No abstract

Post-blast nitrogen oxide fumes (NOx) from surface blasting activities have become an important operational issue in Australian Coal mines. Post-blast fumes are a direct product of the detonation process which can be easily identified as the resultant yellow to orange post-blast clouds. There is general agreement that the conditions leading to fumes are associated with fuel deficiencies or incomplete detonation of the explosive product. From a practical perspective this can be due to one or a combination of factors such as explosive product characteristics, confinement effects, ground conditions, inappropriate blast design parameters, explosive product selection, on-bench practices and potential contamination of explosive product in the blasthole. This paper presents the preliminary results of a project funded by the Australian Coal Association Research Program (ACARP). The main objective of this project is to gain a better understanding of the principal causes of post-blast fumes at the operational level so that incidences can be minimised. Results from a comprehensive literature review, an industry survey and analysis of newly established blast registers have indicated that an appropriate matching of product to ground is essential to minimise fume incidences. For this to occur there must be a clear understanding of the potential impact of the characteristics of key components in any given product formulation and ANFO/ Emulsion blends. Analysis has confirmed the impact of confinement and ground conditions as well as the potential contamination of product with fine drill cuttings near the stemming region. Trends associated with increases in the likelihood of fume incidences from long sleep times were identified but could not be entirely confirmed with the available data. The analysis on overburden blasts showed that it is fair to assume that the likelihood of high level fume incidences may increase when a product is slept for .10 days and that decisions to have product sleeping for longer periods should be supported by a good understanding of the product characteristics and ground conditions (geology and hydrogeology). Further work is required to build capabilities to verify on-bench product specifications and characteristics including the ability to measure in hole density changes, product moisture, verify AN/Emulsion blending ratios and undertake a more through characterisation of ground conditions. It is also important to extend the range of measurement systems to evaluate the performance of the detonation process in situ. To that end the authors have embarked in the development of instrumentation to better understand the impact of changing characteristics of explosive products in situ; a brief description and preliminary results from this research effort are also discussed in this paper.

A better understanding of the detonation performance of an explosive charge can be gained by directly measuring pressure, temperature and velocity of detonation (VOD). This is particularly important with explosives used in the mining industry because their performance is directly influenced by the degree of confinement. A project funded by the Australian Coal Association Research Program was initiated in early 2009 with the view to design and build cost effective prototype instrumentation to measure the relative differences in detonation pressures and temperatures of commercial mining explosives. The project's primary focus was on low density explosives as their detonation performance is not well understood. It was therefore viewed as important to be able to directly measure pressure and temperature during the detonation process of these complex mixtures in production blastholes. The paper describes the prototype instrumentation developed and reports on the results obtained to date in laboratory and full scale conditions

Basic design methodology for a new small multistage Turbodrill (turbine down hole motor) optimized for small size Coiled Tube (CT) Turbodrilling system for deep hard rocks mineral exploration drilling is presented. Turbodrill is a type of axial turbomachinery which has multistage of stators and rotors. It converts the hydraulic power provided by the drilling fluid (pumped from surface) to mechanical power through turbine motor. For the first time, new small diameter (5-6 cm OD) water Turbodrill with high optimum rotation speed of higher than 2,000 revolutions per minute (rpm) were designed through comprehensive numerical simulation analyses. The results of numerical simulations (Computational Fluid Dynamics (CFD)) for turbodrill stage performance analysis with asymmetric blade's profiles on stator and rotor, with different flow rates and rotation speeds are reported. This follows by Fluid-Structural Interaction (FSI) analyses for this small size turbodrill in which the finite element analyses of the stresses are performed based on the pressure distributions calculated from the CFD modeling. As a result, based on the sensitivity analysis, optimum operational and design parameters are proposed for gaining the required rotation speed and torque for hard rocks drilling.

Turbodrill (turbine down hole motor) has been recently proposed by the authors as the preferred drive mechanism with high rotation speed for hard rocks drilling for deep mineral exploration applications. Turbodrill is a type of hydraulic axial turbomachinery in which turbine motor section has multistage of rotors and stators that convert the hydraulic power provided by the drilling fluid to mechanical power with diverting the fluid flow through the stator vanes to rotor vanes. This paper presents a methodology for designing multistage turbodrills with asymmetric rotor and stator blades configurations. The numerical simulation approach and the simulations results carried out using computational fluid dynamics (CFD) code for the proposed small size model of turbodrill stage with different drilling fluid (mud) types and various mass flow rates are presented. As a result optimum operational parameters are proposed for gaining the required rotation speed and torque for hard rocks drilling.