Process for treating heavy oil

A process comprising:

• a. heating a sulfur-containing, heavy hydrocarbon oil containing at least one alkali metal carbonate, in a cracking zone at a temperature of about 450.degree. to 650.degree. and for a time sufficient to produce a gaseous hydrocarbon product and a light hydrocarbon liquid product and convert a substantial portion of the sulfur contained in said heavy hydrocarbon oil to alkali metal sulfide, while maintaining said alkali metal carbonate and said heavy hydrocarbon oil at a weight ratio sufficient to produce a residual coke by-product containing alkali metal carbonate, coke and alkali metal sulfide and having a weight ratio of alkali metal carbonate to coke of at least about 3 to 1,
• b. withdrawing said gaseous hydrocarbon product, said hydrocarbon liquid product and said residual coke by-product from said cracking zone,
• c. transferring said residual coke by-product to a separate gasification zone,
• d. contacting said residual coke by-product with steam in said gasification zone, at a temperature of about 550.degree. to 800.degree.C and under a pressure of about 1 to 10 atmospheres, to gasify at least a portion of said coke and product a H.sub.2 -- and CO.sub.2 --rich gas, while maintaining said residual coke by-product in said gasification zone for a time sufficient to react said stream and said CO.sub.2 with said alkali metal sulfide to convert a substantial portion thereof to alkali metal carbonate and produce a gaseous product and a residual alkali metal carbonate product,
• e. withdrawing said gaseous product and said residual alkali metal carbonate from said gasification zone, and
• f. recycling at least a part of said residual alkali metal carbonate to said cracking zone.