Process for producing high-crystalline petroleum coke

A process for producing a high-crystalline petroleum coke from a petroleum feedstock which comprises the steps of:

• heating the petroleum feedstock in a tube heater to a temperature of 430.degree.-520.degree. C. under a pressure of 4-20 Kg/cm.sup.2 G and in the presence of a small proportion of a basic compound selected from the group consisting of hydroxides and carbonates of alkali and alkaline-earth metals;
• maintaining the feedstock in the tube heater at that temperature for 30-500 seconds to effect cracking and soaking thereof;
• introducing the feedstock thus heat-treated into a high-temperature flashing column, where a flash distillation is effected at a temperature of 380.degree.-480.degree. C. under a pressure of 0-2 Kg/cm.sup.2 G;
• continuously removing non-crystalline substances contained in the feedstock as pitch from the bottom of the flashing column;
• fractionating in a fractionating column the distillate from the flashing column into cracked gas, gasoline, gas oil and heavy residue;
• and
• introducing the heavy residue, after heating to a temperature required for the subsequent delayed coking, into a coking drum, where it is subjected to delayed coking at a temperature of 430.degree.-460.degree. C. under a pressure of 4-20 Kg/cm.sup.2 G for at least 20 hours, thereby forming a high-crystalline petroleum coke having a coefficient of thermal expansion in the direction parallel to the extrusion of less than 1.0 .times. 10.sup.-6 /.degree. C. over 100.degree.-400.degree. C. when measured in the form of an extruded graphite artefact thereof.