US3257309A

US3257309A - Manufacture of petroleum coke

Info

Publication number: US3257309A
Application number: US215813A
Authority: US
Inventors: Paul W Fauchier; John H Smith
Original assignee: Continental Oil Co
Current assignee: ConocoPhillips Co
Priority date: 1962-08-09
Filing date: 1962-08-09
Publication date: 1966-06-21
Anticipated expiration: 1983-06-21
Also published as: ES290521A1; JPS491601B1; DE1471557A1; GB1043734A; NL140752B

Description

June 21, 1966 P. w. FAUCHIER ET 3,257,309

MANUFACTURE OF PETROLEUM COKE Filed Aug. 9, 1962 4 Sheets-Sheet l CAL C/NPD June 21, 1966 P. w. FAUCHIER ET AL 3,257,309

MANUFACTURE OF PETROLEUM COKE 4 Sheets-Sheet 2 Filed Aug. 9, 1962 INVENTORS PAUL W. FAZ/CH/EP JOHN A. S'M/TH paw- 8.?

AITUEA/EY June 21, 1966 P. w. FAUCHIER ET 3,257,309

MANUFACTURE OF PETROLEUM COKE 4 Sheets-Sheet 5 Filed Aug. 9, 1962 w N HN INVENTORS PAUL I44 FAUCH/EE JOHN H. 5114/? H W tfM June 21, 1966 w, FAUcHlER ET AL 3,257,309

MANUFACTURE OF PETROLEUM COKE Filed Aug. 9, 1962 4 Sheets-Sheet 4 INVENTORS PAUL M4 FAUCH/EP Y JOHN H. SMITH mam United States Patent 3,257,309 MANUFACTURE OF PETROLEUM COKE Paul W. Fauchier and John H. Smith, Ponca City, Okla, assignors to Continental Oil Company, Ponca City, Okla, a corporation of Delaware 7 Filed Aug. 9, 1962, Ser. No. 215,813 15 Claims. (Cl. 20846) This invention relates to the manufacture of petroleum coke by delayed cooking processes. More particularly,

the present invention relates to improvements in the method of handling raw coke fines produced during the manufacture of coke by a delayed coking process.

In the delayed coking process, a petroleum fraction is heated to a temperature at which it will thermally decompose. The oil is then fed before decomposition into a drum under conditions which prevent the oil from vaporizing until it has partialy decomposed. This thermal decomposition produces a very heavy tar which undergoes additional decomposition, in so doing depositing a porous coke mass in the drum.

In the usual application of the delayed coking process, residual oil is heated by exchanging heat with the liquid products from the coking process and is then fed into a fractionating tower where any light products which might remain in the residual oil are distilled out.- The oil is then pumped through a furnace where it is heated, to the required temperature and discharged into the bottom of the coke drum. The first stages of thermal decomposition reduce this oil to a very heavy tar or pitch which further decomposes into solid coke. The vapors formed during this decomposition produce pores and channels in the coke through which the incoming oil from the furnace may pass. This process continues until the drum is filled wit-h a mass of coke. The vapors formed in the process leave from the top of the drum and are returned to the fractionating tower where they are fractionated into the desired cuts.

When the drums are ultimately filled with raw coke, they are opened top and bottom, and the coke is removed by cutting it out with high velocity water jets. As the coke mixed with water falls from the coking drum, it is collected in a suitable collection means and then passed to subsequent treatment, which may include a calcining operation in which the raw coke is calcined by subjecting it to temperatures of about 2500 F.

The attrition associated With removing the raw petroleum coke from the delayed coking drums and subsequent coke handling produces a considerable amount of undersized coke fines. In separating the cutting water from the coke, a great deal of coke fines tend to be carried away with the water. It is desirable to recover the raw coke fines and to distributethem evenly throughout the main body of coke.

The :mass of effluent discharged from delayed coking drums will generally comprise three major constituentsrelatively coarse particles of coke, coke fines, and water. The water must be drained, decanted or, in some other manner, separated from the main body of coke before it is passed to storage and preparatory to subsequent processing. Also, it is desirable to achieve at least a partial drying or dewatering of the coke fines to facilitate their subsequent handling. The Water which is removed from the coarser particles of coke is, of course, contaminated with smaller particles or fines, and is unsuitable for discharge into public streams by virtue of pollution problems by such disposal. Moreover, since considerable volumes of Water are utilized for removing the coke from the delayed coking drums, it is highly desirable that this water be conserved and recirculated to the decoking jets.

As to problems posed by the presence of the undersized Patented June 21, 1966 ice fines in the effluent from the coking drums, these fines, if separated and dried completely in an open area, constitute a source of atmospheric contamination or pollution since they are verylight and are easily carried by air currents into the atmosphere.

In delayed coking operations in which the raw coke removed from the delayed coking drums is subsequently passed to a calcining operation, most of the coke fines will be suitably calcined and appear in the final product; however, a portion of the fines are entrained in the combustion gases leaving the calcining kiln and pass out the fines or stacks of the kiln and into the atmosphere. A partial solution to the atmospheric pollution problem thus posed has been achieved by pass-ing the hot effluent gases from the calcining kiln with some of the coke fine-s entrained therein to a cyclone separator. In the cyclone separator, the fines are dropped to the bottom of the separator and are there accumulated prior to passing to a suitable fines storage container. It has been proposed to fluidize these fine-s with air and burn them as fuel in the calcining kiln. It has also been proposed to prepare a slurry of the fines in a suitable gas oil fraction and circulate such slurry to the delayed coking drums for admixture with the heavy petroleum residuum which is charged to the coking drums, wherein the fines are cemented into the new coke being produced in such manner that they lose their identity and are subsequently recovered as part of the main body of coke.

Despite such improved disposition of the coke fines, a consider-able problem continues to be posed by the presence of the fines in a wet or "very moist condition in drums or storage facilities used to contain the raw coke prior to its passage to the calcining kiln. The coke fines will normally be rather unevenly distributed in the main body of coke and will also still contain a substantial quantity of residual water at such time as the raw coke is passed into the coke storage silo upstream from the calcining kiln. The coke fines tend to cake and choke up the coke storage and handling equipment when they are not evenly distributed through the main body of coke. The explanation of this difficulty may be understood by means of a simple analogy. In humid weather salt picks up moisture and tends to cake up, but when larger particles such as rice are mixed with salt, it tends to fiow easily along with the kernels of rice. This is why the coke fines will not tend to cake as much when evenly combined with the coarser coke particles.

Broadly, the present invention provides an improved method and apparatus for handling the eflluent which is discharged from the coking drums used in the delayed coking process. The invention is particularly well adapted to use in a delayed coking process wherein the raw coke from the coking drums is subsequently passed through a calcining kiln after being retained temporarily in a storage facility, such as a coke storage silo. The process achieve-s the major objectives of recovering coke fines from the recycle water and blending the recovered fines uniformly with the main body of coke in such a way that substantially improved economy in the over-all delayed coking process is achieved and the fines which are produced in such delayed coking process are dewatered in a manner which permits them to be more readily and effectively combined with the main body of coke.

More specifically, the present invention contemplates improvements in the process for producing petroleum coke by subjecting a heavy petroleum residuum to delayed coking conditions in a coking drum and then removing the raw coke ifrom the drum by subjecting it to impact by high pressure water jets, which improvements are effected by gravitationally separating the slurry of water and coke fines resulting from the removal of coke from the coking drum by the high pressure water jets; pumping the slurry so separated into a settling basin; separating the water from the coke fines by gravitational filtration and decantation to leave a residue of moist, easily handled coke fines which may be recombined with the main body of coke and are not subject to atmospheric dissipation; and recirculating the water which is separated from the coke fines to the high pressure water jets used to remove the raw coke from the coke drums. The moist fines which remain in the settling basin following the dewatering process may be recombined with the main body of coke in an evenly distributed manner so that the recombined lumps and fines are easily conveyed through conduits, silos, conveyors, etc. prior to subjecting such recombined coke particles to a calcining step. The process as thus practiced results in the treatment of the coke fines in such manner that the fines are easily recombined in an evenly distributed manner with the main body of coke so that no fouling of lines or interference with subsequent processing of the coke occurs. The process also permits the dewatering of the coke fines to be smoothly integrated with the cycle of operations normally conducted in producing coke by the delayed coking procedure.

In practicing the process of the invention, certain novel apparatus is employed. The apparatus is included in and forms an integral part of a system which includes an inclined apron adjoining the delayed coking drums for receiving the raw coke effluent from the coking drums admixed with the water which is used to remove the coke from the drums; means for dragging the coke up the inclined apron for storage and draining; a collecting basin into which the water and coke fines drain; means for pumping the water and fines to settling basins; settling basins in which the fines settle from the water contained therein; means for dewatering said fines; means for cimbining the recovered coke fines uniformly with the main body of coke; and means for recirculating the water from the settling basin to the source of water used to remove the raw coke from the delayed coking drums.

In a preferred embodiment of the invention, two or more settling basins are employed and the water which is removed from the fines in such settling basins is discharged to a common sump from which it may be recirculated to the water jets. By this arrangement, the settling basins may alternately be filled and the fines therein dewatered so that substantially uninterrupted operation of the systems may be effected. The location of the settling basin or basins relative to the apron which receives the efliuent from the coking drums and also the particular construction of the settling basin and the means provided for dewatering the coke fines therein are all salient features of the invention which take into account the characteristic water-retaining properties, as well as the porosity, of the coke fines and which achieve a dewatering of the fines in a highly efficient manner. It is also important that the apparatus be constructed to permit the depth of the bed of fines to be uniform across the settling basins so that the bed of fines remaining in the basins has a reasonably uniform moisture content.

From the foregoing description of the invention, it

will be apparent that it is a major object of the present invention to provide an improved procedure for handling the effluent which is discharged from the coking drums used to produce raw coke by thermal decomposition of a heavy petroleum residuum in a delayed coking process.

An additional object of this invention is to provide a process and apparatus for recovering the wet coke fines resulting from the decoking of coke drums by means of high velocity jets of water, and for recombining said recovered coke fines with the main body of coke in an evenly-distributed manner.

A further object of the present invention is to provide a method for recovering, as useful, valuable product, the wet coke fines which would otherwise present a disposal and contamination problem in the operation of a delayed coking unit.

In addition to the foregoing objects and advantages of the invention, additional benefits and advantages which may be derived from the invention will hereinafter become manifest upon a reading of the following detailed description of the invention in conjunction with a perusalof the accompanying drawings which illustrate the invention.

In the drawings:

FIGURE 1 is a flow diagram schematically illustrating a system utilized for producing coke by the delayed coking process and serving to illustrate a typical environment in which the present invention may be advantageously employed.

FIGURE 2 is a somewhat diagrammatic illustration of the apparatus utilized in practicing the process of the present invention.

FIGURE 3 is a view in section taken along line 33 of FIGURE 2.

FIGURE 4 is a plan view if the settling basins which are utilized for dewatering the coke fines which are removed from the coking drums according to the process of the present invention, and showing the conveyor which is utilized to conduct the dewatered coke fines to the main conveyor where they are recombined with the large lumps or particles of coke. A portion of the conveyor for transferring the dewatered coke fines from the settling basins has been broken away to show the location of filtering means in the bottom of the settling basins.

FIGURE 5 is a view in elevation of the settling basins and the coke fines conveyor shown in FIGURE 4.

FIGURE'6 is a sectional View taken along line 66 of FIGURE 4 and illustrating the construction of the filtering means utilized in the settling basins of the present invention.

FIGURE 7 is a sectional view taken along line 7-7 of FIGURE 4.

FIGURE 8 is a detailed plan view showing the sump which is positioned between the two settling basins utilized in the invention, and illustrating details of construction of the means which are provided for dewatering the coke fines in each of the settling basins, and for removing the filtrate from the filtering means associated with each of the settling basins.

FIGURE 9 is a sectional view taken along line 99 of FIGURE 8 and showing, in addition, the manner in which the coke fines conveyor is positioned over the settling basins and sump.

Referring now. to the drawings in detail, FIGURE 1 is a schematic portrayal of a typical system which may be used for manufacturing petroleum coke by a delayed coking procedure. The selection ofa suitable charge stock for coking operations is well known in the art. The principal stocks which are employed are high boiling virgin and cracked petroleum residua, such as: virgin reduced crude; bottoms from the vacuum distillation of reduced crudes, referred to as vacuum reduced residuum; Duosol extract; thermal tar; and other heavy residua. Blends of these materials are also often used to provide a feed which will yield a suitable coke having a sufficiently low sulphur content.

A heavy petroleum residuum prepared 'by appropriate fractionation of crude oil is passed from the fractionation tower (not shown) via line 10 to a suitable preheater 12.. From the preheater 12 the residuum is charged through line 14 to one or the other of the delayed coking drums 16 or 18. The temperature of the residuum charged to the coke drums is from about 850 F. to 950 F. A stream of vapor is normally recycled to the fractionator from the top of the coke drums at a temperature of about 830 F. and about 30 p.s.i.g. by way of the conduit 20.

The pressure in the coking drums 16 and 18 is maintained at from about 20 to p.s.i. and the drums are well insulated to minimize heat loss so that the reacti temperature lies between about 830 F. and 900 F. The hot charge stock in the coking drums 16 and 18 decomposes over a period of several hours, liberating hydrocarbon vapors which continuously rise through the mass of material contained in the drums. The first stages of thermal decomposition occurring in the charge stock within the coking drums reduce this oil to a very heavy tar or pitch which subsequently undergoes further decomposition into solid coke. The ascending hydrocarbon vapors in the coking drums produce pores and channels in the coke through which the incoming oil from the furnace may pass. This process is continued until the drum in use is filled with a mass of solid coke. The vapors which are evolved in the course of the decomposition occurring within the coking drums are vented from the top of the drums and returned to a suitable fractionating tower (not shown) where they are fractionated into the desired cuts.

After one of the coking drums 16 or 18 has become filled with solid coke, the coke is cooled and is then removed from the drum by means of high impact producing water jets (not shown) which are directed from nozzles incorporated in special boring and cutting tools (not shown). The lumps of coke which are broken free from the walls of the coke drum by the high impact water jets fall from the drum and are mechanically transferred to the drainage and storage apron 38. Water drains from the coke to collecting pit 42 containing a considerable amount of coke fines.

In the description of the delayed coking operation thus far described, there has been included that apparatus and those steps of the processes normally employed in the majority of delayed coking operations. However, in addition to the production of raw coke in the described manner, and the conveyance of this material to a suitable storage facility, it is frequently desirable tofurther treat the coke by a calcining procedure. To this end, coke is fed from the silo 24 into a housing 26 and from thence into an inclined rotary kiln 28. The .coke which is discharged from the silo 24 will contain a substantial portion of undersized coke fines with their distribution in the feed from the silo 24 to the housing 26 being determined by the evenness with which they have been distributed in the coke bed contained in the silo during storage.

Coke passes downwardly from the housing 26 through the kiln 28 where it is calcined at a temperature of about 250-0 F. by contact with hot gases passing upwardly through the kiln and countercurrently to the flow of the coke. The hot gases in the calcining kiln 28 are created partially by the combustion of fuel gas introduced at 29. Primary and secondary sources of air are supplied through lines 29a and 29b, affording an excess of air over that required to combust the fuel gas introduced at 29. The hot gases are also created by combustion of the volatile hydrocarbons from the raw coke with the excess air, although the combustion of such hydrocarbons can be reduced by fluidi-Zing a portion of the fines from cyclone separator 31 and burning such fluidized fines in the kiln 28 by introducing them into the firing hood along with the secondary source of air 29b. Although some of the fines which enter .the calcining kiln 28 with the larger particles of coke are consumed within the kiln, a substantial portion of the fines is not burned and calcined in the kiln along with the larger particles. The calcined coke with a certain amount of calcined fine material is collected in the firing hood 30 at the lower end of the kiln 28 and from the firing hood is conveyed to storage.

As an alternative to discharging the combustiongases from the kiln 28 to the atmosphere by suitable venting of the housing 26, it has heretofore been proposed that the hot gases and entrained fines be passed from the upper end of the kiln 28 and the housing 26 into a cyclone separator 31 where the fines are removed from the hot gases and subsequently mixed with a suitable gas oil or other separator to the coking drums, these fines may be fluidized disposal procedures as have heretofore been proposed will not be discussed.

From the foregoing description of the delayed coking process as it is generally practiced, and from the description of the process in which a post-calcining operation is included as an integral part thereof, it will have become apparent that the mode of treatment of the effluent coke product which is removed from the delayed coking drums 16 and 18 prior to its introduction to the raw coke storage silo 24 is an important consideration. The fines cannot be allowed to become dried to the extent that they may be easily wafted into the atmosphere by air currents, yet they must be dried to an extent such that entrained moisture and water does not interfere with the flow of the coke through the silo and into the kiln. Whether the calcining procedure is employed in the delayed coking process or not, subsequent storage of the coarser particles of coke along with the fines generally makes it necessary that the fines be fairly evenly distributed throughout the entire body of raw coke, and that the water content of the fines be reduced to the greatest possible degree short of being dusty.

It is proposed by the present invention to achieve a more efiicient and satisfactory disposition of the coke fines and water discharged from the coking drums 16 and 17 by the apparatus illustrated in FIGURES 2 through 9, and the process which is practiced in utilizing such apparatus or other apparatus relying upon the same principles. In FIGURES 2 and 3, the coking drums 16 and 18 are shown positioned over one end of a large efiluent receiving apron 32. After the one of the coking drums 16 or 18 which is in use has been filled with a solid bed of coke in the manner hereinbefore described, the coke is removed from the drum by directing jets of water under high pressure against the coke inside the drum to abrade the coke and, by high impact, loosen it from the sides of the drum. The high pressure water is effective to reduce the coke from a solid bed to a number of large chunks or lumps, and also results in the production of a substantial quantity of fines or very small particles, The coke fines, coarser particles of coke and the water fall from the coke drum onto an inclined portion 34 of the apron 32 and then slide down the inclined portion 34 until the mass of material reaches the relatively level portion 36 of the apron.

Extending outwardly and upwardly from the portion 36 of the apron is a second and much larger inclined portion 38 which is flared transversely in the manner best illustrated in FIGURE 2. Extending across the center of the inclined, flared portion 38 of the apron 32 and projecting vertically upward therefrom is a partition 40. Disposed at the end of the apron 32 opposite that end at which the coke drums 16 and 18 are located is a suitable conveyor 42 which moves transversely across the end of the apron 32 and functions to receive large lumps of coke from the apron in a manner hereinafter described.

As indicated by the arrow drawn on the portion 36 of the apron 32 in FIGURE 2, this portion of the apron is slightly inclined transversely so that water (containing coke fines) may gravitate down the portion 36 of the apron into a collecting pit 37 which is positioned adjacent and slightly below the apron 32. A pump 44 is positioned alongside the collecting pit 37 and functions to pump a mixture or slurry of coke fines and water from the collecting pit 37 into one of a pair of settling basins designated generally by

reference characters

46 and 48. A screen (not shown) may be positioned between portion 36 of apron 38 and pit 37, to prevent particles so large as to be detrimental to pump 44 from falling into the pit. A suitable conduit system 50 having

branch lines

50a and 50b is provided between the collecting pit 37 and each of the settling

basins

46 and 48 to permit the slurry from the collecting pit to be pumped into either of the settling basins as desired. A conveyor 52 is centrally positioned over the settling

basins

46 and 48 and extends throughout the length thereof and terminates over the conveyor 42 which extends transversely across one end of the apron 32.

Positioned between and contiguous to the settling

basins

46 and 48 is a sump 54 which functions to receive water removed from the coke fines located in the settling basins in a manner hereinafter described. The water accumulating in the sump 54 is returned by a drain line 56 to a reservoir 58 which may be conveniently positioned alongside the apron 32, and is preferably pumped to storage tank 59, where the water is available for reuse in jetting the coke deposits from the coking drums 16 and 18. Although pit 37 and reservoir 58 may be separated, it is convenient to place them adjacent one another and separated by a common wall 61. Wall 61 may be provided with a valve for opening a connection between pit 37 and reservoir 58, so that if pump 44 breaks down, reservoir 58 can be used as a temporary fines settling basin.

The details of construction of the settling

basins

46 and 48 constitute an important aspect of the present invention and are best illustrated in FIGURES 4 through 7. As shown in FIGURE 4, each of the settling

basins

46 and 48 is generally rectangular in configuration and the

branches

50a and 50b of the conduit system 50 extend across the most distally located ends of each of the respective settling basins. At their proximal ends, each of the settling

basins

46 and 48 is contiguous to, or joined to, the sump 54. The transverse walls 60 of the sump 54 are of lesser height than the longitudinal and end 'walls of the settling

basins

46 and 48 so that the sump Walls form weirs at the discharge ends of the settling basins.

A channelway 62 is formed in the bottom of each of the settling

basins

46 and 48 and is best illustrated in FIGURE 6. Overlying the channelway 62 and supported in elongated recesses or grooves 64 which extend over the lengthof the settling

basins

46 and 48 is a heavy metallic grate 66.' The grate 66 may be supported upon suitable angle iron strips 67 which are received in the recesses 64 formed in the concrete which constitutes the bottom of each of the settling

basins

46 and 48. A screen 68 of relatively fine mesh is positioned on top of the grate 66 and a second grate 70 is then rested atop the screen. The depth of the recess 64 formed in the bottom of the settling

basins

46 and 48 is such that the upper surface of the top grate 70 is approximately flush or even with the bottom of the settling basins.

As illustrated in FIGURE 6, the bottoms of the settling

basins

46 and 48 are preferably sloped inwardly toward the grates 70 so that water will drain toward the center of the basins. In combination, the grates 66 and 70 and the screen 68 which is interposed between the grates constitute a filter element which functions to filter water from the coke fines placed in the settling

basins

46 and 48. The manner of functioning of the grates 66 and 70 and the screen 68 will be described in greater detail hereinafter.

As has previously been indicated, the channelways 62 extend for the full length of the settling

basins

46 and 48. The channelways 62 do not, however, pass through the transverse walls 60 of the sump 54, but, instead, terminate on the side of such walls inside the respective settling basin.

At longitudinally spaced intervals along the length of each of the settling

basins

46 and 48 and positioned at opposite sides thereof are a plurality of supporting members 72 which are preferably constructed of concrete and which are utilized to support or form the base for a plurality of vertically extending stanchions 74 which are best illustrated in FIGURES 5 and 9. The stanchions 74 support transverse beams 76 from which is suspended in any suitable manner the conveyor 52 which is utilized to move dewatered fines from the settling

basins

46 and 48 to the conveyor 42 in a manner hereinafter described.

The Way in which the

branches

50a and 50b of the conduit system 50 are constructed is best illustrated in FIGURE 7. It will be perceived in referring to this figure of the drawings that the branch 50b of the conduit system 50 extends completely across the settling basin 48 in a transverse direction and is provided with a series of radial slots 80 which are positioned on the periphery of the branch 50b of the conduit so that material is ejected from that conduit through the slots in a downward direction. By virtue of this arrangement, the slurry of water and coke fines entering the settling basin 48 from the branch 50b of the conduit system 50 will flow along the length of the settling basin from one end thereof to the other. A settled bed of coke fines will be established in the basin which has a gradient or slope extending from the end of the basin at which the slurry is introduced to the end of the basin at which the walls 60 of the sump are located. The arrangement of the branch 50a in the settling basin 46 is identical to that for branch 50b which is illustrated in FIGURE 7 and functions in the same manner.

The details of construction of the sump 54 and the means which are provided for transferring water from the settling

basins

46 and 48 into the sump 54 are best illustrated in FIGURES 8 and 9. The sump S4 is generally rectangular in horizontal cross section and is provided with a bottom which is sloped downwardly from the walls of the sump toward the middle in order to permit the water accumulated therein to be removed by the drain pipe 56. Extending through each of the transverse sump walls 60 which form weirs at the ends of the settling

basins

46 and 48 are a pair of decanting conduits or swing pipes indicated generally by reference character 84. The decanting conduits 84 each comprise a short tubular section 86 which extends through the respective wall 60 of the sump 54 at a point above the uppermost grate '70. A longer tubular member 88 is swingably connected to the tubular section 86 through a suitable swivel joint 90 so that the free end of the tubular section 88 may be swung downwardly from an elevated status to a position near the bottom of the respective settling basin in the manner shown in FIGURE 9.

Also associated with each of the transverse walls 68 of the sump 54 is another conduit or L-shaped swing pipe designated generally by reference character 92 which includes a short tubular section 94 passing through the respective wall 60 of the sump into the adjacent channelway 62. Swingably connected to the short tubular section 94 through a joint 96 similar to the joints 98 used in the decanting conduits 84 is a longer tubular section 98. The tubular section 98 may, like the sections 88 of the decanting conduits, be swung from a vertical or upper position to a lower position in which its free end is in contact with the bottom of the sump 54 in the manner shown in FIGURE 9.

OPERATION In the operation of the apparatus and process of the invention, the coking drums 16 and 18 are alternately used so that while one of the drums is being discharged of its raw coke contents, the decomposition of the heavy residuum in the second coke drum is taking place with the formation of coke resulting. As the raw coke efiiuent mixed with water from one of the drums is discharged therefrom, it falls down the inclined portion 34 of the apron 32 and comes to rest .on the transversely sloped portion 36. It is then moved by the use of a suitable device, such as a Sauermann dragline up the inclined portion 38 of the apron 32. The teeth of the dragline bucket are such that some of the fines will drain with the water down the inclined portion 38 back onto the portion 36 of the apron. The coarser particles of coke are moved up the apron toward the conveyor 42 which extends transversely across the apron at its end opposite the end at which the coke drums 16 and 18 are located.

Since it may frequently be desirable to produce different grades of coke in the coking drums 16 and 18, the partition 40 is provided so that coke of one grade may be pulled by the dragline up the apron 32 on one side thereof, and the coke of the other grade may be pulled up the other side of the apron with the partition 40 serving to maintain separation between the piles of coke which accumulate at the upper end of the inclined portion 38 of the apron. As has been indicated, water and coke fines from the mass of effluent materials discharged from the coke drums 16 and 18 drain back into the collecting pit 42 by virtue of the incline of the

portions

36 and 38 of the apron 32. The material which accumulates in the collecting pit 37 is a slurry-like material and is pumpable when a suitable slurry pump 44 is employed. The slurry of fines and water from the collecting pit 37 is pumped through the conduit system 50 by the pump 44 and is discharged at one or the other of the

branches

50a and 50b of the conduit system. Normally, one of the branches 5041 or will be utilized in correspondence with the discharge of effluent from one of the coking drums 16 or 18. In other words, the utilization of the

branches

50a and 50b of the conduit system 50 may be correlated to the alternate utilization of the drums 16 and 18 so that one of the settling

basins

46 or 48 may be employed for achieving thedewatering of the coke fines from one of the coking drums, while the other settling basin is receiving the slurry pumped from the collecting pit 37 at the time the other coking drum istbeing discharged onto the apron 32. r

The

branches

50a and 50b of the conduit system 50 are elfective to discharge the Water and coke fines slurry into the settling

basins

46 and 48 through the radial slots,

80 formed in the branches of the conduit system so that the slurry is distributed uniformly across the settling basins and fiowstoward the other end thereof. This results in more of the coke fines being settled out in the ends of the settling basin most distally located with respect to the walls 60 of the sump 54 than at the ends of the settling basins adjacent such walls. In other words, the bed of coke fines which settles to the bottom of the settling basins will be sloped or inclined from the end at which the slurry is discharged from the

branches

50a and 50b of the conduit system 50 to the ends of the basins adjacent the Walls 60 of the sump 54 which form weirs over which water may flow from the settling basins into the sump. By virtue of this settling action of the fines, more of the supernatant water which stands over the settled fines in the settling basin may be decanted by the decanting conduits 84 into the sump 54 than would be the case were'the beds of settled coke fines in the basins of uniform depth throughout the length of the basins. Each of the settling

basins

46 and 48 is of a size such that the normal volume of slurry which is introduced to the settling basins during a complete decoking operation from one of the drums 16 or 18 will be greater than the capacity of the settling basin, so that much of the water in the slurry Will flow over the sump walls 60 at one end of the settling basins. This excess water which flows over the weir-like walls 60 carries with it very little of the coke fine content of the slurry since, as has been pointed out, most of the coke fines have settled to the bottom of the settling

basins

46 and 48 It) pumped into one of the settling

basins

46 or 48, the slurry is permitted to stand in the basin for a period of about an hour or possibly longer, to permit the coke fines to settle to the bottom of the basin. There is thus eventually produced in each of the basins, a two-phase ssytem in which a fairly Well defined interface exists between the bed of settled coke fines in the bottom of the V basin and the relatively clear water or supernatant water which overlies the fines bed.

During the periods of filling the settling basins and settling the coke fines therein, the conduit 92 remains in the upward position. The advantage of this procedure is that water will be prevented from draining rapidly through screen 68 and into sump 54, whereby the larger particles of fines will have time to settle out on the screen to provide in effect a filter cake for more efficient filtering of the fines of smaller particle size from the water. The design and construction of the filtering system is an important feature of the invention in that the employment of the grates 66 and 70 having relatively large porosity as compared to the screen 68 provides. the structural strength necessary to permit workmen to stand upon the grates at a subsequent point in the process of the invention without damaging the grates or breaking or bending the screen 68. The lowermost grate 66 provides a rigid support for the screen 68 to prevent it from becoming weighted down with coke fines to the extent that it sags into the channelway 62 in the bottom of the settling

basins

46 and 48. The uppermost grate 70 functions to permit workmen to stand on the screen 68 and shovel coke fines therefrom without damaging it. The porosity or mesh size of the screen 68 is preferably such that very few of the coke fines can pass therethrough. This mesh sizevis possible in the separation of the coke fines and water because of the relatively great porosity of the coke fines themselves. In other words, even though the pores or openings through the screen 68 become substantially clogged with coke fines, the water can still drain through the screen and into the channelway 62 by virtue of the porosity of the particles of coke. We have found that a suitable screen 68 comprises a center screen of 40 mesh sandwiched between two 4-mesh screens. The upper 4-mesh screen serves to filter out the coarser particles of coke fines and to protect the 40- mesh center screen. The lower 4-mesh screen protects the 40-mesh screen.

After allowing a suificient period of time for a good degree of separation between the coke fines and the supernatant Water to be achieved in the settling

basins

46 and 48, the supernatant Water may be decanted from over the settled bed of coke fines by using the decanting conduits 84. As has been previously explained, the upper end of the long tubular section 88 of the decanting conduits 84 may be swung to a position at which the end is submerged below the surface of the supernatant water in the respective settling basin. In this position, the clearest or most fine-free water in the settling basins may be decanted through the decanting conduits 84 into the sump 54. This particular mode of operation of the decanting conduits 84 also permits the Water tobe decanted from the settling basins with a minimum of turbulence generated by flow of the water into the upper end of the long tubular section 88 of the decanting conduits 84.

As the settling of coke finesprogresses to further clarify the supernatant Water, and as the level of the supernatant water in the settling basins is lowered by decantation, the upper end of the elongated section 88 of the decanting conduit 84 may be lowered further with respect to the walls of the settling basin so that more of the water may be removed from the settling basin into the sump 54. The decanting process may be continued until the free end of the decanting conduits 84 inside the settling

basins

46 and 48 approach the interface between the bed of settled coke fines and the supernatant water. At this point, it will usually be desirable to cease the decantation and lower conduit 92, to permit the rest of the water to be removed from the coke fines by draining and filtration through the screen 68 and conduit 92 into sump 54. Of course, the decantation and the filtration of Water through screen 68 and into sump 54 may both proceed simultaneously so that the dewatering of the fines is considerably expedited. The draining and filtration of watershould proceed for a period of several hours, or overnight, until .the fines bed has dried sufliciently so that a man can stand on the bed and shovel the fines onto conveyor 52. The coke fines on the conveyor 52 are deposited with the coarser coke while it is being loaded onto the conveyor 42 from the end of the apron 32. This system of recombining the coke fines with the coarser coke results in a fairly even distribution of the fines throughout the body of the coke and prevents a problem of fines concentration in aparticular location within the storage facility subsequently utilized, such as the silo 24 shown in FIGURE 1 In the meantime, and prior to the recombination of the dewatered coke fines with the large lumps of coke on the conveyor 42, the second coking drum may be decoked and the slurry of coke fines and water separated from the efliuent has been passed into the second settling basin and has commenced to stratify into the two phases of supernatant water and settled coke fines. It can thus be seen that no interruption is necessary in the alternate charging and decoking of the coking drums 16 and 18.

From the foregoing description of the invention, it will be perceived that there is provided by the described process and apparatus, a means of economically recovering the undersized coke fines which are produced in a delayed coking operation. Moreover, the water which is utilized to remove coke from the coking drums is conserved and is recirculated for repeated use. The coke fines are treated in a manner which permits a certain portion of the water to remain therein so that the fines are not so dry as to present an atmospheric contamination problem. Also, the coke fines are recombined With the coarser particles of coke in an evenly distributed manner so that subsequent fouling or choking of storage facilitie and conduits used to supply the coke to a sub sequent calcining operation is avoided. The process also permits the alternate operation of a plurality of delayed coking drums to be substantially continuously carried on without interference being afforded by the described treatment of the coke fines which are produced.

Although the apparatus which is utilized in a preferred embodiment of the present invention has been described heretofore in considerable detail, such description has been advanced by Way of example only, and a number of the details described may be altered or modified Without departure from the basic principles underlying the invention. Insofar as such modifications or innovations in either the described apparatus or the steps of the process hereinbefore enumerated continue to rely upon the basic principles upon which the present invention is bottomed, such modifications and innovations are deemed to fall within the spirit and scopeof the present invention as defined by the following claims.

We claim:

1. In the process for producing petroleum coke by subjecting a heavy petroleum residuum to delayed coking conditions in a coking drum and removing the raw coke from said drum by subjecting the raw coke in the drum to impact by jets of high pressure water, the improvement comprising:

(a) gravitationally separating a slurry of water andcoke fines from the main bodyof coarser particles of raw coke in the efiiuent mass removed from the coking drum;

(b) pumping the slurry into a settling basin;

(c) gravitationally settling the coke fines in said slurry V to the bottom of said basin;

(d) separating the Water from the coke fines by decantation of the water from the upper portion of said coke from said drum by subjecting the raw coke in the drum to, impact by jets of high pressure Water, the improvement comprising:

(a) placing the efliuent from the coking drum on an inclined surface and permitting water and raw coke fines to gravitate down the inclined surface while retaining the coarser particles of raw coke thereon;

(b) collecting the water and coke fines separated from said coarser particles of coke;

(c) placing the collected water and coke fines in a settling basin;

(d) separating the water from the coke fines by decantation of the water from the upper portion of said basin and by filtration through a screen at the bottom of said basin;

(e) recirculating the water separated from the coke fines to the high pressure Water jets used to remove the raw coke from the coking drums; and

(f) substantially uniformly recombining the recovered coke fines with the coarser particles of coke.

3. A process as claimed in claim 2 wherein said collected water and coke fines are placed in said settling basin by injecting the water and fines as a slurry into said basin at one end thereof ,twhereby more of the fines gravitate to the bottom of said basin adjacent the end thereof at which the slurry is injected than at the opposite end of said basin.

4. In a process of the type wherein raw petroleum coke is produced in a delayed coking drum, and the raw coke is removed from said drum by high pressure water jets, the method of conserving the water employed and the raw coke fines produced which comprises:

(a) separating a pumpable slurry of coke fines and water from the. main body of coke removed from the delayed coking drum by said water jets;

(b) placing the slurry in a settling basin;

(0) separating the water from the coke fines by decantation of the water from the upper portion of said basin and by filtration thnough a screen at the bottom of said basin, and recovering said coke fines;

(d) recirculating the water separated from the coke fines to the high pressure water jets used to remove raw coke from the coking drums.-

5. In combination with delayed coking apparatus including a delayed coking drum and a source of water for removing the raw coke therefrom,

(a) an inclined apron under said drum for receiving r-aw coke effluent from said drum admixed with water;

(b) means for moving the coarser particles of coke up the inclined apron toward the vertically higher end thereof while permitting water and coke fines to gravitate to the lower end of said apron;

(c) a collecting pit positioned adjacent said apron at the lower end thereof for collecting water and coke fines gravitating down said apron;

(d) a generally rectangular settling basin;

(e) means for transferring water and coke fines from said collecting pit to said settling basin and distributing said water and coke fines across one end of said settling basin; (f) filtering means in the bottom of said settling basin; (g) a sump adjacent the other end of said settling basin;

(h) means for decanting water from said generally rectangular settling basin into said sump;

(i) conduit means under said filtering means for transferring to said sump water passed through said filtering means; and

(j) means for recirculating water from said sump to said source of water.

6. The combination claimed in claim wherein said sump and said settling basin have a common wall form ing a partition therebetween and said common wall is of lesser height than the adjoining Walls of said settling basin and sump whereby said common wall is a weir over which water from said settling basin may flow into saidsump.

7. The combintion of claim 5 wherein said filtering means comprises:

(1) a channel in the bottom of said settling basin;

(2) a pair of superimposed, rigid gratings positioned over said channel in a recess formed in said settling basin; and

(3) a screen positioned between said gratings.

8. The combination claimed in claim 5 wherein said means for decanting water from said receptacle comprises:

(1) a conduit passing through one end of said settling basin at a point near the bottom thereof and communicating with said sump; and

(2) a pipe swingably connected to the end of said conduit inside said settling basin and swingable from a horizontal to a vertical position whereby water in said settling basin may be decanted to varying levels.

9. The combination claimed in claim 7 wherein said conduit means comprises:

(1) a conduit placing said channel in communication with said sump; and

(2) a pipe swingably connected to the end of said conduit communicating with said sump and swingable from an upper to a lower position whereby water which is filtered into said channel may be conducted to said sump.

10. The combination claimed in claim 5 and further characterized to include:

(a) a second settling basin adjacent said sump;

(b) a second filtering means in the bottom of said second settling basin;

(c) means for decanting water from said second settling basin to said sump;

(d) conduit means .for transferring to said sump water passed through said second filtering means; and

(e) means for alternately transferring water and coke fines from said collecting pit to said first and second settling basins whereby one of said settling basins may be filled while coke fines are being de-watered in the other of said settling basins.

11. The combination claimed in claim 5 wherein said means (e) comprises:

(1) a conduit system interconnecting said collecting basin and said settling basin and having a radially slotted end portion extending across one end of said settling basin; and

(2) a pump interposed in said conduit system between said collecting basin and said settling basin.

12. Apparatus for separating coke fines from water comprising:

(a) an elongated settling basin;

(b) means for injecting a slurry of coke fines and water into said settling basin uniformly across one end thereof whereby said slurry flows from said one end of the basin to the other end thereof during filling of the basin;

(c) a weir at the end of said basin opposite said slurryinjecting means;

(d) a sump adjacent said settling basin and adjacent to said weir for receiving water flowing over said weir from said basin; I

(e) a filtrate-receiving channelway under said settling basin and extending the length thereof;

(f) filter means in the bottom of said settling basin over said channelway for straining the water from the coke fines;

(g) conduit means connecting said channelway with said sump; and

(h) means for decanting into said sump supernatant water from above the coke fines settled to the bottom of said settling basin.

13. Apparatus as claimed in claim 12 wherein said filter means comprises a pair of rigid metal grates having a screen positioned therebetween for supporting relative large weights while preventing coke fines of smaller particulate size from passing therethrough.

14. Apparatus as claimed in claim 12 wherein said conduit means (g) comprises a generally L-shaped tubular conduit having one of its legs projecting through a wall of said sump and into said filtrate-receiving channelway and having its other leg extending substantially normal to said one leg and swingably secured thereto for rotation in said sump about the axis of. said one leg.

15. Apparatus for separating coke fines from water comprising:

(a) a pair of elongated settling basins arranged in tandem relationship;

(b) means at opposite ends of each of said basins for injecting a slurry of coke fines and water into said basins uniformly across said opposite ends;

(0) weirs at each end of said basins opposite said slurryinjecting means (b);

(d) a sump located between said basins for receiving water flowing over said weirs from said basins;

(e) filtrate-receiving channelways at the bottom of each of said basins and extending the lengths thereof;

(f) filter means, in the bottom of each basin above said channelways, comprising screens for straining the water from the coke fines;

(g) conduit means connecting each of said channelways with said sump; and

(h) two L-shaped swing pipes each having one leg connected to one of said basins and the other leg swingably communicating with said sump for decanting water from said settling basins.

References Cited by the Examiner UNITED STATES PATENTS 2/ 1944 Myers 208--50 9/1945 Schumacher et al. 208-162 12/1962 White 20811 12/1963 Adee 208-50

Claims

1. IN THE PROCESS FOR PRODUCING PETROLEUM COKE BY SUBJECTING A HEAVY PETROLEUM RESIDUUM TO DELAYED COKING CONDITIONS IN A COKING DRUM AND REMOVING THE RAW COKE FROM SAID DRUM BY SUBJECTING THE RAW COKE IN THE DRUM TO IMPACT BY JETS OF HIGH PRESSURE WATER, THE IMPROVEMENT COMPRISING: (A) GRAVITATIONALLY SEPARATING A SLURRY OF WATER AND COKE FINES FROM THE MAIN BODY OF COARSER PARTICLES OF RAW COKE IN THE EFFLUENT MASS REMOVED FROM THE COKING DRUM; (B) PUMPING THE SLURRY INTO A SETTLING BASIN; (C) GRAVITATIONALLY SETTLING THE COKE FINES IN SAID SLURRY TO THE BOTTOM OF SAID BASIN; (D) SEPARATING THE WATER FROM THE COKE FINES BY DECANTATION OF THE WATER FROM THE UPPER PORTION OF SAID BASIN AND BY FILTRATION THROUGH A SCREEN AT THE BOTTOM OF SAID BASIN; (E) RECIRCULATING THE WATER SEPARATED FROM THE COKE FINES TO PROVIDE THE SOURCE OF HIGH PRESSURE WATER USED TO REMOVE THE RAW COKE FROM THE COKE DRUM; AND (F) SUBSTANTIALLY UNIFORMLY RECOMBINING THE RECOVERED COKE FINES WITH THE MAIN BODY OF COARSER LPARTICLES OF RAW COKE.