WO2019192827A1

WO2019192827A1 - Method for treating air flowing into and/or out of a confined space

Info

Publication number: WO2019192827A1
Application number: PCT/EP2019/056646
Authority: WO
Inventors: Fabrice Giroudiere; Aurelien COQUARD; Arnold Lambert; Pascal Alix; Benoît Amaudric du Chaffaut
Original assignee: IFP Energies Nouvelles
Priority date: 2018-04-04
Filing date: 2019-03-18
Publication date: 2019-10-10
Also published as: FR3079758A1; FR3079758B1

Abstract

The invention relates to a method for treating air flowing into and/or out of a confined space, in order to deplete said air of polluting gaseous compounds, particularly NOx, and solid particles, characterised in that at least part of the air to be treated is guided into a washing device (1) in contact with a flow of a liquid effluent (6) comprising at least one compound that is active in relation to at least one of the polluting gaseous compounds, such that said liquid effluent in contact with the air to be treated becomes loaded with particles and acts on said gaseous compound by absorption, then optionally chemical conversion, particularly of the oxidation or reduction type.

Description

METHOD OF TREATING AIR IN AND OUT OR OUT OF A SPACE

CONFINED

Field of the invention

The invention is concerned with the treatment of air in confined, enclosed or semi-enclosed spaces. They may be frequented by a passing population, users, and / or by a more or less permanent population, such as operating personnel or traders.

These may be underground transport networks of railway type. Under the acronym EFS, we define all indoor spaces below ground level, connected to an underground railway line where workers are employed. This definition therefore applies to all areas where people work on a regular basis, including stations, corridors, trains, tunnels, commercial premises, technical rooms and train service centers. In France, seven cities have networks of EFS, otherwise known as "metros".

It can also be underground car parks, or road tunnels.

In these different cases, ventilation and extraction and / or air supply systems are generally provided, which are intended to make the air present in these confined spaces more breathable, by renewing it with "Fresh" air blown outside and / or by extraction and discharge to the outside of stale air. In some cases, a depollution of the stale air is carried out in so-called "bypass" installations, the air being extracted, cleaned up and then reinjected into the tunnel.

However, these systems are insufficient to guarantee a correct air quality in these confined spaces. In fact, for EFS-type rail networks, urban outside air is collected to renew the air. However, urban air can already have a significant level of pollution, particularly in terms of fine particles, and gaseous polluting compounds such as NOx, or other polluting compounds such as volatile organic compounds (or VOC for the acronym Volatile Organic Compound), or sulfur derivatives, such as SOx sulfur oxides, especially because of automobile traffic, district heating, or nearby industrial activities.

As for the confined spaces of the road tunnel or parking lot type, where the air is loaded with particles and pollutant gases due to underground road traffic, this polluted air is extracted to reject it outside, thereby polluting the outside atmosphere close to these confined spaces. Whether the pollutants are emitted in the confined spaces mentioned above, or reintroduced from the outside, we can see that they can be classified into two categories:

solid particles, which generally come from imperfect combustion (soot), but also from the wear of the tires or braking members of the vehicles, or simply from the deterioration of road surfaces (dust). Their small size, of the order of a few microns, explains their maintenance in suspension in the air. For underground railway enclosures (EFS) the major constituents identified are different metals including iron, elemental carbon and organic carbon. It is also possible to add terrigenous dust, especially composed of silica.

gaseous compounds, essentially nitrogen oxides, with NOx including monoxide and / or nitrogen dioxide (NO, NO ₂ ), but also carbon monoxide CO, sulfur derivatives and VOCs. (Note that the NO can spontaneously oxidize to N0 ₂ under the effect of the sun and the presence of oxygen, so even if it is potentially less harmful than N0 ₂ at equal concentrations, it is also potentially a precursor of N0 ₂ ).

There is therefore a real need to treat the air arriving in and / or extracted from these confined spaces, to improve the quality of the air in these spaces, and / or the air in their vicinity.

Prior art

In road tunnels, electrostatic filtration devices have already been considered to trap solid particles, the aim being in fact to improve visibility in tunnels rather than to clean up the atmosphere before discharge to the outside. . As the air flows are often significant, from tens to hundreds of m ³ per second, and concentrations in very small pollutants, milligram per m ³ or less, the most commonly used devices are electrostatic precipitators for particulate pollutants and chemical traps on absorbing surfaces for gaseous pollutants, so as to minimize the pressure drop of the air circulation. The results are often disappointing, especially for particles that can also "poison" chemical traps and render them ineffective.

Tunnels have actually been equipped with an air handling device, mainly in Japan and Norway. In most cases, this involved electrostatic particle filters, without the treatment of gaseous effluents, the objective being effectively to improve the visibility in the tunnels, especially in the "bypass" installations mentioned above. The efficiency of the electrostatic filtration devices depends to a great extent on the speed of the air inside the filters, but also the clogging of the filters. In addition, the step of ionization of the particles, a prerequisite for their electrostatic precipitation, produces nitrogen dioxide (NO ₂ ) by reaction of NO with the ozone (O ₃ ) produced in the ionizer, which is a harmful effect. The patent application EP 0 431 648 has also been concerned with the treatment of air in confined spaces, in particular offices or hospitals, by proposing ozone treatments with oxidation catalysts to eliminate VOCs and biological pollutants, with the disadvantages of using ozone highlighted above.

The object of the invention is therefore to remedy these drawbacks by proposing a new system for treating air in confined spaces, which is more effective both with regard to pollutants in the form of particles and in the form of compounds. gaseous. It is particularly aimed at a new system applicable to large volumes of air to be treated, with implementation and maintenance facilitated.

Summary of the invention

The invention firstly relates to a process for treating air entering and / or leaving a confined space to deplete pollutant gaseous compounds, especially NOx, and solid particles, where the at least a part of the air to be treated is brought into a washing device in contact with a flow of a liquid effluent comprising at least one active compound with respect to the or at least one of the gaseous pollutant compounds , so that said liquid effluent in contact with the air to be treated is charged in particles and acts on said gaseous compound, for example by absorption, then optionally chemical conversion including oxidation or reduction type.

The flow of the liquid effluent may be in the form of a spray of droplets, or in the form of a gravity flow on packings in the washing device.

In one case as in the other, the invention thus chooses a treatment using a liquid phase, and not, as already known, with filters. And this liquid phase makes it possible to treat both the particles and certain compounds such as NOx, in a single operation: in fact, surprisingly, the invention shows that the choice of a liquid phase makes it possible to suspend the particles when they come into contact with the effluent, the suspension allowing easy to embark in the liquid phase and rid the air to treat so.

A spray of droplets promotes air / effluent contact, in terms of air / liquid contact surface and residence time of the air in contact with the liquid. It is the same if we choose a gravity flow on packings, which will "break" the flow and promote the same air / liquid contact.

Optionally, it is conceivable to carry out this treatment in a confined space already equipped with an air treatment device of the electrostatic filter type: on the one hand, it is thus possible to improve the overall efficiency of the air treatment to particles by exploiting existing devices rather than deactivating / disassembling, on the other hand we can take advantage of the ozone treatment of the filter, because ozone tends to oxidize NO to N0 ₂ , and N0 ₂ are more soluble in the liquid phase than NO. Thus, the extraction of NOx is generally facilitated by the washing of the invention.

And with respect to certain gaseous pollutants such as NOx, it has been found that choosing a basic liquid phase, for example by adding KOH, makes it possible to extract NOx, essentially N0 ₂ , from the air. They can then be treated in the wash effluent.

Advantageously, the treatment according to the invention is carried out at ambient temperature and pressure. This is a considerable advantage in view of the location and the flow rates of air to be treated, because it greatly simplifies the implementation of the process, since it thus limits the equipment (no heating or pressurizing means to predict) and the energy consumption of the treatment.

Preferably, the treatment is carried out in a washing device defining an enclosure in which the liquid effluent flows by gravity. Here again, we choose simplicity, using gravity to circulate, from top to bottom, the liquid phase.

The air to be treated can flow into said chamber co-current, countercurrent or cross flow with respect to the flow of the liquid effluent. The choice is made in particular in view of the configuration of the installation in which the processing device is intended to be integrated.

Advantageously, since the confined spaces of interest to the invention are provided with means for supplying and / or extracting air to and from said confined spaces, the washing device is placed in these means. Concretely, these means are in the form of networks of pipes, chimneys and various enclosures in fluid connection one with the other and equipped with fans / extractors ad hoc to ensure the circulation of the air from inside to outside of the confined space and / or vice versa. By placing the washing chamber near these ventilation / extraction means, (either "upstream" or "downstream" thereof, taking as a reference the general direction of flow of the air in these means ), the air to be treated is circulated in the washing chamber possibly without even having recourse to additional forced circulation devices.

Advantageously, the treatment can be controlled by an electronic / computer control system enabling manual, automatic or semi-automatic remote control. Thus, the control system may comprise electronic / computer means connected on the one hand to one or more measuring means associated with the washing device, in particular a pH sensor of the liquid effluent for example, and to one or more means process control, including valve opening / closing control means, and connected on the other hand to a man / machine interface. The monitoring of the process can therefore be done remotely, limiting as much as possible maintenance operations requiring human intervention. The term "semi-automatic" control method includes a method involving electronic / computer means associated with sensor type instrumentations, while maintaining monitoring / human intervention.

According to a preferred embodiment, the liquid effluent is circulated in the closed loop washing device. The liquid effluent can then be regenerated or replaced continuously or by periodic purge. In the vicinity of the enclosure where the washing is carried out, it is possible to provide a "new" effluent container, intended to replace gradually or once after complete purging the "spent" liquid effluent once sufficiently charged / saturated with solid particles or pollutant gases absorbed / converted. It is also possible to provide a "spent" effluent container, intended to recover all or part of the spent effluent, possibly with a settling time sufficient to more easily collect the particles at the bottom of the container. The gaseous pollutant species possibly still present in this spent effluent may be treated on site or subsequently, after emptying the container once full, and recovery of the liquid phase. All suitable fluidic connections (valve-equipped lines) are provided for easy purging or filling of liquid from or to the wash cabinet.

It is therefore understood by "spent effluent" an effluent charged with particles / pollutant gas to such a level that it becomes useful / necessary to evacuate to replace it. This level can be defined according to the degree of saturation in particles / gas, the spent effluent being preferably replaced (a little) before reaching this degree of saturation to preserve its effectiveness. On the contrary, the "new" effluent is to be understood as a "fresh" effluent or a spent effluent that has been reprocessed / cleaned and that is not donated / almost not loaded with particles / polluting gas.

As mentioned above, it is possible to increase the time and the contact surface between the air to be treated and the liquid effluent by choosing in a first variant a gravity flow by providing the inside of the enclosure of the washing device of packings (also called "internal"), of the type used for example in the field of distillation columns. By thus maximizing this contact, the suspension of the particles and the solubilization of the compounds to be treated in the liquid phase comprising the active agent intended for treating them are further improved. This can also reduce the size of the enclosure without decreasing the air / liquid effluent contact time. The gravity flow can be achieved by a plurality of water inlets at the top of the washing device enclosure, which create a plurality of liquid streams flowing up and down and breaking on the packings .

According to a second variant also mentioned above, it is also possible to use one or more spray nozzles or spray nozzles, which spray the liquid effluent in the form of one or more clouds of droplets, traveling up and down the enclosure of the washing device under the effect of gravity. Still with the aim of improving the efficiency of the treatment, the liquid effluent may contain a solubility promoter of the gaseous pollutant compounds. It may be in particular, oxidizing agents such as hydrogen peroxide, which converts at least a portion of the NO to NO ₂ , which, as previously seen, solubilize better in a liquid effluent than NO, which, globally , improves the extraction of NOx by the washing effluent of the invention.

The effluent is preferably at a basic pH, and for this contains at least one alkaline compound such as KOH or NaOH or other basic inorganic or organic compound, this to convert the NO ₂ to non-polluting substances.

In the same way, the invention also relates to any device for implementing the method described above.

It relates in particular to a device for treating air entering and / or leaving a confined space to deplete polluting gas compounds, in particular NOx, and solid particles, which comprises a washing device comprising an enclosure of substantially vertical or oblique orientation which is provided with a liquid effluent inlet, a liquid effluent outlet, an air inlet to be treated and a treated air outlet, with gravity flow from top to bottom of the liquid effluent and comprising at least one active compound with respect to the or at least one of the gaseous polluting compounds, and a co-current, countercurrent or current flow cross of the air to be treated, so that said liquid effluent in contact with air is charged in particles and acts on said or at least one of said gaseous compound, in particular by absorption, then optionally chemical conversion, in particular of the oxidation type or r duction.

Cross flow is preferred because it allows device configurations easier to implement, and because it is particularly effective in promoting exchanges between the air to be treated and the liquid effluent.

Preferably, the interior of the enclosure of the washing device is provided with packings as seen above when the flow of the liquid effluent is done gravity without spraying. This is the easiest embodiment to industrialize and then implement, so the preferred mode.

The device may also include ventilation means to ensure the supply and circulation of air in the enclosure, either means that are specific to it, or means already provided for equipping the extraction means / insufflation of air confined spaces in question.

The device is advantageously provided with an electronic / computer control system enabling manual, automatic or semi-automatic remote control, said control system including electronic / computer means connected on the one hand to one or more means of measurement associated with the washing device, in particular a pH sensor of the liquid effluent, and at least one control means of the process, in particular valve opening / closing control means and connected on the other hand to a man / machine interface. The connections can be provided by any known means (local internet network ...) and use the same connection system as that used, for example, for the monitoring and maintenance of the ventilation / extraction means provided in the tunnels and underground .

It is the same for the power supply of the washing device: it is possible to use the electrical networks already present, in particular for supplying lighting means or for supplying the above-mentioned ventilation / extraction means.

The device according to the invention may also comprise, upstream of the washing device, an electrostatic filter with ozone treatment, this filter producing a first treatment level and, under the action of ozone, coming to oxidize NO in NO ₂ , easier to solubilize in the liquid phase during the subsequent washing treatment.

According to a simplest embodiment, the liquid effluent inlet and the liquid effluent outlet of the chamber are in fluid connection with each other, the liquid effluent circulating in a closed loop. The liquid effluent, which is collected at the bottom of the chamber and which, via a pipe system and, for example, a pumping means, is then reinjected into the enclosure "from above" is then injected into the chamber "from above". top of the speaker.

As the liquid effluent will then gradually load into solid particles and become depleted in reagent, it is necessary to predict how to replace the effluent "used". The device can be provided with a means of purging the liquid effluent, and purging it completely to replace it with a "new" liquid effluent periodically, or as soon as thresholds followed by instrumentation means are reached (fall of pH, particle content ...). It is also possible to provide means for taking part of it, to replace it periodically or continuously.

A "new" effluent container can be provided near the washing chamber, with a possible fluid connection between the container and the chamber.

It is also possible to provide a holding container for temporarily storing "spent" liquid effluent following a complete or complete purge. It is then possible to determine a residence time of the effluent "used" in this container (tank) minimum before emptying to allow the solid particles to fall by gravity to the bottom of said container, which can facilitate the collection and evacuation of solid waste separately from the supernatant liquid phase.

Preferably, the liquid effluent is an aqueous phase, which is the simplest, the least expensive and the least polluting of the liquids. It may contain at least one active agent such as an alkaline compound of type KOH and / or a solubility promoter of the gaseous pollutant compound, such as hydrogen peroxide.

More preferably, the liquid phase is a basic aqueous phase: its pH is for example between 7.5 and 10, preferably between 7.5 and 8.5 or between 7.5 and 8, so a pH preferably slightly basic, which has a beneficial effect on the absorption / reduction of tyoe NOx gases, without requiring precautions too complex / expensive in terms of equipment safety during their implementation.

The invention also relates to the use of the method or device described above for purifying air entering and / or leaving confined spaces, including underground spaces such as road tunnels or rail or underground car parks. This type of volume is therefore understood under the term "confined space", that is to say a covered or underground volume, at least partially enclosed, generally intended for the circulation or parking of means of locomotion of the individual car type. , bus, train, trams ...

detailed description

The invention will be described in detail below by way of nonlimiting examples illustrated by the following figures:

Figure 1: a representation of an exemplary embodiment of a washing device according to the invention in a vertical section;

Figure 2: a representation of a use of the washing device of Figure 1 for treating the air extracted from a road tunnel in a vertical section along the longitudinal axis of the tunnel;

Figure 3: a representation of a use of the washing device of Figure 1 for treating the air entering an underground rail network in a vertical section transverse to the railway;

Figure 4: a representation of a use of the washing device of Figure 1 for treating the incoming and / or outgoing air in an underground car park in a vertical section transverse to the roadway above the car park.

All these figures are very schematic, and the different components represented are not necessarily scaled. The identical references from one figure to another refer to an identical component. The components of the washing device shown are represented in their positioning in normal operation.

With the help of Figure 1, first described the washing device 1 according to the invention alone, before then see its integration to treat air confined spaces of different types. Device 1 does not will be described only by its main components. It comprises an enclosure 2 in the form of a column intended to be oriented substantially along a vertical axis. This column here has a substantially circular section, other variants may provide different sections, square, oval, rectangular ... The enclosure is equipped in the upper part of a flow ramp 3 connected via an inlet 4 in part high in the enclosure to a circulation loop 5. It can provide multiple ramps, or individual nozzles. This ramp sends a plurality of jets, in the form of a plurality of aqueous liquid effluent flows, distributed over the section of the enclosure, in the manner of a shower which, under the effect of gravity, circulates from top to bottom to break on packings (not shown, and which remain optional) and form, in the lower part of the enclosure, a certain level of liquid which is then discharged through an outlet 7 connected to the pipe 5, to allow closed-loop recirculation of the liquid effluent. A pump 8 is provided in the lower part of the pipe, to bring the liquid effluent out through the lower outlet 7 to go up to the inlet 4 at the top.

Alternatively, instead of making a simple gravity flow of the liquid effluent, it can be carried out under pressure pressure via ad hoc ramps / nozzles, to create in the enclosure one or more clouds of droplets running from top to bottom of the enclosure, there is no longer any need for packing. The appropriate settings can be made to best adjust the droplet velocity, and / or change their size and / or the trajectory of the drops or the cloud of drops as a whole.

The chamber is also provided with an air inlet 9 to be treated at the bottom of the enclosure and an air outlet 10 at the top of the enclosure. The inputs and outputs 9, 10 are each connected to pipes.

The air to be treated circulates from bottom to top, counter to the liquid effluent. The quality of the gas-liquid contact (contact surface, exposure time) is improved by placing inside the enclosure 2 specific runoff structures called packings or "internal" in the field of distillation columns, for example . Typically, structured packings (geometric areas ranging from 100 to 750 m ² / m ³ ) or bulk (geometric areas ranging from 70 to 300 m ² / m ³ ) can be used.

To further reduce the pressure drop, it is alternatively possible to circulate the air from top to bottom (this is called co-current flows). It is also conceivable to circulate the air laterally (there are then flows in cross currents).

The liquid effluent, the washing liquid therefore, circulates continuously, is gradually loaded into particles and is converted chemically by the absorption / conversion of gaseous pollutant compounds whose aim is to reduce the content in the air thus treated. When the liquid effluent is overloaded particles or that it no longer absorbs the gaseous compounds targeted, it is drained and replaced by a simple pumping operation. Alternatively, it is also possible to provide continuous renewal by an auxiliary / purge system to limit the volume of effluents to be treated. The system can advantageously be equipped with online analyzers for monitoring and preventive maintenance of the installation, for example by pH control.

The liquid effluent is for example an aqueous phase containing KOH (or NaOH) to ensure a basic pH neutralizing the HNO ₃ resulting from the solubilization of NO ₂ to form a nitrate. Hydrogen peroxide can be added to oxidize HNO ₂ from the solubilization of NO, which increases the solubility of NO by equilibrium displacement. It should be noted that a solution at basic pH also makes it possible to absorb other polluting or at least unwanted gaseous compounds including C0 ₂ , S0 ₂ , H ₂ S.

The mechanisms in aqueous solution for the absorption of NOx in water in the presence of H ₂ O ₂ and NaOH are in particular explained in the techniques of the engineer, G1805 V1-NO (nitrogen oxides).

To give dimensional orders of magnitude, the chamber 2 may have a passage section of between 1 and 170 m ² , for example 90 m ² , which corresponds to a square surface of 13 mx 13 m, and a height included between 2 and 30 m. for example 10 m.

To give orders of magnitude of process parameters, it is possible to take the example of a flow of air to be treated having a flow rate of 55 m ³ / s. The air is at 20 ° C and the pressure is the ambient pressure (1 bar). To absorb almost all NO ₂ and particles, a flow rate of liquid effluent such that the watering rate is at least about 60 m ³ / m ² / h, is provided. The watering rate is defined as the flow of liquid divided by the section of the washing column.

For standard loose packing ("Pâli Rings" 100-300 m ² / m ³ ), it is preferable to limit it to speeds of the order of 0.6 m / s, ie a section of approximately 92 m ² ( typically a square approximately 10 m square). The packing height is 10 m to ensure a 70% reduction in the N0 ₂ content of the air. The minimum flow rate of KOH is 1.54 m ³ / s to ensure a good wetting of the structure.

With a standard structured packing (100-300 m ² / m ³ ) the section can be reduced to about 40-50 m ² or a square of 6-7 m. The height remains comparable. To maintain a relevant wetting rate, the flow of liquid effluent of the order of 0.5 m ³ / s. It should be noted that the packings can occupy only part of the height of the enclosure, and that, alternatively, the washing chamber can also operate without packings, with or without spraying the liquid under pressure.

The device 1 is also equipped with instrumentation, in particular a pH sensor of the liquid effluent, to measure the evolution of its concentration of KOH. The proper functioning of the pump 8 and the ramp 3 can be monitored, cameras can be provided, and the valves equipping the device, including the not shown bleed valve (associated with a possible retention tank), can be controlled.

A control system controls and monitors the device and displays relevant information (alarms, monitoring of measurements by instruments, video image ...) on a remote HMI man machine interface. The connections between the instrumentations, the controllable elements, the control unit and IΊHM are made in a known manner, for example by a local internet network, using optical fibers, modular connectors for Ethernet connection type RJ45 (with possible addition of a switch / LAN closer to the washing device 1).

FIG. 2 shows the application of the washing device of FIG. 1 for treating the air extracted from a road tunnel 20, for example under a mountain or hill 1. In known manner, this type of tunnel is equipped with fresh air inlet (s) 22, here in the lower part of the tunnel, and outlet (s) of polluted air with conduits 23, also called chimneys, here substantially vertical, connecting exit openings in the tunnel ceiling with the outside. These air outlet ducts 23 are provided with extraction means, large fans (not shown) in particular, which force the flow of air from the tunnel to the outside. According to the invention, there is available a washing device 1 in each of these conduits 23, here two are shown, but there may be many more depending on the size of the space to ventilate, the dimensions of the tunnel.

The extraction means equipping these ducts make it possible to force the circulation of air in the washing chamber of the devices, which, depending on the case, can be placed "upstream" or "downstream" thereof by taking as reference the general direction of flow of air in these ducts indicated by arrows in the figure. Thus, with the invention, the purified air that exits the tunnel is purified in order to reject outside air no / less polluted, thereby improving the breathability of the air for people living or moving around the city. outside the tunnel.

Note that the washing devices of the invention may, alternatively, not be arranged directly in the extraction ducts, but in the enclosures or spaces in which these ducts open out. It may then be easier to install them and to maintain them, because of the size of the washing chambers and their peripherals (instrumentation, liquid effluent recirculation loop, possible retention tank under the purge valve, connection cables and power supply ...).

Figure 3 shows the application of the washing device of Figure 1 to treat the air blown into an underground rail network (EFS). Y is shown in vertical cross section a subway tunnel 30 with two subways running on two lanes side by side. The tunnel 30 is provided on the one hand with air supply ducts 31 and air extraction ducts 32 provided with extraction means in the form of large fans 33, ducts present throughout the tunnels with ducts. given intervals. Sound insulators 34 isolate the fans 33 upstream and downstream of the direction of flow of air (arrowed) in the conduits in question. In this configuration, it is arranged in at least one of the air inlet ducts 31, in particular in all, a washing device 1 according to the invention. Here, it is therefore a question of treating the polluted urban external air entering the tunnels, considering that the outside air in this case (car traffic, district heating ...) presents a level of pollution superior to that tunnels, where the subways are electrified.

Optionally, it is also possible to provide the washing devices according to the invention also in the air extraction ducts 32.

The devices inserted in conduits are shown here. As in the previous case, they can also be moved into enclosures or spaces into which these ducts open out. It sometimes happens that these entry and extraction ducts thus open into dummy buildings (that is to say, without inhabitants) equipped with all the appropriate ventilation means, monitoring means ..., and which offer therefore easily accessible spaces for arranging the devices according to the invention in the flow of the incoming air flow (and possibly outgoing).

FIG. 4 represents the application of the washing device of FIG. 1 for treating the air for an underground car park: two basement levels 40, 41 are shown connected by one or more ramps that are not shown, with, as in the case of Figure 3, air intake ducts 43 and air extraction ducts 44 provided with ventilation means 33 themselves provided with sound insulation means 34. It is available in each air intake duct 43, or at least in one of them, a washing device 1 according to the invention, in order to treat the air entering the subterranean.

As here the risk of pollution also comes from the interior of the underground, by the circulation of vehicles in the parking lot and engines, it may also be wise to place washing devices 1 also in the extraction ducts 44. air, to purify polluted urban air entering to increase the quality of the air breathed by people frequenting the car park, but also the outgoing air that is rejected outside, to avoid increasing the level outdoor air pollution. As in the case of FIG. 3, the washing devices according to the invention can also be disposed of not in the ducts themselves, but in the enclosures in which they open outwards, especially at the level of buildings. factitious 35.

In conclusion, the washing device of the invention is inexpensive in energy or installation, it adapts well to the treatment of the air of confined atmospheres, to treat the air that leaves and / or enters it according to the difference in the level of pollution encountered between the outside air and the air of the confined space. It makes it possible to treat both the pollution in particulate form and in gaseous form in a single operation, while operating with an aqueous phase.

Claims

A method of treating air entering and / or leaving a confined space to deplete pollutant gaseous compounds, in particular NOx, and solid particles, characterized in that at least a portion of the air to be treated in a washing device (1) in contact with a flow of a liquid effluent (6) in the form of a basic aqueous phase comprising at least one active compound with respect to the at least one of the gaseous pollutant compounds, such that said liquid effluent in contact with the air to be treated is charged in particles and acts on said gaseous compound by absorption, then optionally chemical conversion, in particular of the oxidation or reduction type.

2. Method according to the preceding claim, characterized in that the basic aqueous phase has a pH of between 7.5 and 10, preferably between 7.5 and 8.5 or between 7.5 and 8.

3. Method according to one of the preceding claims, characterized in that the flow of the liquid effluent is carried out in the form of spraying droplets, or in the form of a gravity flow on packings in the washing device.

4. Method according to one of the preceding claims, characterized in that the treatment is carried out in a washing device (1) defining an enclosure (2) in which the air to be treated flows into said chamber to co- current, counter-current or cross-flow with respect to the flow of the liquid effluent.

5. Method according to one of the preceding claims, characterized in that the confined spaces are provided with supply means (22, 34, 43) and / or extraction (23,32,44) of air to and / or from said confined spaces, means in which it comes to place the washing device (1).

6. Method according to one of the preceding claims, characterized in that the driver control treatment by an electronic control system / computer for manual control, automatic or semi-automatic, remote, said control system comprising electronic means / Computer connected firstly to one or more measuring means associated with the washing device, in particular a pH sensor of the liquid effluent, and to one or more process control means, in particular opening control means. / closing valves, and connected on the other hand to a man / machine interface.

7. Method according to one of the preceding claims, characterized in that circulates the liquid effluent (6) in the washing device (1) closed loop, and in that the effluent is regenerated or replaced liquid continuously or by periodic purge, particularly with a waste effluent container and / or a fresh effluent container disposed near the washing chamber.

8. Method according to one of the preceding claims, characterized in that the liquid effluent is an aqueous phase which contains a solubility promoter of the gaseous pollutant compound, especially hydrogen peroxide for NO, and / or an active agent under form of an alkaline compound such as KOH for N0 ₂ , C0 ₂ , S0 ₂ , and H ₂ S.

9. Device for treating air entering and / or leaving a confined space to deplete gaseous polluting compounds, including NOx, and solid particles, characterized in that it comprises a washing device (1) comprising an enclosure (2) of substantially vertical or oblique orientation which is provided with a liquid effluent inlet (4), an outlet (7) of liquid effluent, and an inlet (9) ) air to be treated and an outlet (10) of treated air, with a flow from top to bottom of the liquid effluent either in the form of a droplet flow or by a gravity flow on packings, and comprising at least one active compound with respect to the or at least one of the gaseous pollutant compounds, such that said liquid effluent in contact with the air is charged with particles and acts on said at least one of said gaseous compound by absorption, then optionally chemical conversion, in particular of the oxid type ation or reduction.

10. Device according to claim 9, characterized in that it comprises ventilation means to ensure the supply and circulation of air in the enclosure.

1 1. Device according to one of claims 9 or 10, characterized in that it is provided with an electronic control system / computer for manual control, automatic or semiautomatic remote, said control system comprising including means electronic / computer connected on the one hand to one or measuring means associated with the washing device, in particular a pH sensor of the liquid effluent, and at least one control means of the method, in particular opening control means / closing valves and connected on the other hand to a man / machine interface.

12. Device according to one of claims 9 to 1 1, characterized in that the liquid effluent inlet and the liquid effluent outlet of the chamber are in fluid connection (5) with each other , the liquid effluent flowing in a closed loop.

13. Device according to one of claims 9 to 12, characterized in that it is provided with a purge means of the liquid effluent, or removal of a portion thereof to replace periodically or continuously .

14. Device according to one of claims 9 to 13, characterized in that it comprises a new effluent container and / or a waste effluent container.

15. Use of the method or device according to one of the preceding claims for purifying air entering and / or leaving confined spaces, including underground spaces such as road tunnels or rail or roadside parking.