Products Prerequisites Minor Elements N: Complete Guide & Do

Beyond the four main oxides of the clinker lives the crowd of the guests: the sodium and the potassium, the sulfur, the chlorine, the magnesia, the phosphorus and the titanium, each entering with the raw materials or the fuels and each playing its own part in the burning, the coating and the final cement. This prerequisite module, the sixth of the products course series (the n3-03-2002 module of the package), teaches the minor elements: their origins, their cycles in the kiln system, their limits in the standards and their consequences for the process and the product.

The module stands between the raw mix ratios and the interactions of the series: the ratios designed the main oxide skeleton, and the minor elements now dress the skeleton with the guests that often decide the operating stability of the plant and the durability of the concrete. The engineer who ignores the guests fights the build-ups and the quality surprises; the engineer who knows them controls the process with the full chemistry in the head.

1. The Place of the Module in the Prerequisites Series

The module is the sixth of the products prerequisite series, and its position is the position of the guests in the chemistry:

• The modules before it: the role module and the Bogue module built the main-oxide picture, and the raw mix ratios module designed the feed: this module adds the guests that the main arithmetic deliberately ignores;
• The module’s own subject: the minor and the trace elements of the clinker: their sources, their volatilities, their concentrations, their cycles and their limits: the chemistry of the few percent that runs the plant;
• The modules after it: the interaction module (the seventh of the series) combines the guests with the main phases in the pair interactions: this module presents each guest alone, and the next module plays the pairs;
• The destination: the products course applies the minor element limits to the certificate chemistry, the durability chapters and the special cements: the guest knowledge returns in every product discussion;

The reader who finishes the module carries the guest table of the clinker in the head: the sources, the limits, the cycles and the symptoms, the full minor-element instrument of the daily plant work.

2. The Guests of the Clinker: Who They Are and Where They Come From

The module opens with the guest list, because the engineer cannot control what he cannot name:

• The alkali metals: the Na2O and the K2O of the clay, the shale and the marl (up to 1-2% combined in the clinkers of the difficult raw materials): the most influential guests of the ordinary cement chemistry;
• The sulfur: the SO3 entering with the pyrite and the sulfate minerals of the raw materials and with the high-sulfur fuels (the petcoke): the guest that pairs with the alkalis in the cycles and the sulfate balance;
• The chlorine: the chloride of the raw materials, the fuels and the alternative fuels (the plastics, the refuse): the most volatile guest and the tightest-limited one;
• The magnesia: the MgO of the dolomitic limestones and the magnesian raw materials: the guest of the soundness limits and the slow expansion when it crystallizes as the periclase;
• The phosphorus, the titanium, the manganese and the traces: the guests of the special raw materials and the alternative fuels: the phosphorus of the phosphate ores, the titanium of the titaniferous materials, the manganese of the color, the chromium, the fluorine and the heavy metals of the fuel ashes;

The guest list chapters establish the sources before the effects: every minor element arrives with a bill of origin, and the plant that knows the bill controls the entry.

3. The Alkalis: The Sodium and the Potassium in the System

The alkali metals are the most studied guests of the clinker, and the module gives them their full chapter:

• The entry and the distribution: the alkalis enter with the clay minerals and the feldspar of the raw materials, and a share of them enters with the alternative fuels: in the kiln a part sublimes into the gas and a part stabilizes in the phases: the split depends on the temperature, the sulfate and the chlorine of the system;
• The gas cycle: the volatile share evaporates in the burning zone, travels with the kiln gas into the preheater, condenses on the cooler meal and returns with it to the kiln: the circulating load multiplies the entering quantity by the factor of several, and the concentrated alkalis build the coatings and the blockages of the riser duct and the lower cyclones;
• The phase effects: the alkalis substitute in the alite and the belite, stabilize the belite and disturb the C3S formation: the alkali-rich clinkers burn toward the lower alite and the higher free lime at the same conditions: the Bogue of the alkali clinkers carries the calculation errors the honest analyst corrects;
• The product effects: the alkalis raise the alkalinity of the pore solution of the concrete and feed the alkali-silica reaction with the reactive aggregates: the low-alkali cement limits (the typical 0.6% Na2O equivalent in the ASTM) exist for the ASR protection, and the module gives the equivalent calculation;

The alkali chapters give the reader the double face of the guests: the process trouble of the cycles and the product concern of the durability, the two fronts the minor element engineer fights at once.

4. The Sulfur: The SO3 of the Fuels and the Raw Materials

The sulfur pairs with the alkalis and the calcium in the most dynamic cycle of the kiln system, and the module teaches the cycle and its control:

• The sources: the pyrite and the organic sulfur of the raw materials, and the sulfur of the coal and the petcoke fuels: the petcoke of the modern plants brings the SO3 loads of the 5-7% fuel sulfur into the system;
• The cycle: the sulfur volatilizes in the burning zone as the SO2, reacts with the alkalis and the lime of the gas into the sulfates, condenses in the cooler zones and returns with the feed: the sulfate cycle concentrates the SO3 in the kiln feed far above the raw materials’ own content, and the concentrated sulfates are the cement of the buildups;
• The sulfate balance of the cement: the clinker SO3 participates in the setting regulation: the alkali sulfates of the clinker supply the soluble sulfate of the pore solution and change the gypsum demand of the finish mill: the plant optimizes the total SO3 (the clinker plus the gypsum) against the strength and the setting;
• The emission side: the SO2 of the kiln exit gas appears when the sulfur exceeds the alkali capture capacity: the wet scrubbing and the stack limits of the environmental chapters: the module gives the sulfur balance of the line with the emission arithmetic;

The sulfur chapters give the reader the balance-sheet view of the guest: every sulfur atom enters, circulates and leaves the system somewhere, and the engineer who tracks the balance controls the cycles before they control him.

5. The Chlorine: The Most Volatile Guest

The chlorine is the extreme case of the volatility, and the module treats it with the rigor its consequences demand:

• The sources: the chlorides of the raw materials and the high-chlorine alternative fuels (the refuse-derived fuel, the plastic wastes and the kiln of the co-processing plants): the chlorine content of the feed is held below the limits of the tenths of a percent;
• The volatility: the chlorine evaporates almost completely in the burning zone and condenses early in the preheater, forming the alkali chlorides of the low melting points: the circulating chlorine builds the sticky deposits and the blockages of the cyclone stages with the chloride glues and the corrosion underneath;
• The limits: the kiln feed chloride is typically held below the 0.015-0.03% and the cement chloride below the 0.10% (and the lower 0.05% for the reinforced concrete of the chloride classes): the tightest limits of the minor element family;
• The bypass: the plants with the chloride or the alkali trouble draw the kiln gas through the bypass valve, cool it, collect the dust rich in the alkalis, the sulfur and the chlorine, and discard a share of the circulating load: the bypass chapters give the design, the flow and the dust destination of the system;

The chlorine chapters give the reader the emergency instrument of the minor element control: the chlorine is the guest that can stop the kiln within the days, and the module teaches the limits, the symptoms and the bypass before the stop happens.

6. The Magnesia: The Guest of the Soundness

The magnesia enters the clinker with the dolomitic materials and lives in the phases or crystallizes as the periclase, and the module explains the two destinies:

MgO behavior	Condition	Consequence	Control
Dissolved in the phases	Moderate MgO, fast cooling	Minor effects, slight phase stabilization	Keep the MgO within the raw material limits
Periclase crystals	High MgO or slow cooling	Slow expansive hydration in the concrete	Fast cooling, MgO feed limit
Excessive MgO	Beyond the ~5-6% of the clinker	Autoclave expansion, soundness failure	Raw material selection, dilution

The magnesia chapters give the reader the soundness arithmetic: the standards test the cement in the autoclave or measure the expansion, and the plant holds the MgO below the limits (typically the 5-6% of the cement by the ASTM and the EN) by the raw material selection and the cooling control: the guest of the slow revenge, respected in advance.

7. The Phosphorus, the Titanium, the Manganese and the Traces of the Special Materials

Beyond the famous four guests stands the second row of the minor elements, the guests of the special raw materials and the alternative fuels, and the module gives them their due:

• The phosphorus: the P2O5 of the phosphate-bearing raw materials and the organic wastes: the guest that stabilizes the belite and suppresses the alite formation above its limits (roughly 0.3-0.5% of the clinker): the phosphatic clinkers of the low strength and the hard burning are the signature of the neglected phosphorus;
• The titanium: the TiO2 of the titaniferous sands and the slag materials: the moderate contents dissolve in the phases without the drama, and the high contents interfere with the alite: the guest that rarely makes the headlines and always deserves the glance of the raw material buyer;
• The manganese: the Mn2O3 of the manganese-bearing materials, tinting the clinker toward the brown and interacting with the iron in the ferrite solid solution: the guest of the color control in the white and the colored cements;
• The fluorine, the chromium and the heavy metals: the fluorine of the mineralizers, the chromium of the raw materials and the furnace wastes, the lead, the zinc, the cadmium and the thallium of the alternative fuel ashes: the guests of the emission limits and the environmental control: each with its entry route, its cycle behavior and its limit in the stack or the product;

The second row chapters complete the guest list: the minor element engineer of the modern plant knows not only the famous four but also the traces of the fuels and the special materials, because the environmental certificate and the product certificate both carry their signatures.

8. The Circulation Table: The Volatility Classes of the Guests

The behavior of every guest in the kiln system follows its volatility, and the module presents the classification table the plant uses to predict the trouble:

Element	Volatility class	Main destination	Typical trouble
Chlorine	Highly volatile	Gas, early condensation	Sticky deposits, chloride blockages
Alkalis (K, Na)	Volatile	Gas, condensation with the meal	Circulating load, buildups, ASR
Sulfur (SO3)	Partially volatile	Gas and clinker split	Cycles, sulfate balance shifts
Zinc, lead	Semi-volatile	Circulation with the dust	Coating influence, dust loads
Magnesia, phosphorus, titanium	Non-volatile	Stay in the clinker	Soundness, phase disturbance

The volatility table is the map of the guest behavior: the plant reads the table, identifies the volatile guests of its own raw materials and fuels, and installs the bypass, the fuel selection or the feed limits before the buildup appears: the anticipation the module trains.

9. The Effects on the Burning: The Guest Symptoms in the Kiln

The guests announce themselves in the kiln behavior, and the module teaches the symptom language of the minor elements:

• The preheater symptoms: the rising pressure drops of the stages, the falling cyclone efficiencies and the chloride-glued deposits: the alkali and the chlorine cycles in action: the module gives the symptom table and the stage-by-stage diagnosis;
• The kiln symptoms: the coating instability, the ring formation in the transition zone (the sulfate and the alkali rings) and the burning zone temperature drift: the guests disturb the thermal equilibrium the main oxide design promised;
• The clinker symptoms: the dusty clinker of the belite stabilization by the phosphorus and the alkalis, the abnormal nodule structure and the colored tints of the manganese and the chromium: the clinker appearances the experienced eye reads at the cooler;
• The dust symptoms: the circulating dust loads, the ESP and the bag filter chemistry and the utility dust disposal: the guests travel with the dust, and the dust management is the guest management by another name;

The burning symptoms chapters give the reader the diagnosis discipline: the minor elements are not the laboratory decoration but the operational voices of the kiln, and the engineer who speaks their language calms the plant.

10. The Effects on the Cement and the Concrete: The Product Side of the Guests

The guests leave the kiln in the clinker and follow the cement into the concrete, and the module gives the product consequences their chapter:

• The soundness: the periclase expansion and the alkali-related expansions tested by the Le Chatelier and the autoclave: the soundness limits of the standards are the magnesia and the free lime limits in the legal dress;
• The setting and the sulfate: the alkali sulfates of the clinker raise the soluble sulfate of the pore solution and change the setting, the workability and the admixture response: the concrete complaints of the alkali-rich cements traced to the clinker entry;
• The durability: the alkali-silica reaction fed by the alkali of the cement, the sulfate attack aggravated by the C3A and the chloride risk of the contaminated fuels: the guests connect directly to the durability chapters of the products course;
• The color and the appearance: the manganese, the chromium and the iron interactions decide the shade of the gray and the white: the architectural clientele of the colored cements judges the guests with the eye;

The product chapters close the guest story of the module: every guest that entered the clinker arrives at the concrete, and the engineer who controls the entry controls the complaints of the decades.

The module adds the quantitative anchors of the product side: the soundness limits of the standards (the Le Chatelier expansion below the 10 mm and the autoclave expansion below the 0.80% of the classical practices), the low-alkali certification at the 0.60% equivalent, the sulfate-resisting tie of the C3A and the chloride classes of the reinforced concrete limits at the 0.05-0.10%: the numbers the product chapters will return to, and the anchors that make the guest knowledge usable in the design office.

11. The Control Practice: The Guest Management of the Plant

The module closes the applied side with the complete control practice of the minor elements, the routine that keeps the guests in their cages:

• The entry control: the raw material selection, the fuel buying specifications and the alternative fuel acceptance criteria: the chloride, the sulfur, the alkali and the phosphorus limits of the purchasing contracts: the control begins at the gate of the plant;
• The process control: the bypass operation, the raw mix dilution with the clean materials, the burning temperature management and the cooling rate control: the process levers that manage the volatile loads and the periclase formation;
• The laboratory control: the XRF of the alkalis, the sulfate, the chloride and the trace elements in the feed, the clinker and the cement, the autoclave and the Le Chatelier of the soundness and the ASR screening of the pore solution: the verification rhythm of the guests;
• The response plans: the blockage cleaning procedures, the ring removal campaigns, the bypass flow tuning and the complaint investigation paths: the prepared responses that shorten every guest crisis;

The control chapters complete the module as the operating manual of the guest management: the minor elements are never eliminated, only managed, and the engineer who manages them runs the stable plant and issues the clean certificates.

The sampling rhythm of the guest control accompanies the manual: the kiln feed analyzed for the alkalis, the sulfate and the chloride on the shift basis, the clinker on the daily basis with the full minor element suite, the bypass dust on the weekly basis and the alternative fuel consignments on the receipt basis: the frequencies follow the volatility of the guest and the speed of the consequence, and the module gives the table of the rhythm the modern laboratories apply.

12. The Alkali-Sulfur-Chlorine Triangle: The Cycle Choreography

The three volatile guests never circulate alone, and the module gives the triangle its chapter because the plant trouble is almost always the trio in the dance:

• The pairing chemistry: the alkalis and the sulfur meet in the gas and the condensate as the alkali sulfates, and the chlorine prefers the alkali chlorides: the two salts differ in the melting and the deposition behavior, and the ratio of the sulfur to the chlorine decides which deposit character the preheater sees: the sticky chloride glues or the powdery sulfate crusts;
• The circulation coupling: the alkali that cannot find the sulfate circulates as the oxide and the hydroxide, the sulfate without the alkali captures the lime, and the chlorine hijacks the alkali from the sulfate: the three guests compete for the partners, and the circulating loads couple with each other: the bypass that removes one partner reshuffles the other two;
• The system diagnosis: the plant measures the alkali, the sulfur and the chlorine balances of the kiln feed, the dust and the gas, and the module gives the balance format and the interpretation of the ratios: the S/Cl and the alkali/SO3 ratios of the feed are the quick predictors of the deposit type;
• The management levers: the fuel selection to change the sulfur entry, the alternative fuel screening for the chlorine, the bypass to export the trio and the raw mix dilution: each lever moves the triangle, and the module teaches the combined strategy of the difficult plants;

The triangle chapter is the crown of the cycle teaching: the guest management is the management of the couplings, and the engineer who sees the triangle in the balance tables controls the preheater stability of any raw material diet.

13. The Minor Elements in the Era of the Alternative Fuels

The alternative fuel programs of the modern plants rewrite the guest account, and the module dedicates its applied chapter to the era of the substitution:

• The new entries: the refuse-derived fuel brings the chloride and the heavy metals, the plastics bring the chlorine, the tires bring the zinc and the sulfur, and the biomass brings the alkali and the phosphorus: the substitution rate is the new variable of the guest balance:
• The new limits: the alternative fuel acceptance analyses, the dose windows of the plant and the regional emission limits: the module gives the acceptance format the procurement departments use;
• The new symptoms: the coating changes, the ring tendencies, the dust chemistry shifts and the cement color variations after the fuel changes: the symptom mapping of the substitution era;
• The opportunity side: the sulfur of the petcoke and the alternative fuels can be managed to serve the sulfate balance of the cement, and the alkali of some fuels can be tolerated within the ASR limits: the substitution is not only the trouble but also the handle: the module keeps the balance of the opportunity and the risk;

The alternative fuel chapters make the reader current with the industry of today: the minor element engineer of the plant with the 70% substitution rate manages the guests live, and the module prepares that live management.

14. The Worked Case: The Plant with the High-Alkali Raw Materials

The module closes the technical body with the complete worked case, the plant that fights the alkali guests from the quarry to the certificates:

• The starting situation: the marl of the quarry at the 1.5% alkalies, the rising preheater pressures, the coating collapses every weeks and the cement approaching the low-alkali limit with the margin disappearing: the case begins where the plants live;
• The diagnosis: the alkali and the sulfur balances computed, the circulating loads measured through the dust and the feed sampling, the deposit samples analyzed and the bypass flow tested: the case walks the complete diagnostic path;
• The remedies: the high-alkali marl benches diluted with the clean limestone, the bypass opened to the calculated flow, the fuel switched to the lower sulfur and the finish mill sulfate re-optimized for the changed clinker: the combined intervention with the numbers of every step;
• The results: the preheater pressures returning to the design, the coating campaign doubled, the cement alkali back in the certification band and the strength statistics recovered: the case proves the module’s teaching with the plant outcomes;

The worked case is the graduation exercise of the module: the reader who followed the numbers by the hand has performed the guest management of the industry, and the interaction module will complete the picture with the pairs.

15. The Frequently Asked Questions

Q: Which minor element causes the most kiln trouble?

A: The chlorine and the alkalis together: the alkali chlorides of the low melting points build the sticky blockages of the preheater, while the sulfur adds its own buildups: the bypass exists for this trio.

Q: What is the typical alkali limit of the low-alkali cement?

A: The conventional limit is the 0.60% of the Na2O equivalent (the Na2O plus the 0.658 times the K2O), the threshold below which the ASR risk with the reactive aggregates is mitigated: the module gives the calculation and the certification practice.

Q: Can the minor elements be removed from the process?

A: Only partially: the bypass removes a share of the circulating alkali and the sulfur dust, the fuel selection limits the chlorine and the sulfur entry, and the raw material selection limits the magnesia and the phosphorus: the module describes each removal lever with its cost.

Q: Why does the Bogue calculation fail on the alkali-rich clinkers?

A> Because the alkalis substitute in the solid solutions of the phases and change the actual compositions the Bogue assumes: the corrected schemes of the previous module apply, and the honest reports note the deviation.

Q: Does the module connect to the durability chapters of the products course?

A: Yes, directly: the alkali-silica reaction, the sulfate attack and the chloride penetration of the durability chapters all have their roots in the minor element loads this module teaches.

16. The Closing of the Module

The sixth module of the prerequisites has given the reader the guest book of the clinker: the alkalis with their cycles, the sulfur with its balance, the chlorine with its volatility, the magnesia with its soundness and the traces of the special raw materials. The engineer who leaves this module sees beyond the main oxides of the certificate, knows where every guest enters, how it circulates and when it attacks the process or the product, and holds the bypass and the selection levers in the hand. The interaction module that follows will pair the guests with the main phases, and the products course will apply the limits to the certificates and the durability of the concrete.

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.