fresh ore in order to avoid circulatory effects due to repeated
passage of solids through the pump and the loop. Fig. 8 shows
that measured data for the crushed rock agree with the par-
tially-stratified model for all three concentrations.
Observed friction losses for the tar sand tailings, the mix-
ture of granite rock in tar sand tailings and the copper ore,
have been evaluated in terms of hydraulic gradient j,, (m
slurry/m pipe) versus mean velocity in Fig. 9. This repre-
sentation is valuable in practice when pump and pipeline
operating characteristics are to be analysed. Experimental
results in 0.39 and 0.44 m i.d. pipes for the tar sand tailings
(d5o=0.2 ram) at concentrations of up to 37.6% showed
pseudohomogeneous flow conditions. However, when gran-
ite rock particles were mixed in mass proportions 1:9 with
the tailings to a total volumetric solids concentration of
31.4%, the friction losses only increased slightly, see Fig. 9.
Similar results were found in a 0.39 m i.d. pipe. The results
with copper ore in Fig. 9 also demonstrate how coarse particle
slurries can be conveyed with comparatively low friction
losses in a pseudohomogeneous way at high solids concen-
trations of about 39% provided the size distribution is broad
and even.
The partially-stratified friction loss model by Wilson et al.
[ 1 ] (see Eq. (6) and Appendix) compared well with meas-
ured results for the hematite ore, having a relative solids
density of 4.1, at a concentration of 23%. However, the fric-
tion loss model tended to underestimate friction losses for the
magnetite ore, having a relative solids density of 4.5, at con-
centrations of 14-29%. The results with the iron ores, at a
concentration of about 23%, showed that observed losses
were about 30% higher for the coarser magnetite ore, which
had about 40% by mass of the particles in the 1--4 mm range,
see Fig. 2. The difference in d85/d5o ( 1.9 for the hematite and
4.2 for the magnetite) are reflected in the model results,
giving V~o-values of 3.76 and 5.73 m/s and M values of 1.50
and 0.47 for the hematite and magnetite, respectively. The
distribution of particle sizes finer than dso was broad for both
products and the mass fraction of -75 Ix• particles were
approximately the same, 23-25%.
The -75 /xm fraction corresponds to a volumetric con-
centration of 6--7% for the iron ores, to be compared to the
maximum volumetric solids concentrations of about 29%. In
order to obtain meaningful rheological measurements for a
non-settling slurry at low concentration, the largest particles
have to be less than about 75 /xm. Viscometric studies for
numerous iron ore slurries by Sellgren [ 19] indicated that
the low concentrated homogeneous slurry with