After operating for a certain period of time, a layer of white scale adheres to the inner and outer walls of the spiral plate heat exchanger. The main reason for the formation of scale is the presence of calcium and magnesium salts with low solubility in water. These salts have a common characteristic: their solubility decreases as the water temperature rises, and they become insoluble salts. The presence of these salts can have the following consequences for the heat exchanger
After the heat exchanger has operated for a certain period of time, a layer of white scale adheres to the inner and outer walls of the heat exchanger. The main reason for the formation of scale is the presence of calcium and magnesium salts with low solubility in water. These salts have a common characteristic: their solubility decreases as the water temperature rises, and they become insoluble salts. The presence of these salts can have the following consequences for the heat exchanger:
1. Scale has poor thermal conductivity, with a thermal conductivity 30 to 50 times lower than that of steel. The presence of scale deteriorates heat transfer on the heating surface, thus preventing the heat transfer surface from achieving the desired temperature drop. According to relevant
information, experiments have shown that the efficiency of a heat exchanger will decrease by about 10% when 1mm of scale is formed
2. Scale attached to the heat transfer surface is difficult to remove, increasing maintenance costs. It not only consumes manpower and material resources, but also damages the heating surface and reduces the lifespan of the heat exchanger
3. After the formation of scale, it reduces the flow cross-section inside and outside the heat transfer surface, increasing the flow resistance of the circulating water inside and outside the heat transfer surface. In severe cases, the flow cross-section becomes very small, or even completely blocked, preventing the heat exchanger from operating normally
To prevent the occurrence of the above consequences, design units or operating units currently often adopt methods such as dosing softening treatment, magnetization and ion rod anti-scaling treatment, and sodium ion exchange treatment. To facilitate a deeper understanding of these softening treatment methods, the principles, formulas, and operation methods of these treatment methods will be introduced separately below
1. Dosing and softening treatment
Dosing softening treatment, characterized by its simplicity, high efficiency, cost-effectiveness, and the elimination of the need for specialized water production equipment, is a highly practical anti-scaling water treatment method. Depending on the dosing method, it can be divided into two types: correction agent treatment and anti-scaling treatment
II. Magnetization Anti-scaling Treatment
The principle of magnetization anti-scaling treatment is to utilize the polarity of water molecules, which means water molecules are covalent compounds. The individual molecules of water are aggregated into bimolecular complexes (H2O)2 or polymolecular complexes (H2O)n through the effects of polarity and hydrogen bonding. When water flows through a high-intensity magnetic field, the interaction between the polymolecular complexes and the ionic magnetic field disassembles the originally single or short-bonded complexes composed of multiple ions into individual or short-bonded complexes. These complexes cut the magnetic field lines of the external magnetic field vertically at a certain speed, generating induced current
Therefore, each ion establishes a new magnetic field in the same direction as the external magnetic field. Adjacent ion molecules with polarity compress and attract each other in an orderly manner, leading to changes in crystallization conditions. The resulting crystals are very loose, with poor compressive and tensile strength, and are very brittle. Their bonding and adhesion forces are also weak, making them difficult to adhere to heated surfaces and form scale
III. Ion-stick anti-scaling water treatment
Ion rod anti-scaling water treatment is a type of water treatment equipment. It is a patented product from the United States in 1987, and was introduced by Changsha York Water Treatment Company. Its application in hot water circulation systems, central air conditioning systems, and circulating cooling water systems has achieved satisfactory anti-scaling effects