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Process Flowsheet Generation & Design Through a Group Contribution Approach. Lo ï c d ’ Anterroches CAPEC Friday Morning Seminar, Spring 2005. Introduction. ???. Synthesis Problem. Question: How to solve this problem?. Raw materials. Products.

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process flowsheet generation design through a group contribution approach

Process Flowsheet Generation & Design Through a Group Contribution Approach

Loïc d’Anterroches

CAPEC

Friday Morning Seminar, Spring 2005

introduction
Introduction

???

Synthesis Problem

  • Question: How to solve this problem?

Raw materials

Products

Find the best sequence of operations to convert

the raw materials into the desired products

Process Flowsheet Generation & Design Through a Group Contribution Approach

introduction1
Introduction

Current Methods

  • Industrial approach
    • Take a master student looking for a 6 month training session

Targets

Data

(input, …)

Data

6 months and some thousands simulations later, the problem is solved.

Process Flowsheet Generation & Design Through a Group Contribution Approach

introduction2
Introduction

Current Methods

  • More academic approaches
    • Knowledge based methods
      • Database of cases and rules built with time from experience.
      • Problem: Not a lot of alternatives, feasible but with no guaranteed optimality, need to solve the model at each decision step.
    • Optimization based methods
      • Setup of a mathematical superstructure in which all the alternatives are represented, setup the optimization to find the best.
      • Problem: Optimality only within the mathematical superstructure, hard to setup, need to solve the model at each decision step.

Process Flowsheet Generation & Design Through a Group Contribution Approach

introduction3
Introduction

General Issues

  • A new method need to address those issues while improving on the drawbacks of the current methods

How to avoid using too many different unit operations but keeping the right ones?

Definition of the problem

Select the needed unit operations

How to do an exhaustive analysis of the alternatives with the correct design parameters for each simulation?

Setup each alternative and simulate it

How to be sure this is the best? Any metrics?

Get the best alternative

Process Flowsheet Generation & Design Through a Group Contribution Approach

introduction4
Introduction

Core Idea and Main Objectives

  • Core Idea
    • Apply the group contribution approach for property estimation to the synthesis, design and modelling of a process flowsheet, with process-groups representing units, bonds representing streams, rules for flowsheet feasibility and a function of group contributions predicting the performance of the flowsheet.
  • Main Objectives
    • Efficient on a large range of problems
    • Ability to integrated and reuse knowledge over the time
    • Computer implementation for ease of use

Process Flowsheet Generation & Design Through a Group Contribution Approach

introduction5
Introduction

Overview of the Presentation

  • Introduction & problem presentation
  • Molecular Group Contribution Approach
  • Flowsheet Group Contribution Approach
    • Presentation
    • Property Model
    • Overview of the Framework
    • Synthesis Algorithm
    • Design of the Process
  • Implementation
  • Conclusion & Future Work

Process Flowsheet Generation & Design Through a Group Contribution Approach

molecular group contribution approach
Molecular Group Contribution Approach

Property Prediction

1. Given a molecule

Ethanol:

2. Represent it as a combination of groups

-CH2-

-CH3

-OH

3. Evaluate the property as the sum of the contributions

Process Flowsheet Generation & Design Through a Group Contribution Approach

molecular group contribution approach1
Molecular Group Contribution Approach

: Ethanol, Tm = 159K

Computer Aided Molecular Design

1. Given a set target property values

150K < Tm < 170K

2. Select the groups that will compose the molecules

-OH; -CH2-; -CH3

3. Combine the groups to form molecules

4. Evaluate the property to find matching molecules

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach
Flowsheet Group Contribution Approach

Presentation

  • Same as for molecules but with flowsheets
    • A process-group (PG) represents a unit or a set of unit operations

Reaction PG

Solvent based separation PG

  • A process-group is mass-balance independent
  • Connectivity is component, P and T dependent

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach1
Flowsheet Group Contribution Approach

Presentation

  • A flowsheet is represented as a combination of process-groups (PGs)

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach2
Flowsheet Group Contribution Approach

Overview of the Framework

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach3
Flowsheet Group Contribution Approach

Property Model

  • Energy index for distillation column process-group
  • pk : Topology factor
  • ak : Regressed contribution of PG k
  • dijk : Driving force between the 2 key components
  • A : Regressed constant
  • Energy index for solvent based separation
  • R : Solvent reflux of solvent
  • dijk : Solvent free force between the 2 components

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach4
Flowsheet Group Contribution Approach

Synthesis Algorithm

Generation of new process alternatives

    • Given a set of inlets and outlets, and, property targets
    • Select the matching PGs (Knowledge based)
    • Generate all the feasible alternatives starting from the inlets
    • Evaluate the target properties
    • Rank the alternatives
  • No mass-balance is performed during the generation of the alternatives.
  • Very fast (still depends on the computer implementation)
  • Combinatorial explosion limited by the constraints

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach5
Flowsheet Group Contribution Approach

Synthesis Algorithm

Retrofit of existing processes

    • Represent the existing process as a combination of PGs
    • Select the PGs with their connections that will be kept as starting structure together with the inlets and outlets. (Several starting structures are possible)
    • Select the matching PGs (Knowledge based)
    • Generate all the feasible alternatives from the starting structures
    • Evaluate the target properties
    • Rank the alternatives
  • Retrofit and synthesis of new alternatives are possible within the same framework.

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach6
Flowsheet Group Contribution Approach

Design of the Process

  • Reverse approach
    • From the process-groups to the process flowsheet.
    • Define the topology of the unit operations within the PG (Optional).
    • Define the unit operation design parameters (all the parameters to fully describe the process, i.e. being able to run a rigorous simulation).

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach7
Flowsheet Group Contribution Approach

Design of the Process

  • Reverse approach for a reaction group
    • Fully based on the Attainable Region concept

Maximize the selectivity to C

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach8

Distillation 1

Distillation 2

Flowsheet Group Contribution Approach

Number of stages

35

30

Feed location

20

12

Top product specifications

Acetone 0.965

Chloroform 0.965

Bottom product specifications

Acetone 0.05

Chloroform 0.05

Design of the Process

  • Reverse approach for a solvent based separation
  • A solvent fraction of 0.7 is selected to match the 0.25 driving force target
  • Ex = 0.138
  • Use of Bek-Pedersen reverse algorithm to get the full column description

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach9
Flowsheet Group Contribution Approach

Implementation

  • Software implementation

Process Flowsheet Generation & Design Through a Group Contribution Approach

flowsheet group contribution approach10
Flowsheet Group Contribution Approach

Implementation

  • Software implementation

Process Flowsheet Generation & Design Through a Group Contribution Approach

conclusion future work
Conclusion & Future Work

What with Respect to the Objectives?

  • Efficient on a large range of problems
    • Current PGs:
      • Simple distillation, pressure swing, solvent based, kinetic reaction, fixed conversion reaction
    • Theoretically computationally efficient1
  • Ability to integrated and reuse knowledge over the time
    • Yes, if an efficient sequence is found, a translation as a PG is possible  ease of use
  • Computer implementation for ease of use
    • Going on.

1. in practice the current implementation of the underlining graph theory could be improved

Process Flowsheet Generation & Design Through a Group Contribution Approach

conclusion future work1
Conclusion & Future Work

Limitations

  • Do not take into account interaction between PGs
    • Snowball effect, controllability of a reaction-separation system
    • The only way is to create a PG including both reaction and separation
  • Steady State
    • Need to go batch
  • Precision of a group contribution method
  • Database of PGs
    • Need to be built with the time

Process Flowsheet Generation & Design Through a Group Contribution Approach

conclusion future work2
Conclusion & Future Work

Future Work

  • Single stage separation
    • Flash, crystallization (Work already done)
  • Try on a full scale complex process
    • Multiple reaction/separation blocks with complex units and recycles between the reaction/separation blocks

Process Flowsheet Generation & Design Through a Group Contribution Approach