Case Study — Process Selection

All commercially produced nitric acid is now prepared by the oxidation of ammonia. The requirement for a nitric acid product of 60%(wt.) immediately restricts the choice of a recommended production process. Only two processes are possible, both highly efficient, each offering distinct advantages under different market conditions. 

The second process is the single-pressure process. This process is essentially identical to the dual-pressure technique except that it 

The single-pressure process is also a higher net exporter of medium-pressure steam and has a lower utility requirement, and is therefore selected as the preferred option. 

The single-pressure ammonia oxidation/absorption process is selected based upon theoperating criteria used in thesingle-pressure process developed by C l Girdler. 

It is also anticipated that this plant will be part of a larger chemical complex. Ammonia will be produced by steam reforming of natural gas. The nitric acid plant will take a portion of the ammonia product, and nitric acid and ammonia will then be used to produce ammonium nitrate. 

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CASE STUDY SITE SELECTION FOR A 150,000,000 IJi/YR POLYSTYRENE PLANT USING THE SUSPENSION PROCESS... 

In this Section the concepts of a precursor, control process and safety, will be applied to a practical case. From this case study, further refinements and a structured way of approaching practice will be derived. To find a suitable case study, the selection criteria and their underlying rationalisations have to be given. In Chapter 2, Bickman (Bickman et al., 1998) stated that selection criteria should be based upon five major issues site selection, data collection process, authorization, accessibility and other support. These five issues, the selection criteria and their advantages and disadvantages are stated below ... 

Eight case studies were selected for application of the Safe Place, Safe Person, Safe Systems framework and OHS management assessment tool. The risk ranking exercise was conducted as a two stage process firstly without taking into account interventions that were already in place so that areas of vulnerability could be identified should any of the current control measures fail (the raw hazard profile) secondly, an assessment... 

In Part IV, the mechanism of the proposed solution will be presented where integration with other components within PEEE will be explained in more details. This includes integration with the modeling environment (CAPE-ModE), RCM-based maintenance management system, fault detection system, design environment, and with operation support system. Case studies are selected from continuous chemical plant i.e. HDS plant, batch chemical plant i.e. PVC, and upstream end of oil refinery process to illustrate the proposed solution. 

Most reactors have evolved from concentrated efforts focused on one type of reactor. Some processes have emerged from parallel developments using markedly different reactor types. In most cases, the reactor selected for laboratory study has become the reactor type used industrially because further development usually favors extending this technology. Descriptions of some industrially important petrochemical processes and their reactors are available (74—76). Following are illustrative examples of reactor usage, classified according to reactor type. 

Load sharing or selective load shedding is of interest to many users of hot gas expanders. A particularly successful European FCC application is illustrated in Figure 6-43. The addition of an expander-generator set to the FCC unit at a major refinery presented a challenge because a trip of the expander could upset the process. The company that is the subject of this application case study, GHH Borsig, solved this problem with the installation of a computerized control system and through computer simulation of trips. 

The intention of this section is to provide a selection of case studies of varying complexity and from different stages of chemical process plant operation. The purpose of these case studies is to indicate that human error occurs at all stages of plant operation, and to emphasize the need to get at root causes. The case studies are grouped under a number of headings to illustrate some of the commonly recurring causal factors. Many of these factors will be discussed in later chapters. 

Our science building at Brigham Young University is not complete. We are still adding equipment and modifying laboratories to accommodate the latest of experiments. In the same way, these two volumes do not represent a completed study of chemical thermodynamics. This is especially true in Chapters 15 and 16 where we have chosen to use the "case study approach in which we introduce selected examples where we apply thermodynamics to the study of processes of an industrial, geological, and biological nature. It is impossible to cover these broad fields in one book. The examples that we have... 

AB diblock copolymers in the presence of a selective surface can form an adsorbed layer, which is a planar form of aggregation or self-assembly. This is very useful in the manipulation of the surface properties of solid surfaces, especially those that are employed in liquid media. Several situations have been studied both theoretically and experimentally, among them the case of a selective surface but a nonselective solvent [75] which results in swelling of both the anchor and the buoy layers. However, we concentrate on the situation most closely related to the micelle conditions just discussed, namely, adsorption from a selective solvent. Our theoretical discussion is adapted and abbreviated from that of Marques et al. [76], who considered many features not discussed here. They began their analysis from the grand canonical free energy of a block copolymer layer in equilibrium with a reservoir containing soluble block copolymer at chemical potential peK. They also considered the possible effects of micellization in solution on the adsorption process [61]. We assume in this presentation that the anchor layer is in a solvent-free, melt state above Tg. The anchor layer is assumed to be thin and smooth, with a sharp interface between it and the solvent swollen buoy layer. 

Theoretical Treatment of State-Selective Charge Transfer Processes. N + He as a Case Study... 

Theoretical treatment of state-selective charge-transfer processes + He as a case study M.C. Bacchus-Montabonnel... 

The data for the case study taken from an agrochemical manufacturing facility is given in Table 4.2. The corresponding Gantt chart is shown in Fig. 4.8. The processes given in Table 4.2 were specifically selected on the basis of a common... 

With knowledge and tools for prediction of the in-sewer processes as the basis, the practitioner is encouraged to integrate these and their relevant corresponding impacts in the management of different types of sewer networks. Case studies selected for this chapter should provide guidance in this respect. Tools in terms of empirical and conceptual models that have been described in the previous chapters are considered useful. 

In Chapter 7 the derived structured protocol will be applied to multiple case studies in the Dutch chemical process industry. Three case studies will be conducted to derive the answers on the posed research questions and to confirm or reject the results from the case histories in the previous Chapter. The case studies will be carefully selected so that the outcomes of the analysis are predictable for all three cases. This replication strengthens the generalization and overall validation of all case studies and the research in general. 

Like the case study discussed in Chapter 5, the case studies that will be selected in this Chapter are also based upon selection criteria based upon the five major issues as stated by Bickman (Bickman et al., 1998) site selection, authorization, data collection process, accessibility, and other support. Moreover, the cases will be chosen in such a way that all cases can be approached in a similar way, increasing the extent in which the quality of the protocol can be judged, as discussed in Chapter 2. 

In this sub-Section the different research areas concerning each of the three selected case studies are shown. The data is collected from the primary process and part of the secondary process, and subsequently analysed to find the underlying problems present in the tertiary process. The primary process and that part of the secondary process which interacts directly with the primary process, e.g. maintenance, internal transportation, etc., is called the operational process and is the area where the required data is collected from. This operational process is shown in this sub-Section by showing the primary processes and secondly by presenting the interacting secondary processes. The tertiary processes will be presented when discussing the analysis of the data retrieved from the operational processes in sub-Section 7.2.4. 

Whenever the solubility curve is crossed for the less stable Form II there is a risk that it will nucleate and contaminate the product. This situation is very probable when the solubility curves of the two polymorphs lie close together, as shown in Figure 21 of the Cimetidine case study. The addition of seed crystals of Form I, close to its solubility curve, and minimization of the supersaturation during the growth process is a good method of control in this instance. Solvent selection to extend the width of the Form II metastable zone would also be desired, as discussed in section 2.4.4. 

The non-random two-liquid segment activity coefficient model is a recent development of Chen and Song at Aspen Technology, Inc., [1], It is derived from the polymer NRTL model of Chen [26], which in turn is developed from the original NRTL model of Renon and Prausznitz [27]. The NRTL-SAC model is proposed in support of pharmaceutical and fine chemicals process and product design, for the qualitative tasks of solvent selection and the first approximation of phase equilibrium behavior in vapour liquid and liquid systems, where dissolved or solid phase pharmaceutical solutes are present. The application of NRTL-SAC is demonstrated here with a case study on the active pharmaceutical intermediate Cimetidine, and the design of a suitable crystallization process. 

NRTL-SAC has been demonstrated through the case study on Cimetidine as a valuable aid to solubility data assessment and targeted solvent selection for crystallization process design. The average model error is typically 0.5 Ln (x) [1] and is sufficient as a solvent screening tool. Methods that can deliver greater accuracy would increase the value and utility of these techniques. It is impressive in the case of Cimetidine that the NRTL-SAC correlation is capable of reasonable accuracy and predictive capability on the basis of just 2 fitted parameters. Further work to extend the solvent database and optimize the descriptive parameters will be beneficial, and are planned by the developers. 

What follows is not an exhaustive or up-to-the-minute survey of the methods available for protein quantitation, but a practical guide to selecting the appropriate assay for each stage of drug development. A case study further illustrates the application of the standard protein methods to the drug development process. The reader is referred to reviews on the topic for further details.12... 

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