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PSE and business decision-making in the chemical engineering curriculum
Process SystemsEngineering2003 B. Chen and A.W. Westerberg(editors) 9 2003 Publishedby ElsevierScienceB.V.
74
PSE and Business Decision-Making in the Chemical Engineering Curriculum Warren D. SeideP, J. D. Seader b, and Daniel R. Lewin c
aDepartment of Chemical and Biomolecular Philadelphia, Pennsylvania 19104-6393
Engineering,
University
of Pennsylvania,
bDepartment of Chemical and Fuels Engineering, University of Utah, Salt Lake City, Utah 84112-9203 CPSE Research Group, Department of Chemical Engineering, Technion, Israel Institute of Technology, Haifa 32000, Israel This manuscript discusses approaches for providing chemical engineering students a modem experience in product and process design with an objective of exposing them to process systems engineering (PSE) and business decision-making. After typical mechanisms for business decision-making are reviewed, a template is introduced that presents the steps in product and process design. These involve a blend of heuristic and algorithmic methods, with emphasis on the usage of modem computer tools, especially the process simulators. Then emphasis is placed on the use of case studies, design projects, and other aspects of product and process design courses, to teach students the role of these steps and computer tools in supporting the high-level business decisions required in the process industries. Abstract
Keywords product design, process design, simulators, equipment design, cost estimation 1. INTRODUCTION Most departments of chemical engineering teach courses in process design and process control as vehicles for introducing students to process systems engineering (PSE) techniques. Recently, the growing involvement of chemical engineers in product design has spurred interest in either including this subject in the process design course or adding it as a new course to the curriculum. In this paper, the objective is to consider the role of PSE and business decision-making in the chemical engineering curriculum through a close examination of a modem product and process design course(s). In this introduction, both the scope of business decision-making and the scope of product and process design are reviewed, followed by brief statements concerning the origin of design projects. Then, in the next section, the key steps in product and process design are examined, many of which result from or influence business decisions. Finally, the last section focuses on those steps and computer tools used by students (and practitioners) that support most directly high-level business decisions.
75 1.1
Business Decision-Making
Companies in the chemical industry, and many other commercial and govemmental organizations, have business decision makers, typically within high-level management, who receive inputs from the many sources discussed below. The many inputs are processed and decisions are issued in three principal categories: (1) the concept is approved with the authors of the proposals authorized to proceed to the next step; usually to prepare a more detailed evaluation, keeping preliminary capital limits in mind, (2) the concept is recycled for further study, given reviews that are the basis for the decision, and (3) the concept is rejected. Note, however, that rejected proposals are often not entirely rejected. In many cases, research and development managers find some combination of time, equipment, and motivated employees able to rework the proposal with a "new look." The inputs, or proposals, often come from business managers, whose teams work with current customers, seeking to learn about customer needs. Inputs also come from application groups, who interact closely with business managers, working to synthesize solutions using existing technologies and promising laboratory results. Often ideas from business managers and application groups are fed to research and development (R&D) groups, who work to invent new products and technologies. Their most promising ideas and concepts are sent usually to a business center in a request for a budget to carry out an engineering study. When approved, process systems engineering work is undertaken to carry out product and process synthesis, preliminary design studies, cost estimates, and profitability analyses. When promising results are obtained, these are the basis for proposals, or inputs, to the business decision makers. Another source of inputs for business decision makers comes from manufacturing sites, which often work to resolve operating problems, leading to ideas for variations on existing products, retrofits, or even new processing methods. Often these ideas are fed to R&D groups, with engineering studies undertaken, as described above. Here, also, the most promising results provide inputs to business decision makers. Finally, it is important to note that most business areas have a group of financial analysts who carry out detailed economic analyses, including sensitivity and uncertainty analyses, to accompany inputs to the business decision makers. 1.2
Product and Process Design
The design of chemical products begins with the identification and creation of potential opportunities to satisfy societal needs and to generate profit. Thousands of chemical products are manufactured, with companies like Minnesota Mining and Manufacturing (3M) having developed over 50,000 chemical products since being founded in 1904. The scope of chemical products is extremely broad. They can be roughly classified as: (1) basic chemical products, (2) industrial products, and (3) consumer products. As shown in Figure l a, basic chemical products are manufactured from natural resources. They include commodity and specialty chemicals (e.g., commodity chemicals- ethylene, acetone, vinyl chloride; specialty chemicals- difluor~ylene, ethylene-glycol mono-methyl ether, diethyl ketone), bio-materials (e.g., pharmaceuticals, tissue implants), and polymeric materials (e.g., ethylene copolymers, polyvinylchloride, polystyrene). The manufacture of
76 industrial products begins with the basic chemical products, as shown in Figure lb. Industrial products include films, fibers (woven and non-woven), and paper. Finally, as shown in Figure l c, consumer products are manufactured from basic chemical and industrial products. These include dialysis devices, hand-warmers, Post-it notes, ink-jet cartridges, detachable wall hangers, solar desalination devices, transparencies for overhead projectors, drug delivery patches, fuel cells, cosmetics, detergents, pharmaceuticals, and many others. Many chemical products are manufactured in small quantities and the design of a product focuses on identifying the chemicals or mixture of chemicals that have the desired properties, such as stickiness, porosity, and permeability, to satisfy specific consumer needs. For these, the challenge is to create a product that has sufficiently high market demand to command an attractive selling price. After the chemical mixture is identified, it is often necessary to design a manufacturing process. Other chemical products, otten referred to as commodity chemicals, are required in large quantifies. These are often intermediates in the manufacture of specialty chemicals and industrial and consumer products. These include ethylene, propylene, butadiene, methanol, ethanol, ethylene oxide, ethylene glycol, ammonia, nylon, and caprolactam (for carpets), together with solvents like benzene, toluene, pher~l, methyl chloride, and tetmhydrofumn, and fuels like gasoline, kerosene, and diesel fuel. These are manufactured in large-scale processes that produce billions of potmds annually in continuous operation. Since they usually involve small well-defined molecules, the focus of the design is on the process to produce these chemicals from various raw materials.
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77 Design projects have many points of origin. Often they originate in the research labs of chemists, biochemists, and engineers who seek to satisfy the desires of customers for chemicals with improved properties for many applications (e.g., textiles, carpets, plastic tubing). In this respect, several well-known products, such as Teflon (polytetrafluoroethylene), were discovered by accident. (At Dt&ont, a polymer residue that had accumulated in a lab cylinder of tetrafluoroethylene was found to provide a slippery surface for cookware and was capable of withstanding elevated temperatures, among many similar applications.) In other cases, an inexpensive source of a raw material(s) becomes available and process engineers are called on to design processes that use this chemical, often with new reaction paths and methods of separation. Other design problems originate when new markets are discovered, especially in the developing countries of Southeast Asia and Africa. Yet another source of design projects are engineers themselves who often have a strong feeling that a new chemical or route to produce an existing chemical may be very profitable, or that a market exists for a new chemical product. When a new chemical product is envisioned, the design project can be especially challenging, as much uncertainty often exists in the chemical(s)or mixture of chemicals best suited for the product, as well as the product configuration, the modes of manufacture, and the market demand. For the manufacture of a commodity chemical, the design project is usually less comprehensive, as the focus is usually on the design of the manufacturing facility or chemical process. 2
STEPS IN PRODUCT AND PROCESS DESIGN
In this section, the objective is to introduce a template that presents the steps in product and process design. These involve a blend of heuristic and algorithmic methods, with emphasis on modem computer tools, especially the process simulators. Note that, because the inputs to and responses from business decision makers are not always clearly positioned, the focus of Section 3 is on those steps and computer tools that support high-level decision-making in the product and process design courses. Figure 2 shows many of the steps in designing chemical products and processes. Beginning with a potential opporttmity, a design team creates and assesses a so-called primitive problem. When necessary, the team seeks to find chemicals or chemical mixtures that have desired properties and performance. Then, when a process is required to produce the chemicals, process creation (or invention) is undertaken. When the gross profit is favorable, a base-case design is developed. In parallel, algorithmic methods are employed to find better process flowsheets. Also, in parallel, plantwide controllability assessment is undertaken to eliminate processes that are difficult to control. When the process looks promising and/or when a configured industrial or consumer product is to be designed, the design team carries out detailed design, equipment sizing, and optimization. These steps are expanded upon in the subsections that follow. 2.1
Create and Assess Primitive Problem
Product and process designs begin with a potential opportunity, often a gleam in the eye of an engineer. Usually, the opportunity arises from a customer need, often identified by interviewing customers. Given an array of needs, an effort is made to arrive at specifications
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79 for the product; for example, desired density, viscosity, and latent heat of crystallization for a solution to be used in a hand-warmer. In many cases, a design team engages in a formal session to identify needs and generate ideas for the product. This involves brainstorming to arrive at concepts that are potentially promising in satisfying the needs. Given an array of ideas, an attempt is made to select the most promising from among them using the principles of thermodynamics, chemical kinetics, heat and mass transfer, etc. In so doing, designers and design teams create and assess primitive problems that are most worthy of further research and development. These steps are discussed thoroughly in Chemical Product Design by Cussler and Moggridge I1].
2.1.1 TypicalOpportunities and Primitive Problems As examples, consider the following three potential opportunities and the kinds of primitive design problems generated:
Example 1 Dialysis Device Consider the possibility of designing an inexpensive (say, less than $10) throw-away product for patients with temporary or permanent kidney failure; a device that provides the only treatment for patients with end-stage renal disease (ESRD), whose kidneys are no longer capable of their function. This treatment, which is required three times per week, for an average of 3-4 hours per dialysis, was performed on more than 200,000 patients in the United States in 1996.
Example 2 Drug to Counter Degradation of Blood In the manufacture of pharmaceuticals, consider the possible production of plasminogen activators, which are powerful enzymes that trigger the proteolytic (breaking down of proteins to form simpler substances) degradation of blood clots that cause strokes and heart attacks. Since the mid-1980s, Genentech, a U. S. company, has manufactured tissue plasminogen activator (tPA), which they currently sell for $2,000 per 100 mg dose, with annual sales of 300 million S/yr. Given that their patent will expire soon, Genentech has developed a next generation, FDAapproved, plasminogen activator called "TNK-tPA, which is easier and safer for clinicians to use. With a rapidly growing market, the question arises as to whether an opportunity exists for another company to manufacture a generic (i.e., without a brand name) form of tPA that can compete favorably with TNK-tPA.
Example 3
Vinyl Chloride Manufacture
Consider the need to manufacture vinyl chloride, H~
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80 an important polymer (usually refen'ed to as just vinyl) that is widely-used for rigid plastic piping, fittings, and similar products. An oppommity has arisen to satisfy a new demand for vinyl chloride monomer, on the order of 800 million pounds per year, in a petrochemical complex on the Gulf Coast, given that an existing plant owned by the company produces 1 billion pounds per year of this commodity chemical. Because vinyl-chloride monomer is an extremely toxic substance, it is required that all new facilities be designed carefully to satisfy govemmental health and safety regulations. Clearly, potential opportunities and primitive problems are generated regularly in the fast-paced corporate, govemment, and university research environments. In product design, especially, it is important to create an environment that encourages the identification of consumer needs, the generation of product ideas, and the selection from among these ideas of the most promising altematives; see Sections 3.2 and 3.3. 2.1.2
Selecting Alternatives - Assessing the Primitive Problem
Normally, the designer or a small design team generates many potential ideas for products and processes as potential solutions for the primitive problem, particularly if these individtmls are well familiar with the existing products or situation. Ideas may also come from potential customers, who may be frustrated with the existing products or situation. The ideas are best generated in a non-critical environment. Often, the best ideas may initially be those that might otherwise receive the most criticism. All of the ideas are collected, organized, discussed, and carefully assessed. Cussler and Moggridge [I] present extensive lists of ideas for several products. From the list of ideas, a selection of the most promising altematives is made, based upon technical or marketing considerations; for example, thermodynamics or advertising potential. For the three primitive problems above, Seider et al. TM present design altematives that are typical of those selected from lists of ideas that serve as a base on which to begin the engineering of a product or a process. At this stage, the alternatives require further, more detailed study, and hence it is important to recognize that, as the engineering work proceeds, some altematives are rejected and new alternatives are generated. This is a crucial aspect of design engineering. On the one hand, it is important to generate large numbers of ideas leading to a few promising alternatives. On the other hand, to meet the competition with a product designed and manufactured in a timely fashion, it is important to winnow those alternatives that might require too extensive an engineering effort to be evaluated; e.g., a process that requires exotic materials of construction or extreme conditions of temperature and/or pressure. 2.1.3
Literature Survey
When generating altemative specific problems, design teams in industry have access to company employees, company files, and the open literature. These resources include the SRI Design Reports, encyclopedias, handbooks, indices, and patents, many of which are available electronically, with an increasing number available on the Intemet. For product design, especially, patents are important sources with which the design team must be aware to avoid the duplication of designs protected by patents. After the 17 years that protect patented products and processes in the United States are over, patents are often helpful in the design of next-generation processes to produce the principal chemicals, or chemicals that
81 have fimilar properties, chemical reactions, and so on. Often patents are licensed for fees on the order of 3-6 percent of gross sales.
2.1.4 Auxiliary Studies While creating and assessing a primitive design problem, design teams often initiate studies of (1) technical feasibility, (2) marketing, and (3) business considerations. For a promising product, the technical feasibility study identifies existing and potentially new manufacturing methods, the advantages and disadvantages of each method, and eventually (as design proceeds), the reasons for selecting a specific method. In the marketing analysis, other manufacturers are identified, as well as plant capacities, price histories of the raw materials and products, regulatory restrictions, and principal uses of the product. Marketing considerations often far outweigh technical considerations. Many products or process designs are rejected by management for marketing reasons. For each promising design, business objectives and constraints are normally considered, usually in a business study. These include plant capacity, product quality, likely size of first plant expansion, mechanical completion and startup dates, maximum capacity available, maximum operating costs as a function of capacity, seasonal demand changes, inventory requirements, and minimum acceptable return on investment. As mentioned in Section 1.1, these studies often justify requests to business centers for a budget to carry out the engineering work, including product and process synthesis, prelinainary design studies, cost estimates, and profitability analyses.
2.1.5
Stimulating Innovation in Product Design
The invention and commercialization of new products, and chemical products in particular, benefits by corporate organization to encourage interactions between researchers, marketers, sales-people, and others. In this regard, companies like 3M and General Electric (G.E.) are noted for their corporate policies that seek to maintain a climate in which innovation flourishes. These hclude the fifteen percent rule, in which managers are expected to allow employees 15% of their time to work on projects of their own choosing, tech forums designed to encourage technical exchange and a cross-fertilization of ideas between persons working in many corporate divisions at widely disparate locations, stretch goals intended to stretch the pace of innovation (for example, at least 30 percent of annual sales should come from products introduced in the last four years), process innovation technology centers staffed with chemical engineers and material scientists to help researchers scale-up a new idea from the bench to production, and six sigma strategies for quality control in manufacturing. For discussions of these approaches, with examples, see the books by GundlingTM, Coe [4], and Seider et al. [2].
2.1.6
Pharmaceutical Products
Special considerations are needed for the design of pharmaceutical products. As the design team creates and assesses the primitive problem, the typical development cycle or time line for the discovery and development of a new chemical entity plays a key role, as discussed by Pisano TM. The key steps begin with discovery, in which exploratory research identifies molecules that prove safe and effective in the treatment of disease, usually involving the exploration of thousands of compounds to locate a handful that are sufficiently promising for further development, and the application of data mining techniques to locate
82 the most promising proteins, and cells within which they can be grown, fi'om numerous data bases of laboratory data. Next, in preclinical development, a company seeks to obtain sufficient data on a drag to justify the more expensive and risky step of testing in humans. Then, in clinical trials, which are administered over three phases (each of duration 1-2 years), the drag is tested on human volunteers. Dmfng the latter phase, the drag is administered to thousands of patients at many locations over several years. Finally, to gain approval, an application is prepared for the FDA requesting permission to sell the drug. Note that as Phases 1 and 2 of the clinical trials proceed, process design is undertaken to produce large quantities of the drag, first for Phase 3 testing and then for commercial operation. These steps are considered in detail for a plant to produce tissue plasminogen activator (tPA) in Seider et al. [2]. Note also that the profit margins are sufficiently high to accelerate the process design of the facility for Phase 3 testing, with little if any process optimization. Subsequently, when FDA approval is obtained, the Phase 3 process is used for commercial operation. 2.2
Find Chemicals Performance
or
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Having
Desired
Properties
and
Having created and assessed the primitive problem, the design team often undertakes For those primitive problems in which desired properties and performance have been specified, it is often necessary to identify chemicals or chemical mixtures that meet these specifications. Examples include: (1) thin polymer films to protect electronic devices, having a high glass-transition temperature and low water solubility, (2) refrigerants that boil and condense at desired temperatures and low pressures, while not reacting with ozone in the Earth's stratosphere, (3) environmentally friendly solvents for cleaning, for example to remove ink pigments, and for separations, as in liquid-liquid extraction, (4) low-viscosity lubricants, (5) proteins for pharmaceuticals that have the desired therapeutic effects, (6) solutes for hand warmers that remain supersaturated at normal temperatures, solidifying at low temperatures when activated, and (7) ceramics having hightensile strength and low viscosity for processing. Often design problems are formulated in which the molecular structure is manipulated, using optimization methods, to achieve the desired properties. For this purpose, methods of property estimation are needed, which often include group contribution methods, and increasingly molecular simulations (using molecular dynamics and Monte-Carlo methods). The search for molecular structure is often iterative, involving heuristics, experimentation, and the need to evaluate many alternatives in parallel, especially in the discovery of pharmaceutical proteins, as discussed by Seider et al. [2].
molecular structure design.
For some chemical products, like creams and pastes, the specification of desired properties is a key to successful product design. Creams and pastes are colloidal systems that contain immiscible liquid phases, as well as solid particles. As described by Wibowo and Ng I6], the first step in their design involves the identification of product quality factors, including functional quality factors (e.g., protects, cleans, and decorates the body, delivers an active pharmaceutical ingredient, ...), rheological quality factors (e.g., pours easily, spreads easily on the skin, does not flow under gravity, stirs easily, coats uniformly, ...), physical quality factors (e.g., remains stable for an extended period, melts at a specified temperature, releases an ingredient at a controlled rate, ...), and sensorial quality factors (e.g., feels smooth, does not feel oily, appears transparent, opaque, or pearlescent, does not cause imtation, ...) Given these specifications, the second step involves product formulation,
83 which involves selection of the ingredients, the emulsion type (if applicable), the emulsifier (if necessary), and determination of the product microstructure. Then, the process creation step, as discussed below, and the product evaluation step follow. In a second paper, Wibowo and Ngiv1 expand upon these steps, and apply them for several products, including dry toner, laundry detergent, shampoo, and cosmetic lotion. 2.3 Process Creation
For those primitive problems for which a process must be designed to produce the chemical products, when funded by a business center, the design team carries out the process creation step. Since strategies for process flowsheet synthesis are well documented tS' 9, 2], especially as they apply to the manufacture of commodity chemicals, these steps are not reviewed herein. Note, however, that when process equipment is selected in the so-called task-integration step, the operating mode (that is, continuous, batch, or semi-continuous)is selected. For processes to manufacture specialty chemicals and pharmaceuticals, especially, the design and scheduling of batch processes gains importance.
2.3.1 Product Type Retuming to Figure 1, the manufacauSng processes shown differ significantly depending on the chemical product type. For the manufacture of basic chemical products, the process flowsheet involves chemical reaction, separation, pumping, compression, and similar operations. On the other hand, for the manufacture of industrial products, extrusion, blending, compounding, and stamping are typical operations. Note also that the focus on quality control of the product shifts from the control of the physical, thermal, chemical, and rheological properties to the control of optical properties, weatherability, mechanical strength, printability, and similar properties. Most strategies for process synthesis focus on the manufacture of basic chemical products, with much work remaining to elucidate strategies for the manufacture of industrial products. For the design of configured industrial and consumer products, where emphasis is placed on the design of three-dimensional products, chemical engineers are nomaaUy not involved in the design of the manufacturing process, which includes parts making, parts assembly and integration, and fmishing. 2.4
Development of Base Case Process
To address the most promising flowsheet altematives for the manufacture of basic chemicals, the design team is usually expanded or assisted by specialized engineers, to develop base-case designs. Again, since these strategies are well documented, they are not reviewed herein. Regarding computer-aided process simulation, it is noteworthy that batch process simulators (for example, BATCH PLUS and SUPERPRO DESIGNER) are gaining favor for the design of processes to manufacture specialty chemicals, especially pharmaceuticals. 2.5
Detailed Process Synthesis using Algorithmic Methods
While the design team develops one or more base-case designs, detailed process synthesis is often undertaken using algorithmic methods. For continuous processes, these methods include: (1) create and evaluate chemical reactor networks for conversion of feed to
84 product chemicals, separation trains for recovering species in multicomponent mixtures, and reactor-separator-recycle networks, and (2) locate and reduce energy usage, create and evaluate efficient networks of heat exchangers with turbines for power recovery, and networks of mass exchangers. For batch processes, these methods create and evaluate optimal sequences and schedules for batch operation. In the manufacture of industrial chemicals, such as films, fibers, and paper, processes are synthesized involving extrusion, blending, compounding, sealing, stamping, and related operations. These processes normally involve large throughputs, and consequently, are usually continuous, with some discrete operations that occur at high frequency, such as sealing and stamping. Methods of process synthesis rely heavily on heuristics and are not as well developed as for the manufacture of basic chemical products. For these processes, the emphasis is on the unit operations that include single- and twin-screw extrusion, coating, and fiber spinning. See, for example, the Principles of Polymer Processing by Tadmor and Gogos [10] and Process Modeling by Denn [11]. 2.6
Plant-wide Controllability Assessment
An assessment of the controllability of the process is initiated after the detailed process fiowsheet has been completed, beginning with the qualitative synthesis of control structures for the entire flowsheet. Then measures are utilized that can be applied before the equipment is sized in the detailed design stage, to assess the ease of controlling he process and the degree to which it is inherently resilient to disturbances. These measures permit altemative processes to be screened for controllability and resiliency with little effort and, for the most promising processes, they identify promising control structures. Subsequently, control systems are added and rigorous dynamic simulations are carried out to confirm the projections using the approximate measures discussed previously. See, for example, the books by Luyben et al. [12], Luyben[13], and Seider et al. [21. 2.7 Detailed Design, Equipment Sizing, and Optimization - Configured Product Design
Depending on the primitive design problem, the detailed design involves equipment sizing of units in a new process for commodity and specialty chemicals, that is, detailed process design, and/or the determination of the product configuration for a configured industrial or consumer product (that uses the chemicals or chemical mixtures produced). Here, also, the steps in equipment sizing and cost estimation for processes involving commodity and specialy chemicals are well documented[14' 21. When the primitive design problem leads to a configured industrial or consumer product, much of the design activity is centered on the three-dimensional structure of the product. Typical chemically-related, industrial and consumer products include, for example, hemodialysis devices, solar desalination traits, automotive fuel cells, handwarmers, multi-layer polymer mirrors, integrated circuits, germ-killing surfaces, insect repelling wristbands, disposable diapers, inkjet cartridges, transparencies for overhead projectors, sticky wall hangers, and many others. In many cases, the product must be configured for ease of use and to meet existing standards, as well as to be manufactured easily. Increasingly, when determining the product configuration, distributed-parameter models, involving ordinary and partial differential equations, are being created. Simple discretization algorithms are often used to obtain solutions, as well as the Finite-element Toolbox in MATLAB and the FEMLAB package.
85 The product invention phase begins in which ideas are generated and screened, with detailed three-dimensional designs developed. For the most promising inventions, prototypes are hailt and tested on a small-scale. Only aider the product passes these initial tests, do the design engineers focus on the process to manufacture the product in commercial quantifies. This scale-up often involves pilot-plant testing, as well as consumer lesting, before a decision is made to enter commercial production. Clearly, the methods of capital cost estimation, profitability analysis, and optimization are applied before and during the design of the manufacturing facility, although when the product can be sold at a high price, due to large demand and limited production, detailed profitability analysis and optimization are less important. For these products, it is most important to reduce the design and manufacturing time to capture the market before competitive products are developed. 3
FOCI ON STEPS AND C O M P U T E R TOOLS IN SUPPORTING HIGH-LEVEL BUSINESS DECISIONS
Given the need to expose chemical engineering students to the principal steps and computer tools in designing chemical products and processes, several vantage points can be taken. In the previous section, these steps and computer tools were elucidated, but the inputs to and responses from business decision makers were difficult to define explicitly, as they occur at various stages, depending on the product and/or process and company situation or policy. In this section, the focus is on imparting to students an appreciation of the steps and computer tools that support the high-level business decisions required in the process industries.
3.1
Case Studies and Design Projects
Virtually all students are engaged in open-ended problem solving in the core courses of chemical engineering. However, most do not solve a comprehensive design project until their senior year. When framed well, students are presented with a letter from management stating a societal need(s) and suggesting a primitive problem(s) to be solved in trying to meet this need(s). See, for example, the three examples in Section 2.1.1. Then, as discussed in Section 2.1.3, student design teams search the literature for competitive products, especially the patent literature for existing businesses and successful products. Also, as discussed in Section 2.1.4, students are expected to initiate studies of marketing and business considerations. These involve assessing consumer needs and the size of the market, as well as determining the sources of competitive product(s), the level of production, the selling prices, potential gross profits, and related issues of importance to business decision makers.
3.2
Management Stimuli
The actions by business decision makers, discussed in Section 2.1.5, contribute toward creating an environment that stimulates technical people to innovate and invent new products. These have been key elements of 3M's business strategy over the past century and have led to their success in introducing numerous successful chemical products TM. Rather than taking a passive role, management actively seeks to stimulate innovation.
86
3.3
Idea Generation in Response to Business Trends and Customer Needs
The idea generation phase, in which a design team brainstorms to arrive at long lists of potential ideas worthy of consideration in developing a viable product(s), is at the heart of product design [11. In addition, together with marketing people, the design team interviews potential customers to obtain their assessment of their most important needs. While difficult to carry out quantitatively in a university setting, it is important that students appreciate hese key steps in responding to business trends and customer needs in the commercial world.
3.4
Detailed Process Simulation, Equipment Design, and Cost Estimation
In solving their design projects, students are taught to formulate decision trees and to use screening measures to eliminate the least promising altematives, initially using approximate measures such as gross profits, and gradually refining these measures as the technical analysis becomes more quantitative. In carrying out this analysis, students often use process simulators and rigorous methods to size equipment and estimate costs. These usually involve the use of extensive data banks of thermophysical property data, equipmentsizing data, and purchase cost data. While business managers do not examine the details, the use of these packages provides business decision makers with a common basis for comparing the bottom lines of competitive designs; for example, involving the investor's rate of retum.
3.5
Sensitivity and Uncertainty Analysis
Furthermore, through the use of computer tools to compare competitive designs, students learn the ease and speed with which they can prepare detailed design studies. They learn to vary parameters in sensitivity analyses, as well as in optimization studies. By the same token, students also learn the ease with which these systems can be misused, possibly leading a design team to present management with a misguided recommendation for a business venture. The need to check calculations and fully document the underlying assumptions and approximations, with estimates of uncertainties, is another important lesson students must learn.
3.6
Design Reports
Training students to transmit their ideas, both orally and in writing, is a key aspect of their education. The experience of writing an extensive design report, with its letter of transmittal, is an important vehicle for teaching students to communicate with persons not involved in the technical details of their project. In addition, the preparation, delivery, and evaluation of an oral presentation to a critical audience, usually populated by faculty and industrial persons, is another key aspect of leaming to influence business decision makers. 4
YOUNG FACULTY PERSPECTIVES
Recent changes in young faculty perspectives suggests future impacts of PSE on business decision-making. With recent advances in experimental synthesis methods at the nano- or meso-scale, a large fraction of the young faculty have been completing doctoral research on structured materials, protein structures and interactions, among similar applied
87 chemistry, physics, and biology projects. These persons are likely to be more stimulated by the design of configured chemical products, such as biochemical sensors, integrated circuits, and multi-layer polymer mirrors, rather than the design of commodity chemical processes. The development of these products, which often command high selling prices (for example, specialized pharmaceuticals), can have a major impact on business decision-making. It seems clear that chemical engineers will focus increasingly on the design of these kinds of products, with significant business and legal considerations. 5
CONCLUSIONS
As the steps in product and process design are being elucidated and computer tools are gaining sophistication, the ties between PSE and business decision-making are being conveyed to undergraduate students more effectively. In addition to clarifying the steps and computer tools, this manuscript has focused on many of the ties. REFERENCES
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [ 11] [12] [13] [14]
E. L. Cussler and G.D. Moggridge, Chemical Product Design, Cambridge University Press 2001. W . D . Seider, J. D. Seader and D. R. Lewin, Product and Process Design Principles: Synthesis, Analysis, and Evaluation, Second Edition, Wiley, New York, 2003. E. Gundling, The 3M Way to Innovation: Balancing People and Profit, Kodansha Intemational, Tokyo, 2000. J.T. Coe, Unlikely Victory: How General Electric Succeeded in the Chemical Industry, AIChE, New York, 2000. G. P. Pisano, The Development Factory: Unlocking the Potential fo Process Innovation, Harvard Business School Press, Cambridge, 1997. C. Wibowo and K. M. Ng, Product-Oriented Process Synthesis and Development: Creams and Pastes, AIChE Journal, 47, 12 (2001) 2746-2767. C. Wibowo and K. M. Ng, Product Centered Processing: Manufacture of ChemicalBased Consumer Products, AIChE Journal, 48, 6 (2002) 1212-1230. J. M. Douglas, Conceptual Design of Chemical Processes, McGraw-Hill, New York, 1988. L. T. Biegler, I. E. Grossmann, and A. W. Westerberg, Systematic Methods of Chemical Process Design, Prentice-Hall, New Jersey, 1997. Z. Tadmor and C. G. Gogos, Principles of Polymer Processing, Wiley, New York, 1979. M.M. Denn, Process Modeling, Longman, New York (1986). W. L. Luyben, B. D. Tyreus and M. L. Luyben, Plantwide Process Control, McGrawHill, New York, 1999. W. L. Luyben, Plantwide Dynamic Simulators in Chemical Processing and Control, Marcel Dekker, New York, 2002. M. S. Peters, K. D. Timmerhaus, and R. West, Plant Design and Economics for Chemical Engineers, Fifth Ed., McGraw-Hill, New York, 2003.
74
PSE and Business Decision-Making in the Chemical Engineering Curriculum Warren D. SeideP, J. D. Seader b, and Daniel R. Lewin c
aDepartment of Chemical and Biomolecular Philadelphia, Pennsylvania 19104-6393
Engineering,
University
of Pennsylvania,
bDepartment of Chemical and Fuels Engineering, University of Utah, Salt Lake City, Utah 84112-9203 CPSE Research Group, Department of Chemical Engineering, Technion, Israel Institute of Technology, Haifa 32000, Israel This manuscript discusses approaches for providing chemical engineering students a modem experience in product and process design with an objective of exposing them to process systems engineering (PSE) and business decision-making. After typical mechanisms for business decision-making are reviewed, a template is introduced that presents the steps in product and process design. These involve a blend of heuristic and algorithmic methods, with emphasis on the usage of modem computer tools, especially the process simulators. Then emphasis is placed on the use of case studies, design projects, and other aspects of product and process design courses, to teach students the role of these steps and computer tools in supporting the high-level business decisions required in the process industries. Abstract
Keywords product design, process design, simulators, equipment design, cost estimation 1. INTRODUCTION Most departments of chemical engineering teach courses in process design and process control as vehicles for introducing students to process systems engineering (PSE) techniques. Recently, the growing involvement of chemical engineers in product design has spurred interest in either including this subject in the process design course or adding it as a new course to the curriculum. In this paper, the objective is to consider the role of PSE and business decision-making in the chemical engineering curriculum through a close examination of a modem product and process design course(s). In this introduction, both the scope of business decision-making and the scope of product and process design are reviewed, followed by brief statements concerning the origin of design projects. Then, in the next section, the key steps in product and process design are examined, many of which result from or influence business decisions. Finally, the last section focuses on those steps and computer tools used by students (and practitioners) that support most directly high-level business decisions.
75 1.1
Business Decision-Making
Companies in the chemical industry, and many other commercial and govemmental organizations, have business decision makers, typically within high-level management, who receive inputs from the many sources discussed below. The many inputs are processed and decisions are issued in three principal categories: (1) the concept is approved with the authors of the proposals authorized to proceed to the next step; usually to prepare a more detailed evaluation, keeping preliminary capital limits in mind, (2) the concept is recycled for further study, given reviews that are the basis for the decision, and (3) the concept is rejected. Note, however, that rejected proposals are often not entirely rejected. In many cases, research and development managers find some combination of time, equipment, and motivated employees able to rework the proposal with a "new look." The inputs, or proposals, often come from business managers, whose teams work with current customers, seeking to learn about customer needs. Inputs also come from application groups, who interact closely with business managers, working to synthesize solutions using existing technologies and promising laboratory results. Often ideas from business managers and application groups are fed to research and development (R&D) groups, who work to invent new products and technologies. Their most promising ideas and concepts are sent usually to a business center in a request for a budget to carry out an engineering study. When approved, process systems engineering work is undertaken to carry out product and process synthesis, preliminary design studies, cost estimates, and profitability analyses. When promising results are obtained, these are the basis for proposals, or inputs, to the business decision makers. Another source of inputs for business decision makers comes from manufacturing sites, which often work to resolve operating problems, leading to ideas for variations on existing products, retrofits, or even new processing methods. Often these ideas are fed to R&D groups, with engineering studies undertaken, as described above. Here, also, the most promising results provide inputs to business decision makers. Finally, it is important to note that most business areas have a group of financial analysts who carry out detailed economic analyses, including sensitivity and uncertainty analyses, to accompany inputs to the business decision makers. 1.2
Product and Process Design
The design of chemical products begins with the identification and creation of potential opportunities to satisfy societal needs and to generate profit. Thousands of chemical products are manufactured, with companies like Minnesota Mining and Manufacturing (3M) having developed over 50,000 chemical products since being founded in 1904. The scope of chemical products is extremely broad. They can be roughly classified as: (1) basic chemical products, (2) industrial products, and (3) consumer products. As shown in Figure l a, basic chemical products are manufactured from natural resources. They include commodity and specialty chemicals (e.g., commodity chemicals- ethylene, acetone, vinyl chloride; specialty chemicals- difluor~ylene, ethylene-glycol mono-methyl ether, diethyl ketone), bio-materials (e.g., pharmaceuticals, tissue implants), and polymeric materials (e.g., ethylene copolymers, polyvinylchloride, polystyrene). The manufacture of
76 industrial products begins with the basic chemical products, as shown in Figure lb. Industrial products include films, fibers (woven and non-woven), and paper. Finally, as shown in Figure l c, consumer products are manufactured from basic chemical and industrial products. These include dialysis devices, hand-warmers, Post-it notes, ink-jet cartridges, detachable wall hangers, solar desalination devices, transparencies for overhead projectors, drug delivery patches, fuel cells, cosmetics, detergents, pharmaceuticals, and many others. Many chemical products are manufactured in small quantities and the design of a product focuses on identifying the chemicals or mixture of chemicals that have the desired properties, such as stickiness, porosity, and permeability, to satisfy specific consumer needs. For these, the challenge is to create a product that has sufficiently high market demand to command an attractive selling price. After the chemical mixture is identified, it is often necessary to design a manufacturing process. Other chemical products, otten referred to as commodity chemicals, are required in large quantifies. These are often intermediates in the manufacture of specialty chemicals and industrial and consumer products. These include ethylene, propylene, butadiene, methanol, ethanol, ethylene oxide, ethylene glycol, ammonia, nylon, and caprolactam (for carpets), together with solvents like benzene, toluene, pher~l, methyl chloride, and tetmhydrofumn, and fuels like gasoline, kerosene, and diesel fuel. These are manufactured in large-scale processes that produce billions of potmds annually in continuous operation. Since they usually involve small well-defined molecules, the focus of the design is on the process to produce these chemicals from various raw materials.
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77 Design projects have many points of origin. Often they originate in the research labs of chemists, biochemists, and engineers who seek to satisfy the desires of customers for chemicals with improved properties for many applications (e.g., textiles, carpets, plastic tubing). In this respect, several well-known products, such as Teflon (polytetrafluoroethylene), were discovered by accident. (At Dt&ont, a polymer residue that had accumulated in a lab cylinder of tetrafluoroethylene was found to provide a slippery surface for cookware and was capable of withstanding elevated temperatures, among many similar applications.) In other cases, an inexpensive source of a raw material(s) becomes available and process engineers are called on to design processes that use this chemical, often with new reaction paths and methods of separation. Other design problems originate when new markets are discovered, especially in the developing countries of Southeast Asia and Africa. Yet another source of design projects are engineers themselves who often have a strong feeling that a new chemical or route to produce an existing chemical may be very profitable, or that a market exists for a new chemical product. When a new chemical product is envisioned, the design project can be especially challenging, as much uncertainty often exists in the chemical(s)or mixture of chemicals best suited for the product, as well as the product configuration, the modes of manufacture, and the market demand. For the manufacture of a commodity chemical, the design project is usually less comprehensive, as the focus is usually on the design of the manufacturing facility or chemical process. 2
STEPS IN PRODUCT AND PROCESS DESIGN
In this section, the objective is to introduce a template that presents the steps in product and process design. These involve a blend of heuristic and algorithmic methods, with emphasis on modem computer tools, especially the process simulators. Note that, because the inputs to and responses from business decision makers are not always clearly positioned, the focus of Section 3 is on those steps and computer tools that support high-level decision-making in the product and process design courses. Figure 2 shows many of the steps in designing chemical products and processes. Beginning with a potential opporttmity, a design team creates and assesses a so-called primitive problem. When necessary, the team seeks to find chemicals or chemical mixtures that have desired properties and performance. Then, when a process is required to produce the chemicals, process creation (or invention) is undertaken. When the gross profit is favorable, a base-case design is developed. In parallel, algorithmic methods are employed to find better process flowsheets. Also, in parallel, plantwide controllability assessment is undertaken to eliminate processes that are difficult to control. When the process looks promising and/or when a configured industrial or consumer product is to be designed, the design team carries out detailed design, equipment sizing, and optimization. These steps are expanded upon in the subsections that follow. 2.1
Create and Assess Primitive Problem
Product and process designs begin with a potential opportunity, often a gleam in the eye of an engineer. Usually, the opportunity arises from a customer need, often identified by interviewing customers. Given an array of needs, an effort is made to arrive at specifications
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79 for the product; for example, desired density, viscosity, and latent heat of crystallization for a solution to be used in a hand-warmer. In many cases, a design team engages in a formal session to identify needs and generate ideas for the product. This involves brainstorming to arrive at concepts that are potentially promising in satisfying the needs. Given an array of ideas, an attempt is made to select the most promising from among them using the principles of thermodynamics, chemical kinetics, heat and mass transfer, etc. In so doing, designers and design teams create and assess primitive problems that are most worthy of further research and development. These steps are discussed thoroughly in Chemical Product Design by Cussler and Moggridge I1].
2.1.1 TypicalOpportunities and Primitive Problems As examples, consider the following three potential opportunities and the kinds of primitive design problems generated:
Example 1 Dialysis Device Consider the possibility of designing an inexpensive (say, less than $10) throw-away product for patients with temporary or permanent kidney failure; a device that provides the only treatment for patients with end-stage renal disease (ESRD), whose kidneys are no longer capable of their function. This treatment, which is required three times per week, for an average of 3-4 hours per dialysis, was performed on more than 200,000 patients in the United States in 1996.
Example 2 Drug to Counter Degradation of Blood In the manufacture of pharmaceuticals, consider the possible production of plasminogen activators, which are powerful enzymes that trigger the proteolytic (breaking down of proteins to form simpler substances) degradation of blood clots that cause strokes and heart attacks. Since the mid-1980s, Genentech, a U. S. company, has manufactured tissue plasminogen activator (tPA), which they currently sell for $2,000 per 100 mg dose, with annual sales of 300 million S/yr. Given that their patent will expire soon, Genentech has developed a next generation, FDAapproved, plasminogen activator called "TNK-tPA, which is easier and safer for clinicians to use. With a rapidly growing market, the question arises as to whether an opportunity exists for another company to manufacture a generic (i.e., without a brand name) form of tPA that can compete favorably with TNK-tPA.
Example 3
Vinyl Chloride Manufacture
Consider the need to manufacture vinyl chloride, H~
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80 an important polymer (usually refen'ed to as just vinyl) that is widely-used for rigid plastic piping, fittings, and similar products. An oppommity has arisen to satisfy a new demand for vinyl chloride monomer, on the order of 800 million pounds per year, in a petrochemical complex on the Gulf Coast, given that an existing plant owned by the company produces 1 billion pounds per year of this commodity chemical. Because vinyl-chloride monomer is an extremely toxic substance, it is required that all new facilities be designed carefully to satisfy govemmental health and safety regulations. Clearly, potential opportunities and primitive problems are generated regularly in the fast-paced corporate, govemment, and university research environments. In product design, especially, it is important to create an environment that encourages the identification of consumer needs, the generation of product ideas, and the selection from among these ideas of the most promising altematives; see Sections 3.2 and 3.3. 2.1.2
Selecting Alternatives - Assessing the Primitive Problem
Normally, the designer or a small design team generates many potential ideas for products and processes as potential solutions for the primitive problem, particularly if these individtmls are well familiar with the existing products or situation. Ideas may also come from potential customers, who may be frustrated with the existing products or situation. The ideas are best generated in a non-critical environment. Often, the best ideas may initially be those that might otherwise receive the most criticism. All of the ideas are collected, organized, discussed, and carefully assessed. Cussler and Moggridge [I] present extensive lists of ideas for several products. From the list of ideas, a selection of the most promising altematives is made, based upon technical or marketing considerations; for example, thermodynamics or advertising potential. For the three primitive problems above, Seider et al. TM present design altematives that are typical of those selected from lists of ideas that serve as a base on which to begin the engineering of a product or a process. At this stage, the alternatives require further, more detailed study, and hence it is important to recognize that, as the engineering work proceeds, some altematives are rejected and new alternatives are generated. This is a crucial aspect of design engineering. On the one hand, it is important to generate large numbers of ideas leading to a few promising alternatives. On the other hand, to meet the competition with a product designed and manufactured in a timely fashion, it is important to winnow those alternatives that might require too extensive an engineering effort to be evaluated; e.g., a process that requires exotic materials of construction or extreme conditions of temperature and/or pressure. 2.1.3
Literature Survey
When generating altemative specific problems, design teams in industry have access to company employees, company files, and the open literature. These resources include the SRI Design Reports, encyclopedias, handbooks, indices, and patents, many of which are available electronically, with an increasing number available on the Intemet. For product design, especially, patents are important sources with which the design team must be aware to avoid the duplication of designs protected by patents. After the 17 years that protect patented products and processes in the United States are over, patents are often helpful in the design of next-generation processes to produce the principal chemicals, or chemicals that
81 have fimilar properties, chemical reactions, and so on. Often patents are licensed for fees on the order of 3-6 percent of gross sales.
2.1.4 Auxiliary Studies While creating and assessing a primitive design problem, design teams often initiate studies of (1) technical feasibility, (2) marketing, and (3) business considerations. For a promising product, the technical feasibility study identifies existing and potentially new manufacturing methods, the advantages and disadvantages of each method, and eventually (as design proceeds), the reasons for selecting a specific method. In the marketing analysis, other manufacturers are identified, as well as plant capacities, price histories of the raw materials and products, regulatory restrictions, and principal uses of the product. Marketing considerations often far outweigh technical considerations. Many products or process designs are rejected by management for marketing reasons. For each promising design, business objectives and constraints are normally considered, usually in a business study. These include plant capacity, product quality, likely size of first plant expansion, mechanical completion and startup dates, maximum capacity available, maximum operating costs as a function of capacity, seasonal demand changes, inventory requirements, and minimum acceptable return on investment. As mentioned in Section 1.1, these studies often justify requests to business centers for a budget to carry out the engineering work, including product and process synthesis, prelinainary design studies, cost estimates, and profitability analyses.
2.1.5
Stimulating Innovation in Product Design
The invention and commercialization of new products, and chemical products in particular, benefits by corporate organization to encourage interactions between researchers, marketers, sales-people, and others. In this regard, companies like 3M and General Electric (G.E.) are noted for their corporate policies that seek to maintain a climate in which innovation flourishes. These hclude the fifteen percent rule, in which managers are expected to allow employees 15% of their time to work on projects of their own choosing, tech forums designed to encourage technical exchange and a cross-fertilization of ideas between persons working in many corporate divisions at widely disparate locations, stretch goals intended to stretch the pace of innovation (for example, at least 30 percent of annual sales should come from products introduced in the last four years), process innovation technology centers staffed with chemical engineers and material scientists to help researchers scale-up a new idea from the bench to production, and six sigma strategies for quality control in manufacturing. For discussions of these approaches, with examples, see the books by GundlingTM, Coe [4], and Seider et al. [2].
2.1.6
Pharmaceutical Products
Special considerations are needed for the design of pharmaceutical products. As the design team creates and assesses the primitive problem, the typical development cycle or time line for the discovery and development of a new chemical entity plays a key role, as discussed by Pisano TM. The key steps begin with discovery, in which exploratory research identifies molecules that prove safe and effective in the treatment of disease, usually involving the exploration of thousands of compounds to locate a handful that are sufficiently promising for further development, and the application of data mining techniques to locate
82 the most promising proteins, and cells within which they can be grown, fi'om numerous data bases of laboratory data. Next, in preclinical development, a company seeks to obtain sufficient data on a drag to justify the more expensive and risky step of testing in humans. Then, in clinical trials, which are administered over three phases (each of duration 1-2 years), the drag is tested on human volunteers. Dmfng the latter phase, the drag is administered to thousands of patients at many locations over several years. Finally, to gain approval, an application is prepared for the FDA requesting permission to sell the drug. Note that as Phases 1 and 2 of the clinical trials proceed, process design is undertaken to produce large quantities of the drag, first for Phase 3 testing and then for commercial operation. These steps are considered in detail for a plant to produce tissue plasminogen activator (tPA) in Seider et al. [2]. Note also that the profit margins are sufficiently high to accelerate the process design of the facility for Phase 3 testing, with little if any process optimization. Subsequently, when FDA approval is obtained, the Phase 3 process is used for commercial operation. 2.2
Find Chemicals Performance
or
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Mixtures
Having
Desired
Properties
and
Having created and assessed the primitive problem, the design team often undertakes For those primitive problems in which desired properties and performance have been specified, it is often necessary to identify chemicals or chemical mixtures that meet these specifications. Examples include: (1) thin polymer films to protect electronic devices, having a high glass-transition temperature and low water solubility, (2) refrigerants that boil and condense at desired temperatures and low pressures, while not reacting with ozone in the Earth's stratosphere, (3) environmentally friendly solvents for cleaning, for example to remove ink pigments, and for separations, as in liquid-liquid extraction, (4) low-viscosity lubricants, (5) proteins for pharmaceuticals that have the desired therapeutic effects, (6) solutes for hand warmers that remain supersaturated at normal temperatures, solidifying at low temperatures when activated, and (7) ceramics having hightensile strength and low viscosity for processing. Often design problems are formulated in which the molecular structure is manipulated, using optimization methods, to achieve the desired properties. For this purpose, methods of property estimation are needed, which often include group contribution methods, and increasingly molecular simulations (using molecular dynamics and Monte-Carlo methods). The search for molecular structure is often iterative, involving heuristics, experimentation, and the need to evaluate many alternatives in parallel, especially in the discovery of pharmaceutical proteins, as discussed by Seider et al. [2].
molecular structure design.
For some chemical products, like creams and pastes, the specification of desired properties is a key to successful product design. Creams and pastes are colloidal systems that contain immiscible liquid phases, as well as solid particles. As described by Wibowo and Ng I6], the first step in their design involves the identification of product quality factors, including functional quality factors (e.g., protects, cleans, and decorates the body, delivers an active pharmaceutical ingredient, ...), rheological quality factors (e.g., pours easily, spreads easily on the skin, does not flow under gravity, stirs easily, coats uniformly, ...), physical quality factors (e.g., remains stable for an extended period, melts at a specified temperature, releases an ingredient at a controlled rate, ...), and sensorial quality factors (e.g., feels smooth, does not feel oily, appears transparent, opaque, or pearlescent, does not cause imtation, ...) Given these specifications, the second step involves product formulation,
83 which involves selection of the ingredients, the emulsion type (if applicable), the emulsifier (if necessary), and determination of the product microstructure. Then, the process creation step, as discussed below, and the product evaluation step follow. In a second paper, Wibowo and Ngiv1 expand upon these steps, and apply them for several products, including dry toner, laundry detergent, shampoo, and cosmetic lotion. 2.3 Process Creation
For those primitive problems for which a process must be designed to produce the chemical products, when funded by a business center, the design team carries out the process creation step. Since strategies for process flowsheet synthesis are well documented tS' 9, 2], especially as they apply to the manufacture of commodity chemicals, these steps are not reviewed herein. Note, however, that when process equipment is selected in the so-called task-integration step, the operating mode (that is, continuous, batch, or semi-continuous)is selected. For processes to manufacture specialty chemicals and pharmaceuticals, especially, the design and scheduling of batch processes gains importance.
2.3.1 Product Type Retuming to Figure 1, the manufacauSng processes shown differ significantly depending on the chemical product type. For the manufacture of basic chemical products, the process flowsheet involves chemical reaction, separation, pumping, compression, and similar operations. On the other hand, for the manufacture of industrial products, extrusion, blending, compounding, and stamping are typical operations. Note also that the focus on quality control of the product shifts from the control of the physical, thermal, chemical, and rheological properties to the control of optical properties, weatherability, mechanical strength, printability, and similar properties. Most strategies for process synthesis focus on the manufacture of basic chemical products, with much work remaining to elucidate strategies for the manufacture of industrial products. For the design of configured industrial and consumer products, where emphasis is placed on the design of three-dimensional products, chemical engineers are nomaaUy not involved in the design of the manufacturing process, which includes parts making, parts assembly and integration, and fmishing. 2.4
Development of Base Case Process
To address the most promising flowsheet altematives for the manufacture of basic chemicals, the design team is usually expanded or assisted by specialized engineers, to develop base-case designs. Again, since these strategies are well documented, they are not reviewed herein. Regarding computer-aided process simulation, it is noteworthy that batch process simulators (for example, BATCH PLUS and SUPERPRO DESIGNER) are gaining favor for the design of processes to manufacture specialty chemicals, especially pharmaceuticals. 2.5
Detailed Process Synthesis using Algorithmic Methods
While the design team develops one or more base-case designs, detailed process synthesis is often undertaken using algorithmic methods. For continuous processes, these methods include: (1) create and evaluate chemical reactor networks for conversion of feed to
84 product chemicals, separation trains for recovering species in multicomponent mixtures, and reactor-separator-recycle networks, and (2) locate and reduce energy usage, create and evaluate efficient networks of heat exchangers with turbines for power recovery, and networks of mass exchangers. For batch processes, these methods create and evaluate optimal sequences and schedules for batch operation. In the manufacture of industrial chemicals, such as films, fibers, and paper, processes are synthesized involving extrusion, blending, compounding, sealing, stamping, and related operations. These processes normally involve large throughputs, and consequently, are usually continuous, with some discrete operations that occur at high frequency, such as sealing and stamping. Methods of process synthesis rely heavily on heuristics and are not as well developed as for the manufacture of basic chemical products. For these processes, the emphasis is on the unit operations that include single- and twin-screw extrusion, coating, and fiber spinning. See, for example, the Principles of Polymer Processing by Tadmor and Gogos [10] and Process Modeling by Denn [11]. 2.6
Plant-wide Controllability Assessment
An assessment of the controllability of the process is initiated after the detailed process fiowsheet has been completed, beginning with the qualitative synthesis of control structures for the entire flowsheet. Then measures are utilized that can be applied before the equipment is sized in the detailed design stage, to assess the ease of controlling he process and the degree to which it is inherently resilient to disturbances. These measures permit altemative processes to be screened for controllability and resiliency with little effort and, for the most promising processes, they identify promising control structures. Subsequently, control systems are added and rigorous dynamic simulations are carried out to confirm the projections using the approximate measures discussed previously. See, for example, the books by Luyben et al. [12], Luyben[13], and Seider et al. [21. 2.7 Detailed Design, Equipment Sizing, and Optimization - Configured Product Design
Depending on the primitive design problem, the detailed design involves equipment sizing of units in a new process for commodity and specialty chemicals, that is, detailed process design, and/or the determination of the product configuration for a configured industrial or consumer product (that uses the chemicals or chemical mixtures produced). Here, also, the steps in equipment sizing and cost estimation for processes involving commodity and specialy chemicals are well documented[14' 21. When the primitive design problem leads to a configured industrial or consumer product, much of the design activity is centered on the three-dimensional structure of the product. Typical chemically-related, industrial and consumer products include, for example, hemodialysis devices, solar desalination traits, automotive fuel cells, handwarmers, multi-layer polymer mirrors, integrated circuits, germ-killing surfaces, insect repelling wristbands, disposable diapers, inkjet cartridges, transparencies for overhead projectors, sticky wall hangers, and many others. In many cases, the product must be configured for ease of use and to meet existing standards, as well as to be manufactured easily. Increasingly, when determining the product configuration, distributed-parameter models, involving ordinary and partial differential equations, are being created. Simple discretization algorithms are often used to obtain solutions, as well as the Finite-element Toolbox in MATLAB and the FEMLAB package.
85 The product invention phase begins in which ideas are generated and screened, with detailed three-dimensional designs developed. For the most promising inventions, prototypes are hailt and tested on a small-scale. Only aider the product passes these initial tests, do the design engineers focus on the process to manufacture the product in commercial quantifies. This scale-up often involves pilot-plant testing, as well as consumer lesting, before a decision is made to enter commercial production. Clearly, the methods of capital cost estimation, profitability analysis, and optimization are applied before and during the design of the manufacturing facility, although when the product can be sold at a high price, due to large demand and limited production, detailed profitability analysis and optimization are less important. For these products, it is most important to reduce the design and manufacturing time to capture the market before competitive products are developed. 3
FOCI ON STEPS AND C O M P U T E R TOOLS IN SUPPORTING HIGH-LEVEL BUSINESS DECISIONS
Given the need to expose chemical engineering students to the principal steps and computer tools in designing chemical products and processes, several vantage points can be taken. In the previous section, these steps and computer tools were elucidated, but the inputs to and responses from business decision makers were difficult to define explicitly, as they occur at various stages, depending on the product and/or process and company situation or policy. In this section, the focus is on imparting to students an appreciation of the steps and computer tools that support the high-level business decisions required in the process industries.
3.1
Case Studies and Design Projects
Virtually all students are engaged in open-ended problem solving in the core courses of chemical engineering. However, most do not solve a comprehensive design project until their senior year. When framed well, students are presented with a letter from management stating a societal need(s) and suggesting a primitive problem(s) to be solved in trying to meet this need(s). See, for example, the three examples in Section 2.1.1. Then, as discussed in Section 2.1.3, student design teams search the literature for competitive products, especially the patent literature for existing businesses and successful products. Also, as discussed in Section 2.1.4, students are expected to initiate studies of marketing and business considerations. These involve assessing consumer needs and the size of the market, as well as determining the sources of competitive product(s), the level of production, the selling prices, potential gross profits, and related issues of importance to business decision makers.
3.2
Management Stimuli
The actions by business decision makers, discussed in Section 2.1.5, contribute toward creating an environment that stimulates technical people to innovate and invent new products. These have been key elements of 3M's business strategy over the past century and have led to their success in introducing numerous successful chemical products TM. Rather than taking a passive role, management actively seeks to stimulate innovation.
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3.3
Idea Generation in Response to Business Trends and Customer Needs
The idea generation phase, in which a design team brainstorms to arrive at long lists of potential ideas worthy of consideration in developing a viable product(s), is at the heart of product design [11. In addition, together with marketing people, the design team interviews potential customers to obtain their assessment of their most important needs. While difficult to carry out quantitatively in a university setting, it is important that students appreciate hese key steps in responding to business trends and customer needs in the commercial world.
3.4
Detailed Process Simulation, Equipment Design, and Cost Estimation
In solving their design projects, students are taught to formulate decision trees and to use screening measures to eliminate the least promising altematives, initially using approximate measures such as gross profits, and gradually refining these measures as the technical analysis becomes more quantitative. In carrying out this analysis, students often use process simulators and rigorous methods to size equipment and estimate costs. These usually involve the use of extensive data banks of thermophysical property data, equipmentsizing data, and purchase cost data. While business managers do not examine the details, the use of these packages provides business decision makers with a common basis for comparing the bottom lines of competitive designs; for example, involving the investor's rate of retum.
3.5
Sensitivity and Uncertainty Analysis
Furthermore, through the use of computer tools to compare competitive designs, students learn the ease and speed with which they can prepare detailed design studies. They learn to vary parameters in sensitivity analyses, as well as in optimization studies. By the same token, students also learn the ease with which these systems can be misused, possibly leading a design team to present management with a misguided recommendation for a business venture. The need to check calculations and fully document the underlying assumptions and approximations, with estimates of uncertainties, is another important lesson students must learn.
3.6
Design Reports
Training students to transmit their ideas, both orally and in writing, is a key aspect of their education. The experience of writing an extensive design report, with its letter of transmittal, is an important vehicle for teaching students to communicate with persons not involved in the technical details of their project. In addition, the preparation, delivery, and evaluation of an oral presentation to a critical audience, usually populated by faculty and industrial persons, is another key aspect of leaming to influence business decision makers. 4
YOUNG FACULTY PERSPECTIVES
Recent changes in young faculty perspectives suggests future impacts of PSE on business decision-making. With recent advances in experimental synthesis methods at the nano- or meso-scale, a large fraction of the young faculty have been completing doctoral research on structured materials, protein structures and interactions, among similar applied
87 chemistry, physics, and biology projects. These persons are likely to be more stimulated by the design of configured chemical products, such as biochemical sensors, integrated circuits, and multi-layer polymer mirrors, rather than the design of commodity chemical processes. The development of these products, which often command high selling prices (for example, specialized pharmaceuticals), can have a major impact on business decision-making. It seems clear that chemical engineers will focus increasingly on the design of these kinds of products, with significant business and legal considerations. 5
CONCLUSIONS
As the steps in product and process design are being elucidated and computer tools are gaining sophistication, the ties between PSE and business decision-making are being conveyed to undergraduate students more effectively. In addition to clarifying the steps and computer tools, this manuscript has focused on many of the ties. REFERENCES
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