CA1189011A - Continuous thermal cracking method of heavy petroleum oil - Google Patents
Continuous thermal cracking method of heavy petroleum oilInfo
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- CA1189011A CA1189011A CA000394287A CA394287A CA1189011A CA 1189011 A CA1189011 A CA 1189011A CA 000394287 A CA000394287 A CA 000394287A CA 394287 A CA394287 A CA 394287A CA 1189011 A CA1189011 A CA 1189011A
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- thermal cracking
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Abstract
SPECIFICATION
Title of the Invention CONTINUOUS THERMAL CRACKING METHOD
OF HEAVY PETROLEUM OIL
Abstract of the Disclosure The specification describes a method for producing thermally-cracked products of high quality such as gas, cracked light oil and pitch by continuously subjecting heavy petroleum oil to thermal cracking in a single-column reactor. More specifically, heavy petroleum oil, which has been heated in a heating furnace to a temperature of a predetermined range, is continuously charged into the lowermost reaction zone of a column-like reactor which is vertically divided into a plurality of reaction zones by means of at least one partition wall defining an opening therethrough to make said reaction zones to communicate with one another. The heavy petroleum oil is subjected in the reactor to thermal cracking while maintaining its temperature, pressure and residence time in the reactor within their respective predetermined ranges and causing oil, which has been treated in each of said reaction zones, to be successively transferred to its upper reaction zone together with bubbles under stirring conditions. Then, the thus-cracked product is continuously discharged from the uppermost reaction zone of the reactor.
Title of the Invention CONTINUOUS THERMAL CRACKING METHOD
OF HEAVY PETROLEUM OIL
Abstract of the Disclosure The specification describes a method for producing thermally-cracked products of high quality such as gas, cracked light oil and pitch by continuously subjecting heavy petroleum oil to thermal cracking in a single-column reactor. More specifically, heavy petroleum oil, which has been heated in a heating furnace to a temperature of a predetermined range, is continuously charged into the lowermost reaction zone of a column-like reactor which is vertically divided into a plurality of reaction zones by means of at least one partition wall defining an opening therethrough to make said reaction zones to communicate with one another. The heavy petroleum oil is subjected in the reactor to thermal cracking while maintaining its temperature, pressure and residence time in the reactor within their respective predetermined ranges and causing oil, which has been treated in each of said reaction zones, to be successively transferred to its upper reaction zone together with bubbles under stirring conditions. Then, the thus-cracked product is continuously discharged from the uppermost reaction zone of the reactor.
Description
Background of the Invention 1) Field of the Invention:
This invention relates to a continous thermal cracking method of heavy petroleum oil. More particularly, it relates to a method for producing thermally-cracked products of high quality such as gas, cracked light oil and pitch from heavy petroleum oil by continuously subjecting the heavy petroleum oil to thermal cracking in a sin~le-column reactor.
This invention relates to a continous thermal cracking method of heavy petroleum oil. More particularly, it relates to a method for producing thermally-cracked products of high quality such as gas, cracked light oil and pitch from heavy petroleum oil by continuously subjecting the heavy petroleum oil to thermal cracking in a sin~le-column reactor.
2) Description of the Prior ~rt:
With a view toward making an effective use of heavy petroleum oil, a wide variety of attempts has been made to ob-tain gas, c.rac]ced light oil and pitch :from such heavy petroleum oil by thermal.ly cracking same.
It is extremely meaningful for the saving of coal for steel industry and for the diversification of coal usable in steel industry to utilize pitch produced from abundant heavy petroleum oil as a binder for the production of coke for steel-making blast furnaces or a substitute for caking coal which is also used to make such coke.
In order to obtain pitch of a quality suitable for the above-mentioned applications through the thermal cracking of heavy petroleum oil, it is necessary that such pitch has a composition abundant in those insoluble to benzene but scarce in those insoluble to quinoline(C~H7N), in other words, a composition rich in ~-resin components which have medium carbonization and polycondensation deg..rees.
It is obviously important for the control of the quality and yield of a product to select optimum reaction conditions. Moreover, it is also important to maintain the thus-selected reaction conditions as uniform as possible throughout the oil under thermal cracking treatment when the treatment is carried out in an industrial scale. It is indispensable to apply sufficient agitation to the oil under thermal cracking treatment for the purpose of keeping such optimum reaction condition as uniform as possible kllxoughout the oil and avoiding the a~glomeratioll of coke-like substances which inevitably occur during its thermal cracking reaction. The agitation or stirring may be effected in accordance with any method commonly employed in the art, namely, by means of mixing propellers, fluid injection or ultrasonic wave. These means may be employed solely or in combination, at will. However, even if.the oil is maintained in a good stirring state owing to an agitation by such means and reaction conditions such as temperature, pressure and residence time are precisely controlled, a part of the oil under treatment.which oil is a mixture of a number of components takes unavoidably a shortcut thxough 9~
a reactor and the final product contains inevitably both substances substantially unchanged from and similar to component substnaces contained in heavy petroleum oil charged into the reactor and substances occurred due to an excessive progress of carbonization and polycondensation by the thermal cracking as the stirring of the oil is caused by crosscurrents, where the thermal cracking treat-ment is conducted in a reaction system of the type that the feed heavy petroleum oil is continuously charged into a conventional single-column reactor and the resultant cracked product is dischar~ed continuously, particularly where the reactor has a large volume and the -treatment is conducted with a relati.vely lon~ resictence time. For the reasons mentioned above, it is impossible to obtain through the use of a single-column reactor pitch enriched especially in the above-described specific components, i.e., ~-resin components. The above drawbacks cannot be improved even if the reaction conditions are controlled precisely.
It cannot be expected to enrich selectively desired components only unless a special measure is taken to avoid the occurrence of a phenomenon that a part of the oil under treatment takes a shortcut through the reactor and, on the contrary, a part of the rest of the oil stays in the reactor for a time period longer than the predeter-mined residence time. As such a measure, Japanese Patent
With a view toward making an effective use of heavy petroleum oil, a wide variety of attempts has been made to ob-tain gas, c.rac]ced light oil and pitch :from such heavy petroleum oil by thermal.ly cracking same.
It is extremely meaningful for the saving of coal for steel industry and for the diversification of coal usable in steel industry to utilize pitch produced from abundant heavy petroleum oil as a binder for the production of coke for steel-making blast furnaces or a substitute for caking coal which is also used to make such coke.
In order to obtain pitch of a quality suitable for the above-mentioned applications through the thermal cracking of heavy petroleum oil, it is necessary that such pitch has a composition abundant in those insoluble to benzene but scarce in those insoluble to quinoline(C~H7N), in other words, a composition rich in ~-resin components which have medium carbonization and polycondensation deg..rees.
It is obviously important for the control of the quality and yield of a product to select optimum reaction conditions. Moreover, it is also important to maintain the thus-selected reaction conditions as uniform as possible throughout the oil under thermal cracking treatment when the treatment is carried out in an industrial scale. It is indispensable to apply sufficient agitation to the oil under thermal cracking treatment for the purpose of keeping such optimum reaction condition as uniform as possible kllxoughout the oil and avoiding the a~glomeratioll of coke-like substances which inevitably occur during its thermal cracking reaction. The agitation or stirring may be effected in accordance with any method commonly employed in the art, namely, by means of mixing propellers, fluid injection or ultrasonic wave. These means may be employed solely or in combination, at will. However, even if.the oil is maintained in a good stirring state owing to an agitation by such means and reaction conditions such as temperature, pressure and residence time are precisely controlled, a part of the oil under treatment.which oil is a mixture of a number of components takes unavoidably a shortcut thxough 9~
a reactor and the final product contains inevitably both substances substantially unchanged from and similar to component substnaces contained in heavy petroleum oil charged into the reactor and substances occurred due to an excessive progress of carbonization and polycondensation by the thermal cracking as the stirring of the oil is caused by crosscurrents, where the thermal cracking treat-ment is conducted in a reaction system of the type that the feed heavy petroleum oil is continuously charged into a conventional single-column reactor and the resultant cracked product is dischar~ed continuously, particularly where the reactor has a large volume and the -treatment is conducted with a relati.vely lon~ resictence time. For the reasons mentioned above, it is impossible to obtain through the use of a single-column reactor pitch enriched especially in the above-described specific components, i.e., ~-resin components. The above drawbacks cannot be improved even if the reaction conditions are controlled precisely.
It cannot be expected to enrich selectively desired components only unless a special measure is taken to avoid the occurrence of a phenomenon that a part of the oil under treatment takes a shortcut through the reactor and, on the contrary, a part of the rest of the oil stays in the reactor for a time period longer than the predeter-mined residence time. As such a measure, Japanese Patent
3!3Q~
Laid-open Nos. 65302/1978 and 119903/1978 propose to connect in series a plurality of reaction tanks, each, having a volume as small as possible from the industrial viewpoint and equipped with agitation and mixing means and to cause oil to be reacted while successively passing through the reaction tanks, thereby making it possible to reduce the drawbacks due to the shortcut passage, prolonged stay and crosscurrent mixing of the oil between the oil inlet and product outlet of the single-column reactor.
llowever, it has been realized that another problem, which w.ill be described below, is involved in the method with respect to the transfer of oil under treatment between each two reaction tanks. The another problem has still been unsolved.
The thermal cracking of heavy petroleum oil can of course be carried out with high efficiency if it is conducted at a reaction temperature as high as possible.
On the other hand, it is important for highly efficient thermal cracking o~ heavy petroleum oil to minimize the occurrence of coking, which is unavoidably promoted at high reaction temperatures. Therefore, the thermal cracking of heavy petroleum oil involves two requirements which are fundamentally contradictory.
In order to meet both of the mutually-incompatible requirements, there would not be any choice other than ~9(~
employ:ng a reaction temperature as low as possible from practical point of view and making the residence time in the reaction zone longer. Since a long residence time is chosen, the flow rate through a conduit between each two reaction tanks is obviously small where a plurality of reaction tanks are connected in series by conduits and oil is delivered through the tanks.
As the flow rate of oil under transfer from one reaction tank to another through a conduit provided therebetween is small, the effective flow area of the conduit is squeezed and then clogged in a short period of time due to coagulation of a mixture of carbonized particles and polycondensation pxoducts and accumulation thereof on the inner wall of the conduit regardless of the diameter o~ the conduit, that is to say, whether the diameter of the conduit is appropriate to the flow rate, too small or too large. As long as a smooth transfer of the oil through the conduit be-tween each two reaction tanks is not kept, the problem of controlling the oil level in each reaction tank will remain practically unsolved. Where it becomes impossible to control the oil level in each reaction tank, the reaction tank loses its gas/liquid separation function and thus requires a separate gas/liquid separation means additionally.
A thermal cracking method of heavy petroleum oil, which is extremely susceptible of inducing coking, is fundamentally different from that of heavy coal oil. It has been found that the method making use of a reactor formed by connecti.n~ a number of reaction tanks in series cannot be operated continually and, in addition, the entire facilities are inevitably made complex, uneconomical and impractical.
For achieving a smooth transfer of oil under treatment through a number of reaction tanks connected in series, attempts were made by using conduits having good smoothness at the inner walls thereof and laying them aslant toward the downstream of the reactor or by disposing the reaction tanks while providi.ng a sufficient h~ight difference between each two adjacent tanks so as to render the conduits be vertically descent conduits. However, such attempts were found to be fruitless in improving the problem.
Even if a conduit having good smoothness is employed, a ~in coke layer appears first of all on the inner surface thereof in the form of a dense film. Then, the coke layer becomes thicker very fast. At this point, the present inventors had realized that it is indispensable to either shorten or omit the transfer conduit for oil under treatment between each two reaction tanks and to provide a sort of delivery means for the oil under treat-ment, leading to an idea of solving the transfer problem ofoil between reaction tanks by disposing a succeeding reaction tank right above its preceding reaction tank, omi-tting a conduit, defining an opening for the passage of the oil to the succeeding reaction tank with a sharp edge, and exerting a delivery force to the oil by virtue of the buoyant forces of bubbles while continuously preventing the oil from being brought into contact with the sharp edge, which defines the opening for the passage of the oil, during the operation by rising bubbles so as to avoid the sticking problem of carboni2ed particles and polycondensation products.
The present inventors p.roceeded with a re~earch tll.~ouc3h a repeated trial production of -test :Eacil.ities and a repeated experiment thereon to establish a continuous thermal cracking method capable of providing from heavy petroleum oil pitch rich in intended components, for example, ~-resin components by solving the fatal drawbacks of the reactor formed of a number of reaction tanks connected in series and, instead, using an apparatus of simple construction and allowing the reaction to proceed while minimizing the shortcut passage and crosscurrent mixing of the oil through the reactor on the basis of the above idea.
The above.research has resulted i.n the completion of the method of this invention, which can produce smoothly a product of high quality by controlling the conten-ts of various components in the resul-ctant pitch product with high selectivity so that its composition can be enriched particularly in desired components and by completely improving the transer of the oil under treatment through the exersion of a delivery force to it owing to rising bubbles.
Objects of the Invention An object of an aspect of this invention is to provide a high-conversion continuous thermal cracking method of heavy petroleum oil capable of affording a reaction product selectively rich in desired components.
~n object of an aspect of this invention is to provide such a continuous thermal crackinq method which can be carriod out continuously a~d stably. Other objects, features and advantages of the present invention will become apparent from the following description and the accompanying drawing.
Brie~ Description of the Drawinc3 The single drawing is a flow sheet of an embodi-ment of the continuous thermal cracking method of heavy petroleum oil according to this invention.
Summary and Detailed Descr_ption of the Invention The present invention is directed to a continuous 9~
thermal cracking method of heavy petroleum oil, which comprises continuously charging said heavy petroleum oil, which has been heated in a heating furnace to a temperature of a predetermined range, into the lowermost reaction zone of a column-like reactor which is vertically divided into a plurality of reaction zones by means of at least one partition wall defining an opening therethrough to make said reaction zones to communicate with one another;
subjecting said heavy petroleum oil to thermal cracking while maintaining its temperature, pressure and residence time in said reactor within their respective predetermined ranges and causing oil, which has been -treated in each of said .reaction zones, to be successively transferred to its upper reaction zone together with bubbles under stirring ~ond.itions; and then continuously discharging the thus-cracked product from the uppermost reaction zone of said reactor. The preheating in the heating furnace is carried out to raise the temperature of the heavy petroleum oil to 450-520C when pitch abundant in ~-resin components is intended. To obtain such pitch, the temperature, pressure and residence time of the oil under treatment in the reactor are generally maintained within 370-450C, 1-20 ata. and 1-10 hours respectively.
Gas and vapor are separated in the uppermost reaction zone. The thermal cracking reaction is proceeded under a flow condition, that may be considered to be a piston flow as the entire reaction system, to minimize the shortcut flow of the oil under treatment and to achieve uniforln dispersion and stirring of the oil under treatment while avoiding completely its crosscurrent mixing as well as to ensure a smooth transfer of the oil between each two reaction zones, whereby to obtain a product of desired quality with a high yield. Since the method of this invention can provide a product of desired ~uality, in other words, a product enriched par-ticularly in desired components, the conversion of the heavy petroleum oil to undesired compo-nents is kept low, thereby obviously resulting in a high yield witll respect to the desired components.
One important feature oE the present method is that, in a thermal cracking reaction of heavy petroleum oil in which gas and vapor occur increasingly as the reaction proceeds, the transfer of oil under treatment to a succeeding reaction zone is carried out smoothly by the aid of the buoyant forces of bubbles that rise in a dispersed state through the oil under treatment vertically along the flowing direction of the oil under treatment, the crosscurrent mi~ing between reaction zones is completely avoided, and the area reduction does not occur at conduits communicating reaction zones together.
Now, the method of this invention is described in accordance with the drawing.
Heavy petroleum oil, which is a raw material, is sucked from a tank 1 into a pump 2 and delivered continuously under pressure to a heating furnace 3 equipped with a helical coil, in which it is heated to a temperature in a range of 450-520C. The thus-preheated heavy petroleum oil is then continuously charged into the lowermost reaction 20ne of a reactor 4. Within the-reactor 4, there are provided four partition walls 9, each, defin:ing an openirlg through a central portion thereof, along the vertical leng-th of the reactor 4, whereby forming five reaction zones 12.
'.rhrough the openings of the partition walls 9, is provided a drive sha~-t 10 for the ro-tation oE s-tirring propellers 11 . ' The number of the partition walls 9 is not particularly limited to any specific figure. It is principally determined by the residence time of oil under treatment in the reactor. Where a longer residence time is employed, more partition walls are required. The number of partition walls may be within 2-10, and generally within 2-5. The distance between each two adjacent parti-tion walls may be set 0.5-2 times the inner diameter of the reactor but is generally set equal to its inner diameter.
To induce good and smooth circulation and mixing of the oil under treatment in a reaction zone space formed between each two partitlon walls, it is most preferable that the distance between the partition walls is equal to the inner diameter of the reactor. If the distance between the partition walls is greater than twice the inner diameter of the reactor, two or more eddy currents are formed, whereby resulting in non-uniform stirring and mixing. On the other hand, if the former distance is less than 0.5 times the inner diameter of the reactor, the formation of an eddy current becomes unstable. Each partition wall is provided with an opening at its central portion, through which opening the oil under treatment can be transferred upwardly into its upper reaction zone while being assisted by the buoyant forces of bubbles.
The stirring propelle]~s 11 are rotated by a drive motor 5 through the drive shaft 10 so as to guidingly deliver the oil rising upwardly through each opening in a radial direction toward the inner wall of the reactor.
Upon arrival at the inner wall of the reactor 4, the oil flows back through an upper portion of each reaction zone 12 to the center of the same reaction zone, and then caused to flow upwardly into the next reaction zone.
The rotation speed of the propellers 11, their configurations ancl their installation heights from their respective lower partition walls must be carefully deter~
mined to prevent the oil under treatment from taking a shortcut through the openings only by the buoyant forces of bubbles.
Each partition wall is generally provided with an upward gradlent of 5-45 from the inner wall of the reactor toward the edge of its opening, whereby preventing bubbles from staying underneath the partition wall. A
suitable number of small openings may also be formed through each of the partition walls along the lower peripheral e~ge thereof so as to permit any precipitate, which may occur on the wall partition, to drop into its lower reaction zone.
The ratio of the opening area of each partition wa.ll to the horizontal cross-sect:iona.l. area of each reaction zone may usually range from 1/10 to 1/4, and more preferably, from l/3 to l/4. The rising speed of bubbles through each opening is determined in such a way that the oil under treatment is not excessivel~ accompanied by the rising bubbles so as to maintain sufficient oil in its lower reaction zone.
The oil under treatment is gradually converted to pitch while generating bubbles owing to the progress of the thermalcracking and polycondensation reactlons as it moves to upper reaction zones and a predetermined conver-sion rate is achieved at the top of the reactor, where the reaction mixture is allowed to continuously flow out of the reactor. Therea.Eter, it flows into a cooling column 7 in which its temperature is cooled down to a lower tempera-ture, for example, helow 350C to terminate the thermal crackin~ reaction. Pitch ls maintained in a liquid state in the cooling column 7 and continuously discharged from the bottom of the column 7 through a pipe 15 by means of a pump 8.
The reactor ~ may be charged with heating steam or the :Like at a su:itable position if necessa.ry.
Any gas and vapor generated by the thermal crackin~ reacti.on and steam in~ected lnto the reactor are discharged from a gas phase space above the uppermost ~r~action zone of the reactor and introduced l.nto a :Erac-tionating column 6, where they are fractionated into cracked gas and thermally crac~ed light oil which are withdrawn respectively through pipes 13, 14. According to the method of this invention, pitch enriched in specific components and thus having excellent quality is produced under stable operational conditions. In addition, the method of this invention is extremely economical, because it requlres only one reactor, whereby simplifying the accompanied piping and other attachments, and the reactor con-tains ineffective space areas very little, thereby rendering the size of the reactor per se reduced, and the installation area required for the entire facilities is considerably small.
The effect of the method of this invention is now described by referring to the following comparative example and examples of this invention.
Examples:
A thermal cracking treatment was effected independently in four reactors as shown in the drawing.
One of the reactors had no partition wall to compare it with the remaining three reactors which had 2r 5 and 10 partition walls respectively. Where partition walls were provided, the movemerlt of oil under treatment was good in the reactor and no obstacles were recognized from the prov.ision of such partition walls, In each of the comparative example and examples of this invention, the reactor had a height of 2,600 mm and an inner diameter of 400 mm. The residence time of the oil in each of the reactors was set for 2 hours.
In the examples of this invention, the partition walls were disposed with an equal interval and the ratio of the opening area to the horizontal cross-sectional area of the reactor was 0.3.
Results obtained through the above experiments are shown in Table l.
As apparent from Table 1, compared with pitch produced in the reactors equipped with the partition walls, the pitch produced in the reaetor equipped with no parti-tion wall is rich in components insoluble to quinoline and also in those insoluble to benzene. Consequently, it eontains lesser ~-resin components.
Furthermore, the content of ~-resin components increases as the number of partition walls increases.
However, this difference is not so much as that experienced between the reactors equipped with partition walls and that having no partition wall. It is thus envisaged that major eontribution to the above efEeet was derived from the faet that the oil under treatment was caused to pass through eaeh o~ t.he reaetors equipped with partition walls .in th~ ~orm o~ an upward stream preventing shorteireuit passage or erosseurrent mixing of the oil.
39~
Table 1 Number of partition walls 0 2 5 10 . . . _ __ . . . ~
Reaction conditions:
.._ _ Feed oil * * * *
Flow rate of feed oil(kgjhr)100 100 100 100 I`emp at the outlet(oc) 490 of reactor ( C) 410 395 390 386 Pressure in reactor(ata.)1.051.051.05 1.05 Yiel~:
Cracked gas(w-t.%) 5.0 4.0 4.5 4.4 Cracked oil(wt.%) 60.0 59.959.9 59.8 Pitc~l(wt.%) 35.0 35.435.6 35.8 Characteristics of pitch:
~ . . __ Soten:in~ poi.nt(C) 175 180 181 183 Components insoluble(wt.%) 48.5 47.6 46.5 46.0 Components insoluble(wt.~) 30.2 15 4 8.5 7.0 to quinoline ~-Resin components(wt.~) 18.3 32.2 38.0 39.0 _ * Reduced-pressure distillation residue of crude Kuwait oil.
** Measured by the ring and ball method.
Laid-open Nos. 65302/1978 and 119903/1978 propose to connect in series a plurality of reaction tanks, each, having a volume as small as possible from the industrial viewpoint and equipped with agitation and mixing means and to cause oil to be reacted while successively passing through the reaction tanks, thereby making it possible to reduce the drawbacks due to the shortcut passage, prolonged stay and crosscurrent mixing of the oil between the oil inlet and product outlet of the single-column reactor.
llowever, it has been realized that another problem, which w.ill be described below, is involved in the method with respect to the transfer of oil under treatment between each two reaction tanks. The another problem has still been unsolved.
The thermal cracking of heavy petroleum oil can of course be carried out with high efficiency if it is conducted at a reaction temperature as high as possible.
On the other hand, it is important for highly efficient thermal cracking o~ heavy petroleum oil to minimize the occurrence of coking, which is unavoidably promoted at high reaction temperatures. Therefore, the thermal cracking of heavy petroleum oil involves two requirements which are fundamentally contradictory.
In order to meet both of the mutually-incompatible requirements, there would not be any choice other than ~9(~
employ:ng a reaction temperature as low as possible from practical point of view and making the residence time in the reaction zone longer. Since a long residence time is chosen, the flow rate through a conduit between each two reaction tanks is obviously small where a plurality of reaction tanks are connected in series by conduits and oil is delivered through the tanks.
As the flow rate of oil under transfer from one reaction tank to another through a conduit provided therebetween is small, the effective flow area of the conduit is squeezed and then clogged in a short period of time due to coagulation of a mixture of carbonized particles and polycondensation pxoducts and accumulation thereof on the inner wall of the conduit regardless of the diameter o~ the conduit, that is to say, whether the diameter of the conduit is appropriate to the flow rate, too small or too large. As long as a smooth transfer of the oil through the conduit be-tween each two reaction tanks is not kept, the problem of controlling the oil level in each reaction tank will remain practically unsolved. Where it becomes impossible to control the oil level in each reaction tank, the reaction tank loses its gas/liquid separation function and thus requires a separate gas/liquid separation means additionally.
A thermal cracking method of heavy petroleum oil, which is extremely susceptible of inducing coking, is fundamentally different from that of heavy coal oil. It has been found that the method making use of a reactor formed by connecti.n~ a number of reaction tanks in series cannot be operated continually and, in addition, the entire facilities are inevitably made complex, uneconomical and impractical.
For achieving a smooth transfer of oil under treatment through a number of reaction tanks connected in series, attempts were made by using conduits having good smoothness at the inner walls thereof and laying them aslant toward the downstream of the reactor or by disposing the reaction tanks while providi.ng a sufficient h~ight difference between each two adjacent tanks so as to render the conduits be vertically descent conduits. However, such attempts were found to be fruitless in improving the problem.
Even if a conduit having good smoothness is employed, a ~in coke layer appears first of all on the inner surface thereof in the form of a dense film. Then, the coke layer becomes thicker very fast. At this point, the present inventors had realized that it is indispensable to either shorten or omit the transfer conduit for oil under treatment between each two reaction tanks and to provide a sort of delivery means for the oil under treat-ment, leading to an idea of solving the transfer problem ofoil between reaction tanks by disposing a succeeding reaction tank right above its preceding reaction tank, omi-tting a conduit, defining an opening for the passage of the oil to the succeeding reaction tank with a sharp edge, and exerting a delivery force to the oil by virtue of the buoyant forces of bubbles while continuously preventing the oil from being brought into contact with the sharp edge, which defines the opening for the passage of the oil, during the operation by rising bubbles so as to avoid the sticking problem of carboni2ed particles and polycondensation products.
The present inventors p.roceeded with a re~earch tll.~ouc3h a repeated trial production of -test :Eacil.ities and a repeated experiment thereon to establish a continuous thermal cracking method capable of providing from heavy petroleum oil pitch rich in intended components, for example, ~-resin components by solving the fatal drawbacks of the reactor formed of a number of reaction tanks connected in series and, instead, using an apparatus of simple construction and allowing the reaction to proceed while minimizing the shortcut passage and crosscurrent mixing of the oil through the reactor on the basis of the above idea.
The above.research has resulted i.n the completion of the method of this invention, which can produce smoothly a product of high quality by controlling the conten-ts of various components in the resul-ctant pitch product with high selectivity so that its composition can be enriched particularly in desired components and by completely improving the transer of the oil under treatment through the exersion of a delivery force to it owing to rising bubbles.
Objects of the Invention An object of an aspect of this invention is to provide a high-conversion continuous thermal cracking method of heavy petroleum oil capable of affording a reaction product selectively rich in desired components.
~n object of an aspect of this invention is to provide such a continuous thermal crackinq method which can be carriod out continuously a~d stably. Other objects, features and advantages of the present invention will become apparent from the following description and the accompanying drawing.
Brie~ Description of the Drawinc3 The single drawing is a flow sheet of an embodi-ment of the continuous thermal cracking method of heavy petroleum oil according to this invention.
Summary and Detailed Descr_ption of the Invention The present invention is directed to a continuous 9~
thermal cracking method of heavy petroleum oil, which comprises continuously charging said heavy petroleum oil, which has been heated in a heating furnace to a temperature of a predetermined range, into the lowermost reaction zone of a column-like reactor which is vertically divided into a plurality of reaction zones by means of at least one partition wall defining an opening therethrough to make said reaction zones to communicate with one another;
subjecting said heavy petroleum oil to thermal cracking while maintaining its temperature, pressure and residence time in said reactor within their respective predetermined ranges and causing oil, which has been -treated in each of said .reaction zones, to be successively transferred to its upper reaction zone together with bubbles under stirring ~ond.itions; and then continuously discharging the thus-cracked product from the uppermost reaction zone of said reactor. The preheating in the heating furnace is carried out to raise the temperature of the heavy petroleum oil to 450-520C when pitch abundant in ~-resin components is intended. To obtain such pitch, the temperature, pressure and residence time of the oil under treatment in the reactor are generally maintained within 370-450C, 1-20 ata. and 1-10 hours respectively.
Gas and vapor are separated in the uppermost reaction zone. The thermal cracking reaction is proceeded under a flow condition, that may be considered to be a piston flow as the entire reaction system, to minimize the shortcut flow of the oil under treatment and to achieve uniforln dispersion and stirring of the oil under treatment while avoiding completely its crosscurrent mixing as well as to ensure a smooth transfer of the oil between each two reaction zones, whereby to obtain a product of desired quality with a high yield. Since the method of this invention can provide a product of desired ~uality, in other words, a product enriched par-ticularly in desired components, the conversion of the heavy petroleum oil to undesired compo-nents is kept low, thereby obviously resulting in a high yield witll respect to the desired components.
One important feature oE the present method is that, in a thermal cracking reaction of heavy petroleum oil in which gas and vapor occur increasingly as the reaction proceeds, the transfer of oil under treatment to a succeeding reaction zone is carried out smoothly by the aid of the buoyant forces of bubbles that rise in a dispersed state through the oil under treatment vertically along the flowing direction of the oil under treatment, the crosscurrent mi~ing between reaction zones is completely avoided, and the area reduction does not occur at conduits communicating reaction zones together.
Now, the method of this invention is described in accordance with the drawing.
Heavy petroleum oil, which is a raw material, is sucked from a tank 1 into a pump 2 and delivered continuously under pressure to a heating furnace 3 equipped with a helical coil, in which it is heated to a temperature in a range of 450-520C. The thus-preheated heavy petroleum oil is then continuously charged into the lowermost reaction 20ne of a reactor 4. Within the-reactor 4, there are provided four partition walls 9, each, defin:ing an openirlg through a central portion thereof, along the vertical leng-th of the reactor 4, whereby forming five reaction zones 12.
'.rhrough the openings of the partition walls 9, is provided a drive sha~-t 10 for the ro-tation oE s-tirring propellers 11 . ' The number of the partition walls 9 is not particularly limited to any specific figure. It is principally determined by the residence time of oil under treatment in the reactor. Where a longer residence time is employed, more partition walls are required. The number of partition walls may be within 2-10, and generally within 2-5. The distance between each two adjacent parti-tion walls may be set 0.5-2 times the inner diameter of the reactor but is generally set equal to its inner diameter.
To induce good and smooth circulation and mixing of the oil under treatment in a reaction zone space formed between each two partitlon walls, it is most preferable that the distance between the partition walls is equal to the inner diameter of the reactor. If the distance between the partition walls is greater than twice the inner diameter of the reactor, two or more eddy currents are formed, whereby resulting in non-uniform stirring and mixing. On the other hand, if the former distance is less than 0.5 times the inner diameter of the reactor, the formation of an eddy current becomes unstable. Each partition wall is provided with an opening at its central portion, through which opening the oil under treatment can be transferred upwardly into its upper reaction zone while being assisted by the buoyant forces of bubbles.
The stirring propelle]~s 11 are rotated by a drive motor 5 through the drive shaft 10 so as to guidingly deliver the oil rising upwardly through each opening in a radial direction toward the inner wall of the reactor.
Upon arrival at the inner wall of the reactor 4, the oil flows back through an upper portion of each reaction zone 12 to the center of the same reaction zone, and then caused to flow upwardly into the next reaction zone.
The rotation speed of the propellers 11, their configurations ancl their installation heights from their respective lower partition walls must be carefully deter~
mined to prevent the oil under treatment from taking a shortcut through the openings only by the buoyant forces of bubbles.
Each partition wall is generally provided with an upward gradlent of 5-45 from the inner wall of the reactor toward the edge of its opening, whereby preventing bubbles from staying underneath the partition wall. A
suitable number of small openings may also be formed through each of the partition walls along the lower peripheral e~ge thereof so as to permit any precipitate, which may occur on the wall partition, to drop into its lower reaction zone.
The ratio of the opening area of each partition wa.ll to the horizontal cross-sect:iona.l. area of each reaction zone may usually range from 1/10 to 1/4, and more preferably, from l/3 to l/4. The rising speed of bubbles through each opening is determined in such a way that the oil under treatment is not excessivel~ accompanied by the rising bubbles so as to maintain sufficient oil in its lower reaction zone.
The oil under treatment is gradually converted to pitch while generating bubbles owing to the progress of the thermalcracking and polycondensation reactlons as it moves to upper reaction zones and a predetermined conver-sion rate is achieved at the top of the reactor, where the reaction mixture is allowed to continuously flow out of the reactor. Therea.Eter, it flows into a cooling column 7 in which its temperature is cooled down to a lower tempera-ture, for example, helow 350C to terminate the thermal crackin~ reaction. Pitch ls maintained in a liquid state in the cooling column 7 and continuously discharged from the bottom of the column 7 through a pipe 15 by means of a pump 8.
The reactor ~ may be charged with heating steam or the :Like at a su:itable position if necessa.ry.
Any gas and vapor generated by the thermal crackin~ reacti.on and steam in~ected lnto the reactor are discharged from a gas phase space above the uppermost ~r~action zone of the reactor and introduced l.nto a :Erac-tionating column 6, where they are fractionated into cracked gas and thermally crac~ed light oil which are withdrawn respectively through pipes 13, 14. According to the method of this invention, pitch enriched in specific components and thus having excellent quality is produced under stable operational conditions. In addition, the method of this invention is extremely economical, because it requlres only one reactor, whereby simplifying the accompanied piping and other attachments, and the reactor con-tains ineffective space areas very little, thereby rendering the size of the reactor per se reduced, and the installation area required for the entire facilities is considerably small.
The effect of the method of this invention is now described by referring to the following comparative example and examples of this invention.
Examples:
A thermal cracking treatment was effected independently in four reactors as shown in the drawing.
One of the reactors had no partition wall to compare it with the remaining three reactors which had 2r 5 and 10 partition walls respectively. Where partition walls were provided, the movemerlt of oil under treatment was good in the reactor and no obstacles were recognized from the prov.ision of such partition walls, In each of the comparative example and examples of this invention, the reactor had a height of 2,600 mm and an inner diameter of 400 mm. The residence time of the oil in each of the reactors was set for 2 hours.
In the examples of this invention, the partition walls were disposed with an equal interval and the ratio of the opening area to the horizontal cross-sectional area of the reactor was 0.3.
Results obtained through the above experiments are shown in Table l.
As apparent from Table 1, compared with pitch produced in the reactors equipped with the partition walls, the pitch produced in the reaetor equipped with no parti-tion wall is rich in components insoluble to quinoline and also in those insoluble to benzene. Consequently, it eontains lesser ~-resin components.
Furthermore, the content of ~-resin components increases as the number of partition walls increases.
However, this difference is not so much as that experienced between the reactors equipped with partition walls and that having no partition wall. It is thus envisaged that major eontribution to the above efEeet was derived from the faet that the oil under treatment was caused to pass through eaeh o~ t.he reaetors equipped with partition walls .in th~ ~orm o~ an upward stream preventing shorteireuit passage or erosseurrent mixing of the oil.
39~
Table 1 Number of partition walls 0 2 5 10 . . . _ __ . . . ~
Reaction conditions:
.._ _ Feed oil * * * *
Flow rate of feed oil(kgjhr)100 100 100 100 I`emp at the outlet(oc) 490 of reactor ( C) 410 395 390 386 Pressure in reactor(ata.)1.051.051.05 1.05 Yiel~:
Cracked gas(w-t.%) 5.0 4.0 4.5 4.4 Cracked oil(wt.%) 60.0 59.959.9 59.8 Pitc~l(wt.%) 35.0 35.435.6 35.8 Characteristics of pitch:
~ . . __ Soten:in~ poi.nt(C) 175 180 181 183 Components insoluble(wt.%) 48.5 47.6 46.5 46.0 Components insoluble(wt.~) 30.2 15 4 8.5 7.0 to quinoline ~-Resin components(wt.~) 18.3 32.2 38.0 39.0 _ * Reduced-pressure distillation residue of crude Kuwait oil.
** Measured by the ring and ball method.
Claims (5)
1. In a continuous thermal cracking method of heavy petroleum oil, the improvement comprises continuously charging said heavy petroleum oil, which has been heated in a heating furnace to a temperature of a predetermined range, into the lowermost reaction zone of a column-like reactor which is vertically divided into a plurality of reaction zones by means of at least one partition wall defining an opening therethrough to make said reaction zones to communicate with one another; subjecting said heavy petroleum oil to thermal cracking while maintaining its temperature, pressure and residence time in said reactor within their respective predetermined ranges and causing oil, which has been treated in each of said reaction zones, to be successively transferred to its upper reaction zone together with bubbles under stirring conditions; and then continuously discharging the thus-cracked product from the uppermost reaction zone of said reactor.
2. The continuous thermal cracking method of heavy petroleum oil as claimed in Claim 1, wherein the temperature in said reactor is maintained within a range of 350-520°C.
3. The continuous thermal cracking method of heavy petroleum oil as claimed in Claim 1, wherein the pressure in said reactor is maintained within a range of 1-20 ata.
4. The continuous thermal cracking method of heavy petroleum oil as claimed in Claim 1, wherein said residence time in said reactor is maintained within a range of 1-10 hours.
5. The continuous thermal cracking method of heavy petroleum oil as claimed in any one of claims 1, 2 or 3, wherein said at least one partition wall ranges from 2 to 10 partition walls.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP392181A JPS57119986A (en) | 1981-01-16 | 1981-01-16 | Thermal cracking method for petroleum heavy oil |
| JP3921/1981 | 1981-01-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1189011A true CA1189011A (en) | 1985-06-18 |
Family
ID=11570609
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000394287A Expired CA1189011A (en) | 1981-01-16 | 1982-01-15 | Continuous thermal cracking method of heavy petroleum oil |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS57119986A (en) |
| CA (1) | CA1189011A (en) |
| DD (1) | DD201804A5 (en) |
| MX (1) | MX161270A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4778586A (en) * | 1985-08-30 | 1988-10-18 | Resource Technology Associates | Viscosity reduction processing at elevated pressure |
| US4818371A (en) * | 1987-06-05 | 1989-04-04 | Resource Technology Associates | Viscosity reduction by direct oxidative heating |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3127418A1 (en) * | 1981-07-11 | 1983-02-03 | Trützschler GmbH & Co KG, 4050 Mönchengladbach | DEVICE FOR SEPARATING IMPURITIES, LIKE DUST, TRASH OR THE LIKE. FROM FIBER GOODS |
| DD249916B1 (en) * | 1986-06-10 | 1989-11-22 | Petrolchemisches Kombinat | METHOD OF PRODUCING LIGHT PRODUCTS AND CONVENTIONALLY UTILIZABLE HEATING OILS FROM HEAVY METAL AND SULFUR RESOURCES |
| JPH02212592A (en) * | 1989-02-10 | 1990-08-23 | Nijiyuuitsuseiki Kaihatsu:Kk | Device for thermal decomposition of waste material |
| JPH03179088A (en) * | 1989-06-08 | 1991-08-05 | Nijiyuuitsuseiki Kaihatsu:Kk | Continuous automated method for thermal decomposition of fluid waste material |
| JP6918731B2 (en) | 2018-02-28 | 2021-08-11 | キヤノン株式会社 | Optical system and imaging device |
-
1981
- 1981-01-16 JP JP392181A patent/JPS57119986A/en active Granted
-
1982
- 1982-01-14 DD DD23673782A patent/DD201804A5/en unknown
- 1982-01-15 MX MX19100982A patent/MX161270A/en unknown
- 1982-01-15 CA CA000394287A patent/CA1189011A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4778586A (en) * | 1985-08-30 | 1988-10-18 | Resource Technology Associates | Viscosity reduction processing at elevated pressure |
| US4818371A (en) * | 1987-06-05 | 1989-04-04 | Resource Technology Associates | Viscosity reduction by direct oxidative heating |
| US5008085A (en) * | 1987-06-05 | 1991-04-16 | Resource Technology Associates | Apparatus for thermal treatment of a hydrocarbon stream |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6256917B2 (en) | 1987-11-27 |
| MX161270A (en) | 1990-08-27 |
| JPS57119986A (en) | 1982-07-26 |
| DD201804A5 (en) | 1983-08-10 |
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