Safety starting method of ammonium nitrate volumetric reactor

Abstract

The present application relates to the technical field of reactor, and provides a safe starting method of ammonium nitrate volumetric reactor, which comprises the following steps: S1, saturated steam is introduced into a steam pipeline connected with the reactor to carry out hydrophobic preheating and pressure increasing operation until the pressure in the steam pipeline is stable; S2, liquid medium is added into the reactor to establish an initial liquid level; S3, saturated steam is introduced into the bottom of the liquid phase in the reactor by using the steam pipeline to heat and pressurize the liquid phase in the reactor, and ammonia gas is introduced into the liquid phase in the reactor to adjust the pH value of the liquid phase; S4, when the temperature of the liquid phase in the reactor, the top pressure, the pH value of the liquid phase and the pH value of the gas phase all reach preset starting conditions, ammonia gas and dilute nitric acid are put into the reactor to start the neutralization reaction to produce.The present application can eliminate the huge temperature difference between the reaction zone and the surrounding liquid phase from the source, improve the safety and stability of the starting process of the device, and improve the production efficiency.

Description

Technical Field

[0001] This invention relates to the field of reactor technology, and specifically to a safe start-up method for an ammonium nitrate volumetric reactor. Background Technology

[0002] In existing technologies, ammonium nitrate is a core raw material for the production of fertilizers and industrial explosives. Its production is inseparable from reactors. During production, ammonia and dilute nitric acid are fed into the reactor, where they react to produce ammonium nitrate. Traditional volumetric reactor start-up methods employ gas-phase heating and direct feeding. This involves first introducing low-pressure steam into the upper gas phase section of the reactor to raise the temperature. Once the gas phase section reaches the target temperature, ammonia and dilute nitric acid are directly added for a neutralization reaction. After feeding, the ammonia and dilute nitric acid react rapidly, releasing a large amount of heat. This creates a significant temperature difference between the reaction zone and the surrounding low-temperature liquid phase, easily causing severe reactor vibration. Prolonged severe vibration can lead to weld cracking, flange leaks, and even ammonium nitrate decomposition and explosion. To mitigate vibration and ensure safety, the feeding rate of ammonia and dilute nitric acid needs to be reduced, resulting in a significantly extended start-up cycle and low production efficiency. Summary of the Invention

[0003] To overcome the above-mentioned defects, embodiments of the present invention provide a safe start-up method for an ammonium nitrate volumetric reactor, which solves the technical problem in the related art that in order to alleviate vibration, it is necessary to reduce the feeding rate of ammonia and dilute nitric acid, which leads to a significant extension of the start-up cycle and low production efficiency.

[0004] At least one embodiment of the present invention provides a safe start-up method for an ammonium nitrate volumetric reactor, comprising the following steps: S1. Steam pipe preheating and pressurization: Saturated steam is introduced into the steam pipe connected to the reactor for preheating and pressurization until the pressure in the steam pipe stabilizes. S2. Establishing the initial liquid level: Add liquid medium into the reactor to establish the initial liquid level; S3. Reactor heating and pressurization: Saturated steam is introduced into the bottom of the liquid phase in the reactor through a steam pipe to heat the liquid phase and pressurize the reactor. At the same time, ammonia is introduced into the liquid phase in the reactor to adjust the pH value of the liquid phase. S4. Feeding and Start-up: When the liquid phase temperature, top pressure, liquid phase pH value and gas phase pH value in the reactor all reach the preset start-up conditions, ammonia and dilute nitric acid are fed into the reactor to start the neutralization reaction for production.

[0005] According to one embodiment of this application, in step S1, the pressure reached after the saturated steam in the steam pipe is pressurized by condensation is 0.35 to 0.50 MPa.

[0006] According to one embodiment provided in this application, in step S2, the liquid medium is an ammonium nitrate solution or demineralized water.

[0007] According to one embodiment provided in this application, in step S2, the mass fraction of the ammonium nitrate solution is ≤70%.

[0008] According to one embodiment provided in this application, in step S2, the initial liquid phase level is ≤ 10% of the maximum liquid level of the reactor.

[0009] According to one embodiment provided in this application, in step S3, the heating rate of the liquid phase is controlled to be 30-60°C / h.

[0010] According to one embodiment provided in this application, in step S3, during the heating and pressurization process, the liquid level is controlled at 15-20% of the maximum liquid level in the reactor.

[0011] In step S3, during the heating and pressurization process, liquid phase pH is measured through the liquid phase pH detection port on the reactor, and the amount of ammonia gas introduced into the reactor is adjusted according to the detection results.

[0012] According to one embodiment provided in this application, in step S4, the preset start-up conditions are: liquid phase temperature in the reactor is 130-150°C, top pressure is 0.20-0.30 MPa, liquid phase pH is 5.5-6.8, and gas phase pH is 9-13.

[0013] This invention provides a safe start-up method for an ammonium nitrate volumetric reactor. Compared with existing technologies, preheating and pressurizing via a steam pipeline eliminates the risk of water hammer in the steam pipeline, preventing violent impacts on the steam pipeline, valves, and reactor. It also provides the reactor with steam that maintains stable temperature, flow rate, and dryness. A liquid medium is added to the reactor to establish an initial liquid level. Saturated steam is then introduced into the bottom of the liquid phase within the reactor via the steam pipeline, raising the temperature and pressure of the liquid phase. Simultaneously, ammonia gas is introduced into the liquid phase to adjust its pH value. When the liquid phase temperature, top pressure, liquid phase pH, and gas phase pH all meet the preset start-up conditions, ammonia and dilute nitric acid are added to the reactor to initiate the neutralization reaction and production. The steam introduced into the bottom of the liquid phase rises through bubbles and fully contacts the liquid phase, achieving uniform heat exchange throughout the liquid phase, rather than the traditional gas-to-liquid conduction heat exchange. This method results in a more uniform liquid phase temperature within the reactor, eliminating the significant temperature difference between the reaction zone and the surrounding liquid phase at its source, and reducing vibrations caused by intense exothermic reactions. There is no longer a need to reduce the feeding rate of ammonia and dilute nitric acid to alleviate vibration, which can shorten the start-up cycle and improve production efficiency. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 The flowchart provided is for an embodiment of the present invention. Figure 2 This is a schematic diagram of the reactor structure in an embodiment of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0017] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0018] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and 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.

[0019] The terms "first," "second," "third," "fourth," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those illustrated or described herein.

[0020] To make the drawings concise and easy to understand, some drawings only show one of the components with the same structure or function, or only one of them is marked. In this article, "one" not only means "only one", but can also mean "more than one", and "several" includes "two" and "more than two".

[0021] Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus. It is understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. The embodiments of this application are described in detail below with reference to the accompanying drawings.

[0022] like Figure 1 As shown, a safe start-up method for an ammonium nitrate volumetric reactor according to an embodiment of the present invention is illustrated. The start-up method includes the following steps: S1. Steam pipe condensate preheating and pressurization: Saturated steam is introduced into the steam pipe connected to the reactor for condensate preheating and pressurization until the pressure in the steam pipe stabilizes. The pressure reached after condensate preheating of the saturated steam in the steam pipe is 0.35-0.50 MPa, preferably 0.40-0.45 MPa. S2. Establishing the initial liquid level: Add liquid medium into the reactor to establish the initial liquid level. The liquid medium is ammonium nitrate solution or demineralized water. The mass fraction of the ammonium nitrate solution is ≤70%, and the initial liquid level is ≤10% of the maximum liquid level of the reactor. S3. Reactor Heating and Pressurization: Saturated steam is introduced into the bottom of the liquid phase in the reactor through a steam pipe to raise the temperature and pressurize the reactor. At the same time, ammonia gas is introduced into the liquid phase to adjust the pH value. The pressure of the saturated steam is 0.35-0.50 MPa, and the heating rate of the liquid phase is controlled at 30-60℃ / h. During the heating and pressurization process, the liquid level is controlled at 15-20% of the maximum liquid level in the reactor. The pH of the liquid phase is measured through the pH detection port on the reactor, and the amount of ammonia gas introduced into the reactor is adjusted according to the detection results. S4. Feeding and Start-up: When the liquid phase temperature, top pressure, liquid phase pH value, and gas phase pH value in the reactor all reach the preset start-up conditions, ammonia and dilute nitric acid are fed into the reactor to start the neutralization reaction for production. The preset start-up conditions are: liquid phase temperature in the reactor is 130-150℃, top pressure is 0.20-0.30MPa, liquid phase pH value is 5.5-6.8, and gas phase pH value is 9-13.

[0023] For step S1, condensate will remain in the steam pipeline after a long period of shutdown. During the initial startup phase, the low temperature in the pipeline will also cause the steam to condense rapidly, producing a large amount of liquid water. If this water is not discharged, the high-speed steam will push the water to form a water hammer, violently impacting the steam pipeline, valves, and reactor, leading to weld cracking, flange leaks, and even equipment damage. The pressure and temperature of saturated steam have a one-to-one correspondence. Only when the pressure inside the steam pipeline is stable can the temperature, flow rate, and dryness of the saturated steam entering the reactor be kept stable, laying the foundation for subsequent precise temperature control.

[0024] Steam pipeline condensate preheating and pressurization: Slowly open the steam pipeline condensate valve, ensuring a continuous and stable outflow of condensate. Slowly open the steam inlet valve to heat the pipeline. For temperatures ≤100℃, control the heating rate at 10-20℃ / h. Once the pipeline reaches approximately 100℃, allow it to stabilize for 10 minutes. Afterward, control the heating rate at 20-30℃ / h, maintaining the condensate valve opening and closely observing the steam flow. As the amount of steam discharged gradually increases, gradually close the condensate valve. For pipeline temperatures >100℃, as the temperature rises, the steam pressure inside the pipeline will also gradually increase. Control the pressurization rate at 0.02-0.05 MPa / min. Stop pressurizing every 0.1 MPa increase, hold for 10-15 minutes, and check the pipeline, valves, flanges, etc., for leaks or deformation. If no abnormalities are found, continue pressurizing. After the pressure stabilizes, re-check the operating status of all parts of the pipeline to ensure there are no leaks or abnormal vibrations.

[0025] This invention eliminates the risk of water hammer in steam pipelines through a preheating and pressurization process that drains water from the pipelines, preventing violent impacts on the pipelines, valves, and reactors, and providing the reactor with steam of stable temperature, flow rate, and dryness. Once the pressure reaches the set range, it remains stable for 3-5 minutes to ensure the steam pipeline is free of leaks, water accumulation, and abnormal vibrations; this is not considered a momentary achievement of the target pressure.

[0026] When the pressure after pressurization by condensate in the steam pipeline is below 0.35 MPa, the steam pressure and temperature are insufficient, leading to increased heating and low efficiency. When the pressure is above 0.50 MPa, the high steam temperature and pressure can cause the reactor to heat up too quickly, resulting in localized temperature differences and vibrations, making operation difficult to control. Therefore, the saturated steam pressure is set to 0.35–0.50 MPa, with the optimal control range being 0.40–0.45 MPa.

[0027] For step S2, this method uses direct heating from the bottom of the liquid phase. A liquid medium must be added to the reactor first to allow the steam to fully contact and exchange heat with the liquid phase. If there is no liquid phase, the steam will be directly introduced into the gas phase space, which will return to the shortcomings of traditional gas phase heating, and the liquid phase heating will be extremely slow.

[0028] Excessively high liquid levels lead to a significant increase in the amount of steam required for heating, prolonged heating time, and increased energy consumption; conversely, excessively low liquid levels cause steam to directly overflow the liquid surface, resulting in violent gas-liquid mixing and triggering reactor vibration and liquid level fluctuations. Therefore, this invention sets the initial liquid level to ≤10% of the reactor's maximum liquid level.

[0029] Prioritize using the dilute ammonium nitrate mother liquor from the previous batch to establish the initial liquid level. This can avoid diluting the material with demineralized water, reduce the material balance time at the beginning of start-up, and further shorten the start-up cycle. If there is no mother liquor, demineralized water can be used as a substitute.

[0030] When the ammonium nitrate solution has a mass fraction exceeding 70%, it is prone to crystallization and precipitation at low temperatures, clogging pipes, valves, and steam nozzles. Conversely, a concentration that is too low will excessively dilute subsequent feed materials, prolonging the product's time to reach standard. An ammonium nitrate solution with a mass fraction ≤70% provides the necessary heat exchange medium for direct heating from the bottom of the liquid phase, completely eliminating the need for traditional gas-phase heating. This balances heating efficiency and energy consumption, avoiding problems such as vibration and overflow caused by excessively high or low liquid levels. Prioritizing the use of mother liquor reduces material dilution, further increasing start-up speed and lowering production costs.

[0031] In step S3, steam is introduced from the bottom of the liquid phase in the reactor. The rising bubbles ensure full contact with the liquid phase, achieving uniform heat exchange throughout the liquid phase, rather than the traditional gas-to-liquid conduction heat exchange. This method results in a more uniform liquid phase temperature within the reactor, eliminating the significant temperature difference between the reaction zone and the surrounding liquid phase, and reducing vibrations caused by intense heat release. It also enables uniform heating of the entire liquid phase in the reactor, eliminating localized temperature differences and fundamentally solving the problem of severe reactor vibration after feeding.

[0032] A heating rate that is too slow will significantly prolong start-up time; a heating rate that is too fast will cause excessive temperature differences between the top and bottom, and inside and outside of the reactor, generating thermal stress and causing equipment deformation. At the same time, local overheating will lead to excessively violent reactions during subsequent feeding. Setting the heating rate to 30-60℃ / h results in no significant vibration in the lower section of the reactor, balancing safety and efficiency.

[0033] When the liquid phase is heated, it will expand in volume, rising from an initial 10% liquid level to 15-20%. A liquid level below 15% will result in insufficient steam heat exchange area, causing steam to short-circuit and directly impact the gas phase. A liquid level above 20% will lead to insufficient gas phase space in the reactor, causing drastic pressure fluctuations and even overflow. Therefore, controlling the liquid level at 15-20% during the heating process can prevent overflow, steam short-circuiting, and other abnormal situations.

[0034] During the heating process, the liquid phase inside the reactor is acidic. If not adjusted, it will severely corrode the inner wall of the stainless steel reactor. Simultaneous pH control during the heating process can reduce equipment corrosion and lay the foundation for a stable reaction in the future. At the same time, adjusting the pH to the optimal reaction range in advance can ensure a stable initial reaction after feeding and avoid reaction runaway caused by local over-acidity or over-alkaliness.

[0035] like Figure 2 As shown, the reactor has a coolant inlet at the bottom. The coolant inlet is connected to the coolant tank through a coolant delivery pump and a coolant regulating valve. The coolant in the coolant tank can enter the reactor through the coolant inlet under the action of the coolant delivery pump to cool the reactor.

[0036] like Figure 2 As shown, the reactor sidewall has a pressure-stabilizing saturated steam inlet, and a switch valve is installed at the pressure-stabilizing saturated steam inlet. Actively introducing external pressure-stabilizing steam into the reactor's gas phase space through the pressure-stabilizing saturated steam inlet achieves active pressure replenishment, rapid pressure building, and negative pressure protection, compensating for the lag and deficiencies of relying solely on self-generated steam for pressure regulation. The saturated steam enters from the upper part of the sidewall, directly entering the top gas phase space of the reactor, avoiding direct impact on the liquid surface and resulting in liquid level fluctuations. The matching switch valve allows for manual and automatic rapid opening and closing, and can immediately cut off the steam supply in emergency situations to avoid excessive pressure replenishment. During the initial start-up phase, when rapid initial pressure establishment is required, traditional methods rely solely on liquid phase heating and evaporation to generate self-generated steam for pressure building, which is slow and results in large pressure fluctuations. This invention allows for the direct introduction of pressure-stabilizing steam at 0.35–0.50 MPa through the pressure-stabilizing saturated steam inlet, which can quickly raise the reactor top pressure to the set range, achieving simultaneous heating and pressurization, and significantly shortening start-up time. During normal operation, if excessive steam emission or fluctuations in feed rate cause a pressure drop, the switch valve can be opened immediately to introduce a small amount of steam to quickly bring the pressure back to the set range, preventing a sudden pressure drop that could lead to liquid-phase boiling, violent reactions, and reactor vibration. During shutdown, steam condensation inside the reactor will generate negative pressure. If the pressure is not replenished in time, the external atmospheric pressure will cause the reactor tank to collapse and deform. In this case, introducing a small amount of pressure-stabilizing steam can maintain a slight positive pressure inside the reactor, thus protecting it.

[0037] like Figure 2 As shown, the reactor has a liquid phase pH sampling port, which is equipped with a liquid phase sampling valve. During the heating and pressurization process, opening the liquid phase sampling valve allows the liquid in the reactor to pass through the valve and enter the mixing tank. After mixing, diluting, and cooling with the demineralized water, the liquid enters the pH detection component for liquid phase pH detection. Based on the detection results, the amount of ammonia added to the reactor is adjusted to stabilize the liquid phase pH value in the reactor between 5.5 and 6.8. Both the mixing tank and the pH detection component are surrounded by water jackets, through which circulating water cools the mixing tank and the pH detection component.

[0038] A liquid phase temperature sensor for detecting the liquid phase temperature is installed at the bottom of the reactor. An ammonia control valve for introducing ammonia gas into the reactor is also installed at the bottom of the reactor. A pressure sensor for detecting the gas phase pressure inside the reactor is installed at the top of the reactor. A pressure-stabilizing saturated steam control valve and a gas phase pH sensor are installed at the top of the reactor. A heating saturated steam control valve is installed on the steam pipe. The outputs of the liquid phase temperature sensor, pressure sensor, and pH detection component are all electrically connected to the input of a controller. The output of the controller is electrically connected to the heating saturated steam control valve, coolant regulating valve, pressure-stabilizing saturated steam control valve, and ammonia control valve. The controller controls the opening of the heating saturated steam control valve and coolant regulating valve based on the liquid phase temperature detected by the liquid phase temperature sensor, maintaining the liquid phase temperature at 130–150°C. The controller controls the opening of the pressure-stabilizing saturated steam control valve based on the pressure value detected by the pressure sensor, maintaining the top pressure inside the reactor at 0.20–0.30 MPa. The controller controls the opening of the ammonia control valve based on the pH value detected by the pH detection component, maintaining the liquid phase pH at 5.5–6.8. The controller controls the opening of the ammonia control valve based on the pH value detected by the gas phase pH sensor, controlling the gas phase pH value to be 9-13.

[0039] For step S4, when the temperature is below 130℃, the feeding should be slow and the heat release of the reaction should be controlled, resulting in a long start-up time; when the temperature is above 150℃, the reactor's heating and pressurization time will be prolonged. Setting the liquid phase temperature to 130-150℃, with a moderate feeding and start-up speed, ensures uniform heat release. The pressure at the top of the reactor was set to 0.20–0.30 MPa, which corresponds to the saturated vapor pressure of the liquid phase at 130–150°C. This pressure is close to the normal operating pressure of the reactor, which is 0.32–0.38 MPa. The feeding and start-up process was safe and stable.

[0040] If the ratio of nitric acid to ammonia is not properly controlled during the start-up of the feeding vehicle when the pH is < 5.5, the liquid phase may become acidic, which can corrode equipment and cause problems such as ammonium nitrate decomposition. When the pH is > 6.8, the liquid phase is too alkaline, which will produce a large amount of free ammonia and increase the load on the exhaust gas treatment. The neutralization reaction is most stable and produces the best product quality when the liquid phase pH is set to a weakly alkaline environment of 5.5 to 6.8.

[0041] Setting the gas phase pH to 9–13 indicates a slightly alkaline gas phase, which means there is an appropriate amount of excess ammonia in the reactor. This prevents acidic gases from corroding the top of the reactor and the gas phase pipes, while ensuring that the exhaust gas emissions meet the standards.

[0042] Example 1: The safe start-up method for the ammonium nitrate volumetric reactor in this example includes the following steps: S1: Steam Pipeline Drain Preheating and Pressurization: Slowly open the steam pipeline drain valve to control the continuous and stable outflow of condensate. Slowly open the steam valve entering the pipeline to heat the pipeline. For temperatures ≤100℃, control the heating rate at 10-20℃ / h. Stabilize the pipeline temperature for 10 minutes after it reaches 100℃. Afterward, control the heating rate at 20-30℃ / h, maintaining the opening of the drain valve and closely observing the water discharge. Ensure the drain valve does not continuously discharge steam. As the amount of discharged steam gradually increases, gradually close the drain valve. At this time, the steam pressure in the pipeline will also gradually rise. Control the pressurization rate at 0.02-0.05MPa / min. Stop pressurizing every 0.1MPa increase, maintain the pressure for 12 minutes, and check the pipeline, valves, flanges, etc. for leaks or deformation. After confirming there are no abnormalities, continue pressurizing. Stop pressurizing when the pressure reaches 0.40MPa. After maintaining the pressure stability, check the operating status of all parts of the pipeline again to ensure there are no leaks or abnormal vibrations. Then, prepare for standby. S2: Liquid level setting for volumetric reactor: Use a neutralization coolant pump to send a 35% dilute ammonium nitrate solution coolant to the bottom of the volumetric reactor. Stop the pump when the DCS level gauge shows 8% liquid level and check the on-site level gauge to make it consistent with the DCS level gauge display.

[0043] S3: Volumetric Reactor Heating and Pressurization: Open the shut-off valve of the liquid phase heating steam pipe in the reactor, and slowly and manually control the heating regulating valve of the DCS system to heat the 45℃ dilute ammonium nitrate solution in the reactor at a rate of 55-60℃ / h. When the temperature of the dilute ammonium nitrate solution reaches 100℃, adjust the heating regulating valve to control the heating rate at 40-55℃ / h, and control the pressure increase rate at the top of the volumetric reactor at 0.01-0.02MPa / min. Before the temperature of the dilute ammonium nitrate solution reaches 130℃, control the pressure at the top of the volumetric reactor at ≤0.20MPa. Observe the liquid level displayed on the DCS. When it reaches 10%, open the ammonium nitrate solution discharge valve to discharge into the neutralization cooling tank to maintain the liquid level. When the temperature of the dilute ammonium nitrate solution reaches 130℃, adjust the heating regulating valve to control the heating rate at 30-40℃ / h, and control the pressure increase rate at 0.01-0.02MPa / min. The DCS displays the pH of the dilute ammonium nitrate solution at 5.3. Ammonia gas is slowly introduced into the liquid phase to gradually adjust the pH to 6.3–6.8. When the temperature of the dilute ammonium nitrate solution reaches 140℃, heating and pressurization are stopped, and the pressure at the top of the volumetric reactor is maintained at 0.28–0.30 MPa.

[0044] S4: Start-up of the volumetric reactor: Turn on the nitric acid pump and use the reflux valve to control the nitric acid pressure to 0.50-0.60 MPa. Open the ammonia regulating valve to introduce ammonia into the reactor liquid phase, controlling the flow rate at 1.0-1.5 t / h. Observe the DCS display; when pH ≥ 6.5, open the nitric acid regulating valve to introduce nitric acid into the reactor liquid phase, controlling the flow rate at 10-20 t / h. Adjust the ammonia flow rate to maintain the pH at 6.3-6.8. Open the regulating valve of the process steam pipeline at the top of the volumetric reactor, controlling the pressure rise rate at the top of the reactor to 0.01 MPa / min and ≤ 0.35 MPa. Observe the liquid level displayed on the DCS. When it reaches 40%, open the ammonium nitrate solution discharge valve to discharge into the neutralization cooling tank. If the neutralization cooling tank level reaches 75%, collect from the dilute ammonium nitrate solution tank, maintaining the liquid level at 40-50%. After the pH value stabilizes, gradually increase the flow rates of ammonia and nitric acid into the reactor, controlling the heating rate of the dilute ammonium nitrate solution in the reactor at 20–30℃ / h. The temperature of the liquid ammonium nitrate solution in the reactor reaches 165℃, and the pressure at the top of the reactor is controlled at 0.32–0.35 MPa / min. Control the flow rates of nitric acid and ammonia according to the production plan, and control the liquid phase pH according to user requirements. Control the liquid phase temperature of the volumetric reactor at 165–172℃, the top gas phase temperature at 170–178℃, the pressure at 0.32–0.38 MPa, and the pH value at 9–13.

[0045] Example 2: The safe start-up method for the ammonium nitrate volumetric reactor in this example includes the following steps: S1: Same as Example 1; S2: Liquid level setting for volumetric reactor: Use a neutralization coolant pump to send a 50% dilute ammonium nitrate solution coolant to the bottom of the volumetric reactor. Stop the pump when the DCS level gauge shows a liquid level of 7%, and check the on-site level gauge to ensure it matches the DCS level gauge reading.

[0046] S3: Volumetric Reactor Heating and Pressurization: Open the shut-off valve of the liquid phase heating steam pipe in the reactor, and slowly and manually control the heating regulating valve of the DCS system to heat the 70℃ dilute ammonium nitrate solution in the reactor at a rate of 55-60℃ / h. When the temperature of the dilute ammonium nitrate solution reaches 100℃, adjust the heating regulating valve to control the heating rate at 40-55℃ / h, and control the pressure increase rate at the top of the volumetric reactor at 0.01-0.02MPa / min. The DCS displays a pH value of 4.7 for the dilute ammonium nitrate solution. Slowly introduce ammonia gas into the liquid phase to gradually adjust the pH to 6.3-6.8. Before the temperature of the dilute ammonium nitrate solution reaches 130℃, control the pressure at the top of the volumetric reactor to ≤0.20MPa. Carefully observe the liquid level displayed on the DCS. When it reaches 10%, open the ammonium nitrate solution discharge valve to discharge into the neutralization cooling tank and maintain the liquid level. When the temperature of the dilute ammonium nitrate solution reaches 130℃, adjust the heating rate of the heating valve to control it at 30-40℃ / h, and the pressurization rate to control it at 0.01-0.02MPa / min. When the temperature of the dilute ammonium nitrate solution reaches 148℃, stop heating and pressurizing, and maintain the pressure at the top of the volumetric reactor stable at 0.28-0.30MPa.

[0047] S4: Start-up of the volumetric reactor: Turn on the nitric acid pump and use the reflux valve to control the nitric acid pressure to 0.50–0.60 MPa. Open the ammonia regulating valve to introduce ammonia into the reactor liquid phase, controlling the flow rate at 1.0–1.5 t / h. Observe the DCS display; when pH ≥ 6.5, open the nitric acid regulating valve to introduce nitric acid into the reactor liquid phase, controlling the flow rate at 10–20 t / h. Adjust and control the ammonia flow rate to maintain pH at 6.2–6.8. Open the regulating valve of the process steam pipeline at the top of the volumetric reactor, controlling the pressure rise rate at the top of the reactor to 0.01 MPa / min and ≤ 0.35 MPa. Observe the liquid level displayed on the DCS. When it reaches 40%, open the ammonium nitrate solution discharge valve to discharge into the neutralization cooling tank. If the neutralization cooling tank level reaches 75%, collect from the dilute ammonium nitrate solution tank, maintaining the liquid level at 40–50%. After the pH value stabilizes, gradually increase the flow rates of ammonia and nitric acid into the reactor, controlling the heating rate of the dilute ammonium nitrate solution in the reactor to 20–30℃ / h. The temperature of the liquid ammonium nitrate solution in the reactor should reach 165℃, and the pressure at the top of the reactor should be controlled at 0.32–0.35 MPa / min. Control the flow rates of nitric acid and ammonia according to the production plan, and control the liquid phase pH according to user requirements. For volumetric reactors, control the liquid phase temperature to 165–172℃, the top gas phase temperature to 170–178℃, the pressure to 0.32–0.38 MPa, and the pH value to 9–13.

[0048] The driving effects of the embodiments and comparative examples of the present invention are shown in Table 1 below: Table 1 Comparison of driving effects between the examples and the comparative examples

[0049] This invention eliminates the risk of water hammer in steam pipelines by preheating and pressurizing them, preventing violent impacts on the pipelines, valves, and reactor. It provides the reactor with steam that maintains stable temperature, flow rate, and dryness. Steam introduced into the reactor from the bottom of the liquid phase rises through bubbles, ensuring full contact with the liquid phase and achieving uniform heat exchange throughout the liquid phase, rather than the traditional gas-to-liquid conduction heat exchange. This method results in a more uniform liquid phase temperature within the reactor, eliminating the significant temperature difference between the reaction zone and the surrounding liquid phase at its source, and reducing vibrations caused by intense exothermic reactions. It also eliminates the need to reduce the feed rates of ammonia and dilute nitric acid to mitigate vibrations, shortening the start-up cycle and improving production efficiency.

[0050] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A safe start-up method for an ammonium nitrate volumetric reactor, characterized in that, Includes the following steps: S1. Steam pipe preheating and pressurization: Saturated steam is introduced into the steam pipe connected to the reactor for preheating and pressurization until the pressure in the steam pipe stabilizes. S2. Establishing the initial liquid level: Add liquid medium into the reactor to establish the initial liquid level; S3. Reactor heating and pressurization: Saturated steam is introduced into the bottom of the liquid phase in the reactor through a steam pipe to heat the liquid phase and pressurize the reactor. At the same time, ammonia is introduced into the liquid phase in the reactor to adjust the pH value of the liquid phase. S4. Feeding and Start-up: When the liquid phase temperature, top pressure, liquid phase pH value and gas phase pH value in the reactor all reach the preset start-up conditions, ammonia and dilute nitric acid are fed into the reactor to start the neutralization reaction for production.

2. The safe start-up method for an ammonium nitrate volumetric reactor according to claim 1, characterized in that, In step S1, the pressure reached after the saturated steam in the steam pipeline is pressurized by condensate is 0.35 to 0.50 MPa.

3. The safe start-up method for an ammonium nitrate volumetric reactor according to claim 1, characterized in that, In step S2, the liquid medium is an ammonium nitrate solution or demineralized water.

4. The safe start-up method for an ammonium nitrate volumetric reactor according to claim 3, characterized in that, The mass fraction of the ammonium nitrate solution is ≤70%.

5. The safe start-up method for an ammonium nitrate volumetric reactor according to claim 1, characterized in that, In step S2, the initial liquid level is ≤ 10% of the maximum liquid level in the reactor.

6. The safe start-up method for an ammonium nitrate volumetric reactor according to claim 1, characterized in that, In step S3, the heating rate of the liquid phase is controlled to be 30-60℃ / h.

7. The safe start-up method for an ammonium nitrate volumetric reactor according to claim 1, characterized in that, In step S3, during the heating and pressurization process, the liquid level is controlled at 15-20% of the maximum liquid level in the reactor.

8. The safe start-up method for an ammonium nitrate volumetric reactor according to claim 1, characterized in that, In step S3, during the heating and pressurization process, liquid phase pH is measured through the liquid phase pH detection port on the reactor, and the amount of ammonia gas introduced into the reactor is adjusted according to the detection results.

9. The safe start-up method for an ammonium nitrate volumetric reactor according to claim 1, characterized in that, In step S4, the preset start-up conditions are: liquid phase temperature in the reactor is 130-150℃, top pressure is 0.20-0.30MPa, liquid phase pH is 5.5-6.8, and gas phase pH is 9-13.

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