Nearby my location we have Gladding McBean, where they have several beehive kilns that are still used for firing sewer pipes. They are pretty big, maybe 25ft tall, 30-40ft diameter, downdraft kiln powered by 6-8 natural gas burners. I believe they fire them up to around Cone 7 and it takes around 3wks (1wk preheat, 1wk firing, 1wk cooling).
here's our students going through the beehive kiln room/warehouse a few years ago when you could still tour the facility:
and one off the net: