BOILING POINT DISTRIBUTION OF CRUDE OILS BASED ON TBP AND ASTM D-86 DISTILLATION DATA

Transcription

1 Petroleum & Coal ISSN Available online at Petroleum & Coal 53 (4) , 211 BOILING POIN DISRIBUION OF CRUDE OILS BASED ON BP AND ASM D-86 DISILLAION DAA Angel Nedelchev, Dicho Stratiev, Atanas Ivanov, Georgy Stoilov Lukoil Neftochim Bourgas Chief Process Engineer Department, 814 Bourgas, Bulgaria, Received July 4, 211, Accepted October 15, 211 Abstract he rue Boiling Point (BP) analysis according to ASM D-2892 standard is the single reliable tool for characterization of crude oil and petroleum mixtures in terms of their boiling point distribution. However, the analytical procedure is expensive and time consuming, which is inappropriate for quick estimation of crude oil distillation characteristics. hirty three crude oil samples were characterized by means of BP distillation and ASM D-86. his paper presents an attempt to test the applicability of the major methods available in the open literature for converting ASM D-86 to BP for the whole range of the distillation curve. he whole distillation curve was obtained by using the Riazi s distribution model ((i-o)/o=[а /В.Ln( 1/(1-x i ))] 1/B ), which demonstrated high accuracy with r All methods demonstrated lower accuracy in converting the ASM D-86 into BP than the reproducibility of the ASM D Key words: crude oil, true boiling point, distillation, ASM D-2892, ASM D Introduction Having in mind that crude oil cost accounts for more than 8% of refinery expenditure the proper operation of crude distillation unit has great impact on refinery profitability. In order to find the adequate technological regime that provides maximum yields of high value products in a crude distillation unit the process engineer needs to have laboratory analyses data of crude oil that is processed in the unit. he rue boiling point distillation (BP) is the single most important information for any crude oil for modeling of a crude distillation column. he BP distillation tends to separate the individual mixture components relatively sharply in order of boiling point and is a good approximation of the separation that may be expected in the plant. Unfortunately the BP analyses are costly and time consuming, a BP analysis takes about 48 hours. hat is why it is impractical to use it as a tool for daily monitoring of the crude distillation unit operation. For refineries, which often switch the crude oils the lack of information about the crude oil quality could negatively impact the optimum operation and in this way the profitability of the crude distillation unit. It was found that boiling point distribution of crude oils and oil fractions obey the Riazi s distribution model [1] : i A B 1 1 x i 1/ B ln (1) Equation 1 can be converted into a linear form : where: Y C C. X 1 2 (2) Y ln ; X 1 ln ln ; 1 x i 1 B ; A B. exp( C1. B ) C 2

2 Ln((i-o)/o) Boiling emperature, oc A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , o = initial boiling point in K; i = temperature at which i per cent is distilled in K; xi = volume or weight part of distillate. Equation 2 has been tested on several hundreds samples of different crude oils, gas condensates, bitumen and oil fractions in the Lukoil Neftochim research laboratory and has been proved to be valid for all tested samples. Figure 1 is an illustration of validity of equation 2 applied to different distillation data of crude oil, straight run atmospheric residue, visbreaker residue, and visbreaker diesel. Regardless of the distillation method used (BP, ASM D-116, ASMD-5236, ASM D-86, ASM D-2887 and distillation according to Bogdanov GOS 112) the boiling point distribution is perfectly approximated by equations 1 and 2. It could be inferred from these data that one can safely extrapolate distillation curve from a set of data that does not cover the full distillation range of an oil. For example data of BP distillation of vacuum residue obtained in one of the Lukoil vacuum distillation units is given in able 1. Due to known limitation of the equipment the distillation was performed for temperature not higher than 54 C. Figure 2 presents graph of equation 2 applied for the data of able 1. It is evident from these data that eq.2 perfectly describes the boiling point distribution of the vacuum residue (r 2 =.9977). aking into account the proof of validity of equation 2 for the whole distillation range we can build the vacuum residue BP distillation curve (Figure 3) based on the data for A and B extracted from Figure 2. able 1 Distillation characteristics of Atmospheric Residue from Ural Crude Oil Properties Atmospheric Residue 1. 2 С, g /сm BP Distillation % % С С 38-4 С С С С С > 54 С Losses y =.586x R 2 =.9977 Ln(Ln(1/(1-xi)) Fig. 2 Application of the Riazi s model (eq.2) for approximation of BP distillation curve of Atmospheric Residue from Ural Crude Oil Distillate, wt.% Fig. 3 Full range BP distillation curve of Atmospheric Residue from Ural Crude Oil obtained by the use of the Riazi s model (eq.2) Following this way of thinking we decided to test applicability of equations 1 and 2 on ASM D-86 distillation of 33 crude oil samples with the aim to build the whole range (from to 99%) crude ASM D-86 distillation curve based on distillation data

3 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , boiling up to 3 C. he ASM D-86 distillation is performed within 45 minutes and for that reason it could be used for daily monitoring of the crude distillation unit operation if the whole crude oil curve is available and it could be converted into BP. Further we tested the ability of the methods available in the open literature for conversion of ASM D-86 into BP distillation of the crude oil samples investigated in this study. he aim of this paper is to discuss the obtained results 2. Experimental BP distillation of all 33 investigated crude oil samples was carried out in the AUODES 8 Fisher column according to АSM-D 2892 for the atmosphere part of the test and according to АSM-D 5236 for the vacuum one. he BP distillation was performed in the AUODES 8 Fisher column at pressure drop from 76 to 2 mmhg and in the AUODES 86 Fisher column from 1 to, 2 mmhg. he results of the BP distillation of the studied crude oil samples are presented in able 2. Distillation of the 33 crude oil samples up to 3 C was performed in accordance with ASM D-86 and the results of the distillation are given in able 3. he density at 2 C was analyzed according to АSM-D Results and Discussions able 4 presents data of BP distillation of the 33 crude oil samples estimated on the base of the parameters A and B computed by eq.2 and assuming =-11.7 C, which is the boiling point of isobutane. he isobutane is assumed to be the lightest compound in a crude oil [1]. he squared correlation coefficient r 2 for all crude oil samples except that of the Light Siberian crude oil is above.99. For the Light Siberian crude the r 2 =.9898 which is also high enough. his implies that the Riazi s distribution model describes very well the BP distillation curve of crude oil. able 5 presents data of ASM D-86 distillation of the 33 crude oil samples estimated on the base of the parameters A and B computed by eq.2. he squared correlation coefficient r 2 for all crude oil samples except that of the Buzachinmski crude oil is above.99. For the Buzachinmski crude the r 2 =.9751 which is also high. his indicates that the Riazi s distribution model also describes very well the ASM D-86 distillation curve of crude oil. It may be concluded that by the use of calculated A and B and the initial boiling point the distillation curve could be safely extrapolated to 99 vol.%. In other words by applying the Riazi s distribution model from ASM D-86 distillation data of a crude oil boiling up to 3 C it can be estimated the amount of compounds boiling above this temperature and build the full range distillation curve. In order to examine the capabilities of the available in the open literature correlations for conversion of ASM D-86 into BP distillation we had to convert the BP distillation data from weight % in volume % because all correlations convert ASM D-86 into BP vol.%. able VI presents data of BP distillation of the 33 crude oil samples in vol.% assuming constant Kw factor for all crude fractions and using the data from able 5. he squared correlation coefficient r 2 for this data set is above.99. here is number of empirical approaches for converting ASM D 86 distillations to true boiling point (BP) distillations. hree of them are the most applicable for engineering purposes. From chronological point of view the earliest method for conversion of the distillation curves is the method of Edmister [2]. It is a graphical approach, which was developed in the period First step in application of the method is definition of the BP 5% as a function of D 86 5% in Fahrenheit using the graph that is illustrated in Figure 3.

4 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , Figure 3 Relationship between ASM D 86 and BP distillation curves developed by Edmister and al. [2] Next step requires making a graphical definition of the temperature differences between the segments of ASM D 86 distillation curve (% 1%; 1% 3%; 3% 5%; 5% 7%; 7% 9% and 9% 1%) by means of the same graph. hese values are needed in order to define the correspondent temperature differences in BP. By means of defined temperature differences in BP and BP5%, which is available in advance, it is easy to draw the BP curve. able VII illustrates the corresponding values from Figure 3, which facilitate conversion procedure. Riazi-Daubert method for the interconversion of ASM D 86 distillations to BP distillations is based on the generalized correlation in the following form [3] : BP a ) b ( ASM D86 (3) where both BP and ASM temperatures are for the same vol.% distilled and are in Kelvin. Constants a and b at various points along the distillation curve with the range of application are given in able 8. able 8 Correlation constants in eq. 3 vol% a b range a, o C

5 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , Daubert and his group developed a different set of equations to convert ASM to BP, which is also known as a Daubert s method [3]. he following equation is used to convert an ASM D 86 distillation at 5% point temperature to a BP distillation 5% point temperature BP ( 5%) [ ASM D86(5%) 255.4] (4) where ASM (5%) and BP (5%) are temperatures at 5% volume distilled in Kelvin. Equation (4) can also be used in a reverse form to estimate ASM from BP. he following equation is used to determine the difference between two cut points: B Y i AX i Where: Y i = difference in BP temperature between two cut points, K; X i = observed difference in ASM D 86 temperature between two cut points, K; A, B = constants varying for each cut point and are given in able IX. able 9 Correlation constants in eq. 5 i Cut point range, % A B o determine the true boiling point temperature at any percent distilled, calculation should begin with 5% BP temperature and addition or subtraction of the proper temperature difference Y i. BP (%) = BP (5%) - Y 4 - Y 5 - Y 6 BP (1%) = BP (5%) - Y 4 - Y 5 BP (3%) = BP (5%) - Y 4 BP (7%) = BP (5%) + Y 3 BP (9%) = BP (5%) + Y 3 +Y 2 BP (1%) = BP (5%) + Y 3 + Y 2 + Y 1 he three approaches for conversion of ASM D 86 distillations to BP distillations were applied to the experimental data for 33 crude oil samples. ables 1-12 present data of absolute deviation calculated as measured value estimated value. he data in tables X-XII indicate that all three methods of conversion of ASM D 86 distillation to BP one used in this work: the Riazi-Daubert Conversion Method, the Daubert Conversion Method and the Edmister Conversion Method do not adequately predict BP distillation from data of ASM D-86 distillation data. he maximum deviation in the boiling temperature for each per cent evaporate should not go beyond 1 C. No one of the conversion method used do not achieve this requirement. herefore, a new method for conversion of ASM D 86 distillation to BP distillation applicable for crude oils should be developed. 4. Conclusions It was found in this work that distribution of boiling point of the compounds containing in 33 crude oil samples measured by BP or ASM D-86 can be approximated by the Riazi s distribution model: (5)

6 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , i A B ln 1 1 x i 1/ B his distribution model allows from incomplete distillation data the entire distillation curve of a crude oil to be built regardless of the method used for measuring of the distillation characteristics. On this base the entire distillation curve can be constructed by the use of ASM D-86 method for measuring of the evaporate boiling up to 3ºC. An attempt to apply the Riazi-Daubert Conversion Method, the Daubert Conversion Method and the Edmister Conversion Method for converting ASM D- 86 into BP of the investigated crude oils was found to be unsuccessful. herefore a new method for conversion of ASM D 86 distillation to BP distillation applicable for crude oils should be developed. Reference [1] Riazi, M.R., A Continuous Model for C 7+ Fraction Characterization of Petroleum Fluids, Ind. Eng. Chem. Res., vol. 36 (1), 1997, pp [2] Edmister, W.C., Pollock, D.H., Phase Relations for Petroleum Fractions, Chem. Eng. Progr., vol. 44, 1948, pp [3] Riazi, M.R., Characterization and Properties of Petroleum Fractions, American Society for esting and Materials, 25.

7 Ln((i-o)/o) Ln((i-o)/o)) Figure 1 Application of the Riazi s model (eq.2) for approximation of distillation curves of different crude and crude oil fractions by the use of different methods for measuring of distillation characteristics Ln((i-o)/o) Ln((i-o)/o) Ln((i-o)/o) Ln((i-o)/) Ln(Ln(1/(1-xi))) Ln(Ln(1/(1-xi))) A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , ASM D-2892 of Crude Oil y =.4828x R 2 = ASM D-5236 of Atm.Residue y =.5797x R 2 = ASM D-116 of Atm.Residue y =.733x R 2 = Ln(Ln(1/1-xi)) -1.5 Ln(Ln(1/1-xi)) -2.5 ASM D-116 of Visbreaker Residue y =.6338x R 2 = GOS 112 (Bogdanov) of Visbreaker Residue y =.8195x R 2 = ASM D-86 of Visbreaker Diesel y =.553x R 2 = Ln(LN(1/(1-xi)) -2.5 Ln(Ln(1/(1-xi)))

8 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 2 BP distillation of 33 crude oil samples Crude Oil Sample ASM D 2892 / D 5236, wt.% IBP UN UAP BUZ LIB LIB GOS SYR LIR LAR HIR AMCO LSYR KUW IRQ LSIB ZAIK ENG HUR UOR KUM URL REM LAZ REBCO REBCO REBCO ABCO ABCO ABCO ABCO ABCO ABCO ABCO

9 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 3 ASM D-86 distillation of 33 crude oil samples ASM D 86 Up to Up to 25ºC, 3ºC, %vol. %vol. Crude Oil Up to Up to Up to Up to Up to Up to Up to IBP, Sample 62ºC, 85ºC, 12ºC, 15ºC, 18ºC, 2ºC, 24ºC, ºC %vol. %vol. %vol. %vol. %vol. %vol. %vol. UN UAP BUZ LIB LIB GOS SYR LIR LAR HIR AMCO LSYR KUW IRQ LSIB ZAIK ENG HUR UOR KUM URL REM LAZ REBCO REBCO REBCO ABCO ABCO ABCO ABCO ABCO ABCO ABCO

10 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 4 BP distillation data (wt.%) of the crude oils under study Crude Oil Sample A B SG 5%wt., 1%wt, 3%wt, 5%wt, 7%wt, 9%wt, 95%wt, R² unesian uapse 92 ºC ºC ºC ºC ºC ºC ºC Buzachinmski Libyan Libyan Gulf of Suetz Syrian Light Iranian Light Arabian Heavy Iranian Arabian AMCO Light Syrian Kuwaitian Iraqi Light Siberrian Zaikinski engiz Heavy Ural Ural + Oil Residue Kumkol Ural REM Light Azerski REBCO REBCO REBCO Average Blend Sept Average Blend Oct Average Blend Apr Average Blend May Average Blend June Average Blend July Average Blend Sept

11 Crude Oil Sample IBP, ºC 5%, ºC 1%, ºC 3%, ºC 5%, ºC 7%, ºC 9%, ºC 95%, ºC R² A B unesian uapse Buzachinmski Libyan Libyan Gulf of Suetz Syrian Light Iranian Light Arabian Heavy Iranian Arabian AMCO Light Syrian Kuwaitian Iraqi Light Siberrian Zaikinski engiz Heavy Ural Ural + Oil Residue Kumkol Ural REM Light Azerski REBCO REBCO REBCO Average Blend Sept Average Blend Oct Average Blend Apr Average Blend May Average Blend June Average Blend July Average Blend Sept A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 5 ASM D-86 distillation data of the crude oils under study

12 Crude Oil Sample 5%, ºC 1%, ºC 3%, ºC 5%, ºC 7%, ºC 9%, ºC 95%, ºC R² A B unesian uapse Buzachinmski Libyan Libyan Gulf of Suetz Syrian Light Iranian Light Arabian Heavy Iranian Arabian AMCO Light Syrian Kuwaitian Iraqi Light Siberrian Zaikinski engiz Heavy Ural Ural + Oil Residue Kumkol Ural REM Light Azerski REBCO REBCO REBCO Average Blend Sept Average Blend Oct Average Blend Apr Average Blend May Average Blend June Average Blend July Average Blend Sept A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 6 BP distillation data (vol.%) of the crude oils under study

13 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 7 Edmister conversion data for transforming of ASM D-86 into BP Segment of Destillation Curve, Volume Percent D-86 5% ºF BP 5% ºF D-86 ºF BP ºF D-86 ºF BP ºF D-86 ºF BP ºF D-86 ºF BP ºF D-86 ºF BP ºF D-86 ºF BP ºF D-86 5% to BP 5% to 1% 1 to 3% 3-5% 5-7% 7-9% 9 to 1%

14 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 1 ASM D-86 to BP volume fraction according to Riazi-Daubert Conversion Method Crude Oil Sample 1%, ºC 3%, ºC 5%, ºC 7%, ºC 9%, ºC 95%, ºC Δ abs Δ abs Δ abs Δ abs Δ abs Δ abs unesian uapse Buzachinmski Libyan Libyan Gulf of Suetz Syrian Light Iranian Light Arabian Heavy Iranian Arabian AMCO Light Syrian Kuwaitian Iraqi Light Siberrian Zaikinski engiz Heavy Ural Ural + Oil Residue Kumkol Ural REM Light Azerski REBCO REBCO REBCO Average Blend Sept Average Blend Oct Average Blend Apr Average Blend May Average Blend June Average Blend July Average Blend Sept Abs. average deviation, C

15 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 11 ASM D-86 to BP volume fraction according to Daubert Conversion Method Crude Oil Sample 1%, ºC 3%, ºC 5%, ºC 7%, ºC 9%, ºC 95%, ºC Δ abs Δ abs Δ abs Δ abs Δ abs Δ abs unesian uapse Buzachinmski Libyan Libyan Gulf of Suetz Syrian Light Iranian Light Arabian Heavy Iranian Arabian AMCO Light Syrian Kuwaitian Iraqi Light Siberrian Zaikinski engiz Heavy Ural Ural + Oil Residue Kumkol Ural REM Light Azerski REBCO REBCO REBCO Average Blend Sept Average Blend Oct Average Blend Apr Average Blend May Average Blend June Average Blend July Average Blend Sept Abs. average deviation, C

16 A. Nedelchev, D. Stratiev, A.Ivanov, G. Stoilov/Petroleum & Coal, 53(4) , able 12 ASM D-86 to BP volume fraction according to Edmister Conversion Method Crude Oil Sample 1%, ºC 3%, ºC 5%, ºC 7%, ºC 9%, ºC 95%, ºC Δ abs Δ abs Δ abs Δ abs Δ abs Δ abs unesian uapse Buzachinmski Libyan Libyan Gulf of Suetz Syrian Light Iranian Light Arabian Heavy Iranian Arabian AMCO Light Syrian Kuwaitian Iraqi Light Siberrian Zaikinski engiz Heavy Ural Ural + Oil Residue Kumkol Ural REM Light Azerski REBCO REBCO REBCO Average Blend Sept Average Blend Oct Average Blend Apr Average Blend May Average Blend June Average Blend July Average Blend Sept Abs. average deviation, C