Process and apparatus for cracking of thermally unstable feedstock

Process for steam cracking of a thermally unstable feedstock comprising the steps of:

• (a). preheating the thermally unstable feedstock at a temperature and a pressure wherein most, preferably substantially all, of the feedstock remains liquid, wherein preheating is achieved using convection heat from a steam cracker furnace,
• (b). combining the preheated feedstock of step (a) with steam to obtain a heated feedstock,
• (c). heating the heated feedstock of step (b) using an evaporator to produce a gasified feedstock by evaporation and a residue,
• (d). heating the gasified feedstock of step (c) using convection heat to obtain a heated gasified feedstock,
• (e). steam cracking of the heated gasified feedstock to obtain cracked gases,
• (f). recovering and cooling down cracked gases of step (e),
• wherein heating at step (c) is not performed within a convection section of a steam cracker furnace.