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Gypsum powder is a versatile material widely used in construction, agriculture, and various industrial applications. A gypsum powder production line transforms raw gypsum mineral into a finely ground product with consistent quality and performance. This article outlines the key stages of a gypsum powder production line, the main types of equipment involved, quality control measures, and environmental considerations.
Natural Gypsum: Mined from sedimentary deposits, natural gypsum typically contains about 20–30% moisture and various impurities (clay, sand, organic matter).
Synthetic Gypsum: A byproduct of industrial processes such as flue-gas desulfurization in power plants. It often has lower levels of impurities.
Additives: Small quantities of retarders (e.g., citric acid) or accelerators (e.g., potassium sulfate) may be added to modify setting time or strength.
Crushing and Pre‑Grinding
Large gypsum rocks are crushed by jaw crushers or impact crushers to particles typically under 50 mm.
A pre‑grinder further reduces the size to under 10 mm, ensuring uniform feed to the next stage.
Calcination (Drying and Dehydration)
Ground gypsum passes through a rotary kiln or flash dryer.
Heat (typically 150–180 °C) drives off most of the chemically bound water, converting CaSO₄·2H₂O (raw gypsum) into CaSO₄·½H₂O (hemihydrate gypsum).
Fine Grinding
The hemihydrate gypsum is milled in a Raymond mill, ball mill, or vertical roller mill to achieve a specific surface area (often 350–550 m²/kg).
Fineness influences the setting time, strength, and workability of the final product.
Classification
A classifier (air separator) separates fine gypsum powder from coarser particles.
Oversized particles return to the mill for regrinding, ensuring uniform particle size distribution.
Packaging and Storage
The finished gypsum powder is conveyed to a storage silo.
Automatic bagging machines pack it into paper or multi‑wall bags (25 kg, 40 kg, or 50 kg) or big bags for bulk users.
Jaw Crusher / Impact Crusher: Initial size reduction of raw gypsum rock.
Rotary Kiln / Flash Dryer: Thermal treatment for dehydration and drying.
Grinding Mill (Raymond, Ball, or Vertical Roller Mill): Achieves required fineness.
Air Classifier: Ensures consistent particle size.
Packaging Machine: Automated filling, sealing, and palletizing.
Chemical Composition: Regular sampling to measure CaSO₄ content, loss on ignition (LOI), and impurity levels (silica, alumina).
Fineness (Blaine or Sieve Analysis): Monitored to ensure appropriate surface area for application requirements.
Setting Time: Initial and final setting times tested per industry standards (e.g., ASTM C472).
Strength Tests: Compressive strength of standard mortar cubes after 1 h, 2 h, and 24 h.
Moisture Content: Ensures shelf stability and prevents caking during storage.
Dust Control: Bag filters and cyclones capture airborne gypsum dust from crushers, mills, and classifiers.
Wastewater Recycling: Process water from dust suppression and equipment cleaning is treated and recycled on‑site.
Energy Recovery: Waste heat from the rotary kiln can preheat the incoming gypsum or drive a steam turbine for electricity generation.
Construction: Wallboard, plaster, stucco, and joint compounds.
Agriculture: Soil amendment to improve structure and supply calcium and sulfur.
Industrial: Cement additive, dental molds, and ceramic components.
A gypsum powder production line combines mechanical crushing, thermal treatment, fine grinding, and classification to produce a consistent, high‑quality powder suitable for diverse applications. Careful control of raw material quality, process parameters, and environmental measures ensures reliable operations and product performance. Continuous monitoring and periodic equipment maintenance help maintain production efficiency and product consistency.
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