Treatment of Heavy Oils to Reduce Olefin Content

Abstract

A process for treating heavy oil to provide a treated heavy oil having a reduced density and viscosity, as well as an olefin content that does not exceed 1.0 wt. %. The process comprises separating the initial heavy oil into a first fraction, which in general contains lower-boiling components, and a second fraction. The second fraction comprises a heavy oil having a p-value of at least 5% greater than the p-value of the initial heavy oil prior to separating the initial heavy oil into the first fraction and the second fraction, and the second fraction has an aromaticity that is no more than 5% less than the aromaticity of the initial heavy oil prior to separating the initial heavy oil into the first fraction and the second fraction. The second fraction then is upgraded to reduce the density and viscosity of the heavy oil. After the second fraction is upgraded, it is recombined with at least a portion of the first fraction to provide a treated heavy oil having an olefin content that does not exceed 1.0 wt. %. The separation of the initial heavy oil into first and second fractions enables one to achieve improved reduction of the density and viscosity of the treated heavy oil while maintaining the olefin content at an acceptable level.

Claims

1. A process for treating a heavy oil to provide a treated heavy oil having a reduced density and viscosity, and an olefin content that does not exceed 1.0 wt. %, comprising: (a) separating an initial heavy oil into a first fraction and a second fraction, wherein said second fraction comprises a heavy oil having a p-value of at least 5% greater than the p-value of said initial heavy oil prior to separating said initial heavy oil into said first fraction and said second fraction, and said second fraction has an aromaticity that is no more than 5% less than the aromaticity of said initial heavy oil prior to separating said initial heavy oil into said first fraction and said second fraction; (b) reducing the density and viscosity of said second fraction; and (c) combining said second fraction with at least a portion of said first fraction to provide a treated heavy oil having an olefin content that does not exceed 1.0 wt. %.

2. The process of claim 1 wherein said first fraction has a boiling range that does not exceed 450 C.

3. The process of claim 2 wherein said first fraction has a boiling range that does not exceed 325 C.

4. The process of claim 3 wherein said first fraction has a boiling range that does not exceed 250 C.

5. The process of claim 4 wherein said first fraction has a boiling range that does not exceed 180 C.

6. The process of claim 5 wherein said first fraction has a boiling range that does not exceed 150 C.

7. The process of claim 1 wherein said second fraction has a p-value which is at least 10% greater than the p-value of said initial heavy oil prior to separating said initial heavy oil into said first fraction and said second fraction.

8. The process of claim 7 wherein said second fraction has a p-value which is at least 15% greater than the p-value of said initial heavy oil prior to separating said initial heavy oil into said first fraction and said second fraction.

9. The process of claim 8 wherein said second fraction has a p-value which is at least 25% greater than the p-value of said initial heavy oil prior to separating said initial heavy oil into said first fraction and said second fraction.

10. The process of claim 1 wherein said second fraction has an aromaticity that is no more than 3% less of the aromaticity of said initial heavy oil prior to separating said initial heavy oil into said first fraction and said second fraction.

11. The process of claim 10 wherein said second fraction has an aromaticity that is at least 3% greater than the aromaticity of said initial heavy oil prior to separation of initial said heavy oil into said first fraction and said second fraction.

12. The process of claim 11 wherein said second fraction has an aromaticity that is at least 5% greater than the aromaticity of said initial heavy oil prior to separation of said initial heavy oil into said first fraction and said second fraction.

13. The method of claim 1 wherein the density and viscosity of said second fraction are reduced by heating said second fraction to a temperature of from about 200 C. to about 600 C.

14. The method of claim 13 wherein the density and viscosity of said second fraction are reduced by heating said second fraction to a temperature of from about 350 C. to about 450 C.

15. The method of claim 14 wherein the density and viscosity of said second fraction are reduced by heating said second fraction to a temperature of from about 380 C. to about 420 C.

16. The method of claim 13 where said second fraction is heated for a period of time of from about 1 minute to about 20 minutes.

17. The method of claim 16 wherein said second fraction is heated for a period of time of from about 3 minutes to about 8 minutes.

18. The method of claim 1 wherein the density and viscosity of said second fraction are reduced by subjecting said second fraction to cavitation.

19. The method of claim 18 wherein said second fraction is subjected to hydrodynamic cavitation.

20. The method of claim 19 wherein said second fraction is subjected to hydrodynamic cavitation by passing said second fraction from a conduit through a cavitation zone, wherein the ratio of the width of said cavitation zone to the width of said conduit is from about 1/230 to 1/75.

21. The method of claim 20 wherein the ratio of the length of the cavitation zone to the width of the cavitation zone is from about 10 to about 125.

22. The method of claim 21 wherein the ratio of the length of the cavitation zone to the width of the cavitation zone is from about 50 to about 125.

23. The method of claim 1 wherein the density and viscosity of said second fraction are reduced by heating said second fraction to a temperature of from about 200 C. to about 600 C., and then subjecting said second fraction to cavitation.

24. The method of claim 23 wherein said second fraction is heated to a temperature of from about 350 C. to about 450 C.

25. The method of claim 24 wherein said second fraction is heated to a temperature of from about 380 C. to about 420 C.

26. The method of claim 23 wherein said second fraction is subjected to hydrodynamic cavitation.

27. The method of claim 26 wherein said second fraction is subjected to hydrodynamic cavitation by passing said second fraction from a conduit through a cavitation zone, wherein the ratio of the width of said cavitation zone to the width of said conduit is from about 1/230 to 1/75.

28. The method of claim 27 wherein the ratio of the length of the cavitation zone to the width of the cavitation zone is from about 10 to about 125.

29. The method of claim 28 wherein the ratio of the length of the cavitation zone to the width of the cavitation zone is from about 50 to about 125.

30. The method of claim 1 wherein the density and viscosity of said second fraction are reduced by subjecting said second fraction to a hydrogen addition process.

Description

[0033] The invention now will be described with respect to the drawings, wherein.

[0034] FIG. 1 is a schematic of an embodiment of the method for treating a heavy oil in accordance with the present invention;

[0035] FIG. 2 is a graph showing density upgrade (% kg/m.sup.3) versus olefin measurement (gBr.sub.2/100 g) of an upgraded heavy oil that was fractionated to remove a 250 C..sup. fraction prior to upgrading, followed by reblending with the 250 C..sup. fraction, compared to a non-fractionated upgraded heavy oil;

[0036] FIG. 3 is a graph showing viscosity upgrade (% cSt) versus olefin measurement (gBr.sub.2/100 g) of an upgraded heavy oil that was fractionated to remove a 250 C..sup. fraction prior to upgrading, followed by reblending with the 250 C..sup. fraction, compared to a non-fractionated upgraded heavy oil;

[0037] FIG. 4 is a graph showing density upgrade (% kg/m.sup.3) versus olefin measurement (gBr.sub.2/100 g) of an upgraded heavy oil that was fractionated to remove a 180 C..sup. fraction prior to upgrading, following by reblending with the 180 C..sup. fraction, compared to a non-fractionated heavy oil; and

[0038] FIG. 5 is a graph showing density upgrade (% kg/m.sup.3) versus olefin measurement (gBr.sub.2/100 g) of an upgraded heavy oil that was fractionated to remove a 325 C..sup. fraction prior to upgrading, followed by reblending with the 325 C..sup. fraction, compared to a non-fractionated heavy oil.

[0039] Referring now to FIG. 1, an initial heavy oil in line 10 is pumped and heated and sent to fractionator 11. Fractionator 11 is operated under conditions such that the heavy oil is separated into two fractions, i.e., a first fraction and a second fraction. In general, the first fraction is a lower-boiling fraction that includes light components such as diluents, water vapor, aliphatic hydrocarbons, and paraffinic hydrocarbons. The second fraction is a heavy oil that has a p-value that is at least 5% greater than the p-value of the initial heavy oil prior to the separation of the initial heavy oil into the first fraction and the second fraction, and has an aromaticity that is no more than 5% less than the aromaticity of the initial heavy oil prior to the separation of the initial heavy oil into the first fraction and the second fraction. In general, fractionator 11 is operated at a temperature of no more than 450 C. Thus, the first fraction boils at a temperature that does not exceed 450 C. Fractionator 11 may be operated, in non-limiting embodiments, at temperatures that exceed slightly, for example, boiling points of 325 C., 250 C., 180 C., or 150 C., thereby providing first fractions that boil at temperatures that do not exceed 325 C., 250 C., 180 C., and 150 C., respectively.

[0040] The first fraction, including the lower-boiling compounds, or light components, is withdrawn from fractionator 11 through line 12 and passed to knock-out drum 17. Off gases are withdrawn from knock-out drum 17 through line 19, while the remainder of the first, or light, fraction is withdrawn from knock-out drum 17 through line 18. Thus, a fraction that has low-boiling point, or that has light, components is separated from the second fraction, whereby the second fraction is a heavy oil that contains a minimal amount of components that may not be converted easily to olefins during further upgrading of the second fraction.

[0041] The second fraction is withdrawn from fractionator 11 through line 13 and subjected to further upgrading to reduce the density and viscosity of the heavy oil, schematically indicated as 14. For example, the second fraction may be subjected to thermal treatment at a temperature of about 200 C. to about 600 C. for a period of time of from about 1 minute to about 20 minutes, and then subjected to hydrodynamic cavitation by passing the second fraction through a restriction or nozzle such as those hereinabove described and at a velocity and pressure as hereinabove described. It is to be understood, however, that the scope of the present invention is not to be limited to any specific upgrading processes for reducing the density and viscosity of the second fraction.

[0042] After the second fraction is upgraded, incondensable gases or off gases are withdrawn from upgrading zone 14 through line 16, while the remainder of the second fraction, which is a heavy oil having a reduced density and viscosity, is withdrawn from upgrading zone 14 through line 15.

[0043] The light fraction in line 18 then is passed to line 15, whereby the first, or light, fraction is recombined with the second fraction. Prior to being passed to line 15, a portion of the light fraction may be withdrawn from line 18 through line 20.

[0044] The recombination of at least a portion of the light fraction from line 18 with the second fraction in line 15 provides a combined heavy oil stream in line 21 that has an olefin content that does not exceed 1.0 wt. %, and has a reduced density and viscosity, whereby such oil is pumpable and transportable, and can be subjected to further processing, such as refining.

EXAMPLES

[0045] The invention now will be described with respect to the following examples; however, the scope of the present invention is not intended to be limited thereby.

Example 1

[0046] A heavy oil having a p-value of 3.20 and an aromaticity of 31% is distilled such that fractions having boiling points of 180 C., 250 C., or 325 C. were removed. The recovered volumes, in percent, of the fractions removed by distillation, and the p-values and aromaticity increases for the remaining heavy oils, are measured for each fraction.

[0047] The results are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Distillation Recovered Temperature Volume P-value Aroma- Aromaticity ( C.) (%) P-value increase (%) ticity Increase (%) Undistilled 0.0% 3.20 0.0% 31% 0.0% 180 13.0% 3.57 11.6% 32% 3.2% 250 18.0% 3.58 11.9% 32% 3.2% 325 22.0% 3.54 10.6% 30% 3.2%

[0048] The above results show that, when fractions that boil at temperatures of no more than 180 C., or no more than 250 C., or no more than 325 C., are removed from the heavy oil, there is provided a heavy oil having improved solubility of asphaltenes, as shown by the increase in the p-value by over 10%, while the aromaticity of the heavy oil remains at acceptable levels.

Example 2

[0049] A heavy oil was distilled or flashed to remove a 250 C..sup. fraction. The inlet temperature at the distillation or fractionation column was 273 C. The 250 C..sup.+ heavy oil fraction then was treated thermally by heating to temperatures of 390 C., 400 C., 410 C., and 420 C. for a period of time of 6 minutes. This oil then was subjected to cavitation by passing the oil through a cavitation nozzle having a length of 1 inch and a diameter of 0.008 inch.

[0050] After the 250 C..sup.+ heavy oil fraction was subjected to cavitation, it was recombined with the 250 C..sup. fraction.

[0051] A second heavy oil sample then was subjected to a thermal treatment and hydrodynamic cavitation as hereinabove described, to reduce the density and viscosity of the heavy oil, but a lower-boiling 250 C. fraction was not removed from this heavy oil sample prior to subjecting the heavy oil to the thermal treatment and hydrodynamic cavitation.

[0052] FIGS. 2 and 3 show the olefin content (measured in terms of the bromine number as gBr.sub.2/100 g) for both samples as a function of density and viscosity upgrades, respectively, for all thermal treatment temperatures. The results show that the removal of the 250 C..sup. fraction from the heavy oil, permits greater density and viscosity reduction with respect to a given level of olefins. Conversely, the removal of the 250 C..sup. fraction from the heavy oil, prior to the upgrading of the heavy oil, provides a heavy oil with an improved reduced olefin content with respect to a given density reduction and a given viscosity reduction.

Example 3

[0053] A heavy oil was distilled or flashed to remove a 180 C..sup. fraction. The inlet temperature at the distillation or fractionation column was 205 C. The 180 C..sup.+ heavy oil fraction then was treated thermally by heating to temperatures of 390 C., 400 C., 410 C., and 420 C. for a period of time of 6 minutes. This oil then was subjected to hydrodynamic cavitation by passing the oil through a cavitation nozzle having a length of 1 inch and a diameter of 0.008 inch. After the 180 C..sup.+ heavy oil fraction was subjected to cavitation, thereby providing a heavy oil with reduced density and viscosity, it was recombined with the 180 C..sup. fraction.

[0054] A second heavy oil sample then was subjected to a thermal treatment and hydrodynamic cavitation as hereinabove described to reduce the density and viscosity of the heavy oil, but a lower-boiling 180 C..sup. fraction was not removed from the heavy oil sample prior to subjecting the heavy oil to the thermal treatment and hydrodynamic cavitation.

[0055] FIG. 4 shows the olefin content (measured in terms of the bromine number as gBr.sub.2/100 g) for both samples as a function of density reduction for all thermal treatment temperatures. The results show that the removal of the 180 C..sup. fraction from the heavy oil, prior to the upgrading of the heavy oil, permits a greater density reduction with respect to a given level of olefins. Conversely, the removal of the 180 C..sup. fraction from the heavy oil, prior to the upgrading of the heavy oil, provides a heavy oil with an improved reduced olefin content with respect to a given density reduction.

Example 4

[0056] A heavy oil was distilled or flashed to remove a 325 C..sup. fraction. The inlet temperature at the distillation or fractionation column was 345 C. The 325 C..sup.+ heavy oil fraction was treated thermally by heating to temperatures of 390 C., 400 C., 410 C., and 420 C. for a period of time of 6 minutes. This oil then was subjected to hydrodynamic cavitation by passing the oil through a cavitation nozzle having a length of 1 inch and a diameter of 0.008 inch.

[0057] After the 325 C..sup.+ heavy oil fraction was subjected to cavitation, thereby providing a heavy oil having a reduced density and viscosity, it was recombined with the 325 C..sup. fraction.

[0058] A second heavy oil sample then was subjected to a thermal treatment and hydrodynamic cavitation as hereinabove described to reduce the density and viscosity of the heavy oil, but a lower-boiling 325 C..sup. fraction was not removed from the heavy oil prior to subjecting the heavy oil to the thermal treatment and hydrodynamic cavitation.

[0059] FIG. 5 shows the olefin content (measured in terms of the bromine number as gBr.sub.2/100 g) for both samples as a function of density upgrades for all thermal treatment temperatures. The results shows that the removal of the 325 C..sup. fraction from the heavy oil, prior to the upgrading of the heavy oil, permits a greater density reduction with respect to a given level of olefins. Conversely, the removal of the 325 C..sup. fraction from the heavy oil, prior to the upgrading of the heavy oils, provides a heavy oil with an improved reduced olefin content with respect to a given density reduction.

[0060] The disclosures of all patents and publications, including published patent applications, are herein incorporated by reference to the same extent as if each patent and publication were incorporated individually by reference.

[0061] It is to be understood, however, that the scope of the present invention is not to be limited to the specific embodiments described above. The invention may be practiced other than as particularly described and still be within the scope of the accompanying claims.