Method and apparatus for heat recovery from cracked gas

A system, comprising:

• a heater;
• at least one reactor coil in communication with the heater and configured to output a reaction product stream;
• a primary heat exchanger in communication with the at least one reactor coil and configured to cool the reaction product stream to form a quenched reaction product stream;
• and
• a secondary heat exchanger in communication with the primary heat exchanger, the secondary heat exchanger including:
• a shell;
• at least one coiled tube bundle inside the shell, the at least one coiled tube bundle including a mandrel and a plurality of coiled tubes arranged in concentric layers around the mandrel;
• and
• at least one tube sheet coupled to the plurality of tubes,
• wherein the quenched reaction product stream flows through a shell side of the secondary heat exchanger and the feed stream flows through a tube side of the secondary heat exchanger to heat the feed stream via indirect heat transfer against the quenched reaction product stream and form a heated feed stream.

A method, comprising:

• partially cooling a cracked gas product from one or more reactor coils with a primary heat exchanger against boiling water from a first temperature in a range between and including 500 degrees C. to 875 degrees C. to a second temperature in a range between and including 550 degrees C. to 700 degrees C. to form a quenched cracked gas product with the second temperature;
• feeding the quenched cracked gas product to an inlet of a second heat exchanger containing at least one coiled tube bundle with a plurality of tube circuits;
• preheating a feed stream to the one or more reactor coils against the quenched crack gas product in at least a first one of the plurality of tube circuits to a third temperature in a range between and including 450 degrees C. to 700 degrees C. to form a preheated feed stream with the third temperature;
• heating one or more process streams in at least a second one of the plurality of tube circuits;
• and
• further heating the preheated feed stream with the one or more reactor coils to form the cracked gas product in an open fluid loop.