PEMFC system and operation method for high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery

Abstract

The present invention discloses a PEMFC system and operation method for high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery, including a liquid ammonia high-pressure supply device, a high-pressure ammonia cracking and purification device, a fuel cell, an ejector and a hydrogen permeation device, wherein the high-pressure ammonia cracking and purification device includes a first heat exchanger, a nested ammonia catalytic cracking device and an ammonia catalytic combustion device, and a purification device, all of which are in a high-pressure working state. The fuel cell uses a high-pressure nitrogen-hydrogen mixed gas as fuel; the adsorption and desorption of ammonia is controlled by adjusting the cracking tail gas temperature, and the desorbed ammonia enters the catalytic combustion device for heat supply, thereby realizing the recovery and utilization of residual ammonia; the hydrogen-containing gas discharged from the fuel cell is diverted, a part of which enters the ammonia catalytic combustion device for heat supply, and a part of which enters the hydrogen permeation device for hydrogen re-enrichment and then re-introduced into the fuel cell, thereby improving the material utilization efficiency of the system. The present invention uses the nitrogen-hydrogen mixed gas purified by high-pressure cracking of ammonia as the fuel of the optimized fuel cell, omitting the steps of hydrogen separation and compression.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a PEMFC system and an operation method for high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery. Background Art

[0002] Hydrogen energy has become one of the focuses in the field of new energy due to its advantages such as zero carbon, no pollution and wide sources. However, hydrogen energy currently faces difficulties in storage and transportation, such as low storage and transportation energy density, high cost and safety issues. In order to solve these problems, the use of ammonia as a hydrogen storage medium for hydrogen storage, transportation and use has attracted the attention of researchers. Ammonia has the advantages of high hydrogen storage density (mass fraction 17.6wt%), easy liquefaction (< 10bar or -33℃ at room temperature), easy storage, difficult explosion and zero carbon emissions. In addition, the processes of ammonia production, storage, transportation and use are relatively mature, which can effectively solve the problems of hydrogen storage, transportation and use. At the ammonia use end, it can be used as an excellent hydrogen storage medium for ammonia-hydrogen storage and conversion, such as ammonia cracking to prepare hydrogen for proton exchange membrane fuel cells; it can also be used as a zero-carbon fuel for direct combustion for energy supply, such as ammonia combustion for ammonia internal combustion engines, ammonia gas turbines, ammonia industrial kilns, etc.

[0003] Although there are patents that have conceptually designed fuel cell systems that use ammonia as raw material and ammonia cracking gas as fuel, very few patents consider material and energy distribution issues. Taking the recycling of residual ammonia as an example, assuming that the hydrogen production rate of the ammonia catalytic cracking unit is 4kg / h, even if the ammonia cracking efficiency is as high as 99%, the residual ammonia content in the cracking tail gas can still reach 0.22kg / h. As a reference value, the theoretical ammonia demand corresponding to the catalytic combustion layer is about 3kg / h, indicating that the residual ammonia in the cracking tail gas has a high utilization value. In addition, the treatment of hydrogen-rich gas at the PEMFC anode outlet also needs to consider material distribution issues.

[0004] To address this problem, the present invention designs a PEMFC system with high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery. The system directly provides fuel for PEMFC through cracking, purification and other processes, and has the advantages of high energy utilization, fast response speed and low cost. In addition, the system material and energy distribution issues are fully considered, the system process is simplified, and the full cycle cost of the power generation system is greatly reduced. Summary of the invention

[0005] The object of the present invention is to provide a PEMFC system and operation method for high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery, so as to solve one or more technical problems existing in the prior art and at least provide a beneficial choice or create conditions.

[0006] The technical solutions adopted to solve the above technical problems are:

[0007] The present invention provides a PEMFC system with high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery. The system does not go through a nitrogen-hydrogen separation process and does not require a gas compression step. The high-pressure cracked gas is directly supplied to the fuel cell system through a high-pressure pipeline. Specifically, the system comprises: a liquid ammonia high-pressure supply device, a high-pressure ammonia cracking and purification device, an ejector, a fuel cell and a hydrogen permeation device, wherein the ammonia high-pressure supply device comprises a liquid ammonia tank, a hydraulic pump and a gasification tank connected in sequence, and the high-pressure ammonia cracking and purification device comprises a first heat exchanger, a purification device, an ammonia catalytic cracking device and an ammonia catalytic combustion device arranged for heat exchange with each other, the inlet of the first heat exchange side of the first heat exchanger is connected to the liquid ammonia high-pressure supply device, and the first heat exchange side of the first heat exchanger is simultaneously connected to the inlets of the ammonia catalytic cracking device and the ammonia catalytic combustion device, and the air inlet of the purification device is connected to the outlet of the ammonia catalytic cracking device through the second heat exchange side of the first heat exchanger, the purification device is used to adsorb and desorb ammonia in the cracked gas, and the purge outlet of the purification device is connected to the inlet of the first heat exchange side of the first heat exchanger through a purge pipeline; the ejector nozzle is connected to the outlet of the purification device; the anode inlet of the fuel cell is connected to the outlet of the ejector, and the anode outlet of the fuel cell is connected to the inlet of the ammonia catalytic combustion device; the inlet of the hydrogen permeation device is connected to the anode outlet of the fuel cell, and the outlet of the hydrogen permeation device is connected to the reflux port of the ejector.

[0008] The PEMFC system provided by the present invention has the following beneficial effects: by adjusting the temperature of the cracking tail gas after heat exchange, the adsorption and desorption of ammonia in the purification device is controlled, and the centralized recovery and utilization of the residual ammonia after cracking is realized, thereby effectively avoiding the waste of ammonia fuel and improving the energy utilization efficiency of the system; the hydrogen-rich gas discharged from the fuel cell is diverted, a part of which enters the ammonia catalytic combustion device for heat supply, and a part of which is passed into the hydrogen permeation device to purify the hydrogen; and the product gas is re-introduced into the anode of the fuel cell for energy conversion, thereby realizing the reasonable distribution of system materials and improving the material utilization efficiency of the system; the hydrogen-rich tail gas at the anode of the fuel cell is used for catalytic combustion and heat supply as the heat source for ammonia cracking; the reaction rate of hydrogen catalytic combustion is faster than that of ammonia catalytic combustion for energy supply; and the nitrogen-hydrogen mixed gas obtained by high-pressure online cracking of ammonia is used as the fuel of the optimized fuel cell, thereby omitting the steps of hydrogen purification, separation and compression, thereby simplifying the system structure and reducing the system cost.

[0009] As a further improvement of the above technical solution, the high-pressure ammonia cracking and purification device also includes a second heat exchanger, the first heat exchange side inlet of the second heat exchanger is connected to the outlet of the ammonia catalytic combustion device, the second heat exchange side inlet of the second heat exchanger is connected to the external air supply system, and the second heat exchange side outlet of the second heat exchanger is connected to the inlet of the ammonia catalytic combustion device.

[0010] The high-temperature combustion gas discharged from the ammonia catalytic combustion device is passed through the second heat exchanger to preheat the air before entering the ammonia catalytic combustion device, thereby achieving energy-saving effects and improving heat utilization.

[0011] The ammonia catalytic cracking unit, the purification unit, and the first heat exchanger are all in a high-pressure working state (≥10bar), and the hydrogen supply pressure requirement of the PEMFC system can be met without the gas compression step. The high-pressure reaction system is realized by a hydraulic pump, a high-temperature and high-pressure corrosion-resistant reactor material, and multiple seals. The hydraulic pump can measure (instantaneous flow and total amount) ammonia, and can also control the pressure of the reactor to achieve stable pressure control. C-276 Hastelloy alloy belongs to the nickel-molybdenum-chromium-iron-tungsten series nickel-based alloy, which is one of the most corrosion-resistant modern metal materials. Inconel 625 is a solid solution-strengthened nickel-based deformable high-temperature alloy with molybdenum and silver as the main strengthening elements, and has excellent corrosion resistance and oxidation resistance. Due to the high operating temperature and pressure of the system, Hastelloy alloy is selected as the main material in consideration of corrosion problems, and the main reactor part adopts Inconel 625, which is more heat-resistant and pressure-resistant. The system adopts a simple and effective flange sealing structure, and the graphite sealing gasket enhances the sealing performance, and the pre-tightening force is applied by the bolts to achieve multiple sealing effects.

[0012] As a further improvement of the above technical solution, a pressure reducing valve is provided between the first heat exchanger and the ammonia catalytic combustion device, which can reduce the pressure of ammonia gas entering the ammonia catalytic combustion device, so that the pressure of ammonia gas is adjusted to the optimal state for catalytic combustion.

[0013] As a further improvement of the above technical solution, the ammonia catalytic combustion device and the ammonia catalytic cracking device are closely connected in the form of inner and outer sleeves. The ammonia catalytic combustion device provides the ammonia catalytic cracking device with the energy required for cracking.

[0014] As a further improvement of the above technical solution, a temperature sensor, a pressure sensor and a mass flow sensor are provided at the inlet of the ammonia catalytic cracking device; a temperature sensor is provided at the inlet of the purification device, and an ammonia concentration sensor is provided at the outlet. The above sensors are connected to the control system to realize real-time supply and regulation of the fuel mixture on demand.

[0015] As a further improvement of the above technical solution, the purification device includes two adsorption columns connected in parallel, which can be used alternately. The purification device eliminates the residual ammonia in the cracking tail gas by chemical or physical adsorption, and after the adsorbed ammonia accumulates to a certain amount, it is desorbed by heating, purging, etc. The desorbed ammonia flows back to the first heat exchange side inlet of the first heat exchanger through the purge pipeline for recycling.

[0016] Specifically, when one of the adsorption columns reaches a saturated adsorption state, the ammonia concentration sensor detects that the ammonia concentration in the purified cracked gas exceeds the upper limit. The control system adjusts the heat exchange efficiency of the first heat exchanger, and desorbs ammonia from the adsorption column by heating and purging, thereby regaining adsorption activity, and the other adsorption column can adsorb residual ammonia at the same time. The adsorbent used in the purification device includes but is not limited to alkaline earth metal halides, transition metal halides, modified activated carbon, molecular sieves, modified metal organic framework materials (MOF), etc.

[0017] As a further improvement of the above technical solution, the ammonia catalytic combustion device is a metal honeycomb material or a ceramic honeycomb material, and the surface thereof is coated with an ammonia catalytic combustion catalyst or a hydrogen catalytic combustion catalyst, including but not limited to precious metal-based catalysts such as Pt, Ag, Pd, Ir, Rh and combinations thereof, and non-precious metal-based catalysts such as Cu, Mn, Cr, Co and combinations thereof. The catalyst carrier includes but is not limited to hexaaluminate, Al2O3, CeO2, ZrO2, TiO2, ZnO, MgO, carbon nanotubes, metal organic framework (MOF), perovskite oxide, etc., and the additive is selected from alkali metals or alkaline earth metals, including but not limited to Li, Na, K, etc.

[0018] The ammonia catalytic cracking device is filled with ammonia cracking catalysts, including but not limited to noble metal-based catalysts such as Ru, Ir, Mo and combinations thereof, and non-noble metal catalysts such as Fe, Ni, Co, Cu, Mo and combinations thereof. Catalyst carriers include but are not limited to MgO, Al2O3, SiO2, ZrO2, TiO2, CeO2, ZnO, CaO, magnesium aluminum spinel type, perovskite type oxides and carbon nanotubes, etc., and additives are selected from alkali metals or alkaline earth metals, including but not limited to Li, Na, K, etc.

[0019] As a further improvement of the above technical solution, the tail gas at the outlet of the anode of the fuel cell is a hydrogen-containing gas with a hydrogen content of <75%. A part of the hydrogen-containing gas enters the ammonia catalytic combustion device for heat supply, and the other part is re-introduced into the anode of the PEMFC stack through a hydrogen permeation device and an ejector to participate in the reaction; the hydrogen permeation device is a low-selectivity palladium membrane reactor with low cost; the hydrogen content of the anode tail gas after separation by the hydrogen permeation device is 75-80%; the palladium membrane reactor is heated by catalytic combustion of hydrogen-containing gas, and the operating temperature is 300-500°C.

[0020] The ammonia catalytic cracking device and the ammonia catalytic combustion device can achieve an ammonia conversion rate of more than 99% at any operating point through catalyst selection, reactor configuration design, energy supply mode and thermal management strategy optimization, and can instantly meet the fuel cell fuel demand online.

[0021] As a further improvement of the above technical solution, the supply mode of the anode fuel gas of the PEMFC stack is continuous "nitrogen discharge" in the circulation mode, the purge gas valve is normally open, and the fuel excess coefficient is increased to 1.2-1.8, so as to realize stable and efficient power generation of PEMFC using ammonia cracking gas as fuel.

[0022] As a further improvement of the above technical solution, the electrochemical performance of the PEMFC stack using nitrogen-hydrogen mixture as fuel will be further improved by adjusting the stack geometry, flow field design and inlet pressure.

[0023] In addition, the present invention also provides an operation method of a PEMFC system, which adopts the above-mentioned PEMFC system, and the specific method is as follows:

[0024] The ammonia provided by the liquid ammonia high-pressure supply device absorbs heat through the first heat exchanger, and then enters the ammonia catalytic cracking device and the ammonia catalytic combustion device, performs catalytic combustion reaction in the ammonia catalytic combustion device and releases heat to the ammonia catalytic cracking device, and performs catalytic cracking reaction in the ammonia catalytic cracking device. The cracked tail gas passes through the first heat exchanger, and then enters the purification device to remove residual ammonia in the cracked tail gas, and then enters the fuel cell to participate in the reaction;

[0025] Part of the hydrogen-rich gas discharged from the fuel cell outlet is passed into the ammonia catalytic combustion device for heat supply, and the other part is passed into the hydrogen permeation device to increase the hydrogen content and then re-introduced into the fuel cell to participate in the reaction;

[0026] When the adsorption capacity of the purification device is saturated, the cracking tail gas is purged and desorbed from the purification device, and the purged exhaust gas is refluxed to the first heat exchanger and then enters the ammonia catalytic cracking device.

[0027] The present invention provides a PEMFC system with high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery, and its beneficial effects are as follows:

[0028] (1) By adjusting the temperature of the cracking tail gas after heat exchange, the adsorption and desorption of ammonia in the purification device is controlled, and the residual ammonia after cracking is recovered and utilized in a centralized manner, which effectively avoids the waste of ammonia fuel and improves the energy utilization efficiency of the system;

[0029] (2) The hydrogen-containing gas discharged from the fuel cell is split, with one part entering the ammonia catalytic combustion device for heat supply and the other part entering the hydrogen permeation device for hydrogen re-enrichment. The hydrogen-rich gas is then reintroduced into the anode of the fuel cell through the ejector for energy conversion, thereby achieving a reasonable distribution of system materials and improving the utilization efficiency of system materials.

[0030] (3) The hydrogen-containing tail gas at the anode outlet of the fuel cell is used for catalytic combustion to provide heat. Compared with the catalytic combustion of ammonia, the reaction rate of hydrogen catalytic combustion is faster;

[0031] (4) The nitrogen-hydrogen mixture produced by high-pressure online cracking of ammonia is used as the fuel for the optimized fuel cell, omitting the steps of hydrogen purification, separation and compression, thereby simplifying the system structure and reducing the system cost.

[0032] (5) By optimizing catalyst selection, reactor configuration design, energy supply mode and thermal management strategy, the ammonia cracking rate can exceed 99%, which can maximize the utilization of the chemical energy stored in the ammonia fuel, reduce the pressure of subsequent purification equipment, and even provide the possibility for PEMFC to achieve ammonia resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments;

[0034] Figure 1 The present invention provides a PEMFC system for high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery, and a schematic diagram of one embodiment thereof. DETAILED DESCRIPTION

[0035] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0036] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0037] In the description of the present invention, if there are words such as "several", it means one or more, "more" means more than two, greater than, less than, exceed, etc. are understood as not including the number, and above, below, within, etc. are understood as including the number.

[0038] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0039] Reference Figure 1 The PEMFC system of the present invention with high pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery is described in the following embodiments:

[0040] The PEMFC system of this embodiment includes: a liquid ammonia high-pressure supply device, a high-pressure ammonia cracking and purification device, a fuel cell 500 , an ejector 900 and a hydrogen permeation device 600 .

[0041] The liquid ammonia high-pressure supply device includes a liquid ammonia tank 800 for storing liquid ammonia, a hydraulic pump 810 for pressurizing the liquid ammonia, and a vaporization tank 820 for vaporizing the liquid ammonia. The liquid ammonia tank 800 is connected to the inlet of the hydraulic pump 810, and the outlet of the hydraulic pump 810 is connected to the inlet of the vaporization tank 820.

[0042] The high-pressure ammonia cracking and purification device includes a first heat exchanger 100, a purification device 200, an ammonia catalytic cracking device 300 and an ammonia catalytic combustion device 400. The first heat exchanger 100 has a first heat exchange side and a second heat exchange side. The outlet of the gasification tank 820 is connected to the first heat exchange side inlet of the first heat exchanger 100, and the first heat exchange side outlet of the first heat exchanger 100 is simultaneously connected to the inlet of the ammonia catalytic cracking device 300 and the inlet of the ammonia catalytic combustion device 400. The outlet of the ammonia catalytic cracking device 300 is connected to the second heat exchange side inlet of the first heat exchanger 100 through a pipeline, and the second heat exchange side outlet of the first heat exchanger 100 is connected to the purification device 200.

[0043] The purification device 200 in this embodiment removes the residual ammonia in the cracking tail gas by chemical or physical adsorption, and after the adsorbed ammonia accumulates to a certain amount, it is desorbed by heating, purging, etc. The adsorbent used in the purification device 200 includes but is not limited to alkaline earth metal halides, transition metal halides, modified activated carbon, molecular sieves, modified metal organic framework materials MOF, etc. Specifically: The purification device 200 of this embodiment includes two adsorption columns, which are used alternately, and the adsorption column with saturated adsorption capacity desorbs ammonia by heating and purging, thereby regaining adsorption activity. The outlet of the second heat exchange side of the first heat exchanger 100 is connected to the inlet of the two adsorption columns through a pipeline, and the outlets of the two adsorption columns are connected to the inlet of the fuel cell 500 through a pipeline. The outlets of the two adsorption columns are also connected to the inlet of the first heat exchange side of the first heat exchanger 100 through a purge pipeline. Correspondingly, a valve is provided at the downstream of the connection between the outlet of each adsorption column and the purge pipeline, and a one-way valve is also provided in the purge pipeline.

[0044] If the adsorption capacity of one of the adsorption columns is saturated, the adsorption column will desorb ammonia by heating and purging, thereby regaining adsorption activity, and the other adsorption column can adsorb at the same time. The desorbed ammonia is transported to the raw ammonia supply pipeline through the purge pipeline for recycling.

[0045] Furthermore, the ejection port of the ejector 900 of the present embodiment is connected to the outlet of the purification device 200, the anode inlet of the fuel cell 500 is connected to the outlet of the ejector 900, the anode outlet of the fuel cell 500 is connected to the inlet of the ammonia catalytic combustion device 400, the inlet of the hydrogen permeation device 600 is connected to the anode outlet of the fuel cell 500, the outlet of the hydrogen permeation device 600 is connected to the reflux port of the ejector 900, and the hydrogen permeation device 600 is a low-selectivity palladium membrane reactor with low cost.

[0046] The fuel cell 500 uses a low-temperature proton exchange membrane fuel cell with an operating temperature of 80-100°C, and the fuel used is a nitrogen-hydrogen mixed gas at the outlet of the purification device 200. The gas at the outlet of the fuel cell 500 stack is a hydrogen-rich gas, a part of which is passed into the ammonia catalytic combustion device 400 for heat supply, and the other part is passed into the hydrogen permeation device 600 to increase the hydrogen content. The product gas is re-introduced into the anode of the fuel cell 500 through the ejector (900) to participate in the reaction, and the hydrogen content of the product gas is 75-80%.

[0047] The ammonia catalytic combustion device 400 is a metal honeycomb material or a ceramic honeycomb material, and the surface thereof is coated with an ammonia catalytic combustion catalyst or a hydrogen catalytic combustion catalyst, including but not limited to precious metal-based catalysts such as Pt, Ag, Pd, Ir, Rh and combinations thereof, and non-precious metal-based catalysts such as Cu, Mn, Cr, Co and combinations thereof. Catalyst carriers include but are not limited to hexaaluminates, Al2O3, CeO2, ZrO2, TiO2, ZnO, MgO, carbon nanotubes, metal organic framework MOF, perovskite oxides, etc., and the additives are selected from alkali metals or alkaline earth metals, including but not limited to Li, Na, K, etc. The hydrogen catalytic combustion catalyst can realize hydrogen catalytic combustion, while the ammonia catalytic combustion catalyst realizes ammonia catalytic combustion.

[0048] The ammonia catalytic cracking device 300 is filled with an ammonia cracking catalyst, including but not limited to noble metal-based catalysts such as Ru, Ir, Mo and combinations thereof, and non-noble metal catalysts such as Fe, Ni, Co, Cu, Mo and combinations thereof. Catalyst carriers include but are not limited to MgO, Al2O3, SiO2, ZrO2, TiO2, CeO2, ZnO, CaO, magnesium aluminum spinel type, perovskite type oxides and carbon nanotubes, etc., and additives are selected from alkali metals or alkaline earth metals, including but not limited to Li, Na, K, etc.

[0049] Furthermore, the ammonia catalytic combustion device 400 and the ammonia catalytic cracking device 300 are tightly connected and installed together in the form of inner and outer sleeves, with the ammonia catalytic combustion device 400 inside and the ammonia catalytic cracking device 300 outside, so that the ammonia catalytic combustion device 400 provides the ammonia catalytic cracking device 300 with the energy required for cracking.

[0050] In some embodiments, the ammonia catalytic combustion device 400 and the ammonia catalytic cracking device 300 may also be closely connected in series.

[0051] Furthermore, the high-pressure ammonia cracking and purification device of this embodiment also includes a second heat exchanger 700, which is also provided with a first heat exchange side and a second heat exchange side. The first heat exchange side inlet of the second heat exchanger 700 is connected to the outlet of the ammonia catalytic combustion device 400 through a pipeline, the second heat exchange side inlet of the second heat exchanger 700 is connected to the external air supply system through a pipeline, and the second heat exchange side outlet of the second heat exchanger 700 is connected to the inlet of the ammonia catalytic combustion device 400 through a pipeline.

[0052] The high-temperature combustion gas discharged from the ammonia catalytic combustion device 400 passes through the second heat exchanger 700 to preheat the air before entering the ammonia catalytic combustion device 400, thereby achieving energy-saving effects and improving heat utilization.

[0053] In addition, a pressure reducing valve 410 is installed at the inlet of the ammonia catalytic combustion device 400. The pressure reducing valve 410 can reduce the pressure of the ammonia gas entering the ammonia catalytic combustion device 400, so that the pressure of the ammonia gas is adjusted to the optimal state for catalytic combustion.

[0054] The adsorption and desorption of the purification device 200 of this embodiment are affected by the temperature and pressure of the cracked tail gas after heat exchange. When the temperature of the cracked tail gas after heat exchange is room temperature, the residual ammonia is absorbed by the adsorbent; when the temperature of the cracked tail gas after heat exchange is high, such as 100°C-200°C, the accumulated adsorbed ammonia is desorbed and swept to the ammonia / hydrogen catalytic combustion layer by the cracked tail gas.

[0055] In order to realize automated control, in this embodiment, a temperature sensor, a pressure sensor and a mass flow sensor are installed at the inlet of the ammonia catalytic cracking device 300; a temperature sensor is installed at the inlet of the purification device 200, and an ammonia concentration sensor is installed at the outlet of the purification device 200. The above sensors are all connected to the control system, so as to realize the on-demand real-time supply and regulation of the fuel mixture.

[0056] One specific embodiment is:

[0057] In this embodiment, the first heat exchanger 100 uses the high-temperature ammonia cracking gas as a heat source to heat the ammonia gas before entering the ammonia catalytic cracking device 300 and the ammonia catalytic combustion device 400 .

[0058] The second heat exchanger 700 uses the high-temperature combustion gas as a heat source to heat the air before entering the ammonia catalytic combustion device 400.

[0059] The ammonia catalytic cracking device 300 is filled with a ruthenium-based catalyst, and the ammonia cracking conversion rate reaches 99% at 450°C; the ammonia catalytic combustion device 400 uses honeycomb metal as a carrier and Pt-Al2O3 as a catalyst, which has catalytic activity for both ammonia and hydrogen, and serves as the main heat source for ammonia cracking. Specifically, the purification device 200 includes two adsorption columns, which are filled with calcium chloride particles to absorb residual ammonia, which can reduce the ammonia content in the cracking tail gas to 0.1ppm. The gas at the outlet of the purification device 200 is a nitrogen-hydrogen mixed gas with a volume ratio of 1:3.

[0060] The two adsorption columns are used alternately, and the adsorption and desorption of ammonia are controlled by adjusting the temperature of the ammonia cracking tail gas after heat exchange. Under normal operating conditions, the temperature of the ammonia cracking tail gas after heat exchange is room temperature, and ammonia adsorption occurs when passing through the adsorption column. When the ammonia adsorption amount of the adsorption column is saturated, the heat exchange temperature of the ammonia cracking tail gas is adjusted to 150°C, at which time ammonia is desorbed and purged by the cracking gas to the ammonia catalytic combustion device 400 for heat supply, so that the adsorption column has the ammonia adsorption capacity again.

[0061] The operation method of the above PEMFC system is as follows:

[0062] The hydraulic pump 810 pressurizes and pumps the liquid ammonia in the liquid ammonia tank 800 to the vaporization tank 820. The liquid ammonia passes through the vaporization tank 820 to be vaporized to form ammonia gas. After the ammonia gas absorbs heat and heats up through the first heat exchanger 100, a part of the ammonia gas enters the ammonia catalytic cracking device 300, and the other part enters the ammonia catalytic combustion device 400. At the same time, the external air absorbs heat and heats up through the second heat exchanger 700 and enters the ammonia catalytic combustion device 400. The ammonia catalytic combustion device 400 undergoes a catalytic combustion reaction and releases heat. The released heat is transferred to the ammonia catalytic cracking device 300, so that the inside of the ammonia catalytic cracking device 300 reaches the set temperature of catalytic cracking. The ammonia gas undergoes a catalytic cracking reaction. The cracked tail gas enters the first heat exchanger 100 and exchanges heat with the ammonia gas from the vaporization tank 820 to heat the ammonia gas from the vaporization tank 820. Then, the cracked tail gas enters the purification device 200. The nitrogen-hydrogen mixture gas is then passed through one of the adsorption columns to adsorb ammonia in the cracking tail gas, remove residual ammonia in the cracking tail gas, and form a nitrogen-hydrogen mixed gas, which enters the fuel cell 500 to participate in the reaction.

[0063] A portion of the hydrogen-rich gas discharged from the outlet of the fuel cell 500 enters the ammonia catalytic combustion device 400 for heat supply, while another portion enters the hydrogen permeation device 600 to increase the hydrogen content, and then re-enters the fuel cell 500 through the ejector 900 to participate in the reaction.

[0064] The two adsorption columns are used alternately, and the adsorption and desorption of ammonia are controlled by adjusting the temperature of the ammonia cracking tail gas after heat exchange.

[0065] When the adsorption capacity of one of the adsorption columns is saturated, the cracking tail gas is purged and desorbed on the adsorption column, and the purged exhaust gas is refluxed to the first heat exchanger 100 and then enters the ammonia catalytic cracking device 300 and the ammonia catalytic combustion device 400. The two adsorption columns are used alternately, and the adsorption and desorption of ammonia are controlled by adjusting the temperature of the ammonia cracking tail gas after heat exchange.

[0066] By adjusting the temperature of the cracking tail gas after heat exchange, the adsorption and desorption of ammonia in the purification device 200 is controlled, and the residual ammonia after cracking is recovered and utilized in a centralized manner, thereby effectively avoiding the waste of ammonia fuel and improving the energy utilization efficiency of the system. The hydrogen-rich gas discharged from the fuel cell 500 is diverted, with one part entering the ammonia catalytic combustion device 400 for heat supply and the other part entering the hydrogen permeation device 600 for purifying hydrogen. The product gas is then re-introduced into the anode of the fuel cell 500 for energy conversion, thereby achieving a reasonable distribution of system materials and improving the material utilization efficiency of the system. The hydrogen-rich tail gas at the anode of the fuel cell 500 is used for catalytic combustion and heat supply as a heat source for ammonia cracking. Compared with the energy supply of ammonia catalytic combustion, the reaction rate of hydrogen catalytic combustion is faster. In addition, the nitrogen-hydrogen mixed gas obtained by high-pressure online cracking of ammonia is used as the fuel of the optimized fuel cell 500, thereby omitting the steps of hydrogen purification, separation and compression, thereby simplifying the system structure and reducing the system cost.

[0067] The preferred embodiments of the present invention are specifically described above, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A PEMFC system with high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery, characterized in that: It includes: A liquid ammonia high-pressure supply device, comprising a liquid ammonia tank (800), a hydraulic pump (810), and a gasification tank (820) connected in sequence; A high-pressure ammonia cracking and purification device, comprising a first heat exchanger (100), a purification device (200), an ammonia catalytic cracking device (300) and an ammonia catalytic combustion device (400) arranged for heat exchange with each other, wherein the inlet of the first heat exchange side of the first heat exchanger (100) is connected to the liquid ammonia high-pressure supply device, the first heat exchange side of the first heat exchanger (100) is simultaneously connected to the inlets of the ammonia catalytic cracking device (300) and the ammonia catalytic combustion device (400), and the air inlet of the purification device (200) is connected to the outlet of the ammonia catalytic cracking device (300) through the second heat exchange side of the first heat exchanger (100), the purification device (200) is used to adsorb and desorb ammonia in the cracked gas, and the purge outlet of the purification device (200) is connected to the inlet of the first heat exchange side of the first heat exchanger (100) through a purge pipeline; An ejector (900), the ejection port of which is connected to the outlet of the purification device (200); A fuel cell (500), wherein the anode inlet is connected to the outlet of the ejector (900), and the anode outlet of the fuel cell (500) is connected to the inlet of the ammonia catalytic combustion device (400); A hydrogen permeation device (600), the inlet of which is connected to the anode outlet of the fuel cell (500), and the outlet of the hydrogen permeation device (600) is connected to the reflux port of the ejector (900); The high-pressure ammonia cracking and purification device further comprises a second heat exchanger (700); a first heat exchange side inlet of the second heat exchanger (700) is connected to an outlet of the ammonia catalytic combustion device (400); a second heat exchange side inlet of the second heat exchanger (700) is connected to an external air supply system; a second heat exchange side outlet of the second heat exchanger (700) is connected to an inlet of the ammonia catalytic combustion device (400); and the high-temperature combustion gas discharged from the ammonia catalytic combustion device (400) passes through the second heat exchanger (700) to preheat the air before entering the ammonia catalytic combustion device (400); A pressure reducing valve (410) is provided between the first heat exchanger (100) and the ammonia catalytic combustion device (400); The ammonia catalytic combustion device (400) and the ammonia catalytic cracking device (300) are closely connected in the form of inner and outer sleeves; The purification device (200) comprises two adsorption columns connected in parallel, which can be used alternately. When one adsorption column is saturated, ammonia is desorbed and recycled. The operation method of the PEMFC system is as follows: The ammonia provided by the liquid ammonia high-pressure supply device absorbs heat through the first heat exchanger (100) and then enters the ammonia catalytic cracking device (300) and the ammonia catalytic combustion device (400). A catalytic combustion reaction is carried out in the ammonia catalytic combustion device (400) and heat is released to the ammonia catalytic cracking device (300). A catalytic cracking reaction is carried out in the ammonia catalytic cracking device (300). The cracked tail gas passes through the first heat exchanger (100) and then enters the purification device (200) to remove residual ammonia in the cracked tail gas. The tail gas then enters the fuel cell (500) to participate in the reaction. A portion of the hydrogen-rich gas discharged from the outlet of the fuel cell (500) is passed into the ammonia catalytic combustion device (400) for heat supply, and another portion is passed into the hydrogen permeation device (600) to increase the hydrogen content, and then is re-passed into the fuel cell (500) to participate in the reaction; When the adsorption capacity of the purification device (200) is saturated, the cracking tail gas is purged and desorbed from the purification device (200), and the purged exhaust gas flows back to the first heat exchanger (100) and then enters the ammonia catalytic combustion device (400).

2. A PEMFC system for high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery according to claim 1, characterized in that: The ammonia catalytic combustion device (400) is a metal honeycomb material or a ceramic honeycomb material, and an ammonia catalytic combustion catalyst or a hydrogen catalytic combustion catalyst is coated on its surface.

3. A PEMFC system for high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery according to claim 1, characterized in that: The inlet of the ammonia catalytic cracking device (300) is provided with a temperature sensor, a pressure sensor, and a mass flow sensor; the inlet of the purification device (200) is provided with a temperature sensor, and the outlet is provided with an ammonia concentration sensor, and the above sensors are connected to a control system.

4. A PEMFC system for high-pressure ammonia cracking and pre-ammonia recovery and post-hydrogen recovery according to claim 1, characterized in that: The ammonia catalytic cracking device (300), the purification device (200), and the first heat exchanger (100) are all in a high-pressure working state of ≥10 bar, and the hydrogen supply pressure requirement of the PEMFC system can be met without the need for a gas compression step. The high-pressure reaction system is realized by a hydraulic pump, high-temperature, high-pressure, and corrosion-resistant reactor materials, and multiple seals; The PEMFC uses ammonia cracking gas as fuel, and the cracking gas is a nitrogen-hydrogen mixed gas that has been absorbed by residual ammonia; The tail gas at the anode outlet of the fuel cell (500) is a hydrogen-containing gas with a hydrogen content of less than 75%. A portion of the hydrogen-containing gas enters the ammonia catalytic combustion device (400) for heat supply, and the other portion is re-introduced into the anode of the PEMFC stack through the hydrogen permeation device (600) and the ejector (900) to participate in the reaction; the hydrogen permeation device (600) is a low-selectivity palladium membrane reactor; the hydrogen content of the anode tail gas after separation by the hydrogen permeation device (600) is 75-80%; The ammonia catalytic cracking device (300) and the ammonia catalytic combustion device (400) can achieve an ammonia conversion rate of more than 99% through catalyst selection, reactor configuration design, energy supply mode and thermal management strategy optimization, and can instantly meet the fuel cell fuel demand online; The supply mode of the anode fuel gas of the PEMFC stack is continuous "nitrogen discharge" in the circulation mode, the purge gas valve is normally open, and the fuel excess coefficient is increased to 1.2-1.8, so as to realize stable and efficient power generation of PEMFC using ammonia cracking gas as fuel.

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