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China is rich in feldspar mineral resources, mainly located in Shanxi, Anhui, Liaoning, Shandong, Yunnan, Hunan and other places. Feldspar frame anhydrous alkali metal or alkaline earth metal aluminosilicate minerals like structure, which framework structure of silicon-oxygen tetrahedra, chemical stability, widely used, mainly comprising Si02, A1203, Na20, K20 and Ca0 Wait. Feldspar is mainly used in the glass and ceramic industry. Al203 is an important chemical component of ordinary glass. It can prevent glass crystallization and improve its mechanical strength and chemical corrosion resistance. Potassium and sodium in feldspar can Replace part of potassium carbonate and soda ash to reduce their dosage and reduce the cost of ingredients. In the ceramic industry, feldspar is mainly used as a component of ceramic billet and glaze, which can reduce the firing temperature of the ceramic body, which is beneficial to porcelain formation and thus reduce energy consumption. In addition, the pyrochlore melt is saturated and distributed in ceramics during high temperature firing. The density of the green body can be increased between the crystal grains of the green body. In addition, feldspar can also be used in chemical, fiberglass, abrasives and other industries, potassium feldspar can also produce potassium fertilizer. However, there are not many high-quality feldspar mineral resources in nature. Most feldspar mines contain a variety of impurities and cannot be directly applied to industrial production. They must be used after removing impurities and purification.
1 impurities in the feldspar mine
The impurities in the feldspar mine vary with the type of deposit. The harmful impurity elements are mainly iron and titanium . The harmful impurity minerals are: quartz , clay mineral, mica , rutile, limonite, magnetite, hematite. Some also contain pyrite, vermiculite, garnet , amphibole, brown stone, tourmaline and so on.
2 Occurrence state of iron and titanium in feldspar mine
There are three forms of iron impurities in feldspar mines: 1 is magnetite, limonite, hematite, and is distributed in the form of fine-grained star-shaped dots between feldspar particles or through feldspar. The mineral grain size is generally coarser and easier to screen; 2 the iron oxide pollutant formed by iron dyeing penetrates the surface of the feldspar or between the minerals to form an iron oxide film, it is difficult to remove such iron oxide; 3 with iron ore, Tourmaline, biotite, amphibole, pyrite, etc. exist. Although the content of such iron-bearing minerals is low, they have a great influence on the quality of feldspar concentrates and are difficult to remove by a single beneficiation method. Titanium impurities in feldspar ore are mainly in the form of ilmenite and rutile.
3 Common methods for removing impurities from feldspar mine
Most of the feldspar mines in China have high impurity content and cannot be directly applied in industrial production. It is necessary to use various processing methods to remove impurities before meeting the requirements of industrial production. There are many methods for mineral processing in feldspar ore, and the following are commonly used.
3.1 Hand selection, washing and de-sludge
Part of the crystal rock type feldspar mine is a high-quality feldspar mine. Its mineral crystals are coarse and pure. Their impurity minerals are mainly bulky muscovite and quartz, which can be removed by hand. In the past 80s, the Giuslino concentrator in Italy installed a 16-type photometric sorting machine. The principle is to use a beam of krypton laser to shoot the feldspar. Ore, this light encounters light-colored ore that can be reflected back. When the dark ore impurity ore cannot be reflected back, the computer will issue a command to automatically remove the impurity ore with compressed air. Compared with the hand selection, the photometric sorting machine can select the impurity ore with a smaller particle size, and both of them can reduce the ore dressing cost of the feldspar mine as a rough selection method.
For feldspar mines produced from feldspar sand or weathered granite , the clay, mica, fine mud and other impurities can be removed by washing, and the Fe203 content of the feldspar mine after washing is reduced, potassium and The sodium content has increased. The principle of washing is that the clay, mica and fine mud have small particle size and small specific gravity, so the sedimentation speed is slow, and it can be separated from the coarse feldspar under the action of water flow. The washing equipment generally uses a washing tank or a vibrating screen. The mining field generally uses a washing tank. The concentrating plant generally uses a vibrating screen. At present, many feldspar mines use this method for impurity removal and purification.
The primary slime in the feldspar mine and the secondary slime produced during the mining process will affect the beneficiation effect. Therefore, it must be removed before the beneficiation. The process of removing the slime is called de-sludge. In addition, when using an amine collector , the flotation slurry should be preliminarily delimed. This is because the amine collector is very sensitive to the slime. RNH3+ is easily adsorbed on the surface of the negatively charged slime particles, which wastes a large amount of collector. It also produces a large amount of viscous foam, which causes the process to lose selectivity and thus affect the flotation effect. Commonly used equipment for deliming is a centrifuge, a mud hopper, a hydrocyclone, etc., usually in a single or composite force field.
Hand selection, washing and deliming are the rough selection and removal processes of feldspar ore, and the feldspar ore after rough selection is selected for decontamination. The selected impurity removal is mainly to remove iron-containing impurity minerals in feldspar ore, such as hematite, magnetite, biotite and limonite; if the feldspar concentrate has strict requirements on titanium content, Remove titanium-containing impurity minerals such as rutile, ilmenite, vermiculite, etc.
3.2 magnetic separation
The iron-bearing minerals, garnet, mica and hornblende in the feldspar mine have certain magnetic properties and can be removed under the action of an external magnetic field. However, the magnetic properties of such minerals are generally weak, and strong magnetic separation is required. The device can be removed. The strong magnetic separation is divided into dry and wet processes, which can be selected according to the characteristics and specific conditions of the feldspar mine. At present, the magnetic separation equipment used for purification of domestic feldspar mines is: permanent magnet type medium strong magnetic field magnetic separator, permanent magnet Roller strong magnetic separator, high gradient magnetic separator and wet flat ring magnetic separator.
The magnetic separation equipment should be selected according to the characteristics and process flow of the feldspar mine. The following points should be noted when selecting:
(1) The permanent magnet magnetic separator is preferably used, and the electromagnetic magnetic separator is used if the permanent magnet magnetic separator cannot meet the requirements;
(2) First adopt weak magnetic separation and then adopt strong magnetic separation;
(3) Dry sorting is required when the feldspar concentrate is high, and wet sorting is required when the material particles are fine;
(4) Select the appropriate sorting particle size and try to remove iron at a coarser particle size;
(5) Avoid mixing iron impurities again during the magnetic separation process. For feldspar mines with more magnetite content, weak magnetic separation (or medium magnetic separation) should be used first, followed by strong magnetic separation, which will not block the strong magnetic separator and reduce the inclusion of magnetite. The loss of K-feldspar can be achieved by wet-type countercurrent type permanent magnetic cylinder magnetic separator for weak magnetic separation and medium magnetic separation. The equipment is more suitable for magnetic mineral recovery.
3.3 flotation
Flotation is a method widely used in the removal of impurities from feldspar, and has been extensively studied at home and abroad. The separation of feldspar from mica, quartz, iron-bearing minerals and titanium-containing minerals can be achieved by flotation.
3.3.1 Separation of feldspar from mica
In general, reverse flotation separation is used to remove mica from feldspar ore. When flotation, the mica should be coarsely ground and not finely ground. This can reduce the loss of feldspar in the mica flotation process. In addition, the mica fine grinding will consume a large amount. Expensive pharmacy, rough grinding can avoid this situation. Mica can be floated in both acidic and alkaline circuits, with acidic flotation being used more. Mica has natural floatability and is easily recovered by flotation of amine cation collector. The flotation methane collector is dodecylamine, and the flotation slurry is adjusted to pH ≈3 with sulfuric acid. Pan Dawei et al. used reverse flotation separation method, using the cationic collectors dodecylamine and octadecylamine as flotation reagents, the addition form, concentration and addition amount of the flotation agent, pH value and concentration of the slurry to the feldspar mine. In addition to the influence of mica, the following conclusions were drawn: the flotation agent used a mixture of dodecylamine and octadecylamine, the mass ratio was 2:1, the dosage of the agent was 0.825 g/kg, and the concentration of the drug was 5 %, the pulp pH = 2 ~ 3, the concentration is 40%, under this condition, the mica effect is the best. At the same time, it is concluded that the mechanism of dodecylamine and octadecylamine to remove mica from feldspar ore is physical adsorption.
3.3.2 Separation of feldspar from quartz
The separation method of feldspar and quartz is mainly flotation method, which has experienced the following three stages of development: fluorine acid method (ie hydrofluoric acid method), fluorine-free acid method, fluorine-free acid-free method. At present, feldspar and quartz separation methods are: feldspar float acid method, a neutral environment and basic silica sand sorting process Britain and France pumice, feldspar float method in which the acid is the most widely used method is the most mature methods, but It should be carried out under strong acidic medium conditions, which will seriously corrode the equipment. Therefore, research on the neutral environment silica sand separation process and alkaline floating quartz method should be strengthened to enable them to be applied to the industry as soon as possible.
3.3.3 Separation of feldspar from iron-bearing minerals
The iron-bearing minerals in the feldspar mine mainly include pyrite, mica, a small amount of red limonite, and iron-containing alkali metal silicates such as tourmaline, garnet, and amphibole. Usually, under acidic conditions with a pH of 5-6, sulfide minerals such as pyrite can be floated with xanthate collectors; under acidic conditions with a pH of 2.5-3.5, mica can be captured with amine cations. Flotation; under acidic conditions of pH 3-4, the iron-containing alkali metal silicate can be floated with a sulfonate collector. Zhang Xin et al conducted a de-ironing test on a feldspar mine in Shandong. The feldspar mine has high iron content. The process used by them is as follows: grinding→de-sludge→high-gradient magnetic separation (removal of mechanical iron and magnetic iron minerals) → ethyl xanthate flotation (removing pyrite) → + kerosine dodecylamine flotation (removal mica) → a modified petroleum sulfonates ZL flotation 1 (ferrous removing alkali metal silicate), to give the The feldspar concentrate with a whiteness of 67.26% and a Fe2O3 content of 0.09% has a good effect of removing iron and whitening.
3.3.4 Separation of feldspar from titanium-bearing minerals
The titanium-bearing minerals in the feldspar mine are mainly ilmenite, rutile and a small amount of vermiculite. Under acidic conditions with a pH of 4-6, rutile can be floated with a fatty acid as a collector, but its floatability decreases in the order of oleic acid, linoleic acid, and linolenic acid. Under acidic conditions with a pH of 2.5, rutile can also be floated with fatty primary amine acetate or petroleum sulfonate, and the selectivity is better. It can also be floated with a mixture of sulfonate and succinic acid amide salt or With the flotation of potassium hydroxy citrate, there is very little literature on the flotation performance of vermiculite. It only introduces the use of oleic acid and its soaps to float the vermiculite, but this method is very sensitive to slime.
3.4 acid leaching
For iron impurities containing extremely fine intercalated crystal structure in feldspar ore, it is difficult to remove by general iron removal method, and acid leaching can achieve better results. Zheng Yu and other experimental studies have found that increasing the acid leaching temperature and sulfuric acid concentration and prolonging the acid leaching time is better than the physical iron removal method of wet magnetic separation and shaker re-election. Their experiments also showed that the presence of iron in the feldspar mine is the main factor affecting the effect of feldspar powder acid leaching. The iron in the form of minerals such as magnetite, hematite and pyrite is soaked with sulfuric acid. It is easy to remove, and iron which exists in the phase of sodium iron amphibole and biotite is more difficult to remove.
3.5 Bioleaching
The biological leaching is mainly to remove the iron-containing minerals in the fine particles of the feldspar. Such iron-containing minerals are difficult to remove by conventional methods, and the biological leaching effect is better. Iron can be the energy source and electron carrier of some microorganisms. It can be dissolved into iron ions after oxidation and reduction reaction with microorganisms. The organic acid produced during the reaction can also dissolve impurity minerals. After washing with water, impurities can be removed. . Microorganisms can promote the decomposition of feldspar ore and remove iron-bearing minerals between the surface layers of feldspar. Therefore, when the quality of feldspar concentrate is high, other methods must be combined with bioleaching. The biological leaching environment has little pollution and simple operation. Foreign countries have already studied this, but domestic research is rare.
3.6 joint process
Some feldspar mines not only have high iron content, but some of them contain iron minerals that penetrate into the feldspar cleavage layer in the form of iron dyeing. It is difficult to remove by traditional single ore dressing method. If the quality of feldspar concentrate is high, it needs to be adopted. Joint process flow. There are many joint processes, such as "magnetic separation and flotation", "reverse flotation - strong magnetic separation", "magnetic separation - de-sludge-flotation", "flotation-sulphuric acid leaching", "de-sludge-strong" Magnetic separation - acid leaching, "peeling a strong magnetic separation", etc., can be selected according to the characteristics of feldspar ore and the accuracy requirements of impurity content.
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