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PSE objectives
Rational use of resources Optimization Decision making problem
Objective function ? Optimization of the optimization ????
Constraints ? Optimization of the model ????
Solution procedure Mathematical formulation of the problem Practical tools
Application Information required ? Applicability ????
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Hierarchical view of the problem
Some decisions have “effects” of higher order of magnitude The problem usually admints hierarchizatrion solution approach as
“Branch & Bound” ( Douglas, Rudd et al., ….)
“Spa
ce o
f de
sign
s”
Stechiometry Benefit < 130Selectivity Benefit < 90
Des
igns
wit
hout
sub
prod
ucts
se
para
tion
Other sep. sys Benefit < 75
Distillation Benefit< 70
Liq-Liq Extr Benefit < 45
Complete design Benefit= 50
Liq-Liq Extr. Benefit < 45
Membranes Benefit < 53
Technical problems
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Points to consider
Divide (synthesis, design, planing, scheduling, control…) … But subproblems are solved “separatelly” ( unlinked)
Suboptimal solutions Unfeasibilities
Simplify (Objectives, constraints (scenario, process model,…) … But another problem is solved
Suboptimal solutions Unfeasibilities
Review is required !!!
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Steps (hierarchy) to solve the preliminar synthesis and design problem (Douglas, 1988)
Douglas, J.M (1988): Conceptual Design of Processes (McGraw-Hill):
Formalization of a hierarchy of decisions
Heuristic sequence of hierarchical steps + Heuristic rules
Rudd, Powers and Siirola (1973): Process Synthesis (Prentice Hall)
proposed a similar apporach (without the heuristic rules)
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General Procedure overview
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Preliminar Synthesis
Establish a “base-case”, including a first approximation in order to: Progressively approach to the specified objective:
Getting closer to chemical species Chemical reaction adjustment (chemical path, selectivity, operating conditions…
Getting closer to flowrates Mass balances, stechiometry, conversions,…)
Getting closer to composition Separation and/or mixing Getting closer to temperature, pressure, phase, … Changes in
temperature, pressure, phase, …
Allocate tasks to equipment units (“task integration”)
RUDD et al. (1973)
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General steps (Douglas, 1988)
1. Proceso “Continuo vs. Discontinuo”: Normalmente, los procesos continuos tienen mucho menor costes de
inversión y operación, incluso para productividades muy pequeñas.
2. Determinar las entradas y salidas del proceso: Número y características principales de las corrientes de entrada y salida.
Presencia co-productos, subproductos y residuos. Presencia de “inertes”. Niveles de concentración Posibilidad de recuperación y reciclo. Purgas
(…)
5. Síntesis de la red de “recuperación de energía” Selección y localización de las unidades de recuperación (intercambiadores,
pero también turbinas, bombas de calor, etc.). Efecto del grado de integración energética en el resto de procesos (sistemas
de reacción y de separación) Cálculo de límites termodinámicos aproximados
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Representation of alternatives
Sistema de separación Sistema de separación
(enumeración jerarquizada) (enumeración explícita)
Condensables (M, EL, PL) vs.Incondensables (EtOH, W, IPA, DEE)
Incondensables (EtOH, W, IPA, DEE)
Condensables (M, EL, PL)
Incondensables (EtOH, W, IPA, DEE)
Condensables (M, EL, PL)
Destilación producto (EtOH, / W, IPA, DEE)
Destilación ETOH, IPA, DEE / W)
Destilación pesadors (EtOH, W, IPA / DEE)
FLASH
ABSORC.
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Representation of alternatives
C1 C2 C3
H1
H2 X
H3
C1 C2 C3
H1 1
H2 3 2
H3
HEN (superestructura) HEN (enumeración: 1 (0HX) +
9 (1HX) + 9*6 + 3*3*2 (2HX)+…)
C1 C2 C3
H1 1
H2 2
H3
1
2
3
H1
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Application: This paper….
Sinthesys / Design Retrofit Focused on energy requirements Hierarchical Approach Different models at the different steps
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Objectives for today
Understand how this paper addresses these points:
Identify the problem to be solved Identify (and “characterize”) the objective
Identify the model(s) Identify the differences among the models Identify/review the modeling issues
Identify the different solution approaches proposed Identify (and understand) the results
Identify the eventual inconsistences vs. the problem Identify the eventual inconsistences vs. the formulated model
What should be done then ??? (discusion)
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Objectives for tomorrow
Issue: Uncertainty
How to face uncertainty
Application to simple problems
Application to the problem posed by this work ?
Discusion
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Identify the problem to be solved
Identify (and “characterize”) the objective
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Identify the models
Model 1 Modeling issues
Model 2 Modeling issues
Model 3 Modeling issues
Diferences / Alternatives
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Identify the solution approaches
Solution approach 1 Issue 1.1
Solution approach 2 Issue 2.1
Differences/alternatives
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Identify (and understand) the results
Identify the eventual inconsistencies vs. the problem Issue 1.1
Identify the eventual inconsistences vs. the model Issue 2.1
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What should be done then ??? (discusion)
Action 1 Issue 1.1
Action 2 Issue 2.1
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