High-Pressure Acid Leaching (HPAL) extracts nickel and cobalt from laterite ore using concentrated sulfuric acid at 250–270°C and 40–50 bar. Pumps handle highly corrosive hot acid, abrasive ore slurry, and high-pressure autoclave feed. This guide covers pump selection for nickel laterite HPAL operations.
HPAL Process and Pump Services
| Service | Fluid | Temp | Pressure | Key Characteristic | Pump Type |
|---|---|---|---|---|---|
| Ore slurry (preparation) | Laterite ore slurry (40–50% solids, ground ＜150 μm) | Ambient–50°C | Low | Very abrasive (silica, laterite), viscous, large flow, settling | Heavy-duty slurry pump (high-chrome/rubber-lined, large passage, expeller seal) |
| Pre-heater feed | Ore slurry (pre-heated to 150–200°C) | 150–200°C | 10–20 bar | Abrasive, hot, high pressure, scaling, corrosive (mild acid) | High-pressure slurry (high-chrome, jacketed, large passage, expeller seal, high-temp) |
| Autoclave feed (HPAL) | Ore slurry + H₂SO₄ (to autoclave) | 200–250°C | 40–55 bar | Extremely corrosive (hot concentrated acid), very abrasive, very high pressure/temp, scaling, hazardous | Multistage high-pressure (titanium/Hastelloy, API 610, BB5, high temp/pressure) or positive displacement |
| Autoclave discharge (slurry) | Leach slurry (Ni/Co dissolved, acid, 40–50% solids) | 250–270°C | 40–50 bar (flash to atmospheric) | Extremely corrosive (hot acid), abrasive, very hot, flashing, scaling, hazardous | Let-down valve + flash tank (pump after flash: slurry titanium/Hastelloy) |
| Flash tank slurry | Leach slurry (after flashing, 100–150°C) | 100–150°C | Atmospheric–5 bar | Corrosive (hot acid), abrasive, hot, scaling, large flow | Slurry pump (titanium/Hastelloy/high-chrome, large passage, hot, expeller seal) |
| Counter-current decantation (CCD) | Leach slurry (thickening, washing) | 80–120°C | Low | Corrosive (acid), abrasive, hot, large flow, settling, precise underflow | Slurry pump (titanium/316L/high-chrome, large passage, underflow control) |
| Mixed hydroxide precipitation (MHP) | Ni/Co solution + MgO/NaOH (pH 6–8) | 50–80°C | Low | Corrosive (alkaline transition), precipitating (Ni/Co hydroxide), scaling, hot, moderate flow | Slurry pump or 316L/duplex (precipitation, hot, large passage, scaling) |
| MHP slurry (product) | Ni/Co hydroxide slurry (20–40% solids) | 50–80°C | Low | Abrasive, hot, viscous, corrosive (alkaline), valuable (loss critical) | Slurry pump or peristaltic (gentle, zero leakage, abrasive, hot) |
| Acid dosing (H₂SO₄) | Concentrated sulfuric acid (93–98%) | Ambient–80°C | High (to autoclave) | Extremely corrosive, high pressure, precise, hazardous, exothermic dilution | Magnetic drive fluoroplastic or multistage high-pressure (Hastelloy/titanium, zero leakage, high pressure) |
| Neutralization (limestone/lime) | Limestone slurry (CaCO₃, 10–30% solids) or lime | Ambient–80°C | Low | Abrasive (limestone), scaling (gypsum), alkaline, viscous, large flow | Slurry pump or peristaltic (abrasive, scaling, alkaline, large passage) |
| Solvent extraction (SX) feed | Clarified Ni/Co solution (acidic, low solids) | 30–50°C | Low–moderate | Corrosive (acid + organic), valuable, moderate flow, clean (after filtration), emulsification | 316L/duplex or fluoroplastic (acid + organic, clean, large passage) |
| SX organic (extractant) | Organic phase (oxime extractant in kerosene/diluent) | 30–50°C | Low | Flammable (kerosene), corrosive (organic), viscous, precise, hazardous | Gear pump or screw pump (positive displacement, flammable-rated, organic-compatible) |
| Wastewater (acid mine drainage) | Acidic wastewater (pH 2–4, heavy metals, sulfate) | Ambient–50°C | Low | Corrosive (acid + heavy metals), scaling, toxic (Ni/Co, Cr), environmental, large flow | 316L/duplex or fluoroplastic (acid-resistant, large flow, corrosion) |
| Tailings (residue) | Leached laterite residue (40–60% solids, acid) | 80–120°C | Low | Very abrasive, corrosive (acid), hot, large flow, settling, environmental (radioactive?) | Heavy-duty slurry (high-chrome/rubber-lined, large flow, acid-resistant, expeller seal) |
| Seal flush / quench water | Clean water (for seals, quench) | Ambient | Moderate | Clean, continuous, precise pressure, critical (seal cooling) | 316L centrifugal (clean, continuous, pressure control) |
Critical: Autoclave Feed (Extreme Corrosion + High Pressure/Temp + Abrasive)
The HPAL autoclave feed pump is the most demanding pump in the nickel industry — one of the most severe pump services in mining:
- Extreme corrosion: Concentrated H₂SO₄ (10–30% in slurry) at 250–270°C. Use titanium (Grade 5/12) or Hastelloy C-276/C-22 wetted parts. NO 316L (rapid corrosion at high temp acid). NO duplex 2205 (not sufficient for hot concentrated acid). PTFE/FFKM or specialized high-temp seals. Jacketed pump (maintain temp). Flush with clean water/coolant on shutdown.
- High pressure + temp: 40–55 bar, 250–270°C. Use multistage BB5 radially split pump (API 610, high pressure rating). High-pressure mechanical seal (Plan 53A/B with barrier fluid, or Plan 32 flush). Thick casing. High-temp bolts. Thermal expansion consideration. NPSH (hot slurry flashes).
- Abrasive + scaling: Laterite ore (silica, goethite) is abrasive. At high temp, silica and gypsum scale. Large passage open impeller. Velocity control (＜3 m/s to reduce erosion-corrosion). Anti-scalant. Periodic cleaning. Wear-resistant liner (titanium + high-chrome combination). Expeller seal (if possible at high pressure — specialized design).
- Hazardous + reliability: Hot acid slurry release = catastrophic. N+1 or 2N redundancy. Safety instrumented system (SIS). Pressure relief. Leak detection. Remote operation. High-integrity seals. Preventive maintenance (strict schedule). Spare pump. Our multistage high-pressure range includes titanium/Hastelloy options for HPAL.
Critical: Acid Dosing (Concentrated H₂SO₄ + High Pressure)
- Concentrated acid + high pressure: 93–98% H₂SO₄ at 40–50 bar (to autoclave). Use magnetic drive fluoroplastic pump (zero leakage, PTFE wetted) for lower pressure, or multistage high-pressure with Hastelloy/titanium for autoclave pressure. PTFE/FFKM seals. Secondary containment. Dilution injection (exothermic — use quench). Flush with water. Gas detection (SO₂, acid mist).
- Precise control: Acid-to-ore ratio critical (leaching efficiency, acid consumption). Use VFD + flow meter. Multiple pumps (N+1). Feedback from autoclave (acid residual, Ni extraction). Calibrate regularly. Our magnetic drive/multistage range provides precise acid dosing.
Critical: MHP Precipitation (Valuable Product + Alkaline + Scaling)
- Valuable product: Ni/Co hydroxide (MHP) is the saleable product — zero leakage mandatory. Use peristaltic hose pump (only hose contacts fluid, zero leakage, gentle) or sealed slurry pump. Secondary containment. Leak detection. Product recovery (flush lines, drain to product tank). Our peristaltic range handles MHP safely.
- Alkaline + scaling: Precipitation with MgO/NaOH at pH 6–8 — CaCO₃/Mg(OH)₂ scaling. Large passage. Velocity ＞2 m/s. Flush with water. Jacketed pump (maintain temp 50–80°C). Periodic acid wash (but product is alkaline — use water flush). Open impeller.
- Abrasive + hot: MHP crystals are abrasive. Use rubber-lined/high-chrome slurry or peristaltic (no impeller to wear). High-temp seals (PTFE/FFKM, carbon/SiC). Flooded suction. Our slurry/peristaltic range handles MHP.
Material Compatibility
| Material | HPAL autoclave feed (250°C, 20% H₂SO₄ + ore) | Concentrated H₂SO₄ (98%, ambient, high pressure) | MHP slurry (70°C, alkaline, Ni/Co hydroxide) | Tailings (100°C, acid + residue) |
|---|---|---|---|---|
| 316L SS | NOT (rapid corrosion hot acid) | NOT (concentrated acid) | Good (alkaline) | NOT (acid + abrasion) |
| Duplex 2205 | NOT (hot concentrated acid) | Fair (concentrated acid passivation) | Good | Fair (acid) |
| Titanium (Gr 5/12) | Good (hot acid, but crevice risk) | Good | Good | Good |
| Hastelloy C-276/C-22 | Excellent (standard for HPAL) | Excellent | Good | Excellent (expensive) |
| PTFE/PFA lined | NOT (temp limit ＜150°C) | Excellent (standard for acid) | Fair (abrasion) | Fair (temp) |
| High-chrome iron (A532 III) | Fair (abrasion, but acid corrosion) | NOT | Good (abrasion) | Good (abrasion + mild acid) |
| Rubber-lined | NOT (temp ＞80°C) | NOT (concentrated acid) | Good (abrasion + alkaline) | Fair (temp ＜80°C) |
| PTFE/FFKM seals | Excellent (high temp) | Excellent | Excellent | Good |
| Expeller seal | NOT (high pressure) | NOT | Good | Excellent (standard slurry) |
Critical: HPAL autoclave = titanium/Hastelloy multistage BB5 (NO 316L/duplex/PTFE for temp). Concentrated acid = PTFE lined/magnetic drive (low pressure) or Hastelloy multistage (high pressure). MHP = peristaltic/sealed slurry (zero leakage, valuable product). Tailings = high-chrome/rubber-lined slurry. All acid = flush + secondary containment + leak detection.
Common Problems and Solutions
Problem 1: Autoclave feed pump fails (hot acid + abrasion). 316L/duplex pump corrodes rapidly in 250°C acid slurry. Solution: use titanium/Hastelloy multistage BB5 pump. High-pressure seal (Plan 53A/B). Jacketed. Flush on shutdown. Strict maintenance. N+1 redundancy. Our titanium/Hastelloy multistage range handles HPAL autoclave feed.
Problem 2: Acid pump leaks (concentrated H₂SO₄). Mechanical seal fails — acid spray, injury, equipment damage. Solution: use magnetic drive fluoroplastic pump (zero leakage). PTFE/FFKM seals. Secondary containment. Dilution quench. Flush with water. Gas detection (SO₂). Our magnetic drive range eliminates acid leakage.
Problem 3: MHP pump leaks (valuable product loss). Seal failure loses Ni/Co product — revenue loss. Solution: use peristaltic hose pump (zero leakage, only hose wears). Or sealed slurry with double seal. Secondary containment. Leak detection. Flush lines to product tank. Our peristaltic range handles MHP with zero product loss.
Problem 4: Autoclave pump scales (silica/gypsum). High-temp silica/gypsum scales impeller/casing — flow drops, pressure drops. Solution: large passage open impeller. Velocity ＜3 m/s (reduce erosion, but ＞2 m/s to prevent settling). Anti-scalant dosing. Periodic water flush (controlled shutdown). Jacketed (maintain temp). Wear monitoring. Our large-passage designs resist scaling.
Problem 5: Tailings pump wears (abrasive residue). Laterite residue wears impeller in 3–6 months. Solution: use high-chrome/rubber-lined slurry pump. Expeller seal. Large passage. Reduce tip speed. Flush with water. Monitor wear. Quick-change parts. Our heavy-duty slurry range extends wear life.
Selection Summary
- Ore slurry (prep): Heavy-duty slurry (high-chrome/rubber-lined, very abrasive, large flow, expeller seal)
- Pre-heater feed: High-pressure slurry (high-chrome, 150–200°C, 10–20 bar, jacketed, large passage)
- Autoclave feed (HPAL): Multistage BB5 (titanium/Hastelloy, 250°C, 40–55 bar, API 610, high-pressure seal, NO 316L/duplex)
- Flash tank slurry: Slurry pump (titanium/Hastelloy/high-chrome, 100–150°C, acid, large passage, expeller seal)
- CCD thickener: Slurry pump (titanium/316L/high-chrome, 80–120°C, acid, underflow control, large passage)
- MHP precipitation: Slurry or 316L/duplex (50–80°C, alkaline, Ni/Co precipitation, scaling, large passage)
- MHP product: Peristaltic or sealed slurry (zero leakage, valuable, abrasive, hot, gentle, NO product loss)
- Acid (H₂SO₄): Magnetic drive fluoroplastic (low pressure) or multistage Hastelloy (high pressure, zero leakage, concentrated acid)
- Neutralization (limestone/lime): Slurry or peristaltic (abrasive, scaling, alkaline, large passage)
- SX feed: 316L/duplex or fluoroplastic (acid + organic, clean, valuable, large passage)
- SX organic: Gear pump or screw pump (flammable kerosene, FKM/PTFE seals, explosion-proof, NO rubber/NBR/EPDM)
- Tailings: Heavy-duty slurry (very abrasive, acid, hot, large flow, settling, expeller seal)
- Wastewater: 316L/duplex or fluoroplastic (acid, heavy metals, large flow, environmental)
- Critical: HPAL autoclave = titanium/Hastelloy multistage BB5 (extreme corrosion + pressure + temp), acid = magnetic drive/Hastelloy (zero leakage), MHP = peristaltic (zero leakage, valuable), scaling = large passage + flush + jacketed, tailings = high-chrome slurry, all = flush + secondary containment + leak detection + N+1 redundancy
- Our multistage titanium/Hastelloy covers autoclave; magnetic drive covers acid; peristaltic covers MHP; slurry covers ore/tailings. For HPAL pump selection, talk to our metallurgy engineers with your ore type, acid concentration, and autoclave conditions.