Process synthesis case studies

Howard, F., 1977. Chemical reactor design for process plants. Case Study 106 Ammonia Synthesis. John Wiley Sons, Inc., New York. 

This book briefly reviews ammonia synthesis, its importance in the chemical process industry, and safety precautions. This case study is integrated into several chapters in the text. See the Introduction for further details. 

There has been a consistent motivation for the work presented in this chapter the application to molecular synthesis in interstellar gas clouds (see, for example, Herbst,22 this volume). The species in these regions are detected spectroscopically and are thus automatically isomerically identified. The routes to the observed neutral species consistently involve ion-molecule reactions followed by dissociative electron-ion recombination.18 The first step in this process is to determine whether an isomeric ion can be formed which is likely to recombine to an observed neutral species. The foregoing discussion has shown that whether this occurs depends on the detailed nature of the potential surface. Certainly, this only occurs in some of the cases studied. Much more understanding will be required before the needs of this application are fulfilled. 

Efforts at synthesis and studies of temperature-dependent solution behaviour of these chemically hydrophobized polyacrylamides are now in progress. However, it is reasonable to point out that in this case, contrary to the hydrophilization of the hydrophobic precursor, the problems associated with additional swelling of the globular core (as the modification proceeds) are absent however, the problem of the choice of working concentration for the precursor is still present since above the coil overlapping concentration the intermolecular aggregation processes at elevated temperatures can compete with the intramolecular formation of core-shell structures. 

A new approach for computerized Inherent Safety Index is also presented. The index is used for the synthesis of inherently safer processes by using the index as a fitness function in the optimization of the process structure by an algorithm that is based on the combination of an genetic algorithm and case-based reasoning. Two case studies on the synthesis of inherently safer processes are given in the end. 

As another case study a process synthesis of an emulsion polymerization process is given (Hurme and Heikkila, 1998). In emulsion polymerization unsaturated monomers or their solutions are dispersed in a continuous phase with the aid of an emulsifier and polymerized. The product is a dispersion of polymers and called a latex. The raw materials are highly flammable unsaturated hydrocarbons and the reaction is exothermic which both cause a risk. The main phases and systems in an emulsion polymerization plant are listed in Table 31. 

Initial work on the design of structured products has been presented by, for example, Meeuse et al. 2000, Wibowo and Ng, 2001, 2002. In this chapter a real life example of a process redesign project where process synthesis techniques were applied to a structured food product, is presented. First, we position this work in the framework of integrated product and process design. Then we describe how we translated existing process synthesis techniques into a useful methodology for structured products. Then the actual case study is presented. Finally some perspectives are given. 

The E-factors of different types of chemical processes are shown in Table 13.4.32 In general, processes performed on a larger scale tend to involve fewer operations and form simpler products. Both facets help lead to lower E-factor values. Remarkably, oil refining generates approximately 10-fold more product than waste. In contrast, pharmaceutical processes can be less than 1% efficient based on waste production. The commercial process of sildenafil (13.73), highlighted in the Case Study below, has been optimized more extensively than the typical pharmaceutical synthesis. 

Lakshmanan L, Biegler LT. A case study for reactor network synthesis the vinyl chloride process. Comput Chem Eng 1997 21 785. 

In the following, the concept of micro modular process engineering is introduced together with the backbone interface developed in order to realize this modular approach. The integration of sensors and an electronic bus system is also described, and the physical characterization of the backbone is discussed within a case study of the enantioselective synthesis of organoboranes. Within the second case study, the sulfonation of toluene with gaseous sulfur tri oxide, the backbone system together with the micro structured devices used is finally assessed based on its application to chemical synthesis. 

One case study within the framework of this project is thus to test the concept of a micro structured reactor plant by applying the fast reaction of the enantioselective synthesis via organoboranes yielding chiral-substituted alcohols. This is typically a batch process carried out in the laboratory using conventional glassware and in the present case has been converted into a continuous process carried out by micro structured devices. This set-up has been used to characterize the physical properties of the backbone system. 

The case studies cover key applications in chemical process industries, from petrochemistry to polymers and biofuels. The selection of processes was confronted with the problem of availability of sufficient design and technology data. The development of the flowsheet and its integration is based on employing a systems viewpoint and systematic process synthesis techniques, amply explained over three chapters. In consequence, the solution contains elements of originality, but in each case this is compared to schemes and economic indices reported in the literature. 

Figure 2.13 illustrates the variation of the economic potential during flowsheet synthesis at different stages as a function of the dominant variable, reactor conversion. EPmin is necessary to ensure the economic viability of the process. At the input/output level EP2 sets the upper limit of the reactor conversion. On the other hand, the lower bound is set at the reactor/separation/recycle level by EP3, which accounts for the cost of reactor and recycles, and eventually of the separations. In this way, the range of optimal conversion can be determined. This problem may be handled conveniently by means of standard optimization capabilities of simulation packages, as demonstrated by the case study of a HDA plant [3]. 

This case study deals with the design and simulation of a medium size plant of lOOkton cumene per year. The goal is performing the design by two essentially different methods. The first one is a classical approach, which handles the process synthesis and energy saving with distinct reaction and separation sections. In the second alternative a more innovative technology is applied based on reactive distillation. 

This case study investigates the possibility of applying reactive distillation to the synthesis of fatty-acid esters as a generic multiproduct process. As representative species we consider the lauric (dodecanoic) acid and some alcohols the series Q-C8, such as methanol, n-propanol and 2-ethyl-hexanol (isooctanol). The generic reversible chemical reaction is ... 

The project deals with a VAM plant capacity of lOOkton per year for an effective operation time of8400 h. The process will be based on the acetoxylation of ethylene conducted in gas phase in the presence of a palladium-based solid catalyst. The case study will tackle the problem of process synthesis and energy integration, as well as the dynamics and control for ensuring flexibility in production rate of 10%, while preserving safety and environment protection. 

The case study of the synthesis of vinyl acetate emphasizes the benefits of a systematic design based on the analysis of the reactor/separation/recycles structure. The core of the process is the chemical reactor, whose behavior in recycle depends... 

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