Research and development status of potassium and sodium feldspar mine iron removal technology

The manufacture of glass is one of the main uses of feldspar . About 60% of feldspar in the United States is used in glass manufacturing, and in Europe and Asia it is about 20% to 40%. Al2O3 in feldspar plays a role in preventing crystallization and improving the mechanical strength and chemical corrosion resistance of glass. It is an indispensable chemical component of ordinary glass. Potassium and sodium in feldspar can partially replace other expensive potassium carbonate. And the amount of soda ash, resulting in a reduction in the cost of the entire batch. In the ceramic industry, the amount is 30%, mainly used in ceramic blank ingredients, ceramic glaze and enamel, followed by chemical, abrasives, glass fiber, welding electrodes and other industries.

1. Application and requirements of potassium sodium feldspar

The manufacture of glass is one of the main uses of feldspar. About 60% of feldspar in the United States is used in glass manufacturing, and in Europe and Asia it is about 20% to 40%. Al2O3 in feldspar plays a role in preventing crystallization and improving the mechanical strength and chemical corrosion resistance of glass. It is an indispensable chemical component of ordinary glass. Potassium and sodium in feldspar can partially replace other expensive potassium carbonate. And the amount of soda ash, resulting in a reduction in the cost of the entire batch. In the ceramic industry, the amount is 30%, mainly used in ceramic blank ingredients, ceramic glaze and enamel, followed by chemical, abrasives, glass fiber, welding electrodes and other industries.

Our quarry products has not yet developed a unified product quality standards, but the requirements of feldspar impurities such as iron content is higher and higher, the glass industry and ceramic industry for K-feldspar of general industrial requirements as shown in Table 1 and Table 2 There are also some application areas that have certain requirements on the whiteness of feldspar raw materials. Therefore, it is necessary to remove the dark minerals such as iron, titanium and mica . For example , Fe2O3+TiO2 of feldspar filler used as ingredients and glaze in some daily-use ceramics is less than 1%.

Table 1 Requirements for feldspar in the glass industry (%)

Table 2 Requirements for potassium feldspar in the ceramic industry (%)

2. The nature of potassium albite

Aluminosilicate minerals are feldspar, potassium, sodium, calcium, barium, alkali metals or alkaline earth metals, the crystal structure is a frame structure. Its main chemical components are SiO2, Al2O3, K2O, Na2O, CaO and the like. The feldspar mineral is the most widely distributed mineral in the earth's crust, accounting for about 50% of the total weight of the earth's crust. It is a ubiquitous rock-forming mineral. 60% of feldspars are found in magmatic rocks, 30% are distributed in metamorphic rocks, and 10% are found in sedimentary rock clastic rocks, but feldspar can only become industrial minerals when it is quite enriched. Feldspar minerals are rich in alkali metals such as potassium and sodium, have a low melting temperature (1100 to 1200 ° C), have a long melting interval, and have strong fluxing and high chemical stability.

China's feldspar resources are very rich, mainly potassium feldspar, but there are few high-quality feldspar mines that can meet industrial requirements. Most of them contain quartz , muscovite, biotite, rutile, magnetite, hematite, limonite, some feldspar ore also contains apatite, pyrite, sphene, hornblende, tourmaline, iron than high, calcined feldspar whiteness or whiteness below standard. In order to improve the industrial value of feldspar and meet the industrial demand for high quality feldspar ore, it is necessary to remove impurity minerals from inferior feldspar ore, especially the removal of iron and titanium oxide.

The existence form of iron in potassium-sodium feldspar is relatively complicated, mainly in the following three cases: First, it is mainly composed of hematite and limonite, which are scattered in the gangue or mica mineral. Generally, it is relatively thick, and the aggregate is easy to be selected. Second, the iron oxide formed by iron dyeing penetrates the surface of the contaminated K-feldspar, or penetrates along the cracks, minerals, and feldspars of the K-feldspar. The iron oxide formed by such iron dyeing greatly increases the difficulty of removing iron; iron-containing gangue minerals such as iron-titanium, biotite, tourmaline, hornblende, epidote, brown stone, pyrite Etc. Although these minerals are generally low in content, they have a great influence on the quality of feldspar concentrates, and such minerals are difficult to remove by conventional single processing methods, which increases the iron removal process and increases the beneficiation process. cost.

3. Research and development status of potassium and sodium feldspar mine iron removal technology

In recent years, a lot of researches have been done on the beneficiation and purification of potassium-sodium feldspar at home and abroad, including the following aspects:

(1) crushing of ore

The pulverization process of the feldspar mine includes crushing and grinding. The pulverization of feldspar is on the one hand to meet the particle size requirements of the final product, and on the other hand is also required for the impurity removal process. At present, feldspar grinding is mainly divided into dry method and wet method. The wet grinding efficiency is higher than that of dry method, and it is not easy to appear “over-grinding” phenomenon. Most of the feldspar processing in the glass industry uses steel rod media grinding, high grinding efficiency, uniform particle size, but iron pollution, resulting in low quality feldspar; ceramic industry using stone wheel milling or porcelain ball grinding, grinding efficiency Low, high energy consumption. On the basis of ensuring the high quality of feldspar products, achieving high-efficiency grinding and continuous production is an important topic in the research of feldspar processing and purification.

Chen Guoan adopted the process of “hammer crushing→pendulum milling→magnetic separation” to obtain high quality feldspar concentrate containing Fe2O30.05%. Gao Huimin et al. adopted the process of “wet rod grinding and spiral grading closed circuit – weak magnetic separation and strong magnetic separation” to make the feldspar concentrate containing Fe2O30.09% after one sorting of feldspar mine with Fe2O3 content of 0.17%. The yield was 92.2%.

(2) washing and de-sludge

Washing is suitable for feldspar produced from weathered granite or feldspar sand mine. It mainly removes impurities such as clay , fine mud and mica, which can reduce the Fe2O3 content in the feldspar ore and increase the potassium and sodium in the feldspar mine. content. The washing process often uses a vibrating screen or a washing tank. It uses clay, fine mud, mica with small particle size or small sedimentation velocity (light specific gravity), and is easily separated from coarse feldspar under the action of water flow.

Desliming is mainly to remove the primary slime in the ore and the secondary slime produced by grinding, etc., to prevent a large amount of fine mud from affecting the sorting effect of subsequent operations (such as flotation, magnetic separation, etc.). Usually de-sludge in a single or composite force field, commonly used equipment such as mud hopper, centrifuge, hydrocyclone. In addition, because the amine collector is very sensitive to slime. RNH3+ is easily adsorbed on the surface of the negatively charged slime particles, which not only consumes a large amount of collector, but also often causes a large amount of viscous foam, which makes the process lose selectivity and reduces the flotation effect. Therefore, when using an amine collector, the flotation slurry needs to be preliminarily delimed.

(3) Magnetic separation

Since iron minerals, biotite, amphibole and tourmaline in feldspar have certain magnetic properties, they can be separated from feldspar under the action of an external magnetic field. Generally, such minerals in feldspar are weak in magnetic properties, and only strong magnetic separation equipment can achieve better sorting effects.

At present, the domestic magnetic separation equipment for feldspar iron removal mainly includes: permanent magnet roller type strong magnetic separator, permanent magnet barrel medium strong magnetic field magnetic separator, electromagnetic flat ring strong magnetic separator, electromagnetic induction roller type strong magnetic Machine selection, high gradient magnetic separator and superconducting magnetic separator.

The high-gradient magnetic separator is the most effective magnetic separation equipment for removing iron minerals and mica from fine-grain minerals. Its background magnetic induction intensity can reach 2.0T (up to 5.0T abroad), and it can be -0.074mm feldspar mine. Purification. Changsha Mine Management Institute used CRIMM type high gradient magnetic separator to carry out beneficiation and purification of Hunan Pingjiang feldspar mine. After primary magnetic ore separation, the Fe2O3 content can be reduced from 0.2% to 0.05%. The Mingguang feldspar mine in Anhui Province uses the Slon vertical ring pulsating high gradient magnetic separator developed by the Zhangzhou Nonferrous Metal Research Institute for beneficiation and purification. The primary ore can reduce the Fe2O3 content from 0.6% to less than 0.3% after primary magnetic separation. The use of high-gradient magnetic separators to remove iron is an effective way to produce high-grade feldspar products. The disadvantage is higher equipment and operating costs.

Wang Huiyun et al. conducted an exploratory magnetic separation test using the rare earth permanent magnet roller type strong magnetic separator, electromagnetic iron separator, SHP wet magnetic separator and wet cylinder magnetic separator. The results show that -44μm potassium The feldspar powder has a fine particle size, and it is difficult to obtain an ultrapure potassium feldspar concentrate having a Fe2O3 content of 0.1% or less or less using a general magnetic separator. The new high-efficiency feldspar iron removal magnetic separator is used to magnetically select Pingjiang-44μm feldspar powder, which can reduce the content of raw ore Fe2O3 from 0.17% to 0.03%, reaching the international leading level.

Gao Huimin and others used high-gradient magnetic separator to carry out iron removal test research, using dry grinding and wet grinding. The results show that in these two methods, the magnetic separation and iron removal effect is very good, after high gradient magnetic separation When the feldspar powder after the iron is used as the glaze, the fired ceramic glaze has no black iron spots, which improves the grade of the porcelain. When the feldspar powder is not used as the glaze, even if its iron content is very low, black spots may sometimes form on the surface of the porcelain.

Zhou Qizhen uses the new DLSD-15 ultra-fine high-gradient wet magnetic separator to remove iron. The iron removal rate is up to 81.51%, and the iron content in the concentrate is low, 0.05%, achieving a good iron removal effect. When the calcination temperature is 1200 ° C, the whiteness of the product after calcination is 23.4 before the iron removal. After the iron removal by the new DLSD series ultra-fine high gradient wet magnetic separator, the whiteness can be as low as 73.8. Up to 74.1, therefore, the whiteness of the product after iron removal is significantly increased, bringing more economic benefits to users.

(4) Flotation

A large number of experimental studies have been carried out on feldspar flotation at home and abroad, mainly focusing on the mechanism of separation and recovery of feldspar from anionic collectors, cationic collectors and active agents.

Flotation is an effective way to purify feldspar beneficiation. On the one hand, flotation can remove iron and titanium minerals in ore. Generally, reverse flotation is used to remove iron and titanium minerals. On the other hand, flotation can realize separation of feldspar from quartz. To further purify the feldspar minerals.

Separation of feldspar from mica: Mica is easily floated under rough conditions, and mica is usually removed by reverse flotation. On the one hand, it is to reduce the loss of feldspar in the mica flotation; on the other hand, the mica grinding is too thin and consumes a lot of expensive chemicals. Mica can be floated either in the acid circuit or in the alkaline circuit, most of which use acidic flotation. The natural floatability of mica makes it easy to recover by flotation with an amine cation collector. The flotation slurry is adjusted to a pH of ≈3 with sulfuric acid, and the collector of the flotation mica is dodecylamine.

Feldspar and quartz separation: Currently, quartz - feldspar separation techniques are basically three: Floating feldspar acidic, neutral and basic method feldspar floating pumice EF. Among them, the most mature and widely used is the acid floating feldspar method, but this process requires strong acidic medium conditions, resulting in serious equipment corrosion. Therefore, the neutral feldspar method and several other methods have good application prospects, representing the development direction of the quartz-feldspar flotation separation process, although these methods are not mature enough at present, and most of them are limited to laboratory research. It is used less in industrial production, but these methods are worthy of further exploration and improvement in order to achieve industrial applications at an early date.

Separation of feldspar from iron-bearing minerals: In general, iron in feldspar minerals mainly occurs in mica, pyrite, a small amount of red limonite and iron-containing alkali metal silicates (such as garnet , Tourmaline and amphibole). Generally, mica can be floated with an amine cation collector under acidic conditions of pH 2.5 to 3.5; pyrite can be floated by a yellow drug collector under acidic conditions of pH 5-6. Sulfide minerals; iron-containing silicates can be floated with sulfonate collectors under acidic conditions of pH 3-4. Gulsoy et al. used two-stage flotation to conduct experimental research from laboratory flotation test to industrial application, and achieved good results. First, tallow amine acetate was used as a collector, and mica was removed at a pH of 2.5 to 3 using 50% MIBC and 50% pine oil as a foaming agent. Then, using sodium oleate, the pH was 5.5 to 6.5, and the titanium and iron oxides were removed under the conditions of a grinding particle size of -300 μm. It finally obtained a high-quality concentrate with TiO2+Fe2O3<0.12%, which was applied in industry. Fan Haibao et al. used a single flotation iron removal with sodium oleate under mild acid conditions of pH 5 to obtain a feldspar concentrate with Fe2O3 <0.2%, meeting industrial requirements.

Separation of feldspar from titanium-bearing minerals: At present, there are few studies on titanium impurities in feldspar at home and abroad. It is only pointed out that titanium in feldspar is mainly present in rutile (or anatase), ilmenite and a small amount of vermiculite. This topic is mainly to explain the development of iron removal technology for potassium albite feldspar mine, so the removal of titanium-containing impurities will not be introduced here.

(5) Combined process such as magnetic-floating

Some high-speed rails are extremely difficult to select feldspar mines, which are not only high in iron, but some of them are infiltrated in the feldspar cleavage form by iron dyeing. For these minerals, if a single sorting process cannot meet the requirements of concentrates , a joint process can be used. Xu Longhua and others used a "magnetic separation-flotation" combined process for a low-grade feldspar in Sichuan to obtain qualified potassium-sodium feldspar concentrate and comprehensive recovery of quartz. Pang Yurong et al. used the “reverse flotation-strong magnetic separation” process to obtain K-feldspar concentrate with a K2O+Na2O content of 13.92% and a Fe2O3 content of 0.2%. Li Xiaoyan and others used the "magnetic separation-de-fist-flotation" combined process to reduce iron in feldspar to 0.051%, titanium dioxide to 0.018%, calcium oxide to 0.05%, potassium oxide to 13.39%, and feldspar yield. Reached 87%.

(6) Other mineral processing techniques

Acid leaching: Acid leaching is an effective method for removing feldspar impurities. It is often used to treat impurities in the feldspar that contain extremely fine intercalated structures. The use of larger sulfuric acid concentration, higher acid leaching temperature and longer acid leaching time, better iron removal effect, are better than the physical iron removal method of shaker re-election and wet magnetic separation. However, the acid leaching process has environmental problems and is generally not used in feldspar processing.

Bioleaching: Iron can be used as an electron carrier and energy source for certain microorganisms. When it reacts with microorganisms, it can be oxidized and reduced to become a soluble ionic state. The organic acid produced in this process will also dissolve the impurity minerals and pass through. The water can be washed to remove the impurity minerals. For iron-containing minerals in extremely slender stone particles, it is difficult to remove by conventional methods, and bioleaching can achieve better results. Microorganisms are not only beneficial to the decomposition of feldspar ore, but also effectively remove iron minerals from the surface of feldspar.

Iveta Styriaková conducted an in-depth study of this method, reducing Fe2O3 from 0.175% to 0.114% and TiO2 from 0.02% to 0.018% by microbial leaching; studies have also shown that dissolved and removed iron and iron in the original feldspar ore The amount is not directly proportional, but also depends on the geological changes of feldspar, the mineral composition and the distribution of iron minerals. Therefore, in order to obtain high quality feldspar concentrate, other methods are needed in combination with microbial treatment.

Iveta Styriaková et al. pretreated the differentiated granite-type feldspar ore with Bacillus spp., and then removed the iron-containing compound by oxalic acid leaching. The organic acid produced by Bacillus spp. The infiltrated iron compound in the gap and the gap dissolves the iron ions. This pretreatment not only benefits the further action of oxalic acid, but also greatly reduces the use concentration and recovery cost of oxalic acid, and the pollution discharge is also reduced. The iron removal method combining heterotrophic bacteria with strong magnetic separation was studied, and the iron removal rate was up to 70%.

With the reduction of high-quality feldspar resources, low-grade feldspar has become the main resource for the processing of feldspar ore. In addition, the downstream enterprises have higher and higher requirements for the grade of feldspar concentrate, which is bound to raise the processing of feldspar mine. High requirements, a single beneficiation and purification process can not meet the market demand, the use of a variety of sorting operations, such as desliming, magnetic separation, flotation and other combined process will become the main way of processing feldspar. With the improvement of the national environmental protection policy, the “fluorine-free and acid-free” feldspar-quartz separation technology represents the development direction of the flotation process. In addition, there have been many studies on bioleaching and beneficiation technology in foreign countries, but there are few in China, and research and application in this area should be strengthened.