Plantilla -10 PSE objectives Rational use of resources Optimization Decision making problem Objective function ? Optimization of the optimization ????

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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

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

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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