The masonry quality of a float glass melting furnace directly affects the service life of the furnace and production operations. In recent years, the service life of float glass melting furnaces has become longer and longer, with some exceeding 8 years. Therefore, strong guarantees should be provided in terms of refractory brick materials, furnace masonry, furnace drying, and normal production operations. During furnace masonry, according to the different materials of refractory bricks, corresponding refractory mortar should be used for masonry except for the parts required to be dry-laid, and the expansion joints of the masonry should be set according to the expansion coefficient of the refractory bricks.
The masonry of a float glass melting furnace is based on the longitudinal centerline of the furnace, the centerline of No. 1 small burner, and the elevation. The masonry requirements for each part are briefly described as follows.
Masonry of Flues
1. Generally, the flues of a float glass melting furnace are constructed in the first stage of the furnace masonry. However, some manufacturers build the main body of the furnace first and then construct the flues in order to meet the ignition schedule. In this case, construction protection should be paid attention to.
2. The construction of the flues is based on the centerline of No. 1 small burner and the centerline of the melting furnace. For convenience, heat - resistant concrete can be used for casting at the junctions of the main flue and branch flues, and at the bends of the branch flues when dealing with arches.
3. Where arches of different spans in the flues meet, the arches should be laid with straight joints, and the walls should be laid with staggered joints. At this time, it should be noted that the length of the arch bricks at the arch head should not be less than 120mm to prevent the arch head bricks from falling off.
4. Expansion joints of the flue walls should be set in sections. Generally, an 8mm expansion joint is set for every 2m. The expansion joints should be laid with staggered joints. Outside the expansion joints, clay bricks should be used for masonry instead of insulating bricks.
5. The outermost layer of the flue wall is red brick. Since the thickness of red bricks is different from that of standard - shaped refractory bricks and they are not matched during masonry, it is required to interlock half - bricks into the wall every 7 - 8 layers of red bricks. The height of the interlocking part can be adjusted by processing the thickness of the insulating bricks.
Masonry of Regenerators
1. The general thickness of the regenerator wall is 578mm. The side walls and end walls are composed of one - and - a - half refractory bricks and one insulating brick. Expansion joints can be set in sections during masonry. The partition walls are entirely composed of two - and - a - half refractory bricks, and expansion joints must be left at both ends of the partition walls.
2. The grating arch is a key part of the regenerator, and safety must be ensured. The arch must be laid along a string line, and each grating arch should not be skewed. The grating arch bricks are leveled with leveling bricks, and the upper surface of the leveling bricks should be as flat as possible to facilitate the laying of checker bricks. The leveling work of the grating arches in float glass melting furnaces takes a long time and requires meticulous construction. Currently, the most common method is to process the lower surface of the leveling bricks appropriately and then lay them with mortar. After laying, a line is snapped according to the required elevation of the leveling bricks on the grating arch bricks. Each brick is numbered, and then the leveling bricks are removed, cut according to the snapped line marks, and then laid back in place with mortar according to the numbering. A line is stretched according to the elevation, and the height is corrected with an angle grinder.
3. When the rear side wall of the regenerator is built to the height of the small burner floor, the construction should be suspended, and the breast wall and small burner should be constructed. The construction of the rear side wall can only continue after the inclined arch and the rear flat arch of the small burner are completed.
4. The checker bricks should be laid vertically and horizontally. After production inspection, the checker bricks should be boxed and packaged according to positive and negative tolerances, and the tolerance range should be marked on the packaging box. For the laying of checker bricks in the same layer, checker bricks within the same tolerance range should be used.
Masonry of the Tank Wall
The tank wall bricks of a float glass melting furnace are generally a whole brick in the height direction and should be stacked according to the numbers in the drawings during masonry. To ensure the horizontal and vertical alignment of the tank wall bricks, a small amount of zirconium - based ramming material can be padded under the tank wall when adjustment is needed.
Masonry of the Breast Wall
1. Adjust the breast wall supporting plates to be on the same horizontal plane, fix the cheek irons. Determine the position of the hooking bricks according to the centerline of the melting furnace, and snap a line on the tank wall bricks. At this time, the centerline of each small burner should also be marked out. Then, place each brick in its corresponding position as marked in the drawings.
2. When the masonry of the flat arch of the small burner is completed, the arch formwork cannot be removed. It can only be removed after the breast wall of the clarifying section is masoned and the jackscrews at both ends are tightened in place, so as to prevent the flat arch from sinking.
3. All the electro - fused zirconia - corundum bricks in the breast wall area are dry - laid. It should be noted that when laying the hooking bricks, wooden wedges must be inserted between the tank wall bricks and the hooking bricks to ensure the hooking bricks are horizontal.
4. Since the bricks in the breast wall area are large and heavy, with some weighing even several hundred kilograms, special attention should be paid to safety during construction.
Masonry of the Main Arch
1. The float glass melting furnace adopts a steel skewback structure. The steel skewbacks must be accurately and stably positioned. A steel wire is stretched along the length of the furnace on the same side to adjust the inclined surfaces of the steel skewbacks to be on the same plane. Thin steel plates can be padded if necessary, but sufficient contact area and stability of the padding irons must be ensured.
2. Supporting the arch formwork. As the thickness of the main arch bricks in a float glass melting furnace is generally 400–500 mm and their mass is large, the arch formwork must have sufficient strength and ensure overall stability. After the arch formwork is supported, a level gauge shall be used for repeated measurement and adjustment to ensure it is at the same height.
3. Before starting arch masonry, 2–3 rings of arch bricks shall be dry-laid for each arch section. This allows for a clear understanding of the size of the mortar joints during masonry.
4. The key bricks of the main arch shall be 100–150 mm higher than the arch crown. For the same arch section, the key bricks shall be driven in simultaneously to ensure uniform stress on the entire arch.
5. Silica mortar has poor masonry suitability, and the main arch bricks are large. To quickly and uniformly apply the mortar to the brick surfaces, the silica mortar must be mixed for sufficient time, with a 4-hour aging period from mixing to use. Therefore, a slightly larger mortar pool is required, and materials shall be prepared in advance.
6. The head joints of the arch bricks must be strictly controlled during masonry and furnace drying. During thermal insulation, sealing materials shall be used for fine construction. The arch head of each arch section is a free end without constraints. If the expansion joint is poorly sealed, fire penetration is likely. Therefore, the arch head shall be tightly constructed during masonry, and the tie rods shall be tensioned tightly. Additionally, a stepped structure for the expansion joint at the arch head is preferably adopted, which shall be sealed with silica hot repair material after furnace drying is completed.
7. The main arch of a float glass melting furnace is relatively long, so the tie rods shall be tensioned multiple times with small increments. To ensure synchronous lifting of the main arch, it is best to set three measuring points along the furnace length on each arch section. These points shall be observed with a level gauge, and measurements shall be taken while tensioning the tie rods to ensure the lifting amount of the entire main arch is basically the same. Generally, when the main arch rises 10 mm, it will disengage from the arch formwork, at which point the tie rods can be locked, and the arch formwork can begin to be removed.
The masonry of the tank bottom, inclined arches of small burners, and other parts is basically similar to that of other industrial furnaces. However, it should be emphasized that almost all refractory materials used for each part of the small burners are currently electro-fused AZS bricks, which have complex shapes and are difficult to install. To ensure masonry quality, these refractory bricks must be precisely ground, pre-arranged, and numbered to reduce installation difficulty. For the installation of L-shaped pendant walls, both imported and domestic ones are currently constructed and installed by the supplier, with on-site guidance provided by design technicians.