Per the Title, the Epic Flameward cannot be cleansed at the Epic Alter using the new cleansing ritual process
From the release notes:
To convert an old Epic item to use the new slots, place the item you would like to convert into the Altar of Epic Rituals along with 50 Siberys Dragonshard Fragments. This performs the “Cleansing Ritual”, which updates items to the new Augment Slots.
This converts the augment slots on the item to the new system. They retain their colors and can accept the new augments, but can no longer use Epic Augment Crystals from before Update 17. This process will remove all currently slotted Epic Augments in the item, and may also remove other modifications, such as Armor Appearance Kits and Stone of Change recipes.
I followed this process as described in the notes and was given an error on 3 attempts.