EP1644121B2 - Separator disc and centrifuge comprising such separator discs - Google Patents

Abstract

The present disclosure relates to a method of increasing the separation effect of a centrifuge having separator discs in a disc stack. Also, the present disclosure relates to a separator disc and a centrifuge.

Description

The invention relates to a centrifuge according to the preamble of claim 1.

Separator plates are commonly made of stainless steel. In particular, the achievable selectivity for the separation of a product into two liquid phases, such as water or oil, can be improved.

It is known to pretreat the metal surface of the standard material of the separator discs, e.g. by an electrical or manual polishing process. Although these measures counteract contamination of the separation plates, but they do not achieve any appreciable increase in selectivity.

It is the object of the invention to increase the selectivity of the centrifuge of the generic type in the separation of a product in at least two phases in a structurally simple manner and preferably to improve the cleaning behavior of the separation plate.

The invention solves this problem by the feature combination of claim 1.

By this measure, the separation efficiency or selectivity is significantly increased or optimized in a structurally simple manner, because by means of the surface energy changing surface treatment, the separation efficiency or selectivity can be precisely adapted to the respective product by specifically the surface energy of the separation plate is changed so that set, for example, at the same time an oil-friendly and a water-friendly surface. The surface treatment also improves the cleanability of the separation plates.

The separating plates consist of a first material which, at least in sections, is provided with at least one coating of at least one other material which changes the surface energy compared to the first material. This measure is easy to implement procedurally and offers the advantages mentioned.

According to an alternative solution, the separation plates consist of a first material, into which at least in sections a material which changes the surface energy compared to the first material has diffused, e.g. with methods similar to surface treatment methods of semiconductor technology, i. e.g. with the aid of a plasma jet or the like. Here, the advantages of claim 1 also arise in an alternative manner.

Also conceivable are combinations of the two aforementioned methods.

The surface treatment can thus lead to chemical and / or physical bonds between the surface and the applied or introduced material.

Preferably, the separator plates - also for reasons of easier manufacturability - on the top and / or bottom completely Oberflächenenergieverändernd surface-treated, i. e.g. provided with the coating.

There are made to vote on the respective phases of a centrifugal product or product to be separated in various areas of the separation plate - preferably made of stainless steel - various surface treatments.

In the case of a separating separator, each separating plate is preferably subdivided into a plurality of functional regions in order to achieve an optimization of the value phase. The surface treatments, e.g. the coating materials are preferably adapted to the surface energy of the light or heavy phase to be separated.

It is also conceivable to make different surface treatments above and below the separation plates or radially inside and outside the separation zone, in particular radially inside and outside of a riser channel, which is often arranged so that the separation zone is in its center.

Further advantageous embodiments can be found in the remaining subclaims.

The invention will be described in more detail with reference to the drawing with reference to an embodiment.

It shows FIG. 1a, b a schematic diagram of the operation of a separation plate according to the invention and a representation of the principle of the invention in comparison to the separation plate according to the prior art using the example of a coating on the separation plate. This figure is purely exemplary. Instead of coatings, the areas of other surface energy could also be generated by other types of surface treatment.

In FIG. 1 are two conical separating plates 1, 2 of a separator plate 3 not shown here for a separator to recognize. The separation plates 1, 2 each have openings 4, which form a climbing channel 5 in interaction. The separating plates 1, 2 are arranged axially spaced from each other, so that in each case a gap 6 is formed between them.

Such a Trenntellerpaket show, for example, the DE 36 07 526 A1 or the DE-OS 19 09 996 , The separating plates 1, 2 are generally made of stainless steel.

It is the upper and lower (after Fig. 1 ) Surfaces 7, 8 of the separation plates 1, 2 are completely or substantially, ie preferably more than 50 percent of their surface, provided with a coating 9, 10 which changes the surface energy relative to a metal plate. This may be formed, for example, ceramic and / or Teflon-based and / or as a lacquer (eg silicon-containing, silicone lacquer or the like.) And be applied depending on the purpose on the top and / or bottom of the separation plate, there also either completely or each sections.

Through the coating 9, 10 of the separating plates 1, 2 whose surface is e.g. water-friendly but oil-friendly ausgestaltbar.

When a dispersion flows into the separator plate gap 6, the dispersion separates into the two phases "water" left of the center M of the riser channel 5 and "oil" right of the center M of the riser channel 5. The water contains one more small residual amount of "oil" in the form of drops to be removed in the Trenntellerpaket 3. On the oil-friendly separator disc surface, the oil droplets on contact stick better than the other phase and coalesce with other drops to form an oil film. Due to the centrifugal force some oil moves to the side of the light phase (oil).

During the separation in the separator plate gap 6, oil droplets form on the water side and water droplets on the oil side. Thus, different demands are placed on the surface. The water side must be oil-friendly, so that the remaining oil drops on the surface better coalesce, while the oil side must have exactly the opposite properties. It can be deduced from this that the separating plates 1, 2 can be divided into a plurality of functional surfaces or into sections with different coatings (here 9 and 10).

It is the coating 9, 10 divided into different areas, i. the coating is matched in the lighter phase on this, so that in the first place this adheres to the separation plates 1, 2, while it is tuned in the heavy phase on the heavy phase, so that here rather this phase at the separation plates. 1 , 2 clings.

It is not only possible to adapt the coating or the surface energy of the coating of the separation plates 1, 2 in the different areas to the different phases to be separated from one another, but it is also possible to adapt the surface energy to the centrifuged material to be processed per se, so that the coating must be chosen differently, for example, for the separation of a water-oil mixture than in the separation of other liquids.

The advantages that can be achieved are the reduction in wear that can be achieved as well as lower coefficients of friction and increased corrosion resistance.

An experiment shows that a bilge water separation in oil and water - as carried out on board a ship, a significant increase in performance is achievable.

Fig. 1b shows in the left figure, the flattened shape of a wider water droplet on an uncoated separation plate and the right figure a corresponding drop of water on a corresponding coated separation plate, which is narrower and significantly higher, but has an equal volume, which favors by the appropriately selected coating of the separation plate becomes.
As regards the theory of coatings, the following should be mentioned in addition. A criterion for adhesions is the surface energy in addition to the surface structure. The treatment of the separation plates by polishing only slightly changes the surface energy. A so-called non-stick layer is not produced by this. A reduction in the adhesions can be explained by the structural change made. The surface energy of the separation plates 1, 2 is in a range of an adhesive layer and is water-friendly (Trennseparator eg water / oil).

• σ^P: nicht dispersive (polare Anteile der Grenzflächenenergie)
  • Dipol - Dipol- Interaktion
  • Wasserstoffbrückenbindung
  • aLewis Säure / Base-Wechselwirkung
  • Charge - Transfer-Wechselwirkung
• σ^D: dispersiver Anteil der Grenzflächenenergie
  • Van der Waals Interaktion

One way of describing the phenomenon of free surface energy can be via a thermodynamic pathway. For a given system, the proportionality factor between its energy and its interface is the so-called interfacial tension or, more precisely, the "free interface energy". To increase the interface of a system, work has to be done. The surface free energy is composed of the dispersive and non-dispersive (polar) energies or interactions. $$\mathrm{\sigma }={\mathrm{\sigma }}^{\mathrm{P}}+{\mathrm{\sigma }}^{\mathrm{D}}$$

• σ ^P : non-dispersive (polar parts of the interfacial energy)
  • Dipole - dipole interaction
  • Hydrogen bonding
  • aLis acid / base interaction
  • Charge - transfer interaction
• σ ^D: dispersive fraction of the interfacial energy
  • Van der Waals interaction

Each atom or molecule has dispersive forces, which are due to the local and temporary fluctuation of the electron shell density. The non-dispersive (polar) forces are a plus that contributes to the overall interaction due to specific (e.g., functional) groups.

If the treated solid is to be brought into contact with a liquid, as is the case during painting, bonding, cleaning, wetting of a liquid on a surface, etc., the surface energy of the solid for a given liquid is the desired value for Determination of the surface energy. Thus, according to the invention, it is also advantageous in the area of the separating plates 1, 2 if a liquid in its surface tension fits exactly to the corresponding parameters of the solid, since in the case of too low energy of the solid there is less wetting of surface parts.

The adhesion can be explained in most cases directly with the surface energies of the two bonding partners. In particular, knowledge of the polar portion is necessary for this purpose. As a simple criterion for optimum adhesion, complete compatibility in terms of energy is required as well as the presence of as large a polar portion as possible on both sides. It follows that the total surface energies - both the dispersive and especially the polar portions of both phases - should be identical in order to achieve complete wetting of the oil. For an anti-adhesion, the lowest possible surface energy is necessary, with a low polar content.

Claims (7)

1. A centrifuge, in particular a separator or solid-jacket worm centrifuge, comprising a centrifugal drum in which a separating-plate stack consisting of separating plates (1, 2) is arranged, which separating plates consist of a first material, characterized by

   - a surface treatment of the separating plates, which at least varies the surface energy in sections, such that the separating plates (1, 2) are provided at least in sections with at least one coating (9, 10) varying the surface energy with respect to the first material and consisting of at least one other material, or that another material varying the surface energy with respect to the first material is diffused at least in sections into the first material;

   - wherein various zones (9, 10) consisting of various materials are applied to or diffused into various regions of the separating plates (1, 2).
2. A centrifuge according to claim 1, characterized in that the separating plates (1, 2) are completely surface-treated on the top side and/or the underside.
3. A centrifuge according to claim 2, characterized in that the surface treatment is adapted to the surface energy of the light or heavy phase to be separated.
4. A centrifuge according to one of the preceding claims 1 to 3, characterized in that the first material is high-grade steel and the coating is ceramic.
5. A centrifuge according to one of the preceding claims 1 to 4, characterized in that various surface treatments varying the surface energy are carried out above and below the separating plates (1, 2).
6. A centrifuge according to one of the preceding claims 1 to 5, characterized in that various surface treatments are carried out radially inside and outside the separating zone.
7. A centrifuge according to one of the preceding claims 1 to 6, characterized in that various surface treatments on the separating plates (1, 2) are carried out radially inside and outside a riser conduit (5).

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