Causes of damage to refractory materials in waste liquid incinerators

The main core equipment for the incineration of organic waste liquid is the incinerator. Different furnace types need to be selected according to the nature and treatment requirements of the waste liquid. At present, the incineration treatment of organic waste liquid is becoming more and more popular, and the refractory materials of the incinerator are the key restrictive factors of this method. Rongsheng Refractory Materials Manufacturer pointed out that no matter what material the lining refractory materials are made of, they will be subjected to long-term high temperature, high pressure, temperature changes, atmosphere changes, and slag erosion on the lining during the industrial production process. The damage forms of refractory materials are usually erosion, scouring, cracking, etc., among which erosion belongs to continuous damage, while cracking and spalling belong to discontinuous damage. The eroded refractory materials will form cracks and crack the refractory materials due to the mismatch of the internal thermal expansion coefficient. The damage mechanism of lining refractory materials is related to factors such as the mineral composition of the lining materials, the organizational mineral structure of the materials, the chemical composition of the materials, and the type of slag.

The damage mechanism of refractory materials used in organic waste liquid incinerators can be summarized into the following four categories:

(1) Mechanical erosion and wear. Mechanical wear is caused by the friction between two relatively moving objects on the contact surface. It can convert the mechanical energy of the object itself into heat energy, resulting in the wear of refractory materials. During the movement in the furnace, the material will have a large mechanical erosion and wear on the lining of the furnace, causing deformation, wear, and even cracking of the lining refractory materials, causing serious damage to the lining of the incinerator.

(2) High-temperature dissolution of refractory materials. In refractory materials, non-main components introduced from raw materials and production processes are called impurities. At high temperatures, impurities easily react chemically with the main components in the raw materials to form a low melting point phase. This process is called high-temperature dissolution of refractory materials.

(3) High-temperature solution penetration. High-temperature solution penetration is also called slag erosion. At high temperatures, slag exists in a molten phase. After the liquid slag corrodes the refractory, it will form a low-melting-point phase with its oxide. Therefore, the essence of slag corrosion is liquid slag corrosion, that is, it is mainly the dissolution of refractory materials in slag and the penetration of slag into the interior of refractory materials.

(4) Gas phase volatilization at high temperatures. Gas phase volatilization of refractory materials mainly refers to the loss caused by oxidation reactions. Evaporation reactions mainly occur in oxidizing refractories. Oxidation reactions mainly occur in non-oxidizing refractories, non-oxide refractories, and oxide composite refractories. Among them, more than half of the damage to refractory materials during service is caused by slag erosion.

One of the key issues in the incineration of organic waste liquid is the erosion of refractory materials. During the incineration process, alkali metal salts in organic waste liquid easily form eutectic salts with low melting points, resulting in coking and slagging in the incinerator at high temperatures. After long-term operation, the refractory lining is severely corroded by the incineration residue, which may cause significant economic losses and safety accidents. Improving the corrosion resistance of refractory materials and extending the service life of refractory materials have practical economic benefits.

According to relevant research, Al2O3−SiO2 refractory materials are thermally corroded by sodium and sulfur vapor in hazardous waste incinerators at 930~1000 ℃. Studies have shown that the reaction between Na2SO4 and SiO2 first leads to the formation of liquid sodium silicate (Na2Si2O5) and slow corrosion creep, followed by nepheline (NaAlSiO4) and albite (Na8Al6Si6O28S) corrosion leading to lining rupture. Since zirconium- and chromium-containing bricks have high heat resistance, people try to improve the corrosion resistance of incinerator refractory materials to organic waste liquid by using zirconium- and chromium-containing bricks. Adding ZrO2 helps the thermal stability and corrosion resistance of Al2O3-Cr2O3 refractory linings in high-temperature incinerators. Some scholars have used the static corrosion method to evaluate the thermal corrosion of incinerator slag with different K and Na contents on Al-Cr-Zr bricks. Studies have shown that Al-Cr-Zr bricks can resist corrosion from K and Na salts; but when the salt content exceeds 4%, the compressive strength of aluminum-chromium-zirconium bricks drops sharply.

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