1. Why Are the First and Second-Stage Boilers Prone to Tube Ruptures?

1.1 Extreme High-Temperature Stress on Materials

• The first-stage boiler directly absorbs heat from red-hot coke, with temperatures exceeding 1000°C (1832°F), causing severe thermal fatigue and material degradation.

• The second-stage boiler, though operating at lower temperatures, still experiences cumulative thermal stress over time.

• Metal creep and deformation occur due to prolonged exposure, weakening tube structures and increasing rupture risks.

1.2 Oxygen Leakage and Explosion Risks

• CDQ systems rely on inert gas (nitrogen or steam) to prevent coke combustion. However, if oxygen leaks into the furnace:

  • It raises the oxygen concentration, creating an explosive gas mixture.

  • Combustible gases like CO (carbon monoxide) can ignite, leading to flash explosions.

  • Poor sealing of the furnace exacerbates this risk.

1.3 Coke Dust and Ash Deposition

• Fine coke particles and ash accumulate on boiler tubes, leading to:

  • Local overheating, which weakens metal structures.

  • Blockages in heat transfer surfaces, reducing efficiency and causing temperature imbalances.

  • Potential spontaneous combustion, further increasing explosion risks.

1.4 Chain Reactions from Tube Ruptures

• A single tube failure can trigger:

  • Steam leaks that impact nearby tubes, leading to multiple ruptures.

  • Disruptions in gas balance, potentially allowing oxygen infiltration and increasing explosion hazards.

1.5 Operational Errors and Sudden Temperature Changes

• Abrupt startup and shutdown procedures can create severe thermal stress, leading to cracks.

• Emergency shutdowns that cool the boiler too quickly cause rapid material contraction, increasing failure risks.

2. Prevention and Mitigation Strategies

2.1 Upgrading Materials and Structural Design

• Use heat-resistant alloys (e.g., T91, T22, nickel-based materials) to withstand prolonged high-temperature exposure.

• Conduct regular ultrasonic and radiographic testing (UT/RT) to detect early signs of cracking or thinning.

2.2 Ensuring a Stable Furnace Atmosphere

• Maintain tight furnace sealing to prevent oxygen leakage.

• Monitor oxygen levels in real time, ensuring O₂ stays below 0.5% to avoid combustion risks.

2.3 Preventing Dust Accumulation and Improving Heat Transfer

• Regular soot-blowing procedures prevent excessive coke and ash buildup.

• Optimize gas flow distribution to ensure even heat transfer and minimize localized overheating.

2.4 Standardizing Operational Procedures

• Implement gradual heating and cooling during startup and shutdown to prevent thermal shock.

• Train operators in emergency shutdown protocols to avoid rapid temperature fluctuations.

2.5 Intelligent Monitoring and Early Warning Systems

• Install real-time temperature, pressure, and oxygen sensors to detect anomalies early.

• Conduct periodic emergency response drills to improve reaction times and minimize human errors.

3. Conclusion

The first and second-stage CDQ boilers are highly susceptible to tube ruptures due to extreme thermal stress, oxygen leaks, dust accumulation, and operational factors. By enhancing material selection, ensuring a stable inert atmosphere, preventing dust buildup, and optimizing operational procedures, the risks can be significantly reduced.

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