Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Stirred tank reactors for chemical reactions

Figure 9.11 Product distribution in a continuous flow stirred-tank reactor for the reactions indicated. (Adapted from O. Levenspiel, Chemical Reaction Engineering, 2nd ed. Copyright 1972. Reprinted by permission of John Wiley Sons, Inc.)... Figure 9.11 Product distribution in a continuous flow stirred-tank reactor for the reactions indicated. (Adapted from O. Levenspiel, Chemical Reaction Engineering, 2nd ed. Copyright 1972. Reprinted by permission of John Wiley Sons, Inc.)...
A review of an alarm history has identified that the bad actors include level, pressure, and temperature alarms that are associated with a liquid-phase, continuous, stirred-tank reactor. The chemical reactions are exothermic, and the CSTR is used at different times to make two products, A or B. The low-level and low-pressure alarm violations occur mainly during shutdown operations, whereas high temperature alarms for the jacket cooling water occur primarily when product B is produced. It is desirable to devise a strategy for reducing these bad actor alarms. [Pg.176]

The reaction-diffusion dynamics of the acid autocatalytic Chlorite-Tetra-thionate (CT) reaction was thoroughly investigated (2). Like other autocatalytic reactions, the CT reaction exhibits a more or less long induction period followed by a rapid switch to thermodynamic equilibrium. In a continuous stirred tank reactor (CSTR), this reaction can exhibit bistability. One state is obtained at high flow rates or at highly alkaline feed flows, when the induction time of the reaction is much longer than the residence time of the reactor. The reaction mixture then remains at a very low extent of reaction and this state is often named the Flow (F) or the Unreacted state. In our experimental conditions, the F state is akaline (pH 10). The other state is obtained for low flow rates or for weakly alkaline feed flows, when the induction time of the chemical mixture is shorter than the residence time of the reactor. It is often called a Thermodynamic (T) or Reacted state because the reaction is almost completed in the CSTR. In our experimental conditions, the T state is acidic (pH 2). The domains of stability of these two states overlap over a finite range of parameter. [Pg.81]

Over 25 years ago the coking factor of the radiant coil was empirically correlated to operating conditions (48). It has been assumed that the mass transfer of coke precursors from the bulk of the gas to the walls was controlling the rate of deposition (39). Kinetic models (24,49,50) were developed based on the chemical reaction at the wall as a controlling step. Bench-scale data (51—53) appear to indicate that a chemical reaction controls. However, flow regimes of bench-scale reactors are so different from the commercial furnaces that scale-up of bench-scale results caimot be confidently appHed to commercial furnaces. For example. Figure 3 shows the coke deposited on a controlled cylindrical specimen in a continuous stirred tank reactor (CSTR) and the rate of coke deposition. The deposition rate decreases with time and attains a pseudo steady value. Though this is achieved in a matter of rninutes in bench-scale reactors, it takes a few days in a commercial furnace. [Pg.438]

FIG. 23-1 Heat transfer to stirred tank reactors, a) Jacket, (h) Internal coils, (c) Internal tubes, (d) External heat exchanger, (e) External reflux condenser. if) Fired heater. (Walas, Reaction Kinetics for Chemical Engineers, McGraw-Hill, 1959). [Pg.2070]

Two complementai y reviews of this subject are by Shah et al. AIChE Journal, 28, 353-379 [1982]) and Deckwer (in de Lasa, ed.. Chemical Reactor Design andTechnology, Martinus Nijhoff, 1985, pp. 411-461). Useful comments are made by Doraiswamy and Sharma (Heterogeneous Reactions, Wiley, 1984). Charpentier (in Gianetto and Silveston, eds.. Multiphase Chemical Reactors, Hemisphere, 1986, pp. 104—151) emphasizes parameters of trickle bed and stirred tank reactors. Recommendations based on the literature are made for several design parameters namely, bubble diameter and velocity of rise, gas holdup, interfacial area, mass-transfer coefficients k a and /cl but not /cg, axial liquid-phase dispersion coefficient, and heat-transfer coefficient to the wall. The effect of vessel diameter on these parameters is insignificant when D > 0.15 m (0.49 ft), except for the dispersion coefficient. Application of these correlations is to (1) chlorination of toluene in the presence of FeCl,3 catalyst, (2) absorption of SO9 in aqueous potassium carbonate with arsenite catalyst, and (3) reaction of butene with sulfuric acid to butanol. [Pg.2115]

Almost all flows in chemical reactors are turbulent and traditionally turbulence is seen as random fluctuations in velocity. A better view is to recognize the structure of turbulence. The large turbulent eddies are about the size of the width of the impeller blades in a stirred tank reactor and about 1/10 of the pipe diameter in pipe flows. These large turbulent eddies have a lifetime of some tens of milliseconds. Use of averaged turbulent properties is only valid for linear processes while all nonlinear phenomena are sensitive to the details in the process. Mixing coupled with fast chemical reactions, coalescence and breakup of bubbles and drops, and nucleation in crystallization is a phenomenon that is affected by the turbulent structure. Either a resolution of the turbulent fluctuations or some measure of the distribution of the turbulent properties is required in order to obtain accurate predictions. [Pg.342]

A particular shape of reactor, its specific internals, arrangements made because of special properties and/or behaviour of the reaction mixture, etc. are used as criteria to qualify a reactor. In fine chemicals manufacture two main groups of cylindrical reactors are in common use, viz. stirred-tank reactors with a small aspect ratio, and column reactors with a relatively large aspect ratio. Both types can be equipped with specific internals depending on process requirements. Researchers and designers are well acquainted with these reactors. A tendency to duplicate known equipment usually wins when considering the choice of reactor for a particular process. As a consequence, more and more stirred-tank reactors and column reactors are in use. [Pg.263]

A cascade of three continuous stirred-tank reactors arranged in series, is used to carry out an exothermic, first-order chemical reaction. The reactors are jacketed for cooling water, and the flow of water through the cooling jackets is countercurrent to that of the reaction. A variety of control schemes can be employed and are of great importance, since the reactor scheme shows a multiplicity of possible stable operating points. This example is taken from the paper of Mukesh and Rao (1977). [Pg.345]

The mass balance of a continuous flow stirred-tank reactor (CSTR) with a first-order chemical reaction is very similar to the problem in Section 2.8.1 (p. 2-20). We just need to add the chemical reaction term. The balance written for the reactant A will appear as ... [Pg.62]

Continuous flow stirred tank reactors are normally just what the name implies—tanks into which reactants flow and from which a product stream is removed on a continuous basis. CFSTR, CSTR, C-star, and back-mix reactor are only a few of the names applied to the idealized stirred tank flow reactor. We will use the letters CSTR as a shorthand notation in this textbook. The virtues of a stirred tank reactor lie in its simplicity of construction and the relative ease with which it may be controlled. These reactors are used primarily for carrying out liquid phase reactions in the organic chemicals... [Pg.269]

The kinetics of a liquid-phase chemical reaction are investigated in a laboratory-scale continuous stirred-tank reactor. The stoichiometric equation for the reaction is A 2P and it is irreversible. The reactor is a single vessel which contains 3.25 x 10 3 m3 of liquid when it is filled just to the level of the outflow. In operation, the contents of the reactor are well stirred and uniform in composition. The concentration of the reactant A in the feed stream is 0.5 kmol/m3. Results of three steady-state runs are ... [Pg.266]


See other pages where Stirred tank reactors for chemical reactions is mentioned: [Pg.143]    [Pg.144]    [Pg.148]    [Pg.150]    [Pg.152]    [Pg.154]    [Pg.162]    [Pg.164]    [Pg.166]    [Pg.168]    [Pg.174]    [Pg.176]    [Pg.178]    [Pg.180]    [Pg.186]    [Pg.188]    [Pg.192]    [Pg.194]    [Pg.198]    [Pg.204]    [Pg.208]    [Pg.212]    [Pg.214]    [Pg.143]    [Pg.144]    [Pg.148]    [Pg.150]    [Pg.152]    [Pg.154]    [Pg.162]    [Pg.164]    [Pg.166]    [Pg.168]    [Pg.174]    [Pg.176]    [Pg.178]    [Pg.180]    [Pg.186]    [Pg.188]    [Pg.192]    [Pg.194]    [Pg.198]    [Pg.204]    [Pg.208]    [Pg.212]    [Pg.214]    [Pg.517]    [Pg.91]    [Pg.21]    [Pg.58]    [Pg.472]    [Pg.135]    [Pg.71]    [Pg.145]    [Pg.285]    [Pg.264]    [Pg.484]    [Pg.255]    [Pg.274]    [Pg.120]   


SEARCH



Chemical reactions reactors

Chemical reactors

Chemical stirred tank

For chemical reactions

For stirred tanks

Reaction stirred reactors

Reaction tanks

Reactor stirred

Reactors chemical reactor

Reactors reaction

Reactors stirred tank reactor

Reactors stirring

Reactors, chemical stirred tanks

Stirred tank reactors

Stirring reactions

Tank reactor

Tank reactor reaction

Tank reactor reactors

© 2024 chempedia.info