Ammonia Nitrogen stripping tower

Technical Description

To strip the basic principle of the method is will air ventilation with waste water, wastewater and the volatile gases dissolved in the liquid to solute gas phase, make the waste water treatment process called get blown off. Be to remove material in liquid and gas phase difference is the concentrations of the liquid into the gas phase by driving force. To remove the basic principle of the method is gas liquid balance and mass transfer speed theory.

Used to remove ammonia nitrogen removal from the water, is the gas into the water, contentious mutual fully contact with liquid, make the water dissolved free ammonia gas and liquid through the interface, to gas phase transfer, so as to achieve the purpose of removing ammonia nitrogen. 

The water of ammonia nitrogen, mostly with ammonium ion (NH4 +) and free ammonia (NH3) the state of balance and exist. The balance equation is as follows:

NH4++OH-NH3+H2O (1)

Ammonia and ammonium ion of distribution between rate is calculated under the available type:

Ka=Kw /Kb=(CNH3·CH+)/CNH4+ (2)

In equation:Ka——Ammonium ion of ionization constants;

       Kw——Water ionization constants;

        Kb——Ammonia water ionization constants;

        C——Matter concentration.

Equation(1)is influenced by PH value, when high pH value, the balance to the right move, free ammonia larger proportion, when pH value for about 11, free ammonia roughly 90%.

By equation (2) can see, pH value is the effect of free ammonia water percentage in one of the major factors. In addition, the temperature can also affect reactive (1) balance, temperature, balance to move right. Table 1 lists the different conditions of ammonia nitrogen the calculated value of the dissociation rate. The data show that, when pH value is more than 10, dissociation rate at 80% or more, when the pH value of 11, dissociation rate is as high as 98% and subject to the influence of the temperature of little.

Different pH, temperature of ammonia nitrogen dissociation rate , see the table below:

There are many factors which can influence to strip rate, excepting gas liquid contact area and way,Gas-liquid exchange equipment, there are also properties of the waste water, water temperature, pH and ratio of gas and liquid, and so on.

Ammonia stripping usually use stripping pond and stripping tower two equipments, however, stripping pond cover big area, and easy to cause secondary pollution, so the stripping of ammonia gas often use tower type equipments.(as picture)

Stripping process application

Stripping method has been widely used in fertilizer plant wastewater and garbage leachate, such as petrochemical, oil refinery wastewater containing ammonia nitrogen. Low concentration wastewater is usually stripped with air at room temperature, while high concentration wastewater is used to blow off steam. Some high concentration wastewater after blow off treatment, still contain higher ammonia, which is often combined with other process.