Thermal cracking method for the production of ethylene and propylene in a molten metal bath

In a process for the thermal cracking of hydrocarbons in which a liquid or gaseous hydrocarbon feedstock selected from the group consisting of refinery gas, gasoline range material, naphthas, gas oils, residual oils, crude oils and mixtures thereof is introduced into a bath of molten metal in a reaction zone and in which gaseous reaction products comprising primarily ethylene and propylene are separated from the molten metal which is circulated back to the reaction zone, the improvement which comprises:

• a. heating said hydrocarbon feedstock to a temperature of between about 1400.degree. F and 1900.degree. F in a reaction zone containing a forced circulation riser and in the presence of a molten metal wherein said feedstock is injected into said forced circulation riser thereby providing circulation of the hydrocarbon feedstock/ molten metal mixture within the reaction zone;
• b. separating the resulting gaseous reaction products from the molten metal by gravity separation;
• c. circulating the molten metal to a reheat zone surrounding the forced circulation riser and then back to the reaction zone;
• d. routing the gaseous reaction products from said reaction zone through a transition zone to a quench zone containing a forced circulation riser, wherein the residence time of said gaseous reaction products in said transition zone is less than 0.2 seconds;
• e. cooling said gaseous reaction products to a temperature of between about 800.degree. F and about 1200.degree. F in said quench zone by contacting said gaseous reaction products with a cooler molten metal;
• f. separating the resulting gaseous reaction products from said cooler molten metal by gravity separation;
• and
• g. circulating the cooler molten metal to a heat removal zone and then back to said quench zone.