Adiabatic tubular reactors

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Block COOLANT (ftPtuu) Sisluy - Data Browser 

2 Cooled Tubular Reactor with Constant-Temperature Coolant 

3 Cooled Reactor with Co-current or Countercurrent Coolant Flow 

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We can rearrange Equation (11-29) to solve for temperature as a funaion of conversion that is 

This equation wilt be coupled with the differential mole balance 

To relate temperature and conversion, we apply the energy balance to an adiabatic PFR. If ail species enter at the same temperature, 3 = 

Solving Equation (11-29), with 0 = 0, IT, = 0, to obtain T as a function of conversion yields 

Equations (Tl 1-2.1) through (Tl 1-2.9) can easily be solved using either Simpson s rule or an ODE solver. 

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Verwijs, J. W., H. van den Berg, and K. R. Westerterp (1996). "Startup Strategy Design and Safeguarding of Industrial Adiabatic Tubular Reactor Systems. AIChE Journal 42, 2 (February), 503-15. 

Vapor feed to an adiabatic tubular reactor is heated to about 700°F in a furnace. The reaction is endothermic. The exit temperature of gas leaving the reactor is to be controlled at 600°F. 

Fig. 26. Temperature profiles through an adiabatic tubular reactor with heat exchange between inlet and outlet streams.

Fig. 1.16. Laboratory-scale reproduction of adiabatic tubular reactor temperature profile...

SO is produced by the catalytic oxidation of S02 in two packed adiabatic tubular reactors arranged in series with intercooling between stages. The molar composition of the mixture entering the first reactor is 7 per cent S02, 11 per cent 02 and 82 per cent N2. The inlet temperature of the reactor is controlled at 688 K and the inlet flow is 0.17 kmot/s. Calculate the mass of catalyst required for each stage so that 78 per cent of the S02 is converted in the first stage and a further 20 per cent in the second stage. 

Another type of stability problem arises in reactors containing reactive solid or catalyst particles. During chemical reaction the particles themselves pass through various states of thermal equilibrium, and regions of instability will exist along the reactor bed. Consider, for example, a first-order catalytic reaction in an adiabatic tubular reactor and further suppose that the reactor operates in a region where there is no diffusion limitation within the particles. The steady state condition for reaction in the particle may then be expressed by equating the rate of chemical reaction to the rate of mass transfer. The rate of chemical reaction per unit reactor volume will be (1 - e)kCAi since the effectiveness factor rj is considered to be unity. From equation 3.66 the rate of mass transfer per unit volume is (1 - e) (Sx/Vp)hD(CAG CAl) so the steady state condition is ... 

Experimental data on multiple steady-state profiles in tubular packed bed reactors have been reported in the literature by Wicke et al. 51 -53) and Hlavacek and Votruba (54, 55) (Table VI). The measurements have been performed in adiabatic tubular reactors. In the following text the effects of initial temperature, inlet concentration, velocity, length of the bed, and reaction rate expression on the multiple steady state profiles will be studied. 

In the last decade we have performed some thousands of experiments in packed adiabatic tubular reactors (CO oxidation), however, we have never observed oscillations. If on certain catalysts (e.g., Pt/Al203) the oscillation are caused by the kinetic mechanism then, apparently, the interactions of heat and mass transfer with chemical reaction suppress the occurence of periodic activity in tubular reactors. 

Figure 5.6 gives a Matlab program for a non-adiabatic tubular reactor. The reactor inlet temperature is assumed to be the same as the steam temperature (Tst = Tjn = All K in the... 

SINGLE ADIABATIC TUBULAR REACTOR SYSTEMS WITH GAS RECYCLE 265... 

MULTIPLE ADIABATIC TUBULAR REACTORS WITH INTERSTAGE COOLING... 

Openloop Response The openloop responses of a single adiabatic tubular reactor system to +20% step changes in recycle flowrate FR are shown in Figure 6.9. The solid lines represent increases in recycle flow and the dashed lines, decreases. The results show that the system produces limit cycle behavior, alternating between high temperatures and low temperatures. This type of dynamic response is called openloop-unstable behavior in this chapter. 

Block diagrams of the linear openloop process are shown in Figure 7.4. The two alternative flowsheets are labeled FS1, in which no furnace is used, and FS2, in which a furnace is used. The reactor transfer function is GR(s), representing the adiabatic tubular reactor. The reactor by itself is openloop-stable. In Figure 7.4a a simple first-order... 

In addition, the conversion X depends on the reactor volume according to the characteristic equations of the adiabatic tubular reactor. 

Figure 4.11 present the complete flowsheet together with the control structure. The reaction takes place in an adiabatic tubular reactor. To avoid fouling, the temperature of the reactor-outlet stream is reduced by quenching. A feed-effluent heat exchanger (FEHE) recovers part of the reaction heat. For control purposes, a furnace is included in the loop. The heat-integrated reaction system is stabilized... 

Reyes, F., W.L. Luyben, Design and control of a gas-phase adiabatic tubular reactor process with liquid recycle, Ind. 

Fig. 14. Hysteresis loci in (Da, tf) and (B, rj) planes for a first-order non-isothermal reaction in an adiabatic tubular reactor.

An axially-dispersed, adiabatic tubular reactor can be described by the following mass and energy balances that are in dimensionless form (the reader should verify that these descriptions are correct) ... 

Consider an adiabatic tubular reactor (Davis, 1984)[15] with the following data length L = 2 m, radius Rp = 0.1 m, inlet reactant concentration cO = 30 moles/m3, inlet temperature TO = 700K, enthalpy AH = -10000 J/mole, specific heat capacity Cp = 1000 J/kg/K, activation energy Ea = 100 J/mole, p = 1200 kg/m3, velocity uO = 3 m/s, and rate constant kO = 5 s-1. Dimensionless concentration (y) and dimensionless temperature (9) are governed by material and energy balances as ... 

Axial diffusion and conduction in an adiabatic tubular reactor can be described by [6]... 

More complicated problems for sequences of stirred tanks can be devised, but they follow the pattern of multibed adiabatic tubular reactors to which we now turn. 

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