These low-value feedstocks convert part of the HFs into more valuable liquid and gas products. In the delayed coking process / a waste feed material is quickly heated in a fired heater or tubular furnace to 480 ° C to 520 ° C and pressures of 344.74 to 3792.12 kPa (50 to 5509 psig). The heated feed material is then passed to a coke drum which is maintained under conditions under which coking occurs, generally at temperatures above 425 ° C (800 ° F), typically between 480 ° C to 520 ° C ( 895 ° F to 9701F), under superatmospheric pressures of 103.42 to 551.58 kPa (15 to 80 psig) to allow the volatiles formed in the coker drum to be removed above and passed to a fractionator, leaving the coke behind. When the coker drum is filled with coke, the heated feed is changed to another drum and additional hydrocarbon vapors are purged from the coke drum with steam. The drum is then rapidly cooled with water to reduce the temperature to below 148.89 ° C (300 ° F) after which the water is drained. When the cooling step is complete, the drum is opened and the coke is separated after drilling and / or cutting using high velocity water jets.
For example, a high-impact, high-velocity water jet is used to cut the coke from the drum. Typically a hole is drilled in the coke of the water jet nozzles located in a drilling tool. The nozzles oriented horizontally on the head of a cutting tool then cut the drum coke. The step of coke removal is added considerably to the production time of the total process. In this way, it would be desirable to be able to produce a free-flowing coke in a coker drum which does not require the expense and time associated with conventional coke removal, ie, it could drain out of the bottom of the drum. Even though the coking drum may appear to be completely cooled, some bed volumes may have been diverted by the cooling water, leaving the coke deviated very hot (warmer than the boiling point of water). This phenomenon is sometimes referred to as "hot spots" or "hot drums", it may be the result of a combination of coke morphologies that is present in the drum, which may contain a combination of more than one type of solid coke product , that is, coke in sponge or coke in shot. Since non-agglomerated grit coke can be cooled more rapidly than other coke morphologies, such as coarse-grained coke masses or sponge coke, it would be desirable to predominantly produce free-flowing coke in a delayed coker / in order to avoid or minimize hot drums. SUMMARY OF THE INVENTION In one embodiment, a delayed coke process is provided comprising: a) preparing a vacuum residue having less than 10% by weight of 482.17 to 599.94 ° C (900 to 1040 ° F) of material in boiling as measured by HTSD (Simulated High Temperature Distillation) and combined with a recycled recycled distillate stream where the distillate recycle stream has a boiling scale within the range of 232.22 ° C to 403.89 ° C
(450 ° F to 750 ° F); b) driving the mixture to a heating zone where it is heated to an effective coking temperature; and c) driving the heated mixture from the heating zone to a coking zone where the vapor products are heated. they pick up and through which coke with reduced incidence of hot drums and relatively free-flowing nature is formed. In a preferred embodiment, the coking zone is in a delayed coker drum, and a substantially free flowing coke product is separated from the coker drum. In yet another preferred modality, an additive is introduced into the feed material either before heating or just being introduced into the coker container, which additive can be a metal-containing or metal-free additive. If it is one that contains metals, it is preferably a non-organic, insoluble organic, or soluble organic miscible metal containing additive which is effective for the formation of coke that flows substantially free. In still another preferred embodiment of the present invention, the metal of the additive is selected from the group consisting of sodium, potassium, iron, nickel, vanadium, tin, molybdenum, manganese, aluminum, cobalt, calcium, magnesium and mixtures thereof. In another embodiment, the metal-containing additive is a finely ground solid with a high surface area, a natural material with a high surface area, or a fine particle / seed-producing additive. These high surface area materials include smoked silica and alumina, catalytic grinder fines, FLEXICOKER, cyclone fines, magnesium sulfate, calcium sulfate, diatomaceous earth, magnesium silicate clays, fly ash containing vanadium and the like. The additives can be used either alone or in combination. In another embodiment, substantially metal-free additives can be used in the practice of the present invention. Non-limiting examples include elemental sulfur, substantially free metal solids of high surface area, such as rice husks, sugars, cellulose, ground coals, self-ground tires and mineral acids such as sulfuric acid, phosphoric acid, and their acid anhydrides. It should be understood that before or after the residue is treated with the additive, a caustic species, preferably in aqueous form, may optionally be added. The caustic can be added before, during, or after the residue is passed from the coker oven and heated to coking temperatures. The spent caustic obtained from hydrocarbon processing can be used. This spent caustic can contain dissolved hydrocarbons, and salts of organic acids, e.g., carboxylic acids, phenols, naphthenic acids and the like. In another embodiment, the process is used in conjunction with automated coke drum waste beheading valves, and the mixture of coke product plus cooling water is throttled out of the bottom of the coke drum through the bottom valve. If an additive is used, it is desirable to avoid heterogeneous areas of coke morphology formation. That is, what locations in the coke drum are not made where the coke is substantially free flowing and other areas where the coke is not flowing substantially free. The dispersion of the additive is achieved by any number of ways, preferably by introducing a side stream of the additive into the feed stream at the desired location. The additive can be added by solubilizing the additive to the vacuum residue, or by reducing the viscosity of the vacuum residue before mixing the additive, e.g., by heating, adding solvent, etc. High energy mixing or use of static mixing devices can be employed to assist in the dispersion of the additive agent, especially additive agents having relatively low solubility in the feed stream. Preferably, all or substantially all of the coke formed in the process is coke that flows substantially free, more preferably, coke in free flowing granulate. It is also preferred that at least a portion of volatile species present in the coker drum during and after coking separate and conduct away from the process, preferably above the coker drum. BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a simplified process flow diagram of a preferred method for obtaining a deep cut heavy oil stream for use in the present invention. This figure shows the modified vacuum distillation system with a steam side separator, as well as a distillation recycling stream from the coking main fractionator. Figure 2 is another simplified process flow diagram of another preferred method for obtaining a deep cut heavy oil stream for use in the present invention. This figure is similar to that of Figure 1 hereof, except that there is an intermediate residue reheat furnace to reheat the stream upstream of the separator. Figure 3 is an optical polarization of transverse polarized light showing the coke formed from a Canadian void residue of transition coke-forming weights containing 12% by weight of boiling material at 537.78 ° C (1000 ° F) as shown in FIG. determined by HTSD. The figure shows small domains that vary in size from 10 to 20 micrometers with some thick mosaic that varies from 5 to 10 micrometers (this microstructure is associated with coke beds in volume that have transition coke morphology). Figure 4 shows the effect of further distilling the feed so that it contains only 2% by weight of boiling material of 537.78 ° C (1000 ° F). The figure is an optical micrograph of transverse polarized light showing coke residue formed from the deepest cut residue and showing a medium / coarse tile structure varying in size from 2 to 10 micrometers (this microstructure is associated with coke beds in volume that have coke morphology in shot). DETAILED DESCRIPTION OF THE INVENTION The petroleum vacuum waste feed materials are suitable for delayed coking. These petroleum residues are frequently obtained after the removal of distillates from raw feedstocks under vacuum and are characterized by being comprised of components of large size and molecular weight, generally containing: (a) asphaltenes and other aromatic structures of high molecular weight that would inhibit the hydrotreatment / hydrofraction regime and cause catalyst deactivation; (b) metal contaminants that occur naturally in crude oil or that result from previous treatment of crude oil, whose contaminants would tend to deactivate the hydrotreating / hydrocracking catalysts and interfere with catalyst regeneration; and (c) a relatively high content of sulfur and nitrogen compounds that give rise to objectionable amounts of S02, S03, and Nox during combustion of the petroleum residue. The nitrogen compounds present in the residue also have a tendency to deactivate catalytic fractionation catalysts. The coke bed morphology is typically described in simplified terms such as sponge coke, shot coke, transition coke, or needle coke. As mentioned above, there are generally three different types of solid delayed coker products having different values, appearances and properties, ie coke in needle, coke in sponge and coke in shot. Coke in needle is the highest quality of the three varieties. Coke in needle, after additional heat treatment, has high electrical conductivity (and a low coefficient of thermal expansion), and is used in production of electric arc steel. It is relatively low in sulfur and metals and is often produced from some of the higher quality coker feed materials that include more aromatic feedstocks such as suspension and decanting oils from catalytic fractionators and thermal fractionation areas. Typically, it is not formed by delayed coking for waste feeds. There are additional descriptors of coke too, even when they are less common. For example, a sandy coke is a coke that after cutting is seen with the naked eye very similar to thick black flat sand. In one embodiment, waste feedstocks include, but are not limited to, residues from atmospheric and vacuum distillation of petroleum crudes or atmospheric or vacuum distillation of heavy oils, half-broken residues, pitting of deasphalting units, carbon liquid, shale oil or combinations of these materials. The heavy bitumens found at atmospheric and vacuum can also be used. Feeding materials typically used in delayed coking are high boiling hydrocarbonaceous materials with an API gravity of 20 ° or less, and a content of Conradson Carbon Residue from 0 to 40 weight percent. Vacuum residues are characterized by a number of parameters, including their boiling point distributions. The boiling point distribution can be obtained by physical distillation in a laboratory, but it is expensive to perform this type of analysis. Another method to determine the boiling point distribution is to use specialized gas chromatographic techniques that have been developed for the petroleum industry. One of these GC methods is Simulated High Temperature Distillation (HTSD). This method is described by D.C. Villanlati, et al., In "High-temperature Simulated Distillation Applications in Petroleum Characterization" in Encyclopedia of Analytical Chemistry, R.A. Meyers (Ed.), P. 6726-6741 John Wiley, 2000, and has been found to be effective in characterizing the boiling point distributions of vacuum residues. Boiling point distributions are reported as% by weight against atmospheric boiling point (AEBP) and are reported in increments of 1% by weight. Vacuum distillation is well known in the industry. A number of variables affect the boiling point distribution of the vacuum distillation unit residues. As refiners tend to try to push more flow through existing units, however, the boiling point distributions of vacuum waste tend to to collect a higher percentage of the lower boiling components. It has been unexpectedly found by the present inventors that the components that are contained in a virgin residue boiling between 482.22 ° C to 560 ° C (900 ° F to 1040 ° F) can have a significant influence on the coke morphology of Delayed coker is that they are present in an abundance in excess of 10% by weight of the complete virgin feed. Specifically / it has been found that when a waste would otherwise make coke in shot it has the fraction of 482.22 ° C to 560 ° C. { 900 ° F to 1040 ° F) in excess of 10% by weight, will make a transition coke, a bonded shot, and may have appreciable percentage of hot drums when coked under "typical" delayed coker conditions, eg, DOT = 437.73 ° C (820 ° F), DOP = 103.42 to 241.32 kPa (15 to 35 psig), and recirculation ratio of minus 10%, where DOT is the drum exit temperature and DOP is the drum outlet pressure. It has been found that by reducing the fraction from 482.22 ° C to 560 ° C (900 ° F to 1040 ° F) the deEBP material to less than 10% by weight again pushes the coke morphology to a less bound coke morphology and less Self-sustaining These deeper waste cuts can be obtained by any means available in an oil refinery. A medium is depicted in Figure 1 herein, where atmospheric waste is conducted through line 10 through an oven 1 where it is heated to a temperature of 371.11 ° C to 426.67 ° C (700 ° F). at 800 ° F) is then sent through line 20 to vacuum distillation tower 2 where the non-condensable material, such as steam and any small amount of remaining light ends are collected overhead through line 30. , preferably by use of an ejector system (not shown). A heavy vacuum gas oil cut is removed through line 40. An intermediate cut is removed through line 50 where it is combined with vacuum residfrom line 60 and is conducted to external separator 3 where a lighter stream, such as one containing at least a fraction of any remaining gas oil, is purified by the use of steam injected through line 70 and sent back to the vacuum distillation tower through the line 80. The cleaned vacuum residare then conducted through line 90 to a delayed coker where it is typically introduced near the bottom of the main fractionator 4, even though it can be fed directly to the coker oven. The residof line 100 of the main fractionator are fed to the coker oven where the recycled distillate is introduced through line 110. Any additives to aid in the coking reaction can be introduced through line 120. The stream of The residue is heated in a coker oven to coking temperatures then sent through line 130 to one or more coker drums (not shown). Figure 2 of the present shows another preferred process scheme for obtaining a deep cut vacuum residue feed to produce shot coke that flows substantially free in a delayed coker. The process scheme is similar to that shown in Figure 1 herein, except that the intermediate cut removed from distillation tower 2 is conducted through line 50 and combined with vacuum distillation residin line 55. and it is sent through the external separator furnace 6 to reheat to substantially the same temperature as that of the furnace 1. The reheated vacuum waste / intermediate cutting stream is conducted through the line 60 to the external discharger 3. The disadvantage of the deeper cut resid however, is that they tend to foul the coker furnace more quickly than the shallower cut resid and this is a potential economic debit because this can increase the frequency of furnace cleaning , which in turn reduces the total production of the coking unit. To mitigate the higher fouling tendency of the deeper cut vacuum residue, a distillate stream can be added to the coker feed. The boiling point distribution of the distillate recycle stream is such that it is an effective oven fouling mitigator, however this end point is sufficiently low that it does not affect the coke morphology. An example of this would be a coker distillate stream with a boiling scale of 232.22 ° C to 403.89 ° C (450 ° F to 750 ° F). The pumped waste feed to a heater at a pressure of 344.74 to 3792.12 kPa (50 to 550 psig), where it is heated to a temperature of 248.89 ° C (480 ° F) to 271.11 ° C (520 ° F). It is then discharged to a coking zone, typically an insulated coker drum, vertically oriented through an inlet in the base of the drum. The pressure in the drum is usually relatively low, such as 103.42 to 551.58 kPa (15 to 80 psig) to allow the volatiles to be removed from above. Typical operating temperatures of the drum will be between 410 ° C and 475 ° C. The hot feed material is fractionated thermally over a period of time (the "coking time") in the coker drum, releasing volatile compounds primarily from hydrocarbon products, which rise continuously through the coke mass and are collected by above. The volatile products are sent to a coke fractionator for coking gas, light gasoline oil / gas distillation and recovery, and heavy gas oil. In one embodiment, a portion of the heavy coker gas oil present in the product stream introduced in the coker fractionator can be captured for recycling and combined with the fresh feed (coker feed components), thereby forming the heater of coker or load of coking oven. In addition to volatile products, delayed coking also forms a solid coke product. The coke bed morphology is typically described in simplified terms such as sponge coke, shot coke, transition coke, and needle coke. The sponge coke, as the name suggests, has a sponge-like appearance with pores of various sizes and bubbles "frozen inside" a solid coke matrix. A key attribute of sponge coke produced by routine coker operation conditions is that the coke is self-supporting, and typically will not fall off the bottom of a headless coker drum, which typically has a head diameter of 1,829 m (6 feet) ). The head of the coker drum can be removed either manually or by using a throttle slide valve. Coke on needle refers to a specialty coke that has a unique anisotropic structure. The preparation of coke whose main component is coke on needle is known to those skilled in the art and is not the subject of this invention. Coke in shot is a distinctive type of coke. It is comprised of individual, substantially spherical particles that look like BBs. These individual particles vary from substantially spherical to slightly ellipsoid with average diameters of 1 mm to 10 mm. The particles can be added in larger sized particles, eg, from tennis ball size to basketball or larger sizes. Shotgun coke can sometimes migrate through the coke bed and into the lower drainage lines of the coke drum and slow down, or even block, the rapid cooling water drainage process. While the shotgun coke has a lower economic value than the sponge coke, it is the desired product coke for purposes of this invention due to its ease of removal of the coker drum resulting in effectively increasing the processing capacity that further bypasses its valve reduced economic
Occasionally it appears to be a binder material present between individual coke particles, and said coke is sometimes referred to as "bonded grit" coke. Depending on the degree of bond in the shot coke bed, the bed may not be self-sustaining, and may flow out of the drum when the drum is opened. This can be called "fall out" or "avalanche" and if it is unexpected, it can be dangerous to the operating personnel and can also damage the equipment. The term "transition coke" refers to coke that has morphology between that of sponge coke and shot coke. For example, coke that has a physical appearance for the most part sponge-like, but with evidence of small bead spheres that are just beginning to form as discrete particles in a type of transition coke. The coke beds are not necessarily comprised of all of one type of coke morphology. For example, the bottom of a coke drum can contain large aggregates of shot, transitioning to a coke section in loose shot, and finally having a layer of sponge rich coke on top of the coke bed. There are additional descriptors for coke, although less common. These additional descriptors include: sandy coke that is a coke that after cutting is seen with the naked eye very similar to thick black flat sand; and needle coke which refers to a specialty coke that has a unique anisotropic structure. The preparation of coke whose main component is needle coke is well known to those of ordinary skill in the art and is not an object of this invention. The term "free flowing" as used herein means that 500 tons 508.02 Mg) of coke plus its interstitial water in a coker drum can be drained in less than 30 minutes through an opening of 152.4 cm (60 inches) of diameter. It has been found that substantially free flow shot coke can be produced by practicing the present invention by ensuring that the waste feed is one having an initial boiling point substantially higher than the waste conventionally used for delayed coking. As mentioned above, conventional delayed coke waste feeds typically have an initial boiling point of 500 ° C to 526 ° C / but the residue feeds of the present invention which have an initial boiling point of 549 ° C to 566 ° C will unexpectedly produce coke of grit on the sponge coke. Conventional coke processing aids, including an anti-foaming agent, can be employed in the process for example, delayed coking wherein a waste feedstock is blown with air to a target softening point as described in the US Pat. USA No. 3,960,704. While shot coke has been produced by conventional methods, it typically agglomerates, to such an extent that water jet technology is needed for its removal. Additives are employed to provide for the formation of the coke in substantially free flowing, desired shot. It is within the scope of this invention to use an appropriate additive to aid in the formation of shot-coke, preferably coke in substantially free-flowing shot. In one embodiment, the additive is an organic soluble metal, such as a metal naphthenate or a metal acetylacetonate, including mixtures thereof. The preferred metals are potassium, sodium, iron, nickel vanadium, tin, molybdenum, manganese, aluminum, cobalt, calcium, magnesium and mixtures thereof. Potassium, sodium, iron, aluminum and calcium are preferred. Additives in the form of species naturally present in refinery stream can be used. For these additives, the refinery stream can act as a solvent for the additive, which can help in the dispersion of the additive in the waste feed. The additives naturally present in refinery stream include nickel, vanadium, iron, sodium and mixtures thereof naturally present in certain residues and waste fractions (ie, certain feed streams). Additive contact and feeding can be achieved by mixing the feed fraction containing additive species (including feed fractions that naturally contain said species) into the feed. In another embodiment, the metal-containing additive is a finely ground solid with a high surface area, a natural material with a high surface area, or a particle / fine seed additive. These high surface area materials include smoked silica and alumina, catalytic fractionator fines, FLEXICO ER cyclone fines, magnesium sulfate, calcium sulfate, diatomaceous earth, magnesium silicate clays, fly ash containing vanadium and the like. Additives can be used either alone or in combination. It is within the scope of this invention that a metal-free additive is used. Non-limiting examples of substantially metal-free additives that can be used in the practice of. The present invention includes elemental sulfur, substantially metal-free solids of high surface area, such as rice husks, sugars, cellulose, ground carbons, self-ground rims. Other additives include oxides >; inorganics such as fumed silica and alumina: salts of oxides, such as ammonium silicate and mineral acids such as sulfuric acid and phosphoric acid, and their acid anhydrides. Preferably, a caustic spice is added to the waste coker feed material. When used, the caustic species may be added before, during, or after heating in the coker oven. The caustic addition will reduce the Total Acid Number (TAN) of the waste coker feed material and also convert naphthenic acids into metal naphthatates, e.g., sodium naphthenate. The uniform dispersion of the additive towards vacuum feed is desirable to avoid heterogeneous areas of coke formation in shot. The dispersion of the additive is achieved by any number of ways, for example, by solubilizing the additive to the vacuum residue, or by reducing the viscosity of the vacuum residue before mixing the additive, eg, by heating, adding solvent , use of organometallic agents, etc. High energy mixing or the use of static mixing devices can be employed to assist in the dispersion of the additive agent. Polarization light microscopy was used in the examples (illustrated in Figures 1 and 2) to compare and contrast green coke sample structures (ie, uncalcined coke). On the macroscopic scale, that is, on a scale that is readily apparent to the naked eye, the petroleum sponge and green shot cokes are quite different - the sponge has a porous sponge-like appearance, and the shot coke has an appearance of spherical group. However, under amplification with an optical microscope, or polarized light optical microscope, additional differences between different samples of green coke can be seen, and these depend on the amount of amplification. For example, using a polarized light microscope, at a low resolution where 10-micrometer particulars are discernible, sponge coke appears highly anisotropic, the center of a typical coke-coke sphere looks much less anisotropic, and the surface of a sphere of coke of grit seems regularly anisotropic. At higher resolutions, e.g., where particulars of 0.5 microns are discernible (this is close to the resolution limit of optical microscopy), a sample of green sponge coke still appears highly anisotropic. The center of a shotgun coke sphere at this resolution is now revealed to have some anisotropy, but the anisotropy is much less than that seen in the sponge coke sample. It should be noted that the optical anisotropy discussed in the present is not the same as the "thermal anisotropy" '/ a term known to those skilled in the coking field. Thermal anisotropy refers to thermal properties of coke volume such as coefficient of thermal expansion, which is typically measured in cokes that have been calcined, and manufactured in electrodes. It is within the scope of this invention that a metal-free additive is used to promote the production of free-flowing coke, preferably free-flowing coke. Non-limiting examples of metal-free additives include elemental sulfur, substantially metal-free solids of high surface area, such as rice husks, sugars, cellulose, ground coals, self-ground tires; inorganic oxides such as tapered silica and alumina; salts of oxides, such as ammonium silicate and mineral acids such as sulfuric acid, phosphoric acid, and acid anhydrides. The present invention will be better understood by reference to the following non-limiting examples which are presented for illustrative purposes. EXAMPLE A vacuum residue is produced in a refinery and has had the vacuum impulse reincorporated in it. The refinery is pushing production and, consequently the residue boiling point distribution is having an increased amount of the lighter portion. The vacuum residue has an API gravity of 3.7, contains 5.4% by weight of S, and 10.0% by weight of hydrogen. The front end boiling point distribution as determined by HTSD is as follows in the column entitled "base case vacuum residue" in the table below. TABLE Vacuum Residue Residue with Distillate Base Case Vacuum Second Stage vacuum HTSD% by weight AEBP, Degrees F AEBP, Degrees F Outside (Degrees C) (Degrees C) IBP 554 (290) 910 (487.78) 1 698 (370) 954 (512.22) 2 813 (433.89) 986 (530) 3 858 (458.89) 1003 (539.44) 4 888 (475.56 1016 (546.67) 5 911 (488.33) 1027 (552.78) 6 929 (498.33) 1036 (557.78) ) 7 944 (506.67) 1045 (562.78) 8 957 (513.89) 9 969 (520.56) 10 980 (526.67) 11 990 (532.22) 13 1007 (541.67) 14 1016 (546.67) 15 1024 (551.11) 16 1032 (555.56) 17 1039 (559.44)% in Weight 1382 - Degrees F (750 ° C) 79.9 73.6 The waste contains 12% by weight of material from 482.22 ° C to 560 ° C (900 ° F to 1040 ° F). Coke base in a pilot plant coker with a drum top temperature of 437.78 ° C (820 ° F), drum top pressure of 103.42 kPa (15 psig) and zero recycle.Coke of product has a morphology bond that appears highly fused through the bed. The microscopic examination of coke under transverse polarized light reveals mostly small domains (10-20 microns) with thick mosaic (5-10 microns). The percentage of coke in shot by the micrographic technique is calculated to be 25%. Through a known relationship with a commercial scale coker, it is projected that this coke would yield a bonded shot that would be self-sustaining in the commercial scale coke drum. The base case residue then has a second stage vacuum distillation that removes a portion of the lighter components. The boiling point distribution of the residue after distillation is shown in the right column of the table, ie, after the second stage vacuum distillation, the residue contains 7% by weight material from 482.22 ° C to 560 ° C (900 ° F to 1040 ° F). The deepest cut residue is coked in the pilot plant coker with a drum top temperature of 437.78 ° C (820 ° F), a drum top pressure of 103.42 kPa (15 psig), and zero recycle. The product coke is 80% coke of shot. The microscopic examination of the coke under polarized cross light reveals mostly medium / thick mosaic (2-10 microns). The percentage of coke in shot with the micrographic technique is calculated to be 75%. Through a known relationship with a commercial scale coker, it is projected that this coke would yield a relatively loose shot that would not be self-sustaining in the commercial scale coke drum.