Acheson process of manufacturing of silicon carbide

 

Acheson Process – The Foundation of Silicon Carbide Manufacturing

Introduction

The Acheson process is one of the most important industrial methods used for producing silicon carbide (SiC), a material known for its exceptional hardness and thermal stability. Developed in the late 19th century, this process revolutionized the abrasives industry and remains widely used today for manufacturing black silicon carbide.

History of the Acheson Process

The process was invented by Edward Goodrich Acheson in 1891. While attempting to create artificial diamonds, he discovered silicon carbide instead. This discovery led to the commercialization of SiC under the trade name “Carborundum.”

What is the Acheson Process?

The Acheson process is a high-temperature method that produces silicon carbide by reacting silica (SiO₂) with carbon (C) in an electric resistance furnace. The process operates at extremely high temperatures, typically between 2000°C and 2500°C.

Chemical Reaction

The core reaction involved in the Acheson process is:

[
SiO_2 + 3C \rightarrow SiC + 2CO
]

  • SiO₂ (Silica): Source of silicon

  • C (Carbon): Reducing agent

  • SiC: Final product (silicon carbide)

  • CO: By-product gas

Raw Materials Used

  • Silica sand (high purity)

  • Petroleum coke (carbon source)

  • Sawdust or wood chips (for porosity)

  • Salt (for impurity removal)

Furnace Design

The Acheson furnace is a rectangular electric resistance furnace consisting of:

  • Graphite Core: Acts as a heating element

  • Raw Material Mixture: Packed around the core

  • Insulating Layer: Maintains high internal temperature

Electric current passes through the graphite core, generating intense heat required for the reaction.

Step-by-Step Process

1. Preparation of Raw Materials

Silica sand and petroleum coke are crushed, sieved, and mixed in proper proportions along with additives like sawdust and salt.

2. Furnace Charging

The mixture is packed around a graphite rod (core) inside the furnace. The arrangement ensures uniform heat distribution.

3. Heating and Reaction

Electric current is applied, raising the temperature to around 2000–2500°C. The chemical reaction takes place, forming silicon carbide crystals around the core.

4. Cooling

After the reaction, the furnace is allowed to cool slowly over 24–48 hours. This cooling phase is crucial for crystal formation.

5. Extraction

The furnace contents are removed. Different zones are observed:

  • Core Zone: High-purity SiC crystals

  • Outer Zones: Lower-grade material or unreacted mixture

6. Crushing and Grading

The SiC mass is crushed, milled, purified, and classified into various grain sizes depending on application requirements.

Types of Silicon Carbide Produced

  • Black Silicon Carbide: Contains some impurities, widely used in abrasives

  • Green Silicon Carbide: Higher purity, used in precision applications

Advantages of the Acheson Process

  • Simple and well-established method

  • Suitable for large-scale production

  • Cost-effective for industrial manufacturing

  • Produces high-quality abrasive materials

Limitations

  • High energy consumption

  • Emission of carbon monoxide (CO) gas

  • Limited control over particle size

  • Environmental concerns

Industrial Applications

Silicon carbide produced by the Acheson process is used in:

  • Abrasives (grinding wheels, sandpapers)

  • Refractory materials

  • Metallurgical processes

  • Electronics and semiconductors

Environmental and Safety Aspects

  • Proper ventilation is required to handle CO gas emissions

  • Dust control systems are necessary during crushing and grading

  • Workers must use protective equipment

Modern Developments

Recent advancements aim to improve the Acheson process by:

  • Increasing energy efficiency

  • Reducing emissions

  • Automating production systems

  • Enhancing product purity


The Acheson process remains a cornerstone in the production of silicon carbide. Despite being over a century old, it continues to be widely used due to its simplicity and effectiveness. With ongoing technological improvements, this process is evolving to meet modern industrial and environmental demands, ensuring its relevance in the future of materials science.

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