What Is Refractory Cement?
Refractory cement is a dry ramming cement composed primarily of coarse, dense alumina grains, silicon metal powder, calcined alumina, and sodium hexametaphosphate. It may also contain other refractory materials like silicon carbide, fused white alumina, chromia, periclase, kyanite, graphite, and cryolite.
Categories of Refractory Cement
- Hydraulic Cements: These undergo a chemical reaction when mixed with water to form a hardened binding matrix. Examples include calcium aluminate cements and alkali-activated aluminosilicate binders.
- Non-Hydraulic Cements: Setting and hardening occur through processes like sintering, fusion, or chemical bonding without requiring water. Examples are phosphate-bonded and silicate-bonded cements.
Refractory Mortar vs. Refractory Cement, What’s the Difference?
Composition and Binding Mechanism
- Refractory mortar typically consists of refractory aggregates (e.g. alumina, bauxite) and inorganic binders like silicates, phosphates, or clays. It hardens primarily through drying and formation of ceramic bonds.
- Refractory cement contains hydraulic binders like calcium aluminate or aluminous cements that harden through chemical reactions with water, forming stable hydrated compounds.
Structural Properties
- Refractory mortars have lower density and higher porosity compared to cements, allowing better thermal insulation.
- Mortars exhibit lower strength but better resistance to thermal shock and cycling due to their porous structure.
- Cements develop higher mechanical strengths and better resistance to erosion and chemical attack from slags and molten materials.
Chemical Stability
- Mortars are designed for stability at high temperatures by using highly refractory oxides like alumina, magnesia, etc.
- Cement compositions are tailored with additives like silicon nitride, silicon oxynitride to enhance resistance against molten iron/slag environments.
Applications of Refractory Cement
Metallurgical and Mineral Processing
Refractory cements are extensively used in metallurgical furnaces, kilns, and reactors due to their excellent heat resistance and corrosion resistance. They are employed for lining furnace walls, troughs, runners, and induction furnaces that handle molten metals, slags, and corrosive atmospheres. 11011 The cements protect the furnace linings from erosion, chemical attack, and thermal stress, ensuring prolonged service life.
Cement and Glass Manufacturing
In the cement industry, refractory cements are crucial for the construction and maintenance of cement kilns, which operate at extremely high temperatures. They are used for patching, repairing, and relining the kiln refractory linings. Similarly, in glass manufacturing, refractory cements are employed for lining glass furnaces and handling molten glass.
Power Generation and Incineration
Refractory cements find applications in power plants, incinerators, and boilers, where they are used for lining combustion chambers, flue gas ducts, and other high-temperature components. Their heat resistance and ability to withstand corrosive atmospheres make them suitable for these demanding environments.
Refractory Monolithic Structures
Refractory cements are used for constructing monolithic refractory structures, such as furnace linings, kiln linings, and other high-temperature applications. They are mixed with refractory aggregates to form castable or rammable refractory concretes, which can be molded or rammed into place and then cured to form a solid, heat-resistant structure.
Oil and Gas Industry
In the oil and gas industry, refractory cements are used for cementing and sealing oil and gas wells, particularly in applications involving underground controlled combustion for enhanced oil recovery. Their heat resistance and chemical stability make them suitable for these harsh environments.
Ceramic and Brick Manufacturing
Refractory cements are employed in the production of refractory bricks, tiles, and other ceramic products. They are used as binding agents and for joining refractory components, ensuring high-temperature resistance and durability in the final products.
Application Cases
| Product/Project | Technical Outcomes | Application Scenarios |
|---|---|---|
| Calderys Caltec Refractory Cement | Provides excellent resistance to thermal shock, abrasion, and chemical attack, ensuring long service life of furnace linings and components. | Metallurgical furnaces, kilns, and reactors handling molten metals, slags, and corrosive atmospheres. |
| Kerneos Refcast Refractory Cement | Offers rapid setting and high early strength development, reducing downtime for repairs and maintenance. | Cement and glass manufacturing plants for patching, repairing, and relining kilns and furnaces. |
| Resco Refractory Cement | Provides excellent resistance to thermal cycling and high-temperature creep, ensuring dimensional stability and preventing cracking. | Power generation plants, incinerators, and boilers for lining combustion chambers and flue gas ducts. |
| Rath Refractory Cement | Offers superior bonding strength and resistance to chemical attack, ensuring long-lasting protection for refractory linings. | Petrochemical and chemical processing plants for lining reactors, vessels, and piping systems. |
| Thermal Ceramics Refractory Cement | Provides excellent insulating properties and resistance to thermal shock, reducing heat loss and energy consumption. | Refractory linings for industrial furnaces, kilns, and ovens in various manufacturing processes. |
Latest innovations of Refractory Cement
Composition Modifications
- Incorporating Si3N4 and/or Si2ON2 reaction components to improve erosion resistance against molten iron, slag, and corrosive environments. This provides better protection for high-temperature sintered cement products used as furnace liners.
- Using zirconium dioxide, aluminum oxide, titanium dioxide, and sodium silicate as primary refractory chemicals, along with acrylic-based materials like styrene acrylic, acrylic thickener, and polyacrylate. This composition enhances thermal insulation and fire resistance properties.
- Employing coarse dense alumina grains, silicon metal powder, calcined alumina, and sodium hexametaphosphate, optionally with silicon carbide, fused white alumina, chromia, periclase, kyanite, graphite, and cryolite. This dry ramming refractory cement composition offers improved heat resistance.
Novel Binders and Additives
- Incorporating colloidal silica as a binding material, along with fused silica, ceramic fiber, and microsilica. This refractory concrete material is suitable for manufacturing refractory products.
- Using emulsions for cement admixture or asphalt emulsions, along with metal fibers and organic fibers. This refractory cement composition maintains high compression strength even at elevated temperatures.
- Utilizing pozzolanic slurry combined with a slurry of hydrated lime, allowing them to cure for an extended period before mixing to form a cementitious composition.
Improved Processing and Formulations
- Employing a fired bond to initially bond the bulk refractory grain mass, which upon firing includes the protective reaction components mentioned in point.
- Incorporating catalyst waste supplement, ground chamotte, and polycarboxylate ester in the refractory concrete composition, along with alumina cement, silica fume, and reactive aluminum oxide. This improves physical and operating characteristics.
- Optimizing temperature, reaction time, and other process parameters to enhance the properties of refractory cement compositions.
Technical Challenges of Refractory Cement
| Enhancing Erosion and Corrosion Resistance | Incorporating Si3N4 and/or Si2ON2 reaction components to improve erosion resistance against molten iron, slag, and corrosive environments for high-temperature sintered cement products used as furnace liners. |
| Optimising Thermal Insulation and Fire Resistance | Utilising zirconium dioxide, aluminium oxide, titanium dioxide, and sodium silicate as primary refractory chemicals, along with acrylic-based materials, to enhance thermal insulation and fire resistance properties. |
| Improving Heat Resistance in Dry Ramming Compositions | Employing coarse dense alumina grains, silicon metal powder, calcined alumina, and sodium hexametaphosphate, optionally with silicon carbide, fused white alumina, chromia, periclase, kyanite, graphite, and cryolite, to offer improved heat resistance in dry ramming refractory cement compositions. |
| Developing Novel Refractory Concrete Materials | Incorporating colloidal silica as a binding material, along with fused silica, ceramic fibre, and microsilica, to produce refractory concrete materials suitable for manufacturing refractory products. |
| Enhancing Mechanical and Performance Properties | Formulating refractory concrete compositions with calcium aluminate cement clinker filler, ground chamotte, microsilica, carbon and polypropylene microfibres, and other additives to improve technological, mechanical, and performance characteristics. |
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