Regenerant efficiency

Another possible modification is the use of seawater as the regenerant. Even though it contains calcium and magnesium, but only 2.7 wt % NaCl, it sometimes can be purified by coagulation, filtration, and chlorination less expensively than salt can be purchased. The lower concentration reduces the regeneration efficiency by 40—50%. 

There also exists a type of resin with no functional groups attached. This resin offers no capacity to the system but increases regeneration efficiency in mixed-bed exchangers. These inert resins are of a density between cation and anion resins and when present in... 

The benefit of WAC over SAC is the extremely high exchange capacity and lower (almost theoretical) regeneration efficiency. There is some additional cost in capital equipment and higher resin prices, but this is more than compensated for by lower operating costs. Weak acid cation resin capacity is flow-sensitive, so flows must match design criteria. The overall dealk/degasser/BX is the most popular IX process of its kind in the world today, followed by BX/SBA(C1). 

In practice, as softening is also required, the process train is BX/SBA(C1), and salt brine provides the regenerant for both units. Also, the quantity of SBA (Cl) regenerant is increased by 5 to 10% through the addition of NaOH solution to improve regeneration efficiencies. 

Thermodynamically, the concept is similar to thermal wave systems and predicted COP s are similar. A cooling COP of 0.9 (based on heat input to the cycle), is predicted for one design with modest regeneration efficiency, evaporating at 5°C and condensing at 40°C. 

However, the conditions are often far from those of industrial situations. In order to better simulate solvent degradation during the PUREX process, a test loop was created in the 1990s in a CEA laboratory (Fontenay-aux-Roses, France), with the EDIT loop (Extraction Desextraction Irradiation Traitement) (21, 22). The laboratory simulation of industrial conditions consisted of a succession of representative physical and chemical treatments after the irradiation of the solvent (i.e., alkali and acid treatments, distillation). Indeed, these treatments can modify the final solvent composition because of the elimination of some compounds or the occurrence of secondary reactions. A few years later, the MARCEL (Module Avance de Radiolyse dans les Cycles d Extraction Lavage) test loop was built at Marcoule to follow the regeneration efficiencies of degraded solvents involved in actinide separation processes (4, 5). 

For the microwave regeneration, firstly, put the adsorption column packed with the polymeric adsorbent on which the saturated amount adsorbed of VOCs was qo in microwave oven, and subsequently, use synchronously microwave to beat the column and N2 to sweep the VOCs desorbed from the adsorbent out. Regeneration efficiency of the adsorbent was measured every thirty seconds by weighing method until regeneration operation ended. 

Regeneration efficiency of the polymeric resin or the desorption efficiency of the adsorbate, Rj%, can be found out according to equation (2). Where q (g/g) was initial amount adsorbed of the adsorbate on the resin before regeneration, and qi (g/g) was transient amount adsorbed of the adsorbate on the resin. 

Figures 1 3 showed the comparison between the microwave and thermal regeneration. It can be seen that the application of microwave to regenerate the polymeric adsorbents can get higher regeneration efficiency than the application of the thermal regeneration method. For three kinds of the polymeric resins that had adsorbed benzene, the regeneration efficiency obtained by using microwave was up to 90%, while the regeneration efficiency obtained by using microwave was merely about 60-70%.

Fig. 4 Effect of Different Resins on the Microwave Regeneration Efficiency. Adsorbate Benzene, Nr Flow Rate 0.12 m /h.

The application of microwave to regenerate the polymeric adsorbents can not only get higher regeneration efficiency in comparison with the use of conventional heat regeneration, but also make the temperatures of the fixed beds be much lower than that when using the heat regeneration. The weaker the polarity of a polymeric adsorbent, the easier its regeneration was. 

High regeneration efficiency low selectivity small beads low crosslinking weak function resins... 

Low leakage (see Chapter 7) a compromise between high selectivity and high regeneration efficiency... 

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