Which Lined Valves Survive Acid Leaching in Hydrometallurgy Plants?

Quick Answer:

PFA-lined valves are most likely to survive acid leaching in hydrometallurgy plants. PFA-lined ball, butterfly, and diaphragm valves are recommended for clear acidic liquors, while rubber-lined full-bore diaphragm valves are for acidic slurries. YOUFUMI manufactures PTFE or PFA linings to survive acid leaching in hydrometallurgy circuits. They hold up to about 180 °C when the liquor carries few solids. Above that temperature, or with coarse slurry, ceramic or titanium parts are the safer choice.

Why Does Hydrometallurgy Service Destroy Ordinary Valves?

Metallurgical service destroys ordinary valves because it attacks them from several directions at once. Corrosive acid, abrasive mineral particles, solids deposition, high differential pressure, flashing/cavitation, and frequent cycling affect the valves. An ordinary valve used for clean water or a simple chemical line may become a leak path, plugged obstructions, or an eroded seat within weeks or months.

Every plant moves acid through three stages: leaching, solution purification, and metal recovery.

1. Leaching is when metal enters solution. Leach liquors often carry sulfuric acid at 50 to 200 g/L. That strength attacks stainless steel and corrodes carbon steel within weeks. Pressure leaching adds heat and pressure on top of the acid.
2. Solution purification separates and concentrates the solution. This stage increases the target-metal concentration and removes impurities so downstream recovery can produce a clean product.
3. Metal recovery is when the metal leaves the solution. It converts the purified solution into a solid product, such as a metal cathode, metal powder, concentrate, or a chemical compound.

These three processes affect valve stability. Cycling also makes it worse, because every stroke of a push-through knife gate discharges some acid. That acid then damages floors, nearby equipment and the valve actuator. Solids add erosion, and metal sulfates add scale around seats and stems.

Upset conditions matter too. A short temperature spike or a local acid pocket at an injection point can exceed the design basis. Check dead legs and drains, because stagnant acid corrodes crevices first.

Where Do Lined Ball and Butterfly Valves Actually Work?

Lined ball and butterfly valves work best where the liquor is clear and below 180 °C, from atmospheric leaching to electrowinning feed.

Leaching and Autoclave Feed

Lined ball valves suit atmospheric tank and heap leach lines, which run from ambient to about 100°C. They isolate pregnant leach solution, acid dosing and raffinate return lines.

Autoclaves are different. Pressure oxidation runs at 225°C to 250°C, which exceeds fluoropolymer limits, so engineers normally specify titanium alloys. Use fluoropolymer linings only on feed preparation and cooling lines.

Solid-Liquid Separation and CCD

Lined butterfly valves belong on the clear overflow and wash water lines of a counter-current decantation (CCD) circuit. The dense solid discharge from the thickener underflow will wear off a softer liner soon enough. Use ceramic components and pinch valves or knife gates.

Solvent Extraction (SX-EW)

Mixer-settler circuits move aqueous liquor and organic extractants such as LIX, Cyanex, and Versatic acid. The organic phase swells and dissolves many elastomer seals but not PFA or PTFE. A clean surface on the fluoropolymer also minimizes extractant accumulation at the settler valve outlet.

In an SX-EW plant, the same lined ball valves also handle strip solution and hot electrolyte.

Electrowinning and Tailings

Electrowinning feed carries hot acidic copper sulfate electrolyte to the cathode cells. Fluoropolymer linings limit metal pickup, which protects cathode purity.

Tailings are different again. Lime dosing for neutralization needs diaphragm valves for fine solids. Tailings slurry lines need hard-faced mining valves, not soft linings.

Which Lining Should You Choose: PTFE, PFA or Ceramic?

Choose PTFE or PFA for corrosive clear liquor, and ceramic for abrasive slurry.

• PTFE: Pressed and sintered liners resist nearly every leach acid up to about 180 to 200 °C. Cost stays far below titanium or Hastelloy bodies.
• PFA: Melt-processable PFA is transfer-molded into the body, so the liner is dense and follows complex shapes. It resists permeation better, and ball and butterfly designs reach 200 °C.
• Ceramic: Alumina or zirconia parts resist abrasion in slurry. They fear impact and thermal shock, so check line vibration and heat-up rates.

PFA handles sulfuric acid up to 98% at 120 °C in conservative ratings, but the valve pressure-temperature curve still governs. Vacuum can pull a liner off the body, and steam cleaning can blister it. State both conditions in the RFQ.

How Do You Match the Valve Type to the Duty?

When matching the valve type to the duty, identify the function first, whether it be isolation, throttling, backflow prevention, or diversion. Afterward, match it to the fluid duty, which is either corrosion, abrasion, solids, pressure, temperature, cycling, or leakage. The usual mistake when selecting valves in wet metallurgy is not based on duty but on the pipe size and material.

• Lined ball valves: Isolate clear liquor, acid transfer and electrolyte lines with low pressure drop.
• Lined butterfly valves: Serve large-diameter liquor lines, where weight and cost matter.
• Lined control valves: Meter acid dosing and throttle clear liquor.
• Ceramic valves: Handle abrasive CCD underflow, where a soft liner wears out fast. A slurry valve with hard trim follows the same logic.

Lined 2 way Ball Valve

Compact Design; Investment Casting; Lining Virgin PFA/FEP; Anti blow-out One-piece Ball and Stem Design; Maintenance-free Stem Seal; Bubble Tight Shutoff; High Permeation Resistance; Low Operating Torque; Vacuum Resistance

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Send the supplier five numbers before ordering: acid strength, upset temperature, solids percent, vacuum risk and cycle frequency. Size actuators for aged valves, not new ones, because thrust grows in service. Fail-safe spring cylinders protect operators when air supply drops, and extended tie-rods allow safe seal changes.

Conclusion

Specify PTFE or PFA lined ball and butterfly valves wherever the liquor is clear and stays below 180 °C. Use ceramic or titanium where solids or autoclave heat take over. State acid strength, upset temperature, solids and vacuum risk in every inquiry.

For leach, extraction and electrowinning liquor lines, start with the YOUFUMI Lined Ball Valve for isolation. Add the YOUFUMI Lined Butterfly Valve for larger lines. Send your process data to YOUFUMI for a lining and valve recommendation.

Lined 3 way Ball Valve

Compact Design; Investment Casting; Lining Virgin PFA/FEP; Anti blow-out One-piece Ball and Stem Design; Maintenance-free Stem Seal; Bubble Tight Shutoff; High Permeation Resistance; Low Operating Torque; Vacuum Resistance

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Frequently Asked Questions

Which type of lining is best suited for acid leaching?

PFA suits most leach liquors because it is dense, transfer-moulded and resists permeation. PTFE gives the same chemical resistance at lower cost for moderate duty. Choose ceramic only where solids dominate.

Can PTFE-lined valves be used for sulfuric acid at 90 °C?

Yes. PTFE linings handle sulfuric acid well above 90 °C, up to about 180 °C in most designs. Check acid strength, solids and steam cleaning first, because steam can blister the liner.

How do they differ from slurry valves?

Soft fluoropolymer liners seal clear corrosive liquor. A slurry valve uses hard trim, ceramic or a metal-seated design to resist solids. Mining valves for tailings and underflow need those harder materials.