Upload
vonhi
View
216
Download
1
Embed Size (px)
Citation preview
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 49
RECOVERY OF URANIUM FROM DENSE SLURRIES VIA
RESIN-IN-PULP
T Udayar, M H Kotze and V Yahorava
ABSTRACT
The revival of uranium as a valued commodity has prompted a drive in the mining
industry to identify the most cost-effective processing routes for the recovery of
uranium from low-grade uranium ores or wastes. Various published studies indicated
that direct recovery of uranium from the leached slurry via resin-in-pulp offers major
capital and operating cost advantages. Mintek, in partnership with Bateman
Engineering, developed the MetRIXTM
RIP technology that allows continuous counter-
current transfer of resin and pulp. Laboratory and pilot plant test work was done on
uranium recovery from a South African gold ore. Based on these results, operating
parameters were developed for a demonstration plant on site at the Harmony’s One
Plant near Welkom in the Free State for the recovery of uranium from their current gold
plant feed prior to cyanidation. This paper summarises the metallurgical results
obtained during various laboratory studies, a pilot plant campaign, and the on-site
demonstration plant operation.
1. INTRODUCTION
During the 1970s the demand for uranium had catapulted, resulting in renewed interest
for processing routes that were cost-effective for the recovery of uranium from low
grade deposits. This resulted in the commercialisation (during the 1970s) of the
NIMCIX technology, a continuous counter-current ion-exchange (CCIX) adsorption
contactor that was developed by Mintek for the recovery of uranium from relatively low
grade, un-clarified solutions. A number of pilot and commercial scale plants were built
and operated successfully, including pilot plants at Rössing and Durban Deep, and full
scale plants at Chemwes and Vaal River South. Currently, NIMCIX columns are still
in use at Anglo Gold Ashanti’s Vaal River South operation and Ezulwini, and they are
being tested at Trekkopje on a relatively large pilot scale (referred to as Midi
Commercial Demonstration plant with a heap stacking rate of a 9 000 t/day). The
NIMCIX columns could be used for both adsorption and elution processes, but it has to
be designed for the specific duty.
The use of resin-in-pulp (RIP) for the recovery of gold, uranium or base metals is still
very limited in the Western World. One of the major uncertainties with regards to the
commercial implementation of RIP has been the potential resin loss or consumption on
a full scale operation. In recent times, all the major resin manufacturers have made
significant technological advances resulting in a number of durable, commercially
available, RIP-grade strong-base resins for the recovery of uranium. This has renewed
interest in RIP as a potential economically attractive processing route for the recovery
of valuable metals from low grade slurries.
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 50
Mintek has been conducting intensive research and development over the past 5 years
on the recovery of uranium from low grade uranium slurries. The MetRIXTM
technology, originally designed for the recovery of base metals from waste slurries, was
evaluated for counter-current transport of resin and pulp. This technology is a joint
development between Mintek and Bateman Engineering. The research included resin
durability and metallurgical performance test work. Based on the results developed
over this period, Harmony Gold Mining Company Limited commissioned Mintek and
Bateman Engineering to demonstrate the MetRIXTM
technology at their Harmony One
Plant near Welkom in the Free State.
This paper summarises metallurgical results obtained during various laboratory studies,
a pilot plant campaign on a uranium-bearing gold ore, and the demonstration plant
operation.
2. EXPERIMENTAL
2.1 Laboratory Scale Test work
2.1.1 Equilibrium adsorption and elution isotherms
Eight point adsorption equilibrium isotherms were generated for the adsorption of
uranium onto the strong-base anion exchange resin, in the sulphate form, by batch
contacting the resin and uranium-rich pregnant leach solution (PLS) at different resin:
solution ratios. Contact was made over a period of 24 hours under ambient conditions.
After adsorption, the uranium-loaded resin was separated from the solution, washed to
remove entrained solution, and then eluted in a column with excess eluate.
For the generation of elution equilibrium isotherms, a batch of resin in the sulphate form
was pre-loaded from uranium PLS. The loaded resin was then contacted with eluant at
8 different resins: eluant ratios over a period of 24 hours. Upon completion of the
equilibrium elution test work, the resin underwent an additional elution step using 2M
HNO3 to remove any residual uranium that might still have been present on the resin.
The uranium stripped with HNO3 was used to calculate the residual uranium
concentrations on the resin.
2.1.2 Kinetics of adsorption and elution
The rate of uranium adsorption onto the ion exchange resin was investigated by
contacting resin with a batch of uranium PLS, under agitation over a period of 24 hours.
Regular sampling of the barren solution was done. The resin loading was determined by
stripping the resin with excess 2 M HNO3.
Uranium loaded resin was contacted with 110 g/L H2SO4 in batch under agitation.
Regular samples were taken and analysed for uranium. At completion of the test, the
resin was separated from the eluate and stripped further with 2M HNO3 to determine the
residual uranium concentration on the resin.
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 51
2.1.3 Pilot plant
The RIP pilot plant campaign for the recovery of uranium was run at Mintek during a
three week period. During this time, the main focus was metallurgical performance of
the resin and not durability. The pilot plant comprised of a leaching section in which
uranium-rich ore was slurried with municipal water, and then leached under optimised
conditions as determined during laboratory scale test work. The ore type used for the
pilot plant was a siliceous gold ore with a U3O8 content of 150 – 350 g/ton.
The leach section was run in a sequential manner to ensure that there was a constant
supply of freshly-leached pulp to the RIP adsorption circuit. This approach was taken
to ensure that the leached pulp did not age, which might have caused speciation changes
in the PLS over time (e.g. silica).
3. RESULTS AND DISCUSSION
Extensive laboratory investigations have been conducted at Mintek to evaluate the
metallurgical performance of various strong-base anion exchange resins for the recovery
of uranium. Various RIP-grade resins, which included both gel and macro porous types,
were tested. These results, and those on new resins, are compiled into a data base which
enables Mintek to recommend resins for specific applications in terms of metallurgical
performance and resin durability.
The ion exchange resins are submitted to a series of basic batch tests, including the
following:
. equilibrium adsorption isotherm in the specific leach liquor/pulp,
. equilibrium stripping isotherm, using different eluants,
. rate of adsorption,
. rate of elution and
. laboratory and pilot-scale durability tests.
The test work described in this paper was done on a RIP-grade strong-base, macro-
porous anion exchange resin. This resin was also used for the demonstration plant
campaign. Only the metallurgical performance of the resin is discussed.
3.1 Laboratory test work results
3.1.1 Uranium adsorption equilibrium isotherms and rate of adsorption
3.1.1.1 Equilibrium and kinetics for Harmony leached pulp
Uranium equilibrium adsorption isotherm and kinetics of uranium uptake, obtained for
Harmony-leached ore, are presented in Figure 1 and Figure 2. The Langmuir
equilibrium isotherm provided the best fit for the equilibrium adsorption data with the
determined constants as follows:
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 52
a = 55.929
b = 0.032
A McCabe-Thiele construction was done using the equilibrium isotherm generated.
Resin to pulp ratio on the pilot plant was chosen to achieve 43 g/L U3O8 loading on the
resin from a leached pulp containing 180 mg/L U3O8 with a target of <2 mg/L of U3O8
in the barren pulp after RIP.
Figure 1: Uranium adsorption equilibrium isotherm (Harmony pulp)
Figure 2: Rate of uranium adsorption (Harmony pulp)
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 53
3.1.1.2 Factors affecting uranium loading
Based on previous experience and information achieved during evaluation of RIP
technology for uranium recovery from the Harmony ore type, the following factors were
expected to have considerable impact on the resin performance:
• silica and
• chlorides
Silica present in uranium leach liquors is known to have an adverse impact on the rate
of adsorption of the metal, especially when the silica levels on the resin become
significant. Evaluation of silica impact on maximum uranium loading and rate of its
uptake was reported previously in some of the published Mintek papers [1, 3]. For resin
used in the current work, it was expected that the uranium adsorption capacity over a 24
hour period would decrease by >35% at silica fouling levels >20% (m/m).
Due to the negative impact of silica on the equilibrium and kinetics of adsorption, it was
therefore targeted to limit silica fouling (e.g. limiting overall resin residence time in the
adsorption circuit).
Another factor found to dramatically impact resin performance, was chlorides [6]. The
source of chlorides in the current project was process water and the levels expected to
be dealt with were 0 to 3 g/L. For prediction of the resin performance depending on the
process water quality that might vary on a site, depending as well on the season,
uranium adsorption equilibrium isotherms were generated using synthetic solution with
different chloride contents. The isotherms were fitted with the Freundlich model and
the constants are shown in
Table 1. The results obtained from the test work are given in Figure 3.
Figure 3: Uranium equilibrium loading: effect of Cl-
0 100 200 300 400 5000
10
20
30
40
50
60
U3O
8 loadin
g,
g/L
U3O
8 in the barren, mg/L 0g/L Cl 1g/L Cl 2g/L Cl 3g/L Cl
Freundlich isotherms
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 54
Table 1: Freundlich equilibrium constants for uranium loading isotherms
Chloride concentrations in synthetic liquor 0 g/L 1 g/L 2 g/L 3 g/L
a 13.62 9.65 7.82 5.62
b 0.22 0.26 0.28 0.32
Quite a significant drop in uranium maximum loading was observed with an increase in
the chloride concentration. The uranium loading was depressed by as much as 23%
when the chloride content was increased from 0 – 3 g/L.
3.1.2 Elution equilibrium isotherm and rate of elution
Results of stripping equilibrium and rate of elution tests are presented in Figure 4.
Equilibrium elution isotherms and rate of stripping indicated that uranium elution by
using 110 g/L H2SO4 has an equilibrium constraint. For effective uranium stripping a
specific volume of eluant was required. Results indicated that the rate of stripping
would be less of a determining factor on the elution efficiency (with relatively long
stripping resin residence times) achieving almost complete uranium elution after 3
hours.
The assumptions made based on equilibrium and kinetics of elution were confirmed by
column elution tests, when stripping was performed at different flow rates (0.5 BV/h to
4 BV/h) as shown in Figure 5. There was minimal difference between the elution
profiles observed within the flow rates evaluated, with almost all flow rates achieving
100% uranium elution after 17 BVs (bed volumes) of eluant were passed through the
resin bed.
Figure 4: Equilibrium stripping isotherm and kinetics of uranium stripping with 110 g/L
H2SO4 as the eluant
0 5 10 15 20
0
1
2
3
4
5
0 2 4 6 8 20 24
0
20
40
60
80
100
U3O
8 i
n t
he
elu
ate
, g
/L
Residual U3O
8 in the resin, g/L
Fra
ctio
na
l st
rip
pin
go
f U
3O
8,
%
Time, hrs
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 55
Figure 5: Effect of different flow rates on elution [2]
3.2 Pilot plant performance
Results obtained from the laboratory scale test were used to predict operating conditions
for a pilot plant campaign using a relatively low grade uranium feed. The pilot plant
was done essentially to confirm and optimise the operating parameters, including:
• number of adsorption stages,
• resin residence time,
• pulp residence time,
• resin loading and
• rate of silica fouling of the resin
The RIP section of the plant consisted of six 5 L, agitated RIP reactors. The reactors
were set-up in series, in a manner that enabled the flow of pulp by gravity through the
six reactors. Figure 6 shows a schematic diagram of the RIP section of the plant
operation. The plant was operated in a carousel mode with continuous flow of uranium-
leached pulp and counter-current batch movement of resin.
The fully loaded resin which exited the RIP adsorption stage from Position 1 went
through an elution step before its re-entry back into the adsorption stage at Position 6.
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 56
Figure 6: Flow diagram of the RIP pilot plan
Table 2: RIP pilot plant test conditions
Condition
tested 1 2 3 4 5 6 7 8 9
Resin inventory
per stage 1% 1.2% 1.2% 1.2% 1.2% 1.2% 1.2% 1.2% 1.6%
Resin residence
time, hrs 2 2 2 2 2 2 2 3 3
Pulp residence
time, min 30 30 24 24 30 37.5 37.5 37.5 37.5
Transfer
numbers 1-16 17-26 27–36 37–43 44–51 52–72 73–80 81–93 94-100
The primary objectives of the RIP pilot plant was to investigate the impact of resin and
pulp residence times on the efficiency of uranium adsorption, and the rate of silica build
up on the resin. The conditions tested are shown in Table 2. The resin: pulp ratio was
chosen based on the equilibrium isotherm presented in Figure 1. The chloride
concentration in the pilot plant PLS was 0 g/L.
CB
A
ED
F
Position 2
Position 3
Position 6
Position 5
Position 4
Position 1
G
DC
B
FE
G
Position 2
Position 3
Position 6
Position 5
Position 4
Position 1
A
Leached uranium pulp
PULP FLOW
RESIN FLOW
barren uranium pulp
Leached uranium pulp
barren uranium pulp
A
resin to elution
Pulp would have
generally been
recycled to feed
but was not in
this case due to
the plant set-up
Reactor A to the plant
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 57
Uranium loading on the resin removed from Stage 1 varied significantly (Figure 7),
primarily due to a variation in the uranium grades of the ore that was fed to the leach
section of the plant. Uranium loadings of 30 – 48 g/L U3O8 were experienced for the
most part of the campaign. These loadings were achieved at equilibrium uranium
concentrations ranging from 64 to 276 mg/L in solution.
Figure 7: Uranium loading during the pilot plant campaign
The impact of resin residence time and pulp residence time on the maximum loading of
uranium achieved was seen to be minimal within the parameters evaluated.
The uranium-loaded resin from Stage 1 was eluted with 110 g/L H2SO4 at a rate of
5 BV/hr until a total of 30 BVs was passed through the resin bed. These conditions
were found to be optimal for consistent stripping of U3O8 from the resin to below 1g/L.
Such residual uranium content on the eluted resin did not have an impact on the
adsorption performance in RIP.
Build-up of silica content on the resin was closely monitored during the pilot plant in
order to determine a rate of silica fouling. As silica loads on the resin a portion of it was
eluted with acid together with uranium (“strippable” silica) and the other portion
remained on the resin (“un-strippable”) silica. Remained silica could be stripped only
with caustic and was allowed to build up for duration of the plant. Thus, rate of “un-
strippable” silica was determined.
The SiO2 content in the PLS over the duration of the pilot plant was <500 mg/L.
Profiles of “strippable” and “un-strippable” silica observed during the pilot plant
campaign are shown in Figure 8. The level of “strippable” silica was seen to be
constantly below 5 g/L (1% m/m); while a constant build-up in “un-strippable” silica
levels was observed. A steep gradient in “strippable” and “un-strippable” silica
observed between 45 and 55 hrs of plant operation was as a result of an excessive acid
addition in the leach circuit. This caused excessive silica to be brought forward to RIP
circuit. As the campaign proceeded, it was clear the amount of ‘un-strippable’ silica
increased progressively.
0 10 20 30 40 50 60 70 80 90 100
0
5
10
15
20
25
30
35
40
45
50
55U3O
8 loadin
g o
n resin
, g/L
Transfer number
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 58
Figure 8: Silica fouling of the resin during the pilot plant campaign
3.3 MetRIX™ demonstration plant
Results obtained during the extensive laboratory and pilot test work conducted at
Mintek were used for evaluation of the MetRIXTM
technology as an option for recovery
of uranium from Harmony’s gold ore. Based on the potential capital and operating cost
savings when compared to the other processing flow sheets considered [7], Harmony
commissioned Mintek and Bateman to install and operate a MetRIXTM
demonstration
plant on their Harmony One Plant near Welkom in the Free State. A photograph of the
plant is shown Figure 9. The demonstration plant was operated over a 47 day period.
Figure 9: Demonstration plant installed on site at Harmony
0 20 40 60 80 100 120
0
5
10
15
20
SiO
2 loadin
g,
g/L
Time, hours
strippable SiO2 un-strippable SiO
2un-strippable SiO2 strippable SiO2
T
6
T
_
3
T
e
th
s
3
A
a
p
r
p
u
m
The
6th S
T U
___
3.3.
The
elut
he
im
3.2
A b
app
prov
esi
prov
used
mV
So
Sou
Uday
____
.1
e de
tion
pla
mpli
ble
roa
vid
iden
vid
d to
V (A
outh
uthe
yar,
___
P
em
n an
ant
fie
Fi
U
eed
ach
ded
nce
de r
o ta
Ag/
hern
ern
r, M
___
Proc
ons
nd
t. T
d f
igu
Ura
o
h) a
d le
e ti
rela
arg
/Ag
n Af
Afr
M H
____
ces
stra
fin
The
flow
ure
aniu
of H
as f
each
ime
ativ
get
gCl
fric
frica
H Ko
___
ss d
atio
nall
e n
w d
10
um
Ha
fee
h p
e w
vely
a p
l).
can
an B
otze
___
des
on p
ly,
neu
diag
0: S
m le
arm
ed t
par
was
y e
pH
Th
n In
Bas
e an
____
scri
pla
a n
utra
gra
Simp
each
mon
to t
ram
s e
effi
1.7
he l
stit
se M
nd V
___
ipt
ant
neu
alise
am
plif
hin
ny’s
the
mete
emp
icie
7 d
leac
tute
Met
V Y
___
ion
inc
utra
ed
is g
ified
ng
s g
e ur
ers
ploy
ent
duri
ch
e of
tals
Yaho
____
n
cor
alis
slu
giv
d fl
gol
ran
fo
yed
ur
ing
tem
f M
s Co
ora
___
rpor
sati
urry
ven
flow
d
nium
or t
d t
rani
g le
mpe
Minin
onf
ava
___
rat
ion
y w
in
w d
ore
m l
the
to l
ium
ach
era
ng a
fere
____
ed
n ci
was
Fig
diag
e t
lea
e d
lim
m le
hin
atur
and
ence
___
4 m
rcu
s re
gur
gra
thic
ch
esi
mit
eac
ng.
re o
d M
e 2
___
mai
uit
etur
re 1
am o
cke
cir
gn
the
chin
M
of 5
Meta
011
____
in s
to
rne
10.
of t
ene
rcu
of
e c
ng.
MnO
50°
allu
1
___
sec
tre
ed t
the
r u
uit.
f th
cost
. C
O2 w
°C w
urgy
___
ctio
eat
to H
e M
und
L
he
ts
Con
was
wa
y
____
ons
the
Ha
MET
der
Lab
lea
of
nce
s u
as a
___
na
e ba
arm
TRIX
rflo
ora
ach
the
entr
used
ach
___
ame
arr
mony
IXTM
ow
ator
h c
e l
rate
d to
iev
____
ely
ren
y’s
TM d
w
ry
ircu
eac
ed
o c
ved
___
, le
pu
s go
dem
was
lea
uit
ch
sul
ont
d vi
___
each
ulp
old
mon
us
ach
.
cir
lph
tro
a d
____
hin
an
d re
nstr
sed
h te
Ho
rcu
huri
l th
dire
___
ng,
nd e
eco
rat
d (
est
owe
uit t
ic a
he E
ect
___
RI
effl
over
ion
(‘re
wo
eve
tha
aci
Eh
ste
____
IP a
lue
ry
n pl
eve
ork
er,
at w
id (
to
eam
____
ads
nts
cir
lan
rse
at
a
wou
(98
ab
m in
___
sorp
s ex
rcui
nt
e’
M
red
uld
8%)
bou
njec
___
ptio
xiti
it.
lea
Mint
duc
d st
) w
ut 4
ctio
___
on,
ing
A
ach
tek
ced
till
was
450
on.
k
T
6
T
_
T
e
U
c
3
P
a
th
u
w
A
s
fr
o
s
r
th
a
R
A
p
U
o
e
w
d
The
6th S
T U
___
Thr
ensu
Ura
com
3.3
Pre-
and
he
used
wer
A s
cre
from
of t
iev
etu
he
adso
RIP
A M
prod
U3O
on
equ
was
data
So
Sou
Uday
____
ree
urin
aniu
mpa
-sc
d gr
pla
d in
re m
sche
een
m s
the
ve b
urne
res
orp
P 1
Mc
duc
O8 i
the
uilib
s ac
a w
outh
uthe
yar,
___
le
ng
um
arab
R
ree
rit.
ant
n o
mec
em
ns w
stag
RI
ben
ed
sin
ptio
and
cCa
ced
in s
e i
briu
chie
was
hern
ern
r, M
___
ach
a c
m le
ble
RIP
enin
It
t. A
ord
cha
mati
wer
ge
IP t
nds
to
, w
on
d e
F
abe
d fr
solu
iso
um
eva
ac
n Af
Afr
M H
____
h t
con
eac
e w
P ad
ng
t w
A d
der
anic
ic l
re u
to
tan
s w
the
with
cir
exit
Fig
e-Th
rom
uti
the
m pe
abl
chie
fric
frica
H Ko
___
ank
nsis
ch
ith
dso
of
was
dif
to
cal
lay
use
sta
nks
was
e ta
h fu
cui
ted
gur
hie
m a
on)
erm
er s
e w
eve
can
an B
otze
___
ks
sten
eff
lab
orp
the
de
ffer
ach
ly
out
ed t
age
on
to
ank
ully
it in
fro
re 1
ele
sy
), r
m (
stag
with
ed d
n In
Bas
e an
____
we
nt s
fici
bor
ptio
e le
cid
rent
hie
agi
t o
to s
vi
nto
fa
k fr
y lo
nto
om
11:
co
ynth
repr
(Fig
ge
h a
dur
stit
se M
nd V
___
ere
sup
ien
rato
on c
eac
ded
t o
eve
itat
f th
sep
ia g
th
acili
rom
oad
o th
m RI
Sim
ons
het
res
gur
wo
res
ring
tute
Met
V Y
___
im
pply
ncie
ory
cir
che
d to
per
10
ted
he
para
grav
e s
itat
m w
ded
he
IP 4
mp
stru
tic
ent
re
ould
sin
g a
e of
tals
Yaho
____
mpl
y o
es
y sc
cui
d p
o in
rati
00%
.
RI
ate
vity
siev
te t
whi
d re
RIP
4.
plifi
ucti
sol
ted
12
d b
n an
tim
f M
s Co
ora
___
lem
f le
of
cale
it
pulp
nsta
ing
% u
IP
the
y.
ve b
the
ich
esin
P 4
fied
ion
luti
d in
2).
be a
nd p
me
Minin
onf
ava
___
men
eac
be
e le
p w
all o
g lin
ura
ads
e re
Ed
ben
e m
it
n ex
4 ta
d flo
n w
ion
n Fi
A
ach
pul
wh
ng a
fere
____
nted
ched
etw
each
was
onl
ne
aniu
sor
esin
duc
nds
mov
wa
xiti
ank
ow
was
n co
igur
An
hiev
lp f
hen
and
ence
___
d t
d p
wee
h te
s do
ly 4
to
um
rpti
n fr
ctor
s at
vem
as p
ing
k.
dia
s d
onta
re 3
as
ved
flow
n th
d M
e 2
___
to o
pulp
en
est
one
4 a
th
m re
ion
from
rs w
t th
men
pum
g fr
Le
agr
don
ain
3.
ssu
d. A
w r
he p
Meta
011
____
ope
p to
72
wo
e in
adso
e o
ecov
ci
m t
we
he t
nt o
mp
rom
each
ram
ne
ning
Th
ump
A u
rate
pla
allu
1
___
era
o th
2%
ork
n o
orp
one
ver
ircu
the
re
top
of r
ped
m R
hed
m of
on
g 2
he d
ptio
ura
e of
ant
urgy
___
ate
he R
-
k fo
orde
ptio
e te
ry o
uit
pu
use
p of
resi
. T
RIP
d p
f th
th
2 g/
dem
on
aniu
f 4
wa
y
____
seq
RIP
85
or th
er t
on
este
ove
is
ulp
ed
f ea
in f
The
P 1
pulp
he R
he
/L C
mon
w
um
.5L
as s
___
que
P p
5%
he
to r
sta
ed d
er 4
giv
in
for
ach
fro
e p
tan
p e
RIP
eq
Cl-
nst
as
m lo
L/h
stab
___
ent
plan
w
lea
rem
ages
dur
4 s
ven
the
r re
h R
m
pulp
nk
ente
P se
quil-
(a
trat
m
oadi
an
ble,
____
tial
nt.
wer
ach
mov
s to
ring
stag
n in
e ta
esin
RIP
tan
p m
and
ere
ect
libr
at e
tion
mad
ing
nd 2
, w
___
ly
re
h re
ve w
o li
g t
ges
n F
ank
n tr
tan
nk
mov
d e
d t
tion
rium
equ
n pl
e t
g in
2.4m
with
___
on
ach
sid
wo
imi
the
s. T
Figu
k.
ran
nk.
to
ved
elut
the
n of
m
ilib
lan
tha
n ex
m3
h th
____
n a
hiev
den
ood
it th
mi
The
ure
Pu
nsfe
. T
tan
d co
ted
ad
f th
ad
briu
nt re
at
xce
/hr
he u
___
ba
ved
ce
dchi
he
ini-
e ad
e 1
ulp
er f
The
nk,
oun
d re
dso
he p
dsor
um
esu
80%
ess
r re
uran
___
atch
d.
tim
ips
ov
-pi
dso
1.
wa
from
e pu
wh
nter
esin
rpt
pla
rpti
w
ults
%
of
espe
niu
____
h b
me
, p
vera
lot
orpt
S
as t
m t
urp
hils
r-cu
n en
tion
ant
ion
ith
s w
ap
f 29
ect
um
____
bas
Th
allo
lan
all
pl
tion
Sub
tran
the
pos
st t
urr
nte
n c
n i
47
ere
ppro
9 g/
ive
co
___
sis,
his
ow
nt d
cos
lant
n s
bme
nsf
e bo
se o
the
rent
erin
ircu
sot
70 m
e pl
oac
/L
ely.
onte
___
th
w
wed
deb
sts
t w
stag
erg
ferr
otto
of t
pu
tly
ng t
uit
ther
mg
lott
ch
U3
. Th
ent
___
hus
was
.
bris
of
was
ges
ged
red
om
the
ulp
to
the
at
rm
g/L
ted
to
O8
his
of
f
d
t
d
f
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 61
the PLS at 80 mg/L U3O8 and a barren pulp containing <5 mg/L U3O8 in solution.
Much higher uranium loadings were achieved during the pilot scale test work, however
the PLS did not contain Cl- and had significantly higher U3O8 concentrations in the
PLS.
Figure 12: Demonstration plant adsorption equilibrium isotherms
The silica fouling rate on the demonstration plant was within the limits predicted based
on the laboratory and pilot plant test work.
3.4 Elution circuit
The loaded resin that exited the RIP 1 tank was collected in a designated buffer tank and
once a sufficient volume of resin had been accumulated, an elution cycle was done.
Sulphuric acid at a concentration of 110g/L was used to strip the uranium loaded resin.
The elution section consisted of the following tanks:
• fresh eluant containing 110 g/L H2SO4,
• 2 intermediate eluates,
• a strong eluate tank containing uranium-rich fraction and
• a wash water tank
The elution circuit was run in a closed loop, with only the uranium-rich fraction exiting
the circuit after each elution cycle.
Uranium-rich eluate contained between 1.9 and 3.6 g/L of U3O8. Such uranium
concentrations were relatively low (when related to the stripping isotherm in Figure 4)
due to the limited number of intermediate eluate tanks and ineffective manual control of
0
5
10
15
20
25
30
35
40
0 20 40 60 80 100
U3O
8lo
adin
gs,
g/L
U3O8 in the barren, mg/L
experimental data experimental data
experimantal data demoplant Freundlich Isotherm
Operating line_demoplant Operational stages_demoplant
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 62
the relative resin and eluant volumes. About 30 BVs of eluant was passed through the
resin column over a 6 hour period, consistently resulting in a residual uranium
concentration of < 0.8 g/L on the resin.
4. CONCLUSIONS
Extensive laboratory and pilot scale test work at Mintek resulted in the selection of the
most cost-effective operating conditions for the recovery of uranium from acidic-
leached slurry via RIP. The pilot plant and demonstration plant adsorption and elution
results correlated reasonably well with the predictions that were made from the
laboratory test work. Moreover, these results confirmed the improved performance of
the MetRIXTM
technology under the optimised operating conditions employed.
The demonstration plant campaign was successful and achieved the following:
• The MetRIXTM
RIP process was successfully demonstrated and the process
targets were achieved.
• A relatively low rate of SiO2 fouling was measured under the final optimum
operating conditions.
• Sufficient elution data were generated for the elution strategy optimization that
would be employed on the full scale plant.
Demonstration of MetRIXTM
technology gave Harmony more confidence in
implementation of RIP technology for uranium recovery from their gold ore.
Commercialisation of MetRIXTM
technology in South Africa would give a boost for
RIP application in various hydrometallurgical areas (base metals, rare earths, etc.).
5. ACKNOWLEDGEMENTS
The authors wish to thank the management of Harmony Gold Mining Company Limited
for permission to publish this paper. A special thanks to the teams at both Mintek and
Bateman Engineering Projects for their support during the test work program, design,
construction and operational phase of the MetRIXTM
demonstration plant. The
assistance from the Harmony One Plant personnel was exceptional during the
commissioning and operational phase of the plant.
6. REFERENCES
1. Yahorava, V., Scheepers, J., Kotze M. H. and Auerswald, D. 2009. Impact of
silica on hydrometallurgical and mechanical properties of RIP grade resins for
uranium recovery. The Southern African Institute of Mining and Metallurgy,
Mintek75 Anniversary.
2. Yahorava, V., Scheepers, J., Kotze M. H. and Auerswald, D. 2009. Evaluation
of various durability tests to assess resins for in-pulp applications. The Southern
African Institute of Mining and Metallurgy. The Sixth Southern African
Conference on Base Metals.
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 63
3. Yahorava, V., Scheepers, J. and Kotze M. H. 2009 .Comparison of various anion
exchange resins for the recovery of uranium by means of RIP. Proceedings,
ALTA Uranium Conference, Perth, Australia, 2010
4. Jooste, M., Kotze, M. H., Auerswald, D. 2010. The advantages of true
continuous counter-current elution in uranium processing. Proceedings, ALTA
Uranium Conference, Perth, Australia, 2010.
5. Auerswald, D., Udayar, T., Kotze, M. H. and Scheepers, J. 2011. Operation of a
Resin-in-Pulp (RIP) plant for recovering uranium from a South African gold
pulp. Proceedings, ALTA Uranium Conference, Perth, Australia, 2011.
6. Wilson, A., Fainerman-Melnikova, M. and Soldenhoff, K. 2011. What are the
options for an integrated IX process to recover uranium from saline and hyper
saline liquors? Proceedings, ALTA Uranium Conference, Perth, Australia, 2011.
7. Van Tonder, D. and Van Hege, B. 2007. Uranium recovery from acid leach
liquors: The optimisation of RIP/SX flow sheets. The Southern African Institute
of Mining and Metallurgy. The Fourth Southern African Conference on Base
Metals.
The Author
Tresha Udayar, Senior Engineer, Mintek
I graduated with a BSc. Degree in Chemical Engineering from the University of
KwaZulu-Natal and thereafter joined Mintek in the Hydrometallurgical Division (2008
– present).
I initially worked in the extraction group on laboratory and pilot scale investigations for
base metal recovery. Thereafter moved to the processing group and worked on
laboratory, pilot and demonstration plant test work (at Harmony Gold Mining Company
Limited) for the recovery of uranium via RIP process routes.
The Southern African Institute of Mining and Metallurgy
6th Southern African Base Metals Conference 2011
T Udayar, M H Kotze and V Yahorava
_____________________________________________________________________________
Page 64