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TECHNICAL PROGRAM
can also be derived from local production experience. Both of these approaches
are based on standard assumptions about the ground response to mining. This
paper examines how the ALPS calculation process can be revised to reflect
ground response characteristics. These include caving and gob formation, pillar
capacity and redistribution of ground stresses. While some of these are not accessible
in the ALPS program, ALPS calculations are easily implemented in a
spreadsheet and thus, can be readily customized as needed. The relevance of stability
factors can be improved by integration local ground behavior and, at the
least, incorporation of these factors may demonstrate why very low ALPS stability
factors can be valid. A parameter study explores how variations in ground
characteristics impact stability factor calculations.
chair:
2:00 PM
Introductions
coal & energy:
Ventilation I
2:00 PM • Monday, February 25
J. Brune, Colorado School of Mines, Golden, CO
2:05 PM
Challenges of CFD Modeling of Open Pit Mines
K. Raj, W. Collingwood and S. Bandopadhyay; Mining and
Geological Engineering, University of Alaska Fairbanks,
Fairbanks, AK
In the mining industry, computational fluid dynamics (CFD) is being extensively
used for simulating air flow in underground mines. CFD modeling of pollutant
transport problems in an open pit mine is relatively new. Modeling the actual pit
geometry of an open pit mine and the open domain is complex. The complexity
is primarily due to the faceted geometry of an open pit with associated numerous
sharp features. Important issues which are not considered carefully at the geometry
level are generally propagated to the subsequent processes. Several challenges
and the pitfalls are encountered while modeling of the pollutant transport in open
pit mines which are related to the geometry, meshing, boundary conditions, and
the turbulence modeling parameterization. An appropriate selection of the mesh
is critical. A detail discussion of the meshing an open pit domain is presented.
The selection of an appropriate turbulence model such as ≡-∝, LES, RSM, etc. to
obtain a better solution is equally significant. This paper will discuss the various
challenges in modeling of the pollutant transport process in an open pit and some
of the approaches adopted to deal with these challenges.
2:25 PM
The Transient Behavior of Mine Ventilation Networks via
Multi-dimensional Numerical Simulation
W. Wedding and A. Wala; University of Kentucky, Lexington, KY
A comparison between two simulation methods, a network based technique with
a compressible multi-dimensional model, is presented. The network model used
is Ventgraph. The multi-dimensional model is a compressible network model
coupled to a three dimensional CFD domain, SC Tetra. Results from both simulation
techniques are included for normal operating conditions as well as a transient
analysis of the influence of a fire upon a coal beltline. The effects of entry
inclination with regards to heat induced buoyancy are examined.
2:45 PM
Application of a CFD-simulation for an Optimization of
Ventilation In Case of the Occurrence of NOx-blast-emissions
E. Clausen, A. Agasty, M. Kellner and O. Langefeld; Institute of
Mining, TU Clausthal, Clausthal-Zellerfeld, Germany
With regard to the current discussions within the EU to set new exposure limits for
NO and NO2 in the workplace, the mining industry will be required to minimize
the pollutant concentrations. This situation is exacerbated by the fact that the
MAK-Commission recommendations, responsible for setting the national pollutant
concentration limits in the Federal Republic of Germany, provide for a reduction
of NOx gases by 90 and 98% at 0.5 ppm for NO and NO2 respectively. In addition
to the diesel vehicles employed underground, the use of explosives, causing
NOx emissions, constitutes a major pollutant source. In order to analyze and evaluate
the behavior of nitrogen oxides after a blast, a simulation was performed with
the help of a three-phase CFD model (air, NO, NO2). Based on the simulation,
different concepts and measures, dependent on the volume of the released nitrogen
oxides, for a purposeful dilution of the air could be tested and assessed in
terms of their effectiveness with regard to optimization of mine ventilation.
3:05 PM
The Effect of Overall Pit Slope and Pit Geometry on the Dispersion
of Pollutants in a Hypothetical Arctic Open-pit Mine
A. Choudhury 1 and S. Bandopadhyay 2 ; 1 Mining Engineering,
Montana Tech of the University of Montana, Butte, MT and
2
Mining and Geological Engineering, University of Alaska Fairbanks,
Fairbanks, AK
Deep open-pit minesare becoming increasingly common in the highly mineralized
arctic and sub-arctic regions. Air inversion is a frequent occurrence in these regions,
and is exacerbated by the natural topography of an open-pit mine. The resulting
inversion cap is known to contribute to the fouling of air in the open pit, resulting
in loss of production. This paper discusses the construction and validation
of a three-dimensional model that simulate the flow of air and the transport of
gaseous contaminants in an arctic open-pit mine and the effect of the geometry of
the mine and the slope angle of the pit on the contaminants profiles in the mine.
3:25 PM
Analysis of Recirculation in Booster Fan Systems Using CFD
J. Wempen and M. Nelson; Mining Engineering, University of Utah,
Salt Lake City, UT
Booster fans, large underground fans, can increase the volumetric efficiency of
ventilation systems by helping to balance the pressure and quantity distribution
throughout a mine, reducing leakage and reducing the total power requirement.
However, in ventilation systems that use booster fans there is a potential for system
recirculation, the leakage of return air to intake air, and also for localized recirculation
near the fan through the bulkhead and airlock doors. Air that is recirculated
locally decreases the system efficiency because the quantity of air flow
through the fan increases without increasing the airflow throughout the system.
To understand the detailed flow characteristics of a ventilation system with a
booster fan, two-dimensional computation fluid dynamics (CFD) models were
developed. The CFD models were used to evaluate how the number of booster
fans, the booster fan placement, the location and geometry of the fan installation,
and the construction of the airlock system affect the flow characteristics and the
localized efficiency of the ventilation system.
3:45 PM
Numerical Modeling of Contaminant Gas Transport in
Underground Openings
P. Rostami; Mining Engineering, UNR, Reno, NV
Transport of contaminant gases can occur due to: advection by forced ventilation,
natural convection, dispersion along the length of the concentration front
and finally transversal dispersion in a cross-section of the airway. In a turbulence
analysis, the diffusion is promoted by a turbulent eddy. This diffusion is very
strong compared to the molecular diffusion, and therefore the result is hardly affected
by the molecular diffusion in a turbulence analysis. Turbulent eddy diffusion
is automatically solved in Computational Fluid Dynamic programs. In case
of non-CFD models, simulating the contaminant transport is achieved using a
dispersion coefficient for individual species, addressing molecular and turbulent
diffusion. The goal of this study is to find the dispersion coefficient as a function
of air velocity for the species of interest and propose a theoretical solution to calculate
a safe distance beyond which the contaminant level is below the threshold
value. Various scenarios were model in a CFD program (cradle V9). From simulation
results, a representative dispersion coefficient is calculated for CO2 and
SO2 gases and later used for prediction of spread and dilution.
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This is the Technical Program as of September 1, 2012. IT IS SUBJECT TO CHANGE.
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