Material selection for the protective sleeve of the thermocouple used for temperature measurement in the rising flue of hazardous waste incinerators

Regarding the material selection for the protective sleeves of the temperature sensing thermocouples in the flue stacks of your hazardous waste incinerators, given the extremely high temperatures and the presence of highly corrosive gases, the following materials can be considered to improve the current situation: 1. **Cermet**: Cermet possesses excellent high-temperature resistance and corrosion resistance, enabling it to maintain stable physical and chemical properties in extreme environments. Such materials are typically used in aerospace and high-temperature industrial applications. 2. **Zirconia**: Zirconia exhibits excellent corrosion resistance and thermal stability at high temperatures, and is commonly used to manufacture corrosion-resistant components and protective coatings for use in high-temperature environments. Furthermore, the low thermal expansion coefficient of zirconia helps maintain structural integrity in environments with frequent temperature changes. 3. **Silicon carbide (SiC)**: Silicon carbide materials are also excellent high-temperature corrosion-resistant materials, capable of maintaining mechanical strength and chemical stability in environments exceeding 1000°C. Suitable for environments containing corrosive gases. When selecting materials, in addition to considering their corrosion resistance and high-temperature tolerance, it is also necessary to take into account the compatibility between the thermocouple and the protective sleeve, as well as the thermal response speed and accuracy of the entire system. It is recommended that you work with professional suppliers of high-temperature resistant materials or thermocouple manufacturers to develop customized solutions based on the specific working environment and requirements. At the same time, small-scale tests are conducted to verify the performance of the material in actual working conditions, thereby allowing for more precise adjustments. .

The material used for the flue determines the material used for the thermometer

Inside the flue, there are refractory bricks along with fireproof mortar

Thanks for sharing. I’ll talk to the temperature sensor manufacturer about cermets. I’ve tried the other two types, but they don’t last more than a few days

On Chuanyi’s samples, the maximum operating temperature for cerametal (molybdenum dioxide) is 1600°C; this option can be tried. It should be noted, however, that the material used for shielding the core also needs to be upgraded. The maximum operating temperature for PtRh6 is 1300°C, so PtRh6 could be considered as a suitable material for shielding the core – you may give it a try. The situation with hazardous waste furnaces is rather complex; if there is no shedding of slag, corundum material can meet the requirements. The damage you mentioned might be due to the insufficient heat resistance of the cladding material. The corundum material is used mostly because slag masses damage the sleeves, which in turn leads to the destruction of the thermocouples. If the performance in such applications is good, please provide feedback. Thank you.

Replace with corrosion-resistant materials: Consider using materials that are more resistant to high temperatures and corrosion for making the protective sleeves. For example, ceramic matrix composites or special high-temperature alloys can be considered; these materials generally exhibit better corrosion resistance and high-temperature tolerance. Optimizing thermocouple selection: For S-type thermocouples, although their measurement range can reach around 1300°C, in corrosive environments, it may be necessary to choose a thermocouple type with greater corrosion resistance. Thermocouples with special coatings or surface treatment techniques can be considered to improve their corrosion resistance. Addition of anti-corrosion coating: Apply a high-temperature and corrosion-resistant coating on the surface of the protective sleeve and thermocouple to minimize direct contact with corrosive substances, thereby extending their service life. If the RLHY-903 high-temperature resistant anti-corrosion coating is used, it exhibits good corrosion resistance at high temperatures and can effectively prevent the erosion by corrosive agents. Controling flue gas temperature: Given that the flue gas temperature can rise to as high as 1260°C, it is possible to lower this temperature appropriately in order to reduce the corrosion rate. By optimizing the combustion process or using more efficient cooling systems, the flue gas temperature can be reduced to a safer and more corrosion-resistant range. Regular maintenance and inspection: Regularly maintain and inspect the thermocouples and protective sleeves to detect and address corrosion issues promptly. In cases of severe corrosion, replace the damaged components promptly to prevent accidents. Improve design and layout: Reassess the design and layout of the combustion furnace to optimize air flow and temperature distribution, thereby reducing localized high temperatures and the accumulation of corrosive substances. For example, considerations could include improving the shape of the combustion chamber, adding mixing devices inside the flue, or adjusting the direction of the flue. Strengthen safety protections: Given that the incinerator handles hazardous waste, it is necessary to ensure that all operations and maintenance tasks are carried out in a safe environment. Take necessary safety precautions, such as wearing protective clothing, safety glasses, and gloves, to reduce the safety risks for operators.

Thank you for sharing. I’ll get in touch with Chuanyi