Claims
- 1. In a process for removing solids from a liquid wherein said liquid is passed through a bed of filter media consisting of discrete, inorganic, artifically produced filter sand having the same chemical composition, the improvement comprising passing said liquid over artifically produced filter sand having grain densities of between about 1.0 and 2.2 grams per cubic centimeter, and grain diameters of between about 0.3 and 10 mm, wherein the grain density decreases with increasing grain diameter, backwashing said artifically produced filter sand and settling said artifically produced filter sand with sand grain diameters distributed from the largest to the smallest in the direction of liquid passage, said discrete, inorganic artifically produced filter sand consists essentially of a preliminary product mixed with a powder selected from the group consisting of amorphous particles, crystalline materials, and mixtures thereof, granulated with addition of water, dried, expanded at a temperature up to about 400.degree. C, melting the outside at a temperature of about 700.degree. C, and cooling to form spheres, said preliminary product produced by:
- (a) forming a solution containing in parts by weight about 1 part sodium silicate, having a molar ratio of Na.sub.2 O:SiO.sub.2 of 1:2.5 to 1:4.5, 0.02 parts to 0.8 parts of inorganic fibrous silicate or finely powdered silicate and 2-10 parts of water;
- (b) adding means for producing foaming gas to the solution; and
- (c) heating the solution to about 140.degree. - 360.degree. C to drive off any free water phase.
- 2. The process of claim 1, wherein said powder is finely ground with said preliminary product in a ratio by weight of about 2 to 6:1; granulated with the addition of water, dried, expanded at a temperature of up to about 400.degree. C and melted above 700.degree. C to form spheres having a density of between about 1.0 and 2.2 g/cm.sup.3 in one operating step.
- 3. The process of claim 2, further comprising the addition of a separating agent to said fine grinding step to produce spheres with a rough surface.
- 4. The process of claim 3, wherein said separating agent is selected from the group consisting of chalk, kieselguhr, ground slag, ground limestone and dolomite meal.
- 5. The process of claim 2, further comprising the addition of about 0.1 to 5 percent by weight of a binder selected from the group consisting of sodium silicate and polyvinyl alcohol to the water added before the granulation step.
- 6. The process of claim 2, wherein said granulated material is dried at temperatures between about 400.degree. C and 700.degree. C to expand the granulated material to spheres and melted above about 700.degree. C to contract the spheres with partial loss of the porous structure.
- 7. The process of claim 1, wherein said crystalline materials are selected from the group consisting of ground quartz and crushed natural silicate.
- 8. The process of claim 1, wherein said amorphous materials are selected from the group consisting of ground slag, fly ash, ground pumice, ground basalt and crushed lava.
- 9. In a process for removing solids from a liquid wherein said liquid is passed through a bed of filter media consisting of discrete, inorganic, artificially produced filter sand having the same chemical composition, the improvement comprising passing said liquid over artifically produced filter sand having grain densities of between about 1.0 and 2.2 grams per cubic centimeter, and grain diameters of between about 0.3 and 10 mm, wherein the grain density decreases with increasing grain diameter, backwashing said artificially produced filter sand and settling said artificially produced filter sand with said grain diameters distributed from the largest to the smallest in the direction of liquid passage said discrete, inorganic, artifically produced filter sand consists essentially of a preliminary product mixed with a powder selected from the group consisting ofamorphous particles, crystalline materials and mixtures thereof, granulated with addition of water, dried, expanded at a temperature up to about 400.degree. C, melting the outisde at a temperature above 700.degree. C, cooling to form spheres, said preliminary product produced by finely grinding a window glass composition and mixing therewith about 0.3 to 1.5 percent by weight of a carbonaceous foaming agent.
Parent Case Info
This is a continuation of Application Ser. No. 217,643, filed Jan. 13, 1972, now abandoned.
US Referenced Citations (5)
Continuations (1)
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Number |
Date |
Country |
Parent |
217643 |
Jan 1972 |
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