Annual Meeting Preliminary Program - Full Brochure (PDF) - SME

TECHNICAL PROGRAM
Mineral & Metallurgical Processing:
Flotation I
9:00 AM • Tuesday, February 26
chairs: S. Miskovic, Univeristy of Utah, Salt Lake City, UT
T. Olson, FLSmidth Minerals, Salt Lake City, UT
J. Hohn, RSR Technologies, Irving, TX
9:00 AM
Introductions
9:05 AM
Evaluatin of an In-plant Pre-aeration Feed System Using Cavitation
for Enhanced Recovery
M. Saracoglu 1 , R. Honaker 1 , E. Yan 2 , J. Kohmuench 2 and M.
Mankosa 2 ; 1 Mining Engineering, Univ of Kentucky, Lexington, KY
and 2 Eriez Manufacturing, Erie, PA
Pre-aeration of flotation feed has proven to be an effective method to improve recovery
and reduce collector requirements. Laboratory tests have revealed that recovery
can be increased by as much as 20 absolute percentage points when treating
difficult-to-float coals. A full-scale in-plant test program is being performed
to evaluate and quantify the technical feasibility and economic benefits of using
a cavitation system to pre-aerate flotation feed of a three-stage StackCell flotation
circuit. The results of this study will be presented and discussed in this publication.
9:25 AM
Picco-Nano Bubble Flotation Using Static Mixer-Venturi-Tube for
Pittsburgh No. 8 Seam Coal
F. Peng and Y. Xiong; Mining Engineering, West Virginia University,
Morgantown, WV
Flotation process is particle hydrophobic surface-based separation technique. To
improve the essential flotation steps of collision and attachment, and reduce detachment
probabilities between air bubbles and hydrophobic particles, a selectively
designed cavitaion venture tube can be used to generate very high numbers of pico
and/or nano bubbles. Fully embraced by those high numbers of tiny bubbles, hydrophobic
particles are readily attracting those tiny bubbles to their surfaces.
Particles and bubbles might attach to larger bubbles for faster flotation. The results
of flotation of Pittsburgh No.8 seam coal are obtained in a 50cm ID and 172cm
height flotation column equipped with static mixer and cavitation venture tube,
using fuel oil no. 2 as collector and MIBC as frother. Combustible material recovery
(CMR) of 85-90% at clean coal product of 6-7% ash are produced from feed of
23% ash, with reduced amount of frother and collector than that in conventional
column flotation. Major operating parameters include feed rate, solid concentration,
reagent dosages, and size effects on CMR are presented and discussed.
9:45 AM
Increasing Flotation Recovery Using the Selective Froth
Recovery System
K. Caldwell; Research, FLSmidth, Midvale, UT
In flotation, coarse and fine particles are harder to float and recent trends in research
and flotation improvement have been toward increasing recovery in these
problem areas. In response to this, FLSmidth has developed the Selective Froth
Recovery (SFR) System. The SFR is a devise that will remove froth using suction
from a desired location or depth within the froth. From current field testing it has
been shown that the SFR system was successful in increasing the amount of
coarse copper recovered from a scavenger float cell. Depending on the depth at
which the SFR device was placed within the cell lower grade coarse concentrate
could be collected or higher grade concentrate similar to the existing froth.
Concentrate was sent from the SFR extraction device to a hydrocyclone for size
classification. When positioned at the top of the froth, the SFR system can be
used to collect froth that has become stiff and is too far from the edge of the cell
to be collected in the launder. The SFR system has been designed to maintain an
offset distance from the slurry level that is adjustable by the user. End design of
the system will be plant specific.
10:05 AM
Study of Hydrodynamic Instability in A Self-aspirated
Flotation Machine
Y. Yang; FLSmidth, Midvale, UT
Flotation machines can be classified as forced-air and self-aspirated cells on the
basis of different aeration methods. The former one uses auxiliary air pump to inject
air into rotor region, while the latter induces air into the rotor region by the
vaccum force generated by rotor rotation movement. Naturally self-aspirated machines
have more complicated hydodynamic characteristics since the rotor bears
more functions. The air suction procedure includes air entrainment, air-liquid interaction,
force-balance and vortex stability problems, which results in unstable
flow in the rotor region under certain operation conditions. The unstable flow
condition leads to asthma, i.e. unconstant air flow rate. In this paper, the Wemco
machine is used as an example to study the hydrodynamic characteristics of selfaspiration
to probe the flow instability problem. At the end, a modified design is
proposed and tested for machine optimization. The investigation is performed in
lab-scale, pilot-scale and commercial size machines and the experimental data
will be presented.
10:25 AM
FLS Forced Air Machine Developments
R. Silva, K. Caldwell, T. Olson and Z. Huang; R&D, FLSmidth,
Salt Lake, Midvale, UT
A methodology was developed to evaluate changes in flotation machine design in
order to improve performance, particularly for forced air machines. This approach
includes: 1) a hydrodynamic testing apparatus to evaluate our in house
CFD and rapid prototype concepts, 2) large scale laboratory flotation machines
and 3) a pilot unit of 1.5 m3. Bubble size, power, pumping capacity, Jg, velocity
profiles, and tip speed tests were performed on both lab size and pilot units following
a sequence that goes from hydrodynamic tests with water and solids to a
flotation kinetic test in the lab and pilot tests. Over 200-laboratory flotation tests
were conducted, with over 100 design combinations showing improved recovery
from the original Dorr Oliver design. From the lab and CFD evaluation, including
an innovated CFD model to predict the flotation probability for the new designs,
designs were chosen with a better potential to be run in a 1.5m3 pilot flotation
cell. As a result, FLSmidth came up with a unique mechanism design (rotor
and stator) to decrease power and improve recovery. In addition, some designs
have been identified to improve fine and/or coarse particle recovery.
10:45 AM
Assessment of Particles-bubbles Collision Frequency Models Using
Large-eddy Simulation of Homogenous Turbulence
S. Ragab and H. Fayed; Virginia Tech, Blacksburg, VA
Collision frequency is a major contributor to the recovery rate constant of flotation
cells, and therefore it must be computed accurately for reliable computation
of the recovery rate within the pulp phase. Abrahamson model and its subsequent
modifications by other researchers is almost always used to compute the
collision frequency, but it is only valid for very high inertia particles (infinite
Stokes number), and therefore it severely overestimates the collision frequency.
New theoretical frequency models have been recently developed for finite inertia
particles, but they need to be validated. In this paper, Large-eddy simulation
(LES) has been used to validate new theoretical models for collision frequency of
bubbles and particles suspended in isotropic homogeneous turbulence. The frequency
found by LES is compared to theoretical frequency models in the practical
range of particle Stokes number. The validated theoretical frequency of collision
models have been implemented into a CFD-based flotation model and
applied to two well known industrial flotation machines.
11:05 AM
CFD Analysis of Two-phase Flow in WEMCO SuperCells
H. Fayed and S. Ragab; Virginia Tech, Blacksburg, VA
Two-phase (water and air) flow in a self aerated WEMCO flotation machine has
been investigated using computational fluid dynamics (CFD). Flow in WEMCO
300 m3 and 500 m3 machines are simulated. Due to the large volume of these
flotation cells, a 72-deg sector has been simulated to reduce the computation
time. The flow is resolved in the hood and disperser holes. Since Wemco machines
are self aerated machines, air flow rate is not known a priori. Inlet and
outlet boundary conditions that allow air to flow in and out of the machine at a
specified atmospheric pressure are imposed. These boundary conditions allow
prediction of air flow rate through the Wemco machines as a function of time instead
of forcing an assumed air flow rate. An overflow tank is utilized to allow
This is the Technical Program as of September 1, 2012. IT IS SUBJECT TO CHANGE.
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Please see the Onsite Program for final details.