas stream (2) is obtained by autothermal reforming or by partial oxidation of a carbon-containing fuel stream (11), wherein the oxygen-containing stream (22) is obtained by an air separation device (23) for obtaining an oxygen stream from ambient air.

12. The method according to claim 1, characterized in that In terms of process technology, the H recovery stream (7) is fed to the fuel stream (11) which is located upstream of the synthesis gas reactor component (13), wherein the hydrogen recovery component (5) outputs a purge stream (8) which is further discharged for combustion.

13. The method according to claim 1, characterized in that The H recovery stream (7) has a higher molar proportion of hydrogen than the recovery stream (6).

14. The method according to claim 1, wherein: The hydrogen recovery component (5) has a pressure swing adsorption device (24) for obtaining a H recovery flow (7) from the recovery flow (6).

15. The method according to claim 1, wherein: The system used in the method has a synthesis gas reactor component (13) for obtaining a synthesis gas stream (2) containing hydrogen and carbon oxides from a carbon-containing fuel stream (11), a methanol reactor component (4) having a first reactor stage (21a), a heat recovery device (10) for recovering heat from the synthesis gas stream (2), a hydrogen recovery component (5) and a recycle compressor (14), the synthesis gas stream (2) is supplied to the first reactor stage (21a) for partial conversion into methanol (1), and the synthesis gas stream (2) is obtained in the synthesis gas reactor component (13) at a pressure higher than the synthesis pressure when the synthesis gas stream (2) is partially converted into methanol (1) in the first reactor stage (21a), and a residual gas stream (15) containing unreacted carbon oxides is produced by the methanol recovery component (5). The present invention relates to a method for preparing a syngas stream (20) comprising: obtaining a syngas stream (15) from an alcohol reactor component (4), supplying the residual gas stream (15) to a circulation compressor (14) to increase the pressure of the residual gas stream (15), supplying the residual gas stream (15) with increased pressure to a methanol reactor component (4) to partially convert it into methanol (1), supplying the synthesis gas stream (2) to a heat recovery device (10) before supplying it to a first reactor stage (21a), supplying a recovery stream (6) having unreacted hydrogen from the unreacted residual gas (16a) from the first reactor stage (21a) to a hydrogen recovery device (5) to obtain an H recovery stream (7) containing unreacted hydrogen of the recovery stream (6), and resupplying the unreacted hydrogen of the recovery stream (6) to the first reactor stage (21a) to at least partially convert it into methanol (1).

Images