Roller kilns and tunnel kilns are core thermal equipment in the production of building ceramics (tiles), daily-use ceramics, sanitary ceramics, and special ceramics. In the face of dual carbon goals, cost pressures, and the need for quality upgrades, the traditional air-assisted combustion method has exposed pain points such as high energy consumption, large temperature differences, difficult emission control, and product color differences. The introduction of oxygen-enriched/full-oxygen combustion technology is driving ceramic kilns towards precise temperature control, ultimate energy saving, ultra-low emissions, and intelligent firing revolutionary breakthroughs.

4.4.1 Technical Core: Deep Coupling of Oxygen-Enriched/Full-Oxygen Combustion and Ceramic Firing Processes

1. Oxygen-enriched combustion: The oxygen concentration in the combustion air is increased to 23%-60%, reducing inert nitrogen.
2. Full-oxygen combustion: Uses >90% pure oxygen for combustion (more suitable for high-temperature sections or special ceramics).
3. Innovative design of special burners:
   • Flat, wide-flame, low-disturbance burner: Produces thin and wide, uniform temperature flames, perfectly matching the narrow and long cross-section of roller kilns/tunnel kilns, avoiding local over-firing or under-firing of bricks, and eliminating color differences 。
   • Multi-stage combustion low-NOx design: Fuel and oxygen are mixed in stages to suppress local high-temperature zones and effectively control NOx generation.
   • High-temperature, anti-coking nozzle: Adapts to the corrosive environment of ceramic glaze volatiles (lead, zinc, boron compounds).
   • High-speed pulse combustion technology (optional): Improves temperature uniformity and response speed.
4. Intelligent control system: Precisely interlinks oxygen concentration, fuel amount, kiln pressure, and temperature curves in various zones to achieve dynamic optimization of the firing system.

4.4.2 Core Application Scenarios and Transformative Advantages

1. Building ceramics (tiles) roller kiln firing

1. Application: High-temperature firing (1100-1250℃) of polished tiles, glazed tiles, antique tiles, and large/slab tiles.
2. Advantages:
   • Significant energy saving and consumption reduction (15%-35%):
     1. Reduces nitrogen heating and flue gas heat loss (flue gas volume reduced by 30%-70%).
     2. Enhances radiative heat transfer, accelerates heating rate, and shortens the firing cycle 。
     3. Improved waste heat utilization efficiency (high flue gas temperature, small volume, and no nitrogen dilution).
   • Ultimate improvement in product quality:
     1. Temperature difference ≤ ±3℃: Revolutionarily improved kiln internal horizontal/vertical temperature uniformity, basically eliminating color difference, deformation, and dimensional deviation 。
     2. Glaze quality upgrade: More uniform glaze melting, improved gloss, flatness, and stain resistance.
     3. Stable water absorption rate: Consistent biscuit firing degree, better physical properties.
   • Ultra-low emissions, easy to meet standards:
     1. NOx reduction by 60%-85%: Inhibits the generation of thermal NOx, emission concentration stable below 50mg/Nm³ 。
     2. Dust/SOx/CO emission reduction: Complete combustion + sharp reduction in flue gas volume, reduced end-of-pipe treatment costs.
     3. No sulfide odor: Complete combustion avoids the sulfurous odor produced by incomplete fuel combustion.
   • Increased production and efficiency:
     1. Fast heating + short cycle → Kiln speed increased by 5%-15% 。
     2. First-grade rate increased by 3%-8% → reduced downgrading losses.
   • Extended kiln life: Uniform temperature field reduces thermal stress on refractory materials and reduces kiln body deformation.

2. Daily-use ceramics and sanitary ceramics tunnel kilns/roller kilns

1. Application: Biscuit firing and glaze firing of bone china, stoneware, and sanitary ware.
2. Enhanced advantages:
   • Precise atmosphere control: Oxygen-enriched environment makes it easier to achieve a strong oxidizing atmosphere (decarbonization, desulfurization) or a weak reducing atmosphere (metal coloration), ensuring pure and stable glaze color 。
   • Reduced pinholes and black spots: Complete combustion avoids carbon particle deposition; uniform high temperature reduces local over-firing and bubble formation.
   • Reduced firing defects: Cracking and deformation rates are significantly reduced.

3. Special ceramics and electronic ceramics sintering

1. Application: Sintering of alumina/zirconia structural ceramics, silicon nitride substrates, MLCCs, and lithium battery cathode materials.
2. Advantages:
   • Ultra-high purity environment: No nitrogen contamination, avoiding the formation of nitrogen compounds at the grain boundaries of ceramic pieces, Improving electrical/mechanical properties 。
   • Precise temperature-atmosphere synergy: Meets the requirements of complex sintering curves (such as integrated degreasing-sintering-annealing).
   • Inhibiting element volatilization: Fast and uniform sintering reduces the loss of easily volatile components such as ZnO and PbO.

4. Ceramic glaze frit furnace

1. Application: Melting of frit (glass phase).
2. Advantages: Similar to glass melting furnaces, energy-saving, emission reduction, improved melt homogeneity, and reduced bubble impurities.

4.4.3, Application Benefits Overview

4.4.4, Key Risk Points and Solutions

1. Oxygen cost optimization:
   • Risk Points: Oxygen cost accounts for incremental operating costs.
   • Countermeasures:
     1. Adopt VPSA/VSA on-site oxygen generation (low energy consumption, suitable for small and medium-scale);
     2. Precise oxygen supply in different temperature zones (full oxygen in high-temperature zones, enriched oxygen or air in medium and low-temperature zones);
     3. Intelligent control system dynamically adjusts oxygen concentration to match the firing stage;
     4. Utilize Off-peak electricity for oxygen generation to reduce costs.
2. Burner layout and flame control:
   • Risk Points: The roller kiln cross-section is flat, and flame impact on bricks or rollers should be avoided.
   • Countermeasures:
     1. Customized Flat wide flame low momentum burner ；
     2. CFD flow field simulation optimization of layout position and angle;
     3. Adopt Multi-level micro-flame groups Replace high-power single burners.
3. Glaze volatiles corrosion and carbon deposition:
   • Risk Points: Lead, zinc, and boron compounds volatilize at high temperatures and corrode burner nozzles.
   • Countermeasures:
     1. Select Special alloys (such as INCONEL601) or ceramic matrix composite nozzles ；
     2. Design Self-cleaning airflow structure ；
     3. Regular maintenance plan.
4. Kiln pressure balance:
   • Risk Points: Dramatic changes in flue gas volume may affect kiln pressure stability (especially with full oxygen).
   • Countermeasures:
     1. Optimize exhaust fan variable frequency control;
     2. Set up an independent kiln pressure control system;
     3. Segmented pressure control strategy.
5. Safety Prevention:
   • Risk Points: Oxygen system leakage and flashback risks.
   • Countermeasures:
     1. Strictly implement safety standards such as EN746-2;
     2. Double shut-off valve + relief valve Oxygen pipeline design;
     3. Flame detection + automatic shutoff Interlock;
     4. Oxygen concentration leakage monitoring and alarm.

4.4.5, Development Trends

1. Modular intelligent combustion unit: Integrates burners, oxygen valve groups, controllers, and sensors into one unit for plug-and-play use.
2. Digital twin and AI optimization: Real-time simulation of the kiln's thermal process, AI dynamic optimization of oxygen-fuel ratio, kiln pressure, and temperature zone settings.
3. Enriched oxygen combustion + electric heating hybrid mode: Enriched oxygen combustion in the high-temperature zone, electric heating in the preheating zone, maximizing the use of green electricity.
4. Hydrogen-compatible burner: Develop low-nitrogen oxygen combustion nozzles specifically for hydrogen to achieve zero-carbon firing.
5. Microwave-enriched oxygen synergistic sintering: Revolutionizing the sintering efficiency and performance of special ceramics.
6. Standardized carbon accounting module: Built-in carbon emission monitoring, automatically generating carbon footprint reports.

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