Dolomite Magnesite Rotary Kiln: Precision Dual-Mineral Calcination, High-Purity Magnesia Products

Dolomite and magnesite are core raw materials for the production of magnesia refractories, lightweight magnesium oxide, and magnesium metal. The key to realizing their value lies in efficient calcination and purification—precise temperature control is required to remove CO₂, moisture, and impurities from the raw materials, while also preventing over- or under-burning of the magnesia components. Conventional calcination equipment often suffers from problems such as poor compatibility with both minerals, large fluctuations in magnesium content, and high energy consumption. The Dolomite Magnesite Rotary Kiln is specifically designed to accommodate the calcination characteristics of both minerals. By leveraging dual-ore process adaptation, precise staged temperature control, and full-process energy conservation, it consistently produces high-purity calcined dolomite (CaO and MgO) and light-burned magnesite (MgO content ≥90%), meeting the high-quality demands of the refractory, magnesium chemical, and magnesium alloy industries.

I. Core Technology: Laying the Foundation for Precise Dual-Mineral Calcination and High-Purity Output

Dolomite (decomposition temperature 700-900°C) and magnesite (decomposition temperature 1000-1200°C) have significantly different calcination characteristics. This equipment leverages core technology to overcome traditional bottlenecks, ensuring both mineral compatibility and product quality:

1. Mineral-Adaptive Pretreatment System

Customized pretreatment processes address the differences in physical properties of the two minerals:

Dolomite (Mohs hardness 3.5-4.5): A combination of jaw crushing and vibrating screening is used to control the particle size to 10-30mm (to prevent calcination pulverization exceeding 15%). Airflow separation is also used to remove clay impurities (reducing the mud content to ≤2%).

Magnesite (Mohs hardness 3.5-5.0): After cone crushing to 5-20mm, the particles enter a permanent magnetic drum separator (magnetic field strength 12,000 GS) to reduce the Fe₂O₃ content from the original ore. Reduced from 1.2%-2.0% to ≤0.5%;

Mixed calcination adaptability: Supports any mix ratio from 3:7 to 7:3 (e.g., in magnesia-calcium refractory production), achieving ±0.5% batching accuracy using a belt scale to meet diverse product needs.

2. Segmented Precision Temperature Control and Corrosion-Resistant Kiln Technology

Dual-Ore Adaptive Temperature Control Curve: The kiln is divided into a preheating section (400-600°C, to remove moisture from the raw materials), a decomposition section (dolomite 700-900°C / magnesite 1000-1200°C, to decompose CO₂), and a holding section (decomposition temperature ±50°C to ensure a complete reaction). The temperature of each section is controlled by a combination of rotary kiln burners (dedicated high-temperature burners) and infrared thermometers, keeping temperature fluctuations within ±15°C. This prevents overburning of dolomite, which reduces CaO activity, and underburning of magnesite, which can cause residual CO₂ that could affect subsequent processing.

II. Application Scenario: Covering the Entire Magnesium Material Production Chain

The equipment can be used to calcine dolomite and magnesite separately or in combination, tailored to downstream needs. It is suitable for the three core industries of refractory materials, magnesium chemicals, and magnesium alloys:

1. Magnesia Refractory Industry

Product Types: Calcined Dolomite (for magnesia-calcium refractory bricks), Light-burned Magnesite (for magnesia refractory mortar and magnesia-chrome bricks);

Applications: Linings for converters and cement rotary kilns in the steel industry. High-purity calcined dolomite refractory bricks offer strong resistance to slag erosion, while refractory mortar made from light-burned magnesite has a bond strength of ≥1.5 MPa, meeting the requirements for long-term, stable operation of high-temperature industrial kilns. Single-line production capacity can be customized from 100,000 to 500,000 tons/year, making it suitable for large refractory groups.

2. Magnesium Chemical Industry

Product Types: Light-burned magnesite (used to produce light magnesium oxide, magnesium sulfate, and magnesium hydroxide), calcined dolomite (used to produce magnesium calcium powder);

Applications: Environmental protection (magnesium hydroxide as a flue gas desulfurizer), pharmaceuticals (medicinal magnesium oxide), and agriculture (magnesium sulfate fertilizer). The equipment controls product activity by adjusting the calcination temperature (for example, when producing magnesium hydroxide for desulfurization, the magnesite calcination temperature is controlled at 1050°C to ensure MgO activity ≥ 60%). It is suitable for small and medium-sized chemical companies with annual production capacity requirements of 50,000-200,000 tons.

3. Magnesium Alloy Industry

Product Types: Calcined Dolomite (used as a flux in magnesium smelting), Light-burned Magnesite (used for magnesium alloy refining and impurity removal);

Applications: Automotive lightweighting (magnesium alloy wheels), aerospace (magnesium alloy structural parts) - The calcined dolomite produced by this equipment has a CaO content of ≥55% and a SiO₂ content of ≤1.0%, reducing energy consumption during magnesium smelting. The light-burned magnesite has a low impurity content, ensuring a magnesium alloy purity of ≥99.5%, making it suitable for large-scale magnesium production of 300,000 to 1,000,000 tons/year by large magnesium companies.

III. Operational Logic: Breaking Down the "Dual Ore Pretreatment - Precision Calcination - Purification" Process

The equipment operates according to the principle of "adapting raw material characteristics - staged temperature-controlled calcination - product quality control." The entire process is divided into six major steps to ensure the stable output of high-purity magnesium products:

1. Raw Material Pretreatment: Adapting to the Characteristics of Dual Ore

Grading Crushing and Impurity Removal: Dolomite is crushed to 10-30mm in a jaw crusher, and then removed by a vibrating screen to remove dirt and impurities. Magnesite is crushed to 5-20mm in a cone crusher and then fed into a permanent magnetic drum separator (magnetic field strength of 12,000 GS) for iron removal, reducing the iron content to ≤0.5%.

Proportioning and Transportation: When calcining separately, the raw materials are directly fed into the raw material silo. When calcining together, the raw materials are precisely proportioned according to the preset ratio (e.g., dolomite:magnesite = 3:7) using a belt scale and then conveyed into the preheater via a sealed bucket elevator to prevent moisture and secondary contamination. 2. Preheating and Drying: Reducing Calcination Energy Consumption

The raw materials enter the "Vertical Preheater for Rotary Kiln" and undergo countercurrent heat exchange with the 1100-1300°C high-temperature flue gas at the kiln outlet. The temperature of the dolomite is raised to 600°C (completely evaporating water, with a moisture content of ≤0.5%), and the temperature of the magnesite is raised to 800°C (preliminary decomposition of some CO₂). The preheated raw materials then enter the rotary kiln through a chute (equipped with a heat-resistant lining).

3. Kiln Calcination: Staged Temperature Control Ensures Purity

Kiln Drive and Temperature Zone Control: The rotary kiln body is tilted (3.5%-5%), supported by support rollers and driven by a gear ring (adjustable speed of 0.3-1.8 rpm). The raw materials move axially as the kiln rotates, passing through the preheating, decomposition, and insulation sections.

Burner Coordinated Temperature Control: Rotary kiln burners (dedicated burners) are installed at the kiln head and automatically adjust the fuel supply (natural gas, pulverized coal, or coke oven gas) according to the raw material type. When calcining dolomite, the decomposition section temperature is maintained at a stable 800 ± 15°C; when calcining magnesite, the decomposition section temperature is controlled at 1100 ± 15°C, ensuring a CO₂ decomposition rate of ≥ 98% and preventing residual carbonates in the product.​

4. Cooling and Purification: Ensuring Product Quality

Cooling: The calcined magnesia product (temperature 800-1000°C) is discharged from the kiln outlet and enters a sleeve-type cooler. Cooling is achieved through countercurrent heat exchange with cold air to below 100°C, preventing oxidation or moisture absorption.

Fine Purification: The cooled product is classified by a vibrating screen (to remove fine particles). If used for high-end refractory materials, it also enters an airflow separator to remove SiO₂ impurities, ensuring a uniform product particle size (5-25mm) and meeting specified composition standards. Unqualified product is returned to the raw material system for re-calcination.

IV. Service Guarantee: A Professional Team Safeguards the Complete Magnesia Material Production Cycle

As a rotary kiln manufacturer deeply engaged in the magnesia equipment field, we provide a comprehensive service chain, from raw material analysis to operational support, addressing the core pain points of dual-ore calcination:

1. Customized Solution Design

Based on the customer's raw material characteristics (composition, hardness, and impurity content of dolomite/magnesite), product requirements (e.g., refractory bricks/chemical applications), and production capacity planning, we provide a customized solution including equipment layout, dual-ore calcination process curves, and return on investment calculations.

Provide pilot testing services: We simulate the calcination process in a small test kiln, optimize temperature parameters and raw material pretreatment processes, and ensure product purity meets mass production standards (e.g., MgO content ≥ 92% for light-burned magnesite).

2. Full-Process Installation and Commissioning

Experienced engineers will be dispatched for on-site installation, focusing on ensuring the precise assembly of the dual-ore temperature control system, online composition analyzer, and waste heat recovery device, ensuring that calcination between different raw materials requires no major equipment adjustments. Following installation, a 30-day continuous trial run will be conducted to test the calcination results for both dolomite and magnesite, optimizing parameters such as rotational speed and fuel supply until product quality and production capacity are stable.

3. Technical Training and Long-Term Operation and Maintenance

Specialized training will be provided to the customer team, covering dual-ore pretreatment techniques, calcination parameter adjustment, impurity control methods, and equipment troubleshooting, ensuring that operators understand the calcination differences between different raw materials.

24/7 after-sales service is provided.

The dolomite-magnesite rotary kiln is not only a "magnesia raw material purifier," but also a "booster for high-quality development of the magnesium industry chain"—it not only solves the compatibility issues of dual-ore calcination but also enhances the value of downstream products through high-purity products. If you need to know about the impurity removal process for specific raw materials (such as high-silicon magnesite), the investment costs of equipment with different production capacities, or would like to obtain cooperation cases for magnesia refractory materials plants, please feel free to contact us. We will provide targeted technical solutions and implementation support.

Dolomite Magnesite Rotary Kiln Equipment Parameters: