CS262355B1 - Method of performing ion exchange - Google Patents

Abstract

A method of performing ion exchange with regeneration of the ion exchange system, in which the treated liquid flows from bottom to top through a combination of fluidized and solid ion exchange beds, where before regeneration the solid and fluidized ion exchange bed portions are mixed with water or water and air, the mixed solid and fluidized ion exchange bed portions are regenerated together and from the thus regenerated ion exchange, a combination of fluidized and solid ion exchange beds is again formed by the flow of water from bottom to top.

Description

The invention relates to a method for carrying out ion exchange and is particularly intended for softening water with a strongly acidic cation exchanger.

At present, most of the ion exchange softening devices operate with a co-current regeneration process. The regenerating agent, sodium chloride NaCl, is regenerated through a pressure filter with a strongly acidic cation exchanger from top to bottom, in the same direction as the treated water during the working period. This method, the so-called co-current regeneration, leads to a relatively high consumption of NaCl for regeneration. It is known that NaCl savings can be achieved by countercurrent regeneration, in which the regenerative agent during the regeneration is conducted in the opposite direction than the treated water during the working period.

However, existing methods of softening water with countercurrent cation exchange regeneration have some serious drawbacks. In a countercurrent process with a bottom-up cation exchanger regeneration, the filter must be equipped with a central grate for draining the waste regenerant, which complicates the filter design or filled the entire filter with an ion exchanger or ion exchanger and internal matter. Moreover, this countercurrent process is demanding for water pretreatment because washing the cation exchanger bed prior to regeneration undermines the bottom-up countercurrent regeneration effect. Therefore, it is necessary to reduce the content of suspended matter in the incoming water by suitable pretreatment to such an extent that the washing of the cation exchanger bed is carried out only periodically.

That's expensive. Another method is a countercurrent system with cation exchanger regeneration from top to bottom and water flow during the bottom-up working period through a fluid cation exchanger bed. The design of the filter is simple, but the disadvantage is that it is necessary to use a relatively low filtration (rising) speed during the working period or a cation exchanger with a larger grain size in order to prevent the cation exchanger from escaping from the filter. The last countercurrent process is a bottom-up exhaustion through a partially fluidized, partially fixed ion-exchange bed, wherein regeneration is carried out from a top-down fixed ion-exchange bed. The disadvantage of this method in water softening is the higher demands on water pretreatment, since the ion exchange column in this method is filled with an ion exchanger from 80 to 90% and periodic washing is carried out in an additional external column. In summary, the current processes for softening countercurrent regeneration water have some major drawbacks in wider industrial applications, so that up to now countercurrent regeneration softening systems have been used only sporadically, especially for large installations and for waters with extremely high hardness and high salt content. .

According to the present invention, the above-mentioned drawbacks are solved by an ion exchange process with an ion exchange system regeneration wherein the treated liquid flows from bottom to top through a combination of a fluidized bed and a fixed ion exchange bed. SUMMARY OF THE INVENTION The principle of the invention is that prior to regeneration, the solid bed of the ion exchange bed is mixed with water or water with air, the mixed portions of the solid bed and the fluid bed are regenerated together. .

The advantage of the process according to the invention is the lower consumption of NaCl for cation exchange regeneration, with low demands on water pretreatment in terms of the content of suspended matter. Another advantage is the simple construction of the ion exchange filter, lower energy consumption for pumping due to lower pressure loss of the ion exchange bed, less own water consumption for washing and washing and reduced salt content in waste water.

The following example illustrates the practice of the present invention. A 150 mm glass column was packed with 15 L of strongly acidic cation exchanger. The column was equipped with a jet bottom at the top and bottom. The cation exchanger was pumped out of tap water with a hardness of 3.6 mmol / l (meaning millimol chemical equivalents) from bottom to top at a flow rate of 300 l / h, corresponding to a specific load of 20 l / h.l and a filtration rate of 19.5 m / h. After exhaustion of the cation exchanger, the cation exchanger bed was mixed simultaneously with water and compressed air, the waste water containing suspended substances was discharged from the filter through the upper nozzle bottom. This was followed by regeneration of 10% NaCl at a dose of 100 g / l cation exchanger for 45 minutes. After regeneration, the regenerant was displaced and the cation exchanger was washed from top to bottom with raw water, and then the cation exchanger was pumped from bottom to top with tap water at a flow rate of 300 l / h. At this flow rate, the upper part of the cation exchanger bed was pressed onto the upper nozzle bottom as a fixed bed, the lower part of the cation exchanger bed was in a fluidized state. Several cycles were thus performed. During the next few cycles the water flow was reduced to 77 l / h during the working period, which corresponds to a filtration (downward) speed of approx. 5 m / h. On the other hand, at this flow rate, the lower part of the ion-exchange bed is in the fixed, the upper part in the fluidized bed. In both of these procedures, the same results in terms of penetration and useful capacity were achieved. The results are shown in Tab. 1.

The method of the invention

Standard procedure

Regeneration dose

NaCl in g / l cation exchanger 100

200

Useful mole / cation capacity 1.1

1,2

Residual hardness of treated water mmol / l 0.03

0.03

Regenerate Consumption in% Stoichiometry

Claims (1)

Method for performing an ion exchange with an ion exchange system regeneration, wherein the treated liquid flows from bottom to top through a combination of a fluid and a fixed ion exchange bed, characterized in that before regeneration the solid and fluid ion exchange bed is mixed with water or water and air. The beds are regenerated together, and from this regenerated ion exchanger, a combination of a fluidized bed and a solid ion exchanger bed is again formed by flowing water from the bottom up.