Continuous equilibrium multistage

EQMULTI - Continuous Equilibrium Multistage Extraction System... 

Calculates continuous, multicomponent, multistage distillation, absorption, and stripping columns by equilibrium-stage and rate-based methods... 

Figure 8.1.37. (a) Continuous countercurrent multistage solvent extraction cascade of N stages (b) graphical determination of stage numbers in such a cascade of equilibrium extraction stages. 

The need for a continuous countercurrent process arises because the selectivity of available adsorbents hi a number of commercially important separations is not high, In die p-xylene system, for instance, if the liquid around the adsorbent particles contains 1% p-xyleiie, llie liquid in the pores contains about 2% p-xylene at equilibrium. Therefore, one stage of contacting cannot provide a good separation, and multistage contacting must be provided in tile same way that multiple trays are required in fractionating materials with relatively low volatilities. 

As solution containing the solute to be sorbed is added to the column, solute will equilibrate section by section, or plate by plate, as shown in Figure 4.4. Once solute has sorbed in the first plate, the water, which is now depleted of analyte, continues to move down the column into the next plate until equilibrium is reached in the first plate. When this occurs, the solution with analyte flows into the next plate, and so forth, until the entire column is at equilibrium, but in a multistage batchlike process. Although the distribution coefficient (ATj) is the same in each plate, the process is established in increments. Because the... 

The physical and chemical behavior of the system requires the definition of key design decision variables. For one-stage and multistage levels those decision parameters and operational variables include operational pressure and temperature, chemical reaction kinetics i.e. equilibrium or rate-limited chemical reaction), mass/heat transfer regime, phase velocity, residence time of the reactive phase and temporal operation i.e. batch, fed batch and continuous). 

Since M. is an open system, its multistage processes continually approach a state of equilibrium that is never quite achieved, at least not while the organism is alive. M. is therefore better described as a steady state, rather than an equilibrium. Let S. be a starting substrate (e.g. a dietary component), which is converted to endproduct E via intermediates Ij, I2,13... I , then S - -> I, I2 I3 E. Reactions I, 2, 3... 

Figure 8.1.44. (a) Continuous countercurrent gas solid adsorber for species i. (b) Operating line and equilibrium curve for a continuous adsorber, (c) Countercurrent multistage gas-solid adsorber for species i. (d) Operating line for a countercurrent multistage adsorber. 

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