Method for preparing guanidine nitrate by continuous dynamic tubular reaction process

Abstract

The invention relates to the technical field of guanidine nitrate preparation, in particular to a method for preparing guanidine nitrate by a continuous dynamic tubular reaction process, which comprises the following steps: uniformly mixing dicyandiamide, target ammonium nitrate and target ammonium carbonate according to a mass ratio of 1: (1-3): (1-0.5); conveying the uniformly mixed material to a feeding section in a dynamic tubular reactor through a first conveying screw rod for mixing treatment, wherein the dynamic tubular reactor further comprises a heating section, a reaction section and a cooling section; sequentially conveying the target mixed material to a heating section for heating melting treatment, a reaction section for synthesis reaction treatment and a cooling section for cooling forming treatment through a second conveying screw rod to obtain an initial product; conveying the initial product into a cooling and crushing device for cooling and slicing to obtain a target guanidine nitrate product. According to the method disclosed by the invention, the mass and heat transfer efficiency can be improved, the online quantity and liquid holdup of the material are reduced, meanwhile, the raw material ratio and the reaction path are optimized, and the safety and the product purity are improved.

Description

Technical Field

[0001] This application relates to the field of guanidine nitrate preparation technology, and in particular to a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process. Background Technology

[0002] Guanidine nitrate, as a high-value-added fine chemical, is a key raw material for energetic materials, pharmaceutical intermediates (sulfonamide drugs), and pesticides (imidacloprid, sulfonylurea herbicides). Its synthesis is a nitration reaction, which has strong exothermic and explosive process risks and is classified as a high-risk chemical process.

[0003] Traditional processes for preparing guanidine nitrate use a batch reactor. However, this method suffers from several drawbacks, including low mass and heat transfer efficiency, large online material volume, poor safety, and low purity of the resulting guanidine nitrate product. Specifically, the batch reactor's low mass and heat transfer efficiency prevents rapid removal of reaction heat, leading to localized overheating and increasing the risk of side reactions (such as melamine formation) or even thermal runaway. Furthermore, the large online material volume and batch operation in the batch reactor result in high liquid holdup, exacerbating the risk of guanidine nitrate decomposition at high temperatures. Ammonium nitrate residue and the high-temperature environment during the reaction can easily trigger explosions, requiring complex temperature control systems with low operational tolerance. The high content of byproducts (biuret, melamine) necessitates additional purification steps, increasing costs.

[0004] Currently, guanidine nitrate is usually prepared by the dicyandiamide method or the urea method. However, both methods require high temperature and long reaction time and are prone to generating melamine byproducts. Although the urea method for preparing guanidine nitrate has low raw material cost, it requires the recycling of silica catalyst, the equipment is prone to scaling, and the product purity is low. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process. This method improves mass and heat transfer efficiency, reduces the amount of material online and liquid holdup, optimizes the raw material ratio and reaction path, and also enhances safety and product purity.

[0006] This application provides a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process, the method comprising:

[0007] The raw materials for preparing guanidine nitrate include dicyandiamide, ammonium nitrate to be treated, and ammonium carbonate to be treated;

[0008] Both the ammonium nitrate and the ammonium carbonate to be treated are ground and pulverized to obtain the target ammonium nitrate and the target ammonium carbonate;

[0009] The dicyandiamide, target ammonium nitrate, and target ammonium carbonate are mixed uniformly at a mass ratio of 1:(1-3):(1-0.5) to obtain a uniformly mixed material.

[0010] The uniformly mixed material is conveyed to the feeding section of a dynamic tubular reactor through a first conveying screw for mixing to obtain the target mixture. The dynamic tubular reactor is equipped with a second conveying screw and also includes a heating section, a reaction section, and a cooling section.

[0011] The target mixture is sequentially conveyed to the heating section for heating and melting, the reaction section for synthesis reaction, and the cooling section for cooling and molding through the second conveying screw to obtain the initial product;

[0012] The initial product is fed to a cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product;

[0013] The temperature of the feeding section is one of 80 to 190°C, and the temperature of the heating section and the reaction section are both one of 90 to 230°C.

[0014] According to some embodiments of this application, the second conveying screw is a dynamic twin screw, and the rotational speed of the second conveying screw is one of 10 to 500 r / min.

[0015] According to some embodiments of this application, the pressure inside the dynamic twin-screw chamber is one of 0.01 to 0.03 MPa.

[0016] According to some embodiments of this application, the step of conveying the uniformly mixed material to the feed section of a dynamic tubular reactor via a first conveying screw for mixing includes:

[0017] The uniformly mixed material is conveyed to a feeder, and then conveyed to the feed section of a dynamic tubular reactor via a first conveying screw for mixing. The feeder and the dynamic tubular reactor are connected via the first conveying screw.

[0018] According to some embodiments of this application, the method for preparing guanidine nitrate using a continuous dynamic tubular reaction process further includes:

[0019] The temperature of the feed section of the dynamic tubular reactor is controlled by the first integrated heating and cooling unit to be one of 80 to 190°C.

[0020] The temperature of the heating section of the dynamic tubular reactor is controlled to be one of 90 to 230°C by the second integrated heating and cooling unit.

[0021] The temperature of the reaction section of the dynamic tubular reactor is controlled by an oil temperature control system to be one of 90 to 230°C.

[0022] According to some embodiments of this application, the first conveying screw is one of a single screw, a twin screw, and a triple screw.

[0023] According to some embodiments of this application, the step of conveying the initial product to a cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product includes:

[0024] The initial product is conveyed through the outlet of the dynamic tubular reactor to the receiving device, and then conveyed through the receiving device to the cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product.

[0025] According to some embodiments of this application, the method for preparing guanidine nitrate using a continuous dynamic tubular reaction process further includes:

[0026] The temperature of the cooling section of the dynamic tubular reactor is controlled to be one of 20 to 80°C by a circulating water cooling mechanism.

[0027] The beneficial effects of this application are reflected in the following: The raw materials for preparing guanidine nitrate include dicyandiamide, ammonium nitrate to be treated, and ammonium carbonate to be treated; both the ammonium nitrate and ammonium carbonate to be treated are ground and pulverized to obtain target ammonium nitrate and target ammonium carbonate; dicyandiamide, target ammonium nitrate, and target ammonium carbonate are uniformly mixed at a mass ratio of 1:(1-3):(1-0.5) to obtain a homogeneous mixture; the homogeneous mixture is conveyed to the feeding section of a dynamic tubular reactor via a first conveying screw for mixing to obtain the target mixture; the dynamic tubular reactor is equipped with a second conveying screw and also includes a heating section, a reaction section, and a cooling section; the target mixture is sequentially conveyed via the second conveying screw to the heating section for heating and melting, the reaction section for synthesis reaction, and the cooling section for cooling and shaping to obtain the initial product; the initial product is conveyed to a cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product; wherein the temperature of the feeding section is one of 80-190℃, and the temperature of the heating section and the reaction section is one of 90-230℃. This application can improve mass and heat transfer efficiency, reduce online material quantity and liquid holdup, optimize raw material ratio and reaction path, and also improve safety and product purity. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart of a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process, as provided in an embodiment of this application.

[0029] Figure 2This is a schematic diagram of the guanidine nitrate synthesis process provided in the embodiments of this application;

[0030] Figure 3 This is a schematic diagram of the process for mixing uniformly mixed materials provided in the embodiments of this application;

[0031] Figure 4 This is a schematic diagram of the process for controlling the temperature of the feeding section, the heating section and the reaction section respectively, provided in the embodiments of this application;

[0032] Figure 5 This is a schematic diagram of the process for controlling the temperature of the cooling section provided in an embodiment of this application;

[0033] Figure 6 This is a schematic diagram of the process for obtaining the target guanidine nitrate product provided in the embodiments of this application. Detailed Implementation

[0034] 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. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] The following description, in conjunction with the accompanying drawings, details a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process, through specific embodiments and application scenarios.

[0036] Guanidine nitrate, as a high-value-added fine chemical, is a key raw material for energetic materials, pharmaceutical intermediates (sulfonamide drugs), and pesticides (imidacloprid, sulfonylurea herbicides). Its synthesis is a nitration reaction, which has strong exothermic and explosive process risks and is classified as a high-risk chemical process.

[0037] Traditional processes for preparing guanidine nitrate use a batch reactor. However, this method suffers from several drawbacks, including low mass and heat transfer efficiency, large online material volume, poor safety, and low purity of the resulting guanidine nitrate product. Specifically, the batch reactor's low mass and heat transfer efficiency prevents rapid removal of reaction heat, leading to localized overheating and increasing the risk of side reactions (such as melamine formation) or even thermal runaway. Furthermore, the large online material volume and batch operation in the batch reactor result in high liquid holdup, exacerbating the risk of guanidine nitrate decomposition at high temperatures. Ammonium nitrate residue and the high-temperature environment during the reaction can easily trigger explosions, requiring complex temperature control systems with low operational tolerance. The high content of byproducts (biuret, melamine) necessitates additional purification steps, increasing costs.

[0038] Currently, guanidine nitrate is usually prepared by the dicyandiamide method or the urea method. However, both methods require high temperature and long reaction time and are prone to generating melamine byproducts. Although the urea method for preparing guanidine nitrate has low raw material cost, it requires the recycling of silica catalyst, the equipment is prone to scaling, and the product purity is low.

[0039] Based on the above, this application provides a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process, which can improve mass and heat transfer efficiency, reduce the amount of material online and liquid holdup, optimize the raw material ratio and reaction path, and also improve safety and product purity.

[0040] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0041] The first aspect of this application specifically provides a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process, such as... Figure 1 As shown, a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process includes, but is not limited to, the following steps:

[0042] Step S100: Obtain the raw materials for the preparation of guanidine nitrate.

[0043] In this step, the raw materials include dicyandiamide, ammonium nitrate to be treated, and ammonium carbonate to be treated.

[0044] Step S200: Both the ammonium nitrate and ammonium carbonate to be treated are ground and pulverized to obtain the target ammonium nitrate and target ammonium carbonate.

[0045] In step S300, dicyandiamide, target ammonium nitrate and target ammonium carbonate are mixed uniformly at a mass ratio of 1:(1-3):(1-0.5) to obtain a uniformly mixed material.

[0046] It should be noted that ammonium carbonate is unstable to both light and heat, and is slightly hygroscopic. At room temperature, ammonium carbonate will decompose significantly, producing ammonia and carbon dioxide. In this process, ammonium carbonate (NH)₂CO₃ will completely decompose at 180°C in the feed section and 193°C in the reaction section, producing ammonia (NH₃), water, and carbon dioxide (CO₂ and H₂O). The role of ammonium carbonate in this process is: (1) The decomposition of ammonium carbonate is an endothermic reaction. In this process, the decomposition of ammonium carbonate can regulate the heat source in the reaction process and reduce the degree of heat accumulation. (2) The water released from the decomposition of ammonium carbonate promotes the hydrolysis of dicyandiamide to produce guanidine.

[0047] For example, referring to Table 1, the effect curves of different amounts of ammonium nitrate and ammonium carbonate added on the reaction are shown. Table 1 is shown below:

[0048]

[0049] As shown in the table above, the optimal raw material ratio for uniformly mixed materials is dicyandiamide:ammonium nitrate:ammonium carbonate = 1:2.0:0.3 (mass ratio). At this ratio, the yield is 94% and the product purity is 91%. Excessive ammonium carbonate (e.g., above 0.5%) will lead to an increase in side reactions and a decrease in yield to below 86%. The ratio must be strictly controlled.

[0050] In step S400, the uniformly mixed material is conveyed to the feed section of the dynamic tubular reactor through the first conveying screw for mixing treatment to obtain the target mixture.

[0051] In this step, a second conveying screw is installed in the dynamic tubular reactor, which also includes a heating section, a reaction section, and a cooling section.

[0052] It should be noted that the screw dynamic tubular reactor is a continuous flow reaction device that combines tubular reactor and dynamic mixing technology. Its core feature is the integration of a rotating screw (or helical element) inside the dynamic tubular reactor. Through the continuous rotation of the second conveying screw, the reactor achieves forced conveying, efficient mixing, shear dispersion, and dynamic control of temperature / concentration distribution of the reactants. It is suitable for high viscosity, multiphase systems, or chemical reaction processes that require enhanced mass / heat transfer.

[0053] In step S500, the target mixture is sequentially conveyed to the heating section for heating and melting treatment, the reaction section for synthesis reaction treatment, and the cooling section for cooling and molding treatment via the second conveying screw to obtain the initial product.

[0054] In this step, the temperature of the feeding section is one of 80 to 190°C, and the temperature of the heating section and the reaction section is one of 90 to 230°C.

[0055] It should be noted that, referring to Table 1, the effect of the temperature in the "heating section" and the "reaction section" on the purity of the product is shown in Table 1 below:

[0056]

[0057] Specifically, referring to Table 2, the data on the inhibitory effect of different reaction temperatures on the formation of byproducts are shown below:

[0058]

[0059] As shown in the table above, the optimal reaction temperature range is 180-200℃, at which point the dicyandiamide residue drops to 0.1%-1.2%, and the yield reaches 92%-94%.

[0060] In step S600, the initial product is conveyed to a cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product.

[0061] It should be noted that, referring to Table 3, under the same raw material ratio, the yield and safety of the dynamic tubular reactor and the batch reactor are compared. Table 3 is as follows:

[0062]

[0063]

[0064] As shown in the table above, under the same raw material ratio, the tubular reactor produces fewer byproducts (2.5% vs. 4% melamine) and is safer (smaller online quantity).

[0065] During the reaction of guanidine nitrate in a dynamic tubular reactor, the system contained impurities including melamine, free nitric acid, and ammonium nitrate. The raw material, dicyandiamide, also contained melamine impurities. Furthermore, guanidine nitrate may decompose at high temperatures during the reaction to produce dicyandiamide, which can further polymerize to form melamine. In pilot-scale experiments, liquid chromatography and titration methods confirmed that the residual impurities in the product were within reasonable limits, specifically: ammonium nitrate residue ≤ 3.5%, free nitric acid ≤ 0.5%, and melamine ≤ 3.3%. See Tables 4 and 5 below for details.

[0066] Table 4: Product Testing Summary

[0067]

[0068]

[0069] As shown in Table 4, the product impurities of guanidine nitrate in the dynamic tubular reactor reaction process can be stably controlled: ammonium nitrate ≤3.5%, free nitric acid ≤0.42%, and melamine ≤3.3%, demonstrating a significant advantage in purity. Moreover, no impurities accumulate during long-term operation, proving the stability of the process.

[0070] This application demonstrates optimal conditions for 72-hour continuous production. The entire process was smooth and controllable, and all indicators of guanidine nitrate met the requirements. The continuous synthesis process exhibited good stability, and the product yield and quality remained stable, achieving the expected results. All batches reacted normally, with no batches showing abnormal reactions, as shown in Table 5 below.

[0071] Table 5. Stability test data for 72 consecutive hours

[0072]

[0073] As shown in Table 5, during continuous production for 72 hours, the product purity (94.2%-94.9%) and yield (94.1%-94.7%) fluctuated by less than 1%, verifying the feasibility of continuous production; there were no abnormal batches, the safety was controllable, and the requirements for industrialization were met.

[0074] It should be noted that, Figure 2In this context, C2H4N4 represents dicyandiamide, NH4NO3 represents ammonium nitrate, CH6N4O3 represents guanidine nitrate, and C2H8N6O3 represents aminoguanidine nitrate. Dicyandiamide and ammonium nitrate undergo a condensation reaction in a dynamic tubular reactor through heating to produce guanidine nitrate (guanidine nitrate), while releasing water. This reaction needs to be carried out under segmented temperature control (80–230℃) and screw stirring (10–500 rpm) to ensure efficient mass and heat transfer.

[0075] Compared with related technologies, this application breaks through the limitations of traditional batch reactors and has the following beneficial effects: (1) Improved mass and heat transfer efficiency: Through the segmented design of the dynamic tubular reactor (feeding section, heating section, reaction section, cooling section) combined with the continuous conveying of the first and second conveying screws, the rapid mixing and uniform flow of materials are realized, significantly improving the heat transfer efficiency; Secondly, precise temperature control (feeding section 80~190℃, heating section and reaction section 90~230℃) avoids local overheating through segmented temperature control, quickly removes reaction heat, inhibits the generation of by-products such as melamine, and reduces the risk of thermal runaway; The continuous production mode (non-traditional batch processing) greatly reduces the liquid holding capacity of the reaction system, reduces the online amount and liquid holding capacity of materials, shortens the high-temperature residence time of materials, and avoids the decomposition and explosion risk of guanidine nitrate. (2) Optimize raw material ratio and reaction path: First, innovate the combination and ratio of raw materials, introduce ammonium carbonate (mass ratio 1:1~3:1~0.5) as a buffer to neutralize the acidic reaction environment, inhibit the generation of by-products such as biuret, and avoid the scaling problem of silica catalyst in the urea process. Also, widen the ratio range of dicyandiamide and ammonium nitrate (1:1~3) to reduce the sensitivity of the traditional process to the ratio and reduce the melamine side reaction caused by the ratio fluctuation. Second, shorten the reaction time and temperature requirements: The rapid heating / cooling capability of the dynamic tubular reactor (screw conveying + segmented temperature control) realizes the rapid switching of material melting-reaction-forming, avoiding the high temperature and long reaction requirements of the traditional process, reducing energy consumption and side reactions. (3) Improve safety and product purity: First, inherently safe design: The fully enclosed continuous process reduces manual operation intervention, lowers the risk of explosion, and the cooling section is directly integrated (cooling and crushing device) to quickly terminate the reaction and avoid high-temperature degradation of the product; Second, improved purity and cost optimization: The content of by-products is reduced (through ratio optimization and temperature control segmentation), reducing the refining steps, eliminating catalyst scaling problems (compared to the urea method), and reducing equipment maintenance costs. (4) Compatible with the core raw materials of the dicyandiamide method (dicyandiamide + ammonium nitrate), but solves the problem of its ratio sensitivity through process innovation, and abandons the catalyst dependence of the urea method. The process is simplified through the synergistic effect of ammonium carbonate to avoid scaling.

[0076] In other words, this application systematically solves four core problems—low mass and heat transfer efficiency, poor safety, numerous by-products, and sensitivity to proportions—through continuous tubular reactor design, segmented temperature control process, and optimized raw material ratio. At the same time, it achieves cost reduction in the process and improvement in product quality, demonstrating significant technological advancement.

[0077] This application obtains raw materials for the preparation of guanidine nitrate, including dicyandiamide, ammonium nitrate to be treated, and ammonium carbonate to be treated. Both the ammonium nitrate and ammonium carbonate to be treated are ground and pulverized to obtain target ammonium nitrate and target ammonium carbonate. Dicyandiamide, target ammonium nitrate, and target ammonium carbonate are uniformly mixed at a mass ratio of 1:(1-3):(1-0.5) to obtain a homogeneous mixture. The homogeneous mixture is conveyed through a first conveying screw to the feeding section of a dynamic tubular reactor for mixing, obtaining the target mixture. The dynamic tubular reactor is equipped with a second conveying screw and also includes a heating section, a reaction section, and a cooling section. The target mixture is sequentially conveyed through the second conveying screw to the heating section for heating and melting, the reaction section for synthesis reaction, and the cooling section for cooling and shaping, obtaining an initial product. The initial product is conveyed to a cooling and pulverizing device for cooling and slicing, obtaining the target guanidine nitrate product. The temperature of the feeding section is one of 80-190°C, and the temperatures of the heating section and the reaction section are one of 90-230°C. This application can improve mass and heat transfer efficiency, reduce online material quantity and liquid holdup, optimize raw material ratio and reaction path, and also improve safety and product purity.

[0078] In one possible implementation, the second conveying screw is a dynamic twin screw, and the rotational speed of the second conveying screw is one of 10 to 500 r / min.

[0079] It should be noted that the reaction of the uniformly mixed material is shown in Table 6 below when the second conveying screw is set to a dynamic twin screw, single screw, and triple screw.

[0080] Table 6:

[0081]

[0082] Therefore, the twin-screw extruder performed best, with guanidine nitrate external standard content of 92% and yield of 94%, which was significantly better than single-screw (75.4%) and three-screw (84.63%) extruders. The twin-screw extruder could effectively reduce ammonium nitrate residue (3.7%) and free nitric acid (0.4%), verifying the enhancing effect of dynamic twin-screw mixing on mass and heat transfer.

[0083] It should be noted that Table 7 shows the reaction of uniformly mixed materials when the dynamic twin-screw extruder rotates at speeds of 50, 100, 200, 300, 400, and 500 rpm. Table 7:

[0084]

[0085] As shown in Table 7, the optimal speed for the dynamic twin-screw extruder is 200 rpm, at which point the yield is 94%.

[0086] In one possible implementation, the pressure inside the dynamic twin-screw chamber is one of 0.01 to 0.03 MPa.

[0087] Reference Figure 3 It is understood that the process of conveying the uniformly mixed material to the feed section of the dynamic tubular reactor via the first conveying screw in step S400 for mixing includes, but is not limited to, the following steps:

[0088] Step S410: The uniformly mixed material is conveyed to the feeder and then conveyed to the feed section of the dynamic tubular reactor through the first conveying screw for mixing.

[0089] In this step, the feeder is connected to the dynamic tubular reactor via a first conveying screw.

[0090] Reference Figure 4 It is understood that a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process also includes, but is not limited to, the following steps:

[0091] Step S501: The temperature of the feed section of the dynamic tubular reactor is controlled by the first integrated heating and cooling unit to be one of 80-190°C.

[0092] Step S502: The temperature of the heating section of the dynamic tubular reactor is controlled by the second integrated heating and cooling unit to be one of 90 to 230°C.

[0093] Step S503: The temperature of the reaction section of the dynamic tubular reactor is controlled by the oil temperature control system to be one of 90-230°C.

[0094] It should be noted that the first integrated heating and cooling unit is used to control the temperature of the feeding section to prevent the material from reacting too early, while the second integrated heating and cooling unit is used to control the temperature of the heating section to initiate the melting reaction. Through segmented temperature control, local overheating or heat accumulation is avoided, ensuring the safety of the reaction and the purity of the product.

[0095] Reference Figure 5 It is understood that a method for preparing guanidine nitrate using a continuous dynamic tubular reaction process also includes, but is not limited to, the following steps:

[0096] Step S504: The temperature of the cooling section of the dynamic tubular reactor is controlled to be one of 20 to 80°C by the circulating water cooling mechanism.

[0097] For example, the temperature of the cooling section can be 25°C, 50°C, or 75°C, and this application embodiment does not limit it.

[0098] It should be noted that the solid mixture is continuously fed into the reactor through the first conveying screw to ensure the uniformity of material distribution. In the dynamic tubular feeding section, dicyandiamide, ammonium nitrate, and ammonium carbonate are mixed evenly in proportion. The feeding temperature (20-190℃) is controlled by the first integrated cooling and heating unit to prevent the material from undergoing localized reactions or decomposition due to premature heating. At the same time, it provides a stable material flow for the subsequent heating section. Uniform raw material mixing is the basis for efficient reaction and avoids the increase of by-products (such as melamine) due to uneven proportions. Low-temperature feeding can inhibit the pre-reaction of dicyandiamide and ammonium nitrate, reduce premature heat release, and reduce safety risks. In the dynamic tubular reactor, the target mixture conveyed in the feed section is heated to a molten state (80–230°C). Heat transfer is accelerated by the shearing and stirring action of the screw, forming a homogeneous fluid. Ammonium carbonate undergoes endothermic decomposition in the heating section (producing NH3, CO2, and H2O). The water in its decomposition products promotes the hydrolysis of dicyandiamide to generate guanidine groups. Simultaneously, the endothermic decomposition partially offsets the exothermic reaction, preventing a sudden temperature rise. The stirring action of the second conveying screw enhances heat transfer, eliminating the "heat accumulation" phenomenon found in traditional batch reactors. The molten state provides fluidity for subsequent condensation reactions, ensuring sufficient contact between reactants. The decomposition of ammonium carbonate regulates heat distribution and provides a reaction medium for guanidine group formation, indirectly improving reaction efficiency. The core condensation reaction takes place in the reaction section of the dynamic tubular reactor. At 80–230°C, dicyandiamide and ammonium nitrate undergo a condensation reaction to produce guanidine nitrate. The rotation of the second conveying screw (10–500 rpm) achieves efficient mixing and shearing of the materials, shortening the reaction time and reducing the formation of byproducts (such as biuret and melamine). Segmented temperature control (e.g., 160℃ for the feed section and 200℃ for the reaction section) combined with heat transfer via a second conveying screw ensures a stable reaction temperature gradient, avoiding the risk of guanidine nitrate decomposition or explosion due to localized overheating. High mass transfer efficiency significantly improves yield (up to 94%), reduces ammonium nitrate residue (≤3.5%) and free nitric acid (≤0.5%), and the continuous flow design reduces the amount of material online, with liquid holdup only 1 / 10 of that of a batch reactor, greatly improving safety. The cooling section of the dynamic tubular reactor rapidly cools the product to room temperature through an external cooling system (e.g., jacketed circulating water), solidifying guanidine nitrate crystals and preventing product decomposition or continued side reactions at high temperatures. After discharge, the product is sliced ​​by a cooling pulverizer to obtain uniform granular products, facilitating subsequent storage and transportation. Rapid cooling in the cooling section locks in the reaction endpoint, preventing prolonged high temperatures from causing guanidine nitrate decomposition (e.g., generating dicyandiamide or melamine), and solidifying into flake or granular products improves purity and physical stability.The entire process is automated through continuous operation of four sections: feeding section, heating section, reaction section, and cooling section. Compared with the traditional batch reactor process, the production efficiency is increased by 3 to 5 times and the energy consumption is reduced by more than 30%. The dynamic tubular reactor has low liquid holdup and fast heat transfer. Combined with segmented temperature control and pressure regulation (≤0.03MPa), the explosion risk of traditional processes is effectively avoided. At the same time, by-products are reduced (melamine residue ≤3.3%), waste treatment costs are reduced, and the recycling of ammonium carbonate further optimizes the utilization rate of raw materials.

[0099] In some embodiments, jacket layers are designed on the outer walls of the feed section, heating section, reaction section, and cooling section of the dynamic tubular reactor, respectively. The heat transfer medium of the first integrated heating and cooling unit circulates through the jacket to the jacket corresponding to the feed section, the heat transfer medium of the second integrated heating and cooling unit circulates through the jacket to the jacket corresponding to the heating section, the heat transfer medium (such as heat transfer oil) of the oil temperature control system circulates through the jacket to the jacket corresponding to the reaction section, and the circulating cooling water circulates through the jacket to the jacket corresponding to the cooling section, thereby realizing direct heating / cooling of the reactor wall.

[0100] In some embodiments, temperature sensors corresponding to the feeding section, heating section, reaction section, and cooling section are installed on the dynamic tubular reactor. Thermocouples or infrared temperature probes are installed in the feeding section, heating section, reaction section, and cooling section of the reactor to provide real-time temperature data feedback to the PLC controller of the corresponding integrated heating and cooling unit, oil temperature control system, or circulating water control mechanism. Based on the sensor signals, the first integrated heating and cooling unit, the second integrated heating and cooling unit, the oil temperature control system, and the circulating water control mechanism automatically switch heating / cooling modes and maintain the set value by adjusting the medium flow rate or temperature. If the temperature of a certain section exceeds the limit, an alarm is triggered and the screw conveyor is automatically stopped to prevent material accumulation and potential risks.

[0101] In some embodiments, coils are built into the heating section and reaction section of the dynamic tubular reactor respectively. By embedding the coils inside the reactor, the hot and cold media flow through the coils and directly exchange heat with the materials, resulting in higher heat transfer efficiency.

[0102] Reference Figure 6 It is understood that step S600 includes, but is not limited to, the following steps:

[0103] In step S610, the initial product is conveyed from the outlet of the dynamic tubular reactor to the receiving device, and then conveyed to the cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product.

[0104] Exemplary Example 1:

[0105] Step 1: Accurately weigh dicyandiamide, ammonium nitrate, and ammonium carbonate, mix them thoroughly, and set aside. The mass ratio of dicyandiamide, ammonium nitrate, and ammonium carbonate is 1:2.0:0.1. Turn on the first and second integrated heating and cooling units, the oil temperature control system, and the circulating cooling mechanism. Set the required feed temperature to 140℃ and the required reaction temperature to 170℃. After preheating and stabilization, use a twin-screw solid feeder as the first conveying screw and start feeding. Adjust the speed of both the first and second conveying screws to 50 rpm to convey the thoroughly mixed material to the feeding section of the dynamic tubular reactor. The material will sequentially undergo mixing (feeding section), heating and melting (heating section), synthesis reaction (reaction section), and cooling and shaping (cooling section). After the reaction is completed, the guanidine nitrate product flows from the outlet into the receiving device and then into the cooling pulverizer for slicing, producing the target guanidine nitrate product. Step 2: After the target guanidine nitrate product has cooled, take a sample, dispense it into a self-sealing bag, and detect the reaction using liquid chromatography. Then, determine the residual content of ammonium nitrate and nitric acid by titration. Through liquid chromatography and acid-base titration, the guanidine nitrate product content is found to be 80%, with a yield of 88%.

[0106] Example 2:

[0107] Step 1: Accurately weigh dicyandiamide, ammonium nitrate, and ammonium carbonate, mix them thoroughly, and set aside. The mass ratio of dicyandiamide, ammonium nitrate, and ammonium carbonate is 1:2.0:0.1. Turn on the first and second integrated heating and cooling units, the oil temperature control system, and the circulating cooling mechanism. Set the required feed temperature to 160℃ and the required reaction temperature to 200℃. After preheating and stabilization, start feeding using a twin-screw solid feeder. Adjust the speed of both the first and second conveying screws to 50 rpm to convey the thoroughly mixed material into the dynamic tubular reactor. The material undergoes mixing, heating and melting (heating section), synthesis reaction (reaction section), and cooling and shaping (cooling section) processes in sequence. After the reaction is completed, the guanidine nitrate product flows from the outlet into the receiving device and then into the cooling pulverizer for slicing, producing the target guanidine nitrate product. Step 2: After the target guanidine nitrate product cools, take samples, dispense them into self-sealing bags, and perform liquid phase analysis to detect the reaction. Then, determine the residual content of ammonium nitrate and nitric acid by titration. The content of guanidine nitrate was found to be 82% and the yield was 89% by liquid chromatography and acid-base titration.

[0108] Example 3:

[0109] Step 1: Accurately weigh dicyandiamide, ammonium nitrate, and ammonium carbonate, mix them thoroughly, and set aside. The mass ratio of dicyandiamide, ammonium nitrate, and ammonium carbonate is 1:2.0:0.1. Turn on the first and second integrated heating and cooling units, the oil temperature control system, and the circulating cooling mechanism. Set the required feed temperature to 160℃ and the required reaction temperature to 200℃. After preheating and stabilization, use a twin-screw solid feeder to feed the material. Adjust the screw speed to 100 rpm to convey the thoroughly mixed material into the dynamic tubular reactor. The material undergoes mixing (feeding section), heating and melting (heating section), synthesis reaction (reaction section), and cooling and shaping (cooling section) processes in sequence. After the reaction is complete, the guanidine nitrate product flows from the outlet into the receiving container and finally enters the cooling pulverizer for slicing, producing the target guanidine nitrate product. Step 2: After the sample cools, take the sample, dispense it into self-sealing bags, and perform liquid phase analysis to detect the reaction. Then, determine the residual content of ammonium nitrate and nitric acid by titration. The content of guanidine nitrate was found to be 82% and the yield was 90% by liquid chromatography and acid-base titration.

[0110] Example 4:

[0111] Step 1: Accurately weigh dicyandiamide, ammonium nitrate, and ammonium carbonate, mix them thoroughly, and set aside. The mass ratio of dicyandiamide, ammonium nitrate, and ammonium carbonate is 1:2.0:0.1. Turn on the first and second integrated heating and cooling units, the oil temperature control system, and the circulating cooling mechanism. Set the required feed temperature to 160℃ and the required reaction temperature to 200℃. After preheating and stabilization, use a twin-screw solid feeder to start feeding. Adjust the speed of both the first and second conveying screws to 200 rpm to transport the thoroughly mixed material to the dynamic tubular reactor. The material undergoes mixing, heating and melting (heating section), synthesis reaction (reaction section), and cooling and shaping (cooling section) processes in sequence. After the reaction is completed, the guanidine nitrate product flows from the outlet into the receiving device and then into the cooling pulverizer for slicing, producing the target guanidine nitrate product. Step 2: After the target guanidine nitrate product cools, take samples, dispense them into self-sealing bags, and perform liquid phase analysis to detect the reaction. Then, determine the residual content of ammonium nitrate and nitric acid by titration. The content of guanidine nitrate was determined to be 85% and the yield was 92% by liquid chromatography and acid-base titration.

[0112] Example 5:

[0113] Step 1: Accurately weigh dicyandiamide, ammonium nitrate, and ammonium carbonate, and mix them thoroughly. The mass ratio of dicyandiamide, ammonium nitrate, and ammonium carbonate is 1:2.0:0.3. Turn on the first and second integrated heating and cooling units, the oil temperature control system, and the circulating cooling mechanism. Set the required feed temperature to 160℃ and the required reaction temperature to 200℃. After preheating and stabilization, use a twin-screw solid feeder to start feeding. Adjust the speed of both the first and second conveying screws to 200 rpm to transport the thoroughly mixed material to the dynamic tubular reactor. The material undergoes mixing, heating and melting (heating section), synthesis reaction (reaction section), and cooling and shaping (cooling section) processes in sequence. After the reaction is completed, the guanidine nitrate product flows from the outlet into the receiving device and finally enters the cooling pulverizer for slicing, producing the target guanidine nitrate product. Step 2: After the target guanidine nitrate product cools, take a sample, dispense it into self-sealing bags, and perform liquid phase analysis to detect the reaction. Then, determine the residual content of ammonium nitrate and nitric acid by titration. The content of guanidine nitrate was found to be 92% and the yield was 94% by liquid chromatography and acid-base titration.

[0114] Example 6:

[0115] Step 1: Accurately weigh dicyandiamide, ammonium nitrate, and ammonium carbonate, and mix them thoroughly. The mass ratio of dicyandiamide, ammonium nitrate, and ammonium carbonate is 1:2.5:0.3. Turn on the first and second integrated heating and cooling units, the oil temperature control system, and the circulating cooling mechanism. Set the required feed temperature to 160℃ and the required reaction temperature to 200℃. After preheating and stabilization, use a twin-screw solid feeder and turn on the feeding device. Adjust the speed of the first and second conveying screws to 200 rpm to convey the thoroughly mixed material into the dynamic tubular reactor. The material undergoes mixing, heating and melting (heating section), synthesis reaction (reaction section), and cooling and shaping (cooling section) processes in sequence. After the reaction is completed, the guanidine nitrate product flows from the outlet into the receiving device and finally enters the cooling pulverizer for slicing, producing the target guanidine nitrate product. Step 2: After the target guanidine nitrate product cools, take a sample, dispense it into self-sealing bags, and perform liquid phase analysis to detect the reaction. Then, determine the residual content of ammonium nitrate and nitric acid by titration. The content of guanidine nitrate was found to be 91% and the yield was 89% by liquid chromatography and acid-base titration.

[0116] The guanidine nitrate content and yield data prepared using the above six examples are shown in the table below:

[0117]

[0118] This application enables the continuous preparation of guanidine nitrate in a dynamic tubular reactor. This reaction process features a large heat exchange area, high heat transfer efficiency, and good mass transfer effect. Combined with segmented temperature control technology, the reaction temperature distribution is more uniform and the temperature control is more precise. The dynamic tubular reactor adopts a continuous reaction, with a small amount of material online, a shorter reaction time, and reduced energy consumption during production. The short material residence time in the dynamic tubular reactor results in high material mass transfer efficiency, reduced material online quantity, and more precise reaction temperature control. This reduces the accumulation of unstable materials under high-temperature conditions and lowers the risk of decomposition or explosion. Furthermore, the reaction conversion rate is higher, and the equipment has a higher degree of automation.

[0119] In the description of the embodiments of this application, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0120] In the description of the embodiments of this application, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0121] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing guanidine nitrate using a continuous dynamic tubular reaction process, characterized in that, include: The raw materials for preparing guanidine nitrate include dicyandiamide, ammonium nitrate to be treated, and ammonium carbonate to be treated; Both the ammonium nitrate and the ammonium carbonate to be treated are ground and pulverized to obtain the target ammonium nitrate and the target ammonium carbonate; The dicyandiamide, target ammonium nitrate, and target ammonium carbonate are mixed uniformly at a mass ratio of 1:(1-3):(1-0.5) to obtain a uniformly mixed material. The uniformly mixed material is conveyed to the feeding section of a dynamic tubular reactor through a first conveying screw for mixing to obtain the target mixture. The dynamic tubular reactor is equipped with a second conveying screw and also includes a heating section, a reaction section, and a cooling section. The target mixture is sequentially conveyed to the heating section for heating and melting, the reaction section for synthesis reaction, and the cooling section for cooling and molding through the second conveying screw to obtain the initial product; The initial product is fed to a cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product; The temperature of the feeding section is one of 80 to 190°C, and the temperature of the heating section and the reaction section are both one of 90 to 230°C.

2. The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process according to claim 1, characterized in that, The second conveying screw is a dynamic twin screw, and the rotational speed of the second conveying screw is one of 10 to 500 r / min.

3. The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process according to claim 2, characterized in that, The pressure inside the dynamic twin-screw chamber is one of 0.01 to 0.03 MPa.

4. The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process according to claim 1, characterized in that, The process of conveying the uniformly mixed material to the feed section of the dynamic tubular reactor via a first conveying screw for mixing includes: The uniformly mixed material is conveyed to a feeder, and then conveyed to the feed section of a dynamic tubular reactor via a first conveying screw for mixing. The feeder and the dynamic tubular reactor are connected via the first conveying screw.

5. The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process according to claim 1, characterized in that, The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process further includes: The temperature of the feed section of the dynamic tubular reactor is controlled by the first integrated heating and cooling unit to be one of 80 to 190°C. The temperature of the heating section of the dynamic tubular reactor is controlled to be one of 90 to 230°C by the second integrated heating and cooling unit. The temperature of the reaction section of the dynamic tubular reactor is controlled by an oil temperature control system to be one of 90 to 230°C.

6. The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process according to claim 1, characterized in that, The first conveying screw is one of a single screw, a twin screw, or a triple screw.

7. The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process according to claim 5, characterized in that, The step of conveying the initial product to a cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product includes: The initial product is conveyed through the outlet of the dynamic tubular reactor to the receiving device, and then conveyed through the receiving device to the cooling and pulverizing device for cooling and slicing to obtain the target guanidine nitrate product.

8. The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process according to claim 1, characterized in that, The method for preparing guanidine nitrate using a continuous dynamic tubular reaction process further includes: The temperature of the cooling section of the dynamic tubular reactor is controlled to be one of 20 to 80°C by a circulating water cooling mechanism.

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