Abstract: Disclosed is a method for the thermal cracking of a heavy petroleum oil to produce a pitch with a high aromaticity having a high softening point, the ratio of H/C of about 0.4 to 1.1 and the fraction insoluble in n-heptane but soluble in quinoline of higher than 55% by weight and an oil mainly composed of aliphatic hydrocarbon by feeding the heavy petroleum oil into a reaction system and bringing it therein into contact with a gas which does not react with the heavy petroleum oil, of a temperature in the range of from 400.degree. C. to 2000.degree. C., which method is improved by using, as the reaction system, a plurality of reaction vessels arranged in series and having their interior temperatures successively lower by a fixed step in the direction of the transfer of the charge.

Abstract: A decoking device suitable for use on a reaction vessel for the thermal cracking of heavy petroleum oils, including an assembly mounted on top of the reaction vessel and having a cylinder and a piston slidably and rotatably received in the cylinder, the cylinder and piston defining a scrubbing liquid chamber which is sealed from the outside. A scrubbing liquid is fed through the scrubbing liquid chamber to a main injection pipe to inject the liquid through a multitude of jet nozzles in the main injection pipe against the inner wall surfaces of the reaction vessel, the main injection pipe being connected to the piston for movement therewith.

Abstract: In a process for the thermal cracking of a heavy hydrocarbon in a cylindrical reactor, a portion of the content material in the reactor is taken out and injected back into the reactor according to a specific procedure to form a "wet wall" or liquid curtain on the inner peripheral wall of the reactor, thereby preventing coking in the reactor. The apparatus includes a radially outwardly extending interior annular recess around an upper portion of the inner wall thereof and forming a part of said inner wall and plural means for tangentially injecting the recycled liquid into said recess.

Abstract: A flow control valve for hot pitch or other viscous material, wherein a valve rod is guided by a guide member which has radial indentations in its center aperture to define a number of narrow axial ridges around the circumference of the valve rod to provide stabilized guidance by linear sliding contact with the valve rod.

Abstract: In a process for the thermal cracking of a heavy hydrocarbon in a cylindrical reactor, a portion of the content material in the reactor is taken out and injected back into the reactor according to a specific procedure to form a "wet wall" or liquid curtain on the inner peripheral wall of the reactor, thereby preventing coking in the reactor.