Method of forming dense, unsintered, granular alkaline earth metal carbonates

A method of converting precipitated barium carbonate into granular form for use in a feedstock to a glass furnace, comprising the steps of

• (a) forming a suspension of the carbonate in water containing a deflocculating agent selected from the group consisting of sodium polyacrylate, potassium polyacrylate, sodium hexametaphosphate, and tetrasodium pyrophosphate, said suspension containing at least about 71 percent of the barium carbonate, based upon the weight of the suspension, and sufficient deflocculating agent to substantially completely deflocculate the barium carbonate;
• (b) adding sufficient salt selected from the group consisting of sodium and potassium carbonates and silicates to the suspension to increase the low shear viscosity of the suspension (measured in centipoises at 25.degree. C. and 39 volume percent solids) by at least about 100 percent, but not so much that the suspension no longer flows;
• (c) spray drying the resultant suspension using a spray drier operating at an inlet temperature of about 400.degree. to 600.degree. C. so as to produce a substantially dry, granular product having a loose bulk density in the range of about 55 to 65 pounds per cubic foot, at least about 80 weight percent of which has a particle size passing 10 mesh but not 150 mesh (Tyler), said drying being conducted without allowing the product to reach 400.degree. C.;
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• (d) heating the resultant granular product in an atmosphere that supports combustion in a zone maintained at a temperature in the range of about 600.degree. to 700.degree. C. for a time long enough to increase the loose bulk density of the product by at least about 10 percent, but not for so long a time as to cause the product to sinter.

A method of converting precipitated strontium carbonate into a granular form for use in a feedstock to a glass furnace, comprising the steps of

• (a) forming a suspension of the carbonate in water containing a deflocculating agent selected from the group consisting of sodium polyacrylate, potassium polyacrylate, sodium hexametaphosphate, and tetrasodium pyrophosphate, said suspension containing at least about 67 percent of the strontium carbonate, based upon the weight of the suspension, and sufficient deflocculating agent to substantially completely deflocculate the strontium carbonate;
• (b) adding sufficient salt selected from the group consisting of sodium and potassium carbonates and silicates to the suspension to increase the low shear viscosity of the suspension (measured in centipoises at 25.degree. C. and 39 volume percent solids) by at least about 100 percent, but not so much that the suspension no longer flows.
• (c) spray drying the resultant suspension using a spray drier operating at an inlet temperature of about 400.degree. to 600.degree. C. so as to produce a substantially dry, granular product having a loose bulk density in the range of about 50 to 60 pounds per cubic foot, at least about 80 weight percent of which has a particle size passing 10 mesh but not 150 mesh (Tyler), said drying being conducted without allowing the product to reach, 400.degree. C.;
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• (d) heating the resultant granular product in an atmosphere that supports combustion in a zone maintained at a temperature in the range of about 600.degree. to 700.degree. C. for a time long enough to increase the tapped bulk density of the product by at least about 20 percent, but not for so long a time as to cause the product to sinter.