FR2851478A1 - Air scrubbing device, especially for pig farms, comprising tank in which air permeates through porous material, e.g. polyethylene, moistened by solution overflowing from dish around air inlet tube - Google Patents

Abstract

In air scrubbing device, comprising a tank having an inlet for air to be purified and at least one outlet for treated air, such that the air within the vat permeates through at least one moistened porous structure, the enters the tank (1) via a tube (3) surrounded by a dish (6) which contains solution for moistening the porous structure (4), rests at least partially on the porous structure and moistens the structure by overflowing.

Description

AIR WASHING DEVICE, PARTICULARLY FOR PIGS

  The invention relates to an air washing device, in particular for pigsties.

  For those living near a pigsty, breeding is synonymous with nuisance, odors becoming more and more the center of concern.

  If the mechanisms of olfaction are almost known, it is still not possible to quantify an odor without resorting to the human nose.

  Over 160 odorous compounds have been identified to date in the gaseous effluent from a pig farm.

  This very large number of odorous molecules poses a problem because in industry for example, it is easy to treat a gaseous effluent which comprises only a few compounds in large quantity, while in the case of a breeding operation, we are in the presence very many compounds, most of which are in small quantities.

  Among the main compounds of the air extracted from pigsties, the following compounds have been detected by chromatography: - acid compounds: acetic acid and especially n-butyric acid, n-valeric acid; nitrogen compounds: indol, scatol, and especially ammonia; - phenol; aldehydes and ketones: acetone, hexanal, acetaldehyde and especially heptanal.

  The odor components present in sufficient quantity to be detected by the human nose, in a piggery atmosphere, are n-butyric acid, n-valeric acid, ammonia and heptanal.

  It seems that the odorous molecules are absorbed on the dust and are dispersed and carried by the wind.

  To reduce the amount of dust, it is possible in particular to modify the presentation of the pig's feed or even to use ambient control systems such as devices for atomizing essential oils and odor masking molecules. in a fine, dry mist.

  You can also place a filter at the outlet of the ventilation system or use an electrostatic precipitation device in which the air extracted from the 5 pigsties passes through a mesh of ionized wires which discharges positively, the air then passing between positive potential plates and earthed plates.

  It has also been proposed to degrade or retain the odorous particles themselves: - by ozonation, ozone having the disadvantage of being dangerous for the health of animals; - biofilter: a sort of tank filled with a very porous material in which microbial populations develop following a seeding, the passage of the gaseous effluent being forced through this filter, the microbial populations oxidizing the compounds odorants.

  The major drawback of this system is that it imposes a fairly large surface area of the order of 1m2 for 4 pigs for fattening.

  Furthermore, the effectiveness of a biofilter remains important only as long as an optimum humidity level is maintained and that no preferential passage for the time is created through the porous material.

  Finally, the bio-filter must be regenerated, which implies a reversal and aeration of the substrate every 6 months approximately.

  During this operation, there are risks of a significant release of odors.

  It has also been possible to envisage passing the air to be deodorized over activated carbon, the price of activated carbon in an easy to handle form remaining high.

  Finally, chemical gas washing has been proposed.

  This chemical washing makes it possible to treat a gaseous effluent by transferring the odorous compounds from the gas phase to the liquid phase.

  During this transfer, a chemical reaction can take place, for example by the use of an oxidant.

  As ammonia is soluble in water, as well as hydrogen sulfide and mercaptans, acids and certain alcohols, washing can therefore be done via an aqueous solution, regulated or not in pH.

  For other compounds such as aldehydes, ketones and aromatic hydrocarbons, the use of solvent is necessary.

  The contact between the gas and the liquid is ensured by the spraying of the washing liquid against the current of the gas, in conventional systems.

  If necessary, washing is followed by bio-purification, the pollutants removed by the water being taken to purifying microorganisms in a separate activation basin.

  The state of the art which has just been presented overall above is notably illustrated in the following documents: - French patent applications published under the numbers 2.183.902, 2.223.070, 2.663.861, 2.761.975, 2.772 .638; - US patents granted under the numbers 3.936.281, 4.107.268, 5.983.834, 6.059.865; - European patent applications published under the numbers 0.933.116, 20 1.066.752; - international patent application published under number 01/93990.

  The document FR 2.183.902 describes a device for purifying exhaust air polluted in particular by olfactory and harmful substances, comprising at least one filter placed in the flow of the air to be purified, consisting of 25 identical units capable of each to operate independently, and each of which comprises an air supply tube, an exhaust tube and a filter housing containing a filter, said units being arranged so that they can be joined by horizontal or vertical juxtaposition.

  This filter device is presented as advantageous compared to the installations for removing olfactory and harmful substances from the exhaust air by washing the latter with water, these installations having a drawback in that the harmful substances are transferred. from the exhaust air to the water, which means that large quantities of water laden with said substances have to be treated in an expensive manner before this water can be discharged into a system of pipes.

  The document FR 2.223.070 describes a process and an apparatus making it possible to deodorize waste gases, by means of the reaction of foul-smelling compounds with acids, and the neutralization of excess acidity by one or more alkaline carbonates. earthy and / or magnesium.

  Acids are formed by the reaction of water with chlorine or sulfur dioxide, these "acid gases" being introduced into a mixer together with the waste gases to be deodorized. The mixture of these waste gases and "gases for acids" circulates against the flow of an aqueous suspension of pulverulent carbonates.

  The device described in this document FR 2.223.070 has in particular two drawbacks: hydrochloric acid is produced in the mixer, causing risks of corrosion and risks of burns during repairs or maintenance; - foul-smelling (sulfur dioxide) and dangerous (chlorine) gases are used to be mixed with the gases to be deodorized.

  The document FR 2,663,861 describes a process for purifying stale air in which a liquid dispersed is dispersed on the stale air admitted into a first enclosure, stale air which is passed through a perforated wall inclined downward comprising a lower liquid discharge orifice, then passes the air through a series of baffles.

  The perforated wall is funnel-shaped, cone-shaped or hemispherical. Baffles are staggered trays and activated carbon filters allow deodorization of the treated air.

  The device described in document FR 2,663,861 is of complex structure, its function being to rid a stale air of the liquid or solid particles which it contains, this air being able to be hot (up to 400 OC) the suppression of odors does not not being an essential goal.

  The document FR 2,761,975 describes a chemical process for recycling and regenerating the oxygen in the ambient air of livestock premises, this process being presented as a variant of the method of ozonation by lamps with ultra-high radiation. violet emitting in the 1850 A line, or the ozonation method by exposure of oxygen under pressure to electric arcs.

  The document FR 2,761,975, after having stressed the aggressive nature of ozone, for the respiratory system, beyond a few ppm, proposes the use of a mixture of benzaldehydes and unsaturated terpenes, dispersed in the ambient air of the breeding premises.

  The air dispersion of this mixture is obtained using sprayers, blowers, compressors, air dispersers with air or compressed gas pressure, turbine molecularizers, bubblers, static or dynamic or thermal evaporators, evaporators by capillarity, as well as natural or artificial absorbent supports in which the mixture to be air-dispersed will have been previously incorporated.

  Benzaldehydes are compounds that irritate humans and can cause lung damage.

  The document FR 2,772,638 describes a process and a device for purifying gaseous and liquid effluents produced in livestock buildings, comprising the steps consisting in: collecting the stale air at the outlet of the building; - prewash stale air in a closed enclosure by spraying the liquid effluent; - oxygenate and homogenize the liquid effluent; - extract stale air enriched with nitrogen from the prewash chamber by a controlled fan; - Introducing this air into an isothermal container of reactive washing continuously followed by biological purification; - recycle the treated effluent in the livestock building.

  The stale air passes through linings of inert material permanently sprayed with a reactive solution.

  The device described in this document FR 2,772,638 is very bulky on the ground, the air to be treated first passing through a partially buried tank 5 containing the liquid effluent before entering an insulated container comprising a first washing zone, a second biologic biofilter treatment zone and a ventilation box.

  The device described in document FR 2,772,638 also has the drawback of requiring a powerful ventilation unit to compensate for the pressure losses generated in the air circulation network to be treated, (in particular filling and mass of the biofilter ).

  Document US Pat. No. 4,107,268 proposes the deodorization of the ambient air of an intensive breeding installation using an aqueous mixture of hydrogen peroxide and sulfuric or phosphoric acid.

  Document US 5,983,834 describes a method and a device for injecting ozone into the ambient air of an intensive breeding facility, in particular a pigsty.

  The document US Pat. No. 6,059,865 describes an installation for deodorizing ambient air in farms, by washing air with the aid of an aqueous solution containing an enzyme.

  The air to be treated is propelled against a rough inclined metal grid on which the aqueous solution flows. This air is returned to approximately 900, by its meeting with the grid and then passes through a spray of water, this spraying being carried out by nozzles with jets perpendicular to the upward vertical air flow.

  The document EP 0.933.116 proposes the washing of the air of the breeding installation by water irradiated with infrared.

  Document EP 1,066,752 in the name of Niemeiji describes an air washing column, comprising a plurality of parallel vertical tubes of synthetic material, with perforated side walls, the air flowing from bottom to top through this openwork tubular structure, water being sprayed above these tubes.

  Document WO 01/93990 describes an air washing device for pigsties, comprising a filtering mat based on corrugated cardboard sprayed with an aqueous solution comprising a denitrifying bacterium.

  The invention aims to provide a compact, economical installation, easy to maintain, allowing the washing of air, especially for pigsties, and ensuring a reduction in odors and an extraction of pollutants, without causing damage to the environment and without use compounds the handling of which is dangerous for humans or animals.

  To this end, the invention relates, according to a first aspect, to an air washing device, in particular for pigsties, comprising a tank provided with a pipe for supplying the air to be washed and at least an outlet for the washed air, the air circulating, in said tank through at least one humidified honeycomb structure, characterized in that the air to be washed enters said tank at the outlet of an inlet pipe around which extends an annular bowl containing the solution to moisten the honeycomb structure, this annular bowl resting at least in part on this honeycomb structure and humidifying it by overflow.

  According to various embodiments, this device has the following characteristics, where appropriate combined: - it comprises at least two blocks of honeycomb structure, resting at a distance from the bottom of the tank, each of these two blocks having an external lateral face disposed opposite 'A window formed in the wall 25 of the tank, and an internal side face of entry of the air flow to be washed; - It comprises more than two blocks of honeycomb structure arranged substantially equidistant from each other in radial directions relative to the direction of entry into the tank of the air flow to be washed; the internal lateral faces of the blocks of honeycomb structure are substantially contiguous two by two so as to define an openwork annular jacket for the entry of air to be washed in the blocks; the inlet pipe for the air to be washed is arranged in the upper part of the tank and the outlets for the washed air are placed in the lower part of the tank, the tank being provided with support means enabling it to rest on the ground, l washed air can thus escape in the vicinity of the ground level; - the tank is made of polymer material such as polyester; the blocks of honeycomb structure forming filter bars are made of polymeric material such as polyethylene; - the tank comprises a body and a dome cover, a lip seal being disposed between the body and the dome, so as to ensure that the washed air leaves through the windows provided for this purpose in the wall of the tank, at look at the honeycomb blocks; - The solution to moisten the honeycomb blocks essentially comprises water and biodegradable oxidizing agents; - Valves allow the emptying of the tank and the supply of solution to the annular bowl.

  Other objects and advantages of the invention will become apparent during the following description of embodiments, which description will be made with reference to the accompanying drawings in which: - Figure t is a side view of a tank according to a embodiment, the components internal to the tank being seen by transparency; - Figure 2 is a top view of the tank shown in Figure 1, 25 after removal of the closing dome.

  This washing device comprises a tank 1 resting on the ground for example by means of a stainless steel support (not shown) This tank 1 is closed by a dome 2 provided with a central opening for connection to an inlet pipe 3 of the gaseous effluents to be treated.

  In an advantageous embodiment, the tank 1 and its cover 2 are made of polyester, a lip seal being placed between these two elements 1, 2.

  Inside the tank 1 are placed filter rolls 4.

  In one embodiment, this filter bars are formed from a polyethylene mesh.

  A part 5 defines an annular bowl 6 resting on the filter bars 4 and is assembled to the inlet pipe for the effluents to be treated 3.

  Water, possibly containing oxidizing agents or treatment agents, is introduced into the annular bowl 6, for example by one or more nozzles, not shown.

  The water overflows from the annular bowl 6 according to the arrows 7 and thus crosses the filter bars 4.

  The gaseous effluents to be treated are aspirated, for example by a fan, and expelled towards the body of the washer, by the inlet pipe 3 and comes through the filter rolls 4 wetted by spraying the water overflowing from the bowl 6.

  The air is expelled radially with respect to the tank 1, according to the arrows 8.

  The tank 1 is provided for this purpose with windows arranged facing each of the filter bars 4.

  In the embodiment shown, eight filter bars 4, for example made of honeycombed polyethylene, are arranged in the tank 1.

  As an indication, for the dimensions specified in the appended drawing, the 20 technical characteristics are as follows: - treatment capacity: 10,000 m3 of air per hour; - footprint: 2.83 m2 on the ground; exchange area of filter bars: 2.16 m2; - output air speed: 1.2 m / second maximum; 25 - odor reduction: 70% guaranteed. The sprinkling of the loaves 4 is adjustable by valve, another valve making it possible to empty the body of the tank or to take samples, for example for chemical or bacteriological measurement.

  The space requirement is minimum relative to the exchange surface and the processing capacity 30 thanks to the radial arrangement of the filter bars 4. - 10

  The selling price of the device is very competitive, this device being intended to be installed for each of the breeding rooms of a pigsty for example, without changing the structure of the breeding building.

  It is therefore not necessary to carry out heavy work on the building to equip it with this air washing device. - he

Claims (10)

  1. Air washing device, in particular for pigsties, comprising a tank (1) provided with a pipe for supplying the air to be washed and at least one outlet for the washed air, the air flowing in said tank (1) through at least one humidified honeycomb structure (4), characterized in that the air to be washed enters said tank (1) at the outlet of an inlet pipe (3) around which extends an annular bowl (6) containing the solution to moisten the honeycomb structure (4), this annular bowl (6) resting at least partially on this honeycomb structure (4) and humidifying it by overflow.   2. Air washing device according to claim 1, characterized in that it comprises at least two blocks of honeycomb structure (4), resting at a distance from the bottom of the tank, each of these two blocks having a lateral face external disposed opposite a window formed in the wall of the tank (1), and an internal side face of entry of the air flow to be washed.   3. Washing device according to claim 2, characterized in that it comprises more than two blocks of honeycomb structure (4) arranged substantially equidistant from each other in radial directions relative to the direction of entry into the tank. of the air flow to be washed.   4. Washing device according to claim 3, characterized in that the internal lateral faces of the blocks of honeycomb structure (4) are substantially contiguous in pairs so as to define an annular openwork jacket for the air inlet to be washed in the blocks (4).   5. Device according to any one of claims 1 to 4, characterized in that the inlet pipe (3) of the air to be washed is disposed in the upper part 12 of the tank (1) and the air outlets washed in the lower part of the tank (1), the tank being provided with support means allowing it to rest on the ground, the washed air thus being able to escape in the vicinity of the ground level.   6. Device according to any one of claims 1 to 5, characterized in that the tank (1) is made of polymeric material such as polyester.   7. Device according to any one of claims 1 to 6, characterized in that the blocks of honeycomb structure forming filter bars (4) are made of polymeric material such as polyethylene.   8. Device according to any one of claims 1 to 7, characterized in that the tank comprises a body and a dome cover, a lip seal being disposed between the body and the dome, so as to ensure that the washed air leaves through the windows provided for this purpose in the wall of the tank, with regard to the alveolate blocks (4).   9. Device according to any one of claims 1 to 8, characterized in that the solution intended to moisten the cellular blocks (4) essentially comprises water and biodegradable oxidizing agents.   10. Device according to any one of claims 1 to 9, characterized in that valves allow the emptying of the tank (1) and the supply of solution to the annular bowl (6).