environmental considerations inrepresentatives of the sponsoring organizations -- dr. subhas sikdar...

U.S. Environmental Protection Agency

Environmental Considerations in Process Design and Simulation

A Jointly Sponsored Workshop

U.S. Department of Energy

In Cooperation With

Battelle Pacific Northwest Laboratory and

The Chemical Manufacturers Association

December 8-9. 1992

Cincinnati, Ohio

Prepared by:

Jack Eisenhauer Shawna McQueen

Energetics, Inc. Columbia, MD

Under Contract to

American Institute of Chemical Engineers

Research Management Consultants, Inc. Rockville, MD

Acknowledgements

This report and the workshop that it describes represents the efforts of many people, The principal manager of the workshop was Dr. Harry Bostian of EPA, who was instrumental in organizing and implementing the workshop and ensuring its success. The key representatives of the sponsoring organizations -- Dr. Subhas Sikdar of EPA, Dr. Brian Volintine of DOE, and Dr. Lawrence Ross of AlChE --developed the idea for the workshop and provided excellent guidance in defining the objectives and its direction. Mi. Scott Butner (Battelle) and Ms. Diana Artemis (CMA) provided additional guidance and support that proved very valuable. The plenary speakers -- Dr. David Allen (UCLA), Mr. Scott Butner, and Dr. Michael Mullins (MTWDIPPR) -- presented outstanding overviews of the future context and challenges of process simulation that helped set the proper tone for the workshop,

The breakout groups, where much of the work was accomplished, were ably assisted by several key people. Dr. Dale Rudd (University of Wisconsin), Dr. Marshall Rafal (OLI Systems, Inc.), Mr. Scott Butner, and Dr. Michael Mullins served as Technical Consultants in their respective groups in addition to serving as participants. Dr. David Stephan, Dr. Leland Vane, and Mr. Jordan Spooner of EPA, and Mr. Paul Rossiter of Research Management Consultants, Inc. (RMCI) provided superb assistance in recording the group interactions, organizing information and reviewing the results, The groups were facilitated by Mr, Richard Scheer, Mr. Jack Eisenhauer, and Ms. Shawna McQueen of Energetics, Inc. and Mr. Richard Skinner of RMCI.

This report was prepared by Mr, Jack Eisenhauer and Ms. Shawna McQueen, with assistance from Mr. Richard Scheer, Mr. Richard Skinner and Mr. Paul Rossiter,

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Environmental Considerations in Process Design and Simulation iii

iv Environmental Considerations in Process Design and Simulation

t r-

t -- I-..-

Executive Summary

Manufacturing wastes amount to nearly 7 billion metric tons per year, making this the largest component of the national waste stream. The chemical process industries, which Include the manufacture of chemicals, petrochemicals, and plastics, generate a major portion of manufacturing wastes, particularly hazardous wastes that may pose health and environmental risks. Furthermore, the chemical process industries bear an enormous cost for managing their wastes. These industries accounted for as much as one-third to one- half of all pollution control expenditures by U.S. industry, estimated at $55 billion in 1990.

Accordingly, there is a critical need to design and operate chemical processing plants so as to minimize the amount of waste generated and discharged to the environment. Developing new process designs or modifying existing ones so that waste generation is minimized can be a very effective strategy for reducing environmental impacts and is generally preferred to end-of-pipe waste treatment and disposal. Preventing pollution and reducing waste generation also helps companies optimize materials use and lower operating costs,

Process simulation models and other design tools allow engineers to design or modify chemical processes by simulating unit operations and arranging them in various process configurations. These tools can be used to minimize waste generation in chemical processes, provided the models contain appropriate environmental information to aid in design decisions. Currently, however, process simulators do not effectively integrate the technical and economic considerations of environmental needs to assist in the design process.

To address this need, the Environmental Protection Agency, the Department of Energy, and the American Institute of Chemical Engineers sponsored a workshop to identify how environmental factors should be incorporated into process simulation and design tools for the chemical process industries. The overall goal of this workshop was to identify the important R&D needed in this area and to develop some perspective on R&D priorities. Each of the sponsoring organizations is funding or considering R&D projects or programs to help make simulators and design tools more effective in accomplishing pollution prevention objectives.

The results of the workshop are based on the opinions and expert judgements of 50 leading practitioners in the field of process design and simulation. The workshop brought together a cross-section of capabilities and perspectives that included university professors, software developers, process designers, and federal R&D managers. This mix of backgrounds encouraged a fruitful exchange of ideas that ranged from new theoretical modeling approaches being pursued in the academic community to the pragmatic data needs of process engineers who must find ways to meet environmental regulations for current operating facilities.

Conducting R&D to improve process simulation is an important step toward integrating environmental factors into process design. With the help of process design tools, pollution prevention concepts can be designed into new processes and production facilities. Companies that successfully incorporate such concepts into their physical infrastructure

Environmental Considerations in Process Design and Simulation V

will find that their investments yield cost savings from waste avoidance that accrue year after year, Furthermore, investments in R&D to improve simulation tools are very modest compared to the substantial investment that industry will make in building new production facilities or complying with environmental requirements for existing facilities.

To help Identify how simulators could be improved, process design needs were considered in four interdependent areas. A separate work group addressed issues and R&D needs for each of these areas:

1) What are the pertinent environmental considerations and how should these be brought into the optimization/design process,

2) What new process models or modifications are required to accommodate environmental factors in process simulation,

3) How can current concepts of process simulators and design tools be modified to Incorporate environmental factors, and

4) What data are required to support process simulation and design with environmental factors.

Distlnct development needs were considered by specialists for the above areas. Each work group developed a priority list of overall needs and a priority list of R&D recommendations for their respective areas. Each group also indicated the appropriate lime period in which R&D results were expected to occur.

A number of common themes of how to include environmental considerations in process design emerged from the work group sessions and the subsequent summary session, during which the results of each group were reported and collectively discussed. Some groups had difficulty differentiating between improvements required specifically to include environmental factors and those that would benefit all process simulation. The following table summarizes the common themes that emerged from the workshop.

Nearly all of the recommended R&D activities were expected by participants to produce significant results within ten years, and nearly half of the R&D activities proposed would provide results in three years or less. This indicates that while R&D is needed on several fronts -- better data, improved modeling, etc. -- R&D investments made today could Improve the availability and quality of chemical process design tools in a relatively short lime period.

~ ~ ~ ~ _ _ ~ ~ _ _ ~ _ _ _ ~ ~ ~

vi Environmental Considerations in Process Design and Simulation

Topic

Process Synthesis

Dilute Streams

-0ptitnizufion

Modeling Techniques

Findings

Developing new and Improved methods for synthesizing chemical processes that meet envlronmental objectives Is one of the most Important needs for incorporating pollution preventlon concepts Into process deslgn. Thls will enable alternative process flow sheets and has applicatlons beyond process slm uiators.

Improving characterlzation and the ability to separate dilute components of streams through acqulsition of data and enhanced modeling Is critical for developlng cost-effective process des1 gns .

Development of new optlmlzatlon strategies will allow users to'ldentlfy process designs that best satlsfy a range of environmental, cost, and operating requirements.

Better modeling Is needed to accommodate process synthesis and optimlzatlon methodologies. The probablllstlc nature of much envlronmentally-based data makes stochastlc modeling essential In developlng effective deslgn tools and simulators. Greater flexibility In modeling Is needed to accommodate different levels of detall, data, and rigor.

Identified Needs

. .

.

. e . - . . .

.

.

Develop expert systems for synthesis Develop tools to identify alternative reaction pathways and catalysts Pursue non-conventlonal technology alternatives Develop methods for deflnlng "ultimate" limltlng process efficiencies Determine If barrlers ile In models or heuristics Couple synthesis and slmulatlon Use mathematical programming to synthesize processes

Improve slmulatlon models and tools to better handle dilute components of process streams Determlne reaction equilibrium partitioning constants Determine reaction rates and byproducts Improve measurement capability to meet process control, regulatory, and other needs Determine data needs for modeling In the dilute region Use computational chemistry to estimate propertles and behaviors of mixtures In the dilute region - Develop large-scale optimization

Develop non-linear optlmlzatlon

Develop methods for dynamic

Enhance stochastlc modeling and

Optlmlze aggregate process models Develop on-line optimization methods

Develop large-scale modellng

methodologies

Strategies

optimization of processes

optlmlzatlon

methodologies (larger than unit operatlons) - .'Improve probabilistic and stochastlc modeling techniques Develop better hierarchical models Develop dynamic slmulatlon models with process control Develop heuristic modeling capabllltles to accommodate uncertainties and provide flexlblllty

9 Take advantage of parallel computing techniques

Environmental Considerations in Process Design and Simulation vii

Rate - Based (Non -Equilibrium) Processes

En viionmental costs

€nvironmental Impact Assessment

Process Characterizcrtion

Findings

Data and research are needed to characterlze rate-based processes that are not adequately modeled In current slmulators.

The lack of envlronmentally- related cost Information In current simulators Is a key barrier In Identifying cost-effective process designs. Untll process slmulators accurately account for waste treatment costs and lntanglbfe costs on a process-by-process basis, pollution prevention approaches may not appear cost competltlve with designs based on end-of-pipe treatment.

Better methods are needed to determlne the environmental Impact of alternative process designs. Tools to quickly determlne whether processes wlli meet environmental standards are needed.

Better characterlzatlon and modeling of unit operations and process streams Is needed to understand the environmental lmpllcatlons of alternative process conflgurations.

Identified Needs

Characterize non-equlllbrlum phenomena Improve Interfacing and sequencing of rate-based processes

Deflne and quantify lntanglble costs Develop methods to allocate costs to speclflc processes and products Develop a flexible cost estimating system Define costs of various end-of-plpe treatments and assoclate reslduals Develop a library of cost models Develop envlr on m en tal cost factors/lntegrate envlronm ental consideratlons with cost

Develop an environmental Impact

Develop qulck rlsk assessment

Include environmental regulatlons In

Quantify or welgh competing

Index

technlques

process simulators

environmental, cost, and energy concerns Link ecological and process models

Improve characterlzatlon and simulation of trace components (of environmental concern) In process streams Integrate property data Into models and simulators Characterize and define benefits of hybrid units Predict envlronmentally-troublesom e byproducts Characterize and simulate alternative waste treatment and recycling technologies

viii En vironmenta/ Considerations in Process Design and Simulation

Table of Contents

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii Executivesummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 PlenarySession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 BreakoutSession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Work Group 1 : Environmental Considerations in Process Design . . . . . . . . . . . . . . 7 Work Group 3: Design Tools and Simulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Work Group 2: Model Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Work Group 4: Data Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Breakout Group Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Summary Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Work Group 1 : Environmental Considerations in Process Design . . . . . . . . . . . . . . 41 Work Group 2: Model Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Work Group 3: Design Tools and Simulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Work Group 4: Data Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Appendix A: Workshop Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1 Appendix B: Agenda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1 Appendix C: Plenary Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

Environmental Considerations in Process Design and Simulation ix

X Environmental Considerations in Process Design and Simulation

f

In t rod uct ion

On December 8 and 9, 1992, a workshop was held to identify requirements for improving process simulation and design tools to better account for environmental factors in the 'simulation and design of chemical processes. The workshop was jointly sponsored by the U.S. Environmental Protection Agency (EPA), the U.S. Department of Energy (DOE), and the American Institute of Chemical Engineers' Center for WasteReduction Technologies (CWRT). The overall purpose of the workshop was to move toward a consensus of critical R&D needs that could be pursued by government agencies, industry groups, individual companies, or joint partnerships among industry, government and universities.

-i 'J

The workshop was conducted as a 1-1 /2 day facilitated working meeting comprised of practitioners in the field of process design and simulation. The invited participants are among the leading U.S, experts in process simulation and design drawn from the industrial user community, software designers, university researchers, and federal R&D managers. The collective knowledge of the participants provided the basis for identifying future requirements for process design methods and simulators, prioritizing R&D needs, and suggesting respective roles of the process design community.

The scope of the workshop was limited to design tools for the chemical process industries, including chemicals, petrochemicals, and related industries. Workshop participants were asked to consider how process simulation can take advantage of the latest advances in design methodology, simulation techniques, computer architecture, and programming models. Among the key issues the participants were asked to consider in determining critical R&D needs were:

What a-re the current limitations or weaknesses of process simulation packages with respect to environmental factors?

What are appropriate measures of pollution and waste in an industrial process?

Can existing software packages be modified to include environmental considerations?

What are appropriate design criteria and objectives to adequately satisfy process design needs?

How should environmental costs be incorporated into model design?

What new data will be required for improving process simulation? What existing data bases can be used?

How can tools be developed to consider fugitive emissions, pollution due to process upsets, and dilute concentrations of pollutants?

What are the implications of side reactions and comparison of alternative reactants and processes on simulation requirements?

Environmental Considerations in Process Design and Simulation 1

What are the design and modeling problems currently being investigated by software developers and what problems are being ignored?

What kinds of resources -- intellectual, management, equipment, and funding -- are required to meet the challenges of advanced process design tools.

Each of the workshop's sponsors -- EPA's Risk Reduction Engineering Laboratory, DOE'S Office of Industrial Technologies, and the AIChE's Center for Waste Reduction Technology -- is pursuing or considering R&D efforts in process simulation and design. It is anticipated that the results of this workshop will provide information to help these organizations to plan future R&D activities and programs that respond to the priority needs of process designers and software developers.

The workshop was conducted in cooperation with Battelle Pacific Northwest Laboratory and the Chemical Manufacturers Association, who participated in the planning and implementation of the workshop,

Workshop participants were carefully selected to ensure a good cross-section of professionals involved in process design and simulation. Participation was limited to 50 people to produce manageable-size working groups while also allowing for broad representation from the process design community. The profile of participants consisted of 16 participants from academia, 18 participants from industry (users, process engineers, software developers, and consultants), and 16 participants from. government agencies and laboratories, A list of participants and their affiliation is provided in Appendix A.

The workshop consisted of three main components. A Plenary Session was held during the first afternoon to provide several perspectives on the needs and challenges of advanced process design and simulation. The purpose of this session was to stimulate

'.thinking for the work sessions, provide a common understanding of the fundamental challenges, and contrast viewpoints on key issues. The Breakout Session consisted of four parallel working groups that each concentrated on a key aspect of process simulation needs, Each group studied an issue in depth, determined the relative importance of acceptable solutions or approaches, and provided recommendations on appropriate actions and organizational roles. Each group was required to consider both short-term solutions (2-3 years) as well as longer-term opportunities. The Summary Session brought together all the working groups to present concise summaries of their breakout session and to engage in a discussion of their findings. A complete workshop agenda is provided in Appendix B,

=

2 Environmental Considerations in Process Design and Simulation

Plenary Session

The first afternoon of the workshop began with a plenary session to help orient participants to the subject and format of the workshop. Dr. Harry E. Bostian opened the workshop and moderated the plenary session. Mr. E. Timothy Oppelt, Director of RREL, welcomed the participants to RREL, which he characterized as a technical "problem solving" component of EPA. Mr. Oppelt indicated the importance of addressing the environmental challenges of the chemical process industries and noted that the assembled group was carefully selected to obtain a balance of perspectives regarding process simulation and design for these industries. He noted that using simulation in advance of design can help optimize production, lower costs, and minimize emissions. in particular, process simulation provides a relatively low-cost way to avoid environmental emissions.

Each of the lead representatives from the sponsoring organizations provided their perspective on the importance of considering environmental factors in process design and simulation and indicated their objectives for the workshop. Dr. Subhas Sikdar, Director of the Water and Hazardous Waste Treatment Research Division of RREL, emphasized the need to develop alternative approaches to end-of-pipe controls and viewed the Inclusion of environmental factors in process simulation as a way to introduce pollution prevention approaches in the design stage. He noted that we face two kinds of challenges: development of techniques that can modify current processes in the short-term and development of tools to enable design of clean processes from scratch in the longer-term. Overall, he hoped the assembled group would help to develop a "technical road map" to help EPA and the other sponsors to direct their efforts in process simulation,

- Dr. Brian Volintine, Program Manager in DOE'S Office of Industrial Technologies, indicated that his organization, the Advanced Industrial Concepts Division, supports long-term, high- risk R8tD to improve industrial productivity, He emphasized the focus of the workshop being. on the participants themselves and the importance of using their expertise and knowledge to identify R&D requirements that can advance the state-of-the-art of process design and simulation tools to provide better optimization for new processes. Dr. Volintine noted that the assembled group was a good representation of the design community that could accomplish this task.

Dr. Lawrence Ross, Director of the Center for Waste Reduction Technologies, noted that the timing of the workshop was excellent. There has been a watershed of interest on integrating economic growth, environmental responsiveness, and energy and material productivity into an efficient system. He emphasized the need for new revolutionary design tools to allow clean design of chemical processes from the ground up. Dr. Ross observed that what is occurring in the area of waste reduction is not new and drew the analogy to the intense pursuit of energy efficiency solutions during the energy crisis of the 1970's. Now, he noted, the driver is not energy efficiency but environmental sensitivity.


The main part of the session included three plenary addresses:

1. Pollution Prevention for Chemical Processes: Defining the Problem

Presented by: Dr. David Allen, Associate Professor and Chair, Chemical Engineering Department, University of California, Los Angeles

2. Designing With Environmental Objectives

Presented by: Mr. Scott Bulner, Senior Development Engineer, Battelle Pacific North west Laboratories

3. Data Needs to Accomplish Process Simulation With Environmental Factors

Presented by: Dr. Michael MullSns, Associate Professor, Department of Chemical Engineering, Michigan Technological University / Design Institute for Physical Property Data

Dr. Allen provided an overview of the waste generation problem within U.S, industry and offered a context for understanding the challenges for process design and simulation, This context consisted of: 1) macro-scaleissues of how industrial sectors interact, 2) meso- scale issues of how various processes are integrated within an industrial complex, and 3) micro-scale issues of how unit operations are combined within a process. Dr. Allen also suggested that current waste streams often contain relatively high concentrations of valuable materials that might be effectively recycled.

Mr. Butner focused on frameworks for designing with environmental objectives, how various environmental considerations can be integrated into design, and possible tools for design. A key concept in his presentation was the need to move from an economic and risk management concept of industrial waste. management to an ecosystems approach. Mr. Butner concluded with four main points: 1) environmental objectives need to be defined before they can be incorporated into design, 2) design tools serve many functions (to describe, analyze, and synthesize processes and to support decision making), 3) designing for environmental objectives places new requirements on design tools, and 4) data requirements for environmental design must be overcome,

'

Dr. Mullins characterized three types of data needed for including environmental factors in process design and simulation: 1) in-plant, 2) end-of-pipe, and 3) wastes in the environment (chemodynamic zone). In-plant data needs include safety data, fate and processing of dilute streams, mixed solvent/electrolyte streams, reaction data, unusual matrices/media, mass transfer data, and the ability to highlight potential hazards or problems within the process. End-of-pipe data needs include processing of dilute streams, specialized treatment needs, electrolyte/solven t systems data, and datu on solids or unusual matrices. Chemodynamic data needs include environmental partitioning, environmental transport and environmental reactivity,

Copies of the slides used in each of these presentations are provided in Appendix C,

4 En vironmental Considerafions in Process Design and Simulation

Breakout Session

The heart of the workshop was the breakout session in which participants were queried on their ideas, views, and judgements regarding four complementary issues. Each group tackled a different aspect of the process design problem,-although there were clear areas of overlap. The four breakout groups were:

1 . Environmental Considerations in Process Design: What are the pertinent environmental considerations and ho w are these brought into the optimization/design process? What is the environmental objective function?

2. Model Needs: What specific process models or modifications of present models are required to achieve the incorporation of environmental considerations?

3. Design Tools and Simulators: How can current concepts of process simulators be modified to incorporate environmental factors? What work and resources are needed to develop the next generation of Simulators?

4. Data Needs: What data are required to support process simulation and design with en vironmen tal factors?

The Work Group Process

Each work group consisted of eight to ten active participants that were preselected to ensure a desirable mix of backgrounds to tackle each topic. Typically at least four industry and four university participants were included in each group, Additional attendees from the sponsoring organizations were included as "observers". Each group

.- * had one of its participants designated as a "Technical Consultan?' who helped clarify techn'ical questtons, raise unaddressed technical issues, and provide a technical review of the session results for the final report, The groups were facilitated by a non- participating staff member from Energetics, Inc. or Research Management Consultants, Inc, An assistant was also used to help write the ideas, keep notes, and organize information.

/

.-,

While each group tackled a unique set of issues, all groups followed a parallel structure. The basic questions presented to each group included:

1. What are the major needs/requirements for advancing process design? 2. What are possible solutions/R&D actions to meet these requirements? 3. What are the relative priorities of needs and solutions? 4. In what time frame will these solutions be applicable? 5. What is(are) the appropriate organization(s) to carry out each option/solution?

Each group addressed these questions in two phases. In the first phase, the group answered the first question regarding major requirements in their topic area, Structured brainstorming was used to generate ideas, and then group members applied critical judgement to sift through the ideas, combining or eliminating them as appropriate.


Category headings were developed by the group to help organize ideas. The first phase was concluded when participants selected their highest priority needs.

- The second phase focused on the second question regarding what R&D or other actions are needed to address the identified needs, The top priority needs from phase one were used as a .basis for developing R&D requirements. Solutions were generated and subsequently analyzed by the group. This produced an R&D "solution set" for recommendations. -

~

Group participants were then asked to identify the appropriate time period in which each R&D effort would provide results. Three time periods were defined: near-term (within 3 years), mid-term (3 to 10 years), and long-term (over 10 years). Group members were also asked what type of organization is appropriate to pursue this R&D (government, industry, university, or federal laboratory), In selecting priorities for phase two, each participant was asked to make selections within specific time periods. This created top priority needs within each time period. Finally, to reinforce the most important areas, each participant was given one "top priority" selection I

Due to time constraints and problems with definitions, the identification of R&D organizations to pursue the actions were not completed by all groups. Some of the groups that did complete this effort were not highly confident of the results since many R&D activities would include participation by more than one organization. Therefore, these results are not included in this report.

The complete results for each of the working groups are provided at the end of this section, A summary of major findings and a discussion of key issues addressed by the group are provided in the following sections.


Work Group 1: Environmental Considerations in Process Design

Background

Identifying and characterizing the environmental factors that should be included in process simulation models and design decisions is an important first step in developing cleaner and more efficient process configurations. Including environmental factors in the design decision is needed because:

1) the real costs (both "process-specific" and "facility-wide but unallocated") associated with dealing with environmental issues in 1992 are vastly different than they were only a few years ago,

2) intangible costs (company image, safety, long-term liability, insurance, etc.) related to environmental issues can be substantial,

3) relatively few environmental considerations have yet been incorporated into current simulation packages, and, therefore,

4) significant prospects exist, in the long-term and the short-term, for reducing both production costs and environmental impacts through better-designed and better- operated processes,

Incorporating "environmental considerations" means optimizing new processes and re- optimizing old processes, considering all production and waste management costs. This enables cost comparison of processes in which wastes are created, handled, stored, treated, and disposed of with processes that either avoid wastes through source reduction and/or productively use wastes through in-process, on-site, or off-site reuse or recycling, Process simulation tools can help in examining these options.

Work Group Assignment

The work group on Environmental Considerations in Process Design (see box, next page) addressed the issue of what environmental factors should be included in process simulators and design tools. This was perhaps the broadest issue addressed by any work group since it helps to define the overall objective function for environmental concerns. The group discussed a variety of R&D or other actions that could be undertaken to address the high priority needs identified by the members.

The group's discussion ranged broadly, and did not focus on environmental factors alone, Topics included economic constraints, public acceptance, and regulatory policies. In general, the participants sought to push the limits of conventional thinking about process design and take a broader perspective in viewing industrial processes as a part of a larger societal context.

Priority €n vironmenta/ Factors

The initial question addressed by the group was 'What environmental factors need to be considered in process design?" The group identified 58 different factors, many of which


went beyond environmental concerns, and organized them into seven major categories:

Process Characterization Pollution Prevention Materia Is Characterization TechnicaVScientific Regulations/Public Policy

Economics Acceptance

At the end of the session the group identified those factors/needs considered to be of highest priority in the development of process simulation and design tools. The results of the group are presented in Exhibit 1.

The sub jec t of Process Characterization received considerable discussion. A broader based process selection capability was viewed as an important step. The group noted that when environmental factors are incorporated into the selection

Work Group 1: Environmental Considerations In Process Design

Participants Organization Mr. Louis Beke Mobil Research & Development

Corporation Dr. James Douglas University of Massachusetts Dr. David A. Glasscock E.I. DuPont de Nemours & Co. Dr. Nazmul Karim Colorado State University Mr. Robert L. Kraft, E.I. DuPont de Nemours & Co. Dr. Charles L. Kusik Arthur D. Little, Inc. Dr. Dale F. Rudd- University of Wisconsin Dr. George Stephanopolis Massachusetts Institute of

Technology Dr. Jeffrey 8. Weinrach Los Alamos National Laboratory

Observers Oraanization Dr. Subhas K. Sikdar

Dr. Alexander Ross

U.S. Environmental Protection Agency U.S. Environmental Protection Agency

Facilitator Assistant Mr. Richard Scheer Energetics, Inc. U.S. Environmental Protection

Dr. David Stephan

Agency

* Also served as Presenter for Summary Session * Also served as Technical Consultant

- - - process, many downstream problems can be minimized or avoided entirely. The ability to ldentify'and evaluafe alternative reaction pathways to reduce byproduct quantity and/or toxicity was also felt to be important in being able to optimize future process designs wlth costs of environmental factors being included. Also discussed was the need to be able to design processes that would be lesssusceptible to "non-routine"eventssuch as accidents and spills or transient procedures such as start-up and shut-down, cleanup between unit campaigns to produce different products, and catalyst regeneration.

In the Pollution Prevention/Recycle category, the group placed waste minimization options and waste re-use options as the highest priorities. In the waste minimization area, wastewater was targeted as the major problem needing to be addressed. Waste reuse options identified by the group included the need for investigating alternative uses for byproducts, examining waste markets and designing the waste quality accordingly (producing "engineered scrap"), and segregating wastes to preserve purity and avoid overmixing. Characterization of process streams was a high priority in the Materials Characterization section and identification of environmental constraints and objectives was rated highly in the TechnicaVScienMic Non-Pollution Prevention category.

____

~

There was much discussion of the importance of addressing public perceptions and policies when creating process designs. The focus was on the need to educate policy makers and the public about the relative magnitude of the various risks involved,


Exhibit 1. Priority Environmental Factors in Process Design*

Technology/Actlvlty Area

Process Chamcterizatlon

Polldon Prevent/ on/Rec ycle

Materials Characterlzaffon

Technlcal/Sclen~c Non- Polluffon Preventlon

Regulaffons/Public Policy Accepiance

Economics

Major Needs*

High Priority

Process Selection Reaction Pathway Non-Routine Actions

Waste Minimization Options (Costs) Waste Treatment, Materials Waste Reuse Options (Costs) Waste Treatment Materials

Characterization of Process Streams

~

Identify Environmental Constraints and Objectives

NONE

Intangible Costs (Liability, Public Relations, Legal, etc.)

Medium Priority

Predict Environmentally Troublesome By-products

Pre-Design Alternatives Avoid Environmentally Troublesome Chemicals (Toxicity Substitution) How to Compare Environmental Desirability of Alternatives?

Quantify Toxicity Ability to Use Recycled Feeds (someone else's waste)

Quick Optimization Techniques Limits of Measurement and Detection Which Problems Can Simulators Solve?

Expectations of Public Plant Location (Public

REAL Costs of Waste

Acceptance)

Treatment and Disposal

* This table shows only the highest priority items identified by the group -- Le., those that received one or more selections from group members. However, ail items identified by the group were considered important. The full list of ideas generated by the group, Including those of lower priority, are presented at the end of this section.

'High' = 3 or more selections; 'Medium' = 1-2 selections.

Participants noted that many of today's regulations are not usually based on a comprehensive scientific evaluation of the risks, and that it is the responsibility of the deslgn/englneering community to provide more factual information to the policy making process. While acknowledging the importance of educating policy makers and the public, the group emphasized researchable topics when setting priorities. Understanding public expectations, and public acceptance of plant location were the only two items In the Regulations/Public Policy Acceptance category that were considered a priority, receiving only one selection each.


One discussion area, related to public acceptance, was the subject of intangible costs in the Economics category. This was viewed as a high priority by the group. Participants

'acknowledged the importance of incorporating the cost of "intangible" items such as liabilities, public relations, and legal fees into process designs. However, group members also recognized that these costs vary greatly and are hard to estjmate a priori, ~

R&D Recommendations

The second question the group addressed was 'What R&D or other actions can be undertaken to address the high priority needs?'

The group identified R&D needs for three of the high priority items:

Process Selection, Non-routine Events, and Intangibie/Non-direct Costs.

The results of the second phase are summarized in Exhibit 2.

Under Process Selection, the need to develop design methods to synthesize chemical processes that satisfy environmental objectives was viewed as the most significant R&D opportunity discussed by the group. The group believed that new design methods could be developed in the near term, and considered the development of better process synthesis tools to be a critical need. The need to quantify the relative importance of competing concerns, particularly environmental/energy/cost trade-offs, was also considered an important R&D need that could produce useable results in the near term.

R&D into new process selection methods having mid- and longer-term impacts was also identified by the group. A mid-term need was the creation of simulation tools for dilute streams. Longer-term needs included investigation into non-conventional technologies and evaluation of alternative reaction path ways for environmental purposes,

R&D activities identified in the Non-Routine Events category did not receive as much attention or priority by the group as those items under process selection. An important mid-term R&D requirement identified by the group was the need to have better dynamic models of plant start up and shut down. Less important was the need to have control systems designed for avoiding upsets. This item was judged to have the potential for near-term results, but was considered to be well underway and not in high need of greater emphasis.

R&D aimed towards gaining a better understanding of Intangible Costs was also identified by the group. Once again, R&D needs received less attention and emphasis than items raised under the process selection category. Several mid-term needs were seen as having relatively high priority. These included methods for quantifying intangible costs and methods to allocate costs to specific processes and products.

____

_____

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10 En vironmen tal Considerations in Process Design and Simulation

Exhibit 2. Environmental Factors in Process Design Priority R&D Recommendations'

Research Activity Area

Priority R&D Recommendations by timeframe'

J = High Priority = Medium Priority

Near Mid long (e3 years) (3-10 years) (>lo years)

Process Selection

Define Objectives and Constraints Characterization of Process Streams

Non- Routine

I Fault-Tree Anaivsis I I

Establish Industry Working Group

' Table shows only the hlghest priority recommendations identified by the group (Le., those that recelved at least one selection). However, ail Items identified by the group were considered Important. The full list of recommendations, including those considered to be of lower prlority, Is presented at the end of this sectlon. limeframe refers to the time at which the results of the research are expected to be commercially available for general use. Priorlties are Indicated In two ways: 1) checked Items were rated as high prioritles (3 or more selections) and bulieted as medium (1-2 selections), and 2) the asterisks indicate the number of 'top priority selections (chmsen Irrespective of timeframe).

~~ ~


Work Group 2: Model Needs

Background

- Modeling plays a very important role in process simulation when environmental factors are considered. The specific areas of involvement are:

3)

,-

~

Modeling unit operations- Certain operations that may have significant environmental implications are not supported by most conventional process simulators. This includes, but Is not limited to, neutralizers, precipitators, air and steam strippers, bioreactors, carbon adsorbers, incinerators, combustors, and solvent extractors.

~

Modeling non-equilibrium phenomena - Conventional process simulators have long focused on equilibrium processes. Many processes that can have important waste impacts require models written to reflect rate-based processes (reaction kinetics, sorption and transport processes).

Modeling chemistry - Most species of environmental concern are present in trace amounts in process effluent streams. Many of these species are also chemicals for which conventional process simulators do not offer sufficient data support. The creation of databanks reflecting nearly the full range of chemicals is the answer to this problem. Generating the actual numerical solution of models with trace species material balances is not nearly as difficult as building the databanks that reflect the range of organic and inorganic chemicals of concern.

Modeling more than just the process - To improve their usefulness, process models should provide information on process sensitivities and gains, in addition to the straight simulation. To take maximum advantage of this information, the underlying databanks should contain the underlying uncertainties in the values provided, wherever possible.

Thermodynamic models - Modeling for environmental factors calls for robust thermodynamic models of both aqueous and nonaqueous systems. In addition, certain applications involve mixed solvent electrolyte systems. To date there is no highly predictive model available to handle the mixed solvent electrolyte systems.

The development of a simulator reflecting a comprehensive solution to the above modeling issues will go a long way towards accomplishing the ultimate objective of incorporating environmental factors into process simulation and design.


The work group on Model Needs tackled the problem of what specific models or modlficatlons to existing models are needed to incorporate environmental factors into process design and simulation. Among the issues considered by the group were:

___

~

What special problems need to be considered regarding basic unit operations and other fundamental process blocks when modeling with environmental factors?

~


What new fundamental blocks or modifications to present model blocks are needed? For example, must equilibrium stage approaches be replaced by mass transfer methods for separation models?

Are there other problems with dilute and diverse c o n s t i t u e n t s w h e n m o d e l i n g f rom a n environmental perspective?

What data will be required to better track the environ men ta Ily-sensi tive byproducts resulting from unit operations?

Priofity Model Needs

Work Group 2: Model Needs

Particirmn ts Organization Dr. Gary Brown Union Carbide Corporation Mr. John Cassata The M.W. Kellogg Company Dr. H. Christopher Frey Carnegie Mellon University Dr. John C. Crittenden Michigan Technological University Dr. Joseph D. Henry, Jr.' Arizona State University Dr. Marshall Rafal" 011 Systems, Inc. Dr. Michael Gibson-Robinson BP America, Inc.

Observers Organization Dr. Brian Volintine Dr. Harry E. Bostian

U.S. Department of Energy U.S. Environmental Protection Agency

Facilitator Assistant Mr. Jack Eisenhauer Energetics, Inc. U.S. Environmental Protection

Dr. Leland M. Vane

Agency


The initial question addressed by the group was "What new process models or modiffcations are required to accommodate environmentai factors in process design and sim~iaffon?~~. The group identified 33 key requirements for improving process models and classified these into seven major categories:

Macro/Meso Approaches Defining the Environmental Micro Modeling Objective Function Modeling "New" Processes Property Data Modeling Phenomena Model Verification

While these categories proved useful for organizing model requirements, they created some uneasiness among participants because there were other equally valid classifications that would have grouped the ideas across these categories. The Participants were asked to identify the highest priority model needs, given all relevant considerations. Their results are provided in Exhibit 3.

Much of the group discussion focused on large-scale process issues requiring macro-scale and meso-scale approaches, with emphasis on modeling hierarchies and plant-level process synthesis. A common theme was the need to understand and model the environmental conditions that result from the interactions among unit operations and larger processes. This includes the need for new large-scale optimization methodologies, improved process synthesis techniques (particularly regarding the interface between models and process synthesis approaches), improved process sensitivity analysis, and use of hierarchical models to enable efficient decision-making and rapid convergence on


Exhibit 3. Priority Model Needs*

Technoiogy/Activity Area

Macro/Meso Approuches

Mlcro-M odellng

Modellng "New" Processes

Modellng Phenomena

II Define Environmental Ob]ectlve Funcffon

Property Data

Major Needs**

High Prlority

Process Synthesis Large-Scale Optimization Methodologies Large-Scale Methodologies (>Unit Operations)

NONE

Hybrid Unit Operation Models

NONE

Penalty Function for Waste Chemicals

NONE

Experimental Verification

Medium Priority

Process Sensitivity Analysis

By-product Tracking Models Feedstock Characterization

Fluid Dynamics/Microscopic

Simulation of New Unit

Models

Models

Processes

Better Stochastic-Based

Parameter Estimation Interface with Probabilistic

Models

Data ~~

Quick Risk Assessment Flexible Cost Estimating System

NONE

NONE

* This table shows only the highest prlorlty Items Identifled by the group -- 1.8.. those that recelved one or more selections from group members. However, all Items Identifled by the group were consldered important. The full list of ideas generated by the group, including those of lower priority, are presented at the end of thls section.

t* 'High' = 3 or more selectlons; 'Medium' = 1-2 selectlons.

appropriate design options, These areas were generally viewed as being very high priority.

Another main area of discussion was on micro-modeling needs, which focus on representing the creation and flow of pollutants and byproducts within specific unit operations and processes. These include needs for byproduct tracking models, modeling of fugitive emissions, fluid dynamics/microscopic models (particularly regarding reactor configurations and separation devices), and feedstock characterization models, among others. Participants felt that while there were very important and distinct needs for improvements in micro-modeling, this was an area currently receiving much attention, As a result, these topics were generally deemed to be of moderate or lower priority.

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In the area of modeling "new' processes, the group felt strongly that there needed to be better models for representing "hybrid" unit operations -- those that combine more than one function into a single device such as reactor/separators (i.eo, catalytic distillation), The need to simulate entirely new unit processes was also viewed as important.

Another topic area addressed by the group was modeling phenomena. This focused on developing better modeling tools and techniques to help properly account for environmental factors, These included better stochastic-based models, improved parameter estimation, and better handling of empirical and probabilistic data.

Two other categories covered topics that were addressed by the other work groups: defining the environmental objective function and data needs. Participants felt strongly that better property data and careful definition of the environmental objective function was critical to improving models. For the most part, however, the group choose to focus their attention on needs specific to modeling. The exception to this was the need to define a penalty function for waste chemicals and to develop quick risk assessment tools, which the group felt were both highly important.

Model verification -- both experimental and plant-level -- were viewed as a fundamental requirement that pertained to all modeling efforts. Experimental verification in particular was viewed as a high priority. In this regard, the group was somewhat split on whether model verification should be explicitly addressed for environmental factors or should be included implicitly as part of "good practices".

R&D Recommendufions

During the second part of the session, participants were asked "Whut R&D or ofheructions should be underfaken to solve fhese problems or meet these needs?". In developing their recommendations, the group felt it was useful to combine and relabel some ideas in order to capture key concepts underlying priority' areas that cut across the existing categories. The five key needs for which the group developed solutions included:

Process Synthesis Process Modeling of Unit Large-Scale Modeling Operations

Process Modeling of Streams C h em ica Is Methodologies Penalty Function for Waste

The group identified 26 distinct areas where R&D is required to meet these needs. The group was also asked to identify the appropriate time period in which the benefits of the R&D would be seen: near-term (c3 years), mid-term (3-10 years), and long-term (>lo years). Priorities were determined within each of these timeframes. In addition, each participant identified his top overall R&D recommendation irrespective of time period. The results are shown in Exhibit 4.

In the area of process synthesis, the group priorities included the need to determine if barriers lie in the models themselves or in the heuristics that are used (near-term), and the development of expert systems to aid in process synthesis (mid-term). There was also some interest in the need for research to better incorporate rate-based processes in simulators and in developing stochastic approaches to process synthesis.


Exhibit 4. Model Needs Priority R&D Recommendations'

Remearch AcUvlty Area

Process Synthesis

large-Scale Modellng Mdhodologier

Process Moddlng: Unlf Omdions

Penalty Funcflon For Wade Ch#nkab

priority RW Recommendations by Tktmf"e2

J = Hiah Priorltv = Medium Priority

I I Near Near/Mld M Id tc3 veanr) (0- 10 years) (3- 10 years) Determine If Barriers Lie in Models or Heuristics

Research on interfacing Rate-Based Processes* Stochastic Process Synthesis Develop Techniques for Multi-0 b]ec tive Process Syn thesls

Develop Efficient Techniques for Process Sensitivities Develop Hlerarch

Development of Parallel

Stochastic Optimization Technique

Methodoioav I I I I

Studv the Underlying Component Properties* I I

Parameter Estimation/ Regression*

Research Into Reactor/ Separator Units Novel Reactor/ Separator

Simulatina for Trace ComDonents*

Develop Quick Risk Assessment Techniques Develop Library of Cost Models

' Table shows only the hlghest priority recommendations identified by the group (i.e., those that received at least one selectlon). However, all Items ldentlfled by the group were consldered Important. The full llst of recommendatlons. lncludlng those considered to be of lower priority, is presented at the end of this section. Tlmefi~me refers to the time at which the results of the research are expected to be commercially available for general use. Priorltles are Indicated in two ways: 1) checked Items were rated as high priorities (3 or more selections) and bulleted as medium (1-2 seiectlons), and 2) the asterisks indicate the number of 'top priority selections (choosen irrespective of timeframe).


Priorities in large scale modeling methodologies centered on the need for better probabilistic and stochastic modeling techniques in the near term, and the development

' of non-linear optimization strategies in the long term.

Process modeling needs were separated into those pertaining to waste/byproduct streams and those related to unit operations. In the near term, the group identified priorities for defining the characteristics and benefits of hybrid units and integrating property data into models and simulators. In the mid term, the group felt there was a need to characterizing non-equilibrium phenomena in more detail, Two areas, developing simulation strategies for trace components and studying the underlying component properties, were viewed as providing results in all time periods.

With respect to the notion of defining a penalty function for waste chemicals, the group felt that defining the costs of various end-of-pipe treatments and associated residuals was needed to create the incentives for pursuing alternative approaches that minimize environmentally harmful constituents, There was also-a need for developing quick risk assessment techniques to help determine the environmental fate of waste byproducts,

While the priorities of the group were clustered in several areas, there was no single R&D requirement that received more than one vote as the top priority. This may reflect a recognltion that the various modeling needs are interdependent and that success in developing models that can accommodate environmental factors will require advances In several key areas,


Work Group 3: Design Tools and Simulators

Bockgroun d

Software design tools, including process flowsheet simulators, can be used to insure that environmental issues are fully considered during the various stages of process design. By incorporating meta-level knowledge about how process systems interact with the environment and about the origins of waste In processes, design tools can bring a greater level of insight to the design engineer who is faced with making process changes that improve environmental performance, Some examples of how design tools could be used to incorporate environmental considerations Include:

1) Fugitive emissions and other non-point sources such as leaks from valve packings and pump seals, tank vents, and cleaning wastes can be incorporated as "process units" in conventional process simulators. Emission factors for these types of equipment can be modeled using empirical correlations or from databases of design information, Many conventional waste treatment unit operations are available today in commercially available simulators. Efforts are underway by the Chemical Manufacturers Association for the prediction or calculation of emission factors from a wide variety of processing equipment.

2) Process simulators should Incorporate the concept of "environmental media" (e.g., dir, water) to help organize and consolidate the flows from the process to the environment, such as those from flares, effluents, and fugitive/non-point sources.

3) Process synthesis tools can be developed that enable optimized design of reaction, separation, and heat exchange networks, leading to greater operating efficiencies and reducing waste generation,

4) Process synthesis and design tools can incorporate the concept of "use clusters" or similar concepts of grouping materials, equipment, or processes by functional requirements, to permit exploration of a wider range of design choices earlier in the process development cycle.

5) Practical tools for managing product/process lifecycle analyses can be developed to permit the evaluation of upstream/downstream impacts of process choices, as well as the impacts of process operation over the full lifecycle of the product (e,g., including between-batch maintenance and cleaning operations, effects of recycling on process operation, etc).

6) Process design tools should be developed that consider dynamic behavior of the process in design and optimization stages, to allow evaluation of the environmental impacts of process upsets, start-up, and shut down, as well as to design processes that are inherently more stable and hence less prone to catastrophic releases.

-

~

The fundamental purpose of these improvements to design tools is to provide the designer with greater insight into the full lifecycle impacts of process design choices, and to provide this insight at the earliest possible stage in the process development cycle.

~


This insight will insure that the tools retain the flexibility needed to accommodate changing environmental requirements.


The work group on Process Design Tools and Simulator needs addressed the overall approaches to design tools and simulation that should be considered when introducing environmental considerations. At the start of the session, the group debated how to focus the discussion, since many of the problems and needs facing simulation are generic in nature, affecting the science of simulation In general, Others are more specific to the incorporation of environmental considerations into present-day and future engineering practices. The group agreed to frame the discussion broadly, in terms of the key technical challenges facing simulation today and In the future, including the problems that must be resolved and the tools that must be

Work Group 3 Design Tools and Simulators

Participants Organization Mr. Robert S. Butner- Battelle Pacific Northwest

Dr. Urmila Diwekar Dr. Paul W. Gallier Dr. F. Merrill Galloway, Jr. Dr. Vasilios Manousiouthakis Mr. John Persichettc Dr. Demetri Petrides

Dr. Warren Seider Dr. Stephen Zitney

Laboratories Carnegie Mellon University Aspen Technology, Inc. B.F. Goodrich Company University of California Simulation Science, Inc. New Jersey Institute of Technology University of Pennsylvania Cray Research

Facilitator Assistant Ms. Shawna McQueen Energetics, Inc. U.S. Environmental

Mr. Jordan Spooner

Protection Agency

* Also served as Presenter for Summary Session hc Also served as Technical Consultant

- developed to incorporate environmental factors into process simulators. The group attempted to limit specific recommendations to in-process concerns for pollution prevention. Issues on waste treatment and dispersion modeling were discussed, but specific recommendations were not pursued.

Priodty Simulation Needs

The Initial question addressed by the group was'What challenges and opportunities affect the development of design tools and simulators?". The group identified 34 key requirements for improving process simulators that they grouped into 5 major categories:

Mathematical Methods Computing Conceptual Design Business Drivers User Environment

The group Identified seven additional requirements that did not easily fit into any of these five categories. After discussing the similarities among these seven items, the group agreed that these are issues that fail outside the scope of their discussion and fit better with the assignments given to other work groups. A category called "Other Group Issues" was created for the purpose of displaying the information to the other workshop participants, but these were not discussed in any detail within the session. The group


identified the highest priority issues, and nearly half of the 34 key needs identified by the work group received at least one selection. The categories and issues identified by the group are displayed in Exhibit 5.

t

Technology/ Actlvlty Area

Malhematical Methods

Conceptual Design

User hvlronment

Computing

Business Drivers

m e r Group Issues

Exhibit 5. Priority Simulation Needs*

Major Needs**

High Priority

Facilities for Dynamic Simulation Stochastic Modeling and 0 p tim iza tion Dynamic Optimization and Optimal Control

Innovative Waste Reduction Approaches Through Process Synthesis

and Simulation Coupling of Synthesis

NONE

NONE

High Cost of New Simulation Development

NONE

Medium Priority ~

Simulation of Multi-Product Batch Plants Simulation of Waste Treatment and Recycling Optimization of Aggregate Process Models Facilities to Locate Regions of Complex Nonlinearity

Imparting Better Understanding and Representation of Process Artificial Intelligence Methods for Scheduling Tools to Assess Energy- Environment Interaction Embedded Expert Systems for Waste Minimization

User Friendliness Better Visualization/Graphics Structural Modeling (Better) Simpler Tools

Methods for Linking Scheduling

Parallel Distributed Computing and Simulation

NONE

Systems Thermodynamic and Rate Data

Thls table shows only the highest prlorlty items identified by the group -- 1.8.. those that received one or more selections from group members. However, ail items identlfied by the group wae considered Important. The full Ust of ideas generated by the group, including those of lower priority, are presented at the end of this sectlon.

.* 'High' = 3 or more selections; 'Medium' = 1-2 selections.

Mathematical Methods contained the largest number of simulation needs, and was discussed at length by the work group. This category contained the item that received the most selections overall from the work group: facilities for dynamic simulation. A

20 En vironmen tal Considerations in Process Design and Simulation

number of technical problems challenge the development of robust tools for dynamic process simulation, including problems associated with solvers for differential algebraic equations, index changes, and bifurcations at phase change boundaries. Another area that received a lot of attention and a number of priority selections by the work group was stochastic modeling and process optimization. Developing stochastic tools and techniques to deal with uncertainty and variability in process simulation was identified as a major requlrement for incorporating environmental factors. Another related high priority item was dynamic optimization and optimal control, Process design toois must account for dynamic behavior within a process during the design and optimization stages so that the environmental implications of changes in operations can be evaluated, Specific technical challenges in this area include addressing inequality constraint strategies and inverse problems. Simulation of multi-product batch plants, and simulation of waste treatment and recycling also received multiple selections from the work group members, There was some discussion of whether to expand the issue of waste treatment and recycling to the category level and address it in more detail. However, the group agreed that given the limited time available, it was not possible to treat the many issues related to waste treatment and recycling in any detail. Two other items received one prlority selection : optimization of aggregate process models and facilities to locate regions of complex nonlinearity.

The Conceptual Design category had fewer issues but received many priority selections from the group. Six of the seven simulation needs received at least one selection each. The group tended to focus on process synthesis problems. The need for Innovative waste reduction approaches through process synthesis was a common theme of the work group. The coupling of synthesis and simulation was also identified as a high priority. The group agreed that tools were needed to impart a better understanding and representation of the total process, and that expert systems could be useful in this respect. Embedded experts systems for waste minimization could be incorporated into

simulators to help users understand the interactions among processes and the nlties for waste reduction at various stages in the process. The need for heuristic

methods of programming was discussed as an essential element of designing approaches to process synthesis and developing expert systems. Other high priority needs identified by the group in this category included artificial intelligence methods for scheduling and tools to assess energ y-environment interactions,

. ,~-

The User Environment category was initially described by the work group as "User Interface." The group felt that "User Environment" provided a broader definition than what was implied by "user interface." Making simulation tools simpler, more accessible, and better suited to the needs of end users was recognized as a key issue in gaining broad industry acceptance of the technology. Two high priority needs identified by the group included improving user friendliness and developing better visualization and graphic inferfaces. One key issue was the need for modular or structural modeling approaches, This concept stimulated discussion of a number of different ideas, including:

developing modular simulation packages designed to model specific processes simulators that allow varying levels of detail and specificity of inputs to produce different levels of modeling (e.g., "quick and dirty," strictly empirical, or rigorous), and "modeling In context," where the design of the model is driven by what the ultimate goals are.


The development of improved, "simpler" (Le., heuristic) tools received one selection, The issue of heuristics and the issues discussed above under structural modeling were discussed by the group further in the category dealing with Conceptual Design.

in the Computing category, two items were selected as priorities by the work group members: methods for linking scheduling and simulation and parallel distributed computing. Finally, the group identified a category called Business Drivers to reflect the reality that software development is a business venture that must bring products to market, and that these products must be affordable and useful to the end users. Within this category, the high cost of developing new simulators was identified as a major problem. Developing and bringing a totally new simulation package to market is very expensive, and the cost can be prohibitive for private companies or academic institutions working on their own. Other topics discussed were the need to reduce the cost of simulation to end users (user time to learn and use the software, cost of hardware) and the fact that software development must be market dfiven versus technology driven. Finally, one area given a high-priority rating under Other Group Issues was the need for systems thermodynamic and rate data,

R&D Recommendations

During the second part of the session, participants were asked to consider the question 'What R&D or actions can be undertaken to solve these problems or meet these needs?". The group organized their recommendations under four headings:

Synthesis User Environment

Dynamic Simulation and Control Optimization

Some of this effort involved simply reorganizing the recommendations that had been identified during the first session of the workshop. The group also combined or rephrased -some ideas to produce a different or broader meaning. The group was asked to select those R&D recommendations that they felt were the highest priority for developing process simulators and design tools that incorporate environmental considerations. While all the ideas generated during this session can be considered important, the selection process provides a measure of their relative importance.

.

The process of placing the recommendations into near-, mid- or long-term timeframes was difficult for the group and generated much discussion and controversy. The main points of contention related to 1) defining at what point the results of research were considered "available" or "beneficial" and 2) a difference in perception as to what is the critical element in the eventual development ofa software tool. On the first point, almost every R&D need that the group identified is presently being worked on in some form or another, and results from the research are available now and may form essential building blocks for subsequent research or work. There were disagreements over the difference between a product being available (e.g,, published test results in a paper), and a product being widely used and applied as a part of routine industry operations. Further, because of how rapidly computer technology evolves, solutions or software developed today may be inadequate in five years. New hardware and software capabilities can drastically expand the scope and timing of any research effort. On the second point, the representatives from academic institutions tended to stress the need for further

___

__

-


fundamental research as the cornerstone to providing design tools of the future, By contrast, the industry and software development representatives expressed concern for the time required to bring such fundamental technology to market in a user friendly format, with quality issues, robustness, and supporting data needs being properly met. The issue raised in the first session regarding whether efforts arelshould be "technology driven or market driven" probably best summarizes the two contrasting points of view. These issues could not be fully resolved by the group and thus the group members as a whole did not agree on the timing of the R&D as it is presented in Exhibit 6.

The participants identified 23 separate R&D recommendations for meeting the needs identified during the group's first session. The Synthesis and User Environment areas received the highest priority, with 17 priority selections each. While work on Dynamic Simulation and Control was rated as important, the group gave It less priority for R&D because sufficient research work has been done to develop software products of some usefulness; the Immediate problems relate to implementation rather than research. Some of the R&D recommendations were transferred directly from ideas previously identified, while others represent new ideas.

In the Synthesis area, the recommendations focus on broadly defined areas. Every R&D need identified in this category received at least one priority selection. For example, the Item that received the highest priority was innovative approaches to waste reduction, which could include many different specific research projects that pertain to new process design Ideas. Synthesis through mathematical programming and coupling of synthesis and dmulution also received a high priority from the group. Another priority was embedded expert systems for waste minimbation. All the R&D was identified as near term except for coupling of synthesis and simulation, which was placed in the mid term category.

Under User Environment, the priority selections were fairly evenly distributed among the recommendations. Again, all of the needs identified received at least one selection from participants. The two highest priorities were identified as better visualization/graphicsand embedded expert systems. The need for educational and teaching tools was identified as a priority, for two purposes: training end-users and educating college students in the principles of process design and simulation to include environmental factors. Both structural modeling and parallel distributed computing were placed in the mid term and the rest were identified as near term,

r ._ *

In Dynamic Simulation and Control, the group selected facilities for dynamic simulation and dynamic optimization as the two highest priority areas. A third priority in this area was model-based control. The Optimization category included,the only long-term R8tD recommendation identified by the work group: optimization of aggregate process models. This was identified as a high priority need as was stochastic modeling and optimization and on-line optimization.

In summary, near-term (product deliverable within 3 years) research needs are strongly focused on Synthesis and User Environment issues. For deliverables in a mid-term period (3-1 0 years), research needs were evenly split among all four categories. Long-term research needs (more than 10 years) were solely in the optimization area. Another point to be made is that while the group did discuss some of the basic issues and needs

~ -~


Exhibit 6. Process Design Tools and Simulation Priority R&D Recommendations'

Research Actlvlty Area

Synttwsls

U u r Envlmnment .(

Dynamic Slmuldon and Control

OpfYmlzafion

Prlorlty RLD Recommendations by Timeframe'

J = High Priority = Medium Priority

Near Mid Long (S- 10 years) (a10 years)

Develop/lmprove Embedded Expert Systems for Waste Minimization Synthesis Through Heuristic Awroaches

Diagnostics I Improve Structural I Modelina CaDabilihr

Interface DAE Solvers

Model-Based Control Simulation of Multi- Product Batch Plants

On-Line Optimization Develop Methods for Scheduling Optimization"

' Table shows only the highest priority recommendations identified by the group (1.e.. those that recelved at least one selection). However, a i items ldentlfled by the group were considered Important. The full list of recommendations, including those considered to be of lower priority, Is presented at the end of this section.

a limeframe refers to the time at which the results of the research are expected to be commercially available for general use. Prlorffles are indicated In two ways: 1) checked Items were rated as high priorities (3 or more selections) and bulleted as medium (1 -2 selections), and 2) the asterisks indicate the number of "top prloritr/' selections (choosen Irrespective of timeframe).


relating to design and analysis of environmental concerns in process engineering, the purpose of the group was not to define these issues but to discuss and make recommendations for design tools that will effectively meet the process engineering needs, To better address the specific issues that were raised by Work Groups 1 and 2 (Environmental Considerations in Process Design and Model Needs), a follow-up review would be needed.


Work Group 4: Data Needs

Background

New and different data requirements are necessary to meet environmentally sound - process design and simulation. These data requirements can be grouped into the following categories: in-plant, end-of-pipe, and wastes in the environment.

~

In-plant needs include safety data, fate and processing of dilute streams, mixed solvent/electrolyte streams, reaction data, unusual matrices/media, mass transfer data, and the ability to highlight potential hazards or problems within the process. The end-of- pipe needs involve processing of dilute streams, specialized treatment needs, electrolyte/solvent systems data, and solids in unusual matrices. In the area of waste in the environment, issues such as environmental fate and transport, multi-media partitioning, transport mechanisms, bioaccumulation and environmental reactivity need to be considered.

Since most "problem" wastes are dilute, it is necessary to consider the physical properties of compounds in this region and the reactions that occur to form trace species. Data gaps for very dilute components often prevent derivation of property values, Data that

' are available are often not useable because they are not reported in a consistent manner or are of questionable quality. In order to properly use the data that exist in government, industry, and academia databases and to organize the data that needs to be collected, new innovative data validation and transfer techniques must be

' 1 developed. These efforts should encompass data scattered throughout open literature, industry consortia, various government and commercial databases, academidindustrial alliances, foreign sources, and also data estimates made via validated algorithms.

The existing barriers among government, academia, and commercial entities must be lowered to facilitate a diffusion of knowledge. Problems concerning uniform data formats, protocols, and quality should be resolved as well as issues regarding proprietary versus "right-to-know" data. Data estimation should also be explored with regard to temperature, aqueous and mixed solvents, biological and safety factors, and the development of more robust molecular-based techniques. Finally, consideration should be given for the creation of a new national environmental library to archive the new data collection,


The work group on Data Needs addressed issues pertaining to the. nature, availability, quality, storage, and retrieval of data required to support process simulation and design with environmental factors. Like the other breakout groups, they addressed the topic in two phases; first by developing ideas on the issues and needs associated with data collection and dissemination, and second by developing recommendations for R8tD to solve these problems or meet the needs.

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Pflority Data Needs

The first question addressed by the . group was 'What are the major data needs required to support process simulation and design with environmental factors?'.

This initial brainstorming session yielded roughly 40 data needs that were classified into seven categories:

Acquisition Strategies Property Models Process Models Data Sets Data Quality cost

The group then indicated which of these they believed to be of highest priority, Each of the seven

Participants Dr. David T. Allen

Work Group 4 Data Needs

Dr. Rakesh Govind Dr. K.F. Liu' Mr. Robert W. Marmara Dr. Fernando C. Vidaurri Dr. E. S. Venkataramani Mr. lvars Lick

Dr. Michael E. Mullins- Dr. Stanley Sandler

Observers Dr. Andre Macek

Facilitator Mr. Richard Skinner R MCI

Organization University of California University of Cincinnati Union Carbide Corporation Exxon Chemical Company Phillips Petroleum Company Merck & Company, Inc. U.S. Environmental Protection Agency Michigan Technological University University of Delaware

Organization National Institute of Standards & Technology

Assistant Mr. Paul Rossiter R MCI


subject headings generated at least one idea selected as a medium or high priority as shown in Exhibit 7. The Strategies, Acquisition, and Property Models categories received the most priority selections.

The group spent a significant amount of time discussing the various Strategies for assembling or presenting the data sets required to support process simulation. Although numerous strategies were suggested, three ideas were thought to have the highest priority and needed further examination. The group concluded that an environmental Impact index, linking of models for process and impacts, and better definition of user requirements would have the greatest impact in selecting strategies for data acquisition. There was also discussion within the group concerning the importance of the interfacing, the sensitivity, and the impact that the data will have on process simulation,

Another main area of discussion was the Acquisition of data. The group defined acquisition as the direct measuring or indirect estimation of data, which led to significant discussion regarding the implications of the two collection methods. While all the ideas discussed under this category were thought to have some significance, good measured data in the dilute region, reaction by-products, and kinetic (rather than equilibrium) data acquisition were thought to have the highest importance. While property and process models received ampie discussion (focus was on the Interaction of data within the models), only computational chemistry and models to handle mixtures in dilute regions were thought to be restricted to long-term needs.


Exhibit 7. Priority Data Needs*

Technology/ Activity Areas

Major Needs*

High Priority

Good Measured Data in

Reaction By-Products Dilute Regions

Process Models I

Strategies

Property Models

NONE

Environmental Impact Index Linking of Models for Process and Impacts

Data Quality

cost

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Models to Handle Mixtures in Dilute Regions Computational Chemistry

NONE

II Datasets I NONE

NONE I1

Medium Priority

Kinetics Versus Equilibrium Electrolytes in Complex

User Requirement

Mixtures

Mixed Media Property

Electrolytes in Complex Models

Mixtures

Sensitivity of Process

Good Modeling Set of Data

Protocols

Environmental Cost Factors * Integration of Environmental

Considerations/Costs

* Thls table shows only the highest priority Items Identified by the group -- 1.8.. those that received 1 or more selectlons from group members. However, all items Identifled by the group were considered important. The full list of Ideas generated by the group, lncludlng those of lower priority, are presented at the end of this section.

'High' = 3 or more selectlons; 'Medium' = 1-2 selections.

Three other categories received substantial discussion from the group: data sets, quality, and cost. Although these subjects were thought to be important, it was felt that the R&D resources and funds might be better allocated in other areas.

R&O Recommendations

During the second session, the group considered the question, 'What R&D or actions can be undertaken to solve these problems or meet these needs?', The group focuses its discussion on developing solutions for the highest priority needs that were previously identified by the group, Accordingly, the group organized its recommendations under four key subject headings:

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Good Measured Data in Dilute Regions Environmental Impact Index Estimation Methods to Handle Mixtures in Dilu

environmental considerations inrepresentatives of the sponsoring organizations -- dr. subhas sikdar...

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