Gas Oil Hydrodesulfurization

Gas oil hydrodesulfurization is designed to reduce the sulfur and other impurities (e.g., nitrogen) present in the raw gas oil cuts. The feed to the unit may be a straight run diesel cut from the crude distillation unit or secondary units such as FCCU (light cycle gas oil) or delayed coker. The feed from these secondary units may contain significant amount of olefinic hydrocarbons, which must be converted to saturates in the diesel hydrotreating unit to improve the storage stability of these products.

The primary improvement in product quality is with respect to sulfur and conradson carbon. The raw diesel cut from most Middle Eastern crudes, for example, may contain as much as 1-2% sulfur. Because of atmospheric pollution concerns, the sulfur content of saleable diesel grades allowable in most countries has fallen very rapidly. Until a few years ago 1.0% sulfur was acceptable. But, because of very rapid increase in the number of vehicles using diesel worldwide, the pollution level has

psi psig psia scf/bbl scf/bbl

600 698 30 35 1350 1105 3072 555 99.6 98.0

1240 140

1200 1390 161

Table 2-7

Kerosene HDS Unit Feed and Product Properties

STABILIZER

HIGH FLASH

LIGHT

HEAVY

PROPERTY

FEED

NAPHTHA

BOTTOMS

NAPHTHA

KERO

ATK

KERO

ANILINE POINT, °F

143

151.5

156.5

API GRAVITY

46.44

58.89

45.40

56.02

47.93

44.82

41.17

DENSITY

0.7952

0.7432

0.7999

0.7546

0.7886

0.8025

0.8195

AROMATICS VOL%

22

10.3

12.3

18.2

19.1

19.9

CLOUD POINT, °F

2

CORROSION, Ag STRIP

ZERO

ZERO

ASTM DISTILLATION °F

(IBP)

192

124

318

256

322

384

452

5 VOL%

306

178

344

264

338

396

464

10

324

202

354

268

342

400

472

20

346

232

368

272

346

404

478

30

362

256

386

276

350

406

484

50

396

292

424

280

362

412

500

70

440

316

468

286

382

422

518

90

504

348

520

296

418

440

544

95

526

360

536

302

436

448

556

(FBP)

556

394

562

326

470

470

576

FLASH POINT °F

138

140

184

226

FREEZE POINT °C

-59

-54

POUR POINT °F

ZERO

SMOKE POINT mm

24

25

27

26

25

SULFUR PPMW

4500

1900

17

6.4

3

3.6

41.1

VIS KIN. @ 122°F

1.1

1.31

0.66

0.99

1.32

2.2

IBP = INITIAL BOILING POINT; FBP = FINAL BOILING POINT.

IBP = INITIAL BOILING POINT; FBP = FINAL BOILING POINT.

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