Reactors fixed basket

The spinning basket and fixed basket reactors can also be used in batch reactions. 

Fig. 6.13. Fixed basket reactor. (Courtesy Autoclave Engineers.)...

Various experimental methods to evaluate the kinetics of flow processes existed even in the last centuty. They developed gradually with the expansion of the petrochemical industry. In the 1940s, conversion versus residence time measurement in tubular reactors was the basic tool for rate evaluations. In the 1950s, differential reactor experiments became popular. Only in the 1960s did the use of Continuous-flow Stirred Tank Reactors (CSTRs) start to spread for kinetic studies. A large variety of CSTRs was used to study heterogeneous (contact) catalytic reactions. These included spinning basket CSTRs as well as many kinds of fixed bed reactors with external or internal recycle pumps (Jankowski 1978, Berty 1984.)... 

Laboratory reactor for studying three-phase processes can be divided in reactors with mobile and immobile catalyst particles. Bubble (suspension) column reactors, mechanically stirred tank reactors, ebullated-bed reactors and gas-lift reactors belong the class of reactors with mobile catalyst particles. Fixed-bed reactors with cocurrent (trickle-bed reactor and bubble columns, see Figs. 5.4-7 and 5.4-8 in Section 5.4.1) or countercurrent (packed column, see Fig. 5.4-8) flow of phases are reactors with immobile catalyst particles. A mobile catalyst is usually of the form of finely powdered particles, while coarser catalysts are studied when placing them in a fixed place (possibly moving as in mechanically agitated basket-type reactors). 

Fig. 17. Stirred-tank gas-liquid-solid basket reactor fixed basket. (Germain, 1973 also from Chaudhari et al., 1986, by courtesy of Marcel Dekker, Inc.)...

The rotating-basket reactor (often known as the Carberry reactor) has been widely used for gas-solid as well as gas-liquid-solid reactions (see Fig. 5-6). Its construction is not very difficult, but it is more complex and expensive to build than a batch or fixed-bed reactor. The catalyst baskets can either be attached to the stirrer [Fig. 5-7(6)] or they can, themselves, be used as the stirrer paddles [Fig. 5-7(a)]. Furthermore, a small variety of rotating catalyst baskets are available (see Fig. 5-8). Baskets must, in general, be small in diameter, so that internal mass-transfer effects are minimized. 

A variation of this system is the fixed basket apparatus shown in Fig. 6.13. Here the gas and liquid reactants are circulated by means of the impellers, placed above and below the catalyst bed, through the catalyst that is held in the circular basket. This type of reactor, however, is usually used for vapor phase reactions.27... 

Goto et al. [158] investigated the question, of which reactor type is best suited for kinetic studies of solid-catalyzed reactions. Three possibilities were investigated (a) the catalyst was suspended with a 6-turbine stirrer (slurry reactor), (b) the catalyst was placed in two baskets fixed to the reactor wall (stationary catalytic basket reactor),... 

The most reliable recycle reactors are those with a centrifugal pump, a fixed bed of catalyst, and a well-defined and forced flow path through the catalyst bed. Some of those shown on the two bottom rows in Jankowski s papers are of this type. From these, large diameter and/or high speed blowers are needed to generate high pressure increase and only small gaps can be tolerated between catalyst basket and blower, to minimize internal back flow. 

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. 

In the Berty reactor, the catalyst is fixed in a basket through which gas is flown in a fast internal recycle forced by a turbine. The gas stirring in the Carberry reactor is realized by a rotating basket. 

The three-phase Robinson-Mahoney reactor (a continuous gas and liquid flow) consisted of a fixed catalyst basket and a magnetic stirrer. The reactor system was automated to ensure reliable and reproducible experiments. Liquid samples of the product stream were taken by an automatic on-line valve and analysed by a gas chromatograph with fused silica capillary column and FI detector. Detailed information on the apparatus [11] and the hydrogenation procedure can be found elsewhere [10]. Gas-liquid and liquid-solid mass transfer resistance were avoided by adjusting the agitation and catalyst loading. An intraparticle mass transfer resistance could not be avoided and this was added to the reactor model in parameter estimation [11]. 

The catalyst, which was prepared by the citrate method and calcined at 700°C, had a BET surface of 10.2 m /g. The experiments were carried out in two types of reactor, i.e. (a) in a Micro-Berty reactor that has a catalyst basket volume of 3.6 cm, (b) in a fixed bed quartz reactor having an internal diameter of 10mm. Gaseous flows were controlled by mass flow controllers, and the pressure in the Berty reactor was adjusted by a backpressure regulator and measured by a pressure transducer. Experimental conditions are compared in the Table 2. 

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