How does wet-process phosphoric acid (WPA) digestion convert fluorapatite rock into H3PO4 and phosphogypsum?

Finely ground beneficiated fluorapatite concentrate (Ca5(PO4)3F, 28% to 34% P2O5) is digested with 98% sulfuric acid and recycled weak phosphoric acid in agitated Prayon or multi-compartment reactors at 75-85 degrees Celsius (Ca5(PO4)3F + 5H2SO4 + 10H2O -> 3H3PO4 + 5CaSO4*2H2O + HF). Calcium precipitates as coarse dihydrate (or hemihydrate) phosphogypsum crystals (~4.75 tonnes per tonne of P2O5) separated on tilting-pan vacuum filters, yielding 28-30% P2O5 filter acid that is concentrated in vacuum flash evaporators to 54% P2O5 Merchant Grade Acid (MGA).

Phosphate Rock, Purified PPA & LFP Battery Lab

Q: How does on-site sulfuric acid synthesis make an integrated phosphate complex a net electricity exporter?

Wet-process digestion requires ~2.68 tonnes of 98% H2SO4 per tonne of P2O5. Burning molten elemental sulfur to SO2 (Delta H = -297 kJ/mol) and catalytically oxidizing SO2 to SO3 over vanadium pentoxide (V2O5) beds (Delta H = -99 kJ/mol) in an on-site double-contact acid plant releases massive exothermic heat. High-pressure waste-heat boilers and heat-recovery systems (HRS) drive condensing/extraction steam turbogenerators producing ~520 kWh of carbon-free electricity per tonne of H2SO4 plus low-pressure steam for the vacuum phosphoric acid evaporators—exceeding the entire mill and chemical complex's electrical demand.

Q: How is evolved fluorine gas captured as commercial hydrofluorosilicic acid (H2SiF6) during WPA evaporation?

Fluorapatite contains 3.5-4.0% fluorine, which reacts with reactive silica during H2SO4 digestion and vacuum concentration to evolve gaseous silicon tetrafluoride (SiF4) and HF (4HF + SiO2 -> SiF4 + 2H2O). Scrubbing the evaporator vapors with recirculating aqueous solution hydrolyzes SiF4 into 20-25% hydrofluorosilicic acid (3SiF4 + 2H2O -> 2H2SiF6 + SiO2), a high-value co-product used to manufacture aluminum fluoride (AlF3) flux for Hall-Héroult aluminum smelters, Betts lead electrorefining electrolyte, and municipal water fluoridation.

Industrial Presets:

Digestion & SX-PPA Parameters

1. Phosphate Rock Feed (Mtpa) 2.8 Mtpa

Annual beneficiated fluorapatite concentrate throughput.

2. Rock

P_{2} O_{5}

Grade (%

P_{2} O_{5}

) 31.0% P₂O₅

Commercial BPL grade (31%

P_{2} O_{5} \approx 67.7

BPL).

3. WPA Digestion & Filter Recovery (%) 95.5%

Dihydrate/hemihydrate reactor + tilting-pan filter efficiency.

4. Battery-Grade SX-PPA Allocation (%) 45% PPA

Share purified via TBP/MIBK SX to LFP-grade

85 % H_{3} {PO}_{4}

5. Phosphorite Uranium Content (ppm U) 120 ppm U

Trace uranium extracted from filter acid via D2EHPA/TOPO.

6. Battery PPA Price ($/t

P_{2} O_{5}

) $1,380/t P₂O₅

Purified phosphoric acid price on a

100 % P_{2} O_{5}

basis.

7. Merchant Grade Acid Price ($/t

P_{2} O_{5}

) $920/t P₂O₅

54%

P_{2} O_{5}

fertilizer-grade acid price (

100 % P_{2} O_{5}

basis).

8. WPA + SX-PPA + Acid Plant CAPEX ($M) $640M

Capital cost for

H_{2} {SO}_{4}

cogen, WPA reactor, SX-PPA & U-SX.

9. Discount Rate / WACC (%) 8.5%

Weighted Average Cost of Capital for 20-year DCF valuation.

Total Recovered

P_{2} O_{5}

Output

828.9 kt/yr P₂O₅

1,144.6 kt 100% H₃PO₄ (2.33 Mt H₂SO₄)

Battery-Grade SX-PPA & LFP

367.4 kt/yr PPA P₂O₅

Synthesizes 817 kt LFP (~495 GWh/yr EV)

Byproduct

U_{3} O_{8}

H_{2} {SiF}_{6}

723 klb/yr U₃O₈

+ 39.8 kt/yr H₂SiF₆ ($149.2M credits)

Annual Revenue & EBITDA

$1,080.82M

EBITDA: $675.23M (62.5%)

20-Year Project NPV & IRR

$4,686.50M

IRR: 74.8% | Payback: 1.4 yrs

Net Cash Cost &

H_{2} {SO}_{4}

Cogen

$309/t P₂O₅

1,210 GWh/yr H₂SO₄ Cogen (1,019 GWh export)

Interactive Process Flowsheet: Fluorapatite WPA Digestion → D2EHPA Uranium SX → TBP/MIBK Battery PPA

Live Telemetry

Stage-by-Stage Wet-Process Digestion, Uranium SX & Purified PPA Mass Balance

Stage-by-stage mass and chemical balance for fluorapatite wet-process phosphoric acid digestion, uranium recovery, and battery-grade PPA solvent extraction
Unit Operation Stage	Governing Reaction / Mechanism	Primary Feed / Reagent	Recoverable Output	Key Process Metric

5×5 Project NPV Sensitivity Matrix (PPA Share vs. Battery PPA Price)

Evaluates 20-year after-tax Net Present Value ( $NPV$ ) and Internal Rate of Return ( $IRR$ ) across simultaneous variations in battery-grade SX-PPA allocation ( $\pm 20 %$ ) and PPA market price ( $\pm $ 250 /t P_{2} O_{5}$ ).

20-Year Discounted Cash Flow (DCF) Pro-Forma Schedule

Includes Year 1 commissioning ramp-up ( $85 %$ utilization), 20-year straight-line depreciation, $25 %$ corporate tax, and $U_{3} O_{8}$ , $H_{2} {SiF}_{6}$ , and cogenerated electricity credits.

20-year discounted cash flow schedule for the wet-process phosphoric acid, SX-PPA, and uranium extraction complex
Year	$P_{2} O_{5}$ Output	Revenue	OPEX	EBITDA	Tax (25%)	Free Cash Flow	PV of FCF	Cumulative FCF

First-Principles Fluorapatite WPA Digestion, Uranium SX & LFP Battery PPA Chemistry

1. Prayon Wet-Process Digestion & Exothermic $H_{2} {SO}_{4}$ Cogeneration

Beneficiated phosphate rock (fluorapatite, ${Ca}_{5} {({PO}_{4})}_{3} F$ ) is digested in multi-compartment agitated reactors at $78 – 82 °C$ (dihydrate route) or $95 – 102 °C$ (hemihydrate route) using $98 % H_{2} {SO}_{4}$ synthesized on-site from molten sulfur:

{Ca}_{5} {({PO}_{4})}_{3} F + 5 H_{2} {SO}_{4} + 10 H_{2} O ⟶ 3 H_{3} {PO}_{4} + 5 {CaSO}_{4} \cdot 2 H_{2} O ↓ + HF ↑

3 {SiF}_{4} (g) + 2 H_{2} O (l) ⟶ 2 H_{2} {SiF}_{6} (aq) + {SiO}_{2} (s)

Because burning elemental sulfur ( $S + \frac{3}{2} O_{2} + H_{2} O \to H_{2} {SO}_{4}$ , $Δ H^{\circ} = - 535 kJ/mol$ ) generates $\sim 520 kWh_{e} /t H_{2} {SO}_{4}$ plus low-pressure steam, an integrated phosphate complex is completely self-sufficient in thermal and electrical energy.

2. TBP/MIBK Solvent Extraction to LFP Battery PPA & D2EHPA Uranium Recovery

Before concentrating $28 % P_{2} O_{5}$ filter acid, trace uranium ( $50 – 220 ppm U$ ) is extracted using synergistic $0.5 M D2EHPA + 0.125 M TOPO$ . Subsequently, TBP/MIBK solvent extraction purifies MGA into $85 % H_{3} {PO}_{4}$ ( $61.6 % P_{2} O_{5}$ ) for iron phosphate ( ${FePO}_{4}$ ) and lithium iron phosphate ( ${LiFePO}_{4}$ ) cathode active material:

{Fe}^{3 +} + H_{3} {PO}_{4} (PPA) + 3 {NH}_{3} \cdot H_{2} O ⟶ {FePO}_{4} \cdot 2 H_{2} O ↓ + 3 {NH}_{4}^{+}

2 {FePO}_{4} + {Li}_{2} {CO}_{3} + C \overset{700 °C}{⟶} 2 {LiFePO}_{4} (s) + CO ↑ + {CO}_{2} ↑

Each metric tonne of purified $P_{2} O_{5}$ ( $14,090 mol P$ ) stoichiometrically synthesizes $2.223 t$ of ${LiFePO}_{4}$ ( $157.76 g/mol$ ), powering $\sim 1.35 MWh$ of EV or grid BESS capacity.

Frequently Asked Questions: Wet-Process Phosphoric Acid, SX-PPA & Uranium Recovery

Finely ground beneficiated fluorapatite concentrate (

{Ca}_{5} {({PO}_{4})}_{3} F

28 %

34 % P_{2} O_{5}

) is digested with

98 %

sulfuric acid and recycled weak phosphoric acid in agitated Prayon or multi-compartment reactors at

75 – 85 °C

(

{Ca}_{5} {({PO}_{4})}_{3} F + 5 H_{2} {SO}_{4} + 10 H_{2} O \to 3 H_{3} {PO}_{4} + 5 {CaSO}_{4} \cdot 2 H_{2} O + HF

). Calcium precipitates as coarse dihydrate (or hemihydrate) phosphogypsum crystals (

\sim 4.75 tonnes

per tonne of

P_{2} O_{5}

) separated on tilting-pan vacuum filters, yielding

28 – 30 % P_{2} O_{5}

filter acid that is concentrated in vacuum flash evaporators to

54 % P_{2} O_{5}

Merchant Grade Acid (MGA).

Traditional thermal phosphoric acid reduces phosphate rock with coke and silica in a submerged-arc electric furnace at

1,500 °C

to elemental white/yellow phosphorus (

P_{4}

) vapor before burning

P_{4}

P_{2} O_{5}

, consuming

\sim 13,500 kWh

of electricity per tonne of

P_{4}

(

\sim 3,000 kWh/t H_{3} {PO}_{4}

). Conversely, purifying wet-process acid via counter-current solvent extraction (using tributyl phosphate, TBP, or methyl isobutyl ketone, MIBK), chemical desulfation, and

H_{2} S

de-arsenication achieves

85 %

battery-grade

H_{3} {PO}_{4}

(

< 5 ppm Fe, Ca, Mg, {SO}_{4}, F

) with

> 85 %

lower electricity consumption and zero furnace

CO

emissions, supplying iron phosphate (

{FePO}_{4}

) precursors for

{LiFePO}_{4}

(LFP) EV/BESS cathodes.

Marine sedimentary phosphorites (such as those in Morocco, Florida, and the Middle East) naturally contain

50 – 200 ppm

uranium substituting for

{Ca}^{2 +}

in the apatite crystal lattice. During sulfuric acid digestion,

\sim 90 %

of this uranium dissolves into the

28 – 30 % P_{2} O_{5}

filter acid as hexavalent uranyl ions (

{UO}_{2}^{2 +}

). Passing cooled, clarified filter acid through a synergistic organic solvent mixture of di(2-ethylhexyl)phosphoric acid (D2EHPA) and trioctylphosphine oxide (TOPO) in kerosene extracts

> 90 %

of the uranium, which is stripped with ferrous iron (

{Fe}^{2 +}

) reduction and precipitated as battery-clean

U_{3} O_{8}

yellowcake while simultaneously decontaminating downstream phosphate products.

Wet-process digestion requires

\sim 2.68 tonnes

98 % H_{2} {SO}_{4}

per tonne of

P_{2} O_{5}

. Burning molten elemental sulfur to

{SO}_{2}

(

Δ H^{\circ} = - 297 kJ/mol

) and catalytically oxidizing

{SO}_{2}

{SO}_{3}

over vanadium pentoxide (

V_{2} O_{5}

) beds (

Δ H^{\circ} = - 99 kJ/mol

) in an on-site double-contact acid plant releases massive exothermic heat. High-pressure waste-heat boilers and heat-recovery systems (HRS) drive condensing/extraction steam turbogenerators producing

\sim 520 kWh

of carbon-free electricity per tonne of

H_{2} {SO}_{4}

plus low-pressure steam for the vacuum phosphoric acid evaporators—exceeding the entire mill and chemical complex's electrical demand.

Fluorapatite contains

3.5 – 4.0 %

fluorine, which reacts with reactive silica during

H_{2} {SO}_{4}

digestion and vacuum concentration to evolve gaseous silicon tetrafluoride (

{SiF}_{4}

) and

HF

(

4 HF + {SiO}_{2} \to {SiF}_{4} + 2 H_{2} O

). Scrubbing the evaporator vapors with recirculating aqueous solution hydrolyzes

{SiF}_{4}

into

20 – 25 %

hydrofluorosilicic acid (

3 {SiF}_{4} + 2 H_{2} O \to 2 H_{2} {SiF}_{6} + {SiO}_{2}

), a high-value co-product used to manufacture aluminum fluoride (

{AlF}_{3}

) flux for Hall-Héroult aluminum smelters, Betts lead electrorefining electrolyte, and municipal water fluoridation.

Related LFP Battery Materials, Uranium & Fluorochemical Simulators

LFP & LMFP Cathode Finance Lab

FePO₄ precursor synthesis, Li₂CO₃ carbothermic sintering, LMFP manganese doping & CAM economics.

Uranium Refining, UF₆ & HALEU Lab

ISR/acid leaching, Alamine 336 SX to U₃O₈, UF₆ fluorination & centrifuge SWU to 19.75% HALEU.

Fluorspar & Anhydrous HF Lab

Acidspar CaF₂ flotation, rotary kiln H₂SO₄ digestion to anhydrous HF, AlF₃ & LiPF₆ electrolyte.

Lead Refining, KIVCET & Betts Lab

Galena KIVCET oxygen flash smelting, Betts H₂SiF₆ electrorefining, Ag/Bi slimes & 4N5 BESS lead.

Lithium Hydroxide & Carbonate Lab

Spodumene decrepitation, acid bake, battery-grade Li₂CO₃ & LiOH·H₂O crystallization.

Rare Earth Refining & NdFeB Lab

Monazite/bastnäsite cracking, P507 mixer-settler SX separation & NdPr permanent magnets.

Battery Electrolyte & LiPF₆ Lab

LiPF₆/LiFSI salt synthesis, EC/DMC carbonate solvents, VC/FEC SEI additives & LFP formulation.

Selenium Refining & CIGS PV Lab

Copper slime SeO₂ roasting, SO₂ reductive precipitation, 6N vacuum distillation & CIGS/ZnSe optics.

Phosphate Rock, Wet-Process $H_{3} {PO}_{4}$ , Purified PPA (LFP) & Uranium Lab

Digestion & SX-PPA Parameters

Interactive Process Flowsheet: Fluorapatite WPA Digestion → D2EHPA Uranium SX → TBP/MIBK Battery PPA

Stage-by-Stage Wet-Process Digestion, Uranium SX & Purified PPA Mass Balance

5×5 Project NPV Sensitivity Matrix (PPA Share vs. Battery PPA Price)

20-Year Discounted Cash Flow (DCF) Pro-Forma Schedule

First-Principles Fluorapatite WPA Digestion, Uranium SX & LFP Battery PPA Chemistry

1. Prayon Wet-Process Digestion & Exothermic $H_{2} {SO}_{4}$ Cogeneration

2. TBP/MIBK Solvent Extraction to LFP Battery PPA & D2EHPA Uranium Recovery

Phosphate WPA, Battery PPA & Uranium Recovery Mastery Quiz

Frequently Asked Questions: Wet-Process Phosphoric Acid, SX-PPA & Uranium Recovery

Related LFP Battery Materials, Uranium & Fluorochemical Simulators

Digestion & SX-PPA Parameters

Interactive Process Flowsheet: Fluorapatite WPA Digestion → D2EHPA Uranium SX → TBP/MIBK Battery PPA

Stage-by-Stage Wet-Process Digestion, Uranium SX & Purified PPA Mass Balance

5×5 Project NPV Sensitivity Matrix (PPA Share vs. Battery PPA Price)

20-Year Discounted Cash Flow (DCF) Pro-Forma Schedule

First-Principles Fluorapatite WPA Digestion, Uranium SX & LFP Battery PPA Chemistry

1. Prayon Wet-Process Digestion & Exothermic H2SO4 Cogeneration

2. TBP/MIBK Solvent Extraction to LFP Battery PPA & D2EHPA Uranium Recovery

Phosphate WPA, Battery PPA & Uranium Recovery Mastery Quiz

Frequently Asked Questions: Wet-Process Phosphoric Acid, SX-PPA & Uranium Recovery

How does wet-process phosphoric acid (WPA) digestion convert fluorapatite rock into H3PO4 and phosphogypsum?

Why is solvent-extracted Purified Phosphoric Acid (SX-PPA) replacing thermal yellow phosphorus (P4) acid for LFP battery cathodes?

How is trace uranium (50-200 ppm) recovered as U3O8 yellowcake from wet-process phosphoric acid?

How does on-site sulfuric acid synthesis make an integrated phosphate complex a net electricity exporter?

How is evolved fluorine gas captured as commercial hydrofluorosilicic acid (H2SiF6) during WPA evaporation?

Related LFP Battery Materials, Uranium & Fluorochemical Simulators

1. Prayon Wet-Process Digestion & Exothermic $H_{2} {SO}_{4}$ Cogeneration