Water Softening Equipment

　　Working Principle

　　When raw water containing hardness ions passes through the resin bed in a water softener, the calcium (Ca²⁺) and magnesium (Mg²⁺) ions in the water are exchanged and adsorbed by the resin, while an equivalent amount of sodium (Na⁺) ions is released. The water that flows out of the softener is thus softened water, free of hardness ions.

　　The exchange process is as follows:

　　2RNa+Ca2+ = R2Ca+2Na 2RNa+Mg2+ = R2Mg+2Na+

　　That is, after water passes through the sodium ion exchanger, the Ca²⁺ and Mg²⁺ ions in the water are exchanged for Na⁺ ions.

　　When a sodium-ion exchange resin becomes exhausted, it must be regenerated to restore its exchange capacity. The regenerant is a salt solution.

　　The regeneration process proceeds as follows:

　　R2Ca + 2NaCl = 2RNa + CaCl2 R2Mg + 2NaCl = 2RNa + MgCl2

　　Following the above treatment, the regeneration process involves flushing the resin bed with brine from the salt tank, which displaces the hardness ions adsorbed on the resin and carries them away in the regeneration waste stream, thereby restoring the resin’s softening and ion-exchange capacity. The specific operational sequence is as follows:

　　As water flows through the resin bed, the ion-exchange resin releases sodium ions, while its functional groups bind with calcium and magnesium ions. This reduces the concentration of calcium and magnesium in the water, thereby lowering its hardness. The hard water is thus transformed into soft water—this is the operating principle of a water-softening system.

　　When a large number of functional groups on the resin have bound with calcium and magnesium ions, the resin’s softening capacity declines. To restore its exchange capacity, a sodium chloride solution is passed through the resin. The high sodium ion concentration in the solution causes the functional groups to release the calcium and magnesium ions, which then bind with the sodium ions. This process is known as “regeneration.”

　　The operating cycle of a water softening system primarily comprises five stages: water production, backwashing, brine intake (regeneration), forward flushing, and brine tank filling. Backwashing serves two main purposes: first, it loosens the resin bed, ensuring thorough contact between the brine solution and the resin to achieve more complete ion exchange; second, it flushes out suspended solids trapped by the resin. This stage typically takes about 5 to 15 minutes. Brine intake (regeneration) involves injecting brine into the resin tank; in conventional systems, a brine pump is used for this purpose, whereas fully automatic systems employ a dedicated built-in injector to draw in the brine. In practice, allowing the brine to flow slowly through the resin bed yields better regeneration results than simply soaking the resin in brine; therefore, water softening systems generally adopt the method of slow brine flow through the resin, a process that usually lasts around 60 minutes, with the exact duration depending on the amount of salt used. Forward flushing is performed to thoroughly rinse away any residual brine, using a flow rate similar to that during normal operation to flush the resin with raw water; the final effluent from this stage should be softened water that meets quality standards. Typically, the quick flush phase lasts 5 to 15 minutes.

　　Application Fields

　　◆Petrochemical System

　　◆ Central air-conditioning cooling and chilled water circulation systems

　　◆Industrial Circulating Water System

　　Hot-water systems for steam boilers, hot-water boilers, and tea boilers

　　◆ Water softening for various industries, including light industry and textiles, food hygiene, hotels, and restaurants.