Flames And Burners: Complete Technical Guide

Flames and burners: the flame of the rotary kiln is the most powerful tool in the cement process: the tool that shapes the raw meal into the clinker: the flame: the luminous jet, the 1,600–1,800°C gas cone, the engine of the sintering: the burner: the lance that delivers the fuel and shapes the air: the multi-channel nozzle, the swirl, the momentum, the primary air: the flame length, the shape and the temperature decide the clinker quality, the refractory life, the fuel consumption and the NOx emissions: the discipline of the flames and the burners is half physics and half craft: this file is the complete manual of the burning: from the chemistry of the flame to the adjustment of the nozzle in the kiln.

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 flame and burner chapter with its burner drawings, the nozzle diagrams, the adjustment tables and the combustion calculation sheets: the same library that holds the kiln design, the firing systems and the refractory chapters: the engineer of the package uses the three files together: this article walks the flame file page by page.

This article follows the file structure: the flame physics first, the burner design second, the flame types third, the adjustment fourth, the clinker and the environmental control last, and the answers of the frequently asked questions at the end: the reader with the document in hand can follow the sections one by one or jump to the diagram of his own burner.

1. The Flame of the Rotary Kiln: The Role in the Burning Process

The flame in the rotary kiln is not the flame of the household burner: it is an industrial device with a precise job: the heat for the burning zone: the hot core radiates to the material bed and to the refractory, and the radiation is the dominant mode of the heat transfer at the kiln temperatures:

• The heat duty: the flame supplies roughly the whole heat of the burning process: the precalcined meal enters the kiln at 850–900°C and must reach the clinkering temperature of 1,350–1,450°C with the liquid phase forming: the flame is the furnace of that transformation;
• The temperature field: the adiabatic flame temperature of the coal-air mixture is about 1,800–2,000°C; the actual gas temperatures in the burning zone run 1,600–1,800°C: the peak of the process: the only place in the plant that hot;
• The radiation: the glowing particles of the coal char and the soot radiate to the material and the lining: the emissivity of the flame is high because of the particles: the “luminous flame” is the radiating flame: the radiative flux is the practical number of the burning zone;
• The residence and the mix: the flame must burn out the fuel completely within the kiln volume: the char particles need the temperature, the oxygen and the time: the flame length must fit the burning zone and the coating:

THE FLAME IS THE ENGINE: the kiln is the boiler and the flame is the fire: the production rate of the kiln is ultimately limited by the heat release of the flame: the engineer reads the flame as the meter of the burning: too long, the heat spreads into the transition zone: too short, the refractory of the burning zone suffers: the balance is the art of the burner adjustment: the whole file is the manual of that art.

2. The Chemistry of the Combustion: The Flame of the Coal

The flame of the cement kiln burns mostly the pulverized coal: the combustion steps of the particle:

• The devolatilization: the coal particle heats, the volatiles release from the particle: the hydrocarbon gases burn with the yellow diffusion flame: the stage takes the first hundredths of a second at the ignition temperature;
• The ignition: the vapor mixture reaches the auto-ignition temperature and the flame anchors: the ignition is helped by the recirculation zone of the hot gas behind the burner: the recirculation is the pilot of the industrial flame;
• The char combustion: after the volatiles, the fixed carbon burns in the solid/gas reaction with the oxygen: the slowest step: the char burn-out requires the temperature above 1,000°C and the time: the long tail of the flame is the char burning;
• The complete combustion: the C and the H to the CO2 and the H2O: the O2 at the kiln exit of 1–3% proves the completion: the CO at the high level signals the partial combustion and the waste of fuel;
• The air requirement: the stoichiometric air of the coal is about 10–12 Nm³/kg: the excess air factor of the kiln 1.05–1.10: the combustion air of the plant enters as the primary (through the burner) and the secondary (from the cooler through the hood):

THE TIMELINE OF THE PARTICLE: the coal particle fires in the milliseconds: the volatile front ignites first, the char follows, the ash remains: the airborne structure of the flame is the superposition of these particle life cycles: the fast-burning volatile front and the slower char field: the practical consequence: the fine coal burns fast and the flame shortens: the coarse coal travels with the char field and the flame lengthens: the file connects the mill fineness to the flame: the fineness is a flame instrument.

3. The Aerodynamics of the Burner: The Jet and the Recirculation

The burner is a jet device: the aerodynamics produces the flame of the correct length and the correct entrainment:

• The jet: the high-velocity stream from the burner nozzle: the primary air and the fuel leave the lance at 100–300 m/s, the modern burners at the top of that range: the jet momentum is the ratio of the primary mass flow and the normal velocity;
• The entrainment: the jet draws in the surrounding secondary air at the conical boundary: the entrainment rate grows with the nozzle velocity and the nozzle diameter: the mix of the fuel with the hot secondary air: the mixing at 1.5–2.5 times the flame length from their origin all around:
• The recirculation zone: the core of the flame behind the nozzle: the region of the low pressure that returns the hot gas: the heat returns to the newly released fuel: the self-flaming of the coal particles: the flame anchor: the loss of the recirculation = the flame lifts and blows away;
• The swirl: the tangential component given by the swirl registers of the vanes: the centrifugal swirler: the rotating flame cone widens the angle: the swirl number decides the radial spread: the swirl up: the flame wider, the recirculation stronger, the NOx higher, the mixing better:
• The momentum of the jet: the product of the primary flow and the velocity: the single most important burner number: the high momentum: the long flame: the low: the short: the file: the momentum calculation of the burner:

THE BURNER AERODYNAMICS: the designer plays the three instruments: the mass flow the primary air, the swirl angle, the nozzle geometry: the three create the recirculation, the entrainment and the flame shape: the modern multi-channel burners make each instrument independent: the axial channel, the swirl channel and the central fuel pipe are all adjustable from the control room or the pivot: the same burner body becomes the different flame shapes in 15 minutes: the craft of the file is the knowledge of the three variables and their interaction.

4. The Burner Design: The Multi-Channel Structure

The main burner of the cement kiln: the concentric pipes of the flame lance:

• The fuel channel: the central pipe or the annular ring: the pulverized coal conveyed in the primary air, the natural gas through the inner lance, the liquid fuel through the atomizer: the fuel variety: the pipe change in the workshop:
• The axial air channel: the inner annulus: the straight high-velocity air: the jet core: the momentum donor: the axial channel carries up to half the primary air: the adjustment of this flow the flame length:
• The swirl channel: the outer annulus with the tangential vanes: the rotating flow: the flame spread: the milled: the radial: the swirl vane angle adjustable: mechanically to the pilot: the air of the rotation:
• Shutter, spacers, and the clearance: the small gaps between the channels: the startup flame, the cooling of the tip: the “dirty” air of the fan: the file: the parts diagram:
• The tip: the burner nozzle: the last piece towards the kiln: the tip: the only hot part: the ceramic or the metallic: the wear: the sacrificial: the file: the tip design: the cone and the slots:

THE MULTI-CHANNEL (or the “multi-jet”): the burner obtains the shape of the flame via the channels: the contents of the coal vary with the position: the pivot: the “burner in” the burner to the kiln axis: the file: the diagrams of the last-generation burners: the multi-air nozzles: the “tongue” “the flat bed”: the burner: the parts: The complete drawing of the burner in the annex of the file: the airflow path, the vanes and the pivot.

5. The Flame Types: The Shape and the Use

The flame of the cement kiln comes in the working families, each with the job:

• The standard flame: the balanced: the length about 10–25% of the kiln length: the maximum at the sintering zone: the stable and the friendly: the work: the majority of the kilns:
• The short flame: the intense: the high momentum, the strong swirl: the hot spot short: the clinker sintering concentrated: the refractory stressed at the zone: the heat: the NOx: used for the hot clinker with the short cement:
• The long flame: the gentle: the low momentum: the heat spread over the length: the raw feed enters the zone covered: the alkaline at the low: the extended: the lower refractory temperature: the slower sintering: the long: the dust: the combination of the fuel with the ash:
• The impingement flame: the flame reaching the kiln wall or the charge: the danger: the refractory spalling, the ring growth, the coating damage: the deflection by the swirler, the position and the aiming:
• The visual classification: the luminous, the semi-luminous and the blue diffusion flame: the coal flame luminous: the natural gas flame blue: the visual sign of the combustion:

THE FLAME THIS: the operator cannot see the “length” in the flames directly: he infers from the kiln shell scanner, the temperature profile and the clinker: the file: the classification: the flame types with the photos of the industrial flames and the descriptions: the training deck of the investigation: the flame of the plant: the “the video”: the record: the burner: every startup: the file: the guide of the interpretation of the thermal image.

6. The Primary Air, the Secondary Air and the Momentum

The air vocabulary of the burning system: the two names and the balance:

• The primary air: the 6–10% of the total combustion air: the carrier of the coal: the burner momentum: the most controllable: the modern burners run at the low primary (the lower the primary the higher the kiln gas efficiency, the more the air the kiln and the better the NOx):
• The secondary air: the 90–94%: from the cooler, at 800–1,000°C: enters the kiln around the burner from the hood: the secondary is the wind of the cooler: the flame relies on the healthy flow: the file: the cooler performance is the burner context:
• The tertiary air: the third stream going not to the kiln but to the calciner: the lateral pipe: the calciner combustion: the distribution of the air between the kiln and the calciner: the ratio: the burning:
• The velocity and the momentum: the primary at 100–300 m/s vs the secondary at the hood at the few m/s: the jet: the momentum is the driving: the mixing of the low-velocity secondary into the high-velocity primary and coal: the file: the momentum calculation: the design:
• The false air: the uncontrollable inflow through the seals, the chutes and the openings: the cold air around the flame: the combustion: the gas volume and the energy: the false air caused by the seals and the flap: the file: the false air menu of the hood:

THE AIR MIX: the plant manages the three streams and the false air: the numbers: the secondary 90%, the primary 8%, the change: the philosophy of the modern burner: “eat far from the primary air” (the low momentum? actually the opposite: the high momentum low mass): the argon: the modern operation; the kiln works: the file: the diagrams: the hood: the flow: the air: the section: the numbers: the file.

7. The Ignition and the Flame Stability: The Anchor

The flame must stay where it belongs: the stability of the flame: the facts:

• The ignition temperature: the pulverized coal: the ~700–800°C for the hard coal in the air: the gas: the mixture: the pilot: the region: the flame: the recirculation: the hot gas: the temperature above the ignition:
• The premixing: the coal arrives with the same pipe as the primary: the air is “primary” (the transport): the vapor: the dilution: the mixture enters the burner chamber: the burning that starts: the return of the recirculating hot stream: the re-ignition of each particle:
• The lift and the blow-off: when the velocity of the air exceeds the burning velocity, the flame lifts off the nozzle: the flame anchors downwind: the unstable: the extinction: the primary air velocity must stay between the lift-off and the flashback limits: the file: the flame-stability envelope:
• The flashback: the flame propagates back into the burner: the tipp heat, the burner damage: the flashback of the premixed gas at the low velocity: the swirl: the file: the flashback prevention:
• The pilot / the starting burner: the ignition at the start: the oil burner, the flame: the gas pilot: the startup atomization: the file: the light-up procedure: the interlock: the flame temperature:

THE STABILITY: the flame: the primary flow: the laminar? The flame: the central: the calculation: the “lift-off” speed of the mixture: the file: the tables: the extinguishing: the flame: the file: the direct: the knowledge: the “the flame is the anchor”: the basic.

8. The Flame and the Clinker: The Sintering Process

The flame: the quality: the clinker: the products of the burning:

• The clinkering: at the burning-zone temperature the raw meal particles of the clinker phases: the clinkering: the melt: begins at the ~1,300°C: the clinker structure forms in the flame zone;
• The sintering rate: the reaction rate of the clinker formation rises exponentially with the temperature: the flame peak in the right position of the kiln: the reaction: the higher: the production: the burning zone, “the bumper”: the throughput set by the flame heat release:
• The zones: the kiln: the decarbonation zone (the pre-hot), the transition zone (the 900–1,200°C), the burning zone of the flame (1,300–1,450°C), the cooling zone: the flame position relates the zones: the flame too far back: the raw moves into the zone un-burned: too near the feed: the “overburn”:
• The coat and refractory: the flame: the coating of the clinker on the refractory bricks: the protective layer: the flame: the salt: the refractory ladle: the flame shape on the bricks: the file: the refractory: the relationship:
• The clinker characteristics: the flame: the burning: the cold/ sous-burned: the underburn (the pasty, dusty, the free lime high): the overburn (the dense, the fused): the correct: the file: the structure-property: the cement: the clinker quality: the flame:

THE CLINKER AS THE FLAME OUTPUT: the kiln operation: the burning zone: the flame: the temperature the man: the clinker: the free lime: the norms: the file: the tables: the ideal temperature of the clinker: the nodule: the flame tuning: the quality: the file: the relation: the practical: “the flame: the quality: the energy”: the cement of the package: the fire: the clinker.

9. The Flame: an Operation of the Burner

The operation of the burner: the daily angle: the field practice:

• The faults: the very long (the fuel burning in the whole kiln), the very short (the refractory overheated), the flaring (the impingement), the ragged (the unstable), the smoky: the seven faults and their signs: the file: the fault table:
• The flame color: the whitish-yellow the hottest, the lemon the normal, the dark red the cooling: the color drift: the archive: the thermal: the changes: the file: the color chart of the flame:
• The luminous flame cameras: the industrial kiln cameras (the CCTV with the shading) in the hood: the view of the flame in the control room: the temperature maps of the field? The pieces: the flame video: the deep: the pull out the data: the analysis: the file: the camera: the instrument:
• The inspection: the burner tip: the entry: the wear: the deposits: the “the knife”: the checklist: the file: the burner inspection log: the nozzle replacement: the interval: the peek:
• The records: the burner log book: the adjustment, the air, the position, the fuel, the observation: the history of the flame: the file: the form: the trace of the fire: the file:

THE BURN: the operator: the day: the flame: the warm-up, the setting: the change: the inspection: the recording: the file: the manual: the check sheets: the “the camera” the monitoring: the practice of the burner: the discipline: the file: the passion: the same.

10. The Burner Design and the Flame for the NOx Reduction

The flame of the kiln produces the nitrogen oxide: the design of the flame is the first NOx control:

• The NOx mechanisms: the thermal NOx at the flame (Zeldovich: T > 1,400°C), the fuel NOx from the nitrogen of the fuel, the prompt NOx: the kiln flame: the hotspot: the NOx: the file: the mechanisms in the diagram:
• The low-NOx burner: the staged combustion: the air is injected stepwise so the “initial flame” burns rich and the oxygen deficit suppresses the thermal NOx: the swirl: the flame recirculation: the internal: the file: the low-NOx at the kiln:
• The conservation: mix and filter: the low-O2 operation near the 1.5–2% at the kiln exit: the thermal NOx: the fuel: the file: the window of the O2 and the NOx:
• The MNDC (Mid-NOx): the calciner and the “re-burn” the kiln-gas NOx at the calciner: the reduction of the total: the “the whole system NOx” file:
• The after-burn (SNCR): the ammonia/urea injection in the “the T window” of the preheater: the upstream, after the flame: the combination: the flame + SNCR the full control: the file:

THE NOx: the modern kiln: the objective of the flame: the low primary: the elephant: the cooler and the kiln: the “the harder the burner” the puzzle: the file: the burn: the NOx: the emissions: the file: the combustion: the complete: the flame: the NOx: the environment: the file: the design: the flame: the NO number: the fire: the NOx of the kiln is the both the process and the environment.

11. The Calculation Tools of the Flame and the Burner

The workbook part of the file: the calculations of the burning:

• The air demand: The combustion: the stoichiometric: the excess: the primary: the secondary: the total: the kilos of air per kilo of clinker: the entry of the heat balance:
• The flame temperature: the adiabatic (the enthalpy balance of the reactants and the products), the radiative correction to the actual: the estimation: the file: the flame temp calculator:
• The residence time: the kiln charge and the flame: the air: the gas: the retention: the char: the file: the residence calculator:
• The momentum: the ratio of the forces: the burner design: the file: the momentum of the burner: the dimensionless: the file: the formula:
• The NOx calculator: the estimate from the fuel N, the primary/secondary and the O2: the rule of thumb: the file: the expected emission: the control plan

THE TOOLS: the Excel: the “flame design workbook” of the package: the inputs the fuel, the air, the temperature: the outputs the flame, the mass, the heat: the design: the file: the numbers: the engineer: the tools: the project: the check: the vendor: the file: the “complete” the examples: the cement: the file.

12. The Flame and the Kiln Operation: The Records of the Fire

The flame of the plant is an operating instrument with its own records: the operation chapter of the file:

• The flame log: the operator’s record of the flame appearance, the time, the fuel settings, the primary air, the NOx reading: the daily history of the fire: the archive: the file: the log sheet template:
• The shell scanner: the temperature of the whole kiln shell: the map of the hot zones: the peak changes, the hotspot, the coating loss: the flame position projected on the shell: the file: the scanner reading exercise:
• The coating management: the refractory protection by the coating: the flame couples with the coating: the stable coating: the shell safe: the file: the coating review: the shutdown:
• The flame audit: the quarterly review of the flame records with the production data: the tuning history, the fuel changes, the NOx compliance: the improvement plan: the file: the audit template:
• The training with the flame: the kiln simulators and the flame observation practice: the operator’s eye: the file: the training program of the burning:

THE RECORDS: the same discipline as the laboratory: the records convert the visible fire into the analysis: the plant that logs the flame and the settings over the years builds its own operating bible: the file: the record forms: the analysis: the trends: the fire: the data: the professional: the cement: the operation: the flame as the operator’s instrument: the complete: the file: the records: the observation: the file of the package: the professional behavior: the same: the flame: the archive: the “burning book” of the plant.

13. Frequently Asked Questions on the Flames and the Burners

What is the optimum length of the kiln flame?

The flame of the influence: about the quarter of the kiln (the 1/4) with the balance of the kiln: the short kiln and the short flame: no absolute: the design adds the fuel: the refractory: the retentions: the file: the classic: “the flame length = 1.5–2× the kiln diameter”: the file: the practical: the flame: matches the production, the heat: they are within the file: the answer: the length is the local tuning not the universal.

How do I shorten or lengthen my flame?

The flame: the momentum (the primary air velocity): the swirl (the vane) and the fuel: the increase the axial air: the flame longer: the fuel coarser: the flame longer: the increase the swirl: the flame shorter and wider: the file: the list of the settings and their effects on the flame: the one at a time: the record: the file: the trade ladder: the answer: the two knobs of the burner.

The flame rises when the raw meal enters the zone?

The “pushing” the displacement by the colder material: the flame: the hotter zone: the “underfeed the impulse”: check the feed stability: the kiln: the burning zone: the file: the table: the correspondence of the feed: the answer: the flame is steady: the irregular feed: the file.

Can the flame be too hot for the refractory?

Yes: the short-hot flame: the thermal shock: the refractory spalling and the coating loss: the document: the refractory selection: the burning zone: the file: the thermal: the refractory: the flame: the “the brick life”: the practical: the ignition: the film: the DP: the control: the flame: the “the melt” the refractory: the file: the refractory life: the flame: the economical.

The NOx is every higher: the flame does not stay the only culprit?

The NOx: the flame: hot spot: the limestone in the raw feed: the sulfur: the kiln: the flame: the O2: the “the operating point”: the file: the hierarchy: the primary (the flame, the O2), the process (the raw mix), the NO (the SNCR): the answer: the flame dimension first, the others after: the file: the matrix.

The burn: the package contains the burner and the flame workbooks?

Yes: the combustion calculators of the Excel in the file: the air mass, the flame temperature, the retention, the momentum: the burner drawings and the flame photos: the part of the 931 files: the one-time price includes all: the library: the file: the flame: the professional: the controlled: the cement: the pay: the instant download: the $249.99: the PayPal: yes, part of the 931.

14. Conclusion: The Flame, the Toolbox of the Burning

The flame and the burner: the physics and the fire: the coal chemistry, the aerodynamics, the air, the ignition, the flame types, the clinker, the refractory, the NOx and the tools: the flame is not magic: it is the systematic consequence of the numbers: the primary, the swirl, the momentum, the temperature: the engineering of the fire: the file puts exactly that in the hands of the engineer.

The Complete Cement Technical Package (931 files: $249.99 one-time: instant download via the PayPal payment) includes the flame and burner file with the combustion tables, the calculator tools, the burner drawings and the operation checklists: the kiln book, the firing system, the refractory: the complete burning library: the one-time price: the cement professional: the library of the process: the complete knowledge: the fire: the package: the PayPal button: the file today: the burners: the flame: the cement: the complete.

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.