| 摘要 |
PURPOSE:To attain thermal cracking of heavy oil in a reduced period of time using a reduced amt. of steam while limiting production of quinoline insolubles, by continuing reaction for a period of time which is in a predetermined proportion to feeding time after feeing of a product from a tube heating furnace into a reaction vessel. CONSTITUTION:A petroleum heavy oil as a stock oil is preheated to about 350 deg.C by a preheater furnace 2. The preheated heavy oil is mixed with a heavy end fraction of a thermal cracking product oil falling as a recycle oil in a distillation column 3. The mixture undergoes first thermal cracking at 490 deg.C or above at a cracking reaction rate of 30-45% in a tube heating furnace 4, thereby obtaining a product. Subsequently, the product is fed through a selector valve 5 into reaction vessels 6, 6' partially fed with the stock oil through a selector valve 7 from the distillation column 3. Selector valves 5, 7 are each actuated at predetermined time intervals so that the stock oil and the above-mentioned product are alternately fed into the two reaction vessels 6, 6'. A single feeding period is set at 50-100min, and 15-25pts. wt. steam, per 100pts.wt. stock oil comprising the use fed to the heating furnace 4 and the one fed to reaction vessels 6, 6' and heated to 500-700 deg.C using a steam superheater 8, is introduced into the reaction vessels 6, 6'. The contents of the reaction vessels 6, 6' are retained for 15-45% of the above-mentioned feeding period, thereby effecting second thermal cracking. The cracking product is quenched and extracted from the vessels.
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