FR2628652A1 - MULTI-LAYERED POROUS STRUCTURE, PARTICULARLY FOR THE SEPARATION OF LIQUID AND SOLID PHASES - Google Patents

Abstract

A multilayer porous structure, in particular for the separation of liquid and solid phases, contains, at least on the surface of the grains constituting an active layer, a hydrophobic binder formed of a silicone resin and / or of an epoxy resin based on bisphenol -AT.

Description

Porous-multilayer structure, especially for phase separation

  liquids and solids The present invention relates to a porous multilayer structure for filtration and / or dispersion, in which at least one of the layers is formed by grains

  cemented solids. The porous layers are mutually so-

  lidarized using an adhesive. The porous filtration and / or dispersion structure according to the invention lends itself to the separation of solid and liquid phases, thus

  than the dispersion of gas in a liquid, or else of liquid

  in other liquids or gases. The structure is-

  lon the invention is particularly applicable, ma-

  advantageous, in the field of wastewater treatment,

  and generally for water treatment.

  During water purification - among others -,

  filtration and decomposition of sub-

  organic organic stanzas; possibly gas

  aggressive are expelled from liquids, where a lot of gas is in-

  thrown into these liquids, the sludge contained by the waters

  used being, moreover, dehydrated (subjected to desicca-

  tion). The filter structure according to the invention can be effectively applied to the aforementioned processes: in certain cases, a liquid containing a solid phase is poured onto the filter structure, so as to separate the solid phase by filtration; in other cases (during dispersion), a gas in the form of fine bubbles

  is injected into the liquid mass, through the structure.

  Various methods are known for filtering and

  dehydrate sludge: one can cite, by way of example, sand bed filtration; filtration by means. rigid filter sheets, sintered gravel, textile and metal screens, as well as mechanical filtration (centrifugation and vacuum filtration, sludge compression, etc.). Desiccation is the classic process

to dewater the sludge.

  The efficiency of known mechanical filtration and dehydration processes is satisfactory, but

  their scope is really limited and their usefulness

  The use of dehydration technologies is limited by the specific high investment and operating costs. This is why filtration techniques

  based mainly on the use of natural substances

  turelles are used for the purification of waste water; among these techniques, sand filtration is the process

most commonly used.

  The grain size of the material in the threads

  very sandy, increases in the direction of flow of the

  liquid. The solid phase from the wastewater and through-

  the sand filter infiltrates the layer of sand,

  while the liquid phase circulates in a transverse movement

  health. As a result, the filtering layer becomes blocked and it cannot, without fail, regain its operational efficiency.

  by eliminating the filtered solid phase, by counter-rinsing

  current, or by detachment and replacement of the clogged layers. Filter structures, consisting of rigid multilayer filter plates, are described in

  US-A-4,452,698 and US-A-4,381,998.

  filtering res, made of a granular material cemen-

  tee, include a backing layer and a wire layer-

  tration; the support layer is naturally permeable,

  but its pores are larger than those of the fil-

  trantes. The material constituting the grains is mineral, -

  the development of filters using, for example, A1203, corundum, silicon carbide, carbide

  boron, etc. These filters are undoubtedly expensive structures.

  reuses. US-A-4,382,863 relates to a similar structure which consists of three layers, and is also expensive. In accordance with Hungarian patent application No. 216/83, a homogeneous filter (single layer) with sintered gravel is used to reduce the pressure of the water table.

  phreatic, for example for the drainage of basements.

  Desiccation of sludge is one of the most critical phases of water treatment. This desiccation of sludge requires a large surface area and its efficiency is

  largely dependent on climatic conditions, it is for-

  what dewatering the sludge - requires a lot of time and removing the dried sludge requires intervention

  manual to protect the drainage system. An exploita-

  subsequent sludge removed manually is prevented

  cherished by the gravel they contain.

  During the treatment of waste water, the gas-liquid system is partly materialized by the elimination of gases contained by the liquid, by resorting to the injection of other gases in this liquid, and partly by the use gas in the biological purification stage. An expulsion of aggressive CO2 by air injection is an example of the first case and a dispersion of air or oxygen in the mass of

  liquid is an example of the second case, to provide the condi-

  vital to the microorganisms present-in the phase-

  liquid. Among the techniques used for this purpose, an in-

  the most efficient process in which injecting air using nozzles is the most efficient

  gas at a constant flow rate is problematic. Another diff-

  difficulty lies in the fact that an injection of gas inter-

  mittent is necessary in most cases, and in the fact that during idle times it can result in blockage of the nozzles caused by the solid phase

enclosed in the liquid.

  The object of the invention is to provide a filtration and / or dispersion structure which ensures filtration with maximum efficiency, the operation of which requires only minimal energy and cost, which is not sensitive to obstruction and which injects the gases, into the

  liquid, with uniform distribution at a constant flow.

  The invention is based on the demonstration that, if the filter grains are connected to the filter layer by means of a hydrophobic adhesive, the film of adhesive

  covering the grains on the surface of the wire structure

  trante receives, during the filtration process, an electric charge whose sign is identical to that of the solid grains in the substance to be filtered, the particles with solid grains, present in this substance to be filtered, being then repelled. So, an effective electrostatic field is surely generated on the edge

  of the outer layer with filtering grains containing the coating

  hydrophobic adhesive, which prevents grains, pre-

  in the substance to be filtered, to adhere to the surface of the filter structure. Instead, a natural filter cake develops from the grains located above the filter structure, this cake not being

  in direct contact with the filter structure. Therefore

  quent, cleaning the filter only requires washing

  exterior since no solid impurity can

  clean inside the filter, and its pores are not obstructed

  not streak. The invention is based, moreover, on the demonstration of the fact that, during biological purification.

  or after the ventilation intended to expel harmful gases

  bles, an external synthetic resin coating prevents

  solid substances and / or microorganisms de

  place on the surface in contact with the liquid, and ob-

  streak the pores acting as nozzles. In this way, a

  biological purification and more efficient gas injection

these are certainly possible.

  According to the invention, on the basis of these

  considerations, the object sought is achieved by a struc--

  porous multilayer structure comprising at least one support layer and at least one active layer whose pore size is smaller than that of. layer pores

  support, at least the active layer consisting of a sub-

  chemically neutral mineral granular stanza (adequate-

  based on silicate), for example basalt grains,

  zeolite, A1203 and one or more binder (s), its character- -

  essential teristics consisting in that a hydro-

  phobe, formed of a silicone resin and / or an epoxy resin

  bisphenol-A xyde, is present at least on the

  surface of the grains constituting the active layer.

  Thus, the subject of the invention is a structure for

  multilayer reuse for the separation of solid systems

  and liquids and for dispersing gaseous and liquid systems

  quides, in particular for the treatment and purification of waste water and sludge, comprising at least one thin active layer, usually upper, and a thick support layer, usually lower, these two layers being

  both porous, but the pores of the active layer

  ve being smaller than those of the support layer, and

  at least the active layer consisting of a mineral substance

  chemically neutral, adequately in substances of

  the silicate industry, preferably ba-

  salt, zeolite, A1203, etc. with one or more binder (s); said structure is characterized by the fact

  that it contains, at least on the surface of the grains

  tituant the active layer, a strongly hydrophobic binder such as a silicone resin and / or an epoxy resin based on bisphenol-A. In this brief, we use

  expressions "usually upper" and "usually"

  so inferior "since the filter structure

  te can be arranged not only horizontally (for example for a filtration by gravitation), but all

as well vertically.

  The silicone resins are suitably chosen from types of resins having siloxane units of functionality between 1 and -A. 4 and / or from products with branched structure obtained by condensation of monomers with functionality between 1 and 3, preferably using phenyl-methyl-polysiloxane and / or

  a phenyl-methyl-polysiloxane polyester and / or a phenyl-

  methyl vinylsiloxane (suitably polymerized with H2O2).

  Such a bisphene-based synthetic resin

  nol-A, produced for example from 4, 4'-dihydroxy-

  diphenylpropane and epichlorohydrin, is used as an epoxy resin having OH functionality groups from 4 to 17, whose molecular weight is between 380 and 3,800, its epoxy equivalent being between 175 and 4,000, its ester equivalent being between 80 and 200, its molecular viscosity being between 5 and 150 p (at 20 C), and whose specific weight is between 1.14 and 1.2. Its formula is as follows: CH2-CH-CH2 '/ -O-R-O-CH2-CH-CH2-O-R- / n -0 CH2-CH-CH

\ / I I 1

O OH O

  The filtering structure is adequately made so that the thickness of the active layer (s) is between 5 mm and 15 mm, and that of the

  support layer (s) is between 50 mm and 150 mm.

  Although the use of relatively small pores

  breasts is judicious on the surface of the porous structure of filtration and / or dispersion which is in contact with liquid, in order to generate a more effective electrostatic field, it is possible to reduce the resistance

  the filter in the opposite direction and therefore use

  quent, larger pores on the side opposite the surface in contact with the liquid; it is also possible to use, for the support layer, a suitably perforated steel plate or any other metallic structure, possibly a plastic structure, for example a screen

  aluminum or plastic.

  The resin, by imparting the hydrophobic and electrostatic field, simultaneously causes the cementation of the filter grains, thereby ensuring a constant pore size.

  In view of the above, according to another case.

  characteristic of the invention, the size of the grains forming the active layer (s) is between 0.2 mm and 1 mm, the pore size of the layer (s) being

between 0.1 mm and 1 mm.

  Preferably, the support layer of the structure

  porous filtration and / or dispersion structure is formed

  by a perforated steel plate or by a perfo- structure

  consisting of another metal or a synthetic material

  that, for example an aluminum screen, or else a layer comprising mineral grains and a binder, the grain size being between 1 mm and 5 mm, the size of the pores being between 0.8 mm and 1.2 mm and around, from

preferably 1 mm.

  The porous structure can be designed provided with

  more than two layers: for example, the two upper layers

  These consist of mineral filter grains and a binder, while the lower layer is a perforated steel plate or a perforated structure made of another metal or a synthetic material, for example an aluminum screen or made of plastic. However, the filter structure can also be produced with a system increasing its mechanical robustness, for example a

  reinforcement of the consistent support structure,

  ference, in steel fittings.

  Another embodiment of the structure po-

  reuse according to the invention is characterized in that it

  consists of three layers, at least one of which is a

  che active external, and the intermediate layer consists of mineral grains and a binder. Preferably, at least

  an outer active layer and an intermediate layer comprising

  take mineral grains and a binder.

  The geometrical configuration of the surface of the active layer and / or of the support layer can deviate from the planar form: it can, for example, be tubular, conical, hemispherical or of oval shape, etc. When a filtration is carried out using the structure according to the invention, a thick solid phase (for example sludge) is certainly formed on the surface

  of the active layer (fulfilling the function of wire layer-

  tr-ante), without however adhering to it. As a result, the sludge can be removed mechanically while the filter

  is regenerated by external washing.

  However, the multilayer porous structure according to the invention is suitable not only for filtration, but also for the dispersion of a gas in a liquid. In this case, the necessary gas is injected from the support layer and the layer initially

  filter performs the function of an active disperser (atomi-

  sister). In such a case in particular, it is advisable to provide the surface with a geometry different from the planar shape. A fine distribution of the injected gas is ensured by the fine pores of the active surface; moreover, the hydrophobic binder located on the surface turned towards the liquid prevents, for example in the event of intermittent functioning, microorganisms, such as for example phytoplankton and monoplankton (algae), to deposit and obstruct the

  pores. In this way, the structure is permanently functioning-

  nelle. The invention is described below in more detail, in support of the following examples: xample 1 A filter structure according to the invention

  is developed for the filtration of common drainage sludge

  nal, calculated for an area of i m2, as follows

  size: active layer - material: aluminum oxide (A1203) - particle size composition: size (FEPA standard) quantity (kg)

22 10.4

36 0.60

0.60

  - binder: epoxy resin adhesive (TIPOX IHS) 1.22 kg - layer thickness: 5 mm

  Coefficient of permeability of the wire plate-

active tration:

  K = 2.1 x 10-3 cm / s, volume of the cavities n = 32%.

  Supporting layer - material: pearl gravel - grain size: 3 mm - 7 mm - binder: epoxy resin adhesive (TIPOX IHS) 2.5 kg - thickness: 45 mm

- mass: 90.0 kg.

  The initial percentage of dry substance in municipal drainage sludge was 2.0% (i.e.

9 2628652

  its percentage of moisture contained was 98.0%). A 4 L "Zetag 57" solution was used as a conditioning agent. The content extracted from dehydrated sludge was 38%. A clear filtration product was obtained, free of suspended matter. FEPA is an international standard relating to

  grain size, the equivalent of which is the hon-

groise n 6 506-84.

  One of the components of the "TIPOX IHS" epoxy resin adhesive is bisphenol-A-diglycidyl-ether-epoxy resin,

  and the other component is a blend of aliphatic polyamine.

  (manufacturer: Tiszamenti VegyimUvek, Tiszaszederkény, Hungary).

  "Zetag 57" is a polyelectrolyte based on po-

  lyacrylamide, produced by "Allied Colloid GmbH" (Hamburg,

R.F.A.).

Example 2

  The sludge from the wastewater of a tannery was filtered by the structure according to the invention, of which 1 m2 was composed as follows: active filtering layer - material: silicon carbide (SIC) - particle size composition: size (FEPA standard) quantity (kg)

22 10.40

36 0.60

0.60

  - binder: silicone resin adhesive (VP 2 261) 1.35 kg

- thickness: 5 mm.

  The active filter plate was subjected to a heat treatment at a temperature of 150 ° C. for 3 hours. Its permeability coefficient and its volume of

  cavities are identical to those of Example 1.

Support layer:

  identical to that described in Example 1.

  The initial percentage of dry substance in

  sewage sludge from the tannery was 1.5 Z (that is

  that is to say that its percentage of humidity contained was 98.5%). In this case also, a solution of "Zetag 57"

  at 4%, was used as a conditioning agent.

  The wastewater contained a chromium share of 1000 mg / l.

  After filtration, a dewatered sludge was obtained.

  dratée containing 30% of extract, as well as a product of

  filtration containing 0.05 mg / l of chromium, free of material

resen suspension.

  The silicone resin adhesive "VP 2 261" is a

  product of "Wacker Chemie Co" (Munich, R.F.A.).

Example 3

  Oily sewage sludge has been filtered

  using the structure described in Example 1. The

  initial dry substance concentration of this sludge was 2%, the percentage of moisture contained was 98%, and a solution of "Zetag 57" at 4% was used as a conditioning agent. After filtration,

  we obtained a dehydrated mud containing 33% of sub-

  dry stance, as well as filtered water suitable for

public sanitation system.

  In the three examples, only a superficial wash

  sky was necessary to regenerate the active surface

ve of the filter plate.

  The resistance of the filter in the layers did not change, even after a long period of use, and a

  further washing was not found necessary.

  Example 4 Using the filter structure described in

  Example 2, air was dispersed in water. Of the-

  air delivery bit, on 1 m2 of surface of the structure

  ture, was 20 m3 / h; amount of oxygen: 100 g 02 / h; power consumption: approx. 0.6 kW / 1000 g 02;

  bubble size: average = 2.5 mm.

  The essential advantage of the invention is that a new lavag.e is not necessary to regenerate

  the structure; only a periodic rinsing of the - is required

  surface, whose requirements in terms of power, time and manpower are minimal. The manufacture of the structure

  is simple and its applicability is multiple.

  It goes without saying that many modifications can

  can be made to the structure described and shown,

  without departing from the scope of the invention.

12 2628652

Claims (9)

-R E V E N D I C A T I O N S   1. Multilayer porous structure for separation   tion of liquid and solid phases and possibly, or   variant, for dispersing liquids or gases, in particular   for the treatment of waste water and sludge,   providing at least one support layer and at least one layer   active at smaller pore size than that of the   support che, at least the active layer consisting of a-   chemically neutral mineral granular substance (adequate   based on silicate), for example basal grains-   te, zeolite, A1203 and one or more binder (s), struc-   ture characterized in that it contains, at least on the surface of the grains constituting the active layer, a hydrophobic binder formed of a silicone resin and optionally, or   alternatively, an epoxy resin based on bisphenol-A.   2. Structure according to claim 1, character-   sed by the fact that binders are types of resins having siloxane units of functionality between   1 and 4 and possibly, or alternatively, types of resi-   branched structures obtained by condensation of mono-   functional mothers between 1 and 3, preferably   phenyl-methyl-polysiloxane and optionally, or in the   laughing, a phenyl-methyl-polysiloxane polyester and even   separately, or alternatively, phenyl-methyl-vinylsiloxane   suitably polymerized with H202.   3. Structure according to claim 1, character-   sed by the fact that the hydrophobic binder consists of a   sine epoxy, which is a synthetic resin made from   bisphenol-A produced, for example, from 4,4'-dihydroxy-   diphenylpropane and epichlorohydrin, having a molecular weight   between 380 and 3800, an epoxy equivalent   between 175 and 4,000, an ester equivalent included between-   be 80 and 200, containing OH functionality groups from 4 to 17, having a molecular viscosity of between p and 150 p (at 20 C) and a specific gravity of between 1.14 and 1.2.   4. Structure according to any one of the claims.   cations 1 to 3, characterized in that the size of the grains forming the active layer (s) is between 0.2 mm and 1 mm, the size of the pore (s)   layer (s) being between 0.1 mm and i mm.   5. Structure according to any one of the claims   1 to 4, characterized in that its' top layer   port is formed by a perforated steel plate or by a layer comprising mineral grains and a binder, the grain size being between 1 mm and 5 mm, the pore size being between 0.8 mm and 1.2 mm and around, preferably 1 mm.   6. Structure according to any one of the claims.   tions 1 to 5, characterized in that the thickness of the active layer (s) is between 5 mm and 15 mm, that of the support layer (s) being between mm and 150 mm.   7. Structure according to any one of the claims.   1 to 6, characterized in that the top layer   port contains a structure, preferably fittings   of steel reinforcement, to increase the metal robustness can i that.   8. Structure according to any one of the claims   1 to 7, characterized in that it consists of three layers, of which at least one external active layer and one intermediate layer comprise grains minerals and a binder.   9. Structure according to any one of the claims.   1 to 8, characterized in that the surface of the   active layer and optionally, or alternatively, the layer   The support che deviates from the flat configuration and is suitably tubular, conical, hemispherical or of oval shape.