Liu Sanping - Beijing General Research Institute of Mining and Metallurgy - Leaching processes for...

TWO STAGES OF LEACHING

PROCESS FOR NICKEL LATERITE

ORES

Representor：Liu Sanping

Beijing General Research of Mining and Matallurgy

E-mail: [email protected]

Shanghai, May 25th 2016

CONTENTS

• Introduction

• Atmospheric Tank – Autoclave Combined Leach

• Autoclave – Autoclave combined Leach

• Conclusions

INTRODUCTION

High pressure acid leaching (HPAL): a standard technology for limonite ores.

•High nickel extraction (ENi >97%);

•Low acid consumption (iron precipitated as hematite);

•High CAPEX and OPEX (high pressure up to 5.5MPa, high temp. up to

250~270C).

Atmospheric tank leaching (ATL): a alternative technology for saprolite ores.

•Low CAPEX and OPEX;

•Lower nickel extraction (ENi 85~93%) ;

•Higher acid consumption (iron leached as Fe3+）

INTRODUCTION

What is the suitable process for the TRANSITION laterite or MIDDLE Ni/Fe/Mg

grade laterite(Ni 1.2%~1.5%) ?

Limonite (high Fe, low Mg)

Saprolite (low Fe, high Mg)

INTRODUCTION

The impact factors for Ni recovery during laterite acid leaching :

•Acid Consumption;

•Reacting Temperature;

•Residence Time；

•Particle Size;

•Solid Concentration;

•……

The reason for Limonite High pressure acid leaching (HPAL):

High Ni recovery needs high Acid concentration(25~35 g/L) in the residual slurry;

Fe precipitation in the high acid concentration slurry needs high temperature

(250~270 oC ).

INTRODUCTION

BGRIMM idea for transition laterite:

HPAL is divided two stages:

Primary leaching: feed – high Fe laterite(smaller particle size), high acid

concentration leaching to make sure high Ni Extraction;

Secondary leaching: feed - high magnesium laterite (bigger particle, saprolite),

high temperature(~150 oC) to make sure Fe precipitation with saprolite leach;

Advantages:

•Reacting Temperature: From 250 oC to150 oC;

•Reacting Pressure: From 5 MPa to 0.5 MPa;

•Reducing Capex and Opex dramatically.

INTRODUCTION BGRIMM’s special flowsheet — an inverse leaching process

Primary leaching: atmosphere tank leaching

•Feed: small particle size portion of laterite ores;

•~95 C, input: 100% acid, 97~99% ENi & EFe;

Secondary leaching: autoclave leaching

•Feed: big particle size portion of laterite ores;

•Around 150~160C, no acid input, 500~600kPa;

•Total ENi 93~96%;

•No acid consumption for 90~95% Fe.

The leaching combination changes the BIG DIFFICULTY of HPAL to “a

common routine process”!

Atmospheric Tank – Autoclave Combined Leach

Effective size classification of laterite ores for the primary and secondary

leaching stages into order to enhance the ENi and to reduce acid

consumption.

- The fine portion ore with higher Fe and lower Mg is fed into the

primary leaching; and

- The coarse portion ore with lower Fe and higher Mg is fed to

the secondary leaching.

A primary to secondary feed ratio (65/35) was determined to be the

optimum to minimize the acid consumption.

Bench Scale Test – Leaching feed classification

Transition

Laterite

-1mm = 47%

+1mm = 53%

High Mg

Low Fe

Grinding

Secondary leaching feed

35% of total feed

(low Fe, high Mg)

Primary leaching feed

65% of total feed

(high Fe, low Mg) High Fe

Low Mg

Feed Distribution

Bench Scale Test – Ore Characteristics

Grade distribution (GD) analysis and Head grade of the primary and secondary

leaching feeds

Grade Distribution Analysis of the

Blended Ore

Feed Assay, %

Ni Fe Si Mg

Primary leach 1.54 18.68 15.19 12.63 Secondary

leach 1.47 11.95 17.76 16.82

The Primary and Secondary Feed Head Grade

Bench Scale Test – Primary Leaching

Laboratory Set-up

The objective of primary leaching is to

extract as much Ni as possible, while

maintaining a reasonably low acid

consumption.

The -1mm slurry from scrubbing and

screening is thickened to the required

solid density for leaching.

During leaching, 98% sulfuric acid, is

added as the leaching agent.


80

82

84

86

88

90

92

94

96

98

100

0 1 2 3 4 5 6 7

Ni E

xtra

ctio

n, %

Leaching Time, hrs

0.90 acid/ore (PL-15)





ENi vs acid dosage, g-acid/g-ore


80

82

84

86

88

90

92

94

96

98

100

0 1 2 3 4 5 6 7

Ni E

xtra

ctio

n, %

Leaching Time, hrs

33% solids( PL-12)

36% solids (PL-23)

39% solids (PL-18)

ENi vs retention time at different slurry density


ptimum conditions:

Feed slurry solids density, % 36

Acid dosage, t-acid/t-ore 1

Temperature, oC 95-100

Retetion time, h 5

Results

Metal extraction (%):

Ni 98.54, Fe 71.66, Mg 97.37

Metal concentration in PLS (g/L):

Ni 5.10, Fe 47.48, Free acid 24.48

Residue (%):

Ni 0.05, Fe 9.80, Mg 0.82, Mass remaining 49.00

Determine optimum parameters - results

Bench Scale Test – Secondary Leaching

To produce an Fe depleted PLS

- Fe concentration is <5g/L, or 50% of Ni concentration

To reduce overall acid and reagent usage

- Take advantage of the acid generated to leach

laterite wiht high Mg grade

Governing reactions:

(1) Fe2(SO4)3 + 4H2O = 2FeOOH + 3H2SO4

(2) MgO + H2SO4 = MgSO4 + H2O

Objectives

One gram Fe3+ precipitated will release 2.6 g acid Autoclave – experimental setup


Effect of the prim/sec ore ratio

62.79 60.80 56.34

73.77

58.01

85.70 90.42

93.81 91.60

80.65

-20.00

0.00

20.00

40.00

60.00

80.00

100.00

48/52 (PS-14)

45/55 (PS-17)

51.5/48.5(PS-18)

54/46 (PS-19)

43/57 (PS-20)

60/40 (PS-23)

62/38 (PS-24)

65/35 (PS-33)

68/32 (PS-26)

58/42 (PS-27)

%Ex

trac

tio

n

Primary:Secondary Ore Ratio (Test Case)

Ni and Fe Extractions

Fe Extractions

Ni Extractions



4.23 4.40

4.10

4.48 4.28

4.44

5.26

4.74 4.78

0.25 0.26 0.36 0.39

0.75 1.01

1.75

4.33

0.63

0.00

1.00

2.00

3.00

4.00

5.00

6.00

48/52 (PS-14) 45/55 (PS-17) 51.5/48.5(PS-18)

54/46 (PS-19)43/57 (PS-20)60/40 (PS-23)62/38 (PS-24)65/35 (PS-33)68/32 (PS-26)58/42 (PS-27)

Co

nce

ntr

atio

n, g

/L

Prim to Sec Ore Ratio (Test Cases)

[Ni] and [Fe] in PLS

[Ni] in PLS, g/L [Fe] in PLS, g/L



0.00 0.00 0.00 0.00

1.88

3.30

13.18

16.48

0.00

3.75 3.87

4.41

1.71 1.51

0.90

0.58

2.50

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

pH

Fre

e A

cid

, g

/L

Prim to Sec Ore Ratio (Test Cases)

Free Acid of PLS, g/L

pH of PLS


Effect of the residence time

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

-20.00

0.00

20.00

40.00

60.00

80.00

100.00

0 0.5 1 1.5 2 2.5 3 3.5

Co

nce

ntr

atio

n, g

/L

Ext

ract

ion

, %

Time, h

Extraction and metal concentration kinetics

Fe extraction

Ni extraction

Mg Extraction

[Ni] in PLS, g/L

[Fe] in PLS, g/L

[Mg] in PLS, g/L


Optimum Parameters

Primary:Secondary Feed Ore Ratio – 65:35

Residence Time – 2hrs

Temperature – 150oC

Determination optimum parameters - results

Pilot Plant Test – Leaching circuit

Pilot plant photos

Pilot Plant Test – Overall Scenario

Pilot Plant Test – Primary Leaching

Primary Leach Stage Operating Conditions

Feed slurry concentration, % solids

36%

Acid:ore ratio, t/t 1

Operating temperature, oC 95

Reaction time, hr 5

Ore Feed grade, %

Ni 1.52

Fe 20.86

Mg 11.75

Pilot Plant Test – Secondary Leaching

Secondary Leach Stage Operating Conditions

Feed slurry concentration, % solids

36

Prim:Sec ore ratio 65:35

Operating temperature, oC 150

Reaction time, hr 2

Fresh Sec Ore Feed grade, %

Ni 1.46

Fe 9.06

Mg 18.19


Composite daily averages from 29 May to 17 June 2013


Composite hourly and daily % Ni extractions


Hourly and daily Ni and Fe concentraction of PLS


4,300 kg of feed ore was leached. Leaching performance achieved is near

identical to that obtained during the bench-scale test.

Primary Leach Results Secondary Leach Results

Ni Fe Mg Ni Fe Mg

Residue Solids Grade (%) 0.05 8.38 1.32 0.15 21.11 1.57

Residue Solution Concentration (g/L) 5.08 56.70 40.11 5.29 3.40 49.41

Solids-based Metal Extraction (%) 98.40 80.63 94.56 93.44 19.94 92.65

Residue Free Acid (g/L) 18.85 15.39

% Mass Remaining (%) 48.10 64.37

Bankable Feasibility Study

General Parameters adopted

Item Amount

Operating Hours 7884 hrs per year

Leach Feed Ore 512,444 t

Ni Grade 1.496 %

Ni Extraction

(Leaching) 94.08 %

Ni Recovery (Overall) 91.64 %

Annual Ni Production 7,027 tpa

Life of Mine 20 years

CAPEX 134 million US$

OPEX 2.65 USD/lb Ni

The CAPEX and OPEX of

BGRIMM’s Inverse leaching

process were less than 10

USD/lb-Ni and 2.65 USD/lb-Ni.

Just 40% of HPAL’s CAPEX.

Consume at least less 290kg-

acid/t-ore than ATL

Ni Extraction is at least 10%

higher than ATL

Autoclave-Autoclave Combined leaching

For some HIGHER Fe transition lateriate:

Feed Weight, % Assay, %

Ni Fe Si Mg

Primary

leach 63% 1.23 28.71 10.36 4.11

Secondary

leach 37% 1.19 11.28 13.42 5.78

Atmospheric Primary leaching

R² = 0.8762

R² = 0.6176

40.00

42.00

44.00

46.00

48.00

50.00

52.00

84.00

86.00

88.00

90.00

92.00

94.00

96.00

98.00

20.0 22.0 24.0 26.0 28.0 30.0 32.0 34.0 36.0 38.0 40.0

Re

sid

ue

So

lids

Frac

tio

n (

%)

Ni E

xtra

ctio

n (

%)

Feed Fe Grade (%)

Ni Extraction (%) Residue Solids Fraction (%) Linear (Ni Extraction (%)) Linear (Residue Solids Fraction (%))

ENi vs Feed Fe Grade

ENi vs Residence time

R² = 0.9939

R² = 0.7425

45.00

46.00

47.00

48.00

49.00

50.00

51.00

52.00

53.00

54.00

92.00

92.50

93.00

93.50

94.00

94.50

95.00

95.50

96.00

4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

Re

sid

ue

So

lids

Frac

tio

n (

%)

Ni E

xtra

ctio

n (

%)

Leaching Time (hrs)



ENi vs Residence time at different acid consumption

85.00

86.00

87.00

88.00

89.00

90.00

91.00

92.00

93.00

94.00

95.00

0 2 4 6 8 10 12 14 16 18 20

Ni E

xtra

ctio

n (

%)

Leaching Time (hrs)

AL-21 (acid/ore = 1) AL-24 (acid/ore = 0.95) AL-25 (acid/ore = 1) AL-27 (acid/ore = 0.95)

Log. (AL-21 (acid/ore = 1)) Log. (AL-24 (acid/ore = 0.95)) Log. (AL-25 (acid/ore = 1)) Log. (AL-27 (acid/ore = 0.95))


Normally, the disadventages of Atmospheric Tank leaching ( Primary leaching )

as Fe grade >25% in the feed ore:

The residence time will be very long to get a acceptable ENi

In order to speed up the primary leaching, autoclave leaching is tried to instead of

atmospheric tank leaching.

Autoclave primary leaching operating conditions:

Reacting Temperature: 150 oC

Residence Time: 2 hrs

Autoclave-Autoclave Combined leaching

Autoclave Primary leaching

45.00

46.00

47.00

48.00

49.00

50.00

51.00

52.00

53.00

54.00

92.00

92.50

93.00

93.50

94.00

94.50

95.00

95.50

96.00

- 1.0 2.0 3.0 4.0

Re

sid

ue

So

lids

Frac

tio

n (

%)

Ni E

xtra

ctio

n (

%)

Leaching Time (hrs)


ENi vs Residence time at different tests

The ENi of autoclave leaching at 2 hrs is close to the atmospheric tank

leaching at 8~10 hrs. the leach speed is accelerated dramatically (only

20%~25% of the atmospheric tank leaching) .

The Capex and Opex will be lower than the previous process.

Conclusions

BGRIMM’s Two-stage leaching(TL, Atmospheric-Autoclave,

Autoclave-Autoclave) process is very flexible to treat transition

laterite ores with high Ni extraction.

TL consumes at least less 290 kg acid/t-ore than the ATL and its

nickel extraction reached more than 92%, at least 10% higher

than ATL.

TL’s CAPEX and OPEX were less than 10 USD/lb-Ni and 2.6

USD/lb-Ni, respectively, just accounting for 40% of the HPAL’s

CAPEX and 65~70% of the ATL’s OPEX.

Acknowledgement

The authors would like to express thanks to our

colleagues in BGRIMM, who have worked for many

years in the related researches.

Thanks！

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