How to handle shutdowns when different fluids flow through the shell side of the heat exchanger

Drain the medium and clean it. Mechanical cleaning + high-pressure water can be used

The cleaning of heat exchangers generally involves physical and chemical methods. Physical cleaning: mechanical cleaning and high-pressure water. Chemical cleaning: inorganic or organic acids are used to dissolve and remove scale or rust from the system. The characteristics are as follows: I. Inorganic acids 1. Hydrochloric acid Advantages: it is inexpensive and readily available; it can form soluble salts with various types of scale and their corrosion products, resulting in effective scale removal. Disadvantages: It contains chloride ions, which can cause cavitation and stress corrosion cracking in stainless steel; it cannot be used to clean stainless steel, and its discharge causes pollution. 2. Sulfuric acid: Advantage: It provides an effective and environmentally friendly way of removing rust and scale from metals. Disadvantage: It cannot remove carbonate scale (the main component of water scale), as the calcium sulfate formed is insoluble, resulting in severe pollution when discharged. 3. Nitric acid: Advantage: It has a strong descaling ability. Disadvantages: It causes significant corrosion of carbon steel, copper, etc., and results in severe pollution emissions. 4. Hydrofluoric acid: Advantages: It reacts rapidly with rust, and the reaction products have high solubility, allowing it to dissolve silicates. Disadvantages: Highly toxic, highly corrosive; causes skin ulcers upon contact. It poses a great risk of corrosion and toxicity to humans, and its release causes severe pollution. 5. Aminosulfonic acid: Advantages: It is a solid inorganic strong acid that is easy to store and use, with low corrosivity. Disadvantages: High price, weak ability to remove iron scale, and causes severe pollution in emissions. II. Organic Acids 1. Citric Acid Advantages: Safe and non-toxic; can be used as a food additive; contains no chloride ions; does not corrode stainless steel; has very little corrosive effect on carbon steel; residues are easy to remove; cleaning waste liquid is easy to handle. Disadvantages: High price, high requirements for operating conditions. 2. Formic acid: Advantages include the absence of chloride ions, its ability to clean stainless steel, good volatility, and easy removal of residues. Disadvantages: It has a strong pungent odor, is expensive, and requires strict operating conditions. 3. Glycolic acid: Advantages include no corrosiveness, significant effectiveness in removing carbonates and iron scale, inhibition of the growth of iron-bacteria, prevention of secondary precipitation; it decomposes at high temperatures without leaving any residues. Disadvantages: High price, high requirements for operating conditions. 4. Oxalic acid: Advantage: It has an extremely strong ability to dissolve iron oxide. Disadvantages: It must be used in combination with other organic acids, and the operating conditions are stringent. 5. Malic acid: Advantages: safe and non-toxic, can be used as a food acidulant, contains no chloride ions, and can be used to clean stainless steel. Disadvantages: It must be used in combination with other organic acids, and the operating conditions are stringent.

What is LZ asking? Is it asking how to stop it, or what to do after it stops? . . . .

What I’m referring to is mainly how to handle the residual material inside the shell of a shell-and-tube heat exchanger after it has been parked! ! I would like to express my gratitude for the information provided by the above-mentioned person