Pretreatment method and regeneration method of Lanlang mixed bed resin

1. Pretreatment of ion exchange resin
Before pretreatment, the water level in the exchanger should be lowered to 400~500mm on the resin surface, the pressure of compressed air is generally 0.1-0.15MPa, the flow rate is 2.0-3.0m3/(m2.s), and the air scrubbing time is 10min. The aim is to eliminate the electrostatic adhesion of the new resin and prepare for the subsequent pretreatment and backwash layering.
Soak about 4%HCl of twice the volume of resin for 4-8h, wash with clean water until the pH is about 5, and then soak about 4%NaOH of twice the volume of resin for 4-8h.
After alkali soaking, without cleaning, directly carry out large backwashing, backwashing at the beginning, the flow rate should be small, after the resin is loosened, gradually increase the backwashing flow rate, so that the expansion rate of the whole resin layer is 50-70%, maintain about 10min, observe whether the stratification is clear. Otherwise, repeat the backwash step until the layering is clear.

2.Regeneration of ion exchange resin
①. After backwashing and stratification, water is put into about 100mm on the surface of the ion exchange resin, open the regeneration pump and middle drainage, and adjust the water balance of the liquid level through the sight mirror, and start to enter the lye and acid solution, so that they are respectively discharged through the Yangyin resin layer and through the middle drainage pipe at the same time. If the acid is finished and the lye is not finished, the lower part of the cleaning water is still passed at the same flow rate to prevent the lye from being string into the lower part and polluting the regenerated positive resin.

Then, the cleaning water is passed at the same flow rate up and down at the same time until the conductivity of the middle discharge water is less than 10μs/cm and Na+ is less than 100 PPB. After that, reduce the flow rate of the lower inlet water and clean it at the same time until the conductivity of the middle outlet water is less than 10μs/cm and Na+ is less than 100 PPB. Conversely, increase the lower inlet flow rate, reduce the upper inlet flow rate, and clean at the same time, to the middle discharge water conductivity is less than 10μs/cm, Na+ is less than 100 PPB.Finally, small washing, and then large washing, until the conductivity is less than 10μs/cm below. In the forward washing process, sometimes in order to improve the forward washing effect, a short time of 2-3min backwashing can be carried out to eliminate dead corner residues.

②. Mixing of cation and anion ion exchange resin
Before mixing, the water level in the exchanger should be lowered to 250-400mm on the resin surface, the pressure of compressed air is generally 0.1-0.15MPa, the flow rate is 2.0-3.0m3/(m2.s), the mixing time is generally 0.5-1.0min, and the resin is easy to wear if the time is too long. In order to prevent the resin from re-separating during the settlement process, and affect the mixing degree of the resin, in addition to the appropriate compressed air must be passed, it is still necessary to have a large enough drainage speed to force the resin to fall quickly and avoid the re-separation of the resin.

③. Is washing
The mixed resin layer should also be washed with dehydrated water at a flow rate of 20-30m/h until the water is qualified (SiO2 content is less than 10-20μg/l, conductivity is less than 0.2μs/cm), before it can be put into operation.

④. After the resin fails in operation, backwash stratification with water. At the beginning of backwash, the flow rate should be small, and after the resin layer is loosened, the flow rate should be gradually increased to about 10m/h, so that the expansion rate of the whole resin layer is 50-70% and maintained for 10-15min, generally achieving a better separation effect.

⑤. After the resin backwashing and lamination, the resin can be regenerated in the next cycle.