Precautions for using heat transfer oil furnaces

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After operating for a period of time, heat transfer oil boilers often experience a decrease in their efficiency in transferring heat, and the root cause of this is the coking that occurs in the delivery pipes. This not only affects the quality of the heat transfer oil, but also poses a hazard to the safe operation of the entire conveying system and the thermal oil boiler. Heat transfer oil is a compound based on polymeric carbon alkanes (with some using biphenyl ether as the base), and the proportion of this base component is over 95%. Under the influence of temperature and oxygen, heat transfer oil undergoes physical and chemical changes, and these changes accelerate over time as the temperature rises. The operating temperature of heat transfer oil should generally be below 330°C. Temperature has a significant impact on the oxidation rate of heat transfer oil and on the by-products formed, which in turn affects its service life. At normal pressure and temperature, alkanes hardly react with air. However, when the temperature rises, the main products of their oxidation are alcohols, aldehydes, fats, carboxylic acids, etc. During deep oxidation and the oxidation of isoparaffins, a mixture of carboxylic acids and small amounts of gums are produced. If local high temperatures cause the heat transfer oil to carbonize locally. (1) The entire oil circulation system should be designed to be smooth. Minimize elbows and valves. Choose a high-efficiency circulation pump. Clean the filter in a timely manner, and it is essential to ensure that the flow rate of the heat transfer oil at high temperatures is not less than 2 m/s. (2) Select the heating furnace appropriately (generally choose type III at 1.5 times its nominal capacity) to avoid overloading and the inefficiency that results from an excessively large scale. Whether the heating capacity of the heating furnace is selected appropriately not only affects its safety and lifespan, but also influences the service life of the heat transfer oil and the production costs. (3) Select a heat transfer oil with good thermal stability and antioxidant properties, as well as strong anti-coking capabilities. When purchasing heat transfer oil, be careful to avoid choosing ones that have an odor or a dark color. The service life of heat transfer oil is evaluated using four parameters: residual carbon, acid value, flash point, and viscosity (Table 1). Conduct oil quality tests every six months to ensure proper control of the quality of the heat transfer oil in use. Upon detecting the problem, replace the heat transfer oil promptly, and identify the reasons for its premature deterioration as well as preventive measures. At the same time, it is essential to ensure that heat transfer oils of different types are not mixed together. (4) Use the hot oil boiler in strict accordance with the operating procedures; avoid rapid temperature increases (the temperature rise rate should be controlled at 10–40°C per hour), as well as overheating and overpressure. Emergency shutdown measures must be taken swiftly and decisively, and the oil level and temperature in the expansion tank should be monitored continuously. If the oil level is low, it should be replenished promptly. Prevent air and moisture from entering the oil circulation system. Since high-temperature heat transfer oil oxidizes more rapidly when in direct contact with air (its oxidation rate doubles for every 10°C increase in temperature), it is necessary to prevent such high-temperature oil from coming into direct contact with air. A better method is to seal the upper space of the expansion tank with nitrogen, creating a protective gas layer, under conditions where nitrogen sealing is feasible. Generally, the temperature of the heat transfer oil in the elevated tank should be kept below 60°C; therefore, the elevated tank is not directly connected in series within the circulation system. (5) Improve the thermal efficiency of the hot oil boiler, and remove ash and scale from the inner walls of the furnace as well as the walls of the coiled tubes in a timely manner to ensure good heat transfer. At the same time, high-quality coal should be used as much as possible, so that the heat generated by the burning coal can be transferred to the heat transfer oil promptly and thoroughly. (6) The heat transfer oil circulation pump must not be stopped while the boiler is insulated. When shutting down the boiler, the circulation pump should only be turned off after the boiler temperature has dropped to the specified range; it should be started first every time the boiler is brought online. In the event of a sudden power outage or a failure in the circulation system, in addition to using ventilation for cooling. It also needs to be replaced with cold heat transfer oil. (7) Regularly clean the pipes carrying the heat transfer oil to reduce the impact of deposits formed at high temperatures on the quality of the oil. Common cleaning methods include mechanical cleaning, steam cleaning, high-pressure water cleaning, and chemical cleaning. The heat transfer oil furnace online cleaner is specifically designed for online cleaning of heat transfer oil systems without shutting down the system. It is primarily used to clean the oil residues and oil coke inside the heat transfer oil furnace system. It is simple and easy to use: 3%-5% of the system’s oil volume should be added directly from the high-level tank, without the need to shut down the furnace. The cleaning process can be carried out during normal production, and it takes about 7 days for the cleaning to be completed once the substance is in operation within the system. It differs significantly from the existing online cleaning products on the market: it enables true online cleaning without shutting down the equipment or furnace, requires a low dosage, yields more noticeable cleaning results, can dissolve solid oil residues, and achieves a cleaning efficiency of 95%. I. Product Features: 1. Simple to use: No need to shut down the furnace or the machine; it can be added directly through the high-level tank while the system is operating normally. 2. Low addition amount: The addition amount is 3%-5% of the system’s oil volume, so there is no need to remove oil from the system. 3. Safe and efficient: Once the cleaning agent is added to the high-level tank, its high density causes it to enter the system slowly, allowing the oil deposits and carbon buildup in the pipes to be gradually dispersed and dissolved. As time passed, the temperature difference and pressure of the external heater gradually returned to normal. 4. Thorough cleaning: The cleaning efficiency of the pipelines inside the system is as high as 95%. 5. Safe and harmless: It is harmless to humans and the natural environment, has good miscibility with heat transfer oils, and can be used directly in systems that are operating normally. 6. High environmental friendliness: No wastewater or waste gases are emitted during the entire cleaning process. 7. Low cost: The cost is significantly lower than that of conventional water-based cleaning methods, and it does not interfere with normal production, **reducing labor costs and additional cleaning expenses.