How Is Calcium Carbide Produced? (Electric Arc Furnace Process)

Calcium carbide (CaC₂) is synthesized via the electric arc furnace process-a high-temperature, energy-intensive method that has been the industrial standard for over a century. This process converts lime (calcium oxide, CaO) and coke (carbon, C) into calcium carbide through carbothermal reduction, leveraging extreme heat to drive the reaction. Below is a detailed breakdown of the steps, equipment, and chemistry involved.

 

1. Raw Materials: Lime and Coke​

The production of calcium carbide begins with two key raw materials:

Lime (Calcium Oxide, CaO): Derived from limestone (CaCO₃) via calcination-heating limestone to ~900°C in kilns to drive off carbon dioxide:

CaCO3​Δ​CaO+CO2​↑

Lime must be high-purity (>95% CaO) to minimize impurities in the final product.

Coke (Carbon, C): A high-carbon fuel, typically anthracite or petroleum coke, with low sulfur (<0.5%) and ash content. Coke acts as both a reducing agent and an energy source.

2. The Electric Arc Furnace: Core Equipment​

The heart of calcium carbide production is the electric arc furnace-a large, cylindrical steel vessel lined with refractory bricks (e.g., magnesite, dolomite) to withstand temperatures exceeding 2000°C. Key features include:

Graphite Electrodes: Three vertical electrodes (positive, negative, and neutral) that generate an electric arc when powered by high-voltage electricity.

Charging System: Hoppers and conveyors to feed lime and coke into the furnace in precise ratios.

Tapping Ports: Outlets at the furnace base to drain molten calcium carbide.

Gas Exhaust: Chimneys to capture and vent carbon monoxide (CO) byproduct.

3. Step-by-Step Production Process​

Step 1: Mixing Raw Materials​

Lime and coke are blended in a 1:3 molar ratio​ (by weight, ~1 ton of lime to 3 tons of coke) to ensure complete reaction. The mixture is dried thoroughly to remove moisture, as water would react with calcium carbide during production, reducing yield.

Step 2: Charging the Furnace​

The dried lime-coke mixture is fed into the electric arc furnace through a hopper. The furnace is preheated to ~1500°C to initiate the reaction.

Step 3: Generating the Electric Arc​

High-voltage electricity (10,000–30,000 volts) is passed through the graphite electrodes, creating an intense electric arc between them. This arc heats the furnace interior to 2000–2500°C-hot enough to melt steel and drive the carbothermal reduction reaction.

Step 4: Carbothermal Reduction Reaction​

At these extreme temperatures, coke (carbon) reduces calcium oxide (lime) to calcium carbide:

CaO+3C2000–2500∘C​CaC2​+CO↑

Key Notes:

The reaction is endothermic (requires heat) but sustained by the electric arc.

Carbon monoxide (CO) gas is released as a byproduct and is either burned for energy (to power the furnace) or vented safely.

Step 5: Tapping and Cooling​

Molten calcium carbide (density ~2.2 g/cm³) collects at the furnace bottom, where it is periodically "tapped" into preheated steel molds or ladles. The liquid carbide cools and solidifies into grayish-black lumps or granules within minutes.

Step 6: Crushing and Screening​

Once cooled, the solid calcium carbide is crushed into smaller pieces (10–50 mm lumps) and screened to separate fines (powder) from usable chunks. The powder is often recycled back into the furnace to improve yield.

Step 7: Packaging and Storage​

Finished calcium carbide is packaged in airtight, moisture-proof containers​ (e.g., steel drums, polypropylene bags with desiccants) to prevent reaction with ambient moisture, which would generate acetylene gas and pose explosion risks.

4. Key Process Controls​

To ensure efficiency and safety, manufacturers monitor:

Temperature: Maintaining 2000–2500°C is critical-too low, and the reaction is incomplete; too high, and energy costs skyrocket.

Raw Material Quality: Impurities (e.g., sulfur, phosphorus) in lime or coke can contaminate calcium carbide, reducing its usability in high-purity applications (e.g., food/agriculture).

Gas Management: CO emissions are controlled via scrubbers or combustion to meet environmental regulations.

5. Industrial Scale and Output​

A single modern electric arc furnace can produce 50–200 tons of calcium carbide per day. Major producers are concentrated in regions with abundant limestone and cheap electricity (e.g., China, Russia, India).

6. Safety and Environmental Considerations​

Hazards: Extreme heat, toxic CO gas, and reactive molten materials require strict safety protocols (e.g., PPE, ventilation).

Waste: Spent refractory linings are recycled, and CO gas is often reused to power plant operations, reducing emissions.

 

 

Why Choose ZhenAn Company for High-Quality Calcium Carbide?​

ZhenAn Company sources calcium carbide from ISO-certified plants that use advanced electric arc furnace technology. Our products offer:

High Purity: 80–98% CaC₂ with low impurities (arsenic <10 ppm, phosphorus <20 ppm).

Consistent Quality: Rigorous testing (e.g., titration, XRF) to ensure batch-to-batch reliability.

Custom Sizes: Lumps, granules, or powder tailored to your application (welding, agriculture, metallurgy).

 

 

📧 Contact us at​ info@zaferroalloy.com to learn more about our calcium carbide production process and product offerings. Let ZhenAn be your trusted partner for reliable industrial chemicals!