Characterization of crude oil by simulated distillation

Abstract

A system and a method for calculating the cetane number, pour point, cloud point and aniline point of gas oil fractions of a crude oil sample from the density and gas chromatographic simulated distribution of the sample.

Claims

1. A system for evaluating a crude oil sample and calculating indicative properties of a gas oil fraction of the crude oil without first distilling the gas oil fraction, the system comprising: a gas chromatograph; a non-volatile memory device that stores calculation modules and data; a processor coupled to the non-volatile memory; a first calculation module that calculates a mid boiling point of the crude oil sample from simulated distillation data obtained from the gas chromatograph; a second calculation module that calculates as one of the indicative properties the cetane number for the gas oil fraction of the crude oil from a two-variable polynomial equation with a first set of predetermined constant coefficients developed using linear regression techniques; a third calculation module that calculates as one of the indicative properties the pour point for the gas oil fraction of the crude oil from the two-variable polynomial equation with a second set of predetermined constant coefficients developed using linear regression techniques; a fourth calculation module that calculates as one of the indicative properties the cloud point for the gas oil fraction of the crude oil from the two-variable polynomial equation with a third set of predetermined constant coefficients developed using linear regression techniques; and a fifth calculation module that calculates as one of the indicative properties the aniline point for the gas oil fraction of the crude oil from the two-variable polynomial equation with a fourth set of predetermined constant coefficients developed using linear regression techniques; a sixth calculation module that determines from the indicative properties the nature of products that can be manufactured from the crude oil; and a seventh calculation module that determines an appropriate refining technology to allow the gasoline and gas oil fractions to be processed most efficiently and effectively; wherein the two variables of the two-variable polynomial equation are the mid boiling point and the density of the crude oil sample.

2. A method for evaluating a crude oil sample to calculate indicative properties of a gas oil fraction of the crude oil without first distilling the gas oil fraction, the method comprising: subjecting said crude oil sample to gas chromatographic simulated distillation (SD) analysis; obtaining the density of the crude oil sample; calculating a mid boiling point of the crude oil sample from SD data obtained from the gas chromatographic SD analysis; calculating as one of the indicative properties the cetane number for the gas oil fraction from a two-variable polynomial equation with a first set of predetermined constant coefficients developed using linear regression techniques; calculating as one of the indicative properties the pour point for the gas oil fraction from the two-variable polynomial equation with a second set of predetermined constant coefficients developed using linear regression techniques; calculating as one of the indicative properties the cloud point for the gas oil fraction from the two-variable polynomial equation with a third set of predetermined constant coefficients developed using linear regression techniques; calculating as one of the indicative properties the aniline point for the gas oil fraction from the two-variable polynomial equation with a fourth set of predetermined constant coefficients developed using linear regression techniques; determining from the indicative properties the nature of products that can be manufactured from the crude oil; and determining an appropriate refining technology to allow the gasoline and gas oil fractions to be processed most efficiently and effectively, wherein the two variables of the two-variable polynomial equation are the mid boiling point and the density of the crude oil sample.

3. The method of claim 2, wherein the SD data is obtained from gas chromatography methods including ASTM D2887, ASTM D5236, ASTM D5399, ASTM D6352-04, ASTM D7213-05e1, ASTM D7398-07, ASTM D7169-05, ASTM D7096-10, ASTM D7500-10, and ASTM D5307-97.

4. The method of claim 2, wherein the SD data is obtained from supercritical fluid chromatography methods.

5. The method of claim 2, wherein the mid-boiling point is the mid-boiling point of whole crude oil.

6. The method of claim 2, wherein the mid-boiling point of the crude oil is calculated at the 50 W % point of the SD data.

7. The method of claim 2, wherein the mid-boiling point of the crude oil is calculated by taking the average of boiling points.

8. The method of claim 2, wherein the mid-boiling point of the crude oil is calculated by taking the weighted average of boiling points.

9. The method of claim 2, wherein correlative SD data is obtained from distillation methods selected from the group composed of ASTM D86, ASTM D1160, ASTM D2892, or any other methods based upon true boiling point distillation, supercritical fluid chromatography, and equilibrium flash.

10. The method of claim 9, wherein the true boiling point distillations were conducted in a column with a number of theoretical trays in the range 0-100.

11. The method of claim 9, wherein the true boiling point distillations were conducted in a column with a number of theoretical trays in the range 10-30.

12. The method of claim 9, wherein the true boiling point distillations were conducted in a column with a number of theoretical trays in the range 15-20.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and features of the present invention will become apparent from the following detailed description of the invention when considered with reference to the accompanying drawings, in which:

(2) FIG. 1 is a graphic plot of simulated distillation data obtained from gas chromatography for three types of crude oil;

(3) FIG. 2 is a process flow diagram of steps carried out to establish a value for indicative properties of a gas oil fraction, using the system and method of the present invention; and

(4) FIG. 3 is a block diagram of a component of a system for implementing the invention, according to one preferred embodiment of the present invention.

DETAILED DESCRIPTION OF INVENTION

(5) Crude oils' simulated distillation were obtained by gas chromatography according to the ASTM Method 5236 and/or its derivation for high temperature.

(6) The indicative properties (i.e., the cetane number, pour point, cloud point and aniline point) of the gas oil fraction boiling in the range 180-370° C. can be predicted from the density (at 15° C./4° C.) and the mid boiling point of the gas oil or whole crude oil (T.sub.MBP), measured in Kelvin. FIG. 2 shows a process flowchart of steps that occur after gas chromatography is completed and the results are tabulated. In step 210, the cetane number is calculated. In step 220, the pour point is calculated. In step 230, the cloud point is calculated. In step 240, the aniline point is calculated. In step 250, the octane number is calculated. While FIG. 2 shows the steps performed sequentially, they can be performed in any order.

(7) That is,
Indicative Property=f(density(15/4).sub.crude oil,T.sub.MBP(K).sub.gas oil)  (1a);
Indicative Property=f(density(15/4).sub.crude oil,T.sub.MBP(K).sub.crude oil)  (1b);

(8) Equations (2) through (5) show, respectively, the cetane number, pour point, cloud point and aniline point that can be predicted from the density and simulated distillation of crude oils.
Cetane Number (CET)=K.sub.CETX1.sub.CET*DEN+X2.sub.CET*DEN.sup.2+X3.sub.CET*DEN.sup.3+X4.sub.CET*(T.sub.MBP/1000)+X5.sub.CET*(T.sub.MBP/1000).sup.2+X6.sub.CET*(T.sub.MBP/1000)+X7.sub.CET*DEN*(T.sub.MBP/1000)  (2);
Pour Point (PP)=K.sub.PP+X1.sub.PP*DEN+X2.sub.PP*DEN.sup.2+X3.sub.PP*DEN.sup.3+X4.sub.PP*(T.sub.MBP/1000)+X5.sub.PP*(T.sub.MBP/1000)+X6.sub.PP*(T.sub.MBP/1000).sup.3+X7.sub.PP*DEN*(T.sub.MBP/1000)  (3);
Cloud Point (CP)=K.sub.CP+X1.sub.CP*DEN+X2.sub.CP*DEN.sup.2+X3.sub.CP*DEN.sup.3+X4.sub.CP*(T.sub.MBP/1000)+X5.sub.CP*(T.sub.MBP/1000)+X6.sub.CP*(T.sub.MBP/1000).sup.3+X7.sub.CP*DEN*(T.sub.MBP/1000)  (4);
Aniline Point (AP)=K.sub.AP+X1.sub.AP*DEN+X2*DEN.sup.2+X3.sub.AP*DEN.sup.3+X4.sub.AP*(T.sub.MBP/1000)+X5.sub.AP*(T.sub.MBP/1000).sup.2+X6.sub.AP*(T.sub.MBP/1000).sup.3+X7.sub.AP*DEN*(T.sub.MBP/1000)  (5);

(9) where:

(10) DEN=density of the crude oil sample;

(11) T.sub.MBP=mid boiling point of the gas oil or crude oil (derived from the simulated distillation curves of crude oils);

(12) and K.sub.CET, X1.sub.CET-X7.sub.CET, K.sub.PP, X1.sub.PP-X7.sub.PP, K.sub.CP, X1.sub.CP-X7.sub.CP, K.sub.AP, and X1.sub.AP-X7.sub.AP are constants that were developed using linear regression techniques, and which are given in Table 3.

(13) TABLE-US-00003 TABLE 3 Cetane Number Pour Point Cloud Point Aniline Point Property (CET) (PP) (CP) (AP) K 544509.8 1344488.4 395024.0 24390.7 X1 −1932359.8 −4907366.2 −1429569.6 −49357.1 X2 2161099.3 5503008.0 1604628.0 52455.3 X3 −796440.7 −2031119.7 −592968.1 −18616.3 X4 142762.7 527938.4 136360.5 −41985.4 X5 −177339.2 −699945.0 −177392.5 65171.0 X6 90209.8 361176.8 91570.3 −33881.4 X7 −30458.6 −87436.2 −25137.2 408.8

(14) Note that as an alternative to determining the mid boiling point of the oil stream at the 50 W % point of the simulated distillation data, it may be calculated by taking the average of boiling points. Alternatively, it may be calculated as a weighted average boiling point (WABP), as shown in equation (6), below.

(15) $\begin{array}{cc}WABP=\frac{\left(T_{10}*10\right)+\left(T_{30}*30\right)+\left(T_{50}*50\right)+\left(T_{70}*70\right)+T_{90}*90)}{10+30+50+70+90},& \left(6\right)\end{array}$

(16) where T.sub.10 is the boiling temperature of oil determined when 10 W % or V % of the fraction is recovered during the distillation, and where T.sub.30, T.sub.50, T.sub.70 and T.sub.90 are determined accordingly. An example calculation of WABP is presented below. When the sample is distilled, the boiling point of the sample is determined to be 149° C. when 10 W % of the sample is recovered. Thus, T.sub.10 is 149° C., and the other figures are determined similarly:

(17) TABLE-US-00004 W % Recovered 10 30 50 70 90 Boiling 149 230 282 325 371 Temperature, ° C.

(18) $WABT=\left[149*10+230*30+282*50+325*70+371*90\right]/\hspace{1em}\left[10+30+50+70+90\right]=315$

(19) The following example is provided to demonstrate an application of equations (2) through (5). A sample of Arabian medium crude with a 15° C./4° C. density of 0.8828 Kg/I was analyzed by gas chromatography using the ASTM D2887 method. The simulated distillation data is shown in Table 4:

(20) TABLE-US-00005 TABLE 4 W % Temp. ° C. 0 1 2 37 3 68 4 83 5 94 6 100 7 113 8 121 9 127 10 138 11 144 12 151 13 157 14 165 15 172 16 175 17 185 18 191 19 196 20 204 21 210 22 216 23 222 24 229 25 235 26 241 27 249 28 255 29 261 30 267 31 272 32 279 33 285 34 290 35 297 36 303 37 308 38 315 39 319 40 326 41 331 42 337 43 342 44 348 45 354 46 360 47 366 48 372 49 378 50 384 51 390 52 396 53 402 54 409 55 415 56 422 57 428 58 434 59 440 60 446 61 452 62 458 63 465 64 471 65 478 66 485 67 492 68 499 69 506 70 513 71 520 72 528 73 535 74 543 75 551 76 559 77 567 78 575 79 583 80 592 81 599 82 608

(21) The mid boiling point of the crude oil is taken from the data at the 50 W % point, which is 384° C. (657 K).

(22) Applying equation 2 and the constants from Table 3,

(23) $\mathrm{Cetane}\mathrm{Number}\left(\mathrm{CET}\right)=K_{\mathrm{CET}}+X{1}_{\mathrm{CET}}*\mathrm{DEN}+X{2}_{\mathrm{CET}}*{\mathrm{DEN}}^2+X{3}_{\mathrm{CET}}*{\mathrm{DEN}}^3+X{4}_{\mathrm{CET}}*\left(T_{\mathrm{MBP}}\text{/}1000\right)+X{5}_{\mathrm{CET}}*{\left(T_{\mathrm{MBP}}\text{/}1000\right)}^2+X{6}_{\mathrm{CET}}*{T\left(T_{\mathrm{MBP}}\text{/}1000\right)}^3+X{7}_{\mathrm{CET}}*\mathrm{DEN}*\left(T_{\mathrm{MBP}}\text{/}1000\right)=(544509.8)+(-1932359.8)\left(0.8828\right)+\left(2161099.3\right){\left(0.8828\right)}^2+\left(-796440.7\right){\left(0.8828\right)}^3+\left(142762.7\right)\left(657\text{/}1000\right)+(-177339.2){\left(657\text{/}1000\right)}^2+\left(90209.8\right){\left(657\text{/}1000\right)}^3+\left(-30458.6\right)\left(0.8828\right)\left(657\text{/}1000\right)=59$

(24) Applying equation 3 and the constants from Table 3,

(25) $\mathrm{Pour}\mathrm{Point}\left(\mathrm{PP}\right)=K_{\mathrm{PP}}+X{1}_{\mathrm{PP}}*\mathrm{DEN}+X{2}_{\mathrm{PP}}*{\mathrm{DEN}}^2+X{3}_{\mathrm{PP}}*{\mathrm{DEN}}^3+X{4}_{\mathrm{PP}}*\left(T_{\mathrm{MBP}}\text{/}1000\right)+X{5}_{\mathrm{PP}}*{\left(T_{\mathrm{MBP}}\text{/}1000\right)}^2+X{6}_{\mathrm{PP}}*{\left(T_{\mathrm{MBP}}\text{/}1000\right)}^3+X{7}_{\mathrm{PP}}*\mathrm{DEN}*\left(T_{\mathrm{MBP}}\text{/}1000\right)=(1344488.4)+\left(-4907366.2\right)\left(0.8828\right)+(5503008.06){\left(0.8828\right)}^2+(-2031119.7){\left(0.8828\right)}^3+(527938.4)\left(657\text{/}1000\right)+(-699945.0){\left(657\text{/}1000\right)}^2+(361176.8){\left(657\text{/}1000\right)}^3+(-87436.2)(0.8828)\left(657\text{/}1000\right)=-10$

(26) Applying equation 4 and the constants from Table 3,

(27) $\mathrm{Cloud}\mathrm{Point}\left(\mathrm{CP}\right)=K_{\mathrm{CP}}+X{1}_{\mathrm{CP}}*\mathrm{DEN}+X{2}_{\mathrm{CP}}*{\mathrm{DEN}}^2+X{3}_{\mathrm{CP}}*{\mathrm{DEN}}^3+X{4}_{\mathrm{CP}}*\left(T_{\mathrm{MBP}}\text{/}1000\right)+X{5}_{\mathrm{CP}}*{\left(T_{\mathrm{MBP}}\text{/}1000\right)}^2+X{6}_{\mathrm{CP}}*{\left(T_{\mathrm{MBP}}\text{/}1000\right)}^3+X{7}_{\mathrm{CP}}*\mathrm{DEN}*\left(T_{\mathrm{MBP}}\text{/}1000\right)=(39502.0)+(-1429569.6)\left(0.8828\right)+\left(1604628.0\right){\left(0.8828\right)}^2+\left(-592968.1\right){(0.8828)}^3+(136360.5)\left(657\text{/}1000\right)+(-177392.5){\left(657\text{/}1000\right)}^2+(91570.3){\left(657\text{/}1000\right)}^3+(-25137.2)(0.8828)\left(657\text{/}1000\right)=-10$

(28) Applying equation 5 and the constants from Table 3,

(29) $\mathrm{Aniline}\mathrm{Point}\left(\mathrm{AP}\right)=K_{\mathrm{AP}}+X{1}_{\mathrm{AP}}*\mathrm{DEN}+X{2}_{\mathrm{AP}}*{\mathrm{DEN}}^2+X{3}_{\mathrm{AP}}*{\mathrm{DEN}}^3+X{4}_{\mathrm{AP}}*\left(T_{\mathrm{MBP}}\text{/}1000\right)+X{5}_{\mathrm{AP}}*{\left(T_{\mathrm{MBP}}\text{/}1000\right)}^2+X{6}_{\mathrm{AP}}*{\left(T_{\mathrm{MBP}}\text{/}1000\right)}^3+X{7}_{\mathrm{AP}}*\mathrm{DEN}*\left(T_{\mathrm{MBP}}\text{/}1000\right)=(24390.7)+(-49357.1)\left(0.8828\right)+(52455.3){\left(0.8828\right)}^2+\left(-18616.3\right){\left(0.8828\right)}^3+\left(-41985.4\right)\left(657\text{/}1000\right)+(65171.0){\left(657\text{/}1000\right)}^2+(-33881.4){\left(657\text{/}1000\right)}^3+(408.8)\left(0.8828\right)\left(657\text{/}1000\right)=66$

(30) The method is applicable for naturally occurring hydrocarbons derived from crude oils, bitumens, heavy oils, shale oils and from refinery process units including hydrotreating, hydroprocessing, fluid catalytic cracking, coking, and visbreaking or coal liquefaction.

(31) FIG. 3 illustrates one embodiment of the present invention, implemented in a computer system 300, with a number of modules. Computer system 300 includes a processor 310, and a memory unit 370. Memory unit 370 stores software program modules and associated data, and in particular stores a cetane number calculation module 210, a pour point calculation module 220, a cloud point calculation module 230, an aniline point calculation module 240, and an octane number calculation module 250.

(32) The system and method of the present invention have been described above and with reference to the attached figure; however, modifications will be apparent to those of ordinary skill in the art and the scope of protection for the invention is to be defined by the claims that follow.