Zone capacity factor

The capacity factor, k, of., a sanple zone is defined as the ratio of the tiee spent by the substance in the stationary phase cospared to the tiae it spends in the aobile phase, and is related to the Rf value by equation (7.2). 

Colin et al. [SSS] have described a different method to construct a diagram that allows the prediction of optimum conditions. Their approach is based on the calculation of so-called critical bands. If the retention surface of a solute j is known, then a forbidden zone may be defined below the capacity factor kj. If the preceding solute i has a capacity factor kp which falls in this critical band, then the resolution between i and j is insufficient. Eqn.(1.20) relates the resolution to the capacity factors of the individual solutes ... 

As was discussed in Chapter 1 resolution, R, is a measure of the distance between two adjacent peaks in terms of the number of average peak widths than can fit between the band (zone) centers. Assuming symmetrical (Gaussian) peaks, when R = 1, peak separation is nearly complete with only about 2% overlap. This case was shown in Chapter 1, Figure 1-4. Resolution results from the physical and chemical interactions that occur as the sample travels through the column. It should, therefore, be no surprise that resolution may also be expressed in terms of the contribution of the individual column characteristics separation factor (selectivity, a), efficiency (narrowness of peak, N), and capacity factor (residence time, k ) of the first component. The equation that describes this interrelationship is... 

Figure 3.13 shows this relationship for a specific value, 0.9, for the availability-based capacity factor L. This figure also shows the amount of electric energy produced per cycle. Because peak electric demands occur at intervals of 6 months or 1 year, Fig. 3.13 may be used to select combinations of number of fuel zones and enrichment that permit these desirable refueling intervals. Three-zone fueling with enrichment of 3.2 percent is one such combination. 

Figure 3.14 shows the total steady-state fuel-cycle cost for an interval of 1.0 year between refuelings as a function of feed enrichment for batch fractions, /, of 5, j, and j. The batch fraction is defined as 1 In, where n is the number of fuel zones. Also plotted in this flgure are levels of constant energy production (E) or capacity factor (/. ) and lines of constant burnup... 

Figure 3.27 Components of steady-state unit fuel-cycle cost, PWR, three-zone fueling, 90 percent avail-ability-based capacity factor, 0.125-year refueling downtime.

The 1060-MWe PWR discussed in Sec. 3.4 is to be operated with steady, four-zone modified scatter refueling, with 1.0 year between successive refuelings. The availability-based capacity factor is 0.8 and the refueling downtime is 0.15 year. The reactor fuel inventory is 88.961 MT heavy metal. 

When specifying a new furnace, input calculations should be based on the true flue gas exit temperature— NOT ON FURNACE TEMPERATURE Coauthor Shannon recommends adding a safety factor of 30% in general, but 40% in the charge zone to accommodate productivity expansion of the mill—the latter because inadequate charge-zone capacity can cause swings in input needs after delays. His experience... 

This equation shows that resolution is a function of three factors, namely, selectivity (a), number of theoretical plates (A), and capacity factor k ). As discussed above, selectively relates to the ability to separate zone centers (difference in Rf values), whereas the number of theoretical plates measures zone spreading throughout the chromatographic system. The capacity factor describes retention of a component by the stationary phase. In HPLC, k is stated in terms of column volumes, and values of 1 to 10 are normal. 

Other factors that can influence the separability of components of complex natural mixtures, such as adsorbent particle size and layer thickness, are similar to those used in analytical TLC. Mostly, adsorbents of wide dispersion of particle size — 5 to 40 pm and layers of 0.5 to 1 mm thickness — are used. Although the capacities of layers increase with their thickness, the separation efficiency decreases for thickness above 1.5 mm. Commercially available precoated preparative plates (e.g., silica, alumina, and RP2 plates) with fluorescence indicators and plates with preadsorbent zones are more convenient and commonly used. 

There has been an attempt to measure the peak capacity in 1DLC and 2DLC by assigning a range of useful retention time between the unretained marker that elutes at ti and some stated value of the retention factor k leading to a zone at tf and plugging in a value for the peak width W. This number is useful but will never be equal to the number... 

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