Examples of Process Changes

The process integration principles outlined above provide the guidelines for process changes in general. It is clear that both composite curve and grand composite curve are very powerful tools that allow us to optimize process integration for the entire 

Lower chemical H2 consumption reduces natural gas consumed at H2 plant. 

Higher distillate selectivity reduces heat release in the new distillate catalyst less quench is required 

Lower quench requirement reduces the recycle gas compressor utilities. 

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Chemical effects are quite commonly observed in Auger spectra, but are difficult to interpret compared with those in XPS, because additional core levels are involved in the Auger process. Some examples of the changes to be seen in the KLL spectrum of carbon in different chemical environments are given in Fig. 2.24 [2.130]. Such spectra are typical components of data matrices (see Sect. 2.1.4.2) derived from AES depth profiles (see below). 

The mechanical properties of ionomers can be appreciably altered by the manner in which the ionomer is prepared and treated prior to testing. Some of the factors that are influential are the degree of conversion (neutralization) from the acid form to the salt form, the nature of the thermal treatment or aging, the type of counterion that is introduced, the solvent that is used for preparation of thin films, and the presence and nature of any plasticizers or additives that may be present. In the scope of this chapter, it is not possible to provide a complete description of the influence of each of these variables on the wide variety of ionomers that are now commercially available or produced in the laboratory. Instead, one or more examples of the changes in properties that may be induced by each of the processing variables is presented and discussed. 

Q fiU Give two physical and two chemical processes that are examples of reversible changes that are not at equilibrium. 

The chemistry of the Purex process has been extensively investigated, and it seems very difficult to find new major improvements. However, some improvements in some process details may contribute to a decrease in reprocessing costs, especially if several changes are made simultaneously. Examples of such changes are presented in next sections. 

Often, the best examples of process efficiency can be found outside the pharmaceutical and biopharmaceutical industries. Other fields such as electronics, space, and software industries have evolved their documentation, training, quality, and change control systems to the point of best in class. These industries are more time sensitive to get product to market and have often evolved their processes to be efficient and decision processes to be very quick. Process owners may expand their knowledge by investigating other industries to find best practices and apply them internally. 

Carbon tetrachloride represents an example of the change to petroleum raw materials in this field. The traditional source of this widely used product has been the chlorination of carbon disulfide, either directly or through the use of sulfur dichloride. Military requirements in World War II caused an increase in demand, and in addition to expansion of the older operations, a new process (28) was introduced in 1943 it involved direct chlorination of methane at 400° to 500° C. and essentially atmospheric pressure. This apparently straight-forward substitution of halogen for hydrogen in the simplest paraffin hydrocarbon was still a difficult technical accomplishment, requiring special reactor construction to avoid explosive conditions. There is also the fact that disposal of by-product hydrochloric acid is necessary here, though this does not enter the carbon disulfide picture. That these problems have been settled successfully is indicated by the report (82) that the chlorination of methane is the predominant process in use in the United States today, and it is estimated that more than 100,000,000 pounds of carbon tetrachloride were so produced last year. 

Figure 4. Examples of process monitoring, (a) Change in effective conductivity at 200 MHz during the diffusion of salt through a soft kaolinite sediment and the hydration of a cemented paste backfill, (b) Change in the real relative permittivity at 1.3 GHz during the hydration of a cemented paste backfill (paste data from D. Simon).

Some examples of Process Safety Change include, but are not limited to ... 

Basic or detailed changes in the way the process is permitted to operate can eliminate or reduce exposure. For example, rather than handling a material as a dry powder, it might be handled as a slurry or in solution. A special case of process change involves the substitution of a less hazardous material in the process for a more hazardous one. If such a substitution is not possible, then it may be necessary to completely isolate the process from the worker, as has been done in the manufacture of HCN (prussic acid). 

Now that we have considered the general properties of the three states of matter, we can explore the processes by which matter changes state. One very familiar example of a change in state occurs when a liquid evaporates from an open container. This is clear evidence that the molecules of a liquid can escape from the liquid s surface and form a gas. Called vaporization, or evaporation, this process is endothermic, because energy is required to overcome the relatively strong intermolecular forces in the liquid. The energy required to vaporize 1 mole of a liquid at a pressure of 1 atm is called the standard heat of vaporization, or the standard enthalpy of vaporization, and is usually symbolized as AH°ap. 

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