Method for the preparation of lower olefines by steam cracking
A method for the preparation of lower olefins by steam cracking, wherein the feed containing heavy hydrocarbons obtained by Fischer-Tropsch synthesis is subjected to steam cracking in a naphtha designed steam cracking furnace for steam cracking the Fischer-Tropsch hydrocarbons into the lower olefins.
1. A method for the preparation of ethene, propene and butene by steam cracking comprising: subjecting a feed comprising heavy hydrocarbons obtained by Fischer-Tropsch synthesis, which Fischer-Tropsch hydrocarbons have an initial boiling point of above 150° C. and a final boiling point of below 400° C., to steam cracking in a naphtha designed steam cracking furnace, wherein the furnace comprises a convection zone provided with a first preheating zone in which the Fischer-Tropsch feed is heated, a second preheating zone in which the heated Fischer-Tropsch hydrocarbons are heated in the presence of steam to form a mixture of liquid and gaseous Fischer-Tropsch hydrocarbons; and a super heating zone in which the liquid and gaseous Fischer-Tropsch hydrocarbons are super heated; and a cracking zone in which the gaseous super heated Fischer-Tropsch hydrocarbons are steam cracked into ethene, propene and butene.
2. The method of claim 1 , wherein the feed for the second preheating zone comprises less than 50 wt. %, liquid Fischer-Tropsch hydrocarbons.
3. The method of claims 1 , wherein the weight ratio of steam to Fischer-Tropsch hydrocarbons is 0.4-0.8.
4. The method of claims 1 , wherein the Fischer-Tropsch hydrocarbons comprise more than 75 wt. % n paraffins.
5. The method of claim 4 , wherein the n-paraffins have a carbon number of 10-20.
6. The method of claim 1 , wherein the Fischer-Tropsch hydrocarbons are essentially free of aromatic compounds, nitrogen compounds and/or sulfur compounds.