recovery of aluminum from industrial and electronic waste via melting with salt flux

RECOVERY OF ALUMINUM FROM INDUSTRIAL AND ELECTRONIC

WASTE VIA MELTING WITH SALT FLUX

Ernesto de la Torre, Santiago Yépez, Alicia Guevara

ESCUELA POLITÉCNICA NACIONALQuito - Ecuador

Facultad de Ing. Química y Agroindustria

Departamento de Metalurgia Extractiva

ALUMINUM PRODUCTION FROM BAUXITE

ALUMINUM RECYCLING

ENERGY CONSUMPTIONEnergy Consumption [kWh/ton]

Aluminum Production from Bauxite (Primary

Production) Aluminum Recycling

(Secondary Production)

17000 750

ALUMINUM RECYCLING ALLOWS TO OBTAIN A 95 % SAVE OF THE ENERGY CONSUMED IN ALUMINUM PRIMARY PRODUCTION

KCl – NaCl SYSTEM

Eutectic Point

Tem

pera

ture

[ºC

]

Concentration [mol %]

Liquid

KCl – NaCl – NaF SYSTEM

MELTING MECHANISM

ALUMINUM INDUSTRIAL AND ELECTRONIC WASTES

EXPERIMENTAL PROCEDURE

CHEMICAL CHARACTERIZATION OF ALUMINUM WASTES

Aluminum wastes

Concentration [%]

Al Mg Fe CuProfile cutting swarf 98,45 0,30 0,23 0,01Extrusion swarf 98,59 0,59 0,30 0,06Heat sinks 98,33 0,52 0,30 0,05Dross 98,13 0,97 0,30 0,05

[Pb], [Ni], [Zn], [Cr], [Mn], [Sn], [Si] = 0,01 < [Concentration] < 0,06 [%]

ALUMINUM DROSS CHARACTERIZATION

Aluminum Oxygen Magnesium

ALUMINUM DROSS Semiquantitative Analysis using

SEMElement Concentration [%]

Al 58,47O 31,24

Mg 9,34Fe 0,94

X Ray Diffraction Analysis

Mineral Formula Concentration [%]

Aluminio Al 97Hierro Fe 1Espinel Al2MgO4 1Óxido de cobre, aluminio y níquel (Cu, Ni)Al2O4 1

ALUMINUM WASTES MELTING WITHOUT SALT FLUX

ALUMINUM WASTES MELTING USING SALT FLUX

ALUMINUM WASTES MELTING USING DIFFERENT CHLORIDES

ChloridesAluminum yield [%]

Profile cutting swarf

Extrusion swarf Heat sinks Dross

KCl 79,2 89,0 91,5 54,0NaCl 74,4 86,0 87,3 51,2MgCl2 9,2 9,5 69,8 39,2

CaCl2, MnCl2, BaCl2, NH4Cl 0 - 5 0 - 5 0 - 50 0 - 40

ALUMINUM SWARF MELTING APPLYING AGITATION

Agitation applyed using a wooden rod

Agitation applyed using a stainless steel

rod

Rod used to apply agitation

Concentration [%]

Al O C

Wooden rod 79,79 5,02 15,19Stainless steel rod 95,85 4,15 Not detected

ALUMINUM SWARF MELTING PROCESS

Aluminum wastes

Temperature [ºC]

Composition [mol %]

Amount of salts[wt %]

Time [hr]

Aluminum yield [%]

Profile cutting swarf 850 KCl = 100

NaCl = 0 100 0,50 93,6

Extrusion swarf 850 KCl = 70

NaCl = 30 50 0,33 98,5

Extrusion swarfProfile cutting swarf

HEAT SINKS MELTING PROCESS

Aluminum wastes

Temperature [ºC]

Composition [mol %]

Amount of salts[wt %]

Time [hr]

Aluminum yield [%]

Heat sinks 850 KCl = 90NaCl = 10 100 1 97,6

ALUMINUM DROSS MELTING PROCESS

Aluminum wastes

Temperature [ºC]

Composition [mol %]

Amount of salts[wt %]

Time [hr]

Aluminum yield [%]

Dross 750 KCl = 50NaCl = 50 30 2 71,6

INFLUENCE OF FLUORIDES ADDITION TO THE SALT FLUX

0 2 4 6 8 100

20

40

60

80

100Sodium fluoride (NaF)

Heat sinks Profiles cutting swarf Extrusion swarf Aluminum drossNaF Concentration [mol %]

Alu

min

um y

ield

[wt %

]

ALUMINUM QUALITY ANALYSIS

Aluminum wastes Concentration [%]Al Mg Fe Si

Profile cutting swarf 99,20 0,01 0,20 0,44Extrusion swarf 99,10 0,04 0,22 0,41Heat sinks 99,10 0,17 0,13 0,46Dross 99,20 0,01 0,20 0,41

[Cu], [Ni], [Zn], [Mn], [Cr], [Ti], [Pb], [Li], [Ga], [V], [Ag]0,0001 [%] < [Concentration] < 0,02 [%]

CONCLUSIONS

Aluminum wastes, (electronic and industrial)

Melting process allows to obtain a product with a concentration of Al > 99 %.

This product meets market requirements.

CONCLUSIONSUsing salt flux that contains mixtures of KCl and NaCl during the melting process, prevents the oxidation of the material and, in the case of the dross, the salt flux allows to remove the spinel layer.

Aluminum wastes

Temperature [ºC]

Composition [mol %]

Amount of salts[wt %]

Time [hr]

Aluminum yield [%]

Profile cutting swarf 850 KCl = 100

NaCl = 0 100 0,50 93,6

Extrusion swarf 850 KCl = 70

NaCl = 30 50 0,33 98,5

Heat sinks 850 KCl = 90NaCl = 10 100 1 97,6

Dross 750 KCl = 50NaCl = 50 30 2 71,6

Fluorides addition causes that the aluminum yield decreases.

Due to an increase in the melting temperature of the salt mixture.

CONCLUSIONS

Ernesto de la Torre , Santiago Yépez, Alicia Guevara

ESCUELA POLITÉCNICA NACIONALQuito - Ecuador

Facultad de Ing. Química y Agroindustria

Departamento de Metalurgia Extractiva

RECOVERY OF ALUMINUM FROM INDUSTRIAL AND ELECTRONIC

WASTE VIA MELTING WITH SALT FLUX