Energy condensed packaged systems: Oxidizer components selection
Trudy Odesskogo Politehničeskogo Universiteta
Introduction. Ammonium nitrate represents the most large-capacity product of nitric industry, widely used as a fertilizer and as an oxidant at energy condensed systems (ECS), including industrial emulsion explosives (IEE) for the mining industry. The experience of emulsion explosives' use to break rocks shows that these systems are as effective as TNT explosives, but have much efficiency and significantly higher safety level at the same time that their explosion products are more
... more environment-friendly. Literature review. Well known is [1...3] that the IEE do represent highly concentrated inverse emulsions of nitrate salts' water melts in the fuel phase, sensitized with microspheres or gas bubbles. It has been found that most of IEE properties are determined by emulsion dispersion, which increases concurrently to increase of "oxidizer -fuel" boundary surface that provides the system's high sensitivity and detonation characteristics [1...3]. However, dispersion increasing the system failure thermodynamic probability also does increase. ECS emulsion base preparation consists in emulsification of inorganic oxidizing salts' highly concentrated water melts (85...90 %) in fuel phase. However, when IEE application temperatures (10...70 °C), the emulsion dispersed phase represents a supersaturated solution that creates salts crystallization and emulsion breaking conditions, and, consequently, involves the ECS detonation capacity loss. Aim of the Research. To obtain a stable high-dispersion emulsion through well-argued selection of the nature and concentration of the oxidizer phase, fuel phase and emulsifier, as well as the emulsification method. Main Body. The modern emulsion explosives do use as an oxidant the ammonium nitrate (NH 4 NO 3 ) sodium (NaNO 3 ) and calcium nitrates (Ca(NO 3 ) 2 ). Calculations show that by the excessive oxygen index determined by the so-called oxygen balance (OB) , the calcium (OB=48,8 %) and sodium (OB=47 %) nitrates are significantly superior over the ammonium nitrate (OB=20,0 %). Thus, to obtain a balanced redox system used as oxidant for sodium and calcium nitrates we must increase the emulsion content in fuel phase that allows a greater thermal expansion of the ECS explosive effect. However, the total replacement of emulsion's ammonium nitrate with the calcium or sodium nitrates is not effective as under thermal decomposition these nitrates do form solid products that reduces the amount of gases released by IE explosion and respectively blast effect . At the same time, using only ammonium nitrate (AN) as an emulsion systems' oxidant requires maintaining high process temperatures when IEE manufacturing. As ECS component, the water represents a salts' solvent and the base to form a dispersed fluid system that provides producing an IEE convenient for pumping into the well with high throughput. The water content in such emulsion depends on the IEE application and type [1, 2]. For liquid emulsion systems purposed for both open and underground mining, the water content is within range of 14...18 % by weight. Case of packaged systems used for underground works, crushing of oversize mining product or when used as a detonator cartridge, the water content is limited to 6...9 wt.%, that is explained by water peculiarities as a system component. Water increases the energy condensing system density and, forming an incompressible liquid phase, maintains a high detonation velocity. Increasing the water content makes the emulsion system Keywords: energy condensed system, oxidizer, ammonium nitrate, calcium nitrate, water content. Reviewer Dr. techn. sciences, Prof. Odesa nat. polytechnic univ. Erayzer L.M.