Stage-wise development

Point F on the figure represents conditions in the kettle or still with Xj, yj, or Xq, yo- Line DF represents slope of the operating line at minimum reflux. The step-wise development from point D cannot cross the intersection, F, where the slope intersects the equilibrium line, and leads to an infinite condition, as point F is approached. Thus, an infinite number of theoretical trays/stages is required, and... 

Drug development is ideally a logical, step-wise procedure in which information from small early studies is used to support and plan later larger, more definitive studies. To develop new drugs efficiently, it is essential to identify characteristics of the investigational drugs in the early stages of development and to plan an appropriate development based on this profile. 

D[-., be available in a range of sires such that the polymer (or molecule) of diameter, D, can pass through the large holes freely or the small holes with some difficulty. Both the pressure drop across the membrane and the concentration of effluent are measured continuously while the flow rales of effluent are increased in step-wise or continuous fashion. At this stage of development only the unconfined time-average radius of gyration is considered as k However other viscometric or projection radii may ultimately be more useful. 

In this section, the equations are presented for the common types of contactors differential contactors and stage-wise contactors. The equations are developed for the case of steady-state, countercurrent contacting of liquid and gas with negligible heat effects, with a single-component absorption. Some discussion of extensions to other situations follows. 

The concept of a mass-transfer unit was developed many years ago to represent more rigorously what happens in a differential contactor rather than a stage wise contactor. For a straight operating line and a straight equilibrium line with an intercept of zero, the equation for calculating the number of mass-transfer units based on the overall raffinate phase Nor is identical to the Kremser equation except for the denominator when the extraction factor is not equal to 1.0 [Eq. (15-23)]. 

The second stage of development is typically aimed at mimicking commercial operations by employing recycle streams to achieve realistic simulations of the integrated process. Isothermal conditions are usually maintained in the reactor, but if heat release is a concern, such as residuum hydrotreating, then it is wise to run adiabatically so that the adiabatic reaction temperature can be established and also how much heat must be removed in the final commercial design. Defining catalyst deactivation, yield patterns, and how various feed types influence the process are typical aspects to explore. 

Stage-wise. In this arrangement, the process development is split along disciplines or along operational lines, causing more than one handover and with a greater spread of the technical responsihilities (Fig. 10) ... 

Figure 10 Technology transfer mechanisms—stage-wise across operational boundaries Either a partially developed process or a developed process (through the last intermediate material) is transferred to the technical arm of the operations area, which carries out the first manufacture activity, with R D playing a secondary or contingent role during the latter. Most often this mechanism results in two technology transfers.

The development of global reaction kinetics is a stage wise scale-up approach. The various stages of this multiscale approach are summarized in Fig. 13.6 and include (a) microreactor experiments over powdered catalyst for the determination of the intrinsic reaction kinetics, (b) synthetic gas bench experiments over small monolith samples to account for intraporous diffusion of species, and (c) validation on steady-state and transient engine tests. 

Where the fate of a major development programme rests on foreign data, it is wise to discuss their acceptability with the appropriate regulatory authorities at an early stage. 

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