Silicon Dioxide and Refractory Materials: Selection and Application of Furnace Lining Materials

In high-temperature industrial production, the selection of furnace lining materials is directly related to equipment safety, operating efficiency, and service life. Silicon dioxide, as a widely used and well-established refractory material, is extensively applied in various industrial furnaces due to its excellent high-temperature resistance, chemical stability, and favorable economic performance. This article systematically introduces the basic properties of silicon dioxide, the classification of refractory materials, and its suitability as a furnace lining material, helping readers better understand the principles behind furnace lining material selection.

I. What Is Silicon Dioxide?

Silicon dioxide (chemical formula: SiO₂) is a non-metallic oxide composed of silicon and oxygen, and it is one of the most abundant inorganic compounds in the Earth’s crust. Silicon is the second most abundant element in nature after oxygen, which explains the widespread occurrence of silicon dioxide in natural environments. It is a major constituent of many rocks and minerals.

Basic Properties of Silicon Dioxide

1. Widely Distributed in Nature
Silicon dioxide is abundant in nature and commonly occurs in forms such as quartz, sand, silica sand, and flint. The sand found on beaches and in riverbeds is primarily composed of silicon dioxide.

2. High Melting Point and Excellent Heat Resistance
Silicon dioxide has a melting point of approximately 1700 °C. It remains structurally stable at high temperatures and does not easily soften or melt, making it widely used in refractory materials and high-temperature industrial applications.

3. High Hardness and Mechanical Strength
Natural quartz has a Mohs hardness of 7, indicating relatively high hardness. This gives silicon dioxide materials good wear resistance and structural stability.

4. Chemical Stability
At room temperature, silicon dioxide is chemically very stable and does not readily react with most acids or alkalis (except hydrofluoric acid). This allows it to maintain its performance over long periods in various chemical environments.

5. Insoluble in Water
Silicon dioxide is almost insoluble in water, enabling it to retain its solid structure even in humid or aqueous environments without dissolution or significant change.

6. Resistance to Thermal Decomposition
Even at elevated temperatures, silicon dioxide does not easily undergo chemical decomposition, demonstrating excellent thermal stability.

Thanks to its high-temperature resistance, hardness, and chemical stability, silicon dioxide is well suited for use in high-temperature, corrosive, or complex environments. It plays an important role in industries such as refractory materials, glass manufacturing, ceramics, electronics, and optical materials.

II. What Are Refractory Materials?

Refractory materials are a class of inorganic non-metallic materials that can be used stably for long periods under high-temperature conditions. These materials do not melt, soften, or undergo significant deformation at high temperatures, and they do not readily react with furnace atmospheres or processed materials. As a result, they maintain structural integrity and stable performance.

Refractory materials are widely used in industrial thermal equipment such as metallurgical furnaces, chemical furnaces, glass furnaces, cement kilns, and electric furnaces. They are indispensable basic materials in high-temperature industries.

Main Characteristics of Refractory Materials

1. Excellent High-Temperature Resistance
Refractory materials can withstand temperatures above 1000 °C, and in some cases exceeding 2000 °C, without melting or severe softening.

2. Strong Resistance to Chemical Corrosion
They can resist erosion from molten slag, molten metals, gases, and dust at high temperatures, reducing material degradation.

3. Good Thermal Shock Resistance
Under conditions of frequent heating, cooling, or rapid temperature changes, refractory materials are less prone to cracking or spalling.

4. High Mechanical Strength
They possess sufficient compressive, flexural, and impact strength at both ambient and high temperatures to withstand furnace loads and mechanical stresses.

Functions of Refractory Materials

1. Manufacturing or lining industrial furnaces, kilns, and smelters
   Serving as structural or lining materials that directly endure high temperatures and material contact.

2. Protecting furnace structures
   Preventing damage to metal shells and other structural components, thereby extending equipment lifespan.

3. Reducing heat loss and improving thermal efficiency
   Minimizing heat dissipation and conserving energy.

4. Enhancing operational safety and service life
   Stable refractory performance reduces the risk of furnace failure and ensures continuous, safe operation.

   
   

III. What Materials Are Commonly Used for Furnace Linings?

Furnace linings are critical components that directly contact high-temperature gases, furnace charges, slag, and molten metals. Their material selection significantly affects furnace safety, durability, and production efficiency. Generally, furnace linings are made of refractory materials, which are classified into acidic, basic, and neutral types based on their chemical characteristics.

1️⃣ Acidic Refractory Materials

Acidic refractories resist acidic slags well but are vulnerable to alkaline substances.

Typical materials:

• Silicon dioxide (SiO₂)

• Silica refractory bricks

Main features:

• Strong resistance to acidic slag corrosion

• Stable performance at high temperatures

• Unsuitable for alkaline environments

Typical applications:

• Glass furnaces

• Blast furnaces

• Furnaces operating with acidic slags

  
  

2️⃣ Basic Refractory Materials

Basic refractories resist alkaline slags and metal oxides but are sensitive to acidic substances.

Typical materials:

• Magnesium oxide (MgO)

• Calcium oxide (CaO)

• Magnesia bricks, dolomite bricks

Main features:

• Strong resistance to alkaline slags

• High strength at elevated temperatures

• Suitable for severe high-temperature and corrosive environments

Typical applications:

• Steelmaking furnaces

• Converters and electric arc furnaces

• Other basic metallurgical furnaces

  
  

3️⃣ Neutral Refractory Materials

Neutral refractories exhibit good stability against both acidic and alkaline slags and have a wide range of applications.

Typical materials:

• Aluminum oxide (Al₂O₃)

• Carbon materials (e.g., graphite)

Main features:

• Good chemical stability

• Adaptable to various furnace atmospheres

• Broad applicability

Typical applications:

• General industrial furnaces

• Special-atmosphere furnaces

• Chemical furnaces and heat-treatment furnaces

  
  

Criteria for Selecting Furnace Lining Materials

1. Operating temperature of the furnace

2. Chemical nature of furnace materials (acidic, basic, or neutral)

3. Service life and economic considerations

IV. Selecting the Right Lining for Your Process

In furnace design and industrial production, proper selection of lining materials plays a decisive role in operational safety, efficiency, and service life. Since operating temperatures, furnace atmospheres, and material characteristics vary widely among processes, multiple factors must be evaluated to ensure long-term stable performance.

Key Factors to Consider

1. Maximum operating temperature

2. Chemical environment inside the furnace

3. Potential chemical reactions with processed materials

4. Thermal shock conditions

5. Degree of mechanical wear

6. Economic cost considerations

Basic Principle of Lining Selection

Furnace lining materials must maintain physical and chemical stability under actual operating conditions—resisting melting, softening, and harmful reactions—while enduring thermal, chemical, and mechanical stresses to ensure safe operation and long-term reliability.

V. Why Is Silicon Dioxide Suitable as a Furnace Lining Material?

Silicon dioxide (SiO₂) is a widely used acidic refractory material commonly applied in glass furnaces and blast furnaces. Its suitability as a furnace lining stems from its excellent high-temperature performance, chemical stability, and cost-effectiveness.

Key Reasons

1. High melting point and excellent heat resistance
With a melting point of approximately 1700 °C, silicon dioxide can withstand high furnace temperatures without melting or softening.

2. Chemical stability
At high temperatures, silicon dioxide remains relatively stable and does not readily react with most furnace materials.

3. Strong resistance to acidic slags
As a typical acidic refractory, silicon dioxide is highly compatible with acidic slags and atmospheres.

4. High hardness and good wear resistance
Its hardness helps resist mechanical wear from material handling, flow, and gas erosion.

5. Low thermal conductivity
Compared with many metals, silicon dioxide has lower thermal conductivity, reducing heat loss and improving furnace thermal efficiency.

Conclusion

Due to its high-temperature resistance, chemical stability, acid corrosion resistance, wear resistance, and insulating properties, silicon dioxide remains a reliable and mature material for furnace linings under appropriate operating conditions.