Industrial boiler water treatment technology is a lot, the overall water treatment can be divided into the pot and the pot water treatment. Boiler water treatment is mainly water softening, that is, before the water into the boiler, through physical, chemical and electrochemical methods to remove calcium, magnesium hardness salt and oxygen in the water, to prevent boiler scaling and corrosion. Pot water treatment is to the boiler (or water tank, water pipeline) within the injection of chemicals to prevent or reduce the boiler scaling and corrosion purposes.

1, industrial boiler water treatment outside the pot

1) pretreatment.

Before the use of raw water should be precipitation, filtration, coagulation and other purification processes. For high hardness or high alkalinity of the raw water, in the ion exchange before softening, should also use chemical methods of pretreatment. Chemical pretreatment methods are: a. Lime softening treatment.

a. Lime softening treatment. Lime modulation into milk of lime CaO + H2O → Ca (OH) 2, configured into a certain concentration of milk of lime solution after adding water

b. Lime soda ash softening treatment. In addition to adding lime, but also add soda ash Na2CO3, its role is to remove non-carbonate hardness. The effect is to remove the non-carbonate hardness.

This method is suitable for raw water whose hardness is greater than its alkalinity.

c. Lime-plaster softening. When the alkalinity of the raw water is greater than the hardness, lime softening alone can only reduce the part of alkalinity corresponding to the carbonate hardness.

The alkalinity of the part corresponding to the carbonate hardness can only be reduced by lime softening, while the remaining alkalinity of the sodium salt can not be removed. The use of simultaneous addition of lime and gypsum (CaSO4) method, you can soften the water at the same time to reduce the sodium alkalinity of the water

2) Softening treatment.

The use of ion exchange softening, the basic principle is that the raw water flows through the cation exchange agent, Ca2+, Mg2+ water cations are adsorbed by the exchange agent.

Cations are adsorbed by the exchange agent, while the exchange agent in the exchangeable ions (Na + or H + ) is dissolved into the water, thus removing the water calcium and magnesium ions, so that the water has been softened.

3) deoxygenation.

Water is often dissolved oxygen (O2), carbon dioxide (CO2) and other gases, so that the boiler is prone to corrosion. GB1576 - 2001 evaporation capacity of ≥ 6 t / h of the boiler must be deoxygenated, and the oxygen content of the target ≤ 0.1 mg / L (the target range of oxygen corrosion rate is slow), and freshwater in the limit of dissolution of oxygen in the temperature of the water, the solubility of water is increased, the solubility decreases.

2, industrial boiler water treatment

Boiler feed water in the furnace outside the softening treatment, can effectively prevent the boiler heating surface scaling. But the need for more equipment and investment, increased personnel and maintenance costs, which is more difficult to realize some small boiler room, this time the use of water treatment in the pot. Pot water treatment is through the boiler feed water to add a certain amount of chemicals, and the formation of scale salt chemical reaction, generating loose scale precipitation, and then discharged through the sewage will be discharged from the pot, in order to achieve the purpose of slowing down or preventing the formation of scale.

1) Add alkali treatment.

Add soda ash Na2 CO3 in the steam bag as the role of chemicals, the use of excess CO2 in the water.

2) Add phosphate treatment.

When the pressure in the furnace is high, the soda ash will be hydrolyzed.

3) Adding sodium humate.

Add the role of sodium humate: sodium humate in alkaline conditions, its carboxyl group or phenolic hydroxyl group of sodium ions, can be exchanged with calcium and magnesium ions in the water, calcium phytate, magnesium precipitation and soften the water; sodium humate colloidal soluble in calcium and magnesium salts, dispersion, adsorption, complexation and other effects of results, not only to prevent the growth of crystals, but also produced by the small viscosity of the mud, mobility enhancement, easy to eliminate with the sewage Sodium humate in alkaline conditions, can be generated with the boiler metal a layer of black protective film, and the structure is close, covering uniform, strong adhesion, is a good corrosion protection film; sodium humate has a strong penetration effect, it can penetrate into the scale and metal contact surfaces, and calcium, magnesium salts occur complex decomposition, so that the old scale and the adhesion of the metal surface is reduced and fall off.

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