TREATMENT METHOD FOR PRODUCING DIESEL FUEL BASE AND METHOD OF CALCULATING DEGREE OF CRACKING OF WAX FRACTION

摘要

An object of the present invention is to provide a method of processing Fischer-Tropsch synthetic oil to manufacture a diesel fuel base stock, the method including: (a) fractionating, in a fractionator, Fischer-Tropsch synthetic oil obtained by a Fischer-Tropsch synthesis method into at least two fractions of a middle fraction containing a component having a boiling point range corresponding to diesel fuel oil and a wax fraction containing a wax component heavier than the middle fraction; (b) bridging the wax fraction into contact with a hydrocracking catalyst in a hydrocracking reactor to obtain a hydrocracked product; (c) separating a gas component from the hydrocracked product to produce hydrocracked oil in a gas-liquid separator disposed in the rear of the hydrocracking reactor used in the step (b); (d) measuring the composition of the gas component seperated in the step (c); (e) calculating a cracking rate in the hydrocracking reaction based on the composition of the gas component measured in the step (d); and (f) controlling an operation condition of the hydrocracking reactor so that the cracking rate calculated in the step (e) agrees with an objective cracking rate. Furthermore, another object of the present invention is to provide a method of calcurating the cracking rate in hydrocracking the wax fraction obtained by fractionating the Fischer-Tropsch synthetic oil in the fractionator.