Conference TAN Crude

High TAN Crude and Its Processing

May 2010

Table of Contents  1

High TAN Crude: resources

properties and acid

distribution  2

Problems existing for high TAN crude processing

 3

Design and operation of CDU CDU for high TAN TAN crude processing

 5

Problems existing in current unit and improvement improvement solutions.

 6

Conclusion

2

1

High TAN crude: resource

properties and distribution

1.1 High TAN crude :resources High TAN crude category  

Acid crude oil：acid number ＞0.5mg KOH/g High TAN crude ：acid number ＞1.0mg KOH/g

High TAN low sulfur heavy crude oil—there are five main oil fields of this kind of crude oil in four continents  High TAN high sulfur heavy crude oil—from Venezuela California USA High TAN low sulfur heavy crude oil distribution  In Europe，is mainly represented by the North Sea crude oil at northwest Europ； n mer mer ca， s ma n y represen e y raz ar m cru e o ；  In Africa，is mainly represented by West Africa Kuito and Sultan Sult an（Fula、Dar Bland）；  In Asia，is mainly represented by China Bohai sea crude oil (such as Pe nglai crude oil) 

3

1



High TAN crude yield during the year of 1998

2004

North Europe (kb/d)

America (kb/d)

West Africa (kb/d)

Far East ( kb/d)

Total (kb/d)

1998

510

910

100

770

2290

1999

580

1160

110

770

2620

2000

600

1415

170

770

2955

2001

630

1675

200

795

3300

2002

725

1815

255

795

3590

2003

765

1875

265

805

3710

2004

740

1935

475

805

3955

Year

4

1



1.2.Main charateristics of typical high TAN crude oil

0.9208

0.907

0.921

0.8829

0.9283

0.9276

0.9338

0.9309

0.9326

0.9

-8

-17.5

10

＜-20

＜-20

-32

3

-13

-8.1

38

67.96

100.8

179.5

14.64

54.83

97.91

509.4

141.9

78.62

23.7

6.7

4.75

7.61

5.28

6.54

6.11

8.98

5.47

6.78

7.7

0.243

0.131

0.221

0.661

0.691

0.32

0.2

0.16

0.68

0.11

2569

-

2235

2538

4439

3000

4700

1874-2300

3700

3370

1.12

4.51

1.4

0.51

1.9

3.57

2.12

3.55-5.05

1.27

3.68

5.42

1.63

1.55

12.58*

19.14

12.19

28.34

17.7*

18.54*

19.87

16.98*

6.37

13.55

1.51

1.52

7.5

10.36

2.92

2.45

12.51

7.89

14.16

4.12 16.56

5.68

9.8

1.19 6

11.02

36.61

8.41

41.96

0.34

＜0.03

＜0.03

1.43

14.46

39.12

11.5

12.22

0.33

1.18

1.28

1.78

＜0.03

0.47

2.42

0.62

0.12

1.55

＜0.10

＜0.10

0.18

＜0.10

8.24

8.34

0.04 0.41

0.42

67.8 11.7

12.25

31.34

7.13-10.53

16.6

0.03 1.17

0.17

0.13-0.62

60.63 0.16

24.7

199.33

1.06 5.77

1.02

13.63

2.92

41.94

＜0.10

0.81

＜0.10

＜0.10

15.6

9.8

38.2

11.85

11.9

11.65

130

21 83

44 75

34 72

3.2 11.85

Sulphur Low sulphur Low sulphur Low sulphur Low sulphur Sulphur contained contained heavy heavy content naphthene meidum heavy content medium content heavy naphthene content medium medium base base medium base medium base medium base base

26 77

46.6

6.92

Low sulphur naphthenic base

Low sulphur heavy content medium base

* Content of gel + asphalt 20 33

179

17.4 12.2

Sulphur Low sulphur contained heavy medium content content paraffin base低 naphthenic base

21 5

5

1



Features of high TAN crude : Low

crude oil API

high density

higher than 0.93kg/m3

most of them is

high viscosity

the content of asphalt and gel are especially high High

TAN (Total Acid Number, for instance, Penglai19-3’s

acid value is 3.57mgKOH/g

but most of them are of

comparatively low sulphur content)

High

TAN crude oils generally have higher nitrogen

content High

TAN crude oils have higher content of heavy

metals High

TAN crude oils have low yielding rate of light oil

distillation.

6

1



1.3 High TAN crude oil distribution

PL19-3 crude TBP( true boiling point) distillation and narrow fraction’s watson K

No.

Boiling point range ℃

Occupation in crude oil% （m/m） Each fraction

Total yield

Density g/cm3 (20℃)

Solidificati on point ℃

Acid degree mgKOH /100mL

Acid Number mgKOH /g

Watson K

1

＜80

0.49

0.49

0.7288

3.77

11.3

2

80～100

0.57

1.06

0.7389

1.26

11.7

3

100～120

0.87

1.93

0.7536

1.89

11.7

4

120～145

1.25

3.18

0.7723

6.29

11.6

5

145～170

1.72

4.90

0.7947

24.53

11.5

6

170～200

2.27

7.17

0.8247

63.96

11.3

～

.

.

8

235～250

1.95

12.90

0.8671

230.7

11.2

9

250～275

3.67

16.57

0.8766

304.5

11.2

10

275～300

3.51

20.08

0.8791

395.9

11.3

11

300～320

3.29

23.37

0.8776

471.4

11.5

12

320～350

5.23

28.60

0.8946

470.6

11.5

13

350～360

1.65

30.25

0.9036

<-40

6.19

11.5

14

360～395

5.72

35.97

0.9096

-30

5.74

11.5

15

395～425

5.67

41.64

0.9166

-14

4.34

11.6

16

425～450

5.74

47.38

0.9342

-10

2.68

11.6

17

450～475

6.27

53.65

0.9347

-6

2.26

11.7

18

475～500

5.06

58.71

0.9347

2

3.23

11.8

19

500～520

3.25

61.96

0.9323

6

3.94

12.0

20

520～545

3.80

65.76

0.9352

24

4.16

12.1

21

＞545

34.24

100

.

.

.

7

1



Typical acid number (or degree) of different draws from CDU for offshore crudes

Acid degree/Acid number mgKOH/100mL /mgKOH/g

Sample name

Penlai19-3 crude oil

Cao FeiDian crude oil

Atmos heric overhead gasoline

0

0

Atm draw 1

228.69

2.05

Atm draw 2

404.44

22.82

Atm draw 3

553.77

149.98

vacuum draw 1

5.88

1.45

vacuum draw 2

5.79

2.89

vacuum draw 3

3.72

3.29

vacuum draw 4

3.79

3.78

Acid degree

Acid value

8

1



高酸原油酸值分布图 14

12

10 ， g / H 值 O 8 K g 酸 m

r e b m n d i c A

6

4

2

0 0

100

200

300

400

500

600

Boiling point，℃

Penglai 19－3－4 Penglai 19－3－2 crude oil Kelamayi No.1 Shan jiashi

Kazakhstan Sultan Fulan2a

Sultan Fulan2b

Xinjiang blended crude oil

9

 1


properties and acid

distribution  2


 3

Design and operation of CDU for high TAN crude processing

 5

Problems existing in current unit and improvement solutions.

 6

Conclusion

10

2

Problems existing in high TAN crude oil processing

High TAN crude oil’s typical properties Material ’s typical pollutants

process challenges and solutions

Process challenges

Solutions

High content of filterable solids

Fouling\Foaming\Desalting efficiency\Environmental protection

Storage tank dewatering\Desalting（listed as process challenge） \Process scale inhibitor\Waste water treatment

High water content

Desalting\Product quality\Corrosion\Foaming\Energy consumption

Storage tank dewatering\desalting（same as above） \ Tower overhead corrosion control

High salt content

High content of organi c chlori de

Corrosion\Fouling\Desalting\Catalyst poisoning

Storage tank dewatering\desalting（same as above） \ Tower overhead corrosion control \Process

Corrosi on\ HDS catalyst poisoning

Tower overhead corrosion control \ HDS reactor bed treatment

Corrosion（containing water and high temperature）

Tower overhead corrosion control \High temperature corrosion control\material upgrading

Corrosion\Product quality\Transportation、storage and safety

Tower overhead corrosion control\ H2S trapping agent

Fouling\Catalyst poisoning\Product quality\ SH&E

Remove impurities in desalting unit\Process scale inhibitor\Waste water treatment

Catalyst poisoning\ FCCU operation

FCCU metal inactivation plan

Fouling\Desalting\Energy consumption

Process scale inhibitor

Fouling\Foaming\Desalting\Corrosion\ WWTP

Storage tank dewatering\Desalting（same as above） \Tower overhead corrosion control\工艺Process scale inhibitor \Waste water treatment

High acid content

（Total acid value，naphthenic acid value） High sulphur content（H2S and mercaptan）

High metal load

（Ca、Hg、 Fe、Se…）

High content of Ni/V Raw mat eria l poor compati bilit y

Upstream additives

11

2


Potential problems in high TAN crude oil processing Problem areas

Problem description

Tank area

•

Electric desalting tank Tower overhead corrosion Heat exchanger system

废水处理

• •

Sump oil in tank increase

•

Tank volume decrease

Oil entrainment in drainage water Emulsion layer thickness increase

• •

High water content in desalted crude oil Treatment capacity decrease

Tower overhead organic acid corrosion increase increasing trend •

•

Fouling increase trend in heat exchanger system

•

问题较多，见下图所示：

•

•

Tower overhead salting

High energy consumption

DA

,

12

2


Main problems lie in CDU and sewage water treatment system Except the huge risks associated with high temperature corrosion, Huizhou refinery CDU has other problems such as increasing amount of sump oil, waste water treatment system difficulties and constrain issues in crude oil sole refining and mixed refining. The graphic below shows existing problems and their locations other than product quality control issue, these locations include tank area electric-desalting tank heat exchanger system overhead system wastewater treatment system etc. Overhead

Heat exchanger system

Crude oil tank

Electric-

Electric-desalting

area

desalting tank drainage

Waste water treatment system

13

2


2.1 High temperature naphthenic acid (NA) corrosion and its effect High temperature naphthenic acid corrosion mainly happens under temperature of 200℃ above especially 220℃、and at the equipment parts which have closely contact with naphthenic acid, the most seriously corroded part is the vacuum distillation column system of atmospheric and vacuum distillation system (including vacuum heater 、transfer line、 vacuum draw 3、 vacuum draw 4 、vacuum tower feeding line and below part 、internal structure parts etc) 



High naphthenic acid corrosion consists of the following 4 main steps: 

Naphthenic acid molecules are transferred onto metal surf ace



Being adsorbed on the metal surface



Desorption of corroded substances

NA corrosion is heavily influenced by temperature. The corros ion at low temperature is not strong. Once in boiling state, especially in high temperature anhydrous environment, the corrosion will be the strongest. Most of the high temperature naphthenic acid corrosions happen in liquid phase, but if naphthenic acid is condensed at gas phase, the gas phase corrosion may happen and the corrosion extent will be influenced by acid value. In addition, the corroded substances Fe(RCOO)2 is oil dissolvable which are formed from the direct reaction between high temperat ure naphthenic acid and metal surface or iron sulfate membrane. It can be easily dissociated from metal surface and carried away by oil, new nude metal surface is exposed and result in new corrosion furthering into metal. For this reason the metal surfaced corroded by naphthenic acid is very smooth and clean without dirt. After long time contact with naphthenic acid, flushing by the acid st ream, the metal surface will form special observable corroded grooves or traces (high speed acid stream will form same directional sharp groove lines, while the low speed acid st ream will form corrosion pits with sharp edges), these are symbols used to identify this kind of corrosion with other corrosions. 14

2 


High temperature NA corrosion influence factor——Temperature 

<200 ℃：in anhydrous case，no corrosion； in water environment the corrosion will increase with increasing temperature；



270～280℃：reach the acid boiling point, also the most serious corrosion；



350～400℃：due to the high temperature melting of FeS membrane，together with the elemental sulphur discomposed from crude oil sulphides, the corrosion on metal equipments becomes violent enhanced by the interaction between naphthenic acid、elemental sulphur and H2S.



>400℃：oil acid is decomposed, corrosion is weakened; At the place where naphthenic acid is thermally decomposed, there will be formation of low molecular mass organic acid or CO2, which have effect on condensate water’s corrosivity.

15

2


8 7

) 6 a / m 5 m ( 率4 速

316L 0Cr13 Cr5Mo 20G

腐2

e t a 1 r n o i 0 s o 250 r r o C

270

290

310

330

350

Temperature 温度(℃)

16

2


 High temperature NA corrosion influence factor——Flow Velocity and Flow

Regime 

There are heavy corrosions in equipment’s elbows、tee joints and the turbulent flow area in pumps.



The included angle between media flow direction and met al wall（0-900）also heavily influence the naphthenic acid corrosion（bigger angle will result in bigger media impact force and hence heavier corrosion ）



If flow’s gas content is higher than 60%, and the gas stream speed is highe than 60m/s ，the corrosion speed of some equipments such as furnace tubes、elbows、vacuum distillation transfer line etc may increase about two order of magnitude.



Under certain temperature，there is a critical velocity for some materials which is between material’s corrosion speed in crude oil and flow velocity. If the flow velocity is lower than this critical value, naphthenic acid corrosion speed will be very low.

The generally controlled flow velocity is： for carbon steel <25-30m/s， SUS316<120m/s(no turbulent flow)

17

2


 High temperature NA corrosion influence factor——Acid Molecular

Weight and Acid Distribution 

Acid value doesn’t directly show the naphthenic acid corrosivity performance; And there is no proportional relation between them.



But as for high acid crude oil, its acid value is used for describing its corrosivity.



Naphthenic acid of light molecular weight needs lower activation energy during reaction with metals, and it is higher activity at low temperature, hence result in heavier corrosion; Naphthenic acid of heavy molecular weight needs higher activation energy during reaction with metal, and it is of lower activity at low temperature.



High acid crude oils from different area are of different acid distribution, hence they have difference on corrosivity, and also the difference on absolute corrosion speed.

e t a r n o i s o r r o C

Temperature ’

18

2


 High temperature naphthenic acid crude (NAC) corrosion influence factor—

—Crude oil Type

High acid crude oils from different areas have difference on their acid distribution and also the difference on their corrosivity. Take SS300 stainless steel for example, the corrosivity of Penglai 19-3 crude oil 、Beijiang crude oil and Lvda10 are different, the inflection point temperature of these three high acid crude oils are 300℃ around、300-310℃ and 310-320℃ respectively，and their corrosivity are definitely different, for sample material, its corrosion speed in these three oils at tem erature of 330℃ are 1mm/a around、0.4mm/a around and 0.3mm/a around respectively.  NAC corrosion influence factor——Material

The corrosivity sequence on the material from strong to weak is as follows ：20G 、Cr5Mo、0Cr13、Cr18-8、00Cr17Ni14Mo2. This is mainly because the different content of alloys in above alloy steel.  NAC corrosion influence factor——Others

Even with very low sulphur content, naphthenic acid is still of heavy corrosion, it is because there is no formation of protective sulphide film; but sulphur can reportedly reduce corrosion at its content of 2-3%.

19

2


2.2 Low temperature corrosion issue resulted from high temperature high acid crude oil’s electric desalting difficulties High acid crude oils are generally of higher density and viscosity, especially the issues of higher content of asphalt and gel, which will result in increased difficulties in electric desalting. Furthermore, the naphthenic acids and their salts are of strong emulsibility, which may bring difficulties to crude oil desalting, make it harder to meet deep desalting requirement, the low temperature part of distillation unit overhead （≤120℃）will be heavily corroded.

H2S-HCl-H2O t

e corrosion

Corrosion at low temperature area is of the same corrosive mechanism as atmospheric & vacuum distillation low temperature corrosion. The corrosive mechanism is that: after the crude oil desalting and dewatering, there are still some non-organic salts like calcium chloride、magnesium chloride、 sodium chloride existing in desalted and dewatered crude oil, the organic chloride additives added in some oil fields during the crude oil deep extraction may form HCl under certain conditions，the corrosions will mainly happen in primary tower overhead and atmospheric tower overhead (top 5 trays and their above), also the tower overhead condensate cooling system, of distillation unit, then followed by vacuum tower overhead. The main influence factors are：Cl-、pH value. The low Clconcentration will result in slight corrosion，high Cl-content will result heavy corrosion. Lower pH value will result in heavier corriosion, while over high pH value（〉8.0）will easily result in condensing system fouling and further the corrosion under fouling. Corrosions resulted from acetic acid added during high acid crude oil extrac tion and formic acid & acetic acid decomposed from crude oil itself. 20

Corrosions resulted from acetic acid

照片1试压时芯子泄漏情况

照片3减二及减一中泵入口壳体腐蚀情况

21

Ca Naphthenate Debris

Collected from V703A bottom

Naphthenate deposit found in a heat exchanger

Collected from V702 water leg

Naphthenate deposit found in an electrical Desalter 22

Corrosion of Small Molecular Acid

23

24

2


2.3 Corrosion resulted from high nitrogen content in high acid crude oil High acid crude oil is of higher nitrogen content, the main three types of corresponding corrosion are as follows： 1 H2S-HCN-H2O type corrosion on catalytic cracking tower overhead and absorb stable tower H2S-HCN-H2O type corrosion happens under the temperature range of 40-50℃， damage of carbon steel will be thickness even reduction、hydrogen blistering and sulfide stressed corrosion cracking；damage of austenitic stainless steel will be sulfide stressed corrosion cracking. 2 NOx-SOx-H2O type corrosion in catalytic cracking regenerator tertiary c clone etc During catalytic cracking catalyst regeneration process, nitride will be converted to NOX， and will result in NOx-SOx-H2O type corrosion (so-called “Niter Embrittlement” in low temperature area of catalytic cracking regenerator 、tertiary cyclone etc, such as the cranidium, when the raining weather or wet ambient form the nitric acid dew point. This is the main course of accident happened in catalytic cracking unit regenerator of domestic refineries. 3 Pipeline blocking and corrosion under fouling resulted from the accumulation of ammonium chloride and ammonium hydrogensulfide in hydrogenation low pressure air cooler. After hydrogenation on raw materials, the elemental nitrogen in nitrogen contained compound is converted to ammonia, NH3 HCl and H2S react in distillates heat exchanger to form NH4Cl and NH4HS，these salts, due to their low solubility, will accumulated on equipment surface and result in blockage in hydrogenation high & low pressure air coolers 、heat exchanges and pipelines and further the corrosion under fouling. 25

2


2.4 High acid crude oils are of high salt content and metal content Higher metal content in crude oil especially the Calcium、Nickel、Vanadium，will mainly influence secondary processing units, such as catalytic cracking、hydrogenation，and will result in catalyst posioning and/or permanent inactivation、catalyst bed blocking and high temperature heat exchanger fouling and coking etc. If the residuum is used as fuel oil, then corrosion of furance tubes and heavy ash accumulation on furnace tube surface will happen which will influence heater’s heat eff iciency and operation safety.

2.5 Product quality issues First is how to realize aviation kerosene smoke point and cetane number indicator, Second is the high nitrogen content makes it difficult to store the oil products under higher stability standard. Because the straight-run naphtha content in high acid heavy c ontent crude oil is usually lower, at the time of oil shortage, the problems will happen with alternative crude oil: the alternative is hard t o match either the atmospheric load of atmospheric & vacuum distillation, or t he reforming load.

2.6 Envrionmental protection Another big headache of high acid crude oil processing is the sewage water treatment There is high acidic organic substances in the organic content which can be extracted from sewage water (it occupies over 90% of the total extractable organic content). Acidic organic substances from different sewage不water source are different. By calculation, final outlet naphthenic acid’s contribution to COD should be 30% above, most of the molecular weight are 300 around, and they are basically C18 liked naphthenic acids.

26

2


’

Oil type Crude oil tank

212-T-02

PH

mg/l

Oil mg/l

Sulphide mg/l

Electrical conductivit y us/cm

Volatile phe nol mg/l

6.8

2230

161.0

33.8

6.8

32500

16.0

ez o u

6.8

2720

213.5

44.4

3.5

23500

6.1

212-T-4

Weizho u

7.4

3700

355

73.6

3.4

42800

5.7

212-T-1

Dalia

7.6

5350

255

106.8

21.8

35200

9.6

211-T-4

Dalia

7.3

4200

129.0

52.3

5.4

1.0

212-T-3

Hange

7.5

4660

119

85.6

4.5

2.1

212-T-04

Jilaso

COD

Ammonia/Ni trogen mg/l

27

2


28

2


29

 1


properties and acid

distribution  2


 3


 5


 6

Conclusion

30

3

Design and operation of CDU for high TAN crude oil processing (take Huizhou refinery as example)

3.2 Electric desalting and atmospheric & vacuum distillation unit

High salt content in crude oil

3 levels tanks design

High density、 viscocity

Electric desalting tank design operation temperature 139℃

High acid value、 oil entrainme nt in drainage water

Install deoiler behind electric desalting tank, together with specially designed back flush structure

Desalting efficienc y to be lower

Increase reverse demulsifier、dispersent， crude oil dewatering demulsifier、desalter ’s process injection system，

32

3


Huizhou refinery 12million tons/year atmospheric & vacuum distillation unit process sketch

33

3


Item Input

t i n u n o i t a l l i s i d m u u c a v & c i r e h p s o m t A

Crude oil

Planned yielding rate

137500

Actual processing amount

Actual yielding rate

127933

Self made fuel gas

206

0.15%

192

0.15%

Atmospheric overhead

6133

4.46%

5174

4.04%

Kerosene

8786

6.39%

6645

5.19%

Blended diesel oil

26469

19.25%

20824

16.28%

336

0.24%

2rd vacuum cut

23554

17.13%

19020

14.87%

3rd vacuum cut

20048

14.58%

16103

12.59%

4th vacuum cut

5225

3.80%

5190

4.06%

Vacuum residue

47080

34.24%

48395

37.83%

Vacuum overhead oil Outp ut

Monthly plan

Light sump oil

500

227

0.18%

Heavy sump oil

1500

1694

1.32%

123464

96.51%

Total output Light yielding

30.34%

32643

25.52%

Total yielding

65.85%

73148

57.18%

Oil residues in system pipeline

4405

3.44%

Processing loss

64

0.05%

34

3


3.3 Equipment material selection (Metallurgy) and corresponding supervising & monitoring system Huizhou refinery 12 million tons/year atmospheric & vacuum distillation unit is designed for t he crude oil with acid value of 3.57mgKOH/g，sulphur content of 0.28～0.3%. In order to supply qualified and approved materials to downstream units, and guarantee 4 years long period operation, we have formulated “high acid crude oil equipment material selection guidance”. 

Main rocess i eline material selection rinci le Metallur 1）For media of 220℃ lower temperature，use carbon steel. 2）For media of 220℃≤ temperature＜288℃，it is recommended to use material of 1Cr5Mo、1Cr9Mo、 0Cr19Ni10Ti、00Cr17Ni14Mo2（SS316L material in this plant are all required for 2.5 more Mo content）. 3）For media of 288℃ higher temperature，recommended material is 00Cr17Ni14Mo2 austenitic stainless steel. 4）For media of temperature ≥ 220℃ and flow velocity ≥ 30m/s，recommended option is 00Cr17Ni14Mo2 austenitic stainless steel. 5）For big diameter pipeline, recommended option is the rolling pipes made by composite material of carbon steel --00Cr17Ni14Mo2 stainless steel. 6）Should the media flow velocity and regime be monitored, as for the area and part which deem to be heavily washed, shall the big radius elbows and slot branching tee joints be applied there. 35

3


Monitor methods 

Corrosion probe monitoring There are totally 17 probes installed in different positions of atmospheric & vacuum distillation unit



Test analysis and monitoring

Crude oil tank、 prior desalting、 1st desalting 、 2rd desalting 、 desalted crude oil

Salt content、water content、metal content、 acid value、sulphur content、

Tank area dewatered crude oil ’s water content≤0.5%、salt content after electric desalting≤3mgNaCl/L、water content after desalting≤0.2%、removal rate of organic metal ions of Ca,Fe,Mg ,Na etc(excluding Ni,V)≥70%

Electric desalting drainage water

Oil contained、PH

Oil content in drainage water≤200ppm water pH: 6-8

Sewage water from atmospheric overhead and vacuum overhead

Fe ion、Cl ion、H2S、NH4 、PH、strong acid

Fe ion ≤1mg/l、probe corrosion rate: ≤0.2mm/y 、PH value:5.5-7.5

Atmospheric overhead oil、vacuum overhead oil、2rd atmospheric cut oil、3rd atmospheric cut oil、2rd vacuum cut oil、3rd vacuum cut oil 、4th vacuum cut oil、vacuum residuum

Acid value、S content、 Fe content、Ni content

Fe≤1mg/L、probe corrosion rate≤0.2mm/y



Drainage

Thickness measuring and coupons fixed at specific points 36

3


List of corrosion monitoring probes of atmospheric & vacuum distillation unit Pipe

mater ial

Material flow t/h

Design temperatu re C

600

304L

1428

224

Continuous low temperature inductor with CS coupon

900

CS

65

118

Code

Position

Type

101-AE-01101

Before feed pressure control valve of flashing tower

Continuous high temperature resistor with P5 coupon

101-AE-01201

Atmospheric overhead oil gas volatilization line

dia met er

Pipe

101-AE-01401

After E-401 pipeline inlet valve


450

CS

18

118

101-AE-01501

After A-101A inlet valve


700

CS

18

93

101-AE-01502

After atmospheric overhead water cooler valve

Continuous low temperature inductor with 09 coupon

500

CS

32

60

101-AE-01701

Before 3 rd vacuum cut backflow control valve

Continuous high temperature inductor with 316 coupon

250

316L

209

307

4th

101-AE-01702

Before vacuum cut output control valve


150

316L

54

361

101-AE-01703

After P-115A inlet valve


700

316L

489

369

101-AE-01801

Vacuum overhead level one vacuumizing device water chiller inlet


900

CS

4.2

180

101-AE-01802

Vacuum overhead level one vacuumizing device water chiller inlet


150

CS

4.2

37

After E-202 1st vacuum cut inlet valve


250

CS

138

142

101-AE-02301

After E-205AB 2rd vacuum cut inlet valve


450

321

800

237

101-AE-02401

After E-206 3rd atmospheric cut inlet valve


200

316L

110

303

200

321

131

253

300

Cr5Mo

223

263

101-AE-02101

101-AE-02601

After E-306 atmospheric cut inlet valve


101-AE-03201

After E-5011st atmospheric middle cut inlet valve

Continuous high temperature inductor with P5 coupon

37

3


Sample name

Analysis item

Performance indicator

Crude oil tank、prior desalting 、1st desalting、2rd desalting、desalted crude oil

Salt content、water content、metal content、acid value 、sulphur content、

Tank area dewatered crude oil’s water content≤0.5%、salt content after electric desalting≤3mgNaCl/L、water content after desalting≤0.2%、 emova ra e o rgan c me a ions of Ca,Fe,Mg ,Na (excluding Ni,V)≥70%

Electric desalting drainage water

Oil contained、PH

Drainage water oil content≤200ppm Drainage water pH: 6-8

Sewage water from atmospheric overhead、 vacuum overhead

Fe ion、Cl ion、H2S、 NH4、PH、strong acid

Fe ion≤1mg/l、probe corrosion rate: ≤0.2mm/y、PH value:5.5-7.5

Atmospheric overhead oil、 vacuum overhead oil、2rd atmospheric cut oil、3rd atmospheric cut oil、2rd vacuum cut oil、3rd vacuum cut oil、4th vacuum cut oil、vacuum

Acid value、S content 、Fe content、Ni content

Fe≤1mg/L、probe corrosion rate ≤0.2mm/y

38

3

Design and operation of CDU for high TAN TAN crude oil proces processing sing (take Huizhou refinery as example)

3.4 Process anti-corrosion It is the integrated multiple treatment system Including the chemical agents of crude oil dewatering demulsifier EC2045A、electric desalting demulsifier EC2506A、reverse demulsifier EC2345A、electric desalting tank demetalization agent EC2047A、low temperature corrosion inhibitor EC1021A、high temperature inhibitor EC1023N、scale inhibitor EC3238A.

C D U

V D U

High temperature corrosion inhibition control area sketch

39

3

Design and operation of CDU for high TAN TAN crude oil proce processing ssing (take Huizhou refinery as example)

3.5Environmental 3.5Env ironmental protection and others Huizhou refinery, has since its operation start up in April 2009, kept its sewage water in whole plant treated to approved level, including the sewage water from electric desalting which have been draining into deep sea via pipeline after approved treatment, the oils contained sewage water have been recycled after approved treatment. Periodic back flush water from electric desalting tank bottom is of high shock to salts contained sewage water treatment. Due to this reason, during back flushing, first put this stream sewage water in high concentration sewage adjustment tank, then blend use and treat it gradually.W We are now trying to use continuous small amount flush to replace periodic flush (once per week). Other possible approaches to treat this highly polluted sewage water are also under developing (such as adding preparations and acidic organic substances extracted from naphtha etc). Due to the correct process technology choosed for subsequent level 2 and level 3 processing units, all units are in smooth operation, all products are in approved excellent quality. But because the atmospheric & vacuum distillation unit is designed based on Penglai 19-3 crude oil, whose light oil yield is only 4.8%, hence when blend it with other type crude oils for refining, the atmospheric distillation tower overhead load restriction is the main concern. Of course, the sulphur content in blend crude oils especially for the refining blended crude oils and sulphur recycle capability are the main restrictions in the selection of crude oil type and amount for refining blending. Another factor needs to be considered regarding blended oil types and blending ratio is the water quality change of sewage water from electric desalting of atmospheric & vacuum distillation unit after the use of blended crude oil, and the acceptable level of sewage water treatment plant. 40

3

Design and operation of CDU for high TAN TAN crude oil proces processing sing (take Huizhou refinery as example)

3.6 Chemical agents injection system design ( sample ) Injection method · It can reduce crude oil desalting cost. · Wide range of adaptability. · It remarkably reduces the oil entrainment in desalting tank salty water.

Crude oil tank ng & deemulsi fer EC2045A

· It can effectively reduce the solid impurities in downstream heat exchangers and other equipments, and fouling on equipment inside walls. · It increases desalting efficiency, reduces corrosion of unit overhead system. · It controls the solid content on crude oil/emulsion oil/emulsio n interface in desalting tank.

Crude oil storage tan、 header feedline

Keep the amount in between 2－24ppm as per each case, usually start from 6ppm.（ If electric desalting tank can fix desalting and dewatering issue, then there is no need to inject demulsifier.）

Basic solution injection

· It removes oil contained in inorganic substances in crude oil. · It helps quick demulsification. · It increases dewatering efficiency in crude oil storage tank. · It reduces crude oil desalting cost. · Wide range of adaptability. · It remarkably reduces the oil entrainment in desalting tank salty water. 41

 1


properties and acid

distribution  2


 3


 4

Operation performance assessment

 5


 6

Conclusion

42

4


4.1 Types and characteristics of the crude oils refined since start up (sample ) Densit y(20℃ )

API degre e

g/cm3

Soli dify ing poin t

Acid value

Wax conte nt

Salt content

Water conten t

Resid ue carbo n

Ash conte nt

Sulph ur

Nitro gen

Gel

Asphal t

80℃

℃

mgKOH/ g

%(m/m )

mgNaCl/L

%(m/m)

%(m/m )

%(m/m )

%(m/m )

%(m/m )

%(m/m )

%(m/m)

20.8 5

-30

3.57

3.8

228

1.1

5.13

0.024

0.28

0.41

17.1

0.8

Viscosity， mm2/s

20℃

40℃

50℃

0.919

21.9

0.9258

20.9

90.8 6

25.7 4

-30

2.38

5.21

53.1

0.1

6.85

0.024

0.28

0.3

13.68

1.36

0.8966

25.6

217. 2

47.2 4

30

3.67

25

21.3

痕迹

8.2

0.205

0.13

0.38

12.82

0.14

0.929

20.27

8

1.34

15.3

13

0.35

7.13

0.23

0.31

20.1

0.1

0.8713

30.81

0.343

0.174

0.9444

18.3

0.8524

33.7

0.8479

34.63 7

462.2

259. 7

0.3 399.2

94.83

22.74

0.8908

0.7

368.4

0.68

2.1

0.05 0.023

8.71 3

13

0.35

23.45

28.6

0.88

2.7

17.1 2

34

0.28

28.6

24.82

0.07

25

0.84

16.7

0.03

24.8 141.6

15

10.0 3

73.5 7

0.16

0.13

4.72

0.22

3.57

0.05

0.11

7.7

0.1

4.49

0.14

0.25

0.189

0.337

0.929

20.73

412.2

0.8992

25.3

103.4

24.9 4

9.40 6

-34

1.28

1.37

66.9

0.2

4.3

0.018

0.52

0.27

12

0.55

0.9338

19.5

691.8

96

25.8 2

-32

2.09

0.45

20

0.6

6.11

0.006

0.69

0.39

16.85

1.74

0.8836

28

25.5

0.558

7.98

31.8

痕迹

5.1

0.011

0.62

0.32

6.65

2.89

9.79 8

2.84

0.05

0.325

43

4


4.2 Treatment effectiveness of electric desalting tank Under very frequent switching between different crude oils and the severe trend of crude oil low quality, electric desalting process has been in good effectiveness and comparatively stable operation.   

The time between start up and May is the optimization and adjustment period, desalting is of lower approval rate, but most of the salt content results are between about 3.0-3.5 after desalting（pass level is 3.0 below） From June to July, the electric desalting units have been in good operation with desalting pass rate of more than 90%. In July, more types of crude oil have been blended, electric desalting effect has been influenced, we try to develop solution. Month

Desalting pass rate，%

Prior-desalting salt content ，mgNaCl/l

Post-desalting salt content ，mgNaCl/l

Sample qty

Approved sample qty

Pass rate

Max

Min

Average

Max

Min

Average

5

18

2

11.11

120.5

12

38.77

9.4

2.64

4.93

6

22

21

95.45

33

4.95

17.66

3.4

1.65

2.77

7

21

20

95.24

135.3

9.07

33.12

4.46

2.18

2.95

44

4


4.3 Electric desalting-demetalization treatment 

The effectiveness is generally good



Electric desalting drainage water has dematalized metal entrainment, which may bring remarkable shock to the sewage water treatment system, hence the sewage water treatment plan should be adjusted and optimized accordingly 5.86

0.01

3.37

0.48

6.63

1.04

35.52

15.22

July crude oil before demetalization

9.6

0.09

9.49

0.59

11.3

2.25

17.05

15.9

Crude oil average before demetalization

7.73

0.05

6.43

0.54

8.97

1.65

26.29

15.56

June crude oil after demetalization

1.95

0

0.2

0.14

0.8

0.06

27.26

9.86

July crude oil after demetalization

0.34

0

1.96

0.37

1.2

0.68

11.69

1.14

Crude oil average after demetalization

1.145

0

1.08

0.255

1

0.37

19.48

5.5

Average demetalization rate

0.8519

1

0.832

0.523

0.8885

0.7751

0.259

0.6465

June crude oil before demetalization

30

0.7221

100.00% 90.00%

25

’

80.00% 70.00%

20 15 10

60.00%

脱前前

50.00%

脱后前前

40.00%

前脱平

30.00% 20.00%

5

10.00% 0

Crude oil average before desalting Crude oil average after desalting Average desalting rate

0.00% Fe

Pb

Al

Zn

Na

K

Ca

Mg

合计

45

4


4.4 Low temperature corrosion resistant 

Overall effect assessment 

In overhead of both atmospheric & vacuum distillation unit the Fe ion content are all ≤1mg/L ，and the probe corrosion rate ≤0.2mm/y，pH value 100% reach the indicator of 5.5-7.5， these figures meant the atmospheric & vacuum distillation unit overhead corro sion is fully under control, all indicators reached advanced standard of both domest ic and international.



Vacuum distillation tower overhead corrosion used to have fluctu ation during early period of start up, especially pH value’s higher fluctuation，after a series of optimization and adjustment, both pH value and Fe ions have been under reliable cont rol，current approval rate is more than 90%



B com arin with robe trend the hi her corrosion rate at atmos heric distillation tower overhead before the charging of neutralizer and corrosion inhibitor is obviously observed, while the corrosion rate has been decreased dramatically since the charging of above two preparations, this indicates that correct anti-corrion measures have been implemented on atmospheric distillation tower overhead with remarkable effects. The sewage water in reflux accumulator of atmospheric distillation tower overhead looks clear and contains lower level Fe. As for vacuum distillation tower overhead, there are large amount of light molecular weight organic acid existing there, which will enter into water tank after cooling in level one condenser, and result in probe corrosion rate increase after E-510W，currently by optimized preparation charging operation, the corrosion rate decrease from highest 3mm/a more to 0.2mm/a less，this proves again the excellent performance of the preparations and site professional service which will guarantee plant’s reliable long period running.



During the start up, test analysis found out large amount of organic acid （about1200－ 1800ppm if translated into acetic acid）in overhead system, which is beyond our expectation. With Nalco’s careful adjustment and treatment plan, the corrosion was quickly under controlled（ferric ion decreased from hundred more ppm to 1ppm）.

46

4

Operation performance assessment “

Tower overhead Fe ion pass rate/%

”

Atmospheric overhead Fe ion content /(mg/L)

Vacuum overhead Fe ion amount /(mg/L)

Month

Total sample amount

Sample pass amount

Pass rate

Max

Min

Average

Max

Min

Average

5

36

29

80.56

1

0.15

0.44

4.2

0.3

1.12

6

43

39

90.70

1

0.05

0.56

1.8

0.5

0.87

.

.

.

.

.

.

8

42

42

100.00

1

0.1

0.45

1

0.4

0.68

9

50

47

94.00

1

0.1

0.46

1.3

0.3

0.77

10

40

40

100.00

0.9

0.2

0.36

1

0.35

0.69

11

41

40

97.56

1

0.2

0.49

1.2

0.2

0.58

累计

298

281

94.30

1.00

0.05

0.48

4.20

0.20

0.80

47

4


48

4


Atmospheric overhead corrosion control

Vacuum overhead corrosion control

49

4


4.5 High temperature NAC corrosion treatment 

Overall effect assessment 

At the circumstance that acid value of crude oil and side line is higher than 3mgKOH/g：side line Fe ion content are all <1.0mg/l，corrosion probe reading is less than 0.2mm/a all reach the required control trargets. This demonstrates that upgraded material cooperated with good high temperature corrosion inhibitor can control the high temperature corrosion resulted from high acid crude oil refining.

Date

2009-6-3

2009-6-22

2009-7-6

2009-7-20

Fe(ppm)

Ni(ppm)

Fe(ppm)

Ni(ppm)

Fe(ppm)

Ni(ppm)

Fe(ppm)

Ni(ppm)

2rd atmospheric cuts

0.27

0.01

0.55

0

0.01

0.03

2

0.39

3rd atmospheric cuts

0.01

0.01

0.2

2

0.03

0.02

0.07

0.11

2rd vacuum cuts

0.01

0.01

0.77

0.01

0.15

0.05

0

0.02

3rd vacuum cuts

0.01

0.01

0.42

0.01

0.81

0.05

0

0.19

4th vacuum cuts

3.19

62.54

12.84

51.68

3.84

20.73

4.6

28.85

Vacuum residues

8.75

92.22

11.92

83.33

8.94

62.83

7.16

53.02

Crude oil

2.93

32.36

8.51

23.97

0.34

26.87

1.29

17.21

50

4


Crude oil salt content Salt content after desalting Desalting rate

51

4


Corrosion control effect of all side lines

30.00

120.00%

25.00

100.00%

20.00

80.00%

15.00

60.00%

脱后原油平均平均脱除率

10.00

40.00%

5.00

20.00%

0.00

0.00% Fe

Pb

Al

Zn

Na

K

Ca

Mg

合计 Total

52

4


High temperature corrosion 70 60

常二线

50

常三线

40

减二线

i N / 30 e F

N / e F

Atm cut 3 Vacu cut 3 Vacu cut 4 Vacu

减四线

20

t 10 n e t n 0 o c

Atm cut 2

减渣

residue Crude oil

原油 ) m p p ( e F

) m p p ( i N

2009-6-3

) m p p ( e F

) m p p ( i N

2009-7-6

) m p p ( e F

) m p p ( i N

2009-8-11

) m p p ( e F

) m p p ( i N

) m p p ( e F

) m p p ( i N

) m p p ( e F

) m p p ( i N

2009-9-14 2009-10-15 2009-11-27

53

4




Probe data analysis 

Probe data analysis indicates that: corrosion rate ＜ 0.2mm/y

54

4


4.6 Fouling control effect 

As it has only been 4 months since the operation start up, accurate assessment of plant fouling control is not available.



The focus of next step is to install temperature sensors on inlets and outlets of main heat exchangers, transmit the temperature data to DCS, calculate the heat exchanging efficiency of certain or a serious of heat exchanger, to judge the current fouling trend and implement further measures accordingly.

4.7 Sewage water and its treatment 

Sewage water from whole plant can be treated to qualified quality, and the salts contained sewa e water will be drained into dee sea b i eline after ualified treatment the oil contained sewage water have been fully recycled after qualified treatment.



Periodic back flush water from bottom of electric desalting tank is of considerable shock to salts contained sewage water treatment（sewage water sample refer to left and right figure） 

Current disposal：during back flush, first put this stream of sewage water into high concentration sewage water regulating tank, then gradually blend and treat it.



Disposal method under development：change periodic (once a week) flush to continuous small flashes Treat this high polluted sewage water with other method (f or example the dispersants)

Centrifuged sample from Mingzhu heater/treater interface

55

4


4.8 Product quality  



All current products are of excellent quality with approval During blended oil refining, the main issues to be considered are the atmospheric distillation load constraining and the effect of sulphur content in blended curde oil. Another factor to be considered for appropriate crude oil blending ratio vacuum distillation electric desalting after crude oils blending, and the acceptance level of sewage water treatment plant.

4.9 Others Product quality of hydrogenation unit： Conflict between diesel cetane number and smoke point Nitrogen content issue Anti-corrosion in coking、catalytic units

56

 1


properties and acid

distribution  2


 3


 4


 5


 6

Conclusion

57

5

Problems existing in current CDU and improvement solutions

Occasional water content during electric-desalting

1、Over high PH value of feed water, the content of NH4 and impurities exceeds limit. 2、High content of gel-asphalt and solid particles.

Improve feed water quality Assess the mix ratio between crude oils Add in asphalt dispersants

3、Crude oil upstream processing used too much additives. Overhead condensate water ammonia nitrogen content exceeds limit

1、Overhead system has large amount of organic acids and acetic acid content is very high, the usage of neutralizer is over limit due to corrosion controlling. 1、It is the sequela of high acid crude oil refining.

High content of solid content、ammonia nitrogen、metal、oil、 COD

2、Disparity within high acid crude oils match. 3、Remarkable difference between current crude oil and design.

Reduce upstream acetic acid usage；reselect the neutralizer；consider to add alkali into crude oil Enhance sewage water processing capability to elevate electric-desalting drum flexibility --add in solid wetting agent --add in asphalt dispersants 58

 1


properties and acid

distribution  2


 3


 4


 5


 6

Conclusion

59

6

Conclusion

Producing clean fuel or high value added petrochemical products from heavy content & low quality crude oil is now a big challenge that oil refining industries have to face. Among the heavy content & low quality crude oil category, high acid crude oil is of high acid value fewer light components high density and viscosity high content gel-asphalt high salt and metal content, which may result in equipment serious corrosion worries of product quality and environmental protection poor processibility aliked problems. World leading refinery with 100% full conversion of high acid heavy crude oil—— CNOOC Huizhou 12 million tons/ ear oil refinin ro ect has been ut into roduction. Even just 1 year has elapsed since its production start up, but until now, it has achieved good outcomes together with remarkable economic returns in the ar ea of electric-desalting high & low temperature corrosion control the processing and treatment of kerosene and diesel wax oil residuum. Its technology expertise and experience have been practiced and approved in the area s of raw material choosing and batching equipment selection process operation and anti-corrosion supervision & monitoring quality control environmental protection management innovation. It is now accumulating more processing experience of high acid crude oil from the operation.

60

Conference TAN Crude

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