Tailoring of High Energy Materials: Part 02: GPeng Model

Gayatri Patel

Final Year B Tech Student

ITER, Bhubaneswar, INDIA

and

Dr Manoj K Patel

Asst Vice President, Reliance Sasan Power Limited, Sasan, INDIA

Mobile No: +91 8249206647

Email ID: manjubeti@rediffmail.com

INTRODUCTION:

“Chemicals” and “mixture of chemicals” that are high energetic materials need special attention. This category subsumes – pyrotechnics and explosives (initiating devices included). These categories of materials have their unique thermodynamic properties.

Thermodynamic properties of high energetic materials can be measured both experimentally as well as through theoretical means. Both the methods have got their own advantages and dis-advantages.

Experimental methods are based on very sophisticated equipments and now a days these are available on PLC Control basis. Results can be obtained within a time frame of 30 minutes per sample. But these experimental methods need high end laboratory, expensive equipments and skilled instrumentation engineer to conduct the experiments. Moreover, the experimental method needs high energy materials to be handled in a chemical laboratory time and again. Additionally, state statutes and safety-security-issues come in to picture in terms of licenses to handle high energetic materials in the laboratory. Hence attempts have been made in the past for effective, theoretical calculations of the detonation parameters and the chemical equilibrium composition of reaction products.

Alternate way thus is to go for – Theoretical Methods. Survey of literature showed that a number of theoretical methods have been available for carrying out thermodynamic calculations of the detonation parameters of condensed explosives. Some of these are, a BKW Fortran [1], ARPEGE [2], Ruby [3], TIGER [4], CHEETAH [5], EXPLO5 [6], MWEQ [7], BARUT-X [8]. Although in many research centers in the world thermo-chemical codes were worked out, access to them is difficult and, moreover, any changes in the codes aren’t possible because they are made available in the compiled form. Therefore, we have worked out and have come up with our own numerical code named GPeng from which one can derive as many as 18 different parameters for a “chemical” or “mixture of chemicals”.

  

THE GPeng MODEL:

Our GPeng is a new model for calculation of thermodynamic properties of chemicals, mixture of chemicals, high energetic materials and pyrotechnics. GPeng is based on such facts as: (a) physical and chemical properties of an energetic material, (b) its atomic composition, (c) enthalpy of formation, (d) entropy of chemicals, (e) molecular reaction dynamics, (f) the mathematical model of an ideal detonation, (g) the principle of extreme of characteristic functions delineated by Gibbs, and (h) thermodynamic equations of state for the real gasses (reaction products) with a wide range of pressure and temperature. In its present form GPeng is able to determine 18 different thermodynamic parameters and these are:

No	Output Parameter from “GPeng”	UoM
01	OF (Oxygen Balance Factor)	No.
02	SF (Strength Factor)	No.
03	del H (Enthalpy)	Kcal/kg
04	So (Entropy)	Cal
05	Gibbs Free Energy	Kcal/kg
06	Volume Expansion Considering Water is Gas	Percent
07	Volume Expansion Considering Water is Liquid	Percent
08	Mole of Oxygen Generated from Decomposition of OB	Mole/kg of Product
09	Mole of Oxygen Required for Complete Combustion of FB	Mole/kg of Product
10	Mole of Gases Generated from OB	Mole/kg of Product
11	Mole of Gases Generated from FB	Mole/kg of Product
12	Mole of Gases Generated from Composition	Mole/kg of Product
13	Absolute Bulk Strength   or  ABS	Kcal/cubic meter
14	Absolute Weight Strength  (i.e. del H)	Kcal/kg
15	Relative Bulk Strength  wrt ANFO or  RBS_ANFO	Percent
16	Relative Weight Strength wrt ANFO or  RWS_ANFO	Percent
17	Relative Bulk Strength  wrt NG or  RBS_NG	Percent
18	Relative Weight Strength  wrt NG or  RWS_NG	Percent

To verify the GPeng Model, its results are compared with that obtained from the experimental methods by using a Parr 6100 Calorimeter.

We are further going to develop this model– (1) to calculate the parameters of combustion, explosion and detonation of condensed energetic materials, (2) to determine the curve of expansion of detonation products, (3) to arrive at a correlation between the parameters obtained through GPeng with Rock Characteristics (GPengRock). 

                       

APPLICATION OF GPeng in SOME CHEMICALS:

 (1)     Ammonium Nitrate (AN):

Ammonium Nitrate is having chemical formula NH4NO3 and its structure is:

On explosion, it undergoes the reaction of:

(NH4)NO3 (c)   → N2 (g) + 1/2 O2 (g) + 2 H2O (g)

Species Name	Preferred Formula	Image	ΔfH°(0 K)	ΔfH°(298.15 K)	Units	Relative  Molecular  Mass
Ammonium nitrate	(NH4)NO3		-350.28	-365.25	kcal/kg	80.04344 ± 0.00095

This reaction path has been considered in the GPeng and the values obtained are:

Results for AN
Output Parameter	UoM	RESULT
SF	No.	0
del H (i.e. Enthalpy)	Kcal/kg	-353
So (i.e. Entropy)	Cal	1555
Gibbs Free Energy	Kcal/kg	-399
Volume Expansion Considering Water is Gas	Percent	350
Volume Expansion Considering Water is Liquid	Percent	150
Mole of Oxygen Generated from Decomposition of OB	Mole/kg of Product	15.63
Mole of Oxygen Required for Complete Combustion of FB	Mole/kg of Product	0
Mole of Gases Generated from OB	Mole/kg of Product	162.45
Mole of Gases Generated from FB	Mole/kg of Product	0
Mole of Gases Generated from Composition	Mole/kg of Product	162.45
Absolute Bulk Strength   or  ABS	Kcal/cubic meter	-395
Absolute Weight Strength  (i.e. del H)	Kcal/kg	-353
Relative Bulk Strength  wrt ANFO or  RBS_ANFO	Percent	51
Relative Weight Strength wrt ANFO or  RWS_ANFO	Percent	34
Relative Bulk Strength  wrt NG or  RBS_NG	Percent	19
Relative Weight Strength  wrt NG or  RWS_NG	Percent	24

(2)     Ammonium Nitrate Fuel Oil (ANFO):

ANFO in its best form is - 94.5% of AN and 5.5% of Diesel Oil. When this mixture undergoes explosion, it releases lot of energy, and its output thermodynamics parameters also have been calculated by using GPeng. Findings are as follows:

RESULTS for ANFO
Output Parameter	UoM	RESULT
SF	No.	18.81
del H (i.e. Enthalpy)	Kcal/kg	-917
So (i.e. Entropy)	Cal	1517
Gibbs Free Energy	Kcal/kg	-963
Volume Expansion Considering Water is Gas	Percent	374.75
Volume Expansion Considering Water is Liquid	Percent	97.75
Mole of Oxygen Generated from Decomposition of OB	Mole/kg of Product	14.77
Mole of Oxygen Required for Complete Combustion of FB	Mole/kg of Product	39.53
Mole of Gases Generated from OB	Mole/kg of Product	153.52
Mole of Gases Generated from FB	Mole/kg of Product	67.64
Mole of Gases Generated from Composition	Mole/kg of Product	221.15
Absolute Bulk Strength   or  ABS	Kcal/cubic meter	-1027
Absolute Weight Strength  (i.e. del H)	Kcal/kg	-917
Relative Bulk Strength  wrt ANFO or  RBS_ANFO	Percent	132
Relative Weight Strength wrt ANFO or  RWS_ANFO	Percent	89
Relative Bulk Strength  wrt NG or  RBS_NG	Percent	49
Relative Weight Strength  wrt NG or  RWS_NG	Percent	62

(2)     An Emulsion Explosives Formulation:

One of the Site Mixed Emulsions (SME) has been designed with chemical parameters in the percentage level of: AN 72 / SN 05 / Water 15.5 / HSD 03 / FO 03 / Emulsifier 01.2 / Wax 0.2.

This mixture was prepared in the laboratory and its enthalpy was measured experimentally with the help of Parr 6100 fully automatic bomb calorimeter.

Bomb calorimeter showed enthalpy of 832 Kcal/kg and GPeng showed that at 840 Kcal/kg. Values thus obtained experimentally and theoretically are very close to each other and rather with 95% confidence limit.

The other values determined for this formulation using GPeng, the output results are as follows:

  

RESULTS for the above SME Formulation
Output Parameter	UoM	RESULT
SF	No.	16.76
del H (i.e. Enthalpy)	Kcal/kg	-840
So (i.e. Entropy)	Cal	1518
Gibbs Free Energy	Kcal/kg	-885
Volume Expansion Considering Water is Gas	Percent	347.36
Volume Expansion Considering Water is Liquid	Percent	70.34
Mole of Oxygen Generated from Decomposition of OB	Mole/kg of Product	15.16
Mole of Oxygen Required for Complete Combustion of FB	Mole/kg of Product	52.78
Mole of Gases Generated from OB	Mole/kg of Product	131.27
Mole of Gases Generated from FB	Mole/kg of Product	91.13
Mole of Gases Generated from Composition	Mole/kg of Product	222.40
Absolute Bulk Strength   or  ABS	Kcal/cubic meter	-940
Absolute Weight Strength  (i.e. del H)	Kcal/kg	-840
Relative Bulk Strength  wrt ANFO or  RBS_ANFO	Percent	121
Relative Weight Strength wrt ANFO or  RWS_ANFO	Percent	82
Relative Bulk Strength  wrt NG or  RBS_NG	Percent	45
Relative Weight Strength  wrt NG or  RWS_NG	Percent	56

Values thus obtained in the above three cases are compared with the experimental values obtained in Bomb Calorimeter. GPeng values are matching with Bomb Calorimeter values to the level of 95% confidence limit.

So, one NEED NOT SPEND lot of time and cost for determining the parameters by using expensive lab equipments. GPeng itself gives rise to these values with good accuracies. The authors, however, welcome suggestions and comments from researchers and explosives scientists in order to fine tune the GPeng further.

REFERENCES:

[1]     Mader Ch.J., FORTRAN BKW: a code computing the detonation properties of explosives, Los Alamos Science Laboratory, Report LA-3704, 1967.

[2]     Cheret R., The numerical study of the detonation products of an explosive substance, French Commission of Atomic Energy, Report CEA-R-4122, 1971.

[3]     Levin H.B., Sharples R.E., Operator’s manual for RUBY, Lawrence Livermore Laboratory, Report UCRL-6815, 1962.

[4]     Cowperthwaite M., Zwisler W.H., Tiger computer program documentation, Stanford Research Institute, Publication No. Z106, 1973.

  

[5]     Fried L.E., CHEETAH 1.39 User’s Manual, Lawrence Livermore National Laboratory, Manuscript UCRL-MA-117541 Rev. 3, 1996.

[6]     Sućeska M., Calculation of the detonation properties of C-H-N-O explosives, Propellants Explos. Pyrotech., 1991, 16, 197-202.

[7]     Papliński A., Equilibrium thermochemical calculations for a great mount of components (in Polish), Biul. WAT, 1993, 42(11), 123-143.

[8]     Cengiz F., Narin B., Ulas A., BARUT-X: a computer code for computing the steady-state detonation properties of condensed phase explosives, 10th Seminar New Trends in Energetic Materials, Pardubice, 2007, 117-127.

[9]		S. J. Klippenstein, L. B. Harding, and B. Ruscic, Ab initio Computations and Active Thermochemical Tables Hand in Hand: Heats of Formation of Core Combustion Species. J. Phys. Chem. A in preparation (2016).
[10]		B. Ruscic, Uncertainty Quantification in Thermochemistry, Benchmarking Electronic Structure Computations, and Active Thermochemical Tables. Int. J. Quantum Chem. 114, 1097-1101 (2014).
[11]		Ab Initio Computations and Active Thermochemical Tables Hand in Hand: Heats of    Formation of Core Combustion Species, Stephen J. Klippenstein, Lawrence B. Harding, and Branko Ruscic, Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States, J. Phys. Chem. A, 2017, 121 (35), pp 6580–6602, DOI: 10.1021/acs.jpca.7b05945, Publication Date (Web): July 31, 2017.

[12] Zygmunt B., Buczkowski D., Influence of Ammonium Nitrate Prills Properties on Detonation Velocity of ANFO, Propellants, Explos., Pyrotech., 2007, 32(5), 411-414.

[13] Buczkowski D., Zygmunt B., Influence of Ammonium Nitrate Prills’ Porosity and Dimesions on Detonation Velocity of ANFO Explosives, Vth Int. Seminar “New Trends in Research of Energetic Materials”, Pardubice, 21-23.04.2003, 45-51.

[14]    Trzciński W.A., Cudziło S., The Application of the Cylinder Test to Determine the Energy Characteristics of Industrial Explosives, Archives of Mining Sciences, (2001), 46(3), 291-307.

[15]    Buczkowski D., Trzciński W. A., Zygmunt B., Examining of Energetic Properties of ANFO Explosive by Using Cylindrical Test, Fifth Int. Armament Conf. Scientific Aspects of Armament”, Waplewo, 9-11.10.2004, 74-82.

[16]    B. Ruscic. Int. J. Quantum Chem. 2014, 114