A temperature control method for a green electricity to green ammonia synthesis tower

Abstract

The application discloses a kind of green electricity green ammonia synthesis tower temperature control method, including annular gap gas and main line gas, annular gap gas and main line gas come from the process gas of compressor outlet, annular gap gas enters the annular gap of synthesis tower wall, control annular gap gas flow is stably maintained at predetermined value, so that the temperature fluctuation range of high-pressure shell is ≤25 ℃, predetermined value is 4%~6% of 100% load total gas intake, and the allowable fluctuation range of annular gap gas flow is ≤±12.5%.By limiting the function of main line gas to main reaction gas flow, and adding an independently controlled annular gap gas passage, the annular gap gas flow remains basically stable when the device load fluctuates greatly, so that the temperature fluctuation range of high-pressure shell is much lower than that of traditional process, and fatigue damage caused by alternating thermal stress is avoided.

Description

Technical Field

[0001] This invention belongs to the field of ammonia synthesis technology, and specifically relates to a method for temperature control in a green ammonia synthesis tower produced from green electricity. Background Technology

[0002] Traditional ammonia synthesis units operate under a "safe, stable, long-term, full-capacity, and high-efficiency" operating condition to achieve low overall energy consumption and maximize economic benefits. Therefore, they typically require continuous operation at around 100% load. Furthermore, the operating flexibility of these units is limited, generally designed for 60% to 110% load, with minimal fluctuations below 80% load—far below the baseline parameter of 1000 cycles within the unit's design life—to ensure economic efficiency targets are met. Therefore, traditional ammonia synthesis units do not require consideration of the adverse effects of changes in the gas flow rate at the synthesis tower's inlet on the high-pressure outer shell of the tower.

[0003] Green energy sources such as wind and solar power are characterized by volatility and instability, resulting in very large load variations in the equipment, ranging from as low as 10% to as high as 110% to 125%. In addition, the frequency of large load variations is at least once a day, and the number of large load fluctuations in the equipment reaches more than 5,000 times within the design service life of the equipment (not less than 15 years).

[0004] If the synthesis tower is designed using traditional ammonia synthesis technology, the main gas functions as both main gas and annular gas. Large flow fluctuations lead to significant temperature fluctuations in the high-pressure outer shell of the synthesis tower, making it prone to fatigue operation and posing a risk to its long-term safe operation. For example, CN101182007A discloses an energy-saving ammonia synthesis process. This scheme diverts the gas entering the synthesis tower in a single pass, primarily directing 25%-30% of the intake into the annular space. If the total intake is unstable, the amount of gas entering the annular space is also dynamically adjusted, which is detrimental to the stable operation of green ammonia synthesis.

[0005] The information disclosed in this background section is intended to enhance understanding of the overall background of the invention. Summary of the Invention

[0006] The purpose of this invention is to provide a method for controlling the temperature of a synthesis tower, thereby overcoming the shortcomings of the prior art, such as unstable green electricity and large temperature fluctuations in the high-pressure outer shell caused by large changes in the load of the equipment.

[0007] To achieve the above objectives, the present invention provides a method for temperature control of a green ammonia synthesis tower using green electricity, comprising annular gas and main gas, wherein the annular gas and main gas are process gas from the compressor outlet, the annular gas enters the annular gap of the synthesis tower wall, and the annular gas flow rate is controlled to be stably maintained at a predetermined value, so that the high-pressure shell temperature fluctuation range is ≤25℃, the predetermined value is 4%~6% of the total gas intake at 100% load, and the annular gas flow rate is allowed to fluctuate within a range of ≤±12.5%.

[0008] Green electricity primarily refers to electricity generated through the conversion of renewable energy sources such as photovoltaics, wind power, hydropower, tidal power, and biomass energy. It encompasses clean electricity forms including solar photovoltaic power generation, onshore / offshore wind power generation, tidal power generation, hydropower, and biomass power generation. This type of electricity is generated by converting natural energy sources (such as solar, wind, hydro, ocean, and biomass energy) into electrical energy through technological means.

[0009] Preferably, in the above technical solution, the synthesis tower includes a high-pressure outer shell and internal components fitted inside the high-pressure outer shell. An annular gap is provided between the high-pressure outer shell and the internal components. An annular gap gas inlet is provided at the upper part of the high-pressure outer shell, and a main line gas inlet is provided at the bottom end cap. The process includes the following steps: Annular gas enters the annular gap through the annular gas inlet, and after descending along the annular gap, it enters the space above the distribution plate of the bottom end cap of the internal components through the small holes of the distribution plate at the bottom of the tower. The main gas enters the bottom of the synthesis tower through the main gas inlet, and then enters the space above the bottom end cap distribution plate of the internal components through the small holes in the distribution plate of the bottom end cap of the internal components. The annular gas flow rate is controlled to be stably maintained at 5% of the total gas volume, with an allowable fluctuation range of ≤±12.5%; The opening degree of the main gas branch valves is fixed after commissioning and the flow rate is passively adjusted according to load fluctuations.

[0010] Preferably, in the above technical solution, the annular gas and the main gas maintain independent flow paths before entering the bottom distribution plate and the bottom end cap distribution plate of the internal components, and then merge in the cavity formed by the bottom distribution plate, the bottom end cap distribution plate of the internal components, and the bottom heat exchanger.

[0011] Preferably, in the above technical solution, the main line air flow rate is a fixed valve opening determined after start-up and commissioning, and remains unchanged. The main line air flow rate is not used as a control means; a fixed opening (determined after start-up and commissioning) is adopted and then remains essentially unchanged, thus passively controlling the system.

[0012] A temperature control device for a green ammonia synthesis tower adapted to the control method described above, wherein a flow regulating device is provided in the annular gas branch to maintain the flow rate of the annular gas branch at 4% to 6% of the total intake gas volume at 100% load.

[0013] Preferably, in the above technical solution, the annular gap between the high-pressure outer shell and the inner components has an annular gas inlet at the top and a small hole at the bottom connected to the tower bottom distribution plate; The main gas inlet at the bottom end cap of the synthesis tower connects to the small hole in the distribution plate at the bottom end cap of the internal components; the annular gas and the main gas come from the process gas at the compressor outlet.

[0014] Preferably, in the above technical solution, the aperture of the small hole in the tower bottom distribution plate is Φ10-Φ25, the opening rate is 20%-30%, and the small holes are distributed in concentric circles, with the distance between adjacent circles being 4-6 times the aperture; the aperture of the small hole in the bottom end cap distribution plate (5) of the inner component is Φ10-Φ25, the opening rate is 20%-30%, and the small holes are distributed in concentric circles, with the distance between adjacent circles being 2-4 times the aperture.

[0015] Preferably, in the above technical solution, the flow regulating device includes a flow meter, a regulating valve and a controller, to achieve flow fluctuation ≤ ±5%.

[0016] Preferably, the above technical solution also includes a temperature protection system, which forces the N1 annular gas to be fully opened to cool the high-voltage casing when the highest temperature of the annular gap is detected to be greater than the highest operating temperature of the high-voltage casing.

[0017] Compared with the prior art, the present invention has the following beneficial effects: High-pressure casing temperature fluctuations are significantly reduced: By limiting the main gas (N2) function to the main reaction gas flow and adding an independently controlled annular gas (N1) passage, the annular gas flow rate remains basically stable when the unit load fluctuates significantly, so that the temperature rise fluctuation range of the high-pressure casing is much lower than that of traditional processes, avoiding fatigue damage caused by alternating thermal stress.

[0018] Enhanced stability under low load conditions: Under low load conditions, the proportion of annular gas flow rate is significantly increased, ensuring that the heat exchanger at the bottom of the tower maintains effective heat recovery capacity and reducing reliance on external heat compensation.

[0019] Improved fatigue resistance: By controlling the stable annular gas flow rate, the temperature fluctuation of the high-pressure shell is always kept below the critical value for fatigue assessment, meeting the requirements for long-term safe operation under high-frequency load fluctuations (>5,000 times).

[0020] Green electricity fluctuation adaptability optimization: The combination of annular gas flow stabilization mechanism and main gas passive regulation enables the synthesis tower to maintain stable high-pressure shell thermal state even when the load changes drastically on a minute-by-minute basis, breaking through the dependence of traditional ammonia synthesis units on load continuity. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a schematic diagram of the gas path in the synthesis tower of the present invention; Figure 3 This is a schematic diagram of the gas path of the synthesis tower in the existing technology.

[0022] In the diagram: 1. High-pressure outer shell; 2. Internal components; 3. Annular gap; 4. Bottom distribution plate of the tower; 5. Bottom end cap distribution plate of the internal components; 6. No. 1 catalytic bed; 7. Upper interlayer heat exchanger; 8. No. 2 catalytic bed; 9. Lower interlayer heat exchanger; 10. No. 3 catalytic bed; 11. Bottom heat exchanger of the tower; 12. Distribution baffle; 13. Flow regulating device. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0024] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0025] Example 1

[0026] A temperature control device for a green ammonia synthesis tower using green electricity includes: an annular gap 3 between a high-pressure outer shell 1 and an inner component 2, an annular gap gas inlet at the top, and a small hole connected to a tower bottom distribution plate 4 at the bottom. The main gas inlet at the bottom end cap of the synthesis tower is connected to the small hole of the bottom end cap distribution plate 5 of the internal component 2; the annular gas branch is equipped with a flow regulating device 13 to maintain the flow rate at 4%~6% of the total intake gas volume at 100% load; the annular gas and the main gas are the heat exchanged process gas from the compressor outlet.

[0027] The diameter of the small holes in the bottom distribution plate 4 is Φ10-Φ25, and the opening rate is 20%-30%. The diameter of the small holes in the bottom end cap distribution plate 5 of the inner part 2 is Φ10-Φ25, and the opening rate is 20%-30%. The small holes are distributed in concentric circles, and the distance between adjacent circles is 2-4 times the diameter of the hole.

[0028] The flow regulating device 13 includes a flow meter, a regulating valve and a controller, and achieves flow fluctuation ≤ ±5%.

[0029] The device is equipped with a temperature protection system. When the highest temperature of the annular gap 3 is detected to be greater than the highest operating temperature of the high-voltage casing, the N1 annular gap gas is forced to be fully opened to cool the high-voltage casing.

[0030] The process gas from the compressor outlet, after heat exchange, is divided into five streams before entering the synthesis tower: 1) N1 annular gas – enters the annular gap 3 of the tower wall from the top of the synthesis tower, flows from top to bottom, then enters the small hole of the distribution plate 4 at the bottom of the tower, and then merges with the N2 main gas to enter the shell side of the heat exchanger, in order to maintain the temperature of the high-pressure shell 1 of the synthesis tower, so as to increase the operational stability and safety of the synthesis tower.

[0031] 2) N2 main gas – cold gas from the bottom heat exchanger of the synthesis tower enters the small hole of the distribution plate of the bottom end cap of the inner part 2 from the bottom end cap of the synthesis tower, and then merges with the N1 annular gas into the shell side of the heat exchanger to adjust the temperature of the process gas from the synthesis tower to 330-420℃. The cold gas from the bottom heat exchanger enters the zero meter layer along the central tube.

[0032] 3) F0 temperature regulating gas – used to adjust the inlet temperature of the No. 1 catalytic bed 6 in the synthesis tower to 350-370℃ to adapt to different operating conditions of the synthesis tower.

[0033] 4) F1 temperature regulating gas - used to adjust the inlet temperature of the No. 2 catalytic bed 8 in the synthesis tower to 380-400℃ to adapt to different operating conditions of the synthesis tower.

[0034] 6) F2 temperature regulating gas - used to adjust the inlet temperature of the No. 3 catalytic bed 10 in the synthesis tower to 380-400℃ to adapt to different operating conditions of the synthesis tower.

[0035] The F1 and F2 temperature-regulating gases from the upper and lower interlayer heat exchangers (tube side 9) and the N2 main gas and N1 annular gas from the bottom heat exchanger (shell side 11) exchange heat with the gases from the reactions at beds #1, #2, and #3, respectively, raising their temperature to 350–380°C. They then rise along the central tube to the zero-meter level of the catalytic bed. After being regulated to a suitable temperature by f0 cooling gas, they enter the #1 radial catalytic bed and react at 490–510°C. They then enter the upper interlayer heat exchanger (tube side 7), where the F1 temperature-regulating gas regulates their temperature to 380–400°C before flowing outwards... The gas enters the No. 2 catalytic bed 8 along the radial direction and reacts at 460-480°C. It then enters the shell side of the lower interlayer heat exchanger 9. After being regulated to 380-400°C by F2 temperature-regulating gas, it enters the No. 3 catalytic bed 10 along the radial direction from the outside to the inside and reacts at 425-450°C. It then enters the tube side of the bottom heat exchanger 11. After being cooled to 330-420°C by N1 annular gas and N2 main gas, it exits the tower and becomes the reaction gas. It then enters the heat recovery, cooling and separation of liquid ammonia, and the circulating gas merges with the fresh gas. After being pressurized and heat-exchanged by the compressor, it enters the synthesis tower.

[0036] The specific adjustment process is as follows: 1) The process gas is divided into five streams: ① N1 annular gas 3, with a basically constant flow rate to ensure small temperature changes in the outer shell of the ammonia synthesis tower and improve the safety of the high-pressure outer shell 1; ② F0 temperature regulating gas, which regulates the inlet temperature of the first bed; ③ F1 temperature regulating gas, which regulates the inlet temperature of the second bed; ④ F2 temperature regulating gas, which regulates the inlet temperature of the third bed; ⑤ N2 main line gas, with the valve opening remaining unchanged when the unit load changes.

[0037] When the unit load changes from high to low, the opening of the valves for F0 temperature regulating gas, F1 temperature regulating gas, and F2 temperature regulating gas decreases, while the flow rate of N1 annular gap 3 gas remains unchanged (Note: the proportion of N1 annular gap 3 gas flow rate to the total flow rate is relatively small). Therefore, the proportion of N1 annular gap 3 gas + N2 main gas flow rate increases (as shown in Tables 1 and 2, the flow rate proportion increases from 15% to 29%). This allows for the recovery of as much reaction heat as possible through the third bed outlet heat exchanger under low load, maintaining the reaction in the synthesis tower and reducing the external heat supply to the synthesis tower.

[0038] 2) Traditional ammonia synthesis units operate under a "safe, stable, long-term, full-capacity, and high-efficiency" operating condition to achieve low overall energy consumption and maximize economic benefits. Therefore, they generally require continuous operation at around 100% load. Furthermore, the operating flexibility of these units is limited, typically designed for 60%–110% load, with minimal fluctuations below 80% load—far below the baseline parameter of 1000 cycles within the unit's design life—to ensure economic benefits are met. Therefore, traditional ammonia synthesis units do not require consideration of the adverse effects of changes in the gas flow rate at the synthesis tower's inlet on the tower's outer shell.

[0039] 3) The improved ammonia synthesis unit (green electricity to green ammonia unit) needs to adapt to the fluctuating and unstable characteristics of green electricity such as wind and solar power. The load of the unit varies greatly, ranging from a minimum of 10% to a maximum of 110% to 125%. In addition, the frequency of large load fluctuations is at least once a day, and the number of large load fluctuations in the unit reaches more than 5,000 times within the design service life of the unit (not less than 15 years).

[0040] If the synthesis tower is designed using traditional ammonia synthesis technology, the N2 main gas serves as both the main gas and the annular gas. If the flow rate fluctuates significantly, the temperature of the high-pressure outer shell 1 of the synthesis tower will fluctuate greatly (as shown in Tables 1 and 2, the temperature rise changes from 34.5℃ to 68.2℃ to 32.7℃). This makes it prone to operating under fatigue conditions, posing a risk to the long-term safe operation of the synthesis tower.

[0041] If the synthesis tower adopts an improved ammonia synthesis process technology design, the N2 main gas will only function as the main gas, while an N1 annular gap 3 gas will be set up to maintain a basically stable flow rate. This will result in large load variations for the ammonia synthesis unit. However, because the flow rate fluctuation of the annular gap 3 gas is small, the temperature fluctuation of the high-pressure shell 1 of the synthesis tower will also be small (as shown in Tables 1 and 2, if the N1 flow rate is perfectly regulated, the temperature rise change is 0℃ = 100℃ - 100℃; as shown in Tables 3 and 4, if the N1 flow rate is perfectly regulated, the temperature rise change is 0℃ = 125℃ - 125℃; as shown in Tables 5 and 6, if the N1 flow rate is perfectly regulated, the temperature rise change is 0℃ = 83.3℃ - 83.3℃). This ensures that the high-pressure shell 1 of the synthesis tower always operates under non-fatigue conditions, which is beneficial to the long-term safe operation of the synthesis tower.

[0042] Table 1 Gas flow rate at 100% load (based on a 300,000-ton ammonia synthesis unit)

[0043] Table 2 Gas flow rate at 10% load (based on a 300,000-ton ammonia synthesis unit)

[0044] Table 3 Gas flow rate at 100% load (based on a 300,000-ton ammonia synthesis unit)

[0045] Table 4 Gas flow rate at 10% load (based on a 300,000-ton ammonia synthesis unit)

[0046] Table 5 Gas flow rate at 100% load (based on a 300,000-ton ammonia synthesis unit)

[0047] Table 6 Gas flow rate at 10% load (based on a 300,000-ton ammonia synthesis unit)

[0048] 4) Flow direction of N1 annular gap 3 gas and N2 main gas in the improved ammonia synthesis unit (green electricity to green ammonia unit): The N1 annular gap 3 gas flows downward from the annular gap 3 between the high-pressure outer shell 1 and the inner part 2 of the synthesis tower, thereby removing the heat transferred from the inner part 2 to the high-pressure outer shell 1 and preventing the high-pressure outer shell 1 from overheating; then it enters the bottom cavity of the inner part 2 through the small holes of the bottom distribution plate 4 and merges with the N2 main gas. The N2 main gas enters from the bottom of the synthesis tower, first passing through the distribution baffle 12, and then entering the small hole of the distribution plate at the bottom of the inner part 2, where it merges with the N1 annular gap 3 gas.

[0049] The gas after N1 annular gas and N2 main gas merge enter the heat exchanger 11 at the bottom of the tower for heat exchange. The heat-exchanged gas then merges with other gases entering the tower and enters the catalyst bed for reaction.

[0050] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for temperature control in a green electricity-to-ammonia synthesis tower, comprising annular gas and main gas, wherein the annular gas and main gas originate from process gas from the compressor outlet, and the annular gas enters the annular space of the synthesis tower wall, characterized in that: The annular gas flow rate is controlled to be stably maintained at a predetermined value, and the high-pressure casing temperature fluctuation range is ensured to be ≤25℃. The predetermined value is 4%~6% of the total intake air volume at 100% load, and the allowable fluctuation range of the annular gas flow rate is ≤±12.5%. The synthesis tower includes a high-pressure outer shell (1) and an inner component (2) fitted inside the high-pressure outer shell. An annular gap (3) is provided between the high-pressure outer shell (1) and the inner component (2). An annular gap gas inlet is provided at the upper part of the high-pressure outer shell (1), and a main line gas inlet is provided at the bottom end cap. The control method includes the following steps: The annular gas enters the annular gap (3) through the annular gas inlet, and after descending along the annular gap (3), it merges with the main gas entering the bottom end cap distribution plate (5) through the small hole of the bottom distribution plate (4) of the tower and enters the bottom heat exchanger (11) for heat exchange. The main gas enters the bottom of the synthesis tower through the main gas inlet, and merges with the annular gas entering the bottom distribution plate (4) through the small hole of the bottom end cap distribution plate (5) of the internal components and enters the bottom heat exchanger (11) for heat exchange. The annular gas flow rate is controlled to be stably maintained at 5% of the total gas volume, with an allowable fluctuation range of ≤±12.5%; The opening of the main gas branch valves is fixed after commissioning and the flow rate is passively adjusted according to load fluctuations. The annular gas and the main gas maintain independent flow paths before entering the bottom distribution plate (4) and the bottom end cap distribution plate (5) of the internal components, and then merge in the cavity formed by the bottom distribution plate (4), the bottom end cap distribution plate (5) of the internal components, and the bottom heat exchanger (11).

2. The control method according to claim 1, characterized in that: A flow regulating device (13) is installed in the annular gap gas branch to maintain the flow rate of the annular gap gas branch at 4% to 6% of the total intake air volume at 100% load.

3. The control method according to claim 1, characterized in that: The bottom distribution plate (4) of the tower has a hole opening rate of 20%-30%, the holes are distributed in concentric circles, and the distance between adjacent circles is 4-6 times the hole diameter; the bottom end cap distribution plate (5) of the inner part has a hole opening rate of 20%-30%, the holes are distributed in concentric circles, and the distance between adjacent circles is 2-4 times the hole diameter.

4. The control method according to claim 2, characterized in that: The flow regulation device (13) includes a flow meter, a regulating valve and a controller, and achieves flow fluctuation ≤ ±5%.

5. The control method according to claim 1, characterized in that: It is also equipped with a temperature protection system. When the highest temperature of the annular gap (3) is detected to be greater than the highest operating temperature of the high-voltage casing, the annular gap gas is forced to be fully opened to cool down the high-voltage casing.

Images