(1) Grinding
In the mineral processing process, the minerals are generally ground, and the valuable minerals are separated from the gangue monomers so that the subsequent process can be successfully completed. In this process, energy consumption is high, usually accounting for 50% -70% of total energy consumption, but energy efficiency is often low, especially for dense ore.
Various minerals have different dielectric constants and different responses to microwaves. As described above, the medium can be classified into a microwave reflection type, a microwave transparent type, a microwave absorption type, and a partial microwave absorption type depending on the different reactions of the materials to the microwave.
Most of the gangue minerals in the ore are quartz and calcite . From the data in the table, they have a very low heating rate, while the useful minerals have a higher heating rate, so they form between the useful minerals and the gangue minerals. Significant local temperature differences that cause thermal stress between them.
Microwave pyrite, kyanite ore, copper, molybdenum, tantalum and niobium ore, Copper, Lead and Zinc MILL metal ore, the effect is obvious. Researchers at the Bandong Institute of Technology in Indonesia studied the effects of microwave pretreatment on the energy consumption of the Nishiganis gold ore. The researchers found that the work index of gold ore decreased by 20%-35% after microwave energy was applied to the ore for different time (5-300 s) before grinding.
(2) crushed ore
Sam Kingman of the University of Nottingham in the United Kingdom used seven years to study the use of microwaves to heat ore. Various ores react differently to microwaves, so different microwave parameters can be selected for different types of ore. For different minerals, choosing the right microwave frequency, strength and heating time are also critical factors.
(3) Magnetic separation
Microwave technology can be used to convert non-magnetic minerals into magnetic minerals, which can be selected by magnetic separation. Coal pyrite pest belongs, using the flotation method reselection and are more difficult to handle. The pyrite (FeS2) is converted into pyrrhotite (Fe1-xS) by microwave irradiation, and it can be sorted out from coal by magnetic separation.
(4) Flotation
University of Birmingham to study the effects of microwave titanium ore flotation.
The specific surface of the ilmenite sample changes significantly with the increase of the microwave irradiation time, and a new phase can be observed. When ilmenite is exposed to the air, oxidation occurs and Fe2+ is oxidized to Fe3+. This oxidation is slow at room temperature, but its oxidation is enhanced as the temperature increases.
Microwave selective heating accelerates the oxidation of iron on the surface of ilmenite. Oxidation improves the adsorption performance of the flotation reagent and improves the flotation effect. Microwave treatment for 10 s increased the recovery of ilmenite by 10%. As the irradiation time is extended, the recovery rate is eventually increased from about 64% to 87%. For untreated ilmenite, to obtain a 60% flotation recovery, the concentration of sodium oleate is required to be 2×10-4 mol/L, while the concentration of sodium oleate required for microwave-treated ilmenite is only 7 ×10-5 mol/L, the dose was reduced by about 65%. It can be seen that the effect of microwave is more obvious.
(5) Leaching
Most metal minerals exist in the form of sulfides in nature. The treatment methods for extracting metals are mainly fire roasting + leaching process. Under the same temperature and the same FeCl3 concentration, the copper sulfide concentrate was leached by microwave heating and conventional heating, and the microwave method was not stirred. Microwave irradiation for 40-50min, the leaching rate of copper can reach 98.8% - 99.05%, the slag contains less than 0.5% copper, and the traditional heating leaching requires more than 3h to achieve the above indicators.
(6) Restore
The reduction of metal oxides into metals at high temperatures is the most important smelting process in pyrometallurgy and has a wide range of applications. Iron, tin , zinc, lead, manganese , chromium , etc. are produced by this method.
(7) Ore pretreatment
Some gold ore is difficult to choose because it contains arsenic and carbon. After the gold ore or gold concentrate is pretreated by microwave roasting, the gold recovery rate can reach more than 90%, while the untreated material can only be about 30%. The use of microwave pretreatment of pyrite-coated gold concentrates increased the cyanidation leaching rate from 74% to over 90%.
(8) Other applications
In addition to the above applications, microwave technology is also used in mineral roasting, activated carbon regeneration, mineral powder drying, preparation of nano-products and sample testing. At present, the research on microwave application in mineral processing is carried out at home and abroad. It is believed that in the near future, high-efficiency, high-quality, low-cost and pollution-free microwave beneficiation technology will be widely promoted.
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