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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~