COKE DRUM UNHEADING DEVICE

Abstract: A coke drum unheading device having an actuator system operable from a location remote from a drum outlet. The actuator is adapted to move a drumhead between closed and open positions and to retain the drumhead in a closed position under load.

Description: BACKGROUND OF THE INVENTION The field of the present invention is apparatus for dispensing and safely controlling bulk materials such as petroleum coke or other analogous products. Facilities for the manufacture of bulk materials such as petroleum coke and the like usually include means for producing and storing the produced output prior to shipment. In the specific case of petroleum coke, high boiling petroleum fractions are processed in one or more large volume drums. Figure I illustrates a typical petroleum coke production facility comprising a pair of coke drums mounted in a concrete and/or steel support structure. The drums are positioned above an apron having openings forming the entrance to coke chutes extending below the apron. In the petroleum coking process high boiling (greater than 425°C) hydrocarbons are heated to about 50°C and put into a large drum where thermal cracking of the molecules takes place. This thermal cracking produces small molecules which exit the drum, and larger molecules which remain in the drum to form a solid residue known as petroleum coke. When one drum fills up with the residue, the inlet hydrocarbon stream is switched to an empty drum. The full drum is then steamed to remove residual hydrocarbon and then the coke mass within the drum is cooled by quenching with water. After cooldown to about 95°C the quench water is drained, the coke drum bottom and top covers (heads) are removed, and the coke is removed using high pressure water jets. The heads are then replaced and the empty drum is available for the feed switch when the other drum fills up. The process is continued using this alternating drum technique. As shown in Figure 1, the outlets of the coke drums are closed during the coke production process step by means of steel drumheads that are secured to the drums by a plurality of bolts disposed about the circumference of the coke drum outlets. For a typical coke production facility, the drumheads are approximately seven feet in diameter and five inches thick. The coke drums are alternately unheaded on a time schedule depending on the charge rate of the unit, the coke yield and the number of drums utilized. In current practice the drumheads are manually removed ("unheaded") by operators who remove the drumhead bolting using pneumatic impact wrenches. In order to maintain coke production schedules and a steady coker unit output stream, it is essential that the unheading operation be safely and expeditiously performed. In the production facility of Figure 1, unheading typically takes about ten to thirty minutes. During the unheading of the coke drums of Figure 1, the drumhead is supported in place by an adjustable unheading cart that is typically mounted on tracks. After the head bolts are removed, the drumhead is lowered from the coke drum outlet. The head and the cart are then rolled to the side to fully expose the open outlet. A collapsible chute is hoisted from the deck to tie the coke drum outlet to the coke chute in the drum support structure to prevent spillage during coke removal. The coke is then "cut" from the drum by (a) high pressure water jet(s). This operation of removing coke from the drum takes around two to six hours. The drum is subsequently reheaded by reinstalling the head bolts. The reheading operation takes around fifteen to forty minutes. The above-described practice has worked relatively satisfactorily over the years for the production of "sponge coke", which forms a mass inside the coke drum that will normally support itself and remain intact, even with the drumhead removed. However, if, as occasionally occurs, the coke drum fails to properly drain off water used for quenching the hot coke, a combined hydrostatic and coke load with a total weight around 100 tons could act on the drumhead, rendering bolt removal difficult and subjecting the unheading cart to excessive loads. An inadequate drain may also result in an uncontrolled discharge from the drum of high temperature (80-95°C) water, steam, coke slurry or coke particle streams as the drumhead is being lowered, subjecting personnel to a hazardous situation. With the use of certain types of feed stocks which are becoming more prevalent, "shot coke" is produced in lieu of sponge coke. "Shot coke" has the consistency of small BB pellets which may or may not be agglomerated into large "coke balls." "Shot coke" and the associated "coke balls" may not form a self supporting mass in the coke drum and may therefore behave as a liquid to impose high hydraulic load on the head similar to water. This fluid-like behavior of the "shot coke" will force the drumhead down with considerable force onto the coke drum unheading cart. The coke can also flow out with significant velocity from the gap between the drum and the partially lowered head, a potential hazard to operating personnel, and, if the unheading cart is pinned in place by the partially lowered head, may spread onto the unheading deck and equipment below the deck. The coke's fluidity also increases the potential for inadequate drainage of quench water by its tendency to plug the drainage outlets, again leading to excessive loads on the drum head and the unheading cart. Thus, "shot coke" production entails the dual problems of safety due to excessive and uncontrolled discharge, and the disruption of production feed cycles due to excessive drum head and unheading card loading. Accordingly, an alternative method of removing a coke drum head, providing the ability to withstand the high bottom head loads developed in the case of an inadequate quench water drain, controlling and directing hot water and particulate discharge via the bottom head, enabling the unheading operators to distance themselves from the coke drum outlet during drum head removal and maximising coke production throughput, would be desirable. EP-A-0 256 096, on which the prior art portions of claims 1 and 13 are based discloses apparatus in which remotely controlled retaining means lower a drum head onto a truck for subsequent transverse removal from beneath the drum head. As compared therewith, the present invention, as defined in claims 1 and 13 removes the need for a transversely movable truck by pivoting the drum head to the lower end of the drum and also provides a simple safety lock which will support the drum head in its closed position against the load of a full drum so that the hydraulic means used for supporting the drum head during its pivotal movement is only required to be load bearing during the actual time of remote controlled movement. Because the drum head simply pivots out of the way there is nothing to impede opening movement of the drum head, should it be under substantial load due to the unsupported weight of relatively fluid "shot coke" in the drum. Summary of the Invention The present invention is directed to a coke drum unheading device adapted to achieve the aforementioned objects. To that end, means are provided for moving the coke drum head between closed and open positions with respect to the coke drum, which means are operable from a location remote from the coke drum outlet. Such means are supported from a suitable fixed structure, preferably from the coke drum itself. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view of a prior art coke drum system with support structure having a section broken away for clarity. Figure 2 is a view of a coke drum system with support structure constructed in accordance with the present invention, having a section broken away for clarity. Figure 3 is a side view of a coke drum bottom section constructed in accordance with the present invention showing a drumhead in an open position. Figure 4 is a front view of a coke drum bottom section constructed in accordance with the present invention showing a drumhead in a closed position. Figure 5 is a cross-sectional view of the coke drum bottom section of Figure 4 taken along line 5-5. Figure 6 is a detailed side view of a safety lock for locking a drumhead in a closed position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the present invention will be described with reference to Figures 2-6. Referring to Figure 2, the unheading device of the present invention is shown in a two-drum system configuration. A first coke drum 1 and a second coke drum 2 of generally cylindrical shape are positioned in a concrete and/or steel drum support structure 4 over a pair of openings 5 and 6, respectively, which are closed by removable covers 3 when coking operations are in progress. The openings 5 and 6 form the entrances to a pair of chutes 7 and 8 extending from the unheading deck 9 that transport the coke from the drums 1 and 2 to a concrete apron for removal and subsequent processing. The coke drums 1 and 2 comprise generally frusto conical bottom sections 11 and 12 which terminate at generally cylindrical drum outlets 13 and 14, respectively. Circumferentially mounted to the bottom sections 11 and 12 are upper stiffener ring assemblies 15 and 16, respectively, that provide support for the actuator means to be described hereinafter. Below the ring assemblies 15 and 16 are additional stiffener ring assemblies 17 and 18 to provide support for a pair of two-ton chain hoists 19 for supporting the collapsible chutes 20. Referring to Figures 2, 3, 4 and 5, the, upper stiffener ring assembly 15 on the coke drum 1 has attached thereto a pair of main load hydraulic cylinders 21 and 221 Similarly, the upper stiffener ring assembly 16 on the coke drum 2 has a pair of main load hydraulic cylinders 23 and 24 mounted thereon. Each pair of hydraulic cylinders 21, 22 and 23, 24 form an actuator system capable of resisting anticipated coke and hydrostatic loads during all phases of the unheading operation. Although the present embodiment discloses a hydraulic actuator system having one end connected to the coke drum, a fixed structure, the fixed structure may be provided by an unheading deck suitably reinforced. Other actuator systems would also be possible. Although not shown in the figures, the actuator systems of the present invention are adapted for operation from locations remote from the coke drum outlets. This enables the unheading operators to avoid the vicinity of the coke drum outlets during unheading operations. Each of the coke drums 1 and 2 also includes a drumhead 25 having a generally T-shaped cover stiffener comprising an actuator support portion 26 and a hinge support: portion 27 extending transversely to the actuator support portion 26. Describing now the actuator system on the coke drum 1, the hydraulic cylinders 21 and 22 are attached to the upper stiffener ring assembly 15 by pairs of support lugs 28 and 29, respectively, using pins of conventional design to provide a pivotal connection. The hydraulic cylinders are attached to the drumhead 25 by means of universal joints 30 and 31 each of which are mounted by pins to the drumhead cover stiffener and one of the hydraulic cylinders to provide a pivotal connection. Hydraulic cylinder plunger dust covers 32 and 33 are provided to keep the cylinder plungers free of coke and other foreign matter. To secure the drumheads 25 to the coke drums when the heads are in a closed position, a circumferential arrangement of bolts 34 is provided extending through mating circumferential flanges on the coke drum outlets 13, 14 and the drumheads 25. Mounted to the outlets 13 and 14 of the coke drums 1 and 2 are pairs of hinge tabs 35. The drumheads 25, in turn, are provided with hinge tabs 36 extending from the hinge support portions 27 of the cover stiffeners. A pin connecting the hinge tabs 35 and 36 provides a pivotal connection between each drumhead 25 and a respective coke drum 1 and 2. Other forms of movable connection would also be possible. Each coke drum 1 and 2 is provided with a pair of safety lock devices 37 that secure the drumheads 25 in place while operators are working thereunder to prevent accidental opening in the event of a hydraulic line or cylinder rupture. The safety locks 37, shown in detail in Figure 6, are pivotally mounted to the drum outlets 13 and 14 by means of safety lock support tabs 38. The safety locks 37 are pivotable between closed and open positions by means of actuators 39. In the closed position the safety locks 37 are aligned with tabs 40 mounted to the drumheads 25 which are sized to support anticipated coke and hydrostatic loads. Referring to Figure 2, lines 50 and 52 serve to feed hot hydrocarbon to the appropriate drum, and following completion of the coking portion of the cycle serve to remove fluid from that drum. The lines 50 and 52 are joined with a flanged connection 54. The line 50 is adapted to remain fixed to the drumhead. During unheading operaticns, a connection 54 is broken to separate the lines 50 and 52 and permit the drumhead, together with the line 50 to be displaced from the coke drum outlet. Thus, an actuator controlled unheading device has been described that is operable from a location remote from a drum outlet and which is capable of withstanding high loads. While embodiments and applications of this invention have been shown and described, it will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein.

Claims: 1. Coking apparatus comprising a coke drum body (1) having an outlet (13) at its lower end, a coke drum head (25) configured to cover and close said outlet, retaining means (34) for retaining the drum head (25) in position closing said outlet (13), and remotely controlled hydraulic means (21,22) for moving the coke drum head (25) from its position closing the outlet (13) following release of said retaining means (34) characterised in that said coke drum head (25) is mounted to the drum body (1) for pivotal movement to and from its outlet closing position under the control of said hydraulic means which comprises a hydraulic actuator piston and cylinder (21,22) connected between said drum head (25) and a location (28,29) in fixed relation to said drum body and in that a releasable safety lock means (37) is mounted to the drum body for holding the drum head in its closed position to prevent accidental pivoting of the drum head in the event of loss of hydraulic fluid pressure in said hydraulic actuator during release of said retaining means. 2. Apparatus as claimed in claim 1, wherein pivotal mounting means for said drum head comprises: a flange hinge tab (35) mounted to said coke drum body (1); a cover hinge tab (36) mounted to said coke drum head (25) and a pin joining said flange hinge tab (35) and said cover hinge tab (36). 3. Apparatus as claimed in either preceding claim, wherein a pair of hydraulic actuator cylinders (21,22) are operatively mounted to pivot said drum head (25) to open and close said outlet (13). 4. Apparatus as claimed in claim 3, further including a pair of universal joints (30,31) operatively positioned between the drum head (25) and the hydraulic actuators (21,22) whereby extension of the hydraulic actuators (21,22) causes pivoting of the drum head (25) relative to the discharge outlet (13). 5. Apparatus as claimed in any preceding claim, further including stiffener means (15) mounted on the lower portion (11) of said drum body for supporting said actuator (21,22), said stiffener means including one or more mounting lugs (29) to provide support for said actuator (21,22). 6. Apparatus as claimed in claim 5, wherein the drum body (1) has an upper cylindrical portion and a lower frustoconical portion (11) terminating at a cylindrical drum outlet (13); the stiffener means comprising a stiffener ring (15) circumferentially mounted on said frustoconical lower portion, said stiffener ring including one or more mounting lugs (29) to provide actuator support. 7. Apparatus as claimed in any preceding claim, wherein said drum head (25) is circular and configured to mate with said drum outlet and has mounted thereto a generally T-shaped cover stiffener including an actuator support portion and a hinge support portion, said hinge support portion having a cover hinge tab (35) extending therefrom, and said actuator support portion having pivotally mounted to the ends thereof a pair of universal joints (30,31) to provide connection to a pair of actuators. 8. Apparatus as claimed in any preceding claim, wherein the drum head (25) has an orifice therethrough, a line (50) connected to the drum head at its orifice extending outwardly therefrom. 9. Apparatus as claimed in claim 8, wherein a feed line (52) is removably connected to the end of said line (50) remote from said drum head. 10. Apparatus as claimed in any preceding claim, in which said safety lock means (37) is pivotally mounted to said drum outlet by support tabs (38), said safety lock means being pivotable between closed and open positions by an actuator (39). 11. Apparatus as claimed in any preceding claim, in which said drum (1) has a frustoconical section (11) adjacent said outlet (13). 12. Apparatus as claimed in claim 8, in which the upper end of the or each hydraulic actuator (21,22) is fixed adjacent the upper end of said frustoconical drum section. 13. A delayed coking method, comprising preheating the hydrocarbon feed to a container drum (1) having a discharge outlet (13) and adapted to produce petroleum coke to induce thermal cracking of hydrocarbon molecules in said hydrocarbon feed and thereby to produce a mass of petroleum coke; subsequently introducing steam into the container drum (1) sufficient in temperature and quantity to remove residual hydrocarbon from hydrocarbon feed and petroleum coke remaining in the container; and thereafter opening the drum (1) by moving, using remotely controlled hydraulic actuator means (21,22), a drum head (25) from a closed position over the discharge outlet (13) to an open position characterised in that a safety lock (37) is engaged between the drum (1) and the drum head (25) before release of the means (34) retaining the drum head in its closed position and is then disengaged following release of the retaining means (34) to permit the hydraulic actuator means (21,22) pivotally to move the drum head about an axis of pivotal connection to the drum (1) from its outlet closing position to a downwardly depending open position.

Inventors: ALEXANDER, DONNIE M., ANTALLFY, LESLIE PETER, REEVES, MARCUS RAY
Applicants: FLUOR CORPORATION
Application year: 1989
Main classification: C10B25
IPC codes: C10B25, F16J13, C10B33