A multi-source waste heat dynamically coupled steady-state ammonia decomposition hydrogen production system and control method

Abstract

The present application belongs to hydrogen production technology field, provide a kind of multi-source waste heat dynamic coupling's steady-state ammonia decomposition hydrogen production system and control method, including hydrogen production branch, waste heat control branch and controller, controller is according to the pressure difference of coke oven raw gas pipeline and converter gas pipeline, temperature data, adjust the opening of corresponding flow regulating valve, realize static pressure decoupling and steady-state mixed temperature, according to heat carrier temperature and ammonia purity, first intelligent distribution three-way valve opening ratio is adjusted, realize the dynamic distribution of waste heat energy, through the priority arbitration mechanism of outlet residual ammonia concentration sensor and intelligent three-way valve, priority guarantee the heat balance of reaction zone, even in extreme fluctuation working condition, also can ensure product hydrogen purity standard through load follow-up adjustment, meet the stringent requirements of downstream hydrogen-based shaft furnace to reducing gas quality, the present application is through waste heat cascade utilization and dynamic coupling's steady-state ammonia decomposition hydrogen production method, reduce energy consumption, improve the utilization efficiency of energy-saving hydrogen.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production technology, specifically relating to a steady-state ammonia decomposition hydrogen production system and control method with dynamic coupling of multiple waste heat sources. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Currently, the vast majority of steel mills worldwide use the blast furnace-converter long-process technology, with coke as the core reducing agent. However, the traditional steel industry is one of the main sources of carbon emissions, accounting for 7-9% of global emissions. To address climate change, the steel industry is seeking fundamental technological changes, such as replacing coke with hydrogen for iron ore reduction. This is expected to reduce carbon dioxide emissions by more than 500,000 tons annually, demonstrating the crucial role of hydrogen in green metallurgy.

[0004] Currently, there are two main technological approaches: hydrogen-rich blast furnace smelting and hydrogen-based direct reduced iron (DRI) + electric arc furnace. Both approaches require a large amount of hydrogen; the entire process revolves around hydrogen.

[0005] However, the existing hydrogen production and supply system faces bottlenecks: industrial iron smelting for hydrogen production mostly uses coke oven gas, consuming large amounts of fossil fuels and generating significant carbon emissions, classifying it as "grey hydrogen"; the storage and transportation of pure hydrogen relies on high-pressure gas or liquid forms, resulting in low hydrogen density and requiring large high-pressure containers or long-tube trailers for transport, leading to low efficiency and safety hazards. In contrast, ammonia, as a mature hydrogen energy carrier, is easily liquefiable (-33℃) and has a high volumetric energy density (108 kg-H2 / m³). 3 Ammonia (NH3) is considered an ideal storage and transportation medium in the hydrogen energy field due to its advantages such as low manufacturing and storage costs (17.8 wt.%) and no CO2 production during combustion. Therefore, green ammonia can be synthesized through various methods, then decomposed in situ at steel plants to generate hydrogen, which is then purified and collected before being fed into a hydrogen-based vertical shaft furnace to reduce iron ore. The core process, ammonia thermal cracking, requires temperatures above 550°C under catalytic conditions, resulting in significant energy consumption. Meanwhile, many energy-intensive industries (such as steel and chemical industries) generate large amounts of high-, medium-, and low-temperature waste heat (200-1000°C). This waste heat is of poor quality, uneconomical, and exhibits drastic temperature fluctuations and pressure mismatches, often resulting in direct emissions and substantial energy waste. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a steady-state ammonia decomposition hydrogen production system and control method based on dynamic coupling of multi-source waste heat. This invention reduces energy consumption and improves the utilization efficiency of energy-saving hydrogen by utilizing waste heat in stages and dynamically coupling steady-state ammonia decomposition hydrogen production.

[0007] According to some embodiments, the present invention adopts the following technical solution: A multi-source waste heat dynamically coupled steady-state ammonia decomposition hydrogen production system includes a hydrogen production branch, a waste heat control branch, and a controller. The hydrogen production branch includes a liquid ammonia storage and supply unit, a first ammonia preheating evaporator, a second ammonia preheating evaporator, an internal regenerative heat exchanger, a microchannel pyrolysis reactor, and a hydrogen-nitrogen separation and purification unit, wherein: The liquid ammonia storage and supply unit provides liquid ammonia to the first ammonia preheating evaporator. The first ammonia preheating evaporator is used to realize the phase change heat absorption, vaporization and preliminary preheating of liquid ammonia. The resulting gaseous ammonia enters the second ammonia preheating evaporator for reheating. The reheated gaseous ammonia enters the internal regenerative heat exchanger for final preheating. The final preheated gaseous ammonia then enters the microchannel pyrolysis reactor for ammonia decomposition to produce hydrogen. The high-temperature hydrogen-nitrogen mixture after decomposition enters the hot gas channel of the internal heat exchanger to reheat the reheated gaseous ammonia. Finally, it enters the hydrogen-nitrogen separation and purification unit for separation and purification to obtain hydrogen with a purity higher than the set value. The waste heat control branch includes an industrial waste heat collector, which includes a high-temperature waste heat collector and a medium-low temperature waste heat collector. The high-temperature waste heat collector is equipped with a coke oven gas pipeline and a converter gas pipeline. Each pipeline is equipped with a temperature sensor, a pressure sensor and a flow regulating valve. The outlets of the two pipelines are connected to a first multi-source waste heat dynamic mixing box for mixing waste heat flue gas with different pressures and temperatures. The mixed steady-state heat carrier is distributed by a first intelligent three-way valve and enters a microchannel pyrolysis reactor and a second multi-source waste heat dynamic mixing box to reheat the initially preheated ammonia. The medium-low temperature waste heat collector is connected to the first ammonia preheating evaporator through an independent pipeline to form a low temperature compensation loop. The independent pipeline is equipped with a temperature sensor and a flow regulating valve. The controller connects to various temperature sensors, pressure sensors, flow regulating valves, and a first intelligent distribution three-way valve. It is used to adjust the opening of the corresponding flow regulating valve based on the pressure difference and temperature data between the coke oven gas pipeline and the converter gas pipeline, thereby achieving static pressure decoupling and steady-state temperature mixing. Based on the heat carrier temperature and ammonia purity, it adjusts the opening ratio of the first intelligent distribution three-way valve to achieve dynamic distribution of waste heat energy.

[0008] As an alternative implementation, the first ammonia preheating evaporator is a falling film ammonia preheating evaporator, which includes a liquid ammonia evaporation hot gas channel and a liquid ammonia evaporation cold gas channel. The liquid ammonia evaporation hot gas channel is used for the flow of industrial secondary high temperature waste heat, and the liquid ammonia evaporation cold gas channel is used for the flow of liquid ammonia to be vaporized. The second ammonia preheating evaporator is a plate-fin ammonia preheating evaporator, which is divided into a plate-fin first heat exchange hot gas channel, a plate-fin second heat exchange hot gas channel, and a plate-fin cold gas channel. The three channels are physically isolated and the heat exchange is non-contact. The plate-fin first hot gas channel carries the high-temperature hydrogen-nitrogen mixed gas from the outlet of the internal regenerative heat exchange hot gas channel. The plate-fin second hot gas channel carries the high-temperature flue gas from the outlet of the second multi-source waste heat dynamic mixing box. The plate-fin cold gas channel carries the ambient temperature ammonia gas from the first ammonia preheating evaporator.

[0009] As an alternative implementation, the internal regenerative heat exchanger is divided into an internal regenerative heat exchange hot gas channel and an internal regenerative heat exchange cold gas channel. The hot gas channel carries the high-temperature hydrogen-nitrogen mixture from the outlet of the microchannel pyrolysis reactor, while the cold gas channel carries gaseous ammonia from the outlet of the second ammonia preheating evaporator.

[0010] As an alternative implementation, the microchannel pyrolysis reactor includes a microchannel pyrolysis reaction channel and a microchannel pyrolysis heating channel. The microchannel pyrolysis heating channel is connected to the industrial high-temperature waste heat flue gas at the reactor outlet in the first intelligent distribution three-way valve. The microchannel pyrolysis reaction channel is filled with a catalyst for transporting gaseous ammonia. A residual ammonia concentration sensor is installed at the outlet of the microchannel pyrolysis reactor. The flue gas in the microchannel pyrolysis heating channel enters the second multi-source waste heat dynamic mixing box, and after the mixing temperature stabilizes, it enters the plate-fin type second heat exchange hot gas channel. Finally, the low-temperature flue gas enters the waste gas treatment device.

[0011] As an alternative implementation, the coke oven raw gas pipeline is equipped with a first temperature sensor, a first branch pressure sensor, and a first branch flow regulating valve; the converter gas pipeline is equipped with a second temperature sensor, a second branch pressure sensor, and a second branch flow regulating valve. The outlets of the two pipes are connected to the first multi-source waste heat dynamic mixing box. The first multi-source waste heat dynamic mixing box is equipped with staggered baffles inside to mix waste heat flue gas with different pressures and temperatures. The outlet pipe is equipped with a mixing output temperature sensor and a mixing output pressure sensor.

[0012] As an alternative implementation, the first intelligent distribution three-way valve has two outlets, namely the reactor outlet and the evaporator outlet. The reactor outlet is connected to the microchannel pyrolysis heating channel to heat the reaction. The evaporator outlet and the hot side outlet of the microchannel pyrolysis heating channel merge and are connected to the second multi-source waste heat dynamic mixing box to reheat the initially preheated ammonia after stabilization. The independent pipeline of the medium and low temperature waste heat collector is equipped with a third temperature sensor and a low temperature supply branch flow control valve.

[0013] The control method based on the above system includes the following steps: Pressure self-balancing control: Real-time monitoring of the static pressure of the coke oven raw gas pipeline and the converter gas pipeline. When the pressure difference between the two pipelines exceeds the threshold, the pressure balancing algorithm is activated to adjust the opening of the flow regulating valves of the two pipelines and eliminate pressure oscillations using the first multi-source waste heat dynamic mixing box. Temperature control: Based on the real-time readings of the temperature sensors of the two pipelines and the preset temperature-enthalpy mapping table, the mass flow ratio of the two flue gases is calculated. Through the coordinated action of the two flow regulating valves, the mixed output temperature sensor value at the outlet of the first multi-source waste heat dynamic mixing chamber is kept stable at the preset target reaction temperature. Dynamic energy gradient distribution: When the temperature fluctuation of the heat carrier is detected to be greater than the set value, a feedforward command is issued in advance to the first intelligent distribution three-way valve to adjust the valve core opening ratio and increase the proportion of flow to the microchannel pyrolysis heating channel, so as to ensure that the heat flux of the core reaction zone is maintained above the heat absorption equilibrium point. Product purity driven control: The residual ammonia concentration at the outlet of the microchannel pyrolysis reactor is detected. When the residual ammonia concentration deviates from the preset concentration threshold, the first intelligent distribution three-way valve is controlled to forcibly close the branch leading to the second ammonia preheating evaporator, so that all steady-state heat carriers are pressed towards the microchannel pyrolysis reactor.

[0014] As an alternative implementation, when the pressure difference exceeds the safety threshold, the pressure self-balancing control command takes precedence over the temperature control command. During the pressure self-balancing stage, the venturi effect generated by the high-pressure fluid is used to carry the flue gas from the converter gas pipeline in, preventing backflow of the flue gas. The energy-mass ratio calculation algorithm is used to calculate and adjust the flow distribution ratio between the coke oven raw gas pipeline and the converter gas pipeline in real time based on the target mixing temperature and the enthalpy conservation equation, combined with the specific heat capacity fitting function method.

[0015] As an alternative implementation, in order to prevent insufficient ammonia preheating caused by the product purity drive control during the product purity drive control process, the flow control valve of the low-temperature supply branch is simultaneously increased, and the low-grade heat energy of the medium-low temperature waste heat collector is used to supplement the heat of the first ammonia preheating evaporator.

[0016] As an alternative implementation, it also includes: When all control and regulation measures reach their limits and still cannot reduce the residual ammonia concentration, adjust the liquid ammonia feed regulating valve to reduce the feed flow rate. By reducing the system load and extending the residence time of ammonia in the microchannel pyrolysis reaction channel, forced compliance with emission standards can be achieved. The system compares the relationship between the current temperature of the microchannel pyrolysis reactor, the liquid ammonia feed rate, and the residual ammonia concentration of the product in real time. When the mixed temperature output temperature sensor is in the set high temperature range, the liquid ammonia feed regulating valve opening is normal or less than the set value, and the residual ammonia concentration sensor detection value at the outlet is continuously higher than the set safety upper limit, the catalyst is determined to be abnormal, and the first intelligent distribution three-way valve is adjusted to further increase the reaction temperature. If the residual ammonia concentration still cannot be restored, a catalyst replacement command is issued.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention significantly reduces hydrogen production energy consumption and carbon emissions: Through multi-stage waste heat utilization throughout the entire process, it completely replaces the traditional electric heating or combustion heating mode. High-grade waste heat is used to drive chemical reactions, and medium- and low-temperature waste heat is responsible for material phase changes, realizing "on-demand distribution" and "pressurized recovery" of energy, which greatly reduces the unit production cost and carbon footprint of hydrogen.

[0018] (2) The present invention has extremely high system operation stability: In response to the pain point of drastic fluctuations in industrial waste heat sources (such as converter flue gas), a dynamic mixing box with baffles and a static pressure decoupling algorithm are introduced. Feedforward regulation is achieved through the "temperature-enthalpy lookup table method" so that the heat carrier entering the reactor always maintains a steady state, ensuring the constant purity of hydrogen production and solving the problem of industrial waste heat being "unusable and unacceptable".

[0019] (3) This invention improves the flexibility of green hydrogen production: it realizes hydrogen production by cracking ammonia on site, without relying on long-distance pipeline transportation or purchasing high-pressure hydrogen. The hydrogen production can be dynamically adjusted according to the steelmaking load, and the production is highly flexible. It can respond quickly when hydrogen demand fluctuates, avoiding hydrogen storage and transportation bottlenecks.

[0020] (4) The present invention achieves a dual improvement in catalyst economy and lifespan: by using Ni-based and Ru-based catalysts in graded loading and combining them with online poisoning warning logic, the amount of precious metals used is reduced, and the catalyst is "thermally regenerated" online by automatically adjusting temperature and pressure conditions, which effectively extends the maintenance cycle of the reactor.

[0021] (5) The present invention achieves a reliable supply of high-purity hydrogen: through the priority arbitration mechanism composed of the outlet residual ammonia concentration sensor and the intelligent three-way valve, the thermal balance of the reaction zone is guaranteed first. Even under extreme fluctuation conditions, the purity of the product hydrogen can be guaranteed by load follow-up adjustment, which meets the stringent requirements of the downstream hydrogen-based vertical furnace for the quality of reducing gas.

[0022] This invention has significant application value in reducing hydrogen production costs, improving industrial energy efficiency, and realizing low-carbon steelmaking.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This is a structural diagram of a steady-state ammonia decomposition hydrogen production system with dynamic coupling of multiple waste heat sources in one embodiment; The thick solid line represents the ammonia material line, the thin solid line represents the waste heat line, and the dotted line represents the signal line. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0030] Example 1 A multi-source waste heat dynamically coupled steady-state ammonia decomposition hydrogen production system includes: a material end and a waste heat end, wherein: like Figure 1As shown, the liquid ammonia storage and supply unit 1 at the material end includes a liquid ammonia storage tank and pipeline system, equipped with a liquid ammonia pump and regulating valve. Liquid ammonia undergoes phase change heat absorption, vaporization, and preliminary preheating via a first falling film ammonia preheating evaporator 2. This evaporator is divided into a liquid ammonia evaporation hot gas channel 21 and a liquid ammonia evaporation cold gas channel 22. The hot gas channel carries industrial secondary high-temperature waste heat, such as radiant heat from hot-rolled steel billets and hot blast furnace tail gas, at approximately 200-400°C. The cold gas channel carries the liquid ammonia to be vaporized. The vaporized ammonia then enters a second plate-fin ammonia preheating evaporator 3 for further preheating, reaching a vaporized temperature of 400-500°C. This second plate-fin heat exchanger is divided into a first plate-fin heat exchange hot gas channel 31 and a second plate-fin heat exchange hot gas channel 32. The gas channel 32 and the plate-fin heat exchanger cold gas channel 33 are connected. The first hot gas channel carries the 400-600℃ high-temperature hydrogen-nitrogen mixed gas from the outlet of the internal regenerative heat exchanger hot gas channel 41. The second hot gas channel carries the high-temperature flue gas from the outlet of the second multi-source waste heat dynamic mixing box 92. The cold gas channel carries the room-temperature gaseous ammonia from the evaporator 2. Then the gaseous ammonia enters the internal regenerative heat exchanger 4 for final preheating. It is divided into the internal regenerative heat exchanger hot gas channel 41 and the internal regenerative heat exchanger cold gas channel 42. The hot gas channel carries the 600-700℃ high-temperature hydrogen-nitrogen mixed gas from the outlet of the microchannel pyrolysis reactor 5. The cold gas channel carries the 400-500℃ gaseous ammonia from the outlet of the second plate-fin ammonia preheating evaporator 3.

[0031] The preheated gaseous ammonia then enters the microchannel pyrolysis reactor 5 for ammonia decomposition to produce hydrogen. The reactor is divided into a microchannel pyrolysis reaction channel 51 and a microchannel pyrolysis heating channel 52. The heating channel is connected to the 750-900℃ industrial high-temperature waste heat flue gas at the reactor outlet in the first intelligent distribution three-way valve 10, while the reaction channel is filled with catalyst and carries gaseous ammonia.

[0032] The decomposed high-temperature hydrogen-nitrogen mixture will enter the internal heat exchanger hot gas channel 41 to reheat the reheated ammonia gas. Then it will enter the second plate-fin type ammonia preheating first heat exchange hot gas channel 31, and finally enter the hydrogen-nitrogen separation and purification unit 6 to separate and purify high-purity hydrogen gas. The method used can be PSA pressure swing adsorption or membrane separation technology, etc. Finally, this high-purity hydrogen gas will enter the hydrogen-based vertical furnace 7 for industrial smelting.

[0033] In this embodiment, different types of catalysts can be selected based on cost and activity requirements. Highly active ruthenium-based catalysts can operate at lower temperatures (650–700°C), but are more expensive; inexpensive nickel-based catalysts are commonly used industrially for cracking conditions above 800°C. In addition, iron-based or cobalt-based catalysts, or alloy catalysts such as Ni-Fe, Ni-Cu-Fe, and Fe-Cr can also be used. In addition to the type of catalyst, this invention also proposes to achieve economic savings and efficiency improvement through catalyst gradation. In the first half of the microchannel pyrolysis reactor 5, cheaper nickel-based and iron-based catalysts are used, while in the second half, ruthenium-based catalysts are used. This not only improves the ammonia decomposition efficiency and reduces the ammonia concentration at the reactor outlet, but also reduces the amount of precious metals used, alleviates the poisoning of ruthenium-based catalysts, and enables longer service life. For the second plate-fin ammonia preheating evaporator 3, the three heat exchange channels are physically isolated and non-contact heat exchange. For flue gas flow, the 550-700°C flue gas from the microchannel pyrolysis heating channel 52 enters the second multi-source waste heat dynamic mixing box 92. After the mixing temperature stabilizes, it enters the plate-fin second heat exchange hot gas channel 32, and finally, the low-temperature flue gas at 100-200°C enters the waste gas treatment device 11.

[0034] Waste heat sources: Traditional steel plants: raw coal gas from coke ovens, converters, and blast furnaces; radiant heat from hot-rolled steel billets. Chemical plants: flue gas from synthesis reactors and catalytic cracking units. Building materials plants: flue gas from the kiln head and tail of cement rotary kilns. The temperature range of waste heat should be determined through investigation (e.g., high-temperature range: 650-900°C; medium-low temperature range: 200-400°C).

[0035] The system includes an industrial waste heat collector 8, which collects high-temperature waste heat from coke oven gas, converter gas, and blast furnace exhaust gas through devices such as high-temperature heat pipes, radiant heat exchangers, and ceramic regenerators; and collects medium- and low-temperature waste heat from the process through flue gas heat exchangers or thermal oil circulation systems. Therefore, it can be divided into a high-temperature waste heat collector 81 and a medium- and low-temperature waste heat collector 82. The high-temperature waste heat collector 81 has two pipes: a coke oven gas pipe 811 and a converter gas pipe 812. The coke oven gas heat source is relatively continuous and stable, while the converter flue gas is a periodic intermittent heat source, extremely hot during blowing and cold when not blowing.

[0036] A first temperature sensor 201, a first branch pressure sensor 301, and a first branch flow regulating valve 401 are installed in the coke oven gas pipeline 811. A second temperature sensor 202, a second branch pressure sensor 302, and a second branch flow regulating valve 402 are installed in the converter gas pipeline 812. The outlets of these two pipelines are connected to a first multi-source waste heat dynamic mixing chamber 91, which has staggered baffles inside to mix waste heat flue gas with different pressures and temperatures. A mixing output temperature sensor 204 and a mixing output pressure sensor 303 are installed on its outlet pipeline. The mixed, stable heat carrier enters a first intelligent distribution three-way valve 10. This valve is a high-temperature proportional regulating three-way heat exchange valve, which includes a valve body, a high-temperature resistant valve core, and an integrated servo actuator. The valve body adopts a three-way Y-type or T-type design. The flow channel structure provides two outlets: a reactor outlet and an evaporator outlet. The reactor outlet is connected to the microchannel pyrolysis heating channel 52 to heat the reaction. The evaporator outlet and the hot-side outlet of the microchannel pyrolysis heating channel 52 merge and are connected to the second multi-source waste heat dynamic mixing box 92, which reheats the initially preheated ammonia after stabilization.

[0037] The medium-low temperature waste heat collector 82 is connected to the falling film liquid ammonia evaporation hot gas channel 21 through an independent pipeline to form a low temperature compensation loop. A third temperature sensor 203 and a low temperature supply branch flow control valve 403 are installed on the pipeline.

[0038] In this embodiment, each flow regulating valve is an electro-pneumatic proportional regulating valve, equipped with a high-precision intelligent electric positioner and displacement sensor. It can receive standard analog control signals (such as 4-20mA) from the central control module 101 and then transmit the actual opening signal back to the analog input module of the central control system, achieving continuous and precise adjustment and distribution of fluid mass flow rate at various points. The first intelligent distribution three-way valve 10 works similarly, enabling equal percentage flow distribution in both outlet directions, thereby completing the dynamic decoupling scheduling of energy from the steady-state heat carrier to the chemical reaction zone and phase change zone.

[0039] This embodiment provides a control method that achieves dynamic decoupling and precise matching between industrial waste heat energy input and ammonia cracking chemical requirements through a multi-dimensional logic control program integrated in the central control module 101. The specific control logic is as follows: Static pressure decoupling and steady-state mixing logic (safety self-balancing logic): The central control module 101 first monitors the static pressure of the coke oven raw gas pipeline 811 and the converter gas pipeline 812 in real time through the pressure sensors of the first and second branches. When the pressure difference between the two branches exceeds the threshold, the central control module 101 activates the pressure balance algorithm, prioritizing the adjustment of the opening of the flow regulating valves of the first and second branches, and using the internal volume and baffle structure of the first multi-source waste heat dynamic mixing box 91 to eliminate pressure oscillations, thereby eliminating the mechanical conditions for backflow from the source; based on the real-time readings of the first and second temperature sensors, the central control module 101 retrieves the built-in temperature-enthalpy (Th) mapping table, automatically calculates the mass flow ratio of the two flue gas lines, and through the coordinated action of the flow regulating valves of the first and second branches, ensures that the mixing output temperature sensor 204 at the outlet of the first multi-source waste heat dynamic mixing box 91 is stable at the preset target reaction temperature, such as any temperature in the range of 800-850℃. When the pressure difference exceeds the safety threshold, the pressure balance command takes precedence over the temperature control command.

[0040] Here it is explained that during the pressure self-balancing stage, the ejector structure can also utilize the Venturi effect generated by high-pressure fluid to draw in the flue gas from the second branch, preventing backflow of the flue gas; the energy-mass ratio calculation algorithm uses the enthalpy conservation equation based on the target mixing temperature: q m1 C p1 T1+q m2 C p2 T2=(q m1 +q m2 C pmix T set The flow distribution ratio between coke oven raw gas pipeline 811 and converter gas pipeline 812 is calculated and adjusted in real time using the specific heat capacity fitting function method.

[0041] Dynamic energy gradient allocation logic (feedforward regulation logic): When the second temperature sensor 202 and the mixing output temperature sensor 204 detect significant fluctuations in the heat carrier temperature due to industrial conditions (such as a converter not being blown), the central control module 101 does not wait for the internal temperature of the reactor to drop, but instead issues a feedforward command to the first intelligent distribution three-way valve 10 in advance. The valve core opening ratio of the three-way valve 10 is adjusted through an internal servo actuator to increase the flow rate to the microchannel pyrolysis heating channel 52, ensuring that the heat flux in the core reaction zone remains above the heat absorption equilibrium point.

[0042] Product purity driven priority arbitration logic (feedback adjustment logic): The system uses the real-time signal of the outlet residual ammonia concentration sensor 501 as the highest priority judgment criterion, and executes the priority arbitration logic. The criterion is that the heat supply priority of the microchannel pyrolysis reactor 5 is greater than the reheating priority of the plate-fin ammonia preheating evaporator 3. When the outlet residual ammonia concentration sensor 501 detects that the residual ammonia concentration deviates from the preset concentration threshold, the central control module 101 determines that the reaction energy is insufficient. At this time, the central control module 101 instructs the first intelligent three-way valve 10 to forcibly close the branch leading to the second plate-fin ammonia preheating evaporator 3, and pressurize all the steady-state heat carrier to the microchannel pyrolysis reactor 5. To prevent the above actions from causing insufficient preheating of gaseous ammonia, the central control module 101 simultaneously increases the flow control valve 403 of the low-temperature supply branch, and uses the low-grade heat energy of the medium-low temperature waste heat collector 82 to supplement the heat of the first falling film ammonia preheating evaporator 2, thereby freeing up high-grade heat energy to prioritize the pyrolysis reaction.

[0043] Load responsiveness and safety protection logic: When the above heat regulation methods reach their limit (such as when the first intelligent three-way valve 10 is fully open to the reactor side) and still cannot reduce the residual ammonia concentration, the central control module 101 instructs the liquid ammonia feed regulating valve 404 to reduce the feed flow rate. By reducing the system load and extending the residence time of ammonia in the microchannel pyrolysis reaction channel 51, forced compliance with emission standards is achieved.

[0044] Catalyst activity online monitoring and poisoning early warning logic: A three-dimensional benchmark model of "temperature-load-conversion rate" is established through simulation experiments. The central control module 101 compares the relationship between the current reactor temperature (Tmix), liquid ammonia feed rate and the product residual ammonia concentration (Q1) of the outlet residual ammonia concentration sensor 501 in real time. When the following characteristics are met: (1) the detection value of the mixed temperature output temperature sensor 204 is in the rated high temperature range; (2) the opening of the liquid ammonia feed regulating valve 404 is normal or small; (3) when the detection value of the outlet residual ammonia concentration sensor 501 is continuously higher than the set safety limit, the central control module 101 determines that the system efficiency reduction is not due to insufficient energy supply, but due to the deactivation or poisoning of the catalyst in the microchannel cracking reactor 5. Then, the "catalyst abnormality alarm signal" is triggered, and the first intelligent distribution three-way valve 10 is adjusted to further increase the reaction temperature and attempt to regenerate and revive through high temperature; if the residual ammonia concentration still cannot be restored, the "replace catalyst" command is issued to prevent unqualified hydrogen from entering the downstream hydrogen-based vertical furnace 7.

[0045] To further illustrate the dynamic adjustment capability of the present invention under complex and varied industrial waste heat conditions, a table of adjustment logic action associations of the system under different typical conditions in this embodiment is provided, as shown in Table 1.

[0046] Table 1 Working conditions Key sensor input Adjustment Actions: 401 / 402 / 403 (Branch Flow Control Valve) Adjustment action: 10 (three-way distribution valve) Adjustment action: 404 (feed valve) Technical effect Heat source fluctuation (converter blowing) <![CDATA[T mix >1100℃]]> Increase the opening of the low-temperature branch valve to perform cold dilution. Increase the flue gas volume at the evaporator outlet Keep unchanged Stabilize the reactor inlet temperature to prevent catalyst sintering at high temperatures. Insufficient heat source (production interruption) <![CDATA[T mix <700℃]]> Fully open the high-temperature branch circuit, and partially close the medium- and low-temperature branch circuits. Forced allocation: 100% of flue gas is directed to the reactor (5) Simultaneously reduce ammonia feed rate Sacrifice yield to maintain purity and ensure reaction depth. Product purity is abnormal (ammonia exceeds the standard). <![CDATA[Q 1（501） >100ppm]]> constant Strip the evaporator of heat and supply it to the reactor. Keep unchanged Rapidly restore catalytic efficiency. Stress instability Pressure difference greater than 10 kPa The static pressure balance algorithm is activated to dynamically adjust the valve openings of the two branches (401, 402). Keep unchanged Keep unchanged Eliminate the safety hazard of backflow of high-temperature media. Suspected catalyst poisoning <![CDATA[Q 1（501） Higher and T mix Meets the standards Keep unchanged Command valve to attempt instantaneous ultra-high temperature operation (thermal regeneration) Issue alarm command The system prompts for catalyst replacement to ensure long-term energy efficiency.

[0047] Example 2 The difference between this embodiment and Embodiment 1 is that the high-temperature waste heat collector 81 is not limited to collecting coke oven and converter flue gas, but can also be connected to the exhaust flue of cement rotary kiln, ceramic kiln or chemical catalytic cracking unit by replacing the front-end heat exchange components.

[0048] In addition, the first intelligent distribution three-way valve 10 and each flow regulating valve can be driven by a pneumatic diaphragm head in addition to electric servo drive, and can be used with a pneumatic positioner to adapt to industrial sites with higher explosion-proof ratings.

[0049] In some embodiments, the first falling film ammonia preheating evaporator 2 and the second plate-fin ammonia preheating evaporator 3 can be replaced by a falling film or plate-fin structure with a sleeve type, a wound tube type, or other compact heat exchange devices with multi-stream heat exchange capabilities.

[0050] In some embodiments, the following modifications can also be made: in addition to pressure swing adsorption (PSA) technology, the hydrogen-nitrogen separation and purification unit 6 can also use palladium membrane (Pd-alloy) separation technology or cryogenic separation technology to meet different production scale requirements.

[0051] With the above alternative solutions, the present invention can adapt to various heat source conditions, and the process configuration and separation and extraction device have strong flexibility, thereby ensuring that ammonia cracking to produce hydrogen can be achieved efficiently and economically under different steel plant sites and production conditions.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A steady-state ammonia decomposition hydrogen production system with dynamic coupling of multiple waste heat sources, characterized in that, It includes a hydrogen production branch, a waste heat control branch, and a controller. The hydrogen production branch includes a liquid ammonia storage and supply unit, a first ammonia preheating evaporator, a second ammonia preheating evaporator, an internal regenerative heat exchanger, a microchannel pyrolysis reactor, and a hydrogen-nitrogen separation and purification unit, wherein: The liquid ammonia storage and supply unit provides liquid ammonia to the first ammonia preheating evaporator. The first ammonia preheating evaporator is used to realize the phase change heat absorption, vaporization and preliminary preheating of liquid ammonia. The resulting gaseous ammonia enters the second ammonia preheating evaporator for reheating. The reheated gaseous ammonia enters the internal regenerative heat exchanger for final preheating. The final preheated gaseous ammonia then enters the microchannel pyrolysis reactor for ammonia decomposition to produce hydrogen. The high-temperature hydrogen-nitrogen mixture after decomposition enters the hot gas channel of the internal heat exchanger to reheat the reheated gaseous ammonia. Finally, it enters the hydrogen-nitrogen separation and purification unit for separation and purification to obtain hydrogen with a purity higher than the set value. The waste heat control branch includes an industrial waste heat collector, which includes a high-temperature waste heat collector and a medium-low temperature waste heat collector. The high-temperature waste heat collector is equipped with a coke oven gas pipeline and a converter gas pipeline. Each pipeline is equipped with a temperature sensor, a pressure sensor and a flow regulating valve. The outlets of the two pipelines are connected to a first multi-source waste heat dynamic mixing box for mixing waste heat flue gas with different pressures and temperatures. The mixed steady-state heat carrier is distributed by a first intelligent three-way valve and enters a microchannel pyrolysis reactor and a second multi-source waste heat dynamic mixing box to reheat the initially preheated ammonia. The medium-low temperature waste heat collector is connected to the first ammonia preheating evaporator through an independent pipeline to form a low temperature compensation loop. The independent pipeline is equipped with a temperature sensor and a flow regulating valve. The controller connects to various temperature sensors, pressure sensors, flow regulating valves, and a first intelligent distribution three-way valve. It is used to adjust the opening of the corresponding flow regulating valve based on the pressure difference and temperature data between the coke oven gas pipeline and the converter gas pipeline, thereby achieving static pressure decoupling and steady-state temperature mixing. Based on the heat carrier temperature and ammonia purity, it adjusts the opening ratio of the first intelligent distribution three-way valve to achieve dynamic distribution of waste heat energy.

2. The steady-state ammonia decomposition hydrogen production system with dynamic coupling of multiple waste heat sources as described in claim 1, characterized in that, The first ammonia preheating evaporator is a falling film ammonia preheating evaporator, which includes a liquid ammonia evaporation hot gas channel and a liquid ammonia evaporation cold gas channel. The liquid ammonia evaporation hot gas channel is used for the flow of industrial secondary high temperature waste heat, and the liquid ammonia evaporation cold gas channel is used for the flow of liquid ammonia to be vaporized. The second ammonia preheating evaporator is a plate-fin ammonia preheating evaporator, which is divided into a plate-fin first heat exchange hot gas channel, a plate-fin second heat exchange hot gas channel, and a plate-fin cold gas channel. The three channels are physically isolated and the heat exchange is non-contact. The plate-fin first hot gas channel carries the high-temperature hydrogen-nitrogen mixed gas from the outlet of the internal regenerative heat exchange hot gas channel. The plate-fin second hot gas channel carries the high-temperature flue gas from the outlet of the second multi-source waste heat dynamic mixing box. The plate-fin cold gas channel carries the ambient temperature ammonia gas from the first ammonia preheating evaporator.

3. The steady-state ammonia decomposition hydrogen production system with dynamic coupling of multiple waste heat sources as described in claim 1, characterized in that, The internal regenerative heat exchanger is divided into an internal regenerative heat exchange hot gas channel and an internal regenerative heat exchange cold gas channel. The hot gas channel carries the high-temperature hydrogen-nitrogen mixture from the outlet of the microchannel pyrolysis reactor, while the cold gas channel carries gaseous ammonia from the outlet of the second ammonia preheating evaporator.

4. The steady-state ammonia decomposition hydrogen production system with dynamic coupling of multiple waste heat sources as described in claim 1, characterized in that, The microchannel pyrolysis reactor includes a microchannel pyrolysis reaction channel and a microchannel pyrolysis heating channel. The microchannel pyrolysis heating channel is connected to the industrial high-temperature waste heat flue gas at the reactor outlet in the first intelligent distribution three-way valve. The microchannel pyrolysis reaction channel is filled with a catalyst for transporting gaseous ammonia. A residual ammonia concentration sensor is installed at the outlet of the microchannel pyrolysis reactor. The flue gas in the microchannel pyrolysis heating channel enters the second multi-source waste heat dynamic mixing box, and after the mixing temperature stabilizes, it enters the plate-fin type second heat exchange hot gas channel. Finally, the low-temperature flue gas enters the waste gas treatment device.

5. The steady-state ammonia decomposition hydrogen production system with dynamic coupling of multiple waste heat sources as described in claim 1, characterized in that, The coke oven raw gas pipeline is equipped with a first temperature sensor, a first branch pressure sensor, and a first branch flow regulating valve; the converter gas pipeline is equipped with a second temperature sensor, a second branch pressure sensor, and a second branch flow regulating valve. The outlets of the two pipes are connected to the first multi-source waste heat dynamic mixing box. The first multi-source waste heat dynamic mixing box is equipped with staggered baffles inside to mix waste heat flue gas with different pressures and temperatures. The outlet pipe is equipped with a mixing output temperature sensor and a mixing output pressure sensor.

6. The steady-state ammonia decomposition hydrogen production system with dynamic coupling of multiple waste heat sources as described in claim 1, characterized in that, The first intelligent distribution three-way valve has two outlets, namely the reactor outlet and the evaporator outlet. The reactor outlet is connected to the microchannel pyrolysis heating channel to heat the reaction. The evaporator outlet and the hot side outlet of the microchannel pyrolysis heating channel merge and are connected to the second multi-source waste heat dynamic mixing box. After the flow is stabilized, the ammonia that has been preheated is reheated. The independent pipeline of the medium and low temperature waste heat collector is equipped with a third temperature sensor and a flow control valve for the low temperature supply branch.

7. A control method based on the system according to any one of claims 1-6, characterized in that, Includes the following steps: Pressure self-balancing control: Real-time monitoring of the static pressure of the coke oven raw gas pipeline and the converter gas pipeline. When the pressure difference between the two pipelines exceeds the threshold, the pressure balancing algorithm is activated to adjust the opening of the flow regulating valves of the two pipelines and eliminate pressure oscillations using the first multi-source waste heat dynamic mixing box. Temperature control: Based on the real-time readings of the temperature sensors of the two pipelines and the preset temperature-enthalpy mapping table, the mass flow ratio of the two flue gases is calculated. Through the coordinated action of the two flow regulating valves, the mixed output temperature sensor value at the outlet of the first multi-source waste heat dynamic mixing chamber is kept stable at the preset target reaction temperature. Dynamic energy gradient distribution: When the temperature fluctuation of the heat carrier is detected to be greater than the set value, a feedforward command is issued in advance to the first intelligent distribution three-way valve to adjust the valve core opening ratio and increase the proportion of flow to the microchannel pyrolysis heating channel, so as to ensure that the heat flux of the core reaction zone is maintained above the heat absorption equilibrium point. Product purity driven control: The residual ammonia concentration at the outlet of the microchannel pyrolysis reactor is detected. When the residual ammonia concentration deviates from the preset concentration threshold, the first intelligent distribution three-way valve is controlled to forcibly close the branch leading to the second ammonia preheating evaporator, so that all steady-state heat carriers are pressed towards the microchannel pyrolysis reactor.

8. The control method as described in claim 7, characterized in that, When the pressure difference exceeds the safety threshold, the pressure self-balancing control command takes precedence over the temperature control command. During the pressure self-balancing stage, the venturi effect generated by the high-pressure fluid is used to carry the flue gas from the converter gas pipeline in, preventing backflow of the flue gas. The energy-mass ratio calculation algorithm is used to calculate and adjust the flow distribution ratio between the coke oven raw gas pipeline and the converter gas pipeline in real time based on the target mixing temperature and the enthalpy conservation equation, combined with the specific heat capacity fitting function method.

9. The control method as described in claim 7, characterized in that, During the product purity drive control process, in order to prevent insufficient ammonia preheating caused by the product purity drive control action, the flow control valve of the low temperature supply branch is increased simultaneously, and the low-grade heat energy of the medium and low temperature waste heat collector is used to supplement the heat of the first ammonia preheating evaporator.

10. The control method as described in claim 7, characterized in that, it further... include: When all control and regulation measures reach their limits and still cannot reduce the residual ammonia concentration, adjust the liquid ammonia feed regulating valve to reduce the feed flow rate. By reducing the system load and extending the residence time of ammonia in the microchannel pyrolysis reaction channel, forced compliance with emission standards can be achieved. The system continuously compares the deviations of the current temperature, liquid ammonia feed rate, and residual ammonia concentration in the microchannel pyrolysis reactor with those in real time to see if they exceed the preset deviation threshold. When the mixed temperature output temperature sensor is in the set high temperature range, the liquid ammonia feed regulating valve opening is normal or less than the set value, and the residual ammonia concentration sensor reading at the outlet is consistently higher than the set safety upper limit, the catalyst is determined to be abnormal, and the first intelligent distribution three-way valve is adjusted to further increase the reaction temperature. If the residual ammonia concentration still cannot be restored, a catalyst replacement command is issued.

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