Cause of Boiler Scale Formation

 

A boiler is a device for heat exchange of water as a medium. During operation, the surface of the boiler contact with water will form thick scale. Then, how is the scale in the boiler formed? The main reasons are the following three aspects:

1. The impurities in the boiler feed water into the boiler, after continuous evaporation and concentration, the concentration of salt in the boiler feed water is continuously increased to reach saturation or over saturation, and the precipitate from the surface of the boiler metal will be precipitated.

2. With the increase of water temperature in the boiler, the solubility of some salts is inversely proportional to the temperature. When the temperature rises, the solubility of the salts drops sharply and forms the scale.

3. Different salts interact or decompose by heat to form insoluble compounds.

In the process of continuous water supply and continuous evaporation of the boiler, the pure water is turned into steam by the boiler, and the salt substance in the water of the furnace is concentrated and the content is increasing. When the salt content of the boiler water reaches saturation or supersaturation, the salts will precipitate from the water and generate solid sediments. The production of scale is not only related to the composition and content of impurities in the boiler feed water, but also depends largely on the running state of the boiler. The greater the evaporation strength of water and the higher the circulation rate, the more easy to produce loose sediment which is easily destroyed by water circulation, and reduce the amount of the aggregation of the scale on the evaporation surface of the boiler. On the contrary, the smaller the evaporation intensity and the lower the circulating rate, the easier it is to form scale on the evaporating surface of the boiler.