About New Type of Multiplicity of Steady States in the Recycle System: Reactor- Separating Unit.
Systematic methods and tools for managing the complexity
Process Synthesis & Design (T4-1P)
Keywords: Recycle systems, multiplisity steady states, stability
A construction of a technological scheme with a recycle of non-reacting feed and intermediate reactants of a reaction is an effective way of their full utilization and a solution of environmental problem. The solution of this problem is especially very important for chemical industry where the waste pollutes the environment.
However a feed back causes an appearance of a multiplicity of the steady states in the reactor. A problem of the steady states multiplicity in chemical reactor with recycle has been examined for along time. The existence of the finite set of steady states (odd number) in the reactor was indicated in many works. But an appearance of qualitatively new properties of the reactor taking place in the recycle system: reactor – separating unit is possible. It is shown as an existence of continuum (infinite set ) steady states in the reactor. Continuum of the steady states is possible to be only in recycle system on the operational mode with a full use of feed and intermediate reactants. Under numeric calculation of recycle system: reactor – distillation column the existence of continuum of steady states is shown as a dependence of the solution of iterative procedure of initial approximation point.
Conditions for the existence of various continuums of steady states in the reactor are found. A continuos stirred tank reactor in which the second-order reactions: A + B – C and A + B – C, A + B – P proceed with full utilization of the feed reactants A and B is shown to be characterized by continuums of steady states in which the concentrations of the reactants in the reactor can take an infinite set of steady values lying within a bounded region (interval). This region (interval) is limited by the condition of the existence of the operational mode with a full use of the feed reactants.
These steady states can not be of asymptotic stability. They can at best be on the boundary of the stability region at a state of neutral balance. Therefore it is necessary to have a system of automatic control to keep up this operational mode.
Presented Tuesday 18, 13:30 to 17:00, in session Process Synthesis & Design (T4-1P).
