A process for cracking a hydrocarbon stream by: combusting fuel in a gas turbine in the presence of compressed air to produce a flue gas, wherein the flue gas drives a turbine to produce electricity in a coupled generator or work to power a coupled rotating equipment; (a) feeding a first portion of the flue gas to a heat exchanger; (b) feeding ambient air to the heat exchanger to be heated by the first portion of the flue gas to provide heated air; (c) feeding a furnace with fuel and a mixture of a second portion of the flue gas and the heated air obtained by step (c) and (d) cracking the hydrocarbon stream in the furnace.