Copper is a renewable resource, and recycled copper is an important raw material for copper smelting. According to the data of the international copper research organization (ICSG), the proportion of recycled copper production in major developed countries is very high, of which the United States accounts for about 60%, Japan for about 45%, and Germany for about 80%; In the past 10 years, the output of recycled copper in the world has accounted for 40-55% of the output of primary copper.

1、 Smelting process of Regenerated Copper

The treatment process of Regenerated Copper depends on raw materials. About 2/3 of high-grade copper waste is directly used in the production of copper products without smelting treatment, and 1/3 of waste copper needs smelting treatment. At present, there are many methods of recycling waste copper at home and abroad, which can be divided into two categories: the first is to directly smelt high-quality waste copper into purple copper or copper alloy for users to use, which is called direct utilization; The second type is to smelt the waste copper into anode plate and then electrorefine it into electrolytic copper for users to use, which is called indirect utilization. Among them, the second method is divided into high-grade and low-grade according to the raw materials, and is divided into one-stage, two-stage and three-stage smelting from the smelting process.

One stage method: purple copper, yellow copper and electrolytic residue with copper grade > 98% are directly added into the refining furnace to refine into anode, and then electrolytic production of cathode copper.

Two stage method: waste copper is melted in the smelting furnace, blown into crude copper, and then refined in the refining furnace - electrolytic refining to produce cathode copper.

Three stage method: waste copper and copper containing waste are smelted in blast furnace (or ISA furnace, tbrc furnace, Kaldor furnace, etc.) - converter converting - anode refining - electrolysis to produce cathode copper. The grade of raw materials can be as low as 1% copper.

The three-stage method has the advantages of high comprehensive utilization rate of raw materials, simple and easy treatment of the smoke and dust produced, high grade of crude copper, easy operation of refining furnace, and high equipment productivity, but it also has the disadvantages of complex process, many equipment, large investment and high fuel consumption. Therefore, the smelting of Regenerated Copper generally adopts the process flow of the combination of two-stage method and three-stage method, which is conducive to reducing energy consumption and improving the comprehensive recycling of valuable metals.

2、 Introduction to main smelting process

1. Kaiser recovery and regeneration system (KRS) of Kaiser smelter of North Germany refinery

Kaiser smelter in North Germany is currently the largest and most advanced recycled copper refinery in the world. Kaisa smelter uses one ISA furnace instead of three blast furnaces and one PS converter to treat residues and miscellaneous copper containing 1% - 80% copper; ISA furnace conducts smelting and converting intermittently. Copper containing residues and miscellaneous copper are first reduced and melted in Isa furnace to produce black copper and silicate slag. Black copper continues to be blown to produce crude copper containing 95% copper.

2. Blast furnace converter reverberatory furnace process in montanwerkebrixlegg smelter, Austria

Montanwerke brixlegg smelter is the only copper smelter in Austria. The raw material is waste copper, with copper content of 15%~99%. The production process consists of blast furnace, PS converter, fixed anode furnace and electrolysis, which is a typical three-stage process.

The characteristics of this process are: different grades of residues and purple copper produce different products with different technological processes. The residual raw materials containing 15% - 70% copper are advanced to blast furnace, and the black copper is produced by coke reduction, and then the crude copper is produced by converter; Black copper and copper alloys containing more than 75% copper are directly fed into the converter, and crude copper containing more than 96% copper is produced and refined in the anode furnace; Impurity copper and crude copper with high copper grade are directly refined in anode furnace; The bright copper with higher copper grade does not need smelting treatment, and is directly added to the induction furnace to produce copper, which has strong adaptability to raw materials.

3. Oxygen top blown rotary converter (tbrc) smelting process in metallo chimique smelter in Belgium

The tbrc furnace of metallo chimique smelter has strong adaptability to raw materials, and the raw materials processed are very miscellaneous, with many varieties. The main raw materials are industrial residues containing 25% - 30% copper, various copper alloys (brass, bronze, etc.), waste motors, sponge copper, cables, miscellaneous copper of various grades, etc., especially low-grade industrial residues containing copper, lead and tin, copper alloys, and refractory miscellaneous copper.

4. Treatment of low-grade waste copper with Kaldor furnace

Kaldor furnace is an advanced smelting technology for treating low-grade waste copper, which is mainly reflected in the high metal recovery rate and good environmental benefits. It can treat waste copper containing 15% - 99% of copper, with strong adaptability. The materials do not need pretreatment, and can be directly put into the furnace, and the oxidation and reduction atmosphere can be controlled. The treatment of low-grade waste copper consists of five steps: feeding, smelting, slag discharge, converting and copper extraction, which are completed in stages in one furnace, and the grade of crude copper can reach 96%. In the reaction process, iron in waste copper raw material is usually used as reducing agent and quartz flux is added. Kaldor furnace treatment of waste copper is an advanced process for the treatment of waste copper by two-stage process abroad, which is also introduced by large domestic smelters, such as Jiangxi copper industry.

5. Refining waste copper in NGL furnace

In view of the shortcomings of the existing waste copper treatment technology, China Ruilin Engineering Technology Co., Ltd. developed the "NGL" furnace waste copper Pyrorefining process.

NGL furnace is developed by combining the advantages of tilting furnace and rotary anode furnace. There are large charging door and slag door on the side, oxidation-reduction port and breathable brick on the other side, and the furnace body can rotate within a certain angle. "NGL furnace refining waste copper complete process and equipment" adopts nitrogen stirring technology in the waste copper refining process for the first time, which effectively strengthens the mass and heat transfer in the refining process and improves the production efficiency. The process uses oxygen entrainment combustion for heat supply, which greatly improves the thermal efficiency, shortens the production cycle, and reduces the amount of flue gas discharged by more than 65%.

The complete set of process and equipment for refining waste copper in NGL furnace began in 2010, and large-scale industrial applications were carried out in Shandong Jinsheng Group Eastern Copper Co., Ltd. and Guangxi Nonferrous Metals Group renewable metals Co., Ltd. respectively. Four sets of 250 ton NGL furnace systems were put into operation in 2012.

Source: tongxinbao

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