With the increase of high calorific value components such as waste plastics in garbage, the calorific value of garbage will continue to increase, and the adoption of low excess coefficient combustion technology, the temperature in the furnace exceeds 1000℃, the low melting point substances in the ash increase, and there are a large number of corrosive HC1 and SOx gas components in the flue gas. The atmosphere in the furnace will also constantly change between the oxidizing atmosphere and the reducing atmosphere, and the use environment of refractory bricks and castables in the combustion chamber will further deteriorate.
Grate furnace
In the grate furnace, the flue gas temperature is usually the highest in the combustion chamber, but there are also large temperature differences in different parts. For example, there is a temperature difference of several hundred degrees between the main combustion zone with high temperature flames and the burnout zone where the slag gradually cools. On the two side walls of the main combustion zone, the garbage layer that is burning at high temperature and constantly moving contacts the refractory layer, and the low melting point slag will melt and adhere to the surface of the refractory layer, eroding the refractory layer, and at the same time, the moving garbage layer will cause friction on the refractory layer. This part requires the refractory material to have high strength, not only wear-resistant and corrosion-resistant, but also resistant to slag erosion. The side walls of the burnout section can be made of ordinary clay refractory materials.
For the parts where the two side walls may contact the garbage layer, refractory materials containing more than 85% SiC are usually used for the main combustion zone with high-temperature flames, and refractory materials containing about 40% SiC are usually used for other parts without high-temperature flames. SiC refractory materials have high strength, good wear resistance, thermal shock resistance and thermal conductivity. Other parts of the combustion chamber usually select materials with appropriate refractoriness according to the temperature distribution in the furnace.
Although SiC materials with more than 85% SiC are used in the main combustion zone, after the temperature in the furnace exceeds 1000℃, a large amount of slag will be sintered and attached to the two side walls, which will continue to melt and grow at high temperatures, and in severe cases, affect the normal movement of the grate. The furnace has to be stopped for cleaning. Moreover, the high temperature above 800℃ oxidizes the SiC material, reduces its corrosion resistance, and seriously reduces its service life. Therefore, the two side walls of the main combustion zone of the grate furnace are usually designed as air-cooled structures. Keeping the surface temperature of the refractory working layer below 800℃ through air cooling can effectively extend the service life of the refractory layer.
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 material is required to have higher wear resistance and strength, and at the same time have good resistance to the turbidity of corrosive gases in the bed layer. High-aluminum wear-resistant castables with a refractoriness of more than 1100°C and a wear resistance of ≤6cm3 according to ASTMO704 are usually used.
Rotary incinerator
In a rotary kiln incinerator, the garbage in the brick 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. High-aluminum wear-resistant castables are generally selected, and high-aluminum refractory bricks and SiC refractory bricks can also be used.
When the boiler water-cooled wall is arranged in the combustion chamber, refractory materials should be laid on the surface of the water-cooled wall to protect the water-cooled wall tubes. Clay refractory materials are usually used. When the temperature in the furnace is high, SiC materials with better thermal conductivity can be used. The combustion chamber refractory material is usually laid with a thickness of 100~150mm, and the water-cooled wall surface is laid with a thickness of 80~100mm.
HOME