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Boiler cleaning: During the production and installation of boilers, scale forms inside them due to oxidation, corrosion, and other factors. Scaling inside the boiler directly affects heat conduction in the heating surfaces, and it also impairs the steam-water circulation. After cleaning, the boiler can develop a corrosion-resistant protective film. In terms of acid cleaning for scale removal, the process is specifically categorized based on the use of different types of cleaning agents and corrosion inhibitors. However, the need to clean a particular boiler depends on factors such as the boiler’s performance, whether it is new, and the composition of the scale. Boiler descaling mainly involves the use of hydrochloric acid for cleaning, hydrochloric acid to remove silicate scales, sulfate scales, and sulfate deposits, as well as hydrochloric acid cleaners to eliminate copper passivation and reduced iron. Cleaning of chemical equipment: In chemical production, scaling can occur due to physical and chemical reactions; however, the causes of scaling vary depending on the type of fouling that forms. 1. Formation of fouling: (1) Solid particle scaling – The main reason for solid particle fouling is the accumulation of particles on the surface of the equipment as a result of its operation. Generally, the surface layer of some cooling systems tends to accumulate dirt relatively easily. (2) Scaling during the crystallization process: Changes in temperature lead to variations in water temperature, which in turn cause evaporation. When slightly soluble salts reach saturation, they crystallize and deposit on the surface of the equipment. (3) Chemical reaction scaling: Some fluids undergo oxidation reactions on the mechanical surface under high temperatures, resulting in scaling. When the temperature changes, monohydrocarbons undergo chemical reactions, resulting in the formation of polymers on the mechanical surface layer. 2. Dirt removal (1) Physical cleaning: Steam cleaning. By utilizing the energy of compressed air, compressed air is added to water before starting the cleaning process to increase the pressure of the water flow. This method uses high-pressure mixed flow to impact the dirt and is commonly used in pipeline cleaning; its main drawback is the limited uniformity of cleaning. High-pressure water jet cleaning: Shot blasting cleaning is primarily carried out using high-pressure water jets. A high-pressure water stream is generated by a high-pressure pump, and nozzles are used to carry out cleaning in a forward or lateral direction. Its advantages include the fact that it does not cause any contamination or damage to the equipment, and it is cost-effective. Shot blasting cleaning utilizes high-speed water flow to increase the velocity of the pellets, thereby separating dirt from the mechanical surface. Its main advantage is that it does not produce any new substances during the cleaning process, nor does it have an impact on water or air. (2) Chemical cleaning – Alkaline cleaning: Cleaning is carried out using strong alkalis, and it is mainly used for steel-based equipment. Its raw materials include NaOH, Na2CO3, etc., and a certain amount of detergent must be added to its aqueous solution to enhance the activity of the solution. This, in turn, can improve the oil-removal effect. Acid cleaning: Acid cleaning relies on the reaction between acid and dirt to remove it. However, acids are quite corrosive; therefore, a certain amount of corrosion inhibitor needs to be added during use. The selection of substances for acid cleaning should also be based on practical circumstances, taking into account factors such as the composition and properties of the dirt as well as the facilities involved.