Bern Klein

Integrated mining, processing and waste disposal systems for reduced energy and operating costs at Xstrata Nickel's Sudbury Operations

Abstract The preconcentration of metal bearing ore through the rejection of coarse, barren waste material is not a new concept. However, the approach has not found wide application in the industry due to several common misconceptions about the principles and potential benefits of the approach. The University of British Columbia (UBC) has been involved in a strategic research programme into mine–mill integration and more specifically ore preconcentration since 1999. From the research it has been concluded that ore preconcentration, either by sorting, or other coarse particle separation methods such as dense media separation, is particularly indicated for improving the economics of heterogenous sulphide mineral deposits through the rejection and disposal of barren waste before milling. These benefits can be maximised through the integration of the technologies into the underground environment. This paper presents the outcome of a comprehensive study by UBC into the application and benefits of the concept at Xstrata Nickels Sudbury Operations.

Time-dependent rheological behaviour of cemented backfill mixture

Abstract When cemented backfill mixture (CBM) is transported through pipelines from a backfill plant to stopes, it experiences shearing forces over the transport time. In this paper, the effects of solids concentration, binder content, shear rate and curing time on the time-dependent rheological behaviour of CBM were studied. It was found that over long periods of shearing at a constant rate greater than 5 s−1, the shear stress decreased at first and then increased gradually with time. When the shear rate was less than 0.5 s−1, shear stress increased slightly firstly with shearing time, then it started to behave similar to the test with a higher shear rate whose shear stress decreased firstly and then increased. The samples that were sheared at a higher shear rate exhibited a lower apparent viscosity and the higher yield stress CBM samples displayed more pronounced shear-thinning properties. It was also found that for transient flow, increasing the solids concentration and the curing time lead to both a higher initial shear stress (τ0) and minimum shear stress (τmin). When the cement to tailings ratio increased, the τ0, τmin and final shear stress after shearing for 3600 s (τ3600) increased at first, and then subsequently decreased. Moreover, changes in the solids concentration profile and the cement hydration property were displayed during the rheological tests.

Determining the weathering characteristics of a waste dump with field tests

Prediction of the relative rates of acid generation and neutralization is required to determine if and when acidic drainage will occur for mining waste. Results of laboratory kinetic tests are routinely used to predict the long-term weathering rates of a waste dump. More specifically, an estimate of the ‘time to acidity’ (lag time) is needed to predict if exposed waste rock will become acidic before underwater disposal. A meaningful prediction requires consideration of the differences between the conditions in the laboratory and an actual waste dump. Field tests, which are less commonly conducted, provide site-specific weathering conditions but return results that are difficult to interpret. The results from field tests were compared to those obtained from laboratory kinetic tests. The field rates of weathering were determined to be an order of magnitude greater than the adjusted laboratory results, which were corrected for both surface area and temperature. The difference between the field and laboratory weathering rates is believed to be caused by inadequate hydrogeological assumptions and deficiencies in the experimental protocols. Insights were gained into building and operating kinetic field tests, interpreting results and understanding the limitations and advantages of field test data for prediction purposes. Field test data were found to be very useful for predicting depletion rates of neutralization potential and for validating sulphide oxidation rates obtained from laboratory tests.

Socially Responsible Mining: the Relationship between Mining and Poverty, Human Health and the Environment

Abstract Increasing global demand for metals is putting strain on the ability of the mining industry to physically keep up with demand (physical scarcity). Conversely, social issues including the environmental and human health consequences of mining as well as the disparity in income distribution from mining revenues are disproportionately felt at the local community level. This has created social rifts, particularly in the developing world, between affected communities and both industry and governments. Such rifts can result in a disruption of the steady supply of metals (situational scarcity). Here we discuss the importance of mining in relationship to poverty, identify steps that have been taken to create a framework for socially responsible mining, and then discuss the need for academia to work in partnership with communities, government, and industry to develop transdisciplinary research-based step change solutions to the intertwined problems of physical and situational scarcity.

Rheological Measurements on Settling Suspensions: Characterization of a Cyanide Leach Pulp

Abstract An elongated concentric cylinder cup and bob viscometer fixture was designed to study the rheological properties of unstable magnetite suspensions. The fixture and its use in characterizing the rheological properties of a cyanide leach slurry are described. The cyanide leach slurry exhibited yield shear thinning flow properties which were modeled using the Casson Equation. The flow properties were affected most by parameters that contributed to the yield stress. Increasing the solid content and pH and decreasing the particle size caused the yield stress to increase. Changes in parameters also affected the Casson viscosity. Increasing the solid content, pH (Ca(OH)2) and grind size increased the viscosity.

Influence of Particle Size on the Basic and Time-Dependent Rheological Behaviors of Cemented Paste Backfill

The rheological properties of cemented paste backfill (CPB) significantly influence the material’s transportability, and these properties are strongly affected by the material’s particle size. This paper mainly focuses on the influence of particles size on the basic and time-dependent rheological behaviors of CPB. The rheology tests and microstructure analysis were conducted using multiple CPB samples with different solid contents, cement contents, and particle sizes. Results show that the CPB samples with finer particle sizes have a lower apparent maximum packing density compared to the CPB samples with larger particle sizes. Fresh CPB mixture samples exhibit shear thinning characteristics which are more pronounced in samples with larger particle sizes and higher volume fraction to apparent maximum packing density (

Cave fragmentation in a cave-to-mill context at the New Afton Mine part I: fragmentation and hang-up frequency prediction

\phi /\phi_{\text{m}}

Energy-Efficient Comminution: Best Practices and Future Research Needs

ϕ/ϕm) ratios. When the