Processing methods process cost considerations

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. 

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. 

We will now look at some other important industrial applications of the chemical principles studied so far. Each of these processes involves at least one step that reaches equilibrium, and so the position of the equilibrium has to be altered in order to make the process economically viable. Although both raising the temperature and increasing the concentration of reactants can speed up reactions, the latter method is costly and the former may destroy some substances in the process. The use of a suitable catalyst is generally more efficient and economical in the long run. A considerable amount of time and money is invested in the development of catalysts. The detailed composition of an industrial catalyst is often a well-guarded secret. 

The system is compact, reliable, and can be fully automated. Moreover, the waste water can be treated batch by batch without any problems. The specific operational costs are about NLG 30-35/m, which is considerably lower than the waste processing costs, but also lower than the costs of alternative methods of treatment (including electro-flotation). 

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],... 

At this juncture, the PEG/maltodextrin (MDX) system [153,154] appears to be the most cost-effective ATPS (cost of MDX is l/kg) though the large-scale operations using real systems have yet to be carried out using this system. The productivity of the purification process increases considerably, especially for intracellular enzymes, which in turn improves the economics of the process, when ATPE is employed instead of conventional methods as indicated by Kroner et al. [151]. 

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. 

Many routes for obtaining template particles are known using molten salt synthesis, hydrothermal synthesis, sol—gel processing, as well as hybrid, multistep methods. The TGG method has been widely used for the development and texturing of piezoelectric ceramics [44]. One of the reasons for this widespread use is the cost consideration, since TGG enables the relatively inexpensive fabrication of textured ceramics with single crystal-Uke properties. However, our present discussion pivots around the mechanical properties. 

During the last few years process synthesis by algorithm methods have made considerable progress. The problem of chemical process synthesis can be stated as follows given a set of reactants with amounts specified, determine both the cost-optimal structure and the optimal design variables of each process unit that can produce a set of specified products. In general, the process synthesis problem can be expressed as a MINLP problem where the integer and continuous variables occur nonlinearly in the performance index. The mathematical form is ... 

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