Method and apparatus for methanol synthesis
Through the combination of the circulating compressor and the heat recovery device, the problem of high cost of increasing hydrogen pressure in the prior art is solved, and a more economical and efficient methanol synthesis process is achieved.
Patent Information
- Application Number
- CN202080040115.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2019-06-13
- Filing Date
- 2020-05-26
- Publication Date
- 2024-12-06
- Estimated Expiration
- 2040-05-26
AI Technical Summary
In existing methanol synthesis equipment, the recovered hydrogen needs to be compressed, resulting in the synthesis gas compressor having to be larger, with higher energy consumption and increased costs.
The unreacted residual gas is circulated and pressurized by a circulating compressor, and the synthesis gas flow is pressurized through a heat recovery device to reduce the dependence on the synthesis gas compressor, avoid repeated pressurization, and increase the pressure of hydrogen.
It reduces the cost of increasing hydrogen pressure, improves the economy of methanol synthesis, reduces energy consumption, and optimizes equipment design.
Smart Images
Figure CN114127037B_ABST
Abstract
Description
[0001] The invention relates to a method for methanol synthesis according to the preamble of claim 1 and to an apparatus for methanol synthesis according to the preamble of claim 16.
[0002] Methanol is usually produced in a reactor of a plant for methanol synthesis, into which a synthesis gas stream containing hydrogen and carbon oxides is fed and in which an exothermic reaction for producing methanol takes place.
[0003] Depending on the way the synthesis gas stream is obtained and on which energy carrier is used as the basis for the synthesis gas, the proportion of hydrogen in the fresh synthesis gas may be lower than the proportion sought. In particular, in order to improve the stoichiometry of the methanol synthesis, it is often appropriate to recover unreacted hydrogen from the residual gas from the reactor and to recycle this hydrogen to the methanol reactor.
[0004] For this type of cycle, the pressure of the recovered hydrogen must be increased before it is fed to the reactor.
[0005] EP 3 205 622 B1 is the prior art closest to the present invention, which discloses a device for methanol synthesis. In this device, a hydrogen stream obtained from the residual gas of methanol synthesis by PSA is fed into the synthesis gas stream. The feeding is operatively carried out upstream of the synthesis gas compressor, so that before feeding to the methanol reactor, the hydrogen pressure from the hydrogen stream is increased together with the synthesis gas by the synthesis gas compressor.
[0006] A disadvantage of this prior art is that the recovered hydrogen needs to be compressed, which means that the synthesis gas compressor must be larger than before and also consumes more energy for compression.
[0007] Starting from this prior art, the object of the present invention consists in improving the process known from the prior art for methanol synthesis such that the pressure of the recovered hydrogen can be increased in a more economical manner.
[0008] For a method for methanol synthesis according to the preamble of claim 1, this object is achieved by the features of the characterizing part of claim 1. For an apparatus for methanol synthesis according to the preamble of claim 16, this object is achieved by the features of the characterizing part of claim 16.
[0009] The inventive concept behind the present invention is that the pressure increase of the hydrogen obtained by the hydrogen recovery unit can also be carried out by a recycle compressor. The recycle compressor is used to circulate most of the unreacted residual gas through the methanol reactor. Usually, only the substream of the unreacted residual gas is fed to the hydrogen recovery unit, because usually the entire substream-minus the hydrogen recovered-can be discharged as a purge gas afterwards. If in order to re-merge the recovered hydrogen with the remaining unreacted residual gas by recycle compressor pressurization, then in some cases, the pressure of the remaining unreacted residual gas must be reduced, because hydrogen recovery is also accompanied by a specific pressure drop. However, it has been shown that, despite this, replacing the pressurization of the recovered hydrogen from the synthesis gas compressor with a recycle compressor will result in cost reduction.
[0010] The proposed method is used for methanol synthesis. In the proposed method, a carbonaceous energy carrier stream is fed to a synthesis gas reactor configuration for obtaining a synthesis gas stream having hydrogen and carbon oxides. The synthesis gas stream thus comprises hydrogen, carbon monoxide and carbon dioxide and may also comprise other components, such as, in particular, nitrogen and noble gases. The synthesis gas stream may also be described as a fresh gas stream.
[0011] Furthermore, in the proposed method, the synthesis gas stream is fed to a heat recovery device to recover heat from the synthesis gas stream and then fed to a synthesis gas compressor for pressurization. The synthesis gas compressor may have multiple stages. It is important that the synthesis gas stream is fed between the heat recovery device and the synthesis gas compressor of another device or multiple other devices. Furthermore, it should be noted that the heat recovery device typically constitutes only one stage of a heat recovery configuration having multiple heat recovery devices. In other words, the synthesis gas stream may be fed to only one heat recovery device in multiple heat recovery devices connected together.
[0012] According to the proposed method, at least part of the pressurized synthesis gas stream is fed to the first reactor stage of the methanol reactor configuration for partial conversion into methanol. Preferably, substantially all of the pressurized synthesis gas stream is fed to the first reactor stage. However, it may also be the case that part of the synthesis gas stream is diverted upstream. The characteristic of partial conversion into methanol is that the conversion is incomplete due to the discharge of the unconverted residue of the educt from the methanol reactor configuration. The methanol reactor configuration may have multiple reactor stages or only a single reactor stage. If the methanol reactor configuration does not have multiple reactor stages, the first reactor stage is the only reactor stage of the methanol reactor configuration. The first reactor stage of the methanol reactor configuration is a reactor stage of such a methanol reactor configuration, to which at least part of the synthesis gas stream feed is fed before it, or the remaining residual gas stream is fed to another reactor stage. Therefore, the first reactor stage is the first operational reactor stage of the methanol reactor configuration. This situation is consistent with the description of the possibility of the synthesis gas stream as a fresh gas stream. Each individual reactor stage of the methanol reactor configuration can therefore have multiple independent reactors for methanol synthesis, which are operably parallel to each other.
[0013] In the proposed method, a residual gas stream with unreacted carbon oxides is obtained from a methanol reactor configuration, and the residual gas stream is fed to a recycle compressor to pressurize the residual gas stream. The residual gas stream may also contain unreacted hydrogen. If the methanol reactor configuration has more than one reactor stage, the residual gas stream may be obtained after any reactor stage. The term "unreacted substances" used here and below is understood to mean substances that have been sent to a reactor stage of a methanol reactor configuration, in particular the first reactor stage, as an educt for methanol synthesis, and then left the reactor stage without participating in the methanol synthesis reaction.
[0014] Furthermore, the proposed method provides for feeding the pressurized residual gas stream to a methanol reactor configuration for partial conversion into methanol. This therefore involves recycling the now pressurized residual gas stream to the methanol reactor configuration from which it has in fact been obtained.
[0015] Furthermore, the proposed method provides that a recycle stream formed from the unreacted residual gas of the first reactor stage is fed to a hydrogen recovery arrangement to obtain an H recycle stream. In the case of unreacted residual gas, this may mean that this is only a portion of the total unreacted gas from the first reactor stage. For example, the recycle stream can be obtained from the unreacted residual gas by diversion.
[0016] The proposed method provides that the H circulation stream has unreacted hydrogen from the unreacted residual gas, which is fed again to the first reactor stage for at least partial conversion into methanol. It may be the case that the unreacted hydrogen is only a part of the total unreacted hydrogen from the first reactor stage and / or a part of the total unreacted hydrogen from the unreacted residual gas. In this case, the unreacted hydrogen of the H circulation stream can be fed back to the first reactor stage directly and indirectly. In the case of indirect feeding, the unreacted hydrogen is then initially fed to other devices.
[0017] The proposed method is characterized in that the pressure of at least part of the unreacted hydrogen of the H circulation stream from the first reactor stage is raised again to its re-feeding to the first reactor stage together with the unreacted carbon oxides by means of a circulation compressor. In other words, for at least part of the unreacted hydrogen in the H circulation stream between the outlet of the unreacted hydrogen from the first reactor stage and the re-feeding of this unreacted hydrogen to the first reactor stage, the pressure is raised by means of a circulation compressor. Since - as previously mentioned - the circulation compressor compresses the residual gas stream with the unreacted carbon oxides, the compression of this unreacted hydrogen is then carried out by means of the circulation compressor together with the unreacted carbon oxides. Preferably, the pressure of substantially all of the unreacted hydrogen of the H circulation stream from the first reactor stage is raised to its re-feeding to the first reactor stage together with the unreacted carbon oxides by means of a circulation compressor.
[0018] In principle, the pressure of the unreacted hydrogen or part of the hydrogen of the H circulation flow can be increased several times before re-feeding to the first reactor stage. Therefore, on the one hand, in addition to being pressurized by the circulation compressor, it is possible to additionally compress by the synthesis gas compressor. This may be the case: this additional compression may only involve part of the unreacted hydrogen. On the other hand, it may also be the case that the unreacted hydrogen or part thereof is pressurized several times by the circulation compressor before re-feeding to the first reactor stage. This is especially the case when circulating from the circulation compressor outlet side to the input side of the circulation compressor.
[0019] However, a preferred embodiment of the present invention is characterized in that the unreacted hydrogen of the H circulation flow is at least partially, preferably substantially all, precisely pressurized once by the circulation compressor together with the unreacted carbon oxides, from the first reactor stage to its re-feeding to the first reactor stage. Therefore, at least part of the unreacted hydrogen of the H circulation flow from the first reactor stage is pressurized only by the circulation compressor together with the unreacted carbon oxides. Therefore, it is not pressurized by another compressor, etc. In this way, unnecessary repeated pressurization is avoided. It should be noted that this requirement of precisely pressurizing once by the circulation compressor only relates to the unreacted hydrogen from the first reactor stage, which is also included in the H circulation flow, and is also preferably only a part of the unreacted hydrogen. Therefore, if - as is usually the case - the unreacted hydrogen is discharged from the first reactor stage, it is not included in the H circulation flow, then the unreacted hydrogen does not need to be precisely pressurized once by the circulation compressor outside the recovery flow. In addition, multiple pressurizations may also be performed.
[0020] As will be described below, the refeeding of unreacted hydrogen to the first reactor stage may be performed indirectly in such a way that hydrogen is fed to the first reactor stage as part of a series of other streams.
[0021] In principle, the pressurization of the above-mentioned unreacted hydrogen can be any amount of pressurization. Preferably, before being at least partially converted into methanol, the unreacted hydrogen is pressurized to a pressure higher than the pressure of the H circulating stream from the hydrogen recovery configuration. Similarly, it can be the case that the unreacted hydrogen is pressurized to a pressure higher than the pressure of the recovery stream when feeding to the hydrogen recovery configuration before it is re-fed to the first reactor stage.
[0022] On the one hand, the pressurization of unreacted hydrogen can be carried out before being fed to the hydrogen recovery configuration. Therefore, it may be the following situation: the recovery stream is pressurized as a whole. However, the pressurization of unreacted hydrogen can also be carried out after being fed to the hydrogen recovery configuration. Therefore, the pressurization of the unreacted hydrogen of the H circulation flow can be carried out, for example, by the overall pressurization of the H circulation flow.
[0023] A synthesis gas reactor arrangement, a synthesis gas compressor, a methanol reactor arrangement, a heat recovery unit, a recycle compressor and a hydrogen recovery arrangement may be included in an apparatus for synthesizing methanol.
[0024] Preferably, the production pressure of the synthesis gas stream obtained by the synthesis gas reactor arrangement is greater than 40 bar, preferably greater than 50 bar, in particular greater than 60 bar, more in particular greater than 70 bar.
[0025] A preferred embodiment of the method is characterized in that the pressure of the pressurized synthesis gas stream is greater than 60 bar, preferably greater than 70 bar, in particular greater than 80 bar, more preferably greater than 90 bar.
[0026] In principle, the residual gas stream fed to the recycle compressor can have any composition, as long as the residual gas stream contains unreacted hydrogen and unreacted carbon oxides (usually in any proportion) from the recovery stream. However, preferably, the hydrogen molar ratio of the residual gas stream fed to the recycle compressor is less than 90%, particularly less than 85%, more particularly less than 80%. Alternatively or in addition, the hydrogen molar ratio of the residual gas stream fed to the recycle compressor is greater than 50%, particularly greater than 60%, more particularly greater than 70%. The hydrogen molar ratio refers to the overall hydrogen molar ratio of the residual gas stream. This includes not only unreacted hydrogen from the H recycle stream, but also other hydrogen in the residual gas stream.
[0027] Preferably, the methanol reactor configuration comprises: a methanol separation device for obtaining unreacted residual gas of the first reactor stage and a raw methanol stream from the first reactor stage. In principle, the methanol separation device can function in any manner. In particular, the methanol separation device can comprise: a condensation device for obtaining unreacted residual gas of the first reactor stage and a raw methanol stream from the first reactor stage by condensation.
[0028] This may be the case when only part of the compressed residual gas stream is fed to the methanol reactor arrangement. In particular and preferably, part of the pressurized residual gas stream is branched off and fed to the synthesis gas reactor arrangement. Thus, particularly preferably, the branched part of the pressurized residual gas stream can be fed to the energy carrier stream.
[0029] As mentioned above, in principle, the methanol reactor configuration may only include a single methanol reactor stage. Another preferred embodiment of the method is characterized in that the methanol reactor configuration has a plurality of reactor stages for methanol synthesis, which are operably connected in series. Therefore, each independent reactor stage can have one or more reactors. In this regard, in particular, the reactors of the reactor stages can be operably connected in parallel. In addition, it can be the case that the corresponding unreacted residual gas is obtained from each of the plurality of reactor stages by the methanol separation device.
[0030] In fact, the reactor stages are operably connected in series, meaning that the residual gas from one reactor stage is fed directly or indirectly to the corresponding adjacent downstream reactor stage, as long as it is not the last reactor stage in a series of reactor stages. In principle, the above-mentioned recycle compressor can be constructed in any way for multiple reactor stages. In a variant, the recycle compressor is operably connected between two reactor stages. This means that at least part of the unreacted residual gas from the reactor stage is fed to the recycle compressor as a residual gas stream, and then the pressurized residual gas stream is fed to the reactor stage arranged downstream of the reactor stage.
[0031] In principle, the H circulation stream can go anywhere, as long as at least a portion of its hydrogen is converted into methanol. According to another preferred embodiment of the method, it is preferred that the H circulation stream is fed to the unreacted residual gas from the reactor stage operably located downstream of the first reactor stage. In other words, after the unreacted hydrogen of the H circulation stream is fed to the reactor stage outside the first reactor stage together with at least part of the unreacted residual gas, the unreacted hydrogen of the H circulation stream is processed. In this way, the H circulation stream "bypasses (by-pass)" one or more reactor stages after the first reactor stage. The advantage of this type of strategy is that, in this way, the pressure drop of the H circulation stream caused by hydrogen recovery is substantially parallel to the pressure drop of the unreacted residual gas of the downstream reactor stage in the reactor stage. In other words, the corresponding pressures of the unreacted residual gas and the H circulation stream are closer to each other, and then the pressure drop generated when the combination is reduced by balancing to a lower pressure level.
[0032] Preferably, the H recycle stream is fed together with the residual gas stream to a recycle compressor for increase.
[0033] According to a preferred embodiment of the method, the residual gas stream is obtained from a reactor stage operably located downstream of the first reactor stage. In other words, the residual gas stream fed to the circulating compressor is not derived from the first reactor stage (i.e., the reactor stage to which at least part of the synthesis gas stream is directly fed), but a downstream reactor stage. In addition, the pressurized residual gas stream from the first reactor stage can be fed to a circulating booster. However, in principle, the pressurized residual gas stream can be fed to another reactor stage in a plurality of reactor stages. Similarly, it can be the following situation: the pressurized residual gas stream is separated and fed to a plurality of reactor stages in a plurality of reactor stages.
[0034] Another preferred embodiment of the proposed method is characterized in that the residual gas stream is obtained from the reactor stage which is in the last operable position of the plurality of reactor stages. This variant and the previous variants imply a reduction in the necessary pressure drop resulting from the combined streams.
[0035] In principle, the recovery stream can be obtained at any position and any source in the methanol reactor configuration. The recovery stream comprises unreacted hydrogen from the unreacted residual gas of the first reactor stage. In the first preferred variation, at least part of the recovery stream is shunted from the unreacted residual gas of the first reactor stage. It can be that at least part of the recovery stream is operably shunted upstream of the recycle compressor.
[0036] However, it may also be the case that the pressure of the recovery stream has been increased by a recycle compressor. Therefore, another preferred embodiment of the method is characterized in that the recovery stream is fed to the hydrogen recovery configuration at a feed pressure that is higher than the residual gas pressure when the residual gas stream is obtained from the methanol reactor configuration. A preferred possible way to increase the pressure of the recovery stream is to first compress it by a recycle compressor. Therefore, preferably, at least part of the recovery stream is diverted from the residual gas stream downstream of the recycle compressor.
[0037] However, it is also possible that more than one stream is fed to the hydrogen recovery configuration to obtain hydrogen therefrom. According to a preferred embodiment of the method, for example, at least a portion of the synthesis gas stream (particularly a pressurized synthesis gas stream) is diverted for feeding to a water-gas shift reaction unit. It may also be the case that all of the synthesis gas stream (preferably pressurized) is fed to a water-gas shift reaction unit. It is also preferred that at least a portion of the other recovery streams are obtained from the water-gas shift reaction unit and fed to the hydrogen recovery configuration to obtain a H circulation stream. In other words, at least a portion of the hydrogen from the H circulation stream is obtained from the other recovery streams. The water-gas shift reaction unit may be included in a configuration for methanol synthesis.
[0038] In particular, at least part of the carbon oxides in the synthesis gas stream (especially pressurized) can be reacted in a water-gas shift reaction unit to form carbon dioxide and hydrogen by a water-gas shift reaction. Thus, by increasing the proportion of hydrogen, the stoichiometry of the methanol synthesis can be improved.
[0039] Similarly, it may generally be the case that the H circulation stream is not initially fed to the first reactor stage. On the contrary, according to another preferred embodiment of the method, the H circulation stream is fed to a synthesis gas stream, in particular a pressurized synthesis gas stream. This specifically means that the H circulation stream is fed to a synthesis gas stream operatively downstream of a synthesis gas reactor configuration. Preferably, the H circulation stream is fed to a synthesis gas stream operatively downstream of a synthesis gas compressor. In other words, the H circulation stream is fed to a synthesis gas stream operatively upstream of the first reactor stage. By feeding the synthesis gas stream to the first reactor stage of a methanol reactor configuration, the result is that the hydrogen of the H circulation stream is fed to the first reactor stage again.
[0040] In addition to the reactor for synthesis gas production, the synthesis gas reactor configuration may have other devices. Thus, the synthesis gas reactor configuration may have a device for desulfurization of the carbon-containing energy carrier stream, a saturation stage for saturating the carbon-containing energy carrier stream with water, a pre-reformer for pre-reforming the carbon-containing energy carrier stream and / or a device for heating the carbon-containing energy carrier stream, which are each operably located upstream of the reactor.
[0041] In principle, the synthesis gas stream can be obtained from the energy carrier stream in any manner. Preferably, in order to obtain the synthesis gas stream, an oxygen-containing stream is fed to the synthesis gas reactor configuration. In principle, the oxygen-containing stream can also contain other components in addition to oxygen. Thus, the oxygen-containing stream can also be ambient air.
[0042] In principle, the synthesis gas stream can be obtained by steam reforming a carbon-containing energy carrier stream. Another preferred embodiment of the method is characterized in that, in a synthesis gas reactor configuration, the synthesis gas stream is obtained by autothermal reforming of a carbon-containing energy carrier stream. In the case of this type of autothermal reforming, catalytic partial oxidation is suitable for the heat required for the endothermic reforming reaction. Unlike pure steam reforming, autothermal reforming provides the advantage that the synthesis gas stream can be provided at a higher pressure. In addition, the synthesis gas stream can be obtained in a synthesis gas reactor configuration by partial oxidation of a carbon-containing energy carrier stream.
[0043] In principle, the autothermal reforming can also be operated using ambient air. Preferably, however, the oxygen-containing stream is obtained from an air separation device for obtaining an oxygen stream from ambient air. In addition, the air separation device can also be configured to obtain a nitrogen stream. In particular, it can then be the case that the oxygen-containing stream consists essentially of oxygen. In this way, the proportion of inert gases in the methanol synthesis is reduced, so that the dimensions of the various devices in the plant can be smaller. Preferably, the plant for methanol synthesis comprises an air separation device.
[0044] According to a preferred embodiment of the method, the H recycle stream is fed to an energy carrier stream. In particular, the H recycle stream can be fed to an energy carrier stream operatively upstream of a syngas reactor arrangement.
[0045] In addition to the H recycle stream, the hydrogen recovery arrangement may also output other streams. Preferably, the hydrogen recovery arrangement outputs a purge. Specifically, the purge may be discharged for combustion.
[0046] In principle, the H circulation stream can have any composition as long as it contains unreacted hydrogen from the unreacted residual gas of the first reactor stage. According to other preferred embodiments of the method, the H circulation stream has a higher hydrogen molar ratio than the recycle stream. This does not refer to the unreacted hydrogen from the unreacted residual gas of the first reactor stage, but to the hydrogen in the entire H circulation stream. In other words, the hydrogen in the H circulation stream is concentrated compared to the recycle stream. Similarly, the H circulation stream preferably has a higher hydrogen molar ratio than the purge.
[0047] In principle, the hydrogen recovery configuration can work according to any principle, for example based on a membrane or a cooling device. A preferred embodiment of the method is characterized in that the hydrogen recovery configuration has a pressure swing adsorption device (PSA) for obtaining a H circulation flow from a recovery flow. In this way, a high hydrogen recovery rate in the H circulation flow can be obtained. Similarly, the pressure drop in the pressure swing adsorption device is still acceptable. Therefore, in principle, high purity hydrogen is not required, but high purity hydrogen can be obtained. Therefore, it can be the case that the H recovery flow is essentially composed of hydrogen.
[0048] The proposed plant is for methanol synthesis. It has: a syngas reactor arrangement for obtaining a syngas stream having hydrogen and carbon oxides from a carbon-containing energy carrier stream; a syngas compressor for pressurizing the syngas stream; a methanol reactor arrangement having a first reactor stage; a heat recovery arrangement for recovering heat from the syngas stream; a hydrogen recovery arrangement and a recycle compressor.
[0049] In the proposed plant, at least part of the pressurized synthesis gas stream is fed to a first reactor stage for partial conversion into methanol.
[0050] Furthermore, in the proposed apparatus, a residual gas stream with unreacted carbon oxides is obtained from a methanol reactor configuration, the residual gas stream is fed to a recycle compressor to pressurize the residual gas stream, wherein the pressurized residual gas stream is fed to a methanol reactor configuration for partial conversion into methanol, a synthesis gas stream is fed to a heat recovery device and then to a synthesis gas compressor, wherein a recovery stream formed from the unreacted residual gas of the first reactor stage is fed to a hydrogen recovery configuration to obtain an H recycle stream, the H recycle stream having unreacted hydrogen from the unreacted residual gas, and the unreacted hydrogen of the H recycle stream is again fed to the first reactor stage for at least partial conversion into methanol.
[0051] The proposed plant is characterized in that the pressure of at least part of the unreacted hydrogen from the H recycle stream of the first reactor stage is raised to the point where it is fed again to the first reactor stage together with the unreacted carbon oxides by means of a recycle compressor.
[0052] Features, advantages and properties of the proposed plant correspond to features, advantages and properties of the proposed method, and vice versa.
[0053] Further details, features, objectives and advantages of the invention will now be described with the aid of the accompanying drawings which illustrate exemplary embodiments. In the drawings:
[0054] Figure 1 shows a flow chart of an apparatus for carrying out the proposed method according to a first exemplary embodiment;
[0055] Figure 2shows a flow chart of an apparatus for carrying out the proposed method according to a second exemplary embodiment;
[0056] Figure 3 shows a flow chart of an apparatus for carrying out the proposed method according to a third exemplary embodiment;
[0057] Figure 4 shows a flow chart of an apparatus for carrying out the proposed method according to a fourth exemplary embodiment;
[0058] Figure 5 shows a flow chart of an apparatus for carrying out the proposed method according to a fifth exemplary embodiment;
[0059] Figure 6 shows a flow chart of an apparatus for carrying out the proposed method according to a sixth exemplary embodiment;
[0060] Figure 7 shows a flow chart of an apparatus for carrying out the proposed method according to a seventh exemplary embodiment;
[0061] Figure 8 A flow chart of a device for carrying out the proposed method according to an eighth exemplary embodiment is shown.
[0062] According to a first exemplary embodiment of the proposed device Figure 1 The apparatus shown is used for the synthesis of methanol 1 and can be operated according to the proposed method.
[0063] The synthesis gas stream 2 is essentially composed of hydrogen, carbon monoxide and carbon dioxide, obtained from an energy carrier stream 11, which is formed by natural gas and is therefore carbon-containing, and is fed to a synthesis gas reactor configuration 13. In the synthesis gas reactor configuration 13, autothermal reforming occurs to obtain the synthesis gas stream 2. For the autothermal reforming, an oxygen-containing stream 22 is supplied, which in this case is obtained from an air separation device 23 and is essentially composed of oxygen. In this case, the air separation device 23 is configured to obtain an oxygen stream from ambient air - that is, in this case, an oxygen-containing stream 22. The synthesis gas stream 2 is obtained at a production pressure of essentially 60 bar. The synthesis gas stream 2 is initially fed to a heat recovery device 10, in which the synthesis gas stream 2 is cooled, and in this way, part of the heat generated during the autothermal reforming is recovered. Next, the synthesis gas stream 2 is fed to the synthesis gas compressor 3 of the device for further pressurization.
[0064] Next, the synthesis gas stream is fed to the first reactor stage 21a of the methanol reactor arrangement 4, in which methanol synthesis is carried out and at least part of the synthesis gas stream 2 is converted into methanol 1. The methanol synthesis is carried out at a synthesis pressure of more than 60 bar, in particular at a synthesis pressure of about 80 bar.
[0065] The plant has a hydrogen recovery arrangement 5 configured as a pressure swing adsorption unit 24 (which may also be referred to as PSA), wherein an H circulation stream 7 is obtained from a recovery stream 6, said H circulation stream 7 consisting essentially of hydrogen. In addition, residual gas is discharged from the hydrogen recovery arrangement 5 as purge 8 and then burned in a combustion heating unit (not shown here) of the plant. The H circulation stream 7 is fed to the synthesis gas stream 2.
[0066] like Figure 1 As can be seen in the figure, the apparatus of the first exemplary embodiment also has a recycle compressor 14 for compressing a residual gas stream 15. The residual gas stream 15 has an unreacted residual gas 16b, which in turn has essentially those synthesis gas components which were not converted into methanol 1 in the methanol reactor arrangement 4. The residual gas stream 15 therefore contains in particular unreacted carbon oxides. The residual gas stream 15 which has been pressurized in this way is fed back into the first part of the methanol reactor arrangement 4.
[0067] Unreacted residual gases 16a, b are obtained from the methanol separation device 17 of the methanol reactor arrangement 4, which in this case comprises two condensation devices 18a, b. By condensation, it produces unreacted residual gases 16a, b on the one hand and corresponding crude methanol streams 19a, b on the other hand. The crude methanol streams 19a, b are subsequently fed to the distillation step 20 of the plant, so that methanol 1 can be obtained from the crude methanol streams 19a, b.
[0068] exist Figure 1 In the device of the exemplary embodiment, the methanol reactor configuration 4 has two reactor stages 21a, b operably connected in series for methanol synthesis. In this exemplary embodiment, the first reactor stage 21a has two isothermal reactors arranged in parallel, and the second reactor stage 21b has a single isothermal reactor. For this, the two condensing devices 18a, b are each fed with a product stream from each reactor stage in the reactor stages 21a, b. For this, the synthesis gas stream 2 is directly fed to the reactor stage 21a and is described as the first reactor stage 21a. The reactor stage 21b is then operably located downstream so that it is fed with the unreacted residual gas 16a from the first reactor stage 21a to be converted into methanol 1.
[0069] exist Figure 1In this exemplary embodiment of the present invention, the recycling stream 6 is branched from the residual gas stream 15, which has been pressurized by the recycle compressor. This residual gas stream 15 fed to the recycle compressor 14 is not obtained from the unreacted residual gas 16a of the first reactor stage 21a, but from the unreacted residual gas 16b of the reactor stage (which is operatively located downstream of the first reactor stage 21a and is therefore referred to as the second reactor stage 21b).
[0070] Similarly, 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 fed to the second reactor stage 21b. Since no complete reaction of the hydrogen has occurred in the second reactor stage 21b either, the unreacted residual gas 16b of the second reactor stage 21b also contains unreacted hydrogen from the first reactor stage 21a.
[0071] Since the recycle stream 6 is branched off from the pressurized residual gas stream 15, the H recycle stream 7 also contains unreacted hydrogen from the unreacted residual gas 16a of the first reactor stage 21a. Specifically, a second part of the pressurized residual gas stream 15 is branched off as the recycle stream 6. Since the H recycle stream 7 is fed to the pressurized synthesis gas stream 2, the unreacted hydrogen from the residual gas 16a of the first reactor stage 21a in the recycle stream 6 (and therefore also from the H recycle stream 7) is fed again to the first reactor stage 21 for conversion into methanol. However, between leaving the first reactor stage 21a and being fed again to the first reactor stage 21a, the unreacted hydrogen of the H recycle stream 7 as a component of the residual gas stream 15 has been pressurized by the recycle compressor 14, in fact precisely once and together with the unreacted carbon oxides in the residual gas stream 15. Since the H recycle stream 7 is fed to the synthesis gas stream 2 operatively downstream of the synthesis gas compressor 3, no hydrogen pressurization occurs in the H recycle stream 7. The residual gas stream 15 compressed by means of the recycle compressor 14 is then fed again directly to the above-mentioned first part of the first reactor stage 21 a .
[0072] Figure 2 A second exemplary embodiment of the proposed device is shown with Figure 1The difference of the exemplary embodiment shown is that the circulation compressor 14 is operably arranged between the first reactor stage 21a and the reactor stage 21b (downstream of the first reactor stage 21a). As a result, the residual gas stream 15 fed to the circulation compressor 14 is obtained from the unreacted residual gas 16a of the first reactor stage 21a. The residual gas stream 15 compressed together with the unreacted carbon oxides by the circulation compressor 14 is fed to the reactor stage 21b, which is downstream of the first reactor stage 21a. The unreacted residual gas 16b from the reactor stage 21b is sent back to the first reactor stage 21a without further compression. Unlike what is shown in the first exemplary embodiment, the recovery stream 6 is obtained from the unreacted residual gas 16a of the first reactor stage 21a. In addition, consistent with the first exemplary embodiment, the diversion of the recovery stream 6 is operably carried out downstream of the circulation compressor 14. Thus, also in the second exemplary embodiment, in the H circulation stream 7, the pressurization of the residual gas 16a from the first reactor stage 21a with unreacted hydrogen takes place precisely once, via the circulation compressor 14 together with unreacted carbon oxides, and this unreacted hydrogen is subsequently fed again to the first reactor stage 21a.
[0073] exist Figure 3 In the third exemplary embodiment of the present invention, the recovery stream 6 is obtained from the residual gas 16a of the first reactor stage 21a in a similar manner to the second exemplary embodiment. However, unlike the second exemplary embodiment, there is no circulation compressor 14 between the first reactor stage 21a and the second reactor stage 21b. In addition, the circulation compressor 14 is operatively located downstream of the second reactor stage 21b, as is the case with the first exemplary embodiment.
[0074] Different from the first exemplary embodiment and the second exemplary embodiment, in the third exemplary embodiment, the H circulation stream 7 is fed to the residual gas 16b of the second reactor stage 21b (which is downstream of the first reactor stage 21a). In particular, the feeding occurs before the pressurization by the circulation compressor 14. In this way, the hydrogen in the H circulation stream 7 corresponding to the unreacted hydrogen of the residual gas 16a from the first reactor stage 21a is pressurized in the recovery stream 6 together with the remaining unreacted residual gas 16b of the second reactor stage 21b by the circulation compressor 14, in particular together with the unreacted carbon oxides. The pressurization is performed before the unreacted hydrogen is fed to the first reactor stage 21a again, which compensates for the insufficient pressurization caused by the lack of a synthesis gas compressor.
[0075] Furthermore, in the third exemplary embodiment, part of the pressurized residual gas stream 15 is branched off and fed to the energy carrier stream 11. This branched part of the pressurized residual gas stream 15 is further pressurized by the synthesis gas compressor 2. For the unbranched part of the residual gas stream 15, exactly one pressurization is performed by the circulation compressor 14. However, the branching of this part of the pressurized residual gas stream 15 can also be omitted.
[0076] according to Figure 4 The device of the fourth exemplary embodiment corresponds to Figure 3 A third exemplary embodiment of the invention. However, it includes a water-gas shift reaction device 9 to which part of the pressurized synthesis gas stream 2 is fed. The water-gas shift reaction occurring in the water-gas shift reaction device 9 results in an increase in the proportion of hydrogen in the diverted part of the pressurized synthesis gas stream 2. In this case, part of the synthesis gas stream 2 from the water-gas shift reaction device 9 has been diverted in this way and has been subjected to a water-gas shift reaction, forming a further recovery stream, which is fed together with the recovery stream 6 to the hydrogen recovery configuration 5. Figure 3 In the same manner as in the exemplary embodiment of the present invention, the H circulation stream 7 is fed to the residual gas 16b of the second reactor stage 21b (which is downstream of the first reactor stage 21a) and is therefore pressurized together with the unreacted carbon oxides by the circulation compressor 14 even in this exemplary embodiment.
[0077] Figure 5 The fifth exemplary embodiment of the present invention is arranged in the same manner as the second exemplary embodiment (on which the fifth exemplary embodiment is also based) between the reactor stages 21a, b of the methanol reactor configuration 4 in a recycle compressor 14. Unlike the second exemplary embodiment, the recycle stream 6 is obtained from the residual gas 16b from the second reactor stage 21b. In this way, the hydrogen pressure in this recycle stream 6 (and therefore also in the H recycle stream 7) is increased by the recycle compressor 14 and in fact in particular before feeding to the second reactor stage 21b.
[0078] Figure 6 The sixth exemplary embodiment is based in principle on Figure 1 A first exemplary embodiment of the present invention. Figure 1 Unlike the first exemplary embodiment of Figure 5 In a similar manner to the fifth exemplary embodiment of the present invention, the recycle stream 6 is obtained from the unreacted residual gas 16a of the second reactor stage 21b. Figure 1 Another difference of the first exemplary embodiment is that Figure 3 and Figure 4In a similar manner to the third and fourth exemplary embodiments of the present invention, the H recycle stream 7 is recycled to the residual gas 16b of the second reactor stage 21b (which is downstream of the first reactor stage 21a). This feed is operatively located downstream of the recovery stream 6 split.
[0079] Figure 7 The seventh exemplary embodiment is initially based on Figure 3 The third exemplary embodiment of the present invention is similar to the third exemplary embodiment of the present invention, but the partially pressurized residual gas flow 15 is not differentiated into the energy carrier flow 11. Compared with the third exemplary embodiment, the seventh exemplary embodiment shows three corresponding alternative connection modes. In this context, the seventh exemplary embodiment includes three sub-exemplary embodiments.
[0080] A first variant proposes a first bypass stream 25a which branches off from the pressurized synthesis gas stream 2 and feeds the unreacted residual gas 16a of the first reactor stage 21a. The feeding of the unreacted residual gas 16a of the first reactor stage 21a is operatively carried out downstream of the diversion of the recovery stream 6. Thus, in this way, part of the synthesis gas stream 2 is diverted to form a further synthesis gas stream 26 which corresponds to the first bypass stream 25a and bypasses the first reactor stage 21a. According to Figure 7 In the embodiment of the present invention, the split flow is operatively located upstream of the feed of the pressurized residual gas stream 15. However, it is also conceivable that the split flow is operatively arranged downstream of the feed of the pressurized residual gas stream 15.
[0081] The second variant is an alternative to the first variant and proposes a second bypass stream 25b which branches off from the pressurized residual gas stream 15 and is fed to the unreacted residual gas 16a of the first reactor stage 21a, and in fact also downstream of the branching of the recovery stream 6. In this way, a partial bypass of the first reactor stage 21a is then carried out by means of the pressurized residual gas stream 15.
[0082] The third variant is an alternative to the first and second variants and proposes a third bypass stream 25c, which is operatively located downstream of the branch of the recovery stream 6 of the unreacted residual gas 16a from the first reactor stage 21a and is fed to the residual gas stream 15 before pressurization. Thus, in this way, part of the unreacted residual gas 16a of the first reactor stage 21a initially bypasses the second reactor stage 21b.
[0083] Figure 8 The eighth exemplary embodiment is based on Figure 5 The fifth exemplary embodiment of the present invention is shown in Figure 1, and three alternative connection variations are shown respectively, in this case, according to the fifth exemplary embodiment. These three connection variations correspond to Figure 7 A connection variant with bypass flows 25a, 25b, 25c is shown in FIG. 7 .
Claims
1. A method for synthesizing methanol (1), wherein: A carbonaceous energy carrier stream (11) is fed to a synthesis gas reactor arrangement (13) to obtain a synthesis gas stream (2) having hydrogen and carbon oxides, the synthesis gas stream (2) is fed to a heat recovery device (10) to recover heat from the synthesis gas stream (2), and subsequently fed to a synthesis gas compressor (3) for pressurization, at least part of the pressurized synthesis gas stream (2) is fed to a first reactor stage (21a) of a methanol reactor arrangement (4) for partial conversion into methanol (1), wherein a residual gas stream (15) having unreacted carbon oxides is obtained from the methanol reactor arrangement (4), the residual gas stream (15) is fed to a recycle compressor (14) to pressurize the residual gas stream (15), and the pressurized residual gas stream (15) is fed to a first reactor stage (21a) of a methanol reactor arrangement (4) for partial conversion into methanol (1). to a methanol reactor arrangement (4) for partial conversion into methanol (1), a recovery stream (6) of the unreacted residual gas (16a) from the first reactor stage (21a) is fed to a hydrogen recovery arrangement (5) to obtain an H circulation stream (7), the H circulation stream (7) having unreacted hydrogen from the unreacted residual gas (16a), the unreacted hydrogen of the H circulation stream (7) being fed again to the first reactor stage (21a) for at least partial conversion into methanol (1), characterised in that the pressure of at least part of the unreacted hydrogen of the H circulation stream (7) from the first reactor stage (21a) is raised to a pressure which is increased by a circulation compressor (14) before it is fed again to the first reactor stage (21a) together with unreacted carbon oxides.
2. The method according to claim 1, characterized in that The methanol reactor configuration (4) includes a methanol separation device (17) for obtaining unreacted residual gas (16a) from the first reactor stage (21a) and a crude methanol stream (19a) from the first reactor stage (21a), and the methanol separation device (17) includes a condensation device (18a) for obtaining the unreacted residual gas (16a) from the first reactor stage (21a) and the crude methanol stream (19a) from the first reactor stage (21a) by condensation.
3. The method according to claim 1, characterized in that Part of the pressurized residual gas stream (15) is diverted and fed to the synthesis gas reactor arrangement (13).
4. The method according to claim 3, characterized in that A partial stream of the pressurized residual gas stream ( 15 ) is fed to the carbon-containing energy carrier stream ( 11 ).
5. The method according to claim 1, characterized in that The methanol reactor configuration (4) comprises a plurality of reactor stages for synthesizing methanol, which are connected in series, a circulating compressor (14) is arranged between two reactor stages (21a, b), and corresponding unreacted residual gas (16a, b) is obtained from each of the plurality of reactor stages through a methanol separation device (17).
6. The method according to claim 5, characterized in that The H recycle stream (7) is fed to the unreacted residual gas (16b) from the reactor stage (21b) which is located downstream of the first reactor stage (21a).
7. The method according to claim 6, characterized in that The H recycle stream (7) is fed together with the residual gas stream (15) to a recycle compressor (14) for pressure increase.
8. The method according to claim 5, characterized in that The residual gas stream (15) is obtained from a reactor stage (21b) which is located downstream of the first reactor stage (21a).
9. The method according to claim 8, characterized in that The recycle compressor (14) feeds the pressurized residual gas stream (15) to the first reactor stage (21a).
10. The method according to claim 8, characterized in that The residual gas stream (15) is obtained from the reactor stage (21b) which is in the last operating position of the plurality of reactor stages.
11. The method according to any one of claims 1 to 10, characterized in that At least part of the recycle stream (6) is diverted from the unreacted residual gas (16a) of the first reactor stage (21a).
12. The method according to claim 11, characterized in that At least part of the recovery stream (6) is branched upstream of the recycle compressor (14).
13. The method according to claim 11, characterized in that The recovery stream (6) is fed to the hydrogen recovery arrangement (5) at a feed pressure which is higher than the residual gas pressure at which the residual gas stream (15) is obtained from the methanol reactor arrangement.
14. The method according to claim 13, characterized in that At least part of the recovery stream (6) is separated from the residual gas stream (15) downstream of the recycle compressor (14).
15. The method according to any one of claims 1 to 10, characterized in that The H recycle stream (7) is fed into the synthesis gas stream (2).
16. The method according to claim 15, characterized in that The synthesis gas stream (2) is pressurized.
17. The method according to any one of claims 1 to 10, characterized in that To obtain the synthesis gas stream (2), the oxygen-containing stream (22) is fed to a synthesis gas reactor arrangement (13), in which the synthesis gas stream (2) is obtained by autothermal reforming or partial oxidation of a carbon-containing energy carrier stream (11).
18. The method according to claim 17, characterized in that The oxygen-containing stream (22) is obtained from an air separation unit (23) for obtaining an oxygen stream from ambient air.
19. The method according to claim 18, characterized in that The oxygen-containing stream (22) consists essentially of oxygen.
20. The method according to any one of claims 1 to 10, characterized in that The H recycle stream (7) is fed to the carbon-containing energy carrier stream (11).
21. The method of claim 20, wherein: The hydrogen recovery arrangement (5) outputs a purge stream (8) which is discharged for combustion.
22. The method according to any one of claims 1 to 10, characterized in that The H recycle stream (7) has a higher hydrogen molar ratio than the recovery stream (6).
23. The method of claim 22, wherein: The H recycle stream (7) has a higher hydrogen molar ratio than the purge stream (8).
24. The method according to any one of claims 1 to 10, characterized in that The hydrogen recovery arrangement (5) has a pressure swing adsorption unit (24) for obtaining a H recycle stream (7) from the recovery stream (6).
25. The method of claim 24, wherein: The H recycle stream (7) consists essentially of hydrogen.
26. The method according to any one of claims 1 to 10, characterized in that The pressure of the unreacted hydrogen of the recycle stream (6) from the first reactor stage (21a) is raised to its re-feed into the first reactor stage (21a) precisely once together with the unreacted carbon oxides by means of a recycle compressor (14).
27. An apparatus for synthesizing methanol (1), comprising: a synthesis gas reactor arrangement (13) for obtaining a synthesis gas stream (2) comprising hydrogen and carbon oxides from a carbon-containing energy carrier stream (11); a gas compressor (3) for pressurizing the synthesis gas stream (2); a methanol reactor arrangement (4) having a first reactor stage (21a); a heat recovery device (10) for recovering heat from the synthesis gas stream (2); a hydrogen recovery arrangement (5) and a recycle compressor (14); wherein: At least part of the pressurized synthesis gas stream (2) is fed to a first reactor stage (21a) for partial conversion into methanol (1), a residual gas stream (15) with unreacted carbon oxides is obtained from the methanol reactor arrangement (4), the residual gas stream (15) is fed to a recycle compressor (14) for pressurizing the residual gas stream (15), the pressurized residual gas stream (15) is fed to the methanol reactor arrangement (4) for partial conversion into methanol (1), the synthesis gas stream (2) is fed to a heat recovery unit (10) and subsequently to a synthesis gas compressor (3), unreacted carbon oxides from the first reactor stage (21a) are recycled to a recycle compressor (14) for pressurizing the residual gas stream (15), the pressurized residual gas stream (15) is fed to a methanol reactor arrangement (4) for partial conversion into methanol (1), A recovery stream (6) of the residual gas (16a) is fed to a hydrogen recovery arrangement (5) to obtain an H recycle stream (7), the H recycle stream (7) having unreacted hydrogen from the unreacted residual gas (16a), the unreacted hydrogen of the H recycle stream (7) being fed again to the first reactor stage (21a) for at least partial conversion into methanol (1), characterised in that the pressure of at least part of the unreacted hydrogen of the H recycle stream (7) from the first reactor stage (21a) is raised to a pressure which is increased by means of a recycle compressor (14) before it is fed again to the first reactor stage (21a) together with unreacted carbon oxides.