Nonferrous metal extraction method

The methods for making non-ferrous metals include pyrometallurgy, hydrometallurgy, and electrometallurgy.

First, pyrometallurgy

Pyrometallurgical Metallurgy is the process of subjecting ore or concentrates to a series of physical and chemical changes in the use of heat from fuel combustion or heat generated by electrical energy or heat released by certain chemical reactions to make metal and gangue or other Impurities are separated to give metallurgical methods. In short, all metallurgical processes carried out at high temperatures belong to pyrometallurgy. It includes three steps of ore preparation, smelting and refining.

(I) Ore preparation

Ore preparation generally includes beneficiation, sintering or roasting.

Concentration is the process of using physical or chemical methods to separate useful minerals from unwanted minerals or unwanted minerals, or to separate a variety of useful minerals. The selected concentrate is used as raw material for processing or smelting. The methods of beneficiation include re-election, flotation, magnetic separation, electric separation, selection and chemical selection.

Sintering is to evenly mix the fine ore with the fuel or the flux, spread it onto the sintering tray of the belt sintering machine or the disc sintering machine through the distributor, and then ignite and burn the lump ore at the temperature of 1250-1300°C. Sintering methods for producing sinters are mainly divided into two types: suction sintering and blast sintering.

Roasting is the process of oxidation, reduction or other chemical changes by heating ore, ore or metal compounds in the air without adding or adding certain materials (such as carbon powder, chlorinating agent, etc.) to a temperature below the melting point of the charge. . The roasting method includes oxidation roasting, roasting roasting, volatile roasting, chlorination roasting, chlorination roasting, reducing roasting, sodium oxide roasting, and calcining.

The various calcinations described above are carried out by fluidized roasting, fixed bed roasting, moving bed roasting, and cyclone roasting, depending on the equipment used.

(b) Smelting

Smelting is actually the process of metal extraction or enrichment using methods such as smelting, reduction, and distillation. In the pyrometallurgical process, two kinds of melts are generally formed: one is a slag formed by merging gangue, flux and fuel ash, and the other is molten slag or a molten metal containing a small amount of impurities. Smelting is generally divided into reduction smelting, smelting smelting, and oxidation blowing. The reduction smelting is carried out in a reducing atmosphere in a high-temperature melting furnace. Added to this charge are rich ore or agglomerates or pellets, slagging flux limestone or quartz stone, coke heat generating agent to produce high temperatures, also as a reducing agent, reducing copper oxide to blister copper, or reduced lead oxide to lead. Sputum smelting is mainly used to treat copper or nickel ore, and is usually carried out in a reverberatory furnace, a geothermal furnace or a blast furnace. Adding acidic fused silica and iron oxide to generate ferrous oxide and gangue slag, slag under the formation of a layer containing the main metal helium, so that the prepared metal in the helium enrichment. Oxidation blowing is carried out in an oxidizing atmosphere, such as blowing copper crucibles, using a horizontal converter to convert air to oxygen or oxygen-enriched air to produce blister copper.

(III) Refining

Refining is the further processing of metals containing small amounts of impurities to increase the purity. According to the different characteristics of metals and impurities, there are additive method, smelting method, rectification method and so on.

Compared with pyrometallurgy and hydrometallurgy and electrometallurgy, pyrometallurgy has the following advantages:

1. The reaction speed is high at high temperatures, the productivity of unit equipment and labor productivity are high, investment is saved, and operating costs are low.

2. By making full use of the energy of the mineralized concentrate itself, the unit energy consumption can be reduced.

3. It is beneficial to the comprehensive utilization of the valuable components of gold and silver in raw materials.

4. The high-temperature slag has a stable composition, low pollution to the environment, and is easy to store.

Disadvantages are high dust emission, high heat radiation and dust.

Second, hydrometallurgy

Hydrometallurgy is the use of suitable solvents to treat ore, concentrates or semi-finished products at low temperatures (generally less than 100°C), with the aid of chemical reactions such as oxidation, reduction, neutralization, hydrolysis and complexation, Metal extraction and separation process. Hydrometallurgy includes leaching, filtration, purification and extraction. Leaching is the use of a suitable solvent to transfer the useful components of the raw material into solution. According to the leaching agent, leaching process, leaching method, leaching reaction characteristics and leaching process, it can be divided into acid leaching, alkali leaching, ammonia leaching, cyanide leaching, chloride leaching, leaching, urea leaching, adding microorganisms Bacteria leaching, pressure leaching, atmospheric leaching, in situ leaching, heap leaching, percolation leaching, agitation leaching, hot ball milling leaching, pipe leaching, fluidization leaching, electro leaching, oxidative leaching, reductive leaching, intermittent leaching, Continuous leaching, multi-stage leaching. Filtration separates the leachate from the residue while washing and recovering the metallurgical solvent and metal ions entrained in the residue. Purification is the purification and enrichment of leach solutions, often using ion exchange and solvent extraction techniques or other chemical precipitation methods. Extraction is the extraction of metals or compounds from the purification solution.

The advantages of hydrometallurgy over pyrometallurgy are:

Suitable for handling low-grade mineral raw materials and complex mineral raw materials; easy to meet the requirements of comprehensive utilization of mineral raw materials; good working conditions, easy to solve environmental pollution problems.

The disadvantages are: low production capacity, large equipment, high cost, large energy consumption, difficulty in recovering precious metals in mineral materials.

Third, electro-metallurgy

Electro-metallurgy is a metallurgical process that uses electric energy to extract, recover, and refine metals from ores or other raw materials, such as electric furnace smelting, molten salt electrolysis, and aqueous solution electrolysis. Furnace smelting is metallurgical production that uses electrical energy to obtain the high temperatures required by metallurgy. Molten salt electrolysis utilizes the electric heat to maintain the required high temperature of the molten salt, and the chemical energy from the direct current conversion is used to reduce the metal from the molten salt. Aqueous electrolysis is the use of chemical energy converted by electrical energy to reduce the metal ions in the solution to metal precipitation, or to deposit the crude metal anode on the cathode via solution refining.