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Contaminants: The contaminants that often occur in heat exchange equipment used in petrochemical production include scale, rust, microbial deposits, and grease deposits. Due to the significant differences in the properties of various types of dirt, the methods of cleaning and the cleaning agents used vary accordingly. Scale: Most inorganic salt deposits seen in industry precipitate from water, appearing in the form of scale. When inorganic salts such as calcium sulfate and calcium silicate are present in water, or when phosphates and similar substances are added during water treatment, the local concentration of these salts increases on the heated surfaces of the equipment due to the evaporation of water caused by heating. When the ion concentration product exceeds the solubility product of the corresponding salt, salt scale is formed and deposits on the surface of the equipment. Products of corrosion on the device’s surface, dust in the air, microorganisms that grow in water, and so on can also become part of scale. However, since the main component of this dirt is inorganic salts, it is called inorganic salt scale. Scale includes carbonate scale, sulfate scale, silicate scale, phosphate scale, and others. Rust is an insoluble substance that forms on the surface of steel as a result of chemical or electrochemical reactions with environmental agents; it is primarily composed of oxides or hydroxides of iron in the +3 or +2 valence state, with occasional traces of iron salts present as well. Steel oxidizes in a dry atmosphere to form an oxide scale composed of Fe, Fe2O3, or Fe3O4. In a humid atmosphere, when steel is corroded, the primary substance formed is mainly Fe2O3·nH2O, followed by Fe3O4 ； When the rust layer dries and oxygen can pass through, Fe3O4 is again oxidized by the passing oxygen to form iron-red Fe2O3. In oxygenated neutral and alkaline aqueous solutions, steel tends to undergo passivation, resulting in the formation of only a very thin oxide film that does not constitute rust. When a passivated state is not achieved, its corrosion products are generally oxides or hydroxides of iron in the +2 or +3 valence state, as well as certain iron salts. Microbial fouling, also known as microbial sludge or muck, is a viscous substance secreted by microorganisms during their reproduction; it binds together inorganic salts, sand and dust, corrosion products, silt, oil residues, and other substances present in the environment, resulting in a sludgy deposit. Common microorganisms in industrial circulating water systems include bacteria, fungi, algae, etc. Oil residue is a viscous, oil-rich deposit composed of oils, oily impurities such as dust and salt particles accumulated in the environment and moisture, as well as products of structural changes on the surface of the object being cleaned. Oils are generally classified into vegetable oils, animal oils, and mineral oils, etc. The oil residues generated during the petrochemical production process are mainly composed of mineral oils—petroleum and its derivatives.