To produce blister copper or a copper alloy is a very profitable industry waste by processing low-grade copper heteroaryl. Low-grade waste copper is widely available and inexpensive. If the environmental requirements are met, the cost of processing this raw material is very low. Practice has also proved that the profit of smelting various low-grade waste copper is higher than that of copper concentrate and high-grade waste copper. At the same time, in the process of processing waste copper, many precious metals will be obtained, which will further increase the profit rate. The Swedish company Caledon's Kaldo technology is developed to meet the requirements of manufacturers for maximum profit while meeting strict environmental regulations.
First, the development history of Caldo technology
In 1976, the first Caldo equipment was put into operation at the ROmmskar smelter in Boliden, northern Sweden. Initially using this apparatus for processing lead-containing dust, now treated with lead concentrate and copper scrap it. In the process of applying the Kraft furnace to treat waste copper, Politon found that it is the most competitive technology for processing low-grade scrap copper, and the economic benefits are very good. Later, this technology was quickly extended to many smelters of different production capacities in other countries to process various materials, for example, to effectively treat lead-lead batteries to produce recycled lead.
In 1992, the Nuova Samim copper smelter near Venice, Italy, used Porden's Caldo technology to process low-grade scrap copper, with an annual output of 25,000 tons of blister copper. In the same year, Iran Lead Zinc Corporation in Zanjan and Carl multiple furnace built a lead smelter, lead oxide ore processing, annual output of 41,000 tons of lead. In 1993, KGHM Copper Company of Poland established a precious metal plant in Glogow to treat anode slime, using a 2m3 Caldo furnace with an annual output of 1,000 tons of silver . Russia's Kasimov uses Caldo technology to dispose of scrap copper and used electronic components. In 2000, SWIL Copper Company of India introduced the Bordeaux technology 11m3 Caldo furnace to treat waste copper, with an annual output of 60,000 tons of copper.
Second, the process of processing waste copper by Caldo furnace
The Caldo furnace can process waste copper raw materials containing more than 30% copper. The raw materials can be mainly divided into the following four categories:
Metals, low volatiles: such as No. 1 or No. 2 copper, iron- copper alloy, etc.
Metals, high volatiles: such as brass chips and bronze chips, car radiators, small pieces of copper, etc.
Non-metallic, low volatile: copper slag, anode furnace refining slag
Non-metallic, low volatility: oxide, crumb or bronze slag of brass and bronze
Various waste materials, such as copper wire, cable and other waste copper raw materials containing organic matter, can be directly fed into the furnace for smelting without pretreatment.
The treatment of waste copper with a Caldo furnace can be divided into five process steps, namely feeding, smelting, slagging and granulation, refining, copper or copper alloy. The ingredients have a great influence on the economics of the process, and the metals, oxides, volatiles, etc. in the raw materials are well balanced. Iron in the waste copper raw material is usually used as a reducing agent for the oxide, and silicon is used as a flux.
Feeding the Caldo furnace through a dump truck (201) does not require pre-treatment of the material. However, avoid adding water and oil directly to the furnace.
After the addition is completed, the oxy-fuel spray gun (103) is inserted into the furnace for smelting. At the beginning, the Caldo furnace first rotated at a slow speed, the speed was 1 rpm, and it continued to accelerate, and finally reached about 5 rpm. The oxygen oil spray gun is first burned with a medium flame. If there is organic matter such as plastic in the raw material, it starts to burn. Then, the oxygenation of the spray gun is automatically changed, the flame becomes a high oxidation state, some organic substances are volatilized and burned together with the air, and are sucked into the direct flue during the volatile combustion process. As more air is drawn into the flue, all plastics and organic matter are eventually completely burned in the direct flue. In order to prevent the formation of harmful compounds, the temperature in the direct flue is maintained at 800-9000C. The metal in the furnace begins to melt as the temperature in the furnace rises. In order to reduce operating costs, the furnace temperature is kept below 12500C. After the smelting stage (about 1.5 hours) is completed, slag is started, at which time the inert slag contains less than 0.5% copper. The resulting slag can be subjected to water quenching and granulation.
The black copper formed in the furnace was subsequently refined, at which time compressed air was blown into the furnace while the Caldo furnace was rotated at 15 rpm. During the refining process, Fe and Zn are first removed, black copper is converted into a copper alloy (gunmetal), and Pb and Sn are further refined to form blister copper. The copper-rich slag obtained in the refining stage is transferred to the next batch for recycling.
The formed blister copper is then poured from the furnace into a copper package for ingot casting.
The total time of one cycle is 4-6 hours. The scale of production depends on the volume of the Caldo furnace. All operations are remotely controlled in the control room. The Caldo furnace treatment of scrap copper actually resulted in three products for sale, namely blister copper, ZnO dust and granulated slag.
Third, the main equipment
Caldo furnace treatment of waste copper mainly includes feeding equipment, Caldo furnace, hood and dust removal system, environmental hood and other auxiliary equipment, such as slag granulation equipment and copper bags.
Caldo furnace
The Caldo furnace consists of the furnace itself (100) and two spray guns, one for the oxygen and fuel spray guns (103) and the other for the refining spray gun (104). Both guns are water cooled and resistant to high temperatures. The water cooling system is equipped with safety protection.
The Caldo furnace is a steel container lined with refractory bricks. It can be rotated at a speed of less than 20 rpm under the drive of a motor. It can also perform 3600 tilting, and the operator can select the appropriate angle for loading, smelting or copper and slag. During the smelting operation of the Caldo furnace, it rotates at an angle of 280 to the horizontal, in order to take advantage of the agitation action it produces during tilting.
Refractory slag using a strong anti-adhesive ability magnesium chrome brick. Generally, two layers are built, and the layer that acts as a safety insurance is close to the steel casing, and the inner layer is the working layer. This ensures that in the smelting process, if the refractory brick is damaged, it will not affect the steel shell of the furnace body and damage the equipment.
The oxy-fuel gun can be removed or moved into the furnace along the carriage driven by the hydraulic motor. The hydraulic accumulator in the drive system ensures that the gun can still move out of the Caldo furnace in the event of a power outage or loss of power. The spray gun is cooled by water and can withstand the high temperatures in the furnace. The safety device in the cooling system shuts off the water supply in the event of a cooling water leak. The refined blister copper and slag are poured directly into different picks.
Cigarette cover and dust removal system
If the waste contains plastic, most of it will burn in the hood (101). The water-cooled collecting hood is tightly attached to the feeding port of the calorific furnace, but the gap is sufficient to inhale an appropriate amount of air to ensure that the flue gas containing CO and hydrocarbons is burned in the collecting hood, and the temperature in the collecting hood can be maintained at 800-9000C to prevent the formation of harmful compounds. The hood is lined with anti-corrosion refractory bricks. There is an emergency flue gas outlet at the top. The fully burnt flue gas is cooled and dedusted through the venturi. Venturi has a large pressure drop during operation to ensure high dust removal efficiency. The collected dust becomes mud and sent to the thickener.
Caldo furnace environmental hood
The entire Caldo furnace is covered with a green hood (150). The dust generated by the smelting process is taken out by the fan and sent out to the bag filter for dust removal and purification before being discharged to the chimney. Therefore, when the Caldo furnace is smelted, the working environment and the surrounding environment are clean. Therefore, Caldo furnace treatment of waste copper can meet the most stringent environmental laws.
Fourth, production indicators
The table below gives an example of the production scale and economic technical indicators of different sizes of Caldo furnaces.
Caldo furnace working volume, m 3 1 2 4 6
Feed amount
The average grade of scrap copper is 40-50%, tons/year 10000 20000 40000 60000
Number of days per year 320 320 320 320
Cycle time, hour 6 6 6 6
Number of cycles / 4 4 4 4 per day
Number of cycles / 1280 1280 1280 1280 per year
Crude copper production, tons / year 4500 10000 20000 24-30000
Slag volume, tons / year 4500 8000 16000 24000
Dust, tons / year 1000 2000 4000 6000
consumption
Oil or gas , m 3 / year 750 1250 1950 2600
Oxidation, million m 3 / year 1.7 2.9 4.5 6
Electricity, MWh/year 1800 3200 5000 6700
SiO 2 , tons / year 240 500 1000 1500
Refractory bricks, tons / year 70 120 250 380
V. Example: Material balance (ton/year) of a Caldo plant with an annual output of 20,000 tons of crude copper
Feed weight (tons) Cu Ni Fe Pb Zn Sn SiO 2 CaO Al 2 O 3
Broken wire 8000 7760 (97%)
Motor 5000 1250 (25%) 3500 (70%) 50 (1%) 7375 (50%)
Brass slag 5000 1500 (30%) 100 (2%) 150 (3%) 100 (2%) 1000 (20%) 50 (1%) 100 (2%)
Copper slag 10000 2000 (20%) 2000 (20%) 400 (4%) 500 (5%) 2000 (20%) 100 (10%) 500 (5%)
Low grade waste 3000 600 (20%) 150 (5%) 30 (1%) 600 (20%) 300 (10%) 150 (5%)
Waste radiator 12000 7800 (65%) 120 (1%) 840 (7%) 1440 (12%) 480 (4%) 120 (1%)
Quartz stone 3000 2850 (95%) 30 (1%) 30 (1%)
Total 46000 20910 (45.5%) 100 (0.22%) 5920 (12.9%) 1340 (2.9%) 3020 (6.6%) 530 (1.1%) 5450 (11.8%) 430 (0.9%) 750 (1.6%)
Discharge
Metal 20870 20750 (99.4%) 60 (0.29%) 0 60 (0.29%) 0 20 (0.1%)
Slag 17000 80 (0.47%) 40 (0.24%) 5920 (34.8%) 80 (0.47%) 1220 (7.18%) 80 (0.47%) 5450 (32%) 430 (2.5%) 750 (4.4%)
Dust 4000 80 (2%) 1200 (30%) 1800 (45%) 430 (10.7%)
Total 20910 100 5920 1340 3020 530 5450 430 155
Conclusion
There are many advantages to treating waste copper with a Caldo furnace:
a) Smelting, reduction and refining can all be done in the same furnace without the need for an external furnace
b) It can handle high-grade scrap copper and low-grade scrap copper. And it is better to deal with low-grade waste copper.
c) Produce stackable inert slag with a low metal content, generally less than 0.5% copper
d) The Caldo furnace is compact, simple in equipment and completely sealed, thus preventing emissions from escaping. Good operating environment, no external pollution, to meet the most stringent environmental requirements
e) Flexible production, suitable for processing various materials, and can be converted between different metals without any modification of the equipment
f) Investment province, good economic returns, large or small factory scale
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