Converter reactors, definition

Kjaer (K9) gives a very comprehensive study of concentration and temperature profiles in fixed-bed catalytic reactors. Both theoretical and experimental work is reported for a phthallic anhydride reactor and various types of ammonia converters. Fair agreement was obtained, but due to the lack of sufficiently accurate thermodynamic and kinetic data, definite conclusions as to the suitability of the dispersed plug flow model could not be reached. However, the results seemed to indicate that the... 

The determination of rate of reaction in a flow system requires knowledge both of the feed rate, v, of a given reactant and of the fraction converted, x. The definition of feed rate as the amount of reactant fed per unit time to the inlet of the reactor is consistent with 1.5.1. The rate of reaction is then given by... 

Since photocatalysis was discovered in the early 1970s, more than 6,200 papers related to this process have been published. Most of the work on this subject has focused on showing that organic molecules can be oxidized in PC reactors. So far, more than 800 organic molecules have been tested for oxidation in PC reactions (Blake, 2001). In most cases, the tested organic molecules were converted to CO2, water, and mineral acids. Therefore, it can be definitely concluded that photocatalysis works for oxidation of organic molecules. The rate of oxidation depends on several factors that will be addressed in the upcoming section. 

In Table 3, reactor specifications and experimental conditions used and efficiency obtained for the different reactors are compared. A more practical engineering definition for efficiency is used instead of more scientific quantum efficiency. The efficiency of each of the reactors, expressed in terms of 50% pollufanf converted per unit time per unit reactor volume per unit electrical power consumed, is compared for the same model component (Orange II dye) and same initial concentration... 

Early work in this field was conducted prior to the availability of powerful radiation sources. In 1929, E. B. Newton "vulcanized" rubber sheets with cathode-rays (16). Several studies were carried out during and immediately after world war II in order to determine the damage caused by radiation to insulators and other plastic materials intended for use in radiation fields (17, 18, 19). M. Dole reported research carried out by Rose on the effect of reactor radiation on thin films of polyethylene irradiated either in air or under vacuum (20). However, worldwide interest in the radiation chemistry of polymers arose after Arthur Charlesby showed in 1952 that polyethylene was converted by irradiation into a non-soluble and non-melting cross-linked material (21). It should be emphasized, that in 1952, the only cross-linking process practiced in industry was the "vulcanization" of rubber. The fact that polyethylene, a paraffinic (and therefore by definition a chemically "inert") polymer could react under simple irradiation and become converted into a new material with improved properties looked like a "miracle" to many outsiders and even to experts in the art. More miracles were therefore expected from radiation sources which were hastily acquired by industry in the 1950 s. 

For the simple network 5.26 and a reaction with no fluid-density variation, the magnitude of the effect is easily calculated The cumulative selectivity of conversion to P (moles of A converted to P per mole of A consumed, see definition 1.11) in batch and continuous stirred-tank reactors as a function of fractional conversion,/A, is... 

The (cumulative) selectivity for K (fraction of reacted A that is converted to K, see definition 1.11) in a batch reactor is... 

We have shown that in order to calculate the time necessary to achieve a given conversion X in a batch system, or to calculate the reactor volume needed to achieve a conversion X in a flow system, we need to know the reaction rate as a function of conversion. In tins chapter we show how this functional dependence is obtained. First there is a brief discussion of chemical kinetics, emphasizing definitions, which illustrates how the reaction rate depends on the concentrations of the reacting species. This discussion is followed by instructions on how to convert the reaction rate law from the concentration dependence to a dependence on conversion. Once this dependence is achieved, we can design a number of isothermal reaction systems. 

Modeling of monolith reactors from first principles presents a valuable tool in the design of such reactors and in the analysis of the underlying phenomena. The results presented show that the reactor behavior can be adequately described and understood by a combination of the reactor s transport characteristics and the intrinsic kinetics obtained with a laboratory reactor of another type. As such we can generalize monolith models to other reaction networks, e.g., extend the given description of the dynamic operation for combined CO oxidation and NO reduction in the automotive exhaust gas converter to include other reactions, like the oxidation of various hydrocarbons and of hydrogen. The availability, however, of a proper kinetic model is a definite prerequisite. 

Notice we require the bed porosity to convert from the rate per volume of particle to the rate per volume of reactor. The bed porosity or void fraction, cb, is defined as the volume of voids per volume of reactor. The volume of catalyst per volume of reactor is therefore 1 cg. This mfonnation can be presented in a number of equivalent ways. We can easily measure the density of the pellet, pp, and the density of the bed, Pb. From the definition of bed porosity, we have the relation... 

The reactor stability decreases with increasing values of a, since the fraction converted at the peak temperature is lower when ATa j is higher. One study showed that the allowable value of 9 for a first-order reaction ranged from 2.4 to 1.1 as a increased from about 7 to 70 [11,12]. There have been many other studies of the stability of tubular reactors and batch reactors, and some complex correlations for the stability limit allowing for changes in coolant temperature with length and the thermal capacity of the reactor wall [13]. However, it is generally not necessary to get the exact stability limit. The conservative criterion that 6> < 1 is often used unless calculations for different conditions show that even with 9 > the reactor is definitely stable to all likely disturbances. 

The CHINON A1 reactor was converted into a nuclear museum which is very much visited. The other gas cooled reactors are being dismantled. The MARCOULE G2 and G3 and CHINON A2 reactors have been dismantled to level 2. CHINON A3 have been dismantled to level 1 and is waiting for administrative authorization to undertake works to reach level 2. St-LAURENT A1 and A2 and BUGEY 1 reactors are in the stage of "definitive stop phase". That means all nuclear fuels have been discharged and transfered to the reprocessing plant. 

By definition, productivity (W) is equal to the production rate at the outlet of the reactor, i.e., moles of reactant A converted into product over time. Both in CSTR or PFR, this production rate depends on the reaction kinetics and we take into account the average residence time in the reactor. For several reactors in series, we have different average residence times. 

Sodium-cooled fast reactors promise to definitely solve the fuel availability problem as they can convert... 

Monolith reactors are composed of a large number of parallel channels, all of which contain catalyst coated on their inner walls (Figure 1.9 [1]). Depending on the porosity of the monolith structure, active metals can be dispersed directly onto the inner channel walls, or the catalyst can be washcoated as a separate layer with a definite thickness. In this respect, monolith reactors can be classified among PER types. However, their characteristic properties are notably dhferent from those of the PBRs presented in Section 1.2.1. Monolith reactors offer structured, well-defined flow paths for the reactive flow, which occurs through random paths in PBRs. In other words, the residence time of the reactive flow is predictable, and the residence time distribution is narrow in monoliths, whereas in a PBR, different elements of the reactive mixture can pass through the bed at different rates, resulting in a wider distribution of residence times. This is a situation that is crucial for reactions where an intermediate species is the desired product and has to be removed from the reactor before it is converted into an undesired species. 

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