The construction of the groove bottom brick structure can be divided into three main stages in sequence: laying of large bricks at the bottom of the groove, fixing the large bricks at the bottom of the groove and pounding of unshaped refractory materials.
1. Laying of large bricks at the bottom of the tank
The laying of large bricks at the bottom of the trough should be positioned from the entrance and installed from the center line to both sides. According to the height of the bricks and the flat elevation of the bottom shell, place 0.5~3mm leveling spacers of different specifications at the four corners of the large bricks at the bottom of the tank as needed. Put the brick down smoothly and press down alternately in two diagonal directions on the brick surface. If there is no shaking feeling, it is qualified. Use a level to measure the elevation of the four flat corners of each brick. It is required to adjust the leveling pads to control the elevation error within ±0.5mm.
Expansion joints should be left between the large bricks at the bottom of the tank as required and measured with a feeler gauge. The value of the expansion joint is determined based on the expansion coefficient of the large bricks at the bottom of the tank and should not be too large or too small. It is recommended to use "┎" type expansion joints, with the upper surface painted in different colors to distinguish different specifications. Before use, measure the thickness of the expansion joint with a vernier caliper. Depending on the thickness, the allowable deviation is within ±(0.15~0.2) mm. Small wood chips are placed under the expansion joints for easy removal and to protect the brick surface. All leveling gaskets and expansion joints require the working surface to be smooth, rust-free and burr-free. Use a mallet to gently tap the brick body to make the bricks and expansion joints fit together, and then use tape to seal the brick joints to prevent impurities from falling into the joints. The gap between the side bricks and the steel shell is fixed with wooden wedges. The surface of the installed base tiles is covered with plywood and plastic sheeting.
2. Fixing of large bricks at the bottom of the trough
Since the density of the big brick at the bottom of the tank is smaller than that of the tin liquid, about 1/3 of the tin liquid, it must be fixed to the bottom shell with studs to prevent it from floating. The fixation of the large bricks at the bottom of the tank can be divided into two parts: welding of studs and filling of graphite products.
2.1 Welding of studs
At present, there are two main methods for welding studs and bottom shells: arc stud welding and manual welding.
2.2 Filling of graphite products
At high temperatures, liquid tin easily reacts with iron through diffusion to form an iron-tin alloy. Under normal circumstances, due to the cooling air at the bottom of the tank, the temperature of the bottom shell is usually lower than 150°C, and the tin liquid seeps into the steel plate through the brick joints and solidifies. However, when unexpected events such as power outages and wind outages occur, the local temperature of the bottom case may exceed the melting point of tin. If the studs are not protected, the molten tin will gradually corrode the studs over time.
Graphite and tin liquid do not wet each other and do not react. Therefore, the use of high-purity graphite products can effectively protect studs.
3. Tamping of unshaped refractory materials
Similar to the protective role played by graphite products, the fixed tank bottom bricks also need to be filled with amorphous refractory materials to protect steel components from the erosion of molten tin. There are two main types of amorphous refractories materials used for trough bottom brick structures: hole sealing materials and edge sealing materials.
3.1 Tamping of sealing material
Sealing material is used to fill the upper taper hole of the stud hole to prevent molten tin from corroding the steel fastener from the top. Zirconium ramming materials are generally used as sealing materials, which have low strength at room temperature and must be sintered at high temperatures to achieve higher strength.
Add an appropriate amount of water to the sealing material according to the instructions and mix it evenly. The mixed material can be held into a ball by hand and can be loosened by light touch, which is considered qualified. The ingredients mixed each time must be used up within 1 to 2 hours, otherwise they need to be prepared again, so the amount of mixing each time should not be too much.
Before adding unshaped refractory materials, use a vacuum cleaner to clean the cone hole, and use a wet cloth to moisten the inner surface of the hole, and then add the sealing material into the hole in 2 to 3 times. For the first time, add material to 1/2 of the hole depth, and then continuously add material while pounding with a pneumatic pick or electric pick to prevent delamination, until the pounded material is filled and is about 5mm higher than the brick surface.. When ramming, it is strictly forbidden to add materials in layers, and ram layer by layer to ensure the ramming quality. Finally, use a spatula to remove the part that is higher than the brick surface, then use a trowel to flatten and roll it out, and cover it with a plastic sheet to protect it.
3.2 Tamping of edge banding materials
The edge sealing material is used to fill the gap between the side bricks and the surrounding side panels to prevent tin liquid from eroding the side panels through the joints of the side bricks. The edge sealing material generally uses hydraulic unshaped refractory high-aluminum castables.
Add appropriate amount of water to the edge sealing material according to the instructions and stir evenly. Use a vacuum cleaner to clean the gap between the edge bricks and the side panels. In order to prevent the edge sealing material from entering the brick joints of the edge bricks and affecting expansion, appropriate measures (such as blocking with thin steel bars) need to be taken to protect the brick joints, and then continuously add material into the gaps while tamping them with flat steel or professional tools. , and finally smooth the upper surface with a trowel. The lip plate at the exit is in a high-temperature closed environment, and the steel wire mesh fixed on the lip plate can strengthen the crack resistance of the edge sealing material. The edge sealing material around the entire tin tank should be finished within one day as much as possible, and construction should not be carried out in sections.
