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Factors Affecting The Working Exchange Capacity Of Ion Exchange Resin

Jul 18, 2020

Factors affecting work exchange capacity

  1) Factors affecting the beginning of R

   It includes the composition of the water source, impurity concentration, temperature, flow rate and requirements for the effluent water quality, the height of the resin layer, the operation mode, and the rationality of the equipment structure.

  A Resin acidity and alkalinity The weak resin has the greatest affinity for hydrogen ions or hydroxide ions, so its regeneration degree is relatively high; the strong resin is on the contrary, the regeneration degree is lower. The alkalinity of type II strong base resin is weaker than that of type I strong base resin, so under general regeneration conditions, its regeneration degree is higher and the initial capacity is also higher.

  B Regeneration agent dosage The larger the amount of regenerating agent, the higher the degree of regeneration of the resin, but as the dosage of regenerating agent increases, the extent of the increase in the degree of regeneration becomes smaller and smaller, and finally stabilizes.

  C Regeneration agent purity The degree of resin regeneration is related to the purity of the regeneration agent. It can be known from the ion exchange balance that the higher the purity of the regenerant, the higher the degree of regeneration.

  D Regeneration fluid temperature The temperature of the regeneration fluid will affect the selectivity coefficient and the speed of ion exchange, thereby affecting the degree of regeneration. The regeneration temperature of the strong base resin also affects the degree of coalescence of silicon, thereby affecting the degree of regeneration.

  E Regeneration fluid flow rate In order to ensure sufficient contact time between the resin and the regeneration fluid, the regeneration fluid flow rate must be limited. In order to prevent the precipitation of calcium sulfate and colloidal silicon during the regeneration process, it is necessary to ensure a sufficient flow rate of the regeneration solution (for this reason, the concentration of the regeneration solution is often reduced to ensure sufficient regeneration time and regeneration flow rate).

  F Regeneration Solution Concentration Under the condition that sufficient regeneration time is guaranteed without precipitation and formation of colloidal silicon, a thicker regeneration solution is beneficial to obtain a higher degree of regeneration of the resin.

  G Ion composition of spent resin The selectivity of different ions is different. Under the same regeneration conditions, the ion composition of the spent resin is different, and the regeneration degree is also different.

   2) Factors affecting R disability

  ① Total amount of ions in the water The larger the total amount of ions to be removed in the water, the higher the working layer height and the higher the residual regeneration degree.

  ② Ion composition in water The greater the affinity of the ions to be removed with the resin, the lower the resin residual capacity. This is detrimental to regeneration. Therefore, for certain processes (such as countercurrent, downstream) and certain regeneration conditions, the composition of counter ions in water has the largest exchange capacity under a certain ratio. The larger the ratio of the ions with the same name (and the ion opposite to the ion charge to be removed) that can replace the ions on the resin to form dissociated substances (such as HCO3-, H+), the more favorable the exchange, the smaller the residual capacity.

  ③ Operating flow rate According to the ion exchange speed, the operating flow rate has a greater impact on the ion exchange process of weak resins. The height of the working layer increases with the increase of the flow rate, so the residual capacity also increases. The residual capacity of the strong resin is less affected by the flow rate.

  ④ Operating water temperature Like the operating flow rate, temperature has a greater impact on the ion exchange of weak resins. The higher the operating water temperature, the lower the residual capacity.

  3) Resin layer height

   Viewed from the entire resin layer, the residual capacity distribution is uneven. The residual capacity of resin in the working layer at the water outlet is the largest. When running under certain conditions, the height of the working layer is related to the height of the resin layer. Therefore, the greater the height of the resin layer, the greater the working exchange capacity.

  4) Properties of resin

"Except for the height of the resin layer, each item mentioned above is related to the properties of the resin itself, which includes the total volume exchange capacity of the resin, the selectivity coefficient and the kinetic properties (these have been introduced previously).

   As far as the exchange of a pair of ions is concerned, the working exchange capacity of the resin is affected by the above-mentioned factors, some of which cannot be expressed by a simple mathematical relationship, and the factors cross-influence each other. When there are several kinds of ions that undergo ion exchange at the same time, and the exchange results in the formation of difficult-to-dissociate substances, the ion exchange phenomenon becomes very complicated. In actual operation, the ion exchange equipment will also have uneven water flow distribution, and the resin regeneration and failure degrees at each point on the same level are also different. After the resin is used for a period of time, its performance will change to a certain extent or be polluted to a certain extent. All these make it difficult to quantitatively describe the working exchange capacity of ion exchange resins.

  5) Measurement results under standard conditions

According to the above, the working exchange capacity measured under different conditions is not comparable. Only the working exchange capacity measured under a unified standard condition (such as the uniform condition specified by ASTM) can be comparable and can be used to compare different productions. Factory products.