CA1210282A - Installation (plant) for thermo-cracking a hydrocarbon starting material to alkene, shell and tube heat exchanger for use in such an installation and process for manufacturing shell and tube heat exchanger - Google Patents
Installation (plant) for thermo-cracking a hydrocarbon starting material to alkene, shell and tube heat exchanger for use in such an installation and process for manufacturing shell and tube heat exchangerInfo
- Publication number
- CA1210282A CA1210282A CA000442653A CA442653A CA1210282A CA 1210282 A CA1210282 A CA 1210282A CA 000442653 A CA000442653 A CA 000442653A CA 442653 A CA442653 A CA 442653A CA 1210282 A CA1210282 A CA 1210282A
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- Prior art keywords
- heat exchanger
- layer
- shell
- tubes
- inert
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
- F28F19/02—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings
-
- 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
- C10G9/002—Cooling of cracked gases
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- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Mechanical Engineering (AREA)
- General 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)
- Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
Abstract
ABSTRACT
The invention relates to an installation (plant) for thermocracking a hydrocarbon starting material to alkenes, comprising a cracking furnace with externally heated reactor tubes (coils) and a shell and tube heat exchanger ("quench", cooler, "transfer line" heat exchanger,TLX) to be used for quenching the reactor effluent and connected to the cracking furnace, wherein on the shell side steam is generated, wherein the internal surface of the tubes of the heat exchanger is coated with an inert layer impermeable to the materials in the reactor effluent which are responsible for the fouling, said layer masking the alloy of which the heating exchanger tubes consist. Said layer has a thickness of preferably 0.5 - 20 µm and is a layer based on an inert metal, in particular aluminium, metal oxide, aluminate, silicate or graphite or is an inert polymeric layer, in particular a layer formed by thermo-setting alkylene quench oil with a peroxide, like benzoyl peroxide. The invention also relates to the heat exchangers.
The invention relates to an installation (plant) for thermocracking a hydrocarbon starting material to alkenes, comprising a cracking furnace with externally heated reactor tubes (coils) and a shell and tube heat exchanger ("quench", cooler, "transfer line" heat exchanger,TLX) to be used for quenching the reactor effluent and connected to the cracking furnace, wherein on the shell side steam is generated, wherein the internal surface of the tubes of the heat exchanger is coated with an inert layer impermeable to the materials in the reactor effluent which are responsible for the fouling, said layer masking the alloy of which the heating exchanger tubes consist. Said layer has a thickness of preferably 0.5 - 20 µm and is a layer based on an inert metal, in particular aluminium, metal oxide, aluminate, silicate or graphite or is an inert polymeric layer, in particular a layer formed by thermo-setting alkylene quench oil with a peroxide, like benzoyl peroxide. The invention also relates to the heat exchangers.
Description
The present invention relates to apparatus :for thermo-cracking a hydrocarbon starting material to alkenes, the apparatus comprising a cracking furnace with externally heated reactor tubes (coils) and a shell and tube heat exchanger connected to the cracking furnace in order to quench the reactor effluen~ ("quench", cooler, "transfer line" heat exchanger, TLX) where-in steam is generated on the shell side.
Such installations (plants), which are generally used in the preparation of alkenes like ethene and propene from starting materials which may vary from natural gas to naphthas and gas oil, are described in Kirk-Othmer, Encyclopedia of Chemical Technology, third edition, vol. 9 (1980) pages 400-408, in particular pages 403-408.
In the course of time a number of general conditions have been found for the cracking furnaces of those installations which should be met regardless of the hydrocarbon starting material, and even control programs controlled by a "computer" have been designed which, as to the power balance, guarantee an optimum operation of the cracking furnaces so that they can be operative for some months at a time.
The reactor effluent of the cracking furnaces is quenched in a shell and tube heat exchanger from 750-900C to 350-560C (Kirk-Othmer l.c., page 407, table 5) to prevent further reactions from taking place under adiabatic conditions after the effluent has left the cracking furnace, since such reactions would affect adversely the yield of alkenes. Simultaneously steam with a pressure of 105-125 bara (bar absolute) :i.s generated.
Ilowever, when quenching the reactor effluent, the inside surfaces of the heat exchanger tubes are fouled, said fouling leading to a decrease in heat transfer while also the sensible heat of the reactor effluent is increasingly used less for the generation of the high pressure steam. The - 1 - ~J~
12~0282 effluent coming from the shell and tube heat exchanger thus has an ever increas-ing temperature.
Up to now it has been assumed that this phenomenon cannot be prevented. Generally the phenomenon was ascribed to condensation of heavy hydrocarbon components from the effluent of the cracking furnace onto the colder heat exchanger surfaces followed by continuing dehydrogenation reactions in the condensate at the temperature prevailing on the wall of the heat exchanger tubes (vide Lohr. B ~ H Dittmann, OGJ, 1978, May 15).
According to Dutch patent application 70 07556 in a different quenching system, wherein a cracker gas mixture is quenched by introducing said gas mixture via an inlet into a quench liquid which is present in a quenching barrel, the problem of fouling and even clogging of the inlet pipe by deposi-tion of tar and carbonaceous materials on the inside of the inlet pipe is prevented, by insulating the inlet pipe on the outer side so that the tempera-ture of the inside of the inlet pipe remains relatively high and condensation of tar and carbonaceous materials appears less easy on the inside. The in-sulating layer has a thickness of some centimeters.
This solution is not possible if a shell and tube heat exchanger is used, as insulation of the tubes of the shell and tube heat exchanger nullifies ~overrides) the entire cooling of the reactor effluent.
It has now been found that the fouling on the inside of the heat exchanger can be decreased and/or inhibited, so that the shell and tube heat exchanger can be in operation for much longer times, if the internal surfaces of the tubes of the heat exchanger are coated with an inert layer, impermeable to the materials from the reactor effluent which are responsible for the foul-ing, said layer masking the alloy of which the heat exchanger tubes consist.
Thus, according to the present invention, there is provided ~210282 a shell and tube heat exchanger adapted for use in an apparatus for cracking a hydrocarbon starting material to alkenes, wherein tubes of the heat ex-changer are formed of alloy and internal surfaces of the heat exchanger tubes are coated with an inert layer, said layer being impermeable to materials in the reactor effluent from a cracking furnace used for the preparation of alkenes, said inert layer effectively masking said alloy of the heat exchanger tubes from said materials in the reactor effluent.
Such a layer should preferably have such a thickness, that it is impermeable to the reactor effluent, but on the other hand it should not be so thick that it impedes the heat transfer.
The minimum thickness should preferably be 0.5 ~m. Preferably it has a thickness of not more than 20 ~m, for, with greater thicknesses, the effect, the temperature drop on the layer, should be too big.
In another aspect, the invention provides apparatus for thermo-cracking a hydrocarbon starting material to alkenes, comprising a cracking furnace with externally heated reactor tubes or coils and a shell and tube heat exchanger in fluid communication with said cracking furnace and usable for quenching reactor effluent from the cracking furnace, said shell and tube heat exchanger including a shell side and one or more tubes formed of alloy, steam being generatable on the shell side of the heat exchanger, wherein internal surfaces of tubes of the heat exchanger are coated with an inert layer im-permeable to the materials in the reactor effluent which are responsible for the fouling, said inert layer effectively masking said alloy of the heat exchanger tubes from said materials in the reactor effluent.
The invention also provides a process for the treatment of a shell and tube heat exchanger, for use in apparatus for cracking a hydrocarbon starting material to alkenes and intended for quenching effluent coming ~2~1L(328;2 from a cracking reactor of such apparatus, wherein internal surfaces of heat exchanger tubes of the exchanger are sprayed with a mixture of an oily fraction, obtained when quenching effluent from a cracking reactor for the preparation of alkenes, and an initiator forming free radicals, draining off the excess of the mixture from the heat exchanger tubes and heating the tubes at a tempera-ture at which the mixture is cured.
According to a preferred embodiment of the invention the inert layer substantially comprises graphite, and/or metal and/or metal oxides, metal salts and/or silicates.
A particularly suitable process which can be used to obtain such a layer uses a viscous mixture of a powdered graphite, metals, metal oxides, metal salts (particle size generally <5 ~m) with a silicone based resin in an aromatic solvent. Said mixture is applied with current spraying methods and is thermoset. Thermosetting takes suitably place at temperatures between 275C
and 375C for 1 1/2 - 5 h. Said thermosetting ~curing) is necessary to vapor-ize the solvent, and to have reticulation take place in the resin component, and optionally to have the resin component decomposed, while silicon remains enclosed in the layer. The result is that a quasi-continuous layer is formed, with a small specific area. Such a layer is highly wear-resistant and resistant to high temperatures.
The impermeability of the layer can be increased by repeating the process several times. Beside graphite especially metals from Group III or IV
of the periodic table and their oxides are suitable, e.g. aluminium, titanium, zirconium. Also silicates and aluminates can be used.
Graphite and aluminium particularly appear to provide satisfactory results (decrease and/or inhibition of the fouling phenomena), while both are cheap and can be easily applied.
. .
~2~02~32 Other processes which can be used to apply a metal layer are known techniques like vaporization under vacuum, (vacuum coating or vacuum metalizing) J forming a deposit of metal by decomposition of a vaporous metal compound (gas plating).
According to a second embodiment of the invention the impermeable layer on the internal surface of the heat exchanger tubes consists of an inert polymeric layer.
Preferably this is a polymeric layer, formed by applying a mix-ture of the oily fraction, which is recovered when quenching the effluent from the cracking reactor (ethylene quench oil), and an initiator forming free radicals, in particular a peroxide, such as benzoyl peroxide, cumene hydroperoxide, on the internal surface of the tubes, draining the excess and thermosetting the remaining mixture.
Such a layer has a structure which highly resembles the fouling layer which normally appears, and it is stable at the temperatures prevailing in the heat exchanger, so that it does not influence the phenomena which appear in the heat exchanger. On this layer, once formed, only a small foul-ing layer appears.
In the process of the present invention preferably a peroxide is used as catalyst, in particular benzoyl peroxide, as peroxides in the polymeri-sation of alkenes and alkene mixtures are effective catalysts.
The amount of catalyst may vary within wide ranges but preferably a mixture is used which comprises 0.5 - 3% of catalyst, such a mixture quickly providing a good polymer layer.
The effect which is obtained with the apparatus according to the invention is elucidated in the following examples, with reference to the accompanying drawing which graphically illustrates the variation in quenched effluent -temperature with time for two diferent groups of heat exchanger tubes.
Example I
In a known installation for the preparation of ethene, with a capacity of 40000 tons/year ethene, gas oil was cracked. The effluent of thè
cracking furnace had the following composition.
~LZ~02~3%
Effluent composition (weight %)
Such installations (plants), which are generally used in the preparation of alkenes like ethene and propene from starting materials which may vary from natural gas to naphthas and gas oil, are described in Kirk-Othmer, Encyclopedia of Chemical Technology, third edition, vol. 9 (1980) pages 400-408, in particular pages 403-408.
In the course of time a number of general conditions have been found for the cracking furnaces of those installations which should be met regardless of the hydrocarbon starting material, and even control programs controlled by a "computer" have been designed which, as to the power balance, guarantee an optimum operation of the cracking furnaces so that they can be operative for some months at a time.
The reactor effluent of the cracking furnaces is quenched in a shell and tube heat exchanger from 750-900C to 350-560C (Kirk-Othmer l.c., page 407, table 5) to prevent further reactions from taking place under adiabatic conditions after the effluent has left the cracking furnace, since such reactions would affect adversely the yield of alkenes. Simultaneously steam with a pressure of 105-125 bara (bar absolute) :i.s generated.
Ilowever, when quenching the reactor effluent, the inside surfaces of the heat exchanger tubes are fouled, said fouling leading to a decrease in heat transfer while also the sensible heat of the reactor effluent is increasingly used less for the generation of the high pressure steam. The - 1 - ~J~
12~0282 effluent coming from the shell and tube heat exchanger thus has an ever increas-ing temperature.
Up to now it has been assumed that this phenomenon cannot be prevented. Generally the phenomenon was ascribed to condensation of heavy hydrocarbon components from the effluent of the cracking furnace onto the colder heat exchanger surfaces followed by continuing dehydrogenation reactions in the condensate at the temperature prevailing on the wall of the heat exchanger tubes (vide Lohr. B ~ H Dittmann, OGJ, 1978, May 15).
According to Dutch patent application 70 07556 in a different quenching system, wherein a cracker gas mixture is quenched by introducing said gas mixture via an inlet into a quench liquid which is present in a quenching barrel, the problem of fouling and even clogging of the inlet pipe by deposi-tion of tar and carbonaceous materials on the inside of the inlet pipe is prevented, by insulating the inlet pipe on the outer side so that the tempera-ture of the inside of the inlet pipe remains relatively high and condensation of tar and carbonaceous materials appears less easy on the inside. The in-sulating layer has a thickness of some centimeters.
This solution is not possible if a shell and tube heat exchanger is used, as insulation of the tubes of the shell and tube heat exchanger nullifies ~overrides) the entire cooling of the reactor effluent.
It has now been found that the fouling on the inside of the heat exchanger can be decreased and/or inhibited, so that the shell and tube heat exchanger can be in operation for much longer times, if the internal surfaces of the tubes of the heat exchanger are coated with an inert layer, impermeable to the materials from the reactor effluent which are responsible for the foul-ing, said layer masking the alloy of which the heat exchanger tubes consist.
Thus, according to the present invention, there is provided ~210282 a shell and tube heat exchanger adapted for use in an apparatus for cracking a hydrocarbon starting material to alkenes, wherein tubes of the heat ex-changer are formed of alloy and internal surfaces of the heat exchanger tubes are coated with an inert layer, said layer being impermeable to materials in the reactor effluent from a cracking furnace used for the preparation of alkenes, said inert layer effectively masking said alloy of the heat exchanger tubes from said materials in the reactor effluent.
Such a layer should preferably have such a thickness, that it is impermeable to the reactor effluent, but on the other hand it should not be so thick that it impedes the heat transfer.
The minimum thickness should preferably be 0.5 ~m. Preferably it has a thickness of not more than 20 ~m, for, with greater thicknesses, the effect, the temperature drop on the layer, should be too big.
In another aspect, the invention provides apparatus for thermo-cracking a hydrocarbon starting material to alkenes, comprising a cracking furnace with externally heated reactor tubes or coils and a shell and tube heat exchanger in fluid communication with said cracking furnace and usable for quenching reactor effluent from the cracking furnace, said shell and tube heat exchanger including a shell side and one or more tubes formed of alloy, steam being generatable on the shell side of the heat exchanger, wherein internal surfaces of tubes of the heat exchanger are coated with an inert layer im-permeable to the materials in the reactor effluent which are responsible for the fouling, said inert layer effectively masking said alloy of the heat exchanger tubes from said materials in the reactor effluent.
The invention also provides a process for the treatment of a shell and tube heat exchanger, for use in apparatus for cracking a hydrocarbon starting material to alkenes and intended for quenching effluent coming ~2~1L(328;2 from a cracking reactor of such apparatus, wherein internal surfaces of heat exchanger tubes of the exchanger are sprayed with a mixture of an oily fraction, obtained when quenching effluent from a cracking reactor for the preparation of alkenes, and an initiator forming free radicals, draining off the excess of the mixture from the heat exchanger tubes and heating the tubes at a tempera-ture at which the mixture is cured.
According to a preferred embodiment of the invention the inert layer substantially comprises graphite, and/or metal and/or metal oxides, metal salts and/or silicates.
A particularly suitable process which can be used to obtain such a layer uses a viscous mixture of a powdered graphite, metals, metal oxides, metal salts (particle size generally <5 ~m) with a silicone based resin in an aromatic solvent. Said mixture is applied with current spraying methods and is thermoset. Thermosetting takes suitably place at temperatures between 275C
and 375C for 1 1/2 - 5 h. Said thermosetting ~curing) is necessary to vapor-ize the solvent, and to have reticulation take place in the resin component, and optionally to have the resin component decomposed, while silicon remains enclosed in the layer. The result is that a quasi-continuous layer is formed, with a small specific area. Such a layer is highly wear-resistant and resistant to high temperatures.
The impermeability of the layer can be increased by repeating the process several times. Beside graphite especially metals from Group III or IV
of the periodic table and their oxides are suitable, e.g. aluminium, titanium, zirconium. Also silicates and aluminates can be used.
Graphite and aluminium particularly appear to provide satisfactory results (decrease and/or inhibition of the fouling phenomena), while both are cheap and can be easily applied.
. .
~2~02~32 Other processes which can be used to apply a metal layer are known techniques like vaporization under vacuum, (vacuum coating or vacuum metalizing) J forming a deposit of metal by decomposition of a vaporous metal compound (gas plating).
According to a second embodiment of the invention the impermeable layer on the internal surface of the heat exchanger tubes consists of an inert polymeric layer.
Preferably this is a polymeric layer, formed by applying a mix-ture of the oily fraction, which is recovered when quenching the effluent from the cracking reactor (ethylene quench oil), and an initiator forming free radicals, in particular a peroxide, such as benzoyl peroxide, cumene hydroperoxide, on the internal surface of the tubes, draining the excess and thermosetting the remaining mixture.
Such a layer has a structure which highly resembles the fouling layer which normally appears, and it is stable at the temperatures prevailing in the heat exchanger, so that it does not influence the phenomena which appear in the heat exchanger. On this layer, once formed, only a small foul-ing layer appears.
In the process of the present invention preferably a peroxide is used as catalyst, in particular benzoyl peroxide, as peroxides in the polymeri-sation of alkenes and alkene mixtures are effective catalysts.
The amount of catalyst may vary within wide ranges but preferably a mixture is used which comprises 0.5 - 3% of catalyst, such a mixture quickly providing a good polymer layer.
The effect which is obtained with the apparatus according to the invention is elucidated in the following examples, with reference to the accompanying drawing which graphically illustrates the variation in quenched effluent -temperature with time for two diferent groups of heat exchanger tubes.
Example I
In a known installation for the preparation of ethene, with a capacity of 40000 tons/year ethene, gas oil was cracked. The effluent of thè
cracking furnace had the following composition.
~LZ~02~3%
Effluent composition (weight %)
2 0.49 CH4 8.21 C0 0.02 _________________________________ 8.72 C2H2 0.16 C2H4 21.22 C2H6 2.87 __________________________________ 24. 25 methyl-acetylene 0.16 prepadiene 0.12 C3H6 13.61 _3_8_______________ ________ _____ 14.30 C4H6 4.86 C4H8 6.57 _4_10______________ ________ ____ 11.48 C5 until 6.21 benzene 2.82 C6 (NA) 2.05 toluene 2.22 C7 (NA) 0.67 o-xylene 0.26 m-xylene 0.43 p-xylene 0.20 ethyl benzene0.32 styrene 0.40 C8 (NA) 0.15 Cg until 2.68 C10 and higher11.83 _________________________________ 41.25 100.0 NA = non - aromatic ~2~ 21~;~
Said effluent, which had a temperature of 800-850C and a pressure of 1.6 bara was quenched in two newly cleaned shell and tube heat exchangers ~TLX) connected in parallel, while on the shell side of the heat exchangers steam with a pressure of llO bara was generated.
One TLX (A) had heat exchanger tubes made from a nickel-chromium-alloy which is usual for these type of tubes.
The other TLX (B) had heat exchanger tubes from the same nickel-chromium-alloy, the internal surface of which was coated with a 5 ~m thick aluminium based layer applied in 3 steps in accordance with the present in-vention.
The temperature of the quenched effluent coming from the TLX (A) in the beginning of ~he test was 420C and the temperature of the quenched effluent coming from TLX (B) was 450C.
The variation in the temperature of the effluents coming from both TLX against the time duration of the test is elucidated in the figure.
Curve A shows the result for TLX (A) .
Curve B shows the result for TLX (B).
One sees that with TLX (A) (Curve A) the temperature of the effluent coming from the TLX, increased to 500C in about 5 days and during the rest of the test the temperature gradually further increased, until after 26 days the maximum allowed temperature of 560C was obtained.
The fouling rate in TLX (B) (Curve B) was substantially constant and the extrapolated attainable hours of service is 60 days instead of 26 as for TLX (A).
Thus it follows that with the second TLX the heat transfer during the whole test was better than with the first TLX.
Both TLX's were thrown out of operation and were inspected.
12~0Z82 TLX (A) appeared to comprise a thick fouling layer.
In TLX ~B) only a slight fouling was present.
Coating the internal surface of the heat exchanger tubes of TLX (B~was carried out by spraying a mixture of 12% by weight of aluminium powder with a particle size of < 2 ~m, 48% by weight of a silicone resin comprising methyl groups and phenyl groups, and 40% by weight of toluene into the tubes, draining the excess and heating the remaining layer for 2 hours at 300C, thus vaporizing the toluene and reticulating the resin~ repeating this processing once, and finally repeating the treatment once with a mixture of 10% by weight of aluminium powder with a particle size of < 2 ~m, 40% by weight of the same silicone resin and 50% by weight of toluene.
Example II
The test of example I was repeated, while a TLX (C) was used, the heat exchanger tubes of which were coated on the inside with a 5 ~m thick layer based on graphite, which was applied as follows:
A mixture of 24% by weight of graphite having a particle size of < 1 ~m, 36% by weight of the same silicone resin as was used when forming the coating according to example I and 40% by weight of toluene was introduced into the tubes, the excess was drained off and the remaining layer was heated for 2 hours at 300C at which temperature the toluene was vaporized and the resin was subjected to reticulation. This processing was repeated once more and finally the processing was repeated Wit}l a mixture of 20% by weight of graphite having a particle size < 1 ~m, 30% by weight of the same silicone resin and 50% by weight of toluene.
The variation in the temperature of the effluent coming from said TLX (C) against the time corresponded to the variation in the temperature of the effluent coming from TLX (B) (example I) against time.
2~32 At the end of the test the heat exchanger tubes were inspected;
only a slight fouling was observed.
Example III
A similar test was carried out as in example I wherein a TLX (D) ~as used having heat exchanger tubes the internal surfaces of which were coated with a polymeric layer, the latter having been formed by mixing the oily fraction obtained when quenching the effluent from the cracking reactor (ethy-lene quench oil) with 1.5% of benzoyl peroxide. The mixture was then introduced into the heat exchanger tubes, the excess drained off and the tubes externally heated at 400C.
The variation in the temperature of the effluen~ coming from TLX
~D) also corresponded to curve B of the figure. At the end of the test the heat exchanger tubes of TLX (D) were inspected. On the polymeric layer a slight fouling had been deposited.
Said effluent, which had a temperature of 800-850C and a pressure of 1.6 bara was quenched in two newly cleaned shell and tube heat exchangers ~TLX) connected in parallel, while on the shell side of the heat exchangers steam with a pressure of llO bara was generated.
One TLX (A) had heat exchanger tubes made from a nickel-chromium-alloy which is usual for these type of tubes.
The other TLX (B) had heat exchanger tubes from the same nickel-chromium-alloy, the internal surface of which was coated with a 5 ~m thick aluminium based layer applied in 3 steps in accordance with the present in-vention.
The temperature of the quenched effluent coming from the TLX (A) in the beginning of ~he test was 420C and the temperature of the quenched effluent coming from TLX (B) was 450C.
The variation in the temperature of the effluents coming from both TLX against the time duration of the test is elucidated in the figure.
Curve A shows the result for TLX (A) .
Curve B shows the result for TLX (B).
One sees that with TLX (A) (Curve A) the temperature of the effluent coming from the TLX, increased to 500C in about 5 days and during the rest of the test the temperature gradually further increased, until after 26 days the maximum allowed temperature of 560C was obtained.
The fouling rate in TLX (B) (Curve B) was substantially constant and the extrapolated attainable hours of service is 60 days instead of 26 as for TLX (A).
Thus it follows that with the second TLX the heat transfer during the whole test was better than with the first TLX.
Both TLX's were thrown out of operation and were inspected.
12~0Z82 TLX (A) appeared to comprise a thick fouling layer.
In TLX ~B) only a slight fouling was present.
Coating the internal surface of the heat exchanger tubes of TLX (B~was carried out by spraying a mixture of 12% by weight of aluminium powder with a particle size of < 2 ~m, 48% by weight of a silicone resin comprising methyl groups and phenyl groups, and 40% by weight of toluene into the tubes, draining the excess and heating the remaining layer for 2 hours at 300C, thus vaporizing the toluene and reticulating the resin~ repeating this processing once, and finally repeating the treatment once with a mixture of 10% by weight of aluminium powder with a particle size of < 2 ~m, 40% by weight of the same silicone resin and 50% by weight of toluene.
Example II
The test of example I was repeated, while a TLX (C) was used, the heat exchanger tubes of which were coated on the inside with a 5 ~m thick layer based on graphite, which was applied as follows:
A mixture of 24% by weight of graphite having a particle size of < 1 ~m, 36% by weight of the same silicone resin as was used when forming the coating according to example I and 40% by weight of toluene was introduced into the tubes, the excess was drained off and the remaining layer was heated for 2 hours at 300C at which temperature the toluene was vaporized and the resin was subjected to reticulation. This processing was repeated once more and finally the processing was repeated Wit}l a mixture of 20% by weight of graphite having a particle size < 1 ~m, 30% by weight of the same silicone resin and 50% by weight of toluene.
The variation in the temperature of the effluent coming from said TLX (C) against the time corresponded to the variation in the temperature of the effluent coming from TLX (B) (example I) against time.
2~32 At the end of the test the heat exchanger tubes were inspected;
only a slight fouling was observed.
Example III
A similar test was carried out as in example I wherein a TLX (D) ~as used having heat exchanger tubes the internal surfaces of which were coated with a polymeric layer, the latter having been formed by mixing the oily fraction obtained when quenching the effluent from the cracking reactor (ethy-lene quench oil) with 1.5% of benzoyl peroxide. The mixture was then introduced into the heat exchanger tubes, the excess drained off and the tubes externally heated at 400C.
The variation in the temperature of the effluen~ coming from TLX
~D) also corresponded to curve B of the figure. At the end of the test the heat exchanger tubes of TLX (D) were inspected. On the polymeric layer a slight fouling had been deposited.
Claims (20)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A shell and tube heat exchanger adapted for use in an apparatus for cracking a hydrocarbon starting material to alkenes, wherein tubes of the heat exchanger are formed of alloy and inter-nal surfaces of the heat exchanger tubes are coated with an inert layer, said layer being impermeable to materials in the reactor effluent from a cracking furnace used for the preparation of alkenes, said inert layer effectively masking said alloy of the heat exchanger tubes from said materials in the reactor effluent.
2. Shell and tube heat exchanger according to claim 1, wherein the impermeable coating layer, which is inert to the reactor effluent, on the internal surfaces of the heat exchanger tubes has a thickness between 0.5 µm and 30 µm.
3. A shell and tube heat exchanger according to claim 1 or 2, wherein the impermeable coating layer is based on an inert metal, metal oxide or metal silicate.
4. A shell and tube heat exchanger according to claim 1 or 2, wherein the impermeable coating consists of a coating based on aluminium.
5. A shell and tube heat exchanger according to claim 1 or 2, wherein the impermeable coating layer is based on graphite.
6. A shell and tube heat exchanger according to claim 1 or 2, wherein the impermeable coating layer is an inert polymeric layer.
7. A shell and tube heat exchanger according to claim 1 or 2, wherein the impermeable coating layer is an inert polymeric layer formed by spraying a mixture of the oily fraction, which is recovered when quenching effluent from a cracking reactor (alkylene quench oil), and an initiator forming free radicals, onto the internal surface of the tubes, following by thermosetting.
8. A shell and tube heat exchanger according to claim 7, wherein the inert polymeric layer is formed by applying a mixture of the oily fraction, which is recovered when quenching effluent from a cracking reactor, and a peroxide as initiator onto the internal surface, following by thermosetting.
9. Apparatus for thermocracking a hydrocarbon starting material to alkenes, comprising a cracking furnace with externally heated reactor tubes or coils and a shell and tube heat exchanger in fluid communication with said cracking furnace and usable for quenching reactor effluent from the crack-ing furnace, said shell and tube heat exchanger including a shell side and one or more tubes formed of alloy, steam being generatable on the shell side of the heat exchanger, wherein internal surface of tubes of the heat exchanger are coated with an inert layer impermeable to the materials in the reactor effluent which are responsible for the fouling, said inert layer effectively masking said alloy of the heat exchanger tubes from said materials in the reactor effluent.
10. Apparatus according to claim 9, wherein the inert layer imper-meable to the materials in the reactor effluent has a thickness between 0.5 µm and 20 µm.
11. Apparatus according to claim 9, wherein the inert layer is based on a material selected from the group consisting of an inert metal, metal oxide, aluminate and silicate.
12. Apparatus according to claim 11, wherein the inert layer is based on aluminium.
13. Apparatus according to claim 9 or 10, wherein the inert layer is based on graphite.
14. Apparatus according to claim 9 or 10, wherein the inert layer is a polymeric layer.
15. Apparatus according to claim 9 or 10, wherein the inert layer is a polymeric layer which is formed by applying a mixture of an oily fraction, which is recovered when quenching effluent from a cracking reactor (alkylene quench oil), and a free radical forming initiator onto said internal surfaces of the tubes, followed by thermosetting said layer.
16. Apparatus according to claim 9 or 10, wherein the inert layer is a polymeric layer which is formed by applying a mixture of an oily fraction, which is recovered when quenching effluent, from a cracking reactor, and a per-oxide as initiator onto said internal surfaces of the tubes, followed by thermosetting.
17. A process for the treatment of a shell and tube heat exchanger, for use in apparatus for cracking a hydrocarbon starting material to alkenes and intended for quenching effluent coming from a cracking reactor of such apparatus, wherein internal surfaces of heat exchanger tubes of the exchanger are sprayed with a mixture of an oily fraction, obtained when quenching effluent from a cracking reactor for the preparation of alkenes, and an initiator forming free radicals, draining off the excess of the mixture from the heat exchanger tubes and heating the tubes at a temperature at which the mixture is cured.
18. A process according to claim 17, wherein said initiator is a peroxide.
19. A process according to claim 18, wherein benzoyl peroxide is used as initiator.
20. A process according to claim 17, 18 or 19, wherein a mixture is used which comprises 1-5% initiator.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8204731 | 1982-12-07 | ||
| NL8204731A NL8204731A (en) | 1982-12-07 | 1982-12-07 | INSTALLATION FOR THERMAL CRACKING OF A HYDROCARBON OUTPUT MATERIAL TO OLEGINS, TUBE HEAT EXCHANGER USED IN SUCH INSTALLATION AND METHOD FOR MANUFACTURING A TUBE HEAT EXCHANGER. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1210282A true CA1210282A (en) | 1986-08-26 |
Family
ID=19840709
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000442653A Expired CA1210282A (en) | 1982-12-07 | 1983-12-06 | Installation (plant) for thermo-cracking a hydrocarbon starting material to alkene, shell and tube heat exchanger for use in such an installation and process for manufacturing shell and tube heat exchanger |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0110486B1 (en) |
| JP (1) | JPS59157494A (en) |
| CA (1) | CA1210282A (en) |
| DE (1) | DE3368282D1 (en) |
| NL (1) | NL8204731A (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1248980B (en) * | 1990-06-22 | 1995-02-11 | Nuovo Pignone Spa | PERFECTED COPPER HEAT EXCHANGER FOR WALL BOILERS |
| US5805973A (en) * | 1991-03-25 | 1998-09-08 | General Electric Company | Coated articles and method for the prevention of fuel thermal degradation deposits |
| AU667945B2 (en) * | 1992-09-22 | 1996-04-18 | General Electric Company | Coated articles and method for the prevention of fuel thermal degradation deposits |
| CA2105188A1 (en) * | 1992-09-22 | 1994-03-23 | George A. Coffinberry | Coated article for hot hydrocarbon fluid and method of preventing fuel thermal degradation deposits |
| CA2113366C (en) * | 1993-01-15 | 2005-11-08 | George A. Coffinberry | Coated articles and method for the prevention of fuel thermal degradation deposits |
| DE4334827C1 (en) * | 1993-10-08 | 1994-10-06 | Mannesmann Ag | Process for decreasing the coking of heat exchange surfaces |
| DE4405884C1 (en) * | 1994-02-21 | 1995-09-07 | Mannesmann Ag | Heat exchange surface in reactors and / or heat exchangers and method for producing a catalytically deactivated metal surface |
| US6265453B1 (en) * | 1999-07-01 | 2001-07-24 | Syntroleum Corporation | Hydrocarbon conversion system with enhanced combustor and method |
| JP2001330394A (en) * | 2000-05-22 | 2001-11-30 | Denso Corp | Exhaust gas heat exchanger |
| CN103968689A (en) * | 2014-05-26 | 2014-08-06 | 英尼奥斯欧洲股份公司 | Waste water cooler used in acrylonitrile manufacture |
| CN112881559B (en) * | 2021-01-20 | 2023-08-18 | 广东产品质量监督检验研究院（国家质量技术监督局广州电气安全检验所、广东省试验认证研究院、华安实验室） | Method for rapidly detecting phthalate content |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL300760A (en) * | ||||
| BE348252A (en) * | ||||
| DE1071105B (en) * | 1956-12-27 | |||
| NL162991C (en) * | 1970-05-25 | 1980-07-15 | Shell Int Research | METHOD AND APPARATUS FOR Deterring gas mixtures. |
| JPS4997949A (en) * | 1973-01-26 | 1974-09-17 | ||
| JPS501446A (en) * | 1973-05-09 | 1975-01-09 | ||
| DE2412421A1 (en) * | 1974-03-15 | 1975-09-25 | Schmidt Sche Heissdampf | HEAT EXCHANGER WITH DOUBLE PIPE ELEMENTS |
| US4054174A (en) * | 1974-03-18 | 1977-10-18 | The Babcock & Wilcox Company | Method of inhibiting deposition of internal corrosion products in tubes |
| JPS5125414A (en) * | 1974-08-28 | 1976-03-02 | Showa Aluminium Co Ltd | NETSUKOKANKYOTAISHOKUARUMINIUMUAWASEZAI |
| US4200518A (en) * | 1979-03-22 | 1980-04-29 | Chevron Research Company | Heat exchanger anti-foulant |
| US4296804A (en) * | 1979-06-28 | 1981-10-27 | Resistoflex Corporation | Corrosion resistant heat exchanger element and method of manufacture |
| JPS5950269B2 (en) * | 1980-05-23 | 1984-12-07 | 住友軽金属工業株式会社 | Coating composition for corrosion protection on the inner surface of heat exchanger tubes |
-
1982
- 1982-12-07 NL NL8204731A patent/NL8204731A/en not_active Application Discontinuation
-
1983
- 1983-12-06 EP EP19830201725 patent/EP0110486B1/en not_active Expired
- 1983-12-06 DE DE8383201725T patent/DE3368282D1/en not_active Expired
- 1983-12-06 CA CA000442653A patent/CA1210282A/en not_active Expired
- 1983-12-07 JP JP23121983A patent/JPS59157494A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| EP0110486B1 (en) | 1986-12-10 |
| EP0110486A1 (en) | 1984-06-13 |
| JPS59157494A (en) | 1984-09-06 |
| NL8204731A (en) | 1984-07-02 |
| JPH0519080B2 (en) | 1993-03-15 |
| DE3368282D1 (en) | 1987-01-22 |
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