EP0591856A1 - Gepulstes Luft-Entkokungsverfahren - Google Patents

Gepulstes Luft-Entkokungsverfahren Download PDF

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Publication number
EP0591856A1
EP0591856A1 EP93115874A EP93115874A EP0591856A1 EP 0591856 A1 EP0591856 A1 EP 0591856A1 EP 93115874 A EP93115874 A EP 93115874A EP 93115874 A EP93115874 A EP 93115874A EP 0591856 A1 EP0591856 A1 EP 0591856A1
Authority
EP
European Patent Office
Prior art keywords
air
decoking
coke
combustion
steam
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93115874A
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English (en)
French (fr)
Inventor
Dennis A. Duncan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Stone and Webster Engineering Corp
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Stone and Webster Engineering Corp
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Filing date
Publication date
Application filed by Stone and Webster Engineering Corp filed Critical Stone and Webster Engineering Corp
Publication of EP0591856A1 publication Critical patent/EP0591856A1/de
Withdrawn legal-status Critical Current

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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
    • C10G9/14—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
    • 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
    • C10G9/18—Apparatus
    • C10G9/20—Tube furnaces
    • 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
    • C10G9/34—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils by direct contact with inert preheated fluids, e.g. with molten metals or salts
    • C10G9/36—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils by direct contact with inert preheated fluids, e.g. with molten metals or salts with heated gases or vapours

Definitions

  • the present invention relates to the field of hydrocarbon cracking and more specifically to the efficient maintenance of hydrocarbon reaction systems which require periodic decoking.
  • the coke by-products form deposits, inter alia , as a layer on the inside of the process tubes of the reactor.
  • the coke deposits increase the pressure drop and inhibit heat transfer across the tubes thereby penalizing the process.
  • the coke must, therefore, be removed periodically to restore the pressure drop and heat transfer to normal levels.
  • the coke removal process is commonly carried out by combustion (also known as steam-air decoking), by steam reaction or by mechanical removal.
  • Steam-air decoking is performed by introducing a small quantity of air in a steam matrix, usually starting at about 1-2% and increasing in stages to about 20% by weight of air relative to steam, into the fouled process tubes to burn-off the coke from the inside of the tubes.
  • steam reaction decoking requires the introduction of steam to the tubes at high temperatures to react with the coke.
  • An example of the steam reaction decoking is found in United States Patent No. 4,376,694.
  • mechanical decoking makes use of physical means for breaking loose and scouring the coke from the inside of the process tubes, generally a high pressure water jet, i.e. at a pressure of from about 700 to 1000 bar.
  • steam-air decoking can be the most efficient, however, to be efficient requires close monitoring of the process to maintain a reasonable burning rate. If the burning rate is too low the decoking operation will require a longer period of time, resulting in the processing operation remaining off stream for a longer period. On the other hand, if the burning rate is too high the excessive temperature will damage or even burn through the process tubes.
  • the above process allows the use of higher weight concentrations of air in steam, i.e. in the range of from about 20% to about 50% by weight.
  • the increased concentration of air results in vigorous burning that might seriously overheat the tubes but for the interruption of the air pulse, allowing the combustion and heat generation to subside or extinguish.
  • Another air pulse is then injected into the steam matrix after a short time interval to rejuvenate or reinitiate the coke combustion, with the on/off sequence repeated until decoking is complete.
  • the frequency of the air pulse and the concentration of the air in steam during the pulse in a particular environment varies with both the geometry of the reactor pathway and the characteristics of the feedstock being processed. As the decoking progresses, the concentration of air in the steam would normally be increased to ensure rapid and thorough combustion of the coke. The frequency of the air pulses would be regulated to prevent large, damaging temperature swings in the tube metal.
  • the rate of burning is established by a CO2 sensing means such as a RANAREX gravitometer or a direct reading CO2 analyzer such as an infrared analyzer.
  • the gravitometer measures the specific gravity of the effluent gas relative to air and thus senses the concentration of carbon dioxide in the effluent, as the molecular weight of CO2 is high relative to that of air.
  • the infra-red CO2 analyzer measures the CO2 content of a gas stream such as the effluent gas directly. The CO2 content and the rate of air injection establishes the rate of coke burning.
  • the CO2 sensing means is closely linked to the decoking effluent by means of a sampling line.
  • the CO2 sensing means is adapted to generate an electrical signal which is used to terminate the pulsing once the CO2 level has dropped below the desired point.
  • Automatic means to control either the total volume of air being injected during a pulse or the frequency of the air pulses, as appropriate, is contemplated. The choice of air volume or frequency controls depends on the mechanical means chosen to regulate the air flow.
  • decoking of a fired tubular furnace for cracking hydrocarbons to ethylene and other olefinic compounds under the present invention is achieved by injecting a pulse of air at a weight concentration relative to the steam flow for a period of time to initiate combustion and burn the coke. At the end of this period the air would be interrupted either totally or partially, subduing or extinguishing the combustion, to avoid raising the temperature of the tubes beyond their design temperature. After the end of the air pulse interruption, a subsequent air pulse is injected into the steam matrix with the on-off cycle repeated many times until the CO2 content of the effluent gas during the air pulse is less than about 0.2 volume % indicating that the effluent is substantially free of CO2.
  • the period of time that the air flow is on and the period it is interrupted, as well as the air concentration during the process are established by the CO2 sensing means and generally change along the decoking process. An air flow is then left on for a period of time to "air polish" the pathway.
  • FIGURE 1 is a schematic view of a reactor furnace for use with the present invention.
  • FIGURE 2 is a graph of the specific gravity of the effluent during decoking under the present process.
  • FIGURE 3 is a graph of the specific gravity of the effluent during decoking under the present process from a downstream gravitometer.
  • FIGURE 4 is a plot of temperature at various points along the length of a process tube during decoking by the present method.
  • FIGURE 5 is a graph of temperature over time which follows the air pulses and the movement of coke burn toward and past a thermocouple.
  • the present invention is shown in the environment of a fired tubular furnace (1) as used for cracking hydrocarbons to ethylene and other olefinic compounds. It is understood that the invention can be used with any suitable cracking furnace or hydrocarbon reaction system which needs periodic decoking.
  • the fired tubular furnace (1) has a convection section (2,) and a cracking section (3).
  • the furnace (1) contains one or more process tubes (4) through which hydrocarbons fed through a hydrocarbon feed line (6) are cracked to produce product gases upon the application of heat, with carbonaceous deposits referred to herein as coke produced as a by-product.
  • Steam from steam conduit 22 is used as a diluent during the reaction process.
  • Heat is supplied by a heating medium introduced to the exterior of the process tubes (4) in the cracking section (3) of the furnace (1) through heating medium inlet (8), and exiting through an exhaust (10).
  • the product gases move through the process tubes (4) and out the product gas exit (12) the product gases are then passed through one or more quench/heat exchangers (14) and (16).
  • the product gases are then directed along line (18) to downstream processing equipment such as a quench tower and separation means (not shown).
  • a valve (20) is placed in the hydrocarbon feed line (6) to interrupt the hydrocarbon feed.
  • an air pulse from an air conduit (24) is injected into the flow of a steam matrix along a steam conduit (22).
  • the relative volume and duration of air flow through the air conduit (24) and into the steam conduit (22) is controlled by a valve (26) placed in the air flow conduit (24).
  • An alternative embodiment includes a nitrogen conduit (not shown) to deliver a nitrogen flow to the steam matrix in place of air when the air flow is interrupted.
  • decoking downstream valving (34) controls direction of the effluent gas and coke spall away from the product separation system (not shown).
  • the valve (34) to the downstream processing system (not shown) is also closed and a decoking effluent valve (36) is opened to direct the decoking effluent along an effluent line (38) to the cracking section (3) of the furnace (1) exterior to the process tubes (4) for coke spall combustion, or optionally to a decoking drum (40) with gas vents (42).
  • valve (34) to the processing system is closed and the effluent valve (36) is opened to direct the effluent away from the separation system upon interruption of the hydrocarbon feed flow and introduction of air into the steam matrix for decoking.
  • Automatic activation of the feed, steam, air, processing and effluent valves (20), (21), (26), (34) and (36) is contemplated to provide an automatic decoking system.
  • CO2 sensing means (28) such as a gravitometer with a range of from about 0.6 to about 1.2, or any CO2 analyzer with a continuous read out, is closely linked to the decoking effluent by means of a sampling line (30).
  • the sampling line (30) is preferably linked to the effluent line (38) downstream of the effluent valve (36) so that sampling takes place only during decoking.
  • the CO2 sensing means (28) preferably measures the content of CO2 in the effluent gas continuously.
  • the CO2 sensing means (28) is adapted to generate an electrical signal which is used to determine the end of the pulsing or decoking cycle and possibly control the volume of air injected into the steam matrix during the air pulse and/or the frequency of air pulses, as appropriate.
  • the sampling line (30a) for the CO2 sensing means (28a) can be taken from product line (18) or from a point closer to the furnace (1) such as at product gas/outlet (12) or between the heat exchangers (14) and (16).
  • sensing means closer to the furnace (1) tend to be more responsive, the downstream sampling at lower temperatures is a simpler installation.
  • the decoking process of the present invention utilizing the above structure, is put into effect after the cracking operation has been run for a period of time resulting in a coke buildup on the walls of the metal tubes (4) of the furnace (1), resulting in an increase in pressure drop and decreased heat transfer across the tube walls.
  • the present process for removal of the coke, or decoking, is employed without the need to shut down or cool the furnace.
  • the present process is initiated by interrupting the hydrocarbon feed at valve (20), closing the product gas valve (34) and opening the decoking valve (36).
  • a pulse of air is introduced into the steam matrix, in conduit (22) from air flow conduit (24) by the opening and closing of the air valve (26).
  • the steam (and air pulse) is then heated in the convection section to about 900°F, up to about 1400°F.
  • the relative volume of air (i.e. concentration in the steam matrix) and duration of the pulse is automatically fixed by the mechanical means used.
  • the signal from the CO2 sensing means (28) is used to stop the pulsing process and initiate an "air polish", as later described, if desired.
  • the concentration of air in the steam matrix during the air pulse is contemplated to be in the range of from about 20 to about 50% by weight and varies loosely inversely with the duration of the pulse, i.e. the greater concentration of air in the steam matrix the shorter the duration.
  • the duration of the pulse is long enough to initiate vigorous combustion of the coke but not so long as to raise the temperature above the predetermined design temperature of the metal process tubes (4) or other reactor components.
  • the preferred duration is estimated to be in the range of about 10 to about 50 seconds when a concentration of about 40 weight % air in steam is used.
  • the interruption of the air flow at valve (26) is for a period of time to subdue or even extinguish combustion and heat generation and allow the process tube temperature to decrease.
  • the duration of the air flow interruption is generally less than the duration of the air pulse, i.e. in the range of from about 5 to about 30 seconds, however, the duration is controlled to ensure that damage to the tubes is avoided and the process is efficiently run.
  • Pulsed air decoking as described in the present disclosure has been tried three times in decoking a bench scale pyrolysis unit (BSU) following propane cracking operations of up to 5 hour duration.
  • BSU bench scale pyrolysis unit
  • a RANAREX gravitometer with a 0.3 to 1.3 range was close-coupled to the cracking tube outlet (12).
  • rapid swings in effluent specific gravity are clearly visible, indicating that the swings in CO2 are instantaneous upon the injection and interruption of an air pulse, virtually like turning on and off a switch.
  • the first set of data recorded on the usual RANAREX gravitometer (28) located much further downstream, shown in FIGURE 3 shows the same back and forth response of effluent specific gravity, or CO2 concentration, as the air was pulsed on and off alternatively with N2.
  • the air pulse duration used was essentially 45 seconds on and 45 seconds off, arbitrarily chosen for the present because the swings on both the upstream and downstream RANAREX gravitometers and on temperature indicators on the exterior of the tubes (4) suggested that duration for maximizing the amount of burn on each air pulse cycle.
  • a constant air concentration to steam of 40 weight % throughout the burn was used.
  • the pulsing was done manually, switching instantaneously from air to nitrogen in the steam matrix thus inducing a swing in effluent specific gravity from 1.08 at maximum CO2 (21%) to the nitrogen level of 0.966.
  • the signal drop slightly below the nitrogen level was due to some steam-carbon reaction which continued when the air was cut off.
  • the TI skin thermocouples spaced along the tube length.
  • the TI at the midpoint of the tube coil (4) where coke buildup usually begins shows the first temperature blip and the other TI's further along the tube coil (4) show temperature increases (50-150°F) sequentially as the burn progresses toward the outlet.
  • the tube (4) has the usual rising temperature profile, the rate of burning speeds up significantly toward the coil outlet (12). Therefore, the burn time or air pulse may be shortened as the decoking progresses down the tube coil (4).
  • the TI's located inside the process stream at the outlet (12) show virtually no temperature change at the start of the decoking process when the burn is in the middle of the tube (4) (where the coke is first laid down).
  • TOT tube outlet temperature
  • TMTs tube metal temperatures
  • a potentiometer was attached to the key TOT measured on the process side, enabling the process effluent temperature swings to be followed very rapidly (see FIGURE 5).
  • the combination of the steam flow (heat sink), the slow response of the 24 point strip chart recorder, and the automatic cutting back by the controllers of the electric heat input is enough to mask the process-side temperature swing (TOT) when the burn is well back in the tube.
  • the temperature swings induced on the tube (4) by the pulsed burn need not be too wide, i.e. about 200°F. At the roughly 1800°F operating temperature of the coil no metallurgical problems occur.
  • the RANAREX signal settled at the level for air. At this point the pulsing process was stopped and the air left on for a period of about 10 minutes to "air polish" the tube coil (4).
  • the chart of FIGURE 2 marked RANAREX No. 2 shows this. On this chart the decoking after 5 hours of cracking propane was finished in about 20 minutes.
  • the coking rate in this 40 foot by 1 4 and 3 ⁇ 8 inch I.D. swaged coil is relatively higher than in the commercial coil it simulates, probably proportional to the difference in surface to throughput ratio (about 19). Using the pulsed air system, less time was spent than normally necessary to complete decoking.

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
EP93115874A 1992-10-05 1993-10-01 Gepulstes Luft-Entkokungsverfahren Withdrawn EP0591856A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US95661292A 1992-10-05 1992-10-05
US956612 1992-10-05

Publications (1)

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EP0591856A1 true EP0591856A1 (de) 1994-04-13

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EP93115874A Withdrawn EP0591856A1 (de) 1992-10-05 1993-10-01 Gepulstes Luft-Entkokungsverfahren

Country Status (10)

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EP (1) EP0591856A1 (de)
JP (1) JPH06316696A (de)
KR (1) KR940009317A (de)
CN (1) CN1085593A (de)
AU (1) AU656485B2 (de)
BR (1) BR9303999A (de)
CA (1) CA2107541A1 (de)
FI (1) FI934349A (de)
MX (1) MX9306082A (de)
NO (1) NO933547L (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0781828A1 (de) 1995-12-27 1997-07-02 Institut Francais Du Petrole Kontinuerliches Pyrolyse- und Entkohlungsverfahren, insbesondere zur Anwendung in der Herstellung
US5976352A (en) * 1996-05-06 1999-11-02 Institut Francais Du Petrole Process for thermal conversion of hydrocarbons to aliphatic hydrocarbons which are more unsaturated than the starting products, combining a steam cracking step and a pyrolysis step
WO2008137932A1 (en) * 2007-05-07 2008-11-13 Lummus Technology Inc. Ethylene furnace radiant coil decoking method
WO2010077461A1 (en) 2009-01-05 2010-07-08 Exxonmobil Chemical Patents Inc. Process for cracking a heavy hydrocarbon feedstream
US8784515B2 (en) 2010-10-14 2014-07-22 Precision Combustion, Inc. In-situ coke removal
EP2772524A1 (de) * 2013-02-28 2014-09-03 Linde Aktiengesellschaft Vorrichtung zur Umschaltung eines Spaltofens zwischen Produktionsmodus und Entkokungsmodus
WO2020165710A1 (en) * 2019-02-12 2020-08-20 Nova Chemicals (International) S.A. Decoking process

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101872205B (zh) * 2009-04-27 2011-11-02 中国石油化工股份有限公司 裂解炉在线快速清焦的自动控制方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2289350A (en) * 1937-12-29 1942-07-14 Texas Co Method of reconditioning furnace tubes
EP0021167A1 (de) * 1979-06-08 1981-01-07 Linde Aktiengesellschaft Verfahren und Vorrichtung zur thermischen Entkokung einer aus Spaltzone und nachfolgendem Spaltgaskühler bestehenden Vorrichtung zum thermischen Spalten von Kohlenwasserstoffen
EP0036151A1 (de) * 1980-03-15 1981-09-23 BASF Aktiengesellschaft Verfahren zur thermischen Entkokung von Spaltgaskühlern
US4849025A (en) * 1987-06-05 1989-07-18 Resource Technology Associates Decoking hydrocarbon reactors by wet oxidation

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4917787A (en) * 1983-10-31 1990-04-17 Union Carbide Chemicals And Plastics Company Inc. Method for on-line decoking of flame cracking reactors

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2289350A (en) * 1937-12-29 1942-07-14 Texas Co Method of reconditioning furnace tubes
EP0021167A1 (de) * 1979-06-08 1981-01-07 Linde Aktiengesellschaft Verfahren und Vorrichtung zur thermischen Entkokung einer aus Spaltzone und nachfolgendem Spaltgaskühler bestehenden Vorrichtung zum thermischen Spalten von Kohlenwasserstoffen
US4376694A (en) * 1979-06-08 1983-03-15 Linde Aktiengesellschaft Method of decoking a cracking plant
EP0036151A1 (de) * 1980-03-15 1981-09-23 BASF Aktiengesellschaft Verfahren zur thermischen Entkokung von Spaltgaskühlern
US4849025A (en) * 1987-06-05 1989-07-18 Resource Technology Associates Decoking hydrocarbon reactors by wet oxidation

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0781828A1 (de) 1995-12-27 1997-07-02 Institut Francais Du Petrole Kontinuerliches Pyrolyse- und Entkohlungsverfahren, insbesondere zur Anwendung in der Herstellung
FR2743007A1 (fr) * 1995-12-27 1997-07-04 Inst Francais Du Petrole Procede de pyrolyse et de decokage en continu applicable notamment a la production d'acetylene
US6027635A (en) * 1995-12-27 2000-02-22 Institute Francais Du Petrole Continuous pyrolysis and decoking process for use in the production of acetylene
US5976352A (en) * 1996-05-06 1999-11-02 Institut Francais Du Petrole Process for thermal conversion of hydrocarbons to aliphatic hydrocarbons which are more unsaturated than the starting products, combining a steam cracking step and a pyrolysis step
US8152993B2 (en) 2007-05-07 2012-04-10 Lummus Technology Inc. Ethylene furnace radiant coil decoking method
EP2150602A1 (de) * 2007-05-07 2010-02-10 Lummus Technology Inc. Verfahren zum entkoken der strahlerschlangen in einem ethylenofen
WO2008137932A1 (en) * 2007-05-07 2008-11-13 Lummus Technology Inc. Ethylene furnace radiant coil decoking method
CN101679879B (zh) * 2007-05-07 2013-03-13 鲁姆斯科技公司 乙烯炉辐射段炉管除焦方法
EP2150602A4 (de) * 2007-05-07 2013-07-24 Lummus Technology Inc Verfahren zum entkoken der strahlerschlangen in einem ethylenofen
WO2010077461A1 (en) 2009-01-05 2010-07-08 Exxonmobil Chemical Patents Inc. Process for cracking a heavy hydrocarbon feedstream
CN102227488A (zh) * 2009-01-05 2011-10-26 埃克森美孚化学专利公司 重质烃原料料流的裂化方法
US8684384B2 (en) 2009-01-05 2014-04-01 Exxonmobil Chemical Patents Inc. Process for cracking a heavy hydrocarbon feedstream
CN102227488B (zh) * 2009-01-05 2014-06-11 埃克森美孚化学专利公司 重质烃原料料流的裂化方法
US8784515B2 (en) 2010-10-14 2014-07-22 Precision Combustion, Inc. In-situ coke removal
EP2772524A1 (de) * 2013-02-28 2014-09-03 Linde Aktiengesellschaft Vorrichtung zur Umschaltung eines Spaltofens zwischen Produktionsmodus und Entkokungsmodus
WO2020165710A1 (en) * 2019-02-12 2020-08-20 Nova Chemicals (International) S.A. Decoking process
US11939544B2 (en) 2019-02-12 2024-03-26 Nova Chemicals (International) S.A. Decoking process

Also Published As

Publication number Publication date
BR9303999A (pt) 1994-06-21
NO933547D0 (no) 1993-10-04
MX9306082A (es) 1994-06-30
KR940009317A (ko) 1994-05-20
FI934349A (fi) 1994-04-06
JPH06316696A (ja) 1994-11-15
FI934349A0 (fi) 1993-10-04
CN1085593A (zh) 1994-04-20
NO933547L (no) 1994-04-06
AU4871593A (en) 1994-04-21
CA2107541A1 (en) 1994-04-06
AU656485B2 (en) 1995-02-02

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