Minimum Mass-Separating Agent

The task of MEN is to transfer certain species (often pollutants) from a set of rich streams (contain contaminants to be removed) to a set of lean streams (often Mass Separating Agents, MSAs). By specifying a minimum composition difference, e, the mass transfer pinch can be located, which is the thermodynamic bottleneck for mass transfer between process streams. 

Analogous to the minimum reflux ratio in distillation, there exists a minimum L/G ratio in absorption. Figure 6.3 compares the operating line to the equilibrium line for absorption. Because the slope of the operating line is L/G, reducing the liquid mass-separating agent flowrate decreases the slope of the line. Compare lines aA and ab for a separation in which the gas enters with concentration of solute which must be removed to Ya and the liquid... 

For separators that produce two products, the minimum number of separators required is equal to one less than the number of products. However, additional separators may be required if mass separating agents are introduced and subsequently removed and/or multicomponent products are formed by blending. 

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