Oxidation Design Considerations

Chemical Oxidation Design Considerations 2.4.1. Cyanide Alkaline Chlorination Process Design 

To illustrate how a chemical oxidation process works, design features of a chemical oxidation process is presented helow assuming an industrial effluent containing cyanide is to be treated. 

Modern ozone systems are completely automated. An ozone monitor provides continuous on-line monitoring of the ozone concentration in the gaseous effluent from the contactor. If the concentration of ozone exceeds a preset level (usually 0.05 ppm), the voltage or frequency of the ozone generator is reduced. 

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Sohds in divided form, such as powders, pellets, and lumps, are heated and/or cooled in chemical processing for a variety of objectives such as solidification or fusing (Sec. 11), drying and water removal (Sec. 20), solvent recoveiy (Secs. 13 and 20), sublimation (Sec. 17), chemical reactions (Sec. 20), and oxidation. For process and mechanical-design considerations, see the referenced sections. 

Specific design considerations for a few substances including acrylic acid, styrene, organic peroxides, ethylene oxide, and 1,3-butadiene are given in CCPS (1995) on the basis of an industiy-practice survey. Detailed information for other substances is distributed by industry... 

Microhotplates, however, are not only used for metal-oxide-based gas sensor applications. In all cases, in which elevated temperatures are required, or thermal decoupling from the bulk substrate is necessary, microhotplate-like structures can be used with various materials and detector configurations [25]. Examples include polymer-based capacitive sensors [26], pellistors [27-29], GasFETs [30,31], sensors based on changes in thermal conductivity [32], or devices that rely on metal films [33,34]. Only microhotplates for chemoresistive metal-oxide materials will be further detailed here. The relevant design considerations will be addressed. 

Fig. 2.1. Schematic diagram of design considerations for monolithic or hybrid metal-oxide-based sensor systems...

We win consider ethylene oxide reactors in more detail in later chapters, because the cooling of these reactors is a major design consideration. 

Assume that we wish to design a high-pressure combustion chamber where complete oxidation of CO to C02 is an important design consideration. For this purpose we extrapolate our global rate expression for CO oxidation to higher pressure. The right-hand side of Eq. 13.6 can be rewritten in terms of mole fractions and the total molar concentration [M],... 

In our design considerations we have extrapolated the global rate expression for CO oxidation outside the conditions for which it was derived, and this extrapolation leads to erronous results. Experimental results on oxidation of CO in a flow reactor at varying pressure are shown in Fig. 13.3. The results clearly show that in the medium temperature range around 1000 K, an increased pressure acts to lower, not increase, the rate of CO oxidation. To secure adequate oxidation of CO, we would probably need to increase the postflame residence time in a high-pressure reactor compared to an atmospheric pressure reactor. 

If both substrates to be bonded are nonconducting, then the adhesive formulation must contain a susceptor material. Susceptors can have a small percentage of magnetic iron oxide, iron filings, or carbon additives. A susceptor can also be a steel screen or perforated steel foil that is embedded in the adhesive bond line. It has been found that graphite fiber composites used in the automotive and aerospace industries are sufficiently conductive that they can be successfully heated with induction. Design considerations must be taken into account in placement of the graphite reinforcement, so that the material heats uniformly. 

The equipment for curium-americium oxide production (illustrated schematically in Fig. 2) is located on a rack within a master-slave manipulator-equipped hot cell in the TRU cell bank. The feed adjustment and raffinate collection vessels are located in a tank pit in another part of the cell bank. General design considerations and operating philosophies for chemical process operations at TRU have been described previously (4) Only equipment items that are unique to the curium-americium oxide production are discussed below. 

A fuel cell stack connects a multitude of cells electrically in series while the media, fuel, oxidant and coolant are frequently supplied in parallel. Electrical series coimection implies that the same electric current is passing through each individual cell thus inducing the same oxidant and fuel consumption in each cell. Fundamental stack design considerations are reviewed in [6]. 

One of the major uses of coal is to bum it directly in power plants our objective is to burn coal in an environmentally acceptable manner. This requires the removal of sulfur so that EPA standards for the omission of sulfur oxides in power plants are met. This paper briefly reviews the present state of the art for the chemical removal of sulfur from coal via an oxidation process. A brief summary of the existing sulfur removal processes and their economics along with the chemistry and kinetics of inorganic and organic sulfur removal from coal and the reactor design considerations are outlined. 

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