Reactor annular tubular

FIGURE 6.39. Annular tubular reactor (radial heat flow reactor). 

Extended light sources may be installed around a tubular reactor or in the axis of an annular irradiated reaction volume. In the first case, an annular (or coaxial) radiation field focalized on the axis of the tubular reactor is created (Figure 10), and, in reaction mixtures of very low absorbance, irradiance as a function of the radius of the cylindrical reactor shows highest values in the axis of the reactor (positive geometry of irradiation, Figure 11 [2,3]). 

The benzene yields given by the data of Figures 4 and 5, 87% at 204°C and 88% at 227°C, may be compared with computed equilibrium yields of 13% and 19%, based on inlet conditions. This clearly shows the advantage of the continuous annular chromatographic reactor over, say, a tubular reactor. The comparison is not entirely straightforward, because dilution of the cyclohexane by He carrier as it disperses circumferentially shifts the equilibrium toward products this would have to be taken into account in any quantitative comparison. The data show only partial separation of benzene and cyclohexane. This partial separation must result in partial suppression of the back reaction, and must also contribute to the observed yield enhancement (in addition to the dilution effect). ... 

In the above examples of catalytic membrane tubular reactors (CMTR), the transport equations for the catalytic membrane zone (i.e.. Equations (10-5) and (10-6)) are considered and solved. A simpler and less rigorous approach to modeling a CMTR is to neglect the membrane layer(s) and account for the catalytic reactions in the tube core or annular region. This approach was adopted by Wang and Lin [1995] in their modeling of a shell-and-tubc reactor with the membrane tube made of a dense oxide membrane (a... 

The literature on measurement of mass transfer in vertical tubular reactors is very sparse. Kasturi and Stepanek (K3, K4) have presented data for a, ki a, and kca measured under identical conditions in the case of annular flow, annular spray flow, and slug flow. For the aqueous systems used (COj, air, NaOH) they have proposed the following correlation for the interfacial area fl = 0.23[(l - a)/QJ(AP/Z)i( whereQt is incm /sec and AP/Z is in N/m . Correlations for true liquid-side and gas-side mass-transfer coefficients by the same authors are difficult to generalize, as viscosity and surface tension were not varied. 

Reactant A is converted irreversibly and exothermically to products in a 2-in.-inner-diameter tubular reactor via first-order chemical kinetics. The reactive mixture in the inner pipe is cooled using a concentric double-pipe heat exchanger. The nonreactive cooling fluid in the annular region flows countercurrently with respect to the reactive fluid. The radius ratio of the double-pipe configuration is If = Rinside/ outside = 0.5, the inlet temperature of the reactive fluid is 340 K,... 

Consider a liquid-phase plug-flow tubular reactor with irreversible nth-order endothermic chemical reaction. The reactive mixture is heated with a fluid that flows cocurrently in the annular region of a double-pipe configuration. The mass and heat transfer Peclet numbers are large for both fluids. All physical properties of both fluids are independent of temperature and conversion, and the inlet conditions at z = 0 are specified. What equations are required to investigate the phenomenon of parametric sensitivity in this system ... 

Equations will be derived for three representative cases the tubular reactor of annular cross-section the isothermal, well-mixed batch reactor and the isothermal batch reactor inside a recirculating system. The chosen exemplifications will deal with these types of reactors that are, without doubt, the most widely used. 

Reactor model. The reactor model was constructed according to the following sequence (i) the annular reactor, radiation distribution model of Romero etal. (1983) was adapted for this particular set-up (ii) the tubular lamp with voluminal and isotropic radiation emission model was applied to this system (iii) a mass balance for an actinometric reaction carried out in a tubular reactor inside the loop of a recycling system was adapted from Martin etal. (1996) and (iv) the verification of the radiation model, actinometer experiments were performed in the reactor to compare theoretical predictions... 

NAFION systems have also been used to construct devices for 1) separating monofunctlonal carboxylic acids like propionic, butyric or valeric acid from other acids (75), 2) nitrating and sulfonatlng aromatics In an annular tubular flow reactor where the Inner tube Is NAFION and the outer tube Is TEFLON fluorocarbon resin (76), 3) sulfonatlng aromatics In a two-compartment cell separated by a membrane sheet (77), and 4) alkylating aromatics with a tightly-packed bundle of parallel tubular NAFION In a stainless steel tube (78). 

The above experiments, if done under conditions equivalent to full scale ones with a well-mixed stirred tank reactor at steady state, give the basic rate of overall reaction plus information on what influences it. These can be used for scale-up calculations, either keeping to a stirred tank, or where appropriate, scaling up a different type of reactor, e.g. a bubble column for Regime I, a cascade of stirred tanks if plug flow is required in Regime II, or a packed tower or gas-liquid annular flow tubular reactor for Regime III or for gas-fllm controlled mass transfer. 

Concentric cells provide another method of maintaining a uniform and small interelectrode gap. The cell shown in Fig. 2.33(b) was developed as a simple annular-flow tubular reactor for laboratory and pilot-scale organic electrosynthesis. While the space-time yield is relatively low (due to the use of essentially two-dimensional electrodes and a dead space within the inner electrode) the reactor is robust and a separator may be incorporated much more readily than for the stacked-disc cell. The resulting reactor provides a convenient modular, flow-through cell, which has been utilized for industrial-scale processes. 

At the time Ruhrchemie made some minor improvements by using concentric tubes in the medium-pressure reactors, with catalyst in the annular space and coohng water flowing around the tube and through the inner space. This was still inefficient at low gas space velocity. The ARGE reactors used by Sasol in 1955 were conventional boihng water tubular reactors with gas recycle to limit heat evolutiom A typical wartime reactor contained 1250 tubes, whereas the early Sasol reactor used more than 2000 tubes. 

Basically, tliere are two classes of anunonia converters, tubular and multiple bed. The tubular bed reactor is limited in capacity to a maximum of about 500 tons/day. In most reactor designs, the cold inlet synthesis gas flows tlirough an annular space between the converter shell and tlie catalyst cartridge. This maintains the shell at a low temperature, minimizing the possibility of hydrogen embrittlement, which can occur at normal synthesis pressures. The inlet gas is then preheated to syntliesis temperature by the exit gas in an internal heat e.xchaiiger, after which it enters tlie interior of the anunonia converter, which contains tlie promoted iron catalyst. 

---