Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G55/00—Treatment of hydrocarbon oils, in the absence of hydrogen, by at least one refining process and at least one cracking process
  • C10G55/02—Treatment of hydrocarbon oils, in the absence of hydrogen, by at least one refining process and at least one cracking process plural serial stages only
  • C10G55/04—Treatment of hydrocarbon oils, in the absence of hydrogen, by at least one refining process and at least one cracking process plural serial stages only including at least one thermal cracking step
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B55/00—Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
  • C10B57/08—Non-mechanical pretreatment of the charge, e.g. desulfurization
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
  • C10G2300/10—Feedstock materials
  • C10G2300/107—Atmospheric residues having a boiling point of at least about 538 °C

Definitions

• the present invention relates to a delayed coking process wherein substantially all of the coke produced is free-flowing anisotropic shot coke.
• a coker feedstock such as a vacuum residuum
• an oxidizing agent such as air
• the oxidized feedstock is then heated to coking temperatures and passed to a coker dram for an effective amount of time to allow volatiles to evolve and to produce a substantially free-flowing anisotropic shot coke.
• Delayed coking has been practiced for many years. The process broadly involves the ⁇ nal decomposition of petioleum residua (resids) to produce gas, liquid streams of vaiious boiling ranges, and coke. Delayed coking of resids from heavy, and heavy sour (high sulfur) crude oils is carried out primarily as a means of disposing of these low value feedstocks by converting part of the resids to more valuable liquid and gas products. Although the resulting coke is generally thought of as a low value by-product, it does have some value as a fuel (fuel grade), electrodes for aluminum manufacture (anode grade), etc.
• the feedstock is rapidly heated in a fired heater or tubular furnace. It is then passed to a coking dram that is maintained at conditions under which coking occurs, generally at temperatures above about 400°C under super-atmospheric pressures.
• the heated residuum feed further decomposes in the coker dram to form volatile components that are removed overhead and passed to a fractionator leaving coke behind.
• the coker dram is full of coke the heated feed is switched to another dram and hydrocarbon vapors are purged from the coke dram with steam.
• the drum is then quenched with water to lower the temperature to about 200-300°F after which the water is drained.
• the drum is opened and the coke is removed after drilling and/or cutting using high velocity water jets.
• a high speed, high impact water jet is used to cut the coke from the dram.
• a hole is typically bored in the coke from water jet nozzles located on a boring tool.
• Nozzles oriented horizontally on the head of a cutting tool cut the coke from the dram.
• the coke removal process adds considerably to the throughput time of the process. That is, since it takes approximately 1 to 6 hours, typically about 3 hours to drill-out and remove the resulting coke mass, the coker dram turn-around time and process costs are increased.
• the coking dram may appeal- to be completely cooled, occasionally, a problem arises which is referred to in the ait as a "hot dram.”
• This problem occurs when areas of the dram do not completely cool. This may be the result of a combination of morphologies of coke in the dram resulting in a non-unifoim dram.
• the dram may contain a combination of more than one type of solid coke product, i.e., needle coke, sponge coke and shot coke.
• BB-sized shot coke may cool faster than another coke, such as large shot coke masses or sponge coke. Avoiding "hot drams" is another reason for producing predominantly shot coke in a delayed coker.
• Isotropic coke is coke that has thermal expansion approximately equal along the three crystalline axes. This is achieved by air blowing a petroleum resid feedstock to a certain softening point and running the coking process at relatively high recycle ratios and preferably with a diluent oil.
• a delayed coking process wherein substantially all of the coke produced is substantially free flowing anisotropic shot coke which process comprises:
• a delayed coking process comprising:
• the oxidizing agent is air.
• a caustic can be added to the oxidized resid coker feedstock before, during, or after heating in the coker furnace.
• Figure 1 hereof is a cross polarized light photomicrograph of coke resulting from a San Joaquin Valley vacuum residuum that was not treated with an oxidizing agent prior to coking.
• the area of view is 170 microns by 136 microns.
• Figure 2 hereof is a photomicrograph of coke resulting from a San Joaquin Valley vacuum residuum that was treated with air for 3 hours at a temperature from 185°C to 225°C prior to coking.
• the area of view is 170 microns by 136 microns.
• Feedstocks suitable for the delayed coking process of the present invention are petroleum vacuum residua.
• Such petroleum residua are frequently obtained after removal of distillates from crade feedstocks under vacuum and are characterized as being comprised of components of large molecular size and weight, generally containing: (a) asphaltenes and other high molecular weight aromatic structures that would inhibit die rate of hydrofreating/hydrocracking and cause catalyst deactivation; (b) metal contaminants occuning naturally in the crade or resulting from prior treatment of the crade, which contaminants would tend to deactivate hydiOtreating/hydrocracking catalysts and interfere with catalyst regeneration; and (c) a relatively high content of sulfur and nitrogen compounds that give rise to objectionable quantities of SO 2 , S0 3 , and NO x upon combustion of the petroleum residuum.
• Nitrogen compounds also have a tendency to deactivate catalytic cracking catalysts.
• Typical examples of coker petroleum feedstocks which are contemplated for use in the present invention, include residues from the atmospheric and vacuum distillation of petioleum crudes or the atmospheric or vacuum distillation of heavy oils, visbroken resids, tars from deasphalting units or combinations of these materials. Atmospheric and vacuum topped heavy bitumens can also be employed.
• these feedstocks are high-boiling hydrocarbonaceous materials having a nominal initial boiling point of about 538°C or higher, an API gravity of about 20° or less, and a Conradson Carbon Residue content of about 0 to 40 weight percent.
• the coking process of the present invention is delayed coking, which is well known in the ait.
• a bottoms fraction such as a petroleum residuum chargestock is pumped to a heater at a pressure of about 50 to 550 psig, where it is heated to a temperature from about 480°C to about 520°C. It is then discharged into a vertically oriented insulated coker dram through an inlet at the base of the dram.
• Pressure in the dram is usually relatively low, such as about 15 to 50 psig to allow volatiles to be removed overhead. Typical operating temperatures of the dram will be between about 410°C and 475°C.
• the hot feedstock thermally cracks over a period of time in the coker dram, liberating volatiles composed primarily of hydrocarbon products, that continuously rise through the coke mass and are collected overhead.
• the volatile products are sent to a coker fractionator for distillation and recovery of coker gases, gasoline, light gas oil, and heavy gas oil. At least a portion of the heavy coker gas oil present in the product stream introduced into the coker fractionator is captured for recycle and combined with the fresh feed (coker feed component), thereby forming the coker heater or coker furnace charge.
• Needle coke is the highest quality of the three varieties. Needle coke, upon further the ⁇ nal treatment, has high conductivity and is used in electric arc steel production. It is relatively low in sulfur and metals and is produced from some of the higher quality coker feedstocks that include more aromatic feedstocks such as sluny and decant oils from catalytic crackers and thermal cracking tars as opposed to the asphaltenes and resins.
• Sponge coke a lower quality coke, sometimes called “regular coke” is most often formed in refineries.
• Low quality refinery coker feedstocks having significant amounts of asphaltenes, heteroatoms and metals produce this lower quality coke. If the sulfur and metals content is low enough, sponge coke can be used for the manufacture of electrodes for the aluminum industry. If the sulfur and metals content is too high, then the coke can be used as fuel. The name “sponge coke” comes from its porous, sponge-like appearance.
• Shot coke has been considered the lowest quality coke because it has the highest sulfur and metals content, the lowest electrical conductivity and is the most difficult to grind.
• the term "shot coke” comes from its shape which is similar to that of BB sized (about 1/16 inch to 3/8 inch) balls. Shot coke, like the other types of coke, has a tendency to agglomerate, especially in admixture with sponge coke, into larger masses, sometimes larger than a foot in diameter. This can cause refineiy equipment and processing problems. Shot coke is usually made from the lowest quality high resin-asphaltene feeds and makes a good high sulfur fuel source, particularly for use in cement kilns and steel manufacture.
• substantially free-flowing anisotropic shot coke can be produced by first treating the residuum feedstock with an oxidizing agent to substantially increase the contents of its asphaltene, and/or polars fractions, such as those containing organically bound oxygen like ketones, carboxylic acids, etc.
• the residuum feed is subjected to the oxidizing agent, preferably air, at effective temperatures, i.e., at temperatures that will encourage the formation of asphaltenes and organically bound oxygen groups to form.
• Such temperatures will typically be from about 150°C to about 325°C, preferably from about 185°C to about 280°C, more preferably from about 185°C to about 250°C.
• the oxidizing agent can be in any suitable form including gas, liquid or solid.
• oxidizing agents that can be used in the practice of the present invention include air, oxygen, ozone, hydrogen peroxide, organic peroxides, hydroperoxides, inorganic peracids, inorganic oxides and peroxides and salts of oxides, sulfuric acid, and nitric acid. Preferred is air.
• a caustic preferably a spent caustic, may optionally be added.
• the spent caustic can also be added before, during, or after the oxidized resid is passed to the coker furnace and heated to coking temperatures.
• the caustic will be an alkali-metal material preferably a spent caustic soda and/or potash stream that is typically used in vaiious refineiy processes.
• Such spent caustic sitesams typically contain one or more of sodium and potassium, sulfur, and other wastes, including organic contaminants that vary depending on the hydrocarbon source but can be organic acids, dissolved hydrocaibons, phenols, naphthenic acids, and salts of organic acids.
• the spent caustic stream will usually have a relatively high water content, typically about 50 wt% to 95 wt% water, more typically from about 65 wt% to about 80 wt%.
• the desired coke morphology that will produce substantially free-flowing coke is a coke micro stracture of discrete micro-domains having an average size of about 1 to 10 ⁇ m, preferably from about 1 to 5 ⁇ m, somewhat like a mosaic ( Figure 2 hereof).
• Coke microstracture that represents coke that is not free-flowing anisotropic shot coke is the micro stracture represented in Figure 1 hereof that show a coke microstracture that is composed substantially of non-discrete, or substantially large flow domains up to about 60 ⁇ m or greater in size, typically from about 10 to 60 ⁇ m.
• U.S. Patent No. 3,960,704 which is incorporated herein by reference, teaches delayed coking wherein a resid feedstock is air blown to a target softening point.
• the air blown feed is ti en passed to delayed coking process that is operated at conditions that will favor the formation of isotropic coke. That is, coke particles having substantially equal thermal expansion properties along the three major crystalline axes.
• This '704 patent requires relatively high recycle ratios and an additional amount of oil as a diluent to produce a pellet- type isotropic coke.
• the recycle ratio of this '704 patent is from about 1 to 5. This co ⁇ elates to 100% to 500% recycle based on fresh feed.
• the resid feedstock be first treated with an oxidizing agent to substantially increase its level of asphaltenes, polars, and organically bound oxygen groups that encourages the formation of aniso ⁇ opic substantially free-flowing shot coke. It is also important to the practice of the present invention that the coker dram be kept at relatively low pressures in order to allow as much of the evolving volatiles to be collected overhead. This helps prevent agglomeration of the resulting shot coke.
• the recycle ratio that is the volumetric ratio of furnace charge (vacuum resid plus recycle oil) to fresh feed to the continuous delayed coker operation should also be kept as low as possible. The use of recycle ratio for delayed coking is taught in more detail in U.S. Patent No. 3, 116,231 which is incorporated herein by reference.
• Microcarbon residue tests were performed on the above feeds to generate cokes to be evaluated by microscopy. The following is the procedure used for the microcarbon tests:
• Figures 1 and 2 are cross polarized light photomicrographs showing the microstructure of the resulting coke from a San Joaquin Valley residuum for both the untreated residuum and the residuum treated with air in accordance with the above procedure.
• the viewing area for both is 170 microns by 136 microns.
• the untreated residuum resulted in a coke with a microstracture that was not discrete fine domains.
• the domains were relatively large (10-30 ⁇ m) flow domains. This indicates that a mixture of shot coke and sponge coke will be produced in the coker dram of a delayed coker.
• the microstracture ( Figure 2) of the resulting coke from the residuum sample that was first air oxidized shows relatively fine (2-5 ⁇ m) discrete fine domains indicating tiiat free-flowing shot coke will be produced in the coker dram of a delayed coker.
• the following changes in flow domain sizes were observed: a Midwest Vacuum Resid (10-50 ⁇ m to 2-3 ⁇ m), a Louisiana Sweet Vacuum Resid (20-60 ⁇ m to 2 to 5 ⁇ m) in six hours, a Maya Vacuum Resid (2-10 ⁇ m - no change), and a Heavy Canadian Vacuum Resid (10-20 ⁇ m to 2-10 ⁇ m).

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• Chemical & Material Sciences (AREA)
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• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

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• 2002
  • 2002-11-12 US US10/293,373 patent/US20030102250A1/en not_active Abandoned
  • 2002-12-02 AR ARP020104644A patent/AR037685A1/es not_active Application Discontinuation
  • 2002-12-03 CA CA002468711A patent/CA2468711A1/en not_active Abandoned
  • 2002-12-03 CN CNA028240057A patent/CN1599784A/zh active Pending
  • 2002-12-03 AU AU2002359593A patent/AU2002359593A1/en not_active Abandoned
  • 2002-12-03 EP EP02794141A patent/EP1451266A1/en not_active Ceased
  • 2002-12-03 JP JP2003549451A patent/JP2006500431A/ja not_active Withdrawn
  • 2002-12-03 WO PCT/US2002/038699 patent/WO2003048271A1/en active Application Filing

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