Slurry reactors semibatch operation

The activity tests of liquid-phase oxidation of aqueous phenol solution were conducted in a semibatch slurry reactor at operating conditions given in the caption of Figure 1. The experimental apparatus, the procedure of these measurements and the analysis of the reaction samples are described in detail in a preceding paper [6]. Additional kinetic and mechanistic investigations were carried out in an isothermal, differentially operated "liquid-saturated" fixed-bed reactor [8, 9] which was packed with a pretreated EX-1144.3 catalyst (Sfld-Chemie... 

In the common case, in slurry bubble column reactors, the catalyst phase remains in the reactor while the liquid phase could remain in the reactor with a continuous flow of gas (semibatch operation). Both gas and liquid could be in plug flow or could be well mixed. 

In a typical slurry bubble column operation, the liquid velocity is one order of magnitude lower than the one of gas, and in general, is very low. This mode of operation can be approximated by a semibatch operation. The semibatch operation is frequently used and is the case where the liquid and the catalyst comprise a stationary phase (sluny) in the reactor. In this case, the material balance, eq. (3.122) is used along with the overall rate based on the bulk gas-phase concentration (see Section 3.4.6). In the following, the semibatch operation is presented. 

Figure 1. Relative activities of some experimental and commercial catalysts for oxidation of aqueous phenol solutions in a semibatch slurry reactor. Operating conditions T 403 K p(02) ...

The setup for testing of catalysts has to be as close as possible to the technical conditions of catalyst application. Therefore, powder catalysts for liquid and gas-liquid reactions are usually tested in slurry reactors, which can be operated continuously, under semibatch conditions (constant pressure of the reaction gas, compensation of gas uptake) or in the complete batch mode (no compensation of gas uptake, record of pressure drop of the gas phase). In contrast, catalysts for continuous fixed-bed applications have to be tested in continuous lab-scale fixed-bed reactors. The latter can be operated under either steady-state or non-steady-state (transient) conditions. 

Slurry reactors involve the coexistence and intense mixing of gas, liquid, and solid phases in the same volume. The possibility to run slurry reactors in the batch, semibatch, or continuous modes differentiates these reactors from others in terms of operational flexibility. In slurry reactors, the roles of the three phases can be different, that is, liquid can be a reactant, a product, or an inert that serves as a contacting medium for gas and solids. Similarly, dissolved gas can either be a reactant or an inert for inducing mixing of liquid and solids via bubbling. The solid phase usually corresponds to the finely dispersed catalyst particles with diameters lower than 5 x 10 m [20]. 

Gas phase olefin polymerizations are becoming important as manufacturing processes for high density polyethylene (HOPE) and polypropylene (PP). An understanding of the kinetics of these gas-powder polymerization reactions using a highly active TiCi s catalyst is vital to the careful operation of these processes. Well-proven models for both the hexane slurry process and the bulk process have been published. This article describes an extension of these models to gas phase polymerization in semibatch and continuous backmix reactors. 

Monoliths exhibit a large flexibility in operation. They are well suited for optimal semibatch, batch, continuous, and transient processing. Catalytic conversion can be combined with in situ separation, catalytic reactions can be combined, heat integration is possible, and all lead to process intensification. In the short term, catalytic monoliths will be applied to replace trickle-bed reactor and slurry-phase... 

Slurry Bubble Column Reactors As in the case of gas-liquid slurry agitated reactors, bubble column reactors may also be used when solids are present. Most issues associated with multiphase bubble columns are analogous to the gas-liquid bubble columns. In addition, the gas flow and/or the liquid flow have to be sufficient to maintain the solid phase suspended. In the case of a bubble column fermenter, the sparged oxygen is partly used to grow biomass that serves as the catalyst in the system. Many bubble columns operate in semibatch mode with gas sparged continuously and liquid and catalyst in batch mode. 

X 10 N/m. Choose room-temperature operation, T = 30°C = 303.16 K. Initial gas volume = nRgT/P = (267.75 x 8314 x 303.16)/ .8 x 10 = 3749 m. Since this volume is very high compared to the reactor volume of 10 m, choose semibatch mode of operation with continuous supply of feed gas and removal of residual gas to maintain the reactor pressure. In view of this, a slurry of Ca(OH)2 in water is prepared and CO2 is bubbled through it for 4 h. The mother liquid phase will be initially saturated with Ca(OH)2. As the reaction proceeds, CaCOj precipitates out. The mother liquor can be separated from the solid CaC03 precipitate by filtration. For ease of operation and control, assume constant gas flow rate. 

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