Yes, you can kept the fully depreciated assets in your book so long the derecognition criteria as per below were not met:
The carrying amount of an item of property, plant and equipment shall be derecognised:
(a) on disposal (i.e. sold); or
(b) when no future economic benefits are expected from its use or disposal. (i.e. written off, which usually trigger by condition specified by Company policy [e.g. unusable condition])
The cost of the said PPE will be offset with the equivalent accumulated depreciation and show a zero NBV at the disclosure of the notes to account.