Electrical separation

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surface charge creation

Separation

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Fel = Qt E

Products

Fg = mg

Main parameter - electrical charge

Electrical charge depends on:

A. Time of life

Qt = Q0 exp (–t/)= Q0 exp(– t/0)

Q0 – electrical charge at the moment of birth (t = 0)Qt – electrical charge at time tt – time – relaxation time – conductivity(–1m–1) – dielectric constant (dimensionless) 0 – electrical permeability of vacuum (8,854·10–12 C2N–1m–2).

log = a + b c

a, b – constant c – relative air moisture

B. Relative air moisture

E

N

+q/m+q/m- q/m - q/m

SiO2

Fe2O3

N - population of particles, E -intensity of electrical field, V/m, q/m -electrical charge per unit mass

material

device mode of work

rate of separation

Qt

Qo, t,

w, , , tt

+

E

mode of electrification

1-V.S.Fomienko, NTIS, US Dep. of Commerce Report, No.JPRS-56579, 1972 lub Gupta et al., Powder technology, 75 (1993) 79-87, 2 - Lewowski, Coal Preparation Journal, 1993, 13, 97-105, 3 –unknown source , 4. CRC Handbook, 67th ed., 1986-87

Work function (work to remove electron), W, eVMaterial Work function, eV SourceCS2 0.99 - 1.117 1BaO 1.10 1(Ba,Sr)CO3 1.25 1SrO 1.27 1CaO 1.60 0.20 1Y2O3 2.00 1Gd2O3 2.10 1Tb2O3 2.10 1Dy2O3 2.10 1Ho2O3 2.10 1Nd2O3 2.30 1Er2O3 2.40 1ThO2 2.54 1Eu2O3 2.60 1La2O3 2.80 1Pr6O11 2.80 1Sm2O3 2.80 1UO2 3.15 1CeO2 3.21 1U 3.63 - 3.90 4BeO 3.80 - 4.70 1FeS2 3.8 2FeO 3.85 1grafit 4.00 1Al. 4.06 - 4.41 4MoO3 4.25 1Pb 4.25 4Ag 4.26 - 4.74 4Pyrex 4.48 3Hg 4.49 4Fe 4.50 - 4.81 4Cu 4.53 - 4.94 4Al2O3 4.70 1MgO 4.70 1Si 4.85n 4SiO2 5.00 1Ni 5.04 - 5.15 4Co 5.00 4Au 5.10 - 5.47 4Pt 5.70 4ZrO2 5.80 1TiO2 6.21 1

Force Fel acting on a charged particle in electrical field

Fel = Qt E = A q E

A - surface area, cm2

q - surface charge,C/cm2

E - electrical field, V/m

Ways of charging (electrification)

- friction (triboelectric)

- ionization (ion bombardment)

- induction

- contact (dissimilar particles)

- other

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Concentrate Tailing

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conducting non-conducting

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conducting

non-conducting

electrical field