Feldspar Powder: Essential Uses in Glass and Ceramic Manufacturing

In nature, pure feldspar is extremely rare. Even minerals commonly referred to as “potassium feldspar” may coexist or mix with sodium feldspar. These natural feldspar minerals are the core raw materials for producing feldspar powder. Feldspar minerals that contain both potassium feldspar and sodium feldspar are called alkali feldspar. Minerals made from sodium feldspar and calcium feldspar are called plagioclase. When feldspar minerals consist of calcium feldspar and barium feldspar, we refer to them as alkaline earth feldspar. Potassium microcline is a variety of potassium feldspar with a triclinic crystal structure. If sodium feldspar is arranged in a regular pattern within it, striped feldspar is formed. After processing, this mineral can be transformed into feldspar powder with specific properties.

Feldspar is one of the most abundant minerals in the Earth’s crust. It is widely distributed in certain sedimentary layers and nearly all igneous rocks. Furthermore, feldspar mining deposits, suitable for processing into feldspar powder, are found in most regions of the world. As a result, the potential for usable mineral reserves is vast. This ensures a solid raw material supply for large-scale feldspar powder production.

Feldspar Powder Preparation

Natural feldspar ores (such as potassium feldspar, sodium feldspar, and calcium feldspar) are the primary raw materials for feldspar powder preparation. This method is cost-effective, scalable, and suitable for industrial-grade powder needs. The core process includes ore pretreatment → crushing → grinding → purification → drying → ultrafine grinding (optional) → classification.

Ore Selection and Pretreatment

• Operation: Manually or mechanically sort ores with ≥80% feldspar content (impurities mainly include quartz, mica, iron minerals, titanium minerals, etc.). Use clean water to wash off attached mud and sand.
• Objective: Select high-purity feldspar ores and remove surface impurities like soil and vegetation.

Crushing

• Fine Crushing: Use an impact crusher to crush to 1-5mm (preparation for grinding).
• Objective: Break large ore pieces into smaller particles for easier grinding.
• Equipment and Process:
• Coarse Crushing: Use a jaw crusher to crush ore to 50-100mm.
• Medium Crushing: Use a cone crusher or impact crusher to further crush to 5-20mm.

Grinding (Primary Crushing)

Objective: Grind the finely crushed particles into micron-level powder (usually 10-100μm) and initially disperse particles.

Common Equipment:

• Raymond Mill (suitable for medium fineness, product particle size 10-74μm).
• Ball Mill (dry or wet grinding, uses steel or ceramic balls for impact grinding, product size can reach 5-50μm).
• Vibration Mill (high efficiency, suitable for brittle minerals, can obtain finer primary powder).

Purification (Key Step, Remove Impurities)

Feldspar ores naturally contain impurities such as quartz (SiO₂), mica (containing K, Al, Si, and water), iron minerals (Fe₂O₃, Fe₃O₄), and titanium minerals (TiO₂), which affect powder properties (e.g., color change after ceramic firing, reduced glass transparency). These impurities must be removed through the following methods: Magnetic separation (Iron Removal)，flotation separation , acid Leaching (Impurity Removal) and heavy separation (Gravity Separation)

Drying

Drying temperature is typically 100-150°C, until moisture content ≤1%

• Objective: Remove moisture from the purified powder (especially after wet grinding or acid leaching).
• Equipment:
• Box Dryer (small scale).
• Drum Dryer (medium scale).
• Spray Dryer (large scale, can dry and granulate simultaneously).

Ultrafine Grinding (Optional, for Submicron/Nanometer Powder)

If finer powder is required (e.g., D50 ≤ 5μm for high-end ceramics or coatings), ultrafine grinding is necessary:

Equipment:

• Air Jet Mill (uses high-speed airflow to impact particles, product size 1-10μm, high purity).
• Stirred Mill (wet grinding, can achieve submicron particle size).
• Planetary Ball Mill (dry or wet grinding, suitable for laboratory or small-scale production).

Classification

Objective: Control the powder’s particle size distribution (e.g., remove coarse or ultrafine particles) to meet different application needs.

Equipment:

• Air Classifier (used with air jet mills).
• Screening Machines (for coarse powder, such as 200 mesh, 325 mesh).

Main Uses of Feldspar Powder

In addition to being a key raw material for the glass industry (accounting for approximately 50-60% of total usage), feldspar is also used extensively in the ceramics industry, which accounts for about 30%. The remaining portion is used in industries such as chemicals, abrasives, fiberglass, and electrodes.

Glass Flux

Feldspar powder is one of the main components in glass mixtures. It contains high levels of Al₂O₃ and low levels of iron. Its melting point is lower than that of aluminum oxide, making it easier to melt. Feldspar not only lowers the melting temperature of the glass but also broadens the melting range. It is primarily used to increase the alumina content in glass compositions, reduce melting temperatures during glass production, and increase the alkali content. This reduces the amount of alkali used. Additionally, feldspar melts slowly into glass and has low crystallization potential. This prevents crystal formation during the glass-making process and avoids product damage. It also helps to adjust the viscosity of the glass. Typically, potassium feldspar or sodium feldspar is used in glass mixtures.

Ceramic Body Ingredients

Before firing, feldspar acts as a fluxing agent. It reduces drying shrinkage and deformation, improves drying performance, and shortens drying time. During firing, feldspar acts as a flux to lower the firing temperature. It promotes the melting of quartz and kaolin. The feldspar glass formed in the molten state diffuses and penetrates in the liquid phase. This accelerates the formation of mullite. The feldspar glass filling between the mullite grains densifies the body. This reduces porosity and improves mechanical strength and dielectric properties. Furthermore, the formation of feldspar glass improves the translucency of the body. The amount of feldspar added to ceramic bodies varies depending on the raw materials and product requirements.

Ceramic Glazes

Ceramic glazes are mainly composed of feldspar, quartz, and clay materials. Feldspar content ranges from 10-35%. In the ceramics industry (both body and glaze), potassium feldspar is predominantly used.

Enamel Raw Materials

Feldspar is mixed with other mineral raw materials to produce enamel. In general, the typical feldspar content in this mixture ranges from 20-30%.

Abrasives

Feldspar is often used as a ceramic binder in the production of grinding wheels. Its content ranges from 28-45%.

Other Uses

Potassium feldspar can also be used as a raw material for extracting potash fertilizers.

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