March 7, 1967 J. F. G. ELLIS 3,308,060

March 7, 1967 J. F. G. ELLIS PETROLEUM DISTILLATION Filed Jan. 28, 1965 NVENTOR. JOHN FRANCIS GRIFFITH ELLS BY MORGAN, FINNEGAN, DURHAM 8, PINE ATTORNEYs

United States Patent Office Patented Mar. 7, 1967 1. PETROLEUM DISTILLATION John Francis Griffith Ellis, Ashford, Middlesex, England, assignor to The British Petroleum Company Limited, 5 London, England Filed Jan. 28, 1965, Ser. No. 428,821. Claims priority, application Great Britain, Feb. 21, 1964, 7,320/64 1 Claim. (C. 208-364) 10 This invention relates to the distillation of petroleum and particularly to the maximum separation of gas oil fractions, i.e. fractions boiling within the range 220-400 C. on a TBP curve, from crude oils. In a conventional crude oil distillation column operat- 5 ing at a pressure of approximately three atmospheres, four side streams are commonly withdrawn, viz. naphtha, kerosine, light gas oil and heavy gas oil. Atmospheric residue is withdrawn from the column base, and a totally condensed overhead distillate from the column head. 20 The maximum yield of straight-run gas oil of a given pour point obtainable from a conventional crude oil distill lation column is limited by the degree of fractionation at the gas oil back end cut point. Thus, improved fractiona tion would increase the gas oil yield..... 25 The internal reflux in a conventional distillation colu has its maximum value at the top of the column and de creases to almost nothing immediately above the flash zone of the column. Both the light and heavy gas oil frac tions are drawn from a zone in the column in which the 30 reflux flow is insufficient to provide the maximum theoreti cally possible yield of gas oil of a given quality. Additional reflux flow above the flash zone can be pro vided by "overflash," i.e. flashing the crude oil to a higher cut point than that demanded by the product require- 35 ments. A flow of liquid is then provided over the trays 2 immediately above the flash zone. The amount of addi tional reflux which can be obtained in this way is, how ever, limited and insufficient to effect maximum gas oil separation. According to the present invention, in a crude oil dis tillation process conducted in a conventional atmospheric column, the heavy gas oil side stream fraction is combined with at least a portion of the atmospheric residue, the combined fraction being refractionated to give an addi tional gas oil product. The term heavy gas oil, in this specification, means the distillate fraction which boils above 300 C. Preferably the heavy gas oil is combined with the front 10-40% weight portion of the atmospheric residue, which is preferably obtained by vacuum flashing the atmospheric residue to give a 10-40% weight overhead portion. This portion is subsequently combined with the heavy at mospheric gas oil, and the mixture fractionated under vacuum in a reboiled column. This method has the ad vantage that close control can be maintained over the frac tionation conditions. Alternatively the whole of the atmospheric residue may be combined with the heavy gas oil before vacuum flash ing the mixture in a tower containing fractionating trays, under flash conditions arranged to give the required reflux in the fractionation section. This method is not so closely controllable however, but may be suitable where mini mum plant alteration is essential. The invention is illustrated by the following example: Example 1 A crude oil of Middle East origin, when fractionated in a conventional atmospheric distillation unit at the rate of 55,800 b.p.s.d., resulted in a material balance over the unit as indicated in Table 1. TABLE 1. Stream TBP range, Sp. gr. at Percent wit, Lb.fhr. o C 60 F on crude Overhead distillate----- to 148 0.700 16.86 17,066 Naphthal- - 48-168 0.775 3, 42 23,746 Kerosine. 68-223 0,796 9.50 64,962 Light gas oil--- - 223-308, 5 0.836 15.84 109,984 Heavy gas oil---------- 308. 5-347 0.870 6.63 46,035 Atmospheric residue--- >347 0.948 47.75 331, 549 Crude charge-------------------------- 0.858 ---------------- 694,342 The product properties from this operation are given in the following Table 2: - TABLE 2 Test Crude Overhead Naphtha Kerosine Light gas Heavy gas Atmospheric feed distillate oil oil residue Sp. gr. at 60 F--------------------------------- 0.853 0.700 0.775 0.796 0.836 0.870 0.948 ASTM distillation, C.: IBP-------------------------------------------------------------------- 143 80 223 305 - ----- - - - - - - - - - - -a- 48 185 238 316 -- - --- - - - - - - - - - - 49 187 244 320 15 189 249 324 152 9i 255 328 154 193 259 331 55 96 265 334 157 98 270 338 - - - - - - - - - - - - - - - -- a--- 158 201 277 342 - - - - - - - - - a - - - - a - - 160 205 285 348 163 20 297 356 66 214 306 366 177 220 319 374 Total distillate, p 99 99 99 99 Residue--------------- 1.

3 4. TABLE 2 -Continued Test Crude Overhead Naphtha Kerosine Light gas Beavy gas Atmospheric feed distillate oil oil residue H2S, percent wt.---------------------------------------------- 0.019 Negative -------------------------------------------------------- Mercaptain Sulphur, percent wt.------------------------------- 0.0475 0.0187 -------------------------------------------------------- Total sulphur, percent wt.----- 1.38 0.062 0.104 0.155 0.65-1.34 2.41.12.48 Reid vapour pressure, p.s.i----------------------------------- 18.9 -------------------------------------------------------------- -- Flash point, F- - - Saybolt colour Aniline point, C----------------------------------------------------- Kin. Viso. at 70F., cs----------------------------------------------------- Kin. visc. at i00 F., cs.------ Kin. visc. at 122 F., cs----- Dieselindex.--------... - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - w - - - - as a - an a w - w - - - - - - - - - - - -n m - - - kin. visc. at 210 F, cs.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.i.--------------...- 33.5 In order to determine the maximum gas oil that could The experiment demonstrates that the yield of gas oil be recovered from the crude oil charge the following ex- boiling above a crude oil TBP cut point of 223 may be periment was performed in the laboratory. increased from 22.47% wt. on crude to 26.72% wt. on Heavy atmospheric gas oil was combined with at- 20 crude; the pour point of the total gas oil remains con mospheric residue in the proportions which they were stant at 15 F., while the specific gravity (measured at drawn from the crude unit. The resulting composite was 60 F.) increases from 0.8462 to 0.8520. At the same put in a 14 plate batch distillation column operating at time the cloud point decreases from 22 F. to 18 F., 2:1 external reflux with a column head pressure of 50 mm. 25 while the diesel index decreases from 58 to 55. Thus an Hg absolute. The distillation was continued until a 20% improvement in both specific gravity and cloud point is wt. (on feed) distillate was obtained. Inspection data on obtained, and although the diesel index decreases slightly the feeds and products are given in Table 3. the decrease is acceptably small. TABLE 3 Test Atmospheric Atmospheric 20% wt. 80% wt. heavy gas oil residue distillate residue Sp. gr. at 60 F----------------------------- 0.8766 Colour (ASTM).--------- 1 C 1.0 Total sulphur, percent wt. 1,12 Kin. visc. at 22 F., cs--- 4.76 Cloud point, F--------- 40 Pour point, F---------- 35 Aniline point, C-- 72.3 Diesel index-------------------------------- 48/49 Distillation (ASTM), C.: IBP----------------------------------- 260.0 ---------------- 2% recovery------------ 27.5 ---------------- 5%--------- 285.5---------------- 10%- 294, 5 ---------------- 20%---------------------- 806.5 ---------------- 30%- 812.5 ---------------- 40%-------------------- 318.0 ---------------- 50%-------------------- 822.0 ---------------- 60%-------------------- 327.0 ---------------- 70%-- 380.5!---------------- 80%- 884.0 ---------------- 90%-- 838.0 ---------------- FBP------------------- 343.0 ---------------- Total distillate, percent vol- 99.0 ---------------- Residue-------------------- 10 ---------------- Loss----------------------------------------------------------------------- Nil ---------------- Bad match. Relevant data on the effect of (i) incorporating the Example 2 whole of the distillate product into the gas oil pool (i.e. The invention has been further demonstrated on exist light gas oil plus vacuum distillate) (ii) incorporating the 55 ing refinery equipment. whole of the heavy atmospheric gas oil into the gas oil A crude oil of Middle East origin when fractionated in pool (i.e. light gas oil plus atmospheric heavy gas oil) are a conventional atmospheric distillation unit, consisting of summarised in Table 4. a primary distillation column and a secondary distillation TABLE 4 Test Atmospherie Atmospheric Vacuum gas Blend of Blend of light gas oil heavy gas oil oil HGO--LGO VGO--LGO Percent wt. On crude-------------------------- 15.84 6.63 0.88 22.47 26.72 Sp. gr. at 60' E.--- 0.8709 0.8776 0.8462 0.8520 Colour (ASTM).-------- 1 L 1.5 1 CO L 1.0 1 L 1.0 Total sulphur, percent w 1.32 1, 12 0.86 0.99, 70 F. c.s. 6.19 100 F., cs 2.90 8.38 6.60 3.84 3.92 Cloisi 2.8. 2 4 3 2 93-------------- Pour point, F ------------ 45 35 15 f2. d 71.2 79.0 72.3 72.9 71.0 59/60 54 48/49 58 55 Bad match.

5 column, at a rate of 82,000 b.p.s.d., resulted in a material balance over the unit as indicated in Table 5. A further two experiments were carried out in which the heavy gas oil stream was shut in and the yield of atmospheric residue increased by the amount that the heavy gas oil was decreased. In both these experiments the crude oil was processed at 82,000 b.p.s.d. and the temperature and pressure at the inlet to the secondary column were maintained constant, and at the same values as were observed for the first experiment. During these latter two experiments a portion of the atmospheric residue was passed to an adjacent vacuum distillation unit operat ing at 21,550 b.s.p.d. and the material balances resulting from the operation of the atmospheric and vacuum distill lation units in the above described manner are indicated in Tables 6 and 7. The product properties resulting from these three ex periments are given in Tables 8, 9 and 10. Relevant data on the effect of (i) incorporating the whole of the heavy atmospheric gas oil into the gas oil pool (i.e. light gas oil plus heavy gas oil) (ii) incorporat 0 5 6. ing the whole of the vacuum gas oil into the gas oil pool (i.e. light gas oil plus vacuum gas oil) are summarised in Table 11. The experiments demonstrate that improved fractiona tion enhances both gas oil yield and gas oil quality, viz: (a) Experiment 3 shows that for constant diesel index the yield of gas oil boiling above a crude oil TBP cut point of 235/236 C. is increased from 21.51% wt. on crude (experiment 1) to 23.09% wt. on crude, i.e. an increase of 7.35% wt. on product; at the same time the pour point is reduced from 25 F. to 20 F., whilst the cloud point also shows a significant reduction from 32 F. to 20 F. (b) Experiment 2 shows that for substantially constant diesel index and cloud point the yield of gas oil boiling above a crude oil TBP cut point of 235/236 C. is in creased from 21.51% wt. on crude (experiment 1) to 26.38% wt. on crude, i.e. an increase of 22.7% wt. on 20 product; although the pour point is adversely raised from 25 F. to 30 F. TABLE 5-MATERIAL BALANCE Stream SG 60/60 F. Percent wt. Lb./hr. IGPH Percent vol. TBP range on crude, C. Crude oil feed----------------- 0.8536 100.00 1,019,720 119,461 100.00---------------- Gas and PFD-------------------- ------------ 3.69 37,628 i 5, 663 4.74 To 35 0.7285 13.30 135,623 18, 6.17 15.58 35-143 0.7737 4.60 46,907 6,063 5.08 143-170 - 0.8031 11.74 119,715 14,907 12.48 170-236 Light gas oil----- - 0.8397 14.48 147, 655 17,584 4.72 236-318 Heavy gas oil-------- 0.871 7,03 71,686 8,229 6.89 318-357.5 Atmospheric residue---------- 0.955 45.6 460, 506 48,398 40.51 >357.5 Total.----------------------------------- 100.00 1,019,720 119, 461 100.00 ---------------- 1 Calculated by difference, TABLE 6.-MATERIAL BALANCE Stream SG 6060 F. Percent wt. Lb./hr. IGPE Percent vol. TBP range on crude, C. Crude oil feed----------------- 0.8536 100.00 1,022,236 119,826 100.00 ---------------- Gas and PFD------------- - - - - - -n - - - - - - - - - - - 4.28 43,752 16,624 5.53 To 46 SRB----------- 0.7288 12.4 126,859 17,407 4.53 46-140 Naphtha. - 0.7732 5.26 53,770 6,954 5.80 40-170 Kerosine.---- - 0.8000 1.28 15, 308 14,414 12.03 170-235 Light gas oil- 0.8403 6.28 166,420 19,805 16.53 235-328.5 Heavy gas oil--------------------------------- Nill-------------------------------- Nil ---------------- Atmospheric residue---------- 0.94.49 50.49 516, 127 54,622 45.58 328.5 Total.----------------------------------- 0000 1,022,236 119,826 100.00 ---------------- Atmospheric residue feed.---- 0.94.49 100.00 296,570 31,386 00.00 >328.5 Vacuum gas oil--------------- 0.8831 20.00 59,314 6,716 21.40 328.5-392.5 Waxy distillate--- - 0,994 41.30 122,483 13,322 42.45 392.5-543 Wacuum residue. -.012 38.70 114,773 11,340 36.13 >543 Total.----------------------------------- 100.00 296,570 31,378 99.98 ---------------- 1 Calculated by difference. TABLE 7-MATERIAL BALANCE Stream SG 60/60 F. Percent wt. Lb./hr. IGP Percent vol. TBP range on crude, C. Crude oil feed--- - - - - 0.8536 0000 1,024,850 120,132 100.00 ---------------- Gas and PFD-------------------------------- 4.10 42,019 1 6,505 5.4 To 42.5 SRB------- 0.7275 2.56 128,721 17,694 14.73 42.5-139 Naphtha- 0.7750 4.81 49,295 6,361 5.30 39-167 Kerosine--- 0.8037 2.01 123,084 15, 315 12.75 167236 Light gas oil- - - - 0.8373 14.70 150, 653 17,993 14.98 236-320 Heavy gas oil------- - - - - - - - - - - - - - -- - - - - Ni-------------------------------- Nill---------------- Atmospheric residue---------- 0.9439 51.82 531,078 56,264 46.83 >320 Total.----------------------------------- 100.00 1,024,850 120,132 100.00 ---------------- Atmospheric residue feed--- 0.9439 100.00 297,390 31,507 100.00 >320 Vacuum gas oil--------------- 0.8772 6.20 48,177 5,492 17.43 320-372.5 Waxy distillate--- 0.9151. 45.70 135,907 14,852 47.14 372.5-543 Vacuum residue--------------- 1.0090 38.0 113,306 11,230 35.64 >543 Total.----------------------------------- 100.00 297,390 31,574 100.21---------------- 1 Calculated by difference.

TABLE 8-INSPECTION DATA, ON PRODUCTS Sample Agha, Jari SRB Naphtha, Kerosine Light Heavy Atm. crude oil gas oil gas oil residue Specific gravity 60/60--------------------------- 0.8536 0.72S5 0.7737 0.8031 0,8397 0.8711 10.955 Specific gravity 14060-------------------------------------------------------------------------------------------------------------- 0.9237 Distillation test, C.: 72 43 179 219 155 281 77 46 187.5 234 222 309 80.5 147.5 190.5 242 285 330.5 83 149 93 250 307 358.5 87.5 50.5 95.5 258.5 325.5 397.0 92.5 52.5 201 265 335 434 97 54.5 204.5 270.5 343 458 102.5 56.5 208 276 348.5 496.5 108.5 158 212.5 282.5 354 538 14 160 219 289.5 359.5 575.5 21 163 226 298 366 -------------- 29 173.5 228 308.5 373.5 146 180.5 275 325.5 397.5 Recovery, percent------------------------------------------- 99.5 98.5 98.5 99 98 Residue, percent--------------------------------------------- LOSS, percent------------ Total sulphur, percent wt Aniline point, C------- Diesel index.------ Cloud point, F------ Pour point (upper), F--------- Carbon residue (Con), percent w 100 F., cs------------------------------------------------ 122 F., cs. 140 F., cs. F. F ESF: I Calculated from value at 140 F. TABLE 9.--INSPECTION DATA, ON PRODUCTS Sample Agha Jari SRB Naphtha Kerosine Light Atm. Vacuum Waxy Wacuum crude oil gas oil residue gas oil distillate residue Specific gravity 6969.------------------- 0.8536 0.7288 0.7732 0.8000 0.8403 0.94.49 0,883 0, 91.94 10121 Specific gravity 14060--------------------------------------------------------------------------- 0.917 ------------ 0.894 0.9847 Distillation test, C.: 75 140 213.5 297.5 273.5 ------------------------ 78 142 233 332 289.5 81 143 241 368 307.5 84 144 249.5 393.5 318.5 89 146 259 422 326.5 94 148 265.5 446.5 334.5 98 150 27 472 342 102 152 277 496 349.5 107 154 542 357 ------------------------ 112 156 - - - - - - - - - - - - - - - - - - - - - -... 120 159 - - - - - - - - - - - - 130 63 154 182 Recovery, percent- 98.5 98.5 Residue, percent 0.5 0.6 LOSS, percent.-- Recovered at 40 y Total sulphur, percent wit Aniline point, C Diesel index.--- Cloud point, F--- Pour point (upper), Carbon Residue (Con), 100 E., cs. A. 122 F., cs---------------------------------------- 140 F., cs 2.20 71.4 ------------ 59/60 ------------ 1 Calculated from value at 140 F.

9 10 TABLE 10.-INSPECTION DATA, ON PRODUCTS Sample Agha Jari SRB Naphtha Kerosine Light Atm. Wacuum Waxy Vacuum crude oil gas oil residue gas oil distillate residue Specific gravity 60/60------------------- 0,8373 1 0.9439 0.8772 10,915.1 11.009) Specific gravity 14060-------------------------------------------------------------------------- 0.9161 ------------ 0.8871 0.981 Distillation IBP------------ test, C. 215 272 27 ------------ 2% vol. recovered 230 312 283 ---- 5%-------------------------------- 239, 5 337 291 ---- 10%------------------------------- 246.5 357.5 298.5 ---- 20%------------------------------- 255.5 384 307 ---- 80%------------------------------- 261.5 41.5 314.5 ---- 40%------------------------------- 267.5 442 321 ---- 50%------------------------------- 273 480 327 ---- 60%------------------------------- 278.5 57 333 ---- 70%------------------------------- 285 340-80%------------------------------- 292.5 348-90%------------------------------- 302.5 360.5 FBP-------- 316 384.5 Recovery, percent Residue, percent-- LOSS, percent------------ Total sulphur, percent wt Aniline point, C-...------ Diesel index.------- Cloud point, F------------------------------------ Pour point (upper), F------------ - Carbon residue (Con), percent wit------. 100 F., cs--------------------------- 122 F., cs. 140 F., cs------------------------------------------------- 170 F., es------------------------------------------------- 210 F., cs------------------------------------------------- Wax content (methy percent wt.----- Melting point of wax------------------------------------------ Calculated from value at 140 F. TABLE 1.-SUMMARIZING TABLE Blend Light gas oil Heavy gas oil Vacuum gas oil of So Blend of LGO al EIGO and WGO Experiment------------------------------------------- 2 3 2 3 2 3 Yield on crude, percent wt.--------------------------- 14.48 16.28 14.70 7.03 Nil 10.10 21.5 26.38 23.09 Front end TBP cut pt., C.- 236 235 236 318 ---------------- 328.5 320 236 235 236 Back end TBP cut pt., C - 318 328.5 320 i 357.5 ---------------- o 372.5 392.5 357.5 372.5 Specific gravity 60/60------ -- 0.8397 0.8403 0.8373 0.871i ---------------- 0.8772 0.8506 0.852 0.8513 Total sulphur, percent wt. 0.75 0.75 0.72 1.2---------------- 1. 41 0.87 I.05 0.94 Cloud point, F--------- 8 8 2 56---------------- 46 32 34 20 Pour point, F---- - O 0 O 55 ---------------- 40 25 30 20 Aniline point, C- 71.2 71.4 71.3 79.0 -------- -------- 72.8 73.6 73.4 72.2 Dieselindex------------------------------------------- 59 59/60 60 54 ---------------- 48/49 57 57/55 57 Distillation test, C IBP----------------------------------------------- 219 213.5 25 155 ---------------- o 271 223 227 224 2% vol. recovered 234 233 230 222 283 239 244 240 5%-------------- 242 241 239, 5 285-291 245.5 252 247.5 10%------- 250 249.5 246, 5 307-298.5 255, 5 260 256 20%----- 258.5 259 255, 5 325.5-307 268 270, 5 265 80%----- 265 265.5 26, 5 335-314.5 278 278 273.5 40%--- 270.5 271 267.5 343-32 285 286 281 50%- 276 277 273 348, 5. 327 294.5 295 288 60%- 282, 5, 283.5 278, 5 354 333 302 306 296, 5 70%- 289.5 290.5 285 359, 5 340 310 37.5 306.5 80%- 298 299.5 292.5 366 -- 348 329, 5 332.5 318 90% 308. 5 310 302.5 373.5 ------------------------ 360.5 348 354 335. 5 FBP--------- 325.5 325 316 397.5-384.5 376.5 385.5 365 Recovery, percent-- 99 99 99 98-98.5 98.5 98.5 98.5 Residue, percent------------- - 1. 2 ------------------------... 5... 5 1.5 1.5 Recovered at 400 C., percent-------------------------------------------------------------------------- 96 -------------------------------- The invention is further illustrated with reference to the distillation column 2 via steam stripper 11 and line the accompanying drawing, which is a schematic flow 12. The mixture is passed to reboiled distillation col diagram of a plant suitable for operating the invention, 60 umn 14, which operates at a moderate vacuum so as to the design of which is based on the information obtained reduce cracking to a minimum, via line 13, and a gas oil in the above Example 1. overhead fraction is recovered via line 15. The yield In the drawing, heated crude oil is fed via line 1 into of gas oil product expressed as a percentage of atmos conventional atmospheric distillation column 2. Atmos- pheric heavy gas oil together with atmospheric residue pheric residue from the base of the column is fed via line 65 is 20% wt., while on rerun column feed it is equivalent 3 to a vacuum column 4 operating at 96 mm. Hg. A to a 47.6% wt. distillate. Residue from this reboiled 33.9% weight (based on feed) flash distillate is re- column is combined via line 14 with that recovered from moved overhead from the vacuum column 4 via line 5 the column 4, so as to give a final residue of 80% weight to a collecting vessel 6, vacuum being drawn via line 7. calculated on atmospheric heavy gas oil and atmospheric Residue from the vacuum column 4, steam stripped at 70 residue feed to the recovery system. a rate of 0.25 lb./hr. steam per imperial gallon/hr. of The gas oil recovery unit will thus produce a good residue via line 8, is removed from the base of the col- quality gas oil with a pour point of 35 F. (as indicated umn via line 9 to storage. The flash distillate is passed in Table 3) at a yield on crude of 10.88% wt., so that via line 10 from the collecting vessel 6 and, after heat when blended with the light gas oil drawn from the exchange, is combined, with heavy gas oil drawn from 75 crude unit (pour point -5 F., yield on crude 15.84%

wt.) the resulting gas oil has a pour point of 15 F. at a yield on crude of 26.72% wt. Other standard items of equipment, e.g. pumps, heat exchangers and the like, are shown in the drawing. Equipment of the type described above could be added to an existing crude distillation unit to increase gas oil recovery. If units already exist for vacuum distill lation of only a part of the atmospheric residue, the above equipment could be integrated with the existing units. In a new refinery where vacuum distillation of atmospheric residue is required, say to produce feed stock for another process, then the above equipment could be integrated with the vacuum distillation unit with corresponding reduction in capital and operating costs. I claim: In a crude oil distillation process, combining the heavy gas oil side stream fraction obtained in an atmospheric O 15 2 pressure fractionation zone with the front 10-40% weight portion of the atmospheric residue obtained in that Zone, said portion being a product of the vacuum flashing of said residue, followed by redistilling of the combined fraction under vacuum in a reboiled fractionation zone, to give an additional gas oil product. References Cited by the Examiner UNITED STATES PATENTS 1,954,839 4/1934 Youker ---------- 208-364 1997,675 4/1935 Bahlke et al. ------- 208-365 2,850,436 9/1958 Beuther et al. ------- 208 355 3,234,118 2/1966 Chen ------------- 208-364 DELBERT E. GANTZ, Primary Examiner. H. LEVINE, S. P. JONES, Assistant Examiners.