Practical Gas Analysis In Cement Factories: Complete Guide

Gas analysis is the eyes of the cement process: the oxygen of the kiln inlet tells the operator how the combustion burns, the carbon monoxide of the preheater warns of the reduced conditions, the sulfur dioxide of the stack speaks of the raw materials and the fuels: the gas analysis is the instrument panel of the burning process, the only direct measurement of what happens inside the red-hot kiln where nothing else can live: this file is the practical course of the gas analysis in the cement factory: the analyzers, the sampling systems, the maintenance, the calibration and the interpretation: the knowledge of the man who reads the process through the gas.

The Complete Cement Technical Package (931 files including the books, the courses, the Excel tools and the presentations: $249.99 one-time: instant download via the PayPal payment) includes this gas analysis guide with its tables, the sampling diagrams and the worked examples: the same library of the cement plant, the full package, the one payment: this article walks the file: the theory of the measurement, the equipment of the plant, the pitfalls of the sampling, the daily practice and the interpretation of the numbers.

The gas analysis is practiced at three levels in the cement factory: the process control (the kiln and the preheater gases), the emission monitoring (the stack gases for the compliance) and the safety monitoring (the carbon monoxide for the fire detection and the dust explosion prevention): the three levels share the same instruments in the family, and the plant engineer must master the three: this page follows the file: section by section, from the sampling probe to the control room.

1. The Gases of the Cement Process: What the Plant Measures

The cement process produces and consumes a handful of gases, and every one of them carries a message for the operator:

The target values of the typical plant: the kiln inlet oxygen between 1.5 and 3.5%, the kiln inlet carbon monoxide below 0.1% (often the alarm at 0.3 to 0.5%), the coal mill oxygen below 12% at the filter for the safety: the numbers vary with the process (the precalciner kilns run differently), and the file documents the reference ranges of the complete process: the table above is the map of the whole guide.

2. The Orsat Analysis: The Classic of the Industry

The Orsat apparatus is the grandfather of the gas analysis: the glass pipettes, the absorbing solutions, the graduated burette: the operator draws the gas sample, absorbs the CO2 in the potassium hydroxide solution, the oxygen in the pyrogallol solution and the CO in the cuprous chloride solution, measuring the volume reduction of each step: the Orsat is still used in the plants of the world because it needs no power, no electronics and no spares beyond the chemicals.

• The measuring principle: the 100 ml sample at the atmospheric pressure: the first absorption (the CO2) removes the carbon dioxide, the second (the O2) the oxygen, the third (the CO) the carbon monoxide: the residual volume after the three absorptions is the nitrogen plus the rest: the volume differences are the percentages: the whole analysis takes fifteen minutes in the skilled hands;
• The sampling: the gas is drawn through the sampling pipe into the aspirator bulb or the suction pump: the sample must be cooled, filtered and dried before it reaches the apparatus: the water vapor condenses and the acids attack the glass, the moisture falsifies the volume measurements;
• The accuracy and the limits: the Orsat resolves the percentages of the order of 0.1 to 0.2%: it is excellent for the CO2 and the O2 of the preheater and the kiln inlet, it is too coarse for the trace CO of the emission compliance: the Orsat is the workshop instrument of the plant: the daily check of the continuous analyzers, the measurements where the electricity fails, the calibration reference of the modern equipment;
• The chemicals: the potassium hydroxide (the CO2), the alkaline pyrogallol (the O2), the cuprous chloride or the ammoniacal cuprous solution (the CO): the chemicals age, the absorption efficiency falls and the analysis drifts: the fresh solutions are the accuracy of the Orsat: the file includes the preparation procedures of the three solutions with the safety notes: the pyrogallol is the nasty one.

The operator who masters the Orsat understands the gas analysis fundamentally: the modern analyzer is a black box to many, the Orsat is the transparent truth: the plants with the Orsat in the laboratory never lose the capability to verify the process when the electronics fail: the file teaches the complete Orsat practice with the step-by-step procedure, the common errors and the worked analysis examples.

3. The Continuous Analyzers: The Oxygen and the Carbon Monoxide

The process control needs the continuous measurement, and the modern plant measures the O2 and the CO in the minutes, the seconds for the fast loops: the analyzer families of the cement plant:

• The paramagnetic oxygen analyzer: the oxygen is paramagnetic, attracted by the magnetic field, most other gases are diamagnetic: the analyzer measures the magnetic susceptibility of the sample: the O2 concentration: the paramagnetic cell is fast, stable and long-lived, the standard of the industry for the O2: the zero and the span calibration with the bottled gases keeps it honest;
• The zirconia oxygen cell: the solid electrolyte cell heated to 700 to 800 degrees Celsius, the Nernst voltage across the cell: the oxygen partial pressure difference between the sample and the reference air: the zirconia probe goes directly into the duct, no sampling system, the fastest response of all: the probe versions for the high temperatures and the dust: the calibration by the reference gas, the cell aging monitored by the internal diagnostics;
• The infrared (NDIR) CO and CO2 analyzer: the nondispersive infrared absorption: the CO2 and the CO absorb the infrared at their characteristic wavelengths: the detector measures the absorption: the NDIR analyzer needs the clean, dry sample and the regular calibration: the interferents (the water vapor, the CO2 in the CO channel) are compensated in the modern instruments;
• The electrochemical cells: the small portable instruments and the emission monitors: the CO and the O2 cells: the low cost, the simple maintenance, the limited lifetime of the cells (1 to 3 years) and the cross-sensitivity to the other gases: the electrochemical analyzers are the instruments of the spot checks and the portable surveys.

The analyzer selection follows the service: the kiln inlet O2 is the job of the paramagnetic or the zirconia analyzer, the CO of the NDIR: the file includes the analyzer comparison table (the principle, the response time, the maintenance, the cost, the lifetime) which the plant uses for the replacement decisions: the analyzer is the instrument of the process, and the right analyzer in the right service is the first half of the reliable gas analysis.

4. The Sampling System: The Heart of the Reliability

The engineers of the gas analysis have a saying: the analyzer is reliable, the sampling system is the problem: the cement process gases are dirty: the dust, the moisture, the alkalies, the sulfur acids: the sample must be extracted, filtered, dried and cooled before the analyzer sees it, and every step of the preparation is a failure opportunity.

• The probe: the stainless steel or the ceramic probe inserted into the duct: the probe tip sits where the gas is representative, not in the dead zone of the wall: the probe purging with the instrument air clears the dust periodically: the probe of the kiln inlet needs the cooling (the water or the air jacket) because the gas temperature reaches 800 to 1100 degrees Celsius;
• The dust filter: the ceramic or the sintered metal filter protects the sampling line: the filter plugs with the dust and the flow falls: the backpulsing filter assemblies clean themselves: the filter element replacement is the most frequent maintenance of the sampling system: the pressure gauges across the filter tell the truth about the plugging;
• The condensation trap and the dryer: the water vapor condenses in the cool line: the condensate dilutes the sample and the acids attack the downstream parts: the cyclone separator, the cooler (the Peltier cooler of the modern systems) and the final moisture trap dry the sample to the dew point below the ambient temperature: the drainage of the trap must never be forgotten, the flooded trap ruins the readings;
• The sample pump and the flow: the diaphragm pump draws the sample through the whole system at the constant flow: the flow meter and the rotameter show the health of the line: the flow falls as the filter plugs, and the analyzer with the falling flow reads the stale gas: the flow alarm is the cheapest safeguard of the entire system;
• The heated line: the sample line heated to 150 to 180 degrees Celsius prevents the condensation of the water and the acids between the probe and the analyzer cabinet: the cold line in the winter is the classic failure of the gas analysis: the file documents the heat tracing specifications and the temperature monitoring.

The sampling system of the cement plant is the largest maintenance item of the gas analysis, and the file teaches its complete engineering: the probe design, the filter selection, the flow calculations, the troubleshooting: the plant that masters the sampling system masters the gas analysis: the analyzer behind the clean sample is the honest analyzer.

5. The Kiln Inlet and the Kiln Exit Gas: The Burning Zone Through the Gas

The most important measurement point of the cement plant is the kiln inlet: the gas there carries the direct signature of the burning zone: the gas analysis at the kiln inlet is the operator’s view into the flame, and the readings must be interpreted in the context of the process.

• The oxygen at the kiln inlet: the excess oxygen of the combustion: the 1.5 to 3.5% typical range: the low oxygen means the reduced combustion, the high oxygen means the wasted fuel and the higher heat losses: the operator adjusts the primary air, the ID fan and the fuel to hold the target: the oxygen responds to the fuel rate within minutes and the control loops of the modern plants close on it;
• The carbon monoxide at the kiln inlet: the incomplete combustion: the CO rises when the oxygen falls, the flame chokes or the fuel quality changes: the high CO means the reduced conditions in the kiln: the reduced clinker: the green core, the free lime problems, the sulfates decomposed: the CO also signals the fire risk at the preheater and the ESP: the alarm limits of the CO (typically 0.3 to 0.5% for the kiln inlet) protect the plant from the explosion;
• The CO2 at the kiln inlet: the balance gas of the calcination and the combustion: the CO2 content of the kiln inlet gas runs 20 to 30% and depends on the calcination degree at the kiln inlet: the precalciner kilns show the higher CO2 because the calcination happens in the preheater: the CO2 reading cross-checks the oxygen and the fuel balance;
• The interpretation pair: the O2 and the CO together form the combustion triangle: the operator watches the pair on the same screen: the oxygen falling with the CO stable means the combustion is good with the less excess air, the oxygen falling with the CO rising means the combustion is choking: the file includes the interpretation table of the O2-CO combinations and the recommended actions for each;
• The NOx as the burning zone mirror: the NOx forms in the high-temperature zones of the flame: the NOx rises with the burning zone temperature: the NOx reading is the mirror of the flame: the operators use the NOx trend together with the kiln shell temperatures and the free lime for the burning zone control: the NOx also carries the emission limits of the plant.

The kiln inlet is the harshest measuring point of the plant: the dust, the alkalies, the 800-1100 degrees: the equipment there must be the best of the plant, and the file includes the complete specification of the kiln inlet sampling and analysis station: the cooling, the filtration, the purging and the maintenance schedule.

6. The Preheater Gas Analysis: The Calcination and the Circulation

The preheater tower is the chemistry lab of the process, and its gases tell the calcination story: the measurement points of the tower, from the bottom to the top, form the vertical profile of the process.

• The calciner gas: the calciner operates with its own combustion and its own oxygen control: the calciner outlet oxygen of 1.5 to 4% typical: the calcination degree of the material leaving the calciner depends on the calciner oxygen and the fuel rate: the gas analysis of the calciner outlet is the control input of the calciner fuel;
• The cyclone gas temperatures and the gas distribution: the CO2 profile across the tower reflects the calcination progression: the gas analysis at the intermediate stages (the O2 and the CO2) confirms the gas distribution between the kiln and the calciner: the imbalanced distribution shows up in the oxygen readings of the individual strings of the multi-string preheaters: the file includes the gas balance calculation method of the multi-string tower;
• The alkali and the sulfur circulation: the volatiles (the alkalis and the sulfur) evaporate in the burning zone and condense in the upper stages: the circulation loops concentrate them: the SO2 at the preheater outlet reflects the raw material sulfur and the circulation strength: the gas analysis at the tower top with the material sampling gives the circulation picture: the plants fighting the alkali loops use the SO2 and the temperature profiles together;
• The CO2 measurement at the preheater: the CO2 percentage at the preheater outlet (the stack gas after the tower) around 25 to 33% depending on the raw material carbonate and the fuel: the CO2 reading combined with the raw meal feed and the fuel flow closes the carbon balance of the tower: the leaky ducts and the false air dilute the CO2: the false air audit of the tower uses the CO2 and the O2 readings at the successive points: the file includes the false air calculation procedure of the preheater.

The preheater gas analysis is the measurement of the heat and the chemistry exchange: the plant that reads the tower gases knows the calcination, the circulation and the false air, the three hidden costs of the tower: the file treats the preheater gas measurement as the complete chapter with the measuring points diagram, the reference values and the interpretation tables.

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7. The Coal Mill Gas: The Explosion Protection

The coal grinding is the most dangerous gas analysis service of the cement plant: the coal dust explodes when the oxygen, the dust concentration and the ignition source meet: the gas analysis of the coal mill is the safety system, and its reliability is the life insurance of the plant.

• The oxygen measurement of the coal mill: the oxygen of the mill outlet and the filter is held below the explosion limit: the typical alarm level of 12% O2 at the filter, with the working range 8 to 11%: the oxygen rises when the inert gas (the hot kiln gas) supply fails or the dilution drops: the rising oxygen trend is the first alarm of the danger, long before the dust concentration becomes critical;
• The CO measurement of the coal mill: the carbon monoxide indicates the smoldering in the mill, the classifier or the filter: the coal dust smolders inside the deposits and the CO rises before the visible fire: the CO alarm at the filter (typical 0.1 to 0.2 % depending on the plant) triggers the automatic nitrogen purge and the mill stop: the CO is the smoke detector of the coal grinding;
• The measurement points: the mill inlet (the oxygen of the inert gas), the mill outlet (the oxygen and the CO), the filter (the oxygen and the CO), the coal silo (the CO for the fire detection in the silo): the silo monitoring with the CO and the temperature probes is the standard of the industry: the silo CO rises before the visible fire and gives the hours of the warning;
• The extraction and the purge systems: the nitrogen inerting at the mill and at the filter, the CO2 extinguishing at the silo: the gas analysis interlocks with the inerting valves: the analyzer failure must fail-safe: the safety interlock logic of the coal mill is the subject of the entire section of the file with the complete logic diagrams.

The coal gas analysis is the discipline of the drilling: the analyzers of the coal mill are tested weekly, the calibration verified, the redundancy (the two analyzers at the critical points) accepted as the standard: the plant that treats the coal safety gas like any other instrument measures the results in the missed disasters, the invisible: the file covers the complete coal gas safety package: the limits, the interlocks, the testing schedules and the incident investigation method.

8. The Emission Monitoring: The Stack and the Compliance

The stack gases of the cement plant are the subject of the emission regulations: the limits of the dust, the SO2, the NOx, the CO and the total organic carbon: the continuous emission monitoring system (CEMS) measures the stack gas and reports to the authority: the compliance chapter of the file covers the complete CEMS practice.

• The measurement train of the CEMS: the dust monitor (the light scattering or the radiometry), the SO2 analyzer (the NDIR or the UV), the NOx analyzer (the chemiluminescence or the UV: the NO2 conversion), the O2 analyzer for the reference (the oxygen basis of the emission limits), the flow meter and the temperature-pressure probes: the data logger stores the averages and the reports;
• The reference values of the limits: the European and the national limits vary, typical limits expressed in mg/Nm3 at 10% O2: the plant must know its own limits: the file does not pretend to give the normative limits of the world, it teaches the logic of the standards (the reference oxygen, the standard conditions, the averaging periods) so the engineer converts the readings correctly: the conversion of the measured values to the reference oxygen basis is the calculation the file teaches with the worked examples;
• The calibration and the verification: the CEMS is calibrated with the certified test gases (the zero and the span), the linearity tests with the 5-point calibration, the annual independent verification by the accredited body: the calibration record is the compliance record: the file includes the calibration schedule and the documentation templates;
• The correlation with the process: the SO2 emission peaks correlate with the raw material sulfur and the lime feed, the NOx with the burning zone temperature: the operator uses the CEMS readings not only for the compliance but for the process: the SNCR injection is controlled by the NOx reading: the SO2 by the lime dosing if the plant desulfurizes;
• The maintenance of the CEMS: the filters, the pumps, the flow, the calibration gases: the scheduled maintenance of the CEMS is not optional: the authority counts the downtime of the CEMS as the non-compliance: the file includes the maintenance schedule of the complete CEMS.

The emission monitoring is the legal face of the plant, and the legal face must be honest: the file covers the CEMS engineering from the probe to the report, and the engineer of the plant will find the answers of the measurement, the testing and the compliance logic in the tables and the procedures of the chapter.

9. The Gas Analysis Instruments: The Maintenance and the Calibration

The analyzer is the instrument of the thousand details: the calibration, the zero and span, the cleanliness, the drift: the maintenance of the gas analyzers is the craft of the plant, and the file devotes its longest chapter to the craft:

• The zero and span calibration: the calibration with the test gases: the zero gas (the nitrogen or the clean air for the CO2 free measurements) and the span gas (the certified concentration): the calibration procedure per analyzer type: the frequency (the daily for the critical, the weekly for the others), the documentation (the calibration log, the drift book), the drift of the analyzer detected by the calibration is the health report of the instrument;
• The cell and the optical path care: the infrared analyzers need the clean cuvette windows: the dust and the deposits on the windows absorb the infrared and the readings drift: the window cleaning, the gas cell inspection, the signal quality (the internal zero reference of the modern NDIR): the file includes the cleaning procedures of the optical paths;
• The electrochemical cell replacement: the cells age, the response slows and the drift grows: the replacement interval (1 to 3 years) and the diagnostics: the cell replacement is the routine of the portable instruments: the file CD: the cell types and the spares;
• The sample flow and the leak checks: the flow meter reading and the leak testing of the complete sampling train: the leaking line dilutes the sample, the leaking cap: the flow: the leak test procedure (the check: the file includes the leak testing of the sampling system with the soap and the pressure test);
• The data and the interface: the analog 4-20 mA signals, the digital fieldbuses, the data logging: the analyzer output to the DCS: the ranges and the alarm settings: the range: the maintenance of the data: the archives of the gas analysis for the process investigations and the compliance.

The reliability of the gas analysis is the product of the maintenance discipline: the plant that treats the analyzer like the motor (the schedule, the records, the spares) gets the decades of the service: the file includes the complete maintenance program of the gas analysis equipment with the checklists, the intervals and the spare parts lists.

10. The Gas Analysis in the Troubleshooting of the Process

The gas analysis is not only the control instrument, it is the diagnostic instrument: the reading tells the troubles of the process and the plant saves the days of the investigation by reading the gas profile first:

• The buildup and the blockage in the preheater: the restricted stage (the cyclone plugging) shows up as the pressure rise and the oxygen imbalance: the blocked stages restrict the gas flow and the false air enters through the damaged doors: the gas profile of the tower (the O2 and the CO2 at each stage) locates the leak and the restriction: the file teaches the gas profiling method for the tower troubleshooting;
• The ring and the snowman at the kiln: the kiln rings restrict the gas flow and the oxygen at the kiln inlet falls while the kiln exit temperature falls: the engineer reads the unusual O2-CO2 pair as the flow restriction and confirms the ring with the kiln shell temperature profile: the gas analysis is the front line of the ring detection;
• The flame pattern and the combustion quality: the pulverized coal combustion depends on the burner adjustment: the CO and the O2 at the kiln inlet change with the burner settings: the operator: the flame: the kiln: the gas analysis is the measurable feedback of the burner tuning: the plants tune the burners with the gas analysis campaign and the coal analysis from the mill;
• The secondary combustion and the CO at the ESP: the CO in the kiln gases forms the combustible mixture with the air in the dust collector: the ESP explosion prevention relies on the CO measurement at the ESP inlet and the interlock (the power cut at the CO limit): the CO measurement there is the safety instrument, its maintenance is the matter of the plant rules: the file includes the complete recommendations of the CO monitoring at the ESP;
• The material balance and the mass balance: the gas analysis closes the oxygen and the carbon balances of the process: the balances verify the flow measurements: the false air in the system, the dust losses, the combustion incompleteness: the file includes the complete mass balance procedure of the kiln system with the gas analysis inputs.

The gas profile of the plant is the fingerprint of the process, and the changes of the profile are the history of the operations: the plant that keeps the gas analysis records and reads them against the process events finds the correlations the industry never documents: the troubleshooting power of the gas analysis is only limited by the logic the engineer applies to the numbers.

11. The Gas Analysis and the Quality of the Clinker

The burning conditions of the clinker are the temperature and the atmosphere of the burning zone: the atmosphere is the gas composition: the reduced conditions of the kiln destroy the clinker quality in the ways the chemistry of the clinker shows late: the gas analysis is the early detection of the reduced burning.

• The reduced burning and the clinker: the oxygen below 1% and the CO raised: the reduced conditions: the ferric iron reduces to the ferrous form in the clinker melt: the clinker darkens, the alite formation suffers, the free lime rises: the reduced clinker sulfates problem: the clinker quality: the gas analysis detects the reduced burning minutes after it starts, the cement quality tests hours later: the operator wins the quality by the gas analysis;
• The fuel and the burnout: the fuel quality changes (the coal, the petcoke, the alternative fuels) show in the combustion: the heavier fuels need the more oxygen and the longer flame: the O2 at the kiln inlet: the operator adjusts the fuel burn: the gas analysis is the bridge between the fuel laboratory results and the burning process;
• The coating and the refractory protection: the burning zone coating needs the controlled temperature and the controlled atmosphere: the flapping coating (the falling coating) the temperature: the gas analysis: the kiln inlet NOx and the shell temperature monitoring together define the coating management: the file includes the practical coating management chapter which combines the gas analysis, the shell scanning and the clinker analysis;
• The clinker in the cooler: the cooler vent air and the secondary air: the cooler is the gas measurement not always: the oxygen of the cooler air: the kiln primary: the balances: the file teaches the cooler gas measurement: the improvement of the secondary air temperature and the fuel saving of the combustion air.

The quality of the clinker is made in the burning zone, and the burning zone is read through the gas: the gas analysis is the most direct quality instrument of the kiln, ahead of the clinker chemistries that arrive hours later: the engineer who watches the gas protects the quality of the cement before the laboratory ever sees the sample.

12. The Maintenance and the Troubleshooting of the Gas Analysis Equipment

The gas analyzers and their sampling systems fail in the predictable patterns, and the maintenance plan of the plant handles them in the order below: the troubleshooting table condenses the experience of the industry into the working tool of the shift:

The complete troubleshooting chapter of the file includes the detailed tables per analyzer type (paramagnetic, zirconia, NDIR, electrochemical), the failure codes of the common instruments and the recommended spare parts stock of the plant: the gas lab of the plant works with the file on the table, and the time of the diagnosis shrinks from the hours to the minutes.

The gas analysis is the combined craft of the mechanical sampling, the chemical measurement and the process interpretation: the file trains the engineer in the complete circle: the probe design, the analyzer, the calibration, the interpretation and the troubleshooting: the professional of the gas analysis is the ownership of the complete system, and the file is the textbook of that craft.

13. The Organization of the Gas Analysis in the Plant

The gas analysis is not only the equipment: it is the organization: the plants that get the decades of the reliable service from their analyzers organize the discipline around the equipment:

• The owner of the instruments: the appointed instrument engineer owns the complete gas analysis: the equipment list, the calibration records, the spare parts, the vendor contacts: the clear ownership is the first organizational rule: the unowned instrument is the abandoned instrument;
• The maintenance schedules: the weekly and monthly checklists printed for the shifts: the cleanliness checks, the calibration records: the file provides the complete schedule templates that the plants copy to their log books;
• The spare parts and the first line: the spare analyzers for the critical points (the kiln inlet, the coal mill), the spare cells, the spare filters, the spare pumps: the critical points of the plant cannot wait for the vendor: the file includes the recommended spare parts list with the quantities of the typical plant;
• The training: the shift operators and the maintenance men trained in the sampling and the calibration: the training program of the file: the operators know the readings meaning, the technicians know the equipment: the training cycle of the plant (the refresher: the new technology) documented in the file;
• The records: the calibration logs, the alarm events, the analyzer downtime, the drift history: the records drive the improvement: the file provides the record templates with the minimum content that the plants and the auditors expect: the gas analysis records of a mature plant tell the story of the equipment: purchase, the operations, the failures, the replacements: the story is the memory of the plant.

The organization of the gas analysis turns the collection of the instruments into the plant’s system of the knowledge: the operator opens the screen and the history of the gas shows the process today versus yesterday versus last year: the trends, the pattern recognition: the plant data: the gas analysis as the information of the plant: the intelligence of the process: the file closes the chapter with the modern practice: the gas analysis in the process control rooms, the trend software and the KPI of the analysis system: the uptime of the analyzers.

The Frequently Asked Questions

What is the most important gas measurement of the cement plant?

The oxygen at the kiln inlet: it is the direct measurement of the combustion conditions, it drives the fuel and the air control, and its failure or its absence is felt immediately in the clinker quality and the fuel consumption: the CO at the kiln inlet is the second, for the reduced conditions and the safety: the coal mill oxygen and CO for the safety of the coal grinding follows: the gas analysis hierarchy of the plant starts with these three.

Why does the CO measurement matter for the explosion safety?

The CO indicates the incomplete combustion and the reducing atmosphere: in the dusty gas streams (the preheater outlet, the ESP inlet, the coal mill) the CO rises before the fire or the smoldering: the CO alarm interlocks the spark suppression, the power cut of the ESP and the inerting of the mill: the CO measurement is the early warning that gives the plant the minutes between the beginning and the disaster: the price of the CO analyzer is nothing against the reconstruction of the plant.

How often should the analyzers be calibrated?

The critical analyzers (the kiln inlet, the coal mill) every day or every shift: the common process analyzers weekly, the CEMS according to the authority rules (typically twice a year with the quarterly tests): the calibration with the bottled zero and span gases, the records kept: the drift beyond the limits launches the investigation: the calibration is also the opportunity to check the whole sampling system: the instrument health.

Can the sampling system be simplified?

The engineers of the cement industry have tried for decades: the direct-installed probes (the zirconia) work for the clean services like the kiln outlet gas and the preheater: at the kiln inlet and the dust-laden points the full sampling train (the cooled probe, the filter, the dryer) is unavoidable: the simplified systems sacrifice the response time and the reliability: the rule of thumb of the file: the higher the dust and the temperature, the more preparation the sample needs.

Which gases are measured with the portable instruments?

The portable emission monitors cover O2, CO2, CO, NOx, SO2 with the electrochemical and the NDIR cells: the portable instrument is used for the spot checks of the process, the commissioning of the new points, the verification of the fixed analyzers and the false air measurements: the portable is the reference of the plant when the sampling is doubted: the portable and the fixed instruments support each other and the file includes their comparison table.

What is the “reference oxygen” in the emission limits?

The emission limits of the cement plants are often expressed at the reference oxygen concentration (typically 10% O2): the measured pollutant concentration is mathematically converted to what it would be if the flue gas were diluted to the 10% oxygen: the conversion accounts for the dilution by the false air: the file teaches the conversion formula: the emissions at the real oxygen: the compliance depends on understanding the reference: the number of the stack: the number of the compliance.

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.