Chemical product engineering: An emerging paradigm within chemical engineering

Abstract

New product development is a crucial task for modern corporations. Facing an increasingly competitive and dynamic market, the ability to continuously identify customer needs and create products that meet such needs is essential to business success. As a result, researchers from fields such as management, marketing, industrial design and engineering have devoted their attention to new product development issues, and many references can be found in the literature covering this topic.1-5 New product development combines strategic and organizational actions with technical effort; the former dealing with the management of the development process, strategic placement and launch of the new product; the latter being chiefly concerned with the design of the product and its manufacturing process. While in some industrial and engineering sectors, such as mechanical and electronic, the technical side of the development process has always been appreciated as a major issue, in the chemical process industries the systematic and efficient design of new products is a relatively recent concern. However, these industries, with chemical engineering as their technical support, seem to be making up for lost time, and chemical product engineering is a fast developing concept among both industrial and scientific communities. The aim of this article is to provide a review of the scope of chemical product engineering by discussing its emergence within chemical engineering. The chemical process industries, which include the petroleum, fine chemicals, pharmaceuticals and health, cosmetics, household care, agro and food, environment and electronics sectors, have been facing dramatic social, economic and technical challenges, on a global and local scale. As a result, they have been undergoing deep and rapid changes in the scope of their activities, in the strategies adopted to remain profitable and achieve sustainable growth, and, hence, in the way they view the chemical engineering profession. Since many of the chemical products of today and tomorrow do not have much in common with those of twenty years ago, the portfolio of skills and technical knowledge required by chemical engineers has also been changing rapidly. Chemical engineering science and practice must address this new reality, updating its scope, and, hence, evolving from both educational and research perspectives. In recent years, the chemical engineering community has become apprehensive about the way new generations of chemical engineers are being trained. Several references addressing these concerns can be found in the literature.6-14 The words of Danckwerts15, which have often been echoed,8, 9, 16-19 are now more applicable than ever: "It would be a great mistake to think of the content of chemical engineering science as permanently fixed. It is likely to alter greatly over the years, in response to the changing requirements of industry and to new scientific discoveries and ideas for their application." According to Cussler and Wei20, chemical engineers have to reinvent themselves in order to address the demands of the current industrial environment. Nonetheless, the core concepts of the discipline (unit operations, heat and mass transfer, equilibrium, thermodynamics, etc.) remain highly relevant, and an evolution rather than a revolution should be sought.7, 13, 18, 20, 21 Chemical engineering has traditionally focused on the synthesis, design, optimization, operation and control of processes that result in the transformation of raw materials into useful products. Such concerns remain highly significant from the industrial point of view. Furthermore, chemical engineering skills are varied and versatile, allowing one to tackle a wide range of problems found in diverse industrial sectors. Thus, the modern chemical process industries demand not only the development of new concepts and tools, but also a change in the usage in which chemical engineering skills are applied. broadening of the body of knowledge associated with the discipline;8-11, 16 adoption of a multifaceted approach to products and processes;6-9, 12-14, 16, 22-31 emergence of chemical product engineering as a well-established teaching and research field. Each of these trends have direct implications for teaching and research (Figure 1). Changes in chemical engineering and practice. The emergence of chemical product engineering in the vocabulary of chemical engineering is closely related to the need for moving the design of chemical products from an empirical art toward a science. Chemical process industries have always launched successful products. However, in view of the dynamic and demanding markets companies have to deal with, more systematic approaches have to be adopted in order to guarantee competitiveness. As a consequence, chemical product engineering is becoming a well-established branch of chemical engineering. The concept has been emerging for the last decade (Figure 2). A recent review36 counted over 300 references related to chemical product engineering available in the open literature (Figure 3). Exponential growth since 1997 is evident. Chronological diagram of important events marking the affirmation of chemical product engineering as a discipline within chemical engineering. References related to chemical product engineering published in the last 20 years. Some authors have discussed the history of chemical engineering in terms of two paradigms — unit operations (developed in the 1920s and 1930s) and transport phenomena (developed in the late 1950s) — and identified chemical product engineering as a possible third paradigm.11, 20, 35 However, although some efforts have been made to elucidate the scope of chemical product engineering and position it in the context of chemical engineering,8-12, 14, 24 the field is broad and developing in many directions, and a consensual structure for the discipline has not been achieved yet.35 Such a structure is essential for its full acceptance as an autonomous and dedicated branch of chemical engineering science. In the remaining sections, a possible structure for chemical product engineering is developed, and the main teaching and research challenges faced by chemical engineers in the context of this discipline are reviewed. Chemical product engineering is a broad field, and to elucidate its scope diverse aspects must be simultaneously considered. In this article, a new conceptual model for the discipline is proposed (Figure 4). The main aim of this model is to structure chemical product engineering in terms of fundamental and inter-related pillars, supporting the major objective of designing new chemical products. Three such pillars are suggested: (1) the chemical product pyramid; (2) the integration of chemical product and process design, and (3) a multifaceted approach. Structure for chemical product engineering. In the proposed model chemical products are seen as a very diverse group, encompassing a great variety of structures and functions. Chemical product engineering deals with chemical-related products substantially different from commodity chemicals, which has traditionally been the main focus of chemical engineering. The term chemical product is used to differentiate them from commodity chemicals. There is often confusion between chemical product design and chemical product engineering. In this article, it is argued that chemical product design is just one facet, albeit the central one, of chemical product engineering. Chemical product design can be seen as the operational and concrete task of converting consumer needs and new technologies into new chemical products. This is encompassed by a larger space of knowledge that corresponds to the chemical product engineering discipline. From a practical point of view, the design of a new chemical product involves the embodiment of property, process and usage functions (which are systematized in a chemical product pyramid). It must be integrated with the design of a manufacturing process. The effective incorporation of the chemical product pyramid and process design to create a successful product marketed on a global scale demands the adoption of a multifaceted approach to products and processes. In the following paragraphs, the proposed structure of chemical product engineering (as illustrated in Figure 4) is discussed in terms of the nature of chemical products, chemical product design and the three pillars supporting it. In the chemical engineering context, product engineering has often been taken as synonymous with formulation engineering and, in this sense, associated with multifunctional products whose structure (in the range 0.1–100 μm) is specifically designed and manufactured to provide the functionality desired by customers. These products, which include shaped and bulk solids, semisolids, liquids and gases (Table 1), have been termed structured products,7-12, 14, 32 engineered products,24 dispersed systems,37 chemical-based consumer products38 or formulated products (as in this article). More recently, Voncken et al.35 introduced the notion of product technology in an attempt to bring a broader designation to product engineering in the chemical engineering context. Chemical process companies, and, hence, chemical engineers, have to deal with a wide range of products beyond commodity chemicals, which can be roughly classified into six categories: (1) specialty chemicals, (2) formulated products, (3) biobased concepts, (4) devices, and (5) virtual chemical products, and (6) technology based consumer goods. Specialty chemicals are pure compounds that, as opposed to commodity chemicals, are produced in small quantities (typically less than 1,000 tonnes/year), and are sold on the basis of a specific benefit or function. The evolution from commodities to specialty chemicals has been an enduring trend among chemical process industries. However, the shift in the activity of these industries over the last twenty years is more extensive than a change from commodity chemicals to specialty chemicals.39 Formulated products (e.g., cosmetic and food consumer goods) now represent a large fraction of their business. These products can be defined as combined systems (typically with 4 to 50 components) designed to meet end-use requirements.11 They are often multifunctional (because they accomplish more than one function valued by the customer) and microstructured or engineered (since their value derives significantly from their microstructure).21, 24 Biobased concepts, including innovative biomaterials, drugs (genomic and post genomic solutions), and tissue and metabolic engineering technologies, have increased in importance within the chemical process industries with the rise of healthcare and wellbeing concerns. The scope of the sector has also expanded to incorporate products that are not pure compounds, mixtures or particular materials. Devices that carry out a physical or chemical transformation, such as an electrolytic device used to convert salt into chlorinated pool disinfectant, and virtual chemical products40 are the focus of a growing number of companies. Products such as post-it notes are consumer goods whose functionality is provided by a chemical/physical technology. This kind of product provides a promising and worthwhile extension of the activities of the chemical process industries. The term chemical product is used in this article to encompass the wide range of goods chemical process companies deal with beyond commodity chemicals, generalizing and standardizing various notations that have been adopted in the literature.11, 19, 21, 40-42 Table 2 illustrates the different categories of chemical products. Although the different categories of chemical products have little in common, based on their appearance or performance, similarities between them do exist in terms of development and manufacturing. The term chemical product engineering should then designate the framework of knowledge, approaches, methodologies and tools employed to analyze, develop and produce the whole range of chemical products and not focus solely on formulated products. While the systematisation of product design is a relatively recent concern in chemical engineering, it is better established in some of its sister disciplines, such as mechanical, electrical, computer and biomedical engineering, where customisation is heavily emphasized.3, 5 By adapting procedures used in these disciplines, Cussler and Moggridge17 developed the concept of chemical product design, an holistic approach to the design and development of new chemical products, comprising four essential steps: (1) identification of needs that should be met by the product; (2) generation of product ideas which potentially satisfy the needs identified; (3) selection of the most promising product idea, and (4) development of a process to manufacture the desired product. Other frameworks specifically addressing the design of chemical products have also been proposed.20, 33, 38, 39, 42 The chemical product design frameworks proposed in the literature are mainly associated with a market-pull view of the development process. However, technology-push strategies also create significant development opportunities. Besides, in accordance with the multifaceted approach that constitutes one pillar supporting chemical product engineering (Figure 4), the discipline is concerned with the entire process of discovery, design, development, manufacturing and marketing of chemical products. Thus, the concepts of chemical product design and chemical product engineering should not be seen as synonymous, just as the traditional concepts of process design and chemical engineering have not been seen as equivalents. Chemical product design can be defined as a systematic procedure or framework of methodologies and tools whose aim is to provide a more efficient and faster design of chemical products able to meet market demands. Chemical product engineering is the whole science and art of creating chemical products, a much larger concept encompassing chemical product design. In other words, chemical product engineering can be seen as the general background of knowledge and practice supporting the concrete task of designing chemical products and their manufacturing processes. A crucial feature of chemical products is that customers generally do not judge their value based on technical specifications, but rather according to functionality and performance attributes, such as smell and handling properties. These attributes, used to express and characterize the quality of the product from the customer perspective, are usually referred to as quality factors. Because quality factors are often inherently qualitative and subjective, quantitative parameters have to be developed to model them. These are called performance indices. Performance indices (and therefore quality factors) are determined by three main factors: (1) the composition and physicochemical properties of the materials forming the product; (2) product structure, which is dependent on the manufacturing process, and (3) product usage conditions. The dependence between performance indices and product composition, product ingredients' properties and product structure (when applicable) has been mathematically systematized through the concept of property function, initially proposed by Rumpf.43 An interesting example to illustrate the concepts of quality factor, performance index and property function comes from perfumery. The performance of a fragrance, which relates to its olfactory perception, has been empirically described in terms of four quality factors: impact (measures the efficacy of the fragrance during the first instants after application); diffusion (refers to the distance over which the fragrance is perceived soon after application); tenacity (expresses the long-term efficacy of the fragrance) and volume (relates to the distance over which the fragrance is noticed some time after application). The odor value can be used to quantitatively express the performance of the fragrance (performance index). Recently, Mata et al.44 applied thermodynamics and transfer phenomena fundamentals to develop a model (property function) relating the odor value of a fragrance to its composition, volatility and threshold concentration of its components, and activity coefficients expressing the interaction between the fragrant components and the solvent. In the case of chemical products, in contrast to commodities, product structure often has a preponderant influence over functionality and end-use properties. The desired product structure requires selection of the proper product ingredients, but is often determined largely by the manufacturing process. Consider chocolate — the crystal form of the cocoa butter, which is determined by the tempering process during manufacture, is key to product quality since it determines chocolate melting point and, therefore, the mouth feel. The relationship between process conditions and structural attributes of a chemical product can be quantified by a process function, the definition being analogous to that of a property function. In addition to product composition, product ingredients' properties and product structure, the circumstances under which a chemical product is used also affect its perceived quality. Parameters describing the way the customer uses the product (such as the magnitude of shear forces as body lotion is applied and quantity of perfume employed) and environmental conditions under which product usage takes place (for example, temperature, humidity level and substrate over which a paint is applied) cannot be directly controlled. Under the Taguchi notation,45 they correspond to noise factors affecting product performance and, therefore, demanding robustness from the product.46 Adopting the same reasoning as for the definition of property and process functions, usage functions relating performance indices to customer interaction parameters and usage environmental conditions can also be established. The concepts of quality factor, performance index, property function, process function and usage function as well as the connection between them are illustrated in Table 3 through simplified examples, based on two chemical products. Three approaches can be followed to derive property functions, process functions and usage functions. When the underlying phenomena behind the relationships are well understood, theoretical expressions can be obtained from a detailed analysis and rigorous modeling. This approach has been successfully applied to derive functions expressing transport phenomena. Order-of-magnitude analysis, based on a description of the phenomena supported by simplifying assumptions, is an alternative approach to obtain functions when a full scientific elucidation of the system is not available. Comparison of causal and opposing effects in solids handling is an example of this approach. For cases, such as that of systems involving solids, in which the underlying physical phenomena are poorly understood, empirical models can be determined through applied statistical approaches.38, 49 The idea of a chemical product pyramid is introduced in this article to systematize the relationships between the product recipe, materials' physico-chemical properties, process variables, product structural attributes, usage variables and product quality factors (Figure 5). The base of the three-sided pyramid is defined by the materials space, process space and usage space, which determine the chemical product space occupying the top of the pyramid. Connections between and within these spaces are established by property functions, process functions and usage functions. This pyramid corresponds to the technical core of chemical product engineering — in practical terms, the discipline is concerned with the development of property functions, process functions and usage functions and their application, through simulation and optimization, to the design and manufacture of chemical products with end-use properties valued by the customer. Chemical product pyramid. Ice cream can be used to illustrate the idea of a chemical product pyramid. Ice cream is valued by consumers for its flavor, its creaminess and smoothness, and its coolness; these are its quality factors. Flavor is determined primarily by the ingredients used — a property function would relate the ingredient recipe to empirical descriptions of flavor perception. Smoothness and creaminess are controlled as much by processing conditions as by the nature of the ingredients — the keys are the stabilization of air bubbles by fat particles, and keeping ice crystals below about 100 μm in size. A process function would describe this. The consumers' perceptions of both flavor and texture are strongly modulated by environmental and use factors. In particular the storage history affects ice crystal size by Ostwald ripening. Serving temperature, ambient conditions and general ambiance also influence perceived flavor and texture. This could be described by a usage function. The property and process functions should be controlled to ensure that the product quality factors are robust to in the usage function. chemical product engineering and process engineering to be two However, they are closely related to other and should be from an integrated perspective, rather than Chemical product engineering the whole process of customer needs and new technology discoveries into products. Since product are strongly dependent on it to a view of product development on the integration of product and process engineering. 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