Calcination of high moisture content phosphate rock

Claim 2

A PROCESS FOR CALCINING PHOSPHATE ROCK CONTAINING 12% OR MORE BY WEIGHT OF WATER WHILE MINIMIZING SEALING IN WHICH THE PHOSPHATE ROCK IS MOVER SERIALLY THROUGH A PLUTALITY OF FLUIDIZED BEDS TO ACCOMPLISH PREHEATING, CALCINATION AND AT LEAST TWO STAGES OF COLLING, COMPRISING THE STEPS OF, FLUIDIZING A PRIMARY COLLING BED WITH AIR FROM A FIRST SOURCE OF PRESSURIZED AIR TO COOL THE PHOSPHATE ROCK, CONDUCTING THE HEATED OFF-GASES OF SAID PRIMARY COOLING BED TO THE CALCINATION BED AS THE FLUIDIZING GAS THEREFOR, PASSING THE CALCINED, PARTIALLY COOLED PHOSPHATE ROCK FROM SAID PRIMARY COOLING BED TO A SECONDARY COOLING BED, FLUIDIZING SAID SECONDARY COOLING BED WITH AIR FROM AN INDEPENDENT SECOND SOURCE OF PRESSURIZED AIR TO FURTHER COOL THE PHOSPHATE ROCK, THE FLUIDIZING AIR STREAM FOR SAID SECONDARY COOLING BED FLOWING IN PARALLEL WITH THE FLUIDIZING AIR STREAM FOR SAID PRIMARY COOLING BED AND SAID CALCINATION BED, MIXING THE HIGH-TEMPERATURE OFF-GASES FROM THE CALCINATION BED WITH THE COOLER OFF-GASSES OF SAID SECONDARY COOLING BED AND CONDUCTING THE MIXED GASES TO THE PREHEATING BED AS THE FLUIDIZING GAS THEREFOR.

Claim 3

The calcination process of claim 1 wherein the temperature of the calcination bed off-gases is in the range from about 800*C to about 900*C and the temperature of the fluidizing gases for the preheating bed is in the range from about 600* to about 700*C.

Claim 4

The process of claim 2 wherein the temperature of the off-gases from the secondary cooling bed is in the range from about 300*C to about 400*C.

Claim 5

The process of claim 3 wherein there are three cooling fluid beds and in the final cooling bed water is sprayed directly on the fluidized bed.

Claim 6

The process of claim 3 wherein air at a temperature of from about 600*C to about 700*C is supplied from an auxiliary source to supplement the fluidizing gases for the preheating bed.

Claim 7

A process for calcining phosphate rock containing 12% or more by weight of water in which the phosphate rock is moved through a succession of fluid beds for treatment, including a fluid bed preheating stage, a fluid bed calcination stage proDucing a calcined product at a temperature of about 850*C and off-gases at substantially the same temperature and a plurality of fluid bed cooling stages, comprising the steps of fluidizing a primary cooling bed with air from a first source of pressurized air to cool the phosphate rock to a temperature of about 540*C, conducting the off-gases of said primary cooling bed at a temperature of about 540*C to the calcination bed as the fluidizing gas therefor, fluidizing a secondary cooling bed with air from an independent second source of pressurized air to cool the phosphate rock to about 350*C, the air flow in the secondary cooling bed being in parallel with the air flow in the primary cooling bed and the calcination bed, mixing the off-gases of the secondary cooling bed at a temperature of about 350*C with the high-temperature off-gases from the calcination bed and conducting the mixed gases at a temperature of about 650*C to the preheating bed as the fluidizing gas therefor and as the medium for preheating the phosphate rock to evaporate the moisture associated therewith.

Claim 8

A process for calcining phosphate rock containing 12% or more by weight of water in which the phosphate rock is moved through a succession of fluid beds for treatment, including a fluid bed preheating stage, a fluid bed calcination stage proDucing a calcined product at a temperature of about 850*C and off-gases at substantially the same temperature and a plurality of fluid bed cooling stages, comprising the steps of fluidizing a primary cooling bed with air from a first source of pressurized air to cool the phosphate rock to a temperature of about 540*C, conducting the off-gases of said primary cooling bed at a temperature of about 540*C to the calcination bed as the fluidizing gas therefor, fluidizing a secondary cooling bed with air from an independent second source of pressurized air to cool the phosphate rock to about 350*C, the air flow in the secondary cooling bed being in parallel with the air flow in the primary cooling bed and the calcination bed, mixing the off-gases of the secondary cooling bed at a temperature of about 350*C with the high-temperature off-gases from the calcination bed and conducting the mixed gases at a temperature of about 650*C to the preheating bed as the fluidizing gas therefor and as the medium for preheating the phosphate rock to evaporate the moisture associated therewith.

Claim 9

The process of claim 6 wherein air at a temperature of about 650*C is supplied to the preheater from an auxiliary air heater to supplement the fluidizing gases for the preheating bed.