CA1126189A - Integrated two stage coking and steam cracking process - Google Patents
Integrated two stage coking and steam cracking processInfo
- Publication number
- CA1126189A CA1126189A CA360,803A CA360803A CA1126189A CA 1126189 A CA1126189 A CA 1126189A CA 360803 A CA360803 A CA 360803A CA 1126189 A CA1126189 A CA 1126189A
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Abstract
ABSTRACT OF THE DISCLOSURE
The invention relates to an integrated, two stage coking and steam cracking process for the production of un-saturated light hydrocarbons. A heavy hydrocarbonaceous oil is first coked in a fluid coking zone. High temperature cracking in the presence of steam is carried out on the vaporous coker conversion product by injecting into the vapors a stream of hot coke particles at a sufficient temperature and in sufficient amount to raise the coker vapors to steam cracking temperature and supply the endo-thermic heat of reaction. The solids are separated from the gas and sent to the fluid coking zone and the gas is quenched to stop olefin degradation reactions.
The invention relates to an integrated, two stage coking and steam cracking process for the production of un-saturated light hydrocarbons. A heavy hydrocarbonaceous oil is first coked in a fluid coking zone. High temperature cracking in the presence of steam is carried out on the vaporous coker conversion product by injecting into the vapors a stream of hot coke particles at a sufficient temperature and in sufficient amount to raise the coker vapors to steam cracking temperature and supply the endo-thermic heat of reaction. The solids are separated from the gas and sent to the fluid coking zone and the gas is quenched to stop olefin degradation reactions.
Description
BACKGROUND O~ THE IN~ENTIO~
This invention relates to an integrated, two stage coking and steam cracking process (cocracking) for the production of unsaturated light hydrocarbons, particularly C2-C4 olefins and dlolePins, use~ul as chemicals and chemical intermedia~esO
Steam cracking is a well known process and is described in U.S. patent 3,641,190 and British Patent 1,077,918. In commer-cial practice, steam cracking ls carried out by passing a hydro-carbon feed mixed with 20 80 mol ~ steam through metal pyrolysis tubes located in a fuel fired furnace to raise the feed to crack-ing temperatures, e.g., about 1400 to 1700F. and to supply the endothermic heat of reaction.
The fluid coking procesq for the production of fuels, such as gas oil and naphtha is well known and is disclosed in U.S. Patent 2,881,130. Integrated ~luid coking and coke gasifica-tion processes are also known and disclosed, for example, in U.S.
patents 3,661,543 and 3,816,084.
Fluid coking processes for the production of chemicals ; and chemical intermediates are also known. See, for example, U.S. patent 2,846,360 and U.S. patent 2,871,183. Generally, when lt was desired to pxoduce chemicals rather than fuel oils, hereto-~ore, the fluld coking process usually included a high temperature trans~er line coklng zone and a fluidized bed coking zone.
It is also known to introduce a small amount of hot solids into a gas-solids separation zone, such as the cyclone separator, used to separate entrained solids ~rom the vaporous coker product so as to prevent coke depo~ition on the walls of the cyclone ~eparator, see for example, U.S. patents 2,763,601;
~,859,168and 2~943r993~
As regards the last three mentloned patents, in order ; to supply heat for the coklng reaction, coke is ~1 , .
.
, . . . .
1 removed from the bottom of the reactor and passed to a
This invention relates to an integrated, two stage coking and steam cracking process (cocracking) for the production of unsaturated light hydrocarbons, particularly C2-C4 olefins and dlolePins, use~ul as chemicals and chemical intermedia~esO
Steam cracking is a well known process and is described in U.S. patent 3,641,190 and British Patent 1,077,918. In commer-cial practice, steam cracking ls carried out by passing a hydro-carbon feed mixed with 20 80 mol ~ steam through metal pyrolysis tubes located in a fuel fired furnace to raise the feed to crack-ing temperatures, e.g., about 1400 to 1700F. and to supply the endothermic heat of reaction.
The fluid coking procesq for the production of fuels, such as gas oil and naphtha is well known and is disclosed in U.S. Patent 2,881,130. Integrated ~luid coking and coke gasifica-tion processes are also known and disclosed, for example, in U.S.
patents 3,661,543 and 3,816,084.
Fluid coking processes for the production of chemicals ; and chemical intermediates are also known. See, for example, U.S. patent 2,846,360 and U.S. patent 2,871,183. Generally, when lt was desired to pxoduce chemicals rather than fuel oils, hereto-~ore, the fluld coking process usually included a high temperature trans~er line coklng zone and a fluidized bed coking zone.
It is also known to introduce a small amount of hot solids into a gas-solids separation zone, such as the cyclone separator, used to separate entrained solids ~rom the vaporous coker product so as to prevent coke depo~ition on the walls of the cyclone ~eparator, see for example, U.S. patents 2,763,601;
~,859,168and 2~943r993~
As regards the last three mentloned patents, in order ; to supply heat for the coklng reaction, coke is ~1 , .
.
, . . . .
1 removed from the bottom of the reactor and passed to a
2 heater where its temperature is moderately raised, viz., to
3 about 1125F., and at least a part is then returned to the
4 reactor. Tn this way the fluidized bed is maintained at its operating temperature, in these patents of about 950-6 1000F. In order to prevent incipient coke deposits from 7 forming on surfaces of the cyclones, e!specially in the 8 region of the inlet which could block them, a relatively 9 small portion of this returning coke is introduced into the cyclone or at a location adjacent to the cyclone inlet 11 for its heating and scouring effect. This problem, which 12 is well recognized in the art, is not the concern of the 13 subject application. Since this scouring coke constitutes 14 a small portion of the entire inventory of coke being re-turned to the reactor, thus is tied to the temperature of 16 the same, it will also be at about 1125F., as the examples 17 in the said patents attest. At such temperatures the coke 18 so introduced cannot bring the coker vapors up to or above 19 the minimum steam cracking temperature of about 1200F. By contrast, no such linkage as to temperature exists according 21 to the present process. However, even if higher temperature 22 coke were to be used, the minor amount in which it is intro-23 duced (170 lbs./bbl. of fresh feed according to U.S. patent 24 2,859,168 and 200-400 lbs./bbl. of fresh feed according to U.S. patent 2,763,601) would be insufficient to raise the 26 vapors to cracking temperature and to sustain the endo-27 thermic steam cracking reaction. Scouring coke is inade-28 quate to perform such function. Thus, its use has been 29 understood to be associated with the prevention of coke deposits on the cyclone surfaces but has not been considexed 31 to be a means of carrying out steam crackiny. For scouring 32 coke the amounk of heat to be added need only be enough to 33 uphold the temperature o~ the vapors and prevent them ~rom 34 depositing coke whereas the heat load is much greater for steam cracking.
36 Consequently, these patents do not disclose or 37 suggest the concept of carrying out steam cracking on the .
,~
1 vapors produced from a fluid coking zone and do not disclose 2 the conditions which would make cocracking ~easible. Sur-3 prisingly, although the temperatures for carrying out these 4 two reactions are disparate, it has now been found that these reactions can be coordinated and caused to take place in the 6 same vessel.
7 SUMMARY OF THE INVENTION ;
8 According to the present invention a carbonaceous 9 material is coked in a first stage fluid coking zone and the resulting vaporous coker conversion product is passed to a 11 second stage reaction zone where it is heate~ in the pre-12 sence of steam to a temperature adapted to crack the same 13 to products including low molecular ~eight unsaturated 14 hydrocarbons. This is achieved by injecting a stream of hot solids at a sufficiently high temperature and in sufficient 16 amount into the vaporous coker conversion product passing 17 to the gas-solids separation zone. The hot solids may be 18 supplied by a coke gasification zone.
Fig. 1 is a schematic- flow plan of one embodiment 21 of the invention; and 22 Fig. 2 is a more detailed schematic view of a 23 coking reactor. Like parts are designated by the same 24 numbers as in Fig. 1.
DETAILED DESCRIPTION
26 Referring to Fig. 1, a carbonaceous material for 27 example having a Conradson carbon residue of about 25 weight 28 percent such as heavy residuum having a boiling point (at 29 atmospheric pressure) of about 1050F.~ is passed by line 10 to reactor 1 into a coking zone 12 in which is maintained 31 a Eluidized bed of solids ~e.g., coke particles o 20 to 32 1000 microns in size) having an upper level indicated at 33 14 above which there i6 a disperse or dilute phase. Car-34 bonaceous feeds suitable Eor the present invention include heavy hydrocarbonaceous oils; heavy and reduced petroleum 36 crudes; petroleum atmospheric distillation bottoms~
37 petroleum vacuum distillation bottoms; pitch, asphalt, 1 bitumen, other heavy hydrocarbon residues; coal; coal 2 slurry; liquid products derived from coal liquefaction pro-3 cesses and mixtures thereof. Typically such feeds have a 4 Conradso~ carbon residue of at least 15 weight percent, generally from about 15 to about 50 weight percent (as to 6 Conradson carbon residue, see ASTM test D-189-65). Reactor 7 1 may be lined internally with a refrac~ory insulating 8 material, not shown. A fluidizing gas, e.g., steam, is ad-9 mitted at the base of coking reactor 1 through line 16 in an amount sufficient to obtain superficial fluidizing gas 11 velocity in the range of 0.5 to 5 feet per second. If a 12 fluidizing gas other than steam is used, steam is addition-13 ally present. Ccke from the heater 2 which ~ay be maintained 14 at a temperature in the range of about 1050 to 1300F., preferably in the range of 1050 to 1150F., is admitted to 16 reactor 1 by line 42 when required to maintain the coking 17 temperature. The coking temperature is in the range of 18 about 950 to about 1150F., preferably about 950 to about 19 1100F., more preferably about 950 to about 1050F. The pressure in the coking zone is maintained in the range from 21 about 5 to about 150, preferably about S to about 45 psig.
22 The lower portion of the coking reactor serves as a strip-23 ping zone to remove occluded hydrocarbons from the coke. A
24 stream of coke is withdrawn from the stripping zone by line 18 and circulated to heater 2. ~ gas~solids separation zone 26 such as cyclones 20 serves to remove entrained solids from 27 vaporous products. The cyclone separator system may be one 28 or more cyclones. A baffle 62 ~refer to Fig. 2) extends 29 from the sides of the reactor 1 above the fluid bed and terminates in a relatively small diameter top which defines 31 a r~stricted vapor passageway or duct 66 for the vapors from 32 the fluid bed to the inlet 64 of the cyclones. Steam crack-3:3 ing takes place in the duct 66 and in the cyclones. The 34 temperature in the steam cracking zone is maintained in the range oE 1200 to 1700F., preferably about 1300 to about 36 1500F., to convert at least a portion of the coking zone 37 conversion product, preferably at least 15% thereof, to . ~ :
:
1 lower olefins and diolefins. This is accomplished by intro-2 ducing a sufficient amount of a stream of hot solids, with-3 drawn from the gasifier 2 by line 58 and then injected by 4 line 60 above the dense fluid bed, into the dilute phase in the duct 66 leading to the inlet of the cyclones. The 6 zone between the outlet of the hot solids feed line 60 and7 the cyclone inlet should be as short a!s possible to keep 8 residence time low (for good selectivity to C2-C4 olefins) 9 but long enough to ensure good mixing and heat transfer between the coke and the gas. Gas residence time in this 11 zone will ~ypically be 0.02 to 0.3 seconds, preferably 0.05 12 to 0.2 seconds. The amount of solids is in the range of 13 about 1200 to 3200 lbs. preferably about 1800 to 2600 lbs.
14 per barrel of fresh feed and they are at a temperature in the range of 1500 to 2000F., preferably 1600 to 1800F.
16 Residence time o~ the coker vapors at steam cracking condi-17 tions, i.e., from the point o~ injection of the coke to the 18 outlet of the cyclone is approximately one second or less, 19 e.g., 0.3 to 0.8 seconds. The resulting vapor/coke product mixture i5 separated in the cyclones, the coke passing down 21 into the coker bed via the diplegs 22. The resulting 22 cracked vapors leave the cyclones through line 24. Line 24 23 passes through a wall 21 separating the reactor from the 24 scrubber 25 as shown in Fig. 2. The vapors leaving line 24 are quenched in the scrubber to about 600-900F. by liquid 26 products from product fractionation. If desired, a stream 27 of heavy material, viz., 950F~ products, condensed in the 28 scrubber rnay be recycled to the coking reactor via line 26.
29 Furthermore, if desired, a portion of the carbonaceous feed may be injected into the scrubber to provide an adequate 31 volume to carry eoke fines back to the coking zone. The 32 eyclone conversion products are removed from scrubber 25 33 via line 28 for Eractionation in a conventional manner.
34 In heater 2, stripped coke rom coking reactor 1 (common].y ealled cold coke) is introduced by line 18 to a fluid bed 36 of hot coke having an upper level indicated at 30. The bed 37 is partially heated by passing a fuel gas into the heater .; .
:. , 1 by line 32. Supplementary heat is applied to the heater by 2 coke circulating in line 34. The gaseous effluent of the 3 heater, including entrained solids, passes through a cyclone 4 which may be a first cyclone 36 and a second cyclone 38 wherein separation of the larger entrained solids occurs.
6 The separated larger solids are returned to the heater bed 7 via the respective cyclone diplegs. T~lë heater gaseous 8 effluent, which is a fuel gas, is removed from heater 2 via 9 line 40.
Hot coke is removed from the fluidized bed in 11 heater 2 and recycled to the reactor 1 by line 42 as may be 12 needed to supply heat thereto. Another portion of coke is 13 removed from heater 2 and passed by line 44 to a gasifica-14 tion zone 46 in gasifier 3 in which is maintained a bed of fluidized coke having a level indicated at 48. If desired, 16 a purge stream of coke may be removed from heater 2 by line 17 50.
18 The gasification zone is maintained at a tempera-19 ture ranging from about 1500 to about 2000F., preferably from about 1600 to about 1800F., and a pressure ranging 21 from about 5 to about 150 psig, preferably from about 10 to 22 about 60 psig and more preferably from about 25 to about 45 23 psig. Steam by line 52 and an oxygen-containlng gas such 24 as air, commercial oxygen or air enriched with oxygen by line 54 are passed via line 56 into gasifier 3. Reaction 26 of the coke particles in the gasification zone with the 27 steam and the oxygen-containing gas produces a hydrogen and 28 carbon monoxide-containing fuel gas. The gasifier product 29 fuel gas, which may further contain some entrained solids, is removed overhead from gasifier 3 by line 32 and intro-31 duced into heater 2 as previously described.
32 In general, the temperature to whlch the coking 33 zone will rise depends on the quantity ~therefore on the 34 temperature) of the hot solids being passed into the duct 66 from the gasifier because, aEter heat exchange with the 36 coker vapors, they are separated by the cyclones and, at 37 e.g., about 1350-1400F., fall into the coking zone.
' 1 A smaller quantity of gasifier solids at a rela-2 tively high temperature ~ill deliver the sarne number of 3 BTU's to the coker vapors as a larger amount of solids at a 4 relatively lower tempexature (properly selected); however, the effect on raising the temperature of the coking zone is 6 less in the former instance ~less solids ~alling into the 7 coking zone). Under these circumstanc~ës it may be desirable 8 to pass hot solids from the heater 2 to the coking zone to ~ maintain coking temperature. Conversely, in the latter in-stance, cooling of this zone may be needed (more solids 11 falling into the coking zone). This can be achieved by 12 passing a portion of the steam requirement thereinto in the 13 form of water which ~1ill absorb its heat of vaporization 14 from the fluid bed; and by not passing hot solids from the heater into the coking zone.
16 For example, when the gasi~ier is operated at 17 1770F., the hot coke rate from the gasifier is 1400 lbso/
18 bbl. of fresh feed, ~he coking bed is at 1050F. and the 19 cyclones are at 1350F., the system is exactly in balance and no water injection is needed for the coking bed nor do 21 any solids have to be recycled rom the heater thereto.
22 As shown in Fig. 2, an inlet line 11 for water is 23 provided between oil feed line 10 and stripping steam line 24 16. An inlet line 15 for a purge stream of steam into the sealed off uppermost portion of the coking reactor is also 26 provided. This purge stream is admitted via line 15 under 27 pressure sufficient to permit escape through the openings 28 formed by the baffle unit and the cyclones or vessel walls 29 so that it mixes with the vapors from the fl~id bed.
In one mode of operating the process, 40,000 31 barrels per da~ of fresh feed which is a vacuum residuun 32 is admittecl via line :lO, 255 K lb/hr of water (K=1000) 33 through line 11, 93 I( lb/hr steam through line 16 and an 34 additional 25 K lb/hr steam through line 15. A stream of 26.8 tons per minute of 1710F. coke particles in 50 I~ lb/hr 36 steam is introduced via line 60 above the level 14 of the ~ense fluid~zed bed into the dilute phase in-the duct 66 leadinq .' .
:. - . ~
1 to the cyclone inlet 64. The hydrocarbon partial pressure 2 in the dilute phase at the cyclone inlet is about 12 psia.
3 Under these conditions the coking bed temperature is 975F~
4 and the cyclone temperature is 1350F.
The yield pattern for vacuum residuum will typi-6 cally include at least about 15 weight ~;C2-C4 olefins/di-7 olefins, e.g., about 10% ethylene, about 7% propylene, about 8 4~ C4's and substantial amounts of cs - 430F., 430-650F.
9 and 650-950F. fractions. Aromatics produced in the pro-cess will be found in the C5+ products. Portions of the Cs+
11 products may be recycled to coking or to steam cracking to 12 give increased yields of the C2-C4 olefins/diolefins.
13 rhus the present process combines coking (typi-14 cally ~ith reactor, heater and gasifier units) and steam cracking to produce ethylene from vacuum residuum. An im-16 portant advantage of the cocracking process is the relative-17 ly low cost of residuum compared with that of naphtha and 18 gas oil fed to conventional steam crackers. Residua cannot 19 be used as feed to the latter because of their high coking tendency which would form intolerable amounts of coke in 21 the pyrolysis tubes. Also, the present process uses as 22 fuel only low cost coke produced in the process from vacuum 23 residuum. Thus the inexpensive feed supplies both the feed 24 and the f~el. Furthermore, the investment cost of a co-cracker is 15% less than the total for separate coking and 26 steam cracking units.
27 Although the process has been described for sim-28 plicity of description with respect to circulating coke as 29 the fluidized medium, it is to be understood that the fluid-ized seed particles on which the coke is deposited may be 3:L silica, alumina, zirconia, magnesia, calcium oxide, alunclum, 32 mullite, bauxite or the like. The ~luidized solids may or 33 may not be catalytic in nature.
.
.
.
.
36 Consequently, these patents do not disclose or 37 suggest the concept of carrying out steam cracking on the .
,~
1 vapors produced from a fluid coking zone and do not disclose 2 the conditions which would make cocracking ~easible. Sur-3 prisingly, although the temperatures for carrying out these 4 two reactions are disparate, it has now been found that these reactions can be coordinated and caused to take place in the 6 same vessel.
7 SUMMARY OF THE INVENTION ;
8 According to the present invention a carbonaceous 9 material is coked in a first stage fluid coking zone and the resulting vaporous coker conversion product is passed to a 11 second stage reaction zone where it is heate~ in the pre-12 sence of steam to a temperature adapted to crack the same 13 to products including low molecular ~eight unsaturated 14 hydrocarbons. This is achieved by injecting a stream of hot solids at a sufficiently high temperature and in sufficient 16 amount into the vaporous coker conversion product passing 17 to the gas-solids separation zone. The hot solids may be 18 supplied by a coke gasification zone.
Fig. 1 is a schematic- flow plan of one embodiment 21 of the invention; and 22 Fig. 2 is a more detailed schematic view of a 23 coking reactor. Like parts are designated by the same 24 numbers as in Fig. 1.
DETAILED DESCRIPTION
26 Referring to Fig. 1, a carbonaceous material for 27 example having a Conradson carbon residue of about 25 weight 28 percent such as heavy residuum having a boiling point (at 29 atmospheric pressure) of about 1050F.~ is passed by line 10 to reactor 1 into a coking zone 12 in which is maintained 31 a Eluidized bed of solids ~e.g., coke particles o 20 to 32 1000 microns in size) having an upper level indicated at 33 14 above which there i6 a disperse or dilute phase. Car-34 bonaceous feeds suitable Eor the present invention include heavy hydrocarbonaceous oils; heavy and reduced petroleum 36 crudes; petroleum atmospheric distillation bottoms~
37 petroleum vacuum distillation bottoms; pitch, asphalt, 1 bitumen, other heavy hydrocarbon residues; coal; coal 2 slurry; liquid products derived from coal liquefaction pro-3 cesses and mixtures thereof. Typically such feeds have a 4 Conradso~ carbon residue of at least 15 weight percent, generally from about 15 to about 50 weight percent (as to 6 Conradson carbon residue, see ASTM test D-189-65). Reactor 7 1 may be lined internally with a refrac~ory insulating 8 material, not shown. A fluidizing gas, e.g., steam, is ad-9 mitted at the base of coking reactor 1 through line 16 in an amount sufficient to obtain superficial fluidizing gas 11 velocity in the range of 0.5 to 5 feet per second. If a 12 fluidizing gas other than steam is used, steam is addition-13 ally present. Ccke from the heater 2 which ~ay be maintained 14 at a temperature in the range of about 1050 to 1300F., preferably in the range of 1050 to 1150F., is admitted to 16 reactor 1 by line 42 when required to maintain the coking 17 temperature. The coking temperature is in the range of 18 about 950 to about 1150F., preferably about 950 to about 19 1100F., more preferably about 950 to about 1050F. The pressure in the coking zone is maintained in the range from 21 about 5 to about 150, preferably about S to about 45 psig.
22 The lower portion of the coking reactor serves as a strip-23 ping zone to remove occluded hydrocarbons from the coke. A
24 stream of coke is withdrawn from the stripping zone by line 18 and circulated to heater 2. ~ gas~solids separation zone 26 such as cyclones 20 serves to remove entrained solids from 27 vaporous products. The cyclone separator system may be one 28 or more cyclones. A baffle 62 ~refer to Fig. 2) extends 29 from the sides of the reactor 1 above the fluid bed and terminates in a relatively small diameter top which defines 31 a r~stricted vapor passageway or duct 66 for the vapors from 32 the fluid bed to the inlet 64 of the cyclones. Steam crack-3:3 ing takes place in the duct 66 and in the cyclones. The 34 temperature in the steam cracking zone is maintained in the range oE 1200 to 1700F., preferably about 1300 to about 36 1500F., to convert at least a portion of the coking zone 37 conversion product, preferably at least 15% thereof, to . ~ :
:
1 lower olefins and diolefins. This is accomplished by intro-2 ducing a sufficient amount of a stream of hot solids, with-3 drawn from the gasifier 2 by line 58 and then injected by 4 line 60 above the dense fluid bed, into the dilute phase in the duct 66 leading to the inlet of the cyclones. The 6 zone between the outlet of the hot solids feed line 60 and7 the cyclone inlet should be as short a!s possible to keep 8 residence time low (for good selectivity to C2-C4 olefins) 9 but long enough to ensure good mixing and heat transfer between the coke and the gas. Gas residence time in this 11 zone will ~ypically be 0.02 to 0.3 seconds, preferably 0.05 12 to 0.2 seconds. The amount of solids is in the range of 13 about 1200 to 3200 lbs. preferably about 1800 to 2600 lbs.
14 per barrel of fresh feed and they are at a temperature in the range of 1500 to 2000F., preferably 1600 to 1800F.
16 Residence time o~ the coker vapors at steam cracking condi-17 tions, i.e., from the point o~ injection of the coke to the 18 outlet of the cyclone is approximately one second or less, 19 e.g., 0.3 to 0.8 seconds. The resulting vapor/coke product mixture i5 separated in the cyclones, the coke passing down 21 into the coker bed via the diplegs 22. The resulting 22 cracked vapors leave the cyclones through line 24. Line 24 23 passes through a wall 21 separating the reactor from the 24 scrubber 25 as shown in Fig. 2. The vapors leaving line 24 are quenched in the scrubber to about 600-900F. by liquid 26 products from product fractionation. If desired, a stream 27 of heavy material, viz., 950F~ products, condensed in the 28 scrubber rnay be recycled to the coking reactor via line 26.
29 Furthermore, if desired, a portion of the carbonaceous feed may be injected into the scrubber to provide an adequate 31 volume to carry eoke fines back to the coking zone. The 32 eyclone conversion products are removed from scrubber 25 33 via line 28 for Eractionation in a conventional manner.
34 In heater 2, stripped coke rom coking reactor 1 (common].y ealled cold coke) is introduced by line 18 to a fluid bed 36 of hot coke having an upper level indicated at 30. The bed 37 is partially heated by passing a fuel gas into the heater .; .
:. , 1 by line 32. Supplementary heat is applied to the heater by 2 coke circulating in line 34. The gaseous effluent of the 3 heater, including entrained solids, passes through a cyclone 4 which may be a first cyclone 36 and a second cyclone 38 wherein separation of the larger entrained solids occurs.
6 The separated larger solids are returned to the heater bed 7 via the respective cyclone diplegs. T~lë heater gaseous 8 effluent, which is a fuel gas, is removed from heater 2 via 9 line 40.
Hot coke is removed from the fluidized bed in 11 heater 2 and recycled to the reactor 1 by line 42 as may be 12 needed to supply heat thereto. Another portion of coke is 13 removed from heater 2 and passed by line 44 to a gasifica-14 tion zone 46 in gasifier 3 in which is maintained a bed of fluidized coke having a level indicated at 48. If desired, 16 a purge stream of coke may be removed from heater 2 by line 17 50.
18 The gasification zone is maintained at a tempera-19 ture ranging from about 1500 to about 2000F., preferably from about 1600 to about 1800F., and a pressure ranging 21 from about 5 to about 150 psig, preferably from about 10 to 22 about 60 psig and more preferably from about 25 to about 45 23 psig. Steam by line 52 and an oxygen-containlng gas such 24 as air, commercial oxygen or air enriched with oxygen by line 54 are passed via line 56 into gasifier 3. Reaction 26 of the coke particles in the gasification zone with the 27 steam and the oxygen-containing gas produces a hydrogen and 28 carbon monoxide-containing fuel gas. The gasifier product 29 fuel gas, which may further contain some entrained solids, is removed overhead from gasifier 3 by line 32 and intro-31 duced into heater 2 as previously described.
32 In general, the temperature to whlch the coking 33 zone will rise depends on the quantity ~therefore on the 34 temperature) of the hot solids being passed into the duct 66 from the gasifier because, aEter heat exchange with the 36 coker vapors, they are separated by the cyclones and, at 37 e.g., about 1350-1400F., fall into the coking zone.
' 1 A smaller quantity of gasifier solids at a rela-2 tively high temperature ~ill deliver the sarne number of 3 BTU's to the coker vapors as a larger amount of solids at a 4 relatively lower tempexature (properly selected); however, the effect on raising the temperature of the coking zone is 6 less in the former instance ~less solids ~alling into the 7 coking zone). Under these circumstanc~ës it may be desirable 8 to pass hot solids from the heater 2 to the coking zone to ~ maintain coking temperature. Conversely, in the latter in-stance, cooling of this zone may be needed (more solids 11 falling into the coking zone). This can be achieved by 12 passing a portion of the steam requirement thereinto in the 13 form of water which ~1ill absorb its heat of vaporization 14 from the fluid bed; and by not passing hot solids from the heater into the coking zone.
16 For example, when the gasi~ier is operated at 17 1770F., the hot coke rate from the gasifier is 1400 lbso/
18 bbl. of fresh feed, ~he coking bed is at 1050F. and the 19 cyclones are at 1350F., the system is exactly in balance and no water injection is needed for the coking bed nor do 21 any solids have to be recycled rom the heater thereto.
22 As shown in Fig. 2, an inlet line 11 for water is 23 provided between oil feed line 10 and stripping steam line 24 16. An inlet line 15 for a purge stream of steam into the sealed off uppermost portion of the coking reactor is also 26 provided. This purge stream is admitted via line 15 under 27 pressure sufficient to permit escape through the openings 28 formed by the baffle unit and the cyclones or vessel walls 29 so that it mixes with the vapors from the fl~id bed.
In one mode of operating the process, 40,000 31 barrels per da~ of fresh feed which is a vacuum residuun 32 is admittecl via line :lO, 255 K lb/hr of water (K=1000) 33 through line 11, 93 I( lb/hr steam through line 16 and an 34 additional 25 K lb/hr steam through line 15. A stream of 26.8 tons per minute of 1710F. coke particles in 50 I~ lb/hr 36 steam is introduced via line 60 above the level 14 of the ~ense fluid~zed bed into the dilute phase in-the duct 66 leadinq .' .
:. - . ~
1 to the cyclone inlet 64. The hydrocarbon partial pressure 2 in the dilute phase at the cyclone inlet is about 12 psia.
3 Under these conditions the coking bed temperature is 975F~
4 and the cyclone temperature is 1350F.
The yield pattern for vacuum residuum will typi-6 cally include at least about 15 weight ~;C2-C4 olefins/di-7 olefins, e.g., about 10% ethylene, about 7% propylene, about 8 4~ C4's and substantial amounts of cs - 430F., 430-650F.
9 and 650-950F. fractions. Aromatics produced in the pro-cess will be found in the C5+ products. Portions of the Cs+
11 products may be recycled to coking or to steam cracking to 12 give increased yields of the C2-C4 olefins/diolefins.
13 rhus the present process combines coking (typi-14 cally ~ith reactor, heater and gasifier units) and steam cracking to produce ethylene from vacuum residuum. An im-16 portant advantage of the cocracking process is the relative-17 ly low cost of residuum compared with that of naphtha and 18 gas oil fed to conventional steam crackers. Residua cannot 19 be used as feed to the latter because of their high coking tendency which would form intolerable amounts of coke in 21 the pyrolysis tubes. Also, the present process uses as 22 fuel only low cost coke produced in the process from vacuum 23 residuum. Thus the inexpensive feed supplies both the feed 24 and the f~el. Furthermore, the investment cost of a co-cracker is 15% less than the total for separate coking and 26 steam cracking units.
27 Although the process has been described for sim-28 plicity of description with respect to circulating coke as 29 the fluidized medium, it is to be understood that the fluid-ized seed particles on which the coke is deposited may be 3:L silica, alumina, zirconia, magnesia, calcium oxide, alunclum, 32 mullite, bauxite or the like. The ~luidized solids may or 33 may not be catalytic in nature.
.
.
.
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Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An integrated, two stage coking and steam cracking process for the production of low molecular weight unsaturated hydrocarbons which comprises:
(a) reacting a carbonaceous material in a first stage coking zone containing a bed of fluidized solids wherein steam is present maintained at fluid coking condi-tions including a temperature in the range of about 950°F.
to about 1150°F. to form a vaporous coking zone conversion product and coke, said coke depositing on said fluidized solids;
(b) passing said vaporous coking zone conversion product with entrained solids to a second stage reaction zone; and (c) introducing hot solids at a sufficient tempera-ture and in sufficient amount into said conversion product entering said second stage reaction zone to raise the con-version product to steam cracking temperatures within the range of 1200° to 1700°F. and supply the endothermic heat of reaction.
(a) reacting a carbonaceous material in a first stage coking zone containing a bed of fluidized solids wherein steam is present maintained at fluid coking condi-tions including a temperature in the range of about 950°F.
to about 1150°F. to form a vaporous coking zone conversion product and coke, said coke depositing on said fluidized solids;
(b) passing said vaporous coking zone conversion product with entrained solids to a second stage reaction zone; and (c) introducing hot solids at a sufficient tempera-ture and in sufficient amount into said conversion product entering said second stage reaction zone to raise the con-version product to steam cracking temperatures within the range of 1200° to 1700°F. and supply the endothermic heat of reaction.
2. The process according to claim 1 in which the hot solids are introduced into a duct above the coking zone leading to a gas-solids separation zone.
3. The process according to claim 1 in which about 1800 to 3200 lbs. solids at a temperature in the range of 1500° to 2000°F. are introduced per barrel of fresh feed.
4. The process according to claim 3 in which the temperature of the solids is in the range of 1600° to 1800°F.
5. The process according to claim 3 in which about 1800 to 2600 lbs. solids are introduced per barrel of fresh feed.
6. The process according to claim 1 in which the coking zone conversion product is steam cracked at temperatures within the range of about 1300 to 1500°F.
7. The process according to claim 1 in which the temperature in the coking zone is in the range of about 950° to about 1050°F.
8. The process according to claims 1, 2 or 3 in which the carbonaceous material is a vacuum residuum.
9. An integrated, two stage coking and steam cracking process for the production of low molecular weight unsaturated hydrocarbons which comprises:
(a) reacting a carbonaceous material in a first stage coking zone containing a bed of fluidized solids wherein steam is present maintained at fluid coking condi-tions including a temperature in the range of about 950°
to about 1100°F. to form a vaporous coking zone conversion product and coke, said coke depositing on said fluidized solids;
(b) introducing a portion of said solids with the coke deposition thereon into a heating zone maintained at a temperature of from about 1050° to about 1150°F.;
(c) introducing a portion of solids from said heating zone to a fluid bed gasification zone maintained at a temperature in the range of about 1600° to about 1800°F.;
(d) passing said vaporous coking zone conversion product with entrained solids to a second stage reaction zone;
(e) withdrawing a portion of hot solids from the gasification zone;
(f) introducing about 1800 to 3200 lbs. of said hot solids, per barrel of fresh feed, into said conversion product entering said second stage reaction zone to raise said conversion product to steam cracking temperatures within the range of about 1300° to 1500°F. thereby to con-vert at least 15 weight percent thereof to C2-C4 olefins and diolefins, (g) separating solids from gas in the second stage reaction zone and sending separated solids to the coking zone and quenching separated gas, and (h) maintaining the coking zone temperature by cooling the coking zone.
(a) reacting a carbonaceous material in a first stage coking zone containing a bed of fluidized solids wherein steam is present maintained at fluid coking condi-tions including a temperature in the range of about 950°
to about 1100°F. to form a vaporous coking zone conversion product and coke, said coke depositing on said fluidized solids;
(b) introducing a portion of said solids with the coke deposition thereon into a heating zone maintained at a temperature of from about 1050° to about 1150°F.;
(c) introducing a portion of solids from said heating zone to a fluid bed gasification zone maintained at a temperature in the range of about 1600° to about 1800°F.;
(d) passing said vaporous coking zone conversion product with entrained solids to a second stage reaction zone;
(e) withdrawing a portion of hot solids from the gasification zone;
(f) introducing about 1800 to 3200 lbs. of said hot solids, per barrel of fresh feed, into said conversion product entering said second stage reaction zone to raise said conversion product to steam cracking temperatures within the range of about 1300° to 1500°F. thereby to con-vert at least 15 weight percent thereof to C2-C4 olefins and diolefins, (g) separating solids from gas in the second stage reaction zone and sending separated solids to the coking zone and quenching separated gas, and (h) maintaining the coking zone temperature by cooling the coking zone.
10. An integrated, two stage coking and steam cracking process for the production of low molecular weight unsaturated hydrocarbons which comprises:
(a) reacting a carbonaceous feed in a first stage coking zone containing a bed of fluidized solids wherein sufficient steam is present to provide 20-80 mol % for the second stage steam cracking reaction and which is maintained at fluid coking conditions including a temperature in the range of about 950° to about 1050°F. to form a vaporous coking zone conversion product and coke, said coke deposit-ing on said fluidized solids;
(b) introducing a portion of said solids with the coke deposition thereon into a heating zone maintained at a temperature of from about 1050° to about 1150°F.;
(c) introducing a portion of solids from said heating zone to a fluid bed gasification zone maintained at a temperature in the range of about 1600° to about 1800°F.;
(d) passing said vaporous coking zone conversion product with entrained solids into a duct above the coking zone leading to a gas-solids separation zone, said duct and said separation zone being a second stage steam crack-ing reaction zone;
(e) withdrawing a portion of hot solids at about 1600° to about 1800°F. from the gasification zone;
(f) introducing about 1800 to 3200 lbs. of said hot solids, per barrel of fresh feed, into said duct in con-tact with said conversion product to raise said conversion product to steam cracking temperatures within the range of about 1300° to 1500°F. with a residence time at such conditions of about one second or less, (g) separating solids from gas in the gas-solids separation zone and sending separated solids to the coking zone and quenching separated gas; and (h) maintaining the coking zone temperature by introducing part of the steam as water.
(a) reacting a carbonaceous feed in a first stage coking zone containing a bed of fluidized solids wherein sufficient steam is present to provide 20-80 mol % for the second stage steam cracking reaction and which is maintained at fluid coking conditions including a temperature in the range of about 950° to about 1050°F. to form a vaporous coking zone conversion product and coke, said coke deposit-ing on said fluidized solids;
(b) introducing a portion of said solids with the coke deposition thereon into a heating zone maintained at a temperature of from about 1050° to about 1150°F.;
(c) introducing a portion of solids from said heating zone to a fluid bed gasification zone maintained at a temperature in the range of about 1600° to about 1800°F.;
(d) passing said vaporous coking zone conversion product with entrained solids into a duct above the coking zone leading to a gas-solids separation zone, said duct and said separation zone being a second stage steam crack-ing reaction zone;
(e) withdrawing a portion of hot solids at about 1600° to about 1800°F. from the gasification zone;
(f) introducing about 1800 to 3200 lbs. of said hot solids, per barrel of fresh feed, into said duct in con-tact with said conversion product to raise said conversion product to steam cracking temperatures within the range of about 1300° to 1500°F. with a residence time at such conditions of about one second or less, (g) separating solids from gas in the gas-solids separation zone and sending separated solids to the coking zone and quenching separated gas; and (h) maintaining the coking zone temperature by introducing part of the steam as water.
11. The process according to claim 1, 9 or 10 in which at least a portion of C5+ products recovered is recycled either to the coking zone or to the second stage reaction zone.
12. An integrated, two stage coking and steam cracking process for the production of low molecular weight unsaturated hydrocarbons which comprises:
(a) reacting a carbonaceous feed in a first stage coking zone in a reactor containing a bed of fluidized solids wherein steam is provided and which is maintained at fluid coking conditions including a temperature in the range of about 950° to about 1050°F. to form a vaporous coking zone conversion product and coke, said coke depositing on said fluidized solids;
(b) introducing a portion of said solids with the coke deposition thereon into a heating zone maintained at a temperature of from about 1050° to about 1150°F.;
(c) introducing a portion of solids from said heating zone to a fluid bed gasification zone maintained at a temper-ature in the range of about 1600° to about 1800°.F.;
(d) passing said vaporous coking zone conversion product with entrained solids into a duct above the coking zone leading to a gas-solids separation zone, said duct and said separation zone being a second stage steam cracking reaction zone and said duct being formed by a baffle to have a path short enough to achieve a low residence time therein of 0,02 to 0.3 seconds, said baffle extending from the sides of the reactor and terminating in a relatively small diameter top defining said duct for passage of the vaporous coking zone conversion product to the inlet of the separation zone;
(e) withdrawing a portion of hot solids at about 1600° to about 1800°F. from the gasification zone;
(f) introducing about 1800 to 3200 lbs. of said hot solids, per barrel of fresh feed, into said duct in contact with said conversion product to raise said conversion product to steam cracking temperatures within the range of about 1300° to 1500°F. thereby to convert at least 15 weight percent thereof to C2-C4 olefins and diolefins;
(g) separating solids from gas in the gas-solids separation zone and sending separated solids to the coking zone and quenching separated gas; and (h) maintaining the coking zone temperature by introducing part of the steam as water.
(a) reacting a carbonaceous feed in a first stage coking zone in a reactor containing a bed of fluidized solids wherein steam is provided and which is maintained at fluid coking conditions including a temperature in the range of about 950° to about 1050°F. to form a vaporous coking zone conversion product and coke, said coke depositing on said fluidized solids;
(b) introducing a portion of said solids with the coke deposition thereon into a heating zone maintained at a temperature of from about 1050° to about 1150°F.;
(c) introducing a portion of solids from said heating zone to a fluid bed gasification zone maintained at a temper-ature in the range of about 1600° to about 1800°.F.;
(d) passing said vaporous coking zone conversion product with entrained solids into a duct above the coking zone leading to a gas-solids separation zone, said duct and said separation zone being a second stage steam cracking reaction zone and said duct being formed by a baffle to have a path short enough to achieve a low residence time therein of 0,02 to 0.3 seconds, said baffle extending from the sides of the reactor and terminating in a relatively small diameter top defining said duct for passage of the vaporous coking zone conversion product to the inlet of the separation zone;
(e) withdrawing a portion of hot solids at about 1600° to about 1800°F. from the gasification zone;
(f) introducing about 1800 to 3200 lbs. of said hot solids, per barrel of fresh feed, into said duct in contact with said conversion product to raise said conversion product to steam cracking temperatures within the range of about 1300° to 1500°F. thereby to convert at least 15 weight percent thereof to C2-C4 olefins and diolefins;
(g) separating solids from gas in the gas-solids separation zone and sending separated solids to the coking zone and quenching separated gas; and (h) maintaining the coking zone temperature by introducing part of the steam as water.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US17236880A | 1980-07-25 | 1980-07-25 | |
| US172,368 | 1980-07-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1126189A true CA1126189A (en) | 1982-06-22 |
Family
ID=22627428
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA360,803A Expired CA1126189A (en) | 1980-07-25 | 1980-09-23 | Integrated two stage coking and steam cracking process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1126189A (en) |
-
1980
- 1980-09-23 CA CA360,803A patent/CA1126189A/en not_active Expired
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