Frameworks of separation theories from two separate worlds: dynamics and thermodynamics

Contemporary separation theories are based on the mass conservation equation with the methods of dynamics, lose the entropy balance equation as a restriction condition, and draw very little from non-equilibrium thermodynamics, cybernetics, information theory and systematology. Thus, they cannot account for the irreversibility of separation processes. In natural sciences, the entropy balance equation is an exclusive way to reveal the evolution that separation systems undergo in order to make solute systems evolve from Boltzmann's disorder to order. The irreversibility of separation processes, which is caused by thermodynamic forces, and described by the entropy balance equation only, is the sourer of both the separation and mixing of solute systems. Therefore, Clausius' heat death (band spreading of one component) and Darwin's evolutionism (separation among different components) simultaneously coexist in separation processes. The framework of non-equilibrium thermodynamic separation theory is made up of three parts. First, the integral optimization function is found on the part of the mixed entropy change of the solute system between the final state and the initial one relating directly to the net separation. It corresponds to the information quantity that solute systems gain from separation systems. The more negative the integral optimization function is, the more information solute systems gain and the better the integral separation efficiency of big separation systems is. Second, according to the entropy balance equation and the conditions of practical separation processes, a separation state function can be discovered to show how separation systems described by macroscopic physicochemical parameters affect the integral optimization function. Lastly, with the methods of modern cybernetics, we will be able to optimize and time-varyingly control separation processes through controlling the operation parameters in separation processes with the separation state function. The non-equilibrium thermodynamic separation theory will keep separation theories up to date with modern physics and intersecting sciences. (C) 1998 Elsevier Science B.V. All rights reserved