A continuous nitroguanidine production system and process

Abstract

The present invention discloses a continuous nitroguanidine production system and process, comprising a concentrated nitric acid storage tank, a solid feeder, a mixing kettle, a transfer kettle, a microchannel reaction assembly, a dilute nitric acid storage tank, a dilution crystallization kettle, a wastewater receiving tank, a washing kettle, and a smoke absorption device; the concentrated nitric acid storage tank and the solid feeder are both connected to the mixing kettle, the discharge port of the mixing kettle is connected to the feed port of the transfer kettle, the transfer kettle is connected to the dilution crystallization kettle via the microchannel reaction assembly, the feed port and water inlet of the dilution crystallization kettle are respectively connected to the dilute nitric acid storage tank and the wastewater receiving tank, the discharge port of the dilution crystallization kettle is connected to an industrial centrifuge, and the filtrate outlet of the industrial centrifuge is connected to the waste acid receiving tank. The present invention provides a continuous nitroguanidine production system capable of preparing 25% aqueous nitroguanidine, which uses 50% dilute nitric acid for crystallization, undergoes multiple water washing treatments and centrifugal dehydration to obtain high-purity nitroguanidine and byproducts, and the byproducts are reused as raw materials to achieve zero waste liquid, no waste gas, and no solid waste.

Description

Technical Field

[0001] The present invention relates to the technical field related to chemical synthesis, and in particular to a continuous nitroguanidine production system and process. Background Art

[0002] Nitroguanidine, also known as olivine picrite, has a molecular formula of CH4N4O2, a molecular weight of 104.07, is a white crystal, and has a density of 1.715 g / cm 3 Nitroguanidine is slightly soluble in water and is a raw material for organic synthesis. It is used as an intermediate in the pesticides imidacloprid and acetamiprid, and is used to synthesize the next intermediate, N-nitroimidazole. Furthermore, it can be reduced to produce aminoguanidine, which is used to synthesize the angina pectoris drug Lecoxan, and is also used in the preparation of explosives and smokeless water-based drugs. It is used in organic synthesis to prepare aminoguanidine and the drug Lecoxan. It can also be used in the preparation of explosives and smokeless gunpowder. Its current preparation method is to dehydrate guanidine nitrate in the presence of concentrated sulfuric acid to produce nitroguanidine. 280g of guanidine nitrate is slowly added to 250mL of pre-cooled concentrated sulfuric acid (relative density 1.84) with stirring. During the addition, the reaction temperature is strictly controlled to be below 20°C. After complete addition, stirring is continued until the mixture is uniform and free of crystals. It is then poured into a mixture of crushed ice and water, thoroughly stirred, filtered, washed with water until neutral, and recrystallized to obtain nitroguanidine.

[0003] However, the existing nitroguanidine preparation process has the following disadvantages: the preparation process is complicated, and a large amount of waste liquid, waste gas or other solid waste is discharged during the preparation process, polluting the environment. In addition, the by-products produced during the preparation of nitroguanidine cannot be reused, resulting in serious waste of resources, and it needs to be improved. Summary of the Invention

[0004] The object of the present invention is to provide a continuous nitroguanidine production system and process to solve the problems mentioned in the above background technology that the existing nitroguanidine preparation process is complicated, a large amount of waste liquid, waste gas or other solid waste is discharged during the preparation process, polluting the environment, and the by-products produced during the preparation of nitroguanidine cannot be reused, resulting in serious waste of resources.

[0005] To achieve the above-mentioned object, the present invention provides the following technical scheme: a continuous nitroguanidine production system, comprising a concentrated nitric acid storage tank, a solid feeder, a mixing kettle, a transfer kettle, a microchannel reaction assembly, a dilute nitric acid storage tank, a dilution crystallization kettle, a wastewater receiving tank, an industrial centrifuge, a washing kettle and a nitrate fume absorption device; the concentrated nitric acid storage tank and the solid feeder are both connected to the mixing kettle, the discharge port of the mixing kettle is connected to the feed port of the transfer kettle, the transfer kettle is connected to the dilution crystallization kettle through the microchannel reaction assembly, the feed port and water inlet of the dilution crystallization kettle are respectively connected to the dilute nitric acid storage tank and the wastewater receiving tank, the discharge port of the dilution crystallization kettle is connected to the industrial centrifuge, the filtrate outlet of the industrial centrifuge is connected to the waste acid receiving tank, the filter cake outlet of the industrial centrifuge is connected to the washing kettle, the washing kettle is provided with a nitrate fume outlet, and the nitrate fume outlet is connected to the nitrate fume absorption device.

[0006] Preferably, the microchannel reaction assembly includes a microchannel reactor and a microchannel cooler, the feed port of the microchannel reactor is connected to the discharge port of the transfer kettle, the discharge port of the microchannel reactor is connected to the feed port of the microchannel cooler, and the discharge port of the microchannel cooler is connected to the feed port of the dilution crystallization kettle.

[0007] Preferably, the microchannel reactor includes a microchannel reactor body, a feed channel, a mixing channel, a reaction channel and a discharge channel which are connected in sequence in the microchannel reactor body, the feed channel and the discharge channel extend to the outside of the microchannel reactor body, the number of the feed channel is at least one, and the reaction channel includes a plurality of channels which are connected in sequence and first diverge and then merge, wherein the confluence point of the previous channel which first diverges and then merges is connected to the input point of the next channel which first diverges and then merges.

[0008] Preferably, the microchannel reactor body is further provided with a curved cooling channel with a heart-shaped bend, an S-shaped bend, a Z-shaped bend or other irregular shapes.

[0009] Preferably, it also includes a temperature control device, which is connected to the jacket medium inlet and outlet of the mixing kettle, the hand-turning kettle, the microchannel reactor, the dilution crystallization kettle, and the washing kettle through pipelines, and is used to control the internal reaction temperature of the mixing kettle, the hand-turning kettle, the microchannel reactor, the dilution crystallization kettle, and the washing kettle.

[0010] Preferably, the waste acid receiving tank is connected to a nitric acid vacuum distillation device.

[0011] Preferably, the nitrate fume absorption device includes a water jet pump, an absorption tower, a wastewater tank and a wastewater pump. The nitric acid tail gas discharged from the nitrate fume outlet enters the nitrate fume absorption device and is then discharged; the nitrate fume absorption device absorbs the wastewater generated by the nitric acid tail gas, and obtains a sodium nitrate solution after neutralization pretreatment with 4% concentration alkali solution.

[0012] A continuous nitroguanidine production process comprises the following steps:

[0013] S1. Pump concentrated nitric acid from the concentrated nitric acid storage tank into the mixing kettle through a metering pump, start stirring, and simultaneously open the refrigerant inlet and outlet valves of the mixing kettle jacket;

[0014] S2. After the concentrated nitric acid in the kettle is cooled to a specific temperature, the solid feeder is started and the guanidine nitrate in the hopper is slowly added to the mixing kettle using an electronic scale to measure the material, and the temperature of the material in the mixing kettle is well controlled;

[0015] S3. Use a gear pump to pass the mixed solution into a microchannel reactor. The temperature in the microchannel reactor is 45±2°C. The reaction time is 10-20 min. The mixed solution is cooled to 0±5°C through the microchannel for crystallization.

[0016] S4, dilute the crystallization kettle and add dilute nitric acid, and then slowly add the reaction kettle mixed material and distilled water into the dilution crystallization kettle;

[0017] S5. Inject the crystallization mixture into the industrial centrifuge through a metering pump, turn on the industrial centrifuge, and continue centrifugation for 3-8 minutes when no liquid flows out of the liquid outlet of the industrial centrifuge. Turn off the industrial centrifuge, and the filter cake is crude guanidine and the filtrate is waste acid;

[0018] S6. Pump the crude guanidine to a washing kettle through a slurry pump for water washing, pump the washed mixture to an industrial centrifuge, centrifuge for 3-8 minutes, and then turn off the industrial centrifuge;

[0019] S7. Repeat step S6 twice to obtain nitroguanidine containing 25% water after the fourth centrifugation.

[0020] Preferably, in S2, the temperature of the material in the mixing kettle is 0±5°C.

[0021] Preferably, in S4, the temperature in the dilution crystallization kettle is not higher than 5°C, and the mixture is stirred for 5-15 minutes after the addition is completed.

[0022] Beneficial effects:

[0023] The invention provides a continuous nitroguanidine production system capable of preparing 25% water-containing nitroguanidine. Guanidine nitrate is mixed with concentrated nitric acid, concentrated nitric acid is used as a dehydrating agent, and 50% dilute nitric acid is used for crystallization. After multiple water washing treatments and centrifugal dehydration, high-purity nitroguanidine and by-products of dilute nitric acid and washing liquid are obtained. The by-products of dilute nitric acid and washing liquid can be reused as raw materials, thereby achieving the goal of eliminating waste liquid, waste gas, and solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0025] Figure 2 The nitroguanidine prepared in the present invention has a spherical crystal structure;

[0026] Figure 3 Nitroguanidine prepared by conventional process has a needle-shaped crystal structure;

[0027] Figure 4 It is a microchannel reactor with a circular reaction channel.

[0028] Among them: 1. concentrated nitric acid storage tank; 2. solid feeder; 3. mixing kettle; 4. transfer kettle; 5. waste acid receiving tank; 6. dilution crystallization kettle; 7. wastewater receiving tank; 8. industrial centrifuge; 9. washing kettle; 10. microchannel reactor; 11. microchannel cooler; 12. first electronic scale; 13. diaphragm metering pump; 14. first low-temperature cooling circulation device; 15. high-temperature circulation device; 16. second low-temperature cooling circulation device; 17. buffer tank; 18. gun smoke absorption device; 19. first hose pump; 20. mud pump; 21. transfer tank; 22. pure water raw material barrel; 23. second electronic scale; 24. diaphragm pump; 25. second hose pump; 26. nitric acid vacuum distillation device; 27. safety tank; 28. gear pump; 29. microchannel reactor body; 30. feed channel; 31. mixing channel; 32. reaction channel; 33. discharge channel. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0030] Example 1

[0031] like Figure 1 As shown, a continuous nitroguanidine production system includes a concentrated nitric acid storage tank 1, a solid feeder 2, a mixing kettle 3, a transfer kettle 4, a microchannel reaction component, a dilute nitric acid storage tank, a dilution crystallization kettle 6, a wastewater receiving tank 7, an industrial centrifuge 8, a washing kettle 9 and a smoke absorption device; the concentrated nitric acid storage tank 1 and the solid feeder 2 are both connected to the mixing kettle 3, wherein the solid feeder 2 is fixedly connected to the feeding port of the mixing kettle 3, and concentrated nitric acid is added between the concentrated nitric acid storage tank 1 and the mixing kettle 3 through a diaphragm metering pump 13. The concentrated nitric acid storage tank 1 is placed on a first electronic scale 12 for material metering.

[0032] The discharge port of the mixing kettle 3 is connected to the feed port of the transfer kettle 4, and the transfer kettle 4 is connected to the dilution crystallization kettle 6 through a microchannel reaction component, wherein a gear pump 28 is provided between the transfer kettle 4 and the microchannel reaction component for pumping the concentrated nitric acid and guanidine nitrate mixture in the transfer kettle 4.

[0033] The feed port and water inlet of the dilution crystallization kettle 6 are respectively connected to the dilute nitric acid storage tank and the wastewater receiving tank 7. The dilute nitric acid storage tank is used for the initial addition of dilute nitric acid used in the dilution crystallization kettle 6; the wastewater receiving tank 7 is used to receive the wastewater after the reaction. At the same time, the wastewater can also be recycled as reaction water in the dilution crystallization kettle 6.

[0034] The discharge port of the dilution crystallization kettle 6 is connected to an industrial centrifuge 8. A second hose pump 25 is provided between the discharge port of the dilution crystallization kettle 6 and the industrial centrifuge 8 for pumping the discharge. The filtrate outlet of the industrial centrifuge 8 is connected to the waste acid receiving tank 5. A slurry pump 20 is provided between the filter cake outlet of the industrial centrifuge 8 and the washing kettle 9, which are connected by pipeline. The washing kettle 9 is equipped with a smoke outlet, which is connected to a smoke absorption device. A transfer tank 21 is provided at the lower end of the industrial centrifuge 8 for storing the crude guanidine to be centrifuged and the nitroguanidine after the first, second, and third water washes.

[0035] In this embodiment, the microchannel reaction assembly includes a microchannel reactor 10 and a microchannel cooler 11. The feed port of the microchannel reactor 10 is connected to the discharge port of the transfer kettle 4, the discharge port of the microchannel reactor 10 is connected to the feed port of the microchannel cooler 11, and the discharge port of the microchannel cooler 11 is connected to the feed port of the dilution crystallization kettle 6.

[0036] The microchannel reactor 10 includes a microchannel reactor body 29, a feed channel 30, a mixing channel 31, a reaction channel 32 and a discharge channel 33 which are connected in sequence in the microchannel reactor body 29, and the feed channel 30 and the discharge channel 33 extend to the outside of the microchannel reactor body 29. The number of the feed channel 30 is at least one, and the reaction channel 32 includes a plurality of sequentially connected channels that first diverge and then merge, wherein the confluence point of the previous channel that first diverges and then merges is connected to the input point of the next channel that first diverges and then merges.

[0037] In this embodiment, the channel that diverges first and then merges can be a quadrilateral, a circle, an ellipse or a heart shape, and one of the endpoints is selected as the input point, and the endpoint on the opposite side is selected as the merging point.

[0038] At least one of the reaction channels between the input point and the confluence point in the channel that splits first and then merges is a heart-shaped bend, an S-shaped bend, a Z-shaped bend or other irregular-shaped bends.

[0039] The microchannel reactor body 29 is further provided with curved cooling channels with heart-shaped, S-shaped, Z-shaped or other irregular shapes.

[0040] The lower ends of the microchannel reactor 10 and the microchannel cooler 11 are provided with discharge ports, which are connected to the safety tank 27 through a pipeline.

[0041] The continuous nitroguanidine production system of this embodiment also includes a temperature control device, which is connected to the jacket medium inlet and outlet of the mixing kettle 3, the transfer kettle 4, the microchannel reactor 10, the dilution crystallization kettle 6, and the washing kettle 9 through pipelines, respectively, and is used to control the internal reaction temperature of the mixing kettle 3, the transfer kettle 4, the microchannel reactor 10, the dilution crystallization kettle 6, and the washing kettle 9.

[0042] In this embodiment, the temperature control device includes a first low-temperature cooling circulation device 14, a high-temperature circulation device 15, and a second low-temperature cooling circulation device 16, wherein the first low-temperature cooling circulation device 14 is connected to the jacket refrigerant inlet and outlet of the mixing kettle 3 and the transfer kettle 4 through a pipeline; the high-temperature circulation device 15 is connected to the cooling channel of the microchannel reactor 10 through a pipeline; the second low-temperature cooling circulation device 16 is connected to the jacket medium inlet and outlet of the dilution crystallization kettle 6 and the washing kettle 9 through a pipeline.

[0043] The waste acid receiving tank 5 is connected to the nitric acid vacuum distillation device 26 via a pipeline. The waste acid received by the waste acid receiving tank 5 can be vacuum distilled by the nitric acid vacuum distillation device 26 to produce dilute nitric acid, which is reused in the dilution crystallization kettle 6.

[0044] The nitrate fume absorption device 18 includes a water jet pump, an absorption tower, a wastewater tank and a wastewater pump. The nitric acid tail gas discharged from the nitrate fume outlet enters the nitrate fume absorption device and is then discharged; the nitrate fume absorption device 18 absorbs the wastewater generated by the nitric acid tail gas and obtains a sodium nitrate solution after neutralization pretreatment with 4% concentration alkali solution.

[0045] Among them, the industrial centrifuge 8 is connected to the washing kettle 9 through the first hose pump 19 and the pipeline, the dilution crystallization kettle 6, the industrial centrifuge 8 and the washing kettle 9 are connected to the buffer tank 17 through the pipeline, and the buffer tank 17 is connected to the smoke absorption device 18 through the pipeline.

[0046] The industrial centrifuge 8 is connected to the pure water raw material barrel 22 through a diaphragm pump 24 and a pipeline. A second electronic scale 23 is provided at the bottom of the pure water raw material barrel 22 to measure the water consumption.

[0047] The process of the present invention uses nitric acid, and the nitric acid tail gas from the concentrated nitric acid storage tank, the intermediate tank and the by-product acid distillation device enters the nitrile fume absorption device composed of a water jet pump, an absorption tower, a wastewater tank and a wastewater pump. After being treated by this absorption system, the tail gas is finally discharged colorless and meets the emission standards.

[0048] Example 2

[0049] like Figure 2 As shown, a continuous nitroguanidine production process comprises the following steps:

[0050] S1, pump concentrated nitric acid from concentrated nitric acid storage tank 1 into mixing kettle 3 by metering pump, start stirring, and open the freezing liquid inlet and outlet valves of mixing kettle 3 jacket at the same time;

[0051] S2, the concentrated nitric acid in the mixing kettle 3 is cooled to a specific temperature, the solid feeder 2 is started and measured by an electronic scale, and the guanidine nitrate in the hopper is added dropwise into the mixing kettle 3, and the temperature of the material in the mixing kettle 3 is controlled to 0±5°C by the first low-temperature cooling circulation device 14;

[0052] S3, the mixed solution is passed into the microchannel reactor 10 by a gear pump 28, and the temperature in the microchannel reactor 10 is controlled by a high-temperature circulation device 15. The temperature requirement is 45±2°C, and the reaction time is 10-20min. After the reaction is completed, the temperature is cooled to 0±5°C by a microchannel cooler 11 for crystallization;

[0053] S4, add dilute nitric acid into the dilution crystallization kettle 6, and slowly add the reaction kettle mixed material and distilled water into the dilution crystallization kettle 6 in sequence. The temperature in the dilution crystallization kettle 6 is not higher than 5°C, and stir for 5-15 minutes after the addition is completed;

[0054] S5, inject the crystallization mixture into the industrial centrifuge 8 through the metering pump, open the industrial centrifuge 8, and continue centrifugation for 3-8 minutes when no liquid flows out of the liquid outlet of the industrial centrifuge 8, close the industrial centrifuge 8, and use the filter cake as crude guanidine and the filtrate as waste acid. The nitroguanidine produced is as follows: Figure 2 As shown;

[0055] S6. The crude guanidine is pumped to the washing tank 9 by the mud pump 20 for water washing, and the washed mixture is pumped to the industrial centrifuge 8 for centrifugation for 3-8 minutes, and the industrial centrifuge 8 is turned off;

[0056] S7. Repeat S6 twice to obtain nitroguanidine containing 25% water after the fourth centrifugation.

[0057] The nitroguanidine containing 25% water is the final product of this embodiment.

[0058] Among them, the waste acid of centrifugal liquid after crystallization can be used as crystallization liquid for the next process, the first washing liquid can be used as dilution liquid for the next crystallization, the second washing liquid can be used as the first washing liquid for the next process, and the third washing liquid can be used as the second washing liquid for the next process.

[0059] Reaction principle of the present invention

[0060] The present invention generates nitroguanidine through the dehydration reaction of concentrated nitric acid and guanidine nitrate, and improves the safety performance of the entire process through microtubule reaction. Pipelines connected with different shapes ensure that the reaction liquid collides multiple times and can be fully and evenly mixed. At the same time, shapes such as water droplets, heart shapes, and rectangle shapes can generate a certain centripetal force when the reaction fluid moves inside the channel, thereby increasing the internal pressure of the liquid and making it easier for the reaction to proceed. The design of the curve avoids the formation of dead corners in the liquid due to the generation of bubbles, avoids reaction imbalance, ensures that the entire reaction proceeds regularly, and improves product quality. Subsequently, dilute acid is used for crystallization to form spherical nitroguanidine, and excess nitric acid in the product is washed away three times with water. The waste acid from the crystallization can be used as the next crystallization liquid, and the washing liquid can be reused. The entire process is stable, no waste liquid or waste gas is generated, and the product quality is stable.

[0061] Comparative Example:

[0062] Nitroguanidine produced by conventional technology.

[0063] in conclusion:

[0064] according to Figure 2 and Figure 3 As shown, the nitroguanidine prepared in this embodiment has a spherical crystal structure (such as Figure 2 ), the nitroguanidine produced by conventional process has a needle-shaped crystal structure (such as Figure 3 ), needle-shaped crystalline nitroguanidine has the disadvantages of poor fluidity, poor mechanical properties, and low bulk density when directly used in explosives. Rod-shaped and spherical crystalline nitroguanidine solves this problem very well, and as the particle size decreases, the fluidity, bulk density, and mechanical properties gradually improve.

[0065] Note: The main function of the rotating kettle in the present invention is feed buffering.

[0066] While embodiments of the present invention have been shown and described, it will be appreciated 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 invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A continuous nitroguanidine production system, characterized in that: The invention comprises a concentrated nitric acid storage tank (1), a solid feeder (2), a mixing kettle (3), a hand-turning kettle (4), a microchannel reaction component, a dilute nitric acid storage tank, a dilution crystallization kettle (6), a wastewater receiving tank (7), an industrial centrifuge (8), a washing kettle (9) and a smoke absorption device; the concentrated nitric acid storage tank (1) and the solid feeder (2) are both connected to the mixing kettle (3); the discharge port of the mixing kettle (3) is connected to the feed port of the hand-turning kettle (4); the hand-turning kettle (4) is connected to the dilution crystallization kettle (6) through the microchannel reaction component; the feed port and the water inlet of the dilution crystallization kettle are respectively connected to the dilute nitric acid storage tank and the wastewater receiving tank (7); the discharge port of the dilution crystallization kettle (6) is connected to the industrial centrifuge (8); the filtrate outlet of the industrial centrifuge (8) is connected to the waste acid receiving tank (5); the filter cake outlet of the industrial centrifuge (8) is connected to the washing kettle (9); the washing kettle (9) is provided with a smoke outlet, and the smoke outlet is connected to the smoke absorption device; The microchannel reaction assembly comprises a microchannel reactor (10) and a microchannel cooler (11), the feed port of the microchannel reactor (10) is connected to the discharge port of the transfer kettle (4), the discharge port of the microchannel reactor (10) is connected to the feed port of the microchannel cooler (11), and the discharge port of the microchannel cooler (11) is connected to the feed port of the dilution crystallization kettle (6); The microchannel reactor (10) includes a microchannel reactor body (29), a feed channel (30), a mixing channel (31), a reaction channel (32) and a discharge channel (33) which are sequentially connected in the microchannel reactor body (29), wherein the feed channel (30) and the discharge channel (33) extend to the outside of the microchannel reactor body (29), the number of the feed channel (30) is at least one, and the reaction channel (32) includes a plurality of sequentially connected channels that first diverge and then merge, wherein the merging point of the previous channel that first diverges and then merges is connected to the input point of the next channel that first diverges and then merges.

2. A continuous nitroguanidine production system according to claim 1, characterized in that: The microchannel reactor body (29) is also provided with a curved cooling channel having a heart-shaped bend, an S-shaped bend, a Z-shaped bend or other irregular shapes.

3. A continuous nitroguanidine production system according to claim 2, characterized in that: The invention also includes a temperature control device, which is connected to the jacket medium inlet and outlet of the mixing kettle (3), the hand-turning kettle (4), the microchannel reactor (10), the dilution crystallization kettle (6), and the washing kettle (9) through pipelines, and is used to control the internal reaction temperature of the mixing kettle (3), the hand-turning kettle (4), the microchannel reactor (10), the dilution crystallization kettle (6), and the washing kettle (9).

4. A continuous nitroguanidine production system according to claim 1, characterized in that: The waste acid receiving tank (5) is connected to the nitric acid vacuum distillation device.

5. A continuous nitroguanidine production system according to claim 1, characterized in that: The nitrate fume absorption device includes a water jet pump, an absorption tower, a wastewater tank and a wastewater pump. The nitric acid tail gas discharged from the nitrate fume outlet enters the nitrate fume absorption device and is then discharged; the nitrate fume absorption device absorbs the wastewater generated by the nitric acid tail gas, and obtains a sodium nitrate solution after neutralization pretreatment with 4% concentration alkaline solution.

6. A continuous nitroguanidine production process, used in the continuous nitroguanidine production system according to claim 1, characterized in that: The steps include: S1. Pump concentrated nitric acid from the concentrated nitric acid storage tank (1) into the mixing kettle (3) through a metering pump, start stirring, and simultaneously open the refrigerant inlet and outlet valves of the jacket of the mixing kettle (3); S2, the concentrated nitric acid in the mixing kettle (3) is cooled to a specific temperature, the solid feeder (2) is started, and the guanidine nitrate in the hopper is slowly added to the mixing kettle (3) by measuring with an electronic scale, and the temperature of the material in the mixing kettle (3) is well controlled; S3. The mixed solution is introduced into the microchannel reactor (10) by using a gear pump (28). The temperature in the microchannel reactor (10) is 45±2°C. The reaction time is 10-20 min. The mixed solution is cooled to 0±5°C by using a microchannel cooler (11) for crystallization. S4, adding dilute nitric acid into the dilution crystallization kettle (6), and slowly adding the reaction kettle mixed material and distilled water into the dilution crystallization kettle (6) in sequence; S5. Inject the crystallization mixture into the industrial centrifuge (8) through a metering pump, start the industrial centrifuge (8), and continue centrifugation for 3-8 minutes when no liquid flows out of the liquid outlet of the industrial centrifuge (8). Then, close the industrial centrifuge (8), and the filter cake is crude guanidine and the filtrate is waste acid; S6. Pump the crude guanidine to a washing kettle (9) through a slurry pump (20) for water washing, pump the washed mixture to an industrial centrifuge (8), centrifuge for 3-8 minutes, and then turn off the industrial centrifuge (8); S7. Repeat S6 twice to obtain nitroguanidine containing 25% water after the fourth centrifugation.

7. A continuous nitroguanidine production process according to claim 6, characterized in that: In S2, the temperature of the material in the mixing kettle is 0±5°C.

8. A continuous nitroguanidine production process according to claim 6, characterized in that: In S4, the temperature in the dilution crystallization kettle is not higher than 5°C, and the mixture is stirred for 5-15 minutes after the addition is completed.

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