Principles for chemical products design

16th European Symposium on Computer Aided Process Engineering and 9th International Symposium on Process Systems Engineering W. Marquardt, C. Pantelides (Editors) © 2006 Published by Elsevier B.V.

PRINCIPLES FOR CHEMICAL PRODUCTS DESIGN Luis A. Cisternasa, Edelmira D. Gálvezb a

Department of Chemical Engineering, University of Antofagasta, Casilla 170, Antofagasta, Chile b Department of Metallurgical Engineering, Northern Catholic University, Casilla 1280, Antofagasta, Chile

Abstract In this work it is suggested to develop a theory for chemical products that defines the bases and serves to guide and put in order the development of knowledge in the area. A nature representation of chemical products is carried out based on the simple observation that a chemical product is a system consisted of different chemical substances, and that it is manufactured for one or more purposes, in other words, it is formed by components, an organization and an environment. This representation is used to identify different kinds of chemical products design problems. Keywords: chemical product, product design, product theory.

1. Introduction Chemical products (ChP) have been present more in the industry than in the academy, and that is why the used language and the available knowledge have served more to the industrial sector and the market. In a recent work it has been set out the necessity to develop a theory to chemical products like the one developed for chemical processes [1]. This statement is based on the observation that the engineering of chemical processes, and the design of chemical processes in particular, have been developed due to the existence of a theory, it means a series of principles and /or laws which allow to explain, classify and communicate the chemical processes phenomena. The flow sheet (graphic language), unitary operations and the principles (thermodynamics, kinetics, control) make up the main elements of this theory. In the case of chemical products this development does not exist, reason for what a language for its representation is not identified, for example in a kind of mathematic or graphic representation, there is not a clear definition neither of products nor for the governing behavior principles. This lack limits the development of chemical products, because there are not solid bases to build on its development. Notice that in spite of some attempts, there is not a procedure yet that allows the design of all kind of chemical processes. The efforts have been focused on the development of tools for the design of any specific process or on the answer of a particular design problem (e.g. energy integration). That is why; it is natural to think that in the case of chemical products, where there is less knowledge, we have to develop tools to solve particular problems. In this case it could be useful to classify the products and the existing design problems. In this work our previous manuscript [1], which is a description of chemical products nature, is extended with the purpose of developing the bases for the development of chemical products engineering and to identify the problems of ChP design.

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2. Chemical Product Design A chemical product, ChP, is defined as a system made up of different chemical substances, which is manufactured for one or more purposes [1]. This definition recognizes that a ChP is a system, it means that a product is made up of arranged parts in a specific form. On the other hand, it recognizes the existence of one or more uses of the product, and that is why a product is not totally defined if there is not a specification of the environment in which it interacts. So, mathematically we can represent a chemical product, Q, in this way: Q = C ∪O ∪ M

(1)

Here, C represents the components, O the organization and M the environment. The performance or the properties of the ChP depend on C, O and M. The components may be represented as:

{

}

C = C j | i = 1,2,...m

(2)

Where Cj is a chemical product that is a component of the main chemical product, m is the number of components which make up the main ChP. Then a product can be broken down into sub components and so on until identifying the primary components (which are single products). Every time we work with an entity without distinguishing components, we identify the single products, in other words, when its performance or properties depend on itself as a whole [1]. This representation allows the description of the components of a ChP like a tree in which its base is made up only for primary components. A ChP made up of several components will be identified as a compound product, whereas a ChP that is made up from just one primary component will be identified as a single product. The organization of a ChP is a description, it could be qualitative, quantitative or both, on how the different components are included. It includes a description of the physical form about every component (e.g. size, shape), and the structure, it means of how the different components are interconnected. Then the organization is made up of organized collections in a tree, where in its top it is found a description of the ChP as a whole, and in its bottom a description of each one of the primary components. So, the organization can be represented in this way: O = {O k | k = 1,2,...n}

(3)

Where Ok is one of the n descriptions that make up the product organization. As every component of the product has a specific organization, the organization of a product includes organizations of each of its components. The environment M, is made up of different niches [1] which interact with the product to fulfill its function. A niche is an environment section in which a particular property of the product interacts. The presence of different niches is not only due to the fact that a product carries out different functions in a particular use, but also the product in its

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life changes the niche. It is to say that different product-environment interactions occur during the processing, storage, the use and disuse of a product. So: M = {N l | l = 1,2,...q}

(4)

Where Nl is one of the q niches that made up the M environment of the ChP Q. The performances or properties, P, of a ChP are a function of the components, its organization and the environment, in other words: P = f (Q) = f (C , O, M )

(5)

When comparing the Eqs. (1) and (5) it is clear that the chemical product definition is given by the components definition, its organization and environment, and not by its properties, that is to say several chemical products can have the same properties. On the other hand, P is a set of properties, like P = {Pi | i = 1,2,...r}

(6)

Where Pi is each one of the properties or performances that characterize to the ChP. In some cases, some or all the properties can only be function of the primary components or only of primary components and its organization. The representation of chemical products through the Eq. (1) may have different applications. For example, it can be useful for the classification of chemical products. Usually the classification of ChP is based on its prices or uses. Both, prices and uses meet the market needs and the interest of companies, this kind of classification has been, in some cases, ambiguous. Based on the Eq. (1), Cisternas [1] has proposed a classification based on the number of components, the organization (structure) and its relation with the environment (see Fig. 1). Number of components Compound 4 products

6

8

5

Single products

Whitout complement

Properties are components properties

1

3

Some key properties are properties as a whole Structure

With complement 2

7

Environment Interaction

Figure 1. Classification of Chemical Products[1]

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Another application may be related to the definition of a new area in chemical engineering: chemical products engineering (CPE): CPE is a service function of chemical engineering that involves a selection of the product to be produced, determination of the functions, environment, components and structures of the chemical product. Area that can be subdivided into two considering that the organization and the environment are fundamental aspects of the ChP: a) Structured chemical product engineering, which can be defined as a branch of CPE concerned with the composition, arrangement and internal structure of chemical products, its relationship with the process and the interaction with the environment. b) Functional Chemical Product Engineering, which can be defined as the aspect of CPE that is concerned with the product objectives, environment, and functions rather than with its components and organization.

3. Applications to the Design Different authors have identified several stages in the design of chemical products [2,3]. In those works, clearly, like in the processes design, synthesis and analysis activities are present. In the synthesis stage different knowledge or tools are needed to identify a potential chemical product, Q, based on the specifications of the wanted product S, that is to say: Q = K (S )

(7)

Where K represents the knowledge used in the synthesis stage and S represents the ChP specifications. Different kinds of knowledge are used in the synthesis stage, which includes heuristics, experience and the designer’s creativity. By its side, the S specifications are a function of the market requirements and also of the experience of those who define them. In general a product specification can be represented by a set of specifications. S = {S l | l = 1,2,...s}

(8)

By its own, the analysis stage includes an evaluation of performance or properties of potential chemical product given by the Eq. (5). So, this process is recursive, where the objective is that product properties, P, are equal, or the closest possible to the product specifications S, that is to say: f (C , O, M ) = K ( S )

(9)

In the solution to the problem represented by the Eq. (9), all of them, C, O, M and S are variable, that is the reason for what this problem rests with an ill structured problem. It is necessary to clarify that the function f(C, O, M) forces to do different design activities like modeling, experimentation, prototype, and so on. Due to the problem to solve with the Eq. (9) is complex, it is recommended to develop particular strategies for different specific problems that can be identified in the Eq. (9).

Principles for Chemical Products Design

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For example, the design of fertilizers can be seen as make up of several steps (see Fig. 2): a) generate the desired specifications of the product, S. This means to specify properties related with product manipulation, NH4+ decomposition reduction, and liberation control of the active component [4]. These specifications depend on the use that will be given to the product and in the market requirements. b) use the available knowledge in the synthesis stage to design a product, that is to say to define their components, C, their organization, O, and their environment M. For our example it means to define the nutrients to include in the fertilizers and the additives, define the form the additives are incorporated in the fertilizer (its structures) and the environment characteristics like roots properties, soil characteristics, climate (temperature, humidity, kind of rains (acid or not)), nutrient demand of plants, etc.[5] c) once defined C,O and M is necessary to analyze if the synthesized product responds appropriately to the product specifications. These steps are carried out several times until achieving that the synthesized product properties reach the desired product specifications. Experimentation will be necessary to evaluate physical properties (as the viscosity), liberation profiles, etc. d) finally, the evaluation criteria should be revised by the light of the characteristics of the prototype product, if the criteria change new product specifications or refinement can be generated. From the fertilizer behavior, through their life cycle, new specifications can be necessary because several factors, as the segregation level, chemical stability, physical characteristics, etc.

4. Structured chemical product Design If the environment, through its niches, has a minor role in the design process, or if it is wanted to focus the design problem on the organization, we can say that the problem of the design rests with a structural design problem of a chemical product. The Eq. (9) can be re-written in this way: f (C , O) = K ( S )

(10)

Where the problem consists on determining the components, and the organization of the product with the purpose of getting the desired specifications S or properties. As the design and the analysis stage progress, the specifications may suffer modifications, whether because new specifications are added or because the specifications are defined again as the knowledge increases over the desired product. It is necessary to indicate that in this kind of problem, there is not a lack of environment or niches, but they are not part of the design problem variables, in other words, they are fixed. The molecular design with a specific set of properties can be considered as a special case of design, where the problem to solve is: f (C ) = K ( S )

(11)

And C is made up of just one component.

5. Functional chemical product Design If the design problem is focused on the search of strategies to replace products, insert products or to find new uses for the already known products, then the design problem

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Evaluation criteria generator

S

Chemical product synthesis

Q

Chemical product analysis

P Appraiser of criteria

S≠P

Figure 2. Chemical product design loop

can be called as functional design of chemical products. The Eq. (9) can be re-written as:

f (M ) = K (S )

(12)

Where the problem consists on determining the environment niches, with the purpose of achieving the searched objectives. Once the niches are defined, the problem can be considered as structural design problem again (Eq.10), where it is necessary rearranging the components and/or the structure as to adapt it to the new environment.

6. Conclusions If a chemical product is considered as made up of components, an organization and an environment, then it is possible to represent it for the union set that represents each of those elements. On the other hand, if it is considered that a product design consists in identifying the components, the organization and the environment that meet efficiently to the desired specifications of a ChP, then it is possible to identify that the problem is recursive and that different design sub problems can be identified from this definition. The last idea allows us to study particular strategies for each of these ChP design problems.

References [1] L.A. Cisternas, Nature of Chemical Products, in K.M. Ng, R. Gani, and K. Dam-Johansen, ed. “Chemical Product Design: Towards a Perspective through Case Studies,” Elsevier, to appear in 2006. [2] E.L. Cussler & G.D. Moggridge, 2001, Chemical product design, Cambridge University press, Cambridge, United Kingdon. [3] M. Hill, 2004, product and process design for structurated products, AIChE J., 50(8), 16561661. [4] U. Bröckel & C. Hahn, 2004, Product design of solid fertilizers, Chem. Eng. Res. & Design, 82(A11), 1453-1457. [5] J.E. Sheehy, P.L. Mitchell, G.J.D. Kirk, A.B. Ferrer, 2005, Can smarter nitrogen fertilizers be designed? Matching nitrogen suply to crop requirements at high yields using a simple model, Field Crops Research, 94, 54-66.