Refractory materials in the air heater occupies a very important place. Understand the characteristics of refractory materials and their use, choose a reasonable way of compliance, not only to meet the daily use of the air heater needs, but also to improve the economic efficiency.
High temperature zones
In the air heater, the vault and the top of the nozzle brick as the high-temperature region, year-round temperature control in 1500 ℃ below, and in its peripheral region to burn fuel main space, high-temperature section requirements of this region for a long time to ensure temperature stability, to reduce overall temperature fluctuations.
In the early days, high alumina bricks were commonly used as refractory materials in the high temperature zone of the air heater, but high alumina bricks could not maintain stable performance under prolonged high temperature conditions. Stable performance at high temperature is the advantage of the dinas brick itself, and its high thermal conductivity and low creep rate at high temperature make dinas brick an ideal heat-resistant material for the air heater at this stage. In particular, outdoor combustion air heater and indoor combustion hot air stoves with vaults.
Dinas bricks is mainly used in vaults and for wall cladding with high-temperature tiles. In other areas, composite bricks can be used instead of dyna bricks to reduce economic costs.Thus, in the upper part of the air heater vault, the use of silicate brick masonry can not only reduce the overall quality but also ensure the stability of the large air heater vault.
Transition zone between high and medium temperatures
In the middle temperature zone of the combustion chamber of the air heater, the temperature is kept below 1100℃ for a long time. As the transition zone between high and low temperature, the refractory materials in this part are usually made of andalusite brick or high alumina brick.
The top of the burner varies depending on the air heater, so that the position of the hot air outlet also differs. At the hot air outlet of the burner, the following are usually used alumina bricks. Depending on the different chemical composition of the raw materials, high alumina bricks are divided into different types and applications, which also leads to great differences in their characteristics. High alumina bricks with low creep are manufactured with bauxite, fused corundum and fused mullite as the main raw materials. They have advantages such as low creep at high temperatures, high resistance to erosion and good thermal shock resistance.
Andalusite bricks have good high-temperature properties. Compared to high alumina bricks and mullite bricks, its resistance to creep at high temperatures is better than the first two. Not only that, red pillar bricks also have high resistance to thermal shock. With its own low creep characteristics, it effectively controls its own volume, making andalusite bricks an ideal refractory material for the medium-temperature and low-temperature section of an air heater.
Low temperature zone
The temperature in the low temperature zone of the cowper is controlled below 900℃, so the refractory materials at the bottom of the heat storage chamber and the combustion chamber in the low temperature zone are mainly composed of fireclay bricks.
In the bottom position of the air heater, ordinary fireclay bricks are used, and low creep fireclay bricks are selected on top of fireclay bricks, so as to ensure the effective transition of temperature gradient, temperature alternation by creep coefficient has more stringent requirements, low creep fireclay bricks have good compressive strength characteristics.
The air heater is an integral part of the iron smelting system. Rational use of refractory materials can effectively extend the service life of hot air furnace to ensure that each region fully fulfills its role and ensures sustainable development while saving resources.