Slurry reactors models

AGITATED SLURRY REACTORS 3.5.1 Agitated slurry reactor models... 

An interesting example of a slurry reactor modeled as a plug-flow reactor for Fis-cher-Tropsch synthesis is given by D. Stem, A. T. Bell, and H. Hememann, Chem. Eng. Sci., 38, 597 (1983). 

In the slurry reactor model, the settling velocity of solid particles is not included therefore, the predicted behavior is close to an EBR. Only the SO2 profile in the gas phase was tested with the model. Although the reliability of the model considering... 

Dente and Ranzi (in Albright et al., eds.. Pyrolysis Theory and Industrial Practice, Academic Press, 1983, pp. 133-175) Mathematical modehng of hydrocarbon pyrolysis reactions Shah and Sharma (in Carberry and Varma, eds.. Chemical Reaction and Reaction Engineering Handbook, Dekker, 1987, pp. 713-721) Hydroxylamine phosphate manufacture in a slurry reactor Some aspects of a kinetic model of methanol synthesis are described in the first example, which is followed by a second example that describes coping with the multiphcity of reactants and reactions of some petroleum conversion processes. Then two somewhat simph-fied industrial examples are worked out in detail mild thermal cracking and production of styrene. Even these calculations are impractical without a computer. The basic data and mathematics and some of the results are presented. 

The simplest theory involved in mass transfer across an interface is film theory, as shown in Figure 3.10. In this model, the gas (CO) is transferred from the gas phase into the liquid phase and it must reach the surface of the growing cells. The rate equation for this case is similar to the slurry reactor as mentioned in Levenspiel.20... 

Slesser and Highet (S15) have proposed a theoretical model for the case of a second-order chemical reaction taking place in a slurry reactor. This model is based on concepts very similar to those employed by Sherwood and Farkas, apart from the obvious complications resulting when one treats a second-order reaction. 

Calderbank et al. (C6) studied the Fischer-Tropsch reaction in slurry reactors of 2- and 10-in. diameters, at pressures of 11 and 22 atm, and at a temperature of 265°C. It was assumed that the liquid-film diffusion of hydrogen from the gas-liquid interface is a rate-determining step, whereas the mass transfer of hydrogen from the bulk liquid to the catalyst was believed to be rapid because of the high ratio between catalyst exterior surface area and bubble surface area. The experimental data were not in complete agreement with a theoretical model based on these assumptions. 

Warna, J., Flores Geant, M., Salmi, T., Hamunen, A., Orte, J., Hartonen, R., and Murzin, D. (2006) Modelling and scale-up of sitosterol hydrogenation process from laboratory slurry reactor to plant scale. Ind. Eng. Chem. Res., 45, 7067-7076. 

Hydrogenation of lactose to lactitol on sponge itickel and mtheitium catalysts was studied experimentally in a laboratory-scale slurry reactor to reveal the true reaction paths. Parameter estimation was carried out with rival and the final results suggest that sorbitol and galactitol are primarily formed from lactitol. The conversion of the reactant (lactose), as well as the yields of the main (lactitol) and by-products were described very well by the kinetic model developed. The model includes the effects of concentrations, hydrogen pressure and temperature on reaction rates and product distribution. The model can be used for optinuzation of the process conditions to obtain highest possible yields of lactitol and suppressing the amounts of by-products. 

A reactor model based on solid particles in BMF may be used for situations in which there is deliberate mixing of the reacting system. An example is that of a fluid-solid system in a well-stirred tank (i.e., a CSTR)-usually referred to as a slurry reactor, since the fluid is normally a liquid (but may also include a gas phase) the system may be semibatch with respect to the solid phase, or may be continuous with respect to all phases (as considered here). Another example involves mixing of solid particles by virtue of the flow of fluid through them an important case is that of a fluidized bed, in which upward flow of fluid through the particles brings about a particular type of behavior. The treatment here is a crude approximation to this case the actual flow pattern and resulting performance in a fluidized bed are more complicated, and are dealt with further in Chapter 23. 

Figure 7-4 Slurry reactor (left) for well-mixed gas-solid reactions and fluidized bed reactor (center) for liquid-solid reactions. At the right is shown a riser reactor in which the catalyst is carried with the reactants and separated and returned to the reactor. The slurry reactor is generally mixed and is described by the CSTR model, while the fluidized bed is described by the PFTR or CSTR models.

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

By using these ratios and the relationships (3.18) and (3.19), we can alter the material balance expressions and the corresponding solutions of the reactor models if we use other rate expressions. It should be noted that in practice, in fixed-beds and slurries of porous particles, the external area of the particle and thus the parameters au and ac are used, respectively. 

An accurate evaluation of kxa is complicated by the heterogeneous nature and poor definition of contaminant/soil systems. Some success has been achieved in modeling mass transfer from a separate contaminant phase. During degradation these nonaqueous phase liquids (NAPLs) often dissolve under conditions where phase equilibrium is not achieved and dissolution is proportional to k a. Experimental determinations and correlations for k-p depend on interfacial area of the NAPL and liquid velocity at the interface (Geller Hunt, 1993). For adsorbed contaminants, kxa varies with soil composition and structure, concentration and age of contamination, and therefore with time. For example, slurry reactor tests indicate that the rate of naphthalene mass transfer decreases with time, with media size, and with aging of the tar prior to testing (Luthy et al., 1994). 

C. Maretto, R. Krishna, Modeling of a bubble column slurry reactor for Fischer-Tropsch synthesis, Catal. Today 52 (1999) 279-289. 

Zhao, H., Multi-scale Modeling of Gas-Liquid (Slurry) Reactors, Ph.D. thesis (in Chinese), Institute of Process Engineering, Chinese Academy of Sciences, Beijing (2006). 

Figure 1. The concentration of epoxided tetrahydroanthraquinone (left scale) and hydrogenated alkyltetrahydroanthraquinone (right scale) in the slurry reactor at 75 °C experimental data ( ), ( ) and model prediction (—), (—),...

Bubble Behavior in a Slurry Bubble Column Reactor Model... 

A Two-Bubble Class Model for Churn Turbulent Bubble Column Slurry Reactor... 

Figures 21a, b show the 4-CP, 4-CC, and HQ concentrations derived from inserting the estimated parameters in the kinetic model and a comparison with the experimental data under different operating conditions. Symbols correspond to experimental data and solid lines to model predictions calculated with Equations (64)-(66) and Equations (71)-(74). Eor these experimental runs, the RMSE was less than 14.4%. These experimental 4-CC and HQ concentrations are in agreement with the proposed kinetic mechanism of parallel formafion of fhe intermediate species (Figure 16), and also with the series-parallel kinetic model reported by Salaices et al. (2004) to describe the photocatalytic conversion of phenol in a slurry reactor under various operating conditions. ...

For all values of the variables studied, the gas-phase dispersion does not show a significant effect on the steady-state or transient characteristics of the liquid-phase or surface concentration. This means that, in modeling three-phase slurry reactors, the gas phase may be assumed to move in plug flow as long as the performance of the reactor is measured in terms of the change in concentration of the liquid phase. 

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