Phosphorus Pentoxide Production Methods and Systems with Fluorine Management

A phosphorus pentoxide production method with fluorine management comprising:

• forming a reducing kiln bed with feed agglomerates below a reducing freeboard in a counter-current rotary kiln, the agglomerates containing phosphate ore particles, carbonaceous material particles, and silica particles;
• generating kiln off gas containing phosphorus in the form of elemental phosphorus;
• and
• either, oxidizing elemental phosphorus outside of the kiln to phosphorus pentoxide and collecting the phosphorus pentoxide as phosphoric acid;
• or, collecting elemental phosphorus from the kiln off gas as elemental phosphorus;
• or, both.

A phosphorus pentoxide production method with fluorine management comprising:

• forming a reducing kiln bed with feed agglomerates in a counter-current rotary kiln, the agglomerates containing phosphate ore particles, carbonaceous material particles, and silica particles;
• generating kiln off gas containing fluorine and phosphorus, the phosphorus being in the form of elemental phosphorus and/or phosphorus pentoxide;
• discharging from the kiln a residue containing processed agglomerates;
• heating the discharged, processed agglomerates and releasing fluorine therefrom;
• reacting the released fluorine with reactive silica to yield fluorosilicic acid;
• and
• collecting the fluorosilicic acid.

A phosphorus pentoxide production method with fluorine management comprising:

• forming a reducing kiln bed with feed agglomerates below a reducing freeboard in a counter-current rotary kiln, the agglomerates containing phosphate ore particles, carbonaceous material particles, and silica particles;
• generating kiln off gas containing fluorine and phosphorus, the phosphorus being in the form of elemental phosphorus;
• oxidizing elemental phosphorus outside of the kiln to phosphorus pentoxide and collecting the phosphorus pentoxide as phosphoric acid containing fluorine;
• reacting the fluorine in the phosphoric acid with reactive silica to yield fluorosilicic acid, the phosphoric acid being at 40-45% strength (as P2O5) when provided for the reaction;
• and
• removing the fluorosilicic acid from the collected phosphoric acid.

A phosphorus pentoxide production method with fluorine management comprising:

• forming a reducing kiln bed with feed agglomerates below a reducing freeboard in a counter-current rotary kiln, the agglomerates containing phosphate ore particles, carbonaceous material particles, and silica particles;
• generating kiln off gas containing fluorine and phosphorus, the phosphorus being in the form of elemental phosphorus;
• collecting elemental phosphorus from the kiln off gas as elemental phosphorus;
• oxidizing elemental phosphorus outside of the kiln to phosphorus pentoxide and collecting the phosphorus pentoxide as phosphoric acid containing fluorine;
• reacting the fluorine in the phosphoric acid with reactive silica to yield fluorosilicic acid;
• removing the fluorosilicic acid from the collected phosphoric acid;
• discharging from the kiln a residue containing processed agglomerates;
• heating the discharged, processed agglomerates and releasing fluorine therefrom;
• separate from the reacting of the fluorine from the reducing kiln off gas, reacting the released fluorine with reactive silica to yield additional fluorosilicic acid;
• and
• collecting the additional fluorosilicic acid.

A phosphorus pentoxide production system with fluorine management comprising:

• a rotary reduction kiln configured to provide a kiln bed of feed agglomerates flowing counter-current to a kiln freeboard and to produce kiln off gas containing reduction products from the kiln bed;
• a phosphorus scrubbing system configured to receive the kiln off gas and to produce phosphoric acid;
• and
• a de-fluorination system configured to receive phosphoric acid from the phosphorus scrubbing system and to remove fluorine, the de-fluorination system including a de-fluorination reaction tank, a silica feeder configured to add reactive silica to the de-fluorination reaction tank, and a fluorosilicic acid vapor vent from the de-fluorination reaction tank.