rotary kiln bauxite

Types of Rotary Kiln Bauxite

Bauxite rotary kiln is used to get bauxite through the calcination process. During this industry process, moisture is removed from bauxite, and alumina content gets increased. The types are as follows:

• Non- Metallic Bauxite

  Non-metal bauxite mainly contains aluminum oxides and some silicates. These include kaolinite and illite. Non-metallic bauxite also has several other compounds that are usually found in soil, such as iron oxides. The bauxite rotary kiln helps to convert this material into refractory products usable in the manufacturing process. Non-metal bauxite is mostly used in various construction and engineering works.

• Bauxite as an Abrasive

  Bauxite contains aluminum oxide, known as corundum, which is then used as an abrasive. Corundum is made by passing the non-metal bauxite through a rotary kiln that gets rid of the moisture content, leading to the formation of alpha alumina. Next, it is crushed into granules of different sizes before undergoing a second crushing process in order to obtain the desired size. Corundum is then mixed with other abrasives like emery and garnet. Because of its hardness, bauxite is usually used for sanding, grinding, and polishing surfaces in manufacturing products.

• Bauxite as Cement Material

  Bauxite clinker is used in cement manufacturing. When non-metallic bauxite undergoes high-temperature treatment, it gets transformed into a solid material called bauxite clinker. It contains compounds like calcium aluminate that is responsible for cement's binding properties. Bauxite cement has a high degree of abrasion resistance, so it is suitable for use in wastewater treatment plants and chemical works. Bauxite cement is also used in constructor and precast concrete, which hardens and gains strength faster than conventional cement.

Features of Rotary Kiln Bauxite

• High Porosity

  The bauxite stone in high porosity means it has undergone a calcination process in a rotary kiln, which leads to the expansion of its pores. For this reason, this bauxite has a larger surface area that enables better absorption of liquids and chemicals. The porosity also makes bauxite a suitable material for refractory bricks and catalysts, as these applications require a porous structure to ensure efficient heat resistance and reaction in the right way.

• Refractoriness and RDT

  Refractoriness is the ability of bauxite to maintain its shape and integrity when subjected to extremely high temperatures. Refractoriness under dielectric test checks the capacity of Materials to function under extreme heat levels without losing their dielectric properties. These two features are usually used in evaluating the quality of bauxite that is meant for refractory applications, such as in kilns, furnaces, and reactors. Bauxite with high refractoriness and RDTE withstand long-term exposure to high temperatures is required for better performance and durability in intense environments.

• Particle Size Distribution

  This is the distribution of stones of different sizes within a certain mixture. This size distribution influences the properties of bauxite, such as its reactivity, mechanical strength, and permeability. The size distribution is determined by sieving the material using different mesh sizes before analyzing the results, and the PSD is important in industries since it influences the effectiveness of the material in different applications like catalysis, metallurgy, and ceramics.

Industrial Applications of Rotary Kiln Bauxite

Rotary bauxite kiln is a key industrial equipment used to produce refractory grade bauxite. Below are the industrial applications:

• Manufacture of Cement

  The bauxite rotary kiln operates at a temperature of between 1000 and 2000°C to produce cement from bauxite materials. The bauxite stones are crushed and mixed with other materials, such as limestone, before being fed into the kiln. Cement production requires an extremely high temperature, hence the use of rotary kilns, because they are capable of reaching up to 1450°C. It can combine all the components resulting in clinker formation. After several hours, the clinker cement product is obtained, which the engineers then cool and grind to produce the final cement.

• Production of Alumina

  The bauxite rotary kiln is widely used for alumina production. This bauxite contains aluminum oxides, which when heated in the rotary kiln, get converted into alumina through the systematic breakdown of bauxite. The process needs extremely high temperatures to guarantee the reaction occurs at the right intensity. Bauxite is also crushed into smaller bits to create a larger surface area for reaction before it is mixed with sodium hydroxide solution. The temperature and pressure are increased to dissolve alumina before settling and filtering. The residue is then washed, and the solution is evaporated to allow saturation. The solution is then seeded to allow crystals to form. The crystals are then harvested, and the mother liquor is recycled. The crystals are washed and then calcined in a kiln to produce alumina.

• Production of Refractory Materials

  Bauxite is widely used to make material that withstands extreme heat and corrosive environments. Bauxite is then subjected to rotary kiln aluminum oxide calcination process to give it high alumina content by removing the silica and iron oxides. The kiln operates at high temperatures that familiarize the bauxite particles with each other on a molecular level, which increases their refractoriness. Bauxite used for refractories is typically cement grade and calcined at temperatures above 800°C to ensure that the bauxite is fully fused.

• Production of Iron Ore Pellets

  Iron ore pellets are made by preparing a slurry from iron ore fines before adding bauxite and limestone additives. The mixture is then dewatered and formed into green pellets before drying and undergoing roasting at 1250°C in the rotary kiln. During roasting, bauxite provides aluminum ions that help form the silicate liquid phase, which acts as a bonding agent during sintering. The lime in the limestone works with bauxite to get rid of magnesium and calcium silicate impurities, thus ensuring iron ores have better quality and higher iron concentration.

How to Choose a Rotary Kiln Bauxite

The following are important considerations seeking rotary kiln bauxite:

• Material Composition

  Corundum bauxite suppliers usually source their bauxite from multiple countries and deposit types. It's important for buyers to fully understand the material composition of the bauxite to ensure it will meet the needs of their target customers. Buyers should seek information about the aluminum oxide content, mineral phase composition, and presence of any harmful characteristics such as radionuclide and silica.

• Grain Size

  Grain or particle size plays a key role in determining the reactivity and resulting texture of calcined bauxite. Different customers have different preferences based on the use they want to put the bauxite into. Buyers should ensure they stock a variety of grain sizes to cater to different customer needs.

• Material Purity

  Buyers should make sure to purchase bauxite with the highest possible material purity. Impurities can impact the effectiveness and efficiency of bauxite in refractory applications. They can also negatively affect the properties of end products. Buyers can validate the material purity of various bauxite types by checking the certificates of analysis from the manufacturers.

• Shipping Arrangements

  Shipping arrangements refer to the cost and time it will take to deliver the products to the buyers' warehouses. Buyers should make sure to take into account the distance from the preferred bauxite source and the shipping method. Also, they should consider the availability of the right shipping method, as well as the average time it takes to clear customs in various countries. All this will help buyers make accurate decisions about inventory management. They should also ensure they are well-informed about the shipping costs as part of their budget when managing the overall business in the importation space.

Q&A

Can bauxite be calcined in a vertical kiln?

Users use vertical and rotary kilns for the same purpose of alumina extraction. However, rotary kilns are preferred over vertical kilns due to the latter's inability to reach the very high temperatures required for effective bauxite calcination.

Is calcined bauxite radioactive?

Calcined bauxite has a small background radiation level. The radioactivity level of calcined bauxite is mainly affected by the source from which it was obtained. For instance, bauxite sourced from granitic regions is likely to contain higher levels of radium and uranium due to the presence of monazite and zircon.

What is the melting point of calcined bauxite?

The melting point of cal bauxite is generally around 2050 °C, but it can vary depending on the mineral composition of specific bauxite batches. For example, bauxite with a higher content of aluminum oxide will have a higher melting point.

Can humans be affected by the radioactivity of bauxite?

Bauxite's natural radioactivity doesn't pose any threats under usual circumstances. However, exposure to dust and particles may lead to respiratory problems. This is a result of fine particles causing irritation in the lungs and may even lead to pneumoconiosis, a disease that is characterized by lung damage.

What harm can be caused by the radioactivity of bauxite?

Unlike other minerals like phosphate rock, the radioactivity of bauxite has very little impact on humans. There is a possibility of the radionuclide contained in bauxite being transferred to water or food chains, which can lead to adverse effects such as damage to lung tissue and an increased risk of lung cancer from inhaling bauxite dust.