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Click to add WeChatLow-potassium feldspar is a kind of feldspar mineral, and its chemical composition is mainly KAlSi₃O₈, and it usually contains a small amount of impurity elements such as sodium (Na), calcium (Ca), and magnesium (Mg). Compared with other feldspar varieties, its potassium (K) content is relatively low. Low-potassium feldspar is generally white, grayish white or flesh-red, with a glass luster, a hardness of 6-6.5, and a density between 2.55-2.63g/cm³. It has good thermal and chemical stability, is not easy to decompose at high temperatures, and can form a good eutectic system with other minerals. These characteristics make it have important application value in industrial fields such as ceramics and glass.
Depending on the nature of its ore, the beneficiation method of low-potassium feldspar is also different. At present, the commonly used processes are mainly magnetic separation, flotation, gravity separation, acid leaching and high-temperature roasting.
Low-potassium feldspar magnetic separation is mainly based on the magnetic difference between minerals. Generally, some magnetic iron ore will be half-born in the low-potassium feldspar minerals, while low-potassium feldspar itself is a non-magnetic or weakly magnetic mineral. Therefore, in the magnetic separation process, the low-potassium feldspar raw material is sent into the magnetic field of the magnetic separator, and the magnetic impurity minerals will be adsorbed on the magnetic pole by the magnetic field, thereby separating from the low-potassium feldspar.
The principle process is usually:
Crushing process: After mining, the raw ore is fed into the crusher for crushing. The particle size is determined according to the requirements. It can be coarse, medium and fine. Then it is ground by ball mill, etc., so that the mineral particles reach the monomer dissociation state. The grinding fineness is usually required to be -0.074mm, accounting for about 60%-80%, so that the subsequent magnetic separation can effectively separate the magnetic impurities.
Magnetic separation: For strong magnetic impurities, a weak magnetic field magnetic separator (magnetic field strength is generally 80-200mT) can be used for preliminary separation; for weak magnetic impurities, a strong magnetic field magnetic separator (magnetic field strength is 400-1200mT) is required for further separation.
This method can quickly and effectively remove magnetic impurities in low-potassium feldspar, improve the purity and whiteness of the product, and has a good purification effect for some low-potassium feldspar ores with high magnetic impurity content. However, the removal effect of some non-magnetic or weakly magnetic iron-containing impurities (such as pyrite, etc.) and other non-magnetic impurities (such as quartz, mica, etc.) is limited, and it is often necessary to use it in combination with other purification methods to achieve higher purification requirements.
Low-potassium feldspar flotation is based on the difference in the chemical properties of the surface materials between minerals, especially the wettability of the mineral surface. In the flotation process of low-potassium feldspar, the properties of the mineral surface are changed by adding flotation reagents. Generally, the pH value of the pulp is between 2-4, so that the surface of the low-potassium feldspar is positively charged. Then, the addition of cationic collectors will adsorb on the surface of the low-potassium feldspar to make it hydrophobic. At the same time, the addition of frothers will produce a large number of stable bubbles, and then the hydrophobic mineral particles will attach to the bubbles and float up to achieve flotation operations.
The principle process is usually as follows:
Grinding and slurry adjustment: After the raw ore is crushed and ground, slurry adjustment is carried out. Adjust the slurry concentration to 25%-35%, and add acid regulators such as sulfuric acid to adjust the pH value to the appropriate range. Then add an appropriate amount of flotation reagents, the amount of which depends on the properties of the ore, to improve the flotation environment and increase the flotation selectivity.
Floatation: The slurry that has been adjusted and added with reagents is sent to the flotation tank for flotation. Generally, roughing is carried out first to obtain coarse concentrate and tailings; the coarse concentrate is then subjected to multiple rounds of fine separation to further remove the gangue minerals and improve the grade of the low-potassium feldspar concentrate; the tailings can be swept and selected according to the situation to recover the residual low-potassium feldspar and improve the recovery rate.
Low-potassium feldspar gravity separation is achieved based on the density difference between minerals. Under the action of external forces such as gravity field or centrifugal field, mineral particles of different densities are layered or graded according to density or particle size, thereby achieving mineral separation. Density of low-potassium feldspar The density of low-potassium feldspar is generally between 2.55-2.63g/cm³, while the density of some gangue minerals (such as quartz with a density of about 2.65g/cm³ and mica with a density of about 2.7-3.1g/cm³) is similar or slightly higher. During the gravity separation process, the mineral particles in the slurry are moved by water flow or mechanical force. The denser gangue mineral particles tend to be enriched at the bottom of the equipment or in a specific area, while the less dense low-potassium feldspar is distributed in other areas.
The main principle process is as follows:
Crushing and screening: The raw ore is first crushed, and then the ore is divided into different particle sizes by screening, generally divided into three particle sizes: coarse, medium and fine. Minerals of different particle sizes have different movement patterns during the gravity separation process, and separate treatment can improve the gravity separation effect.
Gravity separation: The slurry of different particle sizes after screening is fed into the corresponding gravity separation equipment. The slurry is subjected to the combined action of horizontal water flow and vertical shaking on the shaking table, and the particles are distributed in a fan shape on the bed surface according to density and particle size. Low-potassium feldspar particles move to the concentrate end of the bed surface, while gangue minerals move to the tailings end. The products in different areas are collected separately to obtain low-potassium feldspar concentrate and tailings.
The acid leaching method uses acid (hydrochloric acid, sulfuric acid, etc.) to react chemically with impurity minerals in low-potassium feldspar to dissolve and remove impurities, thereby achieving the purpose of purification. During the acid leaching process, the acid reacts with impurity minerals such as iron and titanium in the low-potassium feldspar, and the generated soluble metal chloride enters the solution, which is removed through the subsequent solid-liquid separation step to achieve the effect of purifying low-potassium feldspar.
The principle process is as follows:
Grinding and acid leaching: The raw ore is first crushed and ground to make the mineral particles reach a certain fineness, generally requiring -0.074mm to account for about 70%-80%, in order to increase the contact area between the mineral and the acid and improve the acid leaching effect. Then the ground low-potassium feldspar ore powder is mixed with the acid solution according to a certain liquid-solid ratio (generally 2:1 - 3:1), and the acid leaching reaction is carried out at a certain temperature (usually 60 - 90°C) and stirring conditions. The acid leaching time depends on the nature of the ore and the impurity content, generally 2 - 6 hours.
Solid-liquid separation and neutralization: The ore pulp after acid leaching is separated into solid and liquid by filtering, centrifugation and other methods to obtain low-potassium feldspar solid after acid leaching and acid solution containing impurities. The acid solution needs to be discharged after neutralization treatment to reduce pollution to the environment. The solid product is washed with clean water several times to remove residual acid and soluble impurities, and then dried to obtain the purified low-potassium feldspar product.
The high-temperature roasting method uses the changes in the physical and chemical properties of minerals under high temperature conditions to purify low-potassium feldspar. During the high-temperature roasting process, some impurity minerals in low-potassium feldspar will undergo changes such as decomposition, oxidation or volatilization, thereby separating from low-potassium feldspar.
The principle process is as follows:
Crushing and roasting: The raw ore is crushed to a suitable particle size, generally 10-20mm, and then sent to the roasting furnace for high-temperature roasting. The roasting temperature is generally between 800-1200°C, and the roasting time depends on the properties of the ore and the roasting equipment, usually 1-3 hours. During the roasting process, the roasting temperature and time must be controlled to ensure that the impurity minerals can fully change, while avoiding excessive roasting that causes serious damage to the crystal structure of low-potassium feldspar.
Cooling and mineral separation: The roasted ore is cooled, and then magnetic separation, flotation, gravity separation and other methods are used for mineral separation to further remove impurities and obtain purified low-potassium feldspar products.
The above is an introduction to 5 common low-potassium feldspar purification methods. In actual ore dressing plants, each process method has its own advantages and characteristics and applicable environment. The specific selection depends on the properties of low-potassium feldspar ore, ore dressing plant conditions and other factors. If you want to get an ideal return on investment, it is recommended to conduct ore dressing tests and design a suitable and reasonable purification plan through test analysis.
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