Preparation method and application of a flame retardant for metal hydride fuels to prevent fire spread.

Abstract

This invention provides a method for preparing and applying a flame retardant for preventing crossfire in metal hydride fuels, comprising: Step 1, sequentially adding solvent water, isopropanolamine, and catalyst to a reaction vessel, replacing the air in the reaction vessel with N2, stirring, heating to 120–170°C, reacting for 1–10 hours, and then cooling to 70–90°C to obtain a dimethylpiperazine intermediate; Step 2, injecting a phosphoric acid aqueous solution into the reaction vessel using a metering pump, heating to 180–230°C, reacting for 1–10 hours, removing excess water, and drying to obtain a dimethylpiperazine pyrophosphate flame retardant. The flame retardant for preventing crossfire in metal hydride fuels of this invention is a halogen-free, environmentally friendly flame retardant with phosphorus as the main flame-retardant element. It releases a certain amount of water during combustion, resulting in superior flame retardant performance. The flame retardant for preventing crossfire in metal hydride fuels of this invention solves the problem of crossfire during the initial stage of explosive dispersion of metal hydride fuels and can be applied in the field of explosive chemistry.

Description

Technical Field

[0001] This invention belongs to the field of explosion chemistry technology and relates to flame retardants, specifically to a method for preparing and applying a flame retardant for preventing fire spread of metal hydride fuels. Background Technology

[0002] The energy release process of reducing fuels such as volatile hydrocarbon liquids and high-energy active metal powders is essentially a chemical process involving a rapid oxidation-reduction reaction between the fuel and oxygen in the air. When the reaction timescale is in the millisecond range, combustion usually occurs, while when the reaction timescale is in the microsecond range, explosion or detonation usually occurs. When using these reducing fuels, they must first be rapidly dispersed into the surrounding air using explosives, mixing with oxygen to form an explosive flammable cloud. Then, a secondary detonation device is used to cause the flammable cloud to explode or detonate, achieving the purpose of damaging the target.

[0003] Compared to active metal powders, metal hydrides have advantages such as higher calorific value and the ability to produce explosive hydrogen gas. Metal hydrides are efficient and convenient hydrogen release materials with a hydrogen content as high as 5% to 15%. During their explosion, the completely released hydrogen can participate in combustion and energy release together with the separated metal, increasing the number of water molecules in the combustion products. This significantly reduces the average relative molecular mass of the combustion products and increases the heat of the fuel, thereby greatly increasing its destructive power.

[0004] However, during the dispersion of the aforementioned metal hydride fuels into a cloud of explosives, premature deflagration, commonly known as arc flash, may occur. Arc flash is a combustion accident that occurs during the dispersion process and before secondary detonation. Arc flash causes most of the energy in the cloud to be released in the form of combustion, failing to form an effective shock wave. This significantly reduces the energy release efficiency and explosive destructive power of reducing fuels such as volatile hydrocarbon liquids and high-energy reactive metal powders.

[0005] To address the issue of fuel crossfire during the initial stage of explosive dispersion, two common approaches are altering the charge structure and adding flame-retardant media around the central charge. For instance, the literature "Application of Flame-Retardant Media in Explosive-Driven Fuel Dispersion" (Explosion and Shock, 2020, 40(4): 51-58) demonstrates that by adding ultrafine dry powder extinguishing agent as the main flame-retardant medium around the central charge and by altering the thickness of the flame-retardant medium on the sides and top, crossfire can be effectively prevented.

[0006] Changing the charge structure, such as using T-shaped central charges with intermittent filling of explosives of different diameters and filling the remaining space with porous inert materials, has a good effect on suppressing cloud fire spread. However, the added porous inert materials also weaken the energy of the detonation shock wave while suppressing fire spread. In addition, the inert materials mixed into the combustible cloud are not conducive to the detonation of the cloud. Adding flame-retardant media around the central charge and using ABC ultrafine dry powder extinguishing agent as flame retardant (Explosion and Shock, 2020, 40(4): 51-58) can greatly alleviate the fire spread phenomenon of fuel during the explosion and scattering process. However, the added ultrafine dry powder extinguishing agent, as an inert substance, weakens the energy of the detonation shock wave while suppressing fire spread. In addition, the fine powder inert materials mixed into the combustible cloud also play a certain role in suppressing the secondary detonation of the cloud. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing and applying a flame retardant for preventing crossfire of metal hydride fuels, thereby solving the problem of crossfire during the initial stage of explosive dispersion of metal hydride fuels in existing technologies.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A method for preparing a flame retardant to prevent fire spread, the method comprising the following steps:

[0010] Step 1: Add solvent water, isopropanolamine and catalyst sequentially to the reaction vessel, replace the air in the reaction vessel with N2, stir, raise the temperature to 120-170℃, react for 1-10 hours and then lower the temperature to 70-90℃ to obtain dimethylpiperazine intermediate.

[0011] Step 2: Phosphoric acid aqueous solution is pumped into the reaction vessel using a metering pump, the temperature is raised to 180-230℃, the reaction is carried out for 1-10 hours, excess water is removed and the mixture is dried to obtain dimethylpiperazine pyrophosphate flame retardant.

[0012] The present invention also has the following technical features:

[0013] Preferably, in step one, the temperature is raised to 120-160°C and the reaction is carried out for 10 hours; in step two, the temperature is raised to 180-200°C and the reaction is carried out for 10 hours.

[0014] Specifically, in step one, the catalyst is a Raney-type metal catalyst or a supported metal catalyst.

[0015] Preferably, in step one, the catalyst is Raney nickel, Raney copper, Raney cobalt, diatomaceous earth-supported nickel, alumina-supported nickel, or silica-supported nickel.

[0016] Specifically, in step one, the amount of catalyst used is 0.1% to 1.0% of the mass of isopropanolamine.

[0017] Preferably, in step one, the amount of catalyst used is 0.3% to 0.5% of the mass of isopropanolamine.

[0018] Specifically, in step one, the amount of water used as the solvent is 0.5 to 5 times the mass of isopropanolamine.

[0019] Preferably, in step one, the amount of solvent water used is 1 to 2 times the mass of isopropanolamine.

[0020] Specifically, in step two, the phosphoric acid aqueous solution is a phosphoric acid aqueous solution with a phosphoric acid content greater than 80 wt%.

[0021] Preferably, in step two, the amount of phosphoric acid in the phosphoric acid aqueous solution is 1.0 to 1.2 times the molar amount of isopropanolamine.

[0022] This invention also protects the application of flame retardants prepared by the above-described method for preventing crossfire in metal hydride fuels.

[0023] Specifically, the metal hydrides include lithium hydride, sodium hydride, potassium hydride, magnesium hydride, calcium hydride, aluminum hydride, lithium aluminum hydride, cuprous hydride, nickel hydride, and / or zinc hydride.

[0024] In this application, lithium hydride is used as the dispersing medium, the aforementioned anti-flame-spreading flame retardant is used as the flame retardant, and the dispersing charge is a ring-shaped cylindrical TNT charge. The aforementioned anti-flame-spreading flame retardant completely covers the dispersing charge and the detonator.

[0025] Preferably, the amount of the flame retardant for preventing fire spread is 10g for every 200g of lithium hydride, and the amount of the dispersing column is 5g.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] (I) Compared with the ABC ultrafine dry powder in the prior art, the metal hydride fuel anti-flame retardant of the present invention is a halogen-free environmentally friendly flame retardant with phosphorus as the main flame retardant element. It releases a certain amount of water when burning, and has better anti-flame retardant performance.

[0028] (II) The metal hydride fuel anti-flame-spreading flame retardant of the present invention solves the problem of flame spread in the early stage of metal hydride fuel explosion and can be applied to the field of explosion chemistry technology.

[0029] (III) The present invention prepares the metal hydride fuel anti-flame retardant by a one-pot method, and the preparation process is simple.

[0030] (IV) The metal hydride fuel fire retardant of the present invention uses isopropanolamine and phosphoric acid as the main raw materials, which are widely available, inexpensive and readily available.

[0031] (V) The metal hydride fuel anti-flame-spreading flame retardant of the present invention solves the problem of flame spread in the early stage of metal hydride fuel explosion and can be applied to the field of explosion chemistry technology. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the scattering test apparatus.

[0033] Figure 2(a) High-speed image showing the suppression of fireballs generated during the explosion without the addition of flame retardants.

[0034] Figure 2(b) High-speed image showing the effect of adding existing ABC ultrafine dry powder flame retardant on the instantaneous fireball generated by the explosion.

[0035] Figure 2(c) shows a high-speed image of the suppression of fireballs generated during the explosion by adding the compound flame retardant prepared in Example 1 of the present invention.

[0036] The meanings of the labels in the diagram are as follows: 1-Polyethylene sealing cap, 2-Polyethylene inner tube, 3-Polyethylene outer tube, 4-Detonating detonator, 5-Anti-flame retardant, 6-Dispersing explosive, 7-Spreading medium.

[0037] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, all raw materials used in this invention are known in the prior art, meaning that all raw materials used in this invention are commercially available.

[0039] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0040] Example 1:

[0041] This embodiment provides a method for preparing a flame retardant that prevents fire spread, which is carried out according to the following steps:

[0042] Step 1: 150g of solvent water, 75g of isopropanolamine (1mol) and 0.35g of Raney nickel catalyst were added sequentially to the reaction vessel. The air in the reaction vessel was replaced with N2, and the mixture was stirred and heated to 160℃. After reacting for 10 hours, the temperature was lowered to 70℃ to obtain the 2,5-dimethylpiperazine intermediate.

[0043] Step 2: 126.8 g of 85 wt% phosphoric acid aqueous solution (1.1 mol) was slowly pumped into the reactor using a metering pump. The temperature was raised to 200 °C and the reaction was carried out for 10 h. After removing excess water and drying, 147.3 g of light brown, powdered dimethylpiperazine pyrophosphate flame retardant was obtained, with a yield of 95.0%.

[0044] Example 2:

[0045] This embodiment provides a method for preparing a flame retardant that prevents fire spread. The method is basically the same as that in Example 1, except that the amount of water used as the solvent in Example 1 is changed to 75g, while the other conditions remain unchanged. After removing excess water and drying, 111.6g of light brown, powdered dimethylpiperazine pyrophosphate flame retardant is obtained, with a yield of 72.0%.

[0046] Example 3:

[0047] This embodiment provides a method for preparing a flame retardant that prevents fire spread. The method is basically the same as that in Example 1, except that the catalyst in Example 1 is replaced with nickel supported on alumina. The other conditions remain unchanged. After removing excess water and drying, 145.7g of light brown, powdered dimethylpiperazine pyrophosphate flame retardant is obtained with a yield of 94.0%.

[0048] Example 4:

[0049] This embodiment provides a method for preparing a flame retardant that prevents fire spread. The method is basically the same as that in Example 1, except that the catalyst in Example 1 is replaced with nickel supported on alumina. The other conditions remain unchanged. After removing excess water and drying, 145.7g of light brown, powdered dimethylpiperazine pyrophosphate flame retardant is obtained with a yield of 94.0%.

[0050] Example 5:

[0051] This embodiment provides a method for preparing a flame retardant that prevents fire spread. This method is basically the same as the method in Example 1, except that in this embodiment, the reaction temperature in step one of Example 1 is reduced to 120°C and the reaction time is shortened to 5 hours, while the other conditions remain unchanged. After removing excess water and drying, 106.8 g of light brown, powdered dimethylpiperazine pyrophosphate flame retardant is obtained, with a yield of 68.9%.

[0052] Example 6:

[0053] This embodiment provides a method for preparing a flame retardant that prevents fire spread. This method is basically the same as the method in Example 1, except that in this embodiment, the reaction temperature in step two of Example 1 is reduced to 180°C and the reaction time is shortened to 5 hours, while the other conditions remain unchanged. After removing excess water and drying, 125.3g of light brown, powdered dimethylpiperazine pyrophosphate flame retardant is obtained, with a yield of 80.8%.

[0054] Example 7:

[0055] This embodiment provides an application of a flame retardant for preventing crossfire in metal hydride fuels.

[0056] The flame retardant for preventing fire spread in this embodiment was prepared using the method described in Example 1.

[0057] Application performance testing:

[0058] A schematic diagram of the scattering test apparatus is shown below. Figure 1 As shown. The dispersing medium is placed in the outer tube of the device, while the dispersing charge, detonator, and flame retardant are placed in the inner tube of the device connected to the sealed cap.

[0059] Using 200g of lithium hydride as the dispersing medium, 10g of anti-flame-spreading flame retardant was used in both cases. The dispersing charge consisted of 5g of annular cylindrical TNT charges, and the anti-flame-spreading flame retardant completely coated the dispersing charge and the detonator. The compound prepared in Example 1 and commercially available ABC ultrafine dry powder were selected as anti-flame-spreading flame retardants for comparative testing. High-speed video recording of the fireball generated at the moment of explosion and dispersal was used to compare their anti-flame-spreading performance. Figures 2(a) to 2(c) As shown.

[0060] Taking the moment the detonation signal is output to the detonator as the zero point of timing, for the case without the addition of flame retardant, a clear flash appeared at the center of the throwing test device almost simultaneously with the detonator igniting the dispersed charge (1 ms), and quickly spread to the entire cloud; for the case with the addition of ABC ultrafine dry powder flame retardant, the flame was observed to appear 25 ms after detonation; and for the case with the addition of the compound flame retardant prepared in Example 1, no flame was observed to appear 200 ms after detonation and throwing.

[0061] The above results indicate that the metal hydride fuel anti-flame spread flame retardant prepared by the present invention can effectively suppress the flame spread phenomenon of metal hydride fuel in the early stage of explosion and scattering, and has a better flame retardant effect than the known ABC ultrafine dry powder flame retardant in the prior art.

Claims

1. A flame retardant for preventing crossfire in metal hydride fuels, characterized in that, In this application, the metal hydride is lithium hydride, lithium hydride is used as the dispersing medium, an anti-flame-spreading flame retardant is used as the flame retardant, and the dispersing charge is a ring-shaped cylindrical TNT charge. The anti-flame-spreading flame retardant completely covers the dispersing charge and the detonator. For every 200g of lithium hydride, the amount of the anti-flame-spreading flame retardant is 10g, and the amount of the dispersing charge is 5g. The preparation method of the flame retardant that prevents fire spread is carried out according to the following steps: Step 1: Add solvent water, isopropanolamine and catalyst to the reaction vessel in sequence, replace the air in the reaction vessel with N2, stir, heat to 120-170℃, react for 1-10 hours and then cool to 70-90℃ to obtain dimethylpiperazine intermediate; In step one, the catalyst is Raney nickel, Raney copper, Raney cobalt, diatomaceous earth-supported nickel, alumina-supported nickel, or silica-supported nickel; Step 2: Phosphoric acid aqueous solution is pumped into the reaction vessel using a metering pump, the temperature is raised to 180-230℃, the reaction is carried out for 1-10 hours, excess water is removed and the mixture is dried to obtain dimethylpiperazine pyrophosphate flame retardant.

2. The application as described in claim 1, characterized in that, In step one, the temperature is raised to 120–160°C and the reaction is carried out for 10 hours; in step two, the temperature is raised to 180–200°C and the reaction is carried out for 10 hours.

3. The application as described in claim 1, characterized in that, In step one, the amount of catalyst used is 0.1% to 1.0% of the mass of isopropanolamine.

4. The application as described in claim 1, characterized in that, In step one, the amount of water used as the solvent is 0.5 to 5 times the mass of isopropanolamine.

5. The application as described in claim 1, characterized in that, In step two, the amount of phosphoric acid in the phosphoric acid aqueous solution is 1.0 to 1.2 times the molar amount of isopropanolamine.

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