Feldspar is a potassium, sodium, calcium aluminosilicate mineral composed of silica-oxygen tetrahedron with frame structure.Its main ingredients are SiO2, Al2O3, K2O, Na2O, CaO and MgO, which are important raw materials of manufacturing industry and widely used in chemical industry, abrasive material, glass fiber, welding rod, enamel and filler industries.As glass and ceramic products become increasingly high-grade, the demand for feldspar materials with high purity and low iron is constantly expanding.Although China is rich in feldspar resources, there are few high-quality feldspar mines that can meet the industrial requirements.In feldspar resources, raw ore reserves above grade 1 only account for about 15 ~ 20% of the developed resources, and indexes such as feldspar whiteness or burning whiteness cannot meet the requirements.
I. research status at home and abroad
Low quality purification of sodium potassium feldspar ore dressing technology is research in our country "8 · 5", "9 · 5" science and technology research project of a ceramic material selection of purification technology on the basis of the research and industrial application of high quality in China, feldspar diminishing raw material, and ceramic industries the demand for feldspar, especially high grade feldspar put forward under the background of rapid growth.With the decrease of feldspar rich ore and the development of comprehensive feldspar recovery technology in other mines, the combined separation operation by means of gravity separation, electric separation, magnetic separation and flotation has been introduced, so as to remove associated minerals such as quartz and mica and recover feldspar concentrate rich in potassium and sodium.In recent years, more work has been done in the separation and purification of feldspar at home and abroad, mainly reflected in the following aspects:
1.1 crushing and grinding
Feldspar crushing and grinding on the one hand to meet the requirements of product size, on the other hand is also the need of impurity removal process.Feldspar coarse crushing most use jaw crusher, crushing products generally in about 10mm.At present, there are many studies on the fine crushing and grinding process of feldspar in China, and many related equipment, including roller crusher, impact crusher, impact crusher, hammer crusher, stone grinding, column mill, tower mill, Raymond mill, mixing mill, vibration mill, sand mill and airflow mill.
At present, feldspar grinding is mainly divided into dry and wet grinding methods.Comparatively speaking, wet grinding is more efficient than dry grinding, and the phenomenon of "over grinding" is not easy to occur.From the perspective of application industry, the glass industry feldspar raw materials are mostly processed by steel rod medium grinding, grinding efficiency is high and particle size is uniform, but the introduction of iron pollution, resulting in feldspar product quality is not high;Due to the high requirements for feldspar raw materials in the ceramic industry, stone wheel rolling or porcelain ball grinding is often used. The grinding efficiency is low and the energy consumption is high, so high efficiency and continuous process operation cannot be achieved.On the basis of ensuring the high quality of feldspar products, the realization of high efficiency grinding and continuous production is an important subject in the research of feldspar processing and purification.
1.2 ore washing and desilting
Ore washing is suitable for feldspar produced from weathered granite or feldspar placer, mainly to remove clay, fine mud and mica and other impurities, on the one hand to reduce the content of Fe2O3 in feldspar, on the other hand to increase the content of potassium and sodium in feldspar.Ore washing is to make use of the fine particle size of clay, fine mud, mica and other characteristics of small settlement rate, under the action of water flow to separate it from coarse feldspar.Commonly used equipment is Denver scrubber, vibrating screen, wash tank, mixing bucket and grinding machine, etc.
The main purpose of desliming is to remove the primary slime in the ore and the secondary slime generated by grinding, so as to prevent a large amount of fine slime from affecting the separation effect of the subsequent operations (such as flotation, magnetic separation, etc.).Usually in a single or complex field of desilting, the common equipment is desilting bucket, centrifuge, hydrocyclone and so on.
1.3 magnetic separation
Because the iron ore, mica and garnet in feldspar have certain magnetism, they can be separated from feldspar under the action of external magnetic field.Generally speaking, iron ore and mica in feldspar are weak in magnetism.At present, weifang guote mining equipment co., LTD. Mainly used for feldspar cleaning magnetic separation equipment: permanent magnet roller type strong magnetic separation machine, permanent magnet drum type medium strong magnetic separation machine, wet type flat ring strong magnetic separation machine and high gradient strong magnetic separation machine.
(1) permanent magnet roller type strong magnetic separator
Permanent magnet roller type strong magnetic separator is based on the principle of rare earth permanent magnet repelling magnetic poles. It is composed of a group of permanent magnet disks and soft iron disks, and the magnetic induction intensity on the surface of magnetic roller can reach 2.0t.This equipment is suitable for dry separation of weak magnetic minerals and has become the main equipment for feldspar dry iron removal in recent years. Its characteristics are good separation effect, extremely low operating cost and convenient operation, but it is limited by the lower limit of particle size of materials (generally 0.12mm).
(2) permanent magnet drum type strong magnetic separator
Permanent magnet drum type strong magnetic separator is on the basis of the weak magnetic field permanent magnet simple magnetic separator will be made of permanent magnet material into ndfeb, the magnetic induction intensity in the separation area is generally 0.3 ~ 0.8T.The equipment has two kinds of dry and wet, this kind of equipment is characterized by both dry and wet, low operating cost, but due to the low magnetic field, it is difficult to get feldspar products.
(3) wet flat ring strong magnetic separator
Wet flat ring high intensity magnetic separator is widely used in mines at home and abroad. Its background magnetic induction intensity is 1.2 ~ 1.7t.The advantages of the equipment are wider grain size and larger processing capacity.
(4) high gradient magnetic separator
High gradient magnetic separator is the most effective equipment for fine mineral purification at present. Its background magnetic induction intensity can be up to 2.0t (up to 5.0t in foreign countries), and it can purify feldspore of -74 micron.High gradient magnetic separation is an effective way to produce high-grade feldspar products.
1.4 progress of flotation technology
Flotation is an effective way to remove impurities in feldspar. On the one hand, impurities such as iron and titanium in feldspar can be removed.On the other hand, the separation of feldspar and quartz can be achieved, thus increasing the content of potassium and sodium.At present, there are many researches on the separation of feldspar and quartz, and the selective separation of potassium feldspar and sodium feldspar.
(1) flotation of titanium-bearing gangue minerals
The results show that titanium in feldspar mainly occurs in rutile (or anatase) and a small amount of sphen.Rutile (or anatase) is easily floatable in the ph4-6 range using fatty acids as collectors, but its floatability decreases in the following order: oleic acid > linoleic acid > linolenic acid.Rutile (or anatase) can also be flotation with petroleum sulfonate or aliphatic primary amine acetate at pH2.5.Potassium hydroxamic acid can also be used, or a mixture of succinate and sulfonate using flotation rutile (or anatase).Currently, there are very few references on the flotation properties of sphen, indicating that sphen can be used for oleic acid and soap flotation, but this flotation process is very sensitive to the presence of slime.
(2) flotation of the minerals containing iron gangue
In general, the iron in feldspar minerals occurs mainly in mica, pyrite, a small amount of red limonite, and iron-bearing alkali metal silicates (such as garnet, tourmaline, and amphibole).Generally, under the acidic condition of pH2.5 ~ 3.5, mica can be surfaced by using amine cation collector.Sulphide minerals such as pyrite can be flotation by using xanthate collector at pH5 ~ 6.Ferric silicate can be flotation with sulfonate collector at pH3 ~ 4 acid condition.
(3) flotation separation technology of quartz and feldspar
The traditional method of quartz-feldspar flotation separation is HF acid method, also known as "fluorine-containing acid" method, which USES HF acid pulp to lower than pH2.5 to inhibit quartz, activate feldspar, and realize the separation of feldspar and quartz.However, due to environmental problems and many inconveniences in the use of HF acid, many mineral concentrators are actively studying the fluorine-free separation scheme.In the fluoride-free flotation separation process of quartz-feldspar, the fluoride-free acid method is mature and widely used, but this process requires strong acidic medium conditions, resulting in serious corrosion of equipment.Therefore, fluoroacid-free and other process methods are the future development direction of quartz - feldspar flotation separation process.
(4) flotation separation of potassium feldspar and sodium feldspar
The separation of potassium feldspar (orthoclase and microclase) and sodium feldspar is a challenging subject because most of them are mixed in feldspar deposits, and these minerals have similar chemical structures and similar physicochemical properties.
Based on the above findings, with the continuous reduction of feldspar rich mineral resources, a large number of low-quality feldspar minerals remain to be developed.There are many problems in the traditional feldspar dressing process, such as low grinding efficiency, backward technology and obsolete equipment, which have become important factors restricting the large-scale and large scale of feldspar dressing.Therefore, according to the type and nature of the raw ore, to determine a reasonable mineral processing process, the selection of advanced production equipment, the use of high-efficiency and low-pollution flotation agents become the breakthrough to solve the above problems.It is the future development trend of feldspar mineral processing to realize high efficiency of mineral processing, high quality of products and put into use of new technology and equipment.
The development trend of feldspar purification
With the increasing demand of high-grade feldspar concentrate, but less and less high-grade raw ore, it is necessary to remove impurities with higher iron efficiency and more economic and effective methods.At present, the combined process is easier to obtain concentrate, and for feldspar ore with high iron content, the pretreatment such as acid leaching and stripping is economical and effective.
Biological leaching has the advantages of simple operation and low environmental pollution. Foreign scholars have used it in combination with other methods to obtain high-purity feldspar concentrate with iron content of less than 0.02%.
2.1 biological leaching
Iron can be used as the electron carrier and energy source of some microorganisms. When it interacts with microorganisms, oxidation and reduction reaction will occur and it will become a soluble ionic state. Organic acids generated in this process will also dissolve impurities and minerals.It is difficult to remove iron ore from ultrafine feldspar particles by traditional methods, but biological leaching can achieve better results.Microorganisms are not only conducive to the decomposition of feldspar, but also can effectively remove the interlayer of feldspar.Studies have shown that the amount of iron dissolved and removed is not directly proportional to the amount of iron in the original feldspar ore, but also depends on the geological changes of feldspar, mineral composition and distribution of iron ores.Therefore, to obtain high quality feldspar concentrate, other methods should be combined with microbial treatment.
Through the experiment with heterotrophic bacteria Bacillu SPP granite type feldspar ore processing differentiation in advance, and then use the grass a sour leaching to remove the iron compound, good results have been achieved, Bacilus SPP produced by organic acid ACTS on the mineral particles and the gap between the impregnation of iron compounds and dissolve iron ion release, this process is not only beneficial to advance further role of oxalic acid, can also greatly reduce the cost of the use of the oxalic acid concentration and recycling and pollution emissions are reduced.The iron removal method of heterotrophic bacteria combined with magnetic separation was studied.
2.2 joint process
Some high-speed iron is extremely difficult to select feldspar ore, which not only has high iron content, but also some of the iron ore penetrates into the cleavage of feldspar in the form of iron contamination. For these minerals, if the single separation process cannot meet the requirements of concentrate, the combined process can be adopted.
(1) magnetic - floating joint process
Countries, mining equipment co., LTD., with extremely difficult to choose potassium feldspar experimental study carried out in addition to iron, iron content in the magnetic separation, flotation Ding Yi joint process than the single magnetic separation, flotation process was reduced by 1% or more, by magnetic separation to remove most of the iron content, and then using flotation method into fine iron ore and iron potassium feldspar, much lower than a single magnetic separation of potassium feldspar concentrate iron grade, also lower than single flotation concentrate iron grade, and the yield of close, when the first dry magnetic separation flotation can get good separation effect, but the needs of industrial thousands of magnetic separation for the dehydration and drying, the cost is higher,So wet magnetic separation followed by flotation process is more widely used.
(2) peel - strong magnetic separation process
Although the combined process of magnetic separation and flotation with strong magnetic field can obtain qualified feldspar concentrate products, the process is relatively complex, so the equipment investment and mineral processing cost is relatively high.If feldspar ore is soft and easy to be crushed, a small amount of steel balls can be added to the grinding machine to remove the iron ore inclusions in mica group minerals, while feldspar minerals will not be over-crushed.Compared with the magnetic-floating process, the process has the characteristics of simple process and low processing cost.
(3) a two-cycle flotation process
A two-cycle process was used to remove the oxides of mica, titanium and iron from a certain sodium feldspar in Turkey.Mica was removed by reverse flotation with amine ion (Armac TD) collector at a pH value of 2.5 ~ 3, and titanium and iron oxides were removed by sodium oleate at a pH value of 5.5 ~ 6.5.In the experiment, TiO2+Fe2O3 in feldspar concentrate can be reduced to 0.12% or less under the conditions of appropriate collector dosage, grinding fineness and PH value.The process can be extended to industrial applications and feldspar concentrate meeting commercial requirements can be obtained.
(4) scrub a flotation process
Scrub -2mm grinding products, and then divided into -2+0.25mm and -0.25mm grain grades. The former grain grade product can be used as ceramic ceramic tile, and the latter grain grade product cyclone desilting and flotation can obtain feldspar concentrate for making glaze.
