DEVELOPMENT OF TWO-COMPONENT GASSING SYSTEM TO SENSITIZE EXPLOSIVE EMULSIONS. by KABAMBA KATENDE JONATHAN BTech: Chemical Engineering (Cape Peninsula University of Technology) Dissertation submitted in fulfilment of the requirements for the degree Master of Engineering: Chemical Engineering in the Faculty of Engineering and the Built Environment at the Cape Peninsula University of Technology Supervisor: Prof I. Masalova Co-supervisor: Dr. N.N. Tshilumbu Cape Town, South Africa CPUT copyright information The dissertation/thesis may not be published either in part (in scholarly, scientific or technical journals), or as a whole (as a monograph), unless permission has been obtained from the University and AEL Mining Services. Preamble ABSTRACT This study investigated explosive emulsions used in civilian mining for breaking rocks. These emulsions were highly concentrated (mass fraction greater than 90 %) and consisted of a dispersion of an aqueous solution of industrial grade ammonium nitrate in a fuel phase containing surface active agents. For such emulsions to detonate, they must be sensitized. This is usually done by generation of gas bubbles (voids) in-situ via a gassing reaction, whereby a gassing component is added to the emulsion to react with ammonium nitrate (present in large quantity), which is a one-component method. In this method, any excess of gassing agent gives rise to an undesired extent of gassing reaction, resulting in poor blasting performance. This study reports an alternative approach to sensitizing explosive emulsions, by using a two-component gassing system, one (KI) that was added to the fuel phase or to ammonium nitrate solution in a pre-determined amount prior to emulsification, and the other (H2O2) added to the explosive emulsion after manufacture, when sensitization was required. Thus, the primary goal of this research was to carry out a phenomenological study of the dependence of H2O2 and KI concentrations, as well as the effect of pH on the emulsion density over time, with a view to shedding light on the factors controlling the final gassed emulsion density, and on optimizing the process. Blasting experiments were also conducted to compare the performance of the new method to the one currently being used. Three industrial fuel phases were selected for this study: F800, Bullfinch and R602/45. The H2O2 solution (30 wt%) and KI concentrations were varied from 0.09 to 7.80 wt% and 0.004 to 0.1 wt% respectively. The pH values ranged from 4.4 to 6.5. The research showed that the stoichiometric reaction between KI and H2O2 was dominant rather than the catalytic decomposition of H2O2. It was also found that when KI was added to the fuel phase, the rate of density change increased and the final gassed emulsion density decreased with increasing H2O2 concentration. As with the effect of H2O2, an increase in rate of density change and a decrease in final emulsion density with increasing KI concentration were observed. For KI concentrations of 0.008 wt% (F800) and 0.004 wt% (Bullfinch and R602/45), the reference density was reached and the excess of H2O2 did not affect the extent of gassing reaction or the final gassed emulsion density. Unexpectedly, emulsions in which KI was added to the ammonium nitrate solution yielded exactly the same results. Interestingly, it was demonstrated that regardless of the phase in which KI is initially added prior to emulsification, the gassing reaction neither occurred in the fuel nor the aqueous phase but at the interface formed by the fuel and aqueous phases. i Blasting experiments showed that emulsions sensitized by the new method (two-component system) yielded velocities of detonation 7 to 11% lower than the current method (one- component system). This was probably due to the differences in porosity of emulsions sensitized by different methods. The studies conducted have shown that the use of the two-component (H2O2 and KI) gassing system is suitable to regulate the extent of the gassing reaction in explosive emulsions for pH < 6.0. The two-component gassing system could be used in the explosives industry where consistent blasting performance is required. ii Preamble DECLARATION I, Kabamba Katende Jonathan, hereby declare that, to the best of my knowledge, this thesis represents my own work and has not been submitted previously for examination toward any degree or diploma qualification at any other University. Furthermore, it represents my own opinions and not necessarily those of the Cape Peninsula University of Technology. ……………………………………….. Kabamba Katende Jonathan February 2018 iii Preamble DEDICATION The following have played a vital role in my life and I dedicate this work to them. o My parents Matthieu Katende Kabamba and Therese Cibangu. I would have never made it this far without their spiritual, moral and financial support. o My brothers Glory and Daniel Katende, and sisters Patricia and Gracia Katende. When supported by such champions, one is continuously motivated to succeed. o My uncle Philip Mpiana and his wife Fidelie Mpiana for the love and care they have shown me. o My father in the faith, Ajacent Mwembo, who did not only offer me advice on spiritual matters but also introduced me to the world of books. o My best friend and companion in this journey Arsene Mulindwa for his continuous spiritual and moral support. o My spiritual leaders Rev. Kiluba wa Kiluba, Ebenezer Kiluba and Emmanuel Kongolo; and JTL South Africa. I am grateful for their prayers and support. o Jesus Christ, my Lord and Saviour in whom are hidden all the treasures of wisdom and knowledge. He is the source of inspiration. iv Preamble ACKNOWLEDGMENTS I would like to acknowledge: o AEL Mining Services South Africa for the financial support towards this research, for availing their facilities to conduct my experiments, for permission to publish the results of this study for my dissertation. Opinions expressed in this dissertation are those of the author and not of AEL Mining Services SA. o The Cape Peninsula University of Technology (CPUT) and the Flow Process and Research Unit (FPRC) for availing their facilities to conduct some of my experiments. o Prof. Veruscha Fester for introducing me to my supervisor. o My supervisor Prof. Irina Masalova who has given me a taste for science and research. o My co-supervisor Dr. Nsenda N. Tshilumbu for his patience in teaching me the ABCs of research. Thanks for the lengthy hours invested in equipping me with research skills. o Mr. Naziem George the lab manager for teaching me safe laboratory practices o My amazing teammate and brother Fabrice; and my FPRC friends (Whitney, Willy, Buyisile, Zintle, Jorika, Banielle, Flash and Maverick). v Preamble NOMENCLATURE Symbol Description Unit d Diameter m L Length m M Mass kg M1 Mass of density cup g M2 Mass cup + sensitised emulsion g t Time µs V Volume of density cup cm3 ρ Sensitised emulsion density g/cm3 Abbreviations AN Ammonium nitrate ANS Ammonium nitrate solution TNT Trinitrotoluene VOD Velocity of detonation vi Preamble GLOSSARY Terms Definition Emulsion: Two immiscible liquids (usually oil and water) with one of the liquids dispersed as small spherical droplets in the other. Explosive Emulsions: Emulsion that consists of small droplets of oxidiser solution tightly packed in a fuel. Gassed emulsion: Explosive emulsion in which voids have been introduced using a chemical reaction Gassing: Use of chemical reaction to produce voids within emulsion explosive Over-gassing: Phenomenon in which final sensitized emulsion density drops below desired value leading to poor blast performance Sensitization: Introduction of small, low density voids into emulsion providing hot spots at which an explosion may nucleate Sensitized emulsion: Explosive emulsion in which voids have been introduced Apparent equilibrium density: Gassed explosive emulsion density recorded at the end of the first hours of observation (2 to 3 hours) True equilibrium density Gassed explosive emulsion density recorded after overnight observation Emulsification Process of dispersing one liquid into a second immiscible liquid vii Preamble TABLE OF CONTENTS ABSTRACT ............................................................................................................................ i DECLARATION ..................................................................................................................... iii DEDICATION........................................................................................................................ iv ACKNOWLEDGMENTS ........................................................................................................ v NOMENCLATURE ................................................................................................................ vi GLOSSARY .......................................................................................................................... vii TABLE OF CONTENTS ....................................................................................................... viii TABLE OF FIGURES ............................................................................................................. x LIST OF TABLES ................................................................................................................ xiii CHAPTER 1 .......................................................................................................................... 1 INTRODUCTION ..................................................................................................................