Analysis of Problems in the Use of Blast Furnace waterless Taphole clay

Analysis of Problems in the Use of Blast Furnace taophole mud

blast furnace taophole mud; taphole; problem analysis; improvement measures 

Blast furnace taophole mud is a plastic refractory material used to block the taphole of the blast furnace. This paper analyzes some problems that occur in the use of blast furnace taophole mud, such as long opening time, taphole splashing, taphole blocking failure, high mud pressure, short taphole, etc., and proposes improvement measures.

After the blast furnace has finished tapping iron, the blast furnace taophole mud pushes the iron slag back into the furnace, closes the taphole, and prevents the molten iron from flowing out. It is a plastic refractory material used to block the taphole for smelting ferrosilicon, ferromanganese, ferrochrome, nickel-iron alloys, etc. Blast furnace taophole mud has the following characteristics: it can be opened and filled repeatedly; it maintains the taphole aperture and discharges slag iron stably; it has a certain strength, and can push the slag iron back into the cylinder to complete the taphole blocking operation; it protects the furnace. The properties that blast furnace taphole clay must have: easy combination of new and old taphole clay, plasticity, high temperature resistance, corrosion resistance, easy sintering, high sintering strength, stable volume, easy opening, etc. Due to the harsh use environment of blast furnace taphole clay, some problems are inevitable. This article analyzes the problems that occur during the use of taphole clay.

Problems and improvement measures in the use of blast furnace taphole mud

2.1    Long hole opening time

2.1.1    Common problems (1) Broken iron mouth: The taphole mud in the taphole channel is mixed with slag iron, which makes it difficult to open the hole. The reason for this is that the taphole mud itself has a low Maxwell value, and slag iron is mixed in the process of pushing the slag iron into the furnace. In addition, the depth of the taphole is too long, and the mud bag has irregular cracks, which leads to the mixing of slag iron. (2) The taphole mud is severely sintered. (3) The drill bit is worn, the drill rod strength is low, and the drilling rig power does not meet the standard, which can all lead to difficulties in hole opening.

2.1.2    Improvement measures (1) You can use oxygen burning to open the hole or increase the Maxwell value of the taphole mud (adjust the amount of taphole mud binder). In addition, you can reduce the amount of mud, and wait for the mud bag mixed with slag iron to be slowly consumed. (2) Adjust the taphole mud formula to reduce the sintering strength of the taphole mud. (3) Replace the drill bit regularly and check the status of the taphole machine. 2.2    Sputtering at the tap hole After the tap hole is opened, the iron flow is stable and does not splash, and smoke and dust are the ideal tap hole state. During the tapping process of the blast furnace, the splashing at the tap hole not only affects the service life of the tap hole, the iron ditch and the surrounding equipment, but also poses a great safety hazard. The splashing at the tap hole is related to the condition of the blast furnace and the performance of the taphole mud itself.

2.2.1    Common Problems (1) Sputtering at a new taphole. In production, it is often found that a new taphole is more prone to sputtering. After using it for a few furnaces, the sputtering is reduced. This sputtering is the result of multiple factors during the shutdown and taphole maintenance process. There are several situations in which a new taphole sputters: ① After the furnace is regularly maintained, the taphole is the first to tap iron. At this time, the taphole channel has been eroded by slag for a long time, and dust and slag are gathered, which is relatively messy. The taphole is also relatively short. At this time, the taphole is opened and the molten iron splashes under the action of high-pressure furnace gas. ② During the maintenance of the furnace mouth, a stable gas leakage channel is formed around the taphole. After the first opening, the formed gas leakage channel is not repaired, which induces sputtering. After the taphole is blocked with new gun mud for many times, the formed gas leakage channel is blocked. After the taphole is used many times, the sputtering is reduced. ③ Insufficient iron quantity. When the taphole is newly opened, or when tapping iron from two or more tapholes, the amount of iron passing through each minute is insufficient to meet the requirement of stable tapping. Slag wind is discharged through the channel, causing heavy smoke and splashing. After the iron flow stabilizes, the splashing phenomenon disappears. (2) There are brick joints, cracked channels or air leakage in the mud sleeve around the taphole. The gas in the furnace is discharged from the taphole through the channel, accompanied by slag and iron, causing splashing of the tapping iron. (3) The permeability of the tapping mud is poor, resulting in damp mud. (4) The moisture content of the raw materials is not properly controlled. (5) The furnace condition is not smooth, and the air flow in the furnace is unevenly distributed, resulting in large changes in the tapping pressure and unstable iron flow. At this time, the splashing disappears after the furnace condition stabilizes.

2.2.2    Improvement measures (1) Increase the amount of mud and increase the taphole length. Regularly perform grouting maintenance around the taphole. When the iron quantity is insufficient, avoid tapping iron from multiple tapholes. (2) Regularly perform grouting treatment to block the gas channel. (3) Adjust the formula of taphole mud to improve its air permeability. (4) In the formula of taphole mud, the moisture content of various raw materials must be strictly controlled.

2.3    Plugging failure After plugging and holding pressure, molten iron flows out, and plugging fails. It is necessary to open a new hole and plug again.

2.3.1    Common problems (1) Water content is not properly controlled, and a large amount of volatile gas is generated at high temperature, resulting in a loose structure of the taphole mud after sintering, which is not conducive to preventing the penetration of high-temperature and high-pressure slag iron and the extrusion of high-pressure coal gas in the furnace. (2) The taphole mud itself sintering speed is slow and cannot be effectively sintered within the holding pressure time. (3) Impurities such as foreign moisture, oil, slag iron, dust, and dry and solidified taphole mud cleaned from the muzzle are mixed in. (4) The pressing time is too short. The taphole mud is removed before it is fully dried to form the initial strength. The static pressure of the slag iron inside the furnace and the high-pressure coal gas may break the taphole mud structure, resulting in plugging failure. (5) The slag iron in the furnace is not completely discharged. Plugging with wind is conducive to the emptying of the slag iron inside the furnace. The presence of wind at the tapping mouth at the end of the tapping process means that the slag iron around the tapping mouth is emptied. This is conducive to the smooth driving of the mud gun into the tapping mouth and the formation of a dense mud bag structure. If the gun mud column cannot completely push the slag iron back into the furnace during the plugging process, and the slag iron flow is formed inside the tapping channel, it is easy for a small amount of slag iron to flow out after the gun is removed. (6) Mud leakage occurs, the effective gun mud volume is reduced, and the plugging effect cannot be achieved. The reasons for the mud leakage are: ① Insufficient mud volume; ② Too soft gun mud; ③ Damage to the gun nozzle; ④ The slag iron outside the tapping mouth is not cleaned up; ⑤ The tapping mouth is deformed, etc. (7) The mud gun machine is not cleaned in time or the gun is pressed for a long time, resulting in serious coking inside the mud gun machine and a thinner column of material. The thin gun mud column is not conducive to completely pushing the slag iron and high-pressure gas back into the furnace and forming a complete mud bag accumulation.

2.3.2    Improvement measures (1) Reduce the water content of the taphole mud. (2) Increase the sintering speed of the taphole mud. (3) Improve the storage and use environment of the taphole mud to avoid pollution. (4) Prolong the taphole pressing time appropriately. (5) Drain the slag and iron and block the taphole when there is wind. (6) Specific analysis of the mud leakage phenomenon: increase the amount of mud injection; increase the Maxwell value; replace the damaged taphole mouth in time; clean the slag and iron outside the iron mouth for each furnace; regularly maintain the iron mouth. (7) Reduce the taphole pressing time and regularly clean the inside of the mud taphole machine.

2.4    High mud injection pressure Mud injection requires a higher pressure, and the amount of taphole mud injected becomes less. 2.4.1    Common problems (1) The Maxwell value of the taphole mud is high. (2) The preheating temperature does not meet the temperature requirements, and the taphole mud is not softened enough before mud injection. (3) The taphole depth is large, the taphole opening diameter is small, the hole is skewed, and the mud injection pressure is high. (4) The taphole is not cleaned in time, and coking is serious. (5) The taphole mud is stored for too long or in the open air, and the binder loses its softening ability.

2.4.2    Improvement measures (1) Reduce the Marshal value of the taphole mud. (2) It needs to meet the preheating requirements. At present, the taphole mud is mostly preheated by adding it to the mud tapping machine next to the tapping port before iron is tapped. It is heated by absorbing the heat of the molten iron during the tapping process. Generally, the preheating requirements can be met. (3) After the tapping is removed, the tapping end face is leveled to prevent the drill from deviating. The drill bit should be replaced in time when it is worn or the size is not suitable. (4) Clean the coking inside the mud tapping machine regularly. If the mud tapping machine coking occurs frequently, the amount of the taphole mud binder should be adjusted in time or the tapping time should be reduced. (5) Shorten the storage time of the taphole mud. It is not easy to store it in the open air, especially in the sun. At present, the taphole mud mostly uses a more environmentally friendly resin binder. Compared with the traditional tar binder, it has high high temperature strength and less pollution, but it hardens quickly, has a short shelf life and is expensive. In order to compensate for the deficiency of resin binders, two or more binders are usually mixed and used, such as tar-resin, etc.

2.5    Short tapping mouth Short tapping mouth cannot guarantee the tapping time, which is not conducive to protecting the side wall of the furnace and poses a great safety hazard.

2.5.1    Common problems (1) Tapping time and slag discharge. The process of slag discharge is a process of gradual consumption of tapping mud. As the tapping time increases, the consumption gradually increases. (2) Tapping mud has poor resistance to scouring and slag erosion [2]. (3) Poor furnace condition, molten iron circulation, and thin furnace wall. (4) Poor bonding between new and old tapping mud.

2.5.2    Improvement measures (1) Ensure sufficient mud volume. Sufficient mud volume can continuously form new mud bags and maintain the depth of the tapping mouth. (2) Improve the tapping mud's resistance to scouring and erosion. (3) Maintain a certain furnace wall thickness. The tapping depth is related to the thickness of the furnace wall. For a new furnace, the furnace wall is thick and the tapping depth is deep; for a later furnace, the furnace wall is thin and the tapping depth will also decrease accordingly. (4) Improve the bonding performance of new and old taphole mud to maintain the taphole depth and form a complete mud bag to protect the furnace wall at the taphole.

During the use of blast furnace taophole mud, problems such as long opening time, splashing, plugging failure, high mud pressure, and short iron mouth appear. These are related to the furnace condition, the characteristics of the taophole mud itself, and the usual maintenance and operation process. Only by accurately identifying the problems and formulating targeted improvement measures can the normal operation of the blast furnace be guaranteed.