In glass melting furnaces, the flames generated by fuel combustion flow in a turbulent manner, are strong and powerful, and have a certain scouring effect. The highest flame temperature is 1500~1600℃, and changes with time. Especially when reversing, the temperature fluctuates greatly (tens of degrees Celsius to more than 100 degrees Celsius). The flame is also mixed with batch dust, alkali vapor, boron vapor, lead vapor and carbon particles. The space masonry also bears a certain mechanical load at high temperature. The bricks in the flame space include the kiln roof, breast wall and small furnace part. The damage characteristics of each part and the materials used are described below.
01 Bricks for kiln roof and breast wall
The damage characteristics of this part of the brick body are corrosion (mainly alkaline sulfate condensation, forming honeycomb corrosion) and burning, so it is necessary to use materials that are extremely stable to alkali vapor at high temperature, and have high load softening temperature and creep resistance. The large arch of the melting furnace flame space adopts high-quality silica bricks, and high-quality silica fire clay is used in conjunction.
The 33# fused zirconium corundum bricks used in the breast wall of the melting part have good thermal shock resistance at a high temperature of more than 1200℃. At the same time, they have good corrosion resistance to alkaline vapor and particulate dust in the batch.
The kiln pressure has a certain impact on the use of refractory brick linings in contact with the flame. When the kiln pressure is too large, the flame intensifies the erosion of refractory bricks, especially brick joints. Brick joints are the weakest part of the entire refractory brick lining, and they are generally eroded slowly along the brick joints. Therefore, in the construction of refractory materials, while selecting materials with good performance effects, refractory mud with excellent performance should also be selected, and the width of the brick joints should be minimized to improve air tightness.
02 Bricks for the front wall
The front wall is a relatively weak part of the glass melting furnace pool kiln. There are three main types of damage to it, namely, erosion of the batch, thermal shock and flame erosion. At present, this part mainly uses 33# fused AZS bricks or sintered AZS bricks, and there are also composites of high-quality silica bricks and sintered AZS bricks. In addition to using high-quality bricks, the front wall also needs to be air-cooled.
03 Bricks for small furnaces
The damage characteristics of bricks for small furnaces can be summarized as follows: the flue gas (commonly known as tempering) with powdered materials and alkali vapor and the partially burned flame (or preheated air) periodically move back and forth at high speed, which brings high heat load, periodic temperature changes, atmosphere changes during reversing, scouring of flame gas and erosion of alkali powder. If the combustion in the flame space is incomplete, and the flame continues to burn in the small furnace during tempering, overheating will occur at this time. The erosion of the brick seams of the small furnace arch bricks will cause the sinking of a single arch brick and the loosening of the arch foot. The temperature difference between the inner and outer surfaces of the nozzle brick is large, and it is easy to burst and peel off. If it falls into the glass liquid, it will cause defects. According to the above damage characteristics, bricks for small furnaces are required to be resistant to high temperature, erosion, and scouring, and have a certain degree of thermal shock resistance. At present, among the bricks used in small furnaces, the crater arch bricks, the small furnace inclined arch top layer bricks, the small furnace bottom plate bricks and the small furnace tongue bricks (when burning the producer gas) are the most easily damaged bricks and are also the weak parts of the tank kiln. The crater arch bricks, crater side wall bricks, bottom plate bricks, inclined arch top layer bricks, tongue bricks and nozzle bricks are made of fused AZS bricks (the weakest part should be made of fused AZS41 bricks), but attention should be paid to the spalling phenomenon of the bricks due to crystal transformation in the range of 1000~1200℃. The bottom plate bricks can also be made of sintered dense corundum bricks. The small furnace slope arch and horizontal channel arch are generally made of silica bricks.
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