The smelting methods used in the world to produce electrolytic copper from copper concentrates are divided into two main categories: pyrometallurgical smelting and hydrometallurgical smelting.
At present, more than 80% of refined copper production is produced by pyrometallurgical smelting, and wet smelting produces about 20% of refined copper, as detailed below.
I. Pyrometallurgy
Pyrometallurgical copper is the main method of copper production today, accounting for 80% to 90% of copper production, mainly to deal with sulfide ore. The advantages of copper smelting are strong adaptability of raw materials, low energy consumption, high efficiency, high metal recovery rate. Pyro-refining copper can be divided into two categories: one is the traditional process: such as blast furnace smelting, reflector furnace smelting, electric furnace smelting. The second is the modern enhanced process: such as flash furnace smelting, melting pool smelting.
Due to the global energy and environmental problems since the mid-20th century, energy is becoming increasingly tense, environmental protection regulations are becoming increasingly stringent, the gradual rise in labor costs, prompted by the copper smelting technology from the 1980s onwards to obtain rapid development, forcing the traditional methods have to be replaced by new methods of enhancement, the traditional smelting methods are gradually eliminated. With the rise of flash smelting and melting pool smelting as the representative of the advanced technology of enhanced smelting, the most important breakthrough is the wide application of oxygen or oxygen-enriched. After decades of efforts, flash smelting and bath smelting have basically replaced the traditional pyrometallurgical smelting process.
1,Fire smelting process
Pyrometallurgical process mainly consists of four main steps: matte smelting, copper matte (ice copper) blowing, crude copper pyrometallurgical refining and anode copper electrolytic refining.
Sulfur smelting (copper concentrate - ice copper): mainly the use of copper concentrate ice copper smelting, the purpose is to make the copper concentrate part of the iron oxidation, slag removal, the output of ice copper with high copper content.
Ice Copper Blowing (Ice Copper - Crude Copper): Ice Copper is further oxidized and slagged to remove iron and sulfur from the ice copper to produce crude copper.
Fire refining (crude copper - anode copper): the crude copper through oxidation and slagging to further remove impurity elements, the production of anode copper.
Electrolytic refining (anode copper - cathode copper): through the introduction of direct current, the anode copper is dissolved, pure copper is precipitated at the cathode, and the impurities enter the anode sludge or electrolytic solution, so as to realize the separation of copper and impurities, and produce cathode copper.
2,Classification of pyrometallurgical process
(1) Flash smelting
Flash smelting (flash smelting), including the international nickel company Inco (Inco) flash furnace, Otokumpu (Outokumpu) flash furnace and whirlpool top blowing smelting (ConTop) three kinds. Flash smelting is a smelting method that makes full use of the huge active surface of the finely ground material to enhance the smelting reaction process. The concentrate after deep drying, and the flux by drying together with oxygen-enriched air sprayed into the reaction tower, concentrate particles suspended in space for 1-3s time, and high-temperature oxidizing airflow quickly oxidizing sulfide minerals, and release a large amount of heat to complete the smelting reaction, that is, the matte-making process. The product of the reaction falls into the precipitation tank of the flash furnace for settling, so that the copper matte and slag are further separated. This method is mainly used for copper, nickel and other sulfide ores matte smelting.
Flash smelting began production in the late 1950s, has been popularized and applied in more than forty enterprises, because of continuous improvement in energy saving and environmental protection has significant achievements. The process technology has the advantages of large production capacity, low energy consumption, less pollution, etc. The maximum ore copper production capacity of a single set of systems can reach more than 400,000t/a, applicable to the scale of 200,000t/a above the plant. However, it requires the raw materials to be deeply dried to the water content <0.3%, the concentrate size <1mm, and the impurity lead and zinc in the raw materials should not be higher than 6%. The disadvantages of the process are complex equipment, high soot rate, slag containing high copper, need to be depleted.
(2) Melting pool smelting
Melting pool smelting including Teniente copper refining method, the Mitsubishi method, Osmert method, Warnucoff copper refining method, Isa smelting method, Noranda method, top blowing rotary converter method (TBRC), silver copper refining method, Shuikoushan copper refining method and Dongying bottom blowing oxygen-rich smelting method. Melting pool smelting is to add fine sulfide concentrates to the melt at the same time, to the melt drum into the air or industrial oxygen, in the violent agitation of the melting pool for enhanced melting. Due to the air blowing to the melt pool pressurized air bubbles, when the air bubbles rise through the melt pool, resulting in the "melt column" movement, which will give the melt input a great function. Its furnace type is horizontal, vertical, rotary or fixed, and the blowing method is side blowing, top blowing and bottom blowing.
Melting pool smelting began to be applied in industry in the 1970s. Due to the good heat and mass transfer in the melting pool smelting process, the metallurgical process can be greatly strengthened to achieve the purpose of improving the productivity of the equipment and reducing the energy consumption of the smelting process. And the requirements for the furnace material are not high, all types of concentrates, dry, wet, large grains, powder are applicable, the furnace volume is small, the heat loss is small, energy saving and environmental protection are better, especially the soot rate is significantly lower than the flash smelting.
Second, wet smelting (SX-EW method)
Wet smelting accounts for 10% to 20% of copper production, is a solvent leaching copper ore or copper concentrate so that copper into solution, and then from the purified copper-containing solution to recover copper method. It is mainly used to process low-grade copper ores, oxidized copper ores and some complex copper ores.
Wet copper refining equipment is simpler, near the mine in the vicinity of the production, low production costs, no production of sulfuric acid, no SO2 pollution. However, the impurity content is high, and the copper refining cycle is long, low efficiency, small capacity scale; the precious metal recovery is difficult, and the recovery rate is uncertain; the wet process for treating chalcopyrite concentrate has not been industrially applied, and there are technical barriers.
Although the current wet copper refining in copper production accounted for a small proportion, but from the future development trend of resources, with the gradual depletion of ores, oxidized ores, low-grade difficult to select ores and multi-metal complex copper ores are increasingly utilized, wet refining of copper will become an effective way to deal with these raw materials.
1,Wet smelting process
Wet smelting process mainly includes four steps: leaching, extraction, anti-extraction, metal preparation (electrowinning or replacement). Oxide ore can be leached directly, low-grade oxide ore is heap leached, and rich ore is cao leached. Sulfide ores need to be roasted before leaching in general, or can be leached directly under high pressure. Commonly used solvents for the leaching process include sulfuric acid, ammonia, and high iron sulfate solution.
Third, copper smelting method outlook
World Copper Smelting Development Trends The development trends of copper smelting are summarized as follows:
(1) due to the nature of copper ore, in order to recover the silver and sulfur, the fire method of copper refining still occupies a major position, but the proportion of wet copper refining will be increased.
(2) Copper plant will be pollution-free work, sulfur dioxide exhaust emissions concentration will be below 300ppm, sulfur real recovery rate of 95% to 99%. There will be no wastewater and slag discharge.
(3) Pyro-copper refining will be basically self-heating smelting.
(4) copper matte continuous blowing will be more widely used.
(5) Low-grade ore will be utilized by hydrometallurgy. Wet smelting leaching and extraction efficiency will be further improved.
(6) Computerized on-line control will be the main means of production control.
(7) The scale of the plant will be larger, each process will be a single furnace production, operation work will be more reduced.
With the severity of environmental protection policies and the increase in production costs, from a worldwide perspective, high-cost, technologically backward small smelters will be closed one after another, large and medium-sized smelters will further expand the scale of production and reduce costs. And through technological upgrading and transformation, further improve the utilization rate of raw materials, maximize the smelting process in the recovery of slag, wastewater, waste gas valuable elements will be the most important means of cost reduction.
