Combined generation of hydrogen and electricity by supplying aqueous ammonia

Abstract

Systems and methods for producing hydrogen and power from aqueous ammonia are provided. An exemplary system includes a distillation unit for producing ammonia gas from the aqueous ammonia solution, a compression unit for increasing the pressure of the ammonia gas, a membrane separator for catalytically converting the ammonia gas to nitrogen and hydrogen and removing the hydrogen as a permeate, and a microturbine for combusting the residue to generate energy.

Description

[Technical field]

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 252,780, filed October 6, 2021, and U.S. Utility Patent Application No. 17 / 938,223, filed October 5, 2022, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to the production of hydrogen and electricity from ammonia, more specifically, the catalysis of ammonia to produce hydrogen and residual ammonia, which is combusted in a microturbine to produce electricity and heat. [Background technology]

[0003] Converting oil and natural gas into hydrogen and electricity can have a significant impact on reducing emissions in the transportation sector. By producing hydrogen through advanced processes and combining this technology with carbon capture, utilization and storage (CCUS), hydrogen has the potential to make a significant contribution to a cleaner, safer and cheaper energy future. To transport hydrogen over long distances and on a large scale, it can be converted into ammonia, which can be easily transported in liquid form at moderate temperature and pressure conditions.

[0004] Additionally, ammonia can be burned as a fuel, but technologies that use ammonia directly, such as in internal combustion engines, are still underdeveloped, so incorporating ammonia streams into current technology would be useful. Summary of the Invention

[0005] One embodiment described in the examples provides a system for producing hydrogen and electricity from an aqueous ammonia solution, which includes a distillation unit for producing ammonia gas from the aqueous ammonia solution, a compression unit for increasing the pressure of the ammonia gas, a membrane separator for catalytically converting the ammonia gas into nitrogen and hydrogen and removing the hydrogen as a permeate, and a microturbine for burning the residue to generate energy.

[0006] Another embodiment described in the Examples provides a method for producing hydrogen and electricity from an aqueous ammonia solution, the method including distilling the aqueous ammonia solution to produce ammonia gas and a waste stream, compressing the ammonia gas, catalytically converting the ammonia gas to nitrogen and hydrogen, separating the hydrogen as a permeate in a membrane separator, and combusting the residue in a microturbine to produce electricity. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a system for converting aqueous ammonia into hydrogen and electricity.

[0008] [Diagram 2] 1 is a process flow sheet showing a model of the system.

[0009] [Diagram 3] 1 is a process flowsheet showing a block model showing a heat exchange unit and a membrane separator.

[0010] [Figure 4] FIG. 1 is a process flow diagram showing a method for producing hydrogen and electricity from aqueous ammonia. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Ammonia is an energy-dense compound and can be used directly for energy production, for example by combustion in the burners of gas turbines or boilers. Furthermore, ammonia is a carbon-free substance that can be synthesized by capturing carbon dioxide from natural gas and can be disposed of or used for future applications, such as the formation of so-called blue ammonia. Furthermore, ammonia can be synthesized from hydrogen generated by electrolysis, using electricity provided by renewable sources such as wind or solar power. Ammonia produced using these techniques is called green ammonia. Ammonia is also easier to transport than liquid hydrogen or liquefied natural gas, and its liquefaction temperature is much higher than either of these substances.

[0012] There has therefore been significant research into the use of ammonia as a potential low-carbon fuel for mobility and power generation applications. However, liquid ammonia is toxic and must be handled with appropriate care. Aqueous ammonia solutions are more easily transported.

[0013] The embodiments described in the examples herein provide methods and systems for producing hydrogen and electricity using aqueous ammonia. The aqueous ammonia is distilled to form an ammonia gas stream. The ammonia gas stream can then be processed in a hydrogen separation membrane system, for example using a palladium or palladium alloy membrane, to produce a permeate, which is a purified hydrogen stream that can be used in a fuel cell electric vehicle (FCEV). The retentate stream, which includes, for example, nitrogen, hydrogen, unreacted ammonia, and some water vapor, is combusted in a microturbine to produce electricity for use, for example, in charging an electric vehicle (EV).

[0014] The described technology produces multiple useful products including hydrogen, electricity and heat. The system may be a portable unit for use in refueling stations for FCEVs and EVs, using aqueous ammonia as fuel.

[0015] 1 is a schematic diagram of a system 100 for converting aqueous ammonia to hydrogen and electricity. The system includes a distillation unit 102, a compression unit 104, a heat exchange unit 106, a membrane separator 108, and a micro gas turbine or microturbine 110.

[0016] The feed to the system is an aqueous ammonia solution 112. In some embodiments, the aqueous ammonia solution 112 is about 20% to 40% ammonia by weight in water. In some embodiments, the aqueous ammonia solution 112 is about 20% to 33% ammonia by weight in water. In some embodiments, the aqueous ammonia solution 112 is about 28% ammonia by weight in water. However, it should be noted that any concentration may be used, for example, concentrations less than 20% may be used in some embodiments.

[0017] The aqueous ammonia solution 112 is fed to the distillation unit 102 using, for example, a liquid pump. In some embodiments, the distillation unit 102 is a multi-stage distillation column, and most of the ammonia in the aqueous ammonia solution 112 is distilled to form an ammonia gas stream 114. A waste stream 116 from the distillation unit 102 includes water and some residual ammonia. The waste stream 116 may be collected in a tank and returned to the production facility for use in producing the aqueous ammonia solution 112.

[0018] In some embodiments, separation in distillation unit 102 is enhanced by adjusting the pH of the aqueous ammonia solution 112 to greater than about 8, greater than about 10, between about 8-12, or between about 10-12. This can be done by adding sodium hydroxide to the aqueous ammonia solution 112 in a storage tank upstream of the distillation.

[0019] The ammonia gas stream 114 is compressed in a compression unit 104. In one embodiment, the compression unit 104 is a multi-stage compressor that can include two, three or more compressor stages to increase the pressure to the operating pressure of the membrane separator 108, as shown in the process flowsheet of Figure 2. In some embodiments, the ammonia gas stream 114 is heated using a heat exchange unit 106, including, for example, one or more heat exchangers, prior to feeding the ammonia gas stream 114 to the membrane separator 108.

[0020] The membrane separator 108 uses a high temperature hydrogen selective membrane, for example made of palladium, a palladium alloy, or any other hydrogen separation membrane. In some embodiments, the membrane is a ceramic-based proton conducting membrane. For example, the membrane can be a Y-doped BaZrO3-based oxide, among others. The surface of the membrane can include catalytic sites including metals such as ruthenium, rhenium, platinum, palladium, or nickel, among others, or combinations thereof.

[0021] The membrane separator 108 simultaneously performs catalytic conversion of the ammonia gas stream 114 and selective separation of hydrogen as a permeate stream 118. The catalytic conversion of ammonia and recovery of hydrogen in the membrane separator can be optimized by controlling the membrane surface area to control the pressure. Control of the flow rate can also be used to optimize the process.

[0022] In some embodiments, the catalyst is a catalyst bed disposed within the outer tube of the tubular reactor, with the inner portion of the tubular reactor being separated from the catalyst bed by a hydrogen-selective membrane. The catalyst may include any number of supported metals, such as nickel, ruthenium, or barium, among others. The support may be zirconia, alumina, or a zeolite-based material. In one embodiment, the catalyst is ruthenium supported on yttria-stabilized zirconia (YSZ).

[0023] In some embodiments, the tubular reactor is operated at a temperature of about 350° C. to about 580° C., or about 400° C. to about 530° C., or about 515° C. However, any temperature within this range can be selected based on the desired ammonia input and hydrogen output. In some embodiments, the tubular reactor is operated at a pressure of about 4 bar to about 40 bar, or about 20 bar to 30 bar, or about 25 bar. As with the temperature, the operating pressure can be based on the desired ammonia input and hydrogen output.

[0024] In some embodiments, ammonia is decomposed into nitrogen and hydrogen by an electrochemical process by passing the ammonia through a solid acid electrochemical cell before separating the hydrogen from the resulting nitrogen using a membrane.

[0025] In some embodiments, the hydrogen in the permeate stream 118 is further processed to reach purity specifications for use in fuel cell electric vehicles (FCEVs). In some embodiments, the purity complies with ISO FDIS 14687-2 or SAE J2719 specifications. In some embodiments, the hydrogen in the permeate stream is purified to a concentration of greater than about 95% hydrogen by volume, or greater than about 99% hydrogen by volume, or greater than about 99.9% hydrogen by volume, with the remainder being an inert gas, such as nitrogen. The hydrogen can then be compressed as needed, for example, to about 400 bar (about 40,000 kPa) to about 900 bar (about 90,000 kPa), for distribution to the FCEV or other applications. The residue stream 120, which may include, for example, nitrogen, hydrogen, unreacted ammonia, and water vapor, is sent to the microturbine 110.

[0026] In some embodiments, the microturbine 110 is a commercial microturbine generator available, for example, from Capstone Turbine Corp., Los Angeles, Calif., or Aurelia Turbines Oy., Lappeenranta, Finland, among others. In the microturbine, the residue stream 120 is combusted with air 122 to generate energy 124, for example, in the form of electricity and hot exhaust gases. In some embodiments, a portion of the heat from the hot exhaust gases of the microturbine 110 can be recuperated to increase the efficiency of the microturbine 110, for example, by heating the incoming air stream 122 supplied to the microturbine 110 in a recuperator. In some embodiments, the heat is not recovered and is used entirely in other parts of the process. Depending on the needs of the process, partial recuperation may be performed to increase the amount of heat left for other parts of the process.

[0027] The energy generated 124 is used to power the process. Because the catalytic conversion of ammonia to hydrogen and nitrogen is an endothermic reaction, the exhaust gas is used to provide heat to the membrane separator 108. Additionally, the exhaust gas provides heat used in the boiler(s) of the distillation until 102, for example to vaporize the ammonia in a multi-stage distillation column. Electricity generated by the microturbine 110 is used to power the process, with excess electricity provided to a charging station for EVs.

[0028] Figure 2 is a process flowsheet 200 of the model of system 100. Like numbers are as described with respect to Figure 1. The process was modeled using an Aspen plus (version 10) based process model, and all components of the process were modeled. The heat exchange unit 106 and the membrane separator 108 are shown as blocks 202 in Figure 2 and are separated into individual units in Figure 3. The results from the modeling are shown in the table below. Identification tags on the streams in the process flowsheet correspond to the columns in the table below.

[0029] 3 is a process flowsheet 300 of the model of block 202 showing the heat exchange unit 106 and the membrane separator 108. For modeling purposes, the membrane separator 108 was separated into two units. In the first unit, MEMB1, the catalytic conversion of ammonia is modeled. In the second unit, MEMB1-1, the separation of the permeate stream 118 from the retentate stream 120 is modeled.

[0030] Three scenarios were modeled with different microturbine efficiencies: 39.2%, 28.5% and 23.5%, with assumptions and results presented in the examples below.

[0031] Example 1: Process simulation results assuming a microturbine efficiency of 39.2%

[0032] In this simulation, the feed composition was an aqueous ammonia solution 112 containing 25 wt% ammonia and 75 wt% water. Distillation was carried out in distillation unit 102 at 1.1 bar (110 kPa) with 80 wt% recovery of 100% pure ammonia.

[0033] The membrane separator 108 was operated at 8.1 bar (810 kPa) and a temperature of 450° C. In this simulation, the conversion of ammonia in the ammonia gas stream 114 was 74 wt % and the recovery of hydrogen as the permeate stream 118 was 75 wt %.

[0034] The microturbine 110 was operated at 6.7 bar (670 kPa) with an air-fuel ratio of 2.4. In this simulation, the turbine efficiency was set to 39.2%, which corresponds to an isentropic efficiency of 95% and a turbine efficiency of 85.8%. The microturbine 110 had an exit temperature of 674° C. and produced 194 kW.

[0035] Heat recovery from the flue gas was assumed to reduce the flue gas temperature from 674° C. to 470° C. and then to 150° C. The heat from cooling the flue gas was used to power the membrane separator 108 and the boiler of the distillation unit 102. The electricity generated was used to power the process.

[0036] The process flow calculated by this simulation is shown in Tables 1A to 1C. The results of the simulation are summarized in Table 2. [Table 2]

[0037] Example 2: Process simulation results assuming a microturbine efficiency of 28.5%

[0038] In this simulation, the feed composition was an aqueous ammonia solution 112 containing 25 wt% ammonia and 75 wt% water. Distillation was carried out in distillation unit 102 at 1.1 bar (110 kPa) with 80 wt% recovery of 100% pure ammonia.

[0039] The membrane separator 108 was operated at 8.1 bar (810 kPa) and a temperature of 450° C. The simulation resulted in a conversion of ammonia in the ammonia gas stream 114 of 74 wt % and a recovery of hydrogen as the permeate stream 118 of 75 wt %.

[0040] The microturbine 110 was operated at 6.7 bar (670 kPa) with an air-fuel ratio of 2.4. In this simulation, the turbine efficiency was set to 28.5%, which corresponds to an isentropic efficiency of 68% and a turbine efficiency of 85.8%. The microturbine 110 had an exit temperature of 674°C and produced 141 kW.

[0041] Heat recovery from the flue gas was assumed to reduce the flue gas temperature from 674° C. to 470° C. and then to 150° C. The heat from cooling the flue gas was used to power the membrane separator 108 and the boiler of the distillation unit 102. The electricity generated was used to power the process.

[0042] The process flow calculated by this simulation is shown in Tables 3A to 3C. The results of the simulation are summarized in Table 4. [Table 4]

[0043] Example 3: Process simulation results assuming a microturbine efficiency of 23.5%

[0044] In this simulation, the feed composition was an aqueous ammonia solution 112 containing 25 wt% ammonia and 75 wt% water. Distillation was carried out in distillation unit 102 at 1.1 bar (110 kPa) with 80 wt% recovery of 100% pure ammonia.

[0045] The membrane separator 108 was operated at 8.1 bar (810 kPa) and a temperature of 450° C. The simulation resulted in a conversion of ammonia in the ammonia gas stream 114 of 74 wt % and a recovery of hydrogen as the permeate stream 118 of 75 wt %.

[0046] The microturbine 110 was operated at 6.7 bar (670 kPa) with an air-fuel ratio of 2.4. In this simulation, the turbine efficiency was set to 23.5%, which corresponds to an isentropic efficiency of 60% and a turbine efficiency of 85.8%. The microturbine 110 had an exit temperature of 674°C and produced 141 kW.

[0047] Heat recovery from the flue gas was assumed to reduce the flue gas temperature from 674° C. to 470° C. and then to 150° C. The heat from cooling the flue gas was used to power the membrane separator 108 and the boiler of the distillation unit 102. The electricity generated was used to power the process.

[0048] The process flow calculated by this simulation is shown in Tables 5A to 5C. The results of the simulation are summarized in Table 6. [Table 6]

[0049] 4 is a process flow diagram illustrating a method 400 for producing hydrogen and electricity from aqueous ammonia. The method begins at block 402 with distilling an aqueous ammonia solution to produce ammonia gas. At block 404, the ammonia gas is compressed to produce compressed ammonia gas. At block 406, the compressed ammonia gas is heated to the operating temperature of a membrane separator.

[0050] At block 408, ammonia gas is catalytically converted to hydrogen and nitrogen in a membrane separator. In some embodiments, the ammonia is electrochemically decomposed as described herein. At block 410, hydrogen is removed from the membrane separator as a permeate.

[0051] At block 412, the residue is combusted in the microturbine to produce energy, including heat and electricity from the exhaust from the microturbine.

[0052] At block 414, heat is provided to operating units in the process. As described herein, the operating units include the boilers of the membrane separators and distillation units.

[0053] At block 416, the generated electricity is provided to operational units within the process. At block 418, the hydrogen is provided to the refueling process or provided externally, which may include purifying the hydrogen to meet specifications for use in the refueling process. At block 420, excess electricity is provided for vehicle charging or other uses outside the process.

[0054] Embodiment

[0055] One embodiment described in the examples provides a system for producing hydrogen and electricity from an aqueous ammonia solution, the system including a distillation unit for producing ammonia gas from the aqueous ammonia solution, a compression unit for increasing the pressure of the ammonia gas, a membrane separator for catalytically converting the ammonia gas into nitrogen and hydrogen and removing the hydrogen as a permeate, and a microturbine for burning the residue to generate energy.

[0056] In one embodiment, the distillation unit comprises a multi-stage distillation column.

[0057] In one aspect, the compression unit includes a multi-stage compressor.

[0058] In one embodiment, the system includes a heat exchanger downstream of the compression unit to heat the ammonia gas to the operating temperature of the membrane separator.

[0059] In one embodiment, the membrane in the membrane separator comprises palladium. In one embodiment, the membrane in the membrane separator comprises a palladium alloy.

[0060] In one aspect, the microturbine includes a recuperator.

[0061] In one embodiment, the residue comprises ammonia, hydrogen, nitrogen, or any combination thereof.

[0062] In one embodiment, the system includes a fueling station for a fuel cell electric vehicle (FECV). In one embodiment, the system includes a charging station for an electric vehicle (EV).

[0063] In one aspect, the energy includes heat from an exhaust stream of the microturbine.In one aspect, the energy includes electricity from a generator coupled to the microturbine.

[0064] Another embodiment described in the Examples provides a method for producing hydrogen and electricity from an aqueous ammonia solution, the method including distilling the aqueous ammonia solution to produce ammonia gas and a waste stream, compressing the ammonia gas, catalytically converting the ammonia gas to nitrogen and hydrogen, separating the hydrogen as a permeate in a membrane separator, and combusting the residue in a microturbine to produce electricity.

[0065] In one aspect, the method includes raising the temperature of the ammonia gas to an operating temperature of the membrane separator after compression of the ammonia gas. In one aspect, the method includes providing heat from the microturbine exhaust to a heat exchanger to heat the ammonia gas. In one aspect, the heat from the microturbine exhaust is provided to a boiler that distills the aqueous ammonia solution. In one aspect, the method includes providing power to an operating unit that produces hydrogen and electricity from the aqueous ammonia solution.

[0066] In one embodiment, the method includes purifying hydrogen to meet fuel cell specifications. In one embodiment, the method includes compressing hydrogen for fuel cell electric vehicle (FCEV) refueling operations. In one embodiment, the method includes powering a charging station for electric vehicles (EVs).

[0067] Other implementations are within the scope of the following claims. [Table 1A] [Table 1B] [Table 1C] [Table 3A] [Table 3B] [Table 3C] [Table 5A] [Table 5B] [Table 5C]

Claims

1. 1. A system for producing hydrogen and electricity from an aqueous ammonia solution, comprising: a distillation unit for producing ammonia gas from the aqueous ammonia solution; a compression unit for increasing the pressure of the ammonia gas; a membrane separator for converting the ammonia gas into nitrogen and hydrogen and removing the hydrogen as a permeate; a microturbine for combusting the residue to generate energy. system.

2. The distillation unit comprises a multi-stage distillation column. The system of claim 1 .

3. The compression unit comprises a multi-stage compressor. The system of claim 1 .

4. a heat exchanger downstream of the compression unit for heating the ammonia gas to the operating temperature of the membrane separator; The system of claim 1 .

5. a membrane in the membrane separator containing a catalyst for converting the ammonia gas into nitrogen and hydrogen; The system of claim 1 .

6. the catalyst comprises palladium; The system of claim 5.

7. the catalyst comprises a palladium alloy; The system of claim 5.

8. The membrane in the membrane separator comprises a proton-conducting membrane. The system of claim 1 .

9. The membrane in the membrane separator comprises an electrochemical conversion system. The system of claim 1 .

10. the microturbine includes a recuperator; The system of claim 1 .

11. the residue comprises ammonia, hydrogen, nitrogen, or any combination thereof; The system of claim 1 .

12. Equipped with a fueling station for fuel cell electric vehicles (FECVs), The system of claim 1 .

13. Equipped with a charging station for electric vehicles (EV), The system of claim 1 .

14. the energy includes heat from the exhaust stream of the microturbine. The system of claim 1 .

15. the energy includes electricity from a generator coupled to the microturbine. The system of claim 1 .

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