Improvement and control measures of loss of magnesia-chromium bricks used in copper-smelting converters

A nonferrous metal production company, after several minor repairs to its copper smelting converter, measured and counted the refractory brick loss from the converter eye to the upper furnace mouth and the furnace mouth area. The refractory brick loss is shown in Table 1.
Table 1 Refractory brick loss from the converter eye to the upper furnace mouth and the furnace mouth area

As can be seen from Table 1, the lifespan of the eye bricks and furnace mouth bricks determines the life of the converter.
Improvement and control measures
1. Improve the material of magnesia chrome bricks in the wind eye area
Magnesia-chromium bricks in the wind eye area are required to have strong high temperature resistance, erosion resistance, chemical corrosion resistance, impact vibration resistance and other properties. Therefore, the eye bricks and triangular bricks in the wind eye area were changed from the originally designed fused 20 magnesia chrome bricks (DMGe-20) to the fused 26 magnesia chrome bricks (DMGe-26). The physical and chemical indicators are compared in Table 2.
Table 2 Physical and chemical indicators of fused magnesia chromium bricks

The increased content of chromium oxide (Cr2O3) in magnesia-chrome bricks improves the erosion resistance of magnesia-chrome bricks and slows down the washing speed of magnesia-chrome bricks during use. At the same time, the porosity of DMGe-26 magnesia chrome bricks is significantly reduced, shortening the depth of slag erosion and metal penetration, shortening the hot-end metamorphic layer of magnesia chromium bricks (the length of the metamorphic layer is shortened by about 10mm), and reducing the peeling length of refractory bricks. , slowing down the loss rate of eye bricks.
2. Strictly control the quality of maintenance
2.1 Mechanical aspects
(1) When repairing the eye seat and tee seat, polish the surface of the seat to ensure the flatness of the seat surface. Use anti-loose bolts during installation, and replace ordinary asbestos pads with aluminum-coated asbestos pads to ensure that there are no air leakage gaps at the wind eye seat and tee seat.
(2) Make an eye tube adjustment template and use the template to select two eye tubes as the calibration benchmark. After the center distance of the eye tubes is corrected, it must meet the eye brick masonry requirements, and weld the eye tubes and eye casings. firm.
(3) After the wind eye tube is installed in place, plug the mouth of the wind eye tube with a plug, start the GM fan to supply air to the converter, and suppress the wind pressure to the wind pressure during normal production of the converter (about 0.1MPa). Check the air leakage at each connection point. If the air leakage point is found, deal with it in time to avoid insufficient air intake due to air leakage, resulting in excessive cleaning of the inner tube of the wind eye and the furnace bricks in the wind eye area.
2.2 Kiln masonry aspects
(1) The eye bricks are laid from the middle to both ends. After the bricks are laid, the front and back of the eye bricks are polished to avoid triangular joints in local locations.
(2) The square bricks from the wind eye brick to the upper furnace mouth are set back as required to reduce the height difference between the brick layers in the transition section of the setback and slow down the loss rate of the furnace bricks in the transition section.
(3) The mortar in the brick joints is full and uniform, and the inside and outside are consistent. The joint between the old and new bricks is less than 3mm. The width of the processed bricks is not less than 1/2 of its own width, and the thickness is not less than 2/3 of its own thickness.
(4) When building the upper and lower furnace mouths, weld steel sheets on the furnace mouth to lock the bricks to prevent the furnace mouth bricks from falling off when cleaning the furnace mouth during production.
3. Standardize oven operation
Formulate the specifications for the converter minor repair and drying oven. When drying the oven, use wood and oil guns to dry the oven in stages, and strictly control the temperature rise according to the temperature rise curve to ensure that the deviation between the oven temperature and the theoretical temperature rise curve does not exceed 50°C, and ensure that the thermal expansion of the refractory material meets the material requirements. Avoid damage to refractory bricks caused by large fluctuations in oven temperature.
4. Optimize production operations
(1) Establish the standard for adding cold materials to prevent the furnace temperature from being too high; stably control the taste of matte, formulate standards for the amount of matte in a single furnace, avoid large fluctuations in the amount of matte from washing furnace bricks, and strictly control the output of a single furnace.
(2) During the slag making process, the alkalinity of the slag is appropriately increased, and magnetic iron is formed in the furnace to adhere to the furnace wall, forming “hanging slag” in the furnace to protect the furnace bricks.
(3) During converter production, oxygen must be turned off before shaking the furnace to slow down the oxidation loss of the windshield by oxygen-rich air.
5. Conclusion
Through the implementation of the above measures, the service life of the converter for minor repairs was increased from 90 furnaces to 140 furnaces in 2016. Although the life of the converter has been improved, there is still a considerable gap with other smelters. We will further optimize the converter production operation by transforming the masonry structure of the converter and strictly controlling the quality of the converter maintenance, so as to strive to reduce the number of converter minor repairs. Lifespan increased to 200 furnaces.