Cause analysis and treatment of difficult opening of blast furnace taphole

　　1. Foreword

　　The iron port of the blast furnace is the process channel for discharging slag and iron in the furnace, and the iron port is repeatedly opened and blocked. The iron port channel is subject to mechanical scouring, chemical erosion of slag iron and repeated cold and hot stress tension and compression of mud iron slag. After tapping, an inverted horn channel is formed, the slag iron is discharged completely, and the ventilation is blocked. The plugging material gun mud is pressed into the iron port channel through the mud striking mechanism of the hydraulic mud gun. Under the reaction pressure in the furnace, a mushroom shaped mud bag is formed to maintain the renewal balance of new and old mud, maintain the normal depth of the iron port, protect the hearth at the iron port and prevent local erosion of slag iron. Under normal conditions, the iron mouth is opened smoothly with a certain depth; However, sometimes in the process of opening, when the normal depth is not reached (most of which are at the position where the bell mouth appears), slag iron flows out, and it is impossible to continue drilling through the top of the mud bag. This phenomenon is usually called iron break or fault and iron leakage. The iron leakage port is generally changed from small leakage to large gap. The iron leakage port causes passive tapping outside the furnace, increases the consumption of drill bit and drill pipe, and will cause premature erosion of hearth and furnace wall for a long time.

　　In the production process of blast furnace, some problems often occur during tapping, and the abnormal iron port will cause many accidents. Sometimes these problems are not only related to the quality of equipment or gunite itself, but also have a great relationship with the stability of blast furnace conditions at that time, the change of slag iron composition caused by the change of chemical composition of raw fuel, the operation in front of the furnace, etc. The iron port is difficult to open and has great harm: frequent opening and blocking or burning of iron port cause uncertainty of personnel and equipment safety factors; Blocking the iron port increases the service frequency of the equipment and shortens the service life of the hydraulic equipment; The use of drill bits and drill pipes has increased significantly; If the slag iron cannot be discharged in time, the increase of slag iron storage in the furnace will worsen the permeability in the furnace, and the top air pressure will rise and fluctuate; The molten iron and slag generated in the blast furnace accumulate in the hearth. If they are not discharged in time, the molten iron level will gradually rise to the height of the tuyere area, which will not only lead to poor furnace conditions, but also cause tuyere burn through accidents.

　　How to reduce and eliminate the iron leakage is a problem to be solved jointly by the blast furnace managers, the production technicians of anhydrous blast furnace mud and the iron mouth workers in front of the furnace.
 

　　2. Cause analysis

　　2.1 process reasons:

　　2.1.1 firstly, judge and analyze where it is difficult to feed at the iron mouth. Different channel positions mean different reasons, and the sintering performance of gun mud at different temperatures is also different.

　　2.1.2 the difficulty of opening usually occurs in the ultra-deep iron mouth area, because the drill bit used in the ultra-deep iron mouth opening has been seriously worn, and the cutting ability has gradually weakened, so it is unable to smoothly penetrate the red hot hard shell at the front end of the mud bag. In addition, the powerful impact of the opening machine is easy to crack the mud bag at the front end of the iron mouth to produce slag iron.

　　2.1.3 the volume stability of the blasting mud is poor, the high temperature shrinkage is large, and the mud bag has large cracks, resulting in the infiltration of slag iron; Metal cutting states can be divided into the following types of metal chip states.

　　See Figure 1

　　Strip chip crushing chip unit chip chipping chip

　　Fig. 1 chip status

　　The cutting state of gun mud at high temperature is as follows: the chips are in granular shape with uneven size, belonging to chipping chips. The calcined gun mud has certain brittleness and belongs to brittle material with low tensile strength. During the cutting process, the chips are brittle under the action of tensile stress without plastic deformation, forming irregular fragment like chips. The calcined gun mud contains various hard points. When the tool encounters the hard points in the gun mud during turning, due to the low bonding strength between the hard points and the gun mud matrix, the hard points are peeled off from the gun mud matrix one by one under the extrusion of the tool to form chips of uneven size. This requires the drill bit to have better strength and lower toughness at high temperature.

　　The clay has poor plasticity, which ensures that it will not be broken when being shot from the clay cannon, and it is easy to squeeze into and fill the iron port channel.

　　2.1.4 the mash value of the blasting mud itself is too high. The Macha value increases too fast, the opening in front of the furnace is difficult, and the operation is more difficult, which affects the slag and iron tapping operation.

　　2.1.5 the iron mouth is too shallow due to mud running and emitting.

　　2.1.6 the blast furnace has poor liquid permeability for a long time, and the circulation is too rapid, resulting in the formation of large head shaped mud bags, resulting in leakage at the joint of furnace wall and mud bags.

　　2.2 equipment causes:

　　2.2.1 poor bit quality, such as; The bit alloy falls off or the bit is broken or severely worn.

　　2.2.2 the opening oil system pressure is too small (oil circuit leakage or oil circuit blockage, overflow valve failure, pump failure, etc.), the load is lower than the required value, and the opening efficiency is reduced.

　　2.2.3 the drill pipe is not strong enough, which will cause the deformation of the drill pipe during the overall operation, reduce the drilling stability and increase the feed resistance.

　　2.2.4 the ground angle bolt of the rock drill is loose, so that the trolley running track is not on the same center line with the center of the iron mouth, and the accumulated deviation is too large, resulting in channel offset.

　　2.2.5 the throttle valve or spring of the hydraulic system is broken, which makes the speed of guniting mud too fast, and the mud bag in the iron port channel becomes unstable.

　　2.2.6 it is also difficult to open because the traveling wheel of the opening machine trolley is blocked or the vibration frequency and impact force efficiency of the rock drill are reduced.
 

　　3. Treatment method

　　3.1 pre furnace operation and treatment methods

　　3.1.1 the operation in front of the furnace shall be standardized to stabilize the mud amount and avoid long-term operation of ultra deep taphole.

　　3.1.2 if iron leakage is found at the iron port, it shall be blocked in time. If iron tapping conditions are available, iron tapping shall be carried out in time, and the air can be reduced appropriately. When re drilling mud, it is necessary to reduce the amount of mud, increase the pressure and reduce the speed of mud drilling. Mud drilling shall be carried out in 3 to 5 times, so that the newly entered mud can be fully filled into the cracks in the front mud bag, and iron leakage can be reduced in a physical way.

　　3.1.3 stabilize the quality of blasting mud. With high-quality and high-purity raw materials and carbonaceous raw materials as the binder, the blast mud has greatly improved the iron slag corrosion resistance compared with the water blast mud, which can appropriately prolong the tapping time at the iron port and reduce the tapping times.

　　The process flow of blasting mud mainly includes:

　　① Accurate batching;

　　② Dry milling;

　　③ Oiling and rolling;

　　④ Performance control;

　　⑤ Warehousing and saving;

　　⑥ Maintenance;

　　⑦ Use.

　　The temperature of gunshot mud during mixing and rolling is generally 55 ~ 65 ℃. Dry grind for 5 ~ 10min first, then add the binder and then grind the mud with fine powder. The amount of binder is about 98% of that specified in the formula, and the remaining 2% is used as the adjustment space. The mud milling time varies according to the furnace capacity of the blast furnace and the depth of the iron mouth. Generally, the mud shall be milled for 35 ~ 45min, and multiple samples shall be taken to determine the mash value. According to the test results, the ratio of tar or dry powder shall be increased or decreased, and then the milling shall be continued for about 10min. The first batch of gun mud is produced every day. The mud mill is relatively dry, and an appropriate amount of binder should be added. There is also a certain relationship between the amount of binder added and the temperature. The amount of binder added should be appropriately reduced in summer and increased in winter. Test method of Macha value: collect 3-4 shot mud samples from the mud mill, twist them into shape and put them into the measuring instrument for testing. If the Masha value is qualified, prepare for discharging; If the Martha value is high, add a small amount of binder, and test the Martha value after full mixing; If the Martha value is low, add an appropriate amount of dry materials in proportion, and test the Martha value after full mixing; Mud can be discharged only when the mashing value meets the requirements specified in the standard. The observation and summary show that the daily output of blast furnace increases, so does the mash value of blast furnace mud. For blast furnaces with daily output >6000t, the mash value of blast furnace mud is 0.5 ~ 0.65Mpa, and the daily iron production times are 9 ~ 11. If the strength is too high or excessive, the clay addition can be adjusted, and the expansion agent can be adjusted appropriately to improve the strength of blast furnace mud.

　　3.1.4 regularly calibrate the equipment operating parameters, including pressure, horizontal position, angle, sludge discharge speed, etc. According to the equipment condition, slag iron composition detection, blast furnace charge parameters, etc., the blast furnace mud meeting the production needs is prepared. For each new batch of spare parts, the blasting mud shall be used first after arriving at the site, and the batch consumption shall be carried out after meeting the site use requirements; Ensure that the mud running quality is stable and the iron mouth runs smoothly.

　　3.1.5 pay attention to the operation mode of clay gun in case of long-term poor liquid permeability of blast furnace and excessive circulation, control the iron port channel, slowly adjust the size of clay bag, stabilize the combination of furnace wall and clay bag, and avoid sharp changes in iron port channel and depth.

　　3.1.6 do a good job of equipment spot inspection, pay attention to the quality of spare parts, timely repair and adjust any problems found, especially observe the operation status of the equipment during the test run, so as to avoid opening difficulties caused by equipment abnormalities and form a vicious cycle of repeated impact.
 

　　4. Concluding remarks

　　According to the use statistics of the past three years, if it is difficult to open due to gun mud or equipment, 12 drill pipes will be consumed every day, and the output will be lost by 200 tons. If the drill pipe is 200 yuan / piece, the drill bit is 50 yuan / piece, and the iron efficiency per ton is 200 yuan / ton, the daily consumption and reduction efficiency will be 12*200+12*50 +200*200=43000 yuan.

　　The quality and stability of gun mud is an important indicator to ensure the smooth operation of the iron port. At the same time, measures such as strengthening equipment spot inspection, standardizing furnace front operation and spare parts, and field inspection of gun mud are taken. Timely communicate and improve problems found, so as to avoid multiple incidents and reduce consumption and investment losses.