lead recovery from metallurgical slag by flotation paulo f. a. braga, joão a. sampaio, carlos a. m....
TRANSCRIPT
Lead recovery from metallurgical slag by flotation
Paulo F. A. Braga, João A. Sampaio, Carlos A. M. Baltar, Arnolfo M. Coelho, João A. F. Nunes
•Brazil does not have a primary production of refined metallic lead. The whole production is based upon the recycling of automotive, industrial and telecommunication batteries.
•In 2010 the battery recycling industry produced 115,000 t of metallic lead from 2nd production.
•Moura is the largest recycler/ manufacturer of batteries in Brazil (7.106 units/y).
INTRODUCTION
•Operated at 90% efficiency (the ratio of the number of recycled batteries and the number of new batteries produced).
•With the increase in price of metallic commodities such as lead, several studies were carried out, aiming to:
minimize the loss of this metal in the industrial processes or;
for an additional recovery of the lead from metallic slags.
INTRODUCTION
• Recycling process starts with the removal of metallic parts such as connectors and screws and subsequently with the reduction of the battery scrap and separation of the plastic casing from the lead grates and lead paste.
• Lead paste follows the process of separation, casting, refining and manufacturing of new batteries.
• Plastic is recovered and reused in the production of casing and cover for the new batteries.
• Acid solution is neutralized by lime or limestone.
INTRODUCTION
•A typical automotive battery scrap contains:
INTRODUCTION 32% Pb
3% PbO
17% PbO2
36% PbSO4
• The main reactions of the metallurgical processes are:
2PbSO4 + Na2CO3 + Fe + 9C → 2Pb + FeS.Na2S + 9CO + CO2 (1)
PbO2 + C → CO + PbO (2)
2PbO + C → CO2 +2Pb (3)
PbSO4 + 2C → PbS + 2CO2 (4)
• The present research work aimed to study the flotation process on pilot scale for the
recovery of lead from metallurgical slags rising from the recycling process of
automotive batteries.
• There were also several tests carried out in gravity concentration equipment with the
purpose of assessing this process route for the recovery of lead concentrate.
OBJECTIVE
Chemical analysis of the slag sample:
Compounds Grade (weight %) Compounds Grade
(weight %) Compounds Grade (weight %)
Cr2O3 0.60 K2O 0.21 ZnO 0.80TiO2 0.07 P2O5 0.28 CaO 1.20
CuO 0.12 BaO 0.31 SiO2 2.58
MnO 0.14 Cl 0.66 Na2O 4.37Al2O3 0.16 SnO2 0.72 PbO 16.90Fe2O3 41.60 SO3 29.80
METHODOLOGY
X-ray diffraction (XRD):
metalic lead, magnetite (Fe3O4), hatrurite (Ca3SiO5), galena (PbS); jamesonite (Pb4FeSb6S14) and cotunnite (PbCl2).
Nominal aperture size (µm) Weight (%) Pb Grade (%)
3,800 3.62 17.321,680 1.30 23.641,190 1.42 17.51840 1.31 17.47590 2.49 19.09420 1.60 12.56297 1.34 12.31210 2.64 17.40149 3.41 22.63105 3.80 20.1374 6.12 19.8053 3.00 20.0544 8.22 19.0637 7.78 15.34-37 51.91 12.61
Average 100.00 15.37
Screen size distribution and lead grade per size fraction.
METHODOLOGY
3,8001,680
1,190840
590420
297210
149105 74 53 44 37 -37
0
10
20
30
40
50
60Weight (%)
Pb grade (%)
screen size, mm
Equipments:• jaw crushers• vibrating screen• conditioners• reagent feeder• flotation cells type Denver nº 7 Sub-A• Wilfley laboratory concentrating table• Humphreys spiral concentrator• crossflow 2x4 .
METHODOLOGY
Metering pumps
Flotation Cells
Flotation Circuit
potassium amyl xanthate ( PAX) – collector; methyl isobutyl carbinol (MIBC) - frother;sulphuric acid (H2SO4) - pH adjuster.
Reagents:
Sample Preparation
METHODSSlag of lead (25 t)
Jaw crusher (1”)
Screening (2 mm) Jaw crusher (1/2”)
Screening (2 mm)
Hammer mill (5 mm)
Screening (2 mm)
Screening (-0,7 mm)
Homogenization pile
Discard (+ 0,7 mm)
Flotation Procedure
Slag : 105 - 37 µm (size);
pH: 8 (sulphuric acid);
50 kg/h: slag (flow rate);
150 g/t: PAX (collector);
50 g/t: MIBC (frother).
Reagent system and operating conditions in laboratory scale for flotation tests were previously defined by Baltar (2005).
conditioner tank
Bomba
pump
rougher
Concentrate
feed tank
dosage pump
flotation cell
collector: potassium amyl xantate
frother: MIBC
Tailings
METHODS
Weight recovery (%) Pb (%) Pb recovery (%)Rougher concentrate 38.4 48.8 79.8
Rougher tailings 61.6 7.7 20.2Feed 100 23.5
Flotation test
RESULTS
Wilfley laboratory shaking table test
Products Bulk samplePb (%) Pb recovery (%)
Concentrate 55.9 37.2Middlings 15.6 8.3
Tails 11.8 54.4Feed 17.2 -
ProductsRougher concentrate
Pb (%) Pb recovery (%)Concentrate 72.3 56.5
Middlings 24.4 30.4Tails 19.1 13.1Feed 48.8 -
RESULTS
Products Weight recovery (%) Pb (%) Pb recovery (%)Concentrate 14.4 46.0 34.7
Tailings 85.6 14.6 65.3Feed 100.0 19.1 100.0
Crossflow hydraulic classifier test (elutriation test)
Spiral concentrator testProducts Mass recovery (%) Pb (%) Pb recovery (%)
Concentrate 28.8 22.9 42.1Tailings 71.2 12.7 57.9
Feed 100 15.6 100.0
RESULTS
• Main composition of lead metallurgical slag is: 16.9% PbO, 29.8% SO3 and 41.6% Fe2O3.
• The main mineralogical species are: magnetite (Fe3O4); hatrurite (Ca3SiO5); galena (PbS); jamesonite (Pb4FeSb6S14); cotunnite (PbCl2) and metallic lead.
• The fine fraction -37 m represented 51.9% of the bulk sample and contained 12.61% of lead.
FINAL REMARKS
• The flotation at pilot scale produced lead concentrates at 48.8% Pb and a concentration ratio of 2 and 80% recovery. These results were obtained after fine fraction removal (-37 μm);
• Shaking table tests produced a concentrate at high grade, 55.9% Pb, and 37.2% recovery from the bulk sample;
• Reprocessing the rougher flotation concentrate in the shaking table produced a final concentrate at 72.3% Pb, concentration ratio of 1.5 and 56.5% recovery.
FINAL REMARKS
