isolating plants completely from natural water systems · isolating plants completely from natural...

Isolating Plants Completely from Natural Water Systems

AiChE

Industrial Water Use and Reuse Workshop

Kari Heiskanen, D.Sc.

Oct. 25 2016

© Outotec – All rights reserved

Outline • Introduction

• Water system in terms of quality

• Tests on mineral dissolution

• Technology solutions

• Challenges

• Tools and dreams

25/10/16 AIChE Water Seminar; Denver CO; 2016/ Kari Heiskanen


Introduction

• Rethinking and reinventing the role of

water • The most important solvent and dispersion agent

• Enabling effective use of resources

• We need to take care of its properties and optimize

these properties for each process step

• The traditional role of water • A cost item

• An issue in social license of operation

• We need to clean it at lowest possible cost

• We need to enhance the recycling of it



Introduction Effects of closing the loops In

cre

asin

g p

rocess d

istu

rba

nce

NEW Water Reuse Concepts

closed open

feasibility limit of

existing solutions

Fresh Water Usage

Fines (colloids...)

Cations Fe, As, Ni, Cu,

Ca, Mg ...

Anions: S- species,

Nitrogen, phosp.

Residual reagents and

their diss. prods.

Organics; humic, ...

Biological activity

Etc...

uS

Eh

pH

C °



Water system boundaries (quality)

MWT= Mine Water Treatment

RWT= Raw Water Treatment

ETP = Effluent Treatment Plant

Reagents Dissolved sp.

fines

Dissolved sp.

colloidal

Dissolved sp.

colloidal

Thermodynamics

and kinetics Annual changes



Water quality effectors

•From make-up water • Organic substances, Fe, Mg...., colloidal solids, bacteria etc

•From mine drainage • Nitrogen compounds, Fe2+, Mg... Cl-, oils, organic s. Bact. Salinity, pH

•From grinding and flotation • Dissolution from ore and gangue minerals, fine solids, reagents

• Bulk Reactions (thermodynamics, kinetics)!!

• Surface reactions (thermodynamics, kinetics)

•All this will depend on 1. the mineralogy suite!

2. The techno-economic goals of the plant!



One of the difficult separations is chalcopyrite-pentlandite-pyrrhotite

a1: Fe4,5Ni4,5S8 to (FeS)(NiS)

a2: formation of Me(OH)xS2

a3: oxidation of sulphur species

c1: Ni(OH)x reduction

c2: Fe(III)(OH)x reduction

c3: S0 reduction to S22-

c4:S22- reduction to S2-/ Fe2+ reduction

Fe

4,5Ni

4,5S

8=(Fe

4,5-xNi

4,5-xS

8)+ xFe2+ + xNi2+ +4xe

Fe

4,5Ni

4,5S

8+Ca2+ =(Fe

4,5-xNi

4,5-xCa

adsS

8)+ xFe2+ + xNi2+ + 4x -2( )e

Chalcopyrite: Chemisorption of Xanthate to

surfaces, partial oxidation to dixanthogen

Pentlandite: chemisorption takes place on

nickel sites; then oxidized on the surface to

dixanthogen

Pyrrhotite: physical adsorption of dixanthogen

formed in pyrrhotite oxidation process

Calcium is often used to control the pH to

depress Pentlandite and pyrrhotite.



Mineralogy / ore type <=> water quality



An operational Cu-Ni deposit CuFeS2; (Fe,Ni)9S8; Fe0,94S, hornblende, serpentine



Test site: Water assays



Test site Different water qualities over a year

Raw

water

A

Process

water

B

Cu

Thick. OF

C

Cu

Thick. OF

D

Sept 2014 Jan 2015 March

2015

June 2015

Mg mg/l 1.52 1.51 1.65 1.32

Na mg/l <5 1.4 5 1.3

uS 59.5 34.3 59.2 76

pH 8.26 6.63 6.92 6.56

Aero. Bac 7 600 10 000 500 -

Sept 2014 Jan 2015 March

2015

June 2015

Mg mg/l 36.8 35.8 32.5 41.2

Na mg/l 114 248 278 97

uS 1390 1960 2140 1237

pH 7.67 6.53 7.26 5.94

Aero. Bac 48 000 160 000 2 000 000 -

Process water Raw water



Xanthate; theoretically !

Hydrosulphide (HS-) and trithiocarbonate (CS3-2) have

known negative effect on flotation Dautzenberg et al 1969



Testing of mineral dissolution 1

ORP= on-line Eh Ag/AgCl reference

Grinding long times in a steel lined ball mill




0

50

100

150

200

250

300

0 20 40 60 80 100 120

Conductivity (

uS

/cm

)

Minutes of grinding time

Conductivity River Water

RW1

RW2

RW3

0

50

100

150

200

250

300

350

0 20 40 60 80 100 120

Conductivity

(uS

/cm

)

Minutes of grinding time

Conductivity Tap Water

TW1

TW2

TW3

Conductivity of water




-50

-40

-30

-20

-10

0

10

20

30

40

50

Pure Water Tap Water River Water Thickener Overflow Tailings Pond Pure Water, pH 9mg

/L

Change in calcium concentration




0

10

20

30

40

50

60

70

80

Pure Water Tap Water River Water Thickener Overflow Tailings Pond Pure Water, pH 9

mg

/L

Change in magnesium concentration




0

10

20

30

40

50

60

0 20 40 60 80 100 120 140

mg

/L

Minutes of Grinding

Sulphur

Pure Water

Tap Water

River Water

Pure, pH 9




•Water from the tailings pond

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80 100 120 140

mg

/L

Minutes of Grinding

Tailings Pond

Ca

Mg

Na

K



Needs of cleaning

•The results show some possibilities for two

strategies

1.Cleaning of a small side-flow to control the

overall quality of water to a suitable level - The cleaning need can be well below 10% of the

total water flow - Small modular units

- Several technologies available on the market

2. Use some technologies by designing to

partial operation



Needs of cleaning

•Both alternatives need advanced

measurement technologies

•Both alternatives need very advanced feed

forward type of model/data based

advanced control



Suggestion of new water circulation; divide it into two



Modelling

Joining Outotec HSC SIM Aqua model (water

thermodynamics+kinetics)+ HSC Min model

(mineralogy)+ multilevel Matlab Simulink modelling



Challenges

1. Ore type characterization for water model => model

based water control

2. Robust water quality sensors

3. Combine traditional water chemistry to mineralogy into

complex water models (generic engine+local tuning)

4. Ways of controlling the pH-Eh regime in a large scale?

5. Dry tailings unit cost

6. Control dry tailings deposit stability and dusting

7. Oxygen diffusion and water percolation into tailings

8. Site design

9. Etc...



Tools

Outotec EWT-40 module As removal at Codelco

DAF

Polishing filters 25/10/16 AIChE Water Seminar; Denver CO; 2016/ Kari Heiskanen


Tools: Water quantity and quality mgmt

Holistic solution for monitoring and

managing data on the mine site’s

water balance and water quality

• Wireless online monitoring stations, sensors, secure

data management, software applications, reporting

portal and services

Modular and scalable service

• Real-time information of process and natural waters

to a single database with KPIs for different

stakeholders in the plant

• Dynamic water balance and quality information,

short term forecasts for operational conditions

• Evaluation tool for process changes, water treatment

options and expansion projects

• Services to support the solution

+ Rain/snow

+ Surface runoff

+ Ground water

- Evaporation - Seepage

- Infiltration

WQQM Operating Environment



The dream


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