Method stage, chemical process

Process industry has used the Dow Fire and Explosion Hazard Index (DOW, 1987) and the Mond Index (ICI, 1985) for many years. These indices deal with fire and explosion hazard rating of process plants. Dow and Mond Indices are rapid hazard-assessment methods for use on chemical plant, during process and plant development, and in the design of plant layout. They are best suited to later design stages when process equipment, chemical substances and process conditions are known. 

Hazard and Operability Analysis (Hazop) (Kletz, 1992) is one of the most used safety analysis methods in the process industry. It is one of the simplest approaches to hazard identification. Hazop involves a vessel to vessel and a pipe to pipe review of a plant. For each vessel and pipe the possible disturbances and their potential consequences are identified. Hazop is based on guide words such as no, more, less, reverse, other than, which should be asked for every pipe and vessel (Table 1). The intention of the quide words is to stimulate the imagination, and the method relies very much on the expertise of the persons performing the analysis. The idea behind the questions is that any disturbance in a chemical plant can be described in terms of physical state variables. Hazop can be used in different stages of process design but in restricted mode. A complete Hazop study requires final process plannings with flow sheets and PID s. 

The Dow and Mond Indices and Hazop presented in Chapter 4 are widely used for the safety evaluations of process plants. They cover well those risks and hazards existing on a chemical plant. However a lot of detailed information is needed to complete those analysis. In the early stage of process design many of the required process details are still unknown. Therefore the presented safety analysis methods are not directly applicable in their full mode. 

Edwards and Lawrence (1993) have presented a list of sixteen chemical and physical properties and process parameters which are available at the process route selection stage (Table 5). Seven of these sixteen parameters were included to their index method (PUS). The selected parameters concentrate very much on the chemical process route and chemistry. They have also tested their selection by an expert judgement, which gave support to their work (Edwards et al., 1996). 

Automatization of all stages of the analytical process is a trend that can be discerned in the development of modern analytical methods for chemical manufacture, to various extents depending on reliability and cost-benefit considerations. Among the elements of reliability one counts conformity of the accuracy and precision of the method to the specifications of the manufacturing process, stability of the analytical system and closeness to real-time analysis. The latter is a requirement for feedback into automatic process-control systems. Since the investment in equipment for automatic online analysis may be high, this is frequently replaced by monitoring a property that is easy and inexpensive to measure and correlating that property with the analyte of interest. Such compromise is usually accompanied by a collection of samples that are sent to the analytical laboratory for determination, possibly at a lower cost. 

Although technically stiU being at the development stages. X-ray photodiffraction is aheady being estabhshed as a very promising method for structure analysis of important photoinduced phenomena related to very fundamental physical and chemical processes that accompany the interaction of the matter with light. 

Similar to previous structure identification methods described for metabolites, impurities, and degradants, the knowledge of the physiological or chemical process, in this case the adhesive synthesis process, helped in the rapid interpretation of the MS/MS spectra of the unknown components. No user input about the sample composition is needed for the data-dependent analysis scheme thus, these experiments are simple and rapid to perform. The result is a fairly routine approach to structural screening of unknown mixtures during the manufacturing stage. 

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