PROCESS FOR CONVERSION OF A HYDROCARBON STREAM

Abstract

In a broad aspect the present disclosure relates to a process plant and a process for upgrading a hydrocarbon mixture, withdrawn as a direct stream from a crude distillation unit and an initial boiling point below 200° C., and a fraction of at least 5% boiling above 500° C., 550° C. or 650° C. comprising the steps of a. directing said hydrocarbon mixture to a vacuum flasher unit, b. withdrawing a heavy hydrocarbon fraction from said vacuum flasher unit, c. withdrawing a light hydrocarbon mixture for hydrocracking from said vacuum flasher unit, d. directing said light hydrocarbon mixture for hydrocracking and a stream rich in hydrogen to con-tact a material catalytically active in hydrocracking, e. withdrawing a hydrocracked stream of hydrocarbon from said hydrocracker. with the associated benefit of limiting the amount of asphaltenes, metals and other heavy components contacting said material catalytically active in hydrocracking.

Claims

1. A process for upgrading a hydrocarbon mixture, withdrawn as a direct stream from a crude distillation unit and having an initial boiling point below 200° C., and a fraction of at least 5% boiling above 500° C., 550° C. or above 650° C. comprising the steps of a. directing said hydrocarbon mixture to a vacuum flasher unit, b. withdrawing a heavy hydrocarbon fraction from said vacuum flasher unit, c. withdrawing a light hydrocarbon mixture for hydrocracking from said vacuum flasher unit, d. directing said light hydrocarbon mixture for hydrocracking and a stream rich in hydrogen to contact a material catalytically active in hydrocracking, e. withdrawing a hydrocracked stream of hydrocarbon from said hydrocracker.

2. A process according to claim 1 in which said hydrocarbon mixture is withdrawn as an overflash stream or a part of the overflash stream from a crude oil distillation unit.

3. A process according to claim 1, in which the hydrocarbon mixture directed to said vacuum flasher unit has a temperature of at least 250° C., 300° C. or 380° C.

4. A process according to claim 1, in which the hydrocarbon mixture directed to said vacuum flasher unit has a temperature of less than 450° C., 420° C. or 400° C.

5. A process according to claim 1, in which the pressure of said vacuum flasher unit is below 60 kPa, 80 kPa or 90 kPa.

6. A process according to claim 1, in which the pressure of said vacuum flasher unit is above 0.5 kPa, 2 kPa or 10 kPa.

7. A process according to claim 1, in which the hydrocarbon mixture is directed to said vacuum flasher unit without at substantially the temperature at which it was withdrawn.

8. A process according to claim 1, further comprising the steps of adding steam to said vacuum flashing unit or stripping the light hydrocarbon mixture.

9. A process according to claim 1, further comprising the step of withdrawing a hydrocarbon mixture of which at least 80% boils between 150° C. and 360° C. from said vacuum flasher unit.

10. A process according to claim 1, in which the material catalytically active in hydrocracking comprising a metal component selected from Group VIII and/or VIB of the Periodic System and being supported on a carrier containing one or more oxides taken from the group consisting of alumina, silica, titania, silica-alumina, molecular sieves, zeolites, ZSM-11, ZSM-22, ZSM-23, ZSM-48, SAPO-5, SAPO-11, SAPO-31, SAPO-34, SAPO-41, MCM-41, zeolite Y, ZSM-5, and zeolite beta.

11. A process according to claim 1, in which the reaction step in the presence of a material catalytically active in hydrocracking is carried out a temperature between 200° C. and 400° C., a pressure between 15 and 200 barg, a liquid hourly space velocity between 0.2 hr.sup.−1 and 5 hr.sup.−1, and a hydrogen to hydrocarbon ratio between 100 and 2000 Nm.sup.3/m.sup.3.

12. A process according to claim 11 in which the hydrocracking is carried out under a severity ensuring less than 5% of the product boiling above 360° C.

13. A process plant comprising a crude oil distillation column having an inlet, multiple distillation outlets, an overflash outlet and an overflash inlet, a vacuum flash unit having an inlet, a gas outlet, a light hydrocarbon outlet and a residual hydrocarbon outlet and a hydrocracking reactor having an inlet and an outlet, and containing a material catalytically active in hydrocracking, said process plant being configured for directing a crude oil to the inlet of the distillation column, for said overflash outlet being in fluid communication with the inlet of the vacuum flash unit, the light hydrocarbon outlet of said vacuum flash unit being in fluid communication with the inlet of the hydrocracking reactor, the inlet of said hydrocracking reactor being further in fluid communication with a hydrogen source and the outlet of said hydrocracking reactor being configured for withdrawal of a stream boiling in the diesel range optionally for further processing.

14. A process plant according to claim 12 in which said vacuum flash unit further comprises a means of separation aids such as column packing or trays, and has at least one further hydrocarbon fraction outlet, in which said vacuum flash unit is configured for the further hydrocarbon fraction to have lower boiling point than above said light hydrocarbon outlet.

Description

EXAMPLES

[0045] In the following an example of processing an overflash stream according to one embodiment of the present disclosure an example of processing an overflash stream according to the prior art are given.

[0046] The feed studied in the two examples is shown in Table 1. It is an overflash stream, which is immediately available from the crude distillation tower, and which has a very broad boiling point range, as determined by simulated distillation according to ASTM 7500. The reason for the broad boiling point range is an entrainment of heavy hydrocarbons from the crude feed and that the light components were not stripped from the product.

TABLE-US-00001 TABLE 1 Mass % Temperature [° C.] IBP (SimDis 1%) 160  5 290 10 320 20 360 30 380 40 395 50 405 60 415 70 450 80 490 90 530 95 600 EP (SimDis 99%) 710

Example 1

[0047] In a first example according to the present disclosure, shown in Table 2, corresponding to FIG. 2, an overflash stream is directed to a vacuum flasher, separating the inlet in a diesel fraction, a VGO fraction and a residual fraction. The VGO fraction is directed to the hydrocracker process, which is operated under a severity such that all VGO is hydrocracked to form diesel or lighter products, resulting in a total of 82022 kg/h diesel production withdrawn from the vacuum flasher in stream 28 or the hydrocracker after separation in stream 40.

[0048] The diesel yield, hydrogen consumption and equipment cost of Example 1 are defined as index 100.

Example 2

[0049] A second example according to the prior art, corresponding to FIG. 3, is also shown in Table 2. Here the overflash stream is not separated further prior to hydrocracking. The hydrocracking process was designed according to a limitation of constant hydrogen consumption, relative to Example 1, which results in the feed capacity being only 41% of the feed to Example 1, since the hydrocracking of heavy resid results in a high consumption of hydrogen. In addition the volume of the hydrocracker reactor and the amount of catalyst required are increased, and the requirements to equipment due to the elevated pressure will also be higher. The fractionator required to separate the products will also be more complex and energy intensive than the vacuum flasher required to split the feed in Example 1. All in all the equipment cost is estimated as 133% relative to example 1.

[0050] Example 2 results in only 50% diesel yield at the same hydrogen consumption, and at 133% the equipment cost. Had further hydrogen been available, it would have been possible to increase the diesel yield, but the hydrogen consumption and the equipment cost would have increased significantly.

[0051] It is therefore clear from the two examples that even though the overflash stream had undergone some separation before being withdrawn from the crude distillation column, the benefit from further separating the overflash in a vacuum flash unit is significant and clearly justifies the extra cost of the vacuum flash unit.

TABLE-US-00002 TABLE 2 Example 1 Example 2 Vacuum Overflash directly tower to hydrocracker Overflash feed kg/h 179892 74108 Diesel fraction kg/h 45940 from vacuum flasher Volume to kg/h 56153 74108 hydrocracker Total diesel kg/h 82022 40802 production Hydrocracker p atm 140 175 (start of run) Diesel Index 100 50 Hydrogen Index 100 100 consumption Cost Index 100 133 Cycle length years 2 2