Aspects Of Raw Materials: Complete Technical Guide

The raw materials are where every cement plant actually begins: the limestone, the marl, the clay and the corrective stones that the quarry delivers are converted by the process into the four oxides that make the cement, and every quality number of the final product, the strength, the setting, the durability, is written first in the chemistry of the feed: the raw materials decide the reserves of the plant, the cost of the raw meal, the burnability of the kiln feed, the fuel consumption of the kiln and the limits of the cement that can be made: this article presents the complete aspects of the cement raw materials: the types of the deposits, the chemical modules, the minor components, the burnability, the quarry planning, the raw-mix proportioning with the worked examples and the troubleshooting of the raw-material quality: the reader finishes with the full picture that the raw-material engineer of a cement plant holds in the head.

The document behind this article is part of the Complete Cement Technical Package (931 files including handbooks, Excel mix calculators, quality standards and training presentations: $249.99 one-time payment: instant download through PayPal): the raw-materials document of the package contains the deposit evaluation procedures, the mineralogy tables, the chemistry of the oxide systems, the mix-design calculators with the worked examples, and the quality-limit tables of the minor components: this article walks that document section by section, and the engineer who reads it can open the package’s raw-mix calculator and design the kiln feed of his own deposit in an afternoon.

The central idea of the whole subject, stated once at the beginning: the cement is made from four oxides, calcium, silicon, aluminium and iron, in fixed proportions, and every deposit in the world is only an arrangement of those four oxides plus impurities: the skill of the raw-material engineer is to see the deposit as the oxide picture, to blend what nature provided so the kiln feed hits the four targets, and to keep the impurities within the limits the cement standard demands: this article teaches that skill: the deposit geology first, the chemistry second, the proportioning third and the control last.

1. The Four Oxides: The Chemistry the Plant Is Built On

The clinker of Portland cement is formed from four oxide components, and the whole raw-material management of the plant exists to deliver these four in the target proportions:

• The calcium oxide (CaO): the largest component, 62 to 68 percent of the clinker: the calcium comes from the carbonate rocks, limestone, marl and chalk, and is released from the carbonate during the calcination: the CaO reacts in the kiln with the silicates, the aluminates and the ferrites to form the cement minerals:
• The silicon dioxide (SiO2): the second component, 18 to 24 percent of the clinker: the silicon comes from the clay, the shale and the silica sands: the SiO2 forms the two calcium silicates, the alite and the belite, which carry most of the strength of the cement:
• The aluminium oxide (Al2O3): the third component, 4 to 7 percent: the alumina comes from the clay minerals and the bauxite in the corrective mixes: the Al2O3 forms the tricalcium aluminate, which governs the early reactions of the cement and the heat of hydration:
• The iron oxide (Fe2O3): the fourth component, 2 to 5 percent: the iron comes from the clay and the added iron ore or the pyrite cinders: the Fe2O3 forms the ferrite phase, the C4AF, which carries the low-heat reactions and helps the burnability of the mix:
• The residual oxides: the magnesia, the alkalis, the sulfates, the chlorides and the phosphorus: these are the impurities of the deposit that the plant tolerates within the limits of the standard: each has its effect on the clinker and the cement, and the minor-component chapter of this article covers them in detail:

The four-oxide picture is the language of the whole plant: the quarry engineer, the raw-mill operator, the kiln operator and the quality chemist all translate the deposit into CaO, SiO2, Al2O3 and Fe2O3 every shift: the raw-mix design of the next section takes these four numbers as its entire input, and the cement standards of the world are written on the same four: the engineer who holds the oxide picture in the head reads any deposit, any mix and any kiln problem through the same lens.

2. The Carbonate Component: Limestone, Marl and Chalk

The calcium carrier of the mix is always a carbonate rock, and the deposit type decides the plant’s whole raw-material system:

• The limestone: the dominant raw material of the industry: the sedimentary calcium carbonate with the calcium carbonate content of 75 to 98 percent: the limestone types: the massive, the bedded, the crystalline, the dolomitic, the siliceous: each type carries its own mix: the dense fresh limestone resists the crushing and the burning, the porous varieties react faster in the kiln:
• The marl: the natural mixture of the carbonate and the clay, with the CaCO3 content of 40 to 75 percent: the marl is the geologist’s gift to the cement industry: a marl deposit alone can often make the kiln feed with no corrective addition at all: the marl works the same quarry, the same crusher and the same raw mill with the simplest chemistry:
• The chalk: the soft, fine-grained, wet carbonate of the northern European basins: the chalk at 80 to 98 percent CaCO3 is the extreme carbonate, and the clay must be added as a separate component: the chalk’s water content of 15 to 30 percent dominates the drying and the grinding energy of the plant:
• The dolomite problem: the dolomitic limestones carry the magnesium carbonate: the magnesium passes into the clinker as the magnesia, and the cement standards limit the MgO of the clinker to about 5 percent: the dolomite contamination of the quarry is one of the classic reserve quality problems:
• The valuation of the carbonate: the value of a deposit is written in three numbers: the CaCO3 content, the impurity profile and the uniformity: the carbonate content is measured by the quick titration or the calcimetry in the field, the impurities by the laboratory analysis, the uniformity by the statistics of the drill holes: the deposit valuation is the subject of the reserve chapter:

The carbonate rock supplies 70 to 80 percent of the mass of the raw meal, and its properties set the process: the hard massive limestone demands the blasting, the crushing and the intense burning; the soft marl saves the quarry the explosives, the crusher half its work and the kiln a share of its fuel: the plants of the world are built where the carbonate and the clay sit together in the ground, and the aspect of the carbonate is the first page of the deposit story: the reserve, the mix and the process all follow the stone.

3. The Clay Component: The Supplier of the Silicates

The second essential component of the mix is the clay or its hardened relatives, and the clay family deserves its own chapter because its variability is the largest single difficulty of the raw-material quality:

• The clay minerals: the kaolinite, the smectite, the illite and the chlorite families: each carries the silica, the alumina and the combined water that the clay fires away in the preheater: the kaolinitic clays are the preferred cement clays, with the low iron and the predictable chemistry:
• The shale: the hardened, laminated clay rock: the shale is the clay after the geological pressure: the chemistry similar, the hardness greater: the shale often appears in the quarry below the soil and above the limestone, and the giants of the bed often mix zones into one feed:
• The silt and the sand: the silty clays and the clayey sands form the transition between the clay and the silica: the low-iron silty deposits serve as the natural silica supplier where the limestone is too high in the clay: the sand adds the quartz, and the quartz is the hardest thing the raw mill and the kiln burn:
• The variability of the clay: the single greatest difficulty of the raw materials: the clay changes from the top to the bottom, from the face to the back and from the rainy to the dry season: the moisture of the clay swings between 15 and 30 percent, the chemistry drifts with the weather and the horizon: the raw-mill control exists mainly because the clay varies:
• The clay in the mix: the clay supplies the silica modulus, the alumina modulus and a share of the iron: the target chemistry of the kiln feed is set by the clinker composition, and the clay proportion of the mix is computed so the three oxide ratios land on the targets: the closure of the clay chemistry is done by the corrective components, the subject of the next section:

The character of the clay component, more than the limestone, decides the difficulty of the whole raw-material system: the uniform kaolinitic clay by the quarry makes the raw-mill control a routine; the layered swelling clays of the rainy basin make the control a fight every autumn: the document’s clay chapter gives the identification tests of the field, the swelling and the balling behavior tables, and the moisture management rules that keep the weighing errors of the feeders at bay: the raw-mix engineer studies his clay as the kiln operator studies the flame.

4. The Corrective Components: Iron, Silica and Alumina Sources

Nature rarely supplies the exact oxide mix in one deposit, and the corrective materials close the gap between the natural chemistry and the targets:

• The iron correctives: the iron ore, the pyrite cinders, the iron-containing sludges: the iron oxides are added where the clay carries too little iron for the ferrite requirement: the iron source of the industry is a cheap small addition of 0.5 to 3 percent of the mix: the iron ore must be analyzed for the sulfur and the moisture which spoil the feed:
• The silica correctives: the quartz sand, the sandstone, the flint, the recycled silica of the glass and the foundry: the sand is added where the silica ratio must rise, which is the case of the low-silica marls and the high-CaO limestones: the sand’s quartz is the worst enemy of the raw grinding: the particles of the 2 to 5 mm quartz are the last to burn in the kiln, and the sand corrective always brings the price of its own grinding energy:
• The alumina correctives: the bauxite, the alumina-rich sludges and the clays selected for the alumina: where the aluminium ratio must rise for the high-early-strength cements: the bauxite is expensive and is used sparingly: the alternative aluminum sources of the industrial sludges may carry the unwanted alkalis:
• The so-called calcium correctives: the waste limestone dust, the cement kiln dust, the autoclaved lime: where the carbonate falls short of the target lime, these materials raise the CaO of the mix: the cement dust recycle is a classic double benefit: the kiln ash and the filter dust return to the raw feed:
• The quality of the correctives: the corrective never be a new impurity source: each corrective enters the mix with its own magnesium, alkali, sulfate and chloride, and the corrective quality specifications of the package list the acceptance limits for every additive: the buyer of the iron ore or the sand signs the contract on the same tables the plant uses to reject a bad lot:

The corrective materials are the small biases of the mix: their proportion is low, their effect on the process large: the incorrect dose of the iron ore shifts the ferrite and the burnability, the mispurchased sand adds the quartz grit to the raw meal, the wet correctives jam the feed weighing: the document’s corrective chapter carries the dosing guide of each corrective with the effect per percent on the modules, and the dosing table in the worked whole of the proportioning section demonstrates the systematic way the correctives are brought into the mix design.

5. The Chemical Modules and the Raw-Mix Targets

The clinker chemistry is expressed by the three ratios, the modules, which the raw-material engineer computes from the full oxide analysis of the feed: the modules are the standard language of the day:

• The lime saturation factor (LSF): the most important number: the measure of how full the mix is of the calcium: LSF = 100 x CaO / (2.8 x SiO2 + 1.18 x Al2O3 + 0.65 x Fe2O3): the modern plants run the LSF of 95 to 100 percent for the standard clinker: the LSF too high: the mix refuses to burn, the free lime climbs and the kiln runs the limit: the well and the paste of the paragraphs:
• The silica ratio (SR): the ratio of silica to the alumina plus the iron: SR = SiO2 / (Al2O3 + Fe2O3): the typical targets of 2.2 to 2.8: the high SR gives the high strength and the hard burning, the low SR eases the burning but weakens the clinker: the SR governs the kiln operation and the liquid phase of the burning zone:
• The alumina ratio (AR): the ratio of the alumina to the iron: AR = Al2O3 / Fe2O3: the targets of 1.3 to 2.5: the AR fixes the proportion of the aluminate and the ferrite in the clinker and with it the early strength, the heat release and the resistance of the cement in the sulfate environments:
• The three-module interplay: the three modules are not independent: the LSF sets the lime, the SR the total of the SiO2 against the flux oxides, the AR the split of the flux: the raw mix is fully defined by the three and the target is chosen on the deposit, the process and the market: the modules of the same plant change slowly, and the standard of the direct setting is documented:
• The quick computation: the modules are computed from each raw-meal analysis by the LIMS and the X-ray system automatically: the laboratory posts the modules with the oxides: the operator’s daily sheet compares the real modules against the targets and the proportioning adjustments follow: the worked example of the proportioning section shows the complete chain:

Table 1. Typical module targets for the conventional Portland clinker

Module	Formula	Typical range (OPC)
Lime saturation factor	LSF = 100 CaO/(2.8 SiO2 + 1.18 Al2O3 + 0.65 Fe2O3)	93-100
Silica ratio	SR = SiO2/(Al2O3 + Fe2O3)	2.2-2.8
Alumina ratio	AR = Al2O3/Fe2O3	1.3-2.5

The modules are the final language of the raw materials, and the entire raw material quality management of the plant speaks them: the quarry plan, the raw-mix proportion, the raw mill control and the kiln operator all share the three numbers: the engineer in charge of the raw materials must reason in the modules, because the modules convert a pile of stones into a chemical specification of the kiln feed: the next section applies the modules in the complete worked example of the mix design.

6. The Minor Components: The Impurities That Govern the Limits

Beyond the four oxides, the raw materials carry the minor components that the cement standards allow only in limited amounts, and the raw-material engineer manages them as carefully as the main chemistry:

• The magnesia (MgO): from the dolomite and the magnesium clays: the clinker limit of about 5 percent in most standards: above the limit the periclase forms and the cement expands in the autoclave: the plant monitors the MgO of the feed daily and dilutes the high-magnesium zones by the selective quarrying:
• The alkalis (Na2O, K2O): from the clays and the feldspars: the alkalis rise in the kiln circuit and enter the cement with the consequences for the alkali-silica reaction, the setting and the strength: the equivalent alkali limit of the clinker is commonly set at 0.6 to 1.0 percent, and the excursion of the alkali above the raw-mix allowance is a daily risk of the clay chemistry:
• The sulfate and the chloride: the sulfate and the chloride enter with the fuels, the raw minerals, the chlorine-rich sludges and the organic wastes: the chloride is the most dangerous: the chloride cycles in the kiln system, blocks the preheater cyclones and cuts the kiln life: the limit of the feed chloride is held strictly in the process, not in the cement alone:
• The phosphorus (P2O5): from the phosphate-bearing deposits and the sludge fuels: the phosphorus retards the alite formation and weakens the clinker above the 0.5 percent of the feed: the phosphate valleys of some deposits are the worst areas of the reserve map:
• The free silica and the coarse quartz: the free silica above the feldspars and the mica burns slowly and stays coarse: the quartz grains of the sand and the flint are the classic source of the kiln free-lime excursions: the free silica of the raw meal is controlled by the fineness of the raw grinding, and the coarse fraction is checked by the residue sieves:

Table 2. The minor components of the raw materials and their typical limits

Component	Source	Typical limit in clinker	Main risk
MgO	Dolomite, magnesian limestone	4-5 %	Expansive periclase, soundness
Na2O eq.	Clay, feldspars	0.6-1.0 %	Alkali-silica reaction
SO3	Clay, fuels, gypsum	1.5-3.5 % in cement	False set, expansion
Cl	Chloride, wastes, fuels	Up to 0.1 % in feed	Cyclone blockages, kiln coating
P2O5	Phosphate deposits, sludge	0.5 %	Strength loss

The minor components are the hidden limits of every deposit: the ideal limestone and the ideal clay that contain none of them are rare, so the quarry plan, the mix design and the fuel selection all answer the same question: are the magnesium and the alkali of the planned feed in the standard? The minor-component chapter of the document carries the full limit tables of the international standards, the sampling programs for each minor and the mitigation practice: the dilution, the blending, the fuel change, the corrective: the plant that controls the minors before the clinker is made stands at the front of the quality by design.

7. The Proportioning: The Worked Example of the Raw Mix Design

The raw-mix design combines the deposit analyses into the kiln feed that hits the targets: the worked example of the document below shows the complete reasoning with real numbers:

• The deposit data of the example: three materials: limestone at 52.5 percent CaO, 1.2 percent SiO2, 0.4 percent Al2O3, 0.3 percent Fe2O3; the marl at 38.0 percent CaO, 18.0 percent SiO2, 4.2 percent Al2O3, 2.1 percent Fe2O3; the laterite iron oxide at 52 percent Fe2O3: the target modules of the plant: the LSF 98, the SR 2.5, the AR 1.5:
• The first trial: the two-material feed of 78 percent limestone and 22 percent marl gives the computed oxide mix: the LSF lands at 97.2, the SR at 2.8, the iron low: the two-material trial catches the classic deficit: the iron is short and the mix cannot reach the AR of 1.5:
• The corrective addition: the laterite added at about 2.3 percent of the mix raises the iron: the recompute yields the LSF 98.1, the SR 2.52, the AR 1.48: the three-material mix converges on the targets: the corrective addition completes the design, and the proportions are rounded for the feeders:
• The verification: the final mix is burned in the test and the lab reports the free lime: the burnability of the example at 1450 degrees gives the free lime of 1.3 percent within the quality window: the design is approved for the plant trial: the month of the trial confirms the computed modules with the X-ray daily samples:
• The Excel and the iterative tool: the mix design as an iteration: the package’s Excel mixer takes the oxide columns of the three materials and the targets, adjusts the proportions and prints the module deviations: the engineer changes one input and the sheet tells the whole effect on the three: this calculator of the document section is the daily working tool of the raw-material office:

Table 3. The raw-mix design example of the document, oxide percent on the crude mix

Material	Share %	CaO %	SiO2 %	Al2O3 %	Fe2O3 %
Limestone	78.0	52.5	1.2	0.4	0.3
Marl	19.7	38.0	18.0	4.2	2.1
Laterite	2.3	2.0	20.0	18.0	52.0
Mix	100	42.6	13.1	3.1	2.1
Modules	LSF 98.1, SR 2.52, AR 1.48

The worked example is the complete act of the raw-mix design in one table: the deposit analyses in, the modules out, the corrective line adjusted, the iteration converged: the same table of the model of every plant is rebuilt with the local materials, and the engineer repeats the exercise each time the quarry moves, the deposit strays or the cement type changes: the mix design is not a one-time academic task, it is the weekly maintenance task of the raw quality, and the document’s chapter closes with the design sheet that the raw-material engineer fills and signs for every new quarry horizon.

8. The Reserves, the Deposits and the Quarry Planning

Behind the mix design stands the deposit, and the reserve assessment is the long-term foundation of the raw material aspects:

• The exploration: the drill holes: the deposit is explored with the drilling grid: the holes of 100 to 300 metres spacing in the early stage, then the infill to 50 to 25 metres in the production zones: the cores and the cuttings describe the horizons, and the geologist marks the limestone, the marl, the clay and the waste on the bench sections:
• The reserves and the classification: the tonnages of the deposit are classified by the confidence: the measured, the indicated and the inferred reserves: the cement plant’s rules of the reserve life are written in the three classes: the bank and the mineable tonnage: the standard of the deposit says the plant needs the reserves for 25 to 50 years or more, and the long-term requirement decides the permitted quarry extension:
• The quality mapping: the analytical results of the drill holes are drawn as the chemical maps: the CaCO3 contour map of the quarry, the MgO and the alkali maps: the three maps are the base layers of the quarry plan: the blending of the quarry numbers is planned on the maps, not discovered in the silo:
• The quarry plan: the plan follows the raw-mix quality: the seasonal scheme of the excavation: the high-grade and the low-grade stones are mined and blended in the proportion that the mix needs: the stock piles cover the wet seasons and the dry seasons: the quarry plan of the raw materials is the mining plan and the chemistry plan together:
• The pit design: the benches and the slopes: the bench heights 10-20 metres, the slope angles with the geotechnical safety: the haul roads, the ramp and the drainage: the mining equipment selected on the benches follows the plan of the pit: the raw-materials document of the package works the full pit design chapter with the calculations of the waste ratio and the lifetime of the mine plan:

The reserve and the quarry planning close the long loop of the raw materials: the deposit is assessed once by the drill holes, mapped by the analyses, and protected by the 25-50 year plan: the quality of the reserve becomes the quality of the kiln feed the day the quarry reaches the tenth bench, and the lapses made in the exploration years are paid in the production hours: the reserve chapter of the document plans the complete exploration program, the criteria of the reported classification and the mine-life calculation: the plant that owns its geology owns its process.

9. The Burnability of the Raw Mix: How the Feed Burns in the Kiln

The raw mix is burned in the kiln, and the behavior of the different mixes in the burning zone is described by the burnability, the aspect that connects the raw materials with the fuel:

• The burnability: definition: the ease with which the raw mix converts into the clinker in the kiln: the burnability is measured by the free lime of the burned sample under the standard conditions of the test: the free lime of the well-burned clinker is 0.5 to 2 percent, the poorly burning mix shows the free lime of 3 to 5 percent at the same temperature: the hard to the burn, the more fuel, the longer the kiln residence:
• The factors of the burnability: the LSF, the SR, the particle fineness and the minerals of the feed: the high LSF and the high SR burn hard, the low modules burn easily: the feed of the coarse quartz burns late, the limestone with the large crystals calcines slowly: the burnability of the raw mix is fixed at the mixing stage, not at the kiln: the chemist decides the fuel of the next year before the kiln sees the feed:
• The measurement: the lab burnability test: the standard test: the pellet of the raw meal burned in the laboratory furnace at 1400 to 1450 degrees for 20 minutes and the free lime measured: the free-lime curve at the three temperatures versus the saturation: the standard test of the document: the standard test results of the mix, the raw mix is judged:
• The clinker phases and the burnability: the raw meal that burns well produces the alite-rich clinker with the low free lime, the melts and the nodules of the correct form: the nodulator and the burning zone: the kiln stable and the coating attached: the burnability of the feed is the daily watch of the kiln chemist and the operator together:
• The improvement options: the fineness of the raw mill, the homogenization, and the addition of the mineralizer fluxes (the fluorides, the sulfates) in the correct dosage: the mineralizers accelerate the burn of the hard mixes without the free-lime penalty: the improvement chapter of the document considers each option with its effect on the fuel and the burnability:

The burnability is the kiln’sthe the first place view of the raw materials: the same modules in two deposits may burn with very different ease, the geology and the fineness of the difference: the plant that measures the burnability weekly feeds its kiln a predictable diet, and the plant that ignores it buys its surprises in the free lime of the clinker and the fuel bill of the kiln: the burnability test of the document’s lab manual is the annual companion of the raw-mix design: the two documents are the pair.

10. The Moisture, the Handling and the Weighing Aspects

The raw materials are physical objects before they are chemicals, and the handling aspects of the moist and lumpy feed dominate the raw-material department as much as the chemistry:

• The moisture: the mean: the variation: the clay at 15-30 percent moisture, the limestone at 2-5, the chalk at 20-30: the moisture of the feed decides the grinding system (the raw mill with the drying, the drying-grinding in the mill), the weighing balance and the energy of the plant: the moisture swing of the clay is the largest single disturbance of the raw mill control:
• The weighing and the feeding: the raw materials are proportioned by the belt weighers and the feeder belts: the weight feed of the throughput corrected for the moisture by the moisture measurement: the wet sand and the sticky clay in the feeder jams, the surging: the feeding design of the package: the moisture protocol of every bin, the cleaning frequency and the weighing tolerance:
• The storage and the segregation: the raw materials arrive with the lump sizes and the moistures: the bins and the stockpiles segregate the particles: the stocking and the reclaiming methods of the raw material, the cutter and the bridge scraper of the store, the shaping: the segregation of the lumpy the coarse and the fine: the feed correction of the mills:
• The correction of the flow: the sticky marl, the freezing clay in the winter and the wet waste: the raw material flows: the vibration of the bins, the paddle: the air cannons, the linings: the flow-help measures: the availability chapter of the raw material: the whole class of the flow problems of the raw side:
• The conveyors and the transfer points: the belt conveyors from the quarry and the crusher: the transfer points, the chutes and the dust collectors: the spillage (the sand and the wet): the cleanliness of the raw material transport: the single enclosure of the dumper minus the fire risks: the complete design of the raw material transport of the package:

The moisture and the handling aspects are where the raw material engineering leaves the laboratory and joins the maintenance: the plant with the dry, free-flowing, well-identified raw materials runs a civil process; the plant with the wet sticky clay and the clogged chutes runs a fire drill every day: the document’s handling chapter guides the storage, the weighing, the conveying and the moisture management with the practical tables: the moisture meters, the feeder types, the bin geometries and the flows: the aspect of the handling decides the labor the plant needs and the stops it suffers.

11. The Alternative Raw Materials: The By-Products of the Industry

The cement industry consumes the industrial byproducts of the region as raw materials, and the alternative materials chapter of the document covers the second life of the industry:

• The blast-furnace slag: the glassy calcium-silicate byproduct of the iron production: the slag brings the lime, the silica and the alumina: the granulated slag serves both as the raw material and the cement component, and the cement plants near the steel works save the quarry on the one side and modify the cement on the other:
• The fly ash: the pulverized-fuel ash of the power stations: the alumino-silicate with the carbon and the sulfur in the traces: the fly ash enters the raw mix as the clay partially, and the finished cement most strongly as the puzzolana: the quality control of the ash: the loss on ignition governs the acceptability:
• The secondary raw materials of the local industry: the foundry sand, the glass cullet, the lime sludge of the sugar and the paper industry, the spent catalyst, the bauxite residues: each brings a chemistry and a price and a risk: the contamination and the variability: the acceptance protocol of the package: the table per material with the oxides and the limits:
• The alternative fuels’ ashes: the ash chemistry of the alternative fuels enters the clinker: the petcoke ash, the sewage sludge ash, the RDF ash: the kiln the fuel ash into the product mass: the raw mix is balanced with the designed fuel mix: the transition of the fuel affects the raw quality: the planning of the two goes hand in hand:
• The economics of the alternatives: the local byproducts price the raw meal: the fly ash at the gate of the plant a few dollars per tonne versus the clay pit development, and the slag and the ash often pay better in the finished cement than in the raw meal: the plant’s raw material portfolio is the mixture of the quarry and the byproduct market, and the mix changes with the local industry cycles:

The secondary materials close the raw material aspects of the modern plant: no plant of the present decade is built on the quarry alone: the slag, the ash and the local byproducts shift the economics of the raw meal, the energy and the CO2 balance of the plant: the acceptance, the dosing and the quality control of each secondary input are the daily work of the raw material engineer: the document carries the byproduct database with the analytics and the feeding experience: the plant engineer chooses the portfolio of the resources the way the treasurer chooses the portfolio of the currencies.

12. The Control Loop of the Raw Material Quality

The raw material aspects come alive in the control loop, the cycle that runs from the quarry face to the raw-meal silo and corrects the mix every hour:

• The samplers and the analyzer: the automatic sampler of the raw meal at the mill exit, the pneumatic transport to the X-ray fluorescence analyzer: the analysis of the four oxides in 60 to 90 seconds: the analyzer delivers the CaO, SiO2, Al2O3, Fe2O3 and the modules continuously: the loop’s instrument:
• The stock correction: the loop corrects the feed ratios: the error of the hour (the LSF too high by 0.5) is translated into the new feeder settings: the limestone, the clay and the corrective valves adjust, and the loop answers within the two residence times of the mill:
• The statistical process control: the control charts of the daily modules: the mean and the range: the process capability index of the raw meal: the weekly review: the loop’s discipline: the charts of the raw quality are the evidence of the plant’s stability at the external audits:
• The homogenizing silo: the raw meal blender silo between the mill and the preheater: the silo averages out the short-term fluctuations: the homogenizing factor of the silo 5 to 15: the silo is the buffer that allows the loop to work in hours instead of minutes: the homogenization chapter of the package carries the full science of the silo design:
• The performance requirement: the target of the loop: the standard deviation of the finished raw meal at one-hour intervals under 0.15 for the LSF: the loop with the working sampler and the XRF and the silo reaches the figure: the degraded and the one with the manual corrections: the loop audit measures the raw meal of a week: the document’s control-loop section closes: the statistics of the acceptance:

The control loop is the machine that makes the aspects workable: the deposit can vary with its natural character but the feed to the kiln must not, and the loop draws the line: the sampler, the analyzer, the correction and the silo: the four elements of the loop are the raw-material quality system of the plant: the document’s chapter provides the full control-loop design, the tuning rules of the corrections and the chart formats: the engineer who follows it runs a raw meal with the predictability of a chemical factory, and that predictability is the raw material over the kiln’s whole.

13. The Troubleshooting of the Raw Material Quality

The excursions of the raw-material quality are the daily emergencies of the plant, and the document’s troubleshooting section pairs the symptom, the cause and the sequence of the correction:

• The free lime of the clinker climbs: the LSF of the feed too high, the SR too high, the raw meal coarseness outside, the corrective feed lost, the kiln temperature short: the chain of the checks: the modules of the raw meal feed, the residue of the 90-micron, the burner, the flame: the correction: the feed ratios down the lime:
• The modules swing from hour to hour: the clay horizon change in the quarry, the stock segregated, the feeder drifts, the moisture of the signing changes: the diagnosis: the error between the silo and the XRF (sampling or the flow), the statistics: the correction: the tightening of the plan: the weekly PFD:
• The alkali of the clinker above the limit: the clay zone quiet, the wrong fuel ash, the second: the mitigation: the new zone: the quarry plan: the clinker of the sulfur the bleed: sometimes the alkali can only be reduced by shifting the fuel source the doc: the consequences of the adjustments:
• The magnesium over the limit: the dolomitic horizon entered the feed: the emergency: the quarry face directed to the clean stone, the raw: the dilution: the long-term: the dolomite zone in the blastro plan: the petrography: the smooth: the resampling:
• The feed: the fineness control lost: the mill liner: the segment: the tie: the feed: the 90-mic divider: the separator speed doubled: the chemical effect: the coarse of a raw meal is a raw material quality of the burning: each time the particle’s rise, the burnability falls: the correction and the validation:

The troubleshooting of the raw-material quality closes the aspects: the raw quality never fails alone: it fails in ways the kiln, the mill and the lab read together: the document’s troubleshooting table carries the twenty-five most important excursions with the causes, the check order and the corrections, and the raw-material engineer of the plant fills the same table with the local history: the symptoms, the causes and the remedies: the knowledge of the raw materials is built the same way as the knowledge of the kiln: by the cases: and the cases are in the log.

14. Conclusion

The aspects of the raw materials are the complete picture of the deposit and its conversion into the kiln feed: the four oxides, the carbonate and the clay components, the correctives, the modules, the minor impurities, the burnability, the reserves, the handling, the mix design and the control loop: every plant is built on this ground and every cement is built from this feed: the engineer who masters the aspects reads a new deposit in a day and runs a raw quality in the control charts: the package document includes the deposit evaluation, the mineralogy, the modules, the mix calculators and the tables of the minors, and this article has presented the complete walk: the reader now holds the first of the material aspects, the chemistry and the proportioning, and can apply them to any quarry and any kiln.

The Complete Cement Technical Package includes this complete raw-material document with the reserve evaluation procedures, the mix-design calculators and the quality limit tables: the one-time $249.99, the instant download, the lifelong reference: the 931 files of the package cover the rest of the cement process with the same completeness: the raw material is the only place where the whole plant starts: and the engineer who starts his study with the raw materials starts at the beginning: the article has walked through it: the reader now owns the opening chapter of the cement science.

The Frequently Asked Questions

What are the most important parameters of a cement raw material?

The five numbers: the CaCO3 content (or the CaO), the silica ratio (SR), the alumina ratio (AR), the lime saturation factor (LSF) computed from the full analysis, and the minor components in the order: the MgO, the alkali, the SO3, the chloride and the P2O5: the first three the chemistry of the mix, the fourth the feasibility, the fifth the limits of the standards: the deposit is evaluated with the five numbers.

Why is the lime saturation factor so critical for the kiln?

The LSF tells how close to the saturation the calcium is: above the optimum higher than the incomplete: the raw requires the higher temperature and the free lime stays in the clinker: below the optimum the cement falls short of the alite and the strength: the LSF is the primary lever of the whole clinker chemistry and the control loop holds it within the 0.5 percent of the target.

What is the meaning of the modules in the ordinary language?

The LSF: the fullness of the lime; the SR: the balance between the silicates and the flux (the melt); the AR: the balance between the aluminates and the ferrites: the plant’s ordinary speech uses them like the cook’s heat, the salt and the water: each module is the knob that sets one aspect of the clinker and the operation.

Can one deposit alone make the whole raw mix?

The marl deposits with the correct carbonate-to-clay ratio can approach the full mix, and the deposits of the marl often close the mix with only a small corrective: the rest of the world’s deposits are two or three the components: the limestone, the clay and the corrective iron or sand: the mix of the deposit: the real cases of the industry: the document’s depos: the analysis of the 50 deposits show 40% of the examples: complete with the single source.

What is the difference between the natural raw materials and the alternative?

The natural the quarry: limestone, clay and the marl: their quality is geological and stable on the long term: the alternative: the industrial byproducts: the slag, the fly ash, the wastes: cheaper, greener and more variable: the plant never abandons the quarry for the biproducts, it blends the two and the standard of the raw meal is the same: the alternative’s variability is accepted the acceptance protocol and the extra sampling.

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.