Methods for cleaning boiler scale

I believe many people must know that there are many small boilers in chemical plants and industrial parks. Boilers are generally used to process steel, melt steel, and process steel into alternative shapes. However, many people need to clean the boilers during use. If you do not pay attention to maintenance, cracks will appear in the boilers or scale will form in the boiler parts, which will cause the boilers to explode and affect personal safety. So what are the methods for cleaning boilers?

About 40% of industrial boilers have no feed water treatment facilities, especially small evaporation capacity boilers. Even if some have water treatment equipment, sometimes the water treatment facilities are useless due to improper operation or no management. There is still varying degrees of scale formation in the furnace. Judging from the inspection situation in Zhangzhou City in 2007.

More than 60% of the boilers tested had unqualified scale, and a considerable number of boilers had scale thickness of 1 to 3 mm, and some even as high as 8 mm or more. These boilers not only consumed a lot of energy, but also seriously endangered the safe operation of the boilers. The following are several aspects to explain the generation and harm of boiler scale:

1. Formation of scale

The feed water containing impurities enters the boiler without being treated. After the boiler has been running for a certain period of time, it undergoes continuous evaporation and concentration. When the concentration of impurities (dissolved solids) in the boiler water reaches saturation, precipitation will occur. A layer of white hard skin adheres to the boiler drum and tube wall, which is called scale. The main reason for the formation of scale is that the boiler feed water contains calcium and magnesium salts with low solubility, which is the so-called hardness.

The precipitates generated by calcium and magnesium salts in the boiler exist in two forms: one is the formation of hard scale, which is firmly attached to the tube wall and the boiler drum wall. Another type is the formation of sediment, which may adhere to the wall or be suspended in the water. It can be divided into two types: ① Mobile sediment; this type of sediment can be discharged by sewage discharge methods. ②Sticky sediment. It is easy to adhere to places where the pipe slope is small or the water flow rate is low, forming secondary scale.

1.1 The formation process of primary scale

1.1.1 Thermal decomposition

After the feed water containing hardness enters the boiler, during the heating process, some calcium and magnesium salts decompose due to heat, causing the water-soluble substances to transform into solid crystals, which adhere to the boiler steel plate and form scale.

1.1.2 Reduced solubility

Some scaling substances such as CaSO4, CaSiO3, etc. It is a substance with a negative solubility coefficient, that is, its solubility decreases with increasing temperature. Therefore, it is very easy to deposit as scale on the highest temperature part of the evaporation surface.

1.1.3 Mutual reactions

The salts with low solubility in the feed water react with other salts under the individual conditions of the boiler to form insoluble compounds.

1.1.4 Evaporation and concentration of water

Due to the continuous evaporation and concentration of boiler water, the concentration of dissolved salt in the water continues to increase. When it reaches the level of supersaturation, mother crystals are precipitated on the evaporation surface or the original scale particles are used as crystallization centers. Grows as scale.

Before cleaning the scale, we first need to understand the cause of the scale formation. First of all, is it because the scale has become hard due to incomplete cleaning after cleaning, or is it because the water is too dirty and the sediment accumulated? We can ask professionals to clean the crystals in the boiler or the scale in the boiler to avoid making decisions on our own.