TABLE OF CONTENTS In order to better obtain an understanding of how demineralizers are sized, resin volumes calculated, regenerant dosages determined, and how the constituents of the feed water affect the quality of the effluent, we will perform design calculations for a SAC/SBA demineralizer using resins supplied by a leading manufacturer. The demineralizer will be sized to produce 100 GPM of effluent at a 16hour service run time.
Before starting, a point should be made about the terms used for ion exchange capacities. In the United States, the common value selected for exchange capacities is kilograms per cubic foot, while in Europe the capacities are expressed as equivalents per liter or milliequivalents per milliliter. Some of the following charts indicate both. The example calculations listed below are all based on grains and kilograms.
Assume that inltuent water to the demineralizer has the composition outlined in Table 5-2. Silica is 10 ppm. (Note: Debate seems to exist over whether silica should or should not be considered an anion in water balance calculations. I have left it out of the table, but dissolved silica behaves as an anion in anion exchanger beds and is considered as such in the following anion exchanger calculations.)
| Cations | Concentration (ppm as CaCO 3) | Anions | Concentration (ppm as CaCO 3) |
|---|---|---|---|
| Sodium | 100 | Bicarbonate | 80 |
| Calcium | 50 | Chloride | 70 |
| Magnesium | 50 | Sulfate | 50 |
| Total | 200 | 200 |
At this point, the manufacturer's literature must be used to determine resin...
