Three-Phase Reactor with Complete Backmixing

THREE-PHASE REACTOR WITH COMPLETE BACKMIXING 

For a three-phase reactor with complete backmixing, balances for the entire liquid and gas volumes can be set up. For the liquid phase, the mass balance is written as 

After inserting the definitions for A (gas-liquid mass transfer area) and tip (particle area-to-reactor volume), the mass balance is transformed to 

The mass balance for the gas phase is expressed similar to Equation 6.30  

After inserting Equation 6.2 and the definition of Hy (gas-liquid surface area-to-reactor volume), we obtain 

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THREE-PHASE REACTOR WITH COMPLETE BACKMIXING... 

Let us consider the mass balance of two kinds of three-phase reactors bubble columns and tube reactors with a plug flow for the gas and the liquid phases, and stirred tank reactors with complete backmixing. Modeling concepts can be implemented in most existing reactors backmixing is typical for slurry reactors, bubble columns, and stirred tank reactors, whereas plug flow models describe the conditions in a trickle bed reactor. The interface between the gas and the liquid is supposed to be surroimded by gas and liquid films. Around the catalyst particles, there also exists a liquid film. In gas and liquid films, physical diffusion, but no chemical reactions, is assumed to take place. A volume element is illustrated in Figure 6.15. 

Below we will look at three ideal gas-liquid reactor types a column reactor with a plug flow in the gas and liquid phases, a tank reactor with complete backmixing, and a BR. The main volume elements in gas-liquid reactors are displayed in Figure 7.16. The bulk gas and liquid phases are delimited by thin films where chemical reactions and molecular diffusion occur. However, the reactions do take place in the bulk phase of the liquid as well. 

Another alternative for three-phase catalytic reactors with suspended catalyst particles is to use mechanically agitated tank reactors (Figure 6.7). In a tank reactor, the flow profile can approach complete backmixing. 

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