Chemical analysts

The analyst now has available the complete details of the chemical composition of a gasoline all components are identified and quantified. From these analyses, the sample s physical properties can be calculated by using linear or non-linear models density, vapor pressure, calorific value, octane numbers, carbon and hydrogen content. 

The globalization of the markets for chemicals has led to an increasing number of market and marketing analysts to have a membership ia all of these organizations and to attend meetings ia each geographic area. 

In the past, commodity chemicals were generally priced on the basis of ROl. Capital cost was the most critical item, and those elements that ate related to capital cost were the principal factors in the selling price (excluding taw material cost in some cases). On this basis, a satisfactory ROl resulted in acceptable values for other criteria such as ROS or sales margin. Many analysts favor ROS as a benchmark for comparison because it is up to date and simple and because it is increasingly difficult to determine a tme ROl based on what profits might be on plants built under indation and expensive capital and constmction costs. 

Company practices differ in who does purchasing research and how it is done. Several patterns are evident. The chemical buyer is responsible for preparing the purchase profiles, possibly with in-house Hbrary assistance. Market research analysts are assigned to the purchasing department and prepare some or all of the profiles needed. Outside consultants are used to prepare some of the purchase profiles or as a check on internal procedures and conclusions. 

There is a difference of opinion as to whether a chemical buyer or purchasing-research analyst should be product or division oriented. Those who favor product orientation cl aim they achieve a broader and deeper understanding of the outlook for the chemicals they buy and this leads to sound purchasing strategy. Proponents of the division orientation cl aim that the product-oriented analyst has too many chemicals to foUow (up to 100 specific chemicals in some companies with 10 to 15 as principal purchases). If, instead, division needs are paramount in the mind of the analyst, more profitable buys can be made. The weakness of this latter argument is that in multidivisional, multibillion doUar chemical companies, this division-oriented analyst may have as many chemicals to foUow as a product-oriented counterpart. 

There are a variety of analytical methods commonly used for the characterization of neat soap and bar soaps. Many of these methods have been pubUshed as official methods by the American Oil Chemists Society (29). Additionally, many analysts choose United States Pharmacopoeia (USP), British Pharmacopoeia (BP), or Pood Chemical Codex (FCC) methods. These methods tend to be colorimetric, potentiometric, or titrametric procedures. However, a variety of instmmental techniques are also frequendy utilized, eg, gas chromatography, high performance Hquid chromatography, nuclear magnetic resonance spectroscopy, infrared spectroscopy, and mass spectrometry. 

Analysts must have a strong foundation in plant operations and in the unit under study. The hurdles thrown at analysts increase the proba-bihty that the conclusions drawn will be incorrect. A lack of understanding in the operation of the unit increases the hkelihood that the conclusions will oe inaccurate. An understanding of the chemical... 

An example adapted from Verneuil, et al. (Verneuil, V.S., P. Yan, and F. Madron, Banish Bad Plant Data, Chemical Engineeiing Progress, October 1992, 45-51) shows the impact of flow measurement error on misinterpretation of the unit operation. The success in interpreting and ultimately improving unit performance depends upon the uncertainty in the measurements. In Fig. 30-14, the materi balance constraint would indicate that S3 = —7, which is unrealistic. However, accounting for the uncertainties in both Si and S9 shows that the value for S3 is —7 28. Without considering uncertainties in the measurements, analysts might conclude that the flows or model contain bias (systematic) error. 

Another way to evaluate risks is to calculate the sensitivity of the total risk estimates to changes in assumptions, frequencies, or consequences. Risk analysts tend to be conservative in their assumptions and calculations, and the cumulative effect of this conservatism may be a substantial overestimation of risk. For example, always assuming that short-term exposure to chemical concentrations above some threshold limit value will cause serious injury may severely skew the calculated risks of health effects. If you do not understand the sensitivity of the risk results to this conservative assumption, you may misallocate your loss prevention resources or misinform your company or the public about the actual risk. 

The chemical and physical phenomena involved in chemical process accidents is very complex. The preceding provides the elements of some of the simpler analytic methods, but a PSA analyst should only have to know general principles and use the work of experts contained in computer codes. There are four types of phenomenology of concern 1) release of dispersible toxic material, 21 dispersion of the material, 3) fires, and 4) explosions. A general reference to such codes is not in the open literature, although some codes are mentioned in CCPS (1989) they are not generally available to the public. 

For application in chemical process quantitative risk analysis (CPQRA), the hierarchical format of HTA enables the analyst to choose the level of event breakdown for which data are likely to be available. This is useful for human reliability quantification (see the discussion in Chapter 5). 

This technique is the longest established of all the human reliability quantification methods. It was developed by Dr. A. D. Swain in the late 1960s, originally in the context of military applications. It was subsequently developed further in the nuclear power industry. A comprehensive description of the method and the database used in its application, is contained in Swain and Guttmann (1983). Further developments are described in Swain (1987). The THERP approach is probably the most widely applied quantification technique. This is due to the fact that it provides its own database and uses methods such as event trees which are readily familiar to the engineering risk analyst. The most extensive application of THERP has been in nuclear power, but it has also been used in the military, chemical processing, transport, and other industries. 

A single analyst can perform an event tree analysis, but nonnally a team of 2 to 4 people is preferred. The team approach promotes "brainstonning" tliat results in a well defined event tree structure. The team should include at least one member witli knowledge of event tree analysis, witli tlie remaining members having e.xperience in tlie operations of tlie systems and knowledge of the chemical processes that are to be of interest in tlie analysis. 

Even though it appears that the technology has not been adopted yet, it is expected that TOE MS will be useful to validate the power of the GC X GC separation experiment by proving the separate identities of the vast number of resolved peaks and so show that the analyst who does not use GC X GC is missing valuable chemical compositional information on their samples. In addition, it is just as significant to TOEMS that GC X GC becomes a widespread separation tool, since this will then provide a demand for the powerful capabilities of TOEMS for identification. The GC community must wait for this to be demonstrated, and those who are working in GC X GC development are convinced that the wait will be worth it ... 

One of the commonest procedures carried out by the analyst is the measurement of mass. Many chemical analyses are based upon the accurate determination of the mass of a sample, and that of a solid substance produced from it (gravimetric analysis), or upon ascertaining the volume of a carefully prepared standard solution (which contains an accurately known mass of solute) which is required to react with the sample (titrimetric analysis). For the accurate... 

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