Tubular reactor F

Figure 17.14. Some unusual reactor configurations, (a) Flame reactor for making ethylene and acetylene from liquid hydrocarbons [Patton et al., Pet Refin 37(li) 180, (1958)]. (b) Shallow bed reactor for oxidation of ammonia, using Pt-Rh gauze [Gillespie and Kenson, Chemtech, 625 (Oct. 1971)]. (c) Sdioenherr furnace for fixation of atmospheric nitrogen, (d) Production of acetic acid anhydride from acetic acid and gaseous ketene in a mixing pump, (e) Phillips reactor for low pressure polymerization of ethylene (closed loop tubular reactor), (f) Polymerization of ethylene at high pressure.

Figure 5 depicts the effect of calcination temperature on subsequent catalyst activity after reduction at 300°C (572°F). Activity was measured in laboratory tubular reactors operating at 1 atm with an inlet gas composition of 0.40% CO, 25% N2, and 74.6% H2, and an inlet temperature of 300°C. Conversion of CO is measured and catalyst activity is expressed as the activity coefficient k in the first order equation ... 

Figure 1. Typical reactor temperature profile for continuous addition polymerization a plug-flow tubular reactor. Kinetic parameters for the initiator 1 = 10 ppm Ea = 32.921 kcal/mol In = 26.492 In sec f = 0.5. Reactor parameter [(4hT r)/ (DpCp)] = 5148.2. [(Cp) = heat capacity of the reaction mixture (p) = density of the reaction mixture (h) = overall heat-transfer coefficient (Tf) = reactor jacket temperature (r) = reactor residence time (D) = reactor diameter].

The terms space time and space velocity are antiques of petroleum refining, but have some utility in this example. The space time is defined as F/2, , which is what t would be if the fluid remained at its inlet density. The space time in a tubular reactor with constant cross section is [L/m, ]. The space velocity is the inverse of the space time. The mean residence time, F, is VpjiQp) where p is the average density and pQ is a constant (because the mass flow is constant) that can be evaluated at any point in the reactor. The mean residence time ranges from the space time to two-thirds the space time in a gas-phase tubular reactor when the gas obeys the ideal gas law. 

FIGURE 13.7 Performance of a laminar flow, tubular reactor for the bulk polymerization of styrene Tin = 35°C and F = 1 h. (a) Stability regions, (b) Monomer-conversion within the stable region. 

Tubular reactor was, therefore, applied to minimize a back mixing with fresh KOH and B0C2-AMP. However, only 27% of Boc-AMP was converted to B0C2-AMP due to the phase separation between f-Boc20 and aqueous KOH solution. 

Hessel, V., Lowe, H., Hofmann, C., ScHONFELD, F., WeHLE, D., WeRNER, B., Process development of a fast reaction of industrial importance using a caterpillar micromixer/tubular reactor set-up, in Proceedings of the 6th International Conference on Microreaction Technology, IMRET 6, pp. 39-54 (11-14 March 2002), AIChE Pub. 

The F(t) curve for a laminar flow tubular reactor with no diffusion is shown in Figure 11.6. Curves for the two other types of idealized flow patterns are shown for comparison. 

The relative response at the end of a tubular reactor of length L is identical with the F(t)... 

SJi. The initial startup of an adiabatic, gas-phase packed tubular reactor makes a good example of how a distributed system can be lumped into a series of CSTRs in order to study the dynamic response. The reactor is a cylindrical vessel (3 feet ID by 20 feet long) packed with a metal packing. The packing occupies 5 percent of the total volume, provides 50 ft of area per of total volume, weighs 400 ib yft and has a heat capacity of 0.1 Btu/lb °F. The heat transfer coefficient between the packing and the gas is 10 Btu/h It "F. 

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. 

Figure 15—3 lays out the four-step process, starting with germinating the seed from which everything sprouts. Triethyl aluminum is created from aluminum, hydrogen, and ethylene in step one, which itself has several parts. Powdered aluminum in a toluene slurry is fir-st converted to diethyl aluminum hydride, HA1(C2H5)2, at 212—300 F and 1500 psi. This product is then fed to a tubular reactor with ethylene at 212 F and 300 psi to produce triethyl aluminum. Yields are about 90%. 

Figure 3.5 Plot of hydrogen evolved (mol-H2 per mol-Zr) versus time (min) during the reaction of 1 with methane in a tubular reactor instantaneous (crosses) and cumulated (filled squares) quantity of H2 evolved [Pch4 = 30bar, 3 mLmin", f).ddiiion = room temp., = 423 K, ramp 250°Ch , 1200 min].

The PFR model assumes a flat velocity profile across the whole of the reactor cross-section in reality, this is impossible to achieve although in practice certain combinations of physical conditions are closely described by this assumption. If the Reynolds number, dupln, in a tubular reactor is less than about 2100, then the flow therein will be laminar and where the flow is fully developed, the velocity profile across the reactor will be parabolic in form. If one assumes that diffusion is negligible between adjacent radial layers of fluid, then it is relatively straightforward to derive the forms of E(t), E(0) and F(0) associated with this type of reactor [42]. These are given in the equations... 

Note that, in a laminar-flow tubular reactor, the material on the reactor centre line has the highest velocity, this being exactly twice the average velocity, Q/A, for the whole reactor. This means that, following any tracer test, no response will be observed until the elapsed time exceeds one half of the reactor space time or mean residence time. The following values for 0 and F(0) emphasise the form of the cumulative RTD and the fact that, even up to 10 residence times after a tracer impulse test, 0.25% of the tracer will not have been eluted from the system. 

Figure 17.11. Types of contactors for reacting gases with liquids many of these also are suitable for reacting immiscible liquids. Tanks (a) with a gas entraining impeller (b) with baffled impellers (c) with a draft tube (d) with gas input through a rotating hollow shaft, (e) Venturi mixer for rapid reactions, (f) Self-priming turbine pump as a mixer-reactor, (g) Multispray chamber. Towers (h) parallel flow falling film (i) spray tower with gas as continuous phase (j) parallel flow packed tower (k) counter flow tray tower. (1) A doublepipe heat exchanger used as a tubular reactor.

Figure 17.17. Examples of reactors for specific liquid-gas processes, (a) Trickle reactor for synthesis of butinediol 1.5 m dia by 18 m high, (b) Nitrogen oxide absorption in packed columns, (c) Continuous hydrogenation of fats, (d) Stirred tank reactor for batch hydrogenation of fats, (e) Nitrogen oxide absorption in a plate column, (f) A thin film reactor for making dodecylbenzene sulfonate with S03. (g) Stirred tank reactor for the hydrogenation of caprolactam, (h) Tubular reactor for making adiponitrile from adipic acid in the presence of phosphoric acid.

As i the term in brackets above tends to exp (vit/V) for t < V/v), and F becomes zero(7>. Thus, for an infinite number of tanks the fraction of tracer that has escaped is zero for all times less than the residence time V/v. This is exactly the same as for the case of an ideal tubular reactor with plug flow. 

R. Shinnar, F. J. Doyle, H. M. Budman, and M. Morari. Design considerations for tubular reactors with highly exothermic reactions, AICHE J., 38, 1729 (1992). 

To design a tubular reactor that will operate at 1 atm pressure and 1,400°F ... 

Figure 8-22 shows the F(0) curves for laminar flow in a tubular reactor and for other idealized flow patterns. 

The three ideal reactors form the building blocks for analysis of laboratory and commercial catalytic reactors. In practice, an actual flow reactor may be more complex than a CSTR or PFR. Such a reactor may be described by a residence time distribution function F(t) that gives the probability that a given fluid element has resided in the reactor for a time longer than t. The reactor is then defined further by specifying the origin of the observed residence time distribution function (e.g., axial dispersion in a tubular reactor or incomplete mixing in a tank reactor). 

The reactant mixture then enters the tubular reactor or the radiant coil at the cross-over temperature generally above 1000° F. It is rapidly heated to the cracking temperature by radiant heat supplied by burners in the combustion chamber. The gas leaving the reactor enters the transfer line exchanger where it is rapidly quenched to avoid decomposition of valuable products. 

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

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