US3420711A - Process for defouling equipment contaminated with carbonaceous deposits - Google Patents

Process for defouling equipment contaminated with carbonaceous deposits Download PDF

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Publication number
US3420711A
US3420711A US545357A US3420711DA US3420711A US 3420711 A US3420711 A US 3420711A US 545357 A US545357 A US 545357A US 3420711D A US3420711D A US 3420711DA US 3420711 A US3420711 A US 3420711A
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Prior art keywords
equipment
water
defouling
oxygen
temperature
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US545357A
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English (en)
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Roger P Van Driesen
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Cities Service Research and Development Co
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Cities Service Research and Development Co
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    • 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
    • C10G9/06—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils by pressure distillation
    • C10G9/08—Apparatus therefor
    • C10G9/12—Removing incrustation
    • 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
    • C10G47/00—Cracking of hydrocarbon oils, in the presence of hydrogen or hydrogen- generating compounds, to obtain lower boiling fractions
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G3/00—Apparatus for cleaning or pickling metallic material

Definitions

  • the present invention relates to a process for defouling process equipment. More particularly, the invention provides an effective method for defouling process equipment contaminated with combustible carbonaceous deposits.
  • the equipment utilized in many types of chemical processes becomes fouled from time to time by the formation of combustible carbonaceous contaminants.
  • Exemplary of equipment susceptible to fouling by the formation of carbonaceous contaminants are thermal cracking units, hydrocracking units, polymerization units, etc.
  • a number of procedures have heretofore been used to clean up fouled equipment.
  • the carbonaceous materials may be burned with steam diluted with air or subjected to chemical washing. These procedures have not been entirely satisfactory or practical in many cases.
  • combustion of carbonaceous contaminants in hydrocracking units with steam diluted with air often requires unit shutdown times on the order of days or weeks. Extended shutdown periods of this order cannot, of course, be tolerated from an economic standpoint.
  • an improved process is provided for defouling equipment of combustible carbonaceous contaminants. More particularly, the invention enables relatively rapid combustion of carbonaceous contaminants contained in process equipment. Various other objects and advantages of the invention will become apparent from the following detailed description thereof.
  • the defouling process contemplated by the invention comprises contacting the fouled surfaces of the equipment with an admixture of an oxygen-containing gas and water at an elevated temperature and superatmospheric pressure sufiicient to maintain at least a portion of the water in the liquid phase.
  • an oxygen-containing gas and water at an elevated temperature and superatmospheric pressure sufiicient to maintain at least a portion of the water in the liquid phase.
  • the carbonaceous deposits are rapidly combusted and the heat of combustion is absorbed by the liquid water.
  • the absorption by the water of the heat given off in the combustion avoids excessive temperature increase, and accordingly renders the present invention practical in defouling equipment not capable of withstanding the relatively high temperature attendant prior art steam-air defouling operations.
  • the temperature and pressure conditions at which the contacting with the carbonaceous contaminants within the equipment to be defouled is carried out are such to maintain liquid phase water in contact with the fouled equipment.
  • the temperature of the oxygen containing gas-water mixture introduced into the equipment to be defouled is such that upon combustion of the carbonaceous contaminants, the temperature is not increased to above about 700 F. (approximately the critical temperature of water) by absorption of the heat given off in the combustion reaction. It will, of course, be appreciated that the extent or rate of combustion will be primarily determined by the maximum temperature reached in the contacting ope-ration.
  • the contacting temperature may, with advantage, range from about 400 F. to about 700 F. with the range of 500 F. to about 650 F. being particularly desirable.
  • the pressure at which the defouling operation of the invention is carried out is high enough to maintain at least some liquid phase water in contact with the fouled equipment at the operating temperature.
  • the pressure is maintained within the range of from about 300 p.s.i.g. to about 5,000 p.s.i.g. particularly from about 700 p.s.i.g. to about 4,000 ps.i.g.
  • the oxygen-containing gas useful in the present process may be any gas containing molecular oxygen, such as oxygen itself, air or oxygen-enriched air. Air is preferred.
  • the oxygencontaining gas may preferably be passed through the fouled equipment at rates which result in at least a 50 volume percent inventory of liquid water in the fouled equipment.
  • the oxygen-containing gas may be passed through the equipment at rates ranging from about 0.03 to about 0.5 ft. /sec. per square foot of equipment cross-section, preferably from about 0.05 to about 0.3 ft. /sec. per ft. of cross-section.
  • reference numeral 1 represents equipment to be defouled of combustible carbonaceous solids.
  • Equipment 1 may, for example, be a reactor or ancillary apparatus employed in hydrocracking, thermal cracking, polymerization or like high pressure processes, which becomes fouled from time to time by the formation of combustible carbonaceous byproducts.
  • the supply of feed to the equipment is terminated and the equipment is then generally purged of residual liquid or vaporous material.
  • Defouling of equipment 1 is accomplished in accordance with a preferred embodiment of the present invention by introducing water having an oxygen-containing gas, such as air, substantially completely dissolved therein through inlet 2.
  • the solution of oxygen-containing gas in water passed through the equipment under suitable conditions of pressure and temperature, as noted above, to maintain the water substantially solely in the liquid phase in contact with the fouled equipment, and to combust the carbonaceous contaminants.
  • the oxygen-lean solution is passed from the equipment 1 through line 3 and is introduced into an absorption tower 4. Air is supplied to the absorption tower 4 through line 5 and compressor 6 and is absorbed in the oxygen-lean water. Absorption efiiciency is enhanced by allowing the water to descend through packing bodies 7 supported on a grid 8.
  • the packing bodies are those conventionally used in absorbing towers, including Raschig rings, Berl saddles and the like. Gaseous products of the combustion of the carbonaceous contaminants, e.g., CO and CO are partially stripped from the water, and along with steam and any excess oxygen-containing gas are vented from the absorbing tower through line 9.
  • the water level in the absorbing tower may be maintained as desired by liquid level controller 10 which controls the operation of valve 11 in excess water drawoif line 12.
  • absorber 4 is suitably maintained under a total pressure of from about 300 to about 5,000 p.s.i.g. and preferably 700 to 4,000 p.s.i.g., the oxygen partial pressure being at least about 10 p.s.i., preferably 100 to 500 p.s.i.
  • the temperature within the absorber 4 is preferably such that the vapor pressure of water is less than about 80% of the operating pressure. This practice minimizes the venting of large quantities of steam from the absorber through line 9.
  • the oxygen-rich water is passed from the absorption tower through line 13 and mixed in line 2 with make-up water charged through line 14.
  • the amount and temperature of makeup water added through line 14 are such that there is no substantial vapor buildup in equipment 1 due to gassing off as the temperature is increased by the heat of combustion.
  • by maintaining the air-Water solution substantially solely in the liquid phase possible dangers of explosion or damage to equipment 1 due to extremely rapid combustion occurring in vapor buildup areas are eliminated.
  • the time required for defouling the equipment is, of course, a function of the amount of carbonaceous contaminants contained therein as well as the temperature, total pressure and partial pressure and oxygen concentration, and may be readily determined by those skilled in the art as noted above. Compared to prior art processes employing steam diluted with air, defouling may be accomplished far more readily in accordance with the present invention.
  • EXAMPLE 1 Using the procedure and apparatus arrangement described in reference to the drawing, a hydrogenation unit containing an estimated 800 pounds of combustible carbonaceous contaminants is defouled. Air, at the rate of 60,- 750 s.c.f.h. is added to an absorption tower, and therein is absorbed in oxygen-lean water passed from the hydrogenation unit being defouled.
  • the absorption tower is operated at a temperature of 600 F. and a pressure of 3,000 p.s.i.g., which are essentially the temperature and pressure conditions at which the defouling of the hydrogenation unit is conducted.
  • Oxygen partial pressure is approximately 310 p.s.i.
  • Water having air dissolved therein in the amount of 0.01 mole of per gallon of water, is passed from the bottom of the absorption tower at a rate of 18,700 gallons per hour and is combined with 246 F. make-up water added at the rate of 17,000 pounds per hour.
  • the resultant admixture, which has a temperature of 581 F., is passed to the hydrogenation unit.
  • EXAMPLE 2 This example illustrates the use of the present invention in defouling a hydrocracking unit comprising a coil in which oil and hydrogen are reacted at high temperature and pressure. Coke and high molecular weight carbonaceous contaminants periodically buildup in the coil, thereby hampering efiicient operation of the hydrocracking process.
  • normal defouling procedure involved passing steam diluted with air through the coil. It was necessary to maintain the air concentration at a low level in order to prevent overheating and coil damage. However, on occasion, the coil was damaged by the excessive temperature attendant this type of defouling operation, requiring replacement of at least one coil section.
  • the hydrocracking operation is discontinued and the unit is cooled from operating temperature of 850 F. to about 600 F.
  • the normal heavy oil feedstock is discontinued in favor of a lighter, more volatile oil.
  • the oil feed is discontinued. Circulation of hydrogen at 600 F. vaporizes the oil in two (2) additional hours.
  • the unit is then depressured and purged with flue gas, this operation requiring one 1) hour.
  • the defouling operation is conducted by maintaining the hydrocracking coil substantially completely in contact with a continuous phase liquid water having air dispersed therein. More particularly, water at the rate of 20,000 pounds per hour and air at the rate of 60,250 s.c.f.h. are continuously admixed and pumped through the coil. The temperature at the inlet is 524 F while the temperature at the outlet is 26 higher (i.e. 550 F.) due to the heat given off by combustion of the carbonaceous deposits. Total operating pressure is 1500 p.s.i.g., and oxygen partial pressure is p.s.i.
  • reaction temperature falls off to the inlet condition of 524 F., indicating that the bulk of the carbonaceous deposits has been combusted.
  • the defouling operation is terminated after one (1) hour of operation, and the unit is then purged with flue gas for one (1) hour.
  • Hydrogen and oil feed to the unit are then resumed, and within two (2) hours the unit is again on-stream.
  • the hydrocracking operation proceeds smoothly indicating that the carbonaceous contaminants are substantially completely combusted.
  • Process for defouling process equipment of combustible carbonaceous deposits which comprises contacting the surfaces of the process equipment fouled with carbonaceous deposits with an admixture of water and an oxygen-containing gas at an elevated temperature to combust the carbonaceous deposits and at a superatmospheric pressure sufiicient to maintain the fouled surfaces of the equipment in substantially complete contact with a continuous phase of liquid water with the oxygen-containing gas dispersed therein during combustion of the carbonaceous deposits, the heat of combustion being at least partially absorbed by the liquid Water.

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Metallurgy (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Treating Waste Gases (AREA)
  • Gas Separation By Absorption (AREA)
US545357A 1966-04-26 1966-04-26 Process for defouling equipment contaminated with carbonaceous deposits Expired - Lifetime US3420711A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3653998A (en) * 1968-08-21 1972-04-04 Bissett Berman Corp Electrolytic cell etching
US4902403A (en) * 1987-10-30 1990-02-20 Ashland Oil, Inc. Heat treatment of exchangers to remove coke
US4904368A (en) * 1987-10-30 1990-02-27 Ashland Oil, Inc. Method for removal of furfural coke from metal surfaces

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1470359A (en) * 1917-04-17 1923-10-09 Gasolene Corp Process of removing carbon from metal pipes
US2289350A (en) * 1937-12-29 1942-07-14 Texas Co Method of reconditioning furnace tubes
US2423157A (en) * 1941-11-17 1947-07-01 Reiss August Method of cleaning flues or the like which conduct producer gas
US2563085A (en) * 1948-01-02 1951-08-07 Phillips Petroleum Co Process for removing solid polymeric material from process equipment
US2577254A (en) * 1947-01-20 1951-12-04 Phillips Petroleum Co Removing carbon and carbonaceous deposits from heat exchanger equipment

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1470359A (en) * 1917-04-17 1923-10-09 Gasolene Corp Process of removing carbon from metal pipes
US2289350A (en) * 1937-12-29 1942-07-14 Texas Co Method of reconditioning furnace tubes
US2423157A (en) * 1941-11-17 1947-07-01 Reiss August Method of cleaning flues or the like which conduct producer gas
US2577254A (en) * 1947-01-20 1951-12-04 Phillips Petroleum Co Removing carbon and carbonaceous deposits from heat exchanger equipment
US2563085A (en) * 1948-01-02 1951-08-07 Phillips Petroleum Co Process for removing solid polymeric material from process equipment

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3653998A (en) * 1968-08-21 1972-04-04 Bissett Berman Corp Electrolytic cell etching
US4902403A (en) * 1987-10-30 1990-02-20 Ashland Oil, Inc. Heat treatment of exchangers to remove coke
US4904368A (en) * 1987-10-30 1990-02-27 Ashland Oil, Inc. Method for removal of furfural coke from metal surfaces

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Publication number Publication date
DE1621584A1 (de) 1971-06-24
DE1621584B2 (de) 1971-12-16

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