A quenching system for a plant, operating a cracking furnace, works with liquid as well as gaseous starting materials. The quenching system includes a primary heat exchanger (PQE 10) and a secondary heat exchanger (SQE 11) and a tertiary heat exchanger. A TLX-D exchanger (TLX-D 26) is arranged and configured as the tertiary heat exchanger for dual operation. The TLX-D (26) is connected in series via a TLX-D gas feed line (24) to the SQE 11. The TLX-D (26) is connected to a steam drum (59), which is connected to a feed water line (49), via a TLX-D feed water drain line (34) and a TLX-D riser (46) and a TLX-D downcomer (38). The SQE 11 is connected to the steam drum (59), which is connected to the feed water line (49), via a TLX downcomer (52) and a TLX-riser (57).