Comminution: Complete Technical Guide

Comminution is the industrial name of the oldest mechanical art of the cement plant: the art of breaking: the crushing of the quarry rock into the manageable lumps, the grinding of the lumps into the raw meal powder, the grinding of the clinker into the cement dust: every ton of cement passes through the machines of the size reduction at least twice before it is bagged: and every one of these passes consumes the gold of the plant: the electricity.

The Complete Cement Technical Package (931 files including the books, the courses, the Excel tools and the presentations: $249.99 one-time: instant download through the PayPal payment) includes this comminution file with its tables, the flow diagrams and the worked examples of the equipment: this article walks the file: the definition, the stages of the crushing, the mills of the grinding, the circuits and the energy of the breakage: the reader leaves with the map of the size reduction of his plant and the vocabulary of the designers.

The comminution is the heart of the cement plant budget: the electricity of the crushing and the grinding accounts for the major share of the power bill of the plant, and the technology of every stage decides the efficiency: this page follows the document section by section: the reader can open the PDF and walk the chapters with this article in front of him.

1. The Definition of the Comminution: The Act of the Break

The file opens with the definition of the discipline: the comminution is the reduction of the solid material into the smaller pieces by the mechanical action: the crushing, the splitting, the grinding: the vocabulary of the reduction:

• The crushing: the coarse stages of the reduction: the rock from the quarry down to the gravel: the crushers of the primary, secondary and tertiary stages;
• The grinding: the fine stages: the powder of the raw meal and the finished cement: the mills and their rotations: the worlds of the micron;
• The disintegration: the very fine end of the scale: the surface of the grinding, the agglomeration: the limit of the mechanical methods;
• The product sizes: from the meter blocks of the quarry face to the 80 percent passing 90 micrometers of the finish cement: the scale ratio of the numbers of the size reduction;
• The purposes: the surface for the reaction of the kiln, the homogenization of the blend, the packing of the powder: each stage of the plant grinds for a purpose;

The file defines the discipline as the reduction of the size with the purposed energy: the correct definition anticipates the whole document: the stages, the machines, the circuits: the engineer who holds the definition holds the map of the entire plant: from the jaw crusher of the quarry to the fine classifier of the finish.

2. The Stages of the Reduction: From the Quarry to the Mill

The size reduction is not one act but the staircase of the stages: the file walks the steps of the line:

• The primary crushing: the blocks from the quarry at the meter scale: the jaw or the gyratory crusher reduces them to the 150 to 250 millimetres: the heavy machines of the apron the feed: the first fracture;
• The secondary crushing: the cone and the impact machines take the 200 millimetres down to the 40 to 60: the closed screens of the circuit: the sizing of the raw mill feed;
• The tertiary crushing: the grinding the soft rock: the hammer mills and the rod mills of the wet: the 25 millimetres and below: the feed of the mills;
• The number of the stages: the two or three stages of the conventional plants: the single stage impact crushers of the soft materials: the flow the plant configures: the crushing is the cheapest size reduction;
• The selection criteria: the hardness of the rock, the moisture, the abrasiveness: the abrasion index of the material: the equipment family of the file:

The stages are not random: the energy per ton of the breaking grows as the size drops: the crushing is the cheap stage and the grinding is the expensive one: the file teaches the discipline of the “crush as much as possible, grind as little as possible”: the oldest economy of the cement industry: the mill feed at the smallest the low cost of the break.

3. The Crushers of the Plant: The Types and the Machines

The file dedicates the profiles to the celebrated families of the crushing machines: the reader of the plant sees his own machines on the pages:

• The jaw crusher: the double plate compression: the open side setting from the 100 to the 250 millimetres: the capacities of the several hundred tons per hour: the primary giant of the quarry, the rocker in the pit;
• The gyratory crusher: the conical compression: the circular chamber: the continuous throughput of the thousand tons per hour: the 200 to 350 millimetres product: the machine of the large projects;
• The cone crusher: the secondary and the tertiary: the closed settings from 8 to 50 millimetres: the controlled shape of the product: the crushing of the hard limestone and the granite-like mixes;
• The impact crusher: the hammers and the anvils: the 500 to 1,500 kilowatts of the quarry lines: the cubic product fabric: the soft and the mid-hard rocks of the region;
• The hammer crusher: the single rotor: the 1,000 to 3,000 tons per hour: the feed at the 1,000 millimetres reduced to the 25 millimetres (the classic of the cement limestone): the hammer wear is the cost;

The machine profiles of the file compare the feed sizes, the product, the capacities and the energies per ton: the selection table of the crushers: the engineer of the package opens the file and finds the family of his own machines with the numbers of the operating ranges: the crusher selection for the new line or the modernization is a documented decision.

4. The Laws of the Cominution: The Theories of the Energy

Behind the machines stand the theories: the file presents the classical trio of the comminution laws with the honesty of the engineering textbook:

• The Kick’s law: the energy needed to reduce the material is proportional to the reduction ratio of the chunk: the theory of the coarse crushing: the constant of the large blocks;
• The Rittinger’s law: the energy is proportional to the new surface created: the theory of the fine grinding: the surfaces of the dust: the dominant law of the fine stages;
• The Bond’s third theory: the middle ground: the energy proportional to the square root of the reduction: the work index formula that the industry adopted: the subject of its own guide in the package: the companion file of this chapter;
• The expressed numbers: the work index of the materials: the limestone 8 to 12, the clinker 13 to 16 kilowatt-hours per ton: the numbers of the design tables: the file quotes their ranges and the source;
• The practical truth: the laws are the approximations: the real mill measures what the machine does: the theories are the estimate, the plant data the truth: the file keeps the honesty of the industry;

The laws give the engineer the first estimate of the power of the machine: the work index of the material, the feed and the product sizes, the tonnage: the multiplication reaches the motor: the file presents the laws in the language of the practitioners: the numbers that the estimators carry in their heads.

5. The Mills of the Grinding: The Rotating Worlds

The second half of the comminution is the grinding: the file presents the rotating giant families:

• The ball mill: the horizontal rotating cylinder with the steel balls: the length of the 12 to 15 meters and the diameter of 4 to 5: the speeds of the 15 to 16 rpm: the classical of the cement: the work horse of the world;
• The rod mill: the mill full of the steel rods: the line contact of the break: the coarse raw feed of the wet plants: the companion of the coarse stage;
• The vertical roller mill: the table and the rollers with the hydraulic pressure: the drying-grinding-separation in one machine: the moist raw material feed: the energy saver of the modern plants: the 20 percent savings of the electricity of the raw line;
• The roller press: the two counter-rotating rolls compact the feed into the cakes: the pre-grinder of the ball mill: the 20 to 30 percent savings of the finished cement energy;
• The stirred media mills: the fine and the ultrafine end: the agitation of the small media: the special products and the surface treatments: the expanding family of the fine chemistry;

The mill family of the plant is the largest consumer of the electricity of the entire site: the file compares the machines on the axis of the energy, the drying and the capital: the vertical versus the ball debate fills the corridors of the engineers: the file gives the numbers of both sides and the decision frameworks: the machine is chosen for the rock, the moisture and the product of the plant.

6. The Circuits of the Grinding: The Open and the Closed Route

The mill does not work alone: the circuit of the classification decides the efficiency: the file presents the two classical arrangements:

• The open circuit: the material passes once through the mill: the product of the single pass: the coarse tail in the product: the simplicity and the sensitivity to the feed variation;
• The closed circuit: the separator returnsthe oversize to the mill: the circulating load of the 100 to 350 percent of the fresh feed: the fineness controlled: the efficiency of the classification;
• The separator: the classifier of the powder: the dynamic separators of the third generation: the rotor and the airstream: the fines collected, the coarse returned:
• The loops: the mill’s exit: the bucket conveyor and the elevator to the separator: the double circulation: the plant layout of the modern finish lines;
• The choice: the closed circuit for the finish cement standard, the open for the special coarse: the file with the dedicated chapter of the closed circuit grinding that the package also contains;

The circuit is the management of the energy: the closed mill discards the oversize exploiting the mill on the fines only: the separator sorts the work: the file teaches the circuit design of the raw and the finish, the circulating load arithmetic and the selection of the machine for the quality of the product.

7. The Energy of the Commminution: The Cost of the Break

The energy is the conscience of the comminution: the file dedicates the chapter to the kilowatt-hours of the reduction:

• The crushing: the 0.5 to 2 kilowatt-hours per ton: the cheap stages, the quarry crushers: the cost of the breaking of the big blocks:
• The raw meal grinding: the 15 to 25 kilowatt-hours per ton of the raw meal: the dry ball, less in the vertical mill of the modern: the first grinding bill;
• The finish cement grinding: the 24 to 38 kilowatt-hours per ton of the cement: the largest single line of the electricity of the plant: the 40 percent: the poster of the energy audit:
• The specific energy share: the sum of the crushing and the grinding takes the accounts of the plant the largest share of the electric energy consumed: the whole plant benchmark: the grinding the majority:
• The savings levers: the pre-grinding, the high-pressure rolls, the separators of the third generation and the grinding aids: the cumulative the 10 to 30 percent savings of the total:

The kilowatt-hours are the money: the file presents the energy per stage so the plant allocates the audits: the list of the levers: the employee of the package: the grinding bill of the plant and the phases of the reduction that contribute to it: the file of the energy is also the file of the cost.

8. The Grinding Media and the Liners: The Tools of the Break

The mill is a machine of the media: the file teaches the tools of the tumbling:

• The charge: the 28 to 36 percent of the mill volume of the steel balls: the graded load of the grinding diameters: the repair recipe of the balls;
• The ball sizes: the 17 to 100 millimetres of the grinding media: the top size computed from the feed and the product P80 like the empirical formulas: the trade between the break of the coarse and the fines:
• The liners: the plates and the lifters of the mill shell: the shell-lite ribs that raise and release the load: the wear of the liners: the wave length: the hunting chapter:
• The wear: the 100 to 300 grams of the media per ton of the cement ground: the purchase books of the grinding: the steel and the marketing of the wear:
• The coating: the sticky powder on the balls: the dampness: the blockage of the grinding: the temperature of the mill and the aids fight: the maintenance of the grinding power;

The filing of the media chapter closes with the checklist of the media changes: the measurements of the grinding body of the mill: the survey of the ball charges, the top-ups and the cycles: the worn balls and the distorted mills: the particles: the tools of the break and the health of the grinding is the health of the plant.

9. The Aggregation and the Fineness: The Targets of the Comminution

Every grinding line ends at the sieve: the file documents the targets and the controls of the production:

• The raw meal fineness: the residue on the 90 micrometer 10 to 15 percent: the residue of the 200 micron 1 to 3 percent: the burnability of the meal in the kiln: the coupling of the grinding with the kiln:
• The finish cement fineness: the Blaine 3,200 to 4,000 cm2/g: the residue of the 45 micron: the strength classification of the cement and the application curve:
• The 80 percent of the curve: the P80 of the product: the standard size of the design calculations: the work index connection to the Bond file of the package:
• The control samplings: the hourly residues of the mill outlet: the trend: the change of the liner, the change of the feed: the control loop of the production:
• The separators’ the fineness split: the fines of the product, the coarses of the return: the classification curves of the practice:

The fineness of the product organizes the estate: the comminution is measured by the sieve and the air permeability: the file trains the plant to set the targets, sample the outlets and keep the production curve inside the window: the product of the grinding: the finiteness: the power: the economics of the whole line: the targets are the sheets of the day.

10. The Theory of the Commination in the Maintenance: The Wear and the Fixes

The machines of the break wear faster than anything: the price of the violence: the file chapter of the maintenance:

• The wear surfaces: the liners of the crushers: the fans of the hammer mills: the wear plates of the the elbows: the periodic shutdowns: the replacement of the consumables:
• The ball mill gerbs: the loss of the grinding media: the charge inspection of the 1-2 months: the re-filling of the load to the level of the original:
• The seals and the bearings: the mills’ bearings of the high eccentric loads: the temperature monitoring, the vibration: the trip: the maintenance:
• The downtime accounting: the planned shutdowns versus the break and failures: the maintenance planning is the scheduling of the discipline: the failures of the mill: the emergency of the plant:
• The tracking: the wearing of the machine: the log: the measuring of the liners at every outage: the wear rates, the budgeting of the spare parts: the predictive of the break:

The maintenance of the comminution machines: the practice of the mill: the file: the halt the analysis: the spare parts: the lessons: the machine of the break and the diet of the maintenance: the file subsidizes the cost control of the wear, the domain where the good plants dominate the bad ones.

11. The Troubleshooting of the Comminution: The Cases of the Mill Floors

The file closes the equipment sections with the diagnostic of the daily pains:

• The low throughput: the mill draws the power but the tonnes fall: the feed hardness, the worn balls, the coating: the cascade of the checks in the correct order:
• The overload: the high current trips of the mill: the circulating load rises: the separator lost: the load control: the elevator capacity: the diagnosis of the closure:
• The fineness error: the residue veers the target: the separator speeds: the diaphragm disease: the ball charge maldistribution: the mill packing: the sample the false:
• The abnormal noise and the vibration: the hammer sudden the lodestone: the loose diaphragm: the broken liner the tumbling: the sound of the mill: the operator’s ear, the first instrument:
• The dust: the dedusting filters of the crushers: the choking filters: the negative pressure fails: the environment of the site and the morale of the shift: the clean comminution:

The troubleshooting of the comminution is the art of the causes: the file presents the symptoms and the checklists after the same logic of the medical diagnosis: the measured parameters of the first, the visual inspections second, the shutdown secrets third: the mill of the plant and the health of the grinding: the file is the companion of the operators and the engineers of the breakdown.

12. The Comminution of the Future: The Modernization of the Break

The final industrial chapters of the file open to the road of the improvement: the technologies of the comminution have progressed and the file maps the modern:

• The high-pressure grinding rolls: the energy savers of the finish: the crashing of the particle bed: the 20 to 30 percent cuts of the kWh per ton of the finish:
• The vertical roller mills: the raw meal machine of the day: the combined drying/grinding: the integration of the kiln off-gases: the modern lines: the dry and the energy: (the machines of the raw section of the article):
• The dynamic separators: the third, the fourth generation: the controlled classification curves: the particle distribution of the cement: the 45-micron yields of the plant:
• The grinding additives: the substances of the surface energy: the 10 to 20 percent additional throughput of the mill at the same fineness: the antistatic, the anti: the moisture:
• the controls of the automation: the mill control: the current, the fillings, the separator speeds: the model-based control: the steady operation and the stable product: the control rooms of the modern line:

The future of the comminution is the combination: the file: the efficient machines and the intelligence in the control room: the amortization of the technology: the decision the projects: the engineer of the package: the modernization: the file of the savings of the industry: the break of the modern, the labeled.

13. The Wet and the Dry Comminution: The Water and the Gas

The comminution of the cement industry runs in two climates: the wet and the dry: and the file explains the difference because the moisture decides the machine family of the plant:

• The dry grinding: the standard of the modern cement: the moisture of the feed below the limits of the process: the mills dry the material with the hot gases of the kiln: the raw meal powder of the pneumatic conveyance: the dominant route of the world;
• The wet grinding: the classical slurry process: the water at the 30 to 40 percent in the mill: the fluid slurries of the raw meal: the sludge pumping and the slurry tanks: the energy intensive and the historic route of the plants of the 1950s;
• The semi-dry process: the filter cake of the slurry dried in the grate drier: the marriage of the wet preparation and the dry burning: the legacy of the European plants: the process and its economics;
• The drying inside the mill: the air-swept dry mills: the hot air at 300 to 400 degrees enters the mill with the moist feed: the water evaporated in the first chamber: the raw meal of the humbled moisture at the exit;
• The slurry and the filter: the wet lines crumble the cake: the filter presses of the 2,000 square meters: the residual moisture of the 18 to 22 percent: the fuel penalty of the evaporation: the reason the dry route won the century;

The choice between the wet and the dry is the oldest strategic decision of the cement industry: the wet simplifies the homogenisation, the dry saves the fuel and the modern plants built their lines on the dry route: the file documents both with the flowsheets and the numbers so the engineer of the older line understands his own machines and the engineer of the new projects defends the modern selection.

The intermediate answer of the wet philosophy survives in the wash mills and the slurry basins of the regions with the very moist raw materials: the file treats the theme with the respect of the professional: the comminution is the instrument of the process and the process dictates the route: the reading of the chapter shows the engineer the complete grid: the moisture of the material, the process selection and the equipment of the line: the wet and the dry: the two worlds of the same art.

14. The Comminution and the Environment: Dust, Noise, and the Energy

The honest file completes the picture with the environmental economy of the size reduction:

• The dust: the dust of the crushers and the mills: the bag filters and the dedusting: the leakage: the emissions of the plants: the fabric filters at 10 to 30 milligrams per cubic meter:
• The noise: the crusher houses and the mill rooms: the 90 to 110 decibels around the equipment: the ear protection of the area, the noise barriers, the muffling of the maintenance:
• The energy: the electric consumption of the breaking: the specific energy of the sections: the continuous monitoring: the CO2 of the electricity: the footprint of the comminution:
• The water: the wet grinding circuits: the water and the slurries: the environmental: the water treatment: the closed wet loops:
• The waste: the crushing dust and the rejected media: the recycling of the steel, the sale of the fines: the ecology of the hourly: the low-waste plant:

The comminution of the plant: the industrial footprint: the file teaches the essentials: the plant balance: the dust of the break: the energy of the bill: the cooling: the silent neighbor: the environmental performance of the modern grinding: the chapter closes with the checklist of the environmental compliance.

15. Conclusion

The comminution: the world of the breaking: from the jaw of the quarry to the Blaine of the finish: the file of the package: the machines, the theory, the energy, the maintenance: the yardstick of the industry: the engineer who reads the file reads the machinery of the plant in the language of the sizes and the kilowatt-hours: the plant: the comminution: the knowledge of the break, the competence of the mill: the cement industry and its most physical art: the science of the first fracture.

The Complete Cement Technical Package includes this comminution file with the diagrams, the machine tables and the calculations: the one-time $249.99: the instant download: the library: the book of the break: the engineer of the package, the sizes in hand: the cement of the plant, the grind right: the first hammer, the economy: the file.

The Frequently Asked Questions

The file is the same as the Bond work index guide of the package?

No: this file is the widest map of the comminution of the plant: the types of the crushers, the mills, the circuits and the maintenance: the Bond file is the deep dive of the one calculation: the two documents of the package complement: the map and the compass: the buyer of the bundle saves the both.

What is the share of the electricity of the comminution in the plant?

The grinding of the raw meal and the finish is the largest single consumer of the electrical energy: the 40 to 60 percent of the total electricity of the typical plant goes to the crushing and the grinding: the total is about 90 to 130 kilowatt-hours per ton of the cement for the whole production line: the reduction is the majority: the audit numbers of the file: the distribution by the equipment in the Annex.

The millis of the vertical type are the new standard everywhere?

The vertical roller mill dominates the new raw grinding installations due to the drying combined and the energy: the finish cement grinding still balances the ball and the vertical: the ball mill keeps the advantage in the flexibility and the cement quality of many markets: the file compares the machines with the honest numbers: the choice belongs to the plant and the project.

Can I estimate the size of the mill from this file?

The file gives the design relationships and the reference power tables: the full sizing follows the Bond method of the companion guide and the actual sample tests of the material: the estimator with the two files of the package enters the new project with the complete math: the file of the package: the tonnage, the work index, the power: the design of the mill: the continuous.

The dust of the crushing is a problem of the site, really?

Yes: the crushing of the dry rock is the dusty office of the quarry: the dust generation at the impact points and the transfer openings: the modern plants control the crusher houses with the big suit bag filters: the dust collection: the respiratory protection: the file of the environment: the crushing dust is the subject of the dedicated chapters of the report: the complete chapter.

Where do we start the energy audit of the comminution?

With the meter the file explains: the measurement of the energy of each machine: the kWh per ton of each line: the benchmark against the typical curve: the largest consumers first: the midnight audits: the improvement list: the audit of the plant: the complete audit of the 931-file package: the Excel of the energy: the audit of the envelope: the results.

This file is part of the Complete Cement Technical Package (931 files) available from cementequipment.org. Respective rights holders; library copy for the licensed single user.