Product-based selection techniques

While the development of flue gas clean-up processes has been progressing for many years, a satisfactory process is not yet available. Lime/limestone wet flue gas desulfurization (FGD) scrubber is the most widely used process in the utility industry at present, owing to the fact that it is the most technically developed and generally the most economically attractive. In spite of this, it is expensive and accounts for about 25-35% of the capital and operating costs of a power plant. Techniques for the post combustion control of nitrogen oxides emissions have not been developed as extensively as those for control of sulfur dioxide emissions. Several approaches have been proposed. Among these, ammonia-based selective catalytic reduction (SCR) has received the most attention. But, SCR may not be suitable for U.S. coal-fired power plants because of reliability concerns and other unresolved technical issues (1). These include uncertain catalyst life, water disposal requirements, and the effects of ammonia by-products on plant components downstream from the reactor. The sensitivity of SCR processes to the cost of NH3 is also the subject of some concern. 

Recombinant DNA techniques. Mutagenesis and selection techniques based on classical bacteriological and genetic methods are common procedures to optimize and standardize microorganisms used in food fermentations. Recombinant DNA techniques offer the potential of altering the properties of microorganisms more precisely in terms of production efficiency, product quality, safety, and diversity... 

As we mentioned earlier, the time that is available for each diversity task will likely depend on the nature of the task. Reagent selection may need to be done in a hurry, whereas compound acquisition studies may be afforded rather more time. In the former case, it is clear that the computer time required for diversity analysis/library design must not exceed that available (possibly only days if the library chemistry is already developed, longer if the chemistry is new). For many product-based reagent selection approaches, CPU time is at present a very real obstacle to what might be done. It is to be hoped that more efficient algorithms and exploitation of parallel computation techniques will help alleviate the current difficulties. More fundamentally, the development of approaches based on Markush representations may offer a solution in instances where only simple 2-D descriptors are employed. ... 

The chemical industries are looking for sustainable growth with a high-energy, efficient biomass conversion approach that can be commercialized into value-added platform chemicals to replace petroleum-derived chemicals (Menon and Rao, 2012). The industrial conversion depends on the selective syntiiesis of products at higher yields, with large-scale production, efficient separation techniques, and tire removal of impurities from renewable resources (Ruppert et al., 2012). The preferred targets of the chemical industry based on raw material, process complexity, productivity, and potential market for the top value-added platform chemicals are listed in Table 26.1. 

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