EP1952889A1 - Continuous separation and elimination of liquid inorganic compounds by centrifugation. - Google Patents

Abstract

The method involves separating contaminant presented in a product which is in a mixed phase by pressurized centrifugation using a separating unit of a pressure maintained and hermetic enclosure (1). The product is injected by an inlet (6), and the clear product is evacuated by an outlet (7). The inlet and the outlet are arranged inside an inversed dome shaped movable part (5) of the separating unit, where the movable part is in a form of a bowl. An independent claim is also included for a centrifuge device for separating contaminant contained in a product which is in a mixed phase.

Description

The present invention falls within the field of separating contaminants contained in a product.

More particularly, the invention relates to the elimination of inorganic compounds, such as water, and sediment (soot, tar or other various particles) present within said product. Sediment particles are suspended while the water is present in undissolved form, therefore closely related to said product.

The present invention will find a preferential application in the sampling of organic product, more specifically within the refining and petrochemical trades.

Conventionally, the separation of said suspended contaminants in the product is carried out by filtration of the sediments and coalescence of the water globules, with separation under the effect of gravity.

However, this technique is not entirely satisfactory since it does not eliminate sediments smaller than 5 micrometers (μm) without posing significant problems of clogging of the filter element, or traces of water below 300 parts per million (ppm). It should also be noted that the coalescers are only suitable for low viscosity white hydrocarbons (up to 20 centistokes (cSt) at a temperature of 50 ° C) and may not be suitable for brown products such as crude oil, oils and residues of higher viscosity (up to 1000 cSt for a temperature above 50 ° C). In addition, the maintenance of such devices is often complex and costly, especially for the maintenance or replacement of filters.

In this regard, the operation of so-called "self-cleaning" tangential filters requires a high flow rate of the product to be sampled within the circuit, of the order of more than 1000 liters per hour. In addition, such an installation requires the realization of complex circulation loops with an increase in the diameter of the pipes and the addition of pumping groups to allow the return to the process line.

It has therefore been imagined to separate the contaminants of a product by centrifugation. In a known manner, the density of a hydrocarbon is less than that of water and suspended sediments within such a mixture, so that the latter is divided into a heavier fluid fraction at the periphery, part consisting of by water and sediments, while a part forms a central vein. The latter is then taken from the upper part of the bowl, thus forming the clarified sample.

A disadvantage is that existing centrifuges operate at atmospheric pressure. A known centrifuge has been equipped on a diesel-powered truck engine to remove sediment from it. However, such a device is not suitable for taking a sample free of water. In addition, operating at atmospheric pressure, this centrifuge creates a risk of separation of volatile fractions for a fluid in the mixed phase, as is the case of a light hydrocarbon, such as gasoline.

Another type of centrifuge allows the removal of sediments and finds its application in the storage of marine diesel. But such a device also includes a bowl maintained at atmospheric pressure so that it can not be suitable for a gasoline containing light fractions.

Other known centrifuges aim to evacuate only the sediments. As examples, documents FR 2,607,028 , FR 2 302 140 and GB 969 179 describe the operation of self-debugging centrifuge bowl in which are collected solid particles that should be evacuated. Again, these devices ignore the extraction of water particles and operate at atmospheric pressure.

Another solution is envisaged in the document US 6,095,964 describing a centrifuge for separating solid particles under pressure. Solid contaminants are held within the bowl at the bottom. No extraction is envisaged at the periphery of said bowl, let alone contaminants in the liquid phase, such as water. It is a self-driven bowl through ejectors through which the cleaned product returns to the process. These ejectors have the role of motorizing said bowl.

Other solutions, more complex to implement, allow to work under pressure to extract, once again, the solid particles. For example, the document WO 2006/096113 consider injecting a gas to work under pressure. Such a solution does not make it possible to extract particles such as water and may cause mixtures between the gaseous phases and the treated product.

Centrifuges existing on the market can not satisfy the application of the invention, it was devised a variant for separating under pressure contaminants contained in a sample, solid and especially liquid contaminants.

The invention therefore aims to overcome the drawbacks of the state of the art by proposing a method of separation by centrifugation under pressure of the contaminants contained in a product.

Thus, the present invention relates to a process for the continuous separation of liquid contaminants contained in a product that may be in a mixed phase, characterized in that it consists in separating under pressure said liquid contaminants present in said product by centrifugation within a movable portion in the form of a bowl (5) and to evacuate said liquid contaminants through cells on all or part of the periphery of said bowl.

It also relates to a centrifuge device for carrying out such a method, comprising a hermetic enclosure maintained under pressure and provided with means for continuous separation by centrifugation of said liquid contaminants contained in said product, said separation means comprising a part mobile in the form of a bowl inside which are provided an injection inlet of said product and a discharge outlet of the clarified product, characterized in that it comprises means for peripheral evacuation of liquid contaminants under the shaped cells distributed over all or part of the periphery of said bowl.

According to other features of the invention, said separation means comprise a mobile part in the form of a bowl inside which are provided an injection inlet of said product and an outlet for discharging the clarified product.

Preferably, said evacuation means comprise at least one groove capable of channeling said contaminants, such as water, and to tranquilize the flow of other contaminants, such as sediments.

In particular, said separating means comprise a cover adapted to drive and guide said product towards the periphery of said bowl through pallets.

In addition, said inlet is located in the lower part of said bowl, while said outlet is in the upper part of said bowl.

According to one embodiment, said inlet and outlet are formed through a fixed shaft.

• la figure 1 représente une vue en perspective d'un mode de réalisation du dispositif de centrifugation selon l'invention ;
• la figure 2 est une représentation éclatée en perspective d'un détail de deux pièces dudit dispositif ; et
• la figure 3 est une représentation en coupe d'un détail de l'invention selon un mode particulier de réalisation.

Other characteristics and advantages of the invention will emerge from the following detailed description of non-limiting embodiments of the invention, with reference to the appended figures in which:

• the figure 1 represents a perspective view of an embodiment of the centrifugation device according to the invention;
• the figure 2 is an exploded perspective representation of a two-piece detail of said device; and
• the figure 3 is a sectional representation of a detail of the invention according to a particular embodiment.

The present invention relates to the separation of contaminants, solid and liquid, contained in a product that can be in mixed phase at atmospheric pressure.

More particularly, the invention consists in separating under pressure by centrifugation said liquid contaminants present in said product.

To do this, in an enclosure 1 sealed and maintained under pressure, is injected the product to be clarified. As such, the product is advantageously in the form of a fluid, such as a liquid containing said contaminants.

Under centrifugal force, this fluid separates into at least two distinct phases, a heavier first phase migrating at the periphery and a second, lighter and representative of the clarified sample, forming a central vein 3.

The first phase comprising the contaminants is ejected under the effect of the centrifugal force at the periphery of the centrifuge 2 while the clarified product is taken under pressure at the central vein 3 in the upper part 4.

More specifically, this separation is carried out by centrifugal separation means of said contaminants contained in said product. As mentioned above, these separation means are rotatably mounted in said enclosure 1 and make it possible to clarify the product injected inside the enclosure 1 by separating it into two phases.

Advantageously, the separation means comprise a mobile part 5, called "bowl", inside which is injected and discharged said product. This movable portion 5 is rotatably mounted relative to a fixed shaft 23 extending along an axis AA 'transversely passing through said chamber 1. The product is directly injected and then evacuated within this moving part 5, reciprocally through a entrance 6 and exit 7.

Said inlet 6 and outlet 7 are located at said shaft 23. They are each in the form of a coaxial channel 8 formed from one end of said shaft 23 to an orifice 9 opening laterally inside said bowl 5. The inlet channel 6 is located in the lower part of the bowl 5 while the outlet channel 7 is located in the upper part 4, as visible on the figures 1 and 3 .
According to one embodiment of the invention, represented on the figure 1 , the chamber 1 and the bowl 5 are bell-shaped, with a smaller diameter at the outlet 7 than at the inlet 6, so as to guide the fluid at the central vein 3 towards said outlet 7.

According to the embodiment visible on the figure 3 the moving part 5 has an inverted dome shape.

According to another characteristic, the separation means comprise a lid 11 mounted integral with means 12 for receiving contaminants. These receiving means 12 may be in the form of a container in which accumulate solid contaminants, such as sediments. An advantage of such receiving means 12 lies in the fact that they store the residues without reducing the operation of the device.

In addition, the separating means comprise means 13 for peripheral evacuation of liquid contaminants. These evacuation means 13 may be in the form of cells distributed over all or part of the periphery of said bowl 5. These cells advantageously serve to extract towards the outside of the mobile part 5 the heavier contaminants, such as the water, projected on the periphery.

These cells may be made of any size but, according to a preferred embodiment, they are hollowed by laser drilling on all or part of the periphery of the bowl 5. They have a diameter of the order of several hundredths of a millimeter. More specifically, one embodiment gives particularly satisfactory results with cells having a diameter of 0.07 mm.

The bowl 5 also includes a lid. According to the mode of visible achievement on the figure 2 , the latter consists of a disc 14 whose periphery comprises means 15 for fixing said receiving means 12 so as to form said bowl 5. These fixing means 15 may be in any form so as to maintain said lid 11 and said receiving means 12 integral with each other. In the embodiment visible on the figure 2 said fixing means 15 are in the form of bores regularly distributed around the periphery and facing said receiving means 12 and said cover 11. These bores are intended to receive screws, nuts or the like. Balancing of the assembled lid 11 and bowl 5 is then performed with the assembly rotated by a motor through a movable shaft 24 secured to said bowl 5.

As such, the cover 11 is fixed on the bowl 5 and the assembly is rotated. According to the embodiment visible on the figure 3 , the inlet 6 and outlet 7 of the product to be sampled are produced by coaxial bores in the fixed shaft 23. The latter is rotatably mounted in a bore 25 formed coaxially with the movable shaft 24. The seal between the two fixed shafts 23 and mobile 24 is made through at least one rotating joint 27.

In the embodiment visible on the figure 3 , the fixed shaft 23 comprises channels 8 for injecting and discharging the product extending parallel to the interior of said shaft 23 from its lower end 26. Said inlet 6 and outlet 7 open laterally at different heights, said inlet 6 opening preferably under the outlet 7. The movable shaft 24 comprises vis-à-vis the inlet 6 and outlet 7 the ends of the reciprocally inlet ducts 28 and outlet 29, the opposite ends of these throats opening inside the bowl 5. In addition, the inner end of said ducts 28 and 29 may comprise a groove on all or part of the inner circumference of the bore 25 of the rotating shaft 24 or all or part of the outer periphery of the fixed shaft 23. This groove is formed circularly over the wider section of the ducts 28 and 29 to improve the injection and evacuation of the product reciprocally from and to the inlet 6 and the outlet 7.

Advantageously, the motor is of the pneumatic type and able to operate at variable speeds and speeds, in a nonlimiting manner, of the order of 5,000 to 7,000 revolutions per minute.

The lid 11 also comprises drive means 16 for rotating the liquid in order to optimize the centrifugal effect and thus allow the ejection of the liquid contaminants through said cells, the sediment remaining in the bottom of the bowl. These guide means 16 are preferentially in the form of vanes 17 distributed radially with respect to said cover 11, on the disk 14. In addition, each pallet 17 consists of a plate integral with and orthogonal to the plane of said cover 11. perpendicular to said disk 14.

According to a particular embodiment, visible on the figure 2 each pallet 17 is constituted by a rectangular plate fixed perpendicularly to the disc 14 and tangentially positioned, in particular at one of its ends, to a circle concentric or not with respect to said disc 14. arranged in the form of a ratchet wheel or a spiral. This particular configuration guides the fluid towards the periphery of the mobile part 5.

At this point, on all or part of the peripheral edge of the mobile part 5, means are provided for channeling said fluid. These channeling means make it possible to guide the heavy inorganics, such as water. They thus tranquilize their flow to said cells.
According to the embodiment visible on the figure 2 these channeling means are in the form of a groove 18 formed at the periphery of said bowl 5. This groove 18 is located in a higher position than the inlet port 6 for injecting the sample. Preferably, the groove 18 may be at a height of 4 mm from the bottom of said bowl 5. Thus, the water coalesces on the inner wall 19 of said groove 18, goes up along it and rushes within said groove 18. The water is then evacuated by said cells. The heavier sediments remain at the periphery but in the lower part at the level of said inlet orifice 6. These particles form a cake against the wall 19, without going up along the latter.

After evacuation of the bowl 5, the water stagnates at the bottom 20 of the fixed portion 21 of the chamber 1 provided with an effluent recuperator for evacuating by gravity via a discharge conduit 22.

Finally, the clarified product is recovered and evacuated under pressure from the central vein 3 to the upper level 4 of the bowl 5 while the heavy contaminants are expelled at the periphery under the action of the centrifugal force. Thanks to the guiding means 16 towards the channel groove 18 and the cells, the liquid contaminants, such as water, are expelled outside the mobile part 5, while the sediments stagnate at the bottom of said bowl 5.

Such a separation of contaminants present in a fluid will find particular application in the context of mixed phase sample decontamination in a continuous online analysis, for example in the fields of refining and petrochemistry. The present invention is particularly aimed at hydrocarbon sampling.

Claims (6)

Process for the continuous separation of liquid contaminants contained in a product which may be in the mixed phase, characterized in that it consists in separating under pressure said liquid contaminants present in said product by centrifugation within a mobile part in the form of a bowl (5) and to evacuate said liquid contaminants through cells on all or part of the periphery of said bowl (5). Centrifuge device (2) for carrying out the method according to claim 1, comprising a chamber (1) sealed maintained under pressure and provided with means for continuous separation by centrifugation of said liquid contaminants contained in said product, said separation means comprising a movable part in the form of a bowl (5) inside which are provided an inlet (6) for injecting said product and an outlet (7) for discharging the clarified product, characterized by the fact that comprises means (13) for the peripheral evacuation of liquid contaminants in the form of cells distributed over all or part of the periphery of said bowl (5). Centrifuge device (2) according to claim 2, characterized in that said evacuation means (13) comprise at least one groove (18) adapted to channel said liquid contaminants, such as water, and to tranquilize the flow of other contaminants, such as sediments. Centrifuge device (2) according to any one of claims 2 or 3, characterized in that said separating means comprise a cover (11) adapted to drive and guide said product to the periphery of said bowl (5) through pallets (17). Centrifuge device (2) according to any one of claims 2 to 5, characterized in that said inlet (6) is located in the lower part (10) of said bowl (5). Centrifuge device (2) according to any one of claims 2 to 5, characterized in that said outlet (7) is in the upper part (4) of said bowl (5).

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