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Table of Contents
Chapter 1 Introduction
1.1 Background
1.1.1 Process Emissions
1.1.2 Energy Consumption
1.1.3 Environmental
Impacts
1.1.4 Generic Structure
of Continuous Chemical Processes
1.1.5 Hierarchy of Waste
Management Techniques
1.1.6 Types of Pollution
Prevention Projects
1.1.7 The Effectiveness
of Pollution Prevention
1.1.8 Legislation,
Directives and Guidelines
1.1.9 Framework of
Pollution Prevention Assessments
1.1.10 Case Studies
1.2 Research Objectives
Chapter 2 Literature Survey: Part 1
Environmental Comparison of Designs
2.1 Introduction
2.1.1 The Relative
Importance of Environmental Impacts
2.2 Regional Impact Comparison Approaches
2.2.1 Direct Data
Summation
2.2.2 Effect
Normalisation
2.2.3 Scoring and
Ranking Approaches
2.2.4 Exposure
Prediction Approaches
2.2.6 Detailed Impact
Assessment
2.3 Global Impact Comparison Approaches
2.3.1 Global Warming
Potentials
2.3.2 Photochemical
Ozone Creation Potentials
2.3.3 Ozone Depletion
Potentials
2.4 The Aggregation of Impact Indicators
2.5 Summary
Chapter 3 Literature Survey: Part 2
Pollution Prevention Opportunity Identification
3.1 Introduction
3.2 Guide-Word Techniques
3.3 Process Simulation
3.4 Design Synthesis Approaches & Tools
3.4.1 Reaction
System Synthesis
3.4.2 Separation
System Synthesis
3.4.3 Process
System Interactions
3.4.4 The
Hierarchical Design Procedure
3.4.5 Structured
Identification of Pollution Prevention Opportunities
3.5 Pollution Prevention Software
3.6 Summary
Chapter 4 Pollution Prevention Tool for Continuous Chemical
Processes
4.1 Introduction
4.2 Structure and Data Input Requirements
of P2TCP
4.3 Classification Module
4.3.1 Classification Procedure
4.4 Diagnosis Modules
4.5 Prescription Modules
4.5.1 Prescription
Procedures and Heuristics
4.5.2 Prescription
Approach
4.6 Environmental Comparison Module
4.7 Software Representation
4.8 Summary
Chapter 5 Environmental Comparison Module
5.1 Introduction
5.2 P2TCP Environmental Comparison Module
5.3 The Impact Potential of a Chemica
5.3.1 Impact
Potential based on Biomagnification and Bioconcentration
5.3.2 The Relative
Impact Potential (RIP) of a Chemical
5.3.3
Biomagnification Potential
5.4 Concentration Prediction Basis
5.5 The Proposed Steady State Model
5.6 Transformation Reactions
5.6.1 Breakdown
Products
5.7 Steady-State Model Trends and
Intrinsic Uncertainty
5.8 Proposed Equilibrium Partitioning
Models
5.8.1
Aquatic-Atmospheric Distribution Properties
5.8.2 Proposed
Aquatic-Atmospheric Partitioning Ratio (Ma-w)
5.8.3
Sediment-Water Partitioning
5.8.4
Sediment-Interstitial Water Partitioning
5.8.5 Proposed
Sediment-Water Column Partitioning Ratio (Ms-w)
5.9 Partitioning Trends
5.10 RIP Uncertainty Associated with
Equilibrium Partitioning Data
5.10.1 Methodology
and Analysis
5.10.2 Calculation
of Uncertainty in P2TCP
5.11 Case Study
5.12 Effect Concentrations used to
Determine RIPs
5.12.1 Introduction
5.12.2 Appropriate
Effect Concentration Data
5.13 Exposure and Effect Data Sources
5.14 Conclusion
5.15 Nomenclature
Chapter 6 Reaction System Module
6.1 Introduction
6.2 Reaction System Analysis Structure and
Data Requirements
6.3 Raw Material Conversion Heuristics
6.3.1 Increased
Raw Material Conversion Heuristics
6.3.2 Conflicts
6.4 Interactions in Systems with Multiple
Reactions
6.4.1 Reactant
Interaction Diagnosis
6.4.2 Interaction
Diagnosis Case Study
6.5 General Selectivity Heuristics
6.6 Relative Rate-Concentration Heuristics
6.6.1 Series
Interactions
6.6.2 Parallel
Interactions
6.6.3 Combined
Interactions
6.6.4
Rate-Concentration Heuristic Conflicts
6.7 Relative Rate-Constant Heuristics
6.8 Relative Equilibrium Heuristics
6.8.1 Irreversible
Main and Reversible Side Reaction
6.8.2 Reversible
Main and Irreversible Side Reaction
6.8.3 Reversible
Main and Side Reaction
6.8.4 Heuristics
for Increased Conversion
6.8.5 Heuristics
for Decreased Conversion
6.8.6 Conflicts
6.9 Conflicts between Selectivity
Heuristic Sets
6.9.1
Rate-Concentration and Rate-Constant Heuristic Conflicts
6.9.2 Equilibrium
and Rate-Concentration Heuristic Conflicts
6.9.3 Equilibrium
and Rate-Constant Heuristic Conflicts
6.10 Selectivity & Raw Material
Conversion Conflicts
6.10.1 Conflicts
with General Consideration Heuristics
6.10.2
Rate-Concentration and Raw Material Conversion Heuristic Conflicts
6.10.3
Rate-Constant and Raw Material Conversion Heuristic Conflicts
6.10.4 Equilibrium
and Raw Material Conversion Heuristic Conflicts
6.11 Non-Isothermal Operation
6.11.1 Variables
for Temperature Control in Non-Isothermal Systems
6.11.2 Effects on
Temperature Gradients in Non-Isothermal PFRs
6.11.3
Non-Isothermal, Selectivity and Conversion Heuristic Conflicts
6.11.4 Reactor
Comparison
6.12 Effects on Reaction System Energy
Streams
6.12.1 Reaction
System Energy Balance
6.12.2 Inlet
Temperature
6.12.3 Conversion
6.12.4 Selectivity
6.12.5 Reactor
Temperature
6.13 P2TCP Reaction System Analysis Output
Format
6.14 Case Study
6.14.1 Allyl
Chloride Process Reactions and Data
6.14.2 Typical
Reactor Type and Operating Conditions
6.14.3 Effects of
Operating Conditions
6.14.4 Effects of
Reactor Type
6.14.5 Effects of
Non-Isothermal Operation
6.14.6 Effects on
the Reaction System Energy Streams
6.15 Conclusion
6.16 Nomenclature
Chapter 7 Separation System and System Interactions Module
7.1 Introduction
7.2 Analysis Procedure and Data
Requirements
7.3 Recyclable Component Diagnosis
7.4 Determination of Separation
Alternatives
7.4.1 Structure
for the Identification of Separation Alternatives
7.4.2 Phase
Separation Diagnosis
7.4.3 Separation
Alternatives for Liquid Phase Mixtures
7.4.4 Separation
Alternatives for Vapour or Gas Phase Mixtures
7.5 Comparison of Synthesis and Analysis
Methodologies
7.5.1 Approaches
for the Synthesis of Separation Systems
7.5.2 Separation
Synthesis Case Studies
7.5.3 P2TCP
Results and Comparison with the Synthesis Approaches
7.5.4 Comparison
Summary
7.6 Interactions of the Reaction and
Separation Systems
7.6.1 Decision to
Recycle
7.6.2 Raw Material
Conversion
7.6.3 Selectivity
7.6.4 Excess Raw
Material
7.6.5 Separation
Efficiency
7.7 Optimisation of Individual Unit
Operation
7.8 Case Stud
7.8.1 Commercial
Allyl Chloride Separation System
7.8.2 Data
Requirements
7.8.3 Phase Split
7.8.4 Separation
of the Liquid Stream
7.8.5 Separation
of the Vapour Stream
7.8.6 Operating
Condition Affects on the Vapour Separation Alternatives
7.8.7 Process
System Interactions
7.8.8 Case Study
Summary
7.9 Conclusion
Chapter 8 P2TCP Demonstration
8.1 Mono- and Dichlorobenzene Production
8.2 Identification of P2 Opportunities
Using P2TCP
8.2.1 Starting
P2TCP
8.2.2 Process Data
Entry
8.2.3 Saving and
Retrieving Case Studies
8.2.4
Classification
8.2.5 Diagnosis
8.2.6 Prescriptions
8.2.7 Prescription
Results for the Chlorination Process
8.3 Environmental Comparison of Process
Alternatives
8.3.1 Simulation
Model of the Benzene Chlorination Process
8.3.2 Comparison
of Process Options using P2TCP
8.3.3 Discussion
of Comparison Results
Chapter 9 Discussion
9.1 Environmental Comparison
9.2 Identification of Pollution Prevention
Opportunities
9.2.1 Reaction
Systems
9.2.2 Separation
Systems and Process System Interactions
Chapter 10 Conclusions
10.1 Accomplishments
10.2 Limitations
10.3 Recommendations
References
Appendix 1 Allyl Chloride Process P2TCP
Results
Appendix 2 Unit Operation Modification
Check Lists
2.1 Flash Distillation
2.2 Distillation with
Reflux
Pressure Change
Reflux Ratio
Feed Temperature & Location
Appendix 3 The Program Knowledge Base
Structure
Appendix 4 Studies Using Multi-Comparatment
Models
Appendix 5 Generic Plots of RIP Uncertainty
Appendix 6 Software & Literature Data
Sources
Appendix 7 Chlorination Process P2TCP
Results
Appendix 8 Summary of P2TCP Heuristics
A8.1 Raw Material
Conversion Heuristics
A8.2 General Selectivity
Heuristics
A8.3 Relative
Rate-Concentration Heuristics
A8.4 Relative
Rate-Constant Heuristics
A8.5 Relative
Equilibrium Heuristics
A8.6 Conflicts between
Selectivity Heuristic Sets
A8.7 Conflicts between
Selectivity & Raw Material Conversion Heuristics
A8.8 Non-Isothermal
Operation
A8.9 Reaction System
Energy Requirements
A8.10 Interactions of
the Reactor, Separation and Recycle
ABSTRACT
A demand exists to reduce environmental impacts
caused by the consumption of energy and the generation of wastes in
chemical manufacturing processes. Throughout the life-cycle of a
chemical process opportunities
can be identified to reduce potential impacts. In terms of intrinsic
waste
generation and energy consumption, design modifications are most cost
effective
during conception. However conceptual design is often limited by
resource
constraints and principally driven by economic considerations. The
identification
and comparison of design modifications is not typically practised
consistently or routinely in the context of pollution prevention. In
this research the prototype of a computer based system was developed,
P2TCP (Pollution Prevention Tool for Continuous Processes), to help
designers systematically identify pollution prevention opportunities
and assess designs in terms of environmental impacts on a scientific
basis. The tool is applicable for continuous chemical processes and can
be used during conceptual as well as retrofit design therefore
facilitating the development of inherently cleaner processes.
Available resource limited methodologies for
the assessment and comparison of process designs in terms of regional
scale environmental impacts are often limited by subjectivity. No
consensus has been reached. Relative Impact Potentials (RIPs) are
proposed in this research as a scientific basis for assessment in terms
of regional scale impacts. A resource limited approach was developed
for P2TCP, based on generally available data and
associated assumptions, to render RIPs readily usable. Unlike typical
methodologies, transfer between environmental compartments, degradation
processes and increased exposure associated with bed sediment
concentrations are taken into consideration. The suitability of the
proposed RIP approach to provide a discriminatory basis
is assessed quantitatively in terms of uncertainty.
An expert system, developed for P2TCP,
facilitates the systematic identification of process design
modifications which may result in reduced energy consumption and waste
generation. The heuristics were
derived by applying fundamental chemical engineering principles. Case
studies
are not used as the principle knowledge source but for validation and
for
the identification of further extensions. In the context of pollution
prevention and unlike sequential methodologies used for design
synthesis, each system of a process (reaction and separation) is
analysed independently and then potential interactions are considered.
The analysis performed is resource limited and does not require prior
specification of a process flow diagram facilitating the use of P2TCP
during conceptual as well as retrofit design.
Using P2TCP design
modifications were identified and alternatives compared in the context
of pollution prevention for a number of continuous chemical processes.
Processes considered include the production of allyl chloride, the
manufacture of chlorobenzenes and the separation of a mixed hydrocarbon
stream generated in naphtha reforming units of oil refineries. The
resources required to systematically identify opportunities and the
degree of subjectivity associated with comparison were significantly
reduced.
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