Model complete local-composition equation

The Group Contribution Equation of State (GC-EoS) has two eonlributions to the residual Helmholtz energy of the system a repulsive hard sphere Camahan-Starling type term and an attractive term, which combines the group contribution approach wifli the local-composition mixing rules. A complete explanation of the model is given by Skjold-Jorgensen. ... 

We have considered the situation of only one phase for any mixture composition this means that there is no surface tension and the fluid behavior is completely characterized by the turbulent flow described by the mass and momentum balance equations. To solve these equations, one needs to model the diffusional mixing of the species present in the system and to identify local values of the thermodynamic and transport properties, as considered in Section 3.2. Here we just point out that once the methods for predicting local values of fluid density and viscosity have been worked out, one should be able to integrate Eqs. (10) and (11). 

The genesis of the reactor design equations is the conservation of mass. Since reactor operations involve changes in species compositions, the mass balance is written for individual species, and it is expressed in terms of moles rather than mass. Species balances and the reactor design equations are discussed in detail in Chapter 4. To obtain a complete description of the reactor operation, it is necessary to know the local reaction rates at all points inside the reactor. This is a formidable task that rarely can be carried out. Instead, the reactor operation is described by idealized models that approximate the actual operation. Chapters 5-9 cover the applications of reactor design equations to several ideal reactor conflgurations that are commonly used. 

In a simplified approach we consider a separation section where all the units are lumped in a black-box. The composition of the outlet streams is constant due to the local control. In practice, this is achieved by manipulating internal flow rates or by heat duties. Changing the flow rate or composition of the inlet streams is reflected by a gradual change of the flow rate of outlet streams. When complete reactant recovery is assumed (z4 = 0), the simple model describing the dynamic behaviour of the recycle consists of a first-order differential equation ... 

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