Case Study — Process Description

The major process units include an air compressor to provide feed air to the process, and an ammonia vaporizer and superheater for pretreatment of the feed ammonia. A reactor vessel with a fixed platinum/rhodium catalyst bed quickly oxidizes the ammonia at reaction temperatures approaching 950°C. The reaction yield is 95%. A heat exchanger train immediately following the reactor is used to recover reaction heat. Reaction heat is recovered for both gas expansion (to provide shaft power for the air compressors) and for production of medium-pressure steam (at 380°C and 4000 kPa). The high-level energy available in the process is shared approximately equally between gas expansion and steam production. About 40% of all steam production is delegated to in- house process requirements, leaving about 3200 kg/hour available for export. 

Cooled reaction gases are absorbed in water/weak acid using a sieve tray-type tower. The bottoms from this tower is a so-called red product acid, the colour resulting from dissolved nitrogen oxide impurities. The red product acid is then bleached in a smaller sieve-tray stripping column. Air is bubbled through the red acid to strip out the dissolved nitrogen oxides. Bottoms from this column is the product nitric acid at 60%(wt.) concentration. 

The single-pressure process was discussed in Section 3.2 and shown to possess both economic and operational advantages for this plant size. The process described in this design employs technology developed by C l Girdler in their single-pressure process (see Ref. PTI, pp. 173-183). This section of the report describes specific details of the process. 

Acid from the bottom of the absorber is bleached at 1010 kPa using partially cooled, compressed air. The bleach air, containing nitrogen peroxide stripped from the acid, is then added to the main reaction gas stream at the oxidation vessel. 

The cooling water circuit provides river water (at 20°C) to the steam condenser and compressor intercooler. The use of stainless 

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Each chapter starts with a description of the topic covered in the chapter. This is followed by a short example highlighting a reported incident involving a batch reaction system. The case study is followed by a listing of key issues and process safety practices unique to the topic. The issues and concerns presented in this book, as well as potential design solutions and sources of additional information are presented in the tables. This format concisely conveys the necessary and relevant information in a familiar and convenient format. The organization of the tables is described below. 

A summary of each of the key tools and techniques considered to be important in the product development process is given in Appendix III. This covers such techniques as FMEA, QFD, DFA/DFM and DOE. Included for each is a description of the tool or technique, placement issues in product development, key issues with regard to implementation, and the benefits that can accrue from their use, and finally a case study. It would be advantageous next, however, to determine exactly what a tool or technique does. In general, the main engineering activities that should be facilitated by their use are (Huang, 1996) ... 

In the case study on PVC flooring, process descriptions are based on the Ecoinvent database, version 2.2 [37]. Production data for DEHP are missing and are added,... 

To conclude our description of techniques, the use of nanosecond and picosecond spectroscopy which has been applied to excited state intramolecular proton transfer (ESIPT) will be mentioned briefly (Beens et al., 1965 Huppert et al., 1981 Hilinski and Rentzepis, 1983). A large number of inter-and intramolecular proton transfers have been studied using these methods (Ireland and Wyatt, 1976) but in the case of processes which are thought to involve simple proton transfer along an intramolecular hydrogen bond it is usually only possible to estimate a lower limit for the rate coefficient. 

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. 

The following case study describes the investigation work process for a hypothetical occurrence using a logic tree based multiple root-cause systems approach. An example incident investigation report follows the work process description. The example is intended for instructive purposes only descriptions of process equipment and conditions are not intended to reflect actual operating conditions. 

This situation is the simplest as far as drawing a conclusion is concerned. A researcher may terminate experimenting if the final research objective is a detailed study or description of optimum. In the later case it is necessary to upgrade the first-order design to the second-order one and process the outcomes into a second-order polynomial. 

The description of thermodynamics and chemical properties of the RSP is very process specific, and hence its general detailed discussion would constitute a separate issue. Therefore, we will give only a brief discussion of these topics in the context of the following case studies (Section 3). Further related details can be found in Refs. 68-74. 

This chapter concerns the most important reactive separation processes reactive absorption, reactive distillation, and reactive extraction. These operations combining the separation and reaction steps inside a single column are advantageous as compared to traditional unit operations. The three considered processes are similar and at the same time very different. Therefore, their common modeling basis is discussed and their peculiarities are illustrated with a number of industrially relevant case studies. The theoretical description is supported by the results of laboratory-, pilot-, and industrial-scale experimental investigations. Both steady-state and dynamic issues are treated in addition, the design of column internals is addressed. 

As the title of this section already suggests, this is only a very brief survey of the commonly used PE production processes. A detailed description of the processes, the kinetics, and so on shall not be given, as this is not relevant within the framework of this case study. 

Therefore, when studying interfacial reactions on rocks and soils, it must always be determined what the mechanism of the interfacial reaction is, and what kind of processes take place. Also, it must identify the dominant processes responsible for surface excess concentration. If this is not done, and the resultant process is evaluated without knowing it in conventional ways, incorrect thermodynamic data are obtained. The concepts of adsorption, ion exchange, and surface precipitation have to be clearly differentiated, as done previously. When the character of the process can be neglected, only surface accumulation is considered, and we can speak about sorption, including all of the surface processes. In this case, only aphenomenological description can be given, and no thermodynamics can be applied. 

A case study is presented for the HTU conversion of sugar beet pulp 130 kton/a on a dry basis). A process description is given, and the heat economy is discussed. For the generation of process heat some external fuel is required (2% of the heating value of the feedstock). 

The more important classes of reactors are discussed in Section 11.5 as specific case studies of importance. Most case studies include a description of the theory involved, determination of the rate-controUmg step, process design (including reactor modeling), estimation of design parameters, and... 

The first stage requires the completion of a detailed description of the concepts. This stage is also required for the identification of criteria and case studies that will be used to produce a small version of the expert system in order to demonstrate its overall feasibility. The specifications and concepts, which represent the knowledge that is to be captured, are established by describing the key concepts, interrelationships, and the flow of information that is needed to describe the problem-solving process of the expert system (12). 

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