Gas-Inducing Reactors

In a gas-inducing reactor, both gas and liquid phases are generally considered to be completely backmixed. The use of Eqs. (2.39) and (2.40) for the calculations of the critical speed for gas induction is recommended. The rate of gas induction can be expressed by a dimensionless relation NA = /(FrdJH, Ga, dT/du HJdj). The most important parameters are Fr dJH and dT/di. For a given power input per unit volume, the turbo aerator appears... 

Patwardhan, A.W., and Joshi, J.B. (1999), Design of gas-inducing reactors, Industrial Engineering Chemistry Research, 38(1) 49-80. 

The aforementioned discussion was general in nature and also included conventional contactors such as tray and packed columns. In the case of three-phase (G-L-S) reactions, such conventional contactors are not used. The stirred reactor is the workhorse of the fine chemicals industry. The gas-inducing reactor can be considered as an alternative to stirred reactors when a pure gas is used. However, this reactor has several drawbacks (Chapter 9). In view of this, the venturi loop reactor has been widely used as a safe and energy-efficient alternative to the conventional stirred reactor. Table 3.3 summarizes the preceding discussion in the form of a multiphase reactor selection guide. 

Criteria Trickle bed Stirred tank reactor Gas- inducing reactor Venturi loop reactor Sparged reactors Microstructured Structured trickle beds ... 

Formation of surface vortices in stirred vessels, condition for gas induction in flotation cells/gas-inducing reactors... 

Increase in total pressure implies a higher capital cost of the reactor and is therefore not the optimum solution. As mentioned earlier, the gas-liquid mass transfer and solid-liquid mass transfer coefficients offered by a venturi loop reactor are at least an order of magnitude higher than their nearest competitor, the conventional stirred tank reactor or gas-inducing reactor. Therefore, if the gas-liquid mass transfer coefficient can be so increased by a factor of 10 through the use of a venturi loop reactor, then the sole reason for excessive reactor pressure to achieve the required higher value of mass transfer rate vanishes. In conclusion, the venturi loop reactor can allow operation at much lower pressures as compared to the stirred reactor or its variants. 

Parameter Unit Stirred tank reactor and variants including gas-inducing reactor Venturi loop reactor... 

Self-aspirating nature makes gas-inducing reactors attractive for applications in dead-end situations involving pure/expensive gas phase (Table 3.3). As a result, recycle compressor for the gas is not required. 

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