Liquid-phase tubular reactors

Assuming the case of a first-order chemical reaction, (r = - k Ca), and a non-compressible liquid system, the generalised mass and energy balance equations reduce to 

The general solution approach, to this type of problem, is illustrated by the information flow diagram, shown in Fig. 4.8. The integration thus starts with the initial values at Z = 0, and proceeds with the calculation of r, along the length of the reactor, using the computer updated values of T and Ca, which are also produced as outputs. 

The simultaneous integration of the two continuity equations, combined with the chemical kinetic relationships, thus gives the steady-state values of both, Ca and T, as functions of reactor length. The simulation examples BENZHYD, ANHYD and NITRO illustrate the above method of solution. 

In gas-phase reactors, the volume and volumetric flow rate frequently vary, owing to the molar changes caused by reaction and the effects of temperature and pressure on gas phase volume. These influences must be taken into account when formulating the mass and energy balance equations. 

The Ideal Gas Law can be applied both to the total moles of gas, n, or to the moles of a given component of the gas mixture nj, where 

The simultaneous integration of the two continuity equations, combined with the chemical kinetic relationships, thus gives the steady-state values of both, Ca 

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TABLE 5.1 Scaleup Factors for Liquid-Phase Tubular Reactors. 

Chemical Kinetics, Tank and Tubular Reactor Fundamentals, Residence Time Distributions, Multiphase Reaction Systems, Basic Reactor Types, Batch Reactor Dynamics, Semi-batch Reactors, Control and Stability of Nonisotheimal Reactors. Complex Reactions with Feeding Strategies, Liquid Phase Tubular Reactors, Gas Phase Tubular Reactors, Axial Dispersion, Unsteady State Tubular Reactor Models... 

COUPLED HEAT AND MASS TRANSFER IN NONISOTHERMAL LIQUID-PHASE TUBULAR REACTORS WITH STRONGLY EXOTHERMIC CHEMICAL REACTIONS... 

For the production of MeOAc, let us compare the RD column with a distillation column with either three or five side reactors. Fig. 7.22. The side-reactor could be a tubular reactor, packed with, say, Amberlyst-15 for acid catalysis. It could also be a homogeneous liquid-phase tubular reactor, catalyzed by H2SO4. Clearly the location... 

The prereactor is a cooled liquid-phase tubular reactor containing 9544kg of catalyst. The C5 fresh feed (1040kmol/h) and 313kmol/h of methanol are fed to the reactor. 

This chapter focuses attention on reactors that are operated isotherraally. We begin by studying a liquid-phase batch reactor to determine the specific reaction rate constant needed for the design of a CSTR. After iilustrating the design of a CSTR from batch reaction rate data, we carry out the design of a tubular reactor for a gas-phase pyrolysis reaction. This is followed by a discussion of pressure drop in packed-bed reactors, equilibrium conversion, and finally, the principles of unsteady operation and semibatch reactors. 

Tubular reactors have been the main tools to study continuous flow processes for vapor or gas-phase reactions. These are also used for reaction in tv o flowing phases over a solid catalyst. When the catalyst is in a fixed bed, the contact between the liquid on the outside surface of the particulate is uncertain. For slurry-type solid catalyst the residence time of the catalyst or the quantity in the reactor volume can be undefined. 

Tubular reactors are used for reactions involving a gas and a liquid. In this arrangement, the gas phase is dispersed as bubbles at the bottom of a tubular vessel. The bubbles then rise through the continuous liquid phase that flows downwards as shown in Figure 4-14. An example of this process is the removal of organic pollutants from water by noncatalytic oxidation with pure oxygen. 

Homogeneous reactions are those in which the reactants, products, and any catalysts used form one continuous phase (gaseous or liquid). Homogeneous gas phase reactors are almost always operated continuously, whereas liquid phase reactors may be batch or continuous. Tubular (pipeline) reactors arc normally used for homogeneous gas phase reactions (e.g., in the thermal cracking of petroleum of dichloroethane lo vinyl chloride). Both tubular and stirred tank reactors are used for homogeneous liquid phase reactions. 

An example of the liquid-phase polymerization is the Spheripol process (Figure 12-3), which uses a tubular reactor. Copolymerization... 

Figure 12-3. The Himont Inc. Spheripol process for producing polypropylene in a liquid-phase (1) tubular reactor, (2,4) two-stage flash pressure system (to separate unreacted monomer for recycle), (3) heterophasic copolymerization gas-phase reactor, (5) stripper.

Thus, we can make a reasonably accurate initial guess for Qp. This guess is used to calculate the conversion in a tubular reactor of the given dimensions. When the right guess is made, the mean residence time will be 2h and the fraction unreacted will be 20%. The following code follows the general procedure for liquid-phase PFRs. The fraction unreacted is calculated as the ratio of which is denoted as Phi/Philn in... 

Depart from Geometric Similarity. Adding length to a tubular reactor while keeping the diameter constant allows both volume and external area to scale as S if the liquid is incompressible. Scaling in this manner gives poor results for gas-phase reactions. The quantitative aspects of such scaleups are discussed... 

Cheng, A.T.Y. (1997) A high-intensity gas-liquid tubular reactor under supersonic two phase flow conditions, in Process Intensification in... 

Tubular reactors are generally used for gaseous reactions, but are also suitable for some liquid-phase reactions. 

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