Onion

The synthesis of the correct structure and the optimization of parameters in the design of the reaction and separation systems are often the single most important tasks of process design. Usually there are many options, and it is impossible to fully evaluate them unless a complete design is furnished for the outer layers of the onion. For example, it is not possible to assess which is better. 

Figure 1.6 The onion model of process design. A reactor design is needed before the separation ind recycle system can be designed, and so on. (From Smith and Linnhoff, Trans. IChemE, CkERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...

Having found the best nonintegrated sequence, most designers would then heat integrate. In other words, the total problem is not solved simultaneously but in two steps. Moving outward from the center of the onion (see Fig. 1.6), the separation layer is addressed first, followed by the heat exchanger network layer. 

After maximizing heat recovery in the heat exchanger network, those heating duties and cooling duties not serviced by heat recovery must be provided by external utilities. The outer-most layer of the onion model is now being addressed, but still dealing with targets. 

Once a design is known for the first two layers of the onion (i.e., reactors and separators only), the overall total cost of this design for all four layers of the onion (i.e., reactors, separators, heat exchanger network, and utilities) is simply the total cost of all reactors and separators (evaluated explicitly) plus the total cost target for heat exchanger network and utilities. 

Figure 8.3 Overall cost tradeoffs decomposed according to the onion model.

All too often safety and health (and environmental) considerations are left to the final stages of the design. Returning to the hierarchy of design illustrated by the onion diagram in Fig. 1.6, such considerations would add another layer in the diagram outside the utilities layer. This approach leaves much to be desired. 

The two inner layers of the onion diagram in Fig. 1.6 (the reaction and separation and recycle systems) produce process waste. The process waste is waste byproducts, purges, etc. 

C7H6O4. Crystallizes with IH2O m.p. 199" C. It occurs in the free state in the onion and other plants is a constituent of one group of tannins, and is a product of the alkaline decomposition of resins. 

The discovery of perfect geodesic dome closed structures of carbon, such as C o has led to numerous studies of so-called Buckminster fullerene. Dislocations are important features of the structures of nested fullerenes also called onion skin, multilayered or Russian doll fullerenes. A recent theoretical study [118] shows that these defects serve to relieve large inherent strains in thick-walled nested fullerenes such that they can show faceted shapes. 

Odour. The gas collected in this way has a somewhat onion-like odour, which is much less pronounced than that of the crude gas given off directly from the carbide without subsequent purification. Absolutely pure acetylene, however, is almost odourless. 

Onions, dehydrated Onium Onium salts On-line databases On-line sampling ONO802, [64318-79-2] Onsager model Onychomycosis Onyx... 

Commercial flavor enhancers for pet foods have become big business. Flavor enhancers, primarily so-called digests, provide high acceptance of pet foods and enable the pet to select one food over another. Commercial companies compete with flavors based on the types that pets like. However, owner objections minimize the use of some acceptabiUty enhancers such as some fish products, onions, and gadic. 

Eor the products under its jurisdiction, eg, meat and meat products, the United States Department of Agriculture (USD A) has requirements similar to those of the EDA. However, mustard and spices that impart color must always be listed separately onion and gadic powder may be listed simply as flavors. 

United States exports of spices in 1992 totaled 87.7 million up from 85.2 million in 1991 (Table 4). Dehydrated onion was the most important export spice product at 36.1 million followed by dehydrated gadic, 7.5 million capsicum peppers, 8.9 million black and white pepper, 5.8 million and prepared mustard products, 4.8 million. Canada, Japan, and Germany are the principal markets for United States spice exports. The production in the United States of temperate 2one spices is increa sing every year some of this output is exported as raw spice. 

Other synthetics with cost advantages and large volume productions are L-carvone [6485-40-17, the primary component in natural spearmint essence D-carvone [2244-16-8], the primary component in natural diU and caraway anethol [4180-23-8], in place of anise and fennel spices and smaller amounts of thymol [89-83-8] replacing thyme and disulfide synthetics for onion and gadic. AH of these synthetics must be labeled as artificial which may limit their use among consumers. 

The FDA appHes the Federal Food, Dmg and Cosmetic Act (3) to the spice iadustry and its products. The FDA has estabUshed a definition for spice which is somewhat general. It states, however, that vegetables such as onions, gadic, and celery are regarded as foods, not spices, even if dried. 

Chill Powder. Chili powder is a commercial blend of several spices, ie, chili peppers, oregano, cumin seed, onion and gadic powders, aUspice, perhaps cloves, and others. Chili powder is the basic flavor for many highly spiced dishes, among them chili con came, and is used in cocktail sauces and ground meats. 

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