What is the process of gypsum production?

Gypsum is an incredibly valuable mineral found abundantly in nature. It typically forms between layers of sedimentary rocks and has a soft, chalky texture, appearing almost white. The presence of impurities can give it shades ranging from gray to yellow. Chemically, it consists of calcium sulfate (CaSO₄) combined with two water molecules (H₂O). This compound is also referred to as calcium sulfate hydrate.

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Chemical Formula Of Gypsum

The primary components of gypsum include calcium (Ca), sulfur (S), oxygen (O), and hydrogen (H). Calcium and sulfur combine to create calcium sulfate, while hydrogen and oxygen form water. Thus, the chemical formula is:

Gypsum: CaSO₄ + 2(H₂O)

Formation Of Gypsum

Gypsum forms under two essential conditions:

1. The right combination of minerals.
2. The occurrence of evaporation.

Consequently, gypsum can arise in various environments, such as shallow sea basins, tidal flats, lagoons, hot springs, coastlines, and even volcanic areas. During prehistoric eras, ancient sedimentary gypsum beds were formed as the ancient seas became increasingly concentrated due to evaporation, leading to the creation of significant gypsum deposits. Gypsum crystals formed in saturated seawater and settled to the bottom, a process that continues today through evaporation, resulting in new gypsum crystals. Additionally, gypsum is produced as a by-product when scrubbing sulfur from fossil fuels.

The Process Of Gypsum Production

The gypsum production process starts with mining gypsum ore, typically extracted from quarries and mines. After extraction, the ore is crushed and stored near the plant. Depending on demand, it undergoes further grinding and screening to achieve a size of approximately 2 inches (50 mm) in diameter. If the ore has a moisture content exceeding 0.5%, it is dried in a rotary dryer. After drying, the ore is sent to a roller mill for crushing, achieving 90% of the material at less than 149 micrometers (µm). The fine gypsum product collected from the mill is known as land plaster. This process can also involve drying within the roller mill, making a separate rotary dryer unnecessary.

Five Stages Of Gypsum Production Process

Gypsum production processes can vary from labor-intensive methods to highly mechanized systems. Small plants can produce a few tonnes daily using manual methods, while large-scale operations can produce thousands of tonnes with advanced equipment. Regardless of the scale, the production process generally follows five basic steps:

1. Excavation The first stage of gypsum production involves bringing the mineral ore to the surface. This is accomplished through excavation methods, such as open-cast mining, where overlying strata are removed to expose the ore. If deposits are deeply embedded, shaft mining may be necessary. Heavy machinery is used for this process.

2. Crushing After excavation, the mined ore is crushed for easier handling and processing. Smaller gypsum grains are more efficiently heated than larger, unbroken chunks, thus preventing uneven heating and moisture removal. Jaw crushers are typically employed to break down the ore into manageable sizes.

3. Sieving This process involves separating large gypsum grains from finer ones to ensure high quality. Large chunks may contain impurities that could affect the final product, so they are separated and sent back through the crusher as necessary.

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4. Grinding For quality applications, further grinding is often required. Gypsum can be ground in rod, hammer, or ball mills

5. Heating The final step is heating or calcining, which is critical for removing excess moisture. Various heating technologies can be used, often involving a rotary dryer and a cyclone collector to gather the resultant gypsum powder.

Takeaway

Gypsum powder is derived from natural gypsum ore, which is consistently in demand due to its applications in various fields. Since it is not always available on the surface, finding and extracting it requires effort. Once the gypsum is mined, it undergoes several processing steps, including crushing, sieving, grinding, and heating, resulting in high-quality gypsum suitable for products like Portland Cement, fertilizers, molding plaster, sculptures, and gypsum wallboard.