Why Does Carbon Build Up in Furnace Tubes?
Carbon builds up because hydrocarbon feedstocks partially crack and deposit solid coke on hot tube surfaces during normal operation. Several factors can accelerate buildup:
- High coil outlet temperatures that push feedstocks toward heavy cracking.
- Feed composition shifts, such as heavier liquid feeds versus lighter ethane.
- Steam-to-hydrocarbon ratios that fall below design targets.
- Localized hot spots caused by burner imbalance or refractory degradation.
Houston-area plants running heavier feeds from nearby refinery streams may see faster coke formation than facilities running pure ethane.
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What Are the Risks of Deferred Carbon Removal?
Delaying decoking can increase fuel costs, damage tubes, and create safety risks. Common consequences include:
- Efficiency loss from reduced heat transfer across coke-insulated tube walls.
- Tube overheating that can thin or distort tube metal over time.
- Increased pressure drop across the radiant coil, stressing fittings and welds.
- Unplanned shutdowns that are far more disruptive and expensive than scheduled outages.
In Texas Gulf Coast facilities where uptime directly ties to product margins, even a short unplanned outage carries significant operational consequences.
How Is Carbon Removal Performed?
The two most common decoking methods are steam-air decoking and pigging. Steam-air decoking uses a controlled mixture of steam and air to burn the coke layer out of tubes at elevated temperatures. Mechanical pigging physically drives a cleaning projectile through the tube to scrape deposits loose. The right method depends on tube configuration, deposit hardness, and plant safety protocols.
When Should You Schedule Carbon Removal?
Most ethylene furnaces benefit from a decoking cycle every 30 to 90 days, though actual intervals depend on feedstock, severity, and run targets. Operators typically monitor coil outlet temperature rise and pressure drop as indicators. Scheduling removal proactively during planned turnarounds avoids the risks of running to failure. Regular burner inspections and refractory maintenance can also help extend run lengths between decoke cycles.
Get Expert Support Serving Houston, TX
Decoking is a routine but critical part of keeping ethylene furnaces running at full capacity. Applied Refractory, serving Houston, TX, supports ethylene and petrochemical plants with refractory products and maintenance solutions designed to protect high-temperature equipment through every run cycle. To discuss your furnace needs or request a quote,
contact the team online or call
(936) 776-4070 .You can also explore the full range of
refractory materials and industrial solutions
available for Houston-area facilities. You can also explore the full range of refractory materials and industrial solutions
available for Houston-area facilities.
