Understand the precipitation and accumulation of sediments in circulating water—scale and dirt

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1 Water scale: Water contains various salts such as bicarbonates, carbonates, sulfates, chlorides, and silicates. Among these, the dissolved bicarbonates like Ca(HCO3)2 and Mg(HCO3)2 are the most unstable; when heated or when CO2 is released, a reaction occurs that causes them to decompose into carbonates. Ca(HCO3)2 → CaCO3↓ + H2O + CO2↑. The common components of water scale are calcium carbonate, calcium sulfate, calcium phosphate, magnesium salts, and silicates. 2 Dirt: Oil stains, corrosion products, fine-grained sediment, muddy substances consisting of insoluble salts, colloidal hydroxides, and especially the dead bodies of bacteria and algae along with their sticky secretions are the main components of dirt. The most dirt accumulates in areas with slower flow rates. They are the main cause of under-deposit corrosion, and also serve as a breeding ground for certain bacteria, such as anaerobes, to survive and reproduce. 3 Hazards of scale and dirt ① Reduces heat transfer efficiency or causes uneven heat transfer. Equipment corrosion (underscale corrosion). ②It increases the pressure difference in pipeline transportation and power consumption. Reduces the performance of the corrosion inhibitor. ③Increased unplanned shutdowns at the plant. It can even lead to the direct disposal of certain devices.