Erode G. Mahadevan

Ammonium Nitrate Explosives forCivil Applications

Related Titles

Koch, Ernst-Christian

Metal-Fluorocarbon BasedEnergetic Materials

2012

ISBN: 978-3-527-32920-5

Lackner, M., Winter, F., Agarwal, A. K.(eds.)

Handbook of Combustion

2010

ISBN: 978-3-527-32449-1

Agrawal, J. P.

High Energy MaterialsPropellants, Explosives and Pyrotechnics

2010

ISBN: 978-3-527-32610-5

Meyer, R., Kohler, J., Homburg, A.

Explosives

2007

ISBN: 978-3-527-31656-4

Agrawal, J. P., Hodgson, R.

Organic Chemistry ofExplosives

2007

ISBN: 978-0-470-02967-1

Kubota, N.

Propellants and ExplosivesThermochemical Aspects of Combustion

2007

ISBN: 978-3-527-31424-9

Teipel, U. (ed.)

Energetic MaterialsParticle Processing and Characterization

2005

ISBN: 978-3-527-30240-6

Erode G. Mahadevan

Ammonium Nitrate Explosives forCivil Applications

Slurries, Emulsions and Ammonium Nitrate Fuel Oils

The Author

Dr. Erode G. MahadevanTechnology ConsultantC-22 Vikrampuri ColonySecunderabad 500009India

All books published by Wiley-VCH arecarefully produced. Nevertheless, authors,editors, and publisher do not warrant theinformation contained in these books,including this book, to be free of errors.Readers are advised to keep in mind thatstatements, data, illustrations, proceduraldetails or other items may inadvertently beinaccurate.

Library of Congress Card No.: applied for

British Library Cataloguing-in-PublicationDataA catalogue record for this book is availablefrom the British Library.

Bibliographic information published by theDeutsche NationalbibliothekThe Deutsche Nationalbibliotheklists this publication in the DeutscheNationalbibliografie; detailed bibliographicdata are available on the Internet at<http://dnb.d-nb.de>.

© 2013 Wiley-VCH Verlag & Co. KGaA,Boschstr. 12, 69469 Weinheim, Germany

All rights reserved (including those oftranslation into other languages). No partof this book may be reproduced in anyform – by photoprinting, microfilm, or anyother means – nor transmitted or translatedinto a machine language without writtenpermission from the publishers. Registerednames, trademarks, etc. used in this book,even when not specifically marked as such,are not to be considered unprotected by law.

Composition Laserwords Private Ltd.,Chennai, IndiaPrinting and Binding Markono Print MediaPte Ltd, SingaporeCover Design Adam Design, Weinheim

Printed in SingaporePrinted on acid-free paper

Print ISBN: 978-3-527-33028-7ePDF ISBN: 978-3-527-64570-1ePub ISBN: 978-3-527-64569-5mobi ISBN: 978-3-527-64571-8oBook ISBN: 978-3-527-64568-8

V

Contents

Acknowledgment XIPreface XIII

1 Classification of Explosives 11.1 Initiation Sensitivity 11.2 Size 11.3 Usage 21.4 Physical Form 2

2 Explosive Science 52.1 Introduction 52.1.1 Low Explosives 52.1.2 High Explosives 52.2 Initiation and Detonation 62.2.1 Mechanism 62.3 Propagation and Detonation 72.3.1 Propagation 72.3.2 Detonation 82.3.2.1 Ideal/Nonideal Detonation/Critical Diameter/Ideal Diameter 92.3.2.2 Detonation Pressure and Velocity 92.4 Reaction Chemistry in Explosives 112.4.1 Heat of Reaction 112.4.2 Rules of Hierarchy 122.4.3 Calculation of Oxygen Balance and Fuel Values 12

References 13

3 Ammonium Nitrate Explosives 153.1 Introduction 153.1.1 Chronology 153.2 Design of Commercial Explosives 163.2.1 Importance of Oxygen Balance 163.2.2 Physical, Performance, and Safety Requirements 17

VI Contents

3.3 Tests 173.3.1 Ballistic Mortar Test 183.3.2 Trauzl Lead Block Test 193.3.3 Velocity of Detonation (VOD) 203.3.4 Gap Test and Continuity of Detonation Test 223.3.5 Aquarium Test 233.3.6 Double Pipe Test 233.3.7 Cylinder Test (Crushing Strength) 243.3.8 Plate Dent Test 243.3.9 Underwater Test (UWT) 243.3.10 Crater Test 263.4 Assessment of Safety and Stability Characteristics 273.4.1 Impact Test 273.4.2 Torpedo Friction Test 273.4.3 Accelerated Hot Storage (ageing Test) 273.4.4 Cold Temperature Storage Test 283.4.5 Thermal Stability Tests Using DTA and TGA Procedures 283.5 Summary 29

References 29

4 Ammonium Nitrate and AN/FO 314.1 Introduction and History 314.2 Physical and Chemical Properties of Ammonium Nitrate 324.2.1 Basic Data 324.2.2 Decomposition Chemistry of AN 324.2.3 Phase Transition in AN and its Importance in Explosives 334.3 Manufacture of Ammonium Nitrate 354.3.1 Prilled Ammonium Nitrate 364.4 Ammonium Nitrate Fuel Oil Explosives 394.4.1 Background 394.4.2 AN/FO Manufacture 394.4.2.1 Mixing Process and Equipment 394.4.2.2 Continuous Process 404.4.2.3 Bulk Delivery Systems 404.4.3 Properties of AN/FO 414.4.3.1 Physical 414.4.3.2 Oil Absorbency and Porosity/Bulk Density/Crushing Strength 414.4.3.3 Resistance to Effect of Temperature Cycling 444.4.4 Characteristics of ANFO 454.4.4.1 Density/Strength 454.4.4.2 Strength of the AN/FO Explosive 464.4.4.3 Energy Content of AN/FO 464.4.4.4 Velocity of Detonation and Effective Priming 474.4.4.5 Mechanism of Detonation Propagation in AN/FO 494.4.4.6 Influence of Fuel 50

Contents VII

4.4.4.7 Effect of Moisture/Wet Boreholes/Water-Resistant AN/FO 504.4.4.8 Water-Resistant AN/FO 524.4.4.9 Increasing the Energy of AN/FO and its Fume Characteristics 524.4.5 Safety Considerations in AN/FO 554.4.6 Summary – AN/FO Explosives 564.4.7 Quality Checks 56

References 58Further Reading 58

5 Slurries and Water Gels 595.1 Development 595.2 Design 595.2.1 Large-Diameter Packaged Product (Water Gels) 605.2.2 List of Ingredients 605.2.3 Small-Diameter, Cap-Sensitive Water Gels 605.2.4 Bulk Delivery Product 615.2.5 Basic Concepts of Formulation 615.2.5.1 Oxygen Balance 615.2.5.2 Thumb Rules for Design 625.2.5.3 Role of Water 635.2.5.4 Basic Composition and Process 655.3 Process Technology 665.3.1 Batch Process 665.3.2 Continuous Process 685.3.3 Packaging Systems 685.4 Quality Checks 715.4.1 Raw Materials 715.4.2 End Product Specification 735.4.2.1 Development of New Formulations 735.4.3 Role of Aluminum in Water Gels and Slurry Explosives 745.4.3.1 Atomized and Flake Powders 745.4.3.2 Aluminum Water Reaction 785.4.3.3 Important Tests for AL Powder for Use in AN-Based Water Gel

Explosives 805.4.4 In-Process and Finished Product Checks 845.4.4.1 Oxidizer Blend Composition 845.4.4.2 Solid Ingredients 855.4.4.3 Liquid Ingredients 855.4.4.4 Mixing 855.4.4.5 Packing 865.4.5 Performance Tests 865.4.6 Safety Tests 875.4.6.1 Gap Test/COD 875.4.6.2 COD 875.4.7 Storage Tests 87

VIII Contents

5.4.8 Gel Condition Evaluation 895.4.9 Waterproofness Test 905.4.10 Effect of (Hydrostatic) Pressure 905.5 Process Hazards (Dust Explosions/Fire Hazards/Health Hazards) 915.5.1 Slippery Floor 925.5.2 Health Hazard 925.6 Role of GG 925.6.1 Application in Water Gels and Slurries 935.6.2 Specification of Typical GG Used in Water Gels 945.6.3 Cross-Linking 955.6.4 Mechanism of Hydration 965.7 Permissible Explosives 985.7.1 Design Criteria 985.7.2 Tests for Permissibility 995.7.3 Other Tests requirement 1005.7.3.1 Deflagration Tests 1005.7.4 Behavior of Water Gels in Permissibility Tests 1015.7.5 Toxic Fumes and Typical Formulation 1045.7.6 Strength of Permissible Water Gels 1045.8 General Purpose Small-Diameter Explosives (GPSD) 1055.8.1 Design Criteria and Composition 1055.9 Sensitizers 1065.9.1 Inorganic 1065.9.2 Organic Sensitizers 1075.9.3 Air/Gas/Synthetic Bubble Sensitizers 108

References 111Further Reading 112

6 Emulsion Explosives 1136.1 Introduction 1136.2 Concept of Emulsion Explosives 1136.3 General Composition of Emulsion Explosives 1146.4 Structure and Rheology 1156.5 Composition and Theory of Emulsion Explosives 1176.6 Manufacture 1186.6.1 Types of Emulsion Explosive Products 1186.6.2 Manufacturing Process 1186.6.2.1 Batch Process 1196.6.2.2 Semicontinuous Operation 1196.6.2.3 Fully Continuous Process 1206.6.2.4 Critical Equipment for Production of Emulsion

Explosives 1216.6.2.5 Pumps 1226.6.2.6 Packaging Equipment for Emulsion Explosives 1226.6.3 Raw Material for Emulsion 123

Contents IX

6.6.3.1 Fuel Blends 1236.6.4 Sensitizing in Emulsion Explosives 1256.6.4.1 Air Entrapment or Occlusion while Emulsification by Mechanical

Agitation 1256.6.4.2 Chemical Gassing 1256.6.4.3 Hollow Particles 1266.6.5 Crystal Habit Modifiers 1276.6.6 Emulsion Promoters 1286.6.7 Emulsion Stabilizers 1286.6.8 Emulsion Chemistry and Understanding Emulsifiers: Key to Good

Emulsions 1296.6.9 Concept of HLB and Its Use in Emulsification 1336.6.9.1 Effect of Factors on Stability of Emulsions 1356.6.10 Polymer Systems in Emulsion Explosives 1386.7 Quality Checks 1396.7.1 Raw Materials 1396.7.2 Process Audit 1406.7.3 Special Tests for Emulsions 1416.8 Explosive Properties of Emulsion Matrix/Explosives 1426.8.1 Channel Effect 1446.9 Permissible Emulsions 1456.10 General Purpose Small-Diameter (GPSD) Emulsion Explosives 1476.11 Bulk Emulsions 1496.12 Heavy AN/FO 1516.13 Packaged Large-Diameter Emulsion Explosives 153

References 154Further Reading 155

7 Research and Development 1577.1 Areas of Interest 1587.2 Development Work and Upscaling 1597.3 Management of R&D 161

8 Functional Safety during Manufacture of AN Explosives 1638.1 Introduction – Personal View Point on Safety 1638.2 Safety Considerations in AN Explosives 1658.2.1 In AN/FO 1658.2.2 In Slurries and Emulsions 1668.2.3 Electrostatic Ignition 1678.2.4 Lightning Protection 1688.2.5 Runaway Reactions 1688.2.6 Venting as Means of Protection 1708.2.7 Explosion Suppression Technology 1718.3 Explosion Hazards in Equipment 1728.3.1 Hazards Associated with Pumping of Explosives 172

X Contents

8.3.2 Possible Hazards during Packing 1758.4 Concluding Remarks 176

References 177

9 Economics of AN-Based Explosives 1799.1 In Manufacture 1799.2 In Applications 1819.2.1 Condition of Explosive 1829.2.2 Coupling and Priming 1839.2.3 Stemming and Confinement 1849.2.4 Explosives–Rock Interaction 1859.2.5 Explosives Energy Optimization in Blasting 1859.3 Blast Design 1869.4 Influence of Explosives in Underground Mining 190

References 193

10 Current Status and Concluding Remarks 195

Appendix A 199

Appendix B: Guidelines for Investigation of an Accident 203B.1 Introduction 203B.2 Detailed Inspection 204B.3 Interviewing and Questioning 205B.4 Collection of Samples 205B.5 Examination of Witnesses 206B.6 Examination of Dead/Injured 206

Index 209

XI

Acknowledgment

It is not easy to write an acknowledgment for a book production as the numberof people involved could be very many. The contents of my book are a mix ofmy own thinking and experience, but after stimulating discussions with variouspeople connected with the global explosives industry and practical data collectedover many years. But to my mind the motivation to stay and do research in thisfield was provided by the inspiring personality of Prof. T. Urbanskii with whom Icame into contact while working in IDL industries, Hyderabad. The final impetusto write a book came through Dr. Martin Preuss of Wiley-VcH. I owe a lot to myfamily for their encouragement and support. Apart from these the various personswith whom I interacted in the industry at one time or the other inspired me totry and seek some answers to the phenomenon of explosives but special mentionhas to be made to the great working atmosphere provided by IDL Industries (nowknown as Gulf Oil India) where I spent a greater part of my career and gainedhands-on knowledge in the field of explosives.

I am grateful to all the above for their role in motivating me to write a bookprimarily intended for the new entrants to the field of civil explosives as it standstoday. Hopefully, I have succeeded in satisfying the readers of my book in whateverthey expected from the contents.

I also wish to thank Dr. Martin Graf-Utzman and his staff for assisting me infinalizing this book.

XIII

Preface

Ammonium nitrate (AN) explosives came into prominence in the last threedecades (40 years) for civil applications as it provided a greater margin of safetyto the manufacturer and end user as compared to the then popular nitroglycerine(NG) explosives. Due to rapid industrialization over the last 30 years, there hasbeen a surge in mining and infrastructure activities which in turn has triggeredhigh demand for civil explosives at all types of remote and tough locations. Miningmethodology also underwent a change to cater to these requirements and huge opencast mines which need for their efficient operations large volumes of explosivesdelivered at mine site are operating in great numbers. Such enhanced requirementscould only be satisfied by AN-based civil explosives which can be manufactured inhigh tonnages with a good margin of safety and low capital investment. Thus inmany countries, manufacture and use of NG explosives were reduced drastically orabandoned, and AN explosives were used instead. Rapid development of AN-basedexplosives for all types of applications including underground gassy coal minestook place between 1970 and 1990 to fill in the void left by NG explosives anda number of patents appeared during this time. Over the years, however, themanufacture in industrial scale has settled down to fairly common practices andraw materials.

Despite the importance of the AN-based civil explosives today, there has not beenmuch written and published about these explosives in detail perhaps because oftheir unglamorous nature as compared to military explosives and propellants. It ismy intention to fill this gap by devoting the contents of this book exclusively to thetechnology of manufacture of AN civil explosives. This book will deal with threesuch products – AN/fuel oil explosives (AN/FO), slurry and water gel explosives,and emulsions explosives, in great detail as they comprise nearly 90% of theexplosives used worldwide in civil sector.

Much has been published about the chemistry and science of explosives as wellas test methods employed to determine their characteristics. It is my intentionnot to repeat these but mention only the most important aspects applicable to ANexplosive under consideration here. On the other hand, the book will concentrate onproviding valid data and sensible manufacturing guidelines based on the author’shands-on experience of more than 35 years in this field. There is no attempt hereto bring into print any kind of proprietary information and ‘‘tricks of the trade’’

XIV Preface

being practiced in the industry. The author hopes that the contents will benefitthe persons engaged in the industry to have a better understanding of the role ofthe critical factors involved in manufacturing good explosives in a safe way. It isalso the fond hope of the author that through this book young and fresh mindswill get stimulated to take up research in this subject, which has been woefullyvery meager, and contribute toward better understanding of the basics leadingto safer and hopefully cheaper products in keeping with current environmentalconditions.

I feel the chapters describing the critical role of raw materials like guar gums,aluminum powders, emulsifiers, processing and packing technology, and optimumutilization of explosives energy in field applications will be of great interest to thereader. Strangely while the science of explosives includes aspects of importancefrom complex subjects like thermodynamics, colloid chemistry, powder metal-lurgy, mixing technology, and detonation physics, the commercial manufactureof AN explosives for civil application has reduced to a fairly low technology, highvolume industry where know-how is supreme and know-why is of low impor-tance. Hence there is no theoretical and mathematical approach of the subjectin the book but attempt is made to demystify and simplify concepts of explosivephenomena so as to enable those performing routine jobs in this industry to un-derstand and appreciate more their occupation, thereby deriving more intellectualsatisfaction.

The contents of the book will be of interest to persons engaged in the civilexplosives industry in all its aspects such as manufacturing, quality assuranceand safety, scientists in research establishments, statutory authorities in thefield of civil explosives, individual consultants to the explosive industry, man-agers in the mining industry, and so on. The contents of the book could beused to write up a production and safety manual as also for troubleshoot-ing in existing operations. The blasting engineer may also be able to use itschapter on application to derive the maximum benefit from the use of theexplosives.

The book, after exploring the evolution of these three types of explosives, willcontain individual chapters dealing with science and technology, manufacturing,safety, and future R&D work needed.

Individual chapters are exclusive to the type of the explosive being discussed.The three major explosives dealt with are AN/FO, slurry/watergels, and emulsionexplosives.

Individual chapters describe the following:

• Classification/types/characteristics/definition• Explosives science• Raw materials and their role• Formulation techniques and components• Manufacturing technology• Quality – concept and assurance• Safety – understanding and practice

Preface XV

General topics of interest are contained in

• future R&D work,• comparison with NG explosives,• comparison between ANFO, slurries, and emulsions,• economics of manufacture,• applications,• economics for the end user, and• references and bibliography.

Erode G. Mahadevan

1

1Classification of Explosives

Explosives are classified into different types and categories in various ways depend-ing on their usage, sensitivity to initiation, and finished product packaging.

1.1Initiation Sensitivity

• Cap-sensitive explosives: The explosive can be fully detonated with a measurableunconfined velocity in low diameters (1 inch) by initiating with a single detonatorof No. 6 strength, which is the lowest strength detonator commercially made.

• Booster-sensitive explosives (blasting agent): This type of explosive is detonated onlywhen a booster of sufficient power is used to initiate it. These boosters are madeof high explosives like pentaerythritol tetranitrate (PETN) and trinitro toluene(TNT) and are much more powerful than detonators (Figure 1.1).

Explosives are further classified into primary, secondary, and tertiary explosivesdepending on its level of sensitivity to external stimuli. Standardized testingevaluates the sensitivity in terms of friction, impact, heat, shock and based on theseresults, explosives are classified accordingly.

Nitroglycerine (NG) is very sensitive and classified as a primary explosive.TNT/RDX/dynamites are secondary explosives. These are relatively safe forhandling and can be handled in large-scale production plants with acceptabledegree of safety. Ammonium nitrate (AN) explosives are the least sensitiveand come in the tertiary explosives group. Even though they may have higherdetonation velocities and pressure than NG explosives, they are much safer toproduce in very large quantities.

1.2Size

• Small diameter explosives: These are usually explosives made in diameter of 7/8 to2 in. and generally cap-sensitive.

• Medium diameter explosives: These are usually explosives made in diameters of3–5 in. and are booster-sensitive only.

Ammonium Nitrate Explosives for Civil Applications: Slurries, Emulsions and Ammonium Nitrate Fuel Oils,First Edition. E.G. Mahadevan.© 2013 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2013 by Wiley-VCH Verlag GmbH & Co. KGaA.

2 1 Classification of Explosives

3”(75 mm) ∅

No. 6 Detonator

Exploder

1”(25 mm)

Explosive

No. 6 Detonator

Exploder

Booster

3”(75 mm) ∅

Booster Detonating cord ornonel

Exploder

Explosive

Explosive

′

′

Figure 1.1 Types of initiation.

• Large diameter explosives: These are usually explosives made in diameter of 5–10in. and are booster-sensitive only.

The boosters are in turn set off by either detonator or by a coil of detonating cordwound over and through it (see Figure 1.1).

1.3Usage

The explosives are also classified into general purpose and permissible categories.

• General-purpose explosives: Usually in small diameter and cap-sensitive used forquarrying, tunneling, and cannot be used in underground coal mines.

• Permissible explosives: Cap-sensitive small-diameter explosives from 1 1/4 to 1 5/8in. diameter, allowed by authorities for use in underground coal mines.Depending on the degree of gassiness (methane emission) found, there arefurther subclassifications. These differ from county to county depending on thetest Procedures used.

1.4Physical Form

Classification according to physical form of end product is as follows:

1.4 Physical Form 3

• Cartridged explosive: Here the explosive is in the form of cylindrical package,enclosed in paper or polythene tubings (flexible or rigid).

• Pumpable explosives (bulk explosives): Here the explosive is in the form of a flowymaterial and is capable of being pumped, augured, or poured. There is no outerpackaging at all and the product is directly moved into the bore hole using bulkdelivery trucks.

Any material which cannot be fully set off with a measurable velocity of detonation(VOD) either by detonator or by detonation is considered as ‘‘nonexplosive’’ innature. However such nonexplosive material can be converted into an explosive byincreasing its sensitivity.

5

2Explosive Science

2.1Introduction

Explosives are known in practice as substances which work on the surroundingswhen they are set off. In the open area, their effectiveness is much less than underconfinement because most of the work is done by expanding gases. Gas-producingevent can be due to burning (deflagration) or explosion and detonation. Oneusually differentiates by the reaction velocities and pressures achieved in each ofthe phenomena. Thus while in deflagration, reaction velocities are much slowerthan velocity of sound and the pressures attained are in the range of bars. Indetonation, the reaction velocity, which produces gas due to chemical reaction ofthe explosive with its own ingredients or air, exceeds the speed of sound in thematerial itself; thus there is a supersonic shock wave produced. The wavefronttravels in advance of the release of expanding gases. The shock energy has a highpeak pressure but is transient, whereas the gas energy is a longer lasting eventthough lower in peak pressure attained (see Figure 2.1) [1].

2.1.1Low Explosives

Deflagration and fast-burning substances which still perform some amount ofwork through release of gas are classified as low explosives. Black powder is atypical example. Reaction velocities are normally in the range of 600−1000 m/s(see Figure 2.2) [1].

2.1.2High Explosives

Velocity of detonation (VOD) are in excess of 1800 m/s. Most commercial explosivesand especially the ammonium nitrate (AN) based belong to the high explosivescategory due to their high detonation and gas pressures.

Explosives can also be classified as homogeneous and heterogeneous. Usuallyprimary and secondary explosives are present in the former, whereas in the lattertertiary explosives which are mixtures of chemicals are found.

Ammonium Nitrate Explosives for Civil Applications: Slurries, Emulsions and Ammonium Nitrate Fuel Oils,First Edition. E.G. Mahadevan.© 2013 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2013 by Wiley-VCH Verlag GmbH & Co. KGaA.

6 2 Explosive Science

PressureExplosion pressure

Stable detonation pressure

Surface ofundetonatedexplosive

Pressurespike

Explosion state Unreactedexplosive

Shock frontCJ planeDetonation zone

Figure 2.1 Schematic representations of zones and pressure variations along a detonatingexplosive charge.

Reaction front Reaction front

Cartridge oflow explosive

Cartridge ofhigh explosive

Gas energy

Gasenergy

Shockenergy

Pre

ssur

e

Pre

ssur

e

Figure 2.2 Pressure profiles for low and high explosives.

2.2Initiation and Detonation

2.2.1Mechanism

In order to perform, explosives need to be initiated. The extent of initiationneeded depends on the sensitively of the explosive. Tertiary explosives – AN-based