System and method for on-line spalling of a coker

#The invention disclosed in this patent application is not the subject of federally sponsored research or development.

#This present invention pertains to a coker used in refineries for the processing of hydrocarbons. More particularly, the present invention pertains to an on-line spalling system for a coker heater and a method for use of the system.

#Part of the process of refining crude oil into usable hydrocarbons involves separation of the denser materials from the lighter liquid hydrocarbons. The liquid hydrocarbons removed from the denser materials are further refined into gasoline and chemicals used for a variety of purposes in industry. The refining process involves heating the liquid hydrocarbons in successive steps to a temperature in which the desired hydrocarbon is vaporized. The vaporized hydrocarbon can be removed from the non-vaporized materials and collected in a separate vessel. Cooling of the vaporized hydrocarbon causes the vaporized hydrocarbon to return to the liquid form. Each hydrocarbon has a specific temperature at which it becomes a vapor. By heating the hydrocarbon-containing materials to a specific temperature, a specific product may be isolated and collected. Heating and reheating these hydrocarbon-containing materials to various temperatures eventually results in removal and collection of the valuable hydrocarbons which can then be used for a variety of purposes. Heating of the liquid hydrocarbon initially occurs in a coker heater. U.S. Pat. No. 5,804,038 and Patent Publication No. US 2002/0157987 A1 disclose exemplary coking systems and associated equipment including a coker heater or furnace. U.S. Pat. No. 5,804,038 and Patent Publication No. US 2002/0157987 A1 are incorporated herein by reference in their entirety for all purposes.

#A better understanding of the system and method disclosed herein may be had by examination of the figures wherein:

#FIG. 1 shows a cross section of a pipe from a radiant section of a coker heater with deposits of coke inside the pipe;

#FIG. 2 shows one embodiment of a coker heater with the addition of an off-line pipe, schematically illustrated in dashed lines, for use when one of the on-line pipes is out-of-service for spalling;

#FIG. 1 is a cross section of a typical pipe 2 positioned in a radiant section of a coker heater. The heater burners (not shown) in the radiant section, generally indicated as 9, heat the hydrocarbon-containing material to approximately 920 degrees Fahrenheit (493 degrees centigrade). At this temperature, the liquid hydrocarbons are vaporized for later isolation and collection. What remains on the inside of the pipe 2 are the solid materials, such as coke 3. In many coker heaters presently in use, the inside diameter of the pipe 2 begins at about 4 inches. As liquid hydrocarbons are heated and run through each pipe 2, coke 3 is deposited on the inside of the pipe 2 thus reducing the internal flow area and insulating the center portion of the pipe 2 through which the liquid hydrocarbons flow. As the coke 3 builds up the flow of liquid hydrocarbons is reduced or limited. At a certain point the pipe 2 must be serviced so that the coke 3 buildup can be removed, either in whole or in part, so that efficient and acceptable throughput of liquid hydrocarbons can be achieved.

#A portion of the coke 3 formed on the inside of the pipe 2 shown in FIG. 1 is removed by spalling or cooling the pipe so that as it cools the pipe contracts causing some of the coke 3 deposited on the inside of the pipe 2 to fragment, chip, crack, flake and/or break off. The coke 3 which breaks off due to the cooling of the pipe is removed from the pipe by a steam or boiler water spray. The removed coke 3 is then refined into other usable products. However, the spalling, which takes about two days per pipe typically, does not remove all of the deposited coke 3 so about every eight to ten months, in most refineries, the entire coker is taken off line for mechanical pigging of the pipes to remove all deposited coke 3. This mechanical pigging takes about five days.

#Turning now to FIG. 2, a coker heater 4 consists of four on-line pipes 6A, 6B, 6C and 6D through which liquid hydrocarbons are pumped and heated to the desired temperature. In one embodiment of the system and method of the present invention, an off-line or fifth pipe 6E is added to the coker heater 4 with the four pipes 6A, 6B, 6C and 6D. The liquid hydrocarbon is pumped into the on-line pipes 6A, 6B, 6C and 6D at the influent side 6 of the coker heater 4 and liquid hydrocarbon with the coke removed is passed out the effluent side 7 of the coker heater 4 through the effluent ends 7A, 7B, 7C and 7D of respective on-line pipes 6A, 6B, 6C and 6D. As the liquid hydrocarbon is pumped through the on-line pipes 6A, 6B, 6C and 6D, the liquid hydrocarbon is heated in the radiant section 9. Using a valving system having a plurality of valves 8A, 8B, 8C, 8D and 8E operably positioned at the respective pipe influent ends of pipes 6A, 6B, 6C, 6D and 6E, the respective pipes 6A, 6B, 6C, 6D and 6E can be opened or closed. In this maimer one of the on-line pipes 6A, 6B, 6C or 6D can be closed for spalling and the overall desired throughput maintained by opening valve 8E to the influent end of pipe 6E to divert the liquid hydrocarbon through the off-line pipe 6E and out its effluent end 7E. When the time comes to remove some of the deposited coke, similar to deposited coke 3 in FIG. 1, in one of the on-line pipes 6A, 6B, 6C or 6D, the respective valve 8A, 8B, 8C or 8D is closed, preventing flow of the liquid hydrocarbon to the respective pipe to be spalled and the valve 8E is opened to divert flow to the off-line pipe 6E. The result is that there is no reduction in the throughput of the liquid hydrocarbons through the coker heater 4. Thus all losses of operating profit due to a decrease in the ability to refine liquid hydrocarbons during spalling of the heater pipes is reduced. When the spalling of one pipe is complete, the other valves in the on-line pipes can be closed one at a time (or multiple valves could be closed if desired) and the flow of liquid hydrocarbons continued to be run through the off-line pipe 6E.