Method for determining thermal safety threshold value of explosives and powders based on small ignition probability estimation

Abstract

The invention provides a method for determining a thermal safety threshold value of explosives and powders based on small ignition probability estimation. The method comprises the following steps: step 1, obtaining heat insulation data; step 2, calculating apparent activation energy and pre-exponential factors; and step 3, obtaining an expression of TMRad about T. And 4, determining the thermal safety threshold value of the explosives and powders. Aiming at the thermal safety research of the explosives and powders, the invention provides the safe and efficient method for determining the thermal safety threshold of the explosives and powders based on the estimation of the small ignition probability, so that the problem of result misjudgment caused by small quantity of test explosives and powders when the thermal safety threshold is obtained by purely adopting a DSC (Differential Scanning Calorimetry) method is avoided; and the problem of high test risk caused by large quantity of test explosive and powder samples in obtaining the thermal safety threshold value by a thermal explosion test method is solved. By means of the method, the thermal safety threshold value of the explosives and powders estimated based on the small ignition probability can be obtained, the sample has representativeness, the operation process is safer, redundancy setting of the thermal safety threshold value is sufficient and reasonable, and scientific reference is provided for early warning, prevention and control of production process safety.

Description

Technical Field

[0001] The invention belongs to the technical field of explosives and firearms, relates to the thermal safety of explosives and firearms, and in particular to a method for determining a thermal safety threshold of explosives and firearms based on a small ignition probability estimation. Background Art

[0002] During the synthesis, production, storage, use, transportation and destruction of explosives, they will inevitably be affected by external thermal stimulation, which can easily cause thermal decomposition of materials. The heat accumulation will lead to temperature rise, causing accidental combustion or explosion. In view of the above problems, studying the thermal safety of explosives and analyzing and obtaining thermal safety thresholds within the estimated range of small ignition probability can improve the early warning of thermal runaway of explosives throughout their life cycle, which is of great significance to their safe production and application fields.

[0003] At present, the main experimental research methods for evaluating the thermal safety of explosives are:

[0004] First, the indirect deduction method uses differential scanning calorimetry (DSC) and adiabatic accelerated rate calorimetry (ARC) methods to obtain characteristic values ​​such as decomposition temperature and adiabatic temperature rise, and indirectly deduce parameters such as thermal explosion critical temperature and adiabatic explosion time to evaluate the thermal safety of explosives.

[0005] Second, the direct acquisition method is to directly obtain the critical temperature of thermal explosion through the thermal explosion test method to evaluate the thermal safety of explosives.

[0006] However, the above research process has the following problems:

[0007] First, the amount of explosive sample required for the DSC method is generally 0.1mg to 5mg, the representativeness of the explosive sample is poor, and there is a problem of misjudgment of the results; the amount of explosive sample required for the thermal explosion test method is larger, and there is a higher risk.

[0008] Second, the amount of explosive sample obtained by the ARC method can reach gram level, which is more representative of explosive samples than the DSC method and safer than the thermal explosion test method. However, the adiabatic detonation time obtained by the ARC method and the critical temperature of thermal explosion obtained by the DSC method and the thermal explosion test method are both the upper limits of the thermal stability of explosives under the corresponding test conditions. As thermal safety thresholds to guide synthesis and production, their redundancy is limited. It is necessary to set safer thresholds through scientific analysis to warn of thermal hazards of explosives. Summary of the invention

[0009] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for determining the thermal safety threshold of explosives based on the estimation of small ignition probability, so as to solve the technical problem that the thermal safety threshold determination method in the prior art is difficult to take into account both the accuracy of the results and the safety of the test.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0011] A method for determining the thermal safety threshold of explosives based on the estimation of small ignition probability is carried out according to the following steps:

[0012] Step 1: Obtain adiabatic calorimetry data.

[0013] Step 2: Calculate the apparent activation energy and pre-exponential factor.

[0014] Step 3: Obtain TMR ad Expression about T.

[0015] Step 4: Determine the thermal safety threshold of explosives.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] (I) The present invention provides a relatively safe and efficient method for determining the thermal safety threshold of explosives based on the estimation of the small ignition probability for the thermal safety threshold of explosives, aiming at the study of the thermal safety of explosives. The method avoids the problem of misjudgment of the results caused by the small amount of test explosive samples when the thermal safety threshold is obtained by the DSC method alone, and the problem of high test risk caused by the large amount of test explosive samples when the thermal explosion test method is used to obtain the thermal safety threshold.

[0018] (II) The method of the present invention can be used to obtain the thermal safety threshold of explosives based on the estimation of small ignition probability. The sample is representative, the operation process is safer, and the redundant setting of the thermal safety threshold is sufficient and reasonable, providing a scientific reference for early warning and prevention of production process safety.

[0019] Figure 1 It is the adiabatic thermal curve of CL-20 in the embodiment of the present invention.

[0020] The specific contents of the present invention are further described in detail below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0021] It should be noted that, unless otherwise specified, all materials in the present invention are materials known in the prior art.

[0022] In accordance with the above technical scheme, 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 changes made on the basis of the technical scheme of this application fall within the protection scope of the present invention.

[0023] Example:

[0024] This embodiment provides a method for determining the thermal safety threshold of explosives based on the estimation of small ignition probability. The method is performed according to the following steps:

[0025] Step 1: Obtain adiabatic calorimetry data:

[0026] Adiabatic calorimetry experiments were carried out on explosive samples to obtain adiabatic calorimetry data of the explosive samples.

[0027] In this embodiment, the thermal safety threshold of CL-20 (i.e., hexanitrohexaazaisowurtzitane) single-substance material based on the estimated small ignition probability is taken as an example for specific description. The adiabatic calorimetric data of CL-20 single-substance material, such as Figure 1 shown.

[0028] Step 2: Calculate the apparent activation energy and pre-exponential factor:

[0029] Based on the adiabatic calorimetric data of the explosive sample obtained in step 1, the apparent activation energy E of the explosive sample is calculated according to formulas I to IV: a and the pre-exponential factor A.

[0030] ΔT ad =T end -T0…………………………Formula Ⅰ

[0031]

[0032]

[0033]

[0034] Where:

[0035] ΔT ad is the adiabatic temperature rise, unit: K;

[0036] T end is the decomposition termination temperature of the explosive sample, in K;

[0037] T0 is the initial decomposition temperature of the explosive sample, in K;

[0038] α is the conversion rate;

[0039] t is the reaction time, unit: s;

[0040] T is the temperature of the explosive sample, unit: K;

[0041] A is the pre-exponential factor, unit: s -1 ;

[0042] E a is the apparent activation energy, unit: J·mol -1 ;

[0043] R is the molar gas constant, which is 8.314, and the unit is J·mol-1 ·K -1 .

[0044] Wherein, Formula IV is the reaction level n = 0 It is obtained by taking the logarithm on both sides of the equal sign of , that is, from the zero-order reaction of the most dangerous reaction under adiabatic conditions, to obtain a conservative estimate of the thermal safety threshold.

[0045] Specifically in this embodiment, the adiabatic temperature rise ΔT ad =T end -T0 = 488.264K - 475.259K = 13.005K, obtained according to formula I to formula III Then, it is substituted into Formula IV together with 1 / T, and the linear least squares method is used to fit the curve to calculate the apparent activation energy E a =490384.7 J·mol -1 , pre-exponential factor A = e 124.79 s -1 .

[0046] Step 3: Obtain TMR ad Expressions about T:

[0047] The specific heat release Q is calculated from formula VI and formula VII, and then compared with the apparent activation energy E obtained in step 2. a Substitute the pre-exponential factor A into formula V to obtain TMR ad Expression for the temperature T of explosive samples.

[0048]

[0049]

[0050]

[0051] Where:

[0052] TMR ad The time when the maximum reaction rate of the explosive sample is reached under adiabatic conditions, in seconds;

[0053] c s is the specific heat capacity of the explosive sample, in J·g -1 ·K -1 ;

[0054] R is the molar gas constant, which is 8.314, and the unit is: J·mol -1 ·K -1 ;

[0055] T is the temperature of the explosive sample, unit: K;

[0056] A is the pre-exponential factor, unit: s-1 ;

[0057] E a is the apparent activation energy, unit: J·mol -1 ;

[0058] Q is the specific heat release, unit: J·g -1 ;

[0059] is the thermal inertia correction factor;

[0060] m b is the mass of the explosive sample pool, in g;

[0061] c b is the specific heat capacity of the explosive sample cell, in J·g -1 ·K -1 ;

[0062] m s is the mass of the explosive sample, in g.

[0063] In this embodiment, the specific heat capacity of the CL-20 single substance material c s 0.894 J·g -1 ·K -1 , explosive sample quantity m b is 0.0683g; the explosive sample cell is a Hastelloy explosive sample cell, with a specific heat capacity of c b 0.42 J·g -1 ·K -1 , mass m b is 15.683g, and the thermal inertia correction factor is calculated as:

[0064]

[0065] Then calculate the specific heat release The apparent activation energy E is obtained by step 2 a =490384.7 J·mol -1 , pre-exponential factor A = e 124.79 s -1 Substituting them into formula V, we get:

[0066]

[0067] Step 4: Determine the thermal safety threshold of explosives:

[0068] In the case of a small ignition probability prediction event, the maximum reaction rate arrival time TMR of the explosive sample under adiabatic conditions ad = 100h, when TMR ad=100h, the corresponding explosive sample temperature T is calculated according to formula V in step 3, and the sample temperature T is the explosive thermal safety threshold T estimated based on the small ignition probability. s .

[0069] In this embodiment, according to the six-level criteria proposed by the Zurich Hazard Analysis (ZHA) method (as shown in Table 1), the maximum reaction rate reaching time TMR under adiabatic conditions is ad It is divided into six levels. When the actual explosive sample temperature corresponds to the TMR ad When the time is greater than 100h, it is considered an “almost impossible to occur” event and is judged as an event with a “small ignition probability” estimate.

[0070] Table 1 Evaluation criteria of the six-level criteria of the ZHA method

[0071]

[0072] Specifically in this embodiment, let TMR ad =100h=3.6×10 5 s, and the thermal safety threshold T of the CL-20 single-substance material sample based on the estimated small ignition probability is calculated. s =410.4K=137.4℃.

Claims

1. A method for determining the thermal safety threshold of explosives based on the estimation of small ignition probability, characterized in that: The method proceeds as follows: Step 1: Obtain adiabatic calorimetry data: Conduct adiabatic calorimetry test on explosive samples to obtain adiabatic calorimetry data of explosive samples; Step 2: Calculate the apparent activation energy and pre-exponential factor: Based on the adiabatic calorimetric data of the explosive sample obtained in step 1, the apparent activation energy E of the explosive sample is calculated according to formulas I to IV: a and pre-exponential factor A; Where: ΔT ad is the adiabatic temperature rise, unit: K; T end is the decomposition termination temperature of the explosive sample, in K; T0 is the initial decomposition temperature of the explosive sample, in K; α is the conversion rate; t is the reaction time, unit: s; T is the temperature of the explosive sample, unit: K; A is the pre-exponential factor, unit: s -1 ; E a is the apparent activation energy, unit: J·mol -1 ; R is the molar gas constant, which is 8.314, and the unit is J·mol -1 ·K -1 ; Step 3: Obtain TMR ad Expressions about T: The specific heat release Q is calculated from formula VI and formula VII, and then compared with the apparent activation energy E obtained in step 2. a Substitute the pre-exponential factor A into formula V to obtain TMR ad Expression for the temperature T of explosive sample; Where: TMR ad The time when the maximum reaction rate of the explosive sample is reached under adiabatic conditions, in seconds; c s is the specific heat capacity of the explosive sample, in J·g -1 ·K -1 ; R is the molar gas constant, which is 8.314, and the unit is: J·mol -1 ·K -1 ; T is the temperature of the explosive sample, unit: K; A is the pre-exponential factor, unit: s -1 ; E a is the apparent activation energy, unit: J·mol -1 ; Q is the specific heat release, unit: J·g -1 ; is the thermal inertia correction factor; m b is the mass of the explosive sample pool, in g; c b is the specific heat capacity of the explosive sample cell, in J·g -1 ·K -1 ; m s is the mass of the explosive sample, in g.

2. The method for determining the thermal safety threshold of explosives based on the estimation of small ignition probability according to claim 1, characterized in that: Also includes step four; Step 4: Determine the thermal safety threshold of explosives: In the case of a small ignition probability prediction event, the maximum reaction rate arrival time TMR of the explosive sample under adiabatic conditions ad = 100h, when TMR ad =100h, the corresponding explosive sample temperature T is calculated according to formula V in step 3, and the sample temperature T is the explosive thermal safety threshold T estimated based on the small ignition probability. s .

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