Continuous flow operation

In continuous flow operations, a slurry is continuously added and withdrawn from a single-stage mixer. Progressive buildup must not occur in fillets, and the discharge composition to the mixer must equal the inlet composition. Discharge from the tank occurs at a particular draw-off point, the only point in the tank that requires the mixture to have the same composition as the inlet. 

Continuous flow With continuous flow operations consider (e.g. using a HAZOP procedure) the effects of No flow Reduced flow Reverse flow Increased flow Contaminated flow Flow of a substituted material, etc. 

The process flow stream through a commercial demineralizer, incorporating two stacks in series demineralized water, is shown in Figure 3. Several of the refinements required for continuous-flow operational systems are shown on this diagram, representing a two-stage demineralizer. 

Miyauchi and Vermeulen (M7, M8) have presented a mathematical analysis of the effect upon equipment performance of axial mixing in two-phase continuous flow operations, such as absorption and extraction. Their solutions are based, in one case, upon a simplified diffusion model that assumes a mean axial dispersion coefficient and a mean flow velocity for... 

The experimental programme was mainly concerned with estimating kinetic parameters from isothermal steady state operation of the reactor. For these runs, the reactor was charged with the reactants, in such proportions that the mixture resulting from their complete conversion approximated the expected steady state, as far as total polymer concentrations was concerned. In order to conserve reactants, the reactor was raised to the operating temperature in batch mode. When this temperature had been attained, continuous flow operation commenced. This was... 

In this work we present results obtained both with batch and continuous flow operation of the gas-recycle reactor-separator utilizing Ag and Ag-Sm203 electrocatalysts and Sr(lwt%) La203 catalysts, in conjunction with Linde molecular sieve 5A as the trapping material, and discuss the synergy between the catalytic and adsorption units in view of the OCM reaction network. 

In this work we present results obtained with the YSZ reactor operated in the hatch mode with electrochemical oxygen addition, and with the quartz plug flow reactor operated in the continuous-flow steady-state mode. In the case of continuous flow operation, the molecular sieve trap comprised two packed bed units in parallel in a swing-bed arrangement (Fig. 1), that is, one unit was maintained at low temperature (<70°C) to continuously trap the reactor products while the other was heated for -30 min to 300°C to release the products in a slow stream of He. 

On-line GC analysis (Shimadzu GC 14A) was used to measure product selectivity and methane conversion. Details on the analysis procedure used for batch and continuous-flow operation are given elsewhere [12]. The molecular sieve trap was found to trap practically all ethylene, COj and HjO produced a significant, and controllable via the adsorbent mass, percentage of ethane and practically no methane, oxygen or CO, for temperatures 50-70 C. The trap was heated to -300°C in order to release all trapped products into the recirculating gas phase (in the case of batch operation), or in a slow He stream (in the case of continuous flow operation). 

A simplified mathematical model was developed for the novel OCM reactor. One version of the model, presented here, describes batch operation. A second version addressing continuous flow operation will appear elsewhere [16]. 

Methane can be oxidatively coupled to ethylene with very high yield using the novel gas recycle electrocatalytic or catalytic reactor separator. The ethylene yield is up to 85% for batch operation and up to 50% for continuous flow operation. These promising results, which stem from the novel reactor design and from the adsorptive properties of the molecular sieve material, can be rationalized in terms of a simple macroscopic kinetic model. Such simplified models may be useful for scale up purposes. For practical applications it would be desirable to reduce the recycle ratio p to lower values (e.g. 5-8). This requires a single-pass C2 yield of the order of 15-20%. The Sr-doped La203... 

FIG. 20-41 Four alternative modes of continuous-flow operation with a foam-fractionation column (1) The simple mode is illustrated by the solid lines. 12) Enriching operation employs the dashed reflux line. (3) In stripping operation, the elevated dashed feed line to the foam replaces the solid feed line to the pool. (4) For combined operation, reflux and elevated feed to the foam are both employed. 

Contacting patterns for various combinations of high and low concentration of reactants in continuous flow operations. (Adapted from Chemical Reaction Engineering, Second Edition, by O. Levenspiel. Copyright 1972 Reprinted by permission of John Wiley and Sons, Inc.)... 

Tajbl, Simons, and Carberry lnd. Eng. Chem. Fundamentals, 5 (171), 1966] have developed a stirred tank reactor for studies of catalytic reactions. Baskets containing catalyst pellets are mounted on a drive shaft that can be rotated at different speeds. The unit is designed for continuous flow operation. In order to determine if... 

These alternative processes can be divided into two main categories, those that involve insoluble (Chapter 3) or soluble (Chapter 4) supports coupled with continuous flow operation or filtration on the macro - nano scale, and those in which the catalyst is immobilised in a separate phase from the product. These chapters are introduced by a discussion of aqueous biphasic systems (Chapter 5), which have already been commercialised. Other chapters then discuss newer approaches involving fluorous solvents (Chapter 6), ionic liquids (Chapter 7) and supercritical fluids (Chapter 8). 

The main conclusions to be drawn from this study are that the reactor design works well, and that steady state continuous flow operation requires excellent mixing of the gases and two liquid phases and high conversions. Improvements in the catalyst (ligand) are required to reduce leaching still further, but commercialisation will also require a different reactor design or more than one CSTR in series. 

Chemical precipitation can be accomplished by either batch- or continuous-flow operations. If the flow is less than 30,000 gpd (21 gpm), a batch treatment system may be the most economical. In the batch system, two tanks are provided, each with a capacity of 1 day s flow. One tank undergoes treatment while the other tank is being filled. When the daily flow exceeds 30,000 gpd, batch treatment is usually not feasible because of the large tankage required. Continuous treatment may require a tank for acidification and reduction, then a mixing tank for chemical addition, and a settling tank. 

Both SILC and SILP offer the advantage over SAPC of using ionic liquids instead of water. The low vapor pressure ensures that the supported phase remains liquid under the reaction conditions, and that it is retained during continuous flow operation. 

Figure 7.2 Contacting patterns for various combinations of high and low concentration of reactants in continuous flow operations.

Miyauchi, T., and Vermeulen, T., Longitudinal dispersion in two-phase continuous-flow operations. Ind. Eng. Chem. Fundamentals 2, 113 (1963). 

The steady state method is often used in continuous-flow operation with reaction, which is often the case in full-scale applications. In laboratory-scale investigations, the steady state method can be used with a semi-batch set-up (gas phase continuous) with reaction or a continuous-flow set-up (both gas and liquid phases continuous) with or without reaction. 

Blending—The process of mixing two or more oils having different properties to obtain a final blend having the desired characteristics. This can be accomplished by off-line batch processes or by in-line operations as part of continuous-flow operations. 

Leitner et al. have synthesized the PEG-modified silica stabilized and immobilized palladium nanoparticles for aerobic alcohol oxidation in combination with scC02 as reaction medium under mild conditions, which show high activity and excellent stability under continuous-flow operation [68], ScC02 could diffuse the substrates and products from the active nanoparticles in a gas-like manner. This allows rapid chemical transformation at the active center, ensures efficient removal of the products from the surface, and minimizes the mobility of solid-supported catalytically active species [69]. In this way, catalysts based on palladium nanoparticles together with PEG as stabilizing matrix could avoid aggregating and forming less active and selective Pd-black [20, 60, 70]. 

This work points to the use of compartmentalized metallodendrimers as catalysts for continuous flow operations and cascade-type synthetic applications. However, since the driving force in the applied set-up is based on osmosis (passive diffusion), the product flux is limited. 

Since conditions are not quite the same for a catalyst used intermittently to study 5-mg. samples in a stream of pure hydrogen as they are for one under normal continuous flow operation, some continuous flow experiments were done for comparison. 

Finally, several attempts have been made to develop an absolute molar mass detector based on osmotic pressure measurements. Commercially available membrane osmometers are designed for static measurements, and the cell design with a flat membrane is not suited for continuous flow operation. Different from the conventional design, Yau developed a detector which measures the flow resistance of a column caused by osmotic swelling and deswelling of soft gel particles used for the packing (see Fig. 12) [65,78]. With a microbore gel column, a... 

The complex selective oxidation of an n-butane molecule to MA involves 14 electrons and occurs entirely on the surface of the catalyst. No intermediates have been detected in the effluent product imder conditions of continuous flow operation. Mechanisms of the reaction have been proposed on the basis of a variety of experimental and theoretical findings. The description of the active site is linked to the mechanism and is the subject of considerable debate in the literature. 

A cell for continuous flow operation must be designed with a high electrode surface-electrolyte volume ratio, provided with a feeding system, and, last but not least, connected with suitable auxiliary equipment for continuous removal of the product s) of electrolysis and reestablishment of the electrolyte composition. The continuous workup procedure during electrolysis is somewhat inconvenient in the laboratory, and consequently small continuous flow cells have mostly been operated with recycling to a reservoir before scaling up. Large cells and their industrial applications are discussed in Chapter 31. 

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