Patent GB-593958-A (GB)
Title: Improved process for the treatment of hydrous magnesium carbonate
Filed: 1945-06-14
Abstract: In a process for calcining hydrous crystalline magnesium carbonate, particularly lansfordite, with or without an additive agent to give a refractory, the crystals are warmed and worked into a plastic condition in which the water of crystallization furnishes at least a part of the necessary moisture, and the plastic material is formed into shapes, which are calcined.  The lansfordite may be obtained by separation methods from dolomite in the form of a filter cake.  The addition agent when used should be added in the proportion of 1 to 5 per cent. by weight, and is selected from iron oxide, the borates, phosphates and silicates of sodium and calcium, chrome ore, bauxite, and silica, and should be below 100 mesh in size, particularly iron oxide which should be about 200 mesh.  After mixing, not more than 10 per cent. water is added, and the mixture heated to between 70 and 110 DEG F., for example 80 DEG F., and worked in a pugmill, wet pan, or the like.  The resultant plastic mass can be shaped or moulded into nodules, pellets or granules, or extruded into sheets or rods, avoiding sharp edges or corners, and of a size preferably less than 1/4 inch in thickness.  The pellets are thus dried, for example at 200 to 212 DEG F. to an ignition loss of 68 per cent., and fired in a rotary kiln to above 1600 DEG F., for 2700 DEG F.  In modifications of the pelleting process, the pellets may be made somewhat dry and tumbled to a roughly spherical form, or they may be case hardened by spraying with sodium silicate, or they may be tumbled in a moist condition with the powdered addition agent.ALSO:In a process for calcining hydrous crystalline magnesium carbonate particularly lansfordite with an additive agent to give a refractory, the crystals are warmed and worked into a plastic condition in which the water of crystallisation furnishes at least a part of the necessary moisture, and the plastic material is formed into shapes which are calcined. The lansfordite may be obtained by separation methods from dolomite in the form of a filter cake.  The additive agent should be added in the proportion of 1 to 5 per cent. by weight, and is selected from iron oxide, the borates, phosphates and silicates of sodium and calcium, chrome ore, bauxite, and silica, and should be below 100 mesh in size, particularly iron oxide which should be about 200 mesh. After mixing, not more than 10 per cent. water is added and the mixture heated to between 70 and 110 DEG F., e.g., 80 DEG F. and worked in a pugmill, wet pan or the like.  The resultant plastic mass may be shaped or moulded into nodules, pellets, or granules, or extruded into sheets or rods avoiding sharp edges or corners, and of a size preferably less than 1/4 inch in thickness.  The pellets are then dried, for example at 200 to 212 DEG F. to an ignition loss of 68 per cent., and fired in a rotary kiln to above 1,600 DEG F., for example, 2,700 DEG F.  In modifications of the pelleting process, the pellets may be made somewhat dry and tumbled to a roughly spherical form, or they may be case hardened by spraying with sodium silicate, or they may be tumbled in a moist condition with the powdered additive agent.