A method for determining a critical safety diameter of emulsion droplets in a liquid energetic material synthesis reaction delivery conduit

Abstract

The application discloses a method for determining the critical safety diameter of emulsion droplets in a liquid energetic material synthesis reaction conveying pipeline, which comprises the following steps: solidifying and heating the sampled emulsion, determining the pyrolysis kinetics parameters of the measured emulsion, constructing an adiabatic system model of heat production and heat transfer of the mixed liquid of acid ester emulsion and emulsion droplets by using Comsol, calculating the temperature rise change rule of the mixed liquid adiabatic system under different emulsion droplet sizes, determining the functional relationship between the emulsion droplet particle size and the temperature rise of the mixed liquid adiabatic system, and deriving the critical safety diameter of the emulsion droplets; the emulsion is adsorbed by using porous particle materials, and whether the collision and friction of emulsions with different pore diameters under different rates will cause the emulsion to explode is tested in an impact tank-piston device, the relationship between the emulsion droplet movement rate, the emulsion droplet particle size and the explosion risk is obtained, and the optimal size of the emulsion droplets in the mixed liquid of the liquid energetic material synthesis reaction under the condition of a specific conveying speed is determined.

Description

TECHNICAL FIELD

[0001] The application relates to a method for determining the critical safe diameter of emulsion droplets in a liquid energetic material synthesis reaction conveying pipeline. BACKGROUND

[0002] Liquid energetic materials are widely used in military and civilian fields, but in the production process, due to the uncontrollable purity of raw materials and the fast synthesis reaction speed, the generated emulsion products are extremely susceptible to environmental conditions, and the emulsion products are dispersed and suspended in the form of droplets in the acid ester emulsion, and in the pipeline transportation process, the emulsion droplets will collide with each other, gradually coagulate and settle with the increase of the conveying distance and time, and start the self-catalytic reaction and heat accumulation and temperature rise, and once the self-catalytic speed exceeds a certain critical safety threshold, the reaction system temperature will rise sharply and explosion will occur. Therefore, the research on the critical safe diameter of emulsion droplets in the liquid energetic material synthesis reaction conveying pipeline is a hot issue in the industry.

[0003] Some domestic scholars have carried out partial research and discussion on the friction and collision explosion problem of energetic materials, and have developed a test method for the friction sensitivity and impact sensitivity of energetic materials. In the invention patent with the patent number 202010705274.6, a friction sensitivity test device and method are disclosed, which comprehensively establishes a test environment by using a sample loading system, an explosion chamber, a pendulum mechanism, a temperature and humidity control system, a pressure loading system and a rack, obtains the friction sensitivity data of the explosive according to the friction reaction of the explosive under different temperature, humidity, speed and pressure conditions; in the invention patent with the patent number 202010925198.X, a method and device for characterizing the friction sensitivity of insensitive single-element explosives are disclosed, the test sample is laid on the friction plate, the friction column is vertically pressed to tightly contact the test sample, a fixed load is applied as the loading pressure, and according to the established lifting method test calculation mode, the friction sensitivity value of the insensitive single-element explosive is obtained according to the ignition condition of the test sample in the friction process; in the invention patent with the patent number 202310727384.6, a friction sensitivity test device under thermal coupling is disclosed, which is integrated by a temperature control module, an electrostatic workbench, a friction sensitivity device and a data acquisition and processing module, and obtains the friction sensitivity data according to the friction reaction of the energetic material under thermal coupling; in the utility model patent with the patent number 202221397684.X, a friction sensitivity tester is disclosed, which is integrated by a working base, a function frame, a friction assembly, a hitting assembly, a supporting frame and a swinging assembly, and obtains the friction sensitivity of the measured substance by using an automatic test process according to the physical reaction of the measured substance in the friction process.

[0004] From the above, the current friction, impact sensitivity test device and method of energetic materials research results are remarkable, but its research and test objects mainly focus on solid and shaped energetic materials. However, the synthesis of many energetic materials is completed in liquid phase, and the emulsion droplets formed during the reaction process have the characteristics of flammability and explosiveness. The size of the droplets determines the possibility of the characteristics being excited. On the other hand, the synthesis of energetic materials at this stage is completed in the synthesizer, and the emulsion after synthesis is dispersed and moved in the acid ester emulsion. The collision and friction between the droplets and the pipe, container wall and the droplets are intensified, and the emulsion droplets are more likely to be excited. Therefore, determining the critical safety diameter of the emulsion droplets in the conveying pipeline is a hot issue that needs to be solved in the industry. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides a method for determining the critical safety diameter of emulsion droplets in the conveying pipeline of liquid energetic material synthesis reaction, which can design the best safety size of emulsion droplets according to the speed and distance difference of the conveying process link in the synthesis process of different liquid energetic materials, provide guidance for process line optimization, and solve the problem of self-catalytic reaction intensification caused by collision and coagulation settlement during the emulsion droplet conveying process, further inducing the problem of system heat accumulation and explosion.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0007] A method for determining the critical safety diameter of emulsion droplets in the conveying pipeline of liquid energetic material synthesis reaction, the specific steps are:

[0008] A. Take samples of acid ester emulsion and emulsion from the pipeline outlet position of the liquid energetic material production line separation unit, measure the heat transfer coefficient of the acid ester emulsion and emulsion droplets by using the transient hot wire method, and put them into a cooling system below 0℃ for solidification and preservation for standby;

[0009] B. Take samples of acid ester emulsion and emulsion from the synthesis reaction conveying outlet, and put them into a cooling system below 0℃ for solidification and preservation for standby;

[0010] C. Take several samples of solidified emulsion, put them into a differential scanning calorimeter, start heating from 0℃ until 370℃, repeat the test 5 times at different heating rates K1, K2, K3, K4 and K5, record the heat flow value H of the emulsion during each continuous heating process, determine the melting point T1 of the emulsion, the heat flow H max , the average heat flow value H ave of the heat flow value, and the heat release curve of the emulsion;

[0011] D. The emulsion conversion rate α-time t curve is obtained by dividing the decomposition exothermic curve in step C by the exothermic quantity, and is corresponded with the temperature T-time t recorded by the differential scanning calorimeter to determine the conversion rate α-temperature T relationship; and a first-order derivative is obtained to determine the reaction rate dα / dt-temperature T;

[0012] E. According to the reaction rate dα / dt-temperature T and the conversion rate α-temperature T curve, the activation energy E, the pre-exponential factor A and the decomposition mechanism function model f(α) corresponding to different conversion rates α are determined by Friedman method;

[0013] F. According to the Semenov ideal model, the self-accelerating decomposition temperature T of the emulsion droplet is calculated NR , and the calculation equation is:

[0014]

[0015] In the formula, represents the mass of one drop of emulsion when the emulsion droplet diameter is D i , g; U represents the heat transfer coefficient of the emulsion, J / (cm 2 ·K·s); S is the surface area of one drop of emulsion, cm 2 ; R represents the gas molar constant, 8.314 J / (mol·L).

[0016] G. According to the calculated self-accelerating decomposition temperature of the emulsion droplet and the decomposition mechanism function, the heat production and heat transfer adiabatic system model of the mixed liquid of acid ester emulsion and emulsion droplet is constructed by Comsol, the temperature rise change rule of the mixed liquid adiabatic system under different emulsion droplet sizes is calculated, the function relationship T(D) between the emulsion droplet particle size and the temperature rise of the mixed liquid adiabatic system is determined, and the derivative is obtained to obtain the critical safety diameter D' of the emulsion droplet;

[0017] H. The solidified emulsion is melted in a water bath at 20-25°C, and according to the obtained critical safety diameter D' of the emulsion droplet, the emulsion is adsorbed on the porous particle material with different pore diameters in the diameter interval of D'±0.1D';

[0018] I. When the porous particle material reaches the adsorption standard, the porous particle material containing different emulsion droplet particle sizes is formed, and the number of the porous particle material containing emulsion droplets under the same pore diameter is 300-600, which is ready for use;

[0019] J. Under the same pore diameter, 5-10 porous particle materials containing emulsion droplets are arranged at the bottom of the impact tank-piston device, and one porous particle material containing emulsion droplets with the same pore diameter is arranged on the piston head. The piston is pushed into the tank at different speeds (v1, v2, v3, v4, v5) to make the porous particle materials containing emulsion droplets collide and rub with each other;

[0020] K, record whether explosion occurs in each test, get the relationship between emulsion droplet movement rate, emulsion droplet particle size and explosion risk, and determine the optimal size of emulsion droplets in liquid energetic material synthesis reaction mixed liquid under specific conveying speed conditions.

[0021] Further, the cooling system below 0 DEG C in step A comprises: ice salt bath, dry ice ethanol or liquid nitrogen cooling system.

[0022] Further, the cooling system below 0 DEG C in step B comprises: ice salt bath, dry ice ethanol or liquid nitrogen cooling system.

[0023] Further, the temperature rising rate K1, K2, K3, K4, K5 in step C is not more than 10 DEG C / min.

[0024] Further, the number of pore diameters of the porous particle material in step H is not less than 5 groups.

[0025] Further, the porous particle material in step H comprises: molecular sieve of silicate-aluminate, phosphoaluminate material.

[0026] Further, the adsorption standard in step I comprises: saturated adsorption for 24h, long period adsorption for 8-16h, short period adsorption for 4-10min.

[0027] Further, the collision-friction test of the porous particle material at the same rate in step J is not less than 10 groups.

[0028] Further, the movement rate v1, v2, v3, v4, v5 of the piston in step J is not more than 25m / s.

[0029] Compared with the prior art, the emulsion sample is first solidified and heated in the application, and the pyrolysis kinetic parameters of the measured emulsion are determined, including: heat flow value of the emulsion, melting point of the emulsion, exothermic peak heat flow, and self-accelerating decomposition temperature, an adiabatic system model of heat production and heat transfer of acid ester emulsion and emulsion droplet mixed liquid is constructed by Comsol, the temperature rise change rule of the mixed liquid adiabatic system under different emulsion droplet sizes is calculated, the functional relationship T(D) between the emulsion droplet particle size and the mixed liquid adiabatic system temperature rise is determined, and derivation is carried out to obtain the critical safety diameter D' of the emulsion droplet; then the porous particle material is used to adsorb the emulsion, and whether the collision and friction of the emulsion with different pore diameters in the D'±0.1D' interval under different rates will cause the emulsion to explode in the impact tank-piston device is tested, the relationship between the emulsion droplet movement rate, the emulsion droplet particle size and the explosion risk is obtained, and the optimal size of the emulsion droplet in the liquid energetic material synthesis reaction mixed liquid under specific conveying speed conditions is determined. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1is the overall flow chart of the present application.

[0031] Figure 2 is the decomposition heat flow curve of the solidified emulsion of certain energetic material in the present application.

[0032] Figure 3 is the conversion rate α-temperature T relationship diagram of certain energetic material in the present application.

[0033] Figure 4 is the reaction rate dα / dt-temperature T relationship diagram of certain energetic material in the present application.

[0034] Figure 5 is the function relationship diagram of the emulsion droplet particle size and the adiabatic system temperature rise in the present application.

[0035] Figure 6 is the impact tank-piston device diagram in the present application.

[0036] Figure 7 is the relationship diagram between the emulsion droplet movement rate, the emulsion droplet particle size and the explosion risk in the present application.

[0037] Figure 8 is the simulation verification relationship diagram between the emulsion droplet movement rate, the emulsion droplet particle size and the system temperature rise in the present application.

[0038] In the figure, 1-impact tank; 2-porous granular material piston head containing emulsion droplets; 3-porous granular material containing emulsion droplets at the bottom; 4-piston; 5- eccentric wheel; 6-driving device. DETAILED DESCRIPTION

[0039] The present application will be further described as follows.

[0040] As shown in Figures 1 to 5 , the specific steps of the present application are:

[0041] A, first sample 200 mL of acid ester emulsion and emulsion from the liquid energetic material production line separation unit pipeline outlet position, measure the heat transfer coefficient of acid ester emulsion and emulsion droplets by using transient hot wire method, and put it into the cooling system below 0℃ for solidification preservation and standby;

[0042] B, sample 200 mL of acid ester emulsion and emulsion mixture from the synthesis reaction delivery outlet, and put it into the cooling system below 0℃ for solidification preservation and standby;

[0043] C. Take 20 mg of the coagulated emulsion and put it into a differential scanning calorimeter, and heat it from 0°C to 370°C, repeat the test 5 times at different heating rates, the heating rates are 1°C / min, 2°C / min, 4°C / min, 8°C / min, 10°C / min respectively, record the heat flow value H of the emulsion in each continuous heating process, determine the melting point T1 of the emulsion, the exothermic peak heat flow H max , the average exothermic peak heat flow value H ave , integrate the exothermic peak in the heat flow-time curve to obtain the heat release ΔH of the emulsion and the decomposition exothermic curve, as shown in Figure 2 and Table 1.

[0044] Table 1 Thermal decomposition characteristic values of certain azo energetic materials

[0045]

[0046] D. Obtain the conversion rate α-time t curve of the emulsion from the decomposition exothermic curve and heat release, and correspond to the temperature T-time t recorded by the differential scanning calorimeter, determine the conversion rate α-temperature T relationship, as shown in Figure 3 , and take the first derivative to obtain the reaction rate dα / dt-temperature T, as shown in Figure 4 ;

[0047] E. According to the reaction rate dα / dt-temperature T, conversion rate α-temperature T curve, use Friedman method to determine the activation energy E, pre-exponential factor A and decomposition mechanism function model f(α) corresponding to different conversion rates α, as shown in Table 2.

[0048] Table 2 Activation energy E, pre-exponential factor A and decomposition mechanism function model f(α) of certain azo energetic materials

[0049]

[0050] F. According to Semenov ideal model, calculate the self-accelerating decomposition temperature T NR , the calculation equation is:

[0051]

[0052] In the formula, represents the mass of a drop of emulsion when the diameter of the emulsion drop is D i , g; U represents the heat transfer coefficient of the emulsion, J / (cm 2 ·K·s); S is the surface area of a drop of emulsion, cm 2 ; R represents the gas molar constant, 8.314 J / (mol·L).

[0053] The calculation results are shown in Table 2:

[0054] Table 2 self-accelerating decomposition temperature values of certain azo energetic materials

[0055]

[0056] G, according to the calculated emulsion droplet self-accelerating decomposition temperature, decomposition mechanism function, using Comsol to build acid ester emulsion and emulsion droplet mixed liquid heat production, heat transfer adiabatic system model, as follows:

[0057]

[0058] In the formula, Q represents heat production, J; m represents droplet mass, g; p represents emulsion density, g / cm 3 ; c represents the specific heat capacity of the liquid, J / (g·℃); T represents the liquid temperature, ℃; t represents time; u represents the liquid flow rate, m / s; k represents the thermal conductivity of the liquid, W / (m·℃).

[0059] The temperature rise change rule of the mixed liquid adiabatic system under different emulsion droplet sizes is calculated, the function relationship T(D) between the emulsion droplet particle size and the temperature rise of the mixed liquid adiabatic system is determined, and the derivative is obtained to obtain the critical safety diameter D' of the emulsion droplet, as Figure 5 shown;

[0060] H, melt the solidified emulsion in a water bath at 20-25℃, according to the obtained critical safety diameter D' of the emulsion droplet, select different pore size porous particle materials to absorb the emulsion in the [0.9D', 1.1D'] emulsion droplet diameter interval;

[0061] I, after the porous particle material reaches the adsorption standard, form a porous particle material containing different emulsion droplet particle sizes, and the number of porous particle materials containing emulsion droplets under the same pore size is 300, ready for use;

[0062] J, under the same pore size, arrange 5 porous particle materials at the bottom of the impact tank-piston device, and arrange 1 porous particle material containing emulsion droplets under the same pore size at the piston head, as Figure 6 shown, push the piston into the tank at different speeds (1 m / s, 2 m / s, 5 m / s, 10 m / s, 15 m / s), so that the porous particle materials containing emulsion droplets collide and rub with each other;

[0063] K, record whether explosion occurs in each test, obtain the relationship between the emulsion droplet movement speed v, the emulsion droplet particle size D and the explosion risk P, as Figure 7 shown, and determine the optimal size D" of the emulsion droplet in the liquid energetic material synthesis reaction mixed liquid under the condition of a certain conveying speed.

[0064] L, the physical model of emulsion droplets with particle size range of [0.95D", 1.05D"] and mixed solution was built in Comsol, and the adiabatic system model of heat production and heat transfer was used to calculate the temperature rise law of the system under different motion rates, as shown in Figure 8 Accordingly, the accuracy of the real test results was verified.

Claims

1. A method of determining a critical safety diameter of an emulsion droplet of a liquid energetic material synthesis reaction transfer line, the method comprising: determining a critical diameter of a droplet of the emulsion droplet; and determining a critical diameter of a droplet of a liquid phase of the emulsion droplet. The specific steps are: A. First, sample the acid ester emulsion and emulsion from the liquid energetic material production line separation unit pipeline outlet position, measure the heat transfer coefficient of the acid ester emulsion and emulsion droplets by using the transient hot wire method, and put them into a cooling system below 0°C for solidification and preservation; B. Sample the mixed liquid of acid ester emulsion and emulsion from the synthesis reaction delivery outlet, and put it into a cooling system below 0°C for solidification and preservation; C. The coagulated emulsion is sampled and put into a differential scanning calorimeter, and is subjected to temperature rising from 0°C to 370°C, and the test is repeated 5 times at different temperature rising rates, i.e. K1, K2, K3, K4 and K5, and the heat flow value H of the emulsion in each continuous temperature rising process is recorded, and the melting point T1 and the exothermic peak heat flow H of the emulsion are determined max , the average exothermic peak heat flow value H ave , and the exothermic peak in the heat flow-time curve is subjected to integral processing to obtain the exothermic quantity ΔH of the emulsion and the decomposition exothermic curve; D. Obtain the emulsion conversion rate α-time t curve from the decomposition heat release curve in step C, and determine the conversion rate α-temperature T relationship by corresponding to the temperature T-time t recorded by the differential scanning calorimeter; and perform first-order derivation to obtain the reaction rate dα / dt-temperature T; E. According to the reaction rate dα / dt-temperature T, conversion rate α-temperature T curve, determine the activation energy E, pre-exponential factor A and decomposition mechanism function model f(α) corresponding to different conversion rates α by using the Friedman method; F. The self-accelerating decomposition temperature T is calculated according to the Semenov ideal model NR The calculation equation is: wherein D represents the diameter of the emulsion droplet i ; U represents the heat transfer coefficient of the emulsion, J / (cm 2 ·K·s); S is the surface area of the emulsion droplet, cm 2 ; R represents the gas molar constant, 8.314 J / (mol·L); G. According to the calculated self-accelerating decomposition temperature of the emulsion droplet and the decomposition mechanism function, use Comsol to build an adiabatic system model of the mixed liquid of acid ester emulsion and emulsion droplets, calculate the temperature rise change rule of the mixed liquid adiabatic system under different emulsion droplet sizes, determine the function relationship T(D) between emulsion droplet particle size and mixed liquid adiabatic system temperature rise, and perform derivation to obtain the critical safety diameter D' of the emulsion droplet; H. Melt the solidified emulsion in a water bath at 20-25°C, and according to the obtained critical safety diameter D' of the emulsion droplet, select porous particle materials with different pore diameters to adsorb the emulsion within the D'±0.1D' emulsion droplet diameter interval; I. After the porous particle material reaches the adsorption standard, form a porous particle material containing different emulsion droplet sizes, and the number of porous particle materials containing emulsion droplets under the same pore diameter is 300-600, ready for use; J. Under the same pore diameter, arrange 5-10 porous particle materials containing emulsion droplets at the bottom of the impact tank-piston device, and arrange one porous particle material containing emulsion droplets with the same pore diameter on the piston head. Push the piston into the tank at different speeds v1, v2, v3, v4, v5, so that the porous particle materials containing emulsion droplets collide and rub with each other; K. Record whether an explosion occurs in each test to obtain the relationship between the emulsion droplet movement rate, emulsion droplet size and explosion risk, and accordingly determine the optimal size of the emulsion droplet in the mixed liquid of the liquid energetic material synthesis reaction under a specific delivery speed condition.

2. A method of determining a critical safety diameter of emulsion droplets in a transport pipe of a synthesis reaction of a liquid energetic material according to claim 1, characterized in that, The cooling system below 0°C in step A includes an ice-salt bath, dry ice ethanol or liquid nitrogen cooling system.

3. A method of determining a critical safety diameter of emulsion droplets in a transport pipe of a synthesis reaction of a liquid energetic material according to claim 1, characterized in that, The cooling system below 0°C in step B includes an ice-salt bath, dry ice ethanol or liquid nitrogen cooling system.

4. The method of determining a critical safety diameter of an emulsion droplet in a transport line for a synthesis reaction of a liquid energetic material according to claim 1, wherein The heating rate K1, K2, K3, K4, K5 in step C does not exceed 10°C / min.

5. A method of determining a critical safety diameter of emulsion droplets in a transport line for a synthesis reaction of a liquid energetic material according to claim 1, characterized in that, The adiabatic system model of the mixed liquid of acid ester emulsion and emulsion droplets is built by using Comsol as follows: In the formula, Q represents heat generation, J; m represents droplet mass, g; p represents emulsion density, g / cm 3 ; c represents liquid specific heat capacity, J / (g·°C); T represents liquid temperature, °C; t represents time; u represents liquid flow rate, m / s; and k represents liquid thermal conductivity, W / (m·°C).

6. A method of determining a critical safety diameter of emulsion droplets in a transport line of a synthesis reaction of a liquid energetic material according to claim 1, characterized in that, The number of pore diameters of the porous particle materials selected in step H is not less than 5 groups.

7. A method of determining a critical safety diameter of emulsion droplets in a transport line of a synthesis reaction of a liquid energetic material according to claim 1, characterized in that, The porous particle materials in step H include molecular sieves of silicate and aluminate materials.

8. A method of determining a critical safety diameter of emulsion droplets in a transport line for a synthesis reaction of a liquid energetic material according to claim 1, characterized in that, The adsorption criteria in Step I include: saturated adsorption for 24 hours, long-period adsorption for 8-16 hours, and short-period adsorption for 4-10 minutes.

9. A method of determining a critical safety diameter of emulsion droplets in a transport line for a synthesis reaction of a liquid energetic material according to claim 1, characterized in that, In Step J, the collision-friction test of the porous granular material is carried out at the same rate for not less than 10 groups.

10. A method of determining a critical safety diameter of emulsion droplets in a transport line for a synthesis reaction of a liquid energetic material according to claim 1, characterized in that, In Step J, the movement rate v1, v2, v3, v4, v5 of the piston is not more than 25 m / s.

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