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Application of the TRIZ creativity enhancement approach to design of inherently safer chemical processes
Chemical Engineering and Processing 45 (2006) 507–514
Application of the TRIZ creativity enhancement approach to design of inherently safer chemical processes Rajagopalan Srinivasan a , Andrzej Kraslawski b,∗ a
Department of Chemical & Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore b Lappeenranta University of Technology, Lappeenranta, Finland Received 6 September 2004; received in revised form 1 October 2005; accepted 3 November 2005 Available online 6 January 2006
Abstract The paper gives a brief overview of the creativity supporting methods of potential interest to process engineering community. Information about computer implementations of the presented methods is introduced as well. Creative problem solving can be broadly classified into intuitive and analytical methods—the paper suggests the analytical approaches to creative problem solving as the most promising group for process engineers. Special attention is given to TRIZ, a popular method for systematic creativity. Classical TRIZ needs to be modified in order to be used in a specialised domain such as process engineering. We discuss the changes needed and illustrate the application of the modified TRIZ to the design of inherently safer chemical processes. A discussion of the advantages and drawback of creativity enhancing methods in the context of process engineering is also presented along with directions for future development. © 2005 Elsevier B.V. All rights reserved. Keywords: TRIZ; Creativity; Innovation
1. Introduction During the last few years, several trends can be observed in the processing industries: lowering of profit margins on commodities, growing importance of sustainability considerations and the environmental aspects of production, high costs of R&D, significance of low-tonnage, high value-added products as well as customer-oriented products, compression of the time from development-to-market, and shortening of product life-cycles. These factors motivate process engineers towards increasing product and process innovation. Usually innovativeness is understood as the result of creativity of individuals and the management process inside of an organisation. Traditionally neither aspect of innovation has been of specific interest to process engineers. For example, in Elsevier’s ScienceDirect journal articles database, as of 2004, there are around 8000 articles dealing with creativity, however, only around 150 papers, cite this word in the chemical and process engineering literature in the last 10 years. This reflects the weak interest of the chemical and
∗
Corresponding author. Tel.: +358 5 621 2139; fax: +358 40 591 3379. E-mail address: [email protected] (A. Kraslawski).
0255-2701/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cep.2005.11.009
process engineering community in research on creativity. In this article, we review the literature on creativity that is relevant to the community and using a case study of inherently safer process design, show how some of these ideas can be fruitfully applied. One of the difficulties in the practical study of creativity arises from its imprecise notion and the widespread belief that it is the domain of psychology, philosophy or sociology. There are hundreds of definitions of creativity [1]. For the sake of simplicity, in this paper, we use the following working definition that is convenient for engineering applications: “creativity is a cognitive process leading to the generation of the solutions (products, processes, services, behaviours, etc.) which are new, unexpected, and useful.” Research on creativity usually concentrates on five main aspects: 1. The essence of the notion: How is it defined and to what are the different types? 2. Its assessment: How to measure creativity? 3. The process: How to get a creative idea? 4. The person: What are the features of creative people? and 5. The product: What are the attributes of a creative product)? 6. An excellent review of the different aspects of creativity from the “soft” sciences point-of-view is given by Sternberg [1].
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Creative problem solving is a process comprising of six steps [2]: 1. 2. 3. 4. 5. 6.
problem identification; fact finding; problem definition; idea generation; ideas refining; evaluation.
Our observations of the different aspects of engineering activities and discussions with practitioners have lead to three main conclusions: 1. The main interest of process engineers in creativity is in the methods and tools for the generation of new ideas. 2. The field of application is mainly processes (troubleshooting, de-bottlenecking, synthesis, and design) and products (identification of new products and their formulation). 3. Of the nearly 150 methods for generation of new ideas [1], only a small fraction are of potential use for engineers. In this paper, we therefore focus on the idea generation step of the creative problem solving process. In Section 2, we present a brief overview of the different methods for enhancing creativity support. In Section 3, we illustrate the application of one such method, TRIZ to idea generation for a specific problem in process engineering—design of inherently safer process. 2. Methods for enhancing creativity The generation of ideas consists of manipulation of objects or their features. Several types of manipulation are possible—associations, selections, integrations, adaptations, etc. [3]. These different manipulations can be grouped into three basic models of creativity (an extension of the original classification by [4])—(1) combinational creativity, where ideas are created from a combination and synthesis of existing ideas, and (2) exploratory creativity, which involve creation of new ideas within the framework of existing rules and (3) transformational creativity, which introduces new ways of thinking by altering the framework through new rules and dimensions. The three types of creativity result from different cognitive processes and provide the basis for the following differentiation between discovery, invention, and design. An insight into new interdependencies leads to the processes of discovery; an origination of new artefacts guides the process of invention; a creation of solutions to a new problem directs the processes of design. Creativity enhancement is understood as actions that improve the ability to define the problem and to generate new, useful and unexpected ideas. While it does not guarantee generation of creative solutions, creativity enhancement only makes them more probable by focusing the designer’s thinking and directing his/her attention to the most essential problems. The enhancement of creativity can be realised by education (through removal of the barriers), training (focusing on the person’s cognitive abil-
ities, motivation, and social skills), or application of specific methods (focusing on the problem). These lead to the many methods for enhancing creativity (see [5] for a description of over 150 methods). These methods are not a replacement for fundamental subject knowledge, rather they require a “prepared mind” with solid knowledge of physics, chemistry, biology and mathematics as well as specific domain knowledge (e.g. engineering), to result in the highest quality of solutions. In the specific case of idea generation which is of particular interest for engineers, the various creativity enhancement methods can be classified as either intuitive or analytical. Intuitive methods are based on use of emotion, fantasy, or other sources of inspiration that are difficult to be formalised. These are usually founded on experience and do not have a formalised logical structure or internal coherency. In contrast, analytical methods are wellstructured and are characterised by the systematic search of the solution space. The following intuitive methods are commonly applied to the engineering problems: Brainstorming: It is the most popular creativity enhancement method. Originally introduced by Osborn [6], it is based on the following four rules: evaluation of ideas must be done later; the quantity of the generated ideas is the most important; encouragement of strange and “wild” proposals; and improvement and combination of the generated ideas is welcomed. Many variants such as stop-and-go, Gordon–Little variation, and trigger method are common. The interested reader is referred to Proctor [7] for a detailed description. An example of brainstorming in the chemical engineering domain is hazard and operability (HAZOP) analysis, a popular method for process safety analysis [8]. Synectics: This method developed by Gordon [9] exploits two mechanisms to look at the problem from a different perspective—to make familiar strange and vice versa, i.e., to make the strange seem familiar. To achieve this, a set of four analogies are used—personal (where emotions and feelings are used to identify an individual with the subject of the problem), direct (where the problem is compared with homogeneous facts, information, or technology), symbolic (use of personal images), and fantasy (based on how the problem can be solved in the ‘wildest fantasy’). Detailed description of the synectics method is presented by Proctor [7]. Lateral thinking: This is a group of methods originally introduced by De Bono [10] and is based on a unconventional perception of the problem. The main factors enabling lateral thinking are identification of the dominant ideas, search for new ways of looking at the problem, relaxation of the rigid thinking process, and use of chance to encourage the emergence of the other ideas. Among the analytical methods the most common ones applied to engineering problems are: Morphological analysis: The method was introduced by Zwicky [11] and is based on the combination of the attributes of the product or process (like properties, functions, etc.) with
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the elements of the product or the process. While all possible combinations of the attributes can be considered, its applicability is practically limited to three dimensional analysis of the attributes. A number of variations of the method exist and include attribute listing, SCIMTAR, etc. [7]. Analogies: It is a group of method with case-based reasoning as the most useful for the engineering applications. They exploit similarities between the features of the existing problem and the features of problems or designs known from the past. A good survey of case-based methods is given in Leake [12]. Examples of case-based reasoning applications in process engineering are given by Surma and Braunschweig [13] and Avarmenko et al. [14]. A special class of analogy-based methods is biomimetics which involve analogies with living systems [15]. TRIZ: It is a popular method of systematic creativity support introduced by Altshuller [16]. There are many book on TRIZ e.g. Savransky [17], Salamatov [18]. However, the book by Mann [19] seems to be the best introduction. The main findings of TRIZ are: - there exist the trends in the evolution of technologies; - all innovations start with application of a small number of inventive principles; - the innovative solution of the problem removes the conflicts existing in the system.
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Fig. 1. The general principle of application of TRIZ [19].
The application of the basic principles is realised as shown in Fig. 1 and is based on translating the actual problem into a general one, finding the general solution to this problem, and then transforming the general solution into the solution of the actual problem. The basic principles are implemented in several tools including inventive principles, S-fields, Contradiction Matrix, separation principles, knowledge effects, and trends [19]. The classical TRIZ uses 39 universal characteristics and 40 inventive principles for solving contradictions without compromising on conflicting features of technical systems. The Contradiction Matrix maps the most promising principles to contradictions in any pair of characteristics. A section of the classical Contradiction Matrix is shown in Table 1. There are three steps for solving an inventive problem that contains a technical contradiction:
These have been translated into the following three basic principles of TRIZ:
Step 1. Analyze the technical system; determine the system characteristic that needs to be improved.
Ideality: There is a tendency in the evolution of systems that they always change towards the state where all benefits of their functioning are realised at no cost or harm. Functionality: Every system has its main useful function and all its elements have to fulfil this function. Otherwise it is underused and could be a source of conflicts. The notion of functionality allows for the generalisation of the various aspects of the system functioning resulting in the possibility of transferring know-how between the various fields (technical, medical, biological, etc.). Contradictions: There are two types of contradictions. A technical contradiction takes place when there are two parameters of the system in conflict, and the improvement in the value of one parameter worsens the value of the other. Technical contradictions are solved by applying the Contradiction Matrix (see below). A physical contradiction takes place when a parameter should simultaneously have two different values. Physical contradictions are removed by applying the principles of separation in time and space.
Step 2. State the technical contradiction; identify the characteristic that deteriorates as the other improves.
The relation between the ability to generate new and useful ideas or solutions to problems and the removal of the contradictions has been observed by Altshuler. When analysing the vast amount of patents he detected that the best engineering solutions were obtained by the removal of trade-offs between the design objectives.
Step 3. Resolve the technical contradiction. In this step, the 40 principles are used to remove the technical contradiction. The principles most effective for resolving a specific pair of characteristics are shown in the Contradiction Matrix and should be tried first although other principles may also be applicable. For example, if Principle 1 – segmentation – is used for resolving a conflict, it would lead the designer to think of options related to dividing the object into independent parts, making it sectional (for easy assembly or disassembly), or increasing its degree of segmentation. Depending on the domain and details of the object, this could be achieved in different ways. It is therefore beneficial to customize the characteristics and principles to different problem domains. This would help in the practical use of the Contradiction Matrix in specific contexts. The selection of the characteristics when solving a problem seems to be an issue of experience in the use of typical engineering characteristics. However, the application of TRIZ in a totally new field, for e.g. pharmacology, would probably result in a need for introduction of new physical and chemical characteristics. The issue of “which inventive principle to use” is much more difficult to be answered in a straightforward way as would be expected by the engineer. Some heuristics have been suggested by Mann [19]. The eight most commonly used principles
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Table 1 Classical TRIZ Contradiction Matrix, Altshuller [16]
are segmentation, preliminary action, the other way around, dynamics, periodic action, blessing-in-disguise, self-service, and parameter changes. The other suggestions presented in the book consider, for example, the preferences for the improvement of physical attributes or performance. The applications of TRIZ are numerous, Orloff [20], Moehrle [21]. The general paper by Poppe and Gras [22] outlines the possible ways of introducing TRIZ into process industry. However, there are only a few publications on its applications to chemical and process engineering problems. The examples available in the open literature describe the use TRIZ to: - product design; breathable barriers, Roberts [23]; - equipment design; heat exchanger, Busov et al. [24]; food processing equipment, Totobesola-Barbier et al. [25]; - operation; clogging of filter, Carr [26]; erosion of boiler in fluidised bed combustion, Lee et al. [27]; detection of water leakage, Nagakawa [28]; - trends identification; development of computer aided tools, Braunschweig [29]; - process synthesis and design; distillation systems Li et al. [30], reaction –separation systems Li et al. [31]; waste minimisation Li et al. [32].
In the majority of the applications, TRIZ is used in its original form. However, recently one can observe various attempts aimed at the facilitation of TRIZ use by the presentation of the illustrative examples in the different fields of expertise, e.g. food industry Winkless and Mann [33]; chemical problems, Grierson et al. [34]. Another attempt is to introduce the new TRIZ-like principles into the narrow fields of expertise, e.g. synthesis of distillation systems, Kraslawski et al. [35]. A crucial factor for the widespread application of the creativity enhancing methods is availability of computer implementations which facilitate the movement between the main stages of creative problem solving and ensure the structuring of the whole process. A number of software tools are available, each based on a different method and its interpretation. Table 2 provides a brief description of some popular ones. Other sources of information about software for creativity enhancement are listed in http://www.creax.com/resources/creax net.html#29. It is worth mentioning a group of methods aimed at managing and ordering of generated ideas. The most prominent method is MindMap, an approach developed by Buzan [36]. In the MindMap, the main concept is presented as the centre of a picture and different themes radiate from the central concept as labelled branches. Every label could be further branched. Another method is the fishbone diagram—a graphical
Table 2 Software for creativity enhancement Software
Reference
Description
IdeaFisher Axon Idea Processor ThoughtPath
http://www.ideafisher.com/ http://web.singnet.com.sg/∼axon2000/index.htm http://www.thoughtpath.com/bigidea/bigidea.html
Innovation WorkBench TechOptimizer CREAX Innovation Suite
http://www.ideationtriz.com/ http://www.invention-machine.com/ http://www.creax.com/
Generating new ideas by brainstorming through word association Generating, visualizing and organizing ideas through concept mapping Implementing the principles of synectics—based on patterns useful in creative problem solving TRIZ method with online access to patent databases TRIZ method with online access to patent databases TRIZ—includes physical and chemical phenomena
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representation of all possible causes of the given problem [37]. In the following section, we describe the application of TRIZ to an important process engineering problem. 3. TRIZ for inherently safer process design In this section, we illustrate the application of creativity enhancement when performing safety analysis of a process. The design of inherently safer chemical processes is illustrated by the application of TRIZ. The traditional approach to improve the safety of chemical processes is to introduce additional safety equipment and protective devices such as valves, alarms, safety interlocks, and other active systems to detect leaks and process deviations. When new problems surface, more add-on protective equipments is installed to deal with them. In the end, what results is a system whose design is complicated by numerous layers of expensive, add-on protective equipments which often constitute a significant part of the operating cost of the plant. An inherently safer process avoids or reduces hazards instead of controlling them. It relies on naturally occurring phenomena and robust design and eliminates or greatly reduces the need for instrumentation or administrative controls, thereby reducing the costs related to safety and environmental protection. Such a process can be designed by applying inherent safety principles such as intensification, substitution, attenuation, limitation of effects, simplification, etc., throughout the design process, from conception until completion. These principles help to avoid or reduce hazards by using safer materials and operating conditions, minimizing inventory, and result in a simpler and friendly plant. As the design evolves along its lifecycle, opportunities for safer design decreases and incorporation of inherently safer features become difficult and expensive. Although it is possible to apply inherent safety principles at later stages of design, the scope for implementation is greatest in the earliest stages, in particular during route selection. Decisions made during early design stages concerning the choice of synthesis route for product, throughput, and location for manufacture are crucial and fix 80% of capital cost. The conventional safety analysis tools used to identify and control risks such as checklists and hazard and operability (HAZOP) analysis are inapplicable during the pre-engineering design stages due to the lack of detailed design information. As one solution to this problem, inherent safety metrics that measure the safeness of a design have been proposed [38–41]. An alternative approach is to assist the designer identify creative design solutions that overcome the technical conflicts in designing inherently safer process. This latter approach is explored here. A variety of methods can be used in general for enhancing creativity, as described above. The choice of method depends on the nature of the problem. Analytical methods are usually recommended for solving synthesis problems such as the current one. Among the various analytical methods, morphological analysis requires enumeration and analysis of all possible solutions to the problem. It is therefore not suited for large-scale open-ended design synthesis problems like inherently safer design which are
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usually characterised by exponential growth of the number of alternatives where detailed analysis of all possible alternatives is practically impossible. Analogies are most effective for cases where a sufficiently large experience-base with similar design cases is available. TRIZ, on the other hand, does not suffer from these requirements and can be applied to process design. The characteristics and principles in classical TRIZ were targeted towards physical and mechanical systems. To enable a process designer in solving conflicts that arise when designing a new process plant or when improving the safety of existing ones, elements specific to chemical processing should be incorporated. In this paper, a set of 10 characteristics, 8 principles, and a process design Contradiction Matrix is proposed to deal with inherently safer process design. Characteristics: The 10 characteristics shown in Table 3 relate to properties of materials (such as reactants, catalysts, solvents, materials of construction), unit operations, reactions, equipment, process, and plant. They affect the safety performance, and contradictions occur among them when an inherently safe process is being designed. Principles: The well-known inherent safety principles, Kletz [42], can be adapted to resolve conflicts that arise during design. The main inherent safety principles are intensification, substitution, attenuation, and simplification. Besides these, other principles such as limitation of effects, avoiding knock-on effects, making incorrect assembly impossible, and ease of control are also commonly used. From these, eight specific principles have been developed and are described in Table 4. Contradiction Matrix: Using the above characteristics and principles, the Contradiction Matrix shown in Table 5 can be developed. This matrix aims to provide process designers with promising avenues to resolve conflicts. In the following, we illustrate the modified TRIZ using two different examples. Table 3 Characteristics for design of inherently safer chemical processes Characteristic
Example
1 2 3 4 5
Processing conditions Concentration Quality Size Rate
6
Conversion
7
Complexity
8
Hazardous nature
Temperature, pressure, pH, etc. Reactant, product Product Equipment, particle size Reaction rate, mass transfer rate, production rate Raw material to product conversion Controllability, operability of equipment and process; large number of equipment in flowsheet Toxicity, flammability of material; very high and low temperatures and pressures Releases Capital cost, operating costs
9 10
Environmental impact Economics
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Table 4 TRIZ-based principles for design of inherently safer chemical processes Principle
Examples
1. Change process chemistry
(a) Change materials used, such as raw materials or catalyst use less toxic, volatile, reactive or more stable raw materials (b) Change type of reaction use an alternative reaction to achieve the same desired products
2. Change operation sequence
(a) Change the sequence (b) Do the reverse sequence
3. Change equipment type or design
(a) To reduce inventory—reduce piping, vessel size (b) Design equipment to be self-regulatory, tolerant of errors, to withstand the worst-case scenario (c) To reduce inventory—use continuous reactors instead of batch reactors (d) To increase concentration—use distillation, extraction, separation or crystallization
4. Change processing conditions
(a) Change operating conditions such as temperature or pressure of the system
5. Use simpler design
(a) Use a simpler design for the system, one that is easier to operate and needs fewer controls
6. Generate materials as, when and where required
(a) To reduce storage of intermediates—use as and when produced (b) Generate hazardous materials from less hazardous ones in the particular reaction in which it is to be used (c) Generate hazardous materials at the plant itself just before it is used
7. Make operation simpler
(a) Make procedures clearer, simpler and easier to understand
8. Convert harm into benefit
(a) Use heat from exothermic reactions to heat up other streams (b) Convert toxic intermediates to less toxic ones, or sellable products
3.1. Examples Example 1. The introduction of nitro groups and their (catalytic) hydrogenation is a useful route for the industrial production of amines. Nitro compounds are frequently used in the synthesis of pharmaceuticals, for instance in the synthesis of sildenafil (Viagra), the antibiotic linezolid (Zyvox), and the HIV protease inhibitor amprenavir (Agenerase). Consider the route selection for one such nitro compound. When conventional catalysts are used for the selective hydrogenation of aromatic nitro compounds, problems due to accumulation of toxic arylhydroxylamine intermediates (a family of known carcinogens that are also potentially explosive) often occurs. The challenge for the process chemist/engineer is to develop a safe route. In the following, we describe how the three-step creativity enhancement approach described above can be used for this purpose: Table 5 Contradiction Matrix for design of inherently safer chemical processes
Step 1. To improve the safeness of the process, it is desired to eliminate or reduce the amount of intermediates produced. To do so, the process can be operated under milder conditions so that less toxic intermediate is produced. However, this will result in reduced conversion and yield of the desired product. Step 2. The contradiction can be summarized as follows: Characteristic to be improved: reduce concentration of intermediate (Characteristic 2). Characteristic that is getting worse: conversion of the reaction (Characteristic 6). Step 3. To resolve the contradiction, from Table 5, the suggested principles are Principles 1, 3 and 6. Principle 1, which is to change the process chemistry, is a feasible option in this case.
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A search reveals that Degussa and contract research firm Solvias have commercialized a new class of vanadium-doped precious metal powder catalysts, which offer superior performance for the selective hydrogenation of aromatic nitro compounds Scott [43]. Vanadium acts as a promoter to effect the nitro-group reduction. In doing so, the accumulation of arylhydroxylamine intermediates is avoided since the vanadium-doped catalyst eliminates the formation of arylhydroxylamines by modifying the chemical process for the nitro group reduction. The concentration of the toxic intermediate is reduced to below 1% and the conversion of the reaction is not affected. Hence, replacing the conventional catalyst with this new class of vanadium-doped catalyst, can improve Characteristic 2 without affecting Characteristic 6. This illustrates the application of Principle 1. In this case, Principle 3, changing the equipment type or design is not attractive and Principle 6 is not feasible. Example 2. This example considers a common challenge in batch and semi-batch manufacture—one of tradeoff between hazards related to inventory in reactor versus production throughput. The catalyzed oxidation of a thioether to a sulfone via a sulfoxide intermediate involves a two-stage process. The exothermic reaction entails mixing two liquid phases and is traditionally carried out in semi-continuous mode, in a batch-stirred reactor. Traditionally, 18 h are needed to make the intermediate. Step 1. The large inventory of the hazardous substance leads to the exothermic reaction runaway hazard. The reduction in inventory would lead to a reduction in the production rate. Step 2. The technical contradiction can be stated as: Characteristic to be improved: hazardous nature (Characteristic 8). Characteristic that is getting worse: production rate (Characteristic 5). Step 3. Using the Contradiction Matrix, Table 5, the suggested principle is Principles 3, Change equipment type or design. A literature search reveals that BHR Solutions (England) has developed a compact heat exchanger reactor (HEX) which reduces the reaction time for making the organic intermediate to 30 min, with equivalent yield [44]. The HEX reactor allows the process to work in a continuous fashion. Improved mixing and heat transfer result in shorter residence time, improved economics, and process intensification. The compact reactor consists of a stack of diffusion-bonded, thin plates that have tailored flow channels, produced by chemical etching. Using this new type of reactor, the inventory can be reduced while maintaining an adequate production rate and the technical contradiction can be overcome. Thus, innovative unit designs, processes, and products (catalysts) can be systematically explored or unearthed to improve the safety and environmental impact of the process by using the TRIZ methodology.
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4. Discussion The selection of a suitable creativity enhancement method should be based on the nature of the problem under consideration. Brainstorming usually has low applicability to wellstructured technical problems. Its usefulness is highest when dealing with very early phases of design, when technical and organisational limitations are not essential. Synectics and analogies are useful approaches to enhance creativity however their application requires first a rigorous training. Moreover, the application of these methods to well-structured problems is more difficult. Morphological analysis is very efficient and well suited to deal with technical problems, however the previously mentioned difficulties in the visualisation of the higher-dimensional problems is a key obstacle in its widespread application. Another limiting factor is the requirement of deep knowledge of the problem under consideration since it means an awareness of all variables even at early stages of design. The most structured method, TRIZ, also has its limitations with respect to application to process design. The main problem is the abstract character of the method and the consequent difficulties in its application. The engineer has to identify the problem and allocate it into one of the “generic problems” class. This is usually a difficult exercise requiring considerable practice and a flexible approach to problem formulation. The designer has to translate common engineering problems into the “language” of contradictions or standard solutions. The universality, and in consequence the abstract character of TRIZ, is manifested also by the fact that engineer is not always able to identify in the Contradiction Matrix the technical factors essential for the given problem (especially in the field of material science or biotechnology). This means that there are features missing in the system under consideration from among the technical factors present in the Contradiction Matrix. The rapid development of certain fields of science and technology has resulted in many standard solutions and physical effects that could be of the great interest to the designers being absent. Another common difficulty in the application of TRIZ is a lack of the systematic approach to dealing with the hierarchical generation of conflicts during the process design. The removal of one conflict usually results in the generation of new ones. The problems in dealing with new conflicts arises due to the lack of their formal, mathematical description. When analysing a very few published examples of TRIZ application, a common observation to be made is a concentration of the efforts on the troubleshooting and operation, and a lack of conceptual design problems. The successful applications of TRIZ to product and process design are not published in open literature. Paradoxically, the universality and the great potential of TRIZ are the main obstacles in a broader propagation of the results obtained with the application of this method. In consequence, training of process engineers in the use of this method is difficult, despite the availability of many courses and reference books. The following are some outstanding tasks that could be addressed by process engineers who are interested in creativity research and its practical implementation:
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1. Systematic evaluation of the effectiveness and applicability of the existing creativity enhancing methods for the various classes of process engineering problems. 2. Modifications of existing methods for the needs of the specific problems in process engineering including new product development, process intensification, and process debottlenecking. 3. Development of creativity enhancing software and method implementations specifically oriented towards process engineering and their integration with the computer-aided tools for product and process design. 4. Publication of illustrative examples of application of creativity enhancing methods to process engineering problems. 5. Creation of new methods and tools for identification and re-use of the creative problem-solving strategies developed in the different field of science and technology (economics, medicine, biology, geology, mechanical engineering, information science, etc.). References [1] R.J. Sternberg (Ed.), Handbook of Creativity, Cambridge University Press, Cambridge, UK, 1999. [2] A.B. Van Gundy, Techniques of Structured Problem Solving, Van Nostrand Reinhold Co., New York, 1993. [3] J.F. Hoorn, A Model for Information Technologies that can be Creative C&C’02 October 14–16, Loughborough, United Kingdom, 2002. [4] M.A. Boden, The Creative Mind, Abacus, London, 1990. [5] B. Clegg, P. Birch, Crash Course in Creativity, Kogan Page Limited, London, 2002. [6] A. Osborn, Applied Imagination, Scribner’s, New York, 1953. [7] T. Proctor, Creative Problem Solving for Managers, Routledge, London, 2002. [8] CCPS, Guidelines for Hazard Evaluation Procedures, second ed., American Institute of Chemical Engineers, 1992. [9] W. Gordon, Synectics, Harper and Row, New York, 1961. [10] E. De Bono, Lateral Thinking for Management, McGraw-Hill, New York, 1970. [11] F. Zwicky, The Morphological Method of Analysis and Construction, Wiley-Interscience, New York, 1948. [12] D. Leake, Case-Based Reasoning: Experiences, Lessons, & Future Directions, AAAI Press, Menlo Park, CA, 1996. [13] J. Surma, B. Braunschweig, Case-base retrieval in process engineering: supporting design by reusing flowsheets, Eng. Appl. Artif. Intell. 9 (4) (1996) 385–391. [14] Y. Avramenko, L. Nystr¨om, A. Kraslawski, Selection of internals for reactive distillation column-/case-based reasoning approach, Comput. Chem. Eng. 28 (2004) 37–44. [15] M. French, Invention and Evolution. Design in Nature and Engineering, Cambridge University Press, New York, 1994. [16] G. Altshuller, Creativity as an Exact Science, Gordon & Breach, New York, 1984. [17] S. Savransky, Engineering of Creativity, CRC, Boca Raton, 2000. [18] Y. Salamatov, TRIZ: The Right Soultion at the Right Time, Grafisch Bedirijf van der Schaaf, Enschede, 1999. [19] D. Mann, Hands-On Systematic Innovation, Creax Press, Ieper, Belgium, 2002. [20] M. Orloff, Inventive Thinking Through TRIZ, Springer, Berlin, 2003. [21] M.G. Moehrle, How combinations of TRIZ tools are used in companiesresults of a cluster analysis, R&D Manage. 35 (3) (2005) 285– 296.
[22] G. Poppe, B. Gras, TRIZ in the Process Industry, 2002 (http://www.trizjournal.com/archives/2002/02/c/index.htm). [23] M. Roberts, -Cyclodextrin Molecules and Their Use in Breathable Barriers, 1999 (http://www.triz-journal.com/archives/1999/11/g/index.htm). [24] B. Busov, D. Mann, P. Jirman, Case Studies in TRIZ: A Novel Heat Exchanger, 1999 (http://www.triz-journal.com/archives/1999/12/b/ index.htm). [25] M. Totobesola-Barbier, C. Marouz´e, F. Giroux, A TRIZ-based Creativity Tool for Food Processing Equipment Design, 2002 (http://www.trizjournal.com/archives/2002/10/b/). [26] J. Carr, Analysis of a Problem: Clogging of a Multi-Drum Filter Used in a Textile Application, 1999 (http://www.triz-journal.com/archives/1999/ 08/c/index.htm). [27] J.-G. Lee, S.-B. Lee, J. OH, Case Studies In TRIZ: FBC(Fluidized Bed Combustion) Boiler’s Tube Erosion, 2002 (http://www.trizjournal.com/archives/2002/07/b/index.htm). [28] T. Nakagawa, USIT Case Study (1) Detection of Small Water Leakage from a Gate Valve, 1999 (http://www.osaka-gu.ac.jp/php/nakagawa/ TRIZ/eTRIZ/epapers/eUSITCases990826/eUSITC1Droplet990826.html). [29] B. Braunschweig, TRIZ and the evolution of CAPE tools, in: J. Grievink, J. van Schijndel (Eds.), European Symposium on Computer Aided Process Engineering, vol. 12, Elsevier Science, Amsterdam, 2002, pp. 859–864. [30] X.-N. Li, B.-G. Rong, A. Kraslawski, TRIZ-based creative retrofitting of complex distillation processes-an industrial case study, in: R. Gani, S.B. Jorgensen (Eds.), European Symposium on Computer Aided Process Engineering, vol. 11, Elsevier, 2001, pp. 439–444. [31] X.-N. Li, B.-G. Rong, A. Kraslawski, Synthesis of reactor/separator networks by the conflict-based analysis approach, in: J. Grievink, J. van Schijndel (Eds.), European Symposium on Computer Aided Process Engineering, vol. 12, Elsevier, 2002, pp. 241–246. [32] X.N. Li, B.G. Rong, A. Kraslawski, L. Nystr¨om, A Conflict-based approach for process synthesis with wastes minimization, in: A. Kraslawski, I. Turunen (Eds.), European Symposium on Computer Aided Process Engineering, vol. 13, Elsevier, 2003, pp. 209–214. [33] B. Winkless, D. Mann, Food Product Development and the 40 Inventive Principles, 2001 (http://www.triz-journal.com/archives/2001/05/e/ index.htm). [34] B. Grierson, I. Fraser, A. Morrison, S. Niven, G. Chisholm, 40 Principles—Chemical Illustrations, 2003 (http://www.triz-journal.com/ archives/2003/07/a/01.pdf). [35] A. Kraslawski, B-G. Rong, L. Nystr¨om, Creative design of distillation flowsheets based on theory of solving inventive problems, in: S. Pierruci (Ed.), European Symposium on Computer Aided Process Engineering, vol. 10, Elsevier, 2000, pp. 625–630. [36] T. Buzan, The Mind Map Book, BBC Books, London, 1993. [37] S. Majaro, Managing Ideas for Profit, McGraw-Hill, Maidenhead, 1992. [38] D.W. Edwards, D. Lawrence, Assessing the inherent safety of chemical process routes: Is there a relation between plant costs and inherent safety? Trans. I ChemE 71 (November (Part B)) (1993) 252–258. [39] A.M. Heikkila, Inherent Safety in Process Plant Design. An Index-Based Approach, Technical Research Center of Finland, VTT Publications, Finland, 1999. [40] C. Palaniappan, R. Srinivasan, R.B.H. Tan, Expert system for design of inherently safer chemical processes—Part 1: Route selection stage, Ind. Eng. Chem. Res. 41 (26) (2002) 6698–6710. [41] C. Palaniappan, R. Srinivasan, R. Tan, Expert system for design of inherently safer processes—Part 2: Flowsheet development stage, Ind. Eng. Chem. Res. 41 (26) (2002) 6711–6722. [42] T. Kletz, Process Plants: A Handbook for Inherently Safer Design, Taylor & Francis, 1998. [43] A. Scott, Solvias, Degussa Target Cleaner Amines, Chemical Week, October 16, 2002. [44] Chementator, New Reactor Achieves a Dramatic Reduction in Reaction Time, Chemical Engineering, December 2000, p. 15.
Application of the TRIZ creativity enhancement approach to design of inherently safer chemical processes Rajagopalan Srinivasan a , Andrzej Kraslawski b,∗ a
Department of Chemical & Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore b Lappeenranta University of Technology, Lappeenranta, Finland Received 6 September 2004; received in revised form 1 October 2005; accepted 3 November 2005 Available online 6 January 2006
Abstract The paper gives a brief overview of the creativity supporting methods of potential interest to process engineering community. Information about computer implementations of the presented methods is introduced as well. Creative problem solving can be broadly classified into intuitive and analytical methods—the paper suggests the analytical approaches to creative problem solving as the most promising group for process engineers. Special attention is given to TRIZ, a popular method for systematic creativity. Classical TRIZ needs to be modified in order to be used in a specialised domain such as process engineering. We discuss the changes needed and illustrate the application of the modified TRIZ to the design of inherently safer chemical processes. A discussion of the advantages and drawback of creativity enhancing methods in the context of process engineering is also presented along with directions for future development. © 2005 Elsevier B.V. All rights reserved. Keywords: TRIZ; Creativity; Innovation
1. Introduction During the last few years, several trends can be observed in the processing industries: lowering of profit margins on commodities, growing importance of sustainability considerations and the environmental aspects of production, high costs of R&D, significance of low-tonnage, high value-added products as well as customer-oriented products, compression of the time from development-to-market, and shortening of product life-cycles. These factors motivate process engineers towards increasing product and process innovation. Usually innovativeness is understood as the result of creativity of individuals and the management process inside of an organisation. Traditionally neither aspect of innovation has been of specific interest to process engineers. For example, in Elsevier’s ScienceDirect journal articles database, as of 2004, there are around 8000 articles dealing with creativity, however, only around 150 papers, cite this word in the chemical and process engineering literature in the last 10 years. This reflects the weak interest of the chemical and
∗
Corresponding author. Tel.: +358 5 621 2139; fax: +358 40 591 3379. E-mail address: [email protected] (A. Kraslawski).
0255-2701/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cep.2005.11.009
process engineering community in research on creativity. In this article, we review the literature on creativity that is relevant to the community and using a case study of inherently safer process design, show how some of these ideas can be fruitfully applied. One of the difficulties in the practical study of creativity arises from its imprecise notion and the widespread belief that it is the domain of psychology, philosophy or sociology. There are hundreds of definitions of creativity [1]. For the sake of simplicity, in this paper, we use the following working definition that is convenient for engineering applications: “creativity is a cognitive process leading to the generation of the solutions (products, processes, services, behaviours, etc.) which are new, unexpected, and useful.” Research on creativity usually concentrates on five main aspects: 1. The essence of the notion: How is it defined and to what are the different types? 2. Its assessment: How to measure creativity? 3. The process: How to get a creative idea? 4. The person: What are the features of creative people? and 5. The product: What are the attributes of a creative product)? 6. An excellent review of the different aspects of creativity from the “soft” sciences point-of-view is given by Sternberg [1].
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Creative problem solving is a process comprising of six steps [2]: 1. 2. 3. 4. 5. 6.
problem identification; fact finding; problem definition; idea generation; ideas refining; evaluation.
Our observations of the different aspects of engineering activities and discussions with practitioners have lead to three main conclusions: 1. The main interest of process engineers in creativity is in the methods and tools for the generation of new ideas. 2. The field of application is mainly processes (troubleshooting, de-bottlenecking, synthesis, and design) and products (identification of new products and their formulation). 3. Of the nearly 150 methods for generation of new ideas [1], only a small fraction are of potential use for engineers. In this paper, we therefore focus on the idea generation step of the creative problem solving process. In Section 2, we present a brief overview of the different methods for enhancing creativity support. In Section 3, we illustrate the application of one such method, TRIZ to idea generation for a specific problem in process engineering—design of inherently safer process. 2. Methods for enhancing creativity The generation of ideas consists of manipulation of objects or their features. Several types of manipulation are possible—associations, selections, integrations, adaptations, etc. [3]. These different manipulations can be grouped into three basic models of creativity (an extension of the original classification by [4])—(1) combinational creativity, where ideas are created from a combination and synthesis of existing ideas, and (2) exploratory creativity, which involve creation of new ideas within the framework of existing rules and (3) transformational creativity, which introduces new ways of thinking by altering the framework through new rules and dimensions. The three types of creativity result from different cognitive processes and provide the basis for the following differentiation between discovery, invention, and design. An insight into new interdependencies leads to the processes of discovery; an origination of new artefacts guides the process of invention; a creation of solutions to a new problem directs the processes of design. Creativity enhancement is understood as actions that improve the ability to define the problem and to generate new, useful and unexpected ideas. While it does not guarantee generation of creative solutions, creativity enhancement only makes them more probable by focusing the designer’s thinking and directing his/her attention to the most essential problems. The enhancement of creativity can be realised by education (through removal of the barriers), training (focusing on the person’s cognitive abil-
ities, motivation, and social skills), or application of specific methods (focusing on the problem). These lead to the many methods for enhancing creativity (see [5] for a description of over 150 methods). These methods are not a replacement for fundamental subject knowledge, rather they require a “prepared mind” with solid knowledge of physics, chemistry, biology and mathematics as well as specific domain knowledge (e.g. engineering), to result in the highest quality of solutions. In the specific case of idea generation which is of particular interest for engineers, the various creativity enhancement methods can be classified as either intuitive or analytical. Intuitive methods are based on use of emotion, fantasy, or other sources of inspiration that are difficult to be formalised. These are usually founded on experience and do not have a formalised logical structure or internal coherency. In contrast, analytical methods are wellstructured and are characterised by the systematic search of the solution space. The following intuitive methods are commonly applied to the engineering problems: Brainstorming: It is the most popular creativity enhancement method. Originally introduced by Osborn [6], it is based on the following four rules: evaluation of ideas must be done later; the quantity of the generated ideas is the most important; encouragement of strange and “wild” proposals; and improvement and combination of the generated ideas is welcomed. Many variants such as stop-and-go, Gordon–Little variation, and trigger method are common. The interested reader is referred to Proctor [7] for a detailed description. An example of brainstorming in the chemical engineering domain is hazard and operability (HAZOP) analysis, a popular method for process safety analysis [8]. Synectics: This method developed by Gordon [9] exploits two mechanisms to look at the problem from a different perspective—to make familiar strange and vice versa, i.e., to make the strange seem familiar. To achieve this, a set of four analogies are used—personal (where emotions and feelings are used to identify an individual with the subject of the problem), direct (where the problem is compared with homogeneous facts, information, or technology), symbolic (use of personal images), and fantasy (based on how the problem can be solved in the ‘wildest fantasy’). Detailed description of the synectics method is presented by Proctor [7]. Lateral thinking: This is a group of methods originally introduced by De Bono [10] and is based on a unconventional perception of the problem. The main factors enabling lateral thinking are identification of the dominant ideas, search for new ways of looking at the problem, relaxation of the rigid thinking process, and use of chance to encourage the emergence of the other ideas. Among the analytical methods the most common ones applied to engineering problems are: Morphological analysis: The method was introduced by Zwicky [11] and is based on the combination of the attributes of the product or process (like properties, functions, etc.) with
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the elements of the product or the process. While all possible combinations of the attributes can be considered, its applicability is practically limited to three dimensional analysis of the attributes. A number of variations of the method exist and include attribute listing, SCIMTAR, etc. [7]. Analogies: It is a group of method with case-based reasoning as the most useful for the engineering applications. They exploit similarities between the features of the existing problem and the features of problems or designs known from the past. A good survey of case-based methods is given in Leake [12]. Examples of case-based reasoning applications in process engineering are given by Surma and Braunschweig [13] and Avarmenko et al. [14]. A special class of analogy-based methods is biomimetics which involve analogies with living systems [15]. TRIZ: It is a popular method of systematic creativity support introduced by Altshuller [16]. There are many book on TRIZ e.g. Savransky [17], Salamatov [18]. However, the book by Mann [19] seems to be the best introduction. The main findings of TRIZ are: - there exist the trends in the evolution of technologies; - all innovations start with application of a small number of inventive principles; - the innovative solution of the problem removes the conflicts existing in the system.
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Fig. 1. The general principle of application of TRIZ [19].
The application of the basic principles is realised as shown in Fig. 1 and is based on translating the actual problem into a general one, finding the general solution to this problem, and then transforming the general solution into the solution of the actual problem. The basic principles are implemented in several tools including inventive principles, S-fields, Contradiction Matrix, separation principles, knowledge effects, and trends [19]. The classical TRIZ uses 39 universal characteristics and 40 inventive principles for solving contradictions without compromising on conflicting features of technical systems. The Contradiction Matrix maps the most promising principles to contradictions in any pair of characteristics. A section of the classical Contradiction Matrix is shown in Table 1. There are three steps for solving an inventive problem that contains a technical contradiction:
These have been translated into the following three basic principles of TRIZ:
Step 1. Analyze the technical system; determine the system characteristic that needs to be improved.
Ideality: There is a tendency in the evolution of systems that they always change towards the state where all benefits of their functioning are realised at no cost or harm. Functionality: Every system has its main useful function and all its elements have to fulfil this function. Otherwise it is underused and could be a source of conflicts. The notion of functionality allows for the generalisation of the various aspects of the system functioning resulting in the possibility of transferring know-how between the various fields (technical, medical, biological, etc.). Contradictions: There are two types of contradictions. A technical contradiction takes place when there are two parameters of the system in conflict, and the improvement in the value of one parameter worsens the value of the other. Technical contradictions are solved by applying the Contradiction Matrix (see below). A physical contradiction takes place when a parameter should simultaneously have two different values. Physical contradictions are removed by applying the principles of separation in time and space.
Step 2. State the technical contradiction; identify the characteristic that deteriorates as the other improves.
The relation between the ability to generate new and useful ideas or solutions to problems and the removal of the contradictions has been observed by Altshuler. When analysing the vast amount of patents he detected that the best engineering solutions were obtained by the removal of trade-offs between the design objectives.
Step 3. Resolve the technical contradiction. In this step, the 40 principles are used to remove the technical contradiction. The principles most effective for resolving a specific pair of characteristics are shown in the Contradiction Matrix and should be tried first although other principles may also be applicable. For example, if Principle 1 – segmentation – is used for resolving a conflict, it would lead the designer to think of options related to dividing the object into independent parts, making it sectional (for easy assembly or disassembly), or increasing its degree of segmentation. Depending on the domain and details of the object, this could be achieved in different ways. It is therefore beneficial to customize the characteristics and principles to different problem domains. This would help in the practical use of the Contradiction Matrix in specific contexts. The selection of the characteristics when solving a problem seems to be an issue of experience in the use of typical engineering characteristics. However, the application of TRIZ in a totally new field, for e.g. pharmacology, would probably result in a need for introduction of new physical and chemical characteristics. The issue of “which inventive principle to use” is much more difficult to be answered in a straightforward way as would be expected by the engineer. Some heuristics have been suggested by Mann [19]. The eight most commonly used principles
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Table 1 Classical TRIZ Contradiction Matrix, Altshuller [16]
are segmentation, preliminary action, the other way around, dynamics, periodic action, blessing-in-disguise, self-service, and parameter changes. The other suggestions presented in the book consider, for example, the preferences for the improvement of physical attributes or performance. The applications of TRIZ are numerous, Orloff [20], Moehrle [21]. The general paper by Poppe and Gras [22] outlines the possible ways of introducing TRIZ into process industry. However, there are only a few publications on its applications to chemical and process engineering problems. The examples available in the open literature describe the use TRIZ to: - product design; breathable barriers, Roberts [23]; - equipment design; heat exchanger, Busov et al. [24]; food processing equipment, Totobesola-Barbier et al. [25]; - operation; clogging of filter, Carr [26]; erosion of boiler in fluidised bed combustion, Lee et al. [27]; detection of water leakage, Nagakawa [28]; - trends identification; development of computer aided tools, Braunschweig [29]; - process synthesis and design; distillation systems Li et al. [30], reaction –separation systems Li et al. [31]; waste minimisation Li et al. [32].
In the majority of the applications, TRIZ is used in its original form. However, recently one can observe various attempts aimed at the facilitation of TRIZ use by the presentation of the illustrative examples in the different fields of expertise, e.g. food industry Winkless and Mann [33]; chemical problems, Grierson et al. [34]. Another attempt is to introduce the new TRIZ-like principles into the narrow fields of expertise, e.g. synthesis of distillation systems, Kraslawski et al. [35]. A crucial factor for the widespread application of the creativity enhancing methods is availability of computer implementations which facilitate the movement between the main stages of creative problem solving and ensure the structuring of the whole process. A number of software tools are available, each based on a different method and its interpretation. Table 2 provides a brief description of some popular ones. Other sources of information about software for creativity enhancement are listed in http://www.creax.com/resources/creax net.html#29. It is worth mentioning a group of methods aimed at managing and ordering of generated ideas. The most prominent method is MindMap, an approach developed by Buzan [36]. In the MindMap, the main concept is presented as the centre of a picture and different themes radiate from the central concept as labelled branches. Every label could be further branched. Another method is the fishbone diagram—a graphical
Table 2 Software for creativity enhancement Software
Reference
Description
IdeaFisher Axon Idea Processor ThoughtPath
http://www.ideafisher.com/ http://web.singnet.com.sg/∼axon2000/index.htm http://www.thoughtpath.com/bigidea/bigidea.html
Innovation WorkBench TechOptimizer CREAX Innovation Suite
http://www.ideationtriz.com/ http://www.invention-machine.com/ http://www.creax.com/
Generating new ideas by brainstorming through word association Generating, visualizing and organizing ideas through concept mapping Implementing the principles of synectics—based on patterns useful in creative problem solving TRIZ method with online access to patent databases TRIZ method with online access to patent databases TRIZ—includes physical and chemical phenomena
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representation of all possible causes of the given problem [37]. In the following section, we describe the application of TRIZ to an important process engineering problem. 3. TRIZ for inherently safer process design In this section, we illustrate the application of creativity enhancement when performing safety analysis of a process. The design of inherently safer chemical processes is illustrated by the application of TRIZ. The traditional approach to improve the safety of chemical processes is to introduce additional safety equipment and protective devices such as valves, alarms, safety interlocks, and other active systems to detect leaks and process deviations. When new problems surface, more add-on protective equipments is installed to deal with them. In the end, what results is a system whose design is complicated by numerous layers of expensive, add-on protective equipments which often constitute a significant part of the operating cost of the plant. An inherently safer process avoids or reduces hazards instead of controlling them. It relies on naturally occurring phenomena and robust design and eliminates or greatly reduces the need for instrumentation or administrative controls, thereby reducing the costs related to safety and environmental protection. Such a process can be designed by applying inherent safety principles such as intensification, substitution, attenuation, limitation of effects, simplification, etc., throughout the design process, from conception until completion. These principles help to avoid or reduce hazards by using safer materials and operating conditions, minimizing inventory, and result in a simpler and friendly plant. As the design evolves along its lifecycle, opportunities for safer design decreases and incorporation of inherently safer features become difficult and expensive. Although it is possible to apply inherent safety principles at later stages of design, the scope for implementation is greatest in the earliest stages, in particular during route selection. Decisions made during early design stages concerning the choice of synthesis route for product, throughput, and location for manufacture are crucial and fix 80% of capital cost. The conventional safety analysis tools used to identify and control risks such as checklists and hazard and operability (HAZOP) analysis are inapplicable during the pre-engineering design stages due to the lack of detailed design information. As one solution to this problem, inherent safety metrics that measure the safeness of a design have been proposed [38–41]. An alternative approach is to assist the designer identify creative design solutions that overcome the technical conflicts in designing inherently safer process. This latter approach is explored here. A variety of methods can be used in general for enhancing creativity, as described above. The choice of method depends on the nature of the problem. Analytical methods are usually recommended for solving synthesis problems such as the current one. Among the various analytical methods, morphological analysis requires enumeration and analysis of all possible solutions to the problem. It is therefore not suited for large-scale open-ended design synthesis problems like inherently safer design which are
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usually characterised by exponential growth of the number of alternatives where detailed analysis of all possible alternatives is practically impossible. Analogies are most effective for cases where a sufficiently large experience-base with similar design cases is available. TRIZ, on the other hand, does not suffer from these requirements and can be applied to process design. The characteristics and principles in classical TRIZ were targeted towards physical and mechanical systems. To enable a process designer in solving conflicts that arise when designing a new process plant or when improving the safety of existing ones, elements specific to chemical processing should be incorporated. In this paper, a set of 10 characteristics, 8 principles, and a process design Contradiction Matrix is proposed to deal with inherently safer process design. Characteristics: The 10 characteristics shown in Table 3 relate to properties of materials (such as reactants, catalysts, solvents, materials of construction), unit operations, reactions, equipment, process, and plant. They affect the safety performance, and contradictions occur among them when an inherently safe process is being designed. Principles: The well-known inherent safety principles, Kletz [42], can be adapted to resolve conflicts that arise during design. The main inherent safety principles are intensification, substitution, attenuation, and simplification. Besides these, other principles such as limitation of effects, avoiding knock-on effects, making incorrect assembly impossible, and ease of control are also commonly used. From these, eight specific principles have been developed and are described in Table 4. Contradiction Matrix: Using the above characteristics and principles, the Contradiction Matrix shown in Table 5 can be developed. This matrix aims to provide process designers with promising avenues to resolve conflicts. In the following, we illustrate the modified TRIZ using two different examples. Table 3 Characteristics for design of inherently safer chemical processes Characteristic
Example
1 2 3 4 5
Processing conditions Concentration Quality Size Rate
6
Conversion
7
Complexity
8
Hazardous nature
Temperature, pressure, pH, etc. Reactant, product Product Equipment, particle size Reaction rate, mass transfer rate, production rate Raw material to product conversion Controllability, operability of equipment and process; large number of equipment in flowsheet Toxicity, flammability of material; very high and low temperatures and pressures Releases Capital cost, operating costs
9 10
Environmental impact Economics
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Table 4 TRIZ-based principles for design of inherently safer chemical processes Principle
Examples
1. Change process chemistry
(a) Change materials used, such as raw materials or catalyst use less toxic, volatile, reactive or more stable raw materials (b) Change type of reaction use an alternative reaction to achieve the same desired products
2. Change operation sequence
(a) Change the sequence (b) Do the reverse sequence
3. Change equipment type or design
(a) To reduce inventory—reduce piping, vessel size (b) Design equipment to be self-regulatory, tolerant of errors, to withstand the worst-case scenario (c) To reduce inventory—use continuous reactors instead of batch reactors (d) To increase concentration—use distillation, extraction, separation or crystallization
4. Change processing conditions
(a) Change operating conditions such as temperature or pressure of the system
5. Use simpler design
(a) Use a simpler design for the system, one that is easier to operate and needs fewer controls
6. Generate materials as, when and where required
(a) To reduce storage of intermediates—use as and when produced (b) Generate hazardous materials from less hazardous ones in the particular reaction in which it is to be used (c) Generate hazardous materials at the plant itself just before it is used
7. Make operation simpler
(a) Make procedures clearer, simpler and easier to understand
8. Convert harm into benefit
(a) Use heat from exothermic reactions to heat up other streams (b) Convert toxic intermediates to less toxic ones, or sellable products
3.1. Examples Example 1. The introduction of nitro groups and their (catalytic) hydrogenation is a useful route for the industrial production of amines. Nitro compounds are frequently used in the synthesis of pharmaceuticals, for instance in the synthesis of sildenafil (Viagra), the antibiotic linezolid (Zyvox), and the HIV protease inhibitor amprenavir (Agenerase). Consider the route selection for one such nitro compound. When conventional catalysts are used for the selective hydrogenation of aromatic nitro compounds, problems due to accumulation of toxic arylhydroxylamine intermediates (a family of known carcinogens that are also potentially explosive) often occurs. The challenge for the process chemist/engineer is to develop a safe route. In the following, we describe how the three-step creativity enhancement approach described above can be used for this purpose: Table 5 Contradiction Matrix for design of inherently safer chemical processes
Step 1. To improve the safeness of the process, it is desired to eliminate or reduce the amount of intermediates produced. To do so, the process can be operated under milder conditions so that less toxic intermediate is produced. However, this will result in reduced conversion and yield of the desired product. Step 2. The contradiction can be summarized as follows: Characteristic to be improved: reduce concentration of intermediate (Characteristic 2). Characteristic that is getting worse: conversion of the reaction (Characteristic 6). Step 3. To resolve the contradiction, from Table 5, the suggested principles are Principles 1, 3 and 6. Principle 1, which is to change the process chemistry, is a feasible option in this case.
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A search reveals that Degussa and contract research firm Solvias have commercialized a new class of vanadium-doped precious metal powder catalysts, which offer superior performance for the selective hydrogenation of aromatic nitro compounds Scott [43]. Vanadium acts as a promoter to effect the nitro-group reduction. In doing so, the accumulation of arylhydroxylamine intermediates is avoided since the vanadium-doped catalyst eliminates the formation of arylhydroxylamines by modifying the chemical process for the nitro group reduction. The concentration of the toxic intermediate is reduced to below 1% and the conversion of the reaction is not affected. Hence, replacing the conventional catalyst with this new class of vanadium-doped catalyst, can improve Characteristic 2 without affecting Characteristic 6. This illustrates the application of Principle 1. In this case, Principle 3, changing the equipment type or design is not attractive and Principle 6 is not feasible. Example 2. This example considers a common challenge in batch and semi-batch manufacture—one of tradeoff between hazards related to inventory in reactor versus production throughput. The catalyzed oxidation of a thioether to a sulfone via a sulfoxide intermediate involves a two-stage process. The exothermic reaction entails mixing two liquid phases and is traditionally carried out in semi-continuous mode, in a batch-stirred reactor. Traditionally, 18 h are needed to make the intermediate. Step 1. The large inventory of the hazardous substance leads to the exothermic reaction runaway hazard. The reduction in inventory would lead to a reduction in the production rate. Step 2. The technical contradiction can be stated as: Characteristic to be improved: hazardous nature (Characteristic 8). Characteristic that is getting worse: production rate (Characteristic 5). Step 3. Using the Contradiction Matrix, Table 5, the suggested principle is Principles 3, Change equipment type or design. A literature search reveals that BHR Solutions (England) has developed a compact heat exchanger reactor (HEX) which reduces the reaction time for making the organic intermediate to 30 min, with equivalent yield [44]. The HEX reactor allows the process to work in a continuous fashion. Improved mixing and heat transfer result in shorter residence time, improved economics, and process intensification. The compact reactor consists of a stack of diffusion-bonded, thin plates that have tailored flow channels, produced by chemical etching. Using this new type of reactor, the inventory can be reduced while maintaining an adequate production rate and the technical contradiction can be overcome. Thus, innovative unit designs, processes, and products (catalysts) can be systematically explored or unearthed to improve the safety and environmental impact of the process by using the TRIZ methodology.
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4. Discussion The selection of a suitable creativity enhancement method should be based on the nature of the problem under consideration. Brainstorming usually has low applicability to wellstructured technical problems. Its usefulness is highest when dealing with very early phases of design, when technical and organisational limitations are not essential. Synectics and analogies are useful approaches to enhance creativity however their application requires first a rigorous training. Moreover, the application of these methods to well-structured problems is more difficult. Morphological analysis is very efficient and well suited to deal with technical problems, however the previously mentioned difficulties in the visualisation of the higher-dimensional problems is a key obstacle in its widespread application. Another limiting factor is the requirement of deep knowledge of the problem under consideration since it means an awareness of all variables even at early stages of design. The most structured method, TRIZ, also has its limitations with respect to application to process design. The main problem is the abstract character of the method and the consequent difficulties in its application. The engineer has to identify the problem and allocate it into one of the “generic problems” class. This is usually a difficult exercise requiring considerable practice and a flexible approach to problem formulation. The designer has to translate common engineering problems into the “language” of contradictions or standard solutions. The universality, and in consequence the abstract character of TRIZ, is manifested also by the fact that engineer is not always able to identify in the Contradiction Matrix the technical factors essential for the given problem (especially in the field of material science or biotechnology). This means that there are features missing in the system under consideration from among the technical factors present in the Contradiction Matrix. The rapid development of certain fields of science and technology has resulted in many standard solutions and physical effects that could be of the great interest to the designers being absent. Another common difficulty in the application of TRIZ is a lack of the systematic approach to dealing with the hierarchical generation of conflicts during the process design. The removal of one conflict usually results in the generation of new ones. The problems in dealing with new conflicts arises due to the lack of their formal, mathematical description. When analysing a very few published examples of TRIZ application, a common observation to be made is a concentration of the efforts on the troubleshooting and operation, and a lack of conceptual design problems. The successful applications of TRIZ to product and process design are not published in open literature. Paradoxically, the universality and the great potential of TRIZ are the main obstacles in a broader propagation of the results obtained with the application of this method. In consequence, training of process engineers in the use of this method is difficult, despite the availability of many courses and reference books. The following are some outstanding tasks that could be addressed by process engineers who are interested in creativity research and its practical implementation:
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1. Systematic evaluation of the effectiveness and applicability of the existing creativity enhancing methods for the various classes of process engineering problems. 2. Modifications of existing methods for the needs of the specific problems in process engineering including new product development, process intensification, and process debottlenecking. 3. Development of creativity enhancing software and method implementations specifically oriented towards process engineering and their integration with the computer-aided tools for product and process design. 4. Publication of illustrative examples of application of creativity enhancing methods to process engineering problems. 5. Creation of new methods and tools for identification and re-use of the creative problem-solving strategies developed in the different field of science and technology (economics, medicine, biology, geology, mechanical engineering, information science, etc.). References [1] R.J. Sternberg (Ed.), Handbook of Creativity, Cambridge University Press, Cambridge, UK, 1999. [2] A.B. Van Gundy, Techniques of Structured Problem Solving, Van Nostrand Reinhold Co., New York, 1993. [3] J.F. Hoorn, A Model for Information Technologies that can be Creative C&C’02 October 14–16, Loughborough, United Kingdom, 2002. [4] M.A. Boden, The Creative Mind, Abacus, London, 1990. [5] B. Clegg, P. Birch, Crash Course in Creativity, Kogan Page Limited, London, 2002. [6] A. Osborn, Applied Imagination, Scribner’s, New York, 1953. [7] T. Proctor, Creative Problem Solving for Managers, Routledge, London, 2002. [8] CCPS, Guidelines for Hazard Evaluation Procedures, second ed., American Institute of Chemical Engineers, 1992. [9] W. Gordon, Synectics, Harper and Row, New York, 1961. [10] E. De Bono, Lateral Thinking for Management, McGraw-Hill, New York, 1970. [11] F. Zwicky, The Morphological Method of Analysis and Construction, Wiley-Interscience, New York, 1948. [12] D. Leake, Case-Based Reasoning: Experiences, Lessons, & Future Directions, AAAI Press, Menlo Park, CA, 1996. [13] J. Surma, B. Braunschweig, Case-base retrieval in process engineering: supporting design by reusing flowsheets, Eng. Appl. Artif. Intell. 9 (4) (1996) 385–391. [14] Y. Avramenko, L. Nystr¨om, A. Kraslawski, Selection of internals for reactive distillation column-/case-based reasoning approach, Comput. Chem. Eng. 28 (2004) 37–44. [15] M. French, Invention and Evolution. Design in Nature and Engineering, Cambridge University Press, New York, 1994. [16] G. Altshuller, Creativity as an Exact Science, Gordon & Breach, New York, 1984. [17] S. Savransky, Engineering of Creativity, CRC, Boca Raton, 2000. [18] Y. Salamatov, TRIZ: The Right Soultion at the Right Time, Grafisch Bedirijf van der Schaaf, Enschede, 1999. [19] D. Mann, Hands-On Systematic Innovation, Creax Press, Ieper, Belgium, 2002. [20] M. Orloff, Inventive Thinking Through TRIZ, Springer, Berlin, 2003. [21] M.G. Moehrle, How combinations of TRIZ tools are used in companiesresults of a cluster analysis, R&D Manage. 35 (3) (2005) 285– 296.
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