Preparation system and preparation method of nitrocellulose spherical particles

Abstract

The invention relates to the technical field of nitrocellulose production, in particular to a nitrocellulose spherical particle preparation system and a preparation method thereof.The preparation method comprises the steps that nitrocellulose is dissolved into sticky nitrocellulose; then conveying the viscous nitrocellulose to a pre-forming device for pre-forming treatment, and meanwhile, conveying a diluting solvent to the pre-forming device to obtain a first mixed solution formed by the cylindrical nitrocellulose particles and the diluting solvent; then conveying the first mixed solution to a forming device for forming treatment to obtain a second mixed solution formed by the nitrocellulose spherical particles and the diluting solvent; finally, the second mixed solution is conveyed into a desolventizing tank to be subjected to desolventizing removal treatment, nitrocellulose spherical particles are obtained, the true density of the nitrocellulose spherical particles is improved by about 10 times compared with flocculent nitrocellulose, the nitrocellulose spherical particles have good stacking density, transportation and automatic barrel pouring are convenient, and the dissolving and plasticizing performance of the nitrocellulose spherical particles is also better than that of sheeted nitrocotton. The quality is obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of nitrocellulose production, and in particular to a preparation system and a preparation method of nitrocellulose spherical particles. Background Art

[0002] Nitrocellulose is a cellulose nitrate ester obtained by the esterification reaction of nitric acid and sulfuric acid with cellulose raw materials, commonly known as nitrocellulose or nitrocellulose. The different nitrogen content of nitrocellulose directly determines the size of its energy, which is mainly divided into energetic nitrocellulose with high nitrogen content and industrial nitrocellulose with low nitrogen content. Energetic nitrocellulose is the most important basic material for propellants and gun propellants. From the initial single-base propellant, double-base propellants, modified double-base propellants, and triple-base propellants have also been developed. Industrial nitrocellulose is mainly used in coatings, paints, inks, leather brighteners and other fields.

[0003] At present, nitrocellulose is mainly in the form of flocculent nitrocellulose and compressed nitrocellulose. The bulk density of flocculent nitrocellulose is low, only 0.1-0.15g / mL, and the transportation cost is high. Due to its long fibers, the materials are entangled with each other, making it difficult to achieve automatic barrel pouring and automated production. Bucket pouring refers to pouring nitrocellulose out of the barrel. Compressed nitrocellulose has increased bulk density, which is convenient for transportation and automatic barrel pouring, but the solubility and plasticization properties of compressed nitrocellulose are reduced, affecting subsequent use. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a system for preparing spherical nitrocellulose particles, wherein the system can prepare spherical nitrocellulose particles which are convenient to transport and automatically pour into barrels and have good dissolution performance.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a preparation system of nitrocellulose spherical particles, including a dissolving tank, a diluting solvent tank, a preforming device, a forming device and a desolventizing tank, the discharge port of the dissolving tank is connected to the bottom feed port of the preforming device through a first conveying pipe, the discharge port of the diluting solvent tank is connected to the diluting solvent inlet pipe on the side of the preforming device through a second conveying pipe, the cylindrical particle discharge pipe on the side of the preforming device is connected to the feed port of the forming device through a third conveying pipe, and the discharge port of the forming device is connected to the feed port of the desolventizing tank.

[0006] Furthermore, a first power pump is arranged on the first delivery pipeline, a second power pump is arranged on the second delivery pipeline, and a third power pump is arranged on the third delivery pipeline.

[0007] Furthermore, the preforming device includes a shell, a feed pipe, an extrusion forming orifice plate and a cutting assembly, at least one group of forming structures is arranged on the extrusion forming orifice plate, the shell is arranged vertically, a working cavity is arranged in the middle of the shell, the extrusion forming orifice plate is arranged horizontally in the middle of the working cavity, the working cavity below the extrusion forming orifice plate is a feed cavity, the working cavity above the extrusion forming orifice plate is a cylindrical particle forming cavity, the feed pipe is connected to the bottom of the feed cavity, and the bottom of the feed pipe is the bottom feed port of the preforming device;

[0008] The dilution solvent inlet pipe and the cylindrical particle discharge pipe are arranged on the side wall of the cylindrical particle forming cavity. The cutting assembly includes a rotating shaft and a cutting knife. The cutting knife is arranged on the circumference of the rotating shaft. The rotating shaft is arranged in the cylindrical particle forming cavity in a vertically rotating manner. The cutting knife is located in the cylindrical particle forming cavity and above the outlet of the forming structure.

[0009] Furthermore, the feed cavity is in the shape of a cone with a larger top and a smaller bottom, and further includes a dispersion cone, which is in the shape of an inverted cone and is arranged at the lower part of the extrusion-molded orifice plate, and the dispersion cone is located in the middle of the feed cavity;

[0010] The extruded orifice plate comprises a circular main body and a connecting portion, wherein the connecting portion is arranged outside the circular main body;

[0011] All the molding structures are evenly distributed on the circular main body at intervals, the molding structure is located outside the dispersion cone, and the molding structure includes a plurality of cylindrical molding holes that penetrate vertically, and the cylindrical molding holes are arranged at intervals along the radial direction of the circular main body to the outside;

[0012] The shape of the preforming device is an axisymmetric figure.

[0013] Furthermore, the molding device includes a conveying molding pipe, the cross-section of the conveying molding pipe is circular, one end of the conveying molding pipe is a molding pipe feed port, the other end of the conveying molding pipe is a molding pipe discharge port, the outer surface of the conveying molding pipe is provided with a heating coil, and the conveying molding pipe is provided with at least one set of thermometers and pressure gauges.

[0014] Furthermore, it also includes a heat preservation pipe, a conveying forming pipe and a heating coil arranged inside the heat preservation pipe;

[0015] The conveying and forming pipeline is arranged in a spiral from bottom to top, and the forming pipeline feed port is arranged below the forming pipeline discharge port;

[0016] Three groups of thermometers and pressure gauges are arranged on the conveying forming pipeline, and the three groups of thermometers and pressure gauges are arranged in sequence and at intervals along the conveying direction of the conveying forming pipeline.

[0017] Furthermore, the desolventizing tank is a flash tank, the top of the desolventizing tank is provided with a gas phase discharge port, and the bottom of the desolventizing tank is provided with a liquid phase discharge port;

[0018] It also includes a spherical particle hardening device. The liquid phase outlet of the desolventizing tank is connected to the feed port of the spherical particle hardening device through a fourth conveying pipeline, and a fourth power pump is arranged on the fourth conveying pipeline.

[0019] Furthermore, it also includes a screening device, and the discharge port of the spherical particle hardening device is connected to the feed port of the screening device through a fifth conveying pipeline.

[0020] In addition, the technical problem to be solved by the present invention is to provide a method for preparing spherical nitrocellulose particles, which can prepare spherical nitrocellulose particles that are easy to transport and automatically pour into barrels and have good solubility.

[0021] A method for preparing spherical nitrocellulose particles, wherein the method adopts the above-mentioned preparation system, the particle size of the spherical nitrocellulose particles is 300 μm-1000 μm, and comprises the following steps:

[0022] a. After adding the dissolving solvent into the dissolving tank, add nitrocellulose into the dissolving tank to obtain viscous nitrocellulose;

[0023] b. adding a dilution solvent into a dilution solvent tank, and conveying the dilution solvent to a preforming device, while conveying the viscous nitrocellulose to the preforming device for preforming, to obtain a first mixed solution of nitrocellulose cylindrical particles and the dilution solvent;

[0024] c. conveying the first mixed solution obtained in step b to a molding device for molding to obtain a second mixed solution of nitrocellulose spherical particles and a diluent solvent;

[0025] d. The second mixed solution in step c is transported to a desolventizing tank for desolventizing treatment to obtain nitrocellulose spherical particles.

[0026] Preferably, in step a, the dissolving solvent is ethyl acetate or acetone, the solid content of the viscous nitrocellulose is 20-35% by mass, and the stick drop viscosity is 4-15s;

[0027] In step b, the cross-sectional circular diameter of the cylindrical forming hole in the preforming device is 500-1500 μm, and the height-to-diameter ratio of the obtained nitrocellulose cylindrical particles is 0.5-2;

[0028] In step c, the molding temperature in the molding device is controlled at 50-95°C;

[0029] The method further comprises step e, wherein the spherical nitrocellulose particles obtained in step d are transported to a spherical particle hardening device for further desolventizing treatment.

[0030] The beneficial effects of the present invention are as follows: the preparation system and preparation method of nitrocellulose spherical particles of the present invention are as follows: firstly, nitrocellulose is dissolved into viscous nitrocellulose; then the viscous nitrocellulose is transported to a preforming device for preforming treatment, and a diluting solvent is transported to the preforming device at the same time to obtain a first mixed liquid consisting of nitrocellulose cylindrical particles and a diluting solvent, and the diluting solvent serves as a transport carrier of the nitrocellulose cylindrical particles; then the first mixed liquid is transported to a molding device for molding treatment to obtain a second mixed liquid consisting of nitrocellulose spherical particles and a diluting solvent; finally, the second mixed liquid is transported to a desolventizing tank for desolventizing and removing treatment to obtain nitrocellulose spherical particles. It can be seen that the preparation system and the preparation method thereof can prepare spherical nitrocellulose particles. The particle size of the spherical nitrocellulose particles is 300μm-1000μm, which are micron-level particles. Through a large number of practices and experiments, it is concluded that the true density of the spherical nitrocellulose particles is about 1.48g / mL, and the bulk density is 1.2-1.4g / mL, which is about 10 times higher than that of flocculent nitrocellulose. It has a good bulk density, is convenient for transportation and automatic barrel dumping, and the dissolution and plasticization properties are also significantly improved compared to compressed nitrocellulose, which is conducive to large-scale use. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process of the present invention;

[0032] Figure 2 is a schematic diagram of a preforming device;

[0033] Figure 3 is a schematic cross-sectional view of a preforming device;

[0034] Figure 4 is a schematic diagram of a main shell portion and components connected to the main shell portion;

[0035] Figure 5 is a schematic diagram of an extruded orifice plate;

[0036] Figure 6 is a schematic diagram of a molding device;

[0037] Marked as: dissolving tank 1, diluting solvent tank 2, preforming device 3, shell 31, main shell part 311, cover plate part 312, feed pipe 32, extrusion forming orifice plate 33, circular main body part 331, connecting part 332, forming structure 333, cylindrical forming hole 334, cutting assembly 34, rotating shaft 341, cutting knife 342, feed cavity 351, cylindrical particle forming cavity 352, diluting solvent inlet pipe 36, cylindrical particle discharge pipe 37, dispersion cone 38, forming device 4, conveying forming pipe 41, heating coil 42, thermometer 43, pressure gauge 44, insulation pipe 45, trumpet-shaped nozzle 46, desolventizing tank 5, first power pump 61, second power pump 62, third power pump 63, spherical particle hardening device 7, screening device 8. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0039] like Figures 1 to 6 As shown, the preparation system of nitrocellulose spherical particles of the present invention includes a dissolving tank 1, a diluting solvent tank 2, a preforming device 3, a forming device 4 and a desolventizing tank 5, the discharge port of the dissolving tank 1 is connected to the bottom feed port of the preforming device 3 through a first conveying pipe, the discharge port of the diluting solvent tank 2 is connected to the diluting solvent inlet pipe 36 on the side of the preforming device 3 through a second conveying pipe, the cylindrical particle discharge pipe 37 on the side of the preforming device 3 is connected to the feed port of the forming device 4 through a third conveying pipe, and the discharge port of the forming device 4 is connected to the feed port of the desolventizing tank 5.

[0040] In order to facilitate the transportation of materials in the entire preparation system, Figure 1 As shown, a first power pump 61 is arranged on the first conveying pipeline, a second power pump 62 is arranged on the second conveying pipeline, and a third power pump 63 is arranged on the third conveying pipeline. The first power pump 61, the second power pump 62 and the third power pump 63 are automatically controlled by a controller. The function of the first power pump 61 is to convey the material in the dissolving tank 1 to the preforming device 3, the function of the second power pump 62 is to convey the material in the dilution solvent tank 2 to the preforming device 3, and the function of the third power pump 63 is to convey the material in the preforming device 3 to the forming device 4, and enable the material to have its forming speed in the forming device 4.

[0041] The function of the dissolving tank 1 is to dissolve the nitrocellulose into viscous nitrocellulose, and the dissolving solvent is ethyl acetate or acetone. In the viscous nitrocellulose: by mass percentage, the solid content of the viscous nitrocellulose is 20-35%, and the stick viscosity is: a stainless steel rod with a diameter of 0.8 cm and a weight of 60 g, and the time required to fall 6.0 cm is 4-15 seconds, that is, the stick viscosity is 4-15 seconds.

[0042] The dilution solvent tank 2 is used to store and provide the dilution solvent, which is a solution with a solvent solubility of less than 0.5-1.5%. The dilution solvent in the dilution solvent tank 2 is transported to the preforming device 3 through the second power pump 62 to dilute the nitrocellulose cylindrical particles formed in the preforming device 3. The dilution solvent serves as a transport carrier for the nitrocellulose cylindrical particles and a transport carrier for the nitrocellulose spherical particles in the subsequent process.

[0043] The function of the preforming device 3 is to shape the viscous nitrocellulose into cylindrical nitrocellulose particles and mix the cylindrical nitrocellulose particles with the diluent solvent. A preferred structure of the preforming device 3 of the present invention is: Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the preforming device 3 includes a shell 31, a feed pipe 32, an extrusion forming orifice plate 33 and a cutting assembly 34. At least one group of forming structures 333 is arranged on the extrusion forming orifice plate 33. The shell 31 is vertically arranged, and a working chamber is arranged in the middle of the shell 31. The extrusion forming orifice plate 33 is horizontally arranged in the middle of the working chamber. The working chamber below the extrusion forming orifice plate 33 is a feed chamber 351, and the working chamber above the extrusion forming orifice plate 33 is a cylindrical particle forming chamber 352. The feed pipe 32 and the bottom of the feed chamber 351 are connected. The two parts are interconnected, and the bottom of the feed pipe 32 is the bottom feed port of the preforming device; the dilution solvent inlet pipe 36 and the cylindrical particle discharge pipe 37 are arranged on the side wall of the cylindrical particle forming cavity 352, and the cutting assembly 34 includes a rotating shaft 341 and a cutting knife 342, and the cutting knife 342 is arranged on the circumference of the rotating shaft 341, and the rotating shaft 341 is arranged in the cylindrical particle forming cavity 352 in a vertically rotatable manner, and the cutting knife 342 is located in the cylindrical particle forming cavity 352 and above the outlet of the forming structure 333. The working process of the preforming device 3 is as follows: the discharge port of the first conveying pipe is connected with the feed pipe 32, and the viscous nitrocellulose enters the feed cavity 351 through the first conveying pipe and the feed pipe 32 in sequence. The viscous nitrocellulose entering the feed cavity 351 is then formed into cylindrical rod-shaped nitrocellulose by the molding structure 333. The cutting component 34 works, and the rotating shaft 341 drives the cutting knife 342 to rotate around it. The cutting knife 342 cuts the cylindrical rod-shaped nitrocellulose formed by the molding structure 333 into cylindrical nitrocellulose particles, and the height-to-diameter ratio of the cylindrical nitrocellulose particles is 0.5-2. At the same time, the diluting solvent in the diluting solvent tank 2 enters the cylindrical particle molding cavity 352 through the second conveying pipe and the diluting solvent liquid inlet pipe 36. In the cylindrical particle molding cavity 352, the diluting solvent and the cylindrical nitrocellulose particles are mixed together to form a first mixed liquid, and the first mixed liquid is transported out through the cylindrical particle discharge pipe 37.

[0044] In order to facilitate the transportation and shaping of the viscous nitrocellulose into cylindrical nitrocellulose particles, the temperature of the viscous nitrocellulose can be heated to 80° C. for transportation and shaping.

[0045] In order to improve the molding effect of nitrocellulose cylindrical particles, the viscous nitrocellulose feed end needs to ensure its uniformity. Figure 3 As shown, the feed cavity 351 is in the shape of a cone with a large top and a small bottom, and also includes a dispersion cone 38, which is in the shape of an inverted cone. The dispersion cone 38 is arranged at the lower part of the extrusion molding orifice plate 33, and the dispersion cone 38 is located in the middle of the feed cavity 351. Under the action of the side wall of the cone-shaped feed cavity 351 and the dispersion cone 38, the viscous nitrocellulose entering the feed cavity 351 is uniformly transported to the entrance of the extrusion molding orifice plate 33, thereby improving the molding uniformity and molding effect of the cylindrical rod-shaped nitrocellulose. A more preferred arrangement scheme of the dispersion cone 38 is: the bottom of the dispersion cone 38 coincides with the centerline point of the discharge port of the feed pipe 32.

[0046] In order to facilitate the installation and use of the extruded orifice plate 33, Figure 4 , Figure 5 As shown, the extruded orifice plate 33 includes a circular main body portion 331 and a connecting portion 332. The connecting portion 332 is arranged on the outer side of the circular main body portion 331. A connecting threaded hole is arranged on the connecting portion 332. The extruded orifice plate 33 is detachably arranged in the working chamber of the shell 31 through connecting bolts. Such an arrangement also allows the extruded orifice plate 33 to be replaced.

[0047] The molding structure 333 is a nitrocellulose formed by molding the viscous nitrocellulose into a cylindrical rod. In order to ensure its use effect, a preferred structure of the molding structure 333 of the present invention is: Figure 5 As shown, all the molding structures 333 are evenly distributed on the circular main body 331, and the molding structure 333 is located on the outside of the dispersion cone 38. The molding structure 333 includes a plurality of cylindrical molding holes 334 that pass through the upper and lower parts. The cylindrical molding holes 334 are vertically arranged, and the cylindrical molding holes 334 are arranged along the radial direction of the circular main body 331 and are spaced apart from each other to the outside.

[0048] In order to facilitate the processing of the housing 31 and the use of the housing 31, other components are arranged on the housing 31. Figure 3 As shown, the housing 31 includes a main housing portion 311 and a cover portion 312 , and the cover portion 312 is detachably connected and arranged above the main housing portion 31 , and the detachable connection method is bolts.

[0049] The function of the cutting component 34 is to cut the cylindrical rod-shaped nitrocellulose formed by the forming structure 333 into cylindrical nitrocellulose particles. A preferred structure of the cutting component 34 of the present invention is: Figure 3 As shown, the lower end of the rotating shaft 341 is rotatably connected to the extruded orifice plate 33, the rotating shaft 341 is rotatably connected to the cover plate portion 312, and the upper end of the rotating shaft 341 passes through the cover plate portion 312, and the upper end of the rotating shaft 341 is a power connection end, which is connected to the output shaft of the motor. More preferably, the lower end of the rotating shaft 341 is rotatably connected to the middle of the extruded orifice plate 33, which effectively improves the use effect of the cutting assembly 34.

[0050] In order to facilitate the entry of the dilution solvent and the delivery of the first mixed liquid of the dilution solvent and the nitrocellulose cylindrical particles, the dilution solvent inlet pipe 36 and the cylindrical particle discharge pipe 37 are respectively arranged on the opposite sides of the side wall of the cylindrical particle forming cavity 352.

[0051] In order to further improve the molding effect of the nitrocellulose cylindrical particles, the shape of the preforming device is an axisymmetric figure.

[0052] The function of the molding device 4 is to mold the cylindrical nitrocellulose particles into spherical nitrocellulose particles. In order to ensure the use effect of the molding device 4, a preferred structure of the molding device 4 of the present invention is: Figure 6 As shown, the molding device 4 includes a conveying molding pipe 41, the cross section of the conveying molding pipe 41 is circular, one end of the conveying molding pipe 41 is a molding pipe feed port, the other end of the conveying molding pipe 41 is a molding pipe discharge port, the outer surface of the conveying molding pipe 41 is provided with a heating coil 42, and the conveying molding pipe 41 is provided with at least one set of thermometers 43 and pressure gauges 44. The heating coil 42 heats the conveying molding pipe 41, and the heating can also increase the pressure in the conveying molding pipe 41, so that the material in the conveying molding pipe 41 is in a high temperature and high pressure state. The thermometer 43 and the pressure gauge 44 detect the temperature and pressure of each section of the conveying molding pipe 41 to monitor whether the temperature and pressure in the conveying molding pipe 4 meet the requirements. The working process of the molding device is as follows: a first mixed liquid consisting of cylindrical nitrocellulose particles and a diluent solvent enters the conveying and molding pipe 41 through the third conveying pipe and the molding pipe feed port; under the action of high temperature, the cylindrical nitrocellulose particles soften in the diluent aqueous phase; under the condition of high temperature and high pressure (temperature exceeding the boiling point of the diluent), the cylindrical nitrocellulose particles are in a soft colloid state; under the action of surface tension and water flow, they are reshaped into spherical nitrocellulose particles.

[0053] To ensure the use effect of the molding device, the molding temperature in the molding device is controlled at 50-95° C., and preferably the temperature is controlled in sections. To improve the heating effect of the heating coil 42 , the heating coil 42 is spirally wound around the outer surface of the conveying molding pipe 41 .

[0054] In order to reduce heat loss, Figure 6 As shown, the present invention is further provided with a heat preservation pipe 45 , and the conveying forming pipe 41 and the heating coil 42 are arranged inside the heat preservation pipe 45 .

[0055] In order to reduce the area occupied by the molding device and improve the molding effect of the nitrocellulose spherical particles, the conveying molding pipeline 41 is arranged in a spiral from bottom to top, and the molding pipeline feed port is arranged below the molding pipeline discharge port.

[0056] In order to realize the segmented temperature control of the conveying and molding pipeline 41 and further improve the molding effect of the molding device, three groups of thermometers 43 and pressure gauges 44 are arranged on the conveying and molding pipeline 41, and the three groups of thermometers 43 and pressure gauges 44 are arranged in sequence along the conveying direction of the conveying and molding pipeline 41. The segmented temperature control of the conveying and molding pipeline 41 is: 50-60℃, 60-70℃, 70-80℃.

[0057] In order to facilitate the conveyance of the molded nitrocellulose spherical particles into the desolventizing tank 5, the molding pipeline outlet is located inside the desolventizing tank 5, and a trumpet-shaped nozzle 46 is provided at the molding pipeline outlet.

[0058] The function of the desolventizing tank 5 is to remove the desolvent. In order to ensure its use effect, the desolventizing tank 5 is preferably a flash tank. The top of the desolventizing tank 5 is provided with a gas phase discharge port, and the bottom of the desolventizing tank 5 is provided with a liquid phase discharge port.

[0059] After being treated in a flash tank, the surface of the nitrocellulose spherical particles may contain a small amount of desolventizing solution. In order to further remove the desolventizing solution on the surface of the nitrocellulose spherical particles and harden the nitrocellulose spherical particles, Figure 1 As shown, the present invention is further provided with a spherical particle hardening device 7, and the liquid phase discharge port of the desolventizing tank 5 is connected with the feed port of the spherical particle hardening device 7 through a fourth conveying pipeline, and a fourth power pump 64 is provided on the fourth conveying pipeline. The working principle of the spherical particle hardening device 7 is to evaporate the liquid phase by high-temperature steam, and it includes a vertical hardening shell, and the vertical hardening shell is segmented to add high-temperature steam from bottom to top, so that the temperature in the vertical hardening shell is gradually increased from bottom to top. Under the power of the fourth power pump 64, the nitrocellulose spherical particles enter from the lower part of the vertical hardening shell through the fourth conveying pipeline, and the desolventizing solution on the surface of the nitrocellulose spherical particles is gradually removed.

[0060] In order to screen out qualified nitrocellulose spherical particles, Figure 1 As shown, the present invention is further provided with a screening device 8, and the discharge port of the spherical particle hardening device 7 is connected with the feed port of the screening device 8 through a fifth conveying pipeline.

[0061] A method for preparing spherical nitrocellulose particles, wherein the method adopts the above-mentioned preparation system, the particle size of the spherical nitrocellulose particles is 300 μm-1000 μm, and comprises the following steps:

[0062] a. After adding the dissolving solvent into the dissolving tank 1, nitrocellulose is added into the dissolving tank 1 to obtain viscous nitrocellulose;

[0063] b. Adding a dilution solvent into the dilution solvent tank 2, and conveying the dilution solvent to the preforming device 3, while conveying the viscous nitrocellulose to the preforming device 3 for preforming, to obtain a first mixed solution of nitrocellulose cylindrical particles and the dilution solvent;

[0064] c. conveying the first mixed solution obtained in step b to a molding device 4 for molding to obtain a second mixed solution of nitrocellulose spherical particles and a diluent solvent;

[0065] d. The second mixed solution in step c is transported to the desolventizing tank 5 for desolventizing to obtain nitrocellulose spherical particles.

[0066] In order to improve the preparation effect of nitrocellulose spherical particles, in step a, the dissolving solvent is ethyl acetate or acetone, the solid content of the viscous nitrocellulose is 20-35% by mass percentage, and the stick drop viscosity is 4-15s;

[0067] In step b, the cross-sectional circular diameter of the cylindrical forming hole 334 in the preforming device 3 is 500-1500 μm, and the height-to-diameter ratio of the obtained nitrocellulose cylindrical particles is 0.5-2;

[0068] In step c, the molding temperature in the molding device 4 is controlled at 50-95°C;

[0069] The method further comprises step e, wherein the spherical nitrocellulose particles obtained in step d are transported to the spherical particle hardening device 7 for further desolventizing treatment.

[0070] In summary, the preparation system and preparation method of nitrocellulose spherical particles of the present invention can prepare nitrocellulose spherical particles. The particle size of the nitrocellulose spherical particles is 300μm-1000μm, which belongs to micron-level particles. Through a large number of practices and experiments, it is found that the actual density of the nitrocellulose spherical particles is about 1.48g / mL, and the bulk density is 1.2-1.4g / mL, which is about 10 times higher than that of flocculent nitrocellulose. It has good bulk density, is convenient for transportation and automatic barrel dumping, and the dissolution and plasticization performance is also significantly improved compared with compressed nitrocellulose cotton, which is conducive to large-scale use.

[0071] Example

[0072] Dissolve 1 part of nitrocellulose and 3 parts of ethyl acetate at 50°C to obtain a viscous nitrocellulose with a stick viscosity of 5s. Transport the viscous nitrocellulose to a preforming device 3 for preforming to obtain a first mixed solution of nitrocellulose cylindrical particles and a diluent. The cross-sectional diameter of the nitrocellulose cylindrical particles is 1.0 mm, and the aspect ratio is 1:1. Transport the nitrocellulose cylindrical particles to a forming device 4. In the forming device 4, the first mixed solution flows at a flow rate of 0.25 m / s, and the residence time is 8 min. The temperature in the conveying forming pipe 41 is increased from 50°C to 100°C. ℃ the first section is raised to 60℃, the second section is raised to 70℃, and the third section is raised to 80℃; it is sprayed into the flash tank at 80℃ and 2atm pressure. During flash evaporation, 70% of the diluent in the nitrocellulose spherical particles becomes gas and is discharged from the top, and the nitrocellulose spherical particles and the remaining diluent enter the particle hardening device 7. In the particle hardening device 7, the temperature is raised from 60℃ to 75℃ in the first section, to 85℃ in the second section, and to 95℃ in the third section, to remove more than 99% of the diluent in the nitrocellulose spherical particles, and to screen out nitrocellulose spherical particles with a particle size of 500μm.

[0073] After testing, the true density of the nitrocellulose spherical particles is 1.48 g / mL, the bulk density is 1.36 g / mL, and it has good dissolution and plasticization properties.

Claims

1. A system for preparing spherical nitrocellulose particles, characterized in that: The invention comprises a dissolving tank (1), a diluting solvent tank (2), a preforming device (3), a forming device (4) and a desolventizing tank (5); the discharge port of the dissolving tank (1) is connected to the bottom feed port of the preforming device (3) via a first conveying pipeline; the discharge port of the diluting solvent tank (2) is connected to the diluting solvent inlet pipeline (36) on the side of the preforming device (3) via a second conveying pipeline; the cylindrical particle discharge pipeline (37) on the side of the preforming device (3) is connected to the feed port of the forming device (4) via a third conveying pipeline; and the discharge port of the forming device (4) is connected to the feed port of the desolventizing tank (5).

2. The system for preparing spherical nitrocellulose particles according to claim 1, characterized in that: A first power pump (61) is arranged on the first delivery pipeline, a second power pump (62) is arranged on the second delivery pipeline, and a third power pump (63) is arranged on the third delivery pipeline.

3. The system for preparing nitrocellulose spherical particles according to claim 1, characterized in that: The preforming device (3) comprises a shell (31), a feed pipe (32), an extrusion forming orifice plate (33) and a cutting assembly (34); at least one group of forming structures (333) is arranged on the extrusion forming orifice plate (33); the shell (31) is arranged vertically; a working chamber is arranged in the middle of the shell (31); the extrusion forming orifice plate (33) is arranged horizontally in the middle of the working chamber; the working chamber below the extrusion forming orifice plate (33) is a feed chamber (351); the working chamber above the extrusion forming orifice plate (33) is a cylindrical particle forming chamber (352); the feed pipe (32) is connected to the bottom of the feed chamber (351); and the bottom of the feed pipe (32) is a bottom feed port of the preforming device; The dilution solvent inlet pipe (36) and the cylindrical particle discharge pipe (37) are arranged on the side wall of the cylindrical particle forming cavity (352), and the cutting assembly (34) includes a rotating shaft (341) and a cutting knife (342), wherein the cutting knife (342) is arranged on the circumference of the rotating shaft (341), and the rotating shaft (341) is arranged in the cylindrical particle forming cavity (352) in a vertically rotatable manner, and the cutting knife (342) is located in the cylindrical particle forming cavity (352) and above the outlet of the forming structure (333).

4. The system for preparing nitrocellulose spherical particles according to claim 3, characterized in that: The feed cavity (351) is in the shape of a cone with a larger top and a smaller bottom, and further comprises a dispersion cone (38). The dispersion cone (38) is in the shape of an inverted cone. The dispersion cone (38) is arranged at the lower part of the extrusion forming orifice plate (33), and the dispersion cone (38) is located in the middle of the feed cavity (351). The extruded orifice plate (33) comprises a circular main body (331) and a connecting portion (332), wherein the connecting portion (332) is arranged outside the circular main body (331); All the molding structures (333) are evenly distributed on the circular main body (331) at intervals, the molding structures (333) are located outside the dispersion cone (38), the molding structures (333) include a plurality of cylindrical molding holes (334) that penetrate vertically, and the cylindrical molding holes (334) are arranged at intervals along the radial direction of the circular main body (331) to the outside; The shape of the preforming device (3) is an axisymmetric figure.

5. The system for preparing nitrocellulose spherical particles according to claim 1, characterized in that: The molding device (4) comprises a conveying molding pipe (41), the cross section of the conveying molding pipe (41) is circular, one end of the conveying molding pipe (41) is a molding pipe feed port, the other end of the conveying molding pipe (41) is a molding pipe discharge port, a heating coil (42) is arranged on the outer surface of the conveying molding pipe (41), and at least one set of thermometers (43) and pressure gauges (44) are arranged on the conveying molding pipe (41).

6. The system for preparing nitrocellulose spherical particles according to claim 5, characterized in that: It also includes a heat preservation pipeline (45), and the conveying and forming pipeline (41) and the heating coil (42) are arranged inside the heat preservation pipeline (45); The conveying and forming pipeline (41) is arranged in a spiral from bottom to top, and the forming pipeline feed port is arranged below the forming pipeline discharge port; Three groups of thermometers (43) and pressure gauges (44) are arranged on the conveying and forming pipeline (41), and the three groups of thermometers (43) and pressure gauges (44) are arranged in sequence and at intervals along the conveying direction of the conveying and forming pipeline (41).

7. The system for preparing nitrocellulose spherical particles according to claim 1, characterized in that: The desolventizing tank (5) is a flash tank, the top of the desolventizing tank (5) is provided with a gas phase discharge port, and the bottom of the desolventizing tank (5) is provided with a liquid phase discharge port; It also includes a spherical particle hardening device (7), the liquid phase outlet of the desolventizing tank (5) is connected to the feed port of the spherical particle hardening device (7) through a fourth conveying pipeline, and a fourth power pump (64) is arranged on the fourth conveying pipeline.

8. The system for preparing nitrocellulose spherical particles according to any one of claims 1 to 7, characterized in that: It also includes a screening device (8), and the discharge port of the spherical particle hardening device (7) is connected to the feed port of the screening device (8) through a fifth conveying pipeline.

9. A method for preparing spherical nitrocellulose particles, characterized in that: The preparation method adopts the preparation system according to any one of claims 1 to 8, the particle size of the nitrocellulose spherical particles is 300 μm-1000 μm, and comprises the following steps: a. After adding a dissolving solvent into the dissolving tank (1), nitrocellulose is added into the dissolving tank (1) to obtain viscous nitrocellulose; b. adding a dilution solvent into the dilution solvent tank (2), and conveying the dilution solvent into the preforming device (3); while conveying the dilution solvent into the preforming device (3), the viscous nitrocellulose is conveyed into the preforming device (3) for preforming, thereby obtaining a first mixed solution of nitrocellulose cylindrical particles and the dilution solvent; c. conveying the first mixed solution obtained in step b to a molding device (4) for molding to obtain a second mixed solution of nitrocellulose spherical particles and a diluent solvent; d. The second mixed solution in step c is transported to a desolventizing tank (5) for desolventizing treatment to obtain nitrocellulose spherical particles.

10. The method for preparing spherical nitrocellulose particles according to claim 9, characterized in that: In step a, the dissolving solvent is ethyl acetate or acetone, the solid content of the viscous nitrocellulose is 20-35% by mass, and the stick drop viscosity is 4-15s; In step b, the cross-sectional circular diameter of the cylindrical forming hole (334) in the preforming device (3) is 500-1500 μm, and the height-to-diameter ratio of the obtained nitrocellulose cylindrical particles is 0.5-2; In step c, the molding temperature in the molding device (4) is controlled at 50-95° C.; The method further comprises a step e, wherein the spherical nitrocellulose particles obtained in the step d are transported to a spherical particle hardening device (7) for further desolventizing treatment.

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