Processing methods cost considerations

Synthesis. Exploratory research has produced a wide variety of odorants based on natural stmctures, chemicals analogous to naturals, and synthetic materials derived from available raw materials and economical processing. As in most areas of the chemical industry, the search for new and useful substances is made difficult by the many materials that have been patented and successfully commercialized (4). In the search for new aroma chemicals, many new materials are prepared for screening each year. Chemists who perform this work are involved in a creative exercise that takes its direction from the commercial sector in terms of desirable odor types and specific performance needs. Because of economic limitations, considerations of raw material costs and available processing methods may play a role eady in the exploratory work. 

Although a combination of product quality and cost considerations will dictate the methods used for bulk processing of fruit juices, there are instances where the flavour components present in the juice at e vulnerable to any form of heating din ing concentration. Strawberry juice is perhaps the best example of this, being one of the most heat sensitive of fruits, and it works well with alternative processes for concentration such as freeze-concentration and hyperfiltration. 

Growing scarcity of fresh water in many places in this country and the rest of the world has stimulated the development of several potentially useful processes for saline water demineralization. Because fresh water is such a cheap commodity, these processes must demonstrate the maximum conceivable economy to compete with even the most expensive natural fresh water sources. Nearly all of these methods require considerable energy, either as heat or as electric power. Since this is a large cost item in these processes, solar distillation offers substantial operating economies, but at the expense of large investment requirement. 

As a result of these disadvantages, tremendous efforts over the past 20 years have focused on developing chemistries/processes to improve or replace the Yajima process. At this point, as discussed below, several precursors can be synthesized and/or processed to produce phase pure SiC shapes with controlled microstructures that offer the exceptional properties expected of SiC. Thus, this area of precursor chemistry can now be considered to be mature. Consequently, only engineering and/or cost considerations now dictate which precursor systems are useful for a given application. Furthermore, because the general area of SiC precursors has been reviewed in detail6,7, we focus here only on those precursors and processing methods that provide phase pure SiC. 

Several biotechnological synthetic methods for D-pantothenic add and its precursor D-pantolactone have been developed over the past 15 years. Although all have reached preparative scale and might result in cost-effective production processes, they differ considerably in their process characteristics - for example educts and space-time yields, especially when a fermentation and biotransformation are compared. Compared with the chemical process, the biotechnological processes reduce waste production and provide the possibility of a more environmentally friendly yet still competitive means of production of D-pantothenic acid. 

To understand why HPLC is frequently used in quantitative analytical methods, it is useful to assess whether or not an analytical method is suitable for its intended purpose and, in doing so, consider the deficiencies in methods employing classical measurement steps. Analytical method validation is the process of assessing the fitness for purpose of an analytical method in choosing an analytical method issues such as cost, simphcity, operator experience, availability etc. are of secondary importance to the actual validity of the method under consideration. In the validation procedure, tests are typically carried out for the following properties ... 

A distinction between inactive and active fillers is at present hardly relevant, since the properties of the final product depend more or less strongly upon all the fillers utilized and their use has for a long time not been primarily determined in terms of cost reduction. The efforts of the fdler producers in the direction of improved processing methods and dedicated manufacturing processes take this development into account. The surface treatment of natural and synthetic fillers has also acquired great importance. For years there have been products which in the classic sense are not fillers at all, but are in fact active substances (e.g. silica aerosols). Apart from any cost reduction considerations, fillers have essentially the following functions ... 

More than 5 million tons of acrylonitrile are made annually. It is synthesized industrially by the gas-phase heterogeneous ammoxidation of propene. New catalysts based on Bi-Mo or V-Sb oxides may lead to manufacture of this important compound from propane. Although the new process has a considerably lower selectivity to acrylonitrile, the lower cost of the alkane makes it economically interesting (the propane method can cut at least 20 % from the production costs of the propene route). Nevertheless, increases in the selectivity of the catalysts, especially at higher conversions, will be necessary for this process to compete with the usual process of acrylonitrile synthesis [24]. 

From an economical point of view the overall conversion efficiency of the precursor is another important parameter for cost considerations. This efficiency is defined as the ratio of infiltrated mass to the precursor mass introduced into the reaction chamber. Investigations indicate that the conversion efficiency is dependent on the mass transport method, residual time of the precursor, pressure and temperature, etc. As shown in Figure 5.9 the conversion efficiency of propylene (C3H6) increases with an increase in residence time but decreases with the partial pressure of the precursor gas. In particular, it is worth noting that the conversion efficiency in the I-CVI process is rather low and generally is in the range of 0.78 to 2.14% [17],... 

Savadogo presents the fundamental thermodynamic and kinetic considerations for fabricating inorganic thin-film materials with special emphasis on chemical deposition from mixed solutions, electrodeposition, and sol-gel methods. The exceptional range of materials that have been prepared by these methods is noteworthy, as is the low cost of the processing methods. Treated in detail are the syntheses of the component chemicals, as well as the mechanistic and synergistic role of the components including the important role played by additives. 

TLC-FID produced comparable results to those obtained by GC in the analysis of commercial mixtures of acylglycerides (Ranny et al, 1983). Furthermore, owing to cost considerations, the TLC-FID method was found to be preferable for serial analysis in process control or technical quality control. 

---