There are many kinds of non-ferrous metals and various smelting methods. Although the non-ferrous metal industry has some special requirements for refractory materials, the amount used is not large, accounting for about 5% of the total output of refractory materials. Products usually used for research and development in steel or other industries are not paid enough attention to and research on refractory materials is reported. Not much. The major consumers of refractory materials in the non-ferrous metal industry are non-ferrous heavy metal (copper, nickel, lead, zinc) smelting and aluminum smelting.
The processes of nickel smelting and copper smelting are basically similar, except for the following differences: the product of copper smelting converter is blister copper, while nickel smelting is high matte nickel (nickel matte); copper electrolytic refining uses copper anode plates, while nickel electrolytic refining uses It is Ni3S2 anode plate. In order to have a clearer understanding of the functions of smelting and blowing furnaces and the use conditions of refractory materials in the copper and nickel smelting processes, Figure 1 shows the main processes of the copper smelting industry. In order to improve productivity, reduce energy consumption, and reduce pollution, flash furnaces and Noranda furnaces have developed rapidly in copper and nickel smelting in recent years; while traditional blast furnaces and reverberatory furnaces have decreased. Mineral thermal electric furnaces are used where electricity is cheap. Converters are still used for blowing. In addition, ASARCO shaft furnaces that continuously smelt copper and melt electrolytic copper have also developed to some extent.
Flash Furnace
Preheated air or oxygen-enriched air, dried concentrate and flux are sprayed from the top of the reaction tower into the hot reaction tower. The sulfur and iron in the concentrate immediately undergo an oxidation reaction at an extremely fast speed to generate matte or nickel matte ( Copper matte or nickel matte) and initially slag is formed. After falling into the sedimentation tank, further slag is formed and the separation of matte and slag is completed. The matte is regularly released and sent to the converter for blowing. The slag continuously flows into the slag-depleting electric furnace. The flue gas is recovered and made sulfuric acid.
Due to the high oxygen partial pressure and low temperature in the upper part of the tower, a Fe3O4 protective layer is formed on the tower wall. The lower part of the tower has a high temperature and is subject to the rapid flow and erosion of the melt along the surface. The furnace lining is easy to wear and corrode. In the slag line area of the sedimentation tank wall, due to the flow of a large amount of high-temperature slag, the wall lining is also easy to be melted and damaged. Therefore, the wall lining is also easily damaged in these parts. Fused-cast magnesia-chrome bricks protected by water-cooled copper sheaths. The top of the tower and the top of the sedimentation tank are made of fired magnesia chrome bricks. In order to prevent Fe3O4 from precipitating at the bottom of the furnace, the heat insulation of the furnace bottom should be good. Clay bricks should be laid on the insulation layer, and magnesia-chromium ramming layer should be laid on top, and then magnesia-chromium bricks should be laid.
ReactorNoranda
The Noranda melting furnace is a horizontal cylindrical molten pool melting furnace. Daye Smelting Plant and Shenyang Smelting Plant have such furnaces. The concentrate and flux are thrown into the furnace through the end wall at one end of the furnace body by a throwing machine. There is also a burner at this end to provide auxiliary heat. There is an air outlet on the lower side of the cylinder near the feeding end to blow in oxygen-rich air. At the other end of the furnace body, there is a slag discharge hole under the end wall. There is a matte discharge port on one side of the cylinder at the bottom of the sedimentation area near the slag discharge end, and the matte is discharged regularly. The flue gas is discharged from the furnace mouth at the top of the cylinder at the slag discharge end.
The vulnerable parts of Noranda furnace are: tuyere, tuyere area and slag line area. The use of refractory materials here should be checked regularly, and any damage should be repaired immediately.
Silver Furnace
The silver furnace was developed in my country. The basic principle is similar to the Canadian Noranda furnace. Oxygen-rich blast is used to oxidize the sulfur and iron in the concentrate, and the heat released achieves autothermal smelting. It is also molten pool smelting.
The silver furnace is a fixed rectangular furnace. The molten pool in the furnace has a partition wall, which divides it into two parts: the smelting area and the precipitation area; it realizes dynamic smelting and static separation of slag and matte in one furnace. There is a feeding port on the vault of the smelting area, through which the copper concentrate and flux are put into the smelting area. The charge falling into the molten pool is immediately dispersed in the melt that is violently stirred by the oxygen-rich air blown in from the tuyere, and the oxidation reaction and slagging reaction are quickly completed:
3Fe3O4+FeS+5SiO2→5(2FeO·SiO2)+SO2↑
And the formation of Fe304 is avoided due to the following reaction. The high-temperature melt generated in the smelting area enters the calmer precipitation area through the channel under the partition wall, where slag and matte are separated. Slag and matte are discharged through the slag port and siphon port respectively.
The vulnerable parts of the lining of the silver furnace are: the tuyere in the smelting area, the furnace wall near the furnace arch and middle partition wall in the smelting area, and the slag line in the precipitation area.
Converter
Most copper-smelting and nickel-smelting blowing furnaces are PS (Peirce-Smith) cylindrical horizontal converters. An air outlet is provided on one side of the lower part of the cylinder along the horizontal direction to blow in air or oxygen-enriched air.
The task of the copper smelting converter is not only to remove the iron sulfide in the matte sent from the smelting furnace, but also to blow it until it forms blister copper.
FeS+3O2+SiO2→FeO·SiO2+2SO2↑
Cu2S+3/2O2→Cu2O+SO2↑
2Cu2O+Cu2S→6Cu+SO2↑
The nickel-smelting converter only removes iron sulfide and only blows until Ni3S2 is formed, then stops. As blowing continues, Ni3S2 will be oxidized into NiO and enter the slag.
During the converter blowing process, due to repeated feeding, blowing, slag discharge, and pauses between the upper and lower heats, the temperature in the furnace, especially the temperature in the tuyere area, not only fluctuates greatly, but also fluctuates frequently; in addition, the large amount of slag, Due to the violent erosion of the melt, the tuyere and the furnace lining in the area above the tuyere area are most vulnerable to damage.
Continuous copper smelting
Japan’s Mitsubishi method continuous steelmaking relies on self-flow transportation of smelting melt through a closed launder, connecting the smelting furnace, slag depletion furnace and blowing furnace into a unified whole; completing the smelting process from copper concentrate to blister copper,
Smelting furnace: The concentrate is injected from the top of the furnace, and burners are provided on the sides of the furnace top to supplement heat. The produced matte and slag flow into the depletion electric furnace through the overflow port and the launder. The launder is equipped with gas nozzles to maintain heat.
Slag-depleted electric furnace: Slag and matte are stratified in the electric furnace. The matte flows into the converting furnace from the siphon port through the launder. The upper slag is reduced and depleted under the action of the added coke powder and becomes discarded slag.
Converting furnace: There is a spray gun on the top of the furnace to inject quartz stone and oxygen to continuously blow into blister copper. Since the converting furnace is produced in a continuous manner, the refractory material has no structural spalling problem, so the lining life of the converting furnace is long.
At present, the refractory materials used in copper-nickel smelting furnaces generally choose magnesia refractory bricks, such as magnesia-chromium bricks, direct bonded magnesia bricks, combined magnesia-chromium bricks, fused magnesia-chromium bricks, etc.
