Lumped chemical reactions

Al number of lumped chemical reactions Am number of measured variables... 

To describe the oxidation of methanol in supercritical wato, kinetic models were created partially independently by different groups. These models consist of elementary reactions [24,25,36,37] or lumped chemical reactions [26] in the mathematical form of ordinary differential equations. From a chemical point of view these models are very similar with small differences in single values of kinetic parameters. 

In handling, shipping, and storing DRI, care should be taken to avoid oxidation. Millions of tons of DRI in pehet and lump form have been shipped by barge, ocean vessel, tmck, and rad. The key to avoiding oxidation is simply to keep the material cool and dry. The chemical reactions involved have been well documented. In general, oxidation of DRI takes place in two forms reoxidation and corrosion (2). 

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. 

This involves knowledge of chemistry, by the factors distinguishing the micro-kinetics of chemical reactions and macro-kinetics used to describe the physical transport phenomena. The complexity of the chemical system and insufficient knowledge of the details requires that reactions are lumped, and kinetics expressed with the aid of empirical rate constants. Physical effects in chemical reactors are difficult to eliminate from the chemical rate processes. Non-uniformities in the velocity, and temperature profiles, with interphase, intraparticle heat, and mass transfer tend to distort the kinetic data. These make the analyses and scale-up of a reactor more difficult. Reaction rate data obtained from laboratory studies without a proper account of the physical effects can produce erroneous rate expressions. Here, chemical reactor flow models using matliematical expressions show how physical... 

A good understanding of the detailed chemistry of oxidant formation makes it possible to construct more compact chemical models. These generalized or lumped mechanism models reduce the number of individual chemical reactions by combining similar or sequential reactions and ig-... 

The model includes fundamental hydrocarbon conversion kinetics developed on fresh catalysts (referred to as start-of-cycle kinetics) and also the fundamental relationships that modify the fresh-catalyst kinetics to account for the complex effects of catalyst aging (deactivation kinetics). The successful development of this model was accomplished by reducing the problem complexity. The key was to properly define lumped chemical species and a minimum number of chemical reaction pathways between these lumps. A thorough understanding of the chemistry, thermodynamics, and catalyst... 

Multiple indices, simple lumps and duplicitous kinetics. In A.V. Sapre and F.J. Krambeck (eds.), Chemical Reactions in Complex Mixtures, (pp. 25-41). New York Van Nostrand Reinhold, 1991. 

Here, for the time being, we explicitly assume that no internal energy is being generated through chemical reactions (Gg = 0). Similar model equations are used for the lumped cathode gas model. The solid body thermal equation is ... 

The two extreme hypotheses on mixing produce lumped models for the fluid dynamic behavior, whereas real reactors show complex mixing patterns and thus gradients of composition and temperature. It is worthwhile to stress that the fluid dynamic behavior of real reactors strongly depends on their physical dimensions. Moreover, in ideal reactors the chemical reactions are supposed to occur in a single phase (gaseous or liquid), whereas real reactors are often multiphase systems. Two simple examples are the gas-liquid reactors, used to oxidize a reactant dissolved in a liquid solvent and the fermenters, where reactions take place within a solid biomass dispersed in a liquid phase. Real batch reactors are briefly discussed in Chap. 7, in the context of suggestions for future research work. 

Two different reduced kinetic models have been considered, both involving four lumped chemical species and three and four lumped reactions, respectively. These models describe the time evolution of the following components ... 

Solution The data regarding the species distribution are converted in stoichiometric equations. Table 2.5 gives the independent chemical reactions. Note the presence of a reaction for describing the formation of heavies, lumped as dinitrile succinate. The material balance around the chemical reactor can be easily calculated by using a spreadsheet Table 2.6 presents the results for lkmol propylene, 1.2kmol NH3 and 9.5kmol air. Propylene conversion is 0.983 and the selectivity in acrylonitrile 79.6%. 

Many industrial processes require accurate environmental control. Examples include chemical reactions and processes that are affected by atmospheric conditions biochemical reactions quality, uniformity, and standardization of certain products factors such as rate of crystallization and size of crystals product moisture content or regain deliquescence, lumping, and caking of hygroscopic materials expansion and contraction of macliines and products physical, chemical, and biological cleanliness effects of static electricity odors and fumes conditions in storage and packaging quality of painted and lacquered finishes simulation of stratosphere or space conditions and productivity and comf ort of workers. Controlled atmospheric conditions are... 

Four types of REY zeolite (Si/Al = 4.8) with different crystal sizes and acidic properties were used. The physical and chemical properties of the fresh zeolites are given in Table 6.4. Polyethylene plastics-derived heavy oil, shown in Table 6.2, was used as the feed oil. The cracking reaction was conducted in a tubular reactor filled with catalyst particles under the following conditions time factor W/F = 0.2-3.0 kg-catkg oil h and reaction temperature = 300-450°C. The lumping of reaction products were gas (carbon number 1-4), gasoline (5-11), heavy oil (above 12), and a carbonaceous residue referred to as coke. The index of the gasoline quality used was the research octane number (RON), which was calculated from Equation 6.1 [31]. 

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