Heat exchanger stirred tank

A stirred-tank heat exchanger with a bypass stream is shown in Fig. E18.17 with the available control valves. The possible manipulated variables are mass flow rate W2, valve stem positions Xc and and /, the fraction of mass flow rate wi that bypasses the tank before being added to the exit stream. Using the information given here, do the following ... 

Fig. 5. Hoechst/Rhc ne-Poulenc oxo flow scheme A, stirred tank reactor B, separator C, phase separator D, stripping column E, heat exchanger and F,...

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). 

Reactors may be operated batchwise or continuously, e.g. in tubular, tubes in shell (with or without internal catalyst beds), continuous stirred tank or fluidized bed reactors. Continuous reactors generally offer the advantage of low materials inventory and reduced variation of operating parameters. Recycle of reactants, products or of diluent is often used with continuous reactors, possibly in conjunction with an external heat exchanger. 

Reaction occurs in the loop as well as in the stirred tank, and it is possible to eliminate the stirred tank so that the reactor volume consists of the heat exchanger and piping. This approach is used for very large reactors. In the limiting case where the loop becomes the CSTR without a separate agitated vessel, Equation (5.35) becomes q/Q > 10. This is similar to the rule-of-thumb discussed in Section 4.5.3 that a recycle loop reactor approximates a CSTR. The reader may wonder why the rule-of-thumb proposed a minimum recycle ratio of 8 in Chapter 4 but 10 here. Thumbs vary in size. More conservative designers have... 

Heat can be added to or removed from stirred-tank reactors via external jackets (Figure 7.5a), internal coils (Figure 7.5b) or separate heat exchangers by means of a flow loop (Figure 7.5c). Figure 7.5d shows vaporization of the contents being condensed and refluxed to remove heat. A variation on Figure 7.5d would not reflux the evaporated... 

Figure 4.15 Selective adsorption synthesis of a-cyclodextrin from starch applying a hatch process using a sequence of stirred-tank reactor, heat exchanger modules and adsorption step...

All reactor modes sometimes can be operated advantageously with recycle of part of the product or intermediate streams. When the recycle is heated or cooled appropriately it can serve to moderate undesirable temperature travel. This function is well served with pumparound from a stirred tank through an external heat exchanger. Recycle streams also can be processed for changes in composition before return. 

A stirred tank reactor with a pump-around heat exchanger is arranged as on the sketch. The first order reversible reaction, A B, is to be carried to 80% conversion. The reaction temperature is to be kept at the value at which equilibrium conversion would be 90%. Temperature drop across the exchanger is to 60 K. Reaction in the exchanger circuit is neglected. Operating data are shown on the sketch and other data are k = exp(17.2-5800/T), 1/hr... 

The first application of a rhodium-ligand system was realized in the LPO-process (low pressure oxo Fig. 18). Huge stirred tank reactors are used, equipped with internal heat exchangers to control the heat of reaction. The solution of the catalyst recycle is simple but efficient. The catalyst remains in the reactor, products and unconverted propene are stripped by a huge excess of synthesis gas. Because of strong foaming, only a part of the reaction volume is used. After the gas has left the reactor, the products are removed by condensing, the big part of synthesis gas is separated from the liquid products and recycled via compressors. The liquid effluent of the gas-liquid separator... 

The standard esterification reactor is a stirred tank reactor. Due to the required latent heat for the evaporation of EG and water, heating coils are installed in addition to the heating jacket. In some cases, an external heat exchanger, together with a recirculation pump, is necessary to ensure sufficient heat transfer. During esterification, the melt viscosity is low to moderate (ca. 20 to 800mPas) and no special stirrer design is required. 

Conoco operated a stirred tank Pfaudler glass-lined reactor for the batch S03 sulfonation of detergent alkylate. The plant utilized over-the-fence S03 converter gas (8% S03 in dry air) having 6-8 h batch cycles (264). Allied Chemical Company provided details for batch S03 sulfonation (265,266) and Conoco also published their procedure for S03 batch sulfonation (267). Andrew Jergens Company patented a cyclic batch sulfonation and sulfation process introducing nondiluted S03 vapors into a venturi contacter that emitted reaction product into a stirred reservoir tank where it was recycled from the reservoir vessel through a heat exchanger and back to the venturi in the cyclic loop. The unit operated in a vacuum (268). Derived color quality was unspecified. 

Figure 1 Flowsheet of the RCH/RP hydroformylation process 38 1 Continuous flow stirred tank reactor,424 2 Phase separator, 3 Stripping column, 4 Distillation column, 5 Heat exchanger, 6 Falling film evaporator, 7 Liquid vapor separator.

Fig. 4. Flow diagram of the Ruhrchemie/Rhone-Poulenc process (137) 1, continuous-flow, stirred tank reactor 2, phase separator 3, stripping column 4, distillation column 5, heat exchanger 6, falling film evaporator 7, liquid-vapor separator.

Figure 17. Weak acid recovery plant used by Sachtleben Chemie (based on know-how of Bayer AG) a) Heat exchanger b) Evaporator c) Injection condenser d) Stirred salt maturing vessels e) Filter press f) Bunker for pyrites g) Coal silo h) Bunker i) Mixing screw unit j) Covered store for mixed filter cake k) Calcination furnace 1) Waste-heat boiler m) Cyclone n) Electrostatic precipitator o) Stirred tank p) Storage tank q) Pump r) Cooler...

Figure 17.33. Heat transfer to stirred-tank reactors (a) jacket (b) internal coils (c) internal tubes (d) external heat exchanger (e) external reflux condenser (f) fired heater (Walas, 1959).

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