Reactor global performance

As mentioned, the aim of the study is to develop desulfurization equipment of industrial interest so understanding its general performance is important. Several sets of typical operation data measured under stable operations are listed in Table 7.5. The comparable data are depending on coal type, S02 content in flue gas ranges from 1400 to 11400 mg/m while the permitted discharge level in China is normally 1200 mg/m3. The data show that the designed equipment exhibits satisfactory global performance and meets the requirements for desulfurization by wet process. Under moderate operation conditions, the content of S02 in the cleaned gas can achieve a much lower level than that permitted. Even if the mole ratio of Ca/S is as low as 1.0, a sulfur-removal efficiency of nearly 90% can be achieved (see the fourth row in Table 7.5) while the pressure drop across the reactor is very small, ca. 400 Pa only. 

The new reactor has good global performance for FGD. Under moderate operation conditions, the content of S02 in the cleaned gas can achieve a level much lower than that permitted ... 

The transfer rates presented above results in the characteristic time of physical processes (heat/mass transfer) in conventional reactors ranging from about 1 to 10 s. This means that relatively slow reactions (t,. 10 s) are carried out in the kinetic regime, and the global performance of the reactor is controlled by the intrinsic reaction kinetics. The chemical reactor is designed and dimensioned to get the required product yield and conversion of the raw material. The attainable reactant conversion In the kinetic regime depends on the ratio of the residence time in the reactor to the characteristic reaction time (t). 

To answer this question, one can compare the global performance of two common types of reactors ... 

In the case of chemical reactors, a large number of fundamental phenomena are likely to interact and influence the global performance of the system. The following phenomena are the most commonly studied ... 

Taking into account all these phenomena to quantify their specific influence on the global performance of a reactor would require either the development of very complex and hard to validate models or the experimental realization of cost- and time-consuming measurements dedicated to each of these phenomena. Instead of these fine but complex approaches, the methodology used thereafter proposes a simpler characterization of the phenomena involved, based on the comparison of their characteristic times. 

In addition to these two macromixing reactor models, in this chapter, we also consider two micromixing reactor models for evaluating the performance of a reactor the segregated flow model (SFM), introduced in Chapters 13 to 16, and the maximum-mixedness model (MMM). These latter two models also require knowledge of the kinetics and of the global or macromixing behavior, as reflected in the RTD. 

In December 2006, Westinghouse, a major maker of nuclear power plants (and owned by Toshiba in Japan), announced a multi-billion dollar deal to sell four new nuclear plants to China. The deal, worth about 5 billion, includes work to be performed by U.S. engineering giant Shaw Group, Inc. AREVA Group also has a deal with China for two reactors and approximately 20 years worth of atomic fuel. Thanks to the nuclear efforts in China and other countries in the Far East, more than 20,000 megawatts of nuclear capacity have come online globally since 2000. 

Another type of reactor that may have considerable future potential for use in homogeneous catalytic reactions is called the membrane reactor. These reactors have been successfully used for the commercialization of manufacturing processes based on enzyme catalysis. In fact, 75% of the global production of l-methionine is performed in an enzyme reactor. A membrane is basically an insoluble organic polymeric film that can have variable thickness. The catalyst... 

Coke deposition was performed via cracking reactions of a real feedstock (gas-oil) operated in a fixed bed reactor which allows a wide range of experimental conditions [7] catalyst mass from 0.5 to 10 g reaction temperature from 723 K to 873 K pressure from 1 to 4 bar injected feed mass between 0.4 and 4 g feed injection time from 10 to 300 s. This reactor induces a coke formation very similar in quantity and nature to that observed on industrial plant catalysts [7]. Coke combustion was performed at 1773 K under oxygen flow in a Leco CR12 carbon analyzer. The global carbon content was extracted from the total volume of carbon dioxide produced during combustion... 

The study demonstrates that particle swam optimisation is a powerful optimisation technique, especially when the objective function has several local rninirna. Conventional optimisation techniques could be trapped in local minima but PSO could in general find the global rninimrun. Stacked neural networks can not only given better prediction performance but also provide model prediction confidence bounds. In order to improve the reliability of neural network model based optimisation, an additional term is introduced in the optimisation objective to penalize wide model prediction confidence bormd. The proposed technique is successfully demonstrated on a simulated fed-batch reactor. 

If the values of local mean bubble diameter and local gas flux are available, a fluid dynamic model can estimate the required influence of mass transfer and reactions on the fluid dynamics of bubble columns. Fortunately, for most reactions, conversion and selectivity do not depend on details of the inherently unsteady fluid dynamics of bubble column reactors. Despite the complex, unsteady fluid dynamics, conversion and selectivity attain sufficiently constant steady state values in most industrial operations of bubble column reactors. Accurate knowledge of fluid dynamics, which controls the local as well as global mixing, is however, essential to predict reactor performance with a sufficient degree of accuracy. Based on this, Bauer and Eigenberger (1999) proposed a multiscale approach, which is shown schematically in Fig. 9.13. 

Desmet G., Vereist H., Baron G.V., Local and global dispersion effects in Couette-Taylor flow I. Description and modeling of the dispersion effects IL Quantitave measurements and discussion of the reactor performance, Chem. Eng. Sci. 51 (1996) 8, p. 1287-1298 and 1299-1309... 

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