1. Masonry and lining damage of converter
There are 2 60t converters in our factory. The masonry structure of the converter is: blasthole bricks 520mm, above the blasthole, there are 9 layers of 520mm and 14 layers of 460mm transition zone, below the blasthole zone is 380mn, and the furnace mouth is built with refractory Material, masonry is thicker in the wind eye area and above, in order to enhance the corrosion resistance.
Production practice shows that the vulnerable parts of the converter lining are: furnace mouth, wind eye, end wall. During the blowing process, it is subject to severe mechanical erosion of high-temperature melt, severe erosion of slag and quartz flux, periodic fluctuations of furnace temperature, mechanical collision and abrasion during furnace mouth cleaning and wind eye maintenance, and the operating conditions are extremely harsh, especially for furnaces. The three parts of the mouth, wind eye, and end wall slag line are not only the vulnerable parts of refractory materials, but also the weakest link of the masonry structure, and the parts that require the highest technical content in road construction. The synchronous life of these three parts largely represents the age of the converter.
According to production practice, when the thickness of the bricks in the blast hole area of the converter is less than 90mm, they can no longer be used, and the furnace needs to be stopped for digging. When the remaining parts of the masonry are below 150mm, the furnace needs to be shut down for overhaul.
2. Analysis of factors affecting converter life
There are many reasons for the damage of the converter lining. In summary, they are mainly the result of mechanical force, thermal stress and chemical corrosion.
2.1 The influence of mechanical force
2. 1.1 Damage to brick lining caused by the energy of stirring the melt
Due to the impact force of the blown gas and the rise and expansion of the air flow, a large amount of stirring energy is brought to the melt. When the gas-liquid two-phase mixed fluid impacts the surface of the melt, the melt is sprayed onto the brick lining by the gas-liquid two-phase fluid It causes strong mechanical impact on the furnace lining and creates conditions for chemical erosion. Therefore, choosing a reasonable blast intensity is an important part of improving the life of the converter. A relatively suitable air supply intensity and air supply system will help weaken the melt’s impact on the furnace lining. The impact force extends the life of the converter.
2. 1. 2 Clean up the damage of the wind eye to the wind eye brick
In the blowing process, magnetic iron is inevitably generated. When the wind eye is operated, the melt in the tuyere area is recharged, and nodules are easily formed at the tuyere. The tuyere needs to be cleaned continuously, and the damage effect of mechanical vibration on the brick lining in the tuyere area It is very large, causing the surface of the brick lining in the tuyere area to deteriorate under the action of melt erosion. When the metamorphic layer expands to a certain extent, the brick body will peel off, which seriously affects the furnace life.
2.2 The influence of thermal stress
The resistance of refractory materials to damage caused by temperature changes during heating and cooling is called thermal shock resistance, which is an important indicator of the quality of refractory materials. Most refractory materials are damaged due to poor thermal shock resistance at temperatures much lower than their refractoriness. The thermal damage of refractory materials is mainly related to the thermal stress produced by refractory materials during the production process.
The converter is a periodic operation, and it is inevitable that the temperature of the converter will fluctuate due to the failure of the material, the repair of the furnace port and the failure of the equipment during the production.
2.3 Effects of chemical attack
Chemical attack mainly has two forms: melt erosion (slag, metal solution) and gas erosion. It is manifested in the dissolution, combination and penetration of magnesia refractory materials, which changes the structure of refractory materials and weakens their performance.
2. 3. 1 Melt erosion
The melt contacts and penetrates through the pores, cracks and the interface between the refractory materials. During the contact process, the refractory material dissolves into the melt, and the surface of the refractory material forms an easily soluble compound whose bulk density changes greatly with the raw material. When it dissolves to a certain extent, the infiltration occurs. When the melt penetrates the refractory material to a certain depth, it will produce The metamorphic layer with completely different properties of the raw material changes in volume due to the different structure of the metamorphic layer and the raw material, resulting in structural stress, which leads to cracks in the production of raw materials. Serious cracks cause the metamorphic layer to peel off or crack, and new materials will be generated under the erosion of the melt. Refractory material is seriously damaged by this cycle.
2. 3. 2 Gas erosion
Gas erosion generally refers to the reaction of the so 2 and o 2 in the copper matte with the alkali oxides in the refractory during the blowing process to form metal sulfates, and its density is lower than that of the alkali oxides. The difference in phase bulk density produces stress, which makes the refractory material loose and peels off, and aggravates the damage of the refractory material.
3. Measures to extend converter life
3. 1. Change the masonry method and improve the process standard:
3.1.1 Under normal circumstances, wet masonry will cause the brick body to become damp, which is not conducive to constant temperature dehydration at 400 ℃. The masonry of the converter adopts a combination of dry and wet, that is, the upper and lower 4 layers of the tuyere area and the furnace mouth area are made of wet masonry, and the rest are dry-laid.
3.1.2 The masonry of the tuyere bricks was changed from one end to the middle to both ends to avoid triangle joints and dislocation of the tuyere combination bricks.
3.1.3 Changed from laying on one end and lower furnace mouth reverse arch bricks to masonry from the center to both ends, and proceeded symmetrically, which is conducive to closing and locking on both sides, and preventing the uneven and tight gap between the two bricks from falling off .
3.1.4 The distribution of the brick joints is substantial, uniform, and the inside and outside are consistent. The expansion joints meet the requirements of 2-3 mm. The joints of each part of the brick body shall be locked, and the processed brick body shall not exceed one-third. The processed brick Body is not less than two-thirds of itself.
3.1.5 Magnesium fillers are required to be kneaded into a mass by an expert hand, and scattered from a height of one meter. The thickness of the filler is uniform and the firmness is uniform.
3.1.6 Damaged, broken corners and damp chrome-magnesium bricks must not be used.
3.2. Control the converter cold material to prevent high temperature corrosion
The test proves that when the chrome-magnesia brick has thermal vibration resistance at 850 ℃, it will break and break 18 times, resulting in damage to the brick lining. Therefore, it is necessary to prevent the furnace temperature from rising and falling and violent fluctuations, and to reduce and eliminate the damage to the brick lining caused by thermal stress. In production, the method of controlling the amount of cold material added is used to stabilize the furnace temperature.
3.3. Reasonably control the silicon content of converter slag, reduce chemical corrosion, neutral or weak alkaline slag, and protect the brick lining. Ferroolivine corrodes severely, and it can not only dissolve the surface of the magnesia refractory, but also penetrate into the interior to dissolve. The higher the temperature, the greater the solubility of M g O in converter slag, and the formation of forsterite with a lower softening temperature under load at high temperatures, which reduces the working performance of the magnesia brick. Iron oxides can also saturate periclase and chromite crystal grains, cause crystal grain damage, and cause magnesia bricks to be damaged too quickly. The converter slag contains less than 18% silicon and is alkaline, while the converter slag contains more than 28% silicon and is acidic. Both of them seriously corrode the lining of magnesia bricks. The converter slag contains between 19% and 24% silicon, which is neutral or weakly alkaline and does not corrode the lining of the magnesia brick. In production, the silicon content of converter slag is strictly controlled to stabilize it between 19% and 24%.
3.4. Improve personnel quality
Improve the quality and ability of furnace building, converter operations, and production managers to ensure the quality of furnace building. Improve the ability to respond to emergencies, scientifically and strictly supervise and manage production.
3.5. Reasonable selection of air supply intensity and oxygen enrichment concentration
It is inevitable that the furnace body and the fan do not match during the production process. It is strictly forbidden to use a large fan to supply air to the small furnace body to prevent the tuyere area from being washed out and the melt is severely sprayed. The oxygen-enriched concentration of the converter should not be higher than 27%, and the oxygen-enriched concentration should be greater than 27%, which will wash the brick lining more.
4. Issues that should be paid attention to
The following aspects should also be paid attention to in production:
(1) Formulate scientific standards for shutdown, repair and start-up, such as brick lining removal standards, heating standards, etc., and strictly implement them. (2) When the newly repaired furnace body is started, the operations of "hanging the furnace" and "copperizing" should be carried out to protect the furnace body.
(3) Strict process operation, the control of the furnace temperature at each stage and the judgment of the end point must be accurate. Prevent the occurrence of "overblowing", especially the second-cycle overblowing, which will cause serious damage to the furnace body.
(4) Attach importance to the training of employees and improve the quality of all employees and the level of copper smelting technology.
5. Summary
Through the implementation of the above measures, the energy consumption per ton of copper bricks is well controlled, costs are reduced, and annual benefits are created. As long as attention is paid to masonry quality, process conditions, and elimination of the thermal stress, mechanical force and chemical corrosion factors that damage the chrome-magnesium bricks, the life of the furnace bricks can be prolonged.
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