Method and apparatus for obtaining high purity hydrogen from methanol or ammonia for fuel cell operation - Patents.com

Abstract

The invention comprises a method for obtaining hydrogen from methanol or ammonia, for example for fuel cell operation, which comprises vaporizing methanol or ammonia in a first step, reforming in a second step to form a hydrogen-containing gas mixture, separating hydrogen from this gas mixture in a membrane process at a temperature of 300-600° C. in a third step, and combusting the gaseous residue of the membrane process with ambient air in a fourth step, wherein the second step is a process step separate from and upstream of the third step, and wherein the combustion gases are passed through at least two different heat exchangers. In the flow direction of the combustion gas, (i) firstly, the reaction heat for reforming the methanol or ammonia is provided, and (ii) subsequently, the vaporization heat for vaporizing the reformer feed is provided, and the permeate of the membrane process preheats the ambient air for the burner in the heat exchanger, and (a) the temperature difference between the exiting permeate and the incoming ambient air, and (b) the temperature difference between the exiting combustion gas and the incoming methanol or ammonia are 1-200°C, respectively, and during the third process step, a further temperature increase of up to 0-100°C is performed.

Description

[Technical field]

[0001] The invention comprises a method for obtaining hydrogen from methanol or ammonia, for example for fuel cell operation, which comprises vaporizing methanol or ammonia in a first step, reforming in a second step to form a hydrogen-containing gas mixture, separating hydrogen from this gas mixture in a membrane process at a temperature of 300-600° C. in a third step, and combusting the gaseous residue of the membrane process with ambient air in a fourth step, wherein the second step is a process step separate from and upstream of the third step, and wherein the combustion gases are passed through at least two different heat exchangers. In the flow direction of the combustion gas, (i) firstly, the reaction heat for reforming the methanol or ammonia is provided, and (ii) subsequently, the vaporization heat for vaporizing the reformer feed is provided, and the permeate of the membrane process preheats the ambient air for the burner in the heat exchanger, and (a) the temperature difference between the exiting permeate and the incoming ambient air, and (b) the temperature difference between the exiting combustion gas and the incoming methanol or ammonia are 1-200°C, respectively, and during the third process step, a further temperature increase of up to 0-100°C is performed.

[0002] Furthermore, the invention also includes an apparatus for obtaining high purity hydrogen from methanol or ammonia, for example for use in fuel cell operation, hydrogen stations or for decentralized supply for small scale industrial applications. [Brief description of the drawings]

[0003] [Figure 1] FIG. 1 illustrates the overall process of on-board reforming. [Diagram 2] FIG. 1 illustrates the main steps of the present invention. [Diagram 3] FIG. 2 is a schematic diagram of a process technology variant. [Figure 4] FIG. 13 shows a variant with a reformate heater. [Diagram 5] FIG. 13 shows a variant without a reformate heater. [Figure 6] FIG. 1 illustrates an apparatus for obtaining high purity hydrogen from methanol or ammonia. [Figure 7] FIG. 13 shows a variant with a reformate heater. [Figure 8] FIG. 13 illustrates the effect of temperature difference between the outgoing and incoming streams on the heat exchanger area and energy utilization of the device.

[0004] Hydrogen offers the right prerequisites for becoming an important component of the energy supply of the future. The transport sector in particular faces a major challenge to become even more climate-friendly. In Germany, transport accounts for almost 20 percent of total CO2 emissions, around half of which comes from private transport.

[0005] The introduction of electromobility, including battery electric vehicles and fuel cell electric vehicles, allows the transport sector to reduce its reliance on petroleum-based fuels. In the optimal case, the electricity or hydrogen required to operate the vehicles is produced from renewable energy sources. Hydrogen is being introduced as a new fuel in the transport sector, which does not produce harmful substances when using fuel cell technology.

[0006] For hydrogen to be usable in fuel cell applications, it must be of very high quality, since impurities will affect catalytic converters and membranes.

[0007] Hydrogen is currently mainly produced centrally in relatively large steam methane reforming (SMR) production units. It is then compressed at high pressure (up to 350 bar) or in rare cases liquefied, and transported by suitable transport vehicles to where it is needed, i.e. to hydrogen stations. However, larger hydrogen stations require daily truck deliveries of hydrogen, making the transport of hydrogen by vehicle uneconomical and environmentally unfriendly.

[0008] Besides vehicle transport, there are independent pure hydrogen pipelines. However, to be able to supply hydrogen to hydrogen stations on a large scale, a dedicated high-density hydrogen pipeline network would need to be built, similar to the natural gas network. However, such a pipeline network seems unlikely to become a reality in the near future, due to the very high infrastructure costs and lengthy permitting procedures.

[0009] Furthermore, hydrogen could be produced decentrally in smaller production units, for example by electrolysis or steam methane reforming (SMR), shortening or eliminating transportation routes altogether.

[0010] Water electrolysis requires a very large amount of electricity, but due to the low storage capacity of H2 at hydrogen stations, the required electricity must be supplied on demand from available grid power sources. However, in Germany for example, grid power sources are expected to have a high carbon footprint for the next decade, so that a grid-built electrolysis H2-powered vehicle will emit more CO2 worldwide over the next decade than a diesel or gasoline engine vehicle.

[0011] Methanol (MeOH) is a basic chemical produced on a large scale and has a high energy density of 19.9 MJ / kg, making it an excellent energy source. In contrast to hydrogen, methanol can be transported at low cost (O. Machhammer, "Regenerative Strom aus Deutschland oder e-Fuels aus Chile: Worauf sollte die zukunftige Mobilitat bauen?" Chemie Ingenieur Technik, No. 4, 2021). For transportation, the existing crude oil transportation infrastructure can be used.

[0012] Furthermore, because vehicles can be filled with methanol, they can utilize the existing fuel station network without requiring major modifications.

[0013] Methanol is still used today primarily as a base chemical, e.g. formaldehyde, acetic acid, methyl chloride, methyl methacrylate, methylamine, etc. In these processes, the energy balance plays a subordinate role, and the added value of secondary products is more important.

[0014] Ammonia (NH3) is a basic chemical that is produced on a large scale, for example in fertilizer production. Ammonia is an excellent source of energy, with a mass energy density of 18.6 MJ / kg, roughly the same as that of methanol (MeOH) at 19.9 MJ / kg. Ammonia has a boiling point of -33 °C and can be transported at ambient temperature in low-pressure containers at 10 bar.

[0015] An important feature of future energy sources is their low carbon footprint: in the case of NH3, in addition to the low carbon footprint H2, nitrogen (N2) is also required, which is present in the atmosphere in high concentrations of about 80% and can be obtained easily and cheaply in air separation plants.

[0016] Countries with too little solar radiation and / or wind, and / or with little open space, cannot meet their own demand for hydrogen produced with renewable energies. Therefore, in countries with very favorable prerequisites for renewable energies, such as the MENA countries, efforts are already underway today to produce this future demand for renewable energies. One example is the world's largest green hydrogen / ammonia project (NEOM HELIOS) in Saudi Arabia.

[0017] In the case of material recycling of ammonia, which is a major issue today, for example as fertilizer, the energy balance plays a subordinate role. Of importance in this context is the effect of fertilizer.

[0018] Well-known processes for separating N2 and H2 include distillation, sorption, and membrane processes. The membrane process is preferred since the low boiling points of the two components to be separated are not an issue here.

[0019] Hydrogen can be provided at fuel stations for filling fuel cell (FC) vehicles: for this purpose, hydrogen for intermediate storage is compressed to the required pressure of 950 bar and cooled to the required temperature of -40°C during filling.

[0020] However, the hydrogen required for the fuel cell (FC) can be advantageously obtained in the vehicle (KFZ) from methanol or ammonia by on-board reforming according to Fig. 1. The H2 released in this case can then be converted into electricity in the fuel cell to run the electric vehicle.

[0021] By using methanol or ammonia, it is not necessary to first develop a complex and very expensive H2 transportation and fuel station infrastructure before fuel cell vehicles can be widely deployed.

[0022] In contrast, when using methanol or ammonia as the energy source, the energy balance of the entire process plays an important role. In the entire process from reforming methanol or ammonia to releasing H2, it is advantageous to have less energy loss in order to retain as much of the energy originally used as possible.

[0023] Fuel cells (FCs) require very high purity (>99.99%) hydrogen for their operation. To obtain the highest purity hydrogen on-board from methanol or ammonia, several process steps are required: vaporization and decomposition of methanol or ammonia, and separation of high purity hydrogen from the resulting gas mixture. The thermal energy required for vaporization and decomposition must be supplied externally or provided by burning part of the methanol used, part of the ammonia used, or part of the products of reforming.

[0024] Prior art on-board fuel cell fuel cells has focused primarily on optimized reforming conversion and optimized hydrogen separation. Overall energy efficiency has played a secondary role so far.

[0025] methanol: US Patent No. 5,741,474 discloses a method for obtaining hydrogen from methanol in a membrane reactor, in which methanol is vaporized in a first step and reformed in a membrane reactor, which is a reforming chamber, in a second step to form a hydrogen-containing gas mixture, and the generated hydrogen is simultaneously separated from the gas mixture using a membrane. Methanol and the gaseous residue of the membrane process are burned with air in a burner, so that the heat required for vaporization and reforming is provided by heat exchange. That is, US Patent No. 5,741,474 combines the reforming reaction and the separation of hydrogen in a single process step and in a single chamber, so that the process conditions for these processes are the same. The temperature of reforming therefore corresponds to the temperature of hydrogen separation. Furthermore, US Patent No. 5,741,474 does not disclose continuous heat exchange of the combustion gases, nor preheating of the ambient air for the burner with the permeate.

[0026] WO 2004 / 2616 discloses a process consisting of catalytic methanol reforming at 300-500°C followed by H2 separation using pressure swing adsorption (PSA) or palladium alloy membranes. Energy for reforming and hydrogen separation is provided from internal or external energy sources, but no variant is disclosed that uses the residue of H2 separation as fuel.

[0027] WO 2003 / 86964 describes a reformer for methanol reforming and H2 separation from the reformate using a palladium-based membrane or PSA. Reforming temperatures of 200-700°C are disclosed, and methanol reforming temperatures of 200-400°C are disclosed. As an energy source, the residue of the H2 separation is burned. No data is disclosed on the necessary heat exchanger connections. Furthermore, no description is given of the preheating of the burner air or the methanol. °C

[0028] WO 2003 / 27006 describes the complete on-board system consisting of methanol vaporization and reforming, H2 separation and fuel cell. Reforming and H2 separation are carried out simultaneously in a membrane reactor, which operates at 100 °C. According to the authors, Pd membrane reactors become fragile at high H2 partial pressures (>5 bar) and temperatures (>200 °C). As energy source, catalytic combustion of the residues of the H2 separation and the fuel cell off-gas is described. No data on the necessary heat exchanger connections are disclosed. Furthermore, no preheating of the burner air or the methanol is described.

[0029] Emonts et al. (B. Emonts, J.B. Hansen, H. Schmidt, T. Grube, B. Hohlein, R. Peters, A. Tschauder, "Fuel cell drive system with hydrogen generation in test," Journal of Power Sources, No. 86, pp. 228-236, 2000) describe the controlled behavior test of an on-board fuel cell system consisting of a compact methanol reformer (CMR) and a polymer electrolyte membrane fuel cell (PEMFC). The CMR contains a catalytic burner that provides methanol reforming, hydrogen separation using a palladium membrane, and heat obtained by burning the residue for reforming. A second catalytic burner, fueled by methanol, supplies the vaporization unit. In normal operation, the combustion gases leave the system at a temperature of 180 °C. Reforming and H2 separation are carried out at temperatures of 260-280 °C.

[0030] Y.-M. Lin et al. (Y.-M. Lin, M.-H. Rei, "Study on the hydrogen production from methanol steam reforming in supported palladium membrane reactor," Catalysis Today, No. 67, pp. 77-84, 2001; Y.-M. Lin, G.-L. Lee, M.-H. Rei, "An integrated purification and production of hydrogen with a palladium membrane-catalytic reactor," Catalysis Today, No. 44, pp. 343-349, 1998) describe a preferred temperature range of 300 to 400 ° C for methanol reforming in a membrane reactor equipped with a palladium membrane on an electrically operated stainless steel support. It is disclosed that below 300 ° C, embrittlement occurs in the palladium membrane, and above 400 ° C, intermetallic diffusion occurs between the palladium membrane and the stainless steel support, resulting in a decrease in H2 permeability.

[0031] ammonia: US Patent No. 7,811,529 discloses a method for obtaining hydrogen from ammonia in a membrane reactor, in which the ammonia is vaporized in a first step and reformed in a hydrogen membrane reactor in a second step, and the generated hydrogen is simultaneously separated using a membrane. The ammonia and the gaseous residue of the membrane process are burned with air in a burner, so that the heat required for vaporization and reforming is provided by heat exchange. Thus, US Patent No. 7,811,529 combines the reforming reaction and hydrogen separation in a hydrogen membrane reactor, so that the process conditions for these processes are the same.

[0032] British Patent No. 1,079,660 discloses the entire process consisting of catalytic NH3 decomposition followed by H2 separation through a Pd alloy membrane. The preferred temperature range for NH3 decomposition is described as 650-930°C, but no preferred pressure is disclosed. The energy for NH3 vaporization and decomposition is generated electrically.

[0033] The drawback of using electrical energy for NH3 vaporization and decomposition is that this electricity is generated in the downstream FC with only a maximum efficiency of 70% in the most favorable case, so not only does the NH3 vaporization and decomposition, as well as the H2 separation and the expensive FC, need to be larger than if the residue combustion energy were directly used for NH3 vaporization and decomposition, but also more NH3 is needed due to efficiency losses.

[0034] WO 2018 / 235059 discloses a membrane reactor and a method for on-board electricity generation by NH3 decomposition using low-temperature plasma and simultaneous H2 separation by a Pd-Ag membrane. Due to the permanent H2 separation, almost complete NH3 conversion is already achieved at low temperatures of 200-500 °C and relatively high pressures of 8-10 bar. The decomposition energy is again supplied electrically.

[0035] WO 02 / 071451 2discloses an H2 generation device for on-board applications. At the heart of the device is a compact heat exchanger reactor implemented in a number of channels. In half of the channels, NH3 is decomposed to N2 and H2 at temperatures of 550-650 °C on a ruthenium nickel catalytic converter, while in the other half of the channels, fuel is catalytically combusted to provide heat for the NH3 decomposition. The reformate from the NH3 decomposition, consisting mostly of N2 and H2, is converted to electricity in the FC. To protect the fuel cell from unconverted NH3, the process gas is routed through an adsorption bed beforehand. The adsorbent, preferably acidic, is replaced rather than regenerated on-board. It is proposed that the decomposition energy is provided by catalytic combustion of NH3 or preferably entrained butane. To start the process, the device needs to be brought to reaction temperature by the electricity of a battery. However, the disclosed method, although suitable for electricity generation, is not suitable for the production of high-purity hydrogen, for example for use in fuel stations, due to the lack of separation of N2 and H2. If a mixture of N2 and H2 is fed to the fuel cell instead of pure H2, the efficiency of the fuel cell will be lower.

[0036] L. Lin et al. (L. Lin, Y. Tian, ​​W. Su, Y. Luo, C. Chen, L. Jiang, "Techno-economic analysis and comprehensive optimizaition of an on-site hydrogen refuelling station system unsing ammonia: hybrid hydrogen purification with both high H2 purity and high recovery," Sustainable Energy Fuels, Bd.4, pp.3006-3017, 2020) describe a multi-step method to produce high-purity H2 from NH3 for H2 filling stations. The results are based on simulations. They consider a method with the following process steps: catalytic NH3 decomposition at 500 °C, separation of unconverted NH3 in PSA (pressure swing adsorption), separation of N2 / H2 gas streams by a combination of PSA and membrane processing, and compression of the 99.97% pure product stream to a pressure of 900 bar for the filling station's fuel pumps. 15.5% of the gas stream from NH3 decomposition is combusted to provide the necessary reaction enthalpy. Since the reaction enthalpy for NH3 decomposition is provided by the combustion of reformate (N2, H2, unconverted NH3) and not by the combustion of residue, it follows that the loss of H2 via the residue must be minimized. Furthermore, as will be shown later, this reduces the component pressure difference for N2 / H2 separation, reducing the overall energy efficiency.

[0037] Lamb et al. (KE Lamb, DM Viano, MJ Langley, SSHla, MD Dolan, "High-Purity H2 Production from NH3 via a Ruthenium-Based Decomposition Catalyst and Vanadium-Based Membrane", "Industrial & Engineering Chemistry Research, Bd. 57, pp. 7811-7816, 2018) describe a method for producing high-purity hydrogen from NH3. NH3 decomposition is performed at 5 bar and 450 °C, and membrane separation is performed at 340 °C. On the permeate side, a negative pressure of 0.1 bar was set. For a standalone installation, the authors propose to provide energy for NH3 decomposition by burning the hydrogen remaining in the permeate stream. The authors recommend taking 75% of the hydrogen from NH3 decomposition as product and burning the remaining 25% for NH3 decomposition. Details on the design of the energy transfer for endothermic reforming and vaporization are not disclosed.

[0038] The disadvantage of using membrane reactors is that reforming and H2 separation must necessarily take place at the same temperature level. It is therefore not possible to carry out both reforming and separation processes in the optimum range in a membrane reactor. Process technology compromises are always necessary due to the following interactions: lower temperatures in the membrane reactor favor energy utilization, higher temperatures favor hydrogen separation. On the one hand, the CO2 in the reaction mixture increases due to the continuous separation of H2 during the reforming process. On the other hand, the required reaction heat has to be provided via the heated reactor walls. High CO2 concentrations and high reactor wall temperatures lead to coke deposition. This increases the risk of membrane clogging. To prevent this, additional water has to be introduced into the reaction, which reduces the energy efficiency.

[0039] Although membrane reactors are of great academic interest due to their process technological coupling of reaction and H2 separation, they have been of little practical use to date due to the above-mentioned shortcomings.

[0040] However, when considering the entire process chain consisting of vaporization, reforming and H2 separation from the perspective of highest energy efficiency and lowest investment costs, it surprisingly turns out that decoupling reforming and H2 separation is more expedient in terms of keeping H2 production costs low.

[0041] Therefore, methods are being sought to obtain high-purity hydrogen from methanol or ammonia for the operation of fuel cells, hydrogen stations or for decentralized supply for small-scale industrial applications, where the hydrogen is produced with as little energy loss as possible. Furthermore, they have the advantage of low cost due to low capital expenditure. In addition, a low material requirement relative to the membrane area is also advantageous. Another advantage is the energy efficiency, if the temperature difference between the starting materials methanol or ammonia and the exhaust gas, as well as between the obtained hydrogen product stream and the required burner air, is as low as possible.

[0042] The invention comprises a method for obtaining hydrogen from methanol or ammonia, advantageously for fuel cell operation, which comprises vaporizing the latter in a first step and reforming the latter to form a hydrogen-containing gas mixture in a second step, separating hydrogen from the gas mixture in a membrane process at a temperature between 300 and 600° C. in a third step, and combusting the gaseous residue of the membrane process with ambient air in a fourth step, wherein the second step is a process step separate from and upstream of the third step, and wherein the combustion gases are passed through at least two different heat exchangers. By passing it through in the flow direction of the combustion gas, (i) firstly, it provides reaction heat for reforming methanol or ammonia, and (ii) subsequently, it provides vaporization heat for vaporizing the reformer feed, and the permeate of the membrane process preheats the ambient air for the burner in the heat exchanger, and (a) the temperature difference between the exiting permeate and the incoming ambient air, and (b) the temperature difference between the exiting combustion gas and the incoming methanol or ammonia are 1-200°C, respectively, and during the third process step, a maximum temperature increase of 0-100°C is performed.

[0043] Figure 2 shows the main steps of the invention. Figure 3 shows a schematic diagram of a process technical variant.

[0044] First step: methanol: Methanol and optionally water are fed to the evaporator. Advantageously, the proportion of water in the methanol-water mixture is between 0 and 75 mol percent, preferably between 10 and 70 mol percent, particularly preferably between 25 and 65 mol percent, in particular between 40 and 60 mol percent, and very particularly preferably, the molar ratio of methanol to water is 1:1.

[0045] Advantageously, methanol or a methanol-water mixture is vaporized for the gaseous reformer feed in an evaporator at a pressure of 4-60 bar, which is the same for the entire process, adjusted for pressure loss. Advantageously, the pressure in the evaporator is 5-30 bar, in particular 10-20 bar. The skilled person knows the temperature required for vaporization from the pressure data.

[0046] ammonia: Alternatively, liquid ammonia is taken from the tank, advantageously at -35 to 50°C and 1 to 20 bar, and the pressure is increased further by means of a pump if necessary. Advantageously, the liquid ammonia becomes gaseous reformer feed in an evaporator at a pressure of 2 to 60 bar, which pressure is the same in the entire process, adjusted for pressure loss. Advantageously, the pressure in the evaporator is 4 to 40 bar, particularly preferably 6 to 30 bar, in particular 10 to 20 bar. From the pressure data, the skilled person knows the temperature required for vaporization, advantageously -20°C to 100°C.

[0047] The vaporous NH3 stream, as with methanol, is advantageously split and fed to the reformer feed and a control stream, with the control stream being mixed with the residue stream as required, e.g., at the start-up and control of the process.

[0048] Second step: methanol: Subsequently, the reformer feed, i.e., gaseous methanol or methanol-water mixture, is catalytically reformed at a temperature between 100 and 400° C. to also produce a gaseous reformate. Preferably, the methanol reforming temperature is between 180 and 350° C., in particular between 240 and 300° C. At lower methanol reforming temperatures, the H2 yield increases at the expense of the CO fraction due to the equilibrium of the WGS (water gas shift reaction).

[0049] The methanol reformate contains H2, CO, CO2, H2O, and unconverted MeOH or DME. The composition of the gaseous methanol reformate is preferably 55-75 mol percent H2, 1-8 mol percent CO, 10-25 mol percent CO2, 2-10 mol percent H2O, 0.1-20 mol percent MeOH, and / or DME, and more preferably 60-70 mol percent H2, 1-5 mol percent CO, 15-25 mol percent CO2, 2-9 mol percent H2O, 1-10 mol percent MeOH, and / or DME.

[0050] The conversion of the methanol reforming is advantageously between 70 and 99%, preferably between 80 and 95%, particularly preferably between 85 and 90%.

[0051] Reversal of CO2 hydrogenation in methanol reforming 3 H2+CO2=CH3OH+H2O DH R 0 =-49kJ / mol CH3OH occurs according to the following overall reaction: CH3OH=2H2+CODH R 0 =+90kJ / mol CH3OH

[0052] The methanol used in accordance with the present invention may contain dimethyl ether (C2H6O), usually in a proportion of 1 to 5 weight percent, which is simultaneously reformed to methanol in the presence of H2O.

[0053] Water reacts with CO according to the following overall reaction: H2O+CO=H2+CO2 DH R 0 =-41kJ / mol CO

[0054] This exothermic reaction is called the water-gas shift (WGS) reaction. The water in methanol can advantageously increase the H2 yield and reduce the additional energy used for the overall reforming and WGS process.

[0055] The maximum CO2 generated in the entire process via the WGS reaction and / or combustion of methanol and / or CO matches the CO2 used in producing methanol from CO2 and H2, making the entire process CO2 neutral.

[0056] Advantageously, no hydrogen stream is withdrawn during the second step, i.e. reforming. The second step is therefore advantageously a separate step upstream of the third step. Moreover, the second step is advantageously also separate from the first step and downstream of the first step. An advantageous sequence of process steps is shown in FIG. 4. For example, it may be advantageous to further heat the reformate in an evaporator (reformate heater), since this allows for a smaller surface area of ​​the costly Pd membrane in the downstream membrane module.

[0057] Catalytic converters for methanol reforming have been described in the prior art (see, for example, F. Gallucci et al., "Hydrogen Recovery from Methanol Steam Reforming in a Dense Membrane Reactor: Simulation Study", Ind. Eng. Chem. Res. 2004, 43, 2420-2432, and A. Basile et al., "A dense Pd / g membrane reactor for methanol steam reforming: Experimental study", Catalysis Today, 2005, 104, 244-250). For example, a mixture of CuO / ZnO / Al2O3 is used as the active catalytic converter component, advantageously with a composition of 38 weight percent CuO, 41 weight percent ZnO, 21 weight percent Al2O3, or a mixture with a composition of 31 weight percent CuO, 60 weight percent ZnO, 9 weight percent Al2O3.

[0058] Optionally, the methanol reformate is subsequently heated to a preferred temperature of 300-700° C., preferably 350-600° C., especially 400-500° C. for H2 separation.

[0059] ammonia: The NH3 vapour stream, as in the case of methanol, is advantageously fed to a reformer where it is decomposed into H2 and N2. The energy required for the decomposition is advantageously provided by a heat stream. The ammonia reforming is advantageously carried out at a temperature between 100 and 700° C., preferably between 200 and 600° C., in particular between 300 and 500° C. Advantageously, the ammonia reforming is carried out at a pressure between 2 and 60 bar, preferably between 6 and 30 bar, in particular between 10 and 20 bar.

[0060] The gaseous ammonia reformer advantageously contains H2, N2, and unconverted NH3 in a preferred composition by volume of 60-75 percent H2, 20-25 percent N2, and 0-20 percent NH3.

[0061] The conversion of the ammonia reforming is advantageously between 70 and 99%, preferably between 80 and 95%, particularly preferably between 85 and 90%.

[0062] Advantageously, no hydrogen flow is withdrawn during the second step, i.e. reforming. The second step is therefore advantageously a separate step upstream of and independent of the third step. Moreover, the second step is advantageously also separate from and downstream of the first step.

[0063] Catalytic converters for ammonia reforming have been described in the prior art (see A. Di Carlo et al., "Ammonia decomposition over commercial Ru / Al2O3 catalyst: An experimental evaluation at different operative pressures and temperatures", International. Journal of Hydrogen Energy, 39 (2014) S. 808-814). For example, ruthenium is used as the active catalytic converter component, and ACTA Hypermec 10010 catalyst_(Ru / Al2O3) is advantageous.

[0064] heating: Optionally, the ammonia reformate is subsequently heated to a preferred temperature of 300-700° C., preferably 350-600° C., especially 400-500° C. for H2 separation.

[0065] Third step: Advantageously, at temperatures between 300 and 700°C, preferably between 350 and 700°C, preferably between 350 and 600°C, preferably between 400 and 600°C, especially between 400 and 500°C, the reformate reaches the membrane module for separating H2 (see Y.-M. Lin et al., Mejdell AL, Jondahl M., Peters TA, Bredesen R., Venvik HJ, "Effects of CO and CO2 on hydrogen permeation through a 3mm Pd / Ag 23 wt.% membrane employed in a microchannel membrane configuration", Separation and Purification Technology, 68 (2009) 178-184). High temperatures promote hydrogen permeability through the membrane and reduce the inhibitory effect of CO in the case of H2 membrane separation.

[0066] In the membrane module, the gaseous reformate is split into a high purity hot residue stream, preferably having a purity of >99.99 volume percent H2, and a residue stream containing H2, CO, CO2, H2O, and unconverted MeOH when using methanol, or unconverted NH3 in addition to N2 and H2 when using ammonia.

[0067] The residue using methanol advantageously has the following gas composition: 5-40 mole percent H2, 0.1-12 mole percent CO, 5-66 mole percent CO2, 1-12 mole percent H2O, 0.1-10 mole percent MeOH.

[0068] The residue, under the use of ammonia, preferably contains the following gas composition: 5-35 volume percent H2, 1-40 volume percent NH3, 25-94 volume percent N2, and particularly preferably 10-25 volume percent H2, 5-30 volume percent NH3, 45-85 volume percent N2.

[0069] The H2 flux is advantageously between 0.1 and 5.0 mol H2 / (m2 s), preferably between 0.5 and 4.0 mol H2 / (m2 s), particularly preferably between 1.0 and 3.5 mol H2 / (m2 s), in particular between 1.5 and 3.0 mol H2 / (m2 s).

[0070] The temperature range for H2 separation by membranes, advantageously Pd membranes, is advantageously 400-700°C, particularly preferably 450-600°C, in particular 500-600°C.

[0071] Advantageously, the temperature of the third step (hydrogen separation) is, in the case of methanol, 10-400K higher than the temperature of the second step (reforming), with this temperature difference being preferably 50-300K, in particular 75-200K.

[0072] The second and third steps are carried out as successive, separate and unrelated process steps.

[0073] In the case of methanol, the CO partial pressure for H2 separation by Pd membranes is advantageously 0-5.0 volume percent, particularly preferably 0-2.0 volume percent, in particular 0-0.5 volume percent. Low CO partial pressure is advantageously achieved by the addition of water, a water-gas shift active catalytic converter, low temperature (preferably 150-400°C, in particular 200-250°C).

[0074] In both cases of methanol and ammonia, the H2 partial pressure for H2 separation through the Pd membrane is advantageously 50-80 volume percent, particularly preferably 60-75 volume percent, in particular 65-70 volume percent.

[0075] All three factors, low CO partial pressure, high H2 partial pressure, and high temperature, reduce the effort required for H2 separation.

[0076] Advantageously, as material pairs of the membrane device, i.e. Pd membrane and support material, Pd, Pd-Ag or Pd-Ag-Au and ceramic or stainless steel are used (see A. Unemoto, A. Kaimai, S. Kazuhisa, T. Otake, K. Yashiro, J. Mizusaki, T. Kawada, T. Tsuneki, Y. Shirasaki and I. Yasuda, "The effect of co-existing gases from process of steam reforming reaction on hydrogen permeability of palladium alloy membrane at high temperatures," International Journal of Hydrogen Energy, Nr. 32, pp. 2881-2887, 2007), for example Pd with 20-30 weight percent Ag, in particular 23-24 weight percent Ag.

[0077] The thickness of the Pd layer is preferably 1 to 60 μm, particularly preferably 3 to 20 μm, and especially preferably 5 to 10 μm.

[0078] Basically, all known structures are considered as membrane modules. Among flat membranes, plate modules are the preferred structure. As for hose-type membranes, in addition to hollow fiber modules, capillary modules are also preferred. Particularly preferred are tube-type modules with a diameter of 3 to 50 mm, in particular 5 to 10 mm.

[0079] A large amount of H2 is separated as permeate through the membrane, so on the one hand the purity requirements for the H2 product are met, and on the other hand the heating value of the residue is sufficient to provide heat for vaporization prior to H2 separation, for reforming and, if necessary, for increasing the temperature of the reformate.

[0080] The H2 content of the permeate is advantageously between 95 and 99.999 volume percent H2, particularly preferably between 98 and 99.99 volume percent H2, in particular between 99.0 and 99.95 volume percent H2. Advantageously, the absolute pressure of the permeate is between 0.1 and 5 bar, particularly preferably between 0.5 and 3.0 bar, in particular between 1.0 and 2.0 bar.

[0081] On the permeate side, water vapor is used as a diluent gas for H2 if necessary. The water vapor reduces the H2 partial pressure on the permeate side. This increases the forcing pressure difference and the H2 flux. This measure is advantageous if the PEM fuel cell needs to be continuously overhumidified during operation.

[0082] Advantageously, besides the membrane modules, no PSA (Pressure Swing Adsorption) units are used to separate the hydrogen.

[0083] However, it can be extremely beneficial to ensure or even increase the purity of the permeate by passing it through an adsorbent bed that separates the last residues of CO, CO2, N2 and NH3 from the permeate, thus acting as a "police filter".

[0084] If the CO or CO content in the permeate does not correspond to the requirements of the fuel cell, it can advantageously be passed further through a methanation catalyst bed (see WO 2004 / 002616). 2 etc.).

[0085] It is advantageous that in or during the third process step itself there is a temperature increase of at most 0-100°C, preferably at most 0-50°C, more preferably at most 0-20°C, and in particular no temperature increase or further energy supply. Advantageously, no units in the membrane module have a higher temperature than the gaseous reformate, which is optionally intermediately heated. This measure makes it possible in particular to avoid deposits on the membrane surface, for example the deposition of coke.

[0086] The residue is sent to a burner, which burns the combustion components in the residue, in particular (residual) methanol, carbon monoxide and hydrogen in the case of methanol, and (residual) ammonia and hydrogen in the case of ammonia, advantageously with heated air, thereby providing the energy required for preheating, vaporization, reforming and reformate heating before H2 separation. For this process, air must be taken from the surroundings and compressed to a pressure that corresponds to the sum of all pressure losses in the gas train starting from the burner and leaving the reformer module as exhaust gas. The sum of all pressure losses can be in the range from 50 mbar to 5 bar. As a compressor, for example, an air blower or a jet nozzle can be used.

[0087] In a special embodiment, the expansion of the residue also allows ambient air to be drawn in by a low-cost jet nozzle and compressed to the required pressure within the burner, eliminating the need for expensive, electricity-hungry air compressors.

[0088] Fourth step: The mixture of residue and heated air is then combusted in a burner, for example an atmospheric or catalytic burner. The hot combustion gases are passed through various heat exchangers, advantageously at a temperature of 500-1200° C. in the case of atmospheric burners and advantageously at a temperature of 300-700° C. in the case of catalytic burners, to (i) heat the reformate, (ii) provide reaction heat for the reforming, (iii) provide vaporization heat for vaporizing the methanol or ammonia, and (iiii) preheat the input materials. Optionally, heating of the reformate (i) may be omitted.

[0089] After leaving the burner, the hot combustion gases are advantageously continuously cooled so that the temperature difference with respect to the incoming methanol or ammonia feed stream is between 1 and 200° C., preferably between 5 and 100° C., more preferably between 10 and 80° C., more preferably between 20 and 50° C., in particular between 30 and 40° C. Cooling of the combustion gases is advantageously carried out until the temperature is between 25 and 100° C., preferably between 35 and 60° C., in particular between 40 and 50° C.

[0090] In a preferred embodiment, in addition to the residue, methanol or ammonia in liquid and gaseous state can also be fed to the burner and / or afterburner to provide the energy required for vaporization, reforming and, if necessary, increasing the temperature of the reformate. The methanol or ammonia feed advantageously allows the entire process to be started and controlled during operation at stable operating conditions. This mixing can advantageously take place before, after or directly in the pneumatic conveyor.

[0091] The addition of methanol or ammonia is advantageously controlled by the detectable energy content of the exhaust gas, i.e. the cooled combustion gas leaving the process, and the temperature of the combustion gas from the burner and any afterburner. All this combines to provide energy for vaporization, reforming, and optionally temperature increase before H2 separation. If, for example, the combustion temperature or the exhaust gas amount is reduced, methanol or ammonia is advantageously fed to the burner. In this case, the amount of methanol or ammonia required can vary widely. The amount of methanol or ammonia fed to the burner is advantageously 0-30%, preferably 0-20%, preferably 0-10%, in particular 0-5% of the amount of methanol or ammonia fed to the entire process.

[0092] The air required for the burners is advantageously drawn from the surroundings. The drawn air is then advantageously compressed in order to convey the hot combustion gases through a heat exchanger. Advantageously, this air is compressed from the ambient pressure (1.013 bar) to 1.05-5.0 bar, preferably to 1.1-2.0 bar, in particular to 1.2-1.5 bar. As compressors, all devices known to the person skilled in the art come into consideration, such as blowers, ventilators, compressors, etc. The compressor is advantageously located before the first burner.

[0093] In a special embodiment, no conveyors requiring electrical energy, such as blowers or compressors, are used for the necessary pressure increase of the ambient air in front of the burner and for the conveyance of the hot combustion gases through the heat exchanger. Advantageously, a jet pump is used (see https: / / www.koerting.de / de / strahlpumpen.html?gclid=EAIaIQobChMI7M21hpmw8AIVB-d3Ch0YTgJLEAAYASAAEgKG-fD_BwE), which sucks in the ambient air at a high pressure, advantageously between 5 and 40 bar of the tailings, and compresses it to the required pressure, advantageously between 0.05 and 5 bar. This allows the reforming module to operate autonomously, i.e. without an external energy source, apart from the conveyance of the feed condensate, which requires only very little energy.

[0094] The hot combustion gases generated in the burner advantageously have a temperature of 600 to 1100°C, preferably 700 to 1000°C, particularly preferably 800 to 950°C, in particular 850 to 900°C, when using atmospheric burners, and advantageously have a temperature of 200 to 500°C, preferably 220 to 300°C, when using catalytic burners.

[0095] The combustion gases, when using methanol, advantageously contain H2O, CO2, N2 and residual O2, and advantageously have the following composition: 5-16 volume percent O2, 24-78 volume percent N2, 3-35 volume percent CO2, 3-36 volume percent H2O, particularly advantageously 10-15 volume percent O2, 49-68 volume percent N2, 8-20 volume percent CO2, 9-21 volume percent H2O, in particular 14 volume percent O2, 68 volume percent N2, 9 volume percent CO2, 9 volume percent H2O.

[0096] The combustion gas, when using ammonia, advantageously includes N2, O2, and H2O, and may, for example, have the following composition: 80 volume percent N2, 10 volume percent O2, and 10 volume percent H2O.

[0097] In either case, the composition of the combustion gases is advantageously controlled by the residual O2 concentration. Low O2 values ​​mean a low volumetric flow rate of the combustion gases (low compression), but a high initial temperature of the combustion gases. High O2 values ​​(up to 21 volume percent) have the opposite effect.

[0098] The flow of the combustion gases is shown in FIG.

[0099] The hot combustion gases are passed through multiple heat exchangers in succession and cooled in stages to near ambient temperature (see Figures 2-4) to (0) optionally heat the reformate, (i) for reforming, (ii) to vaporize the condensate, and (iii) optionally to preheat the ammonia, methanol, or methanol and water feeds.

[0100] Advantageously, additional heat exchangers can be installed between the reforming reactor and the membrane module, as well as between the membrane module and the air conveyor, to improve the heat integration or the H2 separation rate through the Pd membrane, if necessary.

[0101] Cooling of the combustion gases after the atmospheric burner is advantageously carried out in the methanol operating mode in the following input temperature range of the combustion gases:

[0102] No intermediate heating of the combustion gases in the afterburner: Variant without reformer heater (see Figure 2): Reformer 700-900°C, evaporator 500-650°C, preheater 150-220°C.

[0103] Variant with reformer heater (see Figure 7): reformer heater 700-900°C, reformer 400-700°C, evaporator 300-500°C, preheater heat exchanger 150-220°C.

[0104] Intermediate heating of the combustion gases after the reformer heat exchanger by the afterburner: Variant without reformer heater (see Figure 5): Reformer 700-900°C, evaporator 500-650°C, preheater 150-220°C.

[0105] Variant with reformer heater (see Figure 4): reformer heater 700-900°C, reformer 700-900°C, evaporator 300-700°C, preheater 150-220°C.

[0106] Cooling of the combustion gases after the atmospheric burner is advantageously carried out in the ammonia operating mode in the following input temperature range of the combustion gases:

[0107] No intermediate heating of the combustion gases in the afterburner: Variant without reformer heater (see Figure 2): Reformer 700-1200°C, evaporator 500-650°C, preheater 150-220°C.

[0108] Variant with reformer heater (see Figure 7): reformer heater 700-1200°C, reformer 400-700°C, evaporator 300-500°C, preheater heat exchanger 150-220°C.

[0109] Intermediate heating of the combustion gases after the reformer heat exchanger by the afterburner: Variant without reformer heater (see Figure 5): reformer 700-1200°C, evaporator 500-650°C, preheater 150-220°C.

[0110] Variant with reformer heater (see Figure 4): reformer heater 700-1200°C, reformer 700-900°C, evaporator 300-700°C, preheater 150-220°C.

[0111] If catalytic burners are used, these are advantageously integrated into the heat exchangers. Preferably, the first catalytic burner is integrated into the reformer heat exchanger or, if a reformer heat exchanger is used, into this reformer heat exchanger (FIGS. 2, 4, 5, 7). Advantageously, if two further catalytic burners are used, these burners are preferably integrated into the reformer and reformer heat exchanger or into the reformer and evaporator heat exchanger. Advantageously, if three further catalytic burners are used, these burners are preferably integrated into the reformer, reformer and evaporator heat exchangers.

[0112] The catalytic burners may advantageously have a common air supply or separate air supplies.

[0113] In the catalytic burner, the temperature is almost constant throughout the flow path, with the combustion side temperature advantageously being 1-300°C, preferably 5-50°C, higher than the reformer temperature (200-500°C) and the evaporator temperature (130-220°C), so that the combustion side temperature is 200-700°C in the reformer and 130-520°C in the evaporator.

[0114] At the same time, advantageously, the permeate of the membrane module, i.e. the separated hydrogen having a temperature of 300-700° C., is cooled in a permeate cooler by preheating the air drawn for the burner. The hot permeate stream is cooled so that the temperature difference with respect to the incoming air stream is 1-200° C., preferably 5-100° C., more preferably 10-80° C., more preferably 20-50° C., in particular 30-40° C. This step is crucial for the energy efficiency of the reformer module.

[0115] The streams leaving the process, ie the cooled permeate stream and the burner off-gas, advantageously have a temperature of 25 to 100°C, preferably 25 to 80°C, in particular 25 to 50°C.

[0116] In a given system, the exhaust gas temperature can be advantageously controlled by the air volume flow rate and / or the combustion gas temperature. If the combustion gas temperature is too high, the amount of suction air is advantageously increased. If the product amount is too low, the control flows S4b and S9b are advantageously increased.

[0117] In terms of high energy efficiency, a small air volume flow rate is better than a large one. However, a small air volume flow rate results in a high combustion gas temperature (for example, 1100 to 1200°C). The combustion gas temperature is limited to 1100 to 1200°C due to the heat resistance of the materials used in the heat exchanger and gas piping.

[0118] For process control, the amount of exhaust gas S18 and the amount of H2 production S8 as well as the temperature of the gas streams S13, S16, S18 are preferably measured. The amount of H2 production preferably controls the inflow amount S1. The gas temperature controls the aspirated air volume flow rate S10 and the control flows S4b and S9b.

[0119] Heat Exchanger Design Advantageously, the logarithmic mean temperature difference (LMTD) used in the design of the heat exchanger is the largest between the heat exchanging streams at each location in the heat exchanger, advantageously ranging from 1 to 100°C, preferably from 10 to 50°C.

[0120] The high temperature difference in the evaporator heat exchanger can advantageously be achieved by intermediate heating of the combustion gases after the reformer heat exchanger with an afterburner, advantageously to 280-800°C, preferably 350-700°C, in particular 550-650°C, as shown in Figures 4 and 5.

[0121] For that purpose, in the afterburner, the cooled combustion gases from the burner, which advantageously still contain residual oxygen, are fed with a part of the residue stream, for example 5 to 40 volume percent, preferably 20 to 30 volume percent, and also advantageously with a methanol or methanol-water or ammonia stream from the evaporator, for example 0.1 to 20%, preferably 0.5 to 10%, in particular 1 to 5% of the evaporated methanol or ammonia.

[0122] As afterburners, all types known to those skilled in the art come into consideration, such as catalytic burners, atmospheric burners, forced air burners, etc. When a catalytic afterburner is used, it is integrated into the evaporator heat exchanger.

[0123] This measure advantageously allows the heat exchanger area of ​​the evaporator and the firing temperature of the first burner to be reduced, which is advantageous in that, on the one hand, the heat exchanger for the evaporator is overwhelmingly large, and, on the other hand, the gas temperatures in the first burner that would otherwise be required, significantly above 900° C., can only be realized with very expensive materials.

[0124] A guide like the following would be beneficial:

[0125] [Table 1]

[0126] In the reforming heat exchanger, i.e. reformer heat exchanger, the catalytic converter and the methanol / water vapor or ammonia vapor are preferably arranged in the external space, and the combustion gas passes through the piping. The pressure in the reaction chamber is preferably 3-60 bar, preferably 10-30 bar, higher than the pressure in the combustion gas chamber.

[0127] Before the membrane separation unit, when the temperature of the raffinate is increased by a reforming heater, the raffinate preferably flows in a pipe and the combustion gas flows in an external space.

[0128] If air preheating is accomplished by cooling hot permeate with an air heater or permeate cooler, preferably the air passes through the ductwork and the H2 passes through the exterior space.

[0129] If a liquid input material (methanol or a methanol-water mixture or ammonia) is preheated and vaporized prior to reforming, the combustion gases preferably pass through piping and the liquid methanol or a methanol-water mixture or liquid ammonia passes through the exterior space.

[0130] Additionally, residue from the fuel cell, which may contain unconverted H2, can be recycled to the reformer where it can be used as energy, further increasing the overall efficiency of the entire system.

[0131] The preferred tube diameters for all heat exchangers are 1 to 6 mm, particularly preferably 2 to 5 mm, and especially 3 to 4 mm (see EP 2526058).

[0132] Other cross-sectional shapes, such as rectangular ducts, are also consistent with these tubular shapes.

[0133] Microdevices are often implemented with rectangular ducts for manufacturing reasons. In principle, the method according to the invention can be implemented not only in millidevices but also in microdevices. The choice between millitechnology and microtechnology depends, inter alia, on the required performance of the reforming module, the required ease of maintenance and the available space. For example, replacing a catalytic converter is easier in a millireactor than in a microreactor.

[0134] The process according to the invention advantageously makes it possible to achieve energy utilisation rates of 95-99.8%, preferably 98-99.5%.

[0135] A further aspect of the invention relates to an apparatus for obtaining high purity hydrogen from methanol or ammonia for operating a fuel cell, based on the method described above (see FIG. 6).

[0136] An apparatus for the described method includes, in one embodiment, - a device for preheating the methanol or methanol-water mixture or ammonia, usually integrated in a downstream evaporator; an evaporation device; a reforming reactor, a membrane device; - at least one burner; at least three heat exchangers, advantageously four heat exchangers and preferably five heat exchangers, - means for introducing and / or discharging liquid in preheaters, evaporators, reforming reactors, membrane units, burners, heat exchangers; Contains:

[0137] advantage: The external energy balance is determined in the process according to the invention only by the energy stored in the feed and exhaust streams. In the theoretical limit, where the feed methanol / water or ammonia and air streams have the same temperature as the exhaust H2 product (cold permeate) and tail gas streams, and the methanol or ammonia is already at reforming pressure, 100% efficiency occurs in the reforming module.

[0138] If no additional energy is supplied from the outside and no excess energy is discharged to the outside, the H2 product stream must have the same calorific value as the methanol or ammonia input. That is, in the case of this reforming module according to the invention, theoretically no conversion energy is lost. Losses occur only due to the discharged stream being hotter than the supplied stream, and due to heat being released to the environment through the device walls, as well as due to the mechanical power of the liquid pump and the air conveyor. Therefore, good heat integration and low flow pressure losses of the combustion gas are important. In addition, all the devices of the reforming module are advantageously contained in a container well insulated with vacuum insulation, for example, a microporous silica plate or sleeve covered with fleece, pre-pressed and shrink-wrapped under vacuum in a gas- and water vapor-tight film.

[0139] Diagrams and symbols:

[0140] [Table 2]

[0141] [Table 3]

[0142] [Table 4]

[0143] [Table 5]

[0144] [Table 6]

[0145] Example 1 - Methanol: FIG. 6 shows an example of the method according to the present invention for 1 kg / h H2 production performance, including the optimum geometric dimensions found for the main equipment of the reforming module based on model calculations.

[0146] A fuel cell vehicle powered by H2 and with a tank-to-wheel efficiency of 60% would provide 1 kg of H2 per hour from the reformer module. 1 kg of H2 per hour corresponds to an output of 33.3 kW, which after conversion would be 20 kW of electricity in the FC. This output is enough to power a medium-sized passenger car for 100 km.

[0147] This example is calculated without heat losses through the reformer module walls.

[0148] According to the method according to the invention, 10.4 kg of feed condensate per hour, i.e. a 1:1 molar ratio methanol-water mixture, must be fed to the reformer module and pumped to a system pressure of 20 bar using a conveying pump. This pressure increase requires P1 = 0.02 kW. el of power is required.

[0149] Counter-flow guidance of the feed condensate and the combustion gas in the evaporator allows both preheating and vaporization of the feed condensate in the evaporator. A combined heat output of 5.4 kW is required for both processes. The feed condensate has a boiling temperature of 188 °C at 20 bar. 10.1 kg of feed condensate vapor is fed to the reformer as reformer feed and 0.3 kg / h is fed to the afterburner as control flow.

[0150] In the reformer, the feed condensate vapor is brought to a reaction temperature of 240°C and catalytically reformed to 68.7 volume percent H2, 2.7 volume percent CO, and 21.7 volume percent CO2. The MeOH equilibrium conversion at 240°C and 20 bar is 93%. The reformate also contains 5.2 volume percent unconverted H2O and 1.7 volume percent unconverted MeOH. Reforming requires 3.8 kW of thermal energy.

[0151] The reformate is then heated to 450° C. in a reformate heat exchanger (reformate heater). Heating requires a thermal power of 1.5 kW.

[0152] In the membrane module, 1 kg per hour of hot permeate is separated and cooled to 45 °C in a permeate cooler or air heater. This cold permeate leaves the reforming module as H2 product. This requires a heat output of 1.6 kW.

[0153] The membrane module produces 9.1 kg of residue per hour, containing 11.0 volume percent H2, 7.6 volume percent CO, 61.8 volume percent CO2, 14.8 volume percent H2O, and 4.8 volume percent MeOH. Of this, 5.8 kg / h is fed to the burner and 3.3 kg / h to the afterburner. The burner requires 18.6 kg / h of air, which is heated to 330° C. in countercurrent flow to the permeate in the permeate cooler or air heater and subsequently compressed to 1.5 bar in an air conveyor to overcome all flow losses. The temperature then rises to 420° C. The H2 product stream leaves the permeate cooler or air heater as a cold permeate at 45° C. and subsequently leaves the reforming module.

[0154] In the burner, 5.8 kg of residue per hour is combusted with compressed air, producing hot combustion gases with a flow rate of 24.4 kg / h and a temperature of 900°C. The combustion gases heat the reformer in a reformer heater with a thermal power of 1.5 kW, where they cool to 720°C. The cooled combustion gas stream is then sent into the reformer, where it provides 3.8 kW of thermal power for the reforming reaction and heats the gaseous reformer feed from 188°C to 240°C.

[0155] The further cooled combustion gases are then intermediately heated again in the afterburner to 650° C. For this purpose, the cooled combustion gases, which still contain about 14 volume percent oxygen, are combusted with 3.3 kg / h of residue and a controlled flow of 0.3 kg / h from the evaporator.

[0156] In the vaporizer and preheater, the intermediately heated combustion gas is cooled to 45° C. in counterflow against a supply of cold feed condensate and exits the reforming module as exhaust gas.

[0157] Along with the input raw condensate, the reformer module is supplied with electricity with an enthalpy of 33.04 kW. In addition to this, an additional 0.52 kW of power must also be provided for the conveying pump and air blower. In total, 33.56 kW of electricity flows into the reformer module and the H2 product stream leaves the reformer module with an enthalpy of 33.33 kW.

[0158] Energy efficiency of the whole process η Pr is defined as follows: η Pr =m H2 * H UH,H2 / m MeOH * H UH,MeOH Here, the mass flow rate of the injected MeOH m MeOH H obtained from (kg / h) 2 The amount (kg / h) and the lower calorific value H UH,H2 = 120MJ / kg and H UH,MeOH = 19.9 MJ / kg was used.

[0159] The energy efficiency of the reforming module, excluding heat loss through the equipment walls, is η Pr =33.33kW / 33.56=99.3%.

[0160] Considering a FC efficiency of 60%, for a vehicle, the efficiency from tank to wheels is 60% * 99.3%=59.6%.

[0161] When the energy utilization of the method based on the present invention, including a FC efficiency of 60%, is compared with the prior art (SIQENS Fuel Cell Technology, "SIQENS Ecoport 800, Energie fur Off-Grid, Notstrom und Mobilitat," 2021 [online]. [Accessed June 9, 2021]), the energy and economic advantages of the present invention are clear.

[0162] Direct fuel cell 30~40% Emonts et al. 56.0% The present invention 59.6%

[0163] Figure 6 shows the thermal output P 熱 In addition, for each material or heat exchange device, the number of pipes N 管 , Pipe inner diameter D 管 , effective pipe length L 管 , device diameter D 装置 , device length L 装置 , pressure loss of gas flowing through the pipe Dp V is shown.

[0164] [Table 7]

[0165] The control valves required to control the process require a certain pressure loss range, so in the simulation, the compression capacity of the air flow was assumed to be 500 mbar. For the gas flow, from air inlet to exhaust gas outlet, the net pressure loss (without control valve) is 80 mbar.

[0166] If the H2 product flow is different from 1 kg / h, other preferred pipe numbers and shapes will result. However, in this case, the specified preferred pipe diameters will not be affected. Number of pipes N 管 and piping length L 管 , and therefore the device diameter D 装置 and device length L 装置 Only the value is changed.

[0167] These values ​​are known to the person skilled in the art and were calculated according to equations described in the VDI Heat Atlas (Verein Deutscher Ingenieure, "VDI-Warmeatlas", 11th ed., HVVuC(GVC), ed., 2013, pp. 1223-1225).

[0168] Example 2 - Ammonia This example is the result of a thermodynamic simulation using a BASF in-house simulator similar to the Aspen Plus simulation program, in terms of quantities and energies.

[0169] To calculate H2 / N2 separation by a Pd membrane, an Excel calculation tool was used, and the calculation rules are described in Saltonstall's publication (C. Saltonstall, "Calculation of the Memebrane Area Required for Gas Separations," Bd. 32, pp. 185-193, 1987).

[0170] In this calculation, the flow pressure losses are not taken into account, since the example does not depend on the design of the device, but it clearly shows the potential of the method according to the invention.

[0171] An example of this is shown in FIG.

[0172] Liquid NH3 is stored in a tank at room temperature (25°C). To produce 1,000 kg of H2 per hour, 6,891 kg / h of NH3 is pumped by a conveying pump to an evaporator with a built-in preheater and vaporized at 20 bar. To achieve this, it is necessary to supply a pump power of 7 kW and 1,920 kW of thermal energy at 49.3°C.

[0173] The equilibrium conversion of NH3 vapor at 400°C and 20.0 bar is 86.0%. A heat flow of 6,700 kW is required to heat the NH3 vapor to the reaction temperature and to actually reform. The reformate can have the following molar composition by volume: 69.3 percent H2, 23.1 percent N2, 6.9 percent NH3.

[0174] This reformate is then heated to 450° C. in a reformate heater, which requires a thermal output of 320 kW.

[0175] The heated reformate is then sent to the membrane module. The Pd membrane has specific values ​​as disclosed by Macchi et al. (G. Macchi, D. Pacheco Tanaka, "Flexible Hybrid separation system for H2 recovery from NG Grids," in WP10-Exploitation workshop D10.16, 2016) and Melendez et al. (J. Melendez, E. Fernandez, F. Gallucci, M. van Sint Annaland, P. Arias and D. Tanaka, "Preparation and characterization of ceramic support ultra-thin Pd-Ag membranes," Journal of Membrane Science, Bd.528, pp.12-23, 2017). According to them, a Pd-Ag membrane with a layer thickness of 5 micrometers has a 6.9% hydrogen permeability at 450 °C. * It has an H2 permeability of 10-7mol m-2 s-1 Pa-1 and an optimal H2 / N2 selectivity of >150,000.

[0176] Through this membrane, 1,000 kg / h of H2 are separated from the heated reformate as hot permeate at 450°C. The residue (5,890 kg / h) has the following molar composition: 10.0 volume percent H2, 67.8 volume percent N2, 22.2 volume percent NH3. A molar H2 concentration in the residue of 10.0% corresponds to a mass flow rate of H2 of 52 kg / h. From the amount of H2 produced in NH3 decomposition of 1,052 kg / h, 1,000 kg / h of H2 is obtained.

[0177] At a permeate pressure of 1.0 bar, separation requires 166 m 2 The permeate has H2 purity >99.99 and leaves the entire process as H2 product stream after being cooled from 450°C to 45°C in a permeate cooler or air heater. For this, 1620kW needs to be taken off the hot permeate stream.

[0178] The tailings are expanded from 20.0 bar to 1.2 bar while 27,460 kg / h of heated air is compressed from 1.0 to 1.2 bar in a 25% efficient jet nozzle for the combustion of the tailings.

[0179] The resulting mixture (33,350 kg / h) is burned and cooled stepwise to 71°C by leaving the burner as combustion gases at 900°C. In the first step, 320 kW is needed to heat the residue from 400°C to 450°C, and in the second step, 6,700 kW is needed to heat the reforming feed from 49.3°C to the reaction temperature and actually reform the NH3. The combustion gases are then cooled to 261°C. Finally, the combustion gases are cooled to 71°C by vaporizing the liquid NH3.

[0180] Liquid NH3 has a lower heating value of 4.90 MWh / kg, and H2 has a lower heating value of 33.33 MWh / kg. Therefore, 6,891 kg / h * A pump power of 4.90 MWh / kg = 33.766 MW plus 7 kW is supplied to the process, producing 1,000 kg / h *33.33MWh / kg=33,333MW is obtained in the form of H2. Therefore, the energy utilization rate of the whole process is 98.7%.

[0181] Comparing the energy utilization of the process according to the present invention with the prior art when using Pd membranes without PSA, the energy and economic advantages of the present invention are as follows: British Patent No. 1,079,660 65% WO 2018 / 235059 <78% WO 02 / 071451 2 85% L. Lin et al. <80% Lamb et al. 90% The present invention >98%

[0182] Example 3 - Comparison of the present invention with the membrane reactor technology according to US Patent No. 5,741,474, i.e., reformer and H2 separation at the same temperature versus reformer and H2 separation at their respective optimum temperatures.

[0183] The process according to the invention, in which reforming and H2 separation are carried out via a membrane at the optimum temperature for each individual process step, is compared with a process in which system considerations require the two process steps to be carried out at the same temperature, as is the case, for example, in a membrane reactor.

[0184] This example is calculated for 1,000 kg / h H2 production by methanol reforming and H2 separation on a Pd membrane, and is the result of a thermodynamic simulation using a BASF in-house simulator, similar to the Aspen Plus simulation program, in terms of volume and energy.

[0185] For the calculation of H2 / N2 separation by Pd membranes, an Excel calculator was used, which was programmed using the calculation rules described in the publication by C. Saltonstall ("Calculation of the Memebrane Area Required for Gas Separations," Bd. 32, pp. 185-193, 1987).

[0186] In this calculation, flow pressure losses are not considered since this example is not based on equipment design.

[0187] The following two cases were compared. Case 1: Reforming and H2 separation are carried out at the same temperature of 250 °C, respectively. Case 2: Reforming and H2 separation are carried out at the same temperature of 450 °C, respectively. Case 3: Reforming and H2 separation are carried out at different temperatures, reforming at 250°C and H2 separation at 450°C.

[0188] In all cases the reformer and H2 separation are operated at 15 bar.

[0189] result:

[0190] [Table 8]

[0191] As a result, it has proven advantageous to adapt the temperature to the respective process step.

[0192] As the temperature in the reformer increases, the energy utilization rate decreases. This is because at higher temperatures, more energy needs to be supplied to the reformer than at lower temperatures. The energy utilization rate is the ratio of the heating value of the hydrogen (product) to the heating value of the input methanol (feed). When the reforming temperature is 450°C, the energy utilization rate is 91.7% (case 2), and when the reforming temperature is 250°C, it increases to 93.5% (cases 1 and 3).

[0193] As the temperature increases during H2 separation using Pd membranes, the required membrane area decreases, and the amount of Pd required to coat the membrane also decreases. At a temperature of 450°C, a membrane area of ​​257 m2 (case 2) or 224 m2 (case 3) is sufficient for H2 separation, whereas at a lower temperature of 250°C, the required membrane area increases 3.5 times to 916 m2 (case 1). Accordingly, the amount of Pd required also increases from 15.4 g (case 2) or 13.4 g (case 3) to 54.9 g (case 1).

[0194] The process according to the invention (case 3) separates reforming and H2 separation in terms of process technology, which allows an optimal adaptation of the temperature to the requirements of both process steps, i.e. the process has advantages in two cost-related categories as well compared to systems such as membrane reactors, where this is not possible.

[0195] Example 4 - Methanol Temperature difference between the incoming and outgoing streams. Figure 8 shows the influence of the temperature difference between the outgoing streams S8 and S18 and the incoming streams S10 and S1 on the heat exchanger area and the energy utilization of the devices A7 and A2+A3. For this purpose, the temperature difference of the method described in Example 1 was changed. The results are based on the model calculations mentioned in Example 1. For reasons of simplification, in all cases the temperature difference between S8 and S10 as well as between S18 and S1 was always chosen to be of the same magnitude, i.e. S8-S10=S18-S1 is always the case.

[0196] The energy utilization increases linearly with decreasing temperature difference, whereas the heat exchanger area increases exponentially with decreasing temperature difference. Figure 8 shows that for temperature differences greater than 100°C, the heat exchanger area does not decrease significantly, but the energy utilization deteriorates significantly. Conversely, for temperature differences less than 10°C, there is no significant improvement in the energy utilization, but the heat exchanger area required for this increases disproportionately in A7 and A2+A3. From this, the conclusion can be drawn that in the method according to the invention, the preferred temperature difference between the outgoing streams S8 and S18 and the incoming streams S10 and S1 should be 5-100°C, preferably 10-80°C, particularly preferably 15-60°C, in particular 20-40°C.

Claims

1. A method for obtaining hydrogen from methanol or ammonia, comprising: vaporizing methanol or ammonia in a first step; reforming the methanol or ammonia to form a hydrogen-containing gas mixture in a second step; separating hydrogen from the gas mixture in a membrane process at a temperature of 300-600°C in a third step; and combusting the gaseous residue of the membrane process with ambient air in a fourth step, wherein the second step is a process step separate from and upstream of the third step; and passing the combustion gas through at least two different heat exchangers. In the flow direction of the combustion gas, (i) firstly, heat of reaction for reforming methanol or ammonia is provided, and (ii) subsequently, heat of vaporization for vaporizing the reformer feed is provided, and the permeate of the membrane process preheats the ambient air for the burner in a heat exchanger, and (a) the temperature difference between the exiting permeate and the incoming ambient air, and (b) the temperature difference between the exiting combustion gas and the incoming methanol or ammonia are each 1 to 200°C, and a maximum temperature increase of 0 to 100°C is achieved during the third process step.

2. 2. The method according to claim 1, characterized in that, in a flow direction of the combustion gas, the combustion gas is passed through at least three different heat exchangers to (0) first heat the reformate gas, then (i) provide the reaction heat for reforming methanol or ammonia, and (ii) subsequently provide the vaporization heat for vaporizing methanol or ammonia.

3. 3. The method according to claim 1 or 2, characterized in that the conversion rate of the modification is 80-95%.

4. 3. The method according to claim 1 or 2, characterized in that in an evaporator heat exchanger, methanol or ammonia passes through an external space of the heat exchanger and the combustion gas passes through a pipe of the heat exchanger.

5. 3. The method according to claim 1 or 2, characterized in that the ambient air is sucked in by means of a jet pump.

6. 3. The method of claim 1, wherein (a) the temperature difference between the outgoing permeate and the incoming ambient air, and (b) the temperature difference between the outgoing combustion gas and the incoming methanol or ammonia, are each between 5 and 100°C.

7. 3. The method according to claim 1, wherein a maximum temperature increase of 0 to 50° C. is carried out during the third process step.

8. 3. The method according to claim 1, wherein in the third step, hydrogen is separated in a membrane process at a temperature of 400 to 600°C.

9. 3. The method according to claim 1 or 2, characterized in that the combustion gases are intermediately heated by a second burner between the reformer heat exchanger and the evaporator heat exchanger.

10. 3. The method according to claim 1 or 2, characterized in that the burner is supplied with methanol or ammonia in addition to the residue of the membrane process.

11. 3. The method according to claim 1 or 2, characterized in that methanol is used to (i) first heat the hydrogen-containing gas mixture from the reforming, (ii) then provide the heat of reaction for the reforming, (iii) subsequently provide the heat of vaporization for vaporizing the reformer feed, and (iv) finally preheat methanol or a methanol-water mixture, in the flow direction of the combustion gas, by passing the combustion gas through at least four different heat exchangers.

12. by passing the combustion gas through at least three different heat exchangers using ammonia; In the flow direction of the combustion gas, (0) first provides the reaction heat for reforming ammonia, then (i) further heats the vaporized ammonia, and (ii) finally provides the vaporization heat for vaporizing the ammonia. or 3. The method according to claim 1 or 2, characterized in that, in the flow direction of the combustion gas, (0) first heats the reformed gas, then (i) provides the reaction heat for reforming ammonia, (ii) further heats the vaporized ammonia, and (iii) finally provides the vaporization heat for vaporizing ammonia.

13. 3. An apparatus for carrying out the method according to claim 1 or 2, comprising: - optionally a device for heating methanol or ammonia; an evaporation device, a reforming reactor, - a membrane device, at least one burner, at least two heat exchangers, means for introducing and / or discharging liquids in the evaporation device, the reforming reactor, the membrane device, the burner, the heat exchanger, and optionally in the device for heating methanol or ammonia; An apparatus comprising:

14. The apparatus according to claim 13, wherein the heat exchanger has a pipe diameter of 1 to 6 mm.

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