The difference between thermocouples used in hot air stoves and armored thermocouples

Thermocouples for hot blast furnaces in steel plants are mainly used in the steel industry to provide hot air for the smelting process. The dome temperature measuring thermocouple operates at high temperatures of 1200-1250 ℃ for a long time, with a maximum operating temperature of 1280 ℃, and has strong vibration during the air supply process. Due to the different coal qualities used by various enterprises, the cleanliness of the produced coal gas also varies. During the combustion process of hot blast stoves, sulfur, phosphorus and other compounds are often present, requiring thermocouple protective sleeves to be able to withstand high-temperature airflow erosion, particle wear and high-temperature gas corrosion. Traditional thermocouple protective sleeves such as steel jade, disilicified keys, and ordinary silicon carbide are prone to brittle fracture, wire contamination, and corrosion due to porosity, high temperature strength, and high temperature brittleness. Thermocouples have a short service life and no reliable operating cycle. The high-temperature corrosion failure time of nickel based high-temperature alloy protective casing in the presence of phosphides in coal gas is about 20-30 hours. Our company has continuously summarized experience and applied the latest achievements in the field of materials in the long-term practice of temperature measurement of various hot blast stove domes. We use special SiC or heat-resistant alloys as the outer protective tube and corundum as the inner protective tube, and have processed the measuring end. We have successfully developed this special thermocouple, which has been used on hot blast stove domes by relevant users for more than six months.
Scope of application and operating temperature
In the case of coal gas containing phosphides, the outer casing adopts a new type of silicon carbide protective casing produced by introducing German technology, and the porosity of this product is approximately zero. Has high airtightness, excellent oxidation resistance, and corrosion resistance; Extremely high hardness and excellent wear resistance; High strength, strength increases with temperature. Isolate the corrosion and erosion of various high-temperature harmful gases on the casing, and use it for a long time at around 1420 ℃.
In the absence of phosphides in gas, the outer casing substrate is made of heat-resistant alloy steel, and through the application of internationally advanced surface treatment technology, a 0.5-1.2mm thick metal ceramic coating material is formed on the surface of the metal casing. Coating materials have the characteristics of high hardness (up to HV1450), high density (≥ 99.5%), low porosity (<0.5%), and strong adhesion to the substrate (≥ 75MPa), and have good high-temperature wear resistance and corrosion resistance. The thermal barrier effect of the coating enables the protective sleeve to be used for a long time at around 1300 ℃. The inner sleeve adopts a steel jade protective tube to provide a clean measurement environment for the platinum germanium thermocouple wire. Fill the inner and outer sleeves of the hot air stove thermocouple with ceramic micro powder with high thermal conductivity to reduce vibration during use.
The hot blast stove thermocouple is specially developed for the steel industry, and it has the advantages of high temperature resistance, corrosion resistance, gas flow erosion resistance, and long service life. Suitable for temperature measurement of hot air vents or pipes on the arch of blast furnaces and hot blast stoves, as well as for temperature measurement of kilns such as natural gas, coal, and cement.
The structural principle of armored thermocouples is composed of a conductor, high insulation magnesium oxide, and a protective tube made of 1Cr18Ni9Ti stainless steel, which is pulled together multiple times. Armored thermocouple products are mainly composed of junction boxes, terminal blocks, and armored thermocouples, and are equipped with various installation and fixing devices. Armored thermocouples are divided into two types: insulated and shell connected.
Armored thermocouples have many advantages such as bending, high voltage resistance, fast thermal response time, and durability. Like industrial sensors, they are commonly used as temperature sensors and are often paired with display instruments, recording instruments, and electronic regulators. At the same time, they can also be used as temperature sensing elements. It can directly measure the temperature of liquids, vapors, gas media, and solid surfaces in the range of 0 ℃~800 ℃ during various production processes. Compared to others, armored thermocouples have advantages such as bendability, high voltage resistance, short thermal response time, and durability.
Armored thermocouples, as temperature measurement sensors, are usually used in conjunction with temperature transmitters, regulators, and display instruments to form process control systems. They are used to directly measure or control the temperature of fluids, vapors, gas media, and solid surfaces within the range of 0-1800 ℃ in various production processes. Armored thermocouples have many advantages such as bending, high voltage resistance, fast thermal response time, and durability. Like industrial assembled thermocouples, they are commonly used as temperature sensors in conjunction with display instruments, recording instruments, and electronic regulators.