After fouling occurs on industrial heat exchangers, it can have various adverse effects on the safe production and efficient operation of the equipment. Industrial heat exchangers mainly include: boilers, sintering furnaces, smelting furnaces, heat transfer oil furnaces, high-frequency furnaces, medium-frequency furnaces, lean furnaces, reaction vessels, coolers, heaters, evaporators, condensers, surface coolers, preheaters, steam condensers, distillers, digesters, flash evaporators, filters, crystallizers, and storage vessels; absorption towers, reaction towers, regeneration towers, synthesis towers, stripping towers, cooling towers, carbonization towers, etc
1. Fouling significantly reduces the heat exchange efficiency of equipment, greatly increases energy consumption, and raises production costs. The thermal conductivity of fouling in heat exchangers varies greatly depending on its chemical composition. The thermal conductivity of fouling generally ranges from 0.05 to 3.0 W/m·k, which is only 1/40 to 1/80 of that of steel and 1/300 of that of copper. In other words, the heat transfer capacity of 1mm thick scale is comparable to that of 40-80mm thick steel plates or 300mm thick copper plates
Due to the extremely low thermal conductivity of dirt, scaling can severely affect the heat transfer performance of heat exchangers, leading to a significant increase in energy consumption for production. Numerous thermal engineering experiments conducted both domestically and internationally have shown that a 1mm thick layer of scale on the heat transfer surface of equipment can result in an additional 8-10% energy consumption by the heat exchanger. In other words, a 1mm thick layer of scale can cause coal-fired boilers to burn an additional 10% of coal and increase the power consumption of central air conditioning by 15-20%. This, in turn, leads to a substantial rise in the production costs of industrial products
2. Scaling deteriorates the heat transfer conditions of heat exchange equipment, causing overheating of the heat transfer surface, which in turn leads to safety accidents such as blistering, cracks, and tube bursting
Due to the poor heat transfer capability of dirt, once the heat transfer surface of the equipment becomes scaled, the temperature on the high-temperature side cannot be quickly conducted to the low-temperature medium. This results in a continuous rise in the metal wall temperature of the heat transfer surface, eventually reaching the creep temperature. When the metal wall temperature reaches or exceeds the creep temperature, the mechanical properties of the metal (such as toughness and plasticity) deteriorate significantly, and the tensile strength and compressive strength decrease substantially, making it prone to high-temperature burn damage and deformation. When the equipment is operating under pressure, the overheated tube wall may experience safety accidents such as bulging, cracking, leakage, and even tube bursting due to a significant decrease in pressure resistance. According to statistics from technical supervision departments in some provinces and cities in China, accidents caused by scaling and water quality account for over 60% of boiler accidents
3. Scaling can lead to corrosion damage beneath the scale, resulting in equipment perforation and leakage, thereby shortening the service life of the equipment
The scale formed on the heat transfer surface of a heat exchanger is usually uneven in terms of its density, thickness, and chemical composition. This uneven scale coverage leads to electrochemical heterogeneity on the metal surface, which can easily trigger electrochemical corrosion reactions. Scale formation also causes certain corrosive components in water, such as H+, OH-, Cl-, Mg2+, S2-, to accumulate on the metal surface beneath the scale and produce chemical corrosion reactions. The result of corrosion is localized metal damage and thinning, which can penetrate the steel plate of the equipment, causing leakage, damage, or even failure of the equipment. This increases the maintenance costs of the equipment. In severe cases, it can lead to premature scrapping of the equipment
4. Scaling can destabilize the production process, affect product quality, and lead to quality accidents
When the heat exchanger becomes fouled, the heat transfer efficiency decreases, leading to deterioration in the heating or cooling conditions of the equipment. This, in turn, affects the production process, causing instrument malfunctions, deviations in temperature and pressure indicators from process design requirements, changes in equipment operating parameters, instability in production processes, and a decrease in product yield and quality, with an increase in the rate of defective products. In severe cases, it may even interrupt production, resulting in unplanned downtime