Classifying – separating – and assorting solids – Sifting – With heating or cooling
Reexamination Certificate
1999-11-19
2002-09-10
Nguyen, Tuan N. (Department: 3653)
Classifying, separating, and assorting solids
Sifting
With heating or cooling
C209S007000, C209S011000, C209S270000, C209S280000
Reexamination Certificate
active
06446812
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an apparatus and a method for separating a solid that can be melted from a mixture with other solids. In particular, it relates to the separation of elemental phosphorus from phosphorus bearing sludges by melting the phosphorus in the sludge inside a screened container.
In processing phosphate rock to obtain phosphorus for use in making fertilizers, detergents, and other products, vast quantities of unuseable sludge is also produced. Since this sludge contains elemental phosphorus, it must be stored in ponds to prevent the spontaneous ignition of the phosphorus in air. Maintaining the ponds is costly, creates legal and environmental problems, and is a loss of valuable phosphorus.
The phosphorus in the ponds can be recovered using mobile sumps—large, open-bottomed tubes. The sumps are forced down into the pond sediment and steam is sparged into the sediment inside the sump, melting the phosphorus. The sediment is pumped out of the sump and the melted phosphorus is separated from the remaining solids by gravity settling and filtration.
SUMMARY OF THE INVENTION
We have discovered an apparatus and method of separating elemental phosphorus and other meltable solids from mixtures with other solids. In our invention, the mixture is placed inside a screen and is heated until the meltable solid melts; the melted solid flows through the screen and is collected, while the other solids remain inside the screen. The apparatus of this invention is more energy efficient than a mobile sump, can handle larger solids, and provides a better separation of phosphorus from other solids.
REFERENCES:
patent: 3193273 (1965-07-01), Miller et al.
patent: 3909291 (1975-09-01), Leong
patent: 4492627 (1985-01-01), Crea
patent: 4538767 (1985-09-01), Pimley
patent: 4585354 (1986-04-01), Thesenfitz
patent: 54-7670 (1979-01-01), None
Luxbacher George Walter
Price Kenneth Raburn
Saran Mohan Singh
Sturdivant Charles N.
Fuerle Richard D.
Glenn Springs Holdings, Inc.
Nguyen Tuan N.
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