ANTI-CLOGGING DEVICE FOR THE UPFLOW OF A FLUID

Abstract

The invention relates to a device for the upflow of a single-phase fluid comprising at least two beds of solid particles and at least one bypass means for a portion of said fluid, and also to the use thereof.

Claims

1. Device for the upflow of a single-phase fluid comprising: at least two beds of solid particles retained on the lower surface thereof by a means for distributing said fluid and on the upper surface thereof by a means for retaining said particles, each bed comprising at least one bypass means for a portion of said fluid, attached to said distribution means and to said retaining means, said bypass means comprising a pipe, the lower end of which opens below the lower surface of said distribution means and the upper end of which opens above said retention means, said pipe comprising a means for restricting the passage actuated by the differential pressure across said bed.

2. Device according to claim 1, comprising at least two bypass means per bed, the means for restricting the passage of said bypass means being actuated by different differential pressures across each of said beds.

3. Device according to claim 1, in which said restriction means comprises: a flared tubular portion, the orifice of which that has the smallest cross section is oriented towards the upstream of the pipe of the bypass means, a movable part, mounted in said flared tubular portion so as to allow a displacement between a closure position and a maximum opening position, the positioning of the movable part being a function of the flow rate of fluid in said flared tubular portion, and a return means that acts on the movable part in order to displace it towards the closure position in which the movable part blocks the orifice of the flared tubular portion that has the smallest cross section.

4. Device according to claim 1, in which said restriction means comprises: at least one plate movably mounted about an axis on the upper end of the pipe of the bypass means so as to allow a displacement between a closure position and a maximum opening position, the positioning of said plate being a function of the flow rate of fluid in the bypass means, and a return means that acts on the plate(s) in order to displace it (them) towards the closure position during which the plate(s) block(s) the end of the pipe.

5. Device according to claim 1, in which a small space is made between the upper surface of the bed and the means for retaining the particles.

6. A process for treating an oil containing triglycerides and/or free fatty acids and/or esters in which said solid particles are an adsorbent chosen from the group formed by porous refractory oxides, clays, zeolites, activated carbons, silicon carbide and mixtures thereof in at least one device according to claim 1, said device being operated at a temperature of between 50 C. and 320 C., at a pressure of between 0.1 and 7 MPa and with a residence time of said oil on said bed of solid particles of between 0.1 and 1.8 hours.

7. The process according to claim 6, in which at least two of said devices are used in parallel.

8. The process according to claim 6, in which said adsorbent is chosen from porous refractory oxides that have a macroporosity.

9. The process according to claim 6, in which said adsorbent is free of catalytic metals chosen from groups 6 and 8 to 12.

10. The process according to claim 6, in which said device is used for pretreatment upstream of a process for hydrotreating said oil.

Description

DESCRIPTION OF THE FIGURES

[0077] FIG. 1 presents a general schematic view of a particular arrangement of the device according to the invention. A single-phase fluid 8 flows upwards through the device 1. Said device comprises two beds of solid particles 2 and 3. For the sake of clarity, only the elements of bed 2 are numbered.

[0078] The beds are retained on their lower surface by a distribution means 4 and by a means for retaining said particles 3. Each bed comprises a bypass means 5 comprising a pipe 6 and a means for restricting the passage 7 actuated by the differential pressure across the bed.

[0079] FIG. 2 presents a particular arrangement of the device according to the invention in which said bypass means is positioned at the periphery of said bed of particles. The numbering is identical to that of FIG. 1.

EXAMPLES

[0080] The example illustrates a use of the device according to the invention and according to the prior art for treating an oil containing triglycerides, free fatty acids and esters. It is illustrated by FIG. 3.

[0081] A device according to the prior art comprising a fixed bed of solid particles of alumina impregnated with calcium phosphate is passed through by a feedstock of rapeseed vegetable oil type, having a density of 875 kg.m.sup.3 and a viscosity of 5 cP. The liquid surface velocity through each of the beds is 7 mm.s.sup.1. The device has an internal diameter of 2 m, corresponding to the diameter of the fixed bed. The fixed bed has a total height of 2 m.

[0082] The differential pressure, also referred to as pressure drop, across the fixed bed increases gradually until it reaches 0.5 bar (0.05 MPa) in around 45 days. When this pressure drop is reached, it is necessary to stop the device in order to clean or replace the fixed bed.

[0083] The change over time of the pressure drop is represented as a solid line in FIG. 3.

[0084] The device according to the invention comprises two catalyst beds each with a diameter of 2 m and a height of 1 m. It is passed through in an upflow manner by one and the same oil feedstock as the device according to the prior art (rapeseed vegetable oil, having a density of 750 kg.m.sup.3 and a viscosity of 5 cP). The liquid surface velocity through each of the catalyst beds is 7 mm.s.sup.1.

[0085] Each of the beds comprises a bypass means comprising a bypass tube and a gradually opening valve was installed on a bypass tube. The diameter of the bypass tube is 0.05 m. Each valve is sized in order to open gradually starting from 0.2 bar (0.02 MPa) of pressure drop, i.e. of differential pressure, in the catalyst bed.

[0086] The two catalyst beds are separated by a height of 50 cm.

[0087] The pressure drop across the device, measured between the inlet of the first bed and the outlet of the second bed, increases gradually with time. A little after 40 days, the gradual opening of the valve of the first bed is observed when the total pressure drop reaches around 0.2 bar (0.02 MPa). The differential pressure continues to increase until the valve of the second bed also begins to open, after around a hundred days.

[0088] The limiting pressure drop of 0.5 bar (0.05 MPa) will be reached after around 110 days, thus making it possible to substantially delay the stopping of the device for the replacement or cleaning of the fixed beds, when the same total amount of solid particles has been used.