On the improvements to the lining of the Ausmelt furnace in our plant
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Some time ago, I had a conversation with a young chief engineer at one of the steel mills in our city (Mr. Wang). Out of curiosity, I asked him about the lining of ironmaking blast furnaces and their lifespan. The lining of the ironmaking blast furnace consists of high-alumina bricks and graphite bricks, giving a lining life of up to 10 years! At that time, I raised the issue that graphite is prone to oxidation and erosion, and President Wang explained the reason: the environment inside an iron smelting blast furnace is a reducing atmosphere (which produces blast furnace gas), and graphite bricks are not easily eroded in such an atmosphere; moreover, graphite has the advantage of being resistant to thermal shock. Our factory uses graphite crucibles for the casting of precious metals such as gold and silver. Given that the gas phase in our plant’s Ausmelt furnace is currently in a reducing atmosphere, adopting a spinel+graphite brick lining in the middle and upper sections of the furnace, following the approach used in ironmaking blast furnaces, would offer the advantage of resistance to sudden temperature changes (the Ausmelt furnace is often shut down for cleaning, and the temperature of the furnace lining changes significantly during these cleaning operations, which can lead to the lining falling off). Regarding the above idea, it certainly cannot be acted upon hastily; it is recommended to use the next maintenance opportunity to conduct a test on the upper lining of the Ausmelt furnace – that is, make partial modifications to the lining and monitor the actual results in order to determine whether it is feasible.
LZ, although graphite bricks are not easily eroded in a reducing atmosphere, it is still necessary to take into account the properties of the slag during the smelting process. Additionally, what is the strength of the graphite bricks? Ausmelt melting is a type of intensive melting process with high stirring intensity in the furnace; are graphite bricks suitable for use in this process?
Graphite bricks have good heat transfer properties, but the nature of the slag and the erosion resistance of the graphite bricks must be taken into account. The Ausmelt furnace uses top-blown nozzles, resulting in strong mixing inside the furnace. Double-layer refractory materials can be considered; the refractory bricks in contact with slag should be made of spinel, as it offers strong resistance to erosion. The inner layer is made of graphite bricks, which offer good heat transfer properties; slag accumulation on the furnace wall helps to extend the lifespan of the furnace lining. I hope for thorough communication.
It is recommended that the building owner consider the issue of alkali metals. What you mentioned regarding smelting in blast furnaces isn’t a problem per se, but the main concerns in such processes are the accumulation of alkali metals and corrosion. In blast furnace smelting: Zinc – zinc volatilizes at 900 degrees; it rises and then condenses on the furnace walls, causing the walls to expand and damaging the furnace shell. Lead – it is easily reduced and settles at the bottom of the furnace due to its high density, thereby damaging the furnace lining. Lead vapor circulates and accumulates in the upper part of the furnace, forming growths that damage the furnace lining. Potassium and sodium – they volatilize and accumulate in the upper part of the furnace, also forming growths that damage the furnace lining. This is for reference only; these issues are common in blast furnaces.
It has been a year since the original poster posted the topic; I wonder if they have taken any action? How effective is it? I hope to be able to tell everyone.
It was very informative, thank you. The only regret is that the original poster didn’t continue; it would have been even better if the verification results could be obtained
Yeah. I don’t know what stage LZ is at now, or what the outcome is
Carbonaceous refractory materials perform well in steelmaking, characterized by their resistance to sudden temperature changes and strong resistance to infiltration; however, their oxidation resistance is poor, which leads to limited use in the non-ferrous metal smelting industry. It would be highly significant if these materials could be adopted in this sector.
I want to know the result. There are still significant differences between iron smelting and non-ferrous metal processing. Please, LZ, tell me the test results. Thank you very much