Producing Refractory Cement: A Comprehensive Guide for High-Temperature Applications

Refractory cement plays a critical role in industrial processes that involve extreme temperatures. Specifically, high-temperature refractory cement, defined as having a refractoriness exceeding 1580°C, is used in a variety of applications, including the binding of refractory aggregates for creating fireproof mortars and concrete used in industrial furnaces and cement rotary kilns. This article provides a detailed guide on the production, types, and application techniques of refractory cement.

Understanding Refractory Cement

Refractory cement encompasses diverse formulations such as aluminate refractory cement, low-calcium aluminate refractory cement, calcium-magnesium aluminate cement, and dolomite refractory cement. These special binders are essential for creating materials that can withstand high temperatures and are used to bind various refractory aggregates like corundum and calcined high-alumina bauxite. The pioneering introduction of low-cement castables, such as pumping and self-flowing casting techniques, led to the development of furnace cement.

Production of High Alumina Refractory Cement

High Alumina Refractory Cement is primarily derived from bauxite and limestone. It consists mainly of calcium aluminate clinker with an alumina content of approximately 50, produced through a process of calcination and subsequent grinding to form a hydraulic binding material. This refractory cement is vital for the production of high-temperature refractory concrete, which often requires the addition of special materials to achieve the desired properties.

Types of High-Temperature Refractory Cements

High-temperature refractory cements can undergo chemical reactions and harden at elevated temperatures, which are often enhanced by the addition of refractory materials like refractory sulfates, borates, and phosphates as binding agents. These additives are crucial in achieving the desired refractoriness and mechanical properties for various applications, from lining cement rotary kilns to industrial furnaces.

Baking Techniques for Refractory Cement

The baking process of refractory cement is crucial to ensure its optimal performance. Proper baking procedures include:

Slow Baking Process: A slow baking process is necessary, especially during the initial stage at 350 degrees Celsius, to prevent localized cracking. If substantial steam continues to emanate after insulation at 350 degrees, the heating rate should be reduced. Extending Insulation Period: In conditions of poor ventilation where moisture is not easily expelled, the insulation period should be extended to allow for thorough drying. Precautions Against Spraying Oil: When using heavy oil for baking, care must be taken to prevent oil from spraying on the lining surface, which can lead to localized cracking. Protective Measures Against Flames: If firewood is used for baking, direct exposure to flames can cause rapid localized heating, necessitating protective measures. Setting Period: Newly cast and tamped refractory cement should set for at least three days before being baked. Gradual Cooling: The cooling process should be gradual to avoid forced ventilation and ensure the longevity of the refractory cement lining.

Implementing these meticulous procedures is essential for obtaining the optimal performance and longevity of refractory cement linings under high-temperature conditions.