Production of Calcium Carbide (CaC₂): The Electric Arc Furnace Process

Calcium carbide (CaC₂) is an inorganic compound synthesized via a high-temperature carbothermal reduction​ process, primarily using an electric arc furnace. This method, developed in the late 19th century, remains the global standard for industrial-scale production due to its efficiency and ability to yield high-purity CaC₂. Below, we break down the production process, from raw materials to final product, with a focus on industrial-scale operations.

 

1. Raw Materials​

The production of calcium carbide relies on two key raw materials:

1.1 Lime (Calcium Oxide, CaO)​

Source: Derived from limestone (CaCO₃), a sedimentary rock abundant in nature.

Processing: Limestone is heated in rotary kilns at ~900°C to drive off carbon dioxide, producing lime:

Quality Requirement: High-purity lime (>95% CaO) is essential to minimize impurities (e.g., silica, alumina) in the final CaC₂.

1.2 Coke (Carbon, C)​

Type: Anthracite coal or petroleum coke, chosen for their high carbon content (>90%) and low sulfur/ash levels.

Role: Acts as both a reducing agent​ (donates electrons to reduce CaO) and an energy source​ (burns to sustain furnace heat).

 

2. The Electric Arc Furnace: Core Equipment​

The electric arc furnace is a cylindrical steel vessel lined with refractory bricks​ (e.g., magnesite, dolomite) to withstand temperatures exceeding 2000°C. Key components include:

Graphite Electrodes: Three vertical electrodes (positive, negative, neutral) that generate an intense electric arc when powered by high-voltage electricity (10–30 kV).

Charging System: Hoppers and conveyor belts 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: Raw Material Preparation​

Lime and coke are crushed, dried (to remove moisture), and blended in a 1:3 molar ratio​ (by weight: ~1 ton of lime to 3 tons of coke). This ratio ensures complete reaction while minimizing unreacted carbon.

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 is passed through the graphite electrodes, creating an electric arc with temperatures of 2000–2500°C. This extreme heat melts the raw materials and drives the carbothermal reduction reaction.

Step 4: Carbothermal Reduction Reaction​

At these temperatures, coke reduces calcium oxide to calcium carbide:

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 treated to meet environmental regulations.

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 within minutes.

Step 6: Crushing and Screening​

Solidified calcium carbide is crushed into smaller pieces (10–50 mm lumps) and screened to separate fines (powder) from usable chunks. Fines are 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 escalate.

Raw Material Quality: Impurities (e.g., sulfur, phosphorus) in lime or coke can contaminate CaC₂, reducing its usability in high-purity applications (e.g., chemical manufacturing).

Gas Management: CO emissions are controlled via scrubbers or combustion to comply with environmental standards.

 

5. Industrial Scale and Output​

A single modern electric arc furnace can produce 50–200 tons of calcium carbide per day. Major production hubs include China, Russia, India, and the United States, where limestone and cheap electricity are readily available.

 

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, steelmaking, chemicals).

 

 

📧 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!