Acmc Vol: Complete Technical Guide

ACMC Volume 2 is the second volume of the ACMC training file set and it walks the cement plant from the moment the crushed limestone leaves the quarry to the moment the finished cement enters the storage silo: the volume covers the raw material preparation, the raw grinding, the homogenization, the pyro-processing line, the clinker cooling, the finish grinding and the dispatch: where the first volume stayed in the quarry, this second volume moves inside the plant gates: the mills, the kiln, the coolers, the separators and the conveying lines that turn the pile of stone into the ton of cement: everything the plant operator, the production engineer and the trainee needs in one documented sequence of the process stages.

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 ACMC Volume 2 together with the full library: the one payment, the entire cement engineering collection, forever: this article is the guided reading of the file: the same order of the production line, the same vocabulary of the plant, the same numbers the operators live with every shift.

The reader follows a synthetic production line here: a dry process plant with a five-stage preheater tower, a calciner, a rotary kiln and a vertical roller mill for the raw meal: the file is generic across the plant types, and this article flags the variants where they exist: the reader gets the full process from the raw mill feed to the truck loading, the way ACMC Volume 2 teaches it.

1. The Position of ACMC Volume 2 in the Series and the Package

ACMC is the acronym of a well-known training series of the cement industry, the Arabic Cement in the Manufacturing Certificate courses that many plants and their affiliated schools use for the training of operators, technicians and engineers: the series is structured in volumes: the first volume covers the quarry and the crushing, and the second volume covers the production line from the raw grinding to the dispatch: within the package, ACMC Volume 2 sits next to the big handbooks of Duda, Lafarge and Holderbank and complements them with the compressed classroom view of the whole plant.

• The audience: new operators that need the whole plant in one file, technicians that refresh the circuits, engineers that teach the internal courses;
• The style: diagrams, flow sheets, plant sketches and short definition boxes: a training file rather than a research book;
• The level: the professional basics of every department: enough numbers and chemistry to run the plant, structured for the classroom;
• The use in the package: the reader that finishes this volume moves to the specialist books (ball mill internals, kiln alignment, refractories, ESPs) with the whole plant already in his head;

There is a discipline in reading the volume like the plant flows: the raw mill feeds the homogenization silos, the silos feed the kiln, the kiln feeds the cooler, the cooler feeds the clinker storage, and the clinker storage feeds the finish mill: the volume signs this order and this article follows it.

2. The Raw Material Preparation and the Dosage of the Mix

The raw mill can only grind what the proportioning feeds it, so the ACMC volume starts at the dosing: the crushed limestone, the clay or the marl and the iron corrective materials arrive on the dosing belt from their storage, each bin under its weigh feeder, and the weighing system sums the mass flows into the target chemical mix that the quality department has calculated.

• The weigh feeders: belt-type gravimetric feeders with the load cell feedback: the throughput in tons per hour set by the control loop that compares the set point with the measured load;
• The target modules: the LSF (the lime saturation factor) in the range 88 to 100, the silica ratio (SM) between 2.0 and 3.0 and the alumina ratio (AM) between 1.3 and 2.5 in the typical modern mix;
• The additives: the iron corrective (laterite or the iron ore with 55 to 65% Fe2O3), the silica correctives (the silistone, the sandstone with >85% SiO2) and the recycled dust and the clinker fines;
• The control dynamics: the X-ray analyzer reads the mix each few minutes and the process control adjusts the individual feeder dosings in closed loop, keeping the LSF deviation in the ±0.5% band of the practice;
• The moisture accounting: the dryers or the vertical mill inlet handle the moisture, but the dosing mass must be corrected for the surface water measured by the belt scales and the near-infrared moisture sensors;

The chemistry of the raw mix is not a laboratory curiosity: it predetermines the burnability of the mix in the kiln, the reactivity of the clinker and the composition of the cement: the ACMC volume gives the tables of the typical mixes of the industry, the values that this article quotes as the practicing ranges of the modern dry plant.

3. The Raw Grinding: The Ball Mills and the Vertical Roller Mills Compared

The raw mill transforms the dosed mixture of 0 to 80 millimeters of the crushing product into the raw meal with a fineness of 80 to 90 micrometers of the residue standards: the two main machines of the industry, the ball tube mill and the vertical roller mill, and the ACME volume compares their character on the same data.

Characteristic	Ball mill (closed circuit)	Vertical roller mill
Drying capacity in % inlet moisture	Up to 12 with the heat from the kiln gases	Up to 20 with the heat of the kiln gases
Power consumption per net ton kWh/t	17 to 22	12 to 16
Space and foundation	Large, heavy foundation	Compact, light footprint
Noise	High (grinding balls)	Low
Maintenance	Liner and ball addition	The roller and the table wear, hydraulic system
Fineness flexibility	Good, stable at the target	Very flexible in the same operation

The typical dry process plant counts on the vertical mill for the raw with the hot kiln gas for the drying: the milling duty and the 12 to 16 kWh/t versus the older ball mill’s 17 to 22 kWh/t is the decisive economy of the modern cement line: the volume teaches both, because the existing ball raw mills still operate and the package must serve those plants also.

4. The Ventilation and the Drying in the Raw Grinding Circuits

The raw material contains up to 12 to 15% of the surface and the crystallization moisture that must leave the system before the miller, and the drying accounts for a large share of the raw plant energy: the ACMC volume explains the two drying modes, the direct and the sweeping, and the actual arrangement of the modern plant.

• The heat source: the preheater and the kiln exhaust gases from 300-400 degrees C are drawn through the mill in the raw grind for the drying, so the mill is the dryers as well;
• The internal sweep: in the vertical mill the nozzle ring and the air flow lift and carry the material, the hot gas dries the particles during their transport to the separator;
• The ball mill drying: in the ball mill with the drying compartment or the drying chamber ahead of the grinding chambers, the hot gas flows with the material and carries the moisture, the ventilation marks the output;
• The maximum moisture: the figures of the practice: the vertical mill accept up to 20% moisture with the gas of 400 C, the ball mill circuit 8 to 12% with the same gas;
• The water added: the excess of the gas temperature is trimmed by the water injections in the mill inlet to protect the mill internals and the class boundaries;

The drying gas and the grinding mill are thus the same machine in the modern raw plant: the tension of the volume is the calculation of the drying capacity, and the balance pages list the typical gas flows and temperatures for the engineer to verify against his own plant.

5. The Homogenization: The Silo and the Air Cushion

The raw meal that leaves the mill varies around the target chemistry by the variations of the quarry and the grinding: the homogenizing silo is the tank that blends these variations to the feed that the kiln can burn: the volume explains the continuous homogenizing silo of the aeration system, the standard of the dry plant.

The classical design runs the raw meal in the central feed pipe, while the aeration pad at the silo cone blows the air in alternating sectors: the air creates the fluidization of the meal, the meal flows to the outlet in the mixing cone, and the slow removal blends the layers that entered at different times: the result is the well-known smoothing factor of the silos: the raw meal reaches the kiln with a standard deviation of CaCO3 in the range of ±0.2 to 0.4% even when the feed varies at five times that range.

6. The Suspension Preheater: The Five-Stage Heat Exchange of the Kiln

From the homogenizing silo the meal enters the preheater tower through the feed and falls over a five-stage cyclone cascade against the hot kiln gas: each cyclone stage transfers the heat from the gas to the dispersed raw meal in less than a second, so that the raw meal reaches the calciner and the kiln with the temperature of 800-850 C, the part of the CO2 already driven off the carbonate.

Stage (top to bottom)	Gas temperature C (approx)	Material function
Stage 1	320-340	The feed the meal, the gas cooled for the mill
Stage 2	450-500	Low temp preheat of the meal toward the feed
Stage 3	550-600	Higher heat transfer, partial the carbonate
Stage 4	650-700	Start of the apparent carbonate decomposition
Stage 5 (bottom)	800-850	The meal heating to the calcination zone

The calciner that sits on the side of the tower (in the modern plants) burns the additional fuel so that 90% of the decarbonization happens before the kiln: the entry of the meal into the kiln is already calcined, the clinkerization in the kiln mostly remains: the in-line or the separate-line calciner with its tertiary air duct is one of the key topics of the volume, the newest plant designs explained in the same training pages.

7. The Kiln: The Rotary Vessel and the Clinker Formation

The rotary kiln is the heart of the line: a steel cylinder, the shell, rotating at 2.5 to 4 rpm on the tyres and the rollers, inclined at 3 to 4% from the feed end to the discharge end: the ACME volume gives its own numbers: the typical kiln of a 4000 tpd line is 4.6 to 4.8 m diameter and 64 to 72 m long, with the shell inside lined with the refractory bricks that protect both the shell of the heat and the corrosion.

• The zones of the kiln: the calcination zone, the 800-1000 C band; the transition zone 1050-1250 C; the burning zone 1350-1450 C where the clinker minerals form; the cooling zone of the outlet;
• The phases in the share: at 1450 C the liquid phase is 20-30% of the clinker batch and binds the alite crystals (C3S 55-65% of the clinker), the belite (15-30%), the aluminate and the ferrite;
• The fuel: the coal, the pet cokes, the natural gas, and the selected AF wastes fired through the main burner at the output end; the secondary fuel in the calciner;
• The flame: the primary air, the swirl and the axial streams, the secondary air from the cooler at 700-900 C; the flame length and the shape tuned to the kiln length from the cold design;
• The material transport: the slope and the rotational movement carry the meal long-produced the kiln, the residence of the material 20-40 minutes, the retention of the gas 2-4 seconds;

ACMC Volume 2 presents the operating check lists of the kiln as well as the name of the departments: the temperature profile, the red spots on the shell, the operation of the kiln drive with the backlighting and the emergency the kiln is and how the plant handles them.

8. The Grate Cooler: The Recovery and the Handling of the Hot Clinker

The clinker exits the kiln at 1300-1400 C: the grate cooler retrieves its heat and reduces its the temperature to about 80-120 C+ the ambient: the modern plant moves to the cross bar / exchangeable row grate coolers with the reciprocating extensions.

• The deck arrangement: the clinker falls on the moving grates, the plate of the air blows up through the deck: the fixed and the moving platen rows maintain the clinker layer 500-800 mm deep;
• The air system: the cooling air from the ambient fans under the deck, at 1.5-2.2 Nm3 per kg of the clinker, the portion of the air becomes the secondary and the tertiary air for the kiln of the calciner at 900-1100 C;
• The recuperation: the first part of the cooler creates the recuperation zone, the flame of the kiln and the calciner drawn from it, the heat recovered 65-75% of the clinker enthalpy;
• The clinker handling: the cooled clinker drops over the end grate to the crusher (the hammer mill) to the 25-40 mm, then the flats and belt conveyors to the clinker store;
• The temperature targets: the discharge at the end 60-100 C above ambient, the under-deck pressures 3-8 kПa, the grate speed control from the bed height and the hearing PSD;

The cooler efficiency is followed as kiln-specific heat consumption: the modern cooler recovers coefficients in the 65-75% of the clamp enthalpy, a difference of every percent translates into the heat consumption of the line: the ACME pages give the measurement method of the cooler performance and its troubleshooting.

9. The Clinker Storage and the Further Handling

The cooled clinker conveys to the large dome or the hall storage that buffer the kiln from the finish mill: the storage must also allow the age of the clinker, the short standing that converts the free lime of the fresh clinker: the practice of 7-21 days of aging for the RIR control before the finish grinding.

In the same group of the conveyors, the volume covers the bucket elevators and the belt conveyors of the clinker transportation, the screw conveyors for the gypsum, the aerators for the dry powders and the pneumatic conveying for the cement of the finish: each express the checking points: the tension of the belt, the roller alignment, the seals and the air valves of the converters.

10. The Finish Mill: The Cement Grinding and the Additives

The finish mill grinds the blended clinker to the fineness of the cement, typically 380-420 m2/kg of the Blaine with the acceptance of the cement: the ball mill the closed circuit prevails for the quality-sensitive eg cement grades, while the vertical mill gains for the final cement of the standard-quality products.

The dosing system for the finish mill mixes the clinker, the gypsum (the SO3 control to the optimum 2.2-3.2% as SO3 in most cements) and the other cement constituents (the limestone filler, the fly ash, the slag) in the target proportions set by the quality standard: the load cells of the lost-in-weight feeders maintain the set point, the temperature control of the mill and the ventilation monitor the limits for the gypsum brake: the cement reaches the target temperature the miller at 100-110 C max outlet, the separator adjusts the fineness.

Parameter	Typical finish ball mill values	Typical finish VRM (CEM II) values
Specific energy kWh/t	29 to 36	22 to 28
Surface area Blaine m2/g	3300-4500 by the grade	3400-4200 by the grade
Residue on 45 micron %	5-15	5-15
Cooling water use	Mill interior cooling + separator	Separator and air cooling
Sound level	95-105 dB near the mill	low, 85-95

The finish circuit is the biggest energy consumer of the plant: 35-45% of the total electricity of the cement plant, against the 25-30% of the raw mill: the ACME volume includes the optimization pages of the separator speed, the ball degree, the venting and the additive optimization, the same rules the finish mill engineers apply weekly.

11. The Cement Transport, Storage and the Silo Technology

The finished cement leaves the mill to the cement silos: the internal or the external storage, the silo capacities in the 4-6 large lorries of the day’s production, the aeration strips at the bottom for the discharge; the cement quality is tested at the silo intake and again at the dispatch to give the final certificate of conformity.

• The aeration: the air pads of the silo bottom with the low pressure blowers fluidize the cement, factor of the outlet the gravity flow to the discharge;
• The bridging: propensity of the hydrated cement to arch in the silo, the aerated floors and the discharge cones prevent the coating;
• The packing: the 50 kg rotary and the valve-packers, the palletizers and the stretch film wrap; 25 kg and big bags at the option;
• The loading: the bulk cement to the tankers and the rail wagons by the bulk loaders with the dust extraction;
• The ship loading: in the export plants, the cement pumps and the air slide conveyor lines load the cement carriers;

12. The Emission Control and the Fan Systems of the Plants

The emission control of the plant keeps the fine particles out of the atmosphere: the bag filters at the mill vents, the cement silo filters and the kiln dedusting are documented the filters: the parameters of the filter design and the compliance values of the volume:

• The raw and the kiln dedust: the electrostatic precipitators or the bag filters captured the kiln and the raw mill gases; C/A values of 10 to 30 mg/Nm3 or below per the local regulations;
• The mill circuit filters: the ball mill vent and the separator of the filters maintain the negative pressure of the mill and the clean air for the gray;
• The electrostatic precipitator: the charging fields, the collecting electrodes and the hammer rapping, the automatic volt-amps control: described in the volume and in the package reduction files in the same package;
• The return of the dust: the collected dust is returned: the kiln dust to the raw mix or the raw mill feed, the finish miller dust and the cement to the finished product: the mass loop of the plant closes;

The syllabus of the ACME second volume ends with these support systems but includes the aux festivals: the fans at the discharge finishes of the tower, the cooling towers of the process and the compressed air utility that serves the instrument air and the aeration to the plant: the complete overview of the operation of a cement plant.

13. The Future: The Computers and the Continuous Lines at ACME

As the second volume closes, it describes operating the modern line: the control room with the DCS, the data inserted at high frequency, the operators watching the mimics and the trends, the interlocking alarms: the same automation in the drives of the kiln, of the burner management, of the mills and of the quality analysers.

The recent plants and the plants of the package include the grinding auxiliaries that improve the mill output and the 3600 to 4500 performance chemistry (the flow enhancers, the strength improvisers), the alternative fuels (with the pre-treatment and the changing rates), and the capture replacements that go to the kiln; this volume keeps the beginner of the turn before the advanced of the specialist.

The Frequently Asked Questions

Does every plant follow the same sequence as ACMC Volume 2?

No: the volume describes the dominant dry process line: the variations are the wet process (slurry kilns), the semi-wet, the Lepol and the various stages of the preheaters between 2 and 6: the basic exchange of the operations, the blending, the burning, the cooling and the grinding: is the same, and the ceramic is in the numbers.

Is the content the most useful for the new operator?

Yes is the course the internal trainings of the plants use: the whole plant in one documented sequence, in the same speed the operator will see the plant during the field walk: it is the conclusion to the acronym that the reader of the volume uses before opening the specialist books in the package.

Does the volume include the algebra of the raw mix?

It gives the pointing tables of the typical mixtures and the expected modules; the detailed algebra of the mix compositions is in the separate files (the cement matrix calculation, the formula handbooks of the package): the volume is the process map that tells WHERE the chemistry happens; the specialist files tell HOW it is computed step by step.

The package includes the units and the tools for these numbers?

The 931 files include the Excel tools: the energy balances, the mill power calculation with the Bond formula, the LSF and the S/Am correction sheets, and the calcination formulation tools; these same values in this article appear in the working tools of the package.

How do I read the volume for the best benefit?

Follow the line: the raw processing, the mix, the raw grinding, the homogenization, the preheating, the kiln, the cooler, the clinker, the finish grinding, the storage: then the specialist volumes: the mill multiplier, the electro filters, the alignment file, each at its turn: the volume is the map of the plant, the specialists are the zoom of its parts.”

Is the volume value the same as this article?

This article is the technical guide to say the same concept in words: the volume itself provides the page diagrams, the tables, the flow sheets and the exercises that this page cannot fully reproduce: it is part of the 931-file package that the article describes and links to just below.

14. The Control Room of the ACMC Volume 2: The Process Instrumentation

The old courses of the ACMC series were written when the control rooms were moving from the panels to the screens, and Volume 2 documents that transition as part of the plant engineering:

• The measured variables of the line: the temperatures at the preheater stages, the pressures of the system, the flows of the fans, the O2 and the CO of the kiln gas, the levels of the silos: each variable has its sensor family and its maintenance routine, and the volume lists them in the instrument tables;
• The alarm hierarchy: the trip conditions of the kiln and the mills (the high CO, the lost flame, the high mill temperature, the empty feed) versus the warning limits: the operator logic of the old plants survives in the modern systems as the basis of the interlocks;
• The manual-to-automatic graduations: the volume shows the control loops of the classic plant: the kiln feed controlled on the kiln drive amperage, the fuel on the burning zone temperature (the pyrometer of the kiln shell or the kiln mouth), the cooler grate on the undergrate pressures: the practicing engineer sees the ancestors of the modern advanced control;
• The sampling and the laboratory loops: the hourly clinker samples, the daily composite feed samples, the X-ray fluorescence of the raw and the clinker: the chemistry measurements complete the loop of the physical instrumentation;

The instrumentation chapter gives the volume its practical balance: the theory of the process is followed by the devices that operate it, and the reader finishes with the mental image of the plant as a system of measurements: the failures of the instruments become the process faults, and the maintenance of the measurements is the invisible production.

15. The Maintenance Discipline: The Inspection Routes of the Plant

The ACMC course tradition always included the maintenance perspective, and Volume 2 carries it through the concrete routines of the plant week:

• The daily route: the bearing temperatures of the mills and the kiln by the thermography or the contact pyrometer, the lubrication checks, the running vibration of the main gearboxes, the visible condition of the mill leakage and the kiln seals: the route card of the day is signed by the mechanical shift;
• The weekly route: the gearbox oil sampling for the water and the particles, the coupling alignment checks, the grate cooler bed inspection through the side doors, the preheater blockages checklist: the findings feed the work order system;
• The planned stops: the mill relining at the scheduled tonnage, the kiln brick inspection at the shell scanning data, the fan rotor balancing, the silo inspections and the cleanings: the volume shows the plan of the maintenance year tied to the production stops;
• The records: each maintenance act registered with the hours and the cost: the history per equipment builds the reliability reports: the spare parts planning of the maintenance warehouse derives from the history tables;

The maintenance chapters of the old courses are precious because they describe the plant without the romantic facade: the equipment fails, the brick wears, the silo walls need the work: the discipline of the inspection routes and the records is what keeps the continuous line continuous, and the reader of the volume is given the actual forms and the checklists of that discipline.

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.