Tubular reactors reverse-flow

To improve the mixing quality in the tubular reactor, Kenics type in-line static mixer reactor was employed. The in-line static mixers were designed to mix two or more fluids efficiently since an improved treinsport process such as flow division, radial eddying, flow constriction, and shear reversal eliminated the gradients in concentration, velocity and temperature. However, only 70 % conversion was achieved with one Kenics mixer unit. As shown in Table 2, five mixer units were required to achieve the maximum conversion. 

While alkane metathesis is noteworthy, it affords lower homologues and especially methane, which cannot be used easily as a building block for basic chemicals. The reverse reaction, however, which would incorporate methane, would be much more valuable. Nonetheless, the free energy of this reaction is positive, and it is 8.2 kj/mol at 150 °C, which corresponds to an equiUbrium conversion of 13%. On the other hand, thermodynamic calculation predicts that the conversion can be increased to 98% for a methane/propane ratio of 1250. The temperature and the contact time are also important parameters (kinetic), and optimal experimental conditions for a reaction carried in a continuous flow tubular reactor are as follows 300 mg of [(= SiO)2Ta - H], 1250/1 methane/propane mixture. Flow =1.5 mL/min, P = 50 bars and T = 250 °C [105]. After 1000 min, the steady state is reached, and 1.88 moles of ethane are produced per mole of propane consumed, which corresponds to a selectivity of 96% selectivity in the cross-metathesis reaction (Fig. 4). The overall reaction provides a route to the direct transformation of methane into more valuable hydrocarbon materials. 

FIGURE 13.1 Types of fixed bed reactors, (a) Axial flow fixed bed reactor Up or down flow, single or multi-stage, with or without inter-stage cooling, single or multi-tubular, (b) Radial flow fixed bed reactor Radially inward or outward flow, straight or reverse flow (direction of inlet and outlet is same or opposite to each other). 

Although this is a reversible rcaciion. measurements were made in the initial phases of the decomposition so that the reverse reaction could be neglected. Consider a system similar to the one used by Nakamura and Siaubi the solution enters a tubular reactor (0.158 cm in diameteri that has oxygen electrodes placed at 5-cm intervals down the lube. Tlie solution flow rate into the reactor is 19.6 cm Vs. 

ADIABATIC PLUG-FLOW TUBULAR REACTOR THAT PRODUCES METHANOL REVERSIBLY IN THE GAS PHASE FROM CARBON MONOXIDE AND HYDROGEN... 

This equation yields the optimum temperature at each conversion for a reversible, exothermic reaction. Note that we generally conduct reversible, exothermic reactions in tubular reactors since they respond faster to a desired temperature change than do batch reactors. However, such reactions can be performed in batch reactors equipped with external heat exchangers for removing heat. The circulation flow rate must be high to achieve the desired operating temperature profde. 

An alternative method of agitation of a tubular reactor is the rotation of the reactor itself. Flow of solids is caused by mounting it in a position slightly inclined to the horizontal, and caking upon the sides is sometimes prevented by the presence of, for example, a loose H section beam or similar heavy article along the length of the tube. The powder feed can enter the end of the reactor via the hollow shaft upon which the reactor rotates. Similarly it can leave via a lower hollow shaft, gas being passed in the reverse direction. 

We have determined in this section the hydrodynamic conditions on a turbulent flow that lead to the RTD laws of a CSTR or a tubular reactor with axial dispersion. The reverse analysis, for deriving turbulence characteristics of a flow from the measurement of a RTD, should be used with caution if it caimot be positively asserted that the flow is turbulent. A laminar flow (e.g. a Poiseuille flow) in a tubular reactor also produces an axial dispersion measured by a RTD, because the product injected on the pipe axis is carried faster than that injected near the walls. Clearly, it would be meaningless to derive turbulence characteristics from the measured RTD law." ... 

Tubular flow reactors—minimum volume for second-order reversible reactions, maximum yield of consecutive reactions, minimum cost with and without recycle, and maximum profit with recycle... 

The synthesis of ammonia, N2 + 3H2 = 2NH3, like the oxidation of SO, (Section 1.5.4 and Figure 1.4), is an exothermic, reversible, catalytic reaction carried out in a multistage tubular flow reactor in which each stage consists of a (fixed) bed of catalyst particles. Unlike SO, oxidation, it is a high-pressure reaction (150-350 bar, at an average temperature of about 450°C). The usual catalyst is metallic Fe. 

The reversible reaction A 2B is conducted at 540°F and 3 atma in a tubular-flow reactor. The feed contains 30 mole % A and the balance inert material, the total being at the rate of 75 lb moles/hr. The rate equation is... 

Interpretation of data to obtain a rate equation requires calculations which are the reverse of those for design. The two procedures differ because in the laboratory it may be feasible to operate at nearly constant temperature, and possibly nearly constant composition in the commercial unit it may be possible to approach isothermal conditions, but constant composition in a tubular-flow reactor is impossible. These differences simplify the analysis of laboratory results, as illustrated in Example 4-3. 

Butadiene and steam (0.5 mole steam/mole butadiene) are fed to a tubular-flow reactor which operates at 1180°F and a constant pressure of 1 atm. The reactor is noncatalytic. Considering only the reversible polymerization reaction to the dimer, determine a) the length of 4-in.-ID reactor required to obtain a conversion of 40% of the butadiene with a total feed rate of 20 lb moles/hr and-(b) the space velocity, measured as (liters feed gas)/(hr)(liters reactor volume) (at 1180°F and 1 atm), required to obtain a conversion of 40%. 

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