Cement Handbook: Complete Technical Guide

The cement handbook is the one-volume reference of the cement technology that the plant engineer, the chemist, the manager and the student can all open at the same table and find the answer: it is the book that covers the whole chain of the cement making, from the geology of the limestone to the strength of the concrete in the wall: the raw materials and their chemistry, the processes of the grinding and the burning, the kiln and the mill, the quality control and the standards, the environmental questions and the economy of the plant: the handbook is written to be read in the office, consulted in the control room and quoted in the meeting: it is the spine of the professional library of the cement engineer.

The Complete Cement Technical Package (931 files including this handbook, the specialized books, the Excel tools, the courses and the presentations: $249.99 one-time: instant download via the PayPal payment) includes the cement handbook as one of its core reference volumes: this article walks the coverage of the handbook: the raw materials, the clinker chemistry, the dry process plant, the grinding and the burning, the cement types, the hydration, the quality control, the standards and the sustainability: the reader finishes with the map of the whole subject, and the handbook itself provides the details for every province on the map.

The cement industry is easy to describe in one sentence and hard to master in a lifetime: the sentence is simple (grind the stone, burn it with the lime and the clay, grind the clinker with the gypsum: the result is the cement), but the mastery sits in the dozens of the sciences that the sentence hides: the thermochemistry of the kiln, the phase chemistry of the clinker, the rheology of the slurry and the concrete, the physics of the grinding, the statistics of the quality control: the handbook exists because the cement profession needs one book that carries the whole of the knowledge with the engineering numbers, and this page gives the reader the tour of the book: the structure of the knowledge, the key numbers and the way the handbook presents the cement industry to its own engineers.

1. The Raw Materials of the Cement: The Limestone and the Correctives

The cement raw materials are the common rocks of the earth’s crust, and the whole chemistry of the process is the reconciliation of four oxides that these rocks provide: the lime (CaO), the silica (SiO2), the alumina (Al2O3) and the iron oxide (Fe2O3): the handbook opens with the geology because nothing downstream works without the correct mix:

• The limestone: the source of the lime: the calcium carbonate (CaCO3) rock that carries 50–55% of the CaO: the quality hinges on the content of the magnesia (MgO, limited to a few percent in the clinker) and the impurities: the typical plant mix runs 72–82% limestone by the weight of the raw feed;
• The clay and the marl: the source of the silica, the alumina and the iron: the weathered clayey rocks contain the quartz, the feldspar, the iron oxides and the moisture: the single deposit that already contains both the lime and the clay (the marl or the natural cement rock) simplifies the plant enormously;
• The sand: the silica corrector that raises the silica when the clay is deficient: the quartz sand grinds hard and wears the mills, so the silica correctives are used sparingly;
• The iron ore or the iron additives: the source of the Fe2O3 for the alumina ratio: the iron ore, the pyrite cinders or the mill scale: small additions, big chemistry effects:
• The corrective materials: the bauxite for the alumina, the slag, the fly ash as the secondary cementitious materials: the modern plants make the clinker from the mix of the natural rocks and the industrial by-products, and the handbook covers the alternative materials in the dedicated chapters;

The chemistry of the raw mix is summarized in the three ratios that the handbook explains as the first tools of the design: the lime saturation factor (the LSF, typically 92–98, that measures how far the mix is from the saturation with the lime), the silica ratio (the SR, typically 2.0–3.0, that balances the C3S against the C2S) and the alumina ratio (the AR, typically 1.2–1.8, that balances the liquid formation in the kiln): these three numbers describe the raw mix the way the coordinates describe the place, and the plant chemist lives by them every day.

2. The Clinker Chemistry: The Four Phases of the Bogue

The clinker, the intermediate product of the kiln, is not a mixture: it is a synthetic rock of the crystalline phases that form at the high temperature, and the cement properties are the properties of those phases: the handbook presents the four principal phases with their roles:

• The alite (C3S, the tricalcium silicate): the 55–65% of the Portland clinker: the phase that develops the early strength of the cement: it reacts fast with the water and rewards the first 28 days of the concrete: the burning at the high temperature and the fast cooling preserve it;
• The belite (C2S, the dicalcium silicate): the 15–25% of the clinker: the phase that develops the later strength: reacts slower, and rewards the months: the belite-rich cements are the low-heat cements of the mass concrete;
• The aluminate (C3A): the 5–12% of the clinker: the phase that reacts with the water so fast that the flash set is prevented only by the gypsum: it contributes the early heat of hydration and the sensitivity to the sulfates: the low C3A cements are the sulfate-resistant cements;
• The ferrite (C4AF, the tetracalcium aluminoferrite): the 5–10% of the clinker: the phase that melts early in the kiln (at about 1,300–1,350°C) and helps the formation of the other phases, gives the grey color of the cement and contributes the moderate hydration:

The clinker contains the few percents of the minor components as well: the free lime (the uncombined CaO, kept below about 1–1.5% for the soundness), the magnesia (below a few percent, above which the periclase expansion threatens), the alkalis (the Na2O and the K2O, whose sulfates affect the setting and the admixture compatibility) and the sulfur: the handbook’s chapter on the clinker quality gives the tolerance bands for each impurity and explains what happens when the band is exceeded: the clinker is the fixed point of the whole process, and the chemical specification of the clinker is the contract between the kiln and the mill.

3. The Process of the Cement: The Wet, the Semi-Wet and the Dry

The cement is made in three families of the processes, and the handbook presents them with the honest comparison of the energy and the equipment:

• The wet process: the raw materials are ground with the water into the slurry of 30–40% water and fed to the long wet kiln: the water is evaporated in the kiln itself, which burns 5,500–6,500 kJ per kg of the clinker: the wet process is the feed of the old plants and the easiest to control, and it survives where the moisture of the raw materials is high or the fuel is cheap;
• The semi-wet and the semi-dry: the slurry is dewatered into the filter cake or the nodules: the Lepol grate-kiln burns the nodules: the intermediate processes at 3,500–4,500 kJ/kg clinker;
• The dry process: the raw meal as a dry powder of 0.5–1% moisture through the suspension preheater and the precalciner: the modern dry plant at 3,000–3,500 kJ/kg clinker with the multistage preheaters of 4–6 stages and the state-of-the-art at 2,900–3,200 kJ/kg: the dry process is the technology of any new plant of the last fifty years, and the handbook devotes the majority of the process chapters to it;

The energy difference dominates the process choice: the wet process burns roughly twice the fuel of the modern dry process, which alone pays for the difference in the equipment: the handbook’s energy tables compare the processes stage by stage, and the reader sees why the industry migrated to the dry: the same chemistry, the same product, the different machinery of the heat.

4. The Raw Grinding: The Mills That Prepare the Meal

The raw mix enters the grinding to reach the fineness that the kiln can burn: the raw meal specification is typically 12–15% residue on the 90 micron sieve and 1.0–1.5% on the 200 micron sieve, and the grinding consumes power and select the equipment:

• The ball mill: the older standard: the rotating drum with the steel balls crushing the feed: robust, easy to operate, energy-hungry: about 18–25 kWh per tonne of the feed in the closed circuit with the separators;
• The vertical roller mill (the VRM): the modern standard: the stationary table and the rotating rollers grind and dry the feed in the same machine with the hot gas from the kiln: 16–22 kWh per tonne and 2–3 times the drying capacity per area: the VRM has taken the new raw grinding plants and most of the retrofits;
• The roll press (the high pressure grinding rolls): the inter-particle crushing between the two rolls at the high pressure: used ahead of the ball mills and the VRMs to reduce the energy of the coarse feed;

The raw grinding determines the homogeneity of the feed: the variations of the fineness become the variations of the burning and the quality, and the plant measures the fineness per shift and steers the separator: the drying duty is equally important: the raw feed arrives with the moisture of 3–10% and must dry to less than 1% in the mill: the hot kiln gas is the dryer, and the balance of the drying and the grinding defines the mill’s gas volume and thus the whole plant’s gas system: the handbook’s chapter on the raw mills is the bridge between the quarry and the kiln.

5. The Preheating and the Precalcination: The Tower of the Kiln Feed

The modern dry kiln hangs its feed from a tower: the suspension preheater of 4–6 cyclone stages and the precalciner vessel that together prepare the feed before the kiln:

• The cyclone stages: the feed descends through the gas in the suspension, heating from the ambient to about 900–1,000°C at the kiln inlet: each stage recovers the heat of the gas, and the 5-stage preheater with the calciner cuts the heat demand to about 3,000–3,200 kJ/kg clinker;
• The precalciner: the vessel where the 60–95% of the fuel burns with the tertiary air: the decarbonation of the limestone (the calcination) starts in the tower and reaches 90–95% before the feed enters the kiln: the kiln itself then only finishes the burning, and its length and the production equipment shrink accordingly;
• The heat transfer: the combined counter-current of the gas and the feed with the suspension that exposes each particle: the preheater is a heat exchanger with the efficiency of the stages: more stages, more recuperation, and the limit of the stages is the dust and the fan power;

The precalciner is the single largest step of the last century of the dry process: before it, the kiln was long and slow; with it, the kiln is shorter, faster, more productive and one-third of the fuel: the handbook’s tower chapter explains the counter-current, the feed splitting, the bypass strategies and the calcination measurement, and the reader understands why the preheater tower is the tall building that looks like nothing else: it is the heat exchanger between the fuel and the stone.

6. The Kiln: The Heart of the Temperature

The rotary kiln is the heart of the plant: the inclined rotating cylinder, 3.5–4.5% slope, turning at 2–5 revolutions per minute, that moves the feed by the rotation a few degrees at a time while the flame at the lower end heats it to the clinkering temperature:

• The physical shape: the tube of 4–6 meters diameter and 55–80 meters length (the length to diameter ratio 15–18), the feed entering the top, the clinker leaving at the bottom after 20–30 minutes of the residence;
• The zones: the feed moves through the calcination zone (800–1,000°C), the upper transition, the burning zone (the clinker at 1,350–1,450°C where the liquid phase forms and the alite crystals grow), the lower transition and the cooling zone (the clinker leaving at 1,300–1,400°C toward the cooler: the zones are the geography of the kiln, and the refractory lining, the burner and the operator each divide the kiln by the zones;
• The heat: the flame at 1,800–2,000°C radiates to the bed and the refractories: the heat transfer is mostly the radiation in the burning zone and the gas convection at the feed end: the specific heat of the modern dry kiln 3,000–3,500 kJ/kg clinker;

The kiln operation is the equilibrium of the four regulators: the kiln feed rate, the fuel rate, the gas draught (the induced draft fan pulling the combustion products) and the kiln speed: the operator balances them so the burning zone temperature sits at the target and the free lime of the clinker stays below 1.5%: the handbook’s chapters on the kiln operation, the flame adjustment and the control loops carry the accumulated experience of the burning practice, and the reader of the handbook inherits it in a form the old operator spent the career collecting.

7. The Clinker Cooler: The Recovery of the Heat and the Grindability

The hot clinker leaves the kiln at about 1,300–1,400°C and must cool rapidly and recover its heat: the grate cooler is the standard: the moving grate carries the clinker bed beneath the cooling air, and the air itself becomes the secondary and the tertiary combustion air of the kiln and the calcinerm:

• The heat recovery: the 50–60% of the clinker heat (about 1,000–1,700 kJ/kg) is returned to the process as the hot air for the flame and the calciner: the remaining heat is lost with the exhaust and the shell the best coolers recover more than 70% of the clinker heat;
• The fast cooling: the clinker cools from 1,400°C to 100–150°C at the cooler discharge in a few dozen minutes: the fast cooling improves the cement quality (the smaller the crystals, the alite preserved) and the easier the subsequent grinding: the grit and the granulometry of the clinker come from the kiln and the cooler together;
• The equipment: the cross-bar coolers and the reciprocating grate coolers replaced the pendulum grate coolers: the bed of 500–800 mm, the air under the grate at 0.8–2 m/s Darcy, the cooler efficiency measured by the recovery of the heat and the inlet temperature of the secondary air (often 1,000–1,150°C):

The cooler is the kiln’s supply of the combustion air: the secondary air of the kiln burner comes through the kiln hood and has been preheated by the clinker bed: the hotter the secondary air, the less the fuel to get the same flame: the cooler is thus both the clinker chiller and the combustion air preheater, and the handbook explains the two roles with the energy flow diagrams.

8. The Cement Grinding: The Clinker and the Gypsum in the Finish

The final grinding makes the cement: the clinker, the gypsum and the additions are ground together to the fineness that the concrete needs, and the parameters of the grinding define the cement hours: the gypsum is the essential 3–5% of the cement (as SO3 at the level of 2.0–3.5% in the cement), whose role is the control of the setting of the aluminate: without the gypsum, the cement flashes; with too much, the cement satates:

• The mills: the closed-circuit ball mills (30–40 kWh per tonne of cement), the vertical roller mills, and the semi-finish circuits with the high-pressure rolls: the modern plants use the VRM or the rollpress+ball combos for the 1.5–2 times the energy of the old ball mills;
• The fineness: the Blaine surface of the ordinary cement 300–400 m²/kg (the 42.5N class about 350–380, the higher classes (52.5) about 400–450): the fineness is the main lever of the early strength, and its cost is the mill energy;
• The additions: the limestone filler, the fly ash, the slag, the silica fume blended into the cement at the mill: the clinker factor of the modern cements (the clinker share of the cement) falls from 95% for the CEM I to 65–80% for the blended: the cement industry today sells the cement, but the content is the clinker + the grind + the chemistry:

The cement grinding carries two contradictory demands: the fineness for the strength and the report and the economy of the energy: the modern mills meet it with the classification loops, the injection of the water, the grinding aids that coat the particles and the careful control of the temperature (the cement at 100–120°C leaving the mill: above that, the gypsum and the setting suffer): the handbook’s grinding chapters compare the circuits with the energy and the quality tables, and the reader selects the route by the local clinker, the price of the power and the desired cement types.

9. The Hydration of the Cement: The Water, the Reaction and the Structure

The cement lives to react with the water, and the handbook’s chemistry chapters describe the hydration that turns the powder into the stone:

• The alite hydration: the C3S reacts with the water to form the calcium-silicate-hydrate (the C-S-H, the strength-giving gel, about 50–60% of the hydrated paste) and the calcium hydroxide (the CH, about 20–25%): the C-S-H is the glue of the concrete, the CH the byproduct that the pozzolans later consume;
• The aluminate and the gypsum: the C3A reacts instantly with the water: the gypsum steps in first and forms the ettringite (the trisulfate), which coats the aluminate and decelerates the setting: later the ettringite converts to the monosulfate: without the gypsum the aluminate sets in the minutes (the flash set), with the gypsum the setting spreads over the hours;
• The setting the times: the cement must set (the initial set above, the final set the — the typical initial set 1–3 hours, the final set 3–6 hours) per the standards, and the vicate of the setting is the prime control of the composition;
• The strength development: the hydration proceeds for months and years: the strength at 28 days is the conventional benchmark; the hydration is never complete in dry buildings because the moisture and the pores limit it: the water-cement ratio is the master variable: the low ratio gives the dense, strong concrete, the high ratio the porous weak one;

The hydration is also the release of the heat: 300–500 kJ per kg of the cement in the first days, more for the C3A-rich cements: the mass concrete (dams, foundations) must control the heat, and the selectable low-heat cements (the low C3A, the high belite, the slag blends) exist exactly for that purpose: the handbook’s hydration chapters take the reader from the mixing to the 28-day strength with the same equations and the tables: the cement chemistry is the beginning of the concrete knowledge, and the handbook hands it in the industry form.

10. The cement types and the standards: the CEM classes and the customer languages

The cement types matter because the construction industry orders the cement by the class and not by the chemistry: the handbook compares the two great classification systems:

• The European EN 197-1: the CEM I (the Portland, 95–100% clinker), the CEM II (the Portland-composite, with the limestone, the fly ash, the slag, the silica, 65–94% clinker), the CEM III (the blast furnace, 36–65% clinker + slag), the CEM IV (the pozzolanic) and the CEM V (the composite): each with the strength classes (32.5, 42.5, 52.5) and the suffix N (normal) or R (early high strength):
• The American ASTM C150: the types I (the general), II (the moderate heat), III (the high early strength), IV (the low heat) and V (the resistant to the sulfate), with the e.g. Type I/II the trade of the general use;
• The local standards: the Portland slag cement, the Portland-pozzolana cement (the IS 1489 in India), the masonry cements of the ASTM:

The class names hide the chemistry: the ASTM Type V is the C3A below 5%, the type III is the ground finer with a higher C3S% and the CEM II/A-LL is the 88–94% clinker with the limestone at the 5–10%: the handbook’s tables map the classes to the chemistry, the fineness and the properties, so the manufacturer the mill makes can be poured either language and the engineer reads the invoice in both: the standards are the language of the cement trade, and the handbook is the dictionary.

11. The Quality Control: The Laboratory of the Plant

The cement plant quality control operates on three time horizons, and the handbook covers the entire laboratory layout:

• The process control: the on-line X-ray analyzers steer the raw mix to the targets of the LSF, SR and AR; the samples of the raw meal, the hot meal and the clinker are analyzed by XRF per 2–4 hours; the free lime of the clinker daily; the microscopes on the polished clinker sections reading the alite, the belite and the liquid;
• The cement testing: the fineness by the Blaine and the residue sieves; the setting times and the soundness (the Le Chatelier test: the expansion must stay within the limits, the floaters of the unsound); the sulfate (the SO3%) on the cement; the compressive strength at 2, 7 and 28 days on the mortars of the EN 196; the initial and the final set;
• The conformity: the batches and the certificates: the quality of the dispatches (the mill to the batches of the strength limits of the value of the class): the plant’s quality manual of the ISO 9000 fold: each batch of the cement leaves with the numbers and the liability of the producer for those numbers:

The strength data feeds the statistics: the plant knows the standard deviation of its 28-day strength (1–2 MPa is the state of the art), and the mix stays above the class minimum with the margin: the handbook’s quality chapter teaches the appropriate sampling (the mitre of the sample representativeness), the calculation of the average and the sigma, and the reactions to the excursions: the quality control is the only place in the plant where the entire process appears as one number: the 28-day strength, and the handbook gives that number its discipline.

12. The environmental performance: the CO2 and the alternative

The cement industry is the largest industrial emitter of the CO2 after the energy, at about 7–8% of the global, and the handbook gives the honest account of the environmental numbers and the mitigations:

• The source of the CO2: about 0.8–0.9 tonnes of the CO2 per tonne of the clinker, of which the process (the decarbonization of the limestone) about 0.53–0.55 tonnes and the fuel about 0.3–0.35 tonnes: the process emission cannot be reduced by the fuel efficiency, which is the central fact of the cement decarbonization;
• The levers: the clinker factor reduction by the blending (each 10% of the clinker replaced by the pozzolans cuts the emissions by about 0.08–0.09 t CO2/t cement), the alternative fuels (the waste-derived fuels replacing the coal), the energy efficiency, and the long-term CCS (the carbon capture at the cement plants at the technological pace);
• The dust and the other emissions: the bag filters hold the dust at the 10–30 mg/Nm³, the NOx at the level of the burners, the SNCR and the SCR, the SO2 by the scrubbing (the dry injection enters the baghouse): the loops of the earlier are the local measures;

The handbook treats the environment not as a separate chapter of the public but as a technical discipline of the operation: the plant that keeps the emissions and the energy within their budgets is the plant that survives the permits and the economy: the decarbonization measures move the cement toward the CEM II and III (which the industry calls the “clinker factor” of the portfolios), and the handbook’s mass and energy tables make the comparisons quantized: the numbers are the book’s own and they do not flatter.

13. The Economy of the Plant: The Energy and the Cost Structure

The handbook closes the process journey with the economy of the cement plant: the plant is a money machine with the fixed anatomy: the energy (the fuel and the power) is the largest variable cost, typically 50–60% of the operating cost with the fuel at a third:

• The fuel: the clinker at 3,000–3,500 kJ/kg, running 4,000 t/d that is about 160-200 t of the coal-equivalent day (the coal at 25 MJ/kg): the coal, the petcoke, the waste-derived fuels: the alternative fuels at 50–80% of the sector’s heat is the modern target;
• The power: the plant 100–110 kWh per tonne of the cement: 60% of the grinding (the raw + the cement+the mills), the fans and the compressors the rest: the specific grinding cost of the clinker and the cement is the biggest single block of the electrical budget;
• The labor and the materials: the wear parts (the grinding media, the refractories, the filters), the labor, the maintenance: the cost structure of the kilns explains why the industry consolidates the large, energy and the modern plants;

The handbook’s economical chapters link the process numbers to the money: a 3,000–3,500 kJ/kg kiln at 4,000 t/d with the fuel at the local price: the annual cost of the kiln alone: the reader the numbers of the fuel, the power and the blending and walks out with the working map of the cement company’s P&L: the handbook that teaches the kilns and the mills without the money would teach an incomplete craft, and this handbook teaches both.

14. The handbook as the tool: the coverage and the layout

The cement handbook is organized for the practical reference: the chapters follow the material flow of the cement plant, and within each the theory, the equipment and the numbers are treated together: the quick orientation that the structure of the handbook gives:

• The materials chapters: the limestone and the correctives, the raw mix design, the chemistry of the clinker and the phases: the single 120-page core of the cement chemistry;
• The process chapters: the quarry, the grinding, the homogenization, the preheater, the kiln, the cooler, the mills, the dispatch: the machinery and the controls of each unit with the dimensional tables;
• The quality chapters: the laboratory, the standards, the statistics, the certifications: the chapter that the QC chemist will keep at the hand;
• The application chapters: the concrete, the mortar, the special cements (the white, the oilwill, the rapid, the sulfate-resistant, the expansive) and the reference of the end-use questions:
• The tables: the conversions, the standards, the limits, the equipment data: the reference tables at the end of each chapter and the index to the whole:

The user of the handbook reads it in two ways: the systematic reader opens at the chapter 1 and walks through the whole process, while the practitioner opens at the index, finds the specific table (the LSF, the kiln size, the mortar proportion) and closes the book in two minutes: the book is designed for both: the uniform chapter structure and the dense tables make the second reader as fast as the first is thorough: the handbook belongs to the genus of the reference literature that the cement industry has produced (the handbooks of the cement associations), and it distills that tradition into the one file of the package.

15. The worked example: the plant of the 5,000 t/d: the numbers of the whole

The handbook closes its process chapters with the worked example that ties the numbers together: a mid-size dry process plant and the flows from the quarry to the packer, in the handbook’s own conventions:

• The raw mix: the limestone at 76%, the clay at 18%, the sand at 3%, the iron charge at 3%: the LSF 95, the SR 2.4, the AR 1.5: the 8,100 t/d of the crushed feed at 8% moisture entering the raw millook at 5,000 t/d of the clinker:
• The kiln: the 5-stage preheater plus the calcinesto: 7,400 t/d of the dry meal at the LOI 35%: the kiln of 4.8 m by 68 m at 3.8% slope: the heat at 3,100 kJ/kg: the clinker output at 5,000 t/d with the free lime 0.8%:
• The grinding: the cement of the CEM II 42.5N at the 8% limestone and 4% gypsum: 5,720 t/d of the cement at 360 m²/kg: the two mills of the 4,000 kW each, the 90 kWh/t of the plant total:
• The dispatch: the 70% the bags, the 30% the bulk: the silos the combined 90,000 tonnes of the storage:

Result: from the 8,000 t/d of the quarried rock to the 5,720 t/d of the dispatched cement, with the 83,000 m³/h of the gas in the preheater and the 120 MWh of the plant power: the handbook ties all the arithmetic of the plant into one worked flow, and the reader that follows it with the boiler tables reproduces the numbers of any plant: the example is the digest of the whole book, the handbook the digest of the whole file collection, and the practitioner who runs both has the complete picture of the cement business: from the chemistry of the CaCO3 to the invoice on the dispatch day.

16. The Frequently Asked Questions

What is the difference between the CEM I and the CEM II cement?

The CEM I is the straight Portland cement with the clinker content of 95–100% and only a small gypsum addition; the CEM II is the Portland-composite cement where a share of the clinker (typically 6–35%) is replaced by the limestone, the fly ash, the slag or the silica fume: the CEM II uses less energy and produces less CO2 per tonne, at some changes in the early strength, according to the type and the extent of the addition used.

What is the lime saturation factor and why does it matter?

The LSF measures how far the raw mix is saturated with the lime against and the silica: it is the ratio of the actual CaO to the maximum CaO that the silica, alumina and iron can combine: the typical raw mix is designed at LSF 92–98: the higher the LSF, the more potential ~the C3S and the strength, but beyond the range the free lime appears and the cement becomes unsound: the LSF is the primary target of the raw mix control.

How much CO2 does the cement industry produce per tonne of cement?

Roughly 0.8–0.9 tonnes of CO2 per tonne of the clinker, and about 0.6–0.7 tonnes per tonne of the finished cement (including the grinding without the chemistry): about 60% of the process CO2 comes from the decarbonization of the limestone itself, a share that no fuel change can remove: the reduction road is the clinker factor, the alternative fuels and, at the end, the carbon capture.

Why is the gypsum added to the cement?

The gypsum (calcium sulfate, usually 2.5–5% as SO3 of 2–3.5%) controls the fast hydration of the aluminate phase: without the sulfate, the cement would flash age within minutes of mixing; with the gypsum, the sulfate forms the ettringite layer that regulates the setting and the whole setting process stretches over the hours: the gypsum dosage is tuned against the C3A content of the clinker.

What is the weather and the temperature that the kiln shell catches?

The kiln shell temperature at the burning zone typically runs 220–350°C at the outside with the healthy refractory and the material coating, and the shell scanner trips the alarm at about 380–400°C: the increasing shell temperature signals the thinning or the loss of the refractory lining, and the plant the burning smear is the classic response: the shell zones are monitored continuously by the infrared scanners.

Is the dry process always better than the wet?

For the new plants, yes: the modern dry process with the multistage preheater and the calciner burns at 3,000–3,500 kJ/kg versus the 5,500–6,500 of the wet, and it produces the higher specific output; the wet process survives where the raw materials are wet by nature and the fuel is cheap, and it still exists in the older plants converted with the risk of the exit: every new written plant of the past decades is dry.

17. Conclusion

the cement grows not because the equipment is complicated but because the whole spans so many disciplines: the geology of the rock, the chemistry of the phases, the machine of the mill and the kiln, the statistics of the laboratory and the economy of the fuel: the cement handbook is the place where the disciplines meet: the reference that the process engineer opens from the Kiln and the QC who opens from the Standards meet on the same page: the handbook is the long investment of a single volume, and the package is the extension of it into the files and the tools of the complete library.

The Complete Cement Technical Package includes the cement handbook and the hundreds files (931 total) that support it: the tools, the books, the courses and the presentations: $249.99, one-time: instant download and the lifetime access: the cement plant solves its problem differently every week, and the answer is almost always somewhere in the knowledge: the handbook and its package put the knowledge at the hand: the pages of the reference, the numbers of the templates, the day of the engineer: the price of the knowledge is the click, the value is the whole career.

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.