Properties And Construction Of Lime Kiln Magnesia Brick

Magnesia brick is a type of basic refractory brick containing 85% MgO with a refractoriness of 2000℃, so it will not reeact with lime and form nodulations.

Magnesia refractory is easy to absorb moisture. After abosorbing moisture, MgO will be transformed into Mg(OH)2. The surface of the brick will turn into pale. Mg(OH)2 will expand, soften and crack during the heating process at low temperature(200-300℃). So, magnesia bricks must be stored properly and used within 2-3 months after leaving the factory. If the surface becomes pale, they must be reheated above 3000℃.
 

Magnesia refractory may crack when cooled subdenly above 850℃, but when heating, if the temperature is risen 1000℃ per hour, it wll not crack. So, the wet expansion can be avoidable by increasing temperature quickly.Since MgO can form Mg(OH)2 with water, it is dry-laid without fire mud or mixture of tung oil and magnesia powder.

 

The expansion of magnesia brick happens at 1200℃ and the coefficient is 1.2%. when laying, the joints can reserve room for expansion. As the temperature of the firing zone is beyond 1200℃, the joints should be wider.