Design process definition

The first chapter provides an overview of process design strategies. Fundamental definitions and a brief review of preparing process flow plans are included. 

In order to illustrate an example of process design for the manufacture of enantiopure drug substances on an industrial SMB system, consider manufacturing 10 ton/ year of an enantiopure drug. The racemic drug by definition is a 50 50 mixture of each enantiomer (products A and B). The goal is to process enantiopure drug substances in order to obtain 99 % purity for both the extract and the raffinate. 

According to Cano-Ruiz and McRae, process design as a part of process development starts with problem framing. At this stage, the concept definition, scope of analysis, design objectives, constraints, evaluation and interruption criteria have to be determined. They argued that framing decisions are often made implicitly, whereas the critical importance... 

Procedural controls, process controls, 98-99 Process controls, 96-100 active controls, 98 inherently safer approach, 97 mitigation techniques, 99 passive controls, 97-98 procedural controls, 98-99 safe operating limits, 99-100 Process definition, documentation, 102-104 Process design, documentation, 105 Process hazard analysis (PHA) risk assessment, 92-93 screening methods, 63 Process risk management decisions, documentation, 105-106... 

We start with a definition of the problem and based on this, we identify the candidates (such as, molecules, mixtures and formulations) through expert knowledge, database search, model-based search, or a combination of all. The next step is to perform experiments and/or model-based simulations (of product behavior) to identify a feasible set of candidates. At this stage, issues related to process design are introduced and a process-product match is obtained. The final test is related to product quality and performance verification. Other features, such as life cycle assessment could also be introduced at this stage. 

Process-product interaction Since a chemical product has to be produced, it is clear that a production process is required. When the product properties depend on the process, we say that the chemical product is dependent on the process. Otherwise, we say that the chemical product is independent on the process. This distinction is important in the design. In the former, the product and process design should be made simultaneously, whereas in the latter, the product and process design can be done independently. We will see how useful these definitions can be in the following sections. 

If such a model-based process design space includes a sufficient portion of the factors affecting product quality variance, the process control space can be projected to define the bounds of normal operation. Based on this definition, the control... 

Even before the optimum plant size was determined, a contractor had been selected and process design work was in progress. The contractor was selected on the basis of competitive cost plus fixed-fee bids. The contract was later converted to a turn-key type, based on the competitive-bid fixed-fee percentage and a definitive cost estimate for completion of the job. This saved about 2 months in over-all job completion time. Through duplication of equipment purchases and construction drawings, it was possible to reduce over-all completion time for three subsequent plants by as much as 8 months from the 17 months required for the first module (Fig. 2). About 29 months were required from Geld discovery to startup of the last Exxon treating facility. 

This chapter introduces the reader to elementary concepts of modeling, generic formulations for nonlinear and mixed integer optimization models, and provides some illustrative applications. Section 1.1 presents the definition and key elements of mathematical models and discusses the characteristics of optimization models. Section 1.2 outlines the mathematical structure of nonlinear and mixed integer optimization problems which represent the primary focus in this book. Section 1.3 illustrates applications of nonlinear and mixed integer optimization that arise in chemical process design of separation systems, batch process operations, and facility location/allocation problems of operations research. Finally, section 1.4 provides an outline of the three main parts of this book. 

A risk analysis is not an objective by itself, but is one of the elements of the design of a technically and economically efficient chemical process [1]. In fact, risk analysis reveals the process inherent weaknesses and provides means to correct them. Thus, risk analysis should not be considered as a police action, in the sense that, at the last minute, one wants to ensure that the process will work as intended. Risk analysis rather plays an important role during process design. Therefore, it is a key element in process development, especially in the definition of process control strategies to be implemented. A well-driven risk analysis not only leads to a safe process, but also to an economic process, since the process will be more reliable and give rise to less productivity loss. 

The scope definition is similar to the definition of the control volume in the thermodynamic analysis or the battery limits in process design, and for the LCA in terms of space and time (e.g., we follow the use of product X in the process from the raw materials to the time it is disposed by the consumer. Throughout the lifetime of the product, we analyze the environmental burden). The reasons for the study are also clearly defined (e.g., is the study necessary to make a decision about a process ), as well as an answer must be given as to who is performing the study and for whom. Consider the following hypothetical example ... 

Group B elements describe the type, quantity, and quality of data to be collected, and the field and laboratory activities that will be used for data acquisition. The sampling process design (Bl) derived from the project DQOs includes the definitions... 

As soon as the final process-design stage is completed, it, becomes possible to make accurate cost estimations because detailed equipmept specifications and definite plant-facility information are available. Direct price quotations based"... 

Many processes require definite conditions of temperature, pressure, contact time, or other variables if the best results are to be obtained. It is often possible to make a partial separation of these optimum conditions from direct economic considerations. In cases of this type, the best design is designated as the optimum operation design. The chemical engineer should remember, however, that economic considerations ultimately determine most quantitative decisions. Thus, the optimum operation design is usually merely a tool or step in the development of an optimum economic design. 

Conceptual estimates are typically prepared during the advanced R D and early process design stages. They are normally used to build the preliminary project economics, prepare preliminary execution plans, and develop cost estimates for the preparation of a complete process design (Phase 1) and a definitive cost estimate. The Phase 0 design package, described in Chapter 6, contains all the information required for conceptual estimates. See Table 9.1 for an example of a conceptual estimate. 

The next issue in the drug discovery process following definition of target and sources of diversity is the definition of a lead structure. Lead structures can arise from biochemical or cell-based screens or through structure-based design. Broach and Thorner provide a more exhaustive description of screening strategies than is possible here (14). 

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