1 Propiedades de Pulpas y su Clasificación DR.pdf

© Paterson & Cooke 2010 .1

1. Propiedades de Pulpas y su Clasificación Slurry Properties and Classification

Overview

• Slurry components

• Material properties

• Slurry terminology

• Basic process relations

• Slurry classification

Curso Transporte de Relaves Espesados y en Pasta 2010

• Slurry hydraulic behaviour

• Pipeline friction loss examples

Slurry Components

W t Water

Solids


© Paterson & Cooke 2010 Page 1.2

Slurry Components

Typical types of solids


Tailings Concentrate Sand Slime

Material Properties

Particle size analysis• Different methods: sieving, elutriation, sedimentation and laser

• Produce different results – use a standard method to ensure consistencyconsistency

• Typical method: +75 μm sieving, -75 μm hydrometer

Finer than 5 μm Clay

5 μm to 74 μm (200 mesh) Silt

74 μm to 420 μm (35 mesh) Fine Sand

420 μm to 2 000 μm (9 mesh) Medium Sand

2 000 t 4 760 (4 h) C S d


2 000 μm to 4 760 μm (4 mesh) Coarse Sand

75 mm to 4 760 μm Gravel


60 %

70 %

80 %

90 %

100 %

ge P

assi

ng

20 %

30 %

40 %

50 %

60 %

Cum

ulat

ive

Per

cent

ag


0 %

10 %

1 µm 10 µm 100 µm 1000 µm 10000 µm

Particle SizeTailings Kimberlite Sand

Material Properties

Particle packing concentration• Freely settled concentration represents the approximate transition

between low and high concentration slurries

Maximum packing concentration represents a concentration that is• Maximum packing concentration represents a concentration that is unachievable for slurry pipeline transport.



Material Properties

Particle micrographs

Platinum Tailings Kimberlite


Heavy Mineral Concentrate

Slurry Terminology

Slurry• Mixture of solid particles and liquid.

• The liquid and solid phases do not react chemically.

Vehicle• Conveying medium, e.g. water or a mixture of water and fine

particles.

Homogeneous mixture• Non and slow settling slurries form mixtures that remain

homogeneous when quiescent for a period of more than an hour.


• The distribution of particles across the pipe section is uniform.


Slurry Terminology

Heterogeneous mixture• The concentration of solid particles across the section of a horizontal

pipe is non-uniform.

For particles with a density greater than the vehicle density the• For particles with a density greater than the vehicle density, the concentration of solid particles increases towards the pipe invert.

Pseudo-homogeneous flow• Flow regime which behaves as single-phase homogeneous flow at

high mean mixture velocities, but becomes heterogeneous at lower mean mixture velocities.

• Pseudo-homogeneous flow can arise with virtually any slurry if the


g y y ytransport velocity is high enough to suspend particles reasonably uniformly by turbulence.

Mean mixture or bulk velocity• Flow rate divided by pipe cross-sectional area.

Slurry Terminology

Laminar flow• Flow behavior is dominated by the fluid viscosity.

• Particles of fluid move in straight streams with no mixing between adjacent streamsadjacent streams.

Turbulent flow• “The paths of individual particles are no longer everywhere straight

but are sinuous, intertwining and crossing each other in a disorderly manner so that thorough mixing of the fluid takes place” – Massey 1979



Slurry Terminology

Rheology• Viscous characteristics of a fluid or homogenous solid-liquid mixture.

• Note the term viscous indicates that laminar flow is being considered (where viscous forces dominate) as opposed to turbulent flow (where(where viscous forces dominate) as opposed to turbulent flow (where inertial forces dominate). Thus, rheology refers to laminar flow phenomenon only.

Rheogram or flow curve• A plot of shear stress versus shear rate for laminar flow conditions.


Slurry Terminology

Rheogram

200

220

Muestra 1

40

60

80

100

120

140

160

180

200

Ten

sió

n d

e co

rte

en l

a p

ared

, o

(Pa)

Cp=74,2%

Cp=74,1%

Cp=71,2%

Cp=69,5%

Cp=67,6%

Cp=65,0%

Cp=64,0%


0

20

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300

Velocidad de Corte, (s-1)


Concentration and Density Relations

Concentration• Volumetric concentration

• Mass concentration

Slurry Density


Mass and Volume Concentration

The volumetric concentration is the ratio of the volume of solids to the total volume of the mixture:

m

svC

The mass concentration is the ratio of the mass of solids to the total mass of the mixture:

M


m

sw M

MC


Slurry DensityThe slurry density is the mass of slurry per unit volume:

mm

M

mm


Concentration and Density

Cv Cw ρm

wwm

Cv = 1 wsw

s

C

ws

wm

Cw = wsv

w

s

C

1

wsm

wms


ρm = wsvw C wsws

wswww C

C

1


Concentration and Density

Consider a slurry at a mass concentration of 65%m.

The volumetric concentration is:• Copper tailings (ρs = 2.8 t/m3): Cv = 39.9%v

• Copper concentrate (ρs = 4.0 t/m3): Cv = 31.7%v


Slurry Classification



Main Slurry Classifications

Particle Settling Characteristics

Rheology

Solids Concentration



According to the particle settling, slurries may be classified into:

• Settling Slurries

• Non an slow settling slurries

• Mixed regime slurries




Mixed Regime

SettlingS

low

Set

tlin

gNonSettling

0 1 / 1 /


0.1 mm/s10 µm

1 mm/s32 µm

Non-Settling Slurries Slow Settling Slurries Settling Slurries

Vt ≤ 0.1 mm/s

(d = 10 µm for Ss = 2.65)

Brownian motion.

Homogeneous even in laminar flow

Vt ≤ 1 mm/s

(d = 32 µm for Ss = 2.65)

Turbulence

Particles settle in laminar flow.

Solid and liquid phases are separate. Liquid properties unaltered by the presence of the solids.

Turbulence and inter-particle collisions.

Concentration gradient in horizontal pipes

(uniform particle distribution).

Normally exhibit non-Newtonian behaviour at higher concentrations.

In a quiescent state, particles do not settle readily.

Frequently referred to as homogeneous slurries.

In a quiescent state, particles settle slowly en masse.

pipes.

In a quiescent state, particles settle readily.

Frequently termed heterogeneous slurries.


Mixed Regime Slurries

Contain a wide range of particle sizes and/or densities.

Fine particles mix with liquid to form a vehicle (Newtonian or non-Newtonian) with the coarser particles being transported inthe vehicle.

Most common slurry type encountered.


Rheology

Newtonian Slurries• Linear relationship between shear stress and shear rate

She

ar S

tres

s

μ

Newtonian τ = μ γ

Laminar flow


• The rheogram passes through the origin and the slope of the flow curve is the mixture viscosity

Shear Rate

Rheology

Non-Newtonian Slurries• Has one or more of the following characteristics:

→non-linear rheogram

→the rheogram does not pass through the origin

→the rheogram varies with time (i.e. dependant on the shear history).

r S

tres

s

Non-Newtonian τ ≠ μ γ


Shear Rate

She

ar Non-Newtonian τ ≠ μ γ

(Next lecture by Angus)



30%m 40%m30%m 40%m



Conventional slurries• The most common slurries in the industry

• Solids concentration under the Cbfree limit

Thickened Slurries• Obtained from high rate or high compression thickeners

• Solids concentration between Cbfree limit and concentration at Yield Stress of 100 Pa


Paste Slurries• Obtained from paste thickeners

• Solids concentrations at Yield Stress above 100 Pa


High Concentration Slurries

High Concentration Non and Slow Settling Slurries High concentration settling slurries

Form paste mixtures.

Contain a high % of fine particle which form a non-

Form dense phase mixtures

Inter-particle contact is the dominant mechanismContain a high % of fine particle which form a non-Newtonian vehicle.

Vehicle yield stress dominates the flow behaviour.

Larger particles do not contribute significantly to the pipeline friction losses.

Generally operated in laminar flow due to

Inter-particle contact is the dominant mechanism supporting the particles.

There are insufficient fine particles to significantly alter the vehicle rheology.

Essentially a settling mixture in which settling is prevented by the high concentration of particles.

For concentrations greater than Cbfree, the pressure


Generally operated in laminar flow due to excessive amount of energy required to achieve turbulent flow.

Examples: high concentration tailings for surface disposal or underground backfill

o co ce a o s g ea e a Cbfree, e p essu egradients are very sensitive to small concentration changes.

Example: cyclone classified tailings backfill.

Paste and Thickened Tailings

High concentration mixed regime slurries

Non-Newtonian rheology• Typically characterized as a Bingham Plastic (discussed during next

lecture by Angus)

• May be time dependant

• Considered fully sheared condition for classification




SlurryPa)

Paste

100

Slurry

Cake

Yie

ld S

tres

s (P

Thickened Tailings


Solids Concentration (%)

20


69,7% - 10 Pa 72,6% - 30 Pa

74,4% - 100 Pa 76,3% - 300 Pa



Slurry Hydraulic Behaviour

Depending on the particle settlement characteristics, rheology and solids concentration, several models may be used to predict the slurry behaviour in transport and to calculate the hydraulic parameters in a slurryto calculate the hydraulic parameters in a slurry pipeline.

Thus, for each type of slurry, different design considerations should be applied related to:• Deposition and transition velocity


• Friction Head losses

• Pump derating

• Pipeline wear

Slurry Hydraulic Behaviour

Settling Slurries• Presentation 3 – Ray

Non-Newtonian Slurries – Pipe Flow• Presentation 4 - Angus

Paste and Thickened Tailings Transport• Presentation 5 - Rob



Pipeline Friction Loss Examples

70 %

80 %

90 %

100 %

ssin

g

20 %

30 %

40 %

50 %

60 %

Cum

ulat

ive

Per

cent

age

Pas


0 %

10 %

1 µm 10 µm 100 µm 1000 µm 10000 µm

Particle SizeMarine Sand HM conc HM Slimes

Marine Sand

Narrow size distribution• d50 = 422 μm

100 %

ρs = 2 600 kg/m3

Ss = 2.65

30 %

40 %

50 %

60 %

70 %

80 %

90 %

um

ula

tive

Pe

rce

nta

ge P

assi

ng


0 %

10 %

20 %

1 µm 10 µm 100 µm 1000 µm 10000 µm

Particle Size

Cu

Marine Sand HM conc HM Slimes


Marine Sand

1.4

1.6

1.8

2.0

Pa/

m)

150 NB Pipe Loop

0 2

0.4

0.6

0.8

1.0

1.2

Pre

ssur

e G

radi

ent

(kP


0.0

0.2

0.00 1.00 2.00 3.00 4.00 5.00

Velocity (m/s)

Water 1.18 t/m3 1.27 t/m3 1.40 t/m3

Marine Sand

0.100

0.120

m p

ipe)

150 NB Pipe Loop

0.020

0.040

0.060

0.080

Hea

d Lo

ss (

m m

ixtu

re /m


0.000

0.00 1.00 2.00 3.00 4.00 5.00

Velocity (m/s)

Water 1.18 t/m3 1.27 t/m3 1.40 t/m3



Narrow size distribution• d50 = 140 μm

90 %

100 %

ρs = 4 530 kg/m3

Ss = 4.53

30 %

40 %

50 %

60 %

70 %

80 %

Cu

mu

lativ

e P

erce

ntag

e P

assi

ng


0 %

10 %

20 %

1 µm 10 µm 100 µm 1000 µm 10000 µm

Particle Size

C



1 4

1.6

1.8

2.0

a/m

)

150 NB Pipe Loop

0.4

0.6

0.8

1.0

1.2

1.4

Pre

ssur

e G

radi

ent (

kPa


0.0

0.2

0.00 1.00 2.00 3.00 4.00 5.00

Velocity (m/s)

Water 1.55 t/m3 1.72 t/m3 2.00 t/m3



0 080

0.100

0.120

m p

ipe)

150 NB Pipe Loop

0.020

0.040

0.060

0.080H

ead

Loss

(m

mix

ture

/m


0.000

0.00 1.00 2.00 3.00 4.00 5.00

Velocity (m/s)

Water 1.55 t/m3 1.72 t/m3 2.00 t/m3

Heavy Mineral Slimes

Wide size distribution• d50 = 3.5 μm

90 %

100 %

ρs = 2 860 kg/m3

Ss = 2.86

30 %

40 %

50 %

60 %

70 %

80 %

Cum

ulat

ive

Per

cent

age

Pas

sing


0 %

10 %

20 %

1 µm 10 µm 100 µm 1000 µm 10000 µm

Particle Size

C




2.0

2.5

a/m

)

150 NB Pipe Loop

0.5

1.0

1.5

Pre

ssur

e G

radi

ent

(kP

a


0.0

0.00 1.00 2.00 3.00 4.00 5.00

Velocity (m/s)

Water 1.28 t/m3 1.31 t/m3 1.34 t/m3


0 140

0.160

0.180

0.200

m p

ipe)

150 NB Pipe Loop

0 020

0.040

0.060

0.080

0.100

0.120

0.140

Hea

d Lo

ss (

m m

ixtu

re /m


0.000

0.020

0.00 1.00 2.00 3.00 4.00 5.00 6.00

Velocity (m/s)

Water 1.28 t/m3 1.31 t/m3 1.34 t/m3


Slurry Properties and Classification

Questions - Preguntas


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