Electromagnetic (EM) Purification of Metals Lucas Nana Wiredu Damoah,

Department of Materials Science and EngineeringDr. Lifeng Zhang,

Department of Materials Science and Engineering

Project Objectives

Background

Approach

Discussion

Concluding Remarks

Future Work

Acknowledgements

Investigate the particle distribution in Aluminum following high frequency EM field application

Investigate the effect of frequency, current and concentration on inclusions separation from silicon under EM field

Nonmetallic inclusions are detrimental to properties. EM field as a potential technology to effective recycle and refine these important materials.

The induced Lorentz force acts on the electrically conductive melt toward the center and the nonmetallic inclusions experience the opposite EM Archimedes force.

100 µm

Distribution of Particles in Aluminum

Before After

Before

After

Distribution of Particles in Silicon

Separation efficiency from Silicon vs. parameters

References1. D. Sarti and R. Einhaus, Silicon feedstock for the multi-crystalline

photovoltaic industry. Solar Energy Materials and Solar Cells, 72(1-4): p. 27-40. (2002).

Nonmetallic inclusion particles were successfully separated from aluminum and silicon by EM field.

Wall temperature should be lower than the melt in order to separate particles from aluminum.

Higher coil currents enhanced separation efficiency but particle concentration shows no clear effect.

Higher frequency appeared to give higher efficiency probably due to stronger induced fluid flow.

High frequency EM field is effective to separate nonmetallic inclusions from metals.

Separation mechanism: induced fluid flow carries particles to the vicinity of the wall where EM Archimedes force traps them.

Higher coil current favors separation efficiency.

Having silicon with already dispersed particles and designing a continuous process are major challenges

Parametric studies for EM particles separation from aluminum.

Attempt will be made at a continuous process design.

Thanks to: DOE Award No. DE-EE0000575 and the Intelligent Systems Center (ISC), Missouri S&T.

Induction Coil

Nonconductive Particle

High FrequencyMagnetic Field

Electromagnetic Force

Accumulation

Liquid Metal

Induced Current

Thermocouple

Insulation fiber

SiO2 crucible

Graphite susceptor

Insulation brick

Induction coilTop-cut Silicon

Quartz tube

IR Pyrometer

Ar gas inlet

Recycling aluminum scraps saves over 90 %, 68 % SoG-Si feedstock is wasted [1].

HSC’s Forecast, 2009

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Coil Current, Irms (A)

Effi

cien

cy,

(%)

f = 78 kHz 1 wt % SiC 3 wt % SiC 5 wt % SiC

f = 64 kHz1 wt % SiC3 wt % SiC