Ammonia catalytic cracking device adopting plasma ignition technology and operation method

Abstract

The invention discloses an ammonia catalytic cracking device adopting a plasma ignition technology and an operation method, and belongs to the field of hydrogen production through ammonia decomposition, and the ammonia catalytic cracking device mainly comprises a plasma ammonia burner, a high-temperature mixer, a catalytic ammonia cracking module, a heat exchange module and a hydrogen separation and purification module. The plasma ammonia burner performs plasma discharge ignition at the starting stage, assists ammonia combustion to generate high-temperature tail gas, the high-temperature tail gas is mixed with liquid ammonia spray to form high-temperature mixed gas, the high-temperature mixed gas is introduced into the catalytic ammonia cracking module, and hydrogen-rich cracking gas is generated under the action of a catalyst; plasma discharge is not needed in the working stage, and hydrogen-rich pyrolysis gas is introduced into the combustor to be directly combusted. The pyrolysis gas heats liquid ammonia in the heat exchange module to improve the energy utilization efficiency of the system, and the cooled pyrolysis gas enters the separation module to purify hydrogen. According to the ammonia cracking device, high-temperature tail gas generated by ammonia-rich combustion of the combustor is directly mixed to preheat ammonia gas, a two-phase heat exchanger does not need to be independently arranged, the device is compact, the energy utilization rate is high, and no harmful combustion tail gas is discharged.

Description

Technical Field

[0001] This invention relates to the field of ammonia decomposition for hydrogen production, specifically to an ammonia catalytic cracking device and its operation method using plasma ignition technology. Background Technology

[0002] Energy crisis, environmental pollution, and climate change are significant challenges facing human society's survival and development. Ammonia (NH3), as an ideal carrier of hydrogen energy, has become one of the main potential fuels for decarbonization in various industries due to its zero-carbon properties, high energy density, and low storage and transportation costs.

[0003] Hydrogen and ammonia are two carbon-free fuels that do not produce CO2 when burned, making them promising new fuels for replacing fossil fuels and reducing carbon emissions. Hydrogen energy has long been considered the most ideal clean energy source and a key research focus in the energy development strategies of many countries. However, its development currently faces critical challenges such as poor safety and immature storage and transportation technologies, hindering its industrialization. Ammonia combustion suffers from difficulties in ignition, low laminar flame velocity, and a narrow flammable range. Furthermore, ammonia combustion produces toxic NO. x Furthermore, when ammonia combustion is incomplete, unburned ammonia and NO... x It will be released into the atmosphere, thus affecting human health.

[0004] Ammonia, as a carbon-free chemical energy carrier, possesses advantages such as high energy density, easy liquefaction and storage, and high safety. With a hydrogen content as high as 17.6%, it can be used for efficient hydrogen storage. Green ammonia can be synthesized from renewable energy sources such as solar, wind, and hydropower, and can serve as an important energy storage medium. It can promote the consumption of new energy power, support the green and low-carbon transformation and development of various industries, and improve the flexibility of the power system, contributing to the construction of a new type of power system.

[0005] In ammonia-based hydrogen storage applications, electrically heated catalytic ammonia cracking is commonly used to produce hydrogen. However, electric heating suffers from high energy consumption and high costs. This invention utilizes plasma ignition ammonia combustion technology to improve the poor combustion characteristics of ammonia, solving the cold start problem of catalytic ammonia cracking systems. Furthermore, the use of ammonia-rich combustion effectively reduces NO₂ levels. x Pollutant generation: This invention employs a scheme of directly mixing combustion exhaust gas with ammonia, directly reducing the cost of metal heat exchangers in traditional two-phase heat exchange schemes. During operation, the pyrolysis gas is directly combusted, requiring no external energy input, effectively reducing the operating costs of traditional electrically heated pyrolysis devices, etc. Summary of the Invention

[0006] The purpose of this invention is to provide an ammonia catalytic cracking device and its operation method using plasma ignition technology, thereby achieving a low-cost, low-operating-cost, and low-pollutant-emission ammonia decomposition hydrogen production device.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A plasma ignition technology ammonia catalytic cracking device, the device comprising a plasma ammonia burner, a high-temperature mixer, a catalytic ammonia cracking module, a heat exchange module, and a hydrogen separation and purification module;

[0009] The plasma ammonia burner includes a plasma generator, a liquid ammonia inlet, a cracked gas inlet, and an air inlet; the plasma generator is connected to a plasma power supply, and the air inlet is connected to an air supply station.

[0010] The inlet of the high-temperature mixer is connected to the exhaust gas outlet of the plasma ammonia burner, and a liquid ammonia injection branch is provided.

[0011] The inlet of the catalytic ammonia cracking module is connected to the outlet of the high-temperature mixer, and the outlet of the catalytic ammonia cracking module is connected to the cracked gas inlet of the plasma ammonia burner.

[0012] The gas hot end inlet of the heat exchange module is connected to the outlet of the catalytic ammonia cracking module, the liquid ammonia inlet is connected to the liquid ammonia supply station, and the liquid ammonia outlet is connected to the liquid ammonia injection branch of the high-temperature mixer and the liquid ammonia inlet of the plasma ammonia burner, respectively.

[0013] The inlet of the hydrogen separation and purification module is connected to the gas cold end outlet of the heat exchange module.

[0014] Furthermore, the air inlet supply pressure of the plasma ammonia burner ranges from 0.1 MPa to 2.5 MPa.

[0015] Furthermore, the liquid ammonia inlet supply pressure of the plasma ammonia burner ranges from 0.1 MPa to 2.5 MPa.

[0016] Furthermore, the inlet gas pressure of the plasma ammonia burner is in the range of 0.1 MPa to 2.5 MPa.

[0017] Furthermore, the plasma generator in the plasma ammonia burner operates during the start-up phase of the ammonia cracking unit and stops operating during the normal operation phase of the ammonia cracking unit.

[0018] Furthermore, the plasma ammonia burner employs an ammonia-rich combustion strategy to reduce NO in the exhaust gas. x Harmful gas emissions.

[0019] Furthermore, the high-temperature mixer has a Venturi ejector structure, where high-temperature exhaust gas and liquid ammonia spray are mixed to form a high-temperature mixed gas at 450℃-750℃.

[0020] Furthermore, the catalytic ammonia cracking module has a honeycomb ceramic or metal porous structure inside, and the surface of the structure is coated with a ruthenium-based catalyst; through optimized impregnation technology, Ru and other nano-metal particles are effectively encapsulated in ordered mesoporous channels.

[0021] Furthermore, the gas hot-end inlet of the heat exchange module is connected to the outlet of the catalytic ammonia cracking module, the liquid ammonia inlet is connected to the liquid ammonia supply station, and the liquid ammonia outlet is connected to the liquid ammonia injection branch of the high-temperature mixer and the liquid ammonia inlet of the plasma ammonia burner, respectively. The liquid ammonia inlet pressure is 0.1MPa-2.5MPa. The high-temperature cracked gas and liquid ammonia exchange heat, heating the liquid ammonia and cooling the cracked gas, thereby improving the system's energy utilization efficiency.

[0022] Furthermore, the hydrogen separation and purification module separates and purifies the hydrogen in the cracked gas, which is then supplied to the hydrogen-using equipment at the back end.

[0023] An operation method for an ammonia catalytic cracking device based on the aforementioned plasma ignition technology includes:

[0024] Start-up phase: The plasma generator discharges and ignites, and the ammonia-rich combustion produces high-temperature exhaust gas;

[0025] High-temperature exhaust gas and liquid ammonia are mixed in a high-temperature mixer to form an ammonia-rich mixture at 450℃-750℃;

[0026] Ammonia-rich mixed gas is cracked in the catalytic ammonia cracking module to generate hydrogen-rich cracked gas;

[0027] Part of the hydrogen-rich cracked gas is fed into a plasma ammonia burner for auxiliary combustion, and the remaining part is purified after heat exchange in a heat exchange module.

[0028] Furthermore, the start-up phase employs an ammonia-rich combustion strategy, with the air-to-liquid ammonia mass ratio lower than the air-fuel ratio of 6.06.

[0029] Furthermore, the operation method also includes a working phase: after the catalytic ammonia cracking module reaches 450℃-750℃, the plasma generator stops working; the hydrogen-rich cracked gas is introduced into the plasma ammonia burner to achieve self-sustaining combustion, and an oxygen-deficient combustion strategy is adopted.

[0030] The beneficial effects of this invention are as follows:

[0031] 1. Plasma discharge ignition is used to improve the combustion characteristics of ammonia, enabling cold start of the ammonia cracking unit; and no plasma discharge is required during normal operation, thus improving the service life of the plasma.

[0032] 2. This invention uses high-temperature exhaust gas and ammonia gas to directly mix and heat the gas, eliminating the need for metal heat exchangers and reducing the cost of ammonia cracking equipment.

[0033] 3. This invention uses ammonia combustion / cracking gas combustion heating to reduce the energy consumption cost of the equipment operation; and uses rich ammonia combustion to reduce harmful exhaust gas emissions.

[0034] 4. Heat exchange between high-temperature pyrolysis gas and liquid ammonia improves the overall energy utilization efficiency of the system. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of an ammonia catalytic cracking device based on plasma ignition technology according to the present invention.

[0036] Wherein: 1 is plasma ammonia burner, 1-1 is plasma generator, 1-2 is liquid ammonia inlet, 1-3 is cracked gas inlet, 1-4 is air inlet, 2 is high-temperature mixer, 2-1 is liquid ammonia injection branch, 3 is catalytic ammonia cracking module, 4 is heat exchange module, 4-1 is liquid ammonia inlet, 4-2 is liquid ammonia heat exchanger, 4-3 is liquid ammonia outlet, and 5 is hydrogen separation and purification module. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0038] Example

[0039] like Figure 1 As shown in the figure, this embodiment discloses an ammonia catalytic cracking device and its operation method using plasma ignition technology. The device mainly includes a plasma generator 1-1 of a plasma ammonia burner 1 connected to a plasma power source, and an air inlet 1-4 connected to an air supply station. The inlet of a high-temperature mixer 2 is connected to the exhaust gas outlet of the plasma ammonia burner 1, and a liquid ammonia injection branch 2-1 is provided therein. The inlet of a catalytic ammonia cracking module 3 is connected to the outlet of the high-temperature mixer 2, and the outlet of the catalytic ammonia cracking module 3 is connected to the cracked gas inlet 1-3 of the plasma ammonia burner 1. The gas hot-end inlet of a heat exchange module 4 is connected to the outlet of the catalytic ammonia cracking module 3, and the liquid ammonia inlet 4-1 is connected to a liquid ammonia supply station; the liquid ammonia outlet 4-3 is connected to the liquid ammonia injection branch 2-1 of the high-temperature mixer 2 and the liquid ammonia inlet 1-2 of the plasma ammonia burner 1, respectively. The inlet of a hydrogen separation and purification module 5 is connected to the gas cold-end outlet of the heat exchange module 4.

[0040] The air supply station can supply air at a relatively stable pressure, with a selectable pressure range of 0.1MPa-2.5MPa and controllable flow rate. The liquid ammonia supply station can supply liquid ammonia at a relatively stable pressure, with a selectable pressure range of 0.1MPa-2.5MPa and controllable flow rate.

[0041] During the start-up phase of the ammonia cracking unit, relatively stable air is introduced through air inlets 1-4 of the plasma ammonia burner 1, with a selectable pressure range of 0.1MPa-2.5MPa and controllable flow rate. Relatively stable liquid ammonia is introduced through liquid ammonia inlets 1-2, with a selectable pressure range of 0.1MPa-2.5MPa and controllable flow rate. The supply pressures of air and liquid ammonia correspond, and the mass ratio of supplied air to liquid ammonia is slightly lower than the air-fuel ratio of 6.06. The plasma generator 1-1 discharges and ignites to generate plasma, improving the poor combustion characteristics of ammonia and assisting in ammonia combustion. Oxygen-deficient and ammonia-rich combustion produces high-temperature exhaust gas, mainly composed of nitrogen, gaseous water, and unburned ammonia. This high-temperature exhaust gas is introduced into the inlet of the high-temperature mixer 2, and liquid ammonia is introduced through the liquid ammonia injection branch 2-1, with a selectable pressure range of 0.1MPa-2.5MPa and controllable flow rate. The high-temperature exhaust gas and liquid ammonia spray are directly mixed to form an ammonia-rich high-temperature mixed gas with a temperature of 450℃-750℃. The ammonia-rich high-temperature mixer feeds into the inlet of the catalytic ammonia cracking module 3, where it generates hydrogen-rich cracked gas under the action of the catalyst. The main components are hydrogen, nitrogen, gaseous water, and residual ammonia. The catalytic ammonia cracking module 3 has a honeycomb ceramic or metal porous structure, with its surface impregnated with a ruthenium-based catalyst. A small portion of the hydrogen-rich cracked gas is fed into the cracked gas inlet 1-3 of the plasma ammonia burner 1 to promote ammonia combustion; the selectable pressure range is 0.1MPa-2.5MPa, and the flow rate is controllable. Most of the hydrogen-rich cracked gas is fed into the gas hot-end inlet of the heat exchange module 4, while liquid ammonia at a relatively stable pressure is fed into the liquid ammonia inlet 4-1, with a selectable pressure range of 0.1MPa-2.5MPa and a controllable flow rate. The two exchange heat through the liquid ammonia heat exchanger 4-2, where the liquid ammonia absorbs heat and its temperature increases, while the cracked gas cools and releases heat and its temperature decreases. The cooled cracked gas is then fed into the hydrogen separation and purification module 5, where it is separated and purified to supply hydrogen to the hydrogen supply equipment. During normal operation of the ammonia cracking unit, the catalytic ammonia cracking module 3 is preheated to its optimal operating temperature of 450℃-750℃. At this temperature, nearly 100% of the ammonia gas introduced into the catalytic ammonia cracking module 3 is cracked. During this stage, the hydrogen-rich cracked gas introduced into the cracked gas inlet 1-3 can improve the poor combustion characteristics of ammonia. The plasma generator 1-1 stops working, while the plasma ammonia burner 1 operates normally; this reduces the discharge time of the plasma generator 1-1, effectively improving the service life of the unit.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An ammonia catalytic cracking device using plasma ignition technology, characterized in that: The device includes a plasma ammonia burner, a high-temperature mixer, a catalytic ammonia cracking module, a heat exchange module, and a hydrogen separation and purification module. The plasma ammonia burner includes a plasma generator, a liquid ammonia inlet, a cracked gas inlet, and an air inlet; The inlet of the high-temperature mixer is connected to the exhaust gas outlet of the plasma ammonia burner, and a liquid ammonia injection branch is provided. The inlet of the catalytic ammonia cracking module is connected to the outlet of the high-temperature mixer, and the outlet of the catalytic ammonia cracking module is connected to the cracked gas inlet of the plasma ammonia burner. The gas hot end inlet of the heat exchange module is connected to the outlet of the catalytic ammonia cracking module, the liquid ammonia inlet is connected to the liquid ammonia supply station, and the liquid ammonia outlet is connected to the liquid ammonia injection branch of the high-temperature mixer and the liquid ammonia inlet of the plasma ammonia burner, respectively. The inlet of the hydrogen separation and purification module is connected to the gas cold end outlet of the heat exchange module.

2. The ammonia catalytic cracking device using plasma ignition technology according to claim 1, characterized in that: The plasma generator is connected to a plasma power supply, and the air inlet is connected to an air supply station with a supply pressure of 0.1MPa-2.5MPa.

3. The ammonia catalytic cracking device using plasma ignition technology according to claim 1, characterized in that: The liquid ammonia inlet supply pressure of the plasma ammonia burner is 0.1MPa-2.5MPa, and the pyrolysis gas inlet supply pressure is 0.1MPa-2.5MPa.

4. The ammonia catalytic cracking device using plasma ignition technology according to claim 1, characterized in that: The high-temperature mixer is a Venturi ejector structure used to mix high-temperature exhaust gas and liquid ammonia spray to form a high-temperature mixed gas at 450℃-750℃.

5. The ammonia catalytic cracking device using plasma ignition technology according to claim 1, characterized in that: The catalytic ammonia cracking module has a honeycomb ceramic or metal porous structure inside, and its surface is impregnated with a ruthenium-based catalyst.

6. The ammonia catalytic cracking device using plasma ignition technology according to claim 1, characterized in that: The inlet pressure of the liquid ammonia is 0.1MPa-2.5MPa.

7. The ammonia catalytic cracking device using plasma ignition technology according to claim 1, characterized in that: The hydrogen separation and purification module is used to process the cracked gas of hydrogen, nitrogen, water and residual ammonia, and the purified hydrogen is supplied to hydrogen-using equipment.

8. A method of operating the apparatus based on any one of claims 1-7, characterized in that: include Start-up phase: The plasma generator discharges and ignites, and the ammonia-rich combustion produces high-temperature exhaust gas; High-temperature exhaust gas and liquid ammonia are mixed in a high-temperature mixer to form an ammonia-rich mixture at 450℃-750℃; Ammonia-rich mixed gas is cracked in the catalytic ammonia cracking module to generate hydrogen-rich cracked gas; Part of the hydrogen-rich cracked gas is fed into a plasma ammonia burner for auxiliary combustion, and the remaining part is purified after heat exchange in a heat exchange module.

9. The method according to claim 8, characterized in that: The start-up phase employs an ammonia-rich combustion strategy, with the air-to-liquid ammonia mass ratio lower than the air-fuel ratio of 6.

06.

10. The method according to claim 8, characterized in that: Operating phase: After the catalytic ammonia cracking module reaches 450℃-750℃, the plasma generator stops working; the hydrogen-rich cracked gas is introduced into the plasma ammonia burner to achieve self-sustaining combustion, and an oxygen-deficient combustion strategy is adopted.

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