Standard Operating Procedure: Tyre Pyrolysis Plant Operations

This Standard Operating Procedure (SOP) outlines the mandatory operational and safety protocols for the thermal degradation of waste tyres via pyrolysis. The objective is to ensure optimal conversion efficiency of tyre feedstock into pyrolysis oil, carbon black, steel wire, and syngas while maintaining the highest safety standards to mitigate fire, explosion, and emission risks. Adherence to this document is compulsory for all plant operators and maintenance personnel to ensure regulatory compliance and operational longevity.

1. Pre-Operational Inspection & Safety Checklist

• System Integrity: Inspect the reactor shell for signs of deformation, thermal fatigue, or leaks. Ensure all manhole gaskets are intact.
• Pressure & Vacuum Systems: Verify that pressure relief valves (PRVs) and vacuum pumps are calibrated and functional.
• Safety Interlocks: Confirm that emergency stop buttons, flame arrestors, and gas leakage detectors are active and calibrated.
• Water Cooling Systems: Check cooling tower levels, pump pressures, and circulation rates to ensure the condenser unit is receiving adequate flow.
• Feedstock Quality: Confirm tyre feedstock is free from hazardous debris, excessive moisture, or non-rubber contamination that could damage the reactor or clog the discharge system.

2. Start-Up & Heating Protocol

• Loading: Load the reactor with processed tyre shreds, ensuring the feed door is hermetically sealed to prevent air ingress.
• Purging: Flush the reactor with Nitrogen (N2) to displace atmospheric oxygen. Conduct an oxygen concentration test to ensure levels are below the explosive limit (typically <1%).
• Ignition: Initiate the burner system. Gradually increase the temperature to the pyrolysis range (usually 350°C–450°C).
• Monitoring: Maintain a steady ramp rate to prevent uneven thermal expansion of the reactor walls.
• Syngas Management: Monitor the syngas output. Once the system reaches self-sustaining temperature, route the syngas to the burner to offset fuel consumption.

3. Steady-State Operation & Process Monitoring

• Temperature Control: Maintain reactor temperature within defined parameters to maximize oil yield and prevent heavy carbon sludge formation.
• Pressure Management: Keep the reactor pressure slightly above atmospheric levels to prevent air leakage, while ensuring it never exceeds the relief valve setpoint.
• Condensation Efficiency: Monitor the temperature at the outlet of the condenser; ensure the oil is cooling sufficiently to maximize recovery.
• Gas Scrubbing: Ensure the gas cleaning system (scrubbers) is active to neutralize acidic components in the syngas before it reaches the burner.

4. Shutdown, Discharge & Maintenance

• Cooling Phase: Once oil flow ceases, shut down the burners. Allow the reactor to cool naturally to below 100°C before attempting to open any seals.
• Final Purging: Purge the system with Nitrogen again to ensure no residual syngas remains before opening the manholes.
• Carbon Discharge: Use appropriate dust suppression methods when discharging carbon black to prevent airborne contamination.
• Preventative Maintenance: Inspect the discharge auger and seals for wear. Clean the condenser pipes to remove any accumulated heavy waxes or blockages.

Pro Tips & Pitfalls

• Pro Tip: Maintain a detailed logbook of every batch, including feedstock type, internal reactor temperature curves, and oil yield volume. This data is critical for identifying efficiency drifts.
• Pro Tip: Use an infrared camera to check for localized "hot spots" on the reactor exterior, which can indicate internal brick lining damage.
• Pitfall: Never open the reactor while it is hot. The presence of residual carbon and oxygen will trigger a "glowing" combustion event, leading to fire or catastrophic reactor failure.
• Pitfall: Ignoring pressure fluctuations. A sudden spike in pressure is a primary indicator of a blockage in the gas line or condenser; ignore this at the risk of an explosion.

Frequently Asked Questions (FAQ)

Q: How often should the gas scrubbers be cleaned? A: Scrubbers should be inspected weekly. However, if you notice a decrease in burner flame quality or a rise in backpressure, the scrubbing media must be cleaned or replaced immediately.

Q: What is the most common cause of oil yield decrease? A: Usually, this is due to leaks in the reactor seal or poor-quality (wet) feedstock. Always ensure the tyre shreds are dry and the reactor gasket is changed regularly.

Q: Why is Nitrogen purging strictly required? A: Pyrolysis oil vapor and syngas are highly flammable. Introducing air into a hot reactor creates an explosive mixture. Nitrogen creates an inert environment, preventing combustion during the heat-up and cool-down phases.