The oxygen-enriched side-blowing molten pool smelting process is adopted. The main equipment is the oxygen-enriched side-blowing molten pool smelting furnace, the settling electric furnace and the continuous blowing furnace. The three are arranged from high to low in sequence. The melt flows through the flow channel between the furnaces. This process is a new process with high efficiency, energy saving and environmental protection. Magnesium ramming material is mainly used in the top of the electric furnace and the ascending flue of the oxygen-enriched side-blowing furnace.
1. Electric furnace top
The electric furnace occupies a very important position in the smelting industry. The use conditions of the electric furnace cover are harsh and the environment is harsh. It is often in a state of high temperature, slag erosion and rapid cooling and heating, and it is easy to be damaged. The life of the electric furnace cover determines the production efficiency of the electric furnace.
The electric furnace top was originally built with silica bricks. In the late 1960s, high-aluminum materials were tried. The refractoriness, high-temperature corrosion resistance and thermal shock stability of high-aluminum materials are better than silica bricks. After the 1990s, the electrode triangle area generally uses a prefabricated furnace cover with high-aluminum or corundum refractory castables and added steel fiber. However, there has been no relevant report on the use of magnesium ramming material as a refractory material for the furnace roof of an electric furnace.
Unlike the integral furnace roof structure, the furnace roof of an electric furnace is composed of several furnace roof blocks. Each furnace roof block is a hollow arched module welded with ordinary steel plates. Both ends are flush with the furnace wall and have the same height. A large number of “V”-shaped nails are welded in the furnace roof block to enhance the firmness of the magnesium ramming material.
During construction, the hollow surface of the furnace roof block is facing up, and the prepared magnesium ramming material is manually filled into the module. It is spread and rammed with a shovel to remove the air in it. The thickness of the ramming material is flush with the edge of the furnace roof. At the same time, a small wooden stick is inserted into the ramming material, which is convenient for drying the ramming material on the one hand, and the drying condition can be observed at any time on the other hand. Because of the presence of the arched structure frame and the “V”-shaped round steel hook, the labor intensity of manual tamping is greatly reduced. The filled furnace roof blocks can be placed in a ventilated place to dry naturally without heating and drying. The filling method of the magnesium ramming material for the electric furnace roof is shown in Figure 1, and the combination of the “V”-shaped round steel hook and the magnesium ramming material is shown in Figure 2.
When in use, the furnace roof block is directly installed on the furnace roof, and no additional water cooling facilities are required.
The inspection of the electric furnace roof after the furnace was shut down for a furnace period (500d) showed that the magnesium ramming material on the furnace roof had good integrity, and no cracks or bursts were found after forced cooling. The strength is very high in the cold state, and the thinnest part of the sintering furnace roof is located near the electrode. Therefore, the magnesium ramming material has good high temperature resistance and melt erosion resistance after sintering.
The use of magnesium ramming material as furnace roof refractory material has the following advantages:
(1) The composition of magnesium ramming material is simple and can be replaced at any time. The cost is only 1/4 of the general castable;
(2) After using magnesium ramming material, the electric furnace top cover does not need to be filled as a whole. The furnace top is divided into blocks, which makes lifting more convenient and safer, and facilitates the handling of furnace conditions and emergencies;
(3) Magnesium ramming material has excellent high temperature resistance, eliminates the auxiliary water cooling device of the electric furnace, reduces energy consumption, and ensures production safety;
(4) The composition of magnesium ramming material is uniform, and it will not be damaged due to different thermal expansion of the material during use, ensuring the service life.
2. Copper water jacket at the flue gas outlet of the oxygen-enriched side-blown furnace
The copper water jacket at the flue gas outlet is used below the ascending flue and is the connecting part between the furnace body and the water-cooled wall of the waste heat boiler. The water-cooled part is a large copper water jacket, which is directly fixed to the outer steel structure by large bolts and is easy to disassemble and install. Adding grooves in the inner wall allows the magnesium ramming mass of the inner lining to be firmly attached to the water jacket (as shown in Figure 3). Due to the presence of refractory ramming mass, the safety of the copper water jacket is greatly enhanced, and oil can be directly burned to increase the temperature when the furnace is opened.
At present, the smelting industry is developing rapidly, and each enterprise has its own characteristics in the use of amorphous refractory materials. The oxygen-enriched side-blowing process uses self-modulated magnesium ramming mass in different parts to reduce production costs and ensure process integrity. After multiple furnace periods of exploration, the use of magnesium ramming mass has become increasingly perfect. The advantages of using this material are as follows:
(1) The refractory material is evenly corroded to ensure safe production. At present, the life of the refractory material has reached 500d.
(2) Used as refractory material on the top of the electric furnace, it can reduce process costs, ensure safe and convenient operation, and reduce energy consumption.
(3) Used as copper water jacket filler, it can ensure the safety of the copper water jacket.
Although the application of magnesium ramming mass is relatively successful, its corrosion mechanism is still unclear. To further optimize the use of magnesium ramming materials, it is necessary to analyze their corrosion mechanism, which will be the future work direction.