In copper smelting, cold material refers to copper raw materials or copper containing materials with lower temperatures compared to the high-temperature melt in the smelting furnace. Cold material can to some extent regulate the temperature, atmosphere, and melt composition inside the furnace, which helps stabilize the melting process, improve production efficiency, and product quality.

Cold materials can be divided into four categories:

1、 Returned materials include refined slag, anode mud, smelting slag, mineral processing recovery materials, etc.

Refining slag refers to the waste residue generated during the copper refining process, which still contains a certain amount of copper and other valuable metals such as gold, silver, etc., and needs to be returned to the smelting furnace for further processing and recovery.

Anode mud refers to the mud like substance formed by the precipitation of insoluble impurities on the anode plate during electrolytic refining of copper. It is rich in precious metals such as gold, silver, platinum, and some copper, and is an important valuable material. It is usually treated specifically before being returned to the furnace as cold material.

Smelting slag beneficiation recovery material refers to the slag generated during the copper smelting process, which is used to recover copper concentrate through beneficiation and other processes, and then returned to the smelting furnace as cold material.

2、 Waste miscellaneous copper

Including waste wires and cables, scrapped copper equipment and components, etc.

Waste wires and cables are one of the main sources of scrap copper, with a high copper content, usually above 90%, but may be accompanied by insulation such as plastic and rubber, requiring pre-treatment to remove impurities before being used as cold material.

Scrap copper equipment and components, such as discarded copper motors, transformers, pipelines, valves, etc., have relatively complex compositions and may contain other metals such as iron, aluminum, tin, etc. in addition to copper. They need to be disassembled, classified, and processed before being added to the smelting furnace.

3、 The purchased copper raw materials include low-grade copper concentrate, oxidized copper ore, etc.

Low grade copper concentrate refers to copper concentrate with relatively low grade purchased from external mines, which has a low temperature before entering the furnace and belongs to the category of cold materials.

Copper oxide ore refers to the copper containing material obtained by processing some copper oxide ore through mineral processing, and can also be added as cold material to the copper smelting process.

4、 Coarse copper mainly refers to rough copper obtained by blowing and refining copper matte. Before further refining, its temperature is relatively low and can be returned as cold material to the refining furnace or other melting equipment for further processing.

In summary, low temperature is the most prominent characteristic of cold materials, which is usually much lower than the high-temperature melt in the melting furnace, generally between room temperature and several hundred degrees Celsius. In addition to the main copper element, cold materials also contain various impurity elements such as iron, lead, zinc, tin, gold, silver, etc. The composition of cold materials from different sources varies greatly. Cold materials come in various forms such as block, powder, granular, and flaky on the surface. For example, scrap copper may be in the form of block shaped scrap equipment or in the form of powdered copper shavings; Outsourced copper concentrates are usually in granular or powdered form

By adding cold materials to the copper smelting process, on the one hand, it can effectively recover copper and other valuable metals, improve resource utilization, and reduce resource waste;

On the other hand, utilizing low-cost cold materials such as scrap copper and low-grade copper concentrate can reduce reliance on high-grade copper concentrate, thereby lowering raw material procurement costs.

After introducing the types and functions of cold materials, what is the general proportion of cold materials added in copper smelting?

There is no fixed ratio! Usually around 20% to 50%, there may be differences due to various factors.

Firstly, let's take a look at the differences between the four processes of adding cold materials:

1、 If flash smelting technology is used, the proportion of cold material added is generally relatively low, usually around 20% to 30%. This is because flash smelting requires high stability and uniformity of the incoming materials to ensure efficient reaction, and excessive addition of cold materials may affect the thermal balance and reaction stability inside the furnace.  

2、 If the Isa melting and Ausmelt melting processes are used, the adaptability to cold materials is relatively strong, and the proportion of cold materials added can be around 30% to 40%. The top blowing method allows the cold material to mix and react well in the molten pool, but a high proportion can also cause some problems.  

3、 If traditional blast furnace melting process is used, the proportion of cold material added is usually around 30% to 50%. Due to the relatively stable melting process of blast furnace, the tolerance of cold material is slightly higher.

In addition to the differences in process, if the grade of copper concentrate is high and impurities are low, the proportion of cold material added can be appropriately increased. For example, when the grade of copper concentrate is above 30%, the proportion of cold material can reach 40% to 50%; If the grade of copper concentrate is low, in order to ensure smelting efficiency and product quality, the proportion of cold material may be controlled at 20% to 30%.

Of course, the quality of the cold material itself is also very important, and factors such as the purity, particle size, and composition uniformity of the return material and waste copper can also affect their addition ratio. Cold materials with good quality and stable composition can be added in relatively high proportions, otherwise the proportion should be reduced.

Finally, it actually depends on the equipment condition and production goals of the enterprise.

A large capacity furnace has a relatively strong ability to withstand cold materials, and the proportion of cold materials added can be appropriately increased. For example, the cold material ratio of a large flash furnace may reach about 30%, while a small furnace may only be able to withstand about 20% of the cold material.

New or well conditioned furnace linings may allow for a higher proportion of cold material to be added to a certain extent. If the furnace lining ages or is damaged, in order to reduce damage to the lining, the proportion of cold material may need to be controlled at a lower level, such as 20% to 30%.

In general, when the equipment allows and the raw material conditions are suitable, the proportion of cold material added can be appropriately increased to increase the processing capacity of raw materials and improve copper production. At this point, the proportion of cold materials may be close to 50%.

But if the quality requirements for copper products are high, such as producing high-purity copper, the proportion of cold material added is usually controlled to be low, usually around 20% to 30%, to reduce the introduction of impurities and ensure product quality.

Article source: Internet

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