Raw‑material crushing soaks up on the order of a quarter of a cement plant’s power—and evidence shows the right circuit, controls, and maintenance can deliver double‑digit energy savings. The choices are mechanical, but the payoff is operational.
A typical modern cement plant consumes about 4 GJ (gigajoules, a unit of energy) per tonne of cement—roughly 1,110 kWh (kilowatt‑hours) in electrical terms—according to Sustainability (Cantini et al.). Roughly 28% of the plant’s electricity goes to raw‑material preparation (crushing and kiln‑feed handling), while finishing (ball mills/grinders) accounts for another ~39% (Sustainability (Cantini et al.)). Even modest improvements here move a real cost needle.
Industry guidance also stresses the cash stakes: electrical energy can be 5–15% of an aggregate operation’s cost, and inefficiencies “will be a detrimental effect on productivity and an overall higher energy cost per ton,” notes a Metso blog (Metso).
In practice, heavy crushing motors run long hours; a 10% performance lift can save hundreds of kWh per hour of operation. Raw crushing plus conveying sits roughly at a quarter of plant power demand, while clinker burning consumes most thermal energy, and finishing remains ~39% of electrical consumption (Sustainability (Cantini et al.)).
Specific energy and circuit benchmarks
The key metric is specific energy (kWh per tonne crushed). Benchmarks vary, but controlled tests show switching from single‑stage to two‑stage crushing can cut specific energy by ~30% (Studia Geotechnica et Mechanica). Running measured power draw against throughput flags degradation early.
Crusher selection by rock and target size
Matching crusher type to rock matters. For soft to medium‑hard limestones (uniaxial strength ≲150 MPa) with low silica, high‑speed hammer/impact crushers can one‑stage the reduction (ROM limestone to ~0–80 mm) if the feed is dry (Infinity for Cement Equipment). Hammers/impactors deliver very high reduction ratios when silica is below about 8–12% (Infinity for Cement Equipment), but rotor wear escalates on high‑silica or sticky feeds.
Where limestone is hard/abrasive (high quartz) or very moist, plants adopt gentler multi‑stage setups—e.g., a jaw followed by cone or roll—to spread the reduction work and avoid overload (Infinity for Cement Equipment). Lab data show two‑stage jaw crushing used ~30% less energy than a single jaw stage for the same product size (Studia Geotechnica et Mechanica).
Product size targets for the raw mill should drive selection. Over‑crushing into fines wastes power. Industry tables cite installing a fine screening machine ahead of the raw mill if needed and adding spare tertiary capacity (e.g., VSI) only when justified (Sustainability (Cantini et al.); Infinity for Cement Equipment).
Catalogs and case studies alike recommend choosing among hammer, impact, jaw, gyratory, or roller based on hardness, abrasiveness, moisture, and throughput (Infinity for Cement Equipment; Infinity for Cement Equipment). Modern high‑efficiency designs—e.g., variable closed‑side settings (CSS, the minimum gap at the crusher discharge) and heavier shafts—increase throughput. One advanced tertiary cone (Sandvik CH865) produced ~25–30% of output below 2 mm, enabling a similar reduction in downstream ball‑mill energy by shifting fine generation into the crusher (Sandvik SRP case study).
Circuit configuration and steady feed
Uniform feed is central. Plants meter material with weighfeeders or gravimetric feeders (devices that dose by weight) to maintain a steady, choke feed—fully loading the chamber—at maximum throughput per kW (Sustainability (Cantini et al.)). Level sensors and variable‑frequency drives (VFDs, motor controllers that adjust speed to load) on conveyors help crosstie feed to real‑time conditions.
Screening and staging also matter. Pre‑screens or scalpers remove fines before primary crushing, avoiding power spent on already small material (Sustainability (Cantini et al.)). Examples in this role include automatic screen units that provide continuous debris removal such as an automatic screen. In lower‑duty or maintenance contexts, a manual screen may be applied.
Intermediate screens in multi‑stage circuits recirculate only the oversize so each machine handles the coarser fraction. One case documented that adding a tertiary crusher plus screen shifted ~25–30% of mass into <2 mm bypassing the mill, cutting overall grinding energy by ~25%—in effect “pre‑grinding” in the crusher (Sandvik SRP case study).
Multi‑stage arrangements are favored where feasible. Lab comparisons show two‑stage fragmentation uses ~30% less crushing energy than one‑step reduction of the same rock (Studia Geotechnica et Mechanica). In practice, that looks like run‑of‑mine limestone → jaw (~80 mm) → cone or impact (<10 mm), letting each machine run near its optimum and trimming kWh/t.
Automation, control, and energy management
Condition monitoring on crushers is now standard. Automated setting regulators (ASR, control systems that adjust CSS) keep product size constant with minimum power draw. Variable‑speed drives match motor speed to load, and data‑driven controls pause crushing when feeds surge or fall outside design limits. Plants also point to ISO 50001 (an energy management standard) as a framework for continuous audits and adjustments in the crushing area.
A study of Italian cement plants highlights low‑cost, “available” fixes—gravimetric feeders, smart screening, and one‑step crushing where appropriate (Sustainability (Cantini et al.); Infinity for Cement Equipment). The same source and equipment guidance repeatedly recommend feed homogenization and stage optimization (Table A2 in Cantini et al.) (Sustainability (Cantini et al.); Infinity for Cement Equipment).
Maintenance discipline and reliability
Liner wear shifts the machine’s geometry. As liners wear, the effective closed‑side gap widens; on cones this reduces the feed opening and throughput—lost capacity that eventually outweighs the savings from deferring a change (Bulk‑Solids Handling). Operating on worn liners is “inefficient use of horsepower”—power rises while tonnage falls. A Metso example quantifies the sensitivity: tilting a cone’s adjustment ring by just 3 mm (from a worn frame seat liner) cut expected fine product from 81% to 73%, implying ~10% less throughput for the same machine (Metso).
Drive systems show similar physics. Loose or misaligned belts slip under load, spiking motor power while tonnage sags. Metso reports that improperly tensioned cone drive belts slow the crusher and trigger large power spikes at low throughput; in summary, “improper drive belt maintenance will result in high horsepower consumption at a low crusher throughput…[causing] a higher energy cost per ton” (Metso). The same logic applies to gears, bearings, and motors: added friction or slip reduces net crushing power and wastes electricity.
Routine checks help prevent drift. Plants apply 30/250/500‑hour inspection and lubrication schedules and change filters/strains to keep dust out of bearings (Bulk‑Solids Handling). Daily plots of power versus throughput catch a rising kWh/t fast—a clear red flag. Portable vibration/thermography and modern IoT sensors underpin predictive programs.
Audit history in the 2010s underscores the cost: neglected maintenance correlates with unexpected stops and 5–10% lower availability, directly lifting cost per kg. Regular upkeep prolongs service life and spreads fixed energy over more tons. Best‑practice notes add that late wear‑part changes “can increase wear on the entire machine,” raising rebuild risk (Bulk‑Solids Handling).
Observed outcomes and data‑backed steps
Attention to crusher health pays. In one cement audit, tuning feed rates and seals—part of crushing‑system maintenance—lifted throughput ~13% and cut specific energy ~3% (UGM Journal (case, finish mill)). Another study reported that high‑grade wear materials extended liner life by 30–40%, saving shutdown time and avoiding idle‑period energy waste. Taken together, sound selection plus diligent maintenance can easily net double‑digit percentage savings in crushing‑circuit energy use.
Strategies summary (with sources)
- Optimize circuit layout: multi‑stage crushing where feasible; tests show ~30% energy drop versus one‑stage (Studia Geotechnica et Mechanica).
- Match crusher to rock: one‑step hammers/impactors for low‑silica limestones (e.g., silica <8%) and split into jaw+cone for harder/abrasive feeds (Infinity for Cement Equipment; Infinity for Cement Equipment).
- Stabilize feed and screen: gravimetric feeders and pre‑screens reduce energy spikes and avoid crushing fines (Sustainability (Cantini et al.)). Where appropriate, plants specify screening hardware such as an automatic screen.
- Be proactive on maintenance: change liners before throughput falls; tension belts weekly; adhere to OEM lube schedules. Neglected liners/belts yield “high horsepower consumption at low throughput,” i.e., wasted kWh (Bulk‑Solids Handling; Metso).
These steps are widely cited in plant audits and case studies (Studia Geotechnica et Mechanica; Infinity for Cement Equipment; Sustainability (Cantini et al.); Metso; Metso).
Sources and technical references
Cantini et al., Sustainability (2021): energy overview; electricity breakdown; crushing measures. Kennedy (Metso blog, 2020): productivity and energy; belt tension impacts. Ciężkowski et al., Studia Geotechnica et Mechanica (2017): single vs. two‑stage energy. Manouchehri et al. (Sandvik/Sandvik SRP, 2020): tertiary cone case. Bulk‑Solids Handling (2017): maintenance and availability; inspection scheduling. Infinity for Cement Equipment (Optimized crusher selection, 2019): crusher matching; silica and wear. Additional technical tables from Cantini et al.: Sustainability (2021). UGM case study: throughput and specific energy.
