PROCESS AND FURNACE FOR THE STREAM CRACKING OF HYDROCARBONS FOR THE PREPARATION OF OLEFINS AND DIOLEFINS

摘要

The present invention relates to a process for the preparation of olefins and diolefins by the cracking of hydrocarbons in the presence of steam, consisting in passing a mixture of hydrocarbons and steam flowing in a cracking tube disposed inside a radiation zone of a furnace. The process is characterizedin that the mean dwell time of the mixture of flowing in the cracking tube between the inlet and the oulet of the radiation zone is from 300 to 1800 milli-seconds, and the reaction volume is greater in the first half of the tube lengththan in the second one. The present invention relates also to a cracking furnacein which the ratio between the length and the mean diameter of the cracking tubeis from 200 to 600, and the tube diameter decreases from the inlet to the outletof the radiation zone.