A method for pulverizing a waste solid composite propellant

Abstract

The present application belongs to the technical field of solid composite propellant recycling, and particularly relates to a method for crushing waste solid composite propellant. First, a composite precipitate of iron hydroxide and aluminum hydroxide is generated by using ferric chloride hexahydrate and aluminum chloride hexahydrate, the precipitate is filtered and washed, and then is mixed with carbon nanotubes and ethanol for ball milling, and finally is calcined to obtain a nano composite grinding aid. After the nano composite grinding aid is prepared into a suspension, the waste solid composite propellant is crushed together with the suspension, and the crushed solid composite propellant particles are separated by screening. The nano composite grinding aid prepared by the present application can improve the performance of the propellant, and the crushing method is particularly suitable for combustion recycling of the waste solid composite propellant. In the combustion recycling, the combustion efficiency and energy release are enhanced, so that the recycling heat value and energy utilization rate of the propellant can be significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of solid composite propellant recycling technology, specifically relating to a method for pulverizing waste solid composite propellants. Background Technology

[0002] Composite propellants are high-energy-density fuels widely used in weapons such as rockets and missiles. However, during production and storage, due to factors such as time and storage conditions, solid composite propellants may experience surface hardening, interface detachment, density reduction, and loss of energetic components. Therefore, aged solid composite propellants generally reach their end-of-life after 5 to 10 years.

[0003] Waste solid composite propellants contain oxidizers, fuels, binders, and other components, which can cause environmental damage and pose certain safety hazards. Therefore, the recovery and resource utilization of the effective components of composite propellants is of significant practical importance. The first step in recycling composite propellants is to pulverize the waste solid composite propellants. Smaller particle sizes facilitate sorting and recycling, and also make it easier to treat them harmlessly, thereby reducing environmental pollution. The inventor's previous patent CN118684252B disclosed a method for recycling waste solid composite propellants, which involves combining the composite propellant with aluminum-containing powder to form a slurry fluid for re-combustion and recovery. This method also requires pulverizing the composite propellant as a prerequisite.

[0004] Waste solid composite propellants are generally pulverized using wet methods. However, when wet pulverizing, the particles of solid composite propellants tend to settle easily, which is not conducive to feeding. Furthermore, solid composite propellants are elastic, and when subjected to pressure, their shape changes, allowing them to be extruded through a relatively small aperture. However, after extrusion, the material rebounds to a larger size, resulting in poor pulverization.

[0005] Grinding aids can improve the crushing effect of waste solid composite propellants, but there are currently few reports on grinding aids specifically for waste solid composite propellants. Existing grinding aids for solid waste are difficult to use in waste solid composite propellants. For example, patent EP123456789A1 discloses an iron-aluminum complex as a grinding aid in various industrial products (including cement and mineral grinding), but the crushing effect of this iron-aluminum complex in elastic materials is not ideal.

[0006] Therefore, finding a method to effectively pulverize waste solid composite propellants is a technical problem that needs to be solved. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for pulverizing waste solid composite propellants.

[0008] The technical means employed in this invention are as follows:

[0009] A method for pulverizing waste solid composite propellant includes the following steps:

[0010] S1. Ferric chloride hexahydrate, aluminum chloride hexahydrate, and water are mixed evenly in a mass ratio of (10~25): (5~15): (60~85). An appropriate amount of ammonia is added to adjust the pH value to 8~10. The resulting precipitate is filtered and washed, and then mixed with carbon nanotubes and ethanol in a mass ratio of (5~10): (1~3): (22~55) and placed in a ball mill for ball milling. After drying and calcination, a nanocomposite grinding aid is obtained.

[0011] S2. The nanocomposite grinding aid is uniformly mixed with water to form a suspension with a density of 1.3~1.9 g / cm³. The suspension and the solid composite propellant are added together to a pulverizing device at a mass ratio of (25~50): (10~20) for pulverization.

[0012] S3. The material obtained after crushing is screened with a sieve to separate and obtain crushed solid composite propellant particles.

[0013] Preferably, the solid composite propellant is a hydroxyl-terminated composite propellant.

[0014] Preferably, in step S1, the grinding media in the ball mill is tungsten carbide balls, the ball milling speed is 250 rpm, the ball-to-material ratio is 50:1, and the ball milling time is 10 h.

[0015] Preferably, in step S1, the calcination is carried out at 600°C for 2 hours in an inert gas atmosphere.

[0016] Preferably, in step S2, the crushing device is a shear-type crushing pump, the rotor speed of the crushing pump is 2000~2500 r / min, the single crushing time is 5min, the single feed amount is 10kg, and the crushing is performed 3~5 times.

[0017] Preferably, in step S3, the aperture of the sieve is 0.2~1 mm.

[0018] Preferably, in step S3, the remaining material after screening is separated into magnetite powder by magnetic separation, and then separated into nano-alumina powder by centrifugation. The magnetite powder and nano-alumina powder are reused as nano-composite grinding aids.

[0019] The beneficial effects of this invention are as follows:

[0020] 1) This invention provides a grinding aid suitable for waste solid composite propellants. Ferric chloride hexahydrate and aluminum chloride hexahydrate are used to synthesize a magnetite-alumina composite material via a co-precipitation method. This composite material is then mixed with carbon nanotubes and ethanol, followed by mechanical ball milling, drying, and calcination to obtain a nano-composite grinding aid. This nano-composite grinding aid, when mixed with water in a specific ratio to form a suspension, and then further mixed with solid propellant in a proportional manner, allows for flexible adjustment of the material concentration. This keeps the propellant particles in a suspended state, enabling them to be pumped to the crushing equipment and preventing sedimentation during the feeding process. This results in a more uniform crushing process and a better crushing effect.

[0021] 2) The nanocomposite grinding aid prepared by this invention has relatively high hardness, which can assist in promoting the grinding and washing process of propellant particles during the crushing process, making the discharge process smoother, improving grinding efficiency, and reducing energy consumption. The nanocomposite grinding aid also has good dispersibility, which can reduce the agglomeration of solid composite propellant particles, help improve propellant performance, and improve combustion efficiency in combustion recovery.

[0022] 3) The crushed waste solid composite propellant of this invention is particularly suitable for combustion recovery. During combustion, the nano-composite grinding aids remaining during separation can undergo redox and catalytic reactions with the solid composite propellant, increasing combustion temperature and heat transfer efficiency. By enhancing combustion efficiency and energy release, the recovery calorific value and energy utilization rate of the propellant can be significantly improved.

[0023] 4) Nanocomposite grinding aids and solid composite propellants have very different properties. Magnetite powder and nano alumina powder in the crushed material can be recovered and recycled through screening, magnetic separation, and centrifugation, which reduces the cost of crushing waste solid composite propellants, improves economic efficiency, and helps to build a resource-saving and environmentally friendly society. Attached Figure Description

[0024] Figure 1 The results are TGA experimental test results of solid composite propellant particles obtained in Examples 1-3 and Comparative Example 4. Detailed Implementation

[0025] The technical solution of the present invention will be described in more detail below with reference to the embodiments.

[0026] Unless otherwise specified, all materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0027] Preparation of nanocomposite grinding aid: Ferric chloride hexahydrate, aluminum chloride hexahydrate, and water were mixed evenly at a mass ratio of 15:10:75. An appropriate amount of ammonia was added to adjust the pH to 9, producing a composite precipitate of ferric hydroxide and aluminum hydroxide. The filtered precipitate was washed and then mixed with carbon nanotubes and ethanol at a mass ratio of 10:1:35 and ball-milled. Tungsten carbide balls were used as the milling media, the rotation speed was set to 250 rpm, the ball-to-material ratio was 50:1, and the milling time was 10 hours. The milled material was dried at 80°C for 4 hours, and then calcined at 600°C in an argon atmosphere for 2 hours to obtain the nanocomposite grinding aid.

[0028] Weigh a certain amount of nanocomposite grinding aid and water, put them into a mixing tank, and stir evenly for 10 minutes at a stirrer speed of 700 r / min to obtain a suspension. Adjust the ratio of magnetite powder to water according to the above method to obtain three groups of suspensions with different densities in Examples 1-3. The specific ratios are shown in Table 1 below.

[0029] Table 1. Suspension formulation and density

[0030] ;

[0031] The suspensions prepared in Examples 1-3 were mixed with waste solid composite propellant at a mass ratio of 35:15 and added to a shear-type pulverizing pump for pulverization. The rotor speed of the shear-type pulverizing pump was 2300 r / min, the single pulverization time was 5 min, the single feed amount was 10 kg, and the pulverization was performed 3 times. The pulverized material was initially sieved through a 0.2 mm sieve to separate solid composite propellant particles. The material smaller than 0.2 mm was recycled as magnetite powder using a magnetic separator, and then further separated into nano-alumina powder using a centrifuge. The centrifuge speed was set to 3500 rpm, and the centrifugation time was 15 min.

[0032] In this embodiment, the proportions of the waste solid composite propellant components are as follows: 35.71 wt% hydroxyl-terminated polybutadiene, 23.21 wt% ammonium perchlorate, 5.36 wt% cyclotrimethylenetrinitramine, 3.57 wt% toluene diisocyanate, 10.71 wt% dioctyl sebacate, and 21.43 wt% aluminum.

[0033] In Comparative Example 1, with the composition of the waste solid composite propellant unchanged, the grinding aid used was magnetite powder with a true density of 4.7 g / cm³ and a magnetic content of 98%. The resulting suspensions all had a density of 1.6 g / cm³.

[0034] In Comparative Example 2, with the composition of the waste solid composite propellant unchanged, nano-alumina was used as the grinding aid. The true density of nano-alumina was 4.0 g / cm³, and the density of the resulting suspension was 1.6 g / cm³.

[0035] In Comparative Example 3, with the composition of the waste solid composite propellant unchanged, calcium carbonate was used as the grinding aid. The purity of the calcium carbonate needed to be above 98%, and the density of the resulting suspension was 1.6 g / cm³.

[0036] Comparative Example 4 did not use grinding aids; the waste solid composite propellant was directly added to a shear-type pulverizer pump for pulverization. The rotor speed of the shear-type pulverizer pump was 2300 r / min, and the pulverization cycle was 10 times.

[0037] The waste solid composite propellant particles obtained in Examples 1-3 and Comparative Examples 1-4 were screened by sieving, and the fineness of the powder is shown in Table 2.

[0038] Table 2. Particle size distribution of pulverized waste solid composite propellant

[0039] ;

[0040] It can be seen that after three grinding cycles, the materials in Examples 1-3 have less than 12.17% particles larger than 1 mm, with a significant portion of particles distributed within a finer particle size range (<0.2 mm and 0.2~0.5 mm). After five grinding cycles, the materials in Comparative Examples 1, 2, and 3 have more than 30.73% particles larger than 1 mm, while Comparative Example 4, after ten grinding cycles, has 46.74% particles larger than 1 mm, and its particle size distribution is smaller than that of the other examples. Experiments show that the nanocomposite grinding aid prepared in this invention can effectively assist in promoting the grinding and washing process of propellant particles during grinding, improving grinding efficiency, reducing the cost of grinding waste solid composite propellants, and improving economic benefits.

[0041] The solid composite propellants after being broken up in Examples 1-3 were subjected to LC-MS testing. The content of each component in the broken solid composite propellant particles is shown in Table 3 below.

[0042] Table 3. Analysis of solid composite propellant content after fragmentation in Examples 1-3

[0043] ;

[0044] It can be seen that magnetite, alumina and carbon nanotubes were present in all three examples after recycling, indicating that the crushed materials had nanocomposite grinding aid residues after magnetic separation and centrifugal recycling, and the higher the density of the suspension used, the higher the proportion of residues.

[0045] To determine the effect of residual nanocomposite grinding aids on the combustion performance of solid composite propellants, TGA experiments were conducted on the solid composite propellant particles obtained in Examples 1-3 and Comparative Example 4. The test results are shown in […]. Figure 1 It can be seen that the decomposition rates of all embodiments are basically consistent within the temperature range of 200-300℃. Within the temperature range of 300-600℃, the decomposition rate of Example 3 decreases the fastest, while the decomposition rates of Examples 1 and 2 decrease relatively quickly, and the rate of decrease in Comparative Example 4 is relatively slow. Within the temperature range of 600-800℃, the burnout rates of the solid composite propellants in Examples 1-3 are all higher than those in Comparative Example 4, indicating that the nanocomposite grinding aid accelerates the decomposition reaction of the solid composite propellant.

[0046] The higher heating value of Examples 1-3 and Comparative Examples 1-4 was tested using the bomb calorimeter method. The test results are shown in Table 4 below.

[0047] Table 4. Higher heating value of solid composite propellant after fragmentation

[0048] ;

[0049] The mean calorific value of the example group and the comparative group was compared using a t-test. p The value is 0.002. The calorific value of the solid composite propellant after being crushed according to this method is generally higher than that of the comparative example, and there are significant differences in calorific value between them. The crushing method of this invention can effectively improve the calorific value of solid composite propellants and improve energy utilization.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for pulverizing waste solid composite propellant, characterized in that, Includes the following steps: S1. Ferric chloride hexahydrate, aluminum chloride hexahydrate, and water are mixed evenly in a mass ratio of (10~25): (5~15): (60~85). An appropriate amount of ammonia is added to adjust the pH value to 8~10. The resulting precipitate is filtered and washed, and then mixed with carbon nanotubes and ethanol in a mass ratio of (5~10): (1~3): (22~55) and ball-milled. After drying and calcination, a nanocomposite grinding aid is obtained. S2. The nanocomposite grinding aid is uniformly mixed with water to form a suspension with a density of 1.3~1.9 g / cm³. The suspension and the solid composite propellant are added together to a pulverizing device at a mass ratio of (25~50): (10~20) for pulverization. S3. The material obtained after crushing is screened with a sieve to separate and obtain crushed solid composite propellant particles.

2. The method for pulverizing waste solid composite propellant according to claim 1, characterized in that, The solid composite propellant is a hydroxyl-terminated composite propellant.

3. The method for pulverizing waste solid composite propellant according to claim 1, characterized in that, In step S1, the grinding media in the ball mill is tungsten carbide balls, the ball milling speed is 250 rpm, the ball-to-material ratio is 50:1, and the ball milling time is 10 h.

4. The method for pulverizing waste solid composite propellant according to claim 1, characterized in that, In step S1, the calcination is carried out at 600°C for 2 hours in an inert gas atmosphere.

5. A method for pulverizing waste solid composite propellant according to claim 1, characterized in that, In step S2, the crushing device is a shear-type crushing pump with a rotor speed of 2000-2500 r / min, a single crushing time of 5 min, a single feed amount of 10 kg, and a total crushing time of 3-5 times.

6. A method for pulverizing waste solid composite propellant according to claim 1, characterized in that, In step S3, the aperture of the sieve is 0.2~1 mm.

7. The method for pulverizing waste solid composite propellant according to claim 1, characterized in that, In step S3, the remaining material after screening is separated into magnetite powder by magnetic separation, and then separated into nano-alumina powder by centrifugation. The magnetite powder and nano-alumina powder are reused as nano-composite grinding aids.

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