In fluidised bed boilers, refractory works in one of the toughest environments in any plant: high-velocity, ash-laden gas, temperature swings and frequent outages. When castable keeps falling off in the same areas, it pays to find the real cause instead of patching the same spot every shutdown.
Anchor problems
Anchors of the wrong material, poorly welded, wrongly spaced or corroded cannot hold the lining. Once a few anchors fail, whole sections come away together.
Too much water in the mix
Extra water makes castable easier to place but weakens it badly, leaving lower strength and poor erosion resistance.
Rushed dry-out
Starting the boiler before the castable has dried out properly traps steam inside the lining. It can crack or spall on the first heat-up, even after a good installation.
Erosion
Cyclone inlets, bed zones and refractory-to-tube interfaces take heavy particle impact. They need abrasion-resistant low cement grades and a good finish.
Missing expansion allowance
Refractory and steel expand differently. Without proper expansion joints, the lining cracks and loosens.
Breaking the cycle
- Inspect failed areas to find the root cause
- Use the right anchor material and spacing for each zone
- Mix with measured water, as per the data sheet
- Follow a controlled dry-out schedule
- Use abrasion-resistant castables in high-wear zones
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