Computational industrial practice

Dente and Ranzi (in Albright et al., eds.. Pyrolysis Theory and Industrial Practice, Academic Press, 1983, pp. 133-175) Mathematical modehng of hydrocarbon pyrolysis reactions Shah and Sharma (in Carberry and Varma, eds.. Chemical Reaction and Reaction Engineering Handbook, Dekker, 1987, pp. 713-721) Hydroxylamine phosphate manufacture in a slurry reactor Some aspects of a kinetic model of methanol synthesis are described in the first example, which is followed by a second example that describes coping with the multiphcity of reactants and reactions of some petroleum conversion processes. Then two somewhat simph-fied industrial examples are worked out in detail mild thermal cracking and production of styrene. Even these calculations are impractical without a computer. The basic data and mathematics and some of the results are presented. 

G. Kaibel and H. Schoenmakers. Process synthesis and design in industrial practice. In J. Grievink and J.V. Schijndel, editors, European Symposium on Computer Aided Process Engineering-12, pages 9-22. Elsevier, Holland, 2002. 

Validation practices for computer systems have been presented in line with current expectations of GxP regulatory authorities and industry practice. This chapter concludes the first part of this book by reviewing some fundamental concepts and industry trends that will affect how we validate in the 21st century. Specific guidance on the validation of different types of computer system can be found in the case studies presented in Chapters 19 through 42 of this book. The authors of these case studies are themselves experienced practitioners, and they have been encouraged to focus then-papers on the key issues affecting their case studies. 

Many chemical and petroleum companies are now using Process Industry Practices (PIP) criteria for the development of P IDs. These criteria include symbols and nomenclature for typical equipment, instrumentation, and piping. They are compatible with industry codes of the American National Standards Institute (ANSI), American Society of Mechanical Engineers (ASME), Instrument Society of America (ISA), and Tubular Exchanger Manufacturers Association (TEMA). The PIP criteria can be applied irrespective of whatever Computer Assisted Design (CAD) system is used to develop P IDs. Process Industries Practice (1998) may be obtained from the Construction Industry Institute mentioned in the References. 

The problem table is a numerical method for determining the pinch temperatures and the minimum utility requirements, introduced by Linnhoff and Flower (1978). It eliminates the sketching of composite curves, which can be useful if the problem is being solved manually. It is not widely used in industrial practice any more, due to the wide availability of computer tools for pinch analysis (see Section 3.17.7). 

The flow sensors most commonly employed in the industrial practice are those that measure the pressure gradient developed across a flow constriction. Then, using the well-known (from fluid mechanics) equation of Bernoulli, we can compute the flow rate. Such devices can be used for both gases and liquids. The orifice plate (Figure 13.5a), venturi tube (Figure 13.5b), and Dali flow tube are typical examples of sensors based on the foregoing principle. The first is more popular due to its simplicity and low cost. The last two are more expensive but also more accurate. 

A more reliable method is called a parallel redundant UPS system, but it requires a more sophisticated control system. Both UPS units are energised to share the common load equally. When one unit fails it is switched out of service and the second unit takes over the full load. Figure 17.3 shows the system which also has an off-load bypass supply switched in service by a static switch. This method can be expanded to incorporate three or more units in parallel, although this is seldom found in oil industry practice. It is a practice used in the computer-based industries such as banking and flnancial investment. It is a method that lends itself to piecemeal expansion. 

Validation practices for corporate computer systems have been presented in line with current expectations of GxP regulatory authorities and industry practice. This chapter now concludes the book by reviewing some fundamental concepts, survival hints and industry trends that will affect how we validate in the 21st century. 

Reflecting on technology developments outlined earlier and potentially higher regulatory expectations and concerns, it is expected that the pharmaceutical industry will request a wide-ranging debate on how much validation is enough. The cost of compliance can be enormous for corporate computer systems. There needs to be a sanity check to verify that industry practice has not drifted to a position where the benefit does not justify the cost. 

All of the previous discussion refers to isothermal conditions. Very few commercial reheating cycles can be adequately represented by an isothermal process. Consequently for the non-isothermal case that is normally encountered in industrial practice it would be necessary to take account of the existence of temperature gradients in the steel, grain-boundary diflusion of the carbon and variability of carbon diffusivity with both carbon content and temperature. This may be possible using a suitable computer program meanwhile an approximate attempt to solve this problem by dividing the heating profile into discrete isothermal steps has been attempted. 

Industrialization practices will have to be qualified and continuously improved in order to achieve sustainable and continuous interoperability, despite continuous evolution of the ICT which is imposed by providers. What will be the next ICT trends after Cloud computing, Linked Services and Big Data and HTML5 ... 

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