subseQ.uent leaching of the. ~ roasted product in presence of. LPG. ~ .80. 'C ... 58.8. 71.7. LPG-pyrolysed products: Effect of roasting time-The percentages of. ~ ... to its boiling point. A definite amount of roasted mass maximum percentages of.
.. 268
INDIAN J. ENG. MATER SCI.,OCTOBER 1994 100
Table
I-Effect
of
roasting
roasted
time
on
product
in
the
subseQ.uent
presence
leaching
of
of
the
~
LPG
~ .80
'C
Roasting: acids min .C,
temperature solid -I, =
particle 6 tog
=
eqliquiddm
size -3 (SjL) and =
650:!:
63-125 ratio pulp
15.C,
LPG
flow
agitation =~m; 0.02 leaching: kgspeed dm
rpm
rate
=
-3, = temperature 292 concentration rpm
2300013
;:.
(HO)f372=
110of
~2=
60
~
40
(H2SO4)
E Roasting
Leaching
time
,
Wt,
time
min
%
metals
dissolved
in
~'
,
;c0
h
HCI
H2SO4
20
~
0 Ti
Fe
Ti
Fe
30
60
90
Roasting I 2
30
38.1 54.5
40.2 55.4
12.0 16.7
17.5 26.6
19.0
31.2
3
56.3
59.5
4
56.7
60.0
5
56.9
19.4
60.3
F.
PI
f
m.axlmum
temp.=:,
(650:!::
15)
conditIons:
45
34.9
42.4
21.9
27.4
2
44.9
50.3
26.2
42.5
3
52.3
56.9
32.2
50.2
4
58.1
59.5
32.5
5
63.2
64.1
32.
7
50.7
6
63.5
64.4
32.
7
50.9
..
-ot?
60
:~:~
3
4
5
;~:~
SfLrati~
=
=
~:~
~~:~
71.2
66.8
48.9
51.7
71.6
67.4
52.3
59.4
71.9
67.8
52.6
59.9
The
mass
(A=
1.5405
A)
Results
and
34.9 46.2
30.4 57.8
and
54.5
62.4
folloWIng
58.2
71.2
systematically
58.8
71.7
LPG-pyrolysed
;~:~
3
90
~:~
Changcs
;~::
41.4
53.2
38.8
34.2
45.2
60.4
41.1
42.0
5
45.8
60.9
41.5
42.5
occurring
leaching
of
H2SO4
with
ilmenite
the
For
treated
leaching,
g
fitted
with
its
(S/L
was
iron
a
=
and
point.
0:02
kg
dm
magnetically
bar.
definite
-3)
was
At
intervals,
were
by
added
by
oxidation
a
eq
dm
the
plastic
solid
coated
(0.5
and
at
analysed
product
g
roasting
effi
ec
t s.o
fth
e
InvestIgated
ilmenite
with
percentages
Ilmernte
at
metals
iron
eq
dm
suI
acid
ph
17
ilmenite.
71
%
obtained
uric
20.5%,
after
75
min
leaching
are
4
of
h
by
the
dissolved of
time
respectively,
in
the
percentages
h
values
75
of
up
iron
The
upto
effect
and
6
of
agents
followed
acid.
These
time.
time
The
easily
respectively,
have
maximum
leaching
roasting
in
and
the
roasting
both
titanium
dissolved
are
as
percentages
the
be
I.
iron
times
1,
sharply.
of
Table
and
versus
in
could
dIfferent
in
roasting
Fig.
increasing
-3
given
titanium
maximum
~ecreased
andiron
at
are
in
dissolved
with
~oasted
HCland
different
the
of
the
obtaIned
dissolved
that
of
50cm36geqdm-3
plotted
tIme
g
and
e.
leachi~g
times
percentages
6
th
been
of
acids
then
sulphuric
59
were
the
of
leaching
found
non-treated
iron
used.
about
r eafter
o~
1
and
and
LPG-roasting
of
was
time-The
in
the
increased
maximum
e
percentages
and
mass
in
1710
experiments
idea
dissol~ed
to
of
is
plate
titanium
roasting
estimated
are
mass
X-ray
PW
radiation
mA
roasting
different
in
been
small
20
have
maximum
min
cm3)
and
acidl7.
-3
and
Th
iron
percentages
(500cm3)
by
Philips
overall
temperatures,
It
roasted
content
nitric
and
hot
of
diluted
with
g
magnetic
aliquots
titanium
HCI
an
equIvalent
titanium
flask
and
a
-3
analysed
CuK(Xt
~V
conditions
a~d
dissolved
non-treated
(6
conical
(HCI)f372
products:
H2SO4
on
get
of
roasting
concentrations.
amount
removed,
for
after
a
duplicate
colorimetrically
dm
the
acid
heated
A
eq
agent
in
agitated
solution
content
same
taken
reflux
g
cm31eaching
was
boiling
6
40
for
masses
exhibited
also
parameters
titanium
dissolved
for
the
50
metals
in
obtained
with
were
of
product
those
H2SO4)
roasting
percentages
leached
HO-or
to
during
the
rpm
(H2SO4)
preliminary
..,
~::~
4
comparing
292
Leachmg
6geqdm-3,
leachin
The
by
=
Ni-filtered
of
to
Effect
~
(5
Discussion
out
74.7
75.8
I.
computerized
Roasting-Several
31.9 68.0
78.5
23°cm.3ffi1n
speed
was
A
using
77.8
5
dissolved
=
agitation
diffraction.
50.1 72.3
75.3
=
0.02kgdm-J,
roasted
powder
3
78.2
metal
50.4
I 2
4
of
bollmgpomt(IIO.C),[Acld]
rpm
carried
75
percentage
C,~~Gflo.wrate
temp
diffractometer
~
weIght
«D):Fe,H2S04.Ro.astmgcondltlons:partlcleslze.=_63-125~m,
31.9
I
120
min
h)versusroastmgtlme'(E?)Ti,H~;.(O):Fe'1:I0;~~):TI,H~4and
31.5
19.8
I
Ig.
time,
leachings
roasting.
in
for
increased
the
to
for
Similarly,
'"
the
BISWAS et alo: DISSOLUTION OF ILMENITE
when hydrochloric acid (6 g eq dm -3) is used as leaching agerit,the maximum percentages of titanium and iron dissolved are increased from 53.5 and 60% for the non-~reated ilmenite to 78.4 and 75.6%, respectively, for roasted ilmenite obtained after 75 min roastingo It appears
that on heating
ilmenite
(TiFeO3
mixed
BY ROAS11NG
269
72.9% iron are obtained, With further increase in the roasting temperature, up to 800°C, the maximum percentages of metals dissolved are decreased sharply. The roasted mass at 800°C for 75 min gives 28.7% titanium and 51.7% iron dissolutions in 6geq dm -3 hydrochloric acid and 17.5% titanium and 48.7% iron dissolution
in 6 g eq dm -3 sulphuric
acid.
possibly with Fe203 1.5 TiO2) in the presence of LPG at ,...,650 °C, the ferric oxide in the pseudo-brookite
From these results, it is concluded that the optimum roasting temperature is 700°C and the roasting above
phase (2Fe203. 3TiO2) is converted gradually into ferrous oxide and ilmenite phase due to reduction oth h d b (2F 0 3T oO CjH2 3F 0
700°C will considerably decrease the dissolution characteristics of the roasted mass together with the
WI
y
rogenorcar
on
TiO2
+ FeO) produced
LPG
at
e2
from
3.
1
2~
0
..0 the
phase
IS
temperatures
more
dIssolved
0
hydrochlonc
m
sulphunc
and
the
phase
transItIon
0 1 d o h o 75 0 h 0 d o0 Iscomp ete WIt m mmatt eroastIngcon ItIons .0 0 .presen stated, If the roastIng IS prolonged after thIS tIme, the 0 0 0 0 be h 0 tlmemte phase IS converted mto another phase (may t
fT oO
...0
e mIxture
0
susceptIble ° t o mves
to
2 an
11 0 F ) h o h IC e w IC
meta
leachmg
wIth
the
acIds
0 1 IS ess
under
t o
Iga
E;'R: !IJect
Ions,
0
if
roasting
t percen
d
1
ft ages
0
0
Th
temperature-
't 0 1 amum
d
o Iron
an
e
0 maxImum
d . 1 d ISSO ve
o m
'
0
dIssolved
g eq
0
agamst
the
roastIng
temperature,
With both leaching agents, it is found that the maximum weight percentages of titanium and iron dis~olved pass through maxima: at a roasting temperature of 700° Co Roasting at 700°C for 75 min gives a product which gives, 82.8% titanium and 79.1 % iron dissolution in 6 g eq dm -3 hydrochloric acid, whereas in 6 g eq dm -3 sulphuric acid medium, the
maximum
dissolutions
of 65%
1
titanium
e
pyro
carbon
YSIS
s h ou Id
0
give "
and
u
reac
Ion
:
~
carbon 0 0
2
and
LPG
at
an d
ot h er
unsaturated
IS
nven
0
0
m
themvestIgatedclosed
e ng
tat
becomes b car
bsence
on
0
system.
f
It
0
IS ltkely, however, that the constItuents of the used 01 ' l' 1 mem t e may some h ow ca t a 1yse lor t he d ot O t b ~ ecomposl Ion 0 car on lromme th ane pro d uce d on I 0 Th o o. pyro YSIS. IS proposItIon has been suggeste d on t h e ground that the carbon deposition takes place only over the ilmenite powder, but not on the edges of the boat or on any other places within the tube. Since roasting time is quite long (over 1 h), it is not possible to perform the roasting at higher temperature due to the~ enormous quantities of carbon deposition. Effect
of
LPG-jiow
0 =60 -III "0 -"0
? -,~ 60
~ r rate-Fig.
.
to
---'
'
~~ 40
3
represents
'
' ;~':- -
E E ~
"
',,'
. --
o~ 20 _.0 ~
~
0
h ane
'
o.
monoxIde
:i 80
0
m
met
temperat ure 1ower th an 700°C and 0 O to l' ft t t 550 °C Th o sIgm can a .IS reac Ion lor d '0 0 l' eposltIon IS very un 1 ke 1y d ue to tea h
"0 ? ."0
~ 20 .,,
propane
.
~80
',,' JY
or
saturated
100
E ~ 0E
ane
weIght
.
' ,
roasted
h d b b t t b 18 H .m t h e y rocar ons u no car on. owever, t t d b d .t .0 1 s u y car on eposl Ion on 1 memte has been b d t 600 ° C Th b d o0 0 serve even a .e car on eposltIon to 2 CO ~ CO + c o d o t th 0 h
100
~E40
the
o
0 molecular
~ ",
on
on 1 y h y d rogen
' lower
deposition
f b t
,
0
6
-3 h d hI 0 d I h oo d 1 tt d ' m y roc onc an su p unc aCI are p 0 e m ' 0 0 Flgo 2, as the maXImum weIght percentages of metals
d
high
and 0 0
solutIons
associated
maTsh s.
800°C
0 tlmemte
0
acId
of
0'
0 PossIbly,
used,
eastly
0
e.
the decomposition
6QO
700
800
Roasting t.mp.ratur.,.c Fig. 2-Plot o! maximum weight per~ntage of metal dissolved (? h) versusroasting temperature,(8~: TI, Hc:I;o(O): Fe,~O;o(~): TI, H2SO4an~(CD):Fe, H~SO4'Roastlngconditlons: partIc~eSIze=.63 -1251!m, time = 75 mIn, LPG flow rate = 230cm3mIn " leachIng d o .° Fo I con Itlons are as m Igo
0
0
100
200
300
LPG flow rate,cm3min-1 Fig. 3-Plot of maximum weight percentage of metal dissolved (5 h) versusLPGflowrateo (8): Ti, HO; (0): Fe,HCI; (~): Ti, H.,SO4 and (.(1): Fe, H2SO4oRoastingconditions: particle size = 63--125 Ilnl, time = 75 mill, temp = (700 + 15 dlOuo ) .CoLeaching con -onsare as in Figo I
270
BISWASet01.:DISSOLUTIONOF ILMENITE BY ROASTING
...flow of particle size on roasting
ra te of 230 cm3 min -1.
.
It is decreased
to only
.-
' = 75 ' t 15)C LPG-fl RoasU..ng. tIm t ure = (700+ e IDln, empera -, ow rate = 230 cm3min-l; leaching: temperature = 110.C. acid concentration= 6g eq dm-3 and pulp agitationspeed= 292rpm (HCI)/372 rpm (H2SO4)
39".74 81 7 and 78 °1 t" 1Olor gas fl ow rate 0f 150,]90,270 d 3]0 3 .-1 . t" an cm mm , respectIve Iy. I t may, t h erelore, be concluded that the optimum LPG flow rate should be about 230 cm3 min -1 and that roasting in presence of a
Particle Max wt % metalsdissolvedMaxwt % metalsdissolved .. HCI .In 6 g eq d m -3 H2SO4 Size,I!m In 6 g eq d m -3
flow rate should greatly decrease the dlower . ] gas t. t f t t .. t d . ISSOU Ion percen age 0 I allIum assocla e WIth ...
Table
> 63 125
2-Effect
Ti
Fe
Ti
Fe
82.8 85.0
80.6 82.1
44.7 52.3
36.5 60.8
< 125 82.8 79.1 65.0 77.8 .cm Table 3-X-ray powderdiffraction patternsof ilmeniteand the LPG-roastedilmenite(at700.C,for 75min presenceof LPG flow rate of 230 cm3min-l) lime .t starting m sample e d, A
(1110) x 100
.t
II
from ASTM mem ecard d, A
A -I-/, . I k uultlona pea s
38.7 23.4 12.6 13.6 11.5 30.1
Q-quartz (minor) H-hematite (minor)
...
2.177 2.103 1.831 1.653 1.635 1.621 1.434
30.0 70.0 2.0 30.0 40.0 55.0 30.0 35.0 2.0 2.0 1.0 2.0 9.0 3.0 1.0
hIgher amounts of carbon deposItIon on the roasted mass. The possible higher residence time of the gas together with little temperature variation in furnace at lowcr ..
gas flow ratc
may be attributed
to higher
de~osl~lo_nIof carbon, below the gas flow rate of 230 mm . Effect ofparticle size-The results given in Table 2 indicate that the roasting and subsequent leaching with hydrochloric acid is little affected by the particle
t lmenIe
size of ilmenite used in roasting. However, for sulphunc acId as leachIng agent, the roastIng as well as
d, A
(1110) x 100
the subsequent dissolution of titanium and iron is decreased with decrease in the particle size. This may be due to enhanced resistance to diffusion through a
3:723. 2.745 2.539 2.347 2.231 1.865 1.723 1.505 1.469
34.9 100.0 57.2 11.3 10.8 35.\ 29.1 17.2 17.3
less porous mass. Roasted Product-Knowing the best condition for theroastingofilmenite,about60gilmenite(in]2sets) have been roasted at (700 :t 15)OCfor 75 min at LPG flow rate of230cm3 min-i. To verify if there was any h .. 1 . d . h . c ange I? I m~rute unng t e roastIng process, t he X-ray dIffractIon patterns of the non-treated and roasted ilmenite were taken for comparison. The d spacings of the two samples are given in Table 3, which
9.923 8.310 4. I 77(Q) 3.454 3.336(Q) 3.236 2.789 2.514(H) 2.436(Q) 2.023 1.632(H)
6.4 44.1 4.2 11.8 51.9 5.1 38.9 5.3 4.2 14.4 10.1
also includes the dvalues of synthetic ilmenite (pure) colle~ted from the ASTM cards. It IS seen from1he table that the X-ray pattern of pure ilmenite with high intensities also appeared in non-treated and the LPG roasted ilmenite samples. Low intensity peaks disappeared. Some additional k .h d ... d . pea s ~It I?o erate m:en.sltl~s appeare m t he source IlmenIte sample, IndIcatIng the presence of other minor crystalline phase (quartz 4.00 & 3.29 .&. and hematite 2.693, 1,694, 1.688 & 1.454 .&.) in the sample as expected. These additional peaks are
LPG
-roas
(1110 x 100
Commonpeaks 3.723 41.4 3.737 2.745 100.02.754100.0 2.534 70.0 2.544 2.344 34.1 2.349 2.231 22.4 2.237 1.865 30.3 1.868 1.725 33.7 1.726 1.503 18.6 1.506 1.467 10.3 1.468 4.000(Q) 3.329(Q) 2.693(H) 1.694(H) 1.688(H) 1.454(H)
ted I..
'
1..~:12(~) ~:~ Q-quartz (major) H-hematite (major)
almost disappeared in the LPG-ro~sted mass to give anot~er ~ew set of peak pattern. HIgh value of the {I spacIng In the roasted mass ({I = 9.923 & 8.310.&.)
f
suggests the formation impurities in ilmenite.
of clay like phase from the
graphIcally the maxImum weIght percentage 0 metals dissolved versus gas flow rate (cm3 min -I) in roasting. It is observed that the maximum weight percentages of both titanium and iron in either of the
Leaching-The material prepared by roasting at (700:t 15)OCfor75 minat LPG flow rate of230cm3 min -I has been used to investigate the effect of various
leaching agents increased with increasing the gas flow rate sharply upto 230 cm I min -I and then gradually
parameters mass.
decreased; particularly in case of titanium dissolution. For example, about 83.2('/0 of titanium was dissolved from the roasted mass in presence of gas
f;tfect {?f aci{1 concentration-The maximum percentages of titanium and iron dissolved in both acids of different concentrations are represented
on leaching characteristics
of roasted
BISWASetaL: DISSOLU110NOF ILMENITE BY ROASTING 100 ;! ~ ~ ~ ~ ~ E .g ~
271
graphically in Fig. 4. It is observed that the maximum weight of titanium dissolutions are decreased significantly for both acids at low concentrations, particularly below 6 g eq dm -3. The iron dissolutions also decrease similarly. In the acid concentration above 6 g eq dm -3, the maximum dissolution percentages show minor increase with increasing concentration. The effect of acid concentration on the titanium and iron dissolutions from the roasted mass is very sharp in the acid concentration range of 4-6 g eq dm -3 for either acid. It is, therefore, concluded that
80 60 40 20 0 0
2
4 6 8 [Acid),g eq dm-3
10
Fig. 4-Plot of maximumweightpercentage of metalsdissolved(5 h)versustheconcentrationof leachingacids.(e): Ti, HCI; (0): Fe, HCl; (~): Ti, H2SO4and «1): Fe,H2SO4.Roastingconditions: particlesize = 63-12511m, time = 75min, temp = (700:t 15).C, L~
