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
  • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
  • C10G9/14—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils in pipes or coils with or without auxiliary means, e.g. digesters, soaking drums, expansion means
  • C10G9/16—Preventing or removing incrustation
• • 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
  • C10B43/00—Preventing or removing incrustations
  • C10B43/02—Removing incrustations
  • C10B43/08—Removing incrustations with liquids
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S585/00—Chemistry of hydrocarbon compounds
  • Y10S585/949—Miscellaneous considerations
  • Y10S585/95—Prevention or removal of corrosion or solid deposits

Definitions

• Coke deposition on the inner surfaces of product vapor cyclone outlet lines of fluid coker reactors has been a problem for some time.
• the product vapors are usually removed overhead through a cyclone located in the upper portion of the reactor. Since these vapors leaving the reaction zone are at or near their dew or condensation point, they will condense on any cooler surface.
• Such surfaces are usually those of vapor lines or conduits which conduct the vapors from the reaction zone to accessory equipment, such as a fractionator. This condensation and subsequent coke deposition is particularly serious on surfaces having temperatures of about 700F. to 1,000F.
• the continual buildup of coke in these product transfer lines causes the pressure drop to increase to intolerable levels which require shutdown and cleaning as noted above.
• U.S. Pat. No. 2,326,525 suggests positively preventing the building up of coke deposits in vapor lines by periodically forcing a plunger equipped with rotating spray nozzles through the buildup of material in the vapor line while spraying oil under pressures in the order of 1,500 to 2,000 pounds at a rate of about 75 to 150 gallons per minute through each of four nozzles.
• the plunger or knocker is used to push through tarry materials or break off hardened coke.
• a further object of the present invention is to provide a process for removing solid coke deposits while onstream without adversely effecting the coking or pyrolysis reaction, the reactor and accessor and downstream refining equipment.
• the quantity of water will vary somewhat depending on the size of the fluid coking unit, however, the quantity of water must be sufficient to effect a sudden rapid change in the coke temperature. It is desirable to reduce the amount of feed to the fluid coking unit during the jetting period by an amount approximately equal to the volume of water which would be vaporized during the jetting operation.
• the foregoing procedure has been successfully accomplished on a large-scale, 7,000 barrel per day fluid coking unit which has heretofore had to be shut down to manually remove coke deposits from the cyclone discharge nozzle. In tests conducted on this unit, the on-stream decoking operation is accomplished in about 30 to minutes at about four to six-month intervals.
• a coking unit includes a reactor having a rates, it is possible to wash the tarry or soft formations from the vapor riser and to scour the walls of coke deposits which may have become baked thereof.
• the opcyclone separator through which the cracked hydrocarbon vapors are passed to remove fluid coke particles prior to the vapors entering a fractionator.
• Fluid coking reactors generally operate at pressures of less than 50 psi. This particular reactor is normally operated at a pressure of less than 20 psi with the maximum reactor pressure being about 25 psi.
• the pressure drop through a clean cyclone is normally about 1 to 4 psi. As coke deposition occurs in the cyclone discharge nozzle, this pressure drop is allowed to increase to about 10 to 12 psi at which time the coke deposit must be removed in order to avoid over pressuring the reactor. Thus. when the pressure drop increases to about 10 to 12 psi, a lance is inserted through a nozzle in the side of the reactor wall and into the vapor cyclone discharge nozzle. The lance contained two small oppositely-opposed holes through which the water jet is caused to be directed at the coke deposit on the inner surfaces of the discharge nozzle.
• holes are preferably sloped to the rear of the lance at an angle of about 5 so as to cause the coke pieces to blow out of the nozzle in the direction of normal hydrocarbon vapor flow.
• the pitch feed rate to the reactor Prior to injecting water, the pitch feed rate to the reactor is decreased by approximately 1,000 barrels and the steam rates are reduced somewhat to compensate for the volume of vaporized water which is to be carried overhead to the fractionator. Water at a temperature of about 50F. to 70F. is fed to the lance under pressure.
• EXAMPLE 1 The fluid coking unit was operating at a rate of about 6,324 barrels per day with a cyclone pressure drop of 9.4 psi. The following tabulated sequence of steps were used to successfully reduce the pressure drop to 3.9 psi:
• EXAMPLE 2 This example presents a log of a second decoking operation conducted approximately four months after the previous decoking operation.
• a process of removing coke deposits from hydrocarbon vapor conduits while continuously passing hydrocarbon vapors through the conduit which comprises contacting the coke deposit with a jet of relatively high pressure water, said water being jetted at a pressure in excess of about 5,000 psi, and at a rate sufficient to thermally shock the contacted coke deposit, whereby the contacted coke is broken into pieces and blown from the conduit.

Landscapes

• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Thermal Sciences (AREA)
• Materials Engineering (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Coke Industry (AREA)
• Pipeline Systems (AREA)
• Cyclones (AREA)

Priority Applications (11)

Applications Claiming Priority (1)

Publications (1)

Family

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Family Applications (1)

Country Status (10)

Cited By (12)

Families Citing this family (3)

Citations (4)

Family Cites Families (4)

• 1974
  • 1974-06-05 US US476725A patent/US3920537A/en not_active Expired - Lifetime
• 1975
  • 1975-05-29 NO NO751904A patent/NO147489C/no unknown
  • 1975-05-30 GB GB23649/75A patent/GB1479860A/en not_active Expired
  • 1975-06-02 CA CA228,203A patent/CA1047426A/en not_active Expired
  • 1975-06-03 DE DE2524570A patent/DE2524570C2/de not_active Expired
  • 1975-06-04 SE SE7506367A patent/SE396766B/xx not_active IP Right Cessation
  • 1975-06-04 JP JP6666475A patent/JPS5738635B2/ja not_active Expired
  • 1975-06-04 DK DK250875AA patent/DK142290B/da unknown
  • 1975-06-04 BR BR4500/75D patent/BR7503511A/pt unknown
  • 1975-06-05 NL NL7506698.A patent/NL166868C/xx not_active IP Right Cessation

Patent Citations (4)

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