Slurry reactor comparison

Slurry Reactors with Mechanical Agitation The catalyst may be retained in the vessel or it may flow out with the fluid and be separated from the fluid downstream. In comparison with trickle beds, high heat transfer is feasible, and the residence time can be made veiy great. Pressure drop is due to sparger friction and hydrostatic head. Filtering cost is a major item. 

Fig. 1. Comparison between LP201 and the commercial catalysts in a slurry reactor 2.2 Circulating slurry bed reactor...

A comparison between a liquid entrained slurry reactor and a mechanically agitated slurry reactor for methanol synthesis was made by Vijayaraghavan et al. [11]. 

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. ...

In comparison with the number of degrees of freedom offered by packed-bed and slurry reactors, the number offered by monoliths is large. Monoliths often consist of just the active catalyst, or they serve as a support (Figure 9) on which a catalytic coating can be applied (Figure 10). In the former case, referred to as the integral type, the catalyst... 

The comparison between slurry and monolith reactors is summarized in Table 1. Based on the known features of slurry and monolith reactors, it can be concluded that the slurry reactors are preferable for mass-transfer-limited processes as far as the overall process rates are concerned. However, due to the low concentration of solid catalyst in slurry reactors, the productivity per unit volume in these reactors is not necessarily higher than that of monolith reactors. For processes occurring in kinetic regime, the monolith reactors are preferable due to their easier operation. The productivity of slurry reactors might apparently be increased by increasing the catalyst concentration. However, suspensions with a high concentration of fine catalyst particles behave as non-Newtonian liquids, with all the negative consequences in heat and mass transfer. 

In this chapter, first, the existing correlations for three-phase monolith reactors will be reviewed. It should be emphasized that most of these correlations were derived from a limited number of experiments, and care must be taken in applying them outside the ranges studied. Furthermore, most of the theoretical work concerns Taylor flow in cylindrical channels (see Chapter 9). However, for other geometries and flow patterns we have to rely on empirical or semiempirical correlations. Next, the modeling of the monolith reactors will be presented. On this basis, comparisons will be made between three basic types of continuous three-phase reactor monolith reactor (MR), trickle-bed reactor (TBR), and slurry reactor (SR). Finally, for MRs, factors important in the reactor design will be discussed. 

The rate constant k is sensitive to temperature and, in principle, should be associated with the temperature of the catalyst particle. However, the high thermal conductivity of liquids (in comparison with that for gases) and the small particle size reduce the temperature difference between liquid and particle. Hence external temperature differences are not normally important in slurry reactors. 

What happens, however, when we translate this to the slurry reactor Now, we also have to make the comparison on the basis of chronological time, but with the holding time I in the reactor as a consideration. Here we have, for example. 

Figure 5.24 (Top) Comparison of the four combinations of deactivation based on chronological time (bottom) comparison based on slurry reactor results. Catalyst 1, + = a of 0.2 h A= a of 0.5 h catalyst 2, O = / of 0.2 h = / of 0.5 h. ...

This comparison is shown on the bottom of Figure 5.24. It is clear in this case that there is no disguise of the superior catalyst by the slurry reactor. Note, though, that the slurry reactor indicates a smaller difference in the performance between Catalyst 1 and Catalyst 2 than might have been expected on the basis of the chronological time comparison. 

Table 17.5 Comparison of loop slurry reactor performance with mechanically agitated reactor (MASK) performance under corresponding conditions (adapted from Leuteritz, 1973)...

COMPARISON OF OPERATING CONDITIONS IN SLURRY REACTORS USED IN COAL TECHNOLOGY... 

The reaction progress is monitored ofF-Une by HPLC. Flow rates, residence times and initial concentrations of 4-chlorophenol are varied and kinetic parameters are calculated from the data obtained. It can be shown that the photocatalytic reaction is governed by Langmuir-Hinshelwood kinetics. The calculation of Damkohler numbers shows that no mass transfer limitation exists in the microreactor, hence the calculated kinetic data really represent the intrinsic kinetics of the reaction. Photonic efficiencies in the microreactor are still somewhat lower than in batch-type slurry reactors. This finding is indicative of the need to improve the catalytic activity of the deposited photocatalyst in comparison with commercially available catalysts such as Degussa P25 and Sachtleben Hombikat UV 100. The illuminated specific surface area in the microchannel reactor surpasses that of conventional photocatalytic reactors by a factor of 4-400 depending on the particular conventional reactor type. 

In terms of industrial use, the aforementioned three-phase slurry reactors are in themselves amenable for qualitative comparison in terms of their physical attributes and the various operating parameters. While the specifics of these attributes are determined by the process chemistry and detailed design (guidelines to which is discussed later in this chapter), Table 6.4 provides at a glance qualitative comparison of these attributes. 

The fate of bubbles in the slurry reactor is a complex issue since they undergo formation and breakup [110, 111]. Single-bubble and two-bubble models have been evaluated [112]. Two models for the churn-turbulent flow regime were developed, and a comparison indicated that increasing reactor... 

Ghasemi S, Sohrabi M, Rahmani M. A comparison between two kinds of hydrodynamic models in bubble column slurry reactor during Fischer-Tropsch synthesis single-bubble and two-bubble class. Chem. Eng. Res. Des. 2009 87 1582-1588. 

Satterfield CN, Huff GA, Stenger HG, Carter JL, Madon RJ A comparison of Pischer-Tropsch synthesis in a fixed-bed reactor and in a slurry reactor, Ind Eng Chem Fundam 24(4) 450-454, 1985. 

Chambrey, S., Fongarland, P., Karaca, H., Pich4 S., Griboval-Constant, A., Schweich, D., Luck, F., Savin, S., and Khodakov, A.Y. (2011) Fischer-Tropsch synthesis in milli-fixed bed reactor comparison with centimetric fixed bed and slurry stirred tank reactors. Catal. Today, 171 (1), 201-206. 

For slurry reactors, the concentration of monomer in the solvent should be used for calculation of kp. This, however, has not been the usual practice in the literature. Usually polymerization rates are normalized with respect to the total pressure or the monomer partial pressure in the head-space of the slurry reactor. The total pressure can differ significantly from the monomer pressure if the solvent vapor pressure is appreciable at the operating temperature. Use of the monomer partial pressure is somewhat better since the concentration of monomer in the solvent is directly proportional to the monomer partial pressure in the pressure range where Henry s law is applicable. However, comparisons of activities in slurry reactors based on the partial pressure of the monomer above the solvent are only valid for a single solvent since the solubility of the monomer is a function of the solvent. 

Results obtained with the Stauffer AA, Type 2.1 catalyst are summarized in Table 1. Previous investigations in our laboratory have shown that the intrinsic rate of gas-phase ethylene homo-polymerization over the Stauffer AA, Type 2.1 catalyst is essentially first order with respect to ethylene concentration hence, the values should be constant since mass and energy transfer processes were probably not significant. Examination of the relative activities in Table 1 shows that the values for the slurry reactor based on Csl ond the value for the gas-phase reactor are essentially the same, t.e. the kp value is independent of solvent and independent of reactor type. If comparison of activities had been based on Csvt erroneous conclusions that the catalyst s activity in the slurry was two to... 

Comparison of activities in slurry and gas-phase reactors for the SMST catalyst is presented in Figure 1 the dashed lines are activities in the slurry reactor based on the concentration of ethylene in the vapor phase, t.e. Csv% while the solid lines adjacent to the solvent designations axe based on the ethylene concentrations in the respective solvent, t.e. Cst> Four general observations can be made from the results presented in Figure 1 one, all the activities are time dependent two, the activity in the gas phase is significantly lower than the activities in the various solvents three, activities in the solvents which are based on Csv (dashed lines) are solvent dependent and four, activities for the solvents... 

Direct comparison of normalized activities was possible for gas and slurry reactors for the j-TiCls catalyst since the activity of this catalyst was essentially constant. However, the differences in activation and deactivation rates observed for the high activity catalysts in gas-phase and slurry reactors makes direct comparisons of activities obtained with these two types of reactors impossible. Quantitative understanding of the differences in activation and desu tivation processes in the two types of reactors or the development of operational procedures which eliminate these differences is required before direct comparison of rate data for slurry and gas-phase reactors is possible. 

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