Patent ID: 8894841

Claim:
A delayed coking process for use in a delayed coking unit that includes at least one drum, the coking unit producing a delayed coking unit product stream and a coke product that is retained in the drum, the coking unit product stream being introduced into a coking product stream fractionator to produce at least a bottoms fraction, an intermediate fraction and a light naphtha fraction, the process comprising: a. analyzing a sample of fresh heavy hydrocarbon feedstock containing asphaltenes that is to be subjected to the delayed coking process to determine the paraffinic solvent-to-asphaltenes ratio required to flocculate substantially all of the asphaltenes in the feedstock; b. introducing the fresh heavy hydrocarbon feedstock containing asphaltenes for preheating into the lower portion of the coking product stream fractionator; c. discharging the bottoms fraction that includes the preheated fresh hydrocarbon feedstock from the fractionator as a coking unit combined feedstream; d. introducing a paraffinic solvent having the formula C n H 2n+2 , where n can be from 3 to 8 or a combined paraffinic and olefinic solvent, the latter having the formula C n H 2n , where n can be from 3 to 8, into the coking unit combined feedstream with a sufficient ratio of solvent-to-feedstream to solvent-flocculate substantially all of the asphaltenes in the coking unit combined feedstream, the solvent being introduced after the discharge of the coking unit combined feedstream from the coking product fractionator and prior to passing the combined coking unit feedstream to the delayed coking drum; e. introducing the coking unit combined feedstream which contains asphaltenes into the coking unit furnace for heating to a predetermined coking temperature; and f. passing the heated combined feedstream containing solvent-flocculated asphaltenes and paraffinic solvent to the delayed coking drum to produce the delayed coking product stream having an increased portion of liquids and depositing a reduced amount of coke on the interior of the drum, as compared to the amount of coke deposited in the absence of the addition of the paraffinic solvent to the same heavy hydrocarbon feedstock.