Comminution: Complete Technical Guide

Comminution is the collective art of reducing the size of the material: the crushing and the grinding that turn the quarry rock into the fine powder that burns in the kiln: it is the first process of the cement plant and the heaviest consumer of its energy: the average dry process plant spends between 60% and 70% of its total electrical energy on the size reduction: roughly 25 kilowatt-hours per ton of cement on the grinding of the raw materials and the finished cement: the comminution is, in plain numbers, the factory’s largest electricity bill.

The Complete Cement Technical Package (931 files including the books, the courses, the Excel tools and the presentations: $249.99 one-time: instant download via the PayPal payment) includes this comminution guide with its tables, the worked examples and the sizing spreadsheets: the archive walks the engineer through the entire size reduction train of the plant: this article gives the reader the linear path of the file: the definition, the laws, the machinery, the energy numbers, and the troubleshooting practices: the knowledge of the comminution, summarized for the daily work.

The process of the comminution begins in the quarry, where the blasting leaves rocks as large as one meter, and ends in the finish mill, where the 95% of the product passes the 45-micron sieve: the journey spans six orders of magnitude in particle size: no single machine covers the span: the plant composes the journey from a chain of machines, and the skill of the engineer is the skill of dividing the task: the right machine, at the right feed size, at the right cost: this page walks the stages of that chain, with the numbers the designer and the operator need.

1. The Definition and the Place of Comminution in Cement Making

Comminution is the mechanical process of reducing the particle size of the material, from the Latin comminuere, to make small: in the cement process it covers everything between the blasted rock and the finished cement powder: the process engineers break the chain into two families: the crushing (coarse reduction, down to about 5 to 25 millimeters) and the grinding (fine reduction, down to 100 microns and below): the two families use different machines, obey different laws and carry different costs, and the file keeps the two worlds apart in its chapters.

• The crushing family: the jaw, the gyratory, the cone, the impact and the hammer crushers: the products in the range of 5 to 150 millimeters: the energy consumption between 0.3 and 1.5 kilowatt-hours per ton: the cheap part of the size reduction;
• The grinding family: the ball mills, the roller mills, the vertical mills and the presses: the products from 2 millimeters down to 10 microns: the specific energies from 15 to 35 kilowatt-hours per ton for the finish grinding: the expensive part of the demand;
• The geometry of the task: the crushing acts by the high-impact compression of individual rocks against the liners; the grinding operates by the tumbling of the charge, the attrition and the bed breakage: the two mechanisms need two machines, and mixing them wastes the energy;
• The purpose beyond the size: the freshly crushed surface is the laboratory of the next process: the raw meal dust rises through the heat exchanger and reacts: every ton of feed to the raw mill must be, above all, dry and proportioned; the comminution stage is what makes the mixing possible: the fine, the blend;

In short, the comminution in the cement plant is the size reduction chain between the two geological extremes: the meter-size quarry block and the 45-micron powder: the engineer who masters the stages masters the largest share of the plant’s electrical costs: the file organizes the whole field in the single reference, and the plant manager who reads it once sees the whole industrial map of the rock to the powder.

2. The Three Laws of Size Reduction: Rittinger, Kick and Bond

The energy consumed by the size reduction has been summarized in three classical laws, each valid in its own size range: the engineer of the package knows all three, because the plant passes through all three bands from the quarry to the finish:

• The Rittinger law: the energy is proportional to the new surface area created: it rules the fine grinding, where the surface becomes enormous: this is the law the finish mill obeys, and why the last microns of the fineness cost the most;
• The Kick law: the energy is proportional to the volume of the material, hence to the size ratio: it rules the coarse crushing, where the new surface is comparatively small: the few blows of the crusher, the cheap first kilometers of the journey;
• The Bond law: the famous third theory sits between the two: its equation is W = 10 × Wi / √P − 10 × Wi / √F: the one practical for the industrial sizing: the Wi is the work index, the property of the material measured in the laboratory;
• The zones of validity: the coarse crushing (Kick), the tumbling grinding (Bond – 80% of the cement practice), the ultrafine (Rittinger): each real mill behaves by the mixing of the laws, and Bond’s formula with its corrections remains the safest for the everyday design;

The three laws tell the same economics: each stage of the comminution should lose as little energy as possible, because the energy in a grind is not linear: it is the constant-sum game described by the squares and the roots of the sizes: the engineer who accepts the three laws accepts the design philosophy: the coarse work is cheap, the fine work is expensive: thus the plant invests in the screening and the classification to avoid grinding the fines again.

3. The Stages of Comminution in the Cement Plant: The Hourglass

The typical dry-process plant reduces its raw material in a fixed sequence of stages, and the flowsheet repeats, with variations, in almost every plant on earth:

• Stage 1, the quarry blasting: the drill and the blast bring the face rock to minus 800 to 1000 millimeters: the blasting is itself a comminution stage: the measurement of the blast fragmentation the decisions of the crusher feed;
• Stage 2, the primary crushing: the jaw or the gyratory crusher at the quarry receives the blasted rock and discharges 150 to 300 millimeters: the hourly rates from 300 up to 2,000 tons per hour at the biggest plants;
• Stage 3, the secondary/tertiary crushing: the cone, the impact or the hammer crushers reduce the 150-mm material to the mill feed of minus 25 millimeters (raw) or minus 50 to 75 (clinker pregrinding): the purchase of the energy separation;
• Stage 4, the raw grinding: the ball mill or the vertical mill grinds the crushed mix to the raw meal of 80 to 90% below 90 microns, at the very 15-25 kilowatt-hours per ton level;
• Stage 5, the finish grinding: the clinker and the gypsum are ground to the cement of 3,200-4,500 cm²/g Blaine: the most energy-intensive stage of the plant: the last 30% of the particles require 50% of the grind energy;

The picture is the hourglass: many steps in the coarse part, one grinding step in the middle, and one more fine grinding at the end: the sequence is fixed by the economy of the laws: the coarse steps move the tonnage cheaply, the fine steps carry the kilowatt-hours: the entire arrangement of the machine parks the plant is the image of these five stages, and the belt and the transfer walk the same story.

4. The Coarse Equipment: The Crusher Selection and its Numbers

The crushing department is selected on three criteria, and the file carries the tables for all three: the capacity (tons per hour), the reduction ratio (the ratio of the feed size to the product size), and the shape of the product:

• The jaw crusher: the primary machine of the limestone plants: reduction ratio 4 to 6, feed up to 1200 by 1500 millimeters: the output of 150 to 300 millimeters: the stroke, the setting, and the clamped liner: the workhorse of the quarry;
• The gyratory crusher: the primary in the very large plants above 1,500 tons per hour: the continuous cycle of the cone carries a higher capacity in a smaller footprint: the cost of the capital is exchanged for the headroom of the future;
• The cone crusher: the standard of the secondary and tertiary stages: the reduction of 5 to 1 per stage: the product shapes quad-ruple: the closed side setting of 8 to 50 millimeters controls the product top size;
• The impact and hammer crushers: the worlds of the limestone: the dryer the material, the better the hammer: capacities to 1,000 tons per hour at the feed of 100 to 400 millimeters: the product of 20 to 50: the easy, the brittle, the calcareous;
• The roll crushers and the sizers: the low-speed, high-torque machines of the sticky and the wet feeds: the tooth rolls pull the material through the fixed gap: the product is uniform and the fines are few: the niche of the difficult;

The numbers that matter to the operator are the closed-side setting (CSS) and the current of the motor: the CSS defines the particle size, the current defines the utilization: the hydraulic-setting crushers change the CSS in seconds during the production: the daily report carries the two numbers: the setters of the professional and the paybacks of the maintenance: the crushing tables of the file give the capacities of the machines in the function of the CSS and the gap.

5. The Fine Equipment: The Tumbling and the Bed Mills and the Charged Medium

Below the crusher sizes, the picture shifts from the Single-pass machines to the drum and the bed mills, and the machinery of the fine section is the longest-lived department of the plant:

• The ball mill (tube mill): the classic rotating drum of 3.0-4.8 meters diameter, 10-15 meters long, with the media ball charge of 28-35% of the volume: the planetary charge cascades and cataracts on the material: the 15-25 kWh/t for raw, 25-40 kWh/t for the finish;
• The vertical roller mill (VRM): the grinding between the rotating table and the hydro-pneumatic rollers: the feed dried in the mill, using the kiln waste gases: 30-50% less electrical energy than the ball mill for the same raw product: the standard of the dry plants of the last decades;
• The roller press (high-pressure grinding roll): the two counter-rotating rolls create the compacted bed of the feed and fracture it along the grain: the pre-grinding machine of the cement plant: the energy saving between 20 and 30% compared with the pure ball circuit;
• The hammer mill in the fine service: the grate product of minus 3-5 mm is used as the feed for the roller mill or the raw mill with the integrating crusher-dryer: the single-machine plants, the simple flows;

The motto of the fine stage: the biggest media cannot grind the finest particles, and the finest media grind nothing else: the media design in the ball mill is the layer cake of sizes, with the media dimension declining the length of the grinding path: the balances and the liners wear: the compartmental mills separate the coarse balls and the fine balls in the two compartments, and the smallest ball size is the index of the product the mill can reach: the grinding the media tables and the charge calculations are the favorite exhibits of the package.

6. The Closed Circuits and the Classifiers: the Separators in the Loop

No grinding department in the modern plant grinds in a straight line: the fine particles are removed as they are formed, and the returned oversize completes the loop:

• The closed circuit: the mill product flows to the classifier; the finished size leaves to storage, the oversize returns to the mill inlet; the circulating load between 100% and 350% of the new feed;
• The separator circuits: the first-generation static, the second-generation centrifugal and the third-generation high-efficiency dynamic separators: the modern circuits use the cage-rotor separators with the cut diameters between 10 and 60 microns;
• The fineness loop: the Blaine target of the cement 3,200-4,300 cm²/g: the separator speed manipulates the fineness within minutes, the loop of the quality control;
• The circulation numbers: the typical finish mill of 160 tons per hour circulating 60 to 150 tons per hour in the separator: the fan of the separator handles 60-90 m³/s of the drying air;

The closed circuit performs the vital economy of the comminution: grinding the oversize only: the particles that have already reached the product size do not return to the mill to soak the energy: the separation has its own price in the power of the fan and the pressure of the draft: the plant that wants the low kWh/ton of the finish in the 2020s grinds the closed circuit, and the plant that wants the complete design walks the separator tables of the file.

7. The Energy Anatomy of Comminution: The Kilowatt-hours Per Ton Table

The table of the specific energies is the single most quoted table in the cement energy audit, and the package reproduces it with the raw values of the industry:

• The primary crushing: 0.2-0.5 kWh/t, the cheapest electric work of the plant;
• The secondary and tertiary crushing: 0.5-1.5 kWh/t, plus the feeder and conveyor losses;
• The raw grinding (ball mill): 16-22 kWh/t; the vertical roller mill 12-16 kWh/t;
• The finish grinding (cement ball mill): 28-40 kWh/t, the touch of the hardest quality; the finish with the roller press 22-30 kWh/t;
• The auxiliary services: the separators, the fans and the mills of the circuits add 4-8 kWh/t of cement;

The reading of the table: the raw grinding plus the finish grinding are over 80% of the comminution energy of the plant: the savings follow the design: the vertical raw mill, the roller press, the improved separator: each number of the table tests the upgrade: the file also carries the Excel audit tool: the engineer enters the kWh readings of the plant and the tool plots the circuit against the world practice, the benchmark of the century: the audit, the month of the truth.

8. The Work Index and the Sizing of the Mill: The Calculation of the Power

The design of every grinding stage starts from the laboratory work index: the file of is the companion document to this guide’s theme: the number Wi of the limestone, the clinker, the slag, measured in the Bond mill:

• The measured values: the limestone 8-12, clinker 12.7-16, slag 15-20, the raw mix 10.5-12.5 kWh/t;
• The sizing steps: the plant defines the feed F80 and product P80, then the Bond equation gives the specific energy W; the tons per hour and the W produce the net mill power, then the efficiency of the drive (0.92-0.96) and the circulating load corrections of 0.9-1.1 add the design; the motor;
• The example of the sizing: the finish mill of 120 tons per hour, the clinker Wi 14, the feed 80% at 5000 microns, the product 80% at 90 microns: W = 10×14/√90 − 10×14/√5000 = 14.8 − 1.98 = 12.8 kWh/t: then P = 60 × 12.8 × 1.1 (the corrections and the drive) ≈ 845 kilowatts installed 950 kW: the line; the process engineer and the mechanical engineer sign the same document;

The numbers show the leverage the engineer works with: the 0.5 kWh/t difference between the fine and coarse feed is not a laboratory subtlety: at 800,000 tons per year of cement that equals 400,000 kWh per year, which is the real currency of the plant: the supply, the engineering and the people: the Bond value is measured, the plant pushes the crusher product, and the mill gets a lighter job: the wheel, the sizing.

9. The Worked Example: The 3,000-Ton-Per-Day Plant from Quarry to Silos

The file gives the full example through the five stages, and the abbreviated version shows the chain in numbers:

• The feed: the quarry blasts and loads 480 tons per hour of limestone at 700 mm 80%; the design = 3,000 tons per day clinker;
• The primary stage: the jaw crusher drags 480 tph of the 700-mm rock to minus 200 mm, at 0.4 kWh/t: the pSum: 192 kilowatts the belt;
• The secondary stage: the hammer crusher reduces the 200 mm to minus 60 mm, at 1.1 kWh/t: the 528 kW on the motor;
• The raw grinding: the raw mill (VRM 3,800 mm) grinds 420 t/h to 90% minus 90 microns at 14 kWh/t: the installed 4,500 kilowatts: the 5,880 kW of the drive;
• The finish grinding: two ball mills of 3,800 x 12,500 mm each finish 110 t/h cement at 38 kWh/t: the installed motors of 4,200 kW each: the silos of the dispatch;

The summary of the example: the five stages convert the meter-size geology into the 45-micron economy, and the total installed comminution power of this 3,000-tpd plant approaches 15,000 kilowatts: the comparison with the 2,500-kilowatt drives of the old plants shows where the industry travelled in fifty years: the comminution department of the modern mill concentrates its megawatts, its instrumentation and its preventive maintenance into the two grinding stages, and this concentration is exactly the reason the package dedicates its biggest single volume to it.

10. The Practice of the Operation: Load, Speed and Conditioning

The physics of every stage is executed in the control room, and the operator’s levers are few but decisive:

• The crusher loading: the feeder speed matches the current: the eye of the operator is on the motor amperes: the 85-95% loading is the economy zone; the staining the surge bin protects the belt;
• The mill inlet: the weigh-belt feed and the sound (the impact of the balls) monitor the level of the charge: the modern mills measure the bearing pressure and the power: the bed height in the roller mill is watched:
• The separator speed: the rotor speed of the cage runner: the fineness of +50 microns the product: the setting of the speed is the setting of the Blaine: the laboratory result confirms the hour;
• The moisture conditioning: the dry grinding hates the moisture: the 1% sample 0 and the feed rod: the vent gas of the kiln and the moisture of the raw: the limit in the mill the 5-8%;
• The media conditioning: the top-up of the balls and the periodical charge auditions: the ball breakage the 0.1% of the charge per month: the correct charge is the mobile of the mill;

The same instruments serve the efficiency: the operator closes the loop between the amperes and the fineness, and the maintenance closes the loop between the liner life and the media: the two loops are the same loop: the smooth, closed comminution of the charging and the free-flowing of the returning: the papers of the file write the procedures of both loops, the control and the maintenance, side by side in their chapter.

11. The Troubleshooting of the Comminution Circuits: The Complaint and the Cause

The symptoms of the mill floor cluster into the classic ‘complaints’, and the file’s troubleshooting chapter maps each complaint to its causes, the quickest first:

• The sudden rise of the mill power: the harder feed (the new seam, the polished crusher), or the overloaded circulating load: measure the separator current and the new feed: the wedge that is the answer;
• The fall of the fineness: the worn balls, the low gas flow of the separator, or the water injection failure: the internals inspection: the media top-up: the frequency of the audits weeks, the cause the days;
• The returned circulation that jumps: the separator rotor wear or the blocked vanes: the power of the separator fan: the check the reject percentage and the diet;
• The premature liner wear: the hard clinker, the coarse feed, the low ball charge rate: equals the condition of the wear plate and the economics of the steel;
• The smell of the set filling material: the smooth, the vibrating feeder: the mill cakes: the moisture, the gypsum, the temperature: the fresh measure of the route;

The art of the troubleshooting is the art of keeping the cause separated: the same symptom of the low production comes from the feed, the media, the liner, the separator and the market power: the file’s decision trees score the likelihood of each cause against the quick tests, and the operator hnings the first test to the highest likelihood: the machine and the procedure; the tool — the crash plan of the skilled.

12. The Comminution Economics: The Energy, The Steel and the Strategy

The comminution bill is not only the electricity: the full cost has three terms, and the file budgets all three:

• The electricity: 28-35 kWh per ton of cement at 0.07-0.12 dollar per kWh: the dominant, the steering term of the plant economics;
• The grinding media: 80-150 grams of steel per ton of cement of media steel, 200-400 for the raw mill: at U.S. dollar per gram in the thousands: the media is the second bill;
• The liners and the wear parts: 10-25 grams per ton of the liner steel: the crusher jaws and the hammer rotations: the maintenance budgets of the crushing;
• The strategy: the pre-grinding roll press: 20-30% cut of the kWh of the finish cement: the vertical mill for the raw: 30-50%: the paybacks of the 2-4 years: the package’s Excel costs the three scenarios of the modernization;

The numbers of the strategy: a mid-size plant grinding 900,000 tons of cement per year at 30 kWh/t pays about 2.2 million dollars per year for the electricity of the finish alone: the 20% saving of the roller-press modernization is a four-year-feel of 1.1 million dollars per year: the concrete the plant, the concrete lever: the comminution is the deepest, most repeatable thrift of the cement plant: the design documents and the decision-makers of the package the file of the modernization: the conversion the red numbers to the black.

13. The Limits and the Honesty of the Comminution Rules

The wise document also flags where the textbook numbers stop being exact, because the engineer in the field needs the boundaries:

• The Bond law under 40-50 microns: the agglomeration and the particle interference take over: the energy rises nonlinearly: the high-efficiency separators, the utilization of the power: the above rule of the hand;
• The wet grinding behavior: the slurry of the wet process flouts the dry grinding rules: the moisture, the viscosity: the wet plants calibrate their own kWh standards;
• The feed variability: the Wi of the quarry’s seam is not the Wi of the stockpile: the measured mixture differs from the average: the sampling discipline borders every energy calculation;
• The machines the interaction: the crusher geometry, the liner profile and the mill speed interact: the rules assume the standard machine, the field modifies: the commissioning trials revisit the numbers;

The honest engineering: the laws and the tables give the plant the century’s statistics, and the plant’s own 10-minute religion measured its own kilometres: the file gives both: the textbook and the audit template: the operator who parks the two data sets will find the truth between the law and the log, and the same honesty keeps the kW numbers from acquiring the magical power their users often grant them.

14. The Grinding Aids and the Temperature Control of the Finish Mill

The finish grinding has a chemical lever in addition to the mechanical ones, and the modern plants use it daily: the grinding aids: the polar organic molecules of 0.01-0.05% dosage that coat the fresh surfaces and reduce the agglomeration of the fine particles: the aids do not change the laws of the comminution, but they free the mill from the sticking of the fines, with measured effects in the production and the quality:

• The mode of action: the aid molecules adsorb on the broken surfaces and screen the re-agglomeration: the coating keeps the balls clean and the circulation free: the effect is strongest at the finest end of the grind;
• The measured benefits: 5-15% more production at the same Blaine, or 2-5% lower cement Blaine at the same power: the typical aid consumption of 200-1,000 grams per ton of cement;
• The formulations: the amines, the glycols, the acids for the storage, the flow aids for the silo and the packing: the multi-function formulations serve the setting and the strength of the concrete, the added value beyond the comminution;
• The water injection: in the entrapped compartment of the ball mill, the water is sprayed to the mill body (up to 0.5-1.0% of the feed) to keep the media temperature below 100 °C and the gypsum unimpaired: the balance of the water and the fineness, the operator’s careful setting;
• The dosage control: the flow-metered pump and the fineness feedback: the aids slide on/off and the quality laboratory records the response: the intervention is visible within the hour, the standard tool of the finish;

The aids are the lowest-cost improvement of the finish milling, and the file documents the application practice: the pump, the injection point, the dosage logic and the quality control: the engineer who buys the package receives the formulations chapter of the best practices, the caution of the additives (the overdosage harms the concrete property) and the economic comparison against the classic levers: the lesson is the mixtures of the small-numeral engineering that the plant makes real money from.

15. The Instrumentation and the Monitoring of the Comminution Circuits

The modern comminution department runs on the continuous data, and the file’s instrumentation chapter maps the sensors to the decisions:

• The power and the current: the mill motor power is the single most informative number of the plant: the power-noise curve, the amperage of the crusher, the load of the mill measured via the power draw: the telemetry of the process;
• The level sensors: the electronic ear and the vibration sensors listen for the falling balls: the load cell and the bearing pressure reports the charge in the roller mills: the level control stabilizes the grinding bed;
• The fineness monitoring: the samplers at the separator and the online particle-size analyzers: the Blaine and the +45-micron residue are the daily law of the finish: the loop of the separator speed closes on the analyzer;
• The weigh-feeding: the belt scales of the feed and the reject: the material balance of the circuit is the foundation of the kWh/ton report: the calibration of the scales is the audit of the audit;
• The vibration and the temperature: the bearing vibration, the gearbox oil, the mill body temperature: the predictive maintenance of the drives: the fixed bus bar of the industrial IoT reports of the package;

The modern control room displays the comminution as the live model, with the power, the feeds, the fineness and the reject on the one screen: the operator watches for the deviations of the trends, the CMMS plans the maintenance from the vibration signatures, and the process engineer benchmarks the kWh/t against the file’s tables: the instrumentation converts the comining art into the measurable science, and the science only becomes the Excel audit the plant’s improvement plan.

16. The Frequently Asked Questions

What is the difference between crushing and grinding?

Crushing is the coarse stage above about 25 millimeters, done in the jaw, cone, impact and hammer crushers with reduction ratios of 4-9: its cost is below 0.5-1.5 kilowatt-hours per ton: the grinding is the fine stage below the millimeter, done in the ball, vertical and pressure mills with ratios of 100-1,000 and energies of 15-40 kWh/t: the two families use different machines, laws and steel consumption laws.

Why is comminution the biggest electricity bill of the cement plant?

The finish grinding to the Blaine of 3,500-4,000 cm²/g requires the highest specific energy of any process: the Rittinger law explains it: the new surface area of a powder is enormous: the same clinker that cost 10 kWh in the crusher costs 30 kWh in the mill, and the plant can only avoid the waste with the classifier loops that starve the fine work.

Does the file cover the selection of the mill?

It covers the complete sizing: the feed characteristics, the Bond work index, the product fineness, the installed power, the volume and the speed of the mill, and the circuit choices between the ball, VRM and roller press: with the worked example of a 3,000 tons per day plant, the material balance and the Excel sizing model are part of the 931-file package.

What is the typical energy of grinding one ton of Portland cement?

The finish grinding of ordinary Portland cement in a ball mill circuit runs 28-40 kilowatt-hours per ton: with the roller press (the HPGR pre-grinding) the circuit drops to 28-32, and the high-efficiency separator trims more: the raw meal grinds at 12-22 kWh/t depending on the mill family and the fineness.

How do I troubleshoot a mill that is losing throughput?

Check in order: the feed moisture and size, the media charge and level, the separator speed and the rotor, the liner profile, and finally the ventilation: the file gives the sequence the order above with the symptoms of each: the throughput fall that appears suddenly is almost always the feed or the separator, while the gradual fall is the steel and the lining.

Is the roller press suitable for raw meal?

The roller press lines are mostly used for the finish grinding and pre-grinding of the cement clinker; for the raw meal the vertical roller mill is the preferred: the drying capacity of the VRM with the kiln gas is the decisive advantage; some plants have used the press for the raw with the dryer share, but the standard flowsheet favors the VRM and the file documents both routes.

17. Conclusion

The comminution is the largest engine of the cement plant: the chain of the five stages, the crushers and the mills, the laws and the separators, the kilowatt-hours and the kilograms of steel: its engineer is the energy manager of the factory, because the one department that touches every ton of the product: from the moment of the blast in the quarry to the instant the bag filler seals the powder, the material is never done walking this size-reduction path, and every saved kilowatt-hour at the wrong stage is lost kilowatt-hour at the right one.

The Complete Cement Technical Package includes this comminution guide with the energy tables, the sizing spreadsheets, the troubleshooting trees and the modernization calculations: the one-time purchase of the 249.99 US dollars, the instant download of the 931 files: the professional tools for the CLI of the cement: the crushing and the grinding, documented the way the plant lives them: order today, and put the comminution engineering under your control.

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.