Boiler scale will cause the following dangers
1. Waste of fuel
Once the boiler is scaled, the heating transmission surface area will be reduced. Thermal performance deteriorates, and the heat released by fuel combustion cannot be transferred to the boiler water in time. A large amount of heat is carried away by the combustion gases, causing the exhaust gas temperature to be too high. exhaust smoke losses increase, the thermal efficiency of the boiler decreases. In order to maintain boiler ratings, more fuel must be added, thereby wasting fuel. Approximately 1 mm of scale wastes 10% more fuel.
2. The heating surface is damaged
A limestone boiler cannot quickly transfer the heat of combustion from the fuel to the boiler water due to malfunction.uv heat transfer. performance, causing an increase in the temperature of the furnace and combustion gases. Therefore, the temperature difference on both sides of the heating surface increases, the temperature of the metal wall increases, and the resistance decreases. Under the action of pressure in the pot, swelling or even explosion occurs.
3. Reduce the boiler power
Once the boiler is scaled up, due to poor heat transfer performance, more energy must be consumed to achieve the nominal evaporation capacity, but as the scale thickness increases, the furnace volume is certain and fuel consumption is limited. The power of the boiler will therefore be reduced.
4. Corrosion
4.1. Metal damage: oxygen, acidic and alkaline substances contained in water will corrode the metal surface of the boiler, renIn the thicker wall, thinnings, dents and even perforations reduce the resistance of the boiler and seriously affect its safe operation. Especially for hot water boilers, the amount of circulating water is large and corrosion is more serious.
4.2. Produce corrosion under scale: Scale containing high-value iron can easily cause corrosion of metals in contact with the scale. Iron corrosion products can easily form scale again. This is a vicious circle that will quickly damage boiler components. In particular, metal corrosion products from oil-fired boilers are more harmful.
5. Co-evaporation of soda and water
In addition to improper operation, the reason for the co-evaporation of soda and water is that The Boiler water contains a large amount of sodium chloride and phosphoric acid.When sodium, fat and silicon compounds are added, or when organic matter and alkalis in the pot water are saponified, foam will be generated on the surface of the liquid during boiling and evaporation some water. water from the pot, forming a co-evaporation of soda and water.
6. Destroy the water cycle
Boilers are divided into natural circulation and forced circulation. The quantity of water circulating in the different boilers must be balanced, whatever. it goes up or down. The tubes must have sufficient cross section. When scale forms on the inner wall of the furnace tube, it will directly cause the cross-sectional area of the tube to be reduced and increased. resistance to water vapor, destroying the normal circulation of boiler water and causing an increase in the temperature of the heated metal wall. WhenThe pipe is blocked by scale. If water circulation stops, the local boiler tube will vaporize due to the increase in tube temperature. , leading to excessive combustion or tube explosion accidents, which directly threaten the normal operation of the boiler.
Once the boiler is scaled, it must be removed, otherwise the safe and economical operation of the boiler cannot be guaranteed. At present, chemical descaling is generally used to remove scale, and the scale is removed by stripping. The thicker the scale, the greater the quantity of medicine required, the greater the labor and capital invested, and the shorter the life of the boiler.
Methods for removing scale: Different types of boiler scale are also different, and different descaling methods are developed for different boilers.
Carbonaceous scale is mainly composed of calcium carbonate and a small amount of magnesium carbonate. Calcium carbonate is mostly white and some is slightly yellow. Due to the different formation conditions, it may be hard and dense scale, which is mainly formed in parts with high heat intensity, it may also be loose soft scale, which is mainly formed in parts with high heat intensity. relatively low temperature, such as energy; -saving boiler appliance parts, water inlet pipe, etc. Generally, hot water boilers are mainly made of limestone. Most limescale is soluble in a 5% hydrochloric acid solution and a large number of bubbles will be produced when the reaction is complete, there will be very little insoluble material in the solution.
Sulfate scaleThe main component est calcium sulfate. Sulfate scales are mostly white, some are slightly yellow, and are particularly hard, dense, and smooth to the touch. This type of scale usually forms on the evaporation surface with the highest temperature and evaporation intensity in the boiler. Sulfate scale rarely bubbles and dissolves very poorly in hydrochloric acid solution. After adding 10% barium chloride solution, a large amount of white precipitate is generated.
Silicate flakeThe main component is xonotlite or forsterite; the other is soft magnesium silicate, the main component is serpentine. The silica content of this balance is greater than 20%. Silicate scale is insoluble in hydrochloric acid. After heating, some of its components slowly dissolve and there is a transparent sand precipitate. It can be slowdissolved by adding 1% HF.
Phosphate scaleThe appearance is gray-white and the texture is relatively loose. Phosphate scale has poor adhesion and is easy to remove by brushing, scraping and other methods. Phosphate scale in parts not exposed to heat is soft and accumulated. Phosphate scale becomes significant as the heat flow intensity of the heating surface and the metal temperature increase, and the scale becomes hard and difficult to remove.
Mixed scaleThis is a mixture of the above types of scale, and it is difficult to say which one is the main ingredient. Mixed scale is mixed in color and can be seen in layers, which is mainly due to the use of different water qualities or different water treatment methods. Most scales form at the junction of the high and low temperature zones of the boiler.Most of the mixed scale can be dissolved in dilute hydrochloric acid, bubbles will also be produced and there will be fragments or sludge of residual scale in the solution.
You can drink it, it's no problem.
The presence of scale indicates that the water is hard. Generally speaking, this water contains soluble metal salts. In other words, this water contains more minerals.
If hard water is boiled, the minerals dissolved in the water will be analyzed by heat, and finally fixed to the periphery of the kettle. Of course, if the scale builds up too much, it will affect the use of the kettle.
However, as long as this hard water has been boiled, it is generally good and can be drunk.
Because as long as it is boiled, most of the things in the water will turn into scale. The remaining water is relatively clean and poses no problems.