water quality management to ensure safer and more efficient boiler operation
Water is the main medium used in boilers, and the level of water quality management directly affects the safety and economy of boiler operation. Due to the high level of specialization in boilers, water quality management has always been a key and difficult issue in boiler management. To help more aquaculture friends do a good job in water quality management, this article will provide a detailed analysis of the hazards and prevention methods of poor boiler water quality
1,The hazards of poor water quality
Unpurified natural water contains many impurities. If this water directly enters the heated water system, it will cause various hazards, which are manifested in the following aspects:
Formation of scale
Water that has not been softened or purified directly enters the boiler and heat exchange. After a period of operation, solid attachments will be generated on the heating surface in contact with water. This phenomenon is called scaling, and these solid attachments are called scale.
Scaling poses a significant threat to boilers:
On the one hand, the thermal conductivity of scale is a hundred times worse than that of metals, and it is extremely easy to form on metal surfaces with high heat loads, such as the water side of furnace tubes and pot shells. Scaling can cause the temperature of the metal pipe wall at the scaling site to be too high, leading to a decrease in metal strength. Under the pressure inside the pipe, local deformation of the pipeline can occur, resulting in bulging and even serious accidents such as pipe bursts.
On the other hand, the generation of scale can also reduce the flow area inside the tube, increase the flow resistance of the circulation inside the tube, and in severe cases, even completely block it, disrupting the normal water circulation of the boiler, hindering heat transfer inside the boiler, and reducing thermal efficiency. In addition, scale can increase the failure rate of boiler equipment, consuming a large amount of manpower, material resources, and financial resources.
Corrosion
Poor water quality can also cause boiler corrosion, mainly in the following three situations:
(1) Oxygen corrosion: Its characteristic is localized pitting corrosion, with strong corrosion penetration, which poses a great threat to the safe operation of boilers.
(2) Caustic embrittlement: Excessive alkalinity of boiler water can lead to severe embrittlement, which can damage the metal structure and reduce the strength of the boiler metal. This phenomenon is called alkaline embrittlement.
(3) Corrosion under scale (iron corrosion): Iron ions in the boiler water will form high valent iron scale in the boiler, which can accelerate the corrosion of metal iron under the scale and generate new scale, forming a vicious cycle of iron corrosion. Therefore, the country has provided clear standards for the iron ion content in the combined water of the boiler in the boiler water quality standards.
Priming
The phenomenon of priming is also one of the boiler accidents, mainly caused by high levels of dissolved solids, fats, and organic compounds in the boiler water. Its main harm is that the steam is severely polluted, resulting in a decrease in steam quality and even unusable; The foam on the water level gauge can not accurately display the water level, which makes the automatic water level control system malfunction and endangers the safety of the boiler.
2, Methods for preventing the impact of poor water quality on boilers
Strengthen water quality management to prevent boiler scaling
Methods to prevent oxygen corrosion are mainly thermal deoxidizer, desorption deoxidizer and chemical deoxidizer, etc. Generally, thermal deoxidizer is more effective and the method is simple and practical. Feedwater dissolved oxygen control in 0.05-0.1mg / L or less, for 6T / h below the low-pressure boiler is not conditional on the setting of thermal deoxidizer, the most ideal method is to make up the softened water and pot furnace water conditioning combined with control of the furnace water alkalinity shall not be less than 8mmol / L, PH value is greater than 10, but can not be more than 13, the use of the correct method of sewage.
Prevent acid corrosion
Maintain the furnace water alkalinity, not less than 8mmol / L, from time to time to monitor the furnace water PH value is not less than 10 .
If it does not reach the standard value, can be adjusted with alkaline agents, you can also use neutral alkali adjustment, the method is: calculated in accordance with the boiler water volume, per ton of water plus 4 kg of neutral alkali or no more than 2 kg of strong alkali adjustment, with pH test paper to standard range can be detected.
Prevent priming
Control the salt concentration of furnace water, increase the number of sewage, pipeline low installing a water trap, the furnace water laboratory, if there is a high fluoride and high iron ion phenomenon, to decomposition treatment or purification process, if the use of iron make-up water tanks or many years of water tanks have not been descaled, should be immediately replaced with stainless steel water tanks.
Chemical cleaning
To do a good job of chemical cleaning of new boilers and operating boilers.For new boilers, before use, must use alkaline agents to remove rust boiler, time control in 24-48 hours, the furnace sediment, oil, rust, etc. to remove, while forming a protective film.For the boiler has been running should also be used to drug descaling, rust removal, the specific method should be based on the thickness of scale and rust condition, to develop a corresponding
cleaning program.
The above is due to the harm caused by poor water quality and treatment methods, these hazards will not only affect the energy costs, affect the operation of equipment, and even cause safety accidents when the situation is serious. Breeding friends must pay great attention to water quality management to ensure that the boiler safe, economical and efficient operation.
