Dolomite rock is a non-metallic mineral with a very wide range of uses. It is an important calcium and magnesium resource on the earth with extremely rich reserves. According to different uses, dolomite rock has different processes.
Dolomite rock processing
The mined dolomite rock is crushed into the dolomite blocks. These dolomite blocks can be used as raw materials for sand and gravel aggregates or as powder mills. The raw materials can also be fired in the kiln.
Process one: Crushing and screening dolomite rock
- Coarse crushing: First, large dolomite rock is sent to a jaw crusher for coarse crushing;
- Fine crushing: Then the dolomite rock is crushed by a cone crusher into small particle size and achieve sufficient dissociation of the useful material of the ore;
- Screening: The crushed dolomite blocks are sent to a vibrating screen for screening treatment. Qualified materials are used as the crushed rocks for the construction industry, while the unqualified materials return the cone crusher for further crushing.
Process two: Milling and classifying dolomite rock
- Milling: The crushed dolomite rock 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;
- Classifying: Dolomite is ground to 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 rubber, glass, building, ceramic, etc. While the unqualified powder will be sent back for re-grinding.
Process three: Calcinating dolomite rock
The crushed dolomite is calcined in a rotary kiln, which is used for refining magnesium metal, producing cement, refractory materials, etc.
- Preheating: The dolomite rock evenly enters the preheater. The high-temperature flue gas at the end of the rotary kiln exchanges heat with the dolomite raw materials, and the raw materials are preheated to above 800°C;
- Calcinating: The preheated dolomite enters the rotary kiln to be calcined at a high temperature of 1250°C to become active calcined white. The temperature of the active calcined white flowing out of the discharge port of the rotary kiln is as high as about 900 ℃ and enters the vertical cooler;
- Cooling: The high-temperature activated calcined white is fully heat exchanged with the combustion-supporting cold air blown at the bottom of the vertical cooler. The activated calcined white is cooled to below 100°C, and the combustion-supporting air is preheated to above 600°C;
- Milling or making balls: After cooling, the activated calcined white is discharged from the cooler and transported for milling or making balls.
Uses for dolomite
Dolomite uses in rubber
The use of dolomite rock to produce rubber general-purpose calcium and magnesium powder, as a new type of additive and coloring agent, can partially or completely replace light calcium powder and lithopone powder.
The performance of dolomite powder in rubber is basically the same as that of light calcium powder, but its cost is lower. And it can prevent crack propagation and greatly increase the reinforcing performance of rubber products.
Dolomite uses in glass products
Dolomite and limestone are the third largest components of glass raw materials except silica sand and soda ash. In the production of bottle glass, soda ash is the most expensive component, while the addition of magnesium oxide in dolomite can further reduce costs.
Dolomite powder uses in the glass industry can provide calcium oxide, adding soda-ash-silica system to act as a flux. And it can reduce glass aging, improve the plasticity of colored glass, and increase the strength of glass.
Dolomite uses in metallurgical industry
1. Magnesium smelting industry
Dolomite rock with a particle size of 30-120mm is an important raw material for the production of metallic magnesium. Its smelting methods mainly includes 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 dolomite that is calcinated with ferrosilicon and fluorite to form balls. The balls are heated in a vacuum furnace at 1100°C. Then the magnesium vapor is cooled and magnesium ingots are obtained.
Dolomite rock is one of the important raw materials of alkaline refractories, mainly used for steel-making converter lining, open hearth furnace, electric furnace wall, and secondly used for thermal equipment such as external refining equipment and cement kilns.
Dolomite gunning materials are developed to repair parts such as converters, electric furnaces, ladle slag lines, and RH insertion pipes, with good results.
Besides, dolomite rock is used for producing refractory bricks, such as zirconium-enhanced dolomite bricks, zirconium-enhanced magnesia dolomite bricks, fused dolomite carbon bricks and fused magnesia dolomite carbon bricks.
Dolomite uses in building materials industry
1. Crushed rocks for the construction industry
One of the main uses of dolomite rock is in the crushed rock for the construction industry. The white dolomite stone is crushed and sized for use as a road base material, an aggregate in concrete and asphalt, railroad ballast, rip-rap, or fill.
2. Magnesium-containing cement
After calcining, dolomite rock is ground into the caustic powder and blended with magnesium chloride solution or magnesium sulfate solution to prepare magnesium oxychloride cement.
In addition, dolomite rock can be calcined into caustic dolomite, and then made into the magnesium-containing cement.
The magnesium-containing cement has the advantages of simple production process, fast setting and hardening, good compression resistance, good elasticity, and strong wear resistance. They are widely used in floor tiles, fast-setting pavement paving, and repair of pavement cracks.
Dolomite uses in Agriculture
1. Dolomite soil amendment
As long-term use of urea fertilizer can cause the soil to be acidic, and too acidic soil will cause the growth of plants to become stunted, ripen poorly and even die, it is necessary to use dolomite soil amendment to adjust the soil pH.
Dolomite soil amendment can neutralize the soil acidity, help plants grow better and increase crop yields by 15-40%. You can use dolomite for plants (lilacs, asparagus, beets, etc.) that require neutral soil or alkaline soil.
2. Dolomite fertilizer
You can use dolomite for gardening or crops, as the magnesium in dolomite can be used as a magnesium fertilizer to compensate for the loss of magnesium content in the soil.
This magnesium-contained dolomite fertilizer can facilitate the adjustment of the fertilizer ratio, reduce agglomeration, and improve the conditions for plants to use soil nutrients.
3. Livestock and poultry feed
As calcium and magnesium are essential nutrients for animals, dolomite powder is added to the livestock and poultry feed as a feed additive. It helps animals to increase the intake of calcium and magnesium, which is very beneficial for promoting their growth and reducing diseases.
Dolomite uses in ceramic
Dolomite rock can not only be used as raw materials for traditional ceramic blanks and glazes, but also be used to prepare new structural ceramics and functional ceramics, such as porous ceramic balls, inorganic ceramic membranes and andalusite-based ceramics.
Dolomite powder is used in blanks and glazes, and MgO and CaCO3 are introduced to replace talc and calcite. MgO can reduce the firing temperature of green body and increasing its transparency. And dolomite glaze is more difficult to smoke than calcite glaze, and crystallization rarely occurs.
Dolomite uses in water treatment
As the calcined dolomite powder has surface adsorption and ion exchange between mineral layers, dolomite rock 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. And it can also remove metal ions such as iron and manganese in industrial wastewater.