With increasingly fierce market competition, reducing production costs has become a key priority for copper smelting plants. One important way to lower operating costs is to reduce refractory brick consumption per ton of copper and extend the service life of converter linings.
The service life of converter refractory bricks is affected by many factors, including matte grade, refractory material quality, lining construction quality, blowing practice, process control and daily operation. This article analyzes a practical case of converter lining damage in a copper smelting plant and discusses effective measures to improve converter campaign life.
The plant operates two 60 t copper matte converters. The lining structure is arranged as follows:
The tuyere brick thickness is 520 mm. Above the tuyere zone, there are nine layers of 520 mm bricks and fourteen layers of 460 mm bricks as the transition zone. Below the tuyere zone, the brick thickness is 380 mm. Refractory materials are also installed around the converter mouth. The tuyere zone and the areas above it are lined with thicker refractory bricks in order to improve corrosion and erosion resistance.
Production practice shows that the most vulnerable areas of the converter lining are:
During the converting process, these areas are exposed to severe working conditions, including high-temperature molten bath erosion, mechanical scouring, slag corrosion, silica flux attack and periodic temperature fluctuations. In addition, converter mouth cleaning and tuyere maintenance may cause mechanical impact and abrasion.
Among all lining areas, the converter mouth, tuyere zone and slag line of the end wall are not only the most easily damaged refractory areas, but also structurally weaker parts of the lining. They are also the most technically demanding parts during lining construction. The synchronized service life of these three areas largely determines the overall campaign life of the converter.
According to production experience, when the remaining brick thickness in the tuyere zone is less than 90 mm, the converter should no longer continue operating and local repair is required. For other lining areas, when the remaining brick thickness is below 150 mm, a major shutdown and relining should be considered.
There are many causes of converter lining damage. In general, they can be summarized into three major categories:
During converting, injected air creates strong impact force. The rising and expanding gas flow brings significant stirring energy into the molten bath. When the gas-liquid two-phase flow impacts the bath surface, molten material can be splashed onto the refractory lining, causing strong mechanical impact on the brick surface.
At the same time, this mechanical scouring also creates favorable conditions for chemical corrosion. Therefore, selecting a proper blowing intensity is an important factor in improving converter lining life. A reasonable air supply intensity and blowing system can help reduce the impact of molten material on the lining and extend the service life of the converter.
During the converting process, magnetite and accretions may form around the tuyere area. When cleaning the tuyere, molten material may flow back into the tuyere zone, causing build-up and blockage. Frequent mechanical cleaning is therefore required.
However, the vibration and impact caused by tuyere cleaning have a serious destructive effect on the surrounding refractory bricks. Under the combined effect of mechanical damage and molten bath corrosion, the surface of the tuyere brick gradually deteriorates. When the deteriorated layer develops to a certain thickness, spalling may occur, seriously affecting converter campaign life.
Thermal shock resistance refers to the ability of a refractory material to resist damage caused by temperature changes during heating and cooling. It is an important performance index for converter lining materials.
Many refractory materials are damaged at temperatures far below their refractoriness because of poor thermal shock resistance. In actual converter operation, the converter works under periodic conditions. Temperature fluctuations may occur due to waiting for material, converter mouth repair, equipment failure or temporary blowing interruption.
Frequent heating and cooling generate thermal stress inside the refractory bricks. Once this stress exceeds the structural strength of the brick, cracks, peeling and spalling may occur. Therefore, maintaining stable furnace temperature is essential for reducing thermal damage to the lining.
Chemical corrosion mainly includes molten bath corrosion and gas corrosion. These reactions dissolve, penetrate or react with magnesia-based refractory materials, changing their structure and weakening their performance.
Molten slag and metal can contact and penetrate the refractory through pores, cracks and grain boundaries. During contact, refractory components may dissolve into the molten phase. On the refractory surface, low-melting compounds may form, and their bulk density and structure can be very different from the original material.
When the molten phase penetrates into the refractory to a certain depth, a deteriorated layer is formed. Because this layer has a different structure from the original brick, volume changes and structural stress occur. This leads to cracking, peeling or spalling.
After the deteriorated layer falls off, a fresh refractory surface is exposed to the molten bath again, and the same corrosion process repeats. This cycle causes continuous and severe lining damage.
Gas corrosion mainly refers to reactions between SO₂, O₂ and basic oxides in the refractory during the converting process. These reactions may generate metal sulfates. Since the density of the reaction products differs from that of the original basic oxides, internal stress is generated.
As a result, the refractory structure becomes loose and weak, leading to peeling and accelerated lining damage.
In general, wet laying may cause bricks to absorb moisture, which is not favorable for dehydration during the 400°C holding stage. Therefore, the converter lining should adopt a combination of dry and wet laying.
The upper and lower four layers around the tuyere zone and the converter mouth area can be wet laid, while other areas should be dry laid.
The tuyere bricks should be laid from the center toward both ends instead of from one end to the other. This helps avoid triangular joints, misalignment and uneven gaps in the tuyere brick assembly.
The upper and lower converter mouth arch bricks should also be laid symmetrically from the center toward both sides. This method is beneficial for closing and locking both sides tightly, preventing uneven gaps and brick loosening.
Brick joints should be fully and evenly filled, with consistent joint thickness from inside to outside. Expansion joints should generally be controlled at 2–3 mm.
Locking treatment should be applied at the connection areas of different lining parts. For processed bricks, the cut portion should not exceed one third of the brick, and the remaining processed brick should not be less than two thirds of its original size.
The magnesia-based filling material should be able to form a lump when squeezed by hand, but should disperse after falling from a height of one meter. The filling layer should be uniform in thickness and compactness.
Broken, chipped or moisture-damaged magnesia-chrome bricks must not be used. Refractory material quality control before installation is a basic requirement for ensuring lining performance.
Tests show that magnesia-chrome bricks may crack after repeated thermal shock cycles at around 850°C. Therefore, sharp temperature fluctuations should be avoided as much as possible.
In production, the amount of cold charge should be controlled to stabilize converter temperature. Reducing sudden temperature drops can help lower thermal stress and prevent premature lining damage.
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Neutral or weakly basic slag can provide a certain protective effect on the refractory lining. However, fayalite has a strong corrosive effect on periclase. It can dissolve the surface of magnesia-based refractories and penetrate into the brick structure.
The higher the temperature, the greater the solubility of MgO in converter slag. At high temperature, low refractoriness compounds such as forsterite may form, reducing the working performance of magnesia bricks.
Iron oxides can also saturate periclase and chromite grains, causing grain damage and accelerating brick wear.
When the silica content of converter slag is below 18%, the slag is strongly basic and can seriously corrode magnesia-based linings. When the silica content is above 28%, the slag becomes acidic and also causes severe corrosion. When the silica content is controlled between 19% and 24%, the slag is generally neutral or weakly basic and is less corrosive to magnesia-based brick linings.
Therefore, in production, the silica content of converter slag should be strictly controlled and stabilized within the range of 19%–24%.
The technical level of lining workers, converter operators and production managers has a direct influence on lining quality and converter service life.
It is necessary to improve the skills of personnel involved in refractory installation, converter operation and production management. Operators should also be trained to respond correctly to unexpected process fluctuations and equipment problems.
Scientific and strict production supervision can help reduce abnormal lining damage and improve overall converter performance.
In production, mismatch between converter size and blower capacity should be avoided. A large blower should not be used on a small converter, as excessive air flow can cause severe tuyere zone erosion, strong bath splashing and accelerated refractory damage.
The oxygen enrichment level should also be properly controlled. In general, the oxygen enrichment concentration should not be too high. When oxygen enrichment exceeds 27%, the scouring effect on the refractory lining may increase significantly.
While the hot-face working lining of a copper matte converter must focus on resistance to slag corrosion, matte penetration, mechanical erosion and thermal shock, the backup lining and insulation layer should not be ignored.
A properly designed backup insulation layer can help:
For selected non-contact backup areas, suitable insulation materials may be considered according to the converter structure, shell temperature, available lining thickness and mechanical load. Possible options include microporous insulation boards, high-temperature calcium silicate boards or ceramic fiber boards.
For example, Firebird microporous insulation boards can be used as a high-efficiency backup insulation material in suitable non-contact zones where reduced heat loss and lower shell temperature are required. For lower-temperature backup areas or auxiliary structures, calcium silicate boards and ceramic fiber products may also be considered.
The final material selection should be based on actual operating temperature, lining structure, compressive load, moisture exposure, installation method and maintenance cycle.
In actual production, the following points should also be emphasized:
Clear standards should be established for converter shutdown, lining demolition, repair, drying and start-up. These standards should be strictly followed to avoid unnecessary lining damage.
For a newly repaired converter, proper coating and copper infiltration operation should be carried out during start-up to form a protective layer and improve lining stability.
Temperature control at each production stage and accurate endpoint judgment are very important. Over-blowing should be strictly avoided, especially in the second blowing period, because it can cause serious damage to the converter lining.
Employee training should be continuously improved. Higher operating skill, better process understanding and stronger awareness of refractory protection are important for extending converter campaign life.
The damage of converter refractory bricks is mainly caused by the combined effects of mechanical force, thermal stress and chemical corrosion. By improving lining construction quality, stabilizing converter temperature, controlling slag composition, optimizing blowing intensity, improving personnel skills and selecting suitable refractory materials, the service life of converter linings can be effectively extended.
For copper matte converters, the hot-face working lining should prioritize corrosion resistance, erosion resistance and thermal shock resistance. At the same time, the backup lining and insulation layer should also be properly designed to reduce heat loss, control shell temperature and support safer, more stable operation.
Through systematic management of refractory materials, lining construction and process operation, refractory brick consumption per ton of copper can be effectively reduced, helping copper smelting plants lower production costs and improve overall economic benefits.
