Capacity at breakpoint

When the resin is incompletely ionised, its effective capacity will be less than the maximum. If equilibrium between resin and liquid is not achieved, a dynamic capacity may be quoted which will depend on the contact time. When equipment is designed to contain the resin, it is convenient to use unit volume of water-swollen resin as the basis for expressing the capacity. For fixed-bed equipment, the capacity at breakpoint is sometimes quoted. This is the capacity per unit mass of bed, averaged over the whole bed, including the ion exchange zone, when the breakpoint is reached. 

To allow algebraic equations to be used to locate ATm, assume that the heat capacities can be approximated by piecewise constant functions of temperature, with discontinuities at temperature breakpoints TBRj. Then for each exchanger, Arm can occur only at either end or at a breakpoint location inside the exchanger. However, a remaining difficulty is that since the intermediate stream temperatures are not known before the resilience test, the breakpoint locations are also not known a priori. 

Figure 6 shows the result of the metal capacity measurement of HDM catalyst with Boscan crude oil. Catalyst deactivation was measured with an accelerated method. The HDM catalyst shown in Figure 6 was the catalyst used as pretreatment catalyst in Catalyst System A. HDS activity, expressed as a reaction rate constant Ks, decreased with increasing MOC. After the point at about 43 wt% of MOC was reached, catalyst activity decreased faster. This point is the breakpoint of the catalyst and the MOC at this point was suggested as the metal capacity. This MOC level was nearly equal to those shown in Figure 5. Cosmo CF-500 series catalyst has been developing for a higher metal capacity.

Figures 5(a) and 5(b) show the simulated breakthrough curves of both total protein and HSV-1 respectively. It should be noticed that the dimensionless time scales in these two figures differ by four orders of magnitude. The breakpoint of HSV-1 is the operating endpoint at which the effluent from the adsorption column can no longer meet the desired sterilization criterion. Since the HSV-1 has a much higher affinity to the bead surface, the breakpoint of HSV-1 appears much later than that of the total protein. To optimize the protein recovery, one should improve the design of the bead surface (better selectivity, higher loading capacity), size, and operating parameters of the filter to further delay the breakpoint of the virus elution. A stochastic approach to model the removal process may be more appropriate in low concentrations of viruses.

If half the bed capacity is used at the breakpoint, a bed 2.2 ft long would suffice. Then a rectangular bed 2 - 3 ft deep could be placed in the middle of a horizontal cylindrical vessel. This would be less expensive than a 23.6-ft diameter cylindrical bed. 

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