The iron mouth of blast furnace is the channel for molten iron and slag to flow out. The working environment of the iron mouth is harsh. Due to long-term scouring and erosion by high-temperature slag and iron, as well as other working reasons such as vibration of the opening machine and mud cannon, the iron mouth is damaged to a certain extent. After the furnace is opened, the special-shaped bricks of the iron mouth channel will be completely eroded in a short time. If the damaged iron mouth channel cannot be repaired in time or is too shallow for a long time, it will cause fatal damage to the iron mouth. Using mud sleeves to replace special-shaped bricks is a common method to solve such problems. Mud sleeves can be completed after damage and can maintain the integrity of the iron mouth channel.
In the past, blast furnaces generally had both iron and slag outlets. Modern blast furnaces do not have slag outlets due to the high pressure in the furnace. When the iron is tapped, the diameter of the iron mouth is small, and the amount of iron tapped is less than the amount of molten iron and slag generated. The molten iron and slag in the furnace continue to increase, and the liquid level in the furnace rises. As the iron mouth is constantly scour and erode, the diameter of the iron mouth increases. When the amount of iron tapping exceeds the amount of molten iron and furnace fish generated in the blast furnace, the liquid level in the blast furnace begins to drop. The total amount of tapping mud required to block the iron mouth of different blast furnaces is different. A large blast furnace requires about 200kg, and the proportion of tapping mud in the iron mouth is only 10%. The remaining 90% of the tapping mud is used to form the front mud bag.
During the operation of the blast furnace, high-temperature slag, molten iron and high-pressure gas jets frequently scour and erode the iron mouth. When blocking the iron mouth, the impact of high-pressure tapping mud and the vibration and impact of the mud gun make the lining bricks around the iron mouth extremely easy to damage. Therefore, it is particularly important to seal and protect the tapping mud of the iron mouth. In order to ensure the quality of the iron mouth, some engineering technicians and researchers have adopted a series of methods: increasing the amount of mud, drilling with a small diameter drill, etc., but these methods have not fundamentally solved the problem.
Blast furnace taphole mud
Taps are made of aggregate, fine powder, binder and additives. After burning, they form carbon bonds. They are refractory plastic materials specially used to plug the taphole of blast furnaces. When the blast furnace taps iron, the molten iron is discharged from the furnace through the hole drilled in the center of the taphole mud in the taphole. Generally, slag begins to appear 20 minutes after tapping, and continues until the molten iron is exhausted. This requires the taphole mud to maintain a uniform taphole aperture and smooth tapping. After tapping iron, it is necessary to use a mud tapping machine to press the taphole mud into the taphole channel so that the taphole mud fills the taphole, prevents the molten iron and slag from flowing out, keeps the taphole at a sufficient depth, and forms mud bags in the furnace to protect the furnace wall and bottom of the taphole area.
Early taphole mud was a cheap and simple product with a relatively simple function and role. The performance requirements were low and it was not taken seriously. In recent years, with the changes and innovations in blast furnace operating technology, blast furnaces have been continuously developing in the direction of large-scale and long-life. Due to high temperature and high pressure operation, the requirements for smelting are improved (high smelting intensity, high wind pressure), which increases the temperature of molten iron, the amount of iron tapping and flow rate, and the amount of slag. As a result, the number of daily iron tapping increases, and the time of iron tapping is prolonged, which puts higher requirements on the quality of the tapping mud for blocking the tapping hole. Now the tapping mud has changed from a simple consumable refractory material to a functional refractory material.
The main function of tapping mud before was to block the tapping hole and stabilize the iron tapping. Now the average life of the blast furnace has been extended to ten to twenty years. The lining bricks of the blast furnace side wall and the hearth area near the inner side of the tapping hole are damaged and eroded by high-pressure molten iron and slag during the tapping process, becoming the weak part of the blast furnace lining, thus affecting the overall life of the blast furnace. Therefore, in addition to the basic functions of tapping mud such as blocking the tapping hole and stabilizing the iron tapping, the functions of protecting the hearth and extending the life of the side bricks at the bottom of the blast furnace have also been continuously discovered and used. At the same time, in order to prevent the side bricks from being directly impacted by molten iron and slag water on the side wall, the tapping hole length is increased, so that the tapping mud forms a mud bag on the furnace wall inside the tapping hole.
Functions of gun mud
During the use of blast furnaces, the taphole is repeatedly opened and filled. Hot molten iron and slag liquid cause physical and chemical erosion to the taphole gun mud. If the gun mud quality is not good enough, a series of problems will occur during use, such as damp taphole, large flow and broken taphole, which will affect normal production and even cause serious personal injury accidents. Therefore, gun mud should have the following properties:
(1) Excellent plasticity: gun mud is easy to fill the taphole and can block the taphole, and it is easy to form a stable mud bag.
(2) Opening property: the taphole can be easily drilled by the opening machine and it is easy to open the hole within the specified time.
(3) Appropriate porosity: it is easy to discharge moisture and gas during drying and rapid sintering.
(4) Appropriate sintering property: appropriate hardening speed and sintering speed, high strength after sintering, and avoid cracks.
(5) High refractoriness: anti-slag iron erosion and scouring.
(6) Production and use: no harm to the body and no pollution to the environment.
(7) Antioxidation property: dense and uniform structure.
(8) Appropriate volume stability: good thermal conductivity and uniform thermal expansion, reducing mud bags and iron mouth stress.
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