Dolomite is a non-metallic mineral with extremely rich reserves. It is an important calcium and magnesium resource on the earth. Dolomite rock (dolostone) is also a sedimentary carbonate rock, dominated by dolomite, but often mixed with quartz, feldspar, calcite, and clay minerals.
Dolomite has a wide range of uses in the industry of construction, steel making, glass, ceramics, agriculture, etc. According to different uses, dolomite rock has different processes.
Processing of Dolomite rock
After mining, dolomite rock is crushed into blocks with a certain particle size. The dolomite blocks can be directly used as raw materials for sand and gravel aggregates or continue to be ground or calcined.
Process 1: Crushing and screening dolomite rock
- 1Coarse crushing: First, large dolomite rock is sent to a jaw crusher for coarse crushing.
- 2Fine crushing: Then the dolomite rock is crushed by a cone crusher into blocks of small particle size to achieve sufficient dissociation of the useful material of the ore.
- 3Screening: The dolomite blocks are sent to a vibrating screen for screening. Qualified materials are directly used in the construction industry as sand and gravel aggregates, or continue to be processed. However, unqualified dolomite will return to the cone crusher for further crushing.
Process 2: Grinding and classifying dolomite rock
- 1grinding: The crushed dolomite is transported from the bottom up to the silo by a bucket elevator and then sent to the Raymond mill for grinding by an electromagnetic vibrating feeder.
- 2Classifying: Dolomite is ground/milled into 325-1250 mesh to produce dolomite powder. The powder will be classified by a classifier. The Qualified dolomite powder will be packed and used in building, ceramic, rubber, etc., while the unqualified powder will be sent back for re-grinding.
Process 3: Calcinating dolomite rock
The crushed dolomite is calcined in a rotary kiln, which is used for producing refractory materials, magnesium alloys, cement, etc.
Dolomite is calcined at 1500°C to obtain magnesia-calcium raw materials, such as dolomite sand, magnesia-calcium sand, and magnesia-calcium iron sand. Then it is made into refractory materials.
How to produce magnesium alloys?
Dolomite rock - Preheating - Calcining – Cooling - Mixing and grinding - Briquetting - Refining magnesium - Magnesium alloy.
- 1Preheating: The dolomite rock evenly enters the preheater to be preheated to above 800°C.
- 2Calcinating: Choose an energy-saving rotary kiln to calcine the dolomite at 1250°C into a higher-grade calcined white.
- 3Cooling: The high-temperature activated calcined white is cooled by a cooler to below 100°C. The air is preheated to above 600°C.
- 4Mixing and grinding: Put dolomite, ferrosilicon (within 20 mm), and fluorite powder into a ball mill for mixed grinding. The particle size is within 100 mesh. The dust removal system is equipped.
- 5Briquetting: Press the powder into briquettes with a briquetting making machine. Another dust removal system can be equipped.
- 6Refining magnesium: Using Electrolysis or Silicothermic Reduction to extract magnesium metal.
- 7Magnesium alloy: Finally, the magnesium alloy is produced by heat treatment or other methods.
- One method is to make caustic powder by calcination. Then add magnesium chloride solution or magnesium sulfate solution to make magnesium oxychloride cement with better stability.
- The other method is to calcinate it into caustic dolomite, and then processed it into magnesium hydroxide cement and magnesium oxide sulfate cement.
11 common uses for dolomite
1. Use of dolomite in steel making
Dolomite in the iron and steel industry is normally used in 4 forms: (1) as a fluxing material; (2) for protection of refractory lining; (3) as a refractory raw material; (4) for producing refractory bricks.
2. Crushed rocks for the construction industry
The most common use for dolomite is the crushed rocks. The white dolomite stone is crushed and sized for use as a road base material, a sand and gravel aggregate in concrete and asphalt, railroad ballast, rip-rap, or fill.
3. Magnesium-containing cement
The magnesium-containing dolomite cement has the advantages of fast setting and hardening, good compression resistance, good elasticity, and strong wear resistance. It is used in floor tiles, fast-setting pavement paving, and repair of pavement cracks.
4. Magnesium smelting
The dolomite with a particle size of 30-120 mm is smelted by Electrolysis and Silicothermic Reaction.
Electrolysis is complex and difficult to obtain economic benefits, so small magnesium plants should not use it.
Silicothermic Reaction is to mix calcinated dolomite with ferrosilicon and fluorite to form balls, and heat them to 1100°C in a vacuum furnace. Then cool the magnesium vapor and cast it into magnesium ingots.
5. Dolomite fertilizer
You can use dolomite for gardening or crops. The reason is that the magnesium in dolomite can be used as a magnesium fertilizer to compensate for the magnesium loss in the soil and help tomatoes, onions, beans, and other plants grow better.
6. Adjust the soil pH value
Dolomite soil amendment adjusts the soil pH value for plants to solve the problems of slow growth, poor maturity and death caused by urea fertilizers. It can also increase crop yields by 15-40%. You can use dolomite for plants like lilacs, asparagus, and beets that require neutral soil or alkaline soil.
7. Livestock and poultry feed
Calcium and magnesium are essential nutrients for animals. Adding dolomite powder to the livestock and poultry feed can help animals increase the intake of calcium and magnesium. It is very beneficial to promote their growth and reduce diseases.
8. Glass products
Dolomite and limestone are the third largest components of glass except for silica sand and soda ash. Soda ash costs the most, while magnesium oxide in dolomite can reduce costs. Dolomite powder can act as a flux, reduce glass aging, increase glass strength and improve the colored glass's plasticity.
9. Ceramic products
Dolomite powder is the raw material for ceramic blanks and glazes. MgO and CaCO3 can replace talc and calcite to reduce the firing temperature of green body and increase transparency. The dolomite glaze is not easy to smoke, and crystallization rarely occurs.
10. Rubber products
Dolomite-containing rubber general-purpose calcium and magnesium powder, as a new type of additive and coloring agent, can replace light calcium powder. Its cost is lower and can prevent crack propagation and increase the reinforcing performance.
11. Water treatment
The calcinated dolomite is used for water treatment with the advantages of low cost and no secondary pollution. Under optimal conditions, it can remove more than 90% boron of wastewater to reach the drinking water standard. It also removes the metal ions (iron, manganese, etc.) in the industrial wastewater.