A wide load servo flexible green ammonia synthesis system

Abstract

The application relates to a wide-load-following flexible green ammonia synthesis system, which comprises a compression unit, a synthesis ammonia and heat recovery unit and a cooling separation unit. Through hydrogen production load control adjustment, the hydrogen flow of the matched compression unit is adjusted and controlled, the tower inlet flow of the synthesis ammonia and heat recovery unit is adjusted and controlled, the process parameters such as the load, the pressure and the temperature of the system are quickly responded and repaired, the fatigue of the temperature and the pressure of the equipment is prevented, and according to the raw material hydrogen flow, the system near-road valve opening degree and the flow are automatically adjusted, the gas flow through the catalyst bed layer is changed with the raw material hydrogen flow, the operation flexibility is 10-110%, and the system pressure is relatively stable.

Description

Technical Field

[0001] This application relates to the field of green ammonia synthesis technology, and more specifically, to a wide-load follow-up flexible green ammonia synthesis system. Background Technology

[0002] In the field of new energy, wind, solar and green electricity can be transformed into a new energy source that can be stored and transported, as well as fertilizers and chemical raw materials, with a wide range of applications.

[0003] Currently, traditional ammonia synthesis generally uses natural gas or coal as raw materials, and the operational flexibility of ammonia synthesis is generally 50-110%. However, for green ammonia generated by wind and solar power, if ammonia synthesis still maintains an operational flexibility of 50-110%, a large amount of energy storage and hydrogen storage will be required. This not only involves huge investment, but also brings safety hazards due to the large number of hydrogen storage tanks.

[0004] Based on the above technical risks and investment economic factors, green ammonia processes with design concepts such as flexible ammonia synthesis, dynamic ammonia synthesis, and multi-stable ammonia synthesis have been introduced at home and abroad. These processes emphasize the improvement of automatic control systems, but neglect the essential improvement of the combination of ammonia synthesis reaction principle and process. The process is basically the same as the traditional ammonia synthesis process.

[0005] In the control loop of a traditional ammonia synthesis compressor, the operation of traditional ammonia synthesis is relatively stable with little fluctuation in the elasticity range, and its control is relatively simple. Generally, the compressor manufacturer can achieve an operational elasticity of 50-110%. In order to adapt to the operational elasticity of green ammonia, some domestic manufacturers have proposed the control concept of "multi-steady state" or "segmented control", but the process has not been changed.

[0006] In traditional ammonia synthesis systems, classic and reliable processes are only suitable for applications with small load fluctuations and infrequent fluctuations. For green ammonia processes, if the traditional ammonia synthesis process is still used without modification, it will lead to temperature collapse in the synthesis tower and fatigue stress caused by repeated pressure and temperature fluctuations, posing a great threat to the stable and safe operation of the plant.

[0007] In traditional ammonia synthesis towers and heat recovery processes, the catalyst bed can be designed with various structures, such as 1-stage, 2-stage, 3-stage, and 4-stage, depending on factors such as production capacity and gas conditions. For large-scale gray ammonia plants, i.e., traditional chemical feedstock ammonia synthesis plants, the catalyst bed structure generally adopts a radial flow structure, while small-scale plants typically use a mixed structure of axial and radial sections. To maximize steam production, a bottom heat exchanger is generally not installed at the synthesis tower outlet to recover heat; only small-scale plants and reactors with low reaction efficiency are equipped with a bottom heat exchanger.

[0008] For the ammonia green process, due to large load fluctuations and the possibility of prolonged low-load production, it is also prone to "temperature collapse" and temperature stress caused by repeated temperature changes. Furthermore, with catalyst beds employing axial flow or ordinary radial flow structures, catalysts are highly susceptible to accumulation and pulverization under conditions of repeated fluctuations in gas flow rate, temperature, and pressure.

[0009] For the reasons mentioned above, domestic synthetic ammonia plants generally only promise a load fluctuation range of 30-110%, requiring the configuration of large amounts of hydrogen and energy storage. The investment and operating costs of green ammonia remain high. With unclear certification and sales channels for green ammonia, the investment and production costs of green ammonia and gray ammonia differ significantly, which restricts the further promotion of green ammonia technology in China.

[0010] Given the uncertainty surrounding the premium for green ammonia, in order to further reduce investment and operating costs and enhance the competitiveness of green ammonia over gray ammonia in terms of investment and operating costs, there is an urgent need to develop a fast-responding, safe, reliable, and flexible green ammonia process with a wide load range of 10-110%. Summary of the Invention

[0011] The purpose of this application is to provide a wide-load-following flexible green ammonia synthesis system, which features rapid response, safety and reliability, and low investment cost. It can also greatly expand the range of operational flexibility, making the operational flexibility reach 10-110%, and solve the problems of small load adjustment range, slow fluctuation response, and poor stable operation in the application of existing traditional ammonia synthesis processes in green ammonia processes.

[0012] To achieve the above objectives, the present invention provides a wide-load follow-up flexible green ammonia synthesis system, comprising: an ammonia synthesis and heat recovery unit and a cooling and separation unit; The ammonia synthesis and heat recovery unit includes an ammonia synthesis tower, an electric furnace inside the tower, and an electric furnace outside the tower. The ammonia synthesis tower is connected to an inlet pipeline, which includes a main inlet gas pipeline, as well as parallel branch inlet gas pipelines and system bypass pipelines. The system bypass pipeline is connected to the cooling and separation unit. The system is equipped with a bypass flow regulation loop on the bypass pipeline and an inlet gas pressure and flow control loop on the main gas inlet pipeline. The inlet gas pressure and flow control loop can receive the hydrogen flow rate converted from wind and solar forecasts and control the actual required gas inlet flow rate by adjusting the valves and flow rates on the system bypass pipeline based on the received actual hydrogen flow rate and the total gas inlet flow rate. The external electric furnace is connected to an inlet gas pipeline for raising the temperature of the tower. An inlet gas temperature and flow control loop is provided between the inlet gas pipeline for raising the temperature of the tower and the ammonia synthesis tower. The inlet gas temperature and flow control loop can control the flow rate of the inlet gas in the inlet gas pipeline based on the received hydrogen flow rate. The ammonia synthesis tower is equipped with multiple catalyst beds. The catalyst beds adopt a suspended radial gas distribution inlet. Cooling devices are installed between different catalyst beds, and a bottom heat exchanger is installed at the bottom of the bottom catalyst bed. The electric furnace inside the tower is connected to an internal heating gas inlet pipeline and a fourth gas inlet pipeline. The two gas inlet pipelines converge inside the tower and are heated by the electric furnace inside the tower before entering a catalyst bed. The flow rate of the gas to be heated is controlled by the inlet temperature of the catalyst bed. During startup, the main adjustment is made to the fourth gas inlet pipe, while during normal low-load operation, the main adjustment is made to the heating gas inlet pipe inside the tower.

[0013] In an optional embodiment, a compression unit is also included, which includes a compressor compression section, a compressor circulation section, an intercooler, and a compressor system buffer unit, wherein the compressor system buffer unit includes a combined buffer tank. The compressor's compression section includes a nitrogen inlet pipeline and a hydrogen inlet pipeline. A nitrogen flow regulation circuit is provided on the nitrogen inlet pipeline, and a proportional regulation control circuit is provided between the nitrogen flow regulation circuit and the hydrogen inlet pipeline.

[0014] In an optional embodiment, the nitrogen inlet pipeline and the hydrogen inlet pipeline merge to form the supplementary gas inlet pipeline of the compressor compression section. The buffer outlet pipeline of the compressor system buffer unit is connected to the supplementary gas inlet pipeline, and a buffer outlet bypass pipeline is provided on the buffer outlet pipeline. A supplementary gas pressure and flow control loop is provided between the buffer outlet bypass pipeline, the buffer outlet pipeline, and the supplementary gas inlet pipeline.

[0015] In an optional embodiment, the compressor system buffer unit is further connected to a buffer intake pipe, a buffer intake bypass pipe is provided on the buffer intake pipe, and a buffer intake pressure and flow control circuit is provided between the buffer intake bypass pipe and the buffer intake pipe.

[0016] In an optional embodiment, an inlet gas flow detection unit is provided on the main inlet gas pipeline, and the inlet gas flow detection unit is electrically connected to the inlet gas pressure and flow control loop.

[0017] In an optional embodiment, a first inlet gas pipeline, a second inlet gas pipeline, a third inlet gas pipeline, and a fourth inlet gas pipeline are provided between the main inlet gas pipeline and the ammonia synthesis tower. The second and third inlet gas pipelines do not heat the inlet gas through an electric furnace inside or outside the tower. The first gas inlet pipe and the fourth gas inlet pipe are respectively connected to the electric furnace inside the tower, and the electric furnace inside the tower is used to heat up the tower for start-up and to stabilize the temperature inside the tower. The first inlet gas pipeline includes the inlet gas pipeline for heating inside the tower and the inlet gas pipeline for heating outside the tower, which serves as the inlet gas pipeline for raising the temperature of the tower.

[0018] In an optional embodiment, temperature regulation loops are respectively provided between the heating gas inlet pipe and the ammonia synthesis tower, between the second gas inlet pipe and the ammonia synthesis tower, and between the third gas inlet pipe and the ammonia synthesis tower.

[0019] In an optional embodiment, the ammonia synthesis tower is connected to a synthetic ammonia outlet pipeline, the fourth inlet gas pipeline serves as the start-up gas inlet pipeline, and a temperature regulation loop is provided between the synthetic ammonia outlet pipeline and the fourth inlet gas pipeline.

[0020] In an optional embodiment, the temperature regulation loop includes an inlet gas temperature controller, which is configured to correspond to different sections of the catalyst bed.

[0021] In an optional embodiment, the connection point between the external heating gas pipeline and the ammonia synthesis tower is arranged corresponding to the location of the catalyst bed in the top section.

[0022] This invention provides rapid response and repair to process parameters such as load, pressure, and temperature of the system through hydrogen load control and regulation, along with hydrogen flow regulation and control in the compression unit and inlet flow regulation and control in the ammonia synthesis and heat recovery unit. This prevents equipment fatigue due to temperature and pressure. Furthermore, it adjusts the inlet gas flow according to the feed hydrogen flow rate, and the gas flow rate in the catalyst bed fluctuates with the feed hydrogen flow rate, ensuring that the system moves with the hydrogen flow and maintaining a relatively stable system pressure within an operational flexibility range of 10-110%.

[0023] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the system structure and control regulation of the compression unit, ammonia synthesis and heat recovery unit, and cooling separation unit in this application; Figure 2 This is a schematic diagram of the process for heat recovery of the catalyst bed in the ammonia synthesis tower in this application.

[0026] icon: 11-Compressor compression section; 12-Compressor circulation section; 13-Intercooler; 14-Compressor system buffer unit; 111 - Nitrogen inlet line; 112 - Hydrogen inlet line; 113 - Makeup gas inlet line; 114 - Buffer outlet line; 115 - Buffer inlet line; 21-Ammonia synthesis tower; 21a-First stage catalyst bed; 21b-Second stage catalyst bed; 21c-Third stage catalyst bed; 22-Steam generator; 23-Boiler feedwater heater; 24-Heat exchanger; 25-External electric furnace; 26-Internal electric furnace; 27-Bottom heat exchanger; 211 - Main inlet gas pipeline; 212 - Inlet gas pipeline; 213 - System bypass pipeline; 214 - First inlet gas pipeline; 214a - Inlet gas pipeline for internal heating; 214b - Inlet gas pipeline for external heating; 215 - Second inlet gas pipeline; 216 - Third inlet gas pipeline; 217 - Fourth inlet gas pipeline; 218 - Synthetic ammonia outlet pipeline; 31-Water cooler; 32-Cool exchanger; 33-Primary ammonia cooler; 34-Secondary ammonia cooler; 35-Ammonia separator; 36-Ammonia flash tank; 10-Nitrogen flow regulation loop; 20-Hydrogen flow regulation loop; 30-Proportional regulation control loop; 40-Supplement gas pressure and flow control loop; 50-Buffer inlet gas pressure and flow control loop; 60-System bypass flow regulation loop; 70-Inlet gas pressure and flow control loop; 80-Inlet gas flow detection unit; 90-Inlet temperature and flow control loop; 100-Temperature regulation loop. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0030] See Figures 1-2 The wide-load follow-up flexible green ammonia synthesis system in this application includes: a compression unit, an ammonia synthesis and heat recovery unit, and a cooling and separation unit; The compression unit includes a hydrogen inlet pipe 112, and a hydrogen flow regulating circuit 20 is provided on the hydrogen inlet pipe 112. The ammonia synthesis and heat recovery unit includes an ammonia synthesis tower 21, an electric furnace 26 inside the tower, and an electric furnace 25 outside the tower. The ammonia synthesis tower 21 is connected to an inlet pipeline, which includes a main inlet gas pipeline 211, a parallel branch inlet gas pipeline 212, and a system bypass pipeline 213. The system bypass pipeline 213 is connected to the cooling and separation unit. The system bypass pipeline 213 is equipped with a system bypass flow regulation loop 60, and the tower gas main pipeline 211 is equipped with a tower gas pressure and flow control loop 70. The tower gas pressure and flow control loop 70 can receive the hydrogen flow rate converted from wind and solar forecasts, and control the actual required tower gas volume by adjusting the valves and flow rates on the system bypass pipeline 213 according to the different hydrogen flow rates received and the total tower gas flow rate.

[0031] The external electric furnace 25 is connected to the tower inlet heating gas pipeline. A tower inlet heating gas temperature and flow control circuit 90 is provided between the tower inlet heating gas pipeline and the ammonia synthesis tower 21. The tower inlet heating gas temperature and flow control circuit 90 can control the tower inlet heating gas flow rate in the tower inlet heating gas pipeline according to the received hydrogen flow rate. The ammonia synthesis tower 21 is equipped with multiple catalyst beds. The catalyst beds adopt a suspended radial gas distribution inlet form. Cooling devices are provided between different catalyst beds. A bottom heat exchanger 27 is provided at the bottom of the bottom catalyst bed. The electric furnace 26 inside the tower is connected to an internal heating gas inlet pipe 214a and a fourth gas inlet pipe 217. The two gas inlet pipes converge inside the tower and enter a catalyst bed after being heated by the electric furnace inside the tower. The flow rate of the gas to be heated is controlled by the inlet temperature of the catalyst bed.

[0032] A temperature and flow control loop 90 for the inlet gas heating pipeline 214a and the ammonia synthesis tower 21 is provided. During normal low-load operation, the temperature and flow control loop 90 can control the flow rate of the inlet gas for heating in the tower according to the inlet temperature of the first catalyst bed 21a. During start-up, the main adjustment is made by the fourth inlet gas pipeline 217. The fourth inlet gas pipeline 217 recovers the heat of the gas exiting the tower through the bottom heat exchanger 27 and then enters the electric furnace 26 in the tower to heat the inlet gas. The flow rate of the fourth inlet gas can be controlled according to the catalyst heating reduction curve and the inlet temperature of the first catalyst bed 21a.

[0033] The regulation in this application mainly involves a hydrogen load control regulation system. The regulation loop refers to the installation of a flow regulating valve and a flow or temperature controller on the pipeline. The opening degree of the flow regulating valve is controlled by the flow or temperature signal fed back by the flow or temperature controller.

[0034] The pressure and flow control loop and the temperature and flow control loop of the inlet gas for heating the tower refer to the installation of flow regulating valves or temperature regulating valves and pressure or temperature controllers on the pipeline. The opening degree of the flow regulating valves or temperature regulating valves is controlled by the pressure or temperature signals fed back by the pressure or temperature controllers. In other words, the definition of the control loop involves the combination of monitoring different parameters.

[0035] The proportional control loop 30 specifically refers to the proportional control between the flow rates of hydrogen and nitrogen, used to adjust the composition of the supplementary gas.

[0036] From the perspective of the system as a whole, it constitutes the hydrogen flow regulation and control of the compression unit involved in the hydrogen load control and regulation system, and the inlet flow regulation and control of the ammonia synthesis and heat recovery unit.

[0037] By setting a hydrogen flow regulation loop 20 on the hydrogen inlet pipeline 112, hydrogen flow regulation control of the compression unit can be formed.

[0038] By setting a system bypass flow regulation loop 60 on the system bypass pipeline 213 and an inlet gas pressure and flow control loop 70 on the inlet gas main pipeline 211, the inlet flow regulation and control of the ammonia synthesis tower 21 can be achieved.

[0039] Furthermore, by electrically connecting the hydrogen flow regulation loop 20 and the system bypass flow regulation loop 60 to the inlet gas pressure and flow control loop 70, a pressure stabilization system for the green ammonia process can be formed.

[0040] The hydrogen flow regulation loop 20, the system bypass flow regulation loop 60, and the inlet gas pressure and flow control loop 70 together constitute the pressure stabilization system of the green ammonia process system.

[0041] The inlet gas pressure and flow control loop 70 can receive wind and solar forecasts and convert them into hydrogen flow rate, and control the actual required inlet gas volume based on the different received hydrogen flow rates and the total inlet gas flow rate.

[0042] Specifically, the inlet gas pressure and flow control loop 70 is the core of the pressure stabilization system, which is implemented by the PIC001 pressure control system. The PIC001 pressure control system includes the calculated value of hydrogen flow into the system FY1 (H2), the calculated value of hydrogen flow feedforward based on wind and solar forecasts FY2 (H2), the total gas flow into the tower FY3, and the system bypass gas flow FY4.

[0043] The actual required gas flow rate FY5 for the tower is calculated by the pressure control of PIC001 under different hydrogen flow rates. The actual required gas flow rate FY5 is calculated by subtracting the total gas flow rate FY3 from the system bypass gas flow rate FY4, which can be controlled by the system bypass valve FV001.

[0044] The pressure stabilization system of the green ammonia process makes full use of the dynamic balance between the actual required gas flow rate and the fixed catalyst quantity. Through dynamic calculation and continuous simulation, the rise and fall of the PIC001 pressure is kept in a smooth state and can be adjusted within the range of 10-110% load, with pressure fluctuation not exceeding 20%, so as to avoid the occurrence of pressure fatigue conditions.

[0045] In addition to the pressure stabilization system mentioned above, the green ammonia synthesis system in this application also includes a temperature stabilization system. The electric furnace 26 inside the ammonia synthesis tower 21, the electric furnace 25 outside the tower, and the temperature and flow control loop 90 of the inlet heating gas between the inlet heating gas pipeline and the ammonia synthesis tower 21 constitute the basis of the control system.

[0046] Specifically, the temperature and flow control loop 90 for the inlet gas is the core of the temperature stabilization system, which is implemented by the TIC001 temperature control system. The external electric furnace 25 and the internal electric furnace 26 complement each other, forming a dual guarantee of heat balance to adapt to rapid load reduction and extremely low load.

[0047] When the load decreases rapidly, reaching a decrease of 5% per minute, the external electric furnace 25 or the internal electric furnace 26 can quickly provide the heat load for the gas entering the tower to raise the temperature; when the load decreases to 10%, the external electric furnace 25 or the internal electric furnace 26 can quickly start to provide a constant temperature heat source and can also operate normally at 10% load.

[0048] The opening degree of the valve for the heating gas entering the electric furnace 25 is determined by the temperature controller TC of the gas entering the tower in the temperature and flow control loop 90, which controls TIC001. Based on the temperature of the gas entering the tower detected by TC, the calculated value of hydrogen flow rate in the system FY1 (H2), and the feedforward calculated value of hydrogen flow rate converted from wind and solar power forecasts FY2 (H2), the opening degree of the valve TV001 for the gas to be heated is calculated.

[0049] From the perspective of catalyst bed optimization, in the ammonia synthesis tower 21 of the ammonia synthesis and heat recovery unit, the catalyst bed includes a multi-stage catalyst bed consisting of a first-stage catalyst bed 21a, a second-stage catalyst bed 21b, and a third-stage catalyst bed 21c. The catalyst bed can be designed into various catalyst bed structures such as 1-stage, 2-stage, 3-stage, and 4-stage according to factors such as production capacity and gas conditions.

[0050] Compared to the existing traditional gray ammonia synthesis process, the catalyst bed structure adopts a suspended radial gas distribution structure, which forms a suspended radial gas distribution inlet form, giving the catalyst a certain buoyancy, preventing the catalyst from being squeezed or pulverized, and allowing for more complete contact between the gas and the catalyst, resulting in higher reaction efficiency.

[0051] An upper interlayer heat exchanger or cold pipes, cold quench gas, or other gas cooling measures are installed between the first catalyst bed 21a and the second catalyst bed 21b; a lower interlayer heat exchanger or cold pipes, cold quench gas, or other gas cooling measures are installed between the second catalyst bed 21b and the third catalyst bed 21c; by installing a bottom heat exchanger 27 at the lower outlet of the bottom catalyst bed (shown as the third catalyst bed 21c in the attached diagram), heat can be recovered and the temperature of the entire tower can be stabilized.

[0052] By introducing the inlet gas that enters the electric furnace 25 outside the tower into the catalyst bed located at the top, as shown in the attached figure, the inlet gas is introduced into the catalyst bed 21a, which can further stabilize the inlet temperature of the synthesis tower.

[0053] It should be noted that in the attached diagram, FC, PC, and TC are flow controllers, pressure controllers, and temperature controllers that can detect and regulate, respectively, while TV and FV are temperature control valves and flow control valves, respectively, which can participate in the control of pipeline material flow.

[0054] The following section provides a further explanation of the control angles for different units.

[0055] The compression unit includes a compressor compression section 11, a compressor circulation section 12, an intercooler 13, and a compressor system buffer unit 14, which includes a combined buffer tank. The compressor compression section 11 has an intake pipeline including a nitrogen intake pipeline 111 and a hydrogen intake pipeline 112. The nitrogen intake pipeline 111 is equipped with a nitrogen flow regulation circuit 10, and the hydrogen intake pipeline 112 is equipped with a hydrogen flow regulation circuit 20, which can regulate the flow of nitrogen and hydrogen respectively.

[0056] By setting a proportional control loop 30 between the nitrogen flow regulation loop 10 and the hydrogen flow regulation loop 20, the proportion of gas components in the feed gas can be adjusted, thereby providing a reference for subsequent regulation and control.

[0057] Nitrogen inlet line 111 and hydrogen inlet line 112 merge to form supplementary gas inlet line 113 of compressor compression section 11. Buffer outlet line 114 of compressor system buffer unit 14 is connected to supplementary gas inlet line 113. Supplementary gas pressure and flow control circuit 40 is provided between buffer outlet line 114 and supplementary gas inlet line 113.

[0058] The compressor system buffer unit 14 is also connected to a buffer intake pipe 115, which is equipped with a buffer intake pressure and flow control circuit 50.

[0059] The installation of the compressor system buffer unit 14 and the intercooler 13, combined with the above-mentioned supplementary gas pressure and flow control circuit 40 and buffer intake gas pressure and flow control circuit 50, can form a flow buffer regulation and pressure control regulation mode, enabling the compressor and its auxiliary equipment to resist pressure fluctuation fatigue and flow pulse fatigue.

[0060] By setting up a supplementary gas pressure and flow control circuit 40 for pressure stabilization and a buffer inlet gas pressure and flow control circuit 50 in the compressor unit, as well as a compressor system buffer unit 14 and a hydrogen flow regulation circuit 20 for buffering, the operation is simplified, the response is fast, and the impact of hydrogen fluctuations on the compressor is mitigated, the operation of the compressor is stabilized, and it can be closely integrated with the operating conditions of wind and solar forecasting and electrolyzer hydrogen production.

[0061] An inlet gas flow rate detection unit 80 is installed on the inlet gas inlet pipeline 212, and the inlet gas flow rate detection unit 80 is electrically connected to the inlet gas pressure and flow control loop 70. By combining the inlet gas flow rate detection unit 80 with the inlet gas pressure and flow control loop 70, the inlet gas flow rate can be acquired in real time and fed back to the inlet gas pressure and flow control loop 70, which facilitates the control loop 70 in controlling the opening degree of the flow control valve FV001 on the system bypass pipeline 213.

[0062] From the perspective of the composition of the temperature stabilization system, a first gas inlet pipeline 214, a second gas inlet pipeline 215, a third gas inlet pipeline 216 and a fourth gas inlet pipeline 217 are provided between the gas inlet pipeline 212 and the ammonia synthesis tower 21. The second and third inlet gas lines 215 and 216 do not heat the gas entering the tower. An electric furnace 26 is installed at the top of the ammonia synthesis tower 21. The heating inlet gas line 214a of the first inlet gas line 214 and the fourth inlet gas line 217 are respectively connected to the electric furnace 26 to maintain the tower temperature and start the heating process.

[0063] The first gas inlet pipeline 214 includes an internal heating gas inlet pipeline 214a and an external heating gas inlet pipeline 214b, which serves as the gas inlet pipeline for raising the temperature of the tower. With this configuration, the external electric furnace 25 or the internal electric furnace 26 can operate in separate, parallel, or series modes, which can realize comprehensive control of the gas inlet and meet the heating requirements of the gas inlet under different working conditions.

[0064] Temperature regulation loops 100 are respectively installed between the heating gas inlet pipe 214a and the ammonia synthesis tower 21, between the second gas inlet pipe 215 and the ammonia synthesis tower 21, and between the third gas inlet pipe 216 and the ammonia synthesis tower 21. Specifically, each temperature regulation loop 100 is an inlet temperature regulation loop 100, which includes flow regulating valves installed on different gas inlet pipes and inlet gas temperature controllers installed in different sections of the catalyst bed in the ammonia synthesis tower 21, ensuring the stability of the synthesis tower inlet temperature.

[0065] Based on the above-mentioned method of introducing the heated gas into the external electric furnace 25 into the catalyst bed located at the top, and the connection point between the external heating gas pipeline 214b and the ammonia synthesis tower 21 is set in accordance with the location of the catalyst bed located at the top, the overall inlet gas temperature of the synthesis tower can be balanced and stabilized.

[0066] The inlet gas temperature regulation loops 100 on different inlet gas pipelines serve as components of the temperature stabilization system. Combined with the inlet gas temperature and flow control loop 90, they form a synthesis tower temperature control system encompassing inlet gas temperature regulation, external electric furnace 25 regulation, and internal electric furnace 26 control, thus creating a dual-loop safety system. The external electric furnace 25 control system, comprised of the inlet gas temperature and flow control loop 90, has no safety gas volume requirement and can remain in a energized standby state for extended periods.

[0067] The ammonia synthesis tower 21 is connected to the ammonia synthesis outlet pipeline 218. The ammonia synthesis outlet pipeline 218 is sequentially equipped with a steam generator 22, a boiler feed water heater 23, a heat exchanger 24, a water cooler 31, a cold exchanger 32, a primary ammonia cooler 33, a secondary ammonia cooler 34, an ammonia separator 35, and an ammonia flash tank 36.

[0068] The ammonia synthesis tower 21, steam generator 22, boiler feedwater heater 23, and heat exchanger 24 constitute the ammonia synthesis and heat recovery unit. The water cooler 31, cold exchanger 32, primary ammonia cooler 33, secondary ammonia cooler 34, ammonia separator 35, and ammonia flash tank 36 constitute the cooling separation unit. By introducing part of the inlet gas in the system's bypass pipeline 213 into the cooling separation unit, and by adjusting the opening of the flow control valve FV001 in conjunction with the inlet gas pressure and flow control loop 70, the overall pressure and flow of the inlet gas can be stabilized.

[0069] In this application, the fourth inlet gas pipeline 217 serves as the start-up gas inlet pipeline. A temperature regulation loop 100 is provided between the synthetic ammonia outlet pipeline 218 and the fourth inlet gas pipeline 217. The temperature controller of the temperature regulation loop 100 is located upstream of the steam generator 22 and can control and adjust the opening of the flow regulating valve on the start-up gas inlet pipeline, thereby ensuring the stability of the overall system temperature under start-up conditions.

[0070] The ammonia synthesis tower 21 in this application is equipped with a suspended radial bed distributor for gas inlet and a gas temperature controller at the catalyst bed inlet to ensure the stability of the inlet temperature of the ammonia synthesis tower 21. A heat exchanger for temperature regulation is installed at the outlet of the ammonia synthesis tower 21 to recover the reaction heat of ammonia synthesis. It is jointly regulated with the steam generator 22 and the heat exchanger 24 to continuously change the proportion of recovered reaction heat according to the change of reaction load. That is, the lower the load of the device, the higher the proportion of recovered reaction heat, so as to maintain the thermal balance of the system under particularly low load.

[0071] Furthermore, the catalyst bed adopts highly active iron-based or other catalysts with strong resistance to fluctuations to adapt to rapid changes in flow rate, temperature, and pressure, so that the ammonia synthesis reaction system has the functions of temperature and flow regulation and rapid stabilization self-repair function to adapt to rapid load changes.

[0072] The pressure stabilization system in this application utilizes the dynamic balance of the actual required gas flow rate and the fixed catalyst quantity to ensure that the pressure rise and fall of PIC001 is gradual through continuous dynamic simulation, enabling stable and reliable operation within the 10-110% load range.

[0073] The PIC001 pressure control system calculates and controls the inlet hydrogen flow rate, wind and solar predicted hydrogen production flow rate, total gas volume entering the tower, and system bypass gas volume, controlling pressure fluctuations to not exceed 20% and reducing pressure fatigue conditions.

[0074] By connecting the feed hydrogen flow rate and the inlet gas pressure and flow rate control loop 70 in series, the inlet gas flow rate can be adjusted according to the feed hydrogen flow rate. The gas flow rate of the catalyst bed fluctuates with the feed hydrogen flow rate, so that it moves with the hydrogen and the operation flexibility can reach the range of 10-110%. The system has a fast response and relatively stable pressure.

[0075] By controlling the system's bypass valves and adjusting the flow rate of the gas entering the tower, it is possible to ensure that the changes in the gas volume at the inlet and outlet of the circulating machine are small and controllable. The entire ammonia synthesis system can act as a large "buffer container." The cooling separation and ammonia refrigeration system have sufficient response time to changes in load. The cooling separation and ammonia refrigeration system is stable, simple, and reliable in operation.

[0076] The following description, in conjunction with the accompanying drawings and embodiments, further illustrates the wide-load follow-up flexible green ammonia synthesis system of the present invention.

[0077] Combination Figure 1 The compression unit includes a compressor compression section 11, a compressor circulation section 12, an intercooler 13, and a compressor system buffer tank. The system has the ability to adjust the hydrogen-nitrogen ratio flow rate. By setting up a supplementary gas pressure and flow control circuit 40 and a buffer intake gas pressure and flow control circuit 50, the system provides the adjustment functions of supplementary gas flow buffering and pressure control, enabling the compressor and its auxiliary equipment to resist pressure fluctuation fatigue and flow pulse fatigue.

[0078] Taking a 200kt / a green ammonia synthesis system as an example, at 100% load, the H2 flow rate into the system is 54888 Nm³. 3 / h corresponds to an N2 flow rate of 18296Nm. 3 / h. When the H2 flow rate decreases, the flow rate proportional regulation control loop 30 automatically reduces the amount of nitrogen entering the system and closes the nitrogen valve in the system. To maintain a stable inlet pressure at the compressor, the pressure stabilization system gradually opens the outlet valve of the compressor system buffer unit 14 according to the magnitude of the decrease in the system inlet flow rate, and the inlet valve of the compressor system buffer unit 14 also gradually opens. Following the flow of hydrogen, the green ammonia compressor control loop can maintain a stable compressor inlet pressure within a load range of 5% to 125%.

[0079] Combination Figure 1 For a 200kt / a green ammonia plant, at 100% load, the total gas flow rate into the tower is FY3 = 243746 Nm³. 3 / h, the actual required gas volume entering the tower FY5 is calculated by subtracting the total gas volume entering the tower FY3 from the system's short-path gas volume FY4. When the load is 100%, FY4 = 0 Nm³. 3 / h, FY5=FY3.

[0080] When the load decreases rapidly and the system pressure drops quickly, the FY4 flow rate will gradually increase to maintain stable system pressure. When the load decreases to 20%, FY3 = 134060 Nm. 3 / h, FY4=48749Nm 3 / h, the actual required gas volume entering the tower is FY5=FY3-FY4=85311Nm 3 / h, the system pressure will not decrease by more than 15%.

[0081] Combination Figure 2 For a 200kt / a green ammonia plant, at 100% load, the inlet temperature riser gas flow rate to the synthesis tower is approximately 1000 Nm³. 3 / h, to maintain the pipeline and heating equipment in a energized standby state. When the load rapidly decreases to 20% load, the gas flow rate for temperature boosting in the tower is gradually increased to 10000 Nm³. 3 / h, the temperature of the catalyst bed 21a is in a stable state.

[0082] Meanwhile, at 100% load, the gas flow through the bottom heat exchanger 27 accounts for about 15% of the total gas flow into the tower; as the load decreases, the proportion of the gas flow through the bottom heat exchanger 27 to the total gas flow into the tower gradually increases. When the load decreases to 20%, the proportion of the gas flow through the bottom heat exchanger 27 to the total gas flow into the tower increases to 45% to maintain the thermal balance of the entire tower.

[0083] The wide-load follow-up flexible green ammonia synthesis system of the present invention has the advantages of fast response and safety and reliability, and the operation flexibility reaches 10-110%, which can be applied to the synthesis and production of green ammonia.

[0084] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0085] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A flexible green ammonia synthesis system with wide load responsiveness, characterized in that, include: Ammonia synthesis and heat recovery unit, as well as cooling and separation unit; The ammonia synthesis and heat recovery unit includes an ammonia synthesis tower, an electric furnace inside the tower, and an electric furnace outside the tower. The ammonia synthesis tower is connected to an inlet pipeline, which includes a main inlet gas pipeline, as well as parallel branch inlet gas pipelines and system bypass pipelines. The system bypass pipeline is connected to the cooling and separation unit. The system is equipped with a bypass flow regulation loop on the bypass pipeline and an inlet gas pressure and flow control loop on the main gas inlet pipeline. The inlet gas pressure and flow control loop can receive the hydrogen flow rate converted from wind and solar forecasts and control the actual required gas inlet flow rate by adjusting the valves and flow rates on the system bypass pipeline based on the received actual hydrogen flow rate and the total gas inlet flow rate. The external electric furnace is connected to an inlet gas pipeline for raising the temperature of the tower. An inlet gas temperature and flow control loop is provided between the inlet gas pipeline for raising the temperature of the tower and the ammonia synthesis tower. The inlet gas temperature and flow control loop can control the flow rate of the inlet gas in the inlet gas pipeline based on the received hydrogen flow rate. The ammonia synthesis tower is equipped with multiple catalyst beds. The catalyst beds adopt a suspended radial gas distribution inlet. Cooling devices are installed between different catalyst beds, and a bottom heat exchanger is installed at the bottom of the bottom catalyst bed. The electric furnace inside the tower is connected to an internal heating gas inlet pipeline and a fourth gas inlet pipeline. The two gas inlet pipelines converge inside the tower and are heated by the electric furnace inside the tower before entering a catalyst bed. The flow rate of the gas to be heated is controlled by the inlet temperature of the catalyst bed. During startup, the main adjustment is made to the fourth gas inlet pipe, while during normal low-load operation, the main adjustment is made to the heating gas inlet pipe inside the tower.

2. The wide-load follow-up flexible green ammonia synthesis system according to claim 1, characterized in that, It also includes a compression unit, which includes a compressor compression section, a compressor circulation section, an intercooler, and a compressor system buffer unit, which includes a combined buffer tank. The compressor's compression section includes a nitrogen inlet pipeline and a hydrogen inlet pipeline. A nitrogen flow regulation circuit is provided on the nitrogen inlet pipeline, and a proportional regulation control circuit is provided between the nitrogen flow regulation circuit and the hydrogen inlet pipeline.

3. The wide-load follow-up flexible green ammonia synthesis system according to claim 2, characterized in that, The nitrogen inlet pipeline and the hydrogen inlet pipeline merge to form the supplementary gas inlet pipeline of the compressor compression section. The buffer outlet pipeline of the compressor system buffer unit is connected to the supplementary gas inlet pipeline, and a buffer outlet bypass pipeline is provided on the buffer outlet pipeline. A supplementary gas pressure and flow control circuit is provided between the buffer outlet bypass pipeline, the buffer outlet pipeline and the supplementary gas inlet pipeline.

4. The wide-load follow-up flexible green ammonia synthesis system according to claim 2, characterized in that, The compressor system buffer unit is also connected to a buffer intake pipe, and a buffer intake bypass pipe is provided on the buffer intake pipe. A buffer intake pressure and flow control circuit is provided between the buffer intake bypass pipe and the buffer intake pipe.

5. The wide-load follow-up flexible green ammonia synthesis system according to claim 1, characterized in that, An inlet gas flow detection unit is installed on the main gas inlet pipeline, and the inlet gas flow detection unit is electrically connected to the inlet gas pressure and flow control circuit.

6. The wide-load follow-up flexible green ammonia synthesis system according to claim 1, characterized in that, A first inlet gas pipeline, a second inlet gas pipeline, a third inlet gas pipeline, and a fourth inlet gas pipeline are provided between the main gas pipeline into the tower and the ammonia synthesis tower. The second and third inlet gas pipelines do not heat the inlet gas through an electric furnace inside or outside the tower. The first gas inlet pipe and the fourth gas inlet pipe are respectively connected to the electric furnace inside the tower, and the electric furnace inside the tower is used to heat up the tower for start-up and to stabilize the temperature inside the tower. The first inlet gas pipeline includes the inlet gas pipeline for heating inside the tower and the inlet gas pipeline for heating outside the tower, which serves as the inlet gas pipeline for raising the temperature of the tower.

7. The wide-load follow-up flexible green ammonia synthesis system according to claim 6, characterized in that, Temperature regulation loops are respectively provided between the heating gas inlet pipe and the ammonia synthesis tower, between the second gas inlet pipe and the ammonia synthesis tower, and between the third gas inlet pipe and the ammonia synthesis tower.

8. The wide-load follow-up flexible green ammonia synthesis system according to claim 1, characterized in that, The ammonia synthesis tower is connected to a synthetic ammonia outlet pipeline, and the fourth inlet gas pipeline serves as the start-up gas inlet pipeline. A temperature regulation loop is provided between the synthetic ammonia outlet pipeline and the fourth inlet gas pipeline.

9. The wide-load follow-up flexible green ammonia synthesis system according to claim 8, characterized in that, The temperature control loop includes an inlet gas temperature controller, which is configured to correspond to different sections of the catalyst bed.

10. The wide-load follow-up flexible green ammonia synthesis system according to claim 6, characterized in that, The connection point between the external heating gas pipeline and the ammonia synthesis tower is set at a location corresponding to the location of the catalyst bed in the top section.

Images