Efficient dehydration method for energetic aqueous waste HTPB propellant

Abstract

This invention provides a highly efficient dehydration method for energetic and water-containing waste HTPB propellant, comprising: Step 1, barrier coupling sheet preparation: Under low temperature conditions of 5-10℃, the energetic and water-containing waste HTPB propellant is placed inside a barrier, protected by an inert gas, and pressed into propellant sheets with a thickness ≤1mm using a two-roller press; Step 2, fiber-like capillary adsorption: The propellant sheets obtained in Step 1 are spread flat on the surface of a multi-level porous fiber-like capillary matrix, and allowed to adsorb statically. Through capillary effect, free water on the surface of the propellant sheets is driven to migrate along the porous channels of the matrix and be captured, removing the surface free water; The fiber-like capillary matrix is ​​composed of a cellulose skeleton phase, a silica aerogel porous control phase, a hydroxylated nanocellulose interface functional phase, and a polyurethane substrate supporting and stabilizing phase; Step 3, negative pressure physical dehydration; Step 4, chemical selective dehydration; Step 5, safe recycling. This invention has high dehydration efficiency, retains thermal stability, is safe and controllable, and has low cost.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials technology, and relates to the safe treatment and resource utilization of energetic materials, specifically to an efficient dehydration method for energetic and water-containing waste HTPB propellant. Background Technology

[0002] The treatment of energetic and water-containing waste HTPB (hydroxyl-terminated polybutadiene) propellants has always been a major challenge in the field of safe disposal and resource utilization of energetic materials. Traditional treatment methods mainly face the following problems: First, the high water content of the propellant increases the danger of transportation and storage; second, the sensitivity and instability of energetic materials make the dehydration process prone to thermal decomposition or combustion and explosion; third, existing single dehydration technologies cannot effectively remove both free water and bound water at the same time, and often affect the thermal stability and subsequent reuse value of the propellant.

[0003] The current industry faces limitations due to single-technology limitations, defects in multi-technology coupling, and damage to thermal stability. This means that a single technology cannot achieve the dehydration goal of "safe, controllable, efficient, thorough, and low-damage." Therefore, the industry practice is to use multi-technology coupling processes (such as "mechanical dehydration + hot air drying + chemical drying" or the "energetic material hydrolysis-ultrasound-fertilizer coupling system" disclosed in patent CN103408341A). However, these still suffer from problems such as lengthy processes (total processing time ≥ 8 hours), high energy consumption (hot air drying accounts for over 60% of energy consumption), safety hazards (risks caused by oxygen contact and sudden temperature changes), component instability damage (such as oxidant side reactions), and thermal stability damage (DSC exothermic peak starting temperature is below 200℃). Therefore, a four-step synergistic process of "barrier protection - capillary adsorption - negative pressure drying - chemical selective dehydration" is adopted. Therefore, the industry believes that using a multi-step synergistic approach to achieve the stepwise removal of "surface free water - internal free water - bound water" can solve these problems. However, the technology has problems such as high cost of preparing multi-level porous fiber-like capillary matrix, difficulty in synergistic control of low temperature negative pressure and mild chemical dehydration, and difficulty in balancing the reaction rate and safety of chemical selective dehydration, which prevents it from being applied in practice. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an efficient dehydration method for energetic and water-containing waste HTPB propellants, thereby solving the technical problem that existing dehydration methods need to further improve dehydration efficiency while ensuring thermal stability.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] An efficient dehydration method for energetic and water-containing waste HTPB propellant, the method comprising the following steps.

[0007] Step 1: Barrier coupling film preparation.

[0008] Under low temperature conditions of 5–10℃, energetic and water-containing waste HTPB propellant is placed inside a barrier, protected by inert gas, and then pressed into propellant flakes with a thickness of ≤1mm using a two-roll press.

[0009] Step two, imitation fiber capillary absorption.

[0010] The propellant flakes obtained in step one are spread on the surface of a multi-level porous fiber-like capillary matrix and allowed to stand for 1 minute for adsorption. Through the capillary effect, the free water on the surface of the propellant flakes is driven to migrate along the porous channels of the matrix and is captured, thus removing the surface free water.

[0011] The fiber-like capillary matrix is ​​composed of a cellulose skeleton phase, a silica aerogel porous control phase, a hydroxylated nanocellulose interface functional phase, and a polyurethane substrate support and stabilizing phase.

[0012] Step 3: Negative pressure physical dehydration.

[0013] The propellant flakes processed in step two were transferred to a vacuum drying oven and dried at 40–50°C and -0.095–-0.08 MPa to remove residual free water.

[0014] Step four: chemical selective dehydration.

[0015] The propellant flakes dried in step three were placed in a sealed reactor. After the air was replaced by inert gas, CaCl2 sol was added and reacted with the molecular sieve fixed bed for 0.5 hours to remove bound water.

[0016] Step 5: Safe recycling.

[0017] After the chemical selective dehydration in step four is completed, the inert gas supply is stopped, the reactor is opened, and the treated propellant flakes are collected and crushed into propellant particles using a low-speed pulverizer.

[0018] The present invention also has the following technical features.

[0019] In step two, the static adsorption time is 1 min; in step three, the drying time is 0.5 h; in step four, the contact reaction time is 0.5 h.

[0020] In steps one and four, the inert gas is nitrogen with a purity of ≥99.99% or carbon dioxide with a purity of ≥99.99%, and the flow rate of the inert gas is 1-2 L / min.

[0021] In step two, the mass ratio of the cellulose framework phase, the silica aerogel porous control phase, the hydroxylated nanocellulose interface functional phase, and the polyurethane substrate support and stabilizing phase is 6:2.5:1.4:0.1.

[0022] In step two, the cellulose skeleton phase is made of cotton fiber pulp with a diameter of 10-20 μm; the silica aerogel porous control phase has a particle size of 50-100 nm and a porosity of ≥90%; the concentration of the hydroxylated nanocellulose interfacial functional phase is 0.3-0.5 wt% and the thickness is 5-10 nm; and the thickness of the polyurethane substrate support stabilizing phase is 1-2 mm.

[0023] In step four, the mass concentration of the CaCl2 sol is 20-30 wt%; the mass ratio of the CaCl2 sol to the propellant flakes is 1:5.

[0024] In step four, the filling amount of the molecular sieve fixed bed is 10% to 20% of the mass of the propellant flakes.

[0025] In step five, the propellant particles are propellant particles with a diameter of 1 to 2 mm.

[0026] In step five, the moisture content of the propellant particles is ≤5wt%; the DSC exothermic peak onset temperature of the propellant particles is ≥220℃.

[0027] In step five, the thermal stability deviation between the propellant particles and the energetic and water-containing waste HTPB propellant in step one is ≤5℃.

[0028] Compared with the prior art, the present invention has the following technical effects.

[0029] (I) High dehydration efficiency: The total treatment time is only 2 hours (far lower than the traditional process of more than 8 hours), and the moisture content is reduced from 90%-95% to less than 5%, achieving the complete removal of "free water and bound water".

[0030] (II) Thermal stability retention: The DSC exothermic peak onset temperature of the treated propellant is ≥220℃, which is comparable to the thermal stability of the original HTPB propellant, and it can be directly used for subsequent pyrolysis regeneration.

[0031] (III) Safety and controllability: The entire process is carried out under inert atmosphere, low temperature (≤50℃), and low pressure (≥-0.095MPa) conditions, with no risk of high temperature or strong impact. There is no thermal decomposition or combustion of the propellant during the process.

[0032] (IV) Low cost: The process is simplified (only 5 steps), no high-energy-consuming equipment is required, the fiber-like capillary matrix can be reused (≥10 times), and the CaCl2 sol and molecular sieve are inexpensive and suitable for large-scale application.

[0033] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, all raw materials and equipment used in this invention are those known in the art.

[0035] This invention solves the problem of rapid surface water removal by introducing a multi-level porous fiber-like capillary matrix, and achieves the removal of bound water by combining low-temperature negative pressure and gentle chemical dehydration. Furthermore, it develops an intelligent control system to precisely regulate the parameters of each step, and ultimately achieves a dual improvement in dehydration efficiency (co-removal of free water and bound water) and thermal stability (DSC exothermic peak onset temperature ≥220℃) while ensuring safety, thus solving the aforementioned unsolvable problems.

[0036] The dehydration method of the present invention includes five steps in sequence: barrier coupling sheet preparation, fiber-like capillary absorption, negative pressure physical dehydration, chemical selective dehydration, and safe recycling. Each step works synergistically to achieve efficient dehydration.

[0037] In this invention, the energetic and water-containing waste HTPB propellant is taken from a retired solid rocket engine, collected after high-pressure water jet separation, and has a water content of 90wt% to 95wt%.

[0038] In this invention, the cellulose backbone phase is cotton fiber pulp (10-20 μm in diameter), which uses cotton fiber pulp commonly known in the art, and is used to provide a matrix support structure.

[0039] In this invention, the porous control phase of silica aerogel is silica aerogel particles (particle size 50-100nm, porosity ≥90%), which are used to construct multi-level capillary channels.

[0040] In this invention, the hydroxylated nanocellulose interfacial functional phase is hydroxylated nanocellulose (concentration 0.3-0.5 wt%). The hydroxylated nanocellulose used is the commonly known hydroxylated nanocellulose in the art, and is used to modify the matrix surface to enhance the adsorption capacity of water molecules.

[0041] In this invention, a polyurethane substrate supports a stable phase: a polyurethane substrate (1-2 mm thick), which is a polyurethane substrate known in the art, used to improve the mechanical strength and solvent resistance of the matrix.

[0042] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0043] Example 1:

[0044] This embodiment provides an efficient dehydration method for energetic and water-containing waste HTPB propellant, which includes the following steps.

[0045] Step 1: Barrier coupling film preparation.

[0046] Under low temperature conditions of 5-10℃, 500g of energetic and water-containing waste HTPB propellant with a water content of 92.5wt% was placed inside a barrier, and nitrogen inert gas with a purity of ≥99.99% was introduced at a flow rate of 2L / min for protection. The propellant was then pressed into a propellant sheet with a thickness of 0.7mm using a two-roller press (model: SY-650, roller diameter 150mm).

[0047] In step one, the barrier is made of 304 stainless steel, has a volume of 10L, and has a built-in pressure sensor and temperature alarm.

[0048] In step one, low temperature and inert atmosphere can inhibit the oxidation and hydrolysis of propellant components; the propellant sheet structure can increase the specific surface area, providing sufficient channels for subsequent moisture removal and preventing internal moisture lock-in.

[0049] Step two, imitation fiber capillary absorption.

[0050] The propellant flakes obtained in step one were spread on the surface of a multi-level porous fiber-like capillary matrix and allowed to stand for 1 minute for adsorption. Through the capillary effect, the free water on the surface of the propellant flakes was driven to migrate along the porous channels of the matrix and be captured, thus removing the surface free water. The surface water content of the propellant flakes was measured and found to have decreased from 92.5 wt% to 75.3 wt%.

[0051] The fiber-like capillary matrix consists of a cellulose skeleton phase, a silica aerogel porous control phase, a hydroxylated nanocellulose interface functional phase, and a polyurethane substrate support and stabilizing phase.

[0052] In step two, the mass ratio of the cellulose framework phase, the silica aerogel porous control phase, the hydroxylated nanocellulose interface functional phase, and the polyurethane substrate support and stabilizing phase is 6:2.5:1.4:0.1.

[0053] In step two, the cellulose backbone phase is made of cotton fiber pulp with a diameter of 10–20 μm and a length of 2–3 mm; the porous control phase of silica aerogel has a particle size of 50–100 nm, an average particle size of 80 nm, and a porosity of 92%; the concentration of the hydroxylated nanocellulose interfacial functional phase is 0.4 wt%, the solid content is 1%, and the thickness is 8 nm; the thickness of the polyurethane substrate support and stabilizing phase is 1.5 mm, and it is cut into a matrix sheet of 500 mm × 500 mm.

[0054] Step 3: Negative pressure physical dehydration.

[0055] The propellant flakes processed in step two were transferred to a vacuum drying oven (model: DZF-6050, temperature control accuracy ±1℃) and dried at 45℃ and -0.092MPa for 0.5h to remove residual free water. After drying, a sample was taken and the moisture content was measured to be 17.8wt% using a Karl Fischer moisture analyzer (model: V20, accuracy 0.001wt%).

[0056] In step three, low temperature (45℃) avoids thermal decomposition of the propellant, and the negative pressure environment accelerates moisture evaporation while inhibiting oxygen intrusion. A drying time of 0.5 hours can reduce the shrinkage and deformation of the HTPB matrix while ensuring dehydration efficiency.

[0057] Step four: chemical selective dehydration.

[0058] After drying in step three, the propellant flakes were placed in a sealed reactor (5L, material: Hastelloy). Nitrogen inert gas with a purity ≥99.99% was introduced at a flow rate of 1.5L / min to replace the air (replacement time 10min). Then, 100g of CaCl2 sol (analytical grade CaCl2 dissolved in deionized water) with a mass concentration of 25wt% was added. The mass ratio of CaCl2 sol to propellant flakes was 1:5. The mixture was then reacted with a 13X molecular sieve fixed bed (filling amount 40g, particle size 3-5mm) for 0.5h (maintaining a nitrogen atmosphere and stirring rate of 50r / min) to remove bound water.

[0059] In step four, CaCl2 sol is a mild water-absorbing system and will not react with the oxidant in the propellant; the molecular sieve fixed bed can adsorb the water volatilized in CaCl2 sol, avoiding secondary adhesion of bound water.

[0060] Step 5: Safe recycling.

[0061] After the chemical selective dehydration in step four is completed, the inert gas supply is stopped, the reactor is opened and the treated propellant flakes are collected. The flakes are then crushed into propellant particles with a particle size of 1.5 mm using a low-speed pulverizer (model: XKJ-100, speed 400 r / min).

[0062] In step five, the water content of the propellant particles was measured using a Karl Fischer moisture analyzer, and the water content was found to be 4.2 wt%. The DSC exothermic peak onset temperature of the propellant particles was ≥225 ℃, measured using a differential scanning calorimeter (DSC, model: DSC214Polyma, heating rate 10℃ / min). The DSC exothermic peak onset temperature of the energetic and water-containing waste HTPB propellant with a water content of 92.5 wt% in step one was 228 ℃ (original unhydrolyzed state). The propellant particles in step five had a DSC exothermic peak onset temperature ≥225 ℃, and a thermal stability deviation ≤5 ℃, which is basically consistent with the thermal stability of the original propellant. Therefore, they are qualified products and can be used for subsequent pyrolysis regeneration.

[0063] Safety verification of propellant particles in step five: After storage at 50℃ and normal pressure for 72 hours, no decomposition gas was generated and no abnormal temperature rise was observed.

[0064] Example 2: This embodiment provides an efficient dehydration method for energetic and water-containing waste HTPB propellant. This method is basically the same as the method given in Embodiment 1, except that the thickness of the propellant sheet is changed (0.5 mm, 1.0 mm, and 1.5 mm respectively), while the other parameters remain unchanged. The final moisture content and processing time are then measured.

[0065] Table 1 Performance parameters for different propellant sheet thicknesses

[0066] As shown in Table 1, when the propellant sheet thickness is ≤1mm, the final moisture content can be controlled below 5wt%, and the treatment time is ≤2h; when the thickness exceeds 1mm, the internal moisture is difficult to remove completely, and the moisture content rises to above 7wt%. Therefore, the propellant sheet thickness is preferably ≤1mm.

Claims

1. A highly efficient dehydration method for energetic and water-containing waste HTPB propellant, characterized in that, The method includes the following steps: Step 1, Barrier Coupling Preparation: Under low temperature conditions of 5-10℃, energetic and water-containing waste HTPB propellant is placed in a barrier, protected by inert gas, and pressed into propellant flakes with a thickness of ≤1mm by a two-roller press. Step 2, mimicking fiber capillary absorption: The propellant flakes obtained in step one are spread on the surface of a multi-level porous fiber-like capillary matrix and allowed to stand for adsorption. Through the capillary effect, the free water on the surface of the propellant flakes is driven to migrate along the porous channels of the matrix and be captured, thus removing the surface free water. The fiber-like capillary matrix is ​​composed of a cellulose skeleton phase, a silica aerogel porous control phase, a hydroxylated nanocellulose interface functional phase, and a polyurethane substrate support and stabilizing phase. Step 3, negative pressure physical dehydration: The propellant flakes processed in step two were transferred to a vacuum drying oven and dried at 40–50°C and -0.095–-0.08 MPa to remove residual free water. Step 4, Chemical Selective Dehydration: The propellant flakes dried in step three were placed in a sealed reactor. After the air was replaced by inert gas, CaCl2 sol was added and reacted with the molecular sieve fixed bed for 0.5 hours to remove bound water. Step 5, Safe Recycling: After the chemical selective dehydration in step four is completed, the inert gas supply is stopped, the reactor is opened, and the treated propellant flakes are collected and crushed into propellant particles using a low-speed pulverizer.

2. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, In step two, the static adsorption time is 1 min; in step three, the drying time is 0.5 h; in step four, the contact reaction time is 0.5 h.

3. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, In steps one and four, the inert gas is nitrogen with a purity of ≥99.99% or carbon dioxide with a purity of ≥99.99%, and the flow rate of the inert gas is 1-2 L / min.

4. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, In step two, the mass ratio of the cellulose framework phase, the silica aerogel porous control phase, the hydroxylated nanocellulose interface functional phase, and the polyurethane substrate support and stabilizing phase is 6:2.5:1.4:0.

1.

5. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, In step two, the cellulose skeleton phase is made of cotton fiber pulp with a diameter of 10-20 μm; the silica aerogel porous control phase has a particle size of 50-100 nm and a porosity of ≥90%; the concentration of the hydroxylated nanocellulose interfacial functional phase is 0.3-0.5 wt% and the thickness is 5-10 nm; and the thickness of the polyurethane substrate support stabilizing phase is 1-2 mm.

6. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, In step four, the mass concentration of the CaCl2 sol is 20-30 wt%; the mass ratio of the CaCl2 sol to the propellant flakes is 1:

5.

7. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, The molecular sieve fixed bed is filled with 10% to 20% of the mass of the propellant flakes.

8. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, In step five, the propellant particles are propellant particles with a diameter of 1 to 2 mm.

9. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, In step five, the moisture content of the propellant particles is ≤5wt%; the DSC exothermic peak onset temperature of the propellant particles is ≥220℃.

10. The efficient dehydration method for energetic and water-containing waste HTPB propellant as described in claim 1, characterized in that, In step five, the thermal stability deviation between the propellant particles and the energetic and water-containing waste HTPB propellant in step one is ≤5℃.

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