Patent EA-001365-B1 (EA)
Title: Delayed coking cycle time reduction
Inventor: NELSEN DAVID K
IPC: C10B23/00
Filed: 1998-06-11
Abstract: 1. A delayed coking process in which a pair of coke drums each supported by a skirt section welded to said drum are alternately filled and emptied, and in which the emptying portion of the cycle comprises the steps of:  (a) steaming out the filled coke drum to remove residual volatile matter from the drum; (b) quenching the hot coke bed with water; (c) draining quench water from the coke drum; (d) opening the top of the coke drum and drilling a pilot hole through the coke bed therein; (e) drilling out the coke from the coke bed between the pilot hole and the coke drum wall by radially directed drill water and removing the coke through an opening in the bottom of the coke drum; (f) closing the top and bottom openings of the coke drum; and  (g) prior to introducing feed into the emptied drum, preheating the empty drum by passing hot coke drum vapors through the drum; the improvement wherein the thermal stresses at the junction of the coke drum and skirt are reduced by applying heat to the exterior portion of said coke drum adjacent the junction of the drum shell and the skirt of said drum prior to introducing hot feed oil into said drum, thereby preventing excessive thermal stresses. 2. The process of claim 1 wherein heat is applied to the exterior of said drum by utilizing a steam jacket surrounding said drum near the junction of the shell and the supporting skirt thereof. 3. The process of claim 1 wherein heat is applied to the exterior of said drum by utilizing an electrical heating band surrounding said drum near the junction of the shell and the supporting skirt thereof. 4. The process of any preceding claim wherein said heat applied to the exterior of said drum is initiated after the drill water is hitting the interior wall of the drum below the junction of the drum shell and its supporting skirt. 5. A delayed coker facility comprised of a coker fractionator, a coker furnace and a pair of coke drums each supported by an attached supporting skirt, the improvement wherein each of said coke drums includes means affixed thereto for externally applying heat at the juncture of said coke drum and its supporting skirt. 6. The delayed coker facility of claim 5 wherein said means for externally applying heat comprises a steam jacket surrounding the juncture of said coke drum and its supporting skirt. 7. A method for increasing the capacity of a coker unit by reducing the cycle time for the alternate filling and emptying of coke drums, wherein cycle time reduction is carried out by externally heating the coke drum in the area where the coke drum is attached to a supporting skirt section during, just prior to, or both prior to and during, the introduction of coking preheated vapors to the interior of the coke drum, comprising reducing the thermal stresses between the coke drum and the attached supporting skirt section by providing a more uniform temperature between said coke drum and said supporting skirt using said external heating, and thereby reducing coke drum preheat time and thereby reducing overall delayed coking cycle time.