High-efficiency feldspar ore beneficiation process technology analysis

As an important raw material for glass and ceramic industries, feldspar's purity directly affects the performance of end products. However, natural feldspar ore is often accompanied by quartz, mica, iron-bearing titanium minerals and other impurities, which need to be purified through systematic beneficiation process. This article will focus on the core feldspar ore removal technology and innovative process.

 First. Primary sorting and pretreatment process

1. Manual picking and photoelectric sorting

For pegmatite-type high-quality deposits, feldspar crystals are coarse and impurity minerals (such as white mica, quartz) can be discerned by the naked eye, the traditional hand picking is still economical. Modern photoelectric sorting technology scans the ore surface with a helium-neon laser, uses the difference in light reflection between light-coloured minerals and dark-coloured impurities, and combines it with an intelligent identification system to achieve automated sorting. This technology can deal with impurities with a particle size of less than 5mm, significantly improving sorting efficiency and reducing labour costs.

2. Hydraulic washing and sludge treatment

Weathered sand ore or granite type feldspar needs to be washed to remove light impurities such as clay and fine mud. Using the difference in particle settling speed, hydraulic classification by using step washing tank or high-frequency vibrating screen can reduce Fe₂O₃ content by 0.3%-0.5%. The presence of sludge interferes with the subsequent flotation results, especially when amine traps are used, and the adsorption of RNH₃⁺ by the sludge leads to wastage of the chemicals. The desliming process often uses hydrocyclones, centrifuges and other equipment to achieve efficient separation of micro-fine particle size in the composite force field.

Second. magnetic separation technology system

1. Classified magnetic separation process

Iron-containing minerals (magnetite, hematite, etc.) and weakly magnetic minerals such as garnet, hornblende, etc. need to be used for strong magnetic separation (field strength ≥ 1.2T). The process design follows the principle of ‘weak first, then strong’: weak magnetic separation (field strength of 0.3-0.5T) gives priority to the removal of strong magnetic minerals to avoid clogging the equipment; strong magnetic separation for weak magnetic impurities. Wet countercurrent permanent magnetic cylinder magnetic separator has become the mainstream equipment due to the optimisation of magnetic circuit and high recovery rate.

2. Equipment selection and operation points

Permanent magnetic priority: permanent magnetic equipment, low energy consumption, simple maintenance, only in the high purity requirements of the electromagnetic model;

Particle size control: coarse-grained (-20 mesh) magnetic separation can reduce over-crushing, reduce the pressure of subsequent processing;

Pollution prevention and control: the use of non-metallic material conveyor belt to avoid secondary iron pollution.

Three. flotation separation technology

1. Separation of feldspar and mica

Mica is easy to combine with cationic collector (dodecylamine, octadecylamine) to float in acidic medium (pH≈3). The optimised conditions are: mixing and blending of trappers (mass ratio 2:1), 5% concentration of chemicals and 40% concentration of slurry. Coarse grinding process (particle size 0.15-0.3mm) can reduce the loss of feldspar and reduce the consumption of chemicals.

2. Separation of feldspar and quartz

Traditional hydrofluoric acid method is limited due to environmental issues, neutral or alkaline flotation has become a research hotspot. Acidic feldspar flotation (pH=2-3) achieves separation by inhibiting quartz, but it is highly corrosive to the equipment; neutral silica sand process (pH=6-7) adopts composite inhibitors (e.g. sodium silicate), which is better for environmental protection.

3. Iron-containing minerals removal

Pyrite: pH=5-6, yellow drug-like traps selective adsorption of sulphide minerals;

Iron-containing silicates: modified petroleum sulfonates (such as ZL-1) efficiently capture tourmaline and garnet at pH=3-4;

Rutile: fatty acid-based trappers perform best in acidic medium (pH=2.5).

Fourth. Deep purification technology

1. Acid leaching process

For microcrystalline structure iron impurities (such as black mica), sulfuric acid acid leaching (concentration 40%, temperature 90 ℃, time 2h) can dissolve more than 90% of iron oxides. However, it is necessary to pay attention to the recycling of acid and environmental protection treatment to avoid secondary pollution.

2. Biological extraction technology

Microorganisms dissolve iron minerals through redox reaction, especially suitable for nanoscale inclusions. This technology is environmentally friendly, but the industrial application needs to optimise the strain culture and reaction cycle.

Fifth. Combined process

Complex deposits need a combination of processes to achieve the depth of purification, typical schemes include:

Magnetic separation - flotation synergistic: first magnetic separation to remove strong magnetic minerals, and then flotation to separate mica, quartz;

Acid leaching - flotation synergy: acid leaching to dissolve the surface iron film, flotation to deal with residual impurities;

Desliming - strong magnetic separation - biological extraction: for high sludge, micro-fine iron stained deposits, comprehensively enhance the whiteness and purity.

Case application: A feldspar mine in southern Shaanxi Province adopts the combined process of ‘magnetic separation - desliming - flotation’, and the Fe₂O₃ content is reduced from 0.36% to 0.04%, and the sintered whiteness is >73%. After desliming, the slime can be used as low-grade ceramic raw materials after secondary magnetic separation, thus realising the full use of resources.

Sixth. the technical outlook

Future feldspar purification will focus on:

Green flotation system: development of fluorine-free, neutral media separation technology;

Upgrading of high gradient magnetic separation: optimising media bar parameters to capture -0.045mm weak magnetic impurities;

Bio-chemical synergy: combining microbial extraction and acid leaching to reduce energy consumption and pollution.

Through technological innovation and process optimisation, the quality of feldspar concentrate can stably reach the industrial standards of SiO₂≤68%, Al₂O₃≥18% and Fe₂O₃≤0.08%, which will help the high-quality development of ceramic and glass industries.