In the process of urbanization, waste disposal has become an important issue. Waste incinerators are widely used because of their good volume reduction effect, low cost and high degree of harmlessness. As the key lining material of waste incinerators, the selection of refractory materials is crucial. This article will discuss the selection criteria and basis of refractory materials for waste incinerators.
Ⅰ. The relationship between the classification of waste incinerators and refractory materials
There are various types of waste incinerators, including grate type, fluidized bed type, intermittent type, rotary type, etc. Different types of incinerators have different requirements for refractory materials due to their different structures and operating conditions. For example:
1. Grate type incinerator: Mechanical grate incinerator has mature technology, stable and reliable operation, and wide adaptability. The biggest advantage of this type of furnace is that the technology is mature, the operation is stable and reliable, and the adaptability is wide. Most of the solid waste can be directly put into the furnace for combustion without any pretreatment.
2. Fluidized bed incinerator: In a fluidized bed incinerator, the dense phase area at the bottom of the furnace is eroded and vibrated by the movement of a large number of bed material particles, so the working layer refractory materials are required to have higher wear resistance and strength, and good resistance to the turbidity of corrosive gases in the bed layer. Wear-resistant castables with a refractoriness of more than 1100°C and wear resistance that meets certain requirements are usually used.
3. Rotary incinerator: In a rotary kiln incinerator, the garbage in the kiln rotates with the rotary kiln and is constantly turned and thrown down, and the temperature of the refractory layer changes continuously. Therefore, materials with good wear resistance and thermal shock resistance are required. Generally, high-aluminum wear-resistant castables are selected, and high-aluminum refractory bricks and SiC refractory bricks can also be used.
Ⅱ. Basis for the selection of refractory materials
The selection of refractory materials needs to comprehensively consider factors such as furnace atmosphere, temperature, slag and stress.
1. Furnace atmosphere: The interior of a waste incinerator is generally an oxidizing atmosphere. When selecting materials, it is often impossible to scientifically define refractory materials. Targeted refractory materials should be selected according to the type of incinerated waste and the atmosphere in the furnace.
2. Temperature: The maximum temperature of a waste incinerator is about 1400℃. As the temperature continues to rise, the situation will also change. Especially for some high-aluminum refractory materials, their own refractory grade is not high, and they are easily affected by temperature and deteriorate.
3. Slag: A large amount of slag will appear during the use of the waste incinerator. Its main components include aluminum oxide, silicon oxide, and iron trioxide, as well as some alkaline oxide materials. Compared with other neutral refractory materials, alkaline refractory materials are more stable and will not fluctuate significantly.
4. Stress: The waste incinerator is mainly affected by several aspects of stress during use, including thermal stress caused by temperature gradient, mechanical stress at the contact part of the metal frame, composition changes caused by oxidation corrosion, and loss of support caused by damage due to corrosion, etc.
In recent years, with the rapid development of waste incinerator technology, its service life has been effectively extended and its stability has been significantly improved. Objectively speaking, the development and application of refractory materials is the key to ensuring the service life of waste incinerators.