Converting from coal to natural gas brings challenges to operating a furnace air-gas system, such as...
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Airflow Changes. Natural gas combustion requires less combustion air than coal. However, with the elimination of the transport air, the combustion air flow requirements may be more than the FD fan can supply. Facilities may need to alter FD fan capacity or use PA fans for supplemental air.
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Plant Dynamics. Natural gas combustion produces a more rapid response in the plant, making the plant more sensitive to changes in fuel flow due to faster kinetics. This may limit load based on a decrease in convective heat transfer. In many cases, flue gas recirculation may be employed to recover this heat transfer.
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Severe Events. A Master Fuel Trip with natural gas leads to a transient furnace pressure excursion that can be 2–3X more severe than that of coal-firing excursions. The fireball collapse is much more rapid with gas. Avoiding these severe pressure excursions may save costly physical furnace reinforcements.
TRAX Furnace Draft Studies help identify potential coal-to-gas conversion problems before implementation in your facility.
Some of the common mitigation strategies include…
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Tuning of draft controls including kicker circuits
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Adjustment of valve and fan actuator speeds
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Fine-tuning of equipment trip set-points
