On 20 Aug, 09:33, (Steve Firth) wrote:

It was extremely large, made out of circular
fireclay sections,

No idea where one would get them from - seriously heavy

Probably unrelated, but a quarl from a ship's boiler furnace (ring of
heavy firebricks where the oil burner enters the furnace) makes a good
start for such a device. Handy for Scrabble too.