EP0052042A2 - Protection of the wall of a centrifugal separator against abrasion by particles separated by centrifugation, and device for carrying out the method - Google Patents

Abstract

The present invention relates to centrifugal separators for the separation of particles suspended in a fluid, comprising a hollow body 1 in which the fluid, generally a gas G laden with particles P, is caused to rotate. In order to prevent wear of the internal wall of the body (1) under the abrasive action of the particles P separated from the fluid G, the internal wall of the body (1) is provided with an anti-abrasion device (5) constituted by relief elements (6) which extend preferably transversely in the direction of flow of the fluid G along the internal wall of the hollow body (1), in a manner such as to form and retain, on the said internal wall, a protective layer comprising the particles P themselves. <IMAGE>

Description

The present invention relates to centrifuges for the separation of particles suspended in a fluid, in particular a gaseous fluid, of the type comprising a hollow body in which the fluid loaded with particles is rotated.

The present invention applies in particular to cyclone separators used in particular, but not exclusively, in industrial dedusting installations. In multi-cyclone dust collectors, consisting of a battery of several tens of cyclones or cells, it is found that the internal wall of the cyclones is worn by abrasion under the action of the particles of the product which is separated by centrifugation of the gaseous fluid to be treated. This wear is more or less rapid depending on the nature of the product to be separated, the speed of the gas to be treated, the resistance and the thickness of the wall of the cyclone body, the conditions of temperature, hygrometry, acidity, etc. ... and it quickly leads to the piercing of the cell wall. As soon as a cell is pierced, the efficiency of the dust collector decreases and the operation is disturbed. It is then necessary to replace the defective cell as soon as possible for two reasons, firstly in order to respect the tolerances of the antipollution regulations and, on the other hand, in order to avoid that the leaks of soot or dust do not cause other damage on the cells or the other neighboring elements. For example, in a conventional multicyclone dust collector, comprising 60 cells which treat, before discharge into the atmosphere, the fumes from an urban waste incineration furnace with a nominal treatment capacity of 1500 kg of waste per hour , it is common to see the first breakthroughs of the most resistant cast-iron cells known on the market after 2,000 to 3,000 hours of operation, with a correlative drop in significant yield. In fact, the dust contained in the smoke from an urban waste incineration oven is very abrasive and it is rare that the lifetime of the cells exceeds 5.0UO hours without experiencing any damage. It is therefore necessary _" to make frequent replacements of defective cells, resulting in high costs of labor and spare parts.

Many attempts have been made by cyclone manufacturers to find a material capable of withstanding wear for longer. In the smoke dedusting technique, cast irons of various hardnesses and thicknesses have been tested. Some manufacturers use ceramics or "Pyrex" glass to make the cell wall. Other manufacturers fill the inner wall of the cells with hard material. These solutions are often expensive and do not always allow a significant increase in the life of the cells to be obtained.

The object of the present invention is to protect against wear, by simple and inexpensive means, the centrifuges of the type described above.

This object is achieved with the method according to the invention by the fact that one creates on the inner wall of the centri a layer of particles separated from the fluid by opposing the sliding of said particles on said internal wall by projecting elements.

The device for implementing the method is characterized in that the wall of revolution of the centrifuge which comprises this wall of revolution and means for circulating, with a rotational movement around the axis, a fluid flow in which are in suspension the particles to be separated in order to centrifuge said particles against said wall, is provided on its internal surface with elements in relief having a surface oriented at least partially transversely to the path of the fluid flow.

In practice, the centrifuge chamber having a cylindrical or cylindro-conical shape and the fluid to be treated being rotated about the axis of the chamber, the elements in relief are continuous elements extending substantially in the axial direction. These raised elements can be integral with the wall and consist of ribs, grooves or other reliefs but they can be formed by added elements, in particular bars, forming a cage and applied tightly to the wall to be protected.

• La figure la montre, en coupe axiale, un séparateur-cyclone classique équipé d'un dispositif anti-abrasion selon l'invention; la figure lb est une demi-coupe, suivant la ligne A-A, du séparateur-cyclone représenté sur la figure la; les figures 2a et 2b, 3a et 3b, 4a et 4b, 5a et 5b sont des vues similaires aux figures la et lb, montrant quatre autres formes d'exécution de l' invention.

Various embodiments of the present invention will now be described, by way of example, with reference to the appended drawings in which:

• The figure shows, in axial section, a conventional cyclone separator equipped with an anti-abrasion device according to the invention; Figure lb is a half-section along line AA of the cyclone separator shown in Figure la; Figures 2a and 2b, 3a and 3b, 4a and 4b, 5a and 5b are views similar to Figures la and lb, showing four other embodiments of the invention.

The cyclone shown in FIGS. 1a and 1b comprises a hollow body 1, for example of cast iron, of cylindro-conical shape and of vertical axis, open at its two ends. A discharge tube 2, with an outside diameter smaller than the inside diameter of the body 1 is arranged coaxially in the open upper end of the body 1 and extends downwards inside the latter. over part of its height. A ring of fixed guide vanes 3 is fixed to the upper end of the body 1 in the annular space between this body 1 and the tube 2.

The gas G charged with particles P is admitted at high speed into the body 1 through its upper end, as indicated by the arrows, and it is channeled by the guide vanes 3 which give it a rotational movement around the axis of the body 1. Under the action of centrifugal force, the particles P are projected against the internal wall of the body 1, along which they slide downwards in an approximately helical path to be discharged through the open lower end 4 of the body 1. The gas G, freed from the particles P, is evacuated through the tube 2.

In the absence of the anti-abrasion device 5 which will now be described, the friction of the particles P on the internal wall of the body 1 wears said wall. This wear can be considerably reduced, or even completely eliminated by means of the anti-abrasion device 5 according to the invention which, in the embodiment shown in FIGS. 1a and 1b, consists of bars 6 extending in the axially and bent to the profile of the internal wall of the body 1. The bars 6 are kept in close contact with the internal wall of the body 1 by retaining rings 7. The number of bars 6 and rings 7 can vary according to the diameter inside and the axial length of the body 1 and according to the operating conditions.

EXAMPLE:

In a conventional multicyclone dust collector comprising 60 cells similar to those shown in FIGS. 1a and 1b, and associated with an urban waste incineration oven with a nominal capacity of 1,500 kg of waste per hour, six of the 60 cells were equipped of an abrasion-resistant device 5 in accordance with that shown in FIGS. 1a and 1b. Each cell had an internal diameter of approximately 250 mm. Each abrasion-resistant device 5 consisted of four vertical bars 6 spaced circumferentially by 90 ° and by two retaining rings 7: The four bars 6 and the two retaining rings were made of 10 mm round iron. in diameter and their total developed length was about 4,000 mm. The test covered 15,000 hours or three years of operation of the furnace at its nominal power. After 2,000 to 3,000 hours of operation, the first breakthroughs were observed in cells not equipped with the abrasion-resistant device 5 of the invention. On the other hand, after three years of use, it has been found that the six cells equipped with the abrasion-resistant device 5 of the invention have not suffered any damage or obstruction and that the abrasion-resistant device 5 itself has is also found to be self-protected against wear. This is due to the fact that the bars 6 retain a portion of the particles P separated from the gas G and allow the establishment of a protective layer C made of said particles, as shown in FIG. 1b.

From the above, it can be seen that the anti-abrasion device 5 makes it possible to considerably increase the life of the cyclones. Tests carried out to date show that the lifespan is at least fivefold.

The abrasion-resistant device 5 of the invention is of very simple and inexpensive construction insofar as its manufacture requires only a small number of very simple operations and the use of a metal without characteristics. special mechanicals, in common use and inexpensive. The only precaution to take for its installation in the body 1 of the cyclone is to take care that the bars 6 are in close contact with the wall to be protected.

In addition to the fact that the anti-abrasion device 5 of the invention makes it possible to considerably increase the life of the cyclones, it also makes it possible to maintain the performance predicted by the manufacturers over time, or even to increase the dust removal efficiency. . Indeed; owing to the fact that the protective layer C slightly decreases the cross section of the gases loaded with particles, the speed of these gases is thereby accelerated and the centrifugation is increased. As a result, the separation of the particles is improved and the adhesion of the protective layer C to the wall is greater, which further improves the protection against wear.

Since the internal wall of the body 1 of the cyclone is perfectly protected against wear, it is now possible to envisage admitting the gases loaded with particles in the cyclone at higher speeds than before, in order to increase the speed of centrifugation, and consequently the dust removal efficiency, without increasing wear and reducing the life of the cyclone. This makes it possible to obtain dust removal results close to those commonly obtained with more sophisticated devices such as electro-filters.

It should be noted that improving the performance of each of the cells of such a multicyclone dust collector necessarily leads to increased protection of all the equipment located downstream of the dust collector, such as: sheet metal work, smoke ducts, collectors, pipes, control devices, volutes and turbines for draft fans, adjustment registers, smokehouses, chimneys, etc ...

It should also be noted that thanks to the anti- abrasion of the invention, the operations of replacing the damaged cells are considerably more spaced in time, or even completely eliminated, which results in a very significant saving in spare parts and labor and allows a more rational use of the ovens themselves.

It will also be noted that the abrasion-resistant device of the invention can be installed in any type of cyclone with axial or tangential entry, of type vertical, horizontal or oblique, etc. without any modification of the existing facilities.

On the other hand, the cells which were hitherto manufactured in noble and thick cast irons can now be produced in ordinary and thin cast iron or even in ordinary thin sheets or in stainless steel according to the envisaged applications (temperature, hygrometry, acidity, etc ...).

Figures 2a and 2b show an embodiment of the cyclone, in which the body 1 is made of sheet metal. In this case, each bar 6 can be constituted by a sheet folded in L and fixed by one of its wings to the internal wall of the body 1 by any suitable means, for example by spot welding. Instead of a sheet bent in L, one can also use iron sections with L, I or C section.

Figures 3a and 3b show another embodiment of the cyclone according to the invention, in which the body 1 is made of cast iron and has on its internal wall eight longitudinal ribs (only five of them are visible in Figures 3a and 3b) which are spaced circumferentially by 45 ° and are integrally formed with the body 1 by molding. The ribs 8 play the same role as the bars 6 of the previous embodiments.

Figures 4a and 4b show another embodiment of a cyclone, in which the body 1 is also made of cast iron. In this case, the body 1 has on its internal wall six longitudinal ribs 8 spaced 60 ° apart and molded with the body 1, as well as other ribs 9, also molded with the body 1, which extend in the circumferential direction and are spaced axially so as to form with the ribs 8 a cellular grid.

Figures 5a and 5b show another embodiment of the invention in which the body 1 is also made of cast iron and has in its inner wall longitudinal grooves 10 coming from molding. The longitudinal edges 11 between the adjacent grooves play the same role as the bars 6 or the ribs 8 of the previous embodiments.

Although in the above description, reference is made more particularly to the treatment of smoke from an urban waste incineration plant, the present invention is applicable in a large number of industries such as: metallurgy, steel industry, glassware, food industries, wood industry, plastics industry, chemical industry, roads, coating and purification stations, sand pits, balastières, thermal power stations, etc. In addition, pneumatic transport, which uses cyclones, becomes possible in the most diverse industries for a large number of reputable abrasive products, such as: dust, soot, dried sludge, ores, sands, gravel, gravel, pebbles, flours, powders, granules, cereal grains, coals, mints, fines, peanuts, nuts, shells, sawdust, shavings, deburring and all products liable to be cycloned.

From the above, it is clear that the present invention is of great economic interest, both by the possibility it gives of protecting existing cyclones with the resulting savings in spare parts and labor, only by the possibility of constructing future cyclones at a lower cost price, through the best results that it provides in terms of particle separation, by reducing atmospheric pollution by discharges into the atmosphere in dust removal techniques, by the energy savings it allows, and by its many fields of application.

It is understood that the embodiments which have been described above have been given by way of purely indicative and in no way limiting, and that numerous modifications can be easily made by those skilled in the art without as well depart from the scope of the present invention. Thus in particular that the number, the shape and the arrangement of the elements in relief provided on the internal wall of the cyclone can vary according to the field of application, the nature of the product to be treated and the operating conditions.

Claims (9)

1. Method for protecting the inner wall of a centrifuge, with a fixed wall, against abrasion by the particles separated by centrifugation of a flow of fluid centrifuged against this wall,
characterized in that a layer of particles separated from the fluid is created on this wall by opposing the sliding of said particles on said internal wall by projecting elements. 2. Centrifuge for the separation of particles (P) suspended in a fluid flow (G), comprising a wall of revolution (1) and means (3) for circulating, with a rotational movement around the axis, said fluid flow in contact with the wall of revolution to centrifuge the separated particles against said wall,
characterized in that relief elements (6,8,9,11) having a surface oriented at least partially transversely to the path of the fluid flow are provided on the internal surface of the wall of revolution (1). 3. Centrifuge according to claim 2,
characterized in that the elements in relief (6) are removable and consist of substantially longitudinal bars whose shape corresponds to that of the generator of the wall of revolution which are kept in close contact with the internal surface of the wall of revolution ( 1) and joined together by bars in the form of rings. 4. Centrifuge according to claim 2,
characterized in that the raised elements (6) consist of bars fixed to the internal surface of the wall of revolution (1). 5. Centrifuge according to claim 2,
characterized in that the raised elements (8,9,11) are in one piece with the wall of revolution (1). 6. Centrifuge according to claim 5,
characterized in that the elements in relief (8, 9) consist of ribs coming from molding with the wall of revolution (1). 7. Centrifuge according to claim-5,
characterized.in that the raised elements (11) consist of edges between grooves (10) formed in the internal surface of the wall of revolution (1). 8. Centrifuge according to any one of claims 2 to 7, in which the wall of revolution (1) has a cylindrical or cylindro-conical shape, characterized in that the elements in relief (6,8,11) extend in the axial direction. 9. Centrifuge according to claim 8,
characterized in that other raised elements (9) extend in the circumferential direction and are spaced axially so as to form a cellular grid with the raised elements (8) which extend in the axial direction.

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