WO2017175760A1 - メタノール製造方法及びメタノール製造装置 - Google Patents
メタノール製造方法及びメタノール製造装置 Download PDFInfo
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- WO2017175760A1 WO2017175760A1 PCT/JP2017/014078 JP2017014078W WO2017175760A1 WO 2017175760 A1 WO2017175760 A1 WO 2017175760A1 JP 2017014078 W JP2017014078 W JP 2017014078W WO 2017175760 A1 WO2017175760 A1 WO 2017175760A1
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/1512—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by reaction conditions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0006—Controlling or regulating processes
- B01J19/0013—Controlling the temperature of the process
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/24—Stationary reactors without moving elements inside
- B01J19/2415—Tubular reactors
- B01J19/2435—Loop-type reactors
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/152—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the reactor used
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C31/00—Saturated compounds having hydroxy or O-metal groups bound to acyclic carbon atoms
- C07C31/02—Monohydroxylic acyclic alcohols
- C07C31/04—Methanol
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00049—Controlling or regulating processes
- B01J2219/00051—Controlling the temperature
- B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Definitions
- the present invention relates to a methanol production method and a methanol production apparatus.
- Synthetic raw material gas a synthetic gas mainly composed of carbon monoxide, carbon dioxide and hydrogen obtained by reforming it
- the reaction conditions are a pressure of 50 to 150 kg / cm 2 and a temperature of 160 to 300 ° C.
- the catalyst used is a catalyst mainly composed of copper / zinc.
- the methanol synthesis reaction is represented by the following formulas (1) and (2).
- Patent Document 1 states that there is a problem that a gas reactant partial pressure is increased in methanol synthesis at a low circulation ratio, which causes overreaction and generation of overheating of the catalyst bed.
- the synthesis raw material gas to be supplied is divided into two flows, and one flow is mixed with the recovered unreacted gas and then introduced into the first synthesis stage, and the other flow is changed to the first flow.
- Patent Document 1 proposes to synthesize methanol in a further synthesis stage before mixing with the outlet gas of the synthesis stage and separating the synthetic methanol.
- Patent Document 1 avoids overheating of the catalyst layer by adjusting the amount of methanol synthesis at the synthesis stage, and the circulation ratio expressed as the unreacted recovered gas flow rate with respect to the feed gas flow rate is 1 to 3. It can be lowered.
- Patent Document 2 shows that performing methanol synthesis under a low pressure has the advantage of reducing the load on the compressor and eliminating the need for a compressor at all, while requiring a large amount of catalyst, Alternatively, it describes the disadvantage that unreacted gas has to be circulated and used at a high circulation ratio.
- the technique described in Patent Document 2 has two synthesis towers in series and condenses and separates the outlet gas of each synthesis tower to reduce the circulation ratio to 4.0 or less. It is characterized by doing. In the example of this Patent Document 2, it is specifically shown that the circulation ratio is changed from 6.0 to 3.5.
- Patent Document 3 states that increasing the raw material partial pressure in the reactor leads to overreaction and high temperature.
- Patent Document 3 does not shorten the expected catalyst life, and as a technique for obtaining a large amount of objects by an economically valid technique, a plurality of reactors are arranged in a synthesis loop, and each reaction is performed.
- a technique has been proposed in which a separator is arranged after the reactor and the pressure is increased between the reactors by a method in which the raw material gas can be supplied before the plurality of reactors.
- Patent Document 3 enables the production of a desired product to be achieved while reducing the amount of circulating gas and controlling the catalyst layer temperature, thereby achieving an acceptable catalyst life. It is described. And in the Example, it is shown that 23% or about 28% of the circulating gas amount was reduced.
- the scale may be limited by the production limit of the reactor.
- the whole plant may be enlarged by arranging a plurality of reactors in parallel.
- Non-Patent Document 1 describes that water generated by methanol synthesis causes considerable catalyst activity deterioration.
- Non-Patent Document 2 describes the progress of methanol synthesis technology. More specifically, it is described that, in the methanol synthesis technology, the manufacturing process has been advanced mainly in pursuit of improvement in energy efficiency and economic efficiency by increasing the size of the plant. In addition, as a concomitant effect of a significant decrease in the amount of unreacted gas circulation, it is possible to reduce the amount of electricity and cooling water used, and to reduce the size of peripheral equipment such as piping in the synthesis loop, circulation machine and heat exchanger It is described that it becomes.
- the methanol synthesis reaction is represented by the above formulas (1) and (2), and is known to be a molecular number reduction reaction and a highly exothermic reaction.
- the suitable reaction temperature range of the copper / zinc-based catalyst generally used at present is 220 to 280 ° C.
- the reaction temperature exceeds 280 ° C., there are disadvantages that the activity of the catalyst is lowered, the equilibrium methanol concentration is lowered, and undesirable side reaction products are increased. Therefore, in order to avoid overheating of the catalyst, at least one of limiting the reaction amount occurring in the catalyst layer and cooling the catalyst layer is required.
- Patent Document 1 is characterized in that the catalyst layer temperature can be appropriately maintained while the circulation ratio is lowered to 1 to 3 by distributing the amount of methanol to be synthesized to a plurality of reactors.
- Patent Document 1 As is apparent from the claims and drawings, unreacted gas is separated from the outlet gas of the first synthesis stage, and the unreacted gas is used as a raw material for the next stage synthesis stage. There is no technical idea of using it. Rather, the claims and drawings of Patent Document 1 only describe that the entire amount of the outlet gas of the first synthesis stage is supplied to the second synthesis stage, and the above technical idea is excluded. Yes.
- Patent Document 2 states that synthesis at a low pressure and a low circulation ratio is made possible by condensation separation of a product containing methanol between synthesis towers.
- the circulation ratio was only changed from 6.0 to 3.5, which did not lead to an improvement in the carbon yield.
- the process like patent document 2 with the intention of improving yield and reducing energy consumption, (1) increasing the synthesis pressure, (2) improving catalytic activity, or (3) If the circulation ratio is further reduced, there is a tendency that the deviation in the methanol production amount in each synthesis tower increases and at the same time, the deviation in the load applied to the catalyst tends to increase. A difference in catalyst deterioration occurs when the catalyst load becomes more uneven.
- Patent Document 3 describes that the desired product to be achieved can be produced while achieving an acceptable catalyst life by reducing the amount of circulating gas and controlling the catalyst bed temperature. However, the example only shows that the amount of circulating gas can be reduced to 72% or 77% with respect to the existing technology, and there is no description about the carbon yield.
- the carbon yield is not taken into account, even if the amount of circulating gas is reduced, the amount of raw material gas can be increased to maintain the production amount, and there is no technical innovation. Also, it is most convenient from the viewpoint of carbon yield to provide purge gas removal at the farthest position in the synthesis loop with respect to the makeup gas inlet.
- the purge gas extraction position in the synthesis loop is preferably just before the circulator.
- the process disclosed in Patent Document 3 is a process of boosting a gas (purge gas taken out from the synthesis loop) that does not need to be boosted by a circulator. This is not appropriate because the amount of processing gas in the circulator increases and the amount of energy used increases.
- the air temperature at the outlet of the cooler is set using only an air fin cooler without using a water-cooled heat exchanger for the purpose of reducing cooling water or reducing equipment costs
- the total amount of condensable gas to be introduced is increased if a circulator is disposed after the equipment used in the condensation separation process.
- the probability that condensed droplets are generated in the circulator increases. Generation of condensed droplets in the circulator causes mechanical failure and energy loss, and it is not appropriate to place the circulator at this position.
- Non-Patent Document 2 in general, the improvement of methanol synthesis technology from the viewpoint of the manufacturing process has been performed mainly in pursuit of improvement in energy efficiency and economic improvement by increasing the size of the plant. Yes.
- Patent Document 1 it is intended to increase the production of methanol, and it can be seen that improvement in economic efficiency is also demanded. From the flow of improvement of such methanol synthesis technology, it is obvious that the condensation and separation of the product between the synthesis stages as described in Patent Document 2 discharges a lot of energy to the environment. Going backwards.
- the amount of circulating gas is 3.5 times the amount of the raw material gas, and the amount of gas flowing while being cooled from the first synthesis tower outlet to the separator is the raw material gas. It becomes 3.5 times or more of the amount. Therefore, it is necessary to cool a large amount of gas, which is not preferable because the load on the cooler increases. Further, with regard to the parallelization performed when pursuing economic improvement by increasing the size of the plant, for example, when the reactors are paralleled, the amount of gas that can be introduced into the reactor increases, so that the size can be increased. However, such parallelization generally does not lead to yield improvement or circulation ratio reduction.
- the present invention has been made in view of at least a part of the above circumstances, and in methanol synthesis, the temperature of the catalyst layer is set to an appropriate temperature range, energy consumption is reduced, and a higher carbon yield is achieved. It is an object to provide a method and a methanol production apparatus.
- a specific process has a plurality of methanol synthesis steps, and introduces unreacted gas separated from the reaction mixture generated in the methanol synthesis step into the subsequent methanol synthesis step. Furthermore, the final unreacted gas separated from the reaction mixture generated in the final methanol synthesis step, partially removed as a purge gas, and mixed with a part of the makeup gas is introduced into the first methanol synthesis step.
- a synthesis loop is formed that allows unreacted gas to pass through each reactor in series.
- Methanol production comprising a synthesis step of synthesizing methanol from a synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide, and a separation step of separating unreacted gas from the reaction mixture obtained through the synthesis step
- a method comprising a synthesis loop having at least two of the synthesis steps and at least two of the separation steps, wherein in the synthesis loop, the final separated from the final reaction mixture in a final separation step after the final synthesis step
- a first mixing step in which the remaining gas obtained by removing the purge gas from the unreacted gas is mixed with 10 to 90 mol% of a makeup gas containing hydrogen, carbon monoxide, and carbon dioxide to obtain a first mixed gas;
- a final mixing step of finally mixing unreacted gas and at least a part of 10 to 90 mol% of the makeup gas to obtain a final mixed gas, and synthesizing methanol from the final mixed gas A first preheating step of preheating the first mixed gas, and a final synthesis step; and the final separation step of separating the final unreacted gas from the final reaction mixture obtained in the final synthesis step.
- a method for producing methanol, wherein the reaction temperature of the catalyst layer is controlled by indirect heat exchange.
- [5] The method for producing methanol according to any one of [1] to [4], further comprising a step of boosting the first mixed gas that has undergone the first preheating step before the first synthesis step. .
- [6] The method for producing methanol according to any one of [1] to [5], wherein the heat source for preheating the first mixed gas in the first preheating step is the first reaction mixture.
- the method for producing methanol according to [6] further including a first reaction mixture decompression step in which the first reaction mixture in which the first mixed gas is preheated is decompressed before the first separation step.
- a methanol production apparatus comprising: a reactor that synthesizes methanol from a synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide; and a separation device that separates unreacted gas from the reaction mixture obtained in the reactor. Having a synthesis loop comprising at least two of said reactors and at least two of said separation devices, wherein in said synthesis loop, the final unseparated from the final reaction mixture in a final separation device after the final reactor.
- a first mixing means for obtaining a first mixed gas by mixing the remaining gas obtained by removing the purge gas from the reaction gas with 10 to 90 mol% of a makeup gas containing hydrogen, carbon monoxide and carbon dioxide;
- a first reactor for synthesizing methanol from one mixed gas, and a first component for separating the first unreacted gas from the first reaction mixture obtained in the first reactor.
- Methanol is synthesized from the final mixed gas, an apparatus, final mixing means for finally mixing unreacted gas and at least a part of 10 to 90 mol% of the makeup gas to obtain a final mixed gas
- a first preheater comprising: the final reactor; and the final separation device that separates the final unreacted gas from the final reaction mixture obtained in the final reactor, and preheating the first mixed gas;
- a final preheater that preheats the final mixed gas; and a circulator that pressurizes the final mixed gas preheated by the final preheater before supplying the final mixed gas to the final reactor, and at least in the final reactor,
- a methanol production device that controls the reaction temperature of the catalyst layer by indirect heat exchange with pressurized boiling water.
- the present invention it is possible to provide a methanol production method and a methanol production apparatus that achieve a higher carbon yield by reducing the amount of energy used by setting the temperature of the catalyst layer to an appropriate temperature range in methanol synthesis.
- the present embodiment a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary.
- the present invention is limited to the following embodiment. It is not a thing.
- the present invention can be variously modified without departing from the gist thereof.
- the same elements are denoted by the same reference numerals, and redundant description is omitted.
- the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified.
- the dimensional ratios in the drawings are not limited to the illustrated ratios.
- the methanol production method of the present embodiment includes a synthesis step of synthesizing methanol from a synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide, and a separation step of separating unreacted gas from a reaction mixture obtained through the synthesis step.
- a synthesis loop having at least two synthesis steps and at least two separation steps, wherein the synthesis loop separates from the final reaction mixture in a final separation step after the final synthesis step
- a first mixing step in which the remaining gas obtained by removing the purge gas from the final unreacted gas is mixed with 10 to 90 mol% of a makeup gas containing hydrogen, carbon monoxide, and carbon dioxide to obtain a first mixed gas;
- a first synthesis step for synthesizing methanol from the first mixed gas, and a first synthesis step for separating the first unreacted gas from the first reaction mixture obtained in the first synthesis step.
- the first reaction mixture When the heat source for preheating the first mixed gas is the first reaction mixture, the first reaction mixture is cooled by the first mixed gas, so that it is more easily condensed. Similarly, when the heat source for preheating the final mixed gas is the final reaction mixture, the final reaction mixture is cooled by the final mixed gas, and thus is more easily condensed.
- the methanol manufacturing apparatus of this embodiment is an apparatus used for said methanol manufacturing method. More specifically, the methanol production apparatus of this embodiment separates unreacted gas from a reactor that synthesizes methanol from synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide, and a reaction mixture obtained in the reactor. And a separation apparatus comprising a synthesis loop comprising at least two reactors and at least two separation apparatuses, wherein the final reaction in the final separation apparatus after the final reactor in the synthesis loop The remaining gas obtained by removing the purge gas from the final unreacted gas separated from the mixture is mixed with 10 to 90 mol%, preferably 10 to 70 mol% of a makeup gas containing hydrogen, carbon monoxide and carbon dioxide.
- a methanol production apparatus that controls the reaction temperature of the catalyst layer by indirect heat exchange with pressurized boiling water at least in the final reactor.
- at least one separation step is provided before the final synthesis step.
- a reaction product containing methanol and an unreacted synthesis gas (hereinafter “unreacted gas”) are obtained from the reaction mixture obtained in the immediately preceding synthesis step.
- unreacted gas unreacted synthesis gas
- methanol is synthesized from the mixed gas obtained by mixing the makeup gas with the unreacted gas.
- the synthesis loop is configured such that the gas that has undergone at least one synthesis step and at least one separation step undergoes the final synthesis step and the final separation step, and the unreacted gas separated in the final separation step is the first. It is formed by being used as a raw material gas in the synthesis process.
- the methanol production apparatus includes at least one circulation machine for pressurization, and the pressurization step is after the final preheating step and before the final synthesis step. Thereby, the energy for raising the reaction temperature in the final synthesis step can be reduced, and the amount of heat recovered in the reactor can be increased in that step.
- the temperature can be raised by the pressure increase in the pressure increasing step, the temperature required when preheating the final mixed gas before that can be reduced. Then, since the temperature difference between the low temperature side fluid and the high temperature side fluid in the preheater used for preheating increases, the heat exchange amount (heat recovery amount) in the preheater increases or the size of the heat exchanger increases. It can also be made smaller. It is preferable to introduce a fluid with high dryness into the circulator. More specifically, after the separation step, the fluid having saturated condensable gas is preheated to increase the dryness, or the fluid is dried by mixing a fluid with a high dryness (for example, makeup gas). It is preferable to increase the degree or both. Thereby, since generation
- this synthesis loop may have a decompression step.
- the depressurizing step is preferably a step of depressurizing the unreacted gas before mixing with the makeup gas thereafter. More specifically, it is preferable that the final unreacted gas depressurization step in which the final unreacted gas obtained in the final separation step is depressurized before the first mixing step. As a result, the pressure in the preceding final separation step can be increased, and the gas-liquid separation efficiency can be further improved.
- the decompression step may be a first unreacted gas decompression step in which the first unreacted gas obtained in the first separation step is decompressed.
- the decompression step is preferably a decompression step in which the reaction mixture is decompressed before the separation step.
- the depressurization step is preferably a final reaction mixture depressurization step of depressurizing the final reaction mixture preheated with the final mixed gas before the final separation step, and the first reaction mixture preheated with the first mixed gas Is preferably a first reaction mixture decompression step in which the pressure is reduced before the first separation step.
- the makeup gas is divided into a plurality of flows and then introduced into the synthesis loop from the mixing step before each synthesis step.
- the reaction product in the reaction mixture is separated and extracted out of the synthesis loop in the separation process, and a purge gas for preventing accumulation of inert components is taken out of the synthesis loop.
- the “reaction mixture” is an exit component of the synthesis step, which is a mixture of components generated by the reaction in the synthesis step and unreacted components, and usually contains methanol.
- the final synthesis step is a step of synthesizing methanol from a mixed gas obtained by mixing the unreacted gas and the makeup gas separated from the reaction mixture that has undergone the synthesis step of synthesizing methanol after the first synthesis step. If there is, it will not be specifically limited.
- the final synthesis step is preferably a step of synthesizing methanol from the second mixed gas (second synthesis step).
- the third synthesis gas obtained by separating the second unreacted gas from the second reaction mixture obtained in the second synthesis step and mixing the second unreacted gas and the makeup gas in the final synthesis step. Therefore, the step of synthesizing methanol (third synthesis step) is also preferable.
- the final synthesis step is more preferably the second synthesis step.
- the final separation step is not particularly limited as long as it is a step of separating unreacted gas from the reaction mixture after the first separation step.
- the final separation step is preferably a second separation step in which the second unreacted gas is separated from the second reaction mixture obtained in the second synthesis step.
- the final separation step is preferably a third separation step in which the third unreacted gas is separated from the third reaction mixture obtained in the third synthesis step.
- the final separation step is more preferably the second separation step.
- Make-up gas is a synthetic raw material gas containing carbon monoxide (CO), carbon dioxide (CO 2 ) and hydrogen (H 2 ), such as natural gas steam reforming gas and coal gasification gas, up to the reaction pressure by a compressor.
- Boosted The reaction pressure may be, for example, 4.9 to 14.7 MPa-G (50 to 150 kg / cm 2 -G), and more preferably 7.8 to 10.8 MPa-G (80 to 110 kg / cm 2). -G).
- M (H 2 mol%) / (2 ⁇ CO mol% + 3 ⁇ CO 2 mol%)
- M is 1.3 to 1.5.
- the makeup gas is divided into a plurality of flows before being introduced into the synthesis loop, and is introduced into the synthesis loop as part of the raw material gas in the plurality of synthesis steps existing in the synthesis loop.
- the preferred range of the makeup gas split ratio varies depending on the synthesis conditions in each synthesis step and the separation conditions in each separation step.
- the molar flow rate of the makeup gas contained in the mixed gas (first mixed gas) supplied to the first methanol synthesis step (first synthesis step) is 10 to 90 mol% with respect to the total amount of makeup gas, Preferably, it is 10 to 70 mol%.
- the molar flow rate of the makeup gas contained in the mixed gas (second mixed gas) supplied to the second synthesis step is 10 to 90 mol%, preferably 10 to 70 mol% with respect to the total amount of the makeup gas. is there.
- the sum of the molar flow rates of the makeup gas supplied to the first synthesis step and the second synthesis step is less than 100% of the total amount of the makeup gas
- the remaining makeup gas is appropriately divided into each methanol synthesis step after the third synthesis step.
- the makeup gas is not dividedly supplied to each methanol synthesis step after the third synthesis step.
- a case of a production method having two synthesis steps and two condensation separation steps using a condensation separation method as a separation method in the separation step will be described.
- the outlet gas temperature in the first condensation / separation step is set to 20 ° C.
- the ratio of the makeup gas introduced into the synthesis loop immediately before the final synthesis step (second synthesis step) makes-up
- the ratio to the total amount of gas is preferably 10 to 90 mol%, more preferably 30 to 90 mol%, and still more preferably 40 from the viewpoint of the carbon yield and the maximum temperature of the catalyst layer. ⁇ 70 mol%.
- the proportion of the makeup gas introduced into the synthesis loop immediately before the final synthesis step is 10 to 90 from the same viewpoint as described above. It is preferable that the amount be 30% by mole, preferably 30 to 90% by mole, more preferably 40 to 70% by mole, and still more preferably 45 to 65% by mole.
- the synthesis gas used as the raw material gas in the synthesis process is preferably heated to 180 to 260 ° C. by a preheater and then supplied to the synthesis process.
- the synthesis gas temperature at the time of supply to the synthesis step is appropriately set depending on the type and amount of the catalyst, the shape of the reactor, the reaction pressure, etc., but the preferred synthesis gas temperature is 200 to 250 ° C. From the viewpoint of energy recovery in the reactor, a more preferable gas temperature at the inlet of the reactor is higher than the temperature of the pressurized boiling water used for cooling the catalyst layer.
- the ratio (split ratio) of the makeup gas mixed in the unreacted gas in each mixing step is preferable to adjust the ratio (split ratio) of the makeup gas mixed in the unreacted gas in each mixing step according to the desired temperature of each reactor in the synthesis step.
- the desired temperature is a temperature in a methanol synthesis reaction described later.
- the makeup gas can be divided into a plurality of flows before introduction into the synthesis loop, and the division ratio can be adjusted. Thereby, the temperature of the reactor in the synthesis process can be easily controlled.
- the reactor used in the synthesis step preferably has a catalyst layer and a mechanism for removing heat generated by the reaction from the catalyst layer (heat removal mechanism).
- the catalyst used for the synthesis is preferably a methanol synthesis catalyst containing copper atoms and zinc atoms as essential components.
- a catalyst is reduced from an oxide state by a reducing gas such as hydrogen, carbon monoxide, or a mixed gas thereof, whereby copper is activated to have catalytic activity.
- the catalyst may contain an aluminum atom and / or a chromium atom as the main third component.
- the catalyst containing copper and zinc as essential components can be prepared by a known method.
- Such a catalyst is prepared, for example, by the methods described in Japanese Patent Publication No. 51-44715, Japanese Patent No. 2695663, Japanese Patent Publication No. 6-35401, Japanese Patent Application Laid-Open No. 10-272361, and Japanese Patent Application Laid-Open No. 2001-205089. can do.
- a preferred catalyst is a methanol synthesis catalyst containing a copper atom and a zinc atom in an atomic ratio (copper / zinc) of 2.0 to 3.0 and an aluminum atom.
- Specific examples of preferred catalysts include the catalysts used in Examples and Comparative Examples of International Publication No. 2011/048976, for example, Examples 2 and 3.
- a more preferable atomic ratio (copper / zinc) of copper atom and zinc atom in the catalyst is in the range of 2.1 to 3.0.
- a methanol synthesis catalyst containing 3 to 20% by mass of alumina is more preferable.
- such a catalyst can be prepared, for example, by the method described in International Publication No. 2011/048976. More specifically, for example, a step of mixing an aqueous solution containing copper, an aqueous solution containing zinc, and an aqueous alkaline solution to form a precipitate containing copper and zinc, and the obtained precipitate and alumina having a pseudoboehmite structure It is prepared by a production method having a step of mixing with a hydrate to obtain a mixture, and a step of molding the obtained mixture to a density of 2.0 to 3.0 g / mL.
- the catalyst used in the present embodiment is not limited to the above catalyst and the catalyst prepared by the above preparation method, and may be another catalyst having equivalent methanol synthesis activity.
- a method for removing heat from the catalyst layer a method of indirectly exchanging heat between the catalyst layer and the pressurized boiling water using pressurized boiling water as a coolant is preferable.
- the pressurized boiling water is water that boils so that latent heat can be used when heat is removed from the catalyst layer.
- a heat removal mechanism according to such a heat removal method for example, a cooling mechanism for circulating pressurized boiling water in a countercurrent direction or a parallel flow direction with respect to the gas flow direction of the catalyst layer, and a catalyst layer A cooling mechanism for circulating pressurized boiling water in a form orthogonal to the gas flow direction can be mentioned.
- a multi-tubular reactor having an inner pipe parallel to the gas flow direction of the catalyst layer, forming a catalyst layer inside the inner pipe, and circulating a coolant outside the inner pipe.
- a multi-tube reactor having an inner pipe parallel to the gas flow direction of the catalyst layer, forming the catalyst layer outside the inner pipe, and circulating the coolant inside the inner pipe, and the gas flow of the catalyst layer Examples include an interlayer cooling reactor in which a coolant is circulated in an inner pipe arranged in a direction orthogonal to the direction.
- the temperature of pressurized boiling water as a coolant is preferably 210 to 260 ° C.
- a preferred use destination of steam generated from pressurized boiling water is raw material steam for steam reforming reaction of natural gas.
- the pressure of the boiling water is preferably higher than the pressure of a general steam reforming reaction (1.5 to 2.5 MPa-G (15 to 25 kg / cm 2 -G)).
- the temperature of the pressurized boiling water is more preferably 220 to 240 ° C., for example.
- the reaction temperature of the catalyst layer may be controlled by indirect heat exchange with pressurized boiling water at least in the final synthesis step, but in all synthesis steps, the catalyst layer is heated by indirect heat exchange with pressurized boiling water. It is preferable to control the reaction temperature.
- the temperature of the pressurized boiling water in each reactor may mutually be the same, or may differ.
- the methanol synthesis reaction in the synthesis step is performed, for example, under conditions of a pressure of 4.9 to 14.7 MPa-G (50 to 150 kg / cm 2 -G) and a temperature of 200 to 300 ° C. And preferred.
- the pressure and temperature in the methanol synthesis reaction are more preferably a pressure of 7.8 to 10.8 MPa-G (80 to 110 kg / cm 2 -G) and a temperature of 200 to 280 ° C., more preferably a pressure of 7.8. 10.8 MPa-G (80-110 kg / cm 2 -G), temperature 200-270 ° C.
- the ratio of the maximum amount to the minimum amount of methanol production in each methanol synthesis step is preferably 1 to 3, more preferably 1 to 2.
- the separation step In the separation step, unreacted gas is separated from the reaction mixture containing the reaction product obtained through the synthesis step. In other words, methanol or methanol and water contained in the reaction mixture and unreacted gas are separated.
- the separation method include a condensation separation method in which an outlet gas from the synthesis step is cooled and a condensate generated by the cooling is separated by a gas-liquid separator, and a membrane separation method using a separation membrane. Then, the condensation separation method is preferable.
- at least two separation steps (condensation separation step) using the condensation separation method are provided in the synthesis loop, and one of them is a final condensation separation step after the final synthesis step. It is preferable.
- the fluid cooled in the condensation / separation step is an outlet gas (gaseous reaction mixture) from the synthesis step before the condensation / separation step, and contains synthesized methanol.
- Examples of the method for obtaining a liquid containing methanol as a condensate include mutual heat exchange with the synthesis gas supplied to the reactor, air cooling with an air fin cooler, and cooling with a coolant such as cooling water and brine. .
- a method of obtaining a condensate may be used singly or in combination of two or more.
- the method of obtaining the condensate using the cooling accompanying expanding the gas by the decompressor which can be used in the method for producing methanol of the present embodiment can be combined.
- the resulting condensate is generally separated using a gas-liquid separator (hereinafter also simply referred to as “separator”).
- the combination of these coolers (condensers) and separators may be a combination of one cooler and one separator, or a combination of multiple coolers and separators. Also good.
- a plurality of coolers and separators are combined, for example, the one described in JP-A-61-257934 can be cited.
- the condenser is divided into two stages, and the heat transfer surface of the condenser in the previous stage
- Examples include a method in which the temperature is set to a temperature not higher than the dew point of the reaction mixture and not lower than the melting point of the paraffins contained in the reaction mixture, and the heat transfer surface temperature of the subsequent condenser is set to 60 ° C. or lower.
- the first condensing and separating step is a step of condensing and separating the outlet gas (gaseous reaction mixture) from the first synthesizing step, and is provided after the first synthesizing step.
- methanol is preferably 35 to 100 mol%, more preferably 35 to 99 mol%, and even more preferably 75 to 96 mol% of methanol contained in the outlet gas from the first synthesis step. Methanol is withdrawn from the synthesis loop.
- the reaction mixture is cooled until a predetermined amount of methanol or a condensate containing methanol and water is produced by cooling.
- a fluid reaction mixture having a methanol partial pressure of 0.69 to 0.88 MPa-G (7.0 to 9.0 kg / cm 2 -G), preferably 20 to 100 ° C., More preferably, it is preferably cooled to 40 to 80 ° C.
- the separation ratio of methanol contained in the outlet gas from the first synthesis step is preferably higher than 75 mol%.
- the separation ratio of methanol contained in the outlet gas from the first synthesis step in the first condensation / separation step is lower than 96 mol%.
- the target temperature after cooling of the reaction mixture is preferably 55 to 90 ° C. from the same viewpoint.
- the amount of water supplied to the reactor is reduced in the synthesis step that follows the separation step.
- sintering of the copper particles considered to be the active point of the catalyst is suppressed, so that the effect of extending the catalyst life is assumed.
- the balance of the reaction amount in the synthesis step before and after the separation step As a result, the catalyst can be used more effectively.
- the separation step between the plurality of synthesis steps 4 to 25 mol% of the methanol contained in the outlet gas from the synthesis step before the separation step is not separated and supplied to the subsequent synthesis step. It is also possible to control the reaction in the subsequent synthesis step and suppress overheating of the catalyst layer. In this case, the amount of condensable gas that is not removed in the separation step increases.
- the exit gas from the final synthesis process is supplied to the final separation process.
- the final separation step at least a part of the methanol contained in the outlet gas (gaseous reaction mixture) from the final synthesis step is separated.
- the outlet gas from the final synthesis step is preferably cooled to 20 ° C. to 50 ° C., for example, 45 ° C., and the gas phase (unreacted gas) and liquid phase are separated by a gas-liquid separator. And separated.
- the reaction product containing methanol separated in each separation step in the synthesis loop is taken out as crude methanol. Since inert components accumulate in the synthesis loop, it is necessary to remove some gas from the system as a purge gas.
- the purge gas extraction position may be an appropriate position within the synthesis loop.
- the purge gas flow rate at this time may be appropriately adjusted so that the circulation ratio described later is within a desired value.
- the circulation ratio is defined by the molar flow rate of the circulating gas with respect to the molar flow rate of the makeup gas.
- the molar flow rate of the circulating gas is the molar flow rate of the remaining gas obtained by removing the purge gas from the final unreacted gas.
- the reaction product containing methanol separated in each separation step in the synthesis loop is taken out as crude methanol.
- the purge gas extraction position in the synthesis loop is preferably a point where the pressure in the synthesis loop becomes low.
- a part of the unreacted gas after the reaction product in the reaction mixture is separated and extracted out of the synthesis loop is branched as a purge gas. It is more preferable that it is before the upgas merging.
- 4 to 25 mol% of the methanol contained in the outlet gas from the synthesis step before the separation step is not separated and supplied to the subsequent synthesis step. It is also possible to control the reaction in the subsequent synthesis step and suppress overheating of the catalyst layer. In this case, disposing the circulator in the subsequent stage of the preheater in the subsequent stage of the separator used in the separation process and in the subsequent stage of the reactor used in the subsequent synthesis process may cause condensation in the circulator. Yes, not appropriate.
- the circulation ratio in the methanol synthesis process is defined by the ratio of the molar flow rate of the circulating gas to the molar flow rate of the makeup gas.
- the circulation ratio is preferably 0.6 or more and 2.0 or less, more preferably 0.8 or more and 1.5 or less. Comparing the gas composition of the makeup gas and the circulating gas, the makeup gas generates more heat in the catalyst layer because the content of carbon monoxide and carbon dioxide, which are raw materials for methanol synthesis, which is an exothermic reaction, is higher. Easy to make. Therefore, by setting the circulation ratio to 0.6 or more, it is possible to further suppress the catalyst overheating mainly resulting from the makeup gas by dilution with the circulation gas.
- the circulation ratio to 2.0 or less, the energy efficiency of the entire process is improved. This is because by relatively increasing the molar flow rate of the makeup gas, among the components contained in the unreacted gas, it is possible to reduce the molar flow rate of hydrogen or the like that does not need to be cooled. This is because the load on the cooler can be reduced.
- the methanol production method of the present embodiment has at least one boosting step in the synthesis loop.
- a circulator is used for boosting in this boosting step.
- This method for producing methanol has at least one pressurization step after the final preheating step and before the final synthesis step.
- the preheater that can be used in the final preheating step is for raising the temperature of the final mixed gas, which is a supply gas to the final synthesis step, to a predetermined temperature.
- the final reaction mixture ( Usually, it is preferably in the form of heat exchange with gas). In this case, the temperature after preheating of the final mixed gas does not exceed the temperature of the final reaction mixture.
- the reactor outlet temperature of the final reaction mixture gradually approaches the temperature of the pressurized boiling water.
- the final mixed gas preheated by the preheater is supplied at a temperature lower than the temperature of the pressurized boiling water, and the amount of reaction heat recovered by the pressurized boiling water is reduced.
- the temperature of the final mixed gas at the reactor inlet is close to the temperature of the pressurized boiling water.
- the pressure ratio before and after the pressure increase in the pressure increasing step is preferably greater than 1.10, and more preferably greater than 1.20.
- the upper limit of this pressure ratio is not particularly limited, but is usually about 2.00.
- the methanol production method of the present embodiment includes another boosting step of boosting the first mixed gas that has undergone the first preheating step before the first synthesis step. You may have.
- At least one decompression step is included in the synthesis loop.
- This method for producing methanol may have a decompression step after the first synthesis step and before or after the first separation step.
- the manufacturing method of methanol of this embodiment is heat with 1st mixed gas. You may have a pressure reduction process after exchange (cooling by the last mixed gas).
- this methanol manufacturing method has a pressure reduction step after the final synthesis step and before the final separation step, and before or after the step of condensing a part of the final reaction mixture. Furthermore, it is also preferable to have a decompression step after the final separation step and before the first mixing step. Further, when the final reaction mixture at the outlet of the reactor is used as a heat source for preheating the final mixed gas, the method for producing methanol according to this embodiment is performed after heat exchange with the final mixed gas (cooling by the final mixed gas). It is preferable to have a decompression step. Having such a decompression step is preferable from the viewpoint of creating room for recovering energy and reducing the amount of energy used.
- Examples of the energy recovery method include energy recovery by power generation using a pressure difference and pressure conversion type energy recovery used for pressurization of other low-pressure fluid.
- the amount of fluid in the pressure reduction step is larger than in the case of having a pressure reduction step after the final separation step.
- the effect of cooling the final reaction mixture by the reduced pressure can reduce the size of the condenser used to condense a portion of the final reaction mixture prior to the final separation step, depending on the separation target temperature, or In some cases, no condenser is required.
- These decompression steps may be either after the reactor outlet gas has passed through the preheater and before the final separation step, after the final separation step and before the first mixing step, or both. May be.
- the synthesis loop may have three or more mixing steps, three or more synthesis steps, and three or more separation steps. Moreover, you may have two or more pressure
- “before the synthesis step” means that, when there is another synthesis step before the synthesis step, it is after the other synthesis step and further before the synthesis step.
- Means “after the preheating step of the synthesis step” means that after the reactor outlet gas of the synthesis step has passed through the preheater, another synthesis step after that synthesis step. When there is, it means that it is before the preheating step of the other synthesis step.
- FIG. 1 is a schematic diagram showing an example of a production apparatus used in the methanol production method of the present embodiment.
- This production apparatus includes reactors 23a and 23b that synthesize methanol from a synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide, and a separation device that separates unreacted gas from the reaction mixture obtained in the reactors 23a and 23b.
- It is a methanol manufacturing apparatus provided with the gas-liquid separators 26a and 26b which are.
- This methanol production apparatus has a synthesis loop including two reactors 23a and 23b and two gas-liquid separators (separation apparatuses) 26a and 26b, and in the synthesis loop, the second reactor 23b is placed behind the second reactor 23b.
- the remaining gas obtained by removing the purge gas from the second unreacted gas separated from the second reaction mixture in the second gas-liquid separator 26b is 10 to 90 mol% of the makeup gas containing hydrogen, carbon monoxide and carbon dioxide. Obtained in the first reactor 23a, a first reactor 23a for synthesizing methanol from the first mixed gas, and a first reactor 23a for synthesizing methanol from the first mixed gas.
- the first gas-liquid separator 26a for separating the first unreacted gas from the first reaction mixture thus obtained, and the first unreacted gas and 10 to 90 mol% of the makeup gas are mixed to obtain a second mixed gas.
- the second reactor 23b From the second mixing means (joining part to the synthesis loop of the line 3b), the second reactor 23b for finally synthesizing methanol from the second mixed gas, and the second reaction mixture obtained in the second reactor 23b
- a second gas-liquid separator 26b for separating the second unreacted gas, a circulator 32b for increasing the pressure of the second mixed gas after passing through the preheater 22b, and a gas-liquid separator 26b from the second reaction mixture Methanol production comprising a decompressor 34b for decompressing the separated unreacted gas, and controlling the reaction temperature of the catalyst layer in the inner tubes 24a and 24b by indirect heat exchange with the pressurized boiling water in the reactors 23a and 23b Device.
- the pressure reduction machine which pressure-reduces the 2nd reaction mixture after passing through the preheater 22b from the reactor 23b exit instead of or in addition to the pressure reduction machine 34b.
- the second reactor 23b, the second gas-liquid separator 26b, the second reaction mixture, and the second unreacted gas correspond to the final reactor, the final separator, the final reaction mixture, and the final unreacted gas, respectively. To do.
- the synthesis raw material gas containing CO, CO 2 and H 2 generated by the steam reforming reaction is pressurized to a predetermined pressure by the compressor.
- a predetermined amount of the pressurized synthesis source gas (make-up gas) flows through the line 3a and is supplied to the synthesis loop.
- the first mixed gas in the line 4a in which the makeup gas is mixed with the circulating gas is supplied to the preheater 22a.
- the first mixed gas that is the reactor supply gas is heat-exchanged with the reactor outlet gas (first reaction mixture) containing the reaction product flowing in the line 7a at the outlet of the reactor 23a.
- the rest of the makeup gas circulates in the line 3b.
- the reactor 23a has an inner tube 24a, and the inner tube 24a is filled with a methanol synthesis catalyst containing copper and zinc as essential components to form a catalyst layer.
- Methanol is synthesized in the process in which the first mixed gas supplied from the line 5a into the reactor 23a passes through the catalyst layer in the inner tube 24a.
- the pressure and temperature of the fluid in the catalyst layer may be within the range of the reaction and temperature in the methanol synthesis reaction.
- the reactor outlet gas (first reaction mixture) containing methanol that has flowed out of the reactor 23a to the line 7a is cooled in the preheater 22a, and further cooled to below the dew point of methanol by the condenser 25a. Condensation is promoted.
- the condensed fluid containing methanol is extracted out of the system from the line 9a with the condensed component as crude methanol in the gas-liquid separator 26a, and the remaining gas phase component flows through the line 8a.
- the makeup gas that has flowed into the line 3b is mixed with the unreacted gas that has flowed through the line 8a from the gas-liquid separator 26a and preheated from the line 4b as the second mixed gas that is the reactor supply gas. Is supplied to the container 22b.
- the second mixed gas preheated to a predetermined temperature is supplied from the line 5b to the circulator 32b, and after being increased to a predetermined reaction pressure, is supplied from the line 6b to the reactor 23b.
- the reactor 23b has an inner tube 24b, and a methanol synthesis catalyst containing copper and zinc as essential components is filled in the inner tube 24b to form a catalyst layer.
- Methanol is synthesized in the process in which the second mixed gas supplied from the line 6b into the reactor 23b passes through the catalyst layer in the inner tube 24b.
- the pressure and temperature of the fluid in the catalyst layer may be within the range of the reaction and temperature in the methanol synthesis reaction.
- the reactor outlet gas (second reaction mixture) containing methanol flowing out from the reactor 23b to the line 7b is cooled in the preheater 22b, and further cooled to a predetermined temperature by the condenser 25b. It is further condensed.
- the second reaction mixture containing the condensed methanol is extracted from the line 9b out of the system with the condensed component as crude methanol in the gas-liquid separator 26b, and the gas phase component (second unreacted gas) passes through the line 8b. Circulate.
- the second unreacted gas flowing through the line 8b is decompressed by the decompressor 34b.
- a portion of the second unreacted gas in an amount that provides a predetermined circulation ratio flows through the line 16 as a circulating gas, merges with the makeup gas that flows through the line 3a, and is circulated to the reactor 23a.
- the remaining unreacted gas is withdrawn from the synthesis loop through the line 15 as a purge gas in order to remove inactive components accumulated in the synthesis loop.
- Cooling of the catalyst layer in the reactor 23a and the reactor 23b is performed by introducing boiler water from the steam drums 33a and 33b into the reactors 23a and 23b through the lines 43a and 43b, respectively, and using it as pressurized boiling water. This is done in the process of recovering the generated water vapor-containing fluid from the lines 44a and 44b to the steam drums 33a and 33b, respectively.
- Water vapor generated by the reaction heat is taken out from the steam drums 33a and 33b to the lines 42a and 42b, and an amount of water that supplements the amount of water vapor is supplied from the lines 41a and 41b to the steam drums 33a and 33b.
- the water vapor taken out from the lines 42a and 42b can be used as raw water vapor necessary for the steam reforming reaction when the raw material gas is produced from natural gas.
- FIG. 3 is a schematic diagram showing another example of a production apparatus used in the methanol production method of the present embodiment.
- the difference from the manufacturing apparatus shown in FIG. 1 is that two circulators and two decompressors are provided in the synthesis loop. That is, one point is that the first mixed gas, which is the reactor supply gas preheated by the preheater 22a, is supplied from the line 5a to the circulator 32a, and after the pressure is increased by the circulator 32a, the reactor is supplied from the line 6a. It is a point supplied to 23a.
- the first mixed gas which is the reactor supply gas preheated by the preheater 22a
- FIG. 4 is a schematic diagram showing still another example of a production apparatus used in the methanol production method of the present embodiment.
- the difference from the production apparatus shown in FIG. 1 is that it comprises three mixing means, reactors, gas-liquid separators, circulators and compressors.
- unreacted gas is produced from reactors 23a, 23b and 23c for synthesizing methanol from synthesis gas containing hydrogen, carbon monoxide and carbon dioxide, and reaction mixtures obtained in the reactors 23a, 23b and 23c.
- Gas-liquid separators 26a, 26b and 26c which are separation devices to be separated, decompressors 34a, 34b and 34c which are devices for decompressing unreacted gas obtained in the gas-liquid separators 26a, 26b and 26c, and a reactor
- This methanol production apparatus has a synthesis loop including three reactors 23a, 23b, and 23c and three gas-liquid separators (separation apparatuses) 26a, 26b, and 26c.
- the third reactor The remaining gas obtained by removing the purge gas from the third unreacted gas separated from the third reaction mixture in the third gas-liquid separator 26c after 23c is used as a makeup gas 10 containing hydrogen, carbon monoxide, and carbon dioxide.
- First mixing means (mixing part to the synthesis loop of the line 3a) to obtain a first mixed gas mixed with ⁇ 90 mol%, a first reactor 23a for synthesizing methanol from the first mixed gas, and a first reaction
- a first gas-liquid separator 26a for separating the first unreacted gas from the first reaction mixture obtained in the vessel 23a, and the first unreacted gas and 50 to 85 mol% of the makeup gas are mixed.
- a second mixing means for obtaining two mixed gases (a merging portion of the line 3b to the synthesis loop), a second reactor 23b for synthesizing methanol from the second mixed gas, and a second reaction obtained in the second reactor 23b.
- a second gas-liquid separator 26b for separating the second unreacted gas from the mixture, and a third mixing means for mixing the second unreacted gas and 5 to 85 mol% of the makeup gas to obtain a third mixed gas (
- the third reactor 23c for finally synthesizing methanol from the third mixed gas, and the third unreacted gas from the third reaction mixture obtained in the third reactor 23c.
- a third gas-liquid separator 26c that circulates the preheaters 22a, 22b, and 22c, and circulators 32a, 32b, and 32c that pressurize the mixed gas that has passed through the preheaters 22a, 22b, and 22c.
- 26b and Pressure reducing devices 34a, 34b and 34c for reducing the pressure of the unreacted gas separated in 26c, respectively.
- In the reactors 23a, 23b and 23c in the inner tubes 24a, 24b and 24c by indirect heat exchange with pressurized boiling water. This is a methanol production apparatus for controlling the reaction temperature of the catalyst layer.
- a decompressor for decompressing the reaction mixture after passing through the preheaters 22a, 22b and 22c from the outlets of the reactors 23a, 23b and 23c. May be provided.
- the third reactor 23c, the third gas-liquid separator 26c, the third reaction mixture, and the third unreacted gas correspond to the final reactor, the final separator, the final reaction mixture, and the final unreacted gas, respectively. To do.
- the synthesis raw material gas containing CO, CO 2 and H 2 generated by the steam reforming reaction is pressurized to a predetermined pressure by the compressor.
- a predetermined amount of the pressurized synthesis source gas (make-up gas) flows through the line 3a and is supplied to the synthesis loop.
- the reactor supply gas (first mixed gas) in the line 4a mixed with the makeup gas is supplied to the preheater 22a.
- the first mixed gas is preheated to a predetermined temperature by heat exchange with the reactor outlet gas (first reaction mixture) containing the reaction product flowing in the line 7a at the outlet of the reactor 23a.
- the pressure is supplied from the line 5a to the circulator 32a, and the pressure is increased to a predetermined reaction pressure, and then the pressure is supplied from the line 6a to the reactor 23a.
- the reactor 23a has an inner tube 24a, and the inner tube 24a is filled with a methanol synthesis catalyst containing copper and zinc as essential components to form a catalyst layer. Methanol is synthesized while the first mixed gas supplied from the line 6a into the reactor 23a passes through the catalyst layer in the inner tube 24a.
- the pressure and temperature of the fluid in the catalyst layer may be within the range of the reaction and temperature in the methanol synthesis reaction.
- the outlet gas (first reaction mixture) containing methanol flowing out from the reactor 23a to the line 7a is cooled in the preheater 22a, and further cooled to below the dew point of methanol by the condenser 25a, thereby condensing the methanol. Promoted.
- the condensed fluid containing methanol is extracted from the line 9a out of the system as a condensed methanol in the gas-liquid separator 26a, and the remaining gas phase is circulated in the line 8a.
- the first unreacted gas taken out to the line 8a is decompressed to a predetermined pressure by the decompressor 34a.
- the gas that has been circulated in the line 3b is mixed with the first unreacted gas that has circulated in the line 8a from the gas-liquid separator 26a, and is supplied from the line 4b as a reactor supply gas (second mixed gas). , And supplied to the preheater 22b.
- the second mixed gas preheated to a predetermined temperature is supplied from the line 5b to the circulator 32b, and is pressurized to a predetermined reaction pressure and then supplied from the line 6b to the reactor 23b.
- the reactor 23b has an inner tube 24b, and a methanol synthesis catalyst containing copper and zinc as essential components is filled in the inner tube 24b to form a catalyst layer.
- Methanol is synthesized in the process in which the second mixed gas supplied from the line 6b into the reactor 23b passes through the catalyst layer in the inner tube 24b.
- the pressure and temperature of the fluid in the catalyst layer may be within the range of the reaction and temperature in the methanol synthesis reaction.
- the reactor outlet gas (second reaction mixture) containing methanol flowing out from the reactor 23b to the line 7b is cooled in the preheater 22b, it is further cooled in the condenser 25b, thereby condensing methanol.
- the condensed fluid containing methanol is extracted from the line 9b out of the system as a condensed methanol in the gas-liquid separator 26b, and the remaining gas phase is circulated in the line 8b.
- the second unreacted gas taken out to the line 8b is decompressed to a predetermined pressure by the decompressor 34b.
- the makeup gas that has flowed into the line 3c is mixed with the second unreacted gas that has flowed through the line 8b from the gas-liquid separator 26b, and is supplied as a reactor supply gas (third mixed gas) from the line 4c. , And supplied to the preheater 22c.
- the third mixed gas preheated to a predetermined temperature is supplied from the line 5c to the circulator 32c, and is pressurized to a predetermined reaction pressure and then supplied from the line 6c to the reactor 23c.
- the reactor 23c has an inner tube 24c, and a methanol synthesis catalyst containing copper and zinc as essential components is filled in the inner tube 24c to form a catalyst layer.
- Methanol is synthesized in the process in which the third mixed gas supplied from the line 6c into the reactor 23c passes through the catalyst layer in the inner tube 24c.
- the pressure and temperature of the fluid in the catalyst layer may be within the range of the reaction and temperature in the methanol synthesis reaction.
- the reactor outlet gas (third reaction mixture) containing methanol flowing out from the reactor 23c to the line 7c is cooled in the preheater 22c, and further cooled to a predetermined temperature by the condenser 25c. It is further condensed.
- the condensed fluid containing methanol is extracted out of the system from the line 9c with the condensed component as crude methanol in the gas-liquid separator 26c, and the gas phase component (third unreacted gas) flows through the line 8c.
- the third unreacted gas taken out to the line 8c is decompressed to a predetermined pressure by the decompressor 34c.
- an amount of the third unreacted gas having a predetermined circulation ratio joins the makeup gas flowing from the line 16 through the line 3a as the circulating gas, to the reactor 23a. Circulated.
- the remaining third unreacted gas is withdrawn from the synthesis loop through the line 15 as a purge gas in order to remove inert components accumulated in the synthesis loop.
- Cooling of the catalyst layers of the reactor 23a, the reactor 23b, and the reactor 23c is performed by introducing boiler water from the steam drums 33a, 33b, and 33c into the reactors 23a, 23b, and 23c from the lines 43a, 43b, and 43c, respectively. It is used in the process where the fluid containing the generated water vapor is recovered from the lines 44a, 44b and 44c to the steam drums 33a, 33b and 33c, respectively, using it as pressurized boiling water. The water vapor generated by the reaction heat is taken out from the steam drums 33a, 33b and the steam drum 33c to the lines 42a, 42b and 42c, respectively. To supply. The steam taken out from the lines 42a, 42b and the line 42c can be used as a raw material steam necessary for a steam reforming reaction when the raw material gas is generated from natural gas.
- the first unreacted gas and at least a part of 10 to 90 mol% of the makeup gas are mixed to obtain the second mixed gas in the intermediate mixing step.
- synthesizing methanol from the second mixed gas corresponds to the intermediate synthesis step
- separating the second unreacted gas from the second reaction mixture corresponds to the intermediate separation step.
- the catalyst used for methanol synthesis was a catalyst (methanol synthesis catalyst A) prepared by the method described in Example 3 of International Publication No. 2011/048976.
- Example 1 In Example 1, the manufacturing apparatus shown in FIG. 1 was used. Each condition was as follows. That is, methanol was synthesized under the condition of a circulation ratio of 1.0 using a gas generated by a steam reforming reaction of natural gas as a raw material gas. Moreover, the methanol synthesis catalyst A was used as a catalyst in the reactors 23a and 23b. The raw material gas was pressurized to 8.0 MPa-G by a compressor. 50 mol% of the pressurized synthesis raw material gas (make-up gas) was circulated in the line 3a and mixed with the circulating gas circulated in the line 16 to obtain a reactor supply gas (first mixed gas).
- the first mixed gas flowing through the line 4a is exchanged with the reactor outlet gas (first reaction mixture) containing the reaction product flowing through the line 7a at the outlet of the reactor 23a by the preheater 22a. Preheating was performed so that the temperature in 5a was 200 ° C. The remaining 50 mol% of the makeup gas was circulated in the line 3b. The first mixed gas after preheating was supplied to the reactor 23a to synthesize methanol (first synthesis step). The pressure of the fluid in the catalyst layer of the reactor 23a was 7.8 MPa-G, and the temperature was between 200 and 254 ° C.
- the outlet gas (first reaction mixture) from the first synthesis step was cooled to 45 ° C. (total pressure 7.6 MPa-G), which is lower than the dew point of methanol, by the condenser 25a to promote the condensation of methanol.
- the first unreacted gas separated by the gas-liquid separator 26a was circulated in the line 8a and mixed with the makeup gas circulated in the line 3b to obtain a reactor supply gas (second mixed gas).
- the line 5b was preheated to a temperature of 190 ° C.
- the second mixed gas flowing in the line 5b was increased so that the pressure in the line 6b became 9.8 MPa-G in the process of passing through the circulator 32b. As the pressure increased, the temperature of the second mixed gas flowing in the line 6b became 230 ° C.
- the second mixed gas after the pressure increase was supplied to the reactor 23b to synthesize methanol.
- the fluid pressure in the catalyst layer was 9.8 MPa-G, and the temperature was between 230 and 265 ° C.
- the outlet gas (second reaction mixture) containing methanol flowing out from the reactor 23b to the line 7b was cooled in the preheater 22b, it was cooled to 45 ° C. by the condenser 25b to further condense the methanol.
- the second unreacted gas separated by the gas-liquid separator 26b is circulated in the line 8b and decompressed in the process of passing through the decompressor 34, and then a part is taken out from the line 15 as a purge gas, and the rest in the line 16 Circulating gas was circulated.
- the molar flow rate of the circulating gas flowing through the line 16 is controlled to be equal to the molar flow rate of the makeup gas.
- the molar flow rate of the purge gas (line 15) relative to the molar flow rate of the second unreacted gas in the line 8b is 19 4%.
- the material balance is shown in Table 1.
- the vertical column is the line number shown in FIG. 1, and the horizontal column is the temperature, pressure and substance flow rate of the fluid flowing through each line.
- the maximum temperature of the catalyst layer in Example 1 was 254 ° C. in the inner tube 24a of the reactor 23a and 265 ° C. in the inner tube 24b of the reactor 23b, which was a very preferable temperature range as the catalyst operating temperature range.
- the temperature of the pressurized boiling water as a coolant was 230 ° C.
- the recovered heat amount was 89.7 MW, and the circulator power was 8.8 MW.
- the molar flow rate (the sum of the methanol molar flow rate in line 9a and the methanol molar flow rate in line 9b) was 97.0% (the carbon yield was calculated in the same manner below).
- Comparative Example 1 In Comparative Example 1, the manufacturing apparatus shown in FIG. 2 was used. The difference from the first embodiment is the position of the circulator in the synthesis loop. Specifically, after the remaining unreacted gas separated in the gas-liquid separator 26a is taken out in the line 8a and the makeup gas from the line 3b is mixed and before passing through the preheater 22b, This is the point where the pressure is increased by the circulator 32b. The composition, the total molar flow rate, the temperature, and the pressure of the makeup gas flowing through the lines 3a and 3b were the same as those in Example 1. Comparative Example 1 is based on the technique of Patent Document 2.
- Table 2 shows the material balance of Comparative Example 1.
- the vertical column is the line number shown in FIG. 2, and the horizontal column is the temperature, pressure and substance flow rate of the fluid flowing through each line.
- the maximum temperature of the catalyst layer in Comparative Example 1 was 254 ° C. in the inner tube 24a of the reactor 23a and 260 ° C. in the inner tube 24b of the reactor 23b. At this time, the temperature of the pressurized boiling water as a coolant was 230 ° C., the amount of recovered heat was 81.8 MW, and the circulator power was 6.5 MW.
- Example 1 The difference between Example 1 and Comparative Example 1 is whether the circulating machine is arranged before the preheater or after the preheater.
- the result of Example 1 having a pressure increasing process after preheating in the preheater increased by +2.3 MW in the input energy to the circulator compared to the result of Comparative Example 1 in which preheating after pressure increasing, the recovered energy in the reactor +7.9 MW increased, and the energy saving effect was 5.6 MW in total.
- Example 2 In Example 2, the manufacturing apparatus shown in FIG. 3 was used. Each condition was as follows. That is, methanol was synthesized under the condition of a circulation ratio of 1.0 using a gas generated by a steam reforming reaction of natural gas as a raw material gas. Moreover, the methanol synthesis catalyst A was used as a catalyst in the reactors 23a and 23b. The raw material gas was pressurized to 8.0 MPa-G by a compressor. 50 mol% of the pressurized synthesis raw material gas (make-up gas) was circulated in the line 3a and mixed with the circulating gas circulated in the line 16 to obtain a reactor supply gas (first mixed gas).
- the first mixed gas that has flowed through the line 4a is heat-exchanged with the outlet gas (first reaction mixture) containing the reaction product that flows through the line 7a at the outlet of the reactor 23a in the preheater 22a, so that the line 5a was preheated to a temperature of 195 ° C.
- the first mixed gas flowing in the line 5a was pressurized so that the pressure in the line 6a became 9.8 MPa-G in the process of passing through the circulator 32a. As the pressure increased, the temperature of the first mixed gas flowing through the line 6a became 230 ° C. The remaining 50 mol% of the makeup gas was circulated in the line 3b.
- the first mixed gas after the pressure increase was supplied to the reactor 23a to synthesize methanol (first synthesis step).
- the fluid pressure in the catalyst layer was 9.8 MPa-G, and the temperature was 230-272 ° C.
- the outlet gas (first reaction mixture) from the first synthesis step was cooled to 45 ° C. (total pressure 9.6 MPa-G), which is lower than the dew point of methanol, by the condenser 25a to promote the condensation of methanol.
- the first unreacted gas separated by the gas-liquid separator 26a is circulated in the line 8a, depressurized in the process of passing through the decompressor 34a, and then mixed with the makeup gas circulated in the line 3b.
- a supply gas (second mixed gas) was obtained.
- the line 5b By exchanging heat between the second mixed gas flowing through the line 4b and the outlet gas (second reaction mixture) containing the reaction product flowing through the line 7b at the outlet of the reactor 23b in the preheater 22b, the line 5b was preheated to a temperature of 195 ° C.
- the second mixed gas flowing in the line 5b was increased so that the pressure in the line 6b became 9.8 MPa-G in the process of passing through the circulator 32b.
- the temperature of the second mixed gas flowing in the line 6b became 230 ° C.
- the second mixed gas after the pressure increase was supplied to the reactor 23b to synthesize methanol.
- the fluid pressure in the catalyst layer was 9.8 MPa-G, and the temperature was between 230 and 269 ° C.
- the material balance is shown in Table 3.
- the vertical column is the line number shown in FIG. 3, and the horizontal column is the temperature, pressure and substance flow rate of the fluid flowing through each line.
- the maximum temperature of the catalyst layer in Example 2 was 272 ° C. in the inner tube 24a of the reactor 23a and 269 ° C. in the inner tube 24b of the reactor 23b, which was a preferable temperature range as the catalyst operating temperature range.
- the temperature of the pressurized boiling water as a coolant was 230 ° C.
- the amount of recovered heat was 97.4 MW
- the circulator power was 14.5 MW in total.
- Example 2 The carbon yield in Example 2 was 97.5%.
- Example 2 increased by +8.0 MW in the input energy to the circulator compared with the result in Comparative Example 1, it increased by +15.6 MW in the recovered energy in the reactor, so that the energy in total was 7.6 MW.
- the reduction effect was shown. Furthermore, if pressure energy is recovered in the pressure reducing operation by the pressure reducer, 2.6 MW energy is recovered in Comparative Example 1 and 5.0 MW energy is recovered in Example 2, so that the total is 10.0 MW. Energy saving effect.
- Example 3 In Example 3, the manufacturing apparatus shown in FIG. 4 was used. Each condition was as follows. That is, methanol was synthesized under the condition of a circulation ratio of 1.0 using a gas generated by a steam reforming reaction of natural gas as a raw material gas. Moreover, the methanol synthesis catalyst A was used as a catalyst in the reactors 23a, 23b, and 23c. The raw material gas was pressurized to 8.0 MPa-G by a compressor. 30 mol% of the pressurized synthesis raw material gas (make-up gas) was circulated in the line 3a and mixed with the circulating gas circulated in the line 16 to obtain a reactor supply gas (first mixed gas).
- the first mixed gas that has flowed through the line 4a is heat-exchanged with the outlet gas (first reaction mixture) containing the reaction product that flows through the line 7a at the outlet of the reactor 23a in the preheater 22a, so that the line 5a was preheated to a temperature of 195 ° C.
- the first mixed gas flowing in the line 5a was pressurized so that the pressure in the line 6a became 9.8 MPa-G in the process of passing through the circulator 32a.
- the temperature of the first mixed gas flowing through the line 6a became 230 ° C. 50 mol% of the makeup gas was passed through line 3b and the remaining 20 mol% was passed through line 3c.
- the first mixed gas after the pressure increase was supplied to the reactor 23a to synthesize methanol (first synthesis step).
- the pressure of the fluid in the catalyst layer of the reactor 23a was 9.8 MPa-G, and the temperature was 230-264 ° C.
- the outlet gas (first reaction mixture) from the first synthesis step was cooled to 80 ° C. (total pressure 9.6 MPa-G) below the dew point of methanol by the condenser 25a to promote the condensation of methanol.
- the first unreacted gas separated by the gas-liquid separator 26a is circulated in the line 8a, depressurized in the process of passing through the decompressor 34a, and then mixed with the makeup gas circulated in the line 3b.
- a supply gas (second mixed gas) was obtained.
- the line 5b By exchanging heat between the second mixed gas flowing through the line 4b and the outlet gas (second reaction mixture) containing the reaction product flowing through the line 7b at the outlet of the reactor 23b in the preheater 22b, the line 5b was preheated to a temperature of 195 ° C.
- the second mixed gas flowing in the line 5b was increased so that the pressure in the line 6b became 9.8 MPa-G in the process of passing through the circulator 32b.
- the temperature of the second mixed gas flowing in the line 6b became 230 ° C.
- the fluid pressure in the catalyst layer was 9.8 MPa-G, and the temperature was between 230 and 265 ° C.
- the outlet gas (second reaction mixture) containing methanol flowing out from the reactor 23b to the line 7b was cooled in the preheater 22b, and then cooled to 45 ° C. with the condenser 25b to further condense the methanol.
- the second unreacted gas separated by the gas-liquid separator 26b is circulated in the line 8b, depressurized in the process of passing through the decompressor 34b, mixed with the makeup gas circulated in the line 3c, and supplied to the reactor.
- a gas (third mixed gas) was obtained.
- the third mixed gas that has flowed through the line 4c is subjected to heat exchange with the outlet gas (third reaction product) containing the reaction product that flows through the line 7c at the outlet of the reactor 23c in the preheater 22c. Preheating was performed so that the temperature at 5c was 195 ° C.
- the third mixed gas flowing in the line 5c was boosted so that the pressure in the line 6c was 9.8 MPa-G in the process of passing through the circulator 32c. As the pressure increased, the temperature of the third mixed gas flowing in the line 6c became 230 ° C.
- the third mixed gas after the pressure increase was supplied to the reactor 23c to synthesize methanol.
- the fluid pressure in the catalyst layer was 9.8 MPa-G, and the temperature was between 230 and 254 ° C.
- the outlet gas (third reaction product) containing methanol flowing out from the reactor 23c to the line 7c was cooled in the preheater 22c, it was cooled to 45 ° C. by the condenser 25c to further condense the methanol.
- the third unreacted gas separated by the gas-liquid separator 26c circulates in the line 8c and is depressurized in the process of passing through the decompressor 34c, and then a part is taken out from the line 15 as a purge gas, and the rest in the line 16 Circulating gas was circulated.
- the molar flow rate of the circulating gas flowing through the line 16 is controlled to be 1.0 times the molar flow rate of the makeup gas.
- the purge gas (line 15) moles relative to the molar flow rate of the third unreacted gas in the line 8b.
- the flow rate was 18.5%.
- the material balance is shown in Table 4.
- the vertical column is the line number shown in FIG. 4, and the horizontal column is the temperature, pressure, and substance flow rate of the fluid flowing through each line.
- the maximum temperature of the catalyst layer in Example 3 is 264 ° C. in the inner tube 24a of the reactor 23a, 265 ° C. in the inner tube 24b of the reactor 23b, and 254 ° C. in the inner tube 24c of the reactor 23c. It was a preferable temperature range. At this time, the temperature of the pressurized boiling water as a coolant was 230 ° C., the amount of recovered heat was 97.5 MW, and the circulator power was 20.0 MW in total.
- Example 3 The carbon yield in Example 3 was 98.5%.
- Example 3 increased by +13.5 MW in the input energy to the circulator compared with the result in Comparative Example 1, it increased by +15.7 MW in the recovered energy in the reactor, so that the total energy was 2.2 MW.
- the reduction effect was shown. Furthermore, if pressure energy is recovered in the pressure reducing operation with the pressure reducer, 2.6 MW energy is recovered in Comparative Example 1 and 7.8 MW energy is recovered in Example 3, so that the total is 7.5 MW. Energy saving effect.
- Example 4 In Example 4, the manufacturing apparatus shown in FIG. 5 was used. Each condition was as follows. That is, methanol was synthesized under the condition of a circulation ratio of 1.0 using a gas generated by a steam reforming reaction of natural gas as a raw material gas. Moreover, the methanol synthesis catalyst A was used as a catalyst in the reactors 23a and 23b. The raw material gas was pressurized to 8.0 MPa-G by a compressor. 50 mol% of the pressurized synthesis raw material gas (make-up gas) was circulated in the line 3a and mixed with the circulating gas circulated in the line 16 to obtain a reactor supply gas (first mixed gas).
- the first mixed gas flowing through the line 4a is exchanged with the reactor outlet gas (first reaction mixture) containing the reaction product flowing through the line 7a at the outlet of the reactor 23a in the preheater 22a. Preheating was performed so that the temperature in 5a was 200 ° C. The remaining 50 mol% of the makeup gas was circulated in the line 3b. The first mixed gas after preheating was supplied to the reactor 23a to synthesize methanol (first synthesis step). The pressure of the fluid in the catalyst layer of the reactor 23a was 7.8 MPa-G, and the temperature was between 200 and 254 ° C.
- the outlet gas (first reaction mixture) from the first synthesis step was cooled to 45 ° C. (total pressure 7.6 MPa-G), which is lower than the dew point of methanol, by the condenser 25a to promote the condensation of methanol.
- the first unreacted gas separated by the gas-liquid separator 26a was circulated in the line 8a and mixed with the makeup gas circulated in the line 3b to obtain a reactor supply gas (second mixed gas).
- the line 5b was preheated to a temperature of 190 ° C.
- the second mixed gas flowing in the line 5b was increased so that the pressure in the line 6b became 9.8 MPa-G in the process of passing through the circulator 32b. As the pressure increased, the temperature of the second mixed gas flowing in the line 6b became 230 ° C.
- the second mixed gas after the pressure increase was supplied to the reactor 23b to synthesize methanol.
- the fluid pressure in the catalyst layer was 9.8 MPa-G, and the temperature was between 230 and 264 ° C.
- the outlet gas (second reaction mixture) containing methanol flowing out from the reactor 23b to the line 7b is cooled in the preheater 22b, the pressure is reduced in the process of passing through the decompressor 34, and cooled to 45 ° C. by the condenser 25b.
- the methanol was further condensed. After the second unreacted gas separated by the gas-liquid separator 26 b was circulated in the line 8 b, a part was taken out as a purge gas from the line 15, and the rest was used as a circulating gas circulated in the line 16.
- the molar flow rate of the circulating gas flowing through line 16 is controlled to be equal to the molar flow rate of makeup gas, so that the molar flow rate of the purge gas (line 15) relative to the molar flow rate of unreacted gas in line 8b is 19.4. %Met.
- the material balance is shown in Table 5.
- the vertical column is the line number shown in FIG. 5, and the horizontal column is the temperature, pressure, and substance flow rate of the fluid flowing through each line.
- the maximum temperature of the catalyst layer in Example 4 was 254 ° C. in the inner tube 24a of the reactor 23a and 264 ° C. in the inner tube 24b of the reactor 23b, which was a very preferable temperature range as the catalyst operating temperature range.
- the temperature of the pressurized boiling water as a coolant was 230 ° C.
- the recovered heat amount was 89.7 MW, and the circulator power was 8.8 MW.
- Example 4 The carbon yield in Example 4 was 96.9%.
- Example 4 the load of the condenser 25b was 31.1 MW, and the recovered energy when energy recovery was performed in the decompressor 34b was 3.9 MW. In the first embodiment, the load on the condenser 25b was 35.1 MW, so in the fourth embodiment, the condenser load can be reduced more than in the first embodiment, which leads to the cost reduction of the condenser itself. became.
- Table 6 shows the energy input to the circulator in each example, the energy recovered by the decompressor, the energy recovered by the reactor, and the recovered energy (net recovered energy) in the entire apparatus that summarizes the balance of those.
- the catalyst layer temperature can be appropriately maintained while the circulation ratio is lowered, the carbon yield in methanol synthesis can be increased, and the amount of energy used can be reduced (in other words, the amount of recovered energy can be increased). ), And the reaction can proceed more efficiently. Therefore, the present invention has industrial applicability in a methanol production method and production apparatus.
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Abstract
Description
特許文献3は、反応器における原料分圧を高くすることで、過反応や高温につながると述べている。そして、この高温によって触媒劣化速度が高くなることにつながる可能性があると指摘している。そこで、特許文献3に記載の技術は、期待される触媒寿命を短くせず、経済的に成り立つ手法で大量の目的物を得る手法として、合成ループ内に反応器を複数配置し、それぞれの反応器後に分離器を配置し、原料ガスを複数の反応器前に供給することも可能な方法で、反応器間で昇圧することを特徴とした技術を提案している。特許文献3は、上記技術により、循環ガス量を低減し、触媒層温度を制御し、それにより、受け入れ可能な触媒寿命を達成した上で、達成すべき所望の生成物の生産を可能にしたと記載している。そして、実施例においては、循環ガス量の23%又は約28%を削減したことが示されている。
加えて、メタノール合成に伴い生じる熱によって触媒のシンタリングが促進されたり、非特許文献1に記載のように、メタノール合成に伴い生成する水が触媒劣化を促進させたりする。そこで、メタノール合成では、触媒を有効に利用するに当たって触媒の負荷を平準化し、効率的に触媒を利用することが求められている。
特許文献3は、循環ガス量を低減し、触媒層温度を制御することで受け入れ可能な触媒寿命を達成した上で、達成すべき所望の生成物の生産を可能にしたと記載している。しかしながら、その実施例では、循環ガス量が既存技術に対して72%又は77%に低減できたことを示しているにすぎず、カーボン収率についての記載もない。カーボン収率について考慮しないのであれば、循環ガス量を低減したとしても、原料ガス量を増加して生産量を維持することが可能であり、技術的な革新性がない。
また、メイクアップガス入口に対して、合成ループにおける最も遠い位置にパージガスの取り出しを設けるのが、カーボン収率の観点から最も都合がよい。一方で、循環機の処理ガス量の観点では、合成ループにおけるパージガスの取り出し位置は循環機の直前がよい。特許文献3に開示されたプロセスは、本来であれば循環機によって昇圧する必要のないガス(合成ループから取り出すパージガス)を昇圧するプロセスとなっている。これでは、循環器の処理ガス量が増大し、エネルギー使用量が増加してしまうので、適切ではない。
加えて、最終の凝縮分離工程ではない凝縮分離工程において、冷却水削減の目的又は機器費削減の目的で、水冷熱交換器を用いずにエアフィンクーラーのみを用いて、冷却器出口ガス温度を55~90℃としてメタノール分離割合を低下させる場合、その凝縮分離の工程に用いる機器の後段に循環機を配置すると、導入される凝縮性気体の総量が増加する。この場合、特に、気液分離直後の飽和状態の凝縮性気体を循環機に導入する場合、循環機内で凝縮液滴が発生する確率が高まる。循環機内で凝縮液滴が発生すると機械的な故障およびエネルギー損失の原因となり、この位置に循環機を配置するのは適切ではない。
また、プラントの大型化による経済性向上を追求する場合に行われる並列化については、例えば反応器を並列化する場合、反応器に導入できるガス量が増加するため大型化は可能となる。しかしながら、そのような並列化は、一般的に収率改善や循環比低減にはつながるものではない。
[1]水素と一酸化炭素と二酸化炭素とを含む合成ガスからメタノールを合成する合成工程と、前記合成工程を経て得られた反応混合物から未反応ガスを分離する分離工程と、を有するメタノール製造方法であって、少なくとも2つの前記合成工程と、少なくとも2つの前記分離工程とを有する合成ループを有し、前記合成ループにおいて、最終合成工程の後の最終分離工程で最終反応混合物から分離した最終未反応ガスからパージガスを取り除いた残りのガスに、水素と一酸化炭素と二酸化炭素とを含むメイクアップガスの10~90モル%と混合して第1混合ガスを得る第1混合工程と、前記第1混合ガスからメタノールを合成する第1合成工程と、前記第1合成工程で得られた第1反応混合物から第1未反応ガスを分離する第1分離工程と、最終的に未反応ガスと前記メイクアップガスの10~90モル%のうちの少なくとも一部とを混合して最終混合ガスを得る最終混合工程と、前記最終混合ガスからメタノールを合成する前記最終合成工程と、前記最終合成工程で得られた前記最終反応混合物から前記最終未反応ガスを分離する前記最終分離工程と、を有し、前記第1混合ガスを予熱する第1予熱工程と、前記最終混合ガスを予熱する最終予熱工程と、前記最終予熱工程を経た前記最終混合ガスを前記最終合成工程の前に循環機によって昇圧する昇圧工程と、を有し、かつ加圧沸騰水との間接熱交換により触媒層の反応温度を制御する、メタノール製造方法。
[2]前記最終予熱工程において前記最終混合ガスを予熱する熱源が、前記最終反応混合物である、[1]に記載のメタノール製造方法。
[3]前記最終混合ガスを予熱した前記最終反応混合物を、前記最終分離工程の前に減圧する最終反応混合物減圧工程を有する、[2]に記載のメタノール製造方法。
[4]前記最終分離工程で得られた最終未反応ガスを、前記第1混合工程の前に減圧する最終未反応ガス減圧工程を有する、[1]~[3]のいずれか1つに記載のメタノール製造方法。
[5]前記第1予熱工程を経た前記第1混合ガスを、前記第1合成工程の前に昇圧する昇圧工程を有する、[1]~[4]のいずれか1つに記載のメタノール製造方法。
[6]前記第1予熱工程において前記第1混合ガスを予熱する熱源が、前記第1反応混合物である、[1]~[5]のいずれか1つに記載のメタノール製造方法。
[7]前記第1混合ガスを予熱した前記第1反応混合物を、前記第1分離工程の前に減圧する第1反応混合物減圧工程を有する、[6]記載のメタノール製造方法。
[8]前記第1分離工程で得られた第1未反応ガスを減圧する第1未反応ガス減圧工程を有する、[1]~[7]のいずれか1つに記載のメタノール製造方法。
[9]前記昇圧工程における昇圧前後の圧力比が1.10を超える、[1]~[8]のいずれか1つに記載のメタノール製造方法。
[10]前記第1分離工程の後、前記最終混合工程の前に、未反応ガスと前記メイクアップガスの10~90モル%のうちの少なくとも一部とを混合して中間混合ガスを得る中間混合工程と、前記中間混合ガスからメタノールを合成する中間合成工程と、前記中間合成工程で得られた中間反応混合物から中間未反応ガスを分離する中間分離工程と、を更に有する、[1]~[9]のいずれか1つに記載のメタノール製造方法。
[11]前記各減圧工程のうち少なくとも1つの工程において、エネルギーを回収する、[3]、[4]、[7]及び[8]のいずれか1つに記載のメタノール製造方法。
[12]水素と一酸化炭素と二酸化炭素とを含む合成ガスからメタノールを合成する反応器と、前記反応器において得られた反応混合物から未反応ガスを分離する分離装置と、を備えるメタノール製造装置であって、少なくとも2つの前記反応器と、少なくとも2つの前記分離装置とを備える合成ループを有し、前記合成ループにおいて、最終反応器の後の最終分離装置において最終反応混合物から分離した最終未反応ガスからパージガスを取り除いた残りのガスに、水素と一酸化炭素と二酸化炭素とを含むメイクアップガスの10~90モル%と混合して第1混合ガスを得る第1混合手段と、前記第1混合ガスからメタノールを合成する第1反応器と、前記第1反応器において得られた第1反応混合物から第1未反応ガスを分離する第1分離装置と、最終的に未反応ガスと前記メイクアップガスの10~90モル%のうちの少なくとも一部とを混合して最終混合ガスを得る最終混合手段と、前記最終混合ガスからメタノールを合成する前記最終反応器と、前記最終反応器において得られた前記最終反応混合物から前記最終未反応ガスを分離する前記最終分離装置と、を備え、前記第1混合ガスを予熱する第1予熱器と、前記最終混合ガスを予熱する最終予熱器と、前記最終予熱器により予熱された前記最終混合ガスを前記最終反応器に供給する前に昇圧する循環機と、を備え、少なくとも前記最終反応器において、加圧沸騰水との間接熱交換により触媒層の反応温度を制御する、メタノール製造装置。
本実施形態においては、少なくとも1つの分離工程が最終合成工程よりも前段に設けられている。また、本実施形態においては、最終分離工程以外の少なくとも1つの分離工程において、その直前の合成工程で得られた反応混合物からメタノールを含む反応生成物と未反応の合成ガス(以下「未反応ガス」という。)とを分離し、この未反応ガスに上記メイクアップガスを混合して得られた混合ガスから、その後段の合成工程においてメタノールを合成する。
本実施形態において、合成ループは、少なくとも1つの合成工程と少なくとも1つの分離工程とを経たガスが最終合成工程と最終分離工程とを経て、最終分離工程において分離された未反応ガスが、第1合成工程における原料のガスとして用いられることで形成される。この合成ループ内でガスを循環させるために、メタノール製造装置は、昇圧のための循環機を少なくとも1つ備え、その昇圧工程は、最終予熱工程の後であって最終合成工程の前である。これによって、最終合成工程において反応温度を高めるためのエネルギーを低減でき、その工程において反応器での熱回収量を増大させることができる。また、昇圧工程における昇圧よって昇温が可能になるため、その前に最終混合ガスを予熱する際に必要となる温度を低下させることができる。そうすると、予熱の際に用いる予熱器での低温側の流体と高温側の流体の温度差が大きくなるため、予熱器における熱交換量(熱回収量)を増大させたり、熱交換器のサイズを小さくしたりすることも可能となる。循環機には乾き度の高い流体を導入することが好ましい。より具体的には、分離工程の後で飽和状態の凝縮性気体を有する流体を予熱することで乾き度を上げるか、あるいは乾き度の高い流体(例えば、メイクアップガス)を混合することで乾き度を上げるか、あるいはその両方を行うことが好ましい。これにより、循環機内での凝縮液滴の発生をより抑制することができるので、機械的な故障やエネルギー損失の増大を更に防止することが可能となる。
また、最終分離工程は、第1分離工程の後に、反応混合物から未反応ガスを分離する工程であれば、特に限定されない。最終分離工程は、第2合成工程で得られた第2反応混合物から第2未反応ガスを分離する第2分離工程であると好ましい。あるいは、最終分離工程は、第3合成工程で得られた第3反応混合物から第3未反応ガスを分離する第3分離工程であると好ましい。これら第2分離工程及び第3分離工程のうち、最終分離工程は、第2分離工程であることがより好ましい。
メイクアップガスは、天然ガスの水蒸気改質ガスや石炭ガス化ガスなどの一酸化炭素(CO)、二酸化炭素(CO2)及び水素(H2)を含む合成原料ガスを圧縮機によって反応圧力まで昇圧したものである。反応圧力は、例えば、4.9~14.7MPa-G(50~150kg/cm2-G)であってもよく、より好ましくは7.8~10.8MPa-G(80~110kg/cm2-G)である。工業的には、メイクアップガスは、例えば天然ガスを原料とした水蒸気改質反応によって得られるものであり、下記式により算出されるCO、CO2及びH2のモル%の関係(M):
M=(H2モル%)/(2×COモル%+3×CO2モル%)
が、1.0より大きく2.0以下であるものが好ましい。さらに好ましいものはMが1.3~1.5である。
本実施形態において、メイクアップガスは、合成ループに導入する前に複数の流れに分割され、合成ループ内に存在する複数の合成工程における原料ガスの一部として、合成ループに導入される。メイクアップガスの分割比率は、各合成工程における合成条件及び各分離工程における分離条件によって好適な範囲が異なる。ただし、最初のメタノール合成工程(第1合成工程)に供給する混合ガス(第1混合ガス)に含まれるメイクアップガスのモル流量は、メイクアップガスの全体量に対して10~90モル%、好ましくは10~70モル%である。次いで第2合成工程に供給する混合ガス(第2混合ガス)に含まれるメイクアップガスのモル流量は、メイクアップガスの全体量に対して10~90モル%、好ましくは10~70モル%である。そして、第3合成工程以降が存在する場合であって、第1合成工程および第2合成工程に供給したメイクアップガスのモル流量の和をメイクアップガスの全体量の100%未満とする場合は、残りのメイクアップガスを第3合成工程以降の各メタノール合成工程に適宜分割する。また、第3合成工程以降が存在する場合であって、第1合成工程および第2合成工程に供給したメイクアップガスのモル流量の和がメイクアップガスの全体量の100%とする場合は、メイクアップガスを第3合成工程以降の各メタノール合成工程には分割供給しない。例えば、1つの実施態様として、分離工程における分離方法として凝縮分離方法を用いて、2つの合成工程と2つの凝縮分離工程とを有する製造方法の場合を説明する。この実施態様では、第1凝縮分離工程の出口ガス温度を20℃~100℃とする場合、最終合成工程(第2合成工程)の直前で合成ループに導入されるメイクアップガスの割合(メイクアップガスの全体量に対する割合。以下同様。)は、カーボン収率及び触媒層の最高温度などの観点から、10~90モル%であると好ましく、より好ましくは30~90モル%、さらに好ましくは40~70モル%である。また、第1凝縮分離工程の出口ガス温度を40℃~80℃とする場合、最終合成工程の直前で合成ループに導入されるメイクアップガスの割合は、上記と同様の観点から、10~90モル%であるとよく、30~90モル%であると好ましく、より好ましくは40~70モル%、さらに好ましくは45~65モル%である。
本実施形態においては、メイクアップガスを合成ループに導入する前に複数の流れに分割し、その分割比率を調整することができる。これにより、合成工程での反応器の温度を容易に制御することが可能となる。
合成工程においては、合成ガスからメタノールを合成する。合成工程において用いられる反応器は、触媒層を有すると共に反応で生じる熱を触媒層から取り除く機構(除熱機構)を有するものであると好ましい。
好ましい触媒の具体例としては、国際公開第2011/048976号の実施例及び比較例、例えば、実施例2及び実施例3に用いられた触媒が挙げられる。また、触媒における銅原子及び亜鉛原子のより好ましい原子比(銅/亜鉛)は、2.1~3.0の範囲である。それに加えて、アルミナを3~20質量%含むメタノール合成触媒がさらに好ましい。かかる触媒は、上述のとおり、例えば、国際公開第2011/048976号に記載の方法により調製することができる。より具体的には、例えば、銅を含む水溶液と亜鉛を含む水溶液とアルカリ水溶液とを混合して銅及び亜鉛を含む沈殿物を生成する工程と、得られた沈殿物と擬ベーマイト構造を有するアルミナ水和物とを混合して混合物を得る工程と、得られた混合物を密度が2.0~3.0g/mLになるように成型する工程とを有する製造方法によって調製される。ただし、本実施形態に用いる触媒は上記の触媒及び上記の調製方法で調製された触媒に限定されるものではなく、同等のメタノール合成活性を有する他の触媒であってもよい。
加圧沸騰水との間接熱交換により触媒層の反応温度を制御するのは、少なくとも最終合成工程においてであればよいが、全ての合成工程において加圧沸騰水との間接熱交換により触媒層の反応温度を制御するのが好ましい。なお、複数の反応器において加圧沸騰水を冷却材に用いる場合、それぞれの反応器における加圧沸騰水の温度は互いに同一であっても異なっていてもよい。
分離工程においては、合成工程を経て得られた反応生成物を含む反応混合物から未反応ガスを分離する。言い換えれば、上記反応混合物に含まれるメタノール又はメタノール及び水と未反応ガスとを分離する。分離方法としては、例えば、合成工程からの出口ガスを冷却し、冷却によって生じる凝縮液を気液分離器によって分離する凝縮分離方法、及び分離膜を用いた膜分離方法が挙げられ、これらの中では凝縮分離方法が好ましい。本実施形態においては、凝縮分離方法を用いた分離工程(凝縮分離工程)が合成ループ内に少なくとも2つ設けられ、それらのうちの1つは、最終合成工程の後の最終凝縮分離工程であることが好ましい。凝縮分離工程において冷却される流体は、当該凝縮分離工程の前の合成工程からの出口ガス(ガス状の反応混合物)であり、合成されたメタノールを含む。メタノールを含む液を凝縮液として得る方法としては、例えば、反応器に供給される合成ガスとの相互熱交換やエアフィンクーラーなどによる空冷、冷却水やブラインなどの冷却材による冷却などが挙げられる。冷却対象となる流体(反応混合物)の冷却前の初期温度と冷却後の目標温度に応じて、凝縮液を得る方法は1種類を単独で又は2種類以上を組み合わせて用いられる。あるいは、本実施形態のメタノールの製造方法において用いられ得る減圧機によってガスを膨張させるのに伴う冷却を利用して凝縮液を得る手法を組み合わせることもできる。得られた凝縮液は、気液分離器(以下、単に「分離器」ともいう。)を用いて分離することが一般的である。これら冷却器(凝縮器)と分離器との組み合わせとしては、冷却器と分離器とを1つずつ組み合わせたものであってもよく、冷却器と分離器とを複数ずつ組み合わせたものであってもよい。冷却器と分離器とが複数組み合わされた例としては、例えば、特開昭61-257934号公報に記載のものが挙げられる。より具体的には、合成工程を経て得られる反応混合物を冷却し、メタノールを主成分とする反応生成物を凝縮し分離するに際し、凝縮器を2段に分け、前段の凝縮器の伝熱表面温度を反応混合物の露点以下、かつ反応混合物中に含まれるパラフィン類の融点以上の温度に設定し、後段の凝縮器の伝熱表面温度を60℃以下とする手法が挙げられる。
凝縮分離工程においては、冷却によって、メタノール、あるいはメタノール及び水を含む凝縮液が所定量生じるまで反応混合物を冷却する。例えば、メタノール分圧0.69~0.88MPa-G(7.0~9.0kg/cm2-G)の流体(反応混合物)を冷却し凝縮させる場合は、好ましくは、20~100℃、より好ましくは40~80℃に冷却することが好ましい。このとき、メタノール収率向上の観点から、第1凝縮分離工程において、第1合成工程からの出口ガスに含まれるメタノールの分離割合は75モル%より高くすることが好ましい。さらに、その後の第2合成工程での反応制御のために、第1凝縮分離工程における第1合成工程からの出口ガスに含まれるメタノールの分離割合は96モル%より低くすることがより好ましい。冷却水の節約の観点からは、第1凝縮分離工程における冷却は、エアフィンクーラーによる冷却(空冷)のみを用いることが好ましい。この場合、反応混合物の冷却後の目標温度は、同様の観点から55~90℃であることが好ましい。
合成ループにおいては不活性成分が蓄積するため、一部のガスをパージガスとして系外に除去する必要がある。このパージガスの取り出し位置は、合成ループ内の適切な位置であればよい。このときのパージガス流量は、後述する循環比を所望の数値内にするよう適宜調整すればよい。ここで、循環比は、メイクアップガスのモル流量に対する循環ガスのモル流量で定義される。本実施形態において、循環ガスのモル流量は、最終未反応ガスからパージガスを取り除いた残りのガスのモル流量である。合成ループ中の各分離工程にて分離されたメタノールを含む反応生成物は、粗メタノールとして取り出される。
合成ループにおけるパージガスの取り出し位置は、循環機の処理ガス量を削減する観点から、合成ループ内での圧力が低くなる箇所が好ましい。加えて、カーボン収率の観点から、反応混合物中の反応生成物を分離して合成ループ外へ抜き出した後の未反応ガスの一部をパージガスとして分岐することが好ましく、そのパージガス取り出し位置がメイクアップガスの合流前であるとより好ましい。さらに、複数の合成工程間の分離工程において、その分離工程の前の合成工程からの出口ガスに含まれるメタノールのうち4~25モル%を分離せずに、その後の合成工程に供給することで、後段の合成工程における反応を制御し、触媒層の過熱を抑制することも可能となる。この場合、その分離工程に用いる分離器の後段であって、続く合成工程に用いる反応器の前段にある予熱機の更に前段に循環機を配置することは、循環機内で凝縮が発生する恐れがあり、適切ではない。
本実施形態のメタノール製造方法は、合成ループ内に少なくとも1つの昇圧工程を有する。この昇圧工程における昇圧には、循環機が用いられる。このメタノールの製造方法は、少なくとも1つの昇圧工程を、最終予熱工程の後であって、かつ最終合成工程の前に有する。最終予熱工程において用いられる得る予熱器は、最終合成工程への供給ガスである最終混合ガスを所定の温度に昇温するものであり、一般的には最終合成工程を経て得られる最終反応混合物(通常はガス状)と熱交換するものであるのが好ましい。この場合、最終混合ガスの予熱後の温度は、最終反応混合物の温度以上にはならない。最終合成工程において用いられ得る反応器として、加圧沸騰水との間接熱交換機構を有する等温反応器を想定した場合、最終反応混合物の反応器出口温度は加圧沸騰水の温度に漸近するため、予熱器で予熱された最終混合ガスは、加圧沸騰水の温度よりも低い温度で供給されることになり、加圧沸騰水による反応熱の回収量が低下することになる。一方、本実施形態においては、昇圧工程を最終予熱工程の後であって、かつ最終合成工程の前に有することによって、最終混合ガスの反応器入口での温度を加圧沸騰水の温度に近く若しくはそれよりも高くすることができ、循環比の低減によって達成された反応熱の回収量の増加をさらに推し進め、さらなる反応熱の回収量増加をもたらす。このような効果をより有効かつ確実に奏する観点から、昇圧工程における昇圧前後の圧力比が1.10を超えると好ましく、1.20を超えるとより好ましい。この圧力比の上限は特に限定されないが、通常は2.00程度である。さらに、上記には劣るものの同様の効果を奏する観点から、本実施形態のメタノール製造方法は、第1予熱工程を経た第1混合ガスを、第1合成工程の前に昇圧する別の昇圧工程を有してもよい。
本実施形態のメタノール製造方法においては、合成ループ内に少なくとも1つの減圧工程を有する。このメタノールの製造方法は、減圧工程を、第1合成工程の後であって、第1分離工程の前又は後に有してもよい。また、第1合成工程に用いられる反応器出口の第1反応混合物が、第1混合ガスの予熱に熱源として用いられる場合は、本実施形態のメタノールの製造方法は、第1混合ガスとの熱交換(最終混合ガスによる冷却)の後に減圧工程を有してもよい。また、このメタノールの製造方法は、最終合成工程の後、最終分離工程の前であって、最終反応混合物の一部を凝縮する工程の前又は後に減圧工程を有するのが好ましい。さらに、最終分離工程の後であって、第1混合工程の前までの間に減圧工程を有するのも好ましい。また、反応器出口の最終反応混合物が、最終混合ガスの予熱に熱源として用いられる場合は、本実施形態のメタノールの製造方法は、最終混合ガスとの熱交換(最終混合ガスによる冷却)の後に減圧工程を有するのが好ましい。このような減圧工程を有することは、エネルギーを回収する余地を生み出し、エネルギーの使用量を削減する点から好ましい。エネルギーの回収方法としては、例えば、圧力差を利用した発電によるエネルギー回収、及び、他の低圧流体の昇圧に利用する圧力変換型エネルギー回収が挙げられる。また、最終反応混合物の最終混合ガスとの熱交換の後であって、最終分離工程の前に減圧工程を有する場合、最終分離工程後に減圧工程を有する場合に比べて、減圧工程における流体量が増加することから、エネルギーを回収する余地をより多く生み出すことができる。さらに、減圧によって最終反応混合物が冷却される効果によって、分離目標温度によっては、最終分離工程の前に最終反応混合物の一部を凝縮するために用いられる凝縮器のサイズを小さくでき、あるいは、その凝縮器が不要になる場合もある。これら減圧工程は、反応器出口ガスの予熱器通過後であって最終分離工程前か、又は、最終分離工程後であって第1混合工程前のいずれかにあってもよく、あるいはそれらの両方にあってもよい。
メタノール合成に用いる触媒は、国際公開第2011/048976号の実施例3に記載の方法によって調製された触媒(メタノール合成触媒A)とした。
実施例1では図1に示す製造装置を用いた。各条件は以下のとおりとした。すなわち、原料ガスとして、天然ガスの水蒸気改質反応で生じるガスを利用し、循環比1.0の条件でメタノールの合成を行った。また、反応器23a及び23bにおける触媒としてメタノール合成触媒Aを用いた。原料ガスは圧縮機により8.0MPa-Gまで昇圧した。昇圧した合成原料ガス(メイクアップガス)のうち50モル%をライン3a内に流通し、ライン16内を流通する循環ガスと混合し、反応器供給ガス(第1混合ガス)を得た。ライン4aを流通した第1混合ガスを、反応器23a出口のライン7a内を流通する反応生成物を含む反応器出口ガス(第1反応混合物)と予熱機22aにて熱交換することで、ライン5aにおける温度が200℃になるよう予熱した。メイクアップガスのうち残りの50モル%をライン3b内に流通させた。予熱後の第1混合ガスを反応器23aに供給してメタノールの合成を行った(第1合成工程)。反応器23aの触媒層における流体の圧力は7.8MPa-G、温度は200~254℃の間であった。
比較例1では、図2に示す製造装置を用いた。実施例1との相違点は、合成ループにおける循環機の位置である。具体的には、気液分離器26aにおいて分離された残りの未反応ガスをライン8aにて取り出し、ライン3bからのメイクアップガスを混合した後であって、予熱器22bを通過する前に、循環機32bにて昇圧した点である。ライン3a及びライン3bを流通するメイクアップガスの組成、合計モル流量、温度、及び圧力をそれぞれ実施例1と同様にした。比較例1は、特許文献2の技術に基づいたものである。
実施例2では図3に示す製造装置を用いた。各条件は以下のとおりとした。すなわち、原料ガスとして、天然ガスの水蒸気改質反応で生じるガスを利用し、循環比1.0の条件でメタノールの合成を行った。また、反応器23a及び23bにおける触媒としてメタノール合成触媒Aを用いた。原料ガスは圧縮機により8.0MPa-Gまで昇圧した。昇圧した合成原料ガス(メイクアップガス)のうち50モル%をライン3a内に流通し、ライン16内を流通する循環ガスと混合し、反応器供給ガス(第1混合ガス)を得た。ライン4a内を流通した第1混合ガスは、反応器23a出口のライン7a内を流通する反応生成物を含む出口ガス(第1反応混合物)と予熱器22aにて熱交換することで、ライン5aにおける温度が195℃になるよう予熱した。ライン5a内を流通する第1混合ガスは、循環機32aを通過する過程でライン6aの圧力が9.8MPa-Gとなるように昇圧した。昇圧に伴い、ライン6a内を流通する第1混合ガスの温度は230℃となった。メイクアップガスのうち残りの50モル%をライン3b内に流通させた。昇圧後の第1混合ガスを反応器23aに供給してメタノールの合成を行った(第1合成工程)。触媒層における流体の圧力は9.8MPa-G、温度は230~272℃の間であった。
実施例3では図4に示す製造装置を用いた。各条件は以下のとおりとした。すなわち、原料ガスとして、天然ガスの水蒸気改質反応で生じるガスを利用し、循環比1.0の条件でメタノールの合成を行った。また、反応器23a、23b及び23cにおける触媒としてメタノール合成触媒Aを用いた。原料ガスは圧縮機により8.0MPa-Gまで昇圧した。昇圧した合成原料ガス(メイクアップガス)のうち30モル%をライン3a内に流通し、ライン16内を流通する循環ガスと混合し、反応器供給ガス(第1混合ガス)を得た。ライン4a内を流通した第1混合ガスは、反応器23a出口のライン7a内を流通する反応生成物を含む出口ガス(第1反応混合物)と予熱器22aにて熱交換することで、ライン5aにおける温度が195℃になるよう予熱した。ライン5a内を流通する第1混合ガスは、循環機32aを通過する過程でライン6aの圧力が9.8MPa-Gとなるように昇圧した。昇圧に伴い、ライン6a内を流通する第1混合ガスの温度は230℃となった。メイクアップガスのうち50モル%をライン3b内に、残りの20モル%をライン3cに流通させた。昇圧後の第1混合ガスを反応器23aに供給してメタノールの合成を行った(第1合成工程)。反応器23aの触媒層における流体の圧力は9.8MPa-G、温度は230~264℃の間であった。
実施例4では図5に示す製造装置を用いた。各条件は以下のとおりとした。すなわち、原料ガスとして、天然ガスの水蒸気改質反応で生じるガスを利用し、循環比1.0の条件でメタノールの合成を行った。また、反応器23a及び23bにおける触媒としてメタノール合成触媒Aを用いた。原料ガスは圧縮機により8.0MPa-Gまで昇圧した。昇圧した合成原料ガス(メイクアップガス)のうち50モル%をライン3a内に流通し、ライン16内を流通する循環ガスと混合し、反応器供給ガス(第1混合ガス)を得た。ライン4aを流通した第1混合ガスを、反応器23a出口のライン7a内を流通する反応生成物を含む反応器出口ガス(第1反応混合物)と予熱器22aにて熱交換することで、ライン5aにおける温度が200℃になるよう予熱した。メイクアップガスのうち残りの50モル%をライン3b内に流通させた。予熱後の第1混合ガスを反応器23aに供給してメタノールの合成を行った(第1合成工程)。反応器23aの触媒層における流体の圧力は7.8MPa-G、温度は200~254℃の間であった。
Claims (12)
- 水素と一酸化炭素と二酸化炭素とを含む合成ガスからメタノールを合成する合成工程と、前記合成工程を経て得られた反応混合物から未反応ガスを分離する分離工程と、を有するメタノール製造方法であって、
少なくとも2つの前記合成工程と、少なくとも2つの前記分離工程とを有する合成ループを有し、
前記合成ループにおいて、最終合成工程の後の最終分離工程で最終反応混合物から分離した最終未反応ガスからパージガスを取り除いた残りのガスに、水素と一酸化炭素と二酸化炭素とを含むメイクアップガスの10~90モル%と混合して第1混合ガスを得る第1混合工程と、前記第1混合ガスからメタノールを合成する第1合成工程と、前記第1合成工程で得られた第1反応混合物から第1未反応ガスを分離する第1分離工程と、最終的に未反応ガスと前記メイクアップガスの10~90モル%のうちの少なくとも一部とを混合して最終混合ガスを得る最終混合工程と、前記最終混合ガスからメタノールを合成する前記最終合成工程と、前記最終合成工程で得られた前記最終反応混合物から前記最終未反応ガスを分離する前記最終分離工程と、を有し
前記第1混合ガスを予熱する第1予熱工程と、前記最終混合ガスを予熱する最終予熱工程と、前記最終予熱工程を経た前記最終混合ガスを前記最終合成工程の前に循環機によって昇圧する昇圧工程と、を有し、かつ
加圧沸騰水との間接熱交換により触媒層の反応温度を制御する、メタノール製造方法。 - 前記最終予熱工程において前記最終混合ガスを予熱する熱源が、前記最終反応混合物である、請求項1に記載のメタノール製造方法。
- 前記最終混合ガスを予熱した前記最終反応混合物を、前記最終分離工程の前に減圧する最終反応混合物減圧工程を有する、請求項2に記載のメタノール製造方法。
- 前記最終分離工程で得られた最終未反応ガスを、前記第1混合工程の前に減圧する最終未反応ガス減圧工程を有する、請求項1~3のいずれか1項に記載のメタノール製造方法。
- 前記第1予熱工程を経た前記第1混合ガスを、前記第1合成工程の前に昇圧する昇圧工程を有する、請求項1~4のいずれか1項に記載のメタノール製造方法。
- 前記第1予熱工程において前記第1混合ガスを予熱する熱源が、前記第1反応混合物である、請求項1~5のいずれか1項に記載のメタノール製造方法。
- 前記第1混合ガスを予熱した前記第1反応混合物を、前記第1分離工程の前に減圧する第1反応混合物減圧工程を有する、請求項6記載のメタノール製造方法。
- 前記第1分離工程で得られた第1未反応ガスを減圧する第1未反応ガス減圧工程を有する、請求項1~7のいずれか1項に記載のメタノール製造方法。
- 前記昇圧工程における昇圧前後の圧力比が1.10を超える、請求項1~8のいずれか1項に記載のメタノール製造方法。
- 前記第1分離工程の後、前記最終混合工程の前に、未反応ガスと前記メイクアップガスの10~90モル%のうちの少なくとも一部とを混合して中間混合ガスを得る中間混合工程と、前記中間混合ガスからメタノールを合成する中間合成工程と、前記中間合成工程で得られた中間反応混合物から中間未反応ガスを分離する中間分離工程と、を更に有する、請求項1~9のいずれか1項に記載のメタノール製造方法。
- 前記各減圧工程のうち少なくとも1つの工程において、エネルギーを回収する、請求項3、4、7及び8のいずれか1項に記載のメタノール製造方法。
- 水素と一酸化炭素と二酸化炭素とを含む合成ガスからメタノールを合成する反応器と、前記反応器において得られた反応混合物から未反応ガスを分離する分離装置と、を備えるメタノール製造装置であって、
少なくとも2つの前記反応器と、少なくとも2つの前記分離装置とを備える合成ループを有し、
前記合成ループにおいて、最終反応器の後の最終分離装置において最終反応混合物から分離した最終未反応ガスからパージガスを取り除いた残りのガスに、水素と一酸化炭素と二酸化炭素とを含むメイクアップガスの10~90モル%と混合して第1混合ガスを得る第1混合手段と、前記第1混合ガスからメタノールを合成する第1反応器と、前記第1反応器において得られた第1反応混合物から第1未反応ガスを分離する第1分離装置と、最終的に未反応ガスと前記メイクアップガスの10~90モル%のうちの少なくとも一部とを混合して最終混合ガスを得る最終混合手段と、前記最終混合ガスからメタノールを合成する前記最終反応器と、前記最終反応器において得られた前記最終反応混合物から前記最終未反応ガスを分離する前記最終分離装置と、を備え、
前記第1混合ガスを予熱する第1予熱器と、前記最終混合ガスを予熱する最終予熱器と、前記最終予熱器により予熱された前記最終混合ガスを前記最終反応器に供給する前に昇圧する循環機と、を備え、
少なくとも前記最終反応器において、加圧沸騰水との間接熱交換により触媒層の反応温度を制御する、メタノール製造装置。
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JP2019182809A (ja) * | 2018-04-16 | 2019-10-24 | 三菱重工業株式会社 | メタノール製造方法 |
WO2020027337A1 (ja) * | 2018-08-02 | 2020-02-06 | 三菱ケミカル株式会社 | 接合体、それを有する分離膜モジュール及びアルコールの製造方法 |
KR102132718B1 (ko) * | 2020-01-14 | 2020-07-13 | 한국과학기술연구원 | 다단 반응기로부터 배출되는 생성물 회수를 이용한 메탄올의 제조장치 및 제조방법 |
JPWO2021106132A1 (ja) * | 2019-11-28 | 2021-06-03 | ||
WO2023157835A1 (ja) * | 2022-02-18 | 2023-08-24 | 日本碍子株式会社 | リアクタモジュール |
WO2023182506A1 (ja) * | 2022-03-25 | 2023-09-28 | 三菱瓦斯化学株式会社 | メタノール製造方法及びメタノール製造装置 |
WO2024004464A1 (ja) * | 2022-06-30 | 2024-01-04 | 三菱瓦斯化学株式会社 | メタノール製造方法及びメタノール製造装置 |
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Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2019182809A (ja) * | 2018-04-16 | 2019-10-24 | 三菱重工業株式会社 | メタノール製造方法 |
JP7134682B2 (ja) | 2018-04-16 | 2022-09-12 | 三菱重工業株式会社 | メタノール製造方法およびメタノール製造システム |
WO2020027337A1 (ja) * | 2018-08-02 | 2020-02-06 | 三菱ケミカル株式会社 | 接合体、それを有する分離膜モジュール及びアルコールの製造方法 |
JPWO2021106132A1 (ja) * | 2019-11-28 | 2021-06-03 | ||
WO2021106132A1 (ja) * | 2019-11-28 | 2021-06-03 | 三菱重工エンジニアリング株式会社 | メタノール製造設備及びメタノール製造方法 |
JP7319493B2 (ja) | 2019-11-28 | 2023-08-02 | 三菱重工業株式会社 | メタノール製造設備及びメタノール製造方法 |
KR102132718B1 (ko) * | 2020-01-14 | 2020-07-13 | 한국과학기술연구원 | 다단 반응기로부터 배출되는 생성물 회수를 이용한 메탄올의 제조장치 및 제조방법 |
WO2023157835A1 (ja) * | 2022-02-18 | 2023-08-24 | 日本碍子株式会社 | リアクタモジュール |
WO2023182506A1 (ja) * | 2022-03-25 | 2023-09-28 | 三菱瓦斯化学株式会社 | メタノール製造方法及びメタノール製造装置 |
WO2024004464A1 (ja) * | 2022-06-30 | 2024-01-04 | 三菱瓦斯化学株式会社 | メタノール製造方法及びメタノール製造装置 |
Also Published As
Publication number | Publication date |
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EP3441381B1 (en) | 2020-05-13 |
US20190152885A1 (en) | 2019-05-23 |
JPWO2017175760A1 (ja) | 2019-02-14 |
EP3441381A1 (en) | 2019-02-13 |
DK3441381T3 (da) | 2020-05-25 |
JP6835071B2 (ja) | 2021-02-24 |
US10556849B2 (en) | 2020-02-11 |
EP3441381A4 (en) | 2019-05-08 |
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