Section 01
Overview
Cement and ceramic raw-material processing is dominated by grinding economics: a 1 t/h cement mill consumes 35-50 kWh per tonne, making electricity the largest single operating cost. Selecting a mill with the right grinding efficiency for the target Blaine (fineness) number determines a plant's competitiveness over a 15-20 year operating life.
Cathay supplies grinding equipment for clinker (cement plants), limestone (raw-mix feed + flue gas desulphurisation), gypsum (wallboard + cement additive), and kaolin (ceramics + paper). Each material has a different work index and target fineness — the mill specification follows.
Reference deployments include cement-plant retrofits in North Africa, lime-plant grinding circuits in the Middle East, and kaolin-processing plants supplying European ceramics manufacturers. Every commissioning includes a kWh-per-tonne audit verifying the design target is met.
Cathay supplies grinding equipment for clinker (cement plants), limestone (raw-mix feed + flue gas desulphurisation), gypsum (wallboard + cement additive), and kaolin (ceramics + paper). Each material has a different work index and target fineness — the mill specification follows.
Reference deployments include cement-plant retrofits in North Africa, lime-plant grinding circuits in the Middle East, and kaolin-processing plants supplying European ceramics manufacturers. Every commissioning includes a kWh-per-tonne audit verifying the design target is met.
Section 02
Operational Challenges
**Blaine fineness consistency.** Cement customers specify a target fineness (e.g., 380 m²/kg for Type I OPC). Variance of >15 m²/kg causes downstream concrete strength variance. Mill operation must keep Blaine within tight control bands — this requires online particle-size monitoring and dynamic separator adjustment.
**Energy cost.** Industrial-scale grinding consumes 30-50 kWh per tonne of cement. At $0.15/kWh, that's $4.50-$7.50 per tonne — often the largest operating cost. Selecting between ball mill, vertical roller mill, and high-pressure grinding rolls comes down to capital-vs-operating cost optimisation.
**Material variability.** Limestone hardness varies between quarry zones; gypsum moisture varies seasonally; kaolin clay can swell or harden depending on moisture content. Grinding circuits must accept variable feed without throughput collapse.
**Refractory wear in dryers.** Rotary dryer refractory lasts 3-5 years on cement raw mix but can drop to 18 months on aggressive chlorides or sulphates. Refractory specification follows the material chemistry, not the dryer rated tonnage.
**Energy cost.** Industrial-scale grinding consumes 30-50 kWh per tonne of cement. At $0.15/kWh, that's $4.50-$7.50 per tonne — often the largest operating cost. Selecting between ball mill, vertical roller mill, and high-pressure grinding rolls comes down to capital-vs-operating cost optimisation.
**Material variability.** Limestone hardness varies between quarry zones; gypsum moisture varies seasonally; kaolin clay can swell or harden depending on moisture content. Grinding circuits must accept variable feed without throughput collapse.
**Refractory wear in dryers.** Rotary dryer refractory lasts 3-5 years on cement raw mix but can drop to 18 months on aggressive chlorides or sulphates. Refractory specification follows the material chemistry, not the dryer rated tonnage.
Section 04
Typical Plant Setup
A representative 25 t/h limestone-grinding circuit for FGD (flue gas desulphurisation) feed:
1. **Primary jaw crusher** — 1m ROM to 100 mm.
2. **Secondary impact crusher** — 100 mm to 25 mm.
3. **Vibrating screen** — closed circuit on impact crusher.
4. **Surge bin (50 t)** — buffer between crushing and grinding shifts.
5. **Rotary dryer** — reduces moisture from 8% to <2% before grinding.
6. **Raymond mill (5R-4128)** with **integrated dynamic separator** — grinds to 80% passing 45 µm (D90 = 100 µm for FGD spec).
7. **Bag filter** on mill discharge — captures fine product, separates from process air.
8. **Pneumatic conveyor** to product silo.
9. **Vacuum truck loading** to FGD storage.
Total connected power: ~520 kW. Specific power consumption: 24 kWh/t. Site footprint: ~60×25 m. Commissioning: 8-10 weeks.
1. **Primary jaw crusher** — 1m ROM to 100 mm.
2. **Secondary impact crusher** — 100 mm to 25 mm.
3. **Vibrating screen** — closed circuit on impact crusher.
4. **Surge bin (50 t)** — buffer between crushing and grinding shifts.
5. **Rotary dryer** — reduces moisture from 8% to <2% before grinding.
6. **Raymond mill (5R-4128)** with **integrated dynamic separator** — grinds to 80% passing 45 µm (D90 = 100 µm for FGD spec).
7. **Bag filter** on mill discharge — captures fine product, separates from process air.
8. **Pneumatic conveyor** to product silo.
9. **Vacuum truck loading** to FGD storage.
Total connected power: ~520 kW. Specific power consumption: 24 kWh/t. Site footprint: ~60×25 m. Commissioning: 8-10 weeks.