EP1505250A1 - Use of a two-phase turbine in a hydrotreating process - Google Patents

Abstract

After passing through the reaction section R, the hydrocarbon feedstock C mixed with the hydrogen H is expanded in the device D. The expansion is carried out by a monophasic turbine until a gas volume ratio of 5% is reached, then the expansion is performed in a two-phase turbine rotodynamic type.

Description

The invention relates to the field of hydrotreatment processes. It proposes to use a two-phase turbine in a process hydrotreating.

The hydrotreatment processes are in particular implemented by the oil industry for the treatment of petroleum effluents in association with hydrogen. For example, hydrocracking involves converting heavy hydrocarbons as light hydrocarbons and hydrorefining mainly to remove the impurities sulfur, nitrogen and / or metals, contained in a hydrocarbon feed.

In general, a hydrotreatment process comprises catalytic reactors, processing units and balloons. Following the function of the balloons in the process, they can be at high pressure (about 10 MPa), at low pressure (between about 0.5 and 1 MPa), at elevated temperature (between about 250 ° C and 300 ° C) or at low temperature (about 50 ° C). The conduits for connecting a high pressure balloon to a low balloon pressure are equipped with an expansion valve. The expansion valve allows reduce the pressure of the fluid transferred through the ducts. The relaxation is performed at constant enthalpy and without energy recovery.

The invention proposes to recover the relaxation energy in the processes hydrotreating.

a) on détend un fluide ayant un taux volumique de liquide égal ou supérieur à 95 % et ayant une pression P1 à travers une turbine monophasique pour obtenir un fluide ayant un taux volumique de gaz inférieur ou égal à 5 % et ayant une pression P2,

b) on détend ledit fluide ayant un taux volumique de gaz inférieur ou égal à 5 % et ayant une pression P2 à travers une turbine diphasique pour obtenir un fluide ayant une pression P3.

In general, the invention relates to a hydrotreatment process comprising the following steps:

a) a fluid having a liquid content equal to or greater than 95% and having a pressure P1 is expanded through a monophasic turbine to obtain a fluid having a gas volume ratio of less than or equal to 5% and having a pressure P2,

b) said fluid having a gas volume ratio of less than or equal to 5% and having a pressure P2 is expanded through a two-phase turbine to obtain a fluid having a pressure P3.

According to the invention, the two-phase turbine may be a turbine rotodynamic.

The monophasic turbine and the two-phase turbine may constitute a single machine comprising at least one impeller and at least one distributor of monophasic design and at least one impeller and at less a diphasic design distributor. Hydraulics of monophasic and diphasic design can be mounted on a single tree.

c) avant l'étape a), on prélève une partie dudit fluide haute pression,

d) on détend ladite partie dudit fluide haute pression au moyen d'un premier dispositif.

The hydrotreatment process according to the invention may comprise the steps:

c) before step a), a portion of said high pressure fluid is withdrawn,

d) said portion of said high pressure fluid is expanded by means of a first device.

e) avant l'étape a), on détend ledit fluide haute pression au moyen d'un deuxième dispositif.

f) après l'étape b), on détend ledit fluide basse pression au moyen d'un troisième dispositif.

The hydrotreatment process according to the invention may also comprise one or more of the following steps:

e) before step a), said high pressure fluid is expanded by means of a second device.

f) after step b), said low pressure fluid is expanded by means of a third device.

According to the invention, one of said first, second and third devices may be an expansion valve or a turbine.

An advantage of the present invention is that it can recover energy in a hydrotreatment process. The energy is recovered during the expansion of a fluid through a turbine. The turbine shaft can be coupled to the shaft of a pump or compressor to compress a fluid. The energy recovered on the turbine shaft can also be transformed in electrical energy.

• la figure 1 représente schématiquement un procédé d'hydrotraitement,
• la figure 2 représente schématiquement le procédé selon l'invention,
• les figures 3 et 4 représentent des variantes du procédé selon l'invention.

The features and advantages of the invention will appear better on reading the description given below of nonlimiting examples of embodiment, with reference to the drawings among which:

• FIG. 1 schematically represents a hydrotreatment process,
• FIG. 2 diagrammatically represents the method according to the invention,
• Figures 3 and 4 show variants of the method according to the invention.

Figure 1 schematically shows a hydrotreatment process. The charge C comprises hydrocarbons, for example vacuum distillates, diesel fuel from conversion process and / or deasphalted residues. This charge C is pumped and sent to reaction section R. From hydrogen It is necessary to carry out the hydrotreatment reactions. Hydrogen H is compressed to also be introduced into the reaction section R. The reaction section R may comprise one or more reactors, at high temperature (for example between 350 ° C. and 450 ° C.) and at high pressure (for example between 5 MPa and 20 MPa). The effluent from the reaction section R is sent to a separator flask 1 in which the liquid and vapor phases are separated at a much lower temperature than that of the temperature of the reaction section R. The vapor phase resulting from the separator 1 is returned using a compressor to the reaction section R to ensure a sufficient hydrogen partial pressure. The sentence liquid in the balloon 1 is at the bubble point at a pressure usually between 5 and 20 MPa. This liquid phase essentially comprises hydrocarbons: heavy hydrocarbons from the load, hydrocarbons more produced by cracking reactions in reaction section R, from dissolved hydrogen in small quantities, hydrogen sulphide amount from desulfurization reactions in the reaction section R. This liquid is discharged from the flask 1 via the duct 2 to the device D, in which it is relaxed before being sent into the low pressure section 6 for fractionation of the reaction products. Stabilized products are discharged through line 24, for example to a storage area. Section 6 also makes it possible to obtain combustible gas evacuated via line 21, possibly liquefied petroleum gas discharged via line 22 (propane and butane) and possibly gasoline discharged through the conduit 23. These three latest products usually contain hydrogen sulphide. The section 6 is subjected to a pressure of between 0.5 and 1.5 MPa and at low temperature (for example between 20 ° C and 100 ° C).

The invention, detailed in FIGS. 2 to 4, aims at improving the recovery of the energy generated by the expansion performed in the device D.

In FIG. 2, the separator balloon 1 and the low pressure section 6 constitute elements of an installation for implementing a hydrotreatment process as described in FIG. 1. The other elements of the installation are not not represented.
The balloon 1 contains a fluid at high pressure. The conduit 2 brings the fluid of the balloon 1 into the monophasic turbine 3. The fluid conveyed through the conduit 2 has a liquid volume ratio greater than 95%. In the turbine 3, the fluid is expanded until the volume ratio of the fluid gas reaches 5%. Beyond a gas volume ratio of 5%, a monophasic turbine can no longer be used without risk of deterioration. The fluid obtained after expansion in the turbine 3 is fed into the two-phase turbine 4 where it is expanded to the pressure prevailing in the low pressure section 6. The conduit 5 brings the fluid from the turbine 4 to section 6 .

In the present description, a monophasic turbine designates a turbine designed to relax a fluid having a gas volume ratio less than 5%. The monophasic turbine 3 may be a turbine of the type rotodynamic, for example a machine equipped with distributors and of impellers constituting hydraulic Francis-type, or a turbine of volumetric type. At the output of a monophasic turbine, (for example a multi-stage turbine, ie with several pairs of distributors and impellers) the expanded fluid must have a gas volume ratio less than 5%. If the fluid is relaxed to contain more than 5% volume of gas, on the one hand the monophasic turbine may be deteriorated and on the other hand the efficiency of the monophasic turbine drops so dramatic. During a relaxation of a fluid having a volume ratio of less than 5% of gas, a single-phase turbine has a greater than 50%.

In the present description, a two-phase turbine designates a turbine designed to relax a fluid having a gas volume ratio greater than 5%. The two-phase turbine 4 may be a turbine of the type rotodynamic comprising impellers and distributors, for example a machine as described by one of the following patents: FR 2 333 139, FR 2 471 501 and FR 2 665 224. During a relaxation of a fluid having a gas volume ratio greater than 5% of gas, a two-phase turbine has a yield higher than 50% without risk of deterioration of the turbine.

The following examples show the energy recovered using the device described with reference to Figure 2.

Example 1

Ballon 1 à 10 MPa et 50°C,

Section 6 à 1,2 MPa

Débit de 176 t/hr (c'est à dire 44 kg/s)

On récupère 170 kW dans la turbine 3 jusqu'à ce que le fluide atteigne un taux volumique de gaz d'environ 5 %, puis on récupère 300 kW dans la turbine 4.

1 to 10 MPa and 50 ° C,

Section 6 to 1.2 MPa

Flow rate of 176 t / hr (ie 44 kg / s)

170 kW is recovered in the turbine 3 until the fluid reaches a gas volume ratio of about 5%, then 300 kW is recovered in the turbine 4.

Example 2

Ballon 1 à 10,3 MPa et 260°C,

Section 6 à 0,6 MPa

Débit de 229 t/hr (c'est à dire 56 kg/s)

On récupère 200 kW dans la turbine 3 jusqu'à ce que le fluide atteigne un taux volumique de gaz d'environ 5 %, puis on récupère 650 kW dans la turbine 4.

1 to 10.3 MPa and 260 ° C,

Section 6 to 0.6 MPa

Flow rate of 229 t / hr (ie 56 kg / s)

200 kW is recovered in the turbine 3 until the fluid reaches a gas volume ratio of about 5%, then 650 kW is recovered in the turbine 4.

The reference numbers of FIGS. 3 and 4 which are identical to reference numerals in Figure 2 denote identical elements.

The variant of the process according to the invention represented by FIG. proposes to unite monophasic and diphasic turbines into a single turbine 7. The turbine 7 is a rotodynamic machine comprising monophasic design impellers and distributors and impellers and distributors of two-phase design output. All impellers and distributors are contained in the same housing. The monophasic and diphasic impellers can be mounted on the same tree. The fluid to be released from the balloon 1 is introduced into the turbine 7 by the duct 2. In the turbine 7 the fluid acts first on impellers and distributors of monophasic design until reaching a rate gas volume of 5%, then on impellers and distributors of two-phase design until the pressure of section 6 is reached. of the turbine 7, the fluid is brought into section 6 via the pipe 5.

The process shown diagrammatically in FIG. 4 proposes to relax a fluid coming from the high pressure flask 1 in a turbine 8, the expanded fluid being introduced into the low pressure section 6. The turbine 8 may consist either of the succession (as described in FIG. 2) of a single-phase turbine and then of a two-phase turbine, or of a single machine (as described with reference to FIG. 3) having impellers and distributors constituting single-phase and two-phase hydraulics. A first valve 9 is arranged in parallel with the turbine 8. A second valve 10 is arranged in series with the turbine 8. The second valve 10 may be arranged upstream or downstream of the turbine 8.
The valve 10 is used to reduce the expansion on the turbine 8 in the case of a very strong expansion, that is to say in the case of a significant value of the difference between the pressure of the balloon 1 and that of the section. 6. The turbine 8 performs an expansion of the high pressure fluid to an intermediate pressure, then the valve 10 performs an expansion of the intermediate pressure fluid until the low pressure prevailing in section 6. The intermediate pressure has a value included between the high pressure prevailing in balloon 1 and the low pressure prevailing in section 6.
The valve 9 is used to reduce the flow rate of the fluid flowing through the turbine 8. Part of the fluid from the balloon 1 is expanded by the valve 9, the other part of the fluid from the balloon 1 being expanded by the turbine 8.
The valves 9 and 10 can be replaced by turbines.

Claims (9)

Hydrotreatment process comprising the following steps: a) a fluid having a liquid content equal to or greater than 95% and having a pressure P1 is expanded through a monophasic turbine to obtain a fluid having a gas volume ratio of less than or equal to 5% and having a pressure P2, b) said fluid having a gas volume ratio of less than or equal to 5% and having a pressure P2 is expanded through a two-phase turbine to obtain a fluid having a pressure P3. A hydrotreatment process according to claim 1, wherein the Two-phase turbine is a rotodynamic turbine. A hydrotreatment process according to claim 2, wherein the monophasic turbine and the two-phase turbine constitute a machine having at least one impeller and at least one distributor of monophasic design and at least one impeller and at least one distributor of two-phase design. Hydrotreatment process according to claim 3, wherein said hydraulics of monophasic and diphasic design are mounted on the same tree. Hydrotreatment process according to one of the preceding claims, comprising the steps: c) before step a), a portion of said high pressure fluid is withdrawn, d) said portion of said high pressure fluid is expanded by means of a first device. Hydrotreating process according to one of the preceding claims, comprising the following step: e) before step a), said high pressure fluid is expanded by means of a second device. Hydrotreating process according to one of the preceding claims, comprising the following step: f) After step b), said low pressure fluid is expanded by means of a third device. Hydrotreating process according to one of Claims 5 to 7, in which which one of said first, second and third devices is a valve of relaxation. Hydrotreating process according to one of Claims 5 to 7, in which which one of said first, second and third devices is a turbine.

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