Soft ceramic fibre components (modules made of batts of ceramic fibre wool material) need to have their surface "rigidized" by the application of a suitable rigidizer product to survive long term exposure to high velocity flue gases. Suitable products are available and are not expensive. Otherwise I understand that they are used to line combustion equipment frequently. "Millboard" type ceramic fibre materials are also used.

If the thing being lined is expected to need frequent access for maintenance, a so-called "body soluble" ceramic fibre should be selected.

Dear moltenmetal,

Thanks for you reply. I have applied a layer stainless steel lining to cover the superwool/isowool blanket, thus I guess it is one of the ways to ensure that the insulation layers are intact. Hopefully this is acceptable.

If superwool/isowool can be used for combustion furnace, then when will we use pyro-bloc for insulation purpose?

You don't generally use the raw "superwool" needled felt "blanket" material as an insulating material in furnaces- rather, "modules" which are bundles of the wool material held together by other materials and attached to the walls by means of lagging clips tend to be used.

Board materials are used where more mechanical robustness is required.

I can't comment on the wisdom, necessity or cost implications of putting an inner stainless steel lining on the insulating material without understanding the application in detail.

Mineral wool board or Ceramic fibre board insulation can be used..

Flame impingement could be a problem but being a ducting system probably not. Nonetheless don't disregard if it is a problem.