Non-ferrous smelting furnaces can generally be divided into the smelting furnace, refining furnace and casting furnace. 

 

The blast furnace is widely used in the smelting process of copper, lead, lead-zinc, antimony and other metals.

 

The blast furnace is composed of the roof, shaft, throat, hearth and tuyere device. 

 

Solid materials such as the charge (ore, sintered ore, etc.), coke and flux are loaded from the roof. High pressure air is blown into the drum through the tuyere device in the lower part of the shaft. When air goes up, it has melting, oxidizing and reducing reaction with the downward materials to complete the smelting process. The molten metal, sulfur and slags are discharged from the throat or hearth. Exhaust gases, dust, gaseous metal or metal oxides are discharged from the exhaust flue in the roof. Currently, most of the furnaces have closed roofs. Refractory materials are only used in the throat and hearth. Since slags there are alkali, magnesia bricks, magnesia chrome bricks and alumina chrome bricks are used in the throat, sidewalls and the bottom. The bottom is inverted arch shaped. 

 

The reverberatory furnace includes smelting and refining reverberatory furnaces. Their structures are basically the same but refining reverberatory furnaces have smaller size. The reverberatory furnace is rectangular and the production is continuous.

 

The operating temperature of the reverberatory furnace is generally 1400-1500℃. The temperature of the exhaust gas is 1150-1200℃. The bottom is composed of asbestos, insulating brick layer, fire clay brick layer, magnesia alumina brick or magnesia brick layer. The walls are built with magnesia alumina bricks or magnesia bricks. In order to prolong the service life, some important parts are built with magnesia chrome bricks. The external walls are generally built with fire clay bricks. The roof always adopts the suspended structure. The roof of small reverberatory furnaces is built with magnesia alumina bricks. 

 

The ISA Furnace is a simple vertical cylindrical furnace. Its core technology is the use of a submerged top-blown combustion lance. The furnace is a vertical cylinder with refractory linings. The lance is inserted from the center of the roof. The lance head is immersed in the slag layer. Air or oxygen-enriched air is blown into the liquid layer underneath the slag layer and forms a strong agitation state. From the top charge was added directly into the bath and involved in the reaction between the melt and oxygen. The charge is rapidly melted and produces slags and lead (copper). 

 

The ISA furnace lead (copper) smelting process is characterized with short mixing time of raw materials and vigorous agitation. So, the working conditions are much more demanding than the traditional lead smelting (copper) method. Therefore, ISA furnace lead (copper) smelting refractory lining must have the following excellent performance: longevity, high efficiency, and low consumption. They should have higher compressive strength at room temperature and high temperature, lower porosity and good corrosion resistance to charge, molten metals and slags. They should be made of high purity raw materials and contain a low content of low-melting point substances. They can effectively resist the damage caused the chemical reaction between the environment and the lining and improve resistance to penetration. They should have good thermal shock resistance and can resist the stress and temperature changes well. 

 

In the bottom, it is always an inverted arch and inclined by about 2% to the discharge outlet. It can also be flat and inclined by about 2% to the discharge outlet. The lining can be divided into three layers. The top is built with fused rebounded magnesia chrome bricks and semi-rebounded magnesia chrome bricks. Underneath the bricks is magnesia chrome ramming mass. The lowermost bottom is low porosity fire clay bricks.

 

The walls are subjected to harsh conditions. The lower part 1000-2000mm away from the bottom is subjected to corrosion and scouring by strongly agitated melt, so fused rebounded magnesia chrome bricks or semi-rebounded magnesia chrome bricks with good high temperature resistance, erosion resistance and corrosion resistance are used. The upper part suffers from the corrosion by molten slag and scouring by high temperature flue gases. The same refractory materials to the lower part are used here. 

 

The roof is complex, and under poor working conditions. It is built with easy-to-construct magnesia chrome castables with good corrosion resistance. Heat-resistant steel fibers can be added to improve its resistance to spalling. 

 

The damage causes and requirements for refractory materials of Kaldor furnaces are the same to ISA Furnaces.

 

The Kaldor furnace is also called oxygen oblique blown converter. Since the furnace is inclined and rotated, it increases the contact of the liquid metal and liquid slag and the reaction efficiency. Since the furnace rotates, it is heated and eroded evenly, which can help to extend the life of the furnace.

 

Due to the use of oxygen, smelting and converting are in the same furnace. This reinforces the smelting process, shortens the process and improves the SO2 concentration in the flue gas.

 

It is important to select the size and shape of the hearth for the smooth progress of the chemical reaction during the smelting process, reducing splashing, reducing the corrosion to the bottom and convenient manufacturing and installation. 

 

Blowing is conducted at high temperature, about 1100-1300℃, so right lining materials should be selected and strict construction plan should be made to ensure the service life of the furnace. 

 

The lining of Kaldor furnaces is composed of fused semi-rebounded magnesia chrome brick, direct bonded magnesia chrome bricks, magnesia and refractory fiber felt. Fused semi-rebounded magnesia chrome brick is in direct contact with liquid metal, liquid slag and gases during the blowing process and subjected to serious chemical corrosion and mechanical erosion. During the rotating process of the furnace, due to its own weight, the stress changes constantly. It combines the features of direct bonded magnesia chrome refractory and fused rebounded magnesia chrome refractory. It has excellent corrosion resistance and good thermal shock resistance. Direct bonded magnesia chrome bricks, as a type of permanent refractory lining material, have great thermal shock resistance and corrosion resistance and can protect the shell. The joints between bricks are filled with magnesia to relieve the pressure on the furnace shell caused thermal expansion and facilitate the construction and demolition of the furnace. 10-30mm refractory fiber felt is pasted on the shell and works as an insulation layer. Practice has proved that, laying a filling layer between the lining and shell can reduce the heat loss of the furnace, save energy and improve the working conditions.