PEM and SOEC cooperative work synthesis gas preparation and methanol synthesis system and method

Abstract

The invention discloses a PEM and SOEC cooperative work synthesis gas preparation and methanol synthesis system and method, and relates to the field of methanol synthesis, and the method comprises the following steps: a PEM hydrogen production unit drives electrolyzed water to react through renewable electric power to generate H2; the SOEC electrolysis unit electrolyzes CO2 at high temperature to generate mixed gas of CO and CO2; the PSA carbon removal unit is used for removing CO2 in the mixed gas and outputting purified CO; the mixer is used for mixing CO and H2 to generate synthesis gas; the methanol synthesis reactor catalyzes synthesis gas to generate methanol; the coordination controller is used for coordinating and controlling the working states of the PEM hydrogen production unit, the SOEC electrolysis unit, the PSA carbon removal unit and the methanol synthesis reactor, so that the system is switched among the states of starting, normal operation, idling, shutdown and emergency shutdown. By adopting a combined scheme of a PEM hydrogen production technology and an SOEC high-temperature electrolysis CO2 technology, the efficiency and sustainability of a methanol production process are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of methanol synthesis, and more specifically, to a synthesis gas preparation and methanol synthesis system and method that utilizes PEM and SOEC in synergy. Background Technology

[0002] With the global energy structure transformation and the advancement of the "dual-carbon" strategic goal, developing renewable energy and realizing the resource utilization of carbon dioxide (CO2) have become important directions in the energy and chemical industries. Green methanol, as a low-carbon fuel, has attracted widespread attention due to its advantages in energy density, transportation convenience, and carbon neutrality potential. Methanol can not only be used in fuel synthesis but also serves as an important chemical raw material, widely applied in plastics, synthetic fibers, pesticides, and pharmaceuticals, among other fields.

[0003] Currently, industrial methanol production mainly relies on fossil resources (such as coal and natural gas) to produce syngas (H2 / CO) through gasification or reforming, which is then used to synthesize methanol via catalytic oxidation. While this method is technically mature and economically feasible, it inevitably generates large amounts of CO2 emissions during production, resulting in a high carbon footprint. Furthermore, its dependence on limited fossil resources presents both energy and environmental challenges. To achieve a green and low-carbon transition, researchers both domestically and internationally have proposed various low-carbon or zero-carbon methanol production technologies. Among these, the "CO2 hydrogenation to methanol" process, utilizing renewable hydrogen and captured CO2 as feedstocks, and methanol synthesis processes based on electrochemical technology, have become important research directions.

[0004] Among the electrochemical methanol production technologies, PEM (Proton Exchange Membrane Electrolysis) water electrolysis for hydrogen production and SOEC (Solid Oxide Electrolysis Cell) CO2 electrolysis technologies have attracted much attention. PEM technology can efficiently decompose water molecules at relatively low temperatures (50–80℃) to generate high-purity hydrogen, offering advantages such as simple operation and high hydrogen purity. It is suitable for obtaining electricity from renewable sources (such as wind and solar power) to achieve green hydrogen production, providing a high-quality hydrogen source for methanol synthesis. SOEC, as a high-temperature electrolysis technology, can efficiently convert CO2 to CO at 700–850℃, providing the necessary syngas component for methanol synthesis. Compared with low-temperature electrolysis technologies, SOEC has higher energy efficiency and conversion rate, effectively utilizing the waste heat generated at high temperatures and reducing external energy requirements.

[0005] Currently, there are two main gasification routes for the preparation of green methanol: (1) PEM hydrogen production and CO2 mixing route: Hydrogen is generated using PEM water electrolysis technology and mixed with captured CO2. Although this method can flexibly adjust the gas ratio to adapt to different methanol production needs, it faces technical challenges such as high reaction temperature and catalyst activity decay. Furthermore, the requirements for the catalyst are extremely stringent, and the selectivity and stability of the materials often fail to meet the requirements for long-term high-efficiency operation. In addition, due to the poor reactivity of CO2, the reaction process easily produces byproducts (such as methane), further reducing the methanol yield and reaction efficiency.

[0006] (2) SOEC co-electrolysis route: SOEC generates syngas (H2 / CO) by electrolyzing CO2 and water vapor at high temperature. Although this method has high energy efficiency and low carbon emissions, its operating temperature is high, which requires high temperature resistance of materials and equipment; and since SOEC is a co-electrolysis reaction, the ratio of hydrogen and carbon monoxide is difficult to control separately, thus making it impossible to accurately control the ratio of the two and affecting the methanol synthesis efficiency. Summary of the Invention

[0007] This invention provides a synthesis gas preparation and methanol synthesis system and method that works in conjunction with PEM and SOEC, in order to overcome at least one technical problem existing in the prior art.

[0008] On the one hand, the present invention provides a synthesis gas preparation and methanol synthesis system that works in concert with PEM and SOEC, including: a PEM hydrogen production unit, an SOEC electrolysis unit, a PSA carbon removal unit, a mixer, a methanol synthesis reactor, and a coordination controller; The PEM hydrogen production unit is connected to renewable electricity and is used to drive the electrolysis of water to generate H2. The SOEC electrolysis unit is connected to renewable electricity and is used to electrolyze CO2 at high temperature to generate a mixture of CO and CO2. The inlet of the PSA decarbonization unit is connected to the outlet of the SOEC electrolysis unit to remove CO2 from the mixed gas and output purified CO. The inlet of the mixer is connected to the H2 output of the PEM hydrogen production unit and the CO output of the PSA carbon removal unit, respectively, to mix CO and H2 to generate syngas. The inlet of the methanol synthesis reactor is connected to the outlet of the mixer for catalytically generating methanol from the synthesis gas. The coordination controller is used to coordinate and control the operating status of the PEM hydrogen production unit, SOEC electrolysis unit, PSA carbon removal unit and methanol synthesis reactor, so that the system switches between startup, normal operation, idle, shutdown and emergency shutdown.

[0009] Optionally, upon receiving a start command, the coordination controller is specifically configured to: Perform a pre-startup check; The SOEC electrolysis unit is controlled to start heating, and when the temperature of the SOEC electrolysis unit reaches a first predetermined temperature, the methanol synthesis reactor is controlled to start preheating. The PEM hydrogen production unit is controlled to start up to generate H2; When the SOEC electrolysis unit reaches the first reduction temperature, H2 is provided to the SOEC electrolysis unit through the PEM hydrogen production unit to achieve fuel electrode reduction of the SOEC electrolysis unit; When the fuel electrode reduction of the SOEC electrolysis unit is completed and the methanol synthesis reactor reaches the second reduction temperature, H2 is supplied to the methanol synthesis reactor through the PEM hydrogen production unit to realize the reduction and activation of the catalyst. When the catalyst reduction and activation are complete and the SOEC electrolysis unit reaches the operating temperature, the SOEC electrolysis unit is controlled to start electrolyzing CO2, and the methanol synthesis reactor is controlled to start increasing the pressure. After the SOEC electrolysis unit has stabilized its gas production, start the PSA decarbonization unit and mixer. The mixer is controlled to mix CO and H2 to generate syngas; The system acquires real-time proportional monitoring data of the synthesis gas output from the mixer. When the proportional data meets the requirements, it controls the synthesis gas to enter the methanol synthesis reactor to start methanol synthesis.

[0010] Optionally, when the system begins normal operation, the coordination controller is specifically used for: Based on the methanol yield target, determine the target yields of CO and H2; The SOEC unit is controlled to adjust the electrolysis power according to the target CO yield; The molar ratio of hydrogen to CO supplied to the methanol synthesis reactor is monitored in real time, and the electrolysis power of the PEM hydrogen production unit is dynamically adjusted to maintain the molar ratio of H2 to CO at a predetermined ratio.

[0011] Optionally, the predetermined ratio of H2 to CO is 2:1.

[0012] Optionally, upon receiving an idle command, the coordination controller is specifically configured to: Reduce the load on the SOEC electrolysis unit and the PEM hydrogen production unit, and stop the feed to the methanol synthesis reactor, so that the methanol synthesis reactor enters a hot standby state and is purged with protective gas. When the SOEC electrolysis unit stops electrolyzing, the SOEC electrolysis unit is controlled to enter a hot standby state and maintained at the operating temperature, and a protective gas is introduced. When the PEM hydrogen production unit stops electrolysis, the PEM hydrogen production unit is controlled to maintain a hot standby state. The PSA decarbonization unit is controlled to stop circulating and remain in standby mode.

[0013] Optionally, upon receiving a shutdown command, the coordination controller is specifically configured to: Disconnect the power supply to the PEM hydrogen production unit and the SOEC unit; Stop supplying synthesis gas to the methanol synthesis reactor and perform a safety pressure release; The methanol synthesis reactor was purged with inert gas. The SOEC electrolysis unit is cooled down, and a reducing protective gas is introduced into the fuel electrode of the SOEC electrolysis unit. Once the temperature of the SOEC electrolysis unit and the methanol synthesis reactor has dropped to a safe level, the power is completely cut off and all valves are closed.

[0014] Optionally, the coordination controller controls the system to shut down urgently upon detecting a fault.

[0015] Optionally, in the event of an emergency system shutdown, the coordination controller is specifically used to: Disconnect the power supply to the PEM hydrogen production unit and the SOEC unit, and introduce a reducing protective gas into the SOEC electrolysis unit; Close the intake valve of the PSA decarbonization unit; Close the synthesis gas inlet valve of the methanol synthesis reactor; The methanol synthesis reactor was subjected to emergency cooling and purged with inert gas.

[0016] Optionally, it also includes a distillation unit and a methanol storage unit; The feed end of the distillation unit is connected to the crude methanol output end of the methanol synthesis reactor, and is used to distill the crude methanol to obtain refined methanol. The feed end of the methanol storage unit is connected to the methanol output end of the distillation unit for storing methanol.

[0017] On the other hand, the present invention also provides a method for preparing methanol, comprising: H2 is generated by electrolyzing water using a PEM hydrogen production unit driven by renewable electricity. CO2 is electrolyzed at high temperature using an SOEC electrolysis unit to produce a mixture of CO and CO2. The PSA carbon removal unit removes CO2 from the mixed gas, outputting purified CO; CO and H2 are mixed using a mixer to generate syngas; The synthesis gas is catalytically converted into methanol using a methanol synthesis reactor; The coordinating controller is used to coordinate and control the operating status of the PEM hydrogen production unit, SOEC electrolysis unit, PSA carbon removal unit and methanol synthesis reactor, so that the system can switch between startup, normal operation, idle, shutdown and emergency shutdown.

[0018] The innovative aspects of this invention include: (1) In this embodiment, the combined scheme of PEM hydrogen production technology and SOEC high-temperature electrolysis CO2 technology significantly improves the efficiency and sustainability of methanol production process, which is one of the innovations of this embodiment.

[0019] (2) In this embodiment, the present invention uses renewable energy to drive PEM hydrogen production and SOEC high-temperature electrolysis of CO2, realizing a green and low-carbon methanol production process, which greatly reduces carbon emissions and improves energy utilization efficiency. This is one of the innovative points of the present invention.

[0020] (3) In this embodiment, by combining PEM hydrogen production and SOEC high-temperature CO2 electrolysis technology, not only can the methanol synthesis reaction proceed smoothly, but the advantages and disadvantages of both can be effectively balanced to achieve overall cost optimization of the system, which is one of the innovative points of this embodiment.

[0021] (4) In this embodiment, the PEM hydrogen production unit and the SOEC electrolysis unit are both modular units that operate independently. They can be flexibly adjusted and expanded according to different needs. Therefore, the gas ratio can be precisely controlled to improve the efficiency of methanol synthesis reaction and reduce the generation of by-products. In addition, SOEC can utilize waste heat when operating at high temperature, which can effectively improve the energy efficiency of the overall system and reduce the external energy demand. This is one of the innovative points of this embodiment. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A scene diagram of a synthesis system provided in an embodiment of the present invention; Figure 2A schematic diagram of a synthesis system provided in an embodiment of the present invention; Figure 3 A schematic diagram illustrating the specific structure of each module of the synthesis system provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the working state of the synthesis system provided in an embodiment of the present invention; Figure 5 A flowchart of a method provided in an embodiment of the present invention; Figure 6 This is another flowchart for preparing methanol provided in an embodiment of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the terms "comprising" and "having," and any variations thereof, in the embodiments and drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0026] This invention discloses a syngas preparation and methanol synthesis system that utilizes PEM and SOEC in synergistic operation. These will be described in detail below.

[0027] Figure 1 This is a scene diagram of a synthesis system provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of a synthesis system provided in an embodiment of the present invention. Figure 3 Please refer to the schematic diagram of the specific structure of each module of the synthesis system provided in the embodiment of the present invention. Figure 1 and Figure 3 The syngas preparation and methanol synthesis system that uses PEM and SOEC working in synergy provided in this embodiment of the invention includes: a PEM hydrogen production unit, an SOEC electrolysis unit, a PSA carbon removal unit, a mixer, a methanol synthesis reactor, and a coordination controller. The PEM hydrogen production unit is connected to renewable electricity and is used to drive the electrolysis of water to generate H2. The SOEC electrolysis unit is connected to renewable electricity to electrolyze CO2 at high temperatures, producing a mixture of CO and CO2. The inlet of the PSA decarbonization unit is connected to the outlet of the SOEC electrolysis unit to remove CO2 from the mixed gas and output purified CO. The inlet of the mixer is connected to the H2 output of the PEM hydrogen production unit and the CO output of the PSA carbon removal unit, respectively, to mix CO and H2 to generate syngas; The inlet of the methanol synthesis reactor is connected to the outlet of the mixer to catalytically convert the synthesis gas into methanol. The coordination controller is used to coordinate and control the operating status of the PEM hydrogen production unit, SOEC electrolysis unit, PSA decarbonization unit and methanol synthesis reactor, enabling the system to switch between startup, normal operation, idle, shutdown and emergency shutdown states.

[0028] Specifically, the syngas preparation and methanol synthesis system that uses PEM and SOEC working together, as provided in this embodiment of the invention, generates hydrogen by electrolyzing water with PEM and generates CO by electrolyzing CO2 at high temperature with SOEC, thereby providing ideal H2 / CO syngas.

[0029] Please refer to Figure 1 and Figure 3 The system comprises a PEM hydrogen production unit and an SOEC electrolysis unit, powered by renewable energy sources to drive both units, achieving a green and low-carbon system. Therefore, both the PEM hydrogen production unit and the SOEC electrolysis unit are connected to renewable energy sources (such as wind and solar power). Figure 1 The wind turbines and photovoltaic panels in the image represent ways to input renewable electricity.

[0030] Driven by renewable electricity, the PEM hydrogen production unit electrolyzes water to generate H2. Simultaneously, the SOEC electrolysis unit operates at a high temperature of 700-850℃. When electricity is input, CO2 entering the stack undergoes an electrolysis reaction to produce CO and oxygen. The SOEC electrolysis unit can utilize waste heat to achieve high-temperature operation, improving energy efficiency and thus reducing external energy demand.

[0031] In addition to CO and oxygen, the exhaust gas produced by the SOEC electrolysis unit also contains unreacted CO2. To ensure that the purity of CO meets the standards required for methanol synthesis, this invention includes a PSA carbon removal unit. Please refer to [reference needed]. Figure 2 and Figure 3The PSA decarbonization unit's inlet is connected to the SOEC electrolysis unit's outlet. Through periodic adsorption and desorption processes, the PSA purifies the exhaust gas generated by the SOEC electrolysis unit, removing CO2 from the mixed gas and outputting purified high-purity CO. Here, CO2 is adsorbed from the SOEC exhaust gas during adsorption, and impurities are periodically desorbed during desorption to ensure continuous CO purification.

[0032] Please refer to Figure 2 and Figure 3 After obtaining H2 and high-purity CO, they can be mixed in a predetermined ratio to produce methanol. Therefore, this invention also includes a mixer and a methanol synthesis reactor. The H2 output of the PEM hydrogen production unit and the CO output of the PSA carbon removal unit are both connected to the inlet of the mixer. The mixer mixes CO and H2 to generate CO and H2 synthesis gas. The output of the mixer is then connected to the inlet of the methanol synthesis reactor, where the synthesis gas undergoes a catalytic reaction to produce methanol. Under suitable temperature and pressure, the catalyst in the methanol synthesis reactor not only accelerates the catalytic reaction but also ensures minimal byproduct formation.

[0033] The methanol produced by the methanol synthesis reactor is crude methanol. To improve product purity, this invention also includes a distillation unit. The feed end of the distillation unit is connected to the crude methanol output end of the methanol synthesis reactor. After removing impurities through distillation, the crude methanol produced by the methanol synthesis reactor is purified to obtain refined methanol. To facilitate the storage and transportation of methanol, the refined methanol output end of the distillation unit is connected to the feed end of a methanol storage device. The methanol is stored in the storage device and then transported to the required location via transportation methods (such as shipping).

[0034] In the methanol synthesis system provided by this invention, each submodule is responsible for a different core task. For example, the PEM hydrogen production unit provides hydrogen, SOEC provides carbon monoxide, and PSA ensures the high purity of the carbon monoxide gas. Each submodule also has different states, such as shutdown, idle, startup, normal operation, and fault or emergency shutdown. To achieve stable operation of the entire system and ensure production efficiency, the switching and coordinated control of the working states between the submodules are crucial. Therefore, this invention also includes a coordination controller. This controller controls the working states of the PEM hydrogen production unit, SOEC electrolysis unit, PSA carbon removal unit, and methanol synthesis reactor, allowing the system to switch between startup, normal operation, idle, shutdown, and emergency shutdown states, thereby ensuring the smooth operation of the entire production process.

[0035] Figure 4 This is a schematic diagram of the working state of the synthesis system provided in an embodiment of the present invention. Please refer to it. Figure 4Reasonable coordination and control can not only improve system efficiency and reduce energy consumption, but also enable rapid emergency handling in case of failure, ensuring the safe operation of equipment. Therefore, it is necessary to precisely control the switching between the start-up, shutdown, idle, operation, and fault shutdown states of each submodule. In this way, the system needs to be able to make flexible adjustments and responses based on real-time data and feedback in each stage and working mode.

[0036] For example, when a start-up command is received, the coordinating controller needs to coordinate the start-up of the PEM hydrogen production unit, SOEC electrolysis unit, PSA carbon removal unit, and methanol synthesis reactor. During the start-up process, each sub-module can run in parallel but independently, which can effectively improve the start-up efficiency.

[0037] During startup, a pre-startup check is required first, checking all safety interlocks and confirming that the system has been inertized. In particular, the inertization check of the SOEC electrolysis unit and the methanol synthesis reactor is required. At the same time, it is also necessary to confirm that each submodule is in a cold shutdown state.

[0038] After the pre-inspection is completed, external heating of the SOEC, such as a high-temperature furnace or integrated heating element, can be started to slowly heat the electrolytic reactor, safely and slowly raising the SOEC from a cold shutdown state to the operating temperature. It should be noted that before heating, the SOEC electrolytic unit must be thoroughly purged with inert gas to check its seal. During the heating process, the heating rate must be strictly controlled, such as 0.5°C to 2°C per minute, to minimize thermal stress caused by thermal expansion mismatch between the electrolytic cell materials. Simultaneously, the temperature in various areas within the reactor must be monitored to ensure that the temperature difference remains within acceptable limits.

[0039] When the SOEC electrolysis unit reaches the first predetermined temperature (e.g., 500°C), the methanol synthesis reactor is preheated, gradually increasing in temperature and pressure from a shutdown state. First, all valves, pumps, compressors, and instruments in the methanol synthesis reactor are checked to ensure there are no leaks and that they have been completely inertized. Then, it is slowly heated to the reduction temperature (e.g., in the range of 150°C to 250°C) to protect the methanol synthesis reactor and catalyst support from thermal stress.

[0040] Simultaneously with the startup of the SOEC electrolysis unit, the PEM hydrogen production unit is started, transitioning it from a shutdown state to a ready-to-operate state. First, a safety self-check and diagnostic are performed. Then, the deionized water pump is started to establish water circulation, ensuring that the water purity, temperature, and flow rate meet requirements. The heater is started to bring the electrolyzer and auxiliary system to the predetermined operating temperature (e.g., 50°C to 80°C). Simultaneously, an inert gas (e.g., nitrogen) is slowly introduced or the system is self-pressurized to establish the initial operating pressure. Once stable and safe operating temperature, pressure, and water flow conditions are reached, the electrolyzer and auxiliary system are ensured to operate under optimal conditions, thereby electrolyzing and generating H2.

[0041] When the SOEC electrolysis unit reaches the first reduction temperature (e.g., 700°C), H2 is supplied to the fuel electrode (i.e., cathode) of the SOEC electrolysis unit through the PEM hydrogen production unit to reduce NiO to conductive Ni, thereby achieving fuel electrode reduction in the SOEC electrolysis unit and ensuring safety. It should be noted that, in addition to using H2 to reduce the fuel electrode, other reducing gases (such as a CO / H2 mixture) can also be used, depending on the specific scenario; this invention does not limit the specific choice.

[0042] Since the methanol synthesis reaction is strongly exothermic, the bed temperature and H2 concentration must be strictly controlled to prevent bed temperature runaway (temperature spike), thereby avoiding catalyst sintering and permanent deactivation. Therefore, when the fuel electrode reduction in the SOEC electrolysis unit is completed and the methanol synthesis reactor reaches the second reduction temperature, H2 is supplied to the methanol synthesis reactor through the PEM hydrogen production unit to reduce the catalyst precursor (CuO) to the active metal (Cu).

[0043] Once the catalyst reduction and activation are complete and the SOEC electrolysis unit reaches its operating temperature (e.g., 750°C), Ni is completely reduced, and the fluid, temperature, and pressure within the SOEC electrolysis unit stabilize. Therefore, the electrolysis of CO2 can be controlled to begin, while simultaneously, the compressor in the methanol synthesis reactor is started to slowly pressurize it to the operating pressure (typically 50 to 100 bar).

[0044] After the SOEC electrolysis unit's gas production stabilizes, start the PSA decarbonization unit to transition it from a shutdown state to preparation for separation operations. First, check the readiness of all valves, pipes, and instruments in the PSA decarbonization unit. Then, prepare the adsorbent, ensuring that the adsorbent (such as molecular sieves or activated carbon) is in a dry and regenerated state. If the adsorbent may have become damp after a long period of shutdown, it will require heat regeneration.

[0045] Next, pressure build-up is performed to pressurize the adsorption towers in the circulation process. This pressurization must be slow and controlled to avoid shear force damage to the adsorbent particles caused by high-speed gas flow, or to prevent bed fluidization. Typically, feed gas or purified product gas is used to pre-pressurize the bed. Simultaneously, an automatic control sequence must be initiated to begin the cyclical steps of adsorption, pressure equalization, desorption, and purging until the pressure and flow rate of each tower reach a stable circulation state. It should be noted that the PSA decarbonization unit can only be started when the SOEC electrolysis unit has entered a stable operating state and provides gas that meets the design feed pressure, temperature, and flow rate of the PSA decarbonization unit.

[0046] Simultaneously with starting the PSA decarbonization unit, the mixer is also started to mix CO and H2 to generate syngas. The ratio of H2 to CO in the syngas output from the mixer is monitored in real time. Only when the ratio data meets the requirements is the start-up phase completed, and the system enters the normal operation phase, controlling the syngas to enter the methanol synthesis reactor to begin methanol synthesis.

[0047] When the system begins normal operation, the coordinating controller needs to determine the target yields of CO and H2 based on the methanol yield target. The SOEC electrolysis unit stably carries out the CO2 electrolysis reaction, continuously producing CO and O2. During electrolysis, the current input can be adjusted according to the target CO yield, thereby regulating the electrolysis power.

[0048] Furthermore, SOEC electrolysis units can flexibly adjust loads during operation (e.g., in response to renewable energy fluctuations), but the rate of load adjustment still needs to be controlled to manage thermal inertia. The electrolysis reaction is endothermic; by adjusting reactant preheating, flow rate, and current density, the electrolysis reactor can be maintained in an isothermal or microthermal equilibrium state. It is important to note that during the electrolysis process, precise control of the CO2 input flow rate and partial pressure is necessary to ensure sufficient unreacted gas on the fuel electrode side as a protective gas to prevent Ni oxidation. Maintaining the voltage near thermal neutral minimizes the need for external heating or cooling. To prevent electrolyte degradation, overvoltage and excessively high current densities must be avoided.

[0049] During normal system operation, the PSA carbon removal unit operates stably between designed high and low pressure cycles, continuously separating CO2 and CO. By precisely coordinating the cycle times of each adsorption tower (adsorption, pressure equalization, desorption, and purging), the purity and recovery rate of the product CO are ensured to meet targets. Pressure fluctuations are the core driving force of the PSA carbon removal unit, therefore, strict control of the pressure during high-pressure adsorption and low-pressure desorption is necessary. Continuous monitoring and adjustment of feed flow rate, pressure, and temperature are crucial, especially when the SOEC electrolysis unit operates under variable loads, as the PSA needs to quickly adapt to changes in feed flow rate and CO2 concentration. Although individual adsorption towers operate intermittently, a continuous and stable CO product gas flow can be achieved through the cyclical alternation of multiple adsorption towers.

[0050] During normal operation, the electrolyzer in the PEM electrolysis unit is energized to decompose water and stably produce hydrogen and oxygen. During operation, the input current (or voltage) can be precisely controlled according to the required H2 target output (i.e., load rate) to adjust its electrolysis power.

[0051] The PEM electrolysis unit features rapid dynamic response, allowing for quick load adjustments during operation. It continuously monitors and controls the electrolyzer temperature, removing reaction heat through a cooling system to maintain it within its optimal operating range. It also maintains stable deionized water flow rate, level, and conductivity. Furthermore, it continuously performs hydrogen and oxygen separation, purification, drying, and pressure management. Finally, it continuously monitors gas purity (especially oxygen content in hydrogen and hydrogen content in oxygen) and pressure to ensure safety limits are not exceeded.

[0052] H2 and CO syngas undergo catalytic conversion in a methanol synthesis reactor to continuously produce methanol. To ensure methanol yield, the molar ratio of H2 to CO supplied to the methanol synthesis reactor needs to be monitored in real time. The H2 supply is dynamically adjusted by dynamically regulating the electrolysis power of the PEM hydrogen production unit to maintain the H2:CO molar ratio at a predetermined level, such as 2:1. It should be noted that methanol synthesis is a reaction with a relatively low single-pass conversion rate; therefore, gas recirculation is necessary to recover unreacted syngas.

[0053] When the system receives an idle command, the coordinating controller coordinates and controls each submodule to maintain near-normal operating temperature and pressure for rapid restart. Both the SOEC electrolysis unit and the PEM hydrogen production unit are energized but electrolysis is stopped, with zero current. At this time, for the PEM hydrogen production unit, auxiliary heating and water circulation systems are needed to maintain the electrolyzer temperature within the operating range to prevent losses caused by thermal cycling and to achieve rapid response. Simultaneously, continuous leak monitoring and gas purging are required to prevent gas mixing. This minimizes energy consumption while minimizing the transition time from shutdown to restarting hydrogen production.

[0054] For SOEC electrolysis units, external heaters are needed to maintain stable reactor temperature. A small amount of inert gas or diluted reducing protective gas (such as CO or H2) is continuously introduced to the fuel electrode side to prevent Ni oxidation and carbon deposition. This minimizes thermal stress, maintains the reactor's chemical stability, and enables rapid restart.

[0055] When the SOEC electrolysis unit enters hot standby (idle) mode, the PSA feed gas flow will be significantly reduced or stopped. Therefore, the PSA system will stop operating for a period, and all towers will be maintained at high pressure or feed pressure to maximize the adsorption capacity of the adsorbent. At this time, the feed gas valve is closed, and the tower body is pressurized to prevent air or impurities from entering, preparing for a rapid restart. Low-temperature / low-flow purging is performed, such as using extremely low flow rates of pure gas (e.g., CO product gas), to maintain bed activity and a slight pressure balance, ready to resume circulation at any time. Thus, when the SOEC resumes gas supply, the PSA decarbonization unit can quickly resume normal circulation to receive and process the CO / CO2 mixture.

[0056] Upon receiving the idle command, the methanol synthesis reactor stops feeding synthesis gas, but introduces heated or low-flow-rate inert / recirculating gas to maintain a high temperature. This not only avoids frequent thermal cycling stress but also fills the reactor with pure inert gas or a low-flow-rate protective gas rich in H2, thus preventing the catalyst from being oxidized and deactivated by impurities (especially O2) at high temperatures. In this way, the catalyst activity can be maintained, and rapid start-up can be achieved.

[0057] Upon receiving a shutdown command, the coordinating controller cuts off the power supply to the PEM hydrogen production unit and the SOEC electrolysis unit, stopping their electrolysis. It also completely stops the PSA carbon removal unit from circulation, placing all adsorption towers in idle or purging mode. Simultaneously, it stops supplying syngas to the methanol synthesis reactor, and the reactor, compressor, distillation tower, and other major equipment cease operation, maintaining ambient or safe temperatures. All high-pressure equipment (such as reactors and high-pressure pipelines) is safely depressurized to atmospheric pressure or a predetermined protective pressure.

[0058] It should be noted that if long-term shutdown or maintenance is required, the adsorbent bed of the PSA carbon removal unit needs to be purged with an inert gas (such as N2) to remove residual corrosive or hazardous gases and protect the adsorbent. Furthermore, when the SOEC is shut down or switched to idle mode, the PSA feed valve must be closed or switched promptly to prevent feed pressure fluctuations from impacting the adsorbent bed.

[0059] Methanol synthesis typically uses Cu, ZnO, or Al2O3 as catalysts, which are extremely sensitive to oxygen and moisture. Therefore, it is necessary to thoroughly purge and isolate the methanol synthesis reactor and related pipelines with inert gases (such as high-purity N2) to remove all residual synthesis gases (CO, CO2, H2) and oxygen, ensuring that the catalyst is in a dry and oxygen-free environment.

[0060] Ni-based fuel electrodes (cathodes) oxidize rapidly when exposed to oxygen-containing environments at high temperatures, leading to performance degradation and even structural damage. Therefore, after disconnecting the power supply, close the inlet and outlet valves and perform a shutdown purging of the SOEC electrolysis unit. When the temperature drops to a safe level (e.g., below 150°C), introduce an inert gas (e.g., N2) or a reducing protective gas (e.g., H2 or CO) into the fuel electrode of the SOEC electrolysis unit for thorough purging and protection, maintaining a seal to prevent air or oxidizing gases from entering. At this point, completely disconnect the power and close all valves, ensuring the PEM hydrogen production unit and the SOEC electrolysis unit are completely shut down.

[0061] To ensure the safe operation of the equipment, in the event of a system failure, the coordinating controller issues an emergency stop command to control the system in an emergency shutdown. This failure could be a malfunction in one or more submodules within the system.

[0062] When a safety or equipment malfunction is detected in the PEM hydrogen production unit, such as excessive gas purity (e.g., excessively high oxygen concentration in hydrogen), severely excessive system pressure or temperature, power failure or external power grid interruption, or severe interruption of water circulation, it is considered a PEM hydrogen production unit malfunction and requires emergency shutdown of the control system.

[0063] When a serious fault or breach of safety limits is detected in the SOEC electrolysis unit, such as gas supply interruption leading to fuel electrode depressurization; excessive temperature difference within the reactor core posing a risk of thermal stress; or safety gas / oxygen leakage causing mixing of fuel electrode and oxygen electrode gases, it is considered a fault in the SOEC electrolysis unit and requires an emergency shutdown of the control system.

[0064] When a serious malfunction is detected in the PSA decarbonization unit, such as a severely excessive feed or outlet pressure; gas purity (product CO or de-CO2 stream) continuously failing to meet standards; or automatic valve jamming or malfunction, it is considered a PSA decarbonization unit malfunction and requires an emergency shutdown of the control system.

[0065] When a malfunction is detected in the methanol synthesis reactor, such as a rapid and uncontrollable rise in reactor bed temperature, leakage of hazardous gases, or failure of the cooling system to remove the heat of reaction, it is considered a malfunction of the methanol synthesis reactor and requires an emergency shutdown of the control system.

[0066] When the system receives an emergency shutdown command, the coordinating controller quickly cuts off the power to the electrolyzer and SOEC electrolysis unit in the PEM hydrogen production unit, stopping electrolysis. The PEM hydrogen production unit automatically performs safety depressurization and inert gas (N2) purging operations to safely discharge or dilute residual gases in the system, while isolating all gas and liquid flow paths, putting the PEM hydrogen production unit into a locked state until the fault is cleared and a safety check is passed before it can be restarted.

[0067] At high temperatures, the SOEC electrolysis unit is rapidly switched to high-flow-rate reducing gas purging of the fuel electrode side to prevent Ni oxidation and protect the reactor body. Controlled cooling is then implemented to prevent thermal shock, but the cooling rate during an emergency shutdown is slightly faster than that during a planned shutdown. The SOEC electrolysis unit is then locked and can only be restarted after the fault has been cleared and a detailed inspection has been conducted.

[0068] For the PSA decarbonization unit, in case of emergency shutdown, immediately close the feed valve of the PSA decarbonization unit and direct the gas produced by the SOEC electrolysis unit to a safe vent or buffer tank. Then, slowly or in a controlled manner reduce the pressure in all adsorption towers to a safe level to prevent sudden pressure release from damaging the equipment or adsorbent. Isolate all inlets and outlets and perform fault diagnosis.

[0069] For methanol synthesis reactors, in the event of an emergency shutdown, immediately close all synthesis gas and H2 inlet valves. Perform a rapid but controlled depressurization, simultaneously activating the emergency cooling system to cool the methanol synthesis reactor, followed by a rapid inert gas purging to remove all combustibles and oxidizing substances, thus protecting the equipment and catalyst.

[0070] Based on the same inventive concept, the present invention also provides a method for preparing methanol. Figure 5 A flowchart of a method provided in an embodiment of the present invention is provided below. Figure 5 The method for preparing methanol provided by the present invention includes: Step 1: The PEM hydrogen production unit is driven by renewable electricity to electrolyze water and generate H2; Step 2: Electrolyze CO2 at high temperature using an SOEC electrolysis unit to generate a mixture of CO and CO2. Step 3: Use the PSA carbon removal unit to remove CO2 from the mixed gas and output purified CO; Step 4: Use a mixer to mix CO and H2 to generate syngas; Step 5: Catalytically convert syngas into methanol using a methanol synthesis reactor; Step 6: Use the coordination controller to coordinate and control the working status of the PEM hydrogen production unit, SOEC electrolysis unit, PSA decarbonization unit and methanol synthesis reactor, so that the system switches between startup, normal operation, idle, shutdown and emergency shutdown.

[0071] Specifically, the synthesis gas preparation and methanol synthesis method of PEM and SOEC working together provided in the embodiments of the present invention generates hydrogen by electrolyzing water with PEM and generates CO by electrolyzing CO2 at high temperature with SOEC, thereby providing an ideal H2 / CO synthesis gas.

[0072] Please refer to Figures 1-5 This method uses renewable energy as the power source to drive the PEM hydrogen production unit and the SOEC electrolysis unit, achieving a green and low-carbon system. Therefore, both the PEM hydrogen production unit and the SOEC electrolysis unit are connected to renewable power sources (such as wind and solar energy). Figure 1 The wind turbines and photovoltaic panels in the image represent ways to input renewable electricity.

[0073] In step 1, driven by renewable electricity, the PEM hydrogen production unit electrolyzes water to generate H2. Simultaneously, in step 2, the SOEC electrolysis unit operates at a high temperature of 700-850°C. When electricity is input, CO2 entering the stack undergoes an electrolysis reaction to generate CO and oxygen. The SOEC electrolysis unit can utilize waste heat to achieve high-temperature operation, improving energy efficiency and thus reducing external energy demand.

[0074] In addition to CO and oxygen, the exhaust gas produced by the SOEC electrolysis unit also contains unreacted CO2. To ensure that the purity of CO meets the standards required for methanol synthesis, this invention includes a PSA carbon removal unit. Please refer to [reference needed]. Figure 2 The PSA decarbonization unit's inlet is connected to the SOEC electrolysis unit's outlet. In step 3, the PSA decarbonization unit purifies the tail gas generated by the SOEC electrolysis unit through periodic adsorption and desorption processes, removing CO2 gas from the mixed gas and outputting purified high-purity CO. Here, CO2 gas in the SOEC tail gas is adsorbed during the adsorption process, and impurities need to be desorbed periodically during the desorption process to ensure continuous CO purification.

[0075] Please refer to Figure 2 and Figure 3After obtaining H2 and high-purity CO, they can be mixed in a predetermined ratio to produce methanol. Therefore, this invention also includes a mixer and a methanol synthesis reactor. The H2 output of the PEM hydrogen production unit and the CO output of the PSA carbon removal unit are both connected to the inlet of the mixer. In step 4, CO and H2 are mixed through the mixer to generate CO and H2 synthesis gas. The output of the mixer is then connected to the inlet of the methanol synthesis reactor. In step 5, the synthesis gas undergoes a catalytic reaction in the methanol synthesis reactor to produce methanol. Under suitable temperature and pressure, the catalyst in the methanol synthesis reactor not only accelerates the catalytic reaction but also ensures minimal byproduct formation.

[0076] In the methanol synthesis system provided by this invention, each submodule is responsible for different core tasks. For example, the PEM hydrogen production unit provides hydrogen, SOEC provides carbon monoxide, and PSA ensures the high purity of the carbon monoxide gas. Each submodule also has different states, such as shutdown, idle, startup, normal operation, and fault or emergency shutdown. To achieve stable operation of the entire system and ensure production efficiency, the switching and coordinated control of the working states between the submodules are crucial. Therefore, this invention also includes a coordination controller. In step 6, the coordination controller controls the working states of the PEM hydrogen production unit, SOEC electrolysis unit, PSA carbon removal unit, and methanol synthesis reactor, allowing the system to switch between startup, normal operation, idle, shutdown, and emergency shutdown states, thereby ensuring the smooth operation of the entire production process.

[0077] It should be noted that step 6 here is only to illustrate that in the methanol preparation process, this step is needed to coordinate and control the state of each sub-module, and does not represent their execution order.

[0078] Figure 6 For another flowchart of methanol preparation provided in this embodiment of the invention, please refer to... Figure 6 The methanol produced by the methanol synthesis reactor is crude methanol. To improve product purity, this invention also includes a distillation unit. The feed end of the distillation unit is connected to the crude methanol output end of the methanol synthesis reactor. In step 7, the crude methanol produced by the methanol synthesis reactor is distilled to remove impurities, yielding refined methanol. To facilitate the storage and transportation of methanol, the refined methanol output end of the distillation unit is connected to the feed end of a methanol storage device. The methanol is stored in the storage device and transported to the required location via transportation methods (such as shipping).

[0079] Please refer to Figure 4Reasonable coordination and control can not only improve system efficiency and reduce energy consumption, but also enable rapid emergency handling in case of failure, ensuring the safe operation of equipment. Therefore, it is necessary to precisely control the switching between the start-up, shutdown, idle, operation, and fault shutdown states of each submodule. In this way, the system needs to be able to make flexible adjustments and responses based on real-time data and feedback in each stage and working mode.

[0080] For example, when a start-up command is received, the coordinating controller needs to coordinate the start-up of the PEM hydrogen production unit, SOEC electrolysis unit, PSA carbon removal unit, and methanol synthesis reactor. During the start-up process, each sub-module can run in parallel but independently, which can effectively improve the start-up efficiency.

[0081] During startup, a pre-startup check is required first, checking all safety interlocks and confirming that the system has been inertized. In particular, the inertization check of the SOEC electrolysis unit and the methanol synthesis reactor is required. At the same time, it is also necessary to confirm that each submodule is in a cold shutdown state.

[0082] After the pre-inspection is completed, external heating of the SOEC, such as a high-temperature furnace or integrated heating element, can be started to slowly heat the electrolytic reactor, safely and slowly raising the SOEC from a cold shutdown state to the operating temperature. It should be noted that before heating, the SOEC electrolytic unit must be thoroughly purged with inert gas to check its seal. During the heating process, the heating rate must be strictly controlled, such as 0.5°C to 2°C per minute, to minimize thermal stress caused by thermal expansion mismatch between the electrolytic cell materials. Simultaneously, the temperature in various areas within the reactor must be monitored to ensure that the temperature difference remains within acceptable limits.

[0083] When the SOEC electrolysis unit reaches the first predetermined temperature (e.g., 500°C), the methanol synthesis reactor is preheated, gradually increasing in temperature and pressure from a shutdown state. First, all valves, pumps, compressors, and instruments in the methanol synthesis reactor are checked to ensure there are no leaks and that they have been completely inertized. Then, it is slowly heated to the reduction temperature (e.g., in the range of 150°C to 250°C) to protect the methanol synthesis reactor and catalyst support from thermal stress.

[0084] Simultaneously with the startup of the SOEC electrolysis unit, the PEM hydrogen production unit is started, transitioning it from a shutdown state to a ready-to-operate state. First, a safety self-check and diagnostic are performed. Then, the deionized water pump is started to establish water circulation, ensuring that the water purity, temperature, and flow rate meet requirements. The heater is started to bring the electrolyzer and auxiliary system to the predetermined operating temperature (e.g., 50°C to 80°C). Simultaneously, an inert gas (e.g., nitrogen) is slowly introduced or the system is self-pressurized to establish the initial operating pressure. Once stable and safe operating temperature, pressure, and water flow conditions are reached, the electrolyzer and auxiliary system are ensured to operate under optimal conditions, thereby electrolyzing and generating H2.

[0085] When the SOEC electrolysis unit reaches the first reduction temperature (e.g., 700°C), H2 is supplied to the fuel electrode (i.e., cathode) of the SOEC electrolysis unit through the PEM hydrogen production unit to reduce NiO to conductive Ni, thereby achieving fuel electrode reduction in the SOEC electrolysis unit and ensuring safety. It should be noted that, in addition to using H2 to reduce the fuel electrode, other reducing gases (such as a CO / H2 mixture) can also be used, depending on the specific scenario; this invention does not limit the specific choice.

[0086] Since the methanol synthesis reaction is strongly exothermic, the bed temperature and H2 concentration must be strictly controlled to prevent bed temperature runaway (temperature spike), thereby avoiding catalyst sintering and permanent deactivation. Therefore, when the fuel electrode reduction in the SOEC electrolysis unit is completed and the methanol synthesis reactor reaches the second reduction temperature, H2 is supplied to the methanol synthesis reactor through the PEM hydrogen production unit to reduce the catalyst precursor (CuO) to the active metal (Cu).

[0087] Once the catalyst reduction and activation are complete and the SOEC electrolysis unit reaches its operating temperature (e.g., 750°C), Ni is completely reduced, and the fluid, temperature, and pressure within the SOEC electrolysis unit stabilize. Therefore, the electrolysis of CO2 can be controlled to begin, while simultaneously, the compressor in the methanol synthesis reactor is started to slowly pressurize it to the operating pressure (typically 50 to 100 bar).

[0088] After the SOEC electrolysis unit's gas production stabilizes, start the PSA decarbonization unit to transition it from a shutdown state to preparation for separation operations. First, check the readiness of all valves, pipes, and instruments in the PSA decarbonization unit. Then, prepare the adsorbent, ensuring that the adsorbent (such as molecular sieves or activated carbon) is in a dry and regenerated state. If the adsorbent may have become damp after a long period of shutdown, it will require heat regeneration.

[0089] Next, pressure build-up is performed to pressurize the adsorption towers in the circulation process. This pressurization must be slow and controlled to avoid shear force damage to the adsorbent particles caused by high-speed gas flow, or to prevent bed fluidization. Typically, feed gas or purified product gas is used to pre-pressurize the bed. Simultaneously, an automatic control sequence must be initiated to begin the cyclical steps of adsorption, pressure equalization, desorption, and purging until the pressure and flow rate of each tower reach a stable circulation state. It should be noted that the PSA decarbonization unit can only be started when the SOEC electrolysis unit has entered a stable operating state and provides gas that meets the design feed pressure, temperature, and flow rate of the PSA decarbonization unit.

[0090] Simultaneously with starting the PSA decarbonization unit, the mixer is also started to mix CO and H2 to generate syngas. The ratio of H2 to CO in the syngas output from the mixer is monitored in real time. Only when the ratio data meets the requirements is the start-up phase completed, and the system enters the normal operation phase, controlling the syngas to enter the methanol synthesis reactor to begin methanol synthesis.

[0091] When the system begins normal operation, the coordinating controller needs to determine the target yields of CO and H2 based on the methanol yield target. The SOEC electrolysis unit stably carries out the CO2 electrolysis reaction, continuously producing CO and O2. During electrolysis, the current input can be adjusted according to the target CO yield, thereby regulating the electrolysis power.

[0092] Furthermore, SOEC electrolysis units can flexibly adjust loads during operation (e.g., in response to renewable energy fluctuations), but the rate of load adjustment still needs to be controlled to manage thermal inertia. The electrolysis reaction is endothermic; by adjusting reactant preheating, flow rate, and current density, the electrolysis reactor can be maintained in an isothermal or microthermal equilibrium state. It is important to note that during the electrolysis process, precise control of the CO2 input flow rate and partial pressure is necessary to ensure sufficient unreacted gas on the fuel electrode side as a protective gas to prevent Ni oxidation. Maintaining the voltage near thermal neutral minimizes the need for external heating or cooling. To prevent electrolyte degradation, overvoltage and excessively high current densities must be avoided.

[0093] During normal system operation, the PSA carbon removal unit operates stably between designed high and low pressure cycles, continuously separating CO2 and CO. By precisely coordinating the cycle times of each adsorption tower (adsorption, pressure equalization, desorption, and purging), the purity and recovery rate of the product CO are ensured to meet targets. Pressure fluctuations are the core driving force of the PSA carbon removal unit, therefore, strict control of the pressure during high-pressure adsorption and low-pressure desorption is necessary. Continuous monitoring and adjustment of feed flow rate, pressure, and temperature are crucial, especially when the SOEC electrolysis unit operates under variable loads, as the PSA needs to quickly adapt to changes in feed flow rate and CO2 concentration. Although individual adsorption towers operate intermittently, a continuous and stable CO product gas flow can be achieved through the cyclical alternation of multiple adsorption towers.

[0094] During normal operation, the electrolyzer in the PEM electrolysis unit is energized to decompose water and stably produce hydrogen and oxygen. During operation, the input current (or voltage) can be precisely controlled according to the required H2 target output (i.e., load rate) to adjust its electrolysis power.

[0095] The PEM electrolysis unit features rapid dynamic response, allowing for quick load adjustments during operation. It continuously monitors and controls the electrolyzer temperature, removing reaction heat through a cooling system to maintain it within its optimal operating range. It also maintains stable deionized water flow rate, level, and conductivity. Furthermore, it continuously performs hydrogen and oxygen separation, purification, drying, and pressure management. Finally, it continuously monitors gas purity (especially oxygen content in hydrogen and hydrogen content in oxygen) and pressure to ensure safety limits are not exceeded.

[0096] H2 and CO syngas undergo catalytic conversion in a methanol synthesis reactor to continuously produce methanol. To ensure methanol yield, the molar ratio of H2 to CO supplied to the methanol synthesis reactor needs to be monitored in real time. The H2 supply is dynamically adjusted by dynamically regulating the electrolysis power of the PEM hydrogen production unit to maintain the H2:CO molar ratio at a predetermined level, such as 2:1. It should be noted that methanol synthesis is a reaction with a relatively low single-pass conversion rate; therefore, gas recirculation is necessary to recover unreacted syngas.

[0097] When the system receives an idle command, the coordinating controller coordinates and controls each submodule to maintain near-normal operating temperature and pressure for rapid restart. Both the SOEC electrolysis unit and the PEM hydrogen production unit are energized but electrolysis is stopped, with zero current. At this time, for the PEM hydrogen production unit, auxiliary heating and water circulation systems are needed to maintain the electrolyzer temperature within the operating range to prevent losses caused by thermal cycling and to achieve rapid response. Simultaneously, continuous leak monitoring and gas purging are required to prevent gas mixing. This minimizes energy consumption while minimizing the transition time from shutdown to restarting hydrogen production.

[0098] For SOEC electrolysis units, external heaters are needed to maintain stable reactor temperature. A small amount of inert gas or diluted reducing protective gas (such as CO or H2) is continuously introduced to the fuel electrode side to prevent Ni oxidation and carbon deposition. This minimizes thermal stress, maintains the reactor's chemical stability, and enables rapid restart.

[0099] When the SOEC electrolysis unit enters hot standby (idle) mode, the PSA feed gas flow will be significantly reduced or stopped. Therefore, the PSA system will stop operating for a period, and all towers will be maintained at high pressure or feed pressure to maximize the adsorption capacity of the adsorbent. At this time, the feed gas valve is closed, and the tower body is pressurized to prevent air or impurities from entering, preparing for a rapid restart. Low-temperature / low-flow purging is performed, such as using extremely low flow rates of pure gas (e.g., CO product gas), to maintain bed activity and a slight pressure balance, ready to resume circulation at any time. Thus, when the SOEC resumes gas supply, the PSA decarbonization unit can quickly resume normal circulation to receive and process the CO / CO2 mixture.

[0100] Upon receiving the idle command, the methanol synthesis reactor stops feeding synthesis gas, but introduces heated or low-flow-rate inert / recirculating gas to maintain a high temperature. This not only avoids frequent thermal cycling stress but also fills the reactor with pure inert gas or a low-flow-rate protective gas rich in H2, thus preventing the catalyst from being oxidized and deactivated by impurities (especially O2) at high temperatures. In this way, the catalyst activity can be maintained, and rapid start-up can be achieved.

[0101] Upon receiving a shutdown command, the coordinating controller cuts off the power supply to the PEM hydrogen production unit and the SOEC electrolysis unit, stopping their electrolysis. It also completely stops the PSA carbon removal unit from circulation, placing all adsorption towers in idle or purging mode. Simultaneously, it stops supplying syngas to the methanol synthesis reactor, and the reactor, compressor, distillation tower, and other major equipment cease operation, maintaining ambient or safe temperatures. All high-pressure equipment (such as reactors and high-pressure pipelines) is safely depressurized to atmospheric pressure or a predetermined protective pressure.

[0102] It should be noted that if long-term shutdown or maintenance is required, the adsorbent bed of the PSA carbon removal unit needs to be purged with an inert gas (such as N2) to remove residual corrosive or hazardous gases and protect the adsorbent. Furthermore, when the SOEC is shut down or switched to idle mode, the PSA feed valve must be closed or switched promptly to prevent feed pressure fluctuations from impacting the adsorbent bed.

[0103] Methanol synthesis typically uses Cu, ZnO, or Al2O3 as catalysts, which are extremely sensitive to oxygen and moisture. Therefore, it is necessary to thoroughly purge and isolate the methanol synthesis reactor and related pipelines with inert gases (such as high-purity N2) to remove all residual synthesis gases (CO, CO2, H2) and oxygen, ensuring that the catalyst is in a dry and oxygen-free environment.

[0104] Ni-based fuel electrodes (cathodes) oxidize rapidly when exposed to oxygen-containing environments at high temperatures, leading to performance degradation and even structural damage. Therefore, after disconnecting the power supply, close the inlet and outlet valves and perform a shutdown purging of the SOEC electrolysis unit. When the temperature drops to a safe level (e.g., below 150°C), introduce an inert gas (e.g., N2) or a reducing protective gas (e.g., H2 or CO) into the fuel electrode of the SOEC electrolysis unit for thorough purging and protection, maintaining a seal to prevent air or oxidizing gases from entering. At this point, completely disconnect the power and close all valves, ensuring the PEM hydrogen production unit and the SOEC electrolysis unit are completely shut down.

[0105] To ensure the safe operation of the equipment, in the event of a system failure, the coordinating controller issues an emergency stop command to control the system in an emergency shutdown. This failure could be a malfunction in one or more submodules within the system.

[0106] When a safety or equipment malfunction is detected in the PEM hydrogen production unit, such as excessive gas purity (e.g., excessively high oxygen concentration in hydrogen), severely excessive system pressure or temperature, power failure or external power grid interruption, or severe interruption of water circulation, it is considered a PEM hydrogen production unit malfunction and requires emergency shutdown of the control system.

[0107] When a serious fault or breach of safety limits is detected in the SOEC electrolysis unit, such as gas supply interruption leading to fuel electrode depressurization; excessive temperature difference within the reactor core posing a risk of thermal stress; or safety gas / oxygen leakage causing mixing of fuel electrode and oxygen electrode gases, it is considered a fault in the SOEC electrolysis unit and requires an emergency shutdown of the control system.

[0108] When a serious malfunction is detected in the PSA decarbonization unit, such as a severely excessive feed or outlet pressure; gas purity (product CO or de-CO2 stream) continuously failing to meet standards; or automatic valve jamming or malfunction, it is considered a PSA decarbonization unit malfunction and requires an emergency shutdown of the control system.

[0109] When a malfunction is detected in the methanol synthesis reactor, such as a rapid and uncontrollable rise in reactor bed temperature, leakage of hazardous gases, or failure of the cooling system to remove the heat of reaction, it is considered a malfunction of the methanol synthesis reactor and requires an emergency shutdown of the control system.

[0110] When the system receives an emergency shutdown command, the coordinating controller quickly cuts off the power to the electrolyzer and SOEC electrolysis unit in the PEM hydrogen production unit, stopping electrolysis. The PEM hydrogen production unit automatically performs safety depressurization and inert gas (N2) purging operations to safely discharge or dilute residual gases in the system, while isolating all gas and liquid flow paths, putting the PEM hydrogen production unit into a locked state until the fault is cleared and a safety check is passed before it can be restarted.

[0111] At high temperatures, the SOEC electrolysis unit is rapidly switched to high-flow-rate reducing gas purging of the fuel electrode side to prevent Ni oxidation and protect the reactor body. Controlled cooling is then implemented to prevent thermal shock, but the cooling rate during an emergency shutdown is slightly faster than that during a planned shutdown. The SOEC electrolysis unit is then locked and can only be restarted after the fault has been cleared and a detailed inspection has been conducted.

[0112] For the PSA decarbonization unit, in case of emergency shutdown, immediately close the feed valve of the PSA decarbonization unit and direct the gas produced by the SOEC electrolysis unit to a safe vent or buffer tank. Then, slowly or in a controlled manner reduce the pressure in all adsorption towers to a safe level to prevent sudden pressure release from damaging the equipment or adsorbent. Isolate all inlets and outlets and perform fault diagnosis.

[0113] For methanol synthesis reactors, in the event of an emergency shutdown, immediately close all synthesis gas and H2 inlet valves. Perform a rapid but controlled depressurization, simultaneously activating the emergency cooling system to cool the methanol synthesis reactor, followed by a rapid inert gas purging to remove all combustibles and oxidizing substances, thus protecting the equipment and catalyst.

[0114] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0115] Those skilled in the art will understand that the modules in the system of the embodiments can be distributed in the system of the embodiments as described in the embodiments, or they can be located in one or more systems different from this embodiment with corresponding changes. The modules of the above embodiments can be combined into one module, or they can be further divided into multiple sub-modules.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for syngas production and methanol synthesis with PEM and SOEC working in cooperation, characterized in that, The system comprises a PEM hydrogen production unit, a SOEC electrolysis unit, a PSA carbon removal unit, a mixer, a methanol synthesis reactor and a coordination controller. The PEM hydrogen production unit is connected to renewable power, and is configured to produce H2 by driving water electrolysis reaction with renewable power. The SOEC electrolysis unit is connected to renewable power, and is configured to electrolyze CO2 at high temperature to produce a mixed gas of CO and CO2. The PSA carbon removal unit is connected to the gas outlet of the SOEC electrolysis unit, and is configured to remove CO2 in the mixed gas and output purified CO. The mixer is connected to the H2 output of the PEM hydrogen production unit and the CO output of the PSA carbon removal unit, and is configured to mix CO and H2 to produce synthesis gas. The methanol synthesis reactor is connected to the output of the mixer, and is configured to catalytically produce methanol from the synthesis gas. The coordination controller is configured to coordinate the working states of the PEM hydrogen production unit, the SOEC electrolysis unit, the PSA carbon removal unit and the methanol synthesis reactor, and to switch the system between start-up, normal operation, idle, shutdown and emergency shutdown. Upon receiving a start-up instruction, the coordination controller is specifically configured to:

2. The system for syngas production and methanol synthesis with cooperation of PEM and SOEC according to claim 1, characterized in that, perform pre-start-up inspection; control the SOEC electrolysis unit to start warming up, and control the methanol synthesis reactor to start preheating when the temperature of the SOEC electrolysis unit reaches a first predetermined temperature; control the PEM hydrogen production unit to start producing H2; provide H2 for the SOEC electrolysis unit through the PEM hydrogen production unit to reduce the fuel electrode of the SOEC electrolysis unit when the SOEC electrolysis unit reaches a first reduction temperature; provide H2 for the methanol synthesis reactor through the PEM hydrogen production unit to activate the catalyst when the fuel electrode of the SOEC electrolysis unit is reduced and the methanol synthesis reactor reaches a second reduction temperature; control the SOEC electrolysis unit to start electrolyzing CO2 when the catalyst is activated and the SOEC electrolysis unit reaches a working temperature, and control the methanol synthesis reactor to start boosting pressure; start the PSA carbon removal unit and the mixer after the SOEC electrolysis unit produces gas stably; control the mixer to mix CO and H2 to produce synthesis gas; monitor the real-time proportion of the synthesis gas output by the mixer, and control the synthesis gas to enter the methanol synthesis reactor to start methanol synthesis when the proportion data meets the requirements. When the system starts normal operation, the coordination controller is specifically configured to:

3. The system for syngas production and methanol synthesis with cooperation of PEM and SOEC according to claim 1, characterized in that, determine the target production of CO and H2 according to the methanol production rate target; control the SOEC unit to adjust the electrolysis power according to the target production of CO; monitor the molar ratio of hydrogen and CO delivered to the methanol synthesis reactor in real time, and dynamically adjust the electrolysis power of the PEM hydrogen production unit to maintain the molar ratio of H2 and CO at a predetermined ratio. The predetermined ratio of H2 and CO is 2:

1.

4. The system for syngas production and methanol synthesis with cooperation of PEM and SOEC according to claim 3, characterized in that, Upon receiving an idle instruction, the coordination controller is specifically configured to:

5. The system for syngas production and methanol synthesis with cooperation of PEM and SOEC according to claim 1, characterized in that, ​ reducing the load of the SOEC electrolysis unit and the PEM methanator unit, and stopping the feed of the methanol synthesis reactor, so that the methanol synthesis reactor enters a hot standby state and is purged with a protective gas; when the SOEC electrolysis unit stops electrolysis, controlling the SOEC electrolysis unit to enter a hot standby state and remain at an operating temperature, and purging with a protective gas; when the PEM methanator unit stops electrolysis, controlling the PEM methanator unit to remain in a hot standby state; controlling the PSA decarbonization unit to stop circulation and remain in a standby state.

6. The system for syngas production and methanol synthesis with cooperation of PEM and SOEC according to claim 1, characterized in that, Upon receiving a shutdown instruction, the coordination controller is specifically configured to: cut off the power supply of the PEM methanator unit and the SOEC unit; stop delivering synthesis gas to the methanol synthesis reactor and perform a safe pressure relief; perform an inert gas purge on the methanol synthesis reactor; cool down the SOEC electrolysis unit, and purge the fuel electrode of the SOEC electrolysis unit with a reducing protective gas; when the temperatures of the SOEC electrolysis unit and the methanol synthesis reactor drop to a safe state, completely power off and close all valves.

7. The system for syngas production and methanol synthesis with cooperation of PEM and SOEC according to claim 1, characterized in that, Upon detecting a fault, the coordination controller controls the system to shut down urgently.

8. The system for the production of syngas and methanol synthesis by cooperation of PEM and SOEC according to claim 7, characterized in that, When the system shuts down urgently, the coordination controller is specifically configured to: cut off the power supply of the PEM methanator unit and the SOEC unit, and purge the SOEC electrolysis unit with a reducing protective gas; close the gas inlet valve of the PSA decarbonization unit; close the synthesis gas inlet valve of the methanol synthesis reactor; perform an emergency cooling on the methanol synthesis reactor, and perform an inert gas purge on the methanol synthesis reactor.

9. The system for syngas production and methanol synthesis with cooperation of PEM and SOEC according to claim 1, characterized in that, Further comprising a rectification unit and a methanol storage; the feed end of the rectification unit is connected to the crude methanol output end of the methanol synthesis reactor, for rectification processing of the crude methanol to obtain refined methanol; the feed end of the methanol storage is connected to the refined methanol output end of the rectification unit, for storing refined methanol.

10. A method of producing methanol using the system according to any one of claims 1 to 9, characterized in that, comprising: driving a PEM methanator unit to perform an electrolysis water reaction to generate H2 by renewable electricity; utilizing a SOEC electrolysis unit to electrolyze CO2 at high temperature to generate a mixed gas of CO and CO2; utilizing a PSA decarbonization unit to remove CO2 in the mixed gas to output purified CO; utilizing a mixer to mix CO and H2 to generate synthesis gas; utilizing a methanol synthesis reactor to catalytically generate methanol from the synthesis gas; utilizing a coordination controller to coordinate and control the working states of the PEM methanator unit, the SOEC electrolysis unit, the PSA decarbonization unit, and the methanol synthesis reactor, so that the system switches between a start-up state, a normal operation state, an idle state, a shutdown state, and an emergency shutdown state.

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