Process equipment stage efficiency

The separation of components by liquid-liquid extraction depends primarily on the thermodynamic equilibrium partition of those components between the two liquid phases. Knowledge of these partition relationships is essential for selecting the ratio or extraction solvent to feed that enters an extraction process and for evaluating the mass-transfer rates or theoretical stage efficiencies achieved in process equipment. Since two liquid phases that are immiscible are used, the thermodynamic equilibrium involves considerable evaluation of nonideal solutions. In the simplest case a feed solvent F contains a solute that is to be transferred into an extraction solvent S. 

CDS of surfaces/equipment coming into direct contact with the product requires special consideration. While CDS procedures of guaranteed efficiency must be applied, it is imperative that no trace of the CDS agents subsequently remain on such surfaces, as this would result in automatic product contamination. The final stage of most CDS procedures, as applied to such process equipment, involves exhaustive rinsing with highly pure water (water for injections WFI). This is followed if at all possible by autoclaving. 

Process control and the associated instrumentation were mentioned in relation to the process selection (Section 3.1). To reiterate those comments, these aspects of plant design must be considered during the process selection stage and at other subsequent stages in the design of the plant. Do not assume that any item of equipment or an entire plant that can be designed can also be operated and controlled efficiently. It should be established early in the design that the control and instrumentation aspects are not only feasible but that the cost is within acceptable limits. 

Normally, the efficiency of a dimerization process is determined by (i) the selectivity to butene-1, (ii) the yield of butene-1 per unit weight of the catalyst, and (iii) the required process equipment [3]. So far, the only commercial process is the EFP-SABIC Alphabutol process, which is an indication of its technical advantages and economic potential. There are other processes which have not as yet reached commercial stage. These processes are offered by Phillips, MIT and Dow. 

Different physical modes are sometimes available for the same unit operation. A distillation column can, for example, be modeled on the basis of theoretical stages or using a rate-based model, taking into account the mass transfer on the column internals. A simulation of this kind can be used to extract the data for the design of the process equipment or to optimize the process itself During recent years, dynamic simulation has become more and more important. In this context, dynamic means that the particular input data can be varied with time so that the time-dependent behavior of the plant can be modeled and the efficiency of the process control can be evaluated. 

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