Hazards of poor water quality for boilers

Poor water quality means that the water contains more harmful impurities. If this water is not treated, it will bring the following dangers when entering the pot:

1. Accumulation

After heating in the pot, the boiling and evaporation of water can cause chemical reactions and continuous enrichment of impurities in the water. When the impurities are saturated in the pot, solids will be released. If the separated solid is suspended in boiler water, it is called water slag; If they firmly adhere to the heated surface, they are called scale.

The hazards of boiler scale can be found in Chapter 2.

2. Corrosion

Another danger of boilers is metal corrosion caused by poor water quality. Its impact is as follows:

(1) Components such as coal economizer, water-cooled wall, convection tube bundle, and damaged metal components of boiler drum may cause corrosion due to poor water quality. As a result, these metal components become thinner, recessed, and even perforated. More severe corrosion (such as caustic brittleness) may lead to damage to the internal structure of the metal. Corrosion of metals leads to a significant decrease in strength. This seriously affects the safe operation of the boiler, shortens its service life, and causes economic losses. Especially for hot water boilers, due to too much circulating water, if the corrosion of the boiler is not treated, it is a serious problem.

(2) Adding metal corrosion products (mainly iron oxide) forms scale in boiler water. After the boiler water is transferred to the heating surface of the boiler, it is easy to form scale with other impurities. When the scale contains iron, the heat transfer effect is poor. For example, a 1-millimeter thick scale containing 8% iron mixed with silica will result in heat loss equivalent to a 4-millimeter thick mixed scale. Therefore, the scale contains iron corrosion products, which greatly reduce the thermal conductivity.

(3) The occurrence of underground corrosion scale containing high-speed rail can easily cause corrosion between metallic iron and scale, and the corrosion products of iron can easily turn into scale, forming a vicious cycle that quickly leads to damage to boiler components. It is particularly harmful to fuel, gas boilers, and metal corrosion products.

Boiler corrosion, especially boiler pressurization, has been solved. Without anti-corrosion measures and equipment, metal corrosion has become a very prominent and serious problem. It not only causes premature wear and tear of boilers, but also easily leads to various accidents, posing a threat to safety production. According to incomplete statistics, more than 1000 boilers in China are scrapped every year due to corrosion.

3. Water foam in the pan

On the steam interface of the cylinder, steam and water cannot be separated quickly. During the boiling and evaporation of boiler water, the liquid surface forms foam, and a large number of water drops are released after the foam film breaks. These water drops with high salt content are constantly taken away by steam. In serious cases, steam and foam enter the steam system together. This phenomenon is called steam water condensation. This situation occurs when the pot contains more sodium chloride, sodium phosphate, fat, and silicates, or when the organic matter in the pot is washed away by alkaline solution. Boiler foaming may cause the following hazards:

(1) Serious steam pollution:

(2) Salt accumulation occurs in the pipelines of the superheater and steam pipeline, which may cause blockage in severe cases;

(3) The temperature of superheated steam decreases;

(4) The water meter is filled with bubbles, making it difficult to identify the liquid level;

(5) The formation of water hammer in the steam cycle system can easily cause damage to steam pipeline connections;

(6) Easy to cause corrosion of steam valves, pipeline bends, and superheaters.