Refractory Silica Bricks: An In – depth Introduction

Refractory Silica Bricks: An In – depth Introduction

I. Product Introduction

Refractory silica bricks are high – performance refractory materials that play a crucial role in various high – temperature industrial applications. These bricks are mainly composed of silica (SiO₂), with a content usually exceeding 93%. The silica in refractory silica bricks exists in different crystalline forms such as tridymite and cristobalite, which contribute to their excellent high – temperature resistance properties.

 

The structure of refractory silica bricks is carefully designed during the manufacturing process. They have a relatively low porosity and high density in order to ensure stability and strength under extreme temperature conditions. This unique structure allows them to withstand the harsh environments of high – temperature industrial processes without significant deformation or damage.

II. Production Process and Manufacturing Procedure

A. Raw Material Selection

The primary raw material for refractory silica bricks is high – quality silica stone. The silica stone should have a high purity of SiO₂ and low levels of impurities. Impurities such as alumina, alkalis (potassium oxide and sodium oxide), and other metal oxides can significantly affect the performance of the bricks. Therefore, strict quality control is applied during the selection process to ensure that only suitable silica stone is used.

B. Crushing and Grinding

Once the silica stone is selected, it is crushed into smaller particles. This process involves using crushers to break the large pieces of silica stone into manageable sizes. After crushing, the particles are further ground to achieve the desired particle size distribution. The grinding process is crucial as it determines the packing density and reactivity of the silica during subsequent processing steps.

C. Mixing with Additives

To improve the performance of the silica bricks, various additives are mixed with the ground silica. Mineralizers such as iron oxide and calcium oxide are added. These mineralizers play an important role in facilitating the transformation of silica during the firing process. They promote the formation of stable crystalline phases like tridymite and cristobalite, which enhance the high – temperature resistance of the bricks. Binding agents are also incorporated to improve the cohesion of the brick during the forming stage.

D. Forming

After thorough mixing, the silica – additive mixture is formed into bricks. There are different forming methods available, depending on the shape and size requirements of the final product. For standard – shaped bricks, mechanical pressing is commonly used. High pressure is applied to ensure the compaction of the material and to obtain a dense brick structure. In some cases, for complex – shaped or large – sized bricks, other forming techniques like vibration forming or casting may be employed.

E. Drying

The formed bricks are then dried to remove any moisture present in the brick body. This drying process is carried out under controlled conditions to prevent cracking or deformation of the bricks. Slow and uniform drying is usually preferred to ensure the stability of the brick structure.

F. Firing

The dried bricks are subjected to high – temperature firing in kilns. The firing temperature is typically in the range of 1400 – 1500°C. During this process, the silica undergoes significant physical and chemical changes. The mineralizers promote the conversion of quartz to more stable high – temperature phases. The firing time and temperature profile are carefully controlled to achieve the desired properties in the refractory silica bricks.

 

III. Specifications

Refractory silica bricks come in a variety of specifications to meet the diverse needs of different industrial applications. Standard brick sizes include 230mm×114mm×65mm (T – 3) as commonly used in many industries. However, there are also custom – made bricks with different dimensions and shapes. For example, in glass melting furnaces, there are curved silica bricks designed to fit the specific geometry of the furnace crown. There are also special – shaped silica bricks with angles and dimensions tailored for specific applications in metallurgical furnaces. The thickness of silica bricks can range from relatively thin ones for small – scale high – temperature equipment to thick – walled bricks for critical parts of large industrial furnaces.

 

IV. Advantages

A. Exceptional High – Temperature Resistance

Refractory silica bricks can endure extremely high temperatures. They can maintain their structural integrity at temperatures ranging from 1600 to 1700°C. This remarkable property makes them ideal for use in high – temperature industrial kilns such as glass melting furnaces and ceramic kilns. They do not rapidly soften or deform under the intense heat of these processes, ensuring long – term stable operation.

B. Good Thermal Shock Resistance

In industrial production, temperature fluctuations are common in kilns. Refractory silica bricks possess excellent thermal shock resistance, enabling them to withstand rapid temperature changes without cracking. This characteristic is of great significance in the glass manufacturing process. During operations like charging and discharging in glass melting furnaces, where temperature variations occur, silica bricks ensure the continuous operation of the furnace under these complex thermal conditions.

C. Chemical Stability in Specific Environments

In certain high – temperature chemical environments, refractory silica bricks exhibit good chemical stability. They have a certain degree of resistance to the erosion of acidic and neutral substances. In the glass melting process, silica bricks do not react with glass raw materials or molten glass, thereby ensuring the quality of the glass. This chemical inertness helps to prevent contamination of the end product.

D. High Volume Stability

With an increase in temperature and over the course of use, refractory silica bricks have relatively small volume changes. This volume stability guarantees the structural stability of the lining inside the kiln. It prevents damage to the furnace lining caused by the expansion or contraction of the bricks, thus prolonging the service life of the kiln.

V. Applications

 

A. Glass Industry

In glass melting furnaces, refractory silica bricks are essential refractory materials. They are widely used in various parts of the furnace, from the crown to certain areas of the sidewalls. During the glass melting process, silica bricks can withstand the heat radiation from high – temperature flames and molten glass, providing a stable high – temperature environment for glass melting. Moreover, the use of silica bricks helps to reduce impurities in the glass, improving the quality and transparency of the glass.

B. Ceramic Industry

Ceramic firing kilns also extensively use refractory silica bricks. Whether in traditional daily – use ceramic firing kilns or modern industrial ceramic firing equipment, silica bricks are employed in key parts of the kiln. During the sintering process of ceramic green bodies, silica bricks can endure high – temperature sintering and remain stable during frequent heating and cooling cycles, ensuring the uniformity of the quality of ceramic products.

C. Metallurgical Industry

In some non – ferrous metal smelting processes, such as the smelting of zinc and lead, refractory silica bricks can be used in parts of the furnace lining. In the smelting of these relatively low – melting – point metals, silica bricks can resist the high – temperature and chemical erosion during the smelting process, maintaining the normal operation of the smelting furnace and improving smelting efficiency and metal quality.