Because scale formation is related to many factors such as the composition and nature of feed water and pot water, the structure of the boiler, and the operating conditions of the boiler, the scale is greatly different in composition. According to its chemical composition, scale can be roughly divided into the following types.
1 , carbonate scale
The carbonate scale is mainly carbonate of calcium and magnesium, and is mainly composed of calcium carbonate, which is more than 50%. Calcium carbonate is mostly white and yellowish. Due to the different conditions of the birth, it can be hard and dense hard scale, which is often found in the hot high-strength part; it can also be loose soft scale, which is often found in low temperature parts, such as the province of boiler. Coal, water inlet, etc. Generally, hot water boilers are mostly carbonate scale.
The carbonate scale is mostly soluble in 5% hydrochloric acid solution, and a large amount of bubbles are generated at the same time. After the reaction is completed, the insoluble matter in the solution is small.
2 , sulfate scale
The main component of the sulfate scale is calcium sulfate, which is more than 50%. Sulfuric acid salt scale is mostly white, but also yellowish, especially hard, dense, and feels smooth. This scale is often formed on the evaporation surface where the temperature in the boiler is high and the evaporation intensity is large.
Sulfate scale rarely produces bubbles in hydrochloric acid solution, and dissolves very little. After adding 10% cesium chloride solution, a large amount of white precipitate is formed.
3 , silicate scale
The composition of silicate scale is more complicated, the content of silica in scale can reach more than 20%, the silicate scale is mostly white, the surface of scale is thorny, it is a very hard scale, and the scale is easy to be in boiler temperature. The high part of the zui is born, and its main component is wollastonite or forsterite.
The silicate scale is not dissolved in hydrochloric acid, and the other components are partially dissolved slowly after heating, and there is a precipitate of a transparent state of sand, which is slowly dissolved by adding 1% HF.
4 , mixing scale
The mixed scale is a mixture of the above various scales, and it is difficult to indicate which one is the main component. Mixed scale and color, can be seen in the level, mainly due to the use of different water quality or different water treatment methods, and more knotted at the junction of the high and low temperature areas of the boiler.
The mixed scale can be mostly dissolved in dilute hydrochloric acid, and bubbles are also generated, and there are fragments or muds of residual scale in the solution.
5 , iron oxide scale
The main component of iron oxide scale is iron oxide, which is mostly caused by the high heat load of the boiler.
On the hot side, it is sometimes generated in the water wall tube and the smoke tube. The outer surface of the iron oxide is often brown and the inner layer is gray.
Iron oxide scale plus dilute hydrochloric acid can be slowly dissolved, the solution is yellow-green, and nitric acid can dissolve quickly, and the solution is yellow.
6 , grease
The grease composition is complex, but the oil content is above 5%. The oily scale is mostly black, hard and soft, and the surface of the scale is not smooth. It is often found in the higher temperature part of the boiler.
The oily scale was ground and the solution was yellow-green after adding diethyl ether.
The above is only a rough classification of scale. In fact, the composition of scale is very complicated. To determine its specific composition and structure, it must rely on composition analysis and phase analysis.
Nosiheptide Feed Additives,Nosiheptide Antibiotics,Nosiheptide Growth Prompter,Nosiheptide Poultry
Shandong Shengli Bioengineering Co., Ltd , https://www.shenglipharm.com