CA1288716C - Process of thermally cracking heavy petroleum oil - Google Patents
Process of thermally cracking heavy petroleum oilInfo
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- CA1288716C CA1288716C CA000525422A CA525422A CA1288716C CA 1288716 C CA1288716 C CA 1288716C CA 000525422 A CA000525422 A CA 000525422A CA 525422 A CA525422 A CA 525422A CA 1288716 C CA1288716 C CA 1288716C
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- cracking
- tank reactor
- cracking furnace
- conversion
- heavy petroleum
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Abstract
PROCESS OF THERMALLY CRACKING
HEAVY PETROLEUM OIL
Abstract A process of thermally cracking a heavy petroleum oil characterized in that the heavy petroleum oil is treated with the use of a combination of one cracking furnace and one perfect mixing type tank reactor, that the heavy petroleum oil is fed to the cracking furnace in the form of a mixture with an aromatic solvent which has a solubility parameter of 8.5-10.0, which is substantially free of toluene insolubles and which contains components which are liquid under the reaction conditions, that the thermal cracking in the cracking furnace is performed at a temperature of 450-520 °C and that the thermal cracking in the tank reactor is performed at a temperature of 400-450 °C to produce a liquid pitch having a volatile matter content of 30-45 wt % and useful as a fuel along with a gaseous product including cracked light oil.
HEAVY PETROLEUM OIL
Abstract A process of thermally cracking a heavy petroleum oil characterized in that the heavy petroleum oil is treated with the use of a combination of one cracking furnace and one perfect mixing type tank reactor, that the heavy petroleum oil is fed to the cracking furnace in the form of a mixture with an aromatic solvent which has a solubility parameter of 8.5-10.0, which is substantially free of toluene insolubles and which contains components which are liquid under the reaction conditions, that the thermal cracking in the cracking furnace is performed at a temperature of 450-520 °C and that the thermal cracking in the tank reactor is performed at a temperature of 400-450 °C to produce a liquid pitch having a volatile matter content of 30-45 wt % and useful as a fuel along with a gaseous product including cracked light oil.
Description
LZ~3~37~L6 PROCESS O~ THERMALLY CRACKING
HEAVY PETROLEUM OIL
Technical Field:
.
This invention relates to a process of continuously thermally cracking a heavy petroleum oil.
Prior Art:
Various methods are known for thermally cracking a heavy petroleum oil and for producing a liquid pitch and a cracked light oil. For example, U. S. patent No. 4,477,344 proposes a method of thermally cracking a heavy hydrocarbon oil with the use of one cracking furnace and two or more perfect mixing type reactors so as to obtain a pitch suitable as a fuel and a cracked light oil. This method is advantageous because the thermal cracking can be conducted in a continuous manner while effectively preventing the occurrence of coking troubles.
However, this method is not fully satisfactory from the standpoint of economy and apparatus efficiency because the method requires the use of two or more perfect mixing type reactors operated at temperatures which are gradually increased in the later stages.
United States patent No~ 4,581,124 discloses a method in which a heavy feed stock is thermally cracked with the use of a combination of one cracking furnace and one tank reactor. In this mekhod, since the conversion rate in the cracking furnace is suppressed to a low degree and the thermal cracking is mainly effected in the tank reactor, coking troubles are apt to occur in the tank reactor. To prevent the occurrence of coking troubles in the tank reactor, a mixture of mesophase pitch and matrix pitch (isotropic pitch) is continuously withdrawn from the tank reactor and is introduced into a separator for the sepration of the mixture into the mesophase pitch and the matrix 87~L~
pitch. The mesophase pitch thus seprated is recovered while the matrix pitch khus separated is recycled to the tank reactor to keep the ratio of the matrix pitch to the mesophase pitch within the tank reactor hiyh. Thus, the prior art method has a drawback because the operation in the separating step becomes complicated due to the necessity for keeping the ratio of the matrix pitch to the mesophase pitch high.
Obiect~
It is an object of an aspect of the present invention to provide a process of thermally cracking a heavy petroleum oil which is devoid of the drawbacks of the conventional technique and which is free of coking troubles.
An object of an aspect of the present invention is to provide a process of thermally cracking a heavy petroleum oil utilizing a combination of one cracking furnace and one tank reactor, which does not encounter coking troubles even when the thermal cracking rate (conversion) in the cracking furnace is increased.
,,, ~
.
.~ ' , 12~
-2a-5ummary and Description of the Invention An aspect of the invention i5 as follows:
A process of thermally cracking a heavy petrolsum oil characterized in that the heavy pekroleum oil is treated with the use of a combinati~n of one cracking furnace and one perfect mixing type tank reactor, that the heavy petroleum oil is fed to the cracking furnace in the form of a mixture with an aromatic solvent which has a solubility parameter of 8.5-10.0, which is substantially free of toluene insolubles and which contains components which are liquid under the reaction conditions, that the thermal cracking in the cracking furnace is performed at a temperature of 450-520 C and a pressure of from ambient pressure to 20 kg/cm2 with a conversion of 50-80 % of the total thermal cracking co~version and that the thermal cracking in the tank reactor is performed at a temperature of 400-450 C under a reduced pressure or under a partial pressure of hydrocarbons of 100-600 mmHg for a period of time of 10-120 minutes with a conversion of not higher than 50 % of the total thermal cracking conversion to produce a liquid pitch having a volatile matter content of 30-45 wt %
and useful as a fuel along with a gaseous product including cracked light oil.
The present invention will now be described in detail below ~) -" ~2~7~6 with reference to the accompanying drawing, in which the sole FIG~RE illustrates a flow diagram for carrying out the process according to the present invention.
Examples of -the heavy petroleum oils used in the present invention include atmospheric and vacuum residues of petroleum crude oils, various cracking residues, asphalt products from solvent deasphalting and native natural asphalt.
When such a heavy hydrocarbon oil is subjected to a thermal cracking treatment in a known manner with the use of a combination of one cracking furnace and one tank reactor, mesophase is formed in a large amount. The mesophase tends to coalesce with each other to grow to large particles. Namely, carbon is apt to form so that coking troubles are liable to occur. ~pon study by the present inventorsr it has been found that such coking troubles in the tank reactor can be effectively prevented from occurring by increasing the conversion in the cracking furnace. When the thermal cracking product obtained in the cracking furnace with a high conversion rate is treated in the succeeding tank reactor, the mesophase produced in the tank reactor is small in size and excellent in dispersibility.
Therefore, precipitation of carbon (coking) hardly occurs and, hence, coking troubles in the tank reactor are prevented.
However, while the occurrence of coking troubles in the tank vessel ma~ be prevented by increasing the conversion of thermal cracking in the cracking furnace, there is caused a new problem that coking troubles are liable to occur in the cracking furnace. The Fresent inventors have made further studies -to solve the problems of the occurrence o~ cokiny troubles and have found khat the problems can be solved by the addition of an 30 aromatic solvent having a solubility parameter of 8.5-10.0 and being substantially free of toluene insolubles.
The process of this invention is conducted with the use of a combination of one cracking furnace and one perfect mixin~
type tank reactor~ In this process, the feed stock is preferably thermally cracked in the cracking furnace until at least 50 ~ of the total thermal cracking conversion is reachedO
~ 871~ii The term "total thermal cracking conversion" used in the present specification is intended to mean the total conversion accomplished in the cracking :~urnace and the tank reactor and is defined by the following equation:
R = [(A - C)/A]x100 (I) = [(A - B)/A + (B - C)/A] x 1 00 (II) wherein R: Total thermal cracking conversion (%) A: The weight of the components in the feed stock which have a boiling point of at least C: The weight of the components contained in the thermal cr.acki.ng product which are obtained in the tank reactor and which have a boiling point of at least 538 C
B: The weight of the components contained in the thermal cracking product which are obtained in the cracking furnace and which have a boiling point of at least 538 C
~(A - B)/A]x100: Conversion (%) in the cracking furnace [(B - C)/A]x100: Conversion (%) in the tank reactor The total thermal cracking conversion is selected according to the kind of the feed stock and the like. Generaly speaking, the total conversion required for obtaining pitch having volatile matter content of 30-45 wt % is 65-75 %.
The reaction conditions adop-ted in the cracking furnace include a temperature of 450-520 C and a pressure of from ambient pressure to 20 kg/cm2. In the cracking furnace, the thermal cracking is conducted so that the conversion in this step is at least 50 - i30 %, preferably 60-75 % of the total thermal cracking conversion. The conversion in the cracking furnace may be control led by the control of the reaction temperature, reaction pressure and residence time.
The reaction conditions in the perfect mi~ing type tank reactor involve a reaction temperature of 400-450 C, a reaction pressure of 100 mmHg to 5 Kg/cm2 and a reaction time of 10-120 LZ~ 7~
s -min, preferably 20-60 min. The perfect mi~iny type tank reactor is operated under a reduced pressure or under a partial pressure of hydrocarbons of 100-600 mmHg by feeding an i~ert gas such as steam. The thermal cracking in the perfect mi~ing type tank reactor is conducted so that the conversion does not exceed 50 %, preferably falls within the range of 25-40 ~ of-the total thermal cracking conversion. The conversion can be controlled by controlling the reaction temperature, partial pressure of hydrocarbon and reaction time. When the reaction temperature and pressure are kept constant, the conversion can be controlled by control of the reaction time. In the perfect mixing type tank reactor, liquid pitch and gaseous pxoduct including cracked light oil are produced. The liquid pitch thus produced contain mesophase. The amount of the mesophase is relatively small, i.e. generally 30 vol ~ or less, especially 15-25 vol %. The mesophase has a particle size of 20-50~m and is excellent in dispersibility in the pitch. The mesophase is hardly carbonized ~formation of coke).
The cracking furnace may be, for example, an external heating type tubular reactor while the tank reactor may be, Eor example, of a type equipped with an agitating apparatus within the reactor. If desired, the tank reactor can be further provided with a wet wall system or a scraper to keep the inside wall of the reactor clean. Any known cracking furnace and the tank reactor may be suitably used for the purpose of the presen-t invention.
In the process according to the present invention, a cracked heavy oil produced in the process may be recycled to the cracking furnace to increase the overall yield of cracked light oil. The cracked heavy hydrocarbon oil suitably used for this purpose has generally a boling point of 340 C or more~ The amount of the cracked oil recycled is 0.1-0.3 part by weigh-t per one part by weight of the feed stock. Too large an amount of the recycled heavy cracked oil causes the increase of the cracked gas and pitch and reduction of total liquid yield.
The above-described process according to the present ~88~
invention uses a combination of one cracking furnace and one perfect mixing type tank reactor for the thermal cracking treatment of petroleum heavy hydrocarbon oil and permits one to continuously obtain a sufficiently lightened, cracked oil and a pitch which is suitable as a fuel and which contains a volatile matter in the amount of 30-45 wt %, without encountering coking troubles in the tank reactor. In the conventional thermal cracking treatment of heavy petroleum hydrocarbon oils using a combination of one cracking furnace and one perfect mixing type tank reactor, the mesophase produced in the tank reactor tends to coalesce to form precipitates of carbon, namely tends to encounter coking troubles. In contrast, the mesophase in the pitch produced according to the process of the present invention, in which the thermal cracking conversion rate in the cracking furnace is made high, has a small particle size, hardly coalesces, and is excellent in dispersibility in the pitch, so that precipitation of carbon scarecely occurs.
In addition to -the above-described merits, the present invention has the following advantages:
(1) Since majority of the reaction heat may be supplied from the cracking furnace, the amount of the heating gas medium can be reduced so that the operation cost can be considerably reduced.
HEAVY PETROLEUM OIL
Technical Field:
.
This invention relates to a process of continuously thermally cracking a heavy petroleum oil.
Prior Art:
Various methods are known for thermally cracking a heavy petroleum oil and for producing a liquid pitch and a cracked light oil. For example, U. S. patent No. 4,477,344 proposes a method of thermally cracking a heavy hydrocarbon oil with the use of one cracking furnace and two or more perfect mixing type reactors so as to obtain a pitch suitable as a fuel and a cracked light oil. This method is advantageous because the thermal cracking can be conducted in a continuous manner while effectively preventing the occurrence of coking troubles.
However, this method is not fully satisfactory from the standpoint of economy and apparatus efficiency because the method requires the use of two or more perfect mixing type reactors operated at temperatures which are gradually increased in the later stages.
United States patent No~ 4,581,124 discloses a method in which a heavy feed stock is thermally cracked with the use of a combination of one cracking furnace and one tank reactor. In this mekhod, since the conversion rate in the cracking furnace is suppressed to a low degree and the thermal cracking is mainly effected in the tank reactor, coking troubles are apt to occur in the tank reactor. To prevent the occurrence of coking troubles in the tank reactor, a mixture of mesophase pitch and matrix pitch (isotropic pitch) is continuously withdrawn from the tank reactor and is introduced into a separator for the sepration of the mixture into the mesophase pitch and the matrix 87~L~
pitch. The mesophase pitch thus seprated is recovered while the matrix pitch khus separated is recycled to the tank reactor to keep the ratio of the matrix pitch to the mesophase pitch within the tank reactor hiyh. Thus, the prior art method has a drawback because the operation in the separating step becomes complicated due to the necessity for keeping the ratio of the matrix pitch to the mesophase pitch high.
Obiect~
It is an object of an aspect of the present invention to provide a process of thermally cracking a heavy petroleum oil which is devoid of the drawbacks of the conventional technique and which is free of coking troubles.
An object of an aspect of the present invention is to provide a process of thermally cracking a heavy petroleum oil utilizing a combination of one cracking furnace and one tank reactor, which does not encounter coking troubles even when the thermal cracking rate (conversion) in the cracking furnace is increased.
,,, ~
.
.~ ' , 12~
-2a-5ummary and Description of the Invention An aspect of the invention i5 as follows:
A process of thermally cracking a heavy petrolsum oil characterized in that the heavy pekroleum oil is treated with the use of a combinati~n of one cracking furnace and one perfect mixing type tank reactor, that the heavy petroleum oil is fed to the cracking furnace in the form of a mixture with an aromatic solvent which has a solubility parameter of 8.5-10.0, which is substantially free of toluene insolubles and which contains components which are liquid under the reaction conditions, that the thermal cracking in the cracking furnace is performed at a temperature of 450-520 C and a pressure of from ambient pressure to 20 kg/cm2 with a conversion of 50-80 % of the total thermal cracking co~version and that the thermal cracking in the tank reactor is performed at a temperature of 400-450 C under a reduced pressure or under a partial pressure of hydrocarbons of 100-600 mmHg for a period of time of 10-120 minutes with a conversion of not higher than 50 % of the total thermal cracking conversion to produce a liquid pitch having a volatile matter content of 30-45 wt %
and useful as a fuel along with a gaseous product including cracked light oil.
The present invention will now be described in detail below ~) -" ~2~7~6 with reference to the accompanying drawing, in which the sole FIG~RE illustrates a flow diagram for carrying out the process according to the present invention.
Examples of -the heavy petroleum oils used in the present invention include atmospheric and vacuum residues of petroleum crude oils, various cracking residues, asphalt products from solvent deasphalting and native natural asphalt.
When such a heavy hydrocarbon oil is subjected to a thermal cracking treatment in a known manner with the use of a combination of one cracking furnace and one tank reactor, mesophase is formed in a large amount. The mesophase tends to coalesce with each other to grow to large particles. Namely, carbon is apt to form so that coking troubles are liable to occur. ~pon study by the present inventorsr it has been found that such coking troubles in the tank reactor can be effectively prevented from occurring by increasing the conversion in the cracking furnace. When the thermal cracking product obtained in the cracking furnace with a high conversion rate is treated in the succeeding tank reactor, the mesophase produced in the tank reactor is small in size and excellent in dispersibility.
Therefore, precipitation of carbon (coking) hardly occurs and, hence, coking troubles in the tank reactor are prevented.
However, while the occurrence of coking troubles in the tank vessel ma~ be prevented by increasing the conversion of thermal cracking in the cracking furnace, there is caused a new problem that coking troubles are liable to occur in the cracking furnace. The Fresent inventors have made further studies -to solve the problems of the occurrence o~ cokiny troubles and have found khat the problems can be solved by the addition of an 30 aromatic solvent having a solubility parameter of 8.5-10.0 and being substantially free of toluene insolubles.
The process of this invention is conducted with the use of a combination of one cracking furnace and one perfect mixin~
type tank reactor~ In this process, the feed stock is preferably thermally cracked in the cracking furnace until at least 50 ~ of the total thermal cracking conversion is reachedO
~ 871~ii The term "total thermal cracking conversion" used in the present specification is intended to mean the total conversion accomplished in the cracking :~urnace and the tank reactor and is defined by the following equation:
R = [(A - C)/A]x100 (I) = [(A - B)/A + (B - C)/A] x 1 00 (II) wherein R: Total thermal cracking conversion (%) A: The weight of the components in the feed stock which have a boiling point of at least C: The weight of the components contained in the thermal cr.acki.ng product which are obtained in the tank reactor and which have a boiling point of at least 538 C
B: The weight of the components contained in the thermal cracking product which are obtained in the cracking furnace and which have a boiling point of at least 538 C
~(A - B)/A]x100: Conversion (%) in the cracking furnace [(B - C)/A]x100: Conversion (%) in the tank reactor The total thermal cracking conversion is selected according to the kind of the feed stock and the like. Generaly speaking, the total conversion required for obtaining pitch having volatile matter content of 30-45 wt % is 65-75 %.
The reaction conditions adop-ted in the cracking furnace include a temperature of 450-520 C and a pressure of from ambient pressure to 20 kg/cm2. In the cracking furnace, the thermal cracking is conducted so that the conversion in this step is at least 50 - i30 %, preferably 60-75 % of the total thermal cracking conversion. The conversion in the cracking furnace may be control led by the control of the reaction temperature, reaction pressure and residence time.
The reaction conditions in the perfect mi~ing type tank reactor involve a reaction temperature of 400-450 C, a reaction pressure of 100 mmHg to 5 Kg/cm2 and a reaction time of 10-120 LZ~ 7~
s -min, preferably 20-60 min. The perfect mi~iny type tank reactor is operated under a reduced pressure or under a partial pressure of hydrocarbons of 100-600 mmHg by feeding an i~ert gas such as steam. The thermal cracking in the perfect mi~ing type tank reactor is conducted so that the conversion does not exceed 50 %, preferably falls within the range of 25-40 ~ of-the total thermal cracking conversion. The conversion can be controlled by controlling the reaction temperature, partial pressure of hydrocarbon and reaction time. When the reaction temperature and pressure are kept constant, the conversion can be controlled by control of the reaction time. In the perfect mixing type tank reactor, liquid pitch and gaseous pxoduct including cracked light oil are produced. The liquid pitch thus produced contain mesophase. The amount of the mesophase is relatively small, i.e. generally 30 vol ~ or less, especially 15-25 vol %. The mesophase has a particle size of 20-50~m and is excellent in dispersibility in the pitch. The mesophase is hardly carbonized ~formation of coke).
The cracking furnace may be, for example, an external heating type tubular reactor while the tank reactor may be, Eor example, of a type equipped with an agitating apparatus within the reactor. If desired, the tank reactor can be further provided with a wet wall system or a scraper to keep the inside wall of the reactor clean. Any known cracking furnace and the tank reactor may be suitably used for the purpose of the presen-t invention.
In the process according to the present invention, a cracked heavy oil produced in the process may be recycled to the cracking furnace to increase the overall yield of cracked light oil. The cracked heavy hydrocarbon oil suitably used for this purpose has generally a boling point of 340 C or more~ The amount of the cracked oil recycled is 0.1-0.3 part by weigh-t per one part by weight of the feed stock. Too large an amount of the recycled heavy cracked oil causes the increase of the cracked gas and pitch and reduction of total liquid yield.
The above-described process according to the present ~88~
invention uses a combination of one cracking furnace and one perfect mixing type tank reactor for the thermal cracking treatment of petroleum heavy hydrocarbon oil and permits one to continuously obtain a sufficiently lightened, cracked oil and a pitch which is suitable as a fuel and which contains a volatile matter in the amount of 30-45 wt %, without encountering coking troubles in the tank reactor. In the conventional thermal cracking treatment of heavy petroleum hydrocarbon oils using a combination of one cracking furnace and one perfect mixing type tank reactor, the mesophase produced in the tank reactor tends to coalesce to form precipitates of carbon, namely tends to encounter coking troubles. In contrast, the mesophase in the pitch produced according to the process of the present invention, in which the thermal cracking conversion rate in the cracking furnace is made high, has a small particle size, hardly coalesces, and is excellent in dispersibility in the pitch, so that precipitation of carbon scarecely occurs.
In addition to -the above-described merits, the present invention has the following advantages:
(1) Since majority of the reaction heat may be supplied from the cracking furnace, the amount of the heating gas medium can be reduced so that the operation cost can be considerably reduced.
(2) Since the feed to be subjected to the thermal cracking treatment in the tank reactor is a product obtained by thermal cracking of a feed stock at a high conversion rate in a cracklng furnace in which the reaction time is not distributed, it is possible to reduce the reaction load in the tank reactor.
Therefore, the tank reactor can be constructed into a small sized reactor. Moreover, the pitch obtained in the tank reactor has uniform properties and is low in content of highly polycondensed components such as mesophase and quinoline insolubles. Such a pitch when used as binder for the preparation of metallugical coke exibits excellent properties as a binder an~ when used as a fuel is excellent in perfect combustibility.
~L28~
Since, in the process o~ the present invention, a greater part of the thermal cracking is effected in the cracking furnace, the reaction conditions in the cracking furnace are inevitably severe. Therefore, coking troubles would occur in the cracking furnace depending on the kind of the feed stock.
Such coking troubles in the cracking furnace can be effectively prevented by admixing the feed stock with an aromatic solvent having a solubility parameter of 8.5-10.0, preferably 8.9-10.0, and being substantially free of toluene insolubles. An aromatic solvent having a solubility parameter of less than 8.5 could be used for the purpose of the present invention if it is used in a large amount. Thus, the use of such a solvent is disadvantageous from the economic point of view.
The term "solubility parameter" used in the present specification is defined by the following equation:
~ = -11.8[1/(1 + C/H)] + 14.8 (III) wherein ~ : Solubility parameter C/H: Carbon to hydrogen atomic ratio of the hydrocarbon The solubility parameter defined by the above equation slightly differs from that containing a function of temperature in the strict sence of the term. However~ the above equation represents effective approximation for t~?e determination of the solubility parameter of hydrocarbon c~ompounds ~D. M. Riggs, R. J. Diefendorf: "14th Biennial conf. on Carbon", Extended Abstract, ~ S A. p. 407, 1979). Solubility parameters of typical petroleum hydrocarbons are exemplified in the following table.
~;~8i~7~
....
Table 1 SubstanceSolubili-ty Parameter(~) n-Heptane 6.6 n-Nonane 6.7 Cyclohexane 6.9 Benzene 8.9 Toluene 8.5 Naphthalene 9.6 Bachaquero vacuum residue 7.91 Arabian vacuum residue 7.76 Cinta vacuum residue7.41 Heptane solubles <9.0 Heptane insolubles and toluene solubles 8.9-9.5 Toluene insolubles and quinoline solubles9.4-10.6 Mesophase carbon 10.0-12.5 The aromatic solvent used in the present invention should be substantially free of toluene lnsolubles. A solvent containing toluene insolubles will cause coking troubles because the toluene insolllbles undergo thermal hysteresis in the cracking furnace to form higher molecular weight componenks.
The aromatic solvent used in the present inven-tion is also required to contain a component which is liquid under the reaction conditions. Thus, a solvent which becomes gaseous under the reaction conditions is not suitable even if it has a solubility parameter of above 8.5, because it fails to show a solvent effect.
The solvent is used in an amount so that the amount of components of the solvent which are liquid under the reaction conditions is ~-50 wt %, preferably 5-20 wt %, based on the weight of the feed stock. The amount and the kind of the solvent are preferably selected so that a mixture of the solvent and the feed stock, when it is subjected to the reaction conditions in the cracking furnace, has a fraction which has a boling point higher than khe boiling point calculated on the normal pressure basis [T(760)] and which shows a solubility parameter of at least 7~9~ The term "boiling point calculated on the normal pressure basis ET(76o)]~ used herein represents the condition of the flush of the cracked product in the cracking furnace and depends on the temperature and partial pressure of hydrocarbons as shown in the following equation:
748 ~ 1 A
T(760) = _ 459.6 (I~) 1/[Tp ~ 459~6) + 0~2145A ~ 0~0002867 wherein T(760) Boiling point calculated on normal pressure basis (F) T : Operation temperature (F) P
A: -C2 _ ~ C22 - 4C3(C1 - lnP) where P = Partial pressure of hydrocarbons (atm) Cl = 8~468~
C2 = -6625~2 C3 = 0~21528X106 Examples o~ suitable aromatic solvent used in the present invention include fluid catalytic cracking residues (solubility parameter: 8 ~ 9 ~ 9 ~ 5) ~ ethylene bottoms (solubility parameter:
25 9~0~9~9) and liquified solvents recycled in coal liquefaction process (solubility parameter: 8~5~9r1)~ The fraction having a boiling point of 420-538 C (solubility parameter: 9~2-9~4) obtained by distilling a fluidized catalytic cracking residue for the removal of super heavy fraction and light fraction is 30 especially preferably used in the present invention.
.
~ 2~
, ., This invention will become more apparent ~rom the following detailed description, taken in conjunction with the appended figure, which is a schematic representation o~ apparatus which may be used in carrying out a process embodying the present invention.
Re~erring now to the FIGURE, the feed stock is fed to the cracking furna~e 1 through a line 5. I this case, before being introduced into the cracking furnace 1, the feed stock is mixed ~2~3~37~l~
with a solvent supplied through a line 20 and, if necessary, a cracked heavy oil recycled from the bot-tom of the Eractionating tower 4 through a line 11. The feed stock which is mixed with the solvent and -the cracked heavy oil is subjected to a thermal cracking treatment in the cracking furnace 1 and the resulting cracked product is fed through a line 7 to a perfect mixing t~pe tank reactor 2 where it is subjected to a further thermal cracking treatment. To the bottom of the tank reactor 2 is supplied through a line 8 high temperature steam (with a temperature of about 400-700 C) which has been fed through a line 6 and heated in the cracking furnace 1 and, if necessary, by means of a steam super heat.er 12. The steam serves to heat a liquid pitch contained in the reactor 2 for the further thermal cracking thereof, to accelerate the stripping of volatile components from the liquid pitch and to decrease the partial pressure of hydrocarbons in the space within the reactor 2. The steam supplied to the reactor 2 is not necessarily high temperature steam heated by means of a steam super heater 12.
When steam which is not heated by means of the super heater is supplied to the reactor 2, the steam serves to strip volatile components from the liquid pitch and to decrease the partial pressure of hydrocarbons in the space within the vessel 2.
The gas components including the cracked oil produced in the reactor 2 are introduced into a fractionating tower 4 through a line 10, whereas the liquid pitch obtained in the reactor 2 is dlscharged threfrom through a line 9 and lntroduced into a pitch coller 3 where the liquid pitch is cooled for the termination of the reaction. The gas components including th~
aromatic solvent in the cooler 3 are withdrawn therefrom through lines 21 and 22, while the liquid pitch in the cooler 3 is discharged therefrom through a line 11 and recovered as a pitch product.
The gas components introduced into the fractionating tower 4 through the line 10 are fractionated into a cracked gas discharged through a line 14, a cracked light oil (boling point of C5-370 C) discharged through a line 15, a cracked heavy oil 7~L6 (bollng point of 370-538 C) discharge~ through a line 16 and a recycling cracked heavy oil (boiling point o~ 538 C or more) discharged through a line 17. The cracked heavy oil discharged through the line 17 is recycled for mixing with the feed stock to be fed to the cracking furnace 1.
The process shown in the FIGURE can be varied and modified in various manners. For example, the fractionating tower 4 may be composed of a combination of two or more fractionating towers. Further, in stead of directly feeding the feed stock to the cracking furnace, the feed stock can be previously introduced into the fractionating tower 4, introducing the mixture of the feed stock and the cracked heavy oil obtained in the bottom of the fractionating tower 4 into the cracking furnace 1 together with the aromatic solvent. Furthermore, the cracked heavy oil discharged through the line 16 may be added to the cracked heavy oil discharged from the bottom of the tower 4 for mixing with the feed stock. The recycling of the cracked heavy oil for mixing with the feed stock is not essential but can be omitted.
The process shown in the FIGURE uses a combination of a cracking furnace and a perfect mixing type tank reactor for the thermal cracking treatment of petroleum heavy hydrocarbon oil and permits one to continuously obtain a sufficiently lightened, cracked oil and a pitch which is suitable as a fuel and which contains a volatile matter in the amount of 30 45 wt P~, without encountering coking troubles in the tank reactor. In the conventional thermal cracking treatment of heavy petroleum hydrocarbon oils, it is necessary to suppress the conversion in the cracking furnace to a low level and to use a plurality of tank reactors. In the present invention, on the other hand, the feed stock may be thermally cracked at a high conversion rate while preventing coking troubles by using a combination of one cracking furnace and one perfect mixing type tank reactor.
The present invention will described in more detail by way of examples.
i 12~ L6 - l 2 -Example A mixed oil (solubility parameter: 8.1) composed of 80 parts by weight of a feed stock (a vacuum bottom from a mixed crude composed of Middle East and Venezuelan crudes) having the properties shown in Table 2 and 20 parts by wei.ght of a solvent (a fraction with a boiling point of between 420 and 53~ C from a fluid catalytic cracking residue) having the properties shown in Table 3 was fed to a cracking furnace at a feed rate of 1.2 kg/hour where it was thermal ly cracked a-t a temperature of 495 C and a pressure of 1.0 kg/cm2G. The resulting cracked product was introduced into a perfect mixing type tank reactor (inside volume: 1.2 liters).. from the bottom of which steam was supplied, where it was further thermal ly cracked at a temperature of 420 C and a partial pressure of hydrocarbons of 340 mmHg with an average reisdence time of 85 min. The liquid phase of the product in the cracking furnace was considered to contain about 13 % by weight of the solvent in terms of T(760).
Table 2 Properties of Feed Stock Specific gravity (15/4 C) 1.0317 Residual carbon (wt %) 21.1 Solubility parameter 7.8 Table 3 Properties of Solvent Specific gravity (15/4 C) 1.125 Residual carbon (wt %) 4.8 Toluene insolubles (wt %) 0.0 30 Solubility parameter 9.3 37~
l3 The above treatment was continue~ ~or 120 hours. Durin~
the operation, neither increase in pressure for feeding the feed stock nor increase in weight of the reacto~ tube of the cracking furnace were observed, indicating that coking did not occur in the cracking furnace. Substantially no coking was found to occur in the tank reactor, too.
The yield of the pitch whose properties were as shown in Table 4 was 28.9 wt % based on the mixed oil feed. During the course of the thermal cracking, a portion of the cracked product from the cracking furnace was sampled to determine the conversion. The conversion in the cracking furnace was thus found to be 42.7 %. The product oil from the tank reactor was also analyzed to reveal that the total conversion was 69.6 %~
Table 4 Properties of Pitch Softening point (C) 166 Volatile matter content (wt ~) 42.9 n-Heptane insolubles (wt %) 73.6 Toluene insolubles (wt %) 51.8 Quinoline insolubles (wt ~) 20.3
Therefore, the tank reactor can be constructed into a small sized reactor. Moreover, the pitch obtained in the tank reactor has uniform properties and is low in content of highly polycondensed components such as mesophase and quinoline insolubles. Such a pitch when used as binder for the preparation of metallugical coke exibits excellent properties as a binder an~ when used as a fuel is excellent in perfect combustibility.
~L28~
Since, in the process o~ the present invention, a greater part of the thermal cracking is effected in the cracking furnace, the reaction conditions in the cracking furnace are inevitably severe. Therefore, coking troubles would occur in the cracking furnace depending on the kind of the feed stock.
Such coking troubles in the cracking furnace can be effectively prevented by admixing the feed stock with an aromatic solvent having a solubility parameter of 8.5-10.0, preferably 8.9-10.0, and being substantially free of toluene insolubles. An aromatic solvent having a solubility parameter of less than 8.5 could be used for the purpose of the present invention if it is used in a large amount. Thus, the use of such a solvent is disadvantageous from the economic point of view.
The term "solubility parameter" used in the present specification is defined by the following equation:
~ = -11.8[1/(1 + C/H)] + 14.8 (III) wherein ~ : Solubility parameter C/H: Carbon to hydrogen atomic ratio of the hydrocarbon The solubility parameter defined by the above equation slightly differs from that containing a function of temperature in the strict sence of the term. However~ the above equation represents effective approximation for t~?e determination of the solubility parameter of hydrocarbon c~ompounds ~D. M. Riggs, R. J. Diefendorf: "14th Biennial conf. on Carbon", Extended Abstract, ~ S A. p. 407, 1979). Solubility parameters of typical petroleum hydrocarbons are exemplified in the following table.
~;~8i~7~
....
Table 1 SubstanceSolubili-ty Parameter(~) n-Heptane 6.6 n-Nonane 6.7 Cyclohexane 6.9 Benzene 8.9 Toluene 8.5 Naphthalene 9.6 Bachaquero vacuum residue 7.91 Arabian vacuum residue 7.76 Cinta vacuum residue7.41 Heptane solubles <9.0 Heptane insolubles and toluene solubles 8.9-9.5 Toluene insolubles and quinoline solubles9.4-10.6 Mesophase carbon 10.0-12.5 The aromatic solvent used in the present invention should be substantially free of toluene lnsolubles. A solvent containing toluene insolubles will cause coking troubles because the toluene insolllbles undergo thermal hysteresis in the cracking furnace to form higher molecular weight componenks.
The aromatic solvent used in the present inven-tion is also required to contain a component which is liquid under the reaction conditions. Thus, a solvent which becomes gaseous under the reaction conditions is not suitable even if it has a solubility parameter of above 8.5, because it fails to show a solvent effect.
The solvent is used in an amount so that the amount of components of the solvent which are liquid under the reaction conditions is ~-50 wt %, preferably 5-20 wt %, based on the weight of the feed stock. The amount and the kind of the solvent are preferably selected so that a mixture of the solvent and the feed stock, when it is subjected to the reaction conditions in the cracking furnace, has a fraction which has a boling point higher than khe boiling point calculated on the normal pressure basis [T(760)] and which shows a solubility parameter of at least 7~9~ The term "boiling point calculated on the normal pressure basis ET(76o)]~ used herein represents the condition of the flush of the cracked product in the cracking furnace and depends on the temperature and partial pressure of hydrocarbons as shown in the following equation:
748 ~ 1 A
T(760) = _ 459.6 (I~) 1/[Tp ~ 459~6) + 0~2145A ~ 0~0002867 wherein T(760) Boiling point calculated on normal pressure basis (F) T : Operation temperature (F) P
A: -C2 _ ~ C22 - 4C3(C1 - lnP) where P = Partial pressure of hydrocarbons (atm) Cl = 8~468~
C2 = -6625~2 C3 = 0~21528X106 Examples o~ suitable aromatic solvent used in the present invention include fluid catalytic cracking residues (solubility parameter: 8 ~ 9 ~ 9 ~ 5) ~ ethylene bottoms (solubility parameter:
25 9~0~9~9) and liquified solvents recycled in coal liquefaction process (solubility parameter: 8~5~9r1)~ The fraction having a boiling point of 420-538 C (solubility parameter: 9~2-9~4) obtained by distilling a fluidized catalytic cracking residue for the removal of super heavy fraction and light fraction is 30 especially preferably used in the present invention.
.
~ 2~
, ., This invention will become more apparent ~rom the following detailed description, taken in conjunction with the appended figure, which is a schematic representation o~ apparatus which may be used in carrying out a process embodying the present invention.
Re~erring now to the FIGURE, the feed stock is fed to the cracking furna~e 1 through a line 5. I this case, before being introduced into the cracking furnace 1, the feed stock is mixed ~2~3~37~l~
with a solvent supplied through a line 20 and, if necessary, a cracked heavy oil recycled from the bot-tom of the Eractionating tower 4 through a line 11. The feed stock which is mixed with the solvent and -the cracked heavy oil is subjected to a thermal cracking treatment in the cracking furnace 1 and the resulting cracked product is fed through a line 7 to a perfect mixing t~pe tank reactor 2 where it is subjected to a further thermal cracking treatment. To the bottom of the tank reactor 2 is supplied through a line 8 high temperature steam (with a temperature of about 400-700 C) which has been fed through a line 6 and heated in the cracking furnace 1 and, if necessary, by means of a steam super heat.er 12. The steam serves to heat a liquid pitch contained in the reactor 2 for the further thermal cracking thereof, to accelerate the stripping of volatile components from the liquid pitch and to decrease the partial pressure of hydrocarbons in the space within the reactor 2. The steam supplied to the reactor 2 is not necessarily high temperature steam heated by means of a steam super heater 12.
When steam which is not heated by means of the super heater is supplied to the reactor 2, the steam serves to strip volatile components from the liquid pitch and to decrease the partial pressure of hydrocarbons in the space within the vessel 2.
The gas components including the cracked oil produced in the reactor 2 are introduced into a fractionating tower 4 through a line 10, whereas the liquid pitch obtained in the reactor 2 is dlscharged threfrom through a line 9 and lntroduced into a pitch coller 3 where the liquid pitch is cooled for the termination of the reaction. The gas components including th~
aromatic solvent in the cooler 3 are withdrawn therefrom through lines 21 and 22, while the liquid pitch in the cooler 3 is discharged therefrom through a line 11 and recovered as a pitch product.
The gas components introduced into the fractionating tower 4 through the line 10 are fractionated into a cracked gas discharged through a line 14, a cracked light oil (boling point of C5-370 C) discharged through a line 15, a cracked heavy oil 7~L6 (bollng point of 370-538 C) discharge~ through a line 16 and a recycling cracked heavy oil (boiling point o~ 538 C or more) discharged through a line 17. The cracked heavy oil discharged through the line 17 is recycled for mixing with the feed stock to be fed to the cracking furnace 1.
The process shown in the FIGURE can be varied and modified in various manners. For example, the fractionating tower 4 may be composed of a combination of two or more fractionating towers. Further, in stead of directly feeding the feed stock to the cracking furnace, the feed stock can be previously introduced into the fractionating tower 4, introducing the mixture of the feed stock and the cracked heavy oil obtained in the bottom of the fractionating tower 4 into the cracking furnace 1 together with the aromatic solvent. Furthermore, the cracked heavy oil discharged through the line 16 may be added to the cracked heavy oil discharged from the bottom of the tower 4 for mixing with the feed stock. The recycling of the cracked heavy oil for mixing with the feed stock is not essential but can be omitted.
The process shown in the FIGURE uses a combination of a cracking furnace and a perfect mixing type tank reactor for the thermal cracking treatment of petroleum heavy hydrocarbon oil and permits one to continuously obtain a sufficiently lightened, cracked oil and a pitch which is suitable as a fuel and which contains a volatile matter in the amount of 30 45 wt P~, without encountering coking troubles in the tank reactor. In the conventional thermal cracking treatment of heavy petroleum hydrocarbon oils, it is necessary to suppress the conversion in the cracking furnace to a low level and to use a plurality of tank reactors. In the present invention, on the other hand, the feed stock may be thermally cracked at a high conversion rate while preventing coking troubles by using a combination of one cracking furnace and one perfect mixing type tank reactor.
The present invention will described in more detail by way of examples.
i 12~ L6 - l 2 -Example A mixed oil (solubility parameter: 8.1) composed of 80 parts by weight of a feed stock (a vacuum bottom from a mixed crude composed of Middle East and Venezuelan crudes) having the properties shown in Table 2 and 20 parts by wei.ght of a solvent (a fraction with a boiling point of between 420 and 53~ C from a fluid catalytic cracking residue) having the properties shown in Table 3 was fed to a cracking furnace at a feed rate of 1.2 kg/hour where it was thermal ly cracked a-t a temperature of 495 C and a pressure of 1.0 kg/cm2G. The resulting cracked product was introduced into a perfect mixing type tank reactor (inside volume: 1.2 liters).. from the bottom of which steam was supplied, where it was further thermal ly cracked at a temperature of 420 C and a partial pressure of hydrocarbons of 340 mmHg with an average reisdence time of 85 min. The liquid phase of the product in the cracking furnace was considered to contain about 13 % by weight of the solvent in terms of T(760).
Table 2 Properties of Feed Stock Specific gravity (15/4 C) 1.0317 Residual carbon (wt %) 21.1 Solubility parameter 7.8 Table 3 Properties of Solvent Specific gravity (15/4 C) 1.125 Residual carbon (wt %) 4.8 Toluene insolubles (wt %) 0.0 30 Solubility parameter 9.3 37~
l3 The above treatment was continue~ ~or 120 hours. Durin~
the operation, neither increase in pressure for feeding the feed stock nor increase in weight of the reacto~ tube of the cracking furnace were observed, indicating that coking did not occur in the cracking furnace. Substantially no coking was found to occur in the tank reactor, too.
The yield of the pitch whose properties were as shown in Table 4 was 28.9 wt % based on the mixed oil feed. During the course of the thermal cracking, a portion of the cracked product from the cracking furnace was sampled to determine the conversion. The conversion in the cracking furnace was thus found to be 42.7 %. The product oil from the tank reactor was also analyzed to reveal that the total conversion was 69.6 %~
Table 4 Properties of Pitch Softening point (C) 166 Volatile matter content (wt ~) 42.9 n-Heptane insolubles (wt %) 73.6 Toluene insolubles (wt %) 51.8 Quinoline insolubles (wt ~) 20.3
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process of thermally cracking a heavy petroleum oil characterized in that the heavy petroleum oil is treated with the use of a combination of one cracking furnace and one perfect mixing type tank reactor, that the heavy petroleum oil is fed to the cracking furnace in the form of a mixture with an aromatic solvent which has a solubility parameter of 8.5-10.0, which is substantially free of toluene insolubles and which contains components which are liquid under the reaction conditions, that the thermal cracking in the cracking furnace is performed at a temperature of 450-520 °C and a pressure of from ambient pressure to 20 kg/cm2 with a conversion of 50-80 % of the total thermal cracking conversion and that the thermal cracking in the tank reactor is performed at a temperature of 400-450 °C under a reduced pressure or under a partial pressure of hydrocarbons of 100-600 mmHg for a period of time of 10-120 minutes with a conversion of not higher than 50 % of the total thermal cracking conversion to produce a liquid pitch having a volatile matter content of 30-45 wt %
and useful as a fuel along with a gaseous product including cracked light oil.
and useful as a fuel along with a gaseous product including cracked light oil.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60288217A JPH0633358B2 (en) | 1985-12-20 | 1985-12-20 | Pyrolysis treatment method for petroleum heavy oil using aromatic solvent |
| JP60-288,217 | 1985-12-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1288716C true CA1288716C (en) | 1991-09-10 |
Family
ID=17727333
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000525422A Expired - Lifetime CA1288716C (en) | 1985-12-20 | 1986-12-16 | Process of thermally cracking heavy petroleum oil |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH0633358B2 (en) |
| CA (1) | CA1288716C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112592104B (en) * | 2020-11-04 | 2022-08-02 | 成都泰和沥青发展有限公司 | Asphalt mixture with petroleum residual oil |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ZA845721B (en) * | 1983-08-01 | 1986-03-26 | Mobil Oil Corp | Process for visbreaking resids in the presence of hydrogen-donor materials |
-
1985
- 1985-12-20 JP JP60288217A patent/JPH0633358B2/en not_active Expired - Lifetime
-
1986
- 1986-12-16 CA CA000525422A patent/CA1288716C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0633358B2 (en) | 1994-05-02 |
| JPS62146988A (en) | 1987-06-30 |
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