Factors affecting air flotation white water recycling

The main factors that affect the recovery of air flotation white water are: the quality of dissolved water, the amount of dissolved water, the pH of white water, the addition of flocculant, the level of dissolved air tank and starching cycle.

1. PH Value of White water

If the PH value is low, flocculation effect of white water solid will be poor, and effluent will be relatively turbid. In addition, when the PH value is less than 5, the bubble rise speed will be fast, and stay in white water for a short time, affecting the air float effect.

It is generally thought that when processing paper white water with air float method, PH value must be greater than 7. In fact, PH value is generally controlled at 6.6 ~ 7.2. Some plants which have limited original white water conditions, need to add NaOH to adjust the PH value to be the best. But too high PH value will also affect the air float effect.

2. Flocculant

Flocculant’s role is to form vanadium particles, to promote fiber flocculation, to improve air float efficiency. Without adding flocculant, suspended solids removal rate is generally 60 ~ 70%, and clarified water is relatively turbid; adding a certain flocculant (alkali or aluminum chloride), suspended solids removal rate can be up to 90%, and when flocculant dosage is increased, suspended solids removal rate increases.

Added flocculant must be fully mixed to ensure that there is a certain chemical reaction time to ensure the air flotation effect, the chemical reaction time is generally 15 to 30 minutes.

3. Dissolved water consumption and quality

Increasing the amount of dissolved water can improve the air float effect, but not too much to increase the air floating load. In general, the amount of dissolved water is 15 to 20% (for treated water). The quality of dissolved water is an important factor in determining the effect of air floatation.

4. Dissolved tank water level

Water level fluctuations of dissolved water tank affects the efficiency of air floatation. When the water level is too low, the clarified water becomes turbid. Therefore, it is necessary to control and stabilize the water level of the dissolved water tank.In production practice, it is generally through adjusting blowoff valve of dissolved water tank to control and stabilize the water level of dissolved tank.

5. Starching cycle

The longer the starching cycle is, the thicker the slurry layer will be, and the higher the concentration will be, which is conducive to the storage and utilization of the slurry, and white water recovery effect will be good. If the cycle is too long, the slurry layer is too thick, it will affect starching operation; and if the cycle is short, starching time are too much, it will affect the clarity of clear water.