Lime Neutralization Slurry Storage & Tank Compatibility

Storing Lime Neutralization Slurry? Start Here

Lime neutralization slurry is an aqueous suspension of hydrated lime, calcium hydroxide Ca(OH)₂, in water — typically 15 to 38 percent solids by weight in high-density commercial blends. It is one of the workhorse reagents of water treatment: dosed into acid mine drainage, acidic process water, and industrial wastewater, the dissolved hydroxyl alkalinity neutralizes free acidity and raises pH so dissolved heavy metals (iron, zinc, copper, nickel, cadmium) precipitate as insoluble hydroxides. Because the slurry is a formulation rather than a pure dissolved chemical, its behavior in a tank is governed by three things at once: very high alkalinity (pH near 12.5), abrasive suspended grit, and a tendency to form calcium-carbonate scale when exposed to air. Material of construction matters because a tank must shrug off caustic alkalinity, resist grit abrasion at fill and agitation points, and stay smooth enough that lime scale does not lock up valves and outlets.

Is Polyethylene (HDPE / XLPE) Compatible With Lime Neutralization Slurry?

Yes — polyethylene is well suited to lime slurry service. Published HDPE chemical-resistance charts rate saturated and concentrated calcium hydroxide as A / Excellent, and polyethylene is broadly resistant to strong alkalis including sodium, potassium and calcium hydroxide across the full concentration range. The high pH that attacks aluminum does not degrade poly. Just as important for a slurry, the smooth, non-stick poly bore resists the lime-scale buildup that plagues rougher surfaces, and it shrugs off the mild grit abrasion seen in storage and day tanks better than FRP, which is the classic abrasion casualty in lime systems.

Practical guidance: size the tank wall and resin grade for the slurry specific gravity (a high-density lime slurry runs heavier than water), keep the contents agitated or recirculated so solids do not pack into a hard heel, and detail the outlet to drain cleanly. HDPE or XLPE is a sound, economical choice; stainless or lined steel is reserved for the most aggressively gritty preparation duty.

Material compatibility at a glance

Lime neutralization slurry is highly alkaline (pH ~12) but the alkalinity itself is benign to polyethylene. The real material drivers are abrasion from suspended lime grit and carbonate scaling. HDPE/XLPE and lined or stainless steel handle both; aluminum is attacked by the high pH and is unsuitable.

Ratings: S suitable · C conditional / limited · U unsuitable. Verify against the cited resistance charts and your concentration/temperature before specifying.

The safety that actually matters

• Strongly alkaline (pH ~12 to 12.8) — causes serious eye damage (H318) and skin irritation; wear chemical splash goggles, face shield and gloves.
• Airborne lime mist or dried dust is harmful if inhaled (H332) and may cause respiratory irritation (H335); use local ventilation and a fitted respirator when dust is generated.
• Reaction with acids is exothermic; add slurry to acidic streams under control to avoid splashing and heat buildup.
• Spilled slurry dries to a hard, slippery film and is harmful to aquatic life (H402); contain spills and keep out of storm drains and surface water.
• Settled solids form a dense heel that can over-stress tank floors and fittings; keep agitated and follow confined-space rules before vessel entry.
• Always consult the specific product SDS — solids content, additives and exact hazard classification vary by supplier and blend.

Common questions

Will lime slurry damage a polyethylene tank?

No. Polyethylene is rated excellent against calcium hydroxide, including saturated solutions, and the high alkalinity of lime slurry does not degrade HDPE or XLPE. The main design concerns are slurry weight (specific gravity) and keeping solids suspended, not chemical attack.

Why is HDPE often preferred over FRP for lime slurry?

FRP is the classic abrasion casualty in lime systems — grit wears the resin at agitators, pumps and fill points. The smooth, non-stick poly bore both resists that abrasion and discourages calcium-carbonate scale, which is why poly is widely used for lime storage and day tanks.

What pH should I expect from lime slurry?

A saturated lime suspension sits around pH 12 to 12.8 (representative). The exact value depends on solids content and temperature; treat the figure as SDS-dependent and confirm against your product data sheet.

Do I need a tank designed for slurry rather than clear liquid?

Yes. Lime slurry settles and can pack into a hard heel, and high-density blends are heavier than water. Specify a tank with adequate wall thickness for the slurry specific gravity, provide agitation or recirculation, and detail the outlet so it drains cleanly to limit scaling and grit accumulation.