Reactor internal recycle

Jankowski et al (1978) discuss in detail the great variety of gradientless reactors proposed by several authors with a pictorial overview in their paper. All of these reactors can be placed in a few general categories (1) moving catalyst basket reactors, (2) external recycle reactors, and (3) internal recycle reactors. 

The older internal recycle reactors of Berty et al (1969), and Berty (1974) are shown on Figures 2.4.3 a, b. The reactor of Romer and Luft (1974) uses no mechanical moving parts. The recirculation is generated by the feed gas as it expands through a nozzle. A major disadvantage of using a jet is that feed rate and recirculation rate are not independent. Due to the low efficiency of jet pumps, recycle rates are quite low. 

The operational characteristics of the older Berty reactors are described in Berty (1974), and their use in catalyst testing in Berty (1979). Typical uses for ethylene oxide catalyst testing are described in Bhasin (1980). Internal recycle reactors are easy to run with minimum control or automation. 

The experimental setup uses the ROTOBERTY internal recycle reactor. The catalyst basket of this is charged with W = 35.5 g or V = 44.3 cm of OXITOX that contains 0.25 mol, i.e., 26.5 g of sodium carbonate. 

Figure 5.4-19. Internally recycled reactor (Berty reactor).

Internally recycled reactor (Berty) High temperature, high pressure catalytic processes High transport rates, intense mixing Limited ease of variation of parameters... 

Catalytic hydrogenation in supercritical carbou dioxide has been studied. The effects of temperature, pressure, and CO2 concentration on the rate of reaction are important. Hydrogenation rates of the two double bonds of an unsaturated ketone on a commercial alumina-supported palladium catalyst were measured in a continuous gra-dient-less internal-recycle reactor at different temperatures, pressures, and C02-to-feed ratios. The accurate control of the organic, carbon dioxide, and hydrogen feed flow rates and of the temperature and pressure inside the reactor provided reproducible values of the product stream compositions, which were measured on-line after separation of the gaseous components (Bertucco et al., 1997). 

Bertucco, A., Canu, P., Devetta, L. Catalytic Hydrogenation in Supercritical C02 Kinetic Measurements in a Gradientless Internal-Recycle Reactor. Ind. Eng. Chem. Res. 1997, 36, 2626 - 2633. 

Amoco internal recycle reactor High-pressure, high-temperature coal, petroleum, and chemical-related operations... 

Internal recycle reactors are designed so that the relative velocity between the catalyst and the fluid phase is increased without increasing the overall feed and outlet flow rates. This facilitates the interphase heat and mass transfer rates. A typical internal flow recycle stirred reactor design proposed by Berty (1974, 1979) is shown in Fig. 18. This type of reactor is ideally suited for laboratory kinetic studies. The reactor, however, works better at higher pressure than at lower pressure. The other types of internal recycle reactors that can be effectively used for gas-liquid-solid reactions are those with a fixed bed of catalyst in a basket placed at the wall or at the center. Brown (1969) showed that imperfect mixing and heat and mass transfer effects are absent above a stirrer speed of about 2,000 rpm. Some important features of internal recycle reactors are listed in Table XII. The information on gas-liquid and liquid-solid mass transfer coefficients in these reactors is rather limited, and more work in this area is necessary. 

Differential internal recycle reactors have become important tools in recent years for the investigation of catalytic processes and a number of such reactors have been reported in literature with the main emphasis on the actual reactor design [1,2]. In this work a similar reactor, which has been developed by the main investigator for gas-phase reactions under low pressure and high temperature, where it proved its suitability, is described. [3]... 

Zwahlen A. G., Agnew J. Modification of an Internal Recycle Reactor of the Berty Type for Low-Pressure High Temperature Catalytic Gas-Phase Reaction CHEMECA 1987, I, 50.1-50.7, Melbourne, Australia. 

Internal recycle reactor with a stationary packed bed... 

The difficulties inherent to the external recycle reactor are avoided in an internal recycle reactor. Basically, an internal recycle reactor consists of a basket, in which a variable amount of catalyst can be placed, and an impeller for the internal circulation of the gas in the reactor. One of the most popular recycle reactors is the Berty reactor [29] shown in Figure 5.5. The Berty reactor has a magnetically driven blower and the gas from the turbine flows through a draft tube to the top of the catalyst bed. The flow rate through the bed can be calculated by measuring the pressure drop over the bed, if pressure taps on either side of the catalyst are available. For a catalyst to be studied in this reactor, the... 

Many authors have proposed reactors with similar basic principles. The best known are those of Garanin et al. [44], Livbjerg and Villadsen [45] and new versions of Berty reactor [34]. Variants of internal recycling reactors have also been proposed by Bennett et al. [43] who tried to decrease the ratio of reactor volume to catalyst volume. In this arrangement the amount of reactant adsorbed increases compared to that in the gas space as a result the dynamics of the adsorption - desorption processes can be detected through the gas phase measurements. 

The advantages of internal recycle reactors for catalyst investigations have been outlined by Berty [46,47], Like other differential reactors, a single experiment yields the... 

Internal recycle reactors with moving catalyst bed... 

Equation (2) (as an ordinary differential equation) and Eq. (3) apply now with Eq. (4). As already implied, a laboratory well-mixed reactor for heterogeneous catalysis is more difficult to realize than a PFR. Many versions have been used 12), and Froment and Bischoff 13) illustrate reactors with external recycle, with internal recycle 1,14), and with an internal spinning basket 15). When using these reactors for experiments in the transient regime, it is important to keep to a minimum the volume outside the bed of catalyst. Internal recycle reactors involve bearings exposed to hot reactive gases and require a magnetic drive system for leak-proof operation. Exter-... 

Figure 1. Pd promotion of initial activity for methanol synthesis from COj/Hj in the internal recycle reactor relative to Cu/Zn/Al-1...

Table 3. Methanol production from COj/Hj (differential conversion), COj/Hj + H O (differential conversion) and COj/Hj (finite conversion, internal recycle reactor)...

The results at differential conversions with water addition can be compared with methanol production at the finite conversion in the internal recycle reactor where the water concentration as a result of water production was similar (Table 3). The two types of experiment are analogous in that at differential conditions in the microflow reactor the catalyst was uniformly exposed to the feed concentration, whereas at finite conversions in the internal recycle reactor the catalyst was uniformly exposed to the product concentration. The methanol production rate at finite conversion was similar to the methanol production rate from COj/Hj/HjO at differential conditions for both the Cu/Zn/Al-1 and Pd impregnated catalyst. Therefore, the kinetics at the particular finite conversions, well away from equilibrium, can also be described by methanol production by CO2 hydrogenation, and the inhibition of this reaction associated with the presence of the product water. Furthermore, the Pd promotion was similar under the two reaction regimes (Table 3), reinforcing the conclusion that Pd promotion of CO2 hydrogenation is active only in the presence of water. 

The methanol synthesis activities of Samples 1-6 were determined before, during and after pulsing H2S end are tabulated in Table I. All the samples except 3 were in a single-pass tubular reactor. Sample 3 was tested in an internal recycle reactor, the amount of which (5 cm ) was about five times of those tested in the tubular reactor. For the same amount of fresh feed and pulsed H2S, the methanol yield of Sample 3 and its sulfur content were much lower than those of other samples. The typical effect of pulsing H2S to the feed gas stream is... 

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