Luis A. Cisternas Director – CICITEM Research Center for Mining and Department of Chemical Engineering Universidad de Antofagasta Antofagasta - Chile Seminar – Process Design for Mineral Operations PASI 2008 PASI 2008 Pan American Advanced Studies Institute Program on Emerging Trends in PSE Process Design for Mineral Operations
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Luis A. CisternasDirector – CICITEM
Research Center for Miningand
Department of Chemical EngineeringUniversidad de Antofagasta
Antofagasta - Chile
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Process Design for Mineral Operations
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MotivationGeneral StrategyCrystallization Design Problem Flotation Circuit Design ProblemFinal Remark
Outline
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Motivation
•High price cycle unprecedented•Lowering the cost of production•Achieving the balance of acceptable economic, environmental and social effects.•Improve energy efficiency
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The engineer`s loverCarlo Carrá
Italian 1881-1966
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Problems: Process design has multiple dimensions
Roberto MattaChilean 1911-2002
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Solution: Look as Picasso
Pablo Picasso Spanish 1881-1973
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The Onion Model
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Crystallization design problem overviewFractional CrystallizationFractional Crystallization with Heat Integration & Cake Washing
Crystallization DesignProblem
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Crystallization is extensively used in different industrial applications, including the production of a wide range of materials such as fertilizers, detergents, foods, and pharmaceutical products, as well as in the treatment of waste effluents
Crystallization design problem overview
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The crystallization stages are usually accompanied by other separation techniques. Leaching. Various types of crystallization exist: cooling, evaporation, reactions, and drowning-outThe characteristics of the product affects a series of other associated operations. filtration & washing. The separation is limited by multiple saturation points. Temperature changes & external chemical agents. Kinetic factors and metastability may affect the design.
Problems
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The greatest advantages obtained in the use of the phase diagram are the possibilities for the visualization of the behavior of phase equilibria, describing the processes, and obtaining mass balances with the help of the lever arms rule. The phase diagrams, however, also have a series of limitations as a design tool
Phase Diagram
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Phase Diagram
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Examples-Astrakanite
astrakanite.gms
REACTIVECRYSTALLIZATION
18.7 ‘C
COOLING CRYSTALLIZATION
25 ‘C
Astrakanite
EVAPORATIVE CRYSTALLIZATION
50 ‘C
Astrakanite
Water Water
MgSO .6H O24Na SO .10H O2 4 2
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Fractional Crystallization with Heat Integration & Cake WashingState Superstructure Task superstructure.Heat integration.Cake Washing•Cisternas L.A., J.Y. Cueto and R.E. Swaney, “Flowsheet Synthesis of Fractional Crystallization Process with Cake Washing”, Computer and Chemical Engineering, 28, 613-623 ( 2004)• Cisternas L.A., C. Guerrero and R. Swaney,, “Separation System Synthesis of Fractional Crystallization Processes with Heat Integration”, Computer and Chemical Engineering, 25, 595-602 2001
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Task Superstructure
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wl (w + w h )m m mG
outt,mG
inl,t
Leaching
CrystallizationEvaporative
CoolingCrystallization
t
iΣn n,i(w + h x )
Task Network
MultipleSaturation
Points
ProductIntermed.
Solvent
Feed
Product
Solvent
Product
n
l m
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k−1
k
1
K
Rk−1
Rk
MultipleSaturation
Points
ProductIntermed.
Solvent
Feed
Product
Solvent
Product
Heat Integration
Papoulias S.A., & I.E. Grossmann (1983), A structural optimization approach to process synthesis-II. Heat recovery networks. Comp. and Chem. Engng., 7, 707
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Cake Washing
Parallel Options
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Mathematical ModelMass balance for each component in multiple saturation nodes (SM):
Mass balance for each component in intermediate product nodes (SI):IiSsxwxw I
sSLqlill
sSLqlill
outin
∈∈=⋅−⋅ ∑∑∩∈∩∈
,0)(
,)(
,
IiSsxhwhx IsSLql
illlsSLql
ilinout
∈∈=− ∑∑∩∈∩∈
,0)(
,')(
,
Iout
llIi
ilill SssSLqlymUhxxw ∈∩∈≤−+⋅∑∈
),(0)( ,,
IsSLql
l Ssymout
∈=−∑∩∈
01)(
Specification for feeds flow rates in feed nodes (SF):)(,,
)(, sIiSsCxw FF
Fis
sSlill
out
∈∈=⋅∑∈
State Superstructure
IiSsxhwxwxwhx MsSLqLwl
illlsSl
illsSl
illsSLql
iloutoutinin
∈∈=−⋅−⋅+ ∑∑∑∑∩∪∈∈∈∩∈
,0)()(
,)(
,)(
,)(
, '
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Task Superstructure
Mass balance between the thermodynamic state network and task network
∑∑∈∈
∈∈=+)(
,, ),(,sTt
Minin
tlIi
ill SssSlGhxw
∑∈
∈∈=+)(
, ),(,sTt
Moutout
ltlll SssSlGhww
Mass balance in the task network:
∑∑∈∈
∈∈=)(
,)(
, ,,sSl
Moutlt
sSl
intl
outin
SsTtGG
Task selection and energy balance:
True)(
)(),(
0000
)(,)(2),(1,
,
,
,
,
,
,
,,,
,2,1,,,
)(,,,
,,
,
=
∈∈
⎥⎥⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢⎢⎢
⎣
⎡
====
¬
∨
⎥⎥⎥⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢⎢⎢⎢
⎣
⎡
∈=∈∈+=
==
∑∈
st
M
Sst
Cst
st
st
st
outs
outltst
Sst
ind
outd
intl
Dst
outlt
Cst
Cst
sSl
intlstst
stst
st
yg
sSssTt
QQ
VCFC
y
sSlGHSQsSlsSlGHQGHQQ
GVCFC
y
in
βα
IF carnallite is fed to node 3 (stream 14) THEN the task is reactive crystallization
014,3 ≥− wtrcn yy
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Cake Washing
Mass balance for each component in wash/reslurry stage:
Efficiency constraint for wash/reslurry stage:Degree of impurity:Wash or reslurry/filter selection:
IiLwlLwEe
CvCfQrQw
zzrzwypwymwyprymr
yyyryw
QrCsQrCvfwQrCvrCv
CffCfrCfwhnrQr
Qwzzr
zwypwymw
yyprymry
yryw
QwCsQwCvwCv
CfwCfQr
whnwQw
zrzzw
yprymr
yypwymwy
yryw
el
el
el
el
ieliel
iel
iel
iel
iel
iel
ieliel
el
el
elel
lelel
el
llelel
el
ieliel
iel
iel
iel
ieliel
ieliel
el
el
el
elel
el
el
llelel
iel
ieliel
iel
iel
ieliel
ieliel
el
el
∈∈∈
⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢
⎣
⎡
=
=
=
=
=
=
=
=
=
=
=
¬
¬
∨
⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢
⎣
⎡
+
+=
+=
=
=
=
=
=
=
=
=
¬
∨
⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢
⎣
⎡
+=
=
=
=
=
=
=
=
=
=
¬
−−
,),(
0000
000
00
)(
0
000
0
0
00
,
,
,
,
,,,,
,,
,,
,,
,,
,,
,,,,
,
,
,,
0,,
,
0,,
,
,,,,
,,
,,
,,
,1,,,
,,,,
,
,
,
,,
,
,
0,,
,,
,,,,
,,
,,
,1,,,
,,,,
,
,
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Heat Integration
KkTCwTCwQQRRkkkk Cl
Clkpl
Hl
Hlkpl
Un
Un
Vm
Vmkk ∈Δ−Δ=+−− ∑∑∑∑
∈∈∈∈− )()(1
objective function minimizes the total venture cost:
∑∑∑∑∑ ∑∈∈∈∈ ∈
+++++++Lwl e
elelUn
Unn
Vm
Vmm
Sst
Sst
Cst
Cststst
Ss sTtCvCfQcQcQcQcVCFC
M
)()(min ,,,,,,,,)(
Objective Function
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Example: Sylvinite
The MILP formulation contains 299 equations, 218 continuous variables, and 27 binary variables.
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Example: Astrakanite
Astrakanite
Water Water
Reactivecrystallization
at 18.7ºC
Filtration
WashingWashsolvent
Washsolvent
Na SO .10H Ocake
2 4 2 MgSO .7H Ocake
4 2
Washing
Filtration Filtration
Coolingcrystallization
at 25ºC
R
StEvaporative
crystallizationat 50ºC
Astrakanitecake
The MILP formulation contains 1209 equations, 1201 continuous variables, and 145 binary variables. Solution time was 84 s for OSLv2 (GAMS) with a 1.7 GHz Pentium 4 processor.
MgSO4·Na2SO4·4H2O
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•Flotation Circuit problem overview•Superstructures for task, state and equipment selection •Mathematical model•Examples
Flotation Circuit DesignProblem
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Flotation design problem overview
Mineral flotation processes consist of several units that are grouped into banks and interconnected in a predefined manner in order to divide the feed into concentrate and tailing. The behavior of these processes depends on the configuration of the circuit and the physical and chemical nature of the slurry treated
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Figures From http://cache.eb.com/eb/image?id=1534&rendTypeId=4http://cape.uwaterloo.ca/images/pal1.gif
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The design of these circuits is carried out based on the experience of the designer, with the help of laboratory tests and simulations. Some attempts have been described in the literature on automated methods for the design of these types of circuits. However, methods for the design of flotation circuits have not yet progressed to the stage where an optimum circuit configuration can be completely derived automatically.
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Superstructures for task, state & equipment
Superstructures are developed in a hierarchical form:•First level: separation task superstructure •Second level: processing systems are presented which must carry out rougher, cleaner, and scavenger operations and define states. •Third level: equipment selection (column versus mechanical bank; grinding-classification circuit)
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Tasks
Rougher
Feed
Concentrate
Tail Scavenger
Tail
Concentrate
Final Flotation
Tail
Cleaner
Concentrate
FinalFlotation
Concentrate
Tails
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Task Superstructure
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State Superstructures
Mixing with/without grinding
Mixing without grinding
Mechanical cell bank or column
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Equipment Superstructures
Grinding-classification circuits
( ) ( )( ) ( ) ( )( )huD2aa1huD2aa1huD2
1a41R 22C −−−+
⎟⎟⎠
⎞⎜⎜⎝
⎛
−=expexp
exp
( )N111Rωτ+
−=
Mechanical cell bank or column
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Grinding circuits
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∑∑∑∑γ
=Γ
K JjkP
K JjkPjk
W
W
,,
,,,
Floatability Index
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2.5
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
0 2 4 6 8 10 12Milling time, minutes
Floa
tabi
lity
inde
x fo
r circ
uit p
rodu
ct
Grinding without classification
Grinding - classification
Classification - grinding
Classification - grinding - classification
Feed mass flow rate, tphPercentage feed composition
2.5
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
0 2 4 6 8 10 12Milling time, minutes
Floa
tabi
lity
inde
x fo
r circ
uit p
rodu
ct
Grinding without classification
Grinding - classification
Classification - grinding
Classification - grinding - classification
Feed mass flow rate, tphPercentage feed composition
242
244
246
248
250
252
254
0 2 4 6 8 10 12Milling time, minutes
Floa
tabi
lity
inde
x fo
r circ
uit p
rodu
ct
Grinding without classification
Grinding - classification
Classification - grinding
Classification - grinding - classification
Feed mass flow rate, tphPercentage feed composition
242
244
246
248
250
252
254
0 2 4 6 8 10 12Milling time, minutes
Floa
tabi
lity
inde
x fo
r circ
uit p
rodu
ct
Grinding without classification
Grinding - classification
Classification - grinding
Classification - grinding - classification
Feed mass flow rate, tphPercentage feed composition
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Material Balances
Feedstock flows
Material Balances Flotation Steps
Mathematical Model
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( )
1 1
1 1
1 1 1 1
1 1 1 1
2 1 1 2 1
3 1 1
, ,
, ,
, , , , , ,
, , , , , , , ,
, , , , , , , , , ,
, , , , , ,1
b cs s
f f f fs b s c
V V b V V cs b s k s c s k
k kb c
s k s k s k s k
b b cs k s k s k s k s k
b bs k s k s k
y y
C C C C
C C W C C W
W WI W WI
WI T W WI T
WI T W
⎡ ⎤⎢ ⎥
= =⎢ ⎥⎢ ⎥
= ∑ = ∑⎢ ⎥∨⎢ ⎥
= =⎢ ⎥⎢ ⎥
= =⎢ ⎥⎢ ⎥
= −⎢ ⎥⎣ ⎦ ( )1
3 1 1
, ,
, , , , , ,1
cs k
c cs k s k s k
W
WI T W
⎡ ⎤⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥
= −⎢ ⎥⎣ ⎦
Equipment Selection
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Objective Function
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Example
The procedure was applied to the design of a copper concentration plant, whose species are: k=1 (100% chalcopyrite), k=2 (50% silica, 50% chalcopyrite) and k=3 (100% silica).
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Economic results in millions of US$ for a metal price of 1.00 US$/lb where the k=3 recovery is comparable to the k=2 recovery.(NG)= no grinding, (G)= grinding w/o classification, (G-C)= grinding – classification, (C-G)= classification – grinding.
Cycle Process, Magritte Radiation, Van Gogh fluids, EscherCompression, Baldaccini
Final Remark
Complete list of references on design of separation based on crystallization, design of flotation circuits, design of leaching process, and design of solvent extraction circuits