WO2010010264A1 - Process for the deodorization of foul-smelling effluents, and installation for the implementation of the process - Google Patents

Abstract

Process for the deodorization of the air generated by foul-smelling effluents, according to which: the chamber in which the foul-smelling air is generated is put under vacuum, prior to it being discharged to the outside at atmospheric pressure, the polluted air is treated by photocatalysis within a zone of overpressure.

Description

 METHOD FOR DEODORIZING MALODORANT EFFLUENTS AND INSTALLATION FOR IMPLEMENTING THE METHOD

The subject of the invention is a process for the deodorization of malodorous effluents. It also relates to the development of an installation for implementing the method.

In the following description, the method of the invention is more particularly illustrated in connection with the drying of sewage sludge and composting exclusively by solar radiation, that is to say without external heat input other than radiation. UV. Nevertheless, this particular embodiment is not limiting and the method of the invention is of interest for all applications where the treatment of odors is required. Without this being limiting, mention may in particular be made of the treatment of odors generated by animal meal, distilleries, tanneries, animal husbandry, rendering, as well as by the food industry.

The question of the drying of sewage sludge and composting sludge appears as a problem for which no satisfactory solution has yet been found. Presently, the sludge is dried in drying greenhouses and the moisture resulting from this drying is discharged to the outside, causing major odor problems. In some cases, deodorization systems are put in place but they do not remain sufficiently efficient.

Document DE 42 28 526 A1 describes an installation for the treatment of air generated by the compost consisting in creating a vacuum in the compost storage chamber and then forcing the air through a biofilter, which is arranged, protected from light, within a tower. To be regenerated, the biofilter needs to be regulated in temperature and to be crossed regularly by fresh air.

Document FR-A-2 888 270 has proposed a solution consisting in degrading pollutants from paper sludge or composting by photocatalysis.

The principle of photocatalysis is well known. Schematically, the photocatalytic reaction is initiated by activating a semiconductor solid called photocatalyst agent, for example titanium dioxide (TiO ₂ ) by UV radiation a wavelength of 380 nm causing electronic changes within the semiconductor and leading, in the presence of air or water, the creation of oxygen radicals on the surface of the semiconductor. These radicals attack the organic compounds adsorbed on the semiconductor and, by successive chemical reactions, involving the oxygen of air and water, degrade organic compounds until the carbon of the carbon chains is completely converted to carbon dioxide (CO ₂ ).

In the aforementioned document, photocatalysis is provided by means of specific supports called "filter media" associating fibrous support itself and photocatalyst agent by means of a binding agent. These supports are positioned in the embrasure of the openings of a building, that is to say in an area naturally illuminated by UV. The building being under overpressure, the air circulates from the inside to the outside through the supports, which thus ensure the depollution of the air.

The major drawback of this installation lies in its inability to handle large quantities of sludge insofar as the media area needed to treat the effluents effectively is much too high. In addition, the buildings are regularly open due to the comings and goings of the trucks coming to pour the sludge. This results in an inevitable leakage of odors to the outside, the phenomenon being reinforced by the overpressure generated inside the building.

In other words, the problem to be solved by the invention is to develop a method of the same type as that described in the aforementioned document, and an installation for implementing the method that can ensure the treatment of a maximum amount of sludge in an enclosure of the most limited size possible, and more generally which does not have the aforementioned drawbacks.

To do this, the Applicant has developed a process consisting of concentrating the stale air in a depression zone and treating it, by photocatalysis, in an overpressure zone. More specifically, the subject of the invention is a process for the deodorization of air generated by malodorous effluents, according to which: the chamber in which the malodorous air is generated is depressurized, prior to its evacuation to the outside at atmospheric pressure, the polluted air is treated by photocatalysis within an overpressurized zone.

In other words, the invention consists in storing the effluents in a vacuum chamber, then in interposing between the vacuum zone and the outside where the air is at atmospheric pressure, an overpressure zone provided with a system photocatalysis thus attracting polluted air to a specific area and treating it before it is discharged to the outside.

According to the invention, the photocatalyst treatment consists of treating the air, under UV irradiation, by passing through a permeable support containing a photocatalyst agent.

Advantageously, the photocatalysis treatment consists of treating the air by passing between at least two permeable supports separated from each other by an artificial UV source, the face at least of the supports facing the light source containing a photocatalyst agent .

In a particular embodiment, the deodorization process of the invention relates more particularly to a method of solar drying, sludge in which solar radiation is solely responsible for the heat input.

The invention also relates to an installation for implementing the method.

This installation is characterized in that it comprises at least two enclosures respectively a first vacuum enclosure, in which polluted air is generated, a second chamber under pressure, provided with means able to destroy by photocatalysis the organic pollutants present in them. effluents.

Such an installation can take two different embodiments.

According to a first embodiment, the first enclosure is provided with openings distributed over all or part of its periphery, and the second enclosure is present in the form of caissons arranged inside the first enclosure and made integral with at least one of the openings, advantageously of all the openings, the caissons being provided with means able to destroy by photocatalysis the organic pollutants present in the effluents .

The installation is advantageously completely dismountable associating metal uprights with tarpaulins.

Advantageously, the section of the caissons is identical in size to that of the embrasure of the openings so that all the polluted air trapped, then treated in the boxes, is evacuated by said openings.

According to the invention, the depression of the first chamber and overpressure caissons is obtained by the implementation on the rear wall of each box, a fan ensuring the communication of air from the enclosure in depression to the inside of the box in overpressure.

In a second embodiment, the second enclosure is in the form of an independent module outside the first enclosure and communicating with it, the second enclosure being provided with openings distributed over all or part of its periphery, said openings being provided with means able to destroy by photocatalysis the organic pollutants present in the polluted air.

In other words, in this embodiment, the boxes arranged inside the main enclosure of the first embodiment are offset and arranged outside the enclosure.

Therefore, the subject of the invention is also a module that can be implemented in the installation described above, the module being characterized in that it is advantageously of parallelepipedal general shape and intended to communicate with the first enclosure, the module being provided with openings distributed over all or part of its periphery, said openings being provided with means able to destroy by photocatalysis the organic pollutants present in the polluted air. This embodiment is more particularly adapted to the treatment of odors generated in existing enclosures, which is equipped with a photocatalytic processing module.

In practice, the first enclosure communicates with the module through a pipe, the depression of the enclosure and the overpressure of the module being obtained by the implementation of a ventilation means arranged upstream , downstream, or at any point of said pipeline. The pipe may also be in the form of a discharge chimney forming part of the vacuum enclosure, on which the module fits.

Furthermore, in addition to a ventilation system capable of ensuring operation in depression / overpressure, the installation may comprise, between the main enclosure and the module, a pretreatment means of the exhaust air from the enclosure. It may be a filter or dust collector capable of capturing the fines present in the air in the case where the material to be treated is reduced to powder. This prevents clogging filter media ensuring photocatalytic treatment. It may be a washing tower capable of removing NH3 present in the effluent to be treated by dissolving in water. Most of the time, the pretreatment means is arranged on the pipe separating the first chamber of the module.

Whatever the embodiment, the means able to destroy by photocatalysis the organic pollutants present in the effluents in practice combine at least one permeable support covered on at least one of its faces with a photocatalyst agent (also called photocatalytic support) with at least one source of artificial UV radiation, the UV source being opposite the face of the support covered with photocatalytic agent.

In an advantageous embodiment, the photocatalytic supports are held within a frame arranged in the embrasure of the openings of the first enclosure according to the first embodiment, or the module according to the second embodiment. Ideally, the photocatalytic supports are two in number and are separated by an artificial UV source positioned opposite the face of the support treated with the photocatalytic composition. Of course, both sides of the supports can be treated with the photocatalytic composition. Preferably, the support positioned closest to the outside present two sides treated so that, in the event that the enclosure or the modules would be in contact with natural UV, the effectiveness of the photocatalysis is enhanced.

In another embodiment, the supports are three in number, respectively, from the outside to the inside of the box or the module, two supports held back to back, in contact or not with each other and an independent support, the independent support being separated from the other supports by at least one UV radiation source. In this case, the two supports held back to back are covered with photocatalytic agent on their outer face, that is to say outside side for one and side light source for the other. The third support is in turn covered with photocatalytic agent at least on the side facing the light source.

In a preferred embodiment relating to the first embodiment and depending on the size of the first enclosure, the frame comprises four windows intended to each receive a series of two or three supports as previously described.

Regarding the permeable support itself, it associates, as already said, fibrous support and photocatalytic agent by means of a binding agent. Such supports are more particularly described in EP-A-069 950, as well as in WO 00/13950 and WO 04/033069.

In a preferred embodiment, the permeable support is in the form of three superimposed layers, respectively an inner layer and two outer layers, the inner layer consisting of 80 to 95% by dry weight of activated carbon, the complement to 100 % being constituted by chemical, organic and / or inorganic fibers, the outer layers comprising from 5 to 25% by dry weight of activated carbon, the 100% complement consisting of chemical, organic and / or inorganic fibers.

In the remainder of the description and in the claims, the term "organic and / or inorganic chemical fibers" is used to designate organic fibers with the exception of activated carbon fibers, in particular cellulose fibers and synthetic fibers. of the type, for example polyester, polyethylene, polypropylene, polyamide, polyvinyl chloride, polyvinyl alcohol, acrylic, nylon, fibers artificial, for example viscose, cellulose acetate; natural fibers, for example cotton, wool, wood pulp, and among inorganic fibers, especially mineral fibers, for example glass or ceramic.

With regard to the layer based on photocatalyst agent, it contains in practice between 5 and 40 g / m ² , advantageously 20 g / m ² of photocatalyst agent chosen from the group comprising metal oxides, the oxides comprising alkaline earths, actinide oxides and rare earth oxides. In practice, the photocatalyst agent is in the form of a mixture comprising between 10 and 60 parts in sec, advantageously 50 parts of an aqueous colloidal dispersion of silica dioxide, the 100% complement consisting of TiC> ₂ anatase . Likewise, the SiC ₂ particles represent from 1 to 50% by weight of the colloidal dispersion, having a diameter of between 10 and 40 nm.

When the support contains activated carbon as previously indicated, it may advantageously be in the form of particle fibers or activated carbon powder, with a particle size of between 2 and 300 μm.

The invention and the advantages resulting therefrom will emerge from the following exemplary embodiments, in support of the appended figures.

Figure 1 is a schematic representation of a sludge drying greenhouse according to a first embodiment of the invention.

Figure 2 is a view of the interior of said greenhouse. FIG. 3 represents the detail of the pressure booths arranged at the openings of the greenhouses according to FIGS. 1 and 2.

Figures 4a and 4b correspond to a preferred embodiment of the photocatalyst means according to the first embodiment.

FIG. 5 is a detailed schematic sectional representation of photocatalysis means according to the first or second embodiment of the invention.

Figure 6 is a schematic representation of the invention according to a second embodiment.

FIG. 7 is a schematic perspective view of the module of FIG. 6. FIG. 8 is a detailed view of some of the elements of FIG. In this example, the invention is more particularly described in relation to the drying of sewage sludge by means of a greenhouse by solar radiation.

I / First Embodiment of the Invention

As shown in Figure 1, this greenhouse designated by the general reference (1) is a greenhouse completely removable. More specifically, it has a roof (2), as well as side faces (3), the front face (4) being provided with an opening (5) for the supply of sewage sludge. This greenhouse has a series of transverse uprights (6) each connected by a fabric (7) both at the level of the roof (2) and at the periphery (3), the fabric allowing the UV radiation to pass. According to the invention, the periphery of the building is provided with openings (8) in the embrasure of which are arranged the photocatalyst systems defined by the general reference (9).

In Figure 1, one can also see the presence of the boxes (10) arranged inside the building (1), which are clearly shown in Figure 2. Each box (10) has, in its largest section, a section identical to the section of the openings (8). Furthermore, the rear faces (11) of the boxes are provided with fans (12) communicating with the heart of the enclosure. In the enclosure, the air is stirred into depression by means of fans (13).

The boxes are more particularly shown in FIG. 3. Each box, in its widest section (14), is secured to a frame (15) in which the photocatalyst unit (16) is arranged.

This unit is detailed in Figures 4a, 4b. More specifically, the photocatalyst unit (16) has a front face (17) and a rear face (18) integral with the frame (15). The front face (17) is provided with 8 superposed permeable supports 2 to 2 (19) distributed symmetrically, while the rear face (18) is provided with 4 permeable supports (20) located opposite the permeable supports (19) of the front face (17). The supports (19) are separated from the supports (20) via a plurality of UV radiation sources (21) distributed over the surface of the supports. The arrangement of the supports at one of the four windows of the photocatalyst unit is shown in section in FIG. 5. This figure shows the UV radiation sources (21) and the fan (12). The references (19-1, 19-11 and 20) respectively represent the three supports held in the frame or frame (15) at the front and rear faces. To ensure the photocatalytic reaction, the permeable support (20) is coated on the face facing the UV lamp (21) with a layer of a photocatalytic agent (22). The same layer (22) is applied to the surface of the support (19-11) facing the UV lamp (21). In addition, the layer (22) is applied to the outer face of the support (19-1) facing the opening of the building. It should be noted that the supports (19-1 and 19-II) are in contact with each other and placed in a textile envelope not shown.

The operation of the installation is as follows.

The sludge is stored for drying in the greenhouse and spread over the entire soil of the greenhouse. The atmosphere is depressed due to the presence of fans on the rear wall of the boxes, then the polluted air is conducted in the boxes by depression / overpressure phenomenon. In the caissons, the polluted air is treated by photocatalysis to escape, once treated, through the openings of the building. In this way, the smell of sludge remains confined in the building.

II / Second embodiment of the invention

In Figure 6, there is shown an installation of the invention according to a second embodiment.

This installation comprises an enclosure (23) supposed to exist in which the sewage sludge is stored. In the diagram, the enclosure is devoid of opening and this in a completely arbitrary manner. This enclosure communicates with a second enclosure also designated "module" (24) through a pipe (25). As shown in Figure 8, on the pipe (25) are successively arranged a fan (26) and a dust collector (27). Like the fans present at the rear of the boxes, the fan (26) arranged on the pipe (25) ensures a vacuum phenomenon in the chamber (23) and overpressure in the module (24). The dust collector is optional and remains useful in the event that the air flow to be treated is loaded into fines. Figure (7) relates more particularly to the structure of the module (24). According to a first feature, this structure is completely removable thus allowing easy implementation that can adapt to any type of site. In the embodiment shown, the module of parallelepipedal general shape, provided with 4 faces, respectively two small sides (28, 29), two large sides (30, 31) and a not shown roof. The small side (29) is connected to the pipe (25) and provided with an access door (32) for performing maintenance. The long sides (30, 31) are equipped with the same units of phtocatalysis as those shown in Figure (5). In this embodiment, each large side and the short side (28) are provided respectively with three panels and a photocatalyst panel (33).

The installation works according to the same principle as in the first embodiment. Its advantage is to be able to adapt on existing storage enclosures.

Such a system makes it possible, thanks to the concentration of air in specific areas, to ensure the photocatalysis treatment of a very large quantity of sludge with buildings of limited size. The process is applicable to the drying of sewage sludge as well as to the treatment of composting sludge without, however, being limiting.

Claims

1 / A process for the deodorization of the air generated by malodorous effluents, according to which: the chamber in which the malodorous air is generated is depressed, - Before venting outside at atmospheric pressure, the polluted air is treated, by photocatalysis, in a zone under pressure. 2 / A method according to claim 1, characterized in that the photocatalysis consists of treating the air, under UV irradiation, by passing through a permeable support containing a photocatalyst agent. 3 / A method according to claim 1, characterized in that the photocatalysis consists in treating the air by passing between at least two permeable supports separated from each other by an artificial UV source, the face of the supports opposite the light source containing a photocatalyst agent. 4 / Apparatus for implementing the method according to one of claims 1 to 3, characterized in that it comprises at least two enclosures respectively a first vacuum enclosure, in which is generated polluted air, a second pressure booster, equipped with means able to destroy by photocatalysis the organic pollutants present in the effluents. 5 / Apparatus according to claim 4, characterized in that the first chamber (1) is provided with opening (8) distributed over all or part of its periphery, and in that the second chamber is in the form of caissons ( 10) arranged inside the first chamber and made integral with at least one of the openings (8), the boxes (10) being provided with means capable of destroying by photocatalysis the organic pollutants present in the effluents. 6 / Apparatus according to claim 5, characterized in that the section (14) of the boxes is of identical size to that of the embrasure of the openings (8). 7 / Apparatus according to claim 5, characterized in that each box (10) has a rear wall (11) provided with a fan (12) ensuring the communication of air from the vacuum chamber to the inside the box in overpressure. 8 / Apparatus according to claim 4, characterized in that the second chamber is in the form of a module (24) independent outside the first chamber (23) and communicating therewith, the second chamber being provided with openings distributed over all or part of its periphery, said openings being provided with means (33) capable of destroying by photocatalysis the organic pollutants present in the polluted air. 9 / installation according to claim 8, characterized in that the first chamber (23) communicates with the module (24) through a pipe (25), the depression of the enclosure (23) and the setting overpressure module (24) being obtained by the implementation of a ventilation means (26) arranged upstream, downstream, or at any point of said pipe (25). 10 / Module (24) capable of being implemented in the installation object of claims 4 and 8 to 9, characterized in that it is intended to communicate with the first enclosure (23), and is provided with openings distributed over all or part of its periphery, said openings being provided with means (33) capable of destroying by photocatalysis the organic pollutants present in the polluted air. 11 / installation according to one of claims 4 to 10, characterized in that the means capable of destroying by photocatalysis organic pollutants present in the effluent combine at least one permeable support, one side at least is covered with a photocatalyst agent with at least one source of artificial UV radiation. 12 / Apparatus according to claim 11, characterized in that the permeable supports covered with a photocatalyst agent are two in number and are separated by an artificial UV source positioned opposite the face of the support treated with the photocatalytic composition. 13 / Apparatus according to claim 11, characterized in that the permeable support (19, 20) is a support based on organic and / or inorganic fibers coated with a layer based on photocatalyst agent. 14 / Apparatus according to claim 11, characterized in that the permeable support (19, 20) comprises three superimposed layers, respectively an inner layer and two outer layers, the inner layer consisting of 80 to 95% by dry weight of activated carbon the 100% complement consisting of organic and / or inorganic chemical fibers, the outer layers comprising 5 to 25% by dry weight of activated carbon, the 100% complement consisting of organic and / or inorganic chemical fibers. 15 / Apparatus according to claim 10, characterized in that the photocatalyst agent is selected from the group comprising metal oxides, oxides including alkaline earth, actinide oxides and rare earth oxides.