Recirculation batch reactor

Recirculating batch reactors (Figure 9.2-2) [23,24] are mainly used for kinetic studies of enzymatic reactions performed in dense gases. 

The dehydrogenation of iso-butane was carried out in a recirculating batch reactor.12 Reaction products were analyzed by gas chromatography using flame ionization. The vanadium and vanadium carbide powder materials were purchased from Aldrich Chemical Co. Their bulk compositions were confirmed by the X-ray diffraction measurements. Prior to the dehydrogenation reactions, these powder materials were heated for 1 h at 900 K in pure H2 at a flow rate of 200 cm3 per minute. 

Cu/MFI 1-Propanamine 1 -Propanamine-N-(1-propylidene) Dimerization + dehydrogenation 82 52 66 mbar propanamine 1.3 bar He 573 K 2h gradientless recirculating batch reactor [22]... 

Catalyst testing in MPO was performed by a specifically designed recirculation batch reactor operating at 650°C and 1.7 atm total pressure with a flow rate of 1,000 stp cm min" (He N2 CH4 02=6 l 2 l) and a catalyst sample of 50 mg unless otherwise specified [5-11]. 

A considerable reaction rate increase with increasing flow rate in a recirculating batch reactor has been observed [10]. The correlation was not linear. The production rate was defined as millimoles product obtained per kilogram enzyme per hour contact time in the enzyme bed with the same enzyme as used by van Ejs et al. [42]. Much higher flow rates were applied, namely 50-300 mm/s, for which the pressure drop along the enzyme column was considerable. Pressure drops were of the order of 20 bar. It was speculated that part of the flow is forced through the pores of the enzyme support at high flow rates and pressure drops. More active surface becomes available to the substrate and the reaction rate per kg enzyme increases. 

The particular configuration of the PEC cell is determined by the type of light source (discussed below) as well as the rates of gas production from water splitting (lower rates may require smaller volume cells). Figure 9.3 shows some examples of PEC reactors, including a (a) batch, (b) flow and (c) recirculating batch reactor. 

Fig. 9.3 Schematic images of examples of photoelectrochemical reactors (a) Batch reactor, (b) Flow reactor, c Recirculating batch reactor (evacuation is optional)...

EXAMPLE 4.2 Performance of Recirculating Batch Reactors at Limiting Current Density... 

When used as a recirculating batch reactor, the spectrophotometer-computer interface can monitor but not record the "% trans-... 

In terms of cost and versatility, the stirred batch reactor is the unit of choice for homogeneous or slurry reactions and even gas/liquid reactions when provision is made for recirculation of the gas. They are especially suited to reactions with half-lives in excess of 10 min. Sam-... 

Table 4-4 summarizes the ratings of the various reactors. The CFSTR and the recirculating transport reactor are the best choices because they are satisfactory in every category except for construction. The stirred batch and contained solid reactors are satisfactory if the catalyst under study does not decay. If the system is not limited by internal diffusion in the catalyst pellet, larger pellets could be used and the stirred-contained solids reactor is the better choice. However,... 

Batch-, stirred-tank-, extractive semibatch-, recirculating batch-, semicontinuous flow-, continuous packed-bed-, and continuous-membrane reactors have been used as enzyme reactors, with dense gases used as solvents. 

Figure 9.2-2. Operating principle of dense-gases enzymatic reactor types a), extractive semibatch b), recirculating batch c), semicontinuous flow.

If the reactor does not operate adiabatically, then its design must include provision for heat transfer. Figure 1.4 shows some of the ways in which the contents of a batch reactor may be heated or cooled. In a and b the jacket and the coils form part of the reactor itself, whereas in c an external heat exchanger is used with a recirculating pump. If one of the constituents of the reaction mixture, possibly a... 

Various laboratory reactors have been described in the literature [3, 11-13]. The most simple one is the packed bed tubular reactor where an amount of catalyst is held between plugs of quartz wool or wire mesh screens which the reactants pass through, preferably in plug flow . For low conversions this reactor is operated in the differential mode, for high conversions over the catalyst bed in the integral mode. By recirculation of the reactor exit flow one can approach a well mixed reactor system, the continuous flow stirred tank reactor (CSTR). This can be done either externally or internally [11, 12]. Without inlet and outlet feed, this reactor becomes a batch reactor, where the composition changes as a function of time (transient operation), in contrast with the steady state operation of the continuous flow reactors. 

Various levels of models can be used to describe the behavior of pilot-scale jacketed batch reactors. For online reaction calorimetry and for rapid scale-up, a simple model characterizing the heat transfer from the reactor to the jacket can be used. Another level of modeling detail includes both the jacket and reactor dynamics. Finally, the complete set of equations simultaneously describing the integrated reactor/jacket and recirculating system dynamics can be used for feedback control system design and simulation. The complete model can more accurately assess the operability and safety of the pilot-scale system and can be used for more accurate process scale-up. 

Levenspid earlier presented, in 1972, a qualitative discussion about the product distribution related to photochemical reactions comparing batch and batch recirculation photochemical reactors. The essentials of this discussion can be transferred to photo-initiated AOPs (at least to the H2O2-UV process), which at low concentrations of a pollutant M ([M] <100 mg L ) usually follow an overall first order reaction kinetics (Bolton et al, 1996). 

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