Aluminum hydroxide (ATH) ultrafine processing adopts two mature technical routes: dry grinding and wet grinding. The selection directly determines final particle size, whiteness, dispersion, production cost and applicable downstream industries. Due to ATH’s special characteristics—easy thermal dehydration, prone to iron contamination and severe agglomeration after ultra-fining, dry and wet processes show obvious gaps in equipment configuration, product quality and operating conditions. This article systematically compares core differences, advantages, drawbacks and suitable scenarios.
1. Basic Process Flow
Dry Grinding Process
Raw ATH lump → Low-temperature drying (moisture ≤1.5%) → Magnetic iron removal → Quantitative feeding
→ Ultrafine Mill (Ring Roller Mill / ACM Mill / Jet Mill) + dynamic air classifier closed circuit
→ Cyclone & bag dust collection → Optional surface modification → Finished dry powder packaging
Wet Grinding Process
ATH + deionized water mixing to prepare slurry (solid content 35~55%) → Add dispersant
→ Horizontal zirconia bead mill wet pulverization → Filtration & washing
→ Low-temperature spray / flash drying → Fluidized bed de-agglomeration → Finished powder
2. Detailed Comparison of Key Indicators
| Comparison Item | Dry Grinding of ATH | Wet Grinding of ATH |
|---|---|---|
| Achievable Fineness | Regular: D50 2–15 μm Limited to reach stable D50＜1 μm; easy agglomeration for submicron grade |
Superior ultrafine capability Stable D50 0.3–3 μm, ideal for submicron ATH |
| Particle Agglomeration | Dry particle collision generates static electricity; easy soft agglomeration Hard agglomerates difficult to completely eliminate |
Liquid phase inhibits static aggregation; dispersant fully separates primary particles Better primary particle dispersion |
| Whiteness & Impurity Control | High risk of iron pollution if without ceramic lining Require multi-stage magnetic separation; risk of local overheating discoloration |
Adopt full ceramic grinding chamber + zirconia beads Low iron contamination; slurry washing removes soluble impurities (Na₂O), easier to obtain ultra-high whiteness ATH |
| Temperature Control Risk | Friction heat accumulates fast. Must equip water jacket cooling. Once temperature＞130℃, ATH loses crystal water and deteriorates performance |
Good heat dissipation in water medium; low temperature rise during grinding Greatly reduces risk of thermal decomposition of ATH |
| Moisture of Final Product | Finished powder moisture ≤0.8%, directly usable for plastic, cable compounding | After drying, moisture can meet requirements; but incomplete drying easily causes high residual moisture |
| Surface Modification | Convenient. Integrate stearic acid / silane modification inside grinding system; continuous one-step production | Modification is relatively complicated; mostly finished after drying in separate equipment Water-based modifiers required if modified in slurry |
| Energy Consumption | Lower overall energy consumption, no large-scale drying after grinding | Higher power consumption: slurry stirring, grinding, filtration and drying consume massive energy |
| Production Capacity & Floor Space | Large-scale lines available (5–30t/h), compact layout, less auxiliary equipment | Unit capacity is generally smaller; supporting facilities (tanks, filter, dryer) occupy larger workshop area |
| Operating Cost | Low water consumption; fewer post-processing steps; simple daily maintenance | Large water consumption, wastewater treatment required; higher consumable cost of zirconia beads |
| Production Continuity | Fully continuous production, easy automatic control, stable batch consistency | Semi-continuous process; slurry transfer increases process links |
3. Advantages & Disadvantages Analysis
Dry Grinding for ATH
✅ Advantages
- Simple process flow, low investment and operating cost for large-scale production
- Dry powder output directly meets demands of halogen-free flame retardant cables, rubber and ordinary plastic fillers
- Convenient online surface activation modification
- No wastewater discharge, eco-friendly without water treatment system
❌ Disadvantages
- Hard to stably produce submicron ATH below D50 1μm
- Static-induced agglomeration affects powder dispersion in resin
- Strict requirements for equipment cooling system to avoid thermal dehydration
- High demand for ceramic lining if high whiteness is required
Recommended Equipment: Water-cooled ring roller mill, ACM air classifier mill
Best Application: Mass production D50 3–15μm ATH for low-smoke halogen-free cables, general artificial stone, coatings, common flame retardant filler
Wet Grinding for ATH
✅ Advantages
- Capable of submicron ultrafine grinding to obtain narrow particle size distribution
- Excellent dispersion performance of finished powder; fewer agglomerates
- Stable low-temperature working environment; effectively protect ATH crystal water
- Slurry washing removes soluble alkali impurities to improve electrical insulation performance (critical for electronic materials)
❌ Disadvantages
- High capital investment and higher electricity & water cost
- Must configure drying equipment; improper drying will cause secondary agglomeration
- Produces wastewater that needs purification treatment
- Complex process control with more intermediate links
Recommended Equipment: Horizontal zirconia bead mill + low-temperature spray dryer
Best Application: Submicron high-purity ATH, electronic packaging thermal conductive filler, high-grade solid surface material, high-transparency composite filler
4. Common Misunderstandings in ATH Processing
- Misunderstanding: Wet grinding always produces higher whiteness powder
Fact: Whiteness mainly depends on raw material iron content and anti-abrasion lining. Dry grinding with full ceramic lining + multi-stage iron remover can also reach high whiteness. Wet process has advantages in removing soluble impurities rather than inherent mineral iron. - Misunderstanding: Finer powder must adopt wet grinding
Fact: If target D50＞2μm, qualified products can be achieved by mature dry closed-circuit grinding. Wet process is only necessary for stable submicron grades. - Misunderstanding: Dry grinding inevitably causes ATH dehydration
Fact: With water jacket cooling and reasonable air volume control, material temperature can be steadily controlled below 110°C; crystal water of ATH remains intact.
5. Selection Guidance Summary
- If your target: D50 ≥2μm, large output, flame retardant for cables/plastics, control comprehensive cost → Dry grinding system is preferred
- If your target: D50 0.3~2μm, electronic-grade ATH, high dispersion, high insulation requirement, premium solid surface materials → Wet grinding system is the better choice
There is no absolute better route between wet and dry grinding for ATH. The optimal solution should match target fineness, output scale, end product application, budget and factory environmental conditions. Most large ATH manufacturers build two production lines simultaneously: dry line for bulk standard flame retardant powder, and wet line for high-end submicron customized products, following the ATH process design standards shared on ath-mill.com.
