WO2005061078A1

WO2005061078A1 - Air cleansing apparatus

Info

Publication number: WO2005061078A1
Application number: PCT/DK2004/000904
Authority: WO
Inventors: Preben Staehr
Original assignee: Turbovent A/S
Priority date: 2003-12-22
Filing date: 2004-12-22
Publication date: 2005-07-07

Abstract

Air cleansing apparatus including an air exhaust, a ventilator, a moistening chamber with a number of nozzles, an air intake and a liquid collecting unit, where a central part is entirely or partly designed as a double-walled pipe section, that is with an internal and an external pipe, and that the apparatus furthermore includes an air diffuser which is disposed downstream of the ventilator at one end of the internal pipe.

Description

Air Cleansing Apparatus

Field of the Invention

The present invention concerns an air cleansing apparatus including an air exhaust, a ventilator, a moistening chamber with a number of nozzles, an air intake and a liquid collecting unit.

Background of the Invention

It may be very difficult to place certain works, e.g. farms and production facilities, in the vicinity of or in urban areas due to various emissions - odour or dust nuisances - with which the works are influencing the surroundings.

These emissions are often the cause of great discontent among neighbours in the nearby living areas, either due to strong disagreeable smell or an unwanted content of chemical substances or dust particles.

In order to protect the environment and to reduce the health hazards for people living in the nearby living areas, a number of laws and regulations have been issued concerning the allowed emission level and the allowed content of harmful substances in the emissions.

For health reasons, in farming it is necessary to ventilate the stable areas in order to avoid respiratory injuries on animals and staff working or staying in the stable areas for a long time.

An uncontrolled emission of odours, chemical substances and/or dust particles often occur anyway because the simple ventilation systems mostly in use leads the air directly from a building, e.g. a pigsty, to the ambient surroundings.

Just because the air is not cleaned before exhaust, these types of ventilation systems do not fulfil the stricter requirements in the acts and regulations of the respective countries with regard to the maximum contents of dust/particles in the exhaust air. This fact has forced the agricultural establishment/the industry to invest in improved ventilation systems which are able to clean the exhausted air at the same time as the buildings are ventilated.

An incitement for introducing such improved ventilation systems has been, e.g. in farming, that farmers thereby have got permission to increase their production (number of animals) if they can prove at the same time that the increased production does not increase the load on the environment.

Systems that wholly or partly comply with the relevant acts and regulations, and which may comprise one or a combination of a plurality of the following types of systems are prior: Scrubbers, filters, cyclones or the like.

The disadvantage of these prior art systems is, however, that they are only capable of cleansing the air from one or more certain substances/particles, implying that such cleaning facilities become inflexible and relatively expensive in operation, particularly in cases where the air is to be cleaned form all unwanted substances/particles. At the same time, such systems are very complex and costly with regard to purchasing, installation and operation.

Object of the Invention

On that background, it is the purpose of the invention to indicate an air cleansing apparatus for cleansing the air from a building, said apparatus being cheap in making, with a technically simple design, while simultaneously a high degree of purification of the air from dust, particles and possible harmful organic substances is attained by means of the apparatus.

Description of the Invention

This is achieved by an apparatus as specified in the preamble of claim 1 , the apparatus characterised in that a central part is entirely or partly designed as a double-walled pipe section, that is with an internal and an external pipe, and that the apparatus furthermore includes an air diffuser which is disposed downstream of the ventilator at one end of the internal pipe. It is described below, how an air cleansing apparatus according to the present invention is established and used in a pigsty.

In order to control the temperature and the indoor climate in a pigsty, there will provided a ventilation system with an apparatus according to the present invention which provides for the air to be replaced in the stable, whereby the temperature can be regulated, and dust/harmful particles are separated off, entailing that the indoor climate is improved.

The apparatus is placed by way of example in the existing ventilation system or, in case of a new building, as substitute for a part of the piping of the ventilation system.

In an embodiment, the apparatus is designed so that the external pipe forms the air intake downwards and is connected to the air exhaust upwards, entailing that all air sucked into the apparatus by means of the ventilator is moistened and led through the air diffusor and thereby cleansed from dust and odour particles.

The nozzles are disposed in the moistening chamber immediately after the air intake and before the ventilator and will supply atomised water to the sucked in air, whereby it is possible to absorb dust and odour particles in the water droplets.

As the onus is on getting many little liquid droplets into the airflow for capturing dust/particles, the nozzles are to be disposed either in the airstream or in immediate vicinity of the airstream.

In the preferred embodiment of the present invention, the disposition of the nozzles in the flow of air is such that the nozzles spray liquid co-currently in the sucked in airstream.

Alternatively, the nozzles may be disposed so that they spray liquid laterally into the airstream.

There may be applied a combination of nozzle dispositions if the case is air - containing many particles or heavy particles to be captured, or - with particles to be captured and where a number of chemical reactions are to take place in the moistening chamber.

Experiment has shown that in order to attain the best absoφtion of dust and odour particles in the water droplets, these are to have the greatest possible surface area and have a low surface tension.

In order to attain the largest possible surface of the atomised water droplets, the nozzle is to be designed so that small droplets are to be produced when the water is pressed through the nozzle.

One way of doing this is to feed pressurised air to the water pressurised air before the nozzle, so that the water is fragmented into smaller droplets and so that drop sizes less than 100 μm may be attained. Another way is to put the water under pressure and to establish atomisation of water by discharging the water through a high pressure nozzle.

In order to reduce the surface tension of the water droplets, the water may be supplied with various additives, as by way of example soaps or similar products. However, it is to be safeguarded that these additives are not environmentally harmful by themselves, as by cleansing of the air by means of an apparatus according to the invention a minor entrainment of water particles to the surroundings may occur.

Alternatively, additives may be added to the water that e.g. reacts chemically with the particles in the airstream so that the particles in question are precipitated in the water.

That may by way of example be additives reacting with sulphur, phosphorous, potassium and/or sodium.

The pipe section connecting the air intake and the air exhaust, is wholly or partly over a central part entirely or partly designed as a double-walled pipe section, i.e. with an internal pipe and an external pipe.

The double-walled pipe section is required for separating and leading dust and odour particles away from the air, as sucked in stable air is conducted in the internal pipe from the air intake and on to the air exhaust, while on the internal side of the external pipe water containing separated dust and odour particles is conducted down to the liquid collecting unit.

The ventilator sucks air into the apparatus through the air intake and further on through the moistening chamber, after which the air passes the ventilator and is forced on to the air diffusor which provides for the airstream to be deflected outwards, whereby the water droplets are flung out against the internal side of the external pipe, where the water drops are accumulated and run down along the internal side of the external pipe and down to the liquid collecting unit.

The ventilator will typically be of such size that besides providing the flow of air through the system, it can force the air on through the pipe system of the ventilation system.

The rotating movement imparted to the airstream by ventilator and air diffuser will cause the heavy part - the water drops - to be flung outwards due to the centrifugal force, while the lighter part - the cleansed air - is retained at the centre of the pipe section.

For avoiding spilling of water, the apparatus is provided with a liquid collecting unit which is disposed at a sufficient distance under the air intake of the pipe section, so that the ventilator may suck in the necessary amount of air, and simultaneously with certainty may collect all water running down the internal side of the external pipe.

The liquid collecting unit has a surface which is greater than the cross-section of the air intake of the pipe section. If, for example, the system is designed with a circular pipe, the liquid collecting unit will have a smallest diameter which is at least equal to the outer diameter of the circular pipe. Typically, the surface of the liquid collecting unit will have slightly larger diameter than the diameter of the air intake of the pipe section. The liquid collecting unit may furthermore have upright sides and a funnel-shaped surface, whereby liquid and liquid splashes are captured in the liquid collecting unit and conducted towards a drain in the liquid collecting unit.

If the remaining pipe system is made of pipes with circular cross-section, the apparatus is designed so that at least the external pipe has circular cross-section, so that it is easy to connect the apparatus to the pipe system in an existing ventilation system or to the pipe system in a newly projected ventilation system.

Also, the pipe section of the apparatus may have a polygonal cross-section, preferably rectangular, corresponding to the polygonal cross-section of the remaining pipe system of the ventilation system.

In order to achieve easy mounting of the ventilator in the apparatus and to ensure optimal operation of the ventilator simultaneously with ensuring that the separated water can run down along the internal side of the external pipe, at least the internal pipe has circular cross-section and is arranged coaxially within the external pipe.

This means that if the external pipe has a circular cross-section, there will be the same spacing all the way around in the double-walled pipe section between the internal pipe and the external pipe.

It is, however, possible that the external pipe has a polygonal cross-section enclosing the internal pipe, which will not entail an inferior efficiency of the cleansing of the air but may imply unwanted air resistance in the apparatus.

It will furthermore be possible to use all possible combinations of polygonal and circular cross-sections. There will, however, be configurations between different types of cross-sections, which would be better that other, e.g. as in the preferred embodiment where the double-walled pipe section has a circular cross-section with two coaxial pipes.

As the air intake is connected to the lower part of the external pipe, and the water with the separated particles runs down along the internal side of the external pipe, it is necessary that the external pipe forms a drainage zone for the lower liquid collecting unit so that the water can fall down into the liquid collecting unit without being entrained in the airstream that is sucked into the apparatus.

This drainage zone is designed so that the liquid is brought in a position where the force of gravity is greater than the suction force from the ventilator. In a preferred embodiment of the invention, the drainage zone is designed so that the external pipe has expanding cross-section downwards/outwards.

The downwards/outwards expanding cross-section of the external pipe entails that the speed of the airstream is reduced in the air intake, whereby the entrainment force is reduced, causing that the water may run down to the edge of the air intake and gather into large drops that, due to the force of gravity, may fall down into the liquid collecting unit instead of being sucked into the apparatus again.

In the same way, the lower edge of the internal pipe is designed with a downwards/outwards expanding cross-section. This ensures that all air sucked into the moistening chamber is sucked up through the ventilator to the air diffuser.

In order to separate dust and odour particles from the water, the apparatus includes a separation chamber disposed immediately after the air diffuser.

In an embodiment of the invention, this separation chamber is constituted by the external pipe which at least has a greater diameter than the internal pipe from where the air diffusor is conducting the air.

This entails that the airspeed is reduced when coming from the internal pipe and out into the separation chamber, implying that the airstream loses some energy, thereby being incapable of entraining the water droplets which instead will run down along the side of the external pipe.

In an embodiment of the invention, the air diffuser is constituted by a circular air diffuser with a number of mutually adjustable uniform slats where the air diffuser fills the entire cross-section of the internal pipe so that it fits the diameter of the internal pipe, entailing that all air is deflected by the mutually adjustable uniform slats.

By way of example in cases where cleansing of the air is not desired, the slats may be set in a vertical position so that no deflection of the air occurs but the air can pass directly through the apparatus. Furthermore, the slats may be used for closing the through-flow of air when the system is not in use.

As an alternative to a circular air diffuser there may be used a four-edged tilting damper which is naturally installed in the apparatus where the external pipe has a cross-section which is not circular, but four-edged, with the same dimensions as the tilting damper which may have a number of slats leading the air towards one side.

In a preferred embodiment of the invention, the slats are upwards/outwards designed with a klothoid shape, ensuring that the airstream may be deflected up to 90° in relation to the longitudinal axis of the internal pipe and with minimal air resistance through the air diffuser.

The slats may have other shapes than klothoid, but it is essential that the airstream is deflected inwards against the internal side of the external pipe, as the water drops are thereby flung against the side surface and gathered into larger drops, simultaneously with the airstream losing energy at the impact. Due to gravity, the large water drops will therefore run down along the internal side of the external pipe instead of following the airstream.

In an alternative embodiment of the invention, the following is valid:

- the internal pipe forms the air intake downwards and upwards it is connected to the air exhaust, the internal pipe together with the external pipe forms a draining zone, - the internal pipe in the draining zone has expanding cross-section downwards/outwards,

- the internal pipe and the external pipe are connected upwards with an annular collar with a number of openings,

- the separation chamber includes a perforated section, and the perforated section is preferably a reticular pipe wall.

The internal pipe extends the whole way from the air exhaust down through the separation chamber and the moistening chamber, and downwards it forms the air intake of the apparatus, implying that the entire apparatus is structured as a double- walled pipe section.

The sucked in airstream is conducted through the internal pipe, while the interspace between the internal pipe and the external pipe is used for conducting the water down to the collecting unit.

In order to avoid entrainment of water running in the interspace, the internal pipe forms a draining zone together with the external pipe, where the internal pipe has a downwards/outwards expanding cross-section in the draining zone.

As the air intake, due to the outwards expanding cross-section of the internal pipe, is provided larger and large diameter, the airspeed at the lower edge of the internal pipe will be lower than at the entrance to the ventilator.

Since the airspeed is lowest down at the ultimate edge, it will also be more difficult for the air stream to entrain liquid running down the internal pipe around the edge and up into the apparatus again.

In order to separate off the particles from the air and to lead the water droplets out into the interspace between the external pipe, and the internal pipe includes a separation chamber with a perforated section which the air may penetrate.

Water droplets will be flung against the perforated section and will subsequently gather into larger and larger liquid drops which, due to the force of gravity, will overcome the entrainment force from the air stream and lastly run down an external side of the internal pipe.

In an embodiment of the invention, the perforated section is a reticular pipe wall that forms a barrier for the liquid drops in the air stream, and an accumulation of liquid drops will therefore occur on the reticular wall, and eventually the drops will gather. When they reach a certain size, they will be heavy enough to run down externally of the internal pipe and down into the liquid collecting unit.

Liquid droplets in the air stream which are not captured by the reticular pipe wall, will be flung against the inner side of the external pipe, where the liquid drops will gather and run down the external pipe and down into the collecting unit.

In an embodiment of the invention, the reticular pipe wall is made of a metal net. Alternatively, the net may be made of plastic and/or fabric. However, the important thing is that the reticular material can resist the air pressure produced by the airstream which is conducted out against the reticular pipe wall.

Instead of a reticular pipe wall there may be used a pipe wall where there is a number of apertures, by way of example a plate with circular openings which are disposed either randomly across the plate or in a predetermined pattern.

In order that the air can escape from the interspace between the internal and the external pipes, the internal and external pipes are joined upwards so that the air will be forced back into the internal pipe and further on to the air exhaust of the system.

In order to ensure that the air is led in the right direction in the interspace between the internal and the external pipe, the system is designed so that the internal and the external pipes are connected upwards with an annular collar.

This collar provides that the internal pipe is joined and assembled in a construction where the collar, besides being in one assembled piece, also provides that the two pipes are disposed coaxially.

In order to prevent the air from flowing back, the collar is equipped with a number of openings through which the air may pass from the interspace and out into the air exhaust and mix with the air stream that possibly will pass through the air diffuser and go directly through the separation chamber. In stables it may be optimal to use a plurality of individual of air cleansing apparatuses. The independent apparatuses will typically be suspended at different locations in the ridge of the stable so that the air can be cleansed evenly in the whole stable.

The apparatuses may furthermore be used in systems for cleansing air from e.g. factories where the apparatuses are either to stand outside or on the floor in a building. Therefore, these systems are constructed so that they include one or more of the said apparatuses in an external cladding.

In that way, individual apparatuses may be disposed along the wall of a building, or a battery of apparatuses may be placed outside in a combined unit.

In order to reduce the liquid consumption, the system furthermore includes a liquid reservoir, so that the liquid can be reused. The nozzles may be connected to the liquid reservoir via a pump, while the liquid collecting unit has a second connection to the liquid reservoir, so that the liquid in principle may circulate endlessly.

However, there is a limit to how many times the liquid can be circulated, depending on how great the liquid reservoir is, as the liquid absorbs a certain amount of dust particles and other particles each time it is used. The liquid must not be too unclean since it is to be pumped from the liquid reservoir and up and out through the nozzles.

In an embodiment of the invention, the liquid reservoir includes a precipitation part where impurities are settled, while simultaneously the pipe to the pump for the nozzles is disposed at a certain level above the bottom of the liquid reservoir so that precipitated impurities are not drawn up in the pump/nozzles. If the liquid reservoir is large enough, a precipitation section can replace the filter unit.

The precipitation section is, however, to be emptied periodically, either with a dredge pump or by discharging into a liquid manure tank, or similar.

In order to avoid that the liquid becomes so unclean that it possibly blocks the nozzles, the system includes a filter unit. This filter unit may be placed so that: it is disposed between the liquid collecting unit and the liquid reservoir so that liquid from the liquid collecting unit first runs through the filter unit and is clean when continuing to the liquid collecting unit, or - it is disposed between the liquid reservoir and the pump for the nozzles so that impurities become sorted off before the liquid reaches the nozzles.

In an embodiment of the invention, the liquid reservoir and/or filter unit are common to a number of the said systems, where it will be a centrally disposed large liquid reservoir and a filter unit for cleaning the liquid connected to a number of systems.

The only condition for this configuration is that pipes are drawn to and from the systems and the liquid reservoir/filter unit.

The provided piping can be double-walled and coaxial so that only one pipe string is drawn between each system to the liquid reservoir/filter unit.

If ammonium and/or sulphur are removed by supplying additives to liquid, a certain amount of raw materials may be accumulated by recirculating the liquid, where the raw materials may either be obtained from the liquid or the liquid may be sprayed directly on the field as fertiliser.

An apparatus as described in the present invention may find application in the agricultural sector but may also find application in other industries where air of varying quality is exhausted and which has to be cleansed from dust and/or odour particles, by way of example:

- households, for improving the indoor climate; large kitchens where exhaustion is provided in connection with cooking ranges and ovens; exhaust gas cleansing in environmentally hazardous works, e.g. meat and bone meal factories, feed factories, and similar; public transportation, by way of example trains, busses and ferries where the indoor climate is to be improved. Alternatively, the apparatus may be used as moistening system where the air is furthermore cleansed. This may by way of example be used in spray mist systems in fruit and greengrocery sections in the supermarkets.

Description of the drawing

The invention is explained in more detail in the following with reference to the drawing in which

Fig. 1 shows a sketch of an embodiment of an apparatus according to the invention;

Fig. 2 shows a plane side view of a second embodiment of an apparatus according to the invention;

Fig. 3 shows a sketch of a system with a number of apparatuses according to the invention;

Fig. 4 shows a perspective view of a preferred embodiment of an apparatus according to the invention, shown with horizontal disposition;

Fig. 5 shows a plane side view of the apparatus shown in Fig. 4;

Fig. 6 shows a perspective view of a wing section of air diffuser;

Fig. 7 shows a Nautilus spiral of which the internal and the external wing section edges, respectively, of air diffuser are determined;

Fig. 8 shows how the lower edge of the external wing section of air diffuser is angularly set in relation to the direction of flow of the air; and

Fig. 9 shows a perspective view of a preferred embodiment of an air diffuser for an apparatus according to the invention. Detailed Description of the Invention

The apparatus 1 shown in Fig. 1 includes an air intake 2, a double-walled pipe section 3, an air exhaust 4 and a lower liquid collecting unit 5. The double-walled pipe section 3 is designed with an internal pipe 6 and an external pipe 7.

In the first part of the internal pipe 6, a moistening chamber 8 is provided, where in the vicinity of the air intake 2 there is provided a number of nozzles 10 disposed in front of a ventilator 1 1 which is located at the entrance/centre of the moistening chamber 8. The ventilator 11 is driven by a motor 12. An air diffuser 13 is disposed after the ventilator 1 1 and is furthermore marking the transition to a separation chamber 9. Air diffuser 13 has a number of adjustable uniform slats 14.

The part of the internal pipe 6 constituting the separation chamber 9 is designed as a reticular pipe wall 15 in this embodiment. Downwards, the internal pipe 6 and the external pipe 7 form the air intake 2, as the internal pipe 6 extends down under the lower edge part of the external pipe 7, so that an annular opening is formed, the air intake 2, between the internal pipe 6 and the external pipe 7.

It is clearly seen that the internal pipe has a downwards/outwards expanding cross- section. Under the air intake 2 is disposed a liquid collecting unit 5 which has a diameter at least corresponding to the diameter of the external pipe 7. At the centre of the liquid collecting unit 5 there is provided a drain 16. Upwards, the internal pipe 6 and the external pipe 7 form the air exhaust 4, as the internal pipe 6 and the external pipe 7 are connected with an annular collar 17 in which is formed a number of openings 18.

The apparatus shown in Fig. 2 includes an external pipe 21, a central pipe section 22 designed as a double-walled pipe section where the external pipe 21 surrounds an internal pipe 23. Downwards, the external pipe 21 is connected with an air intake 24 which has a downwards/outwards expanding cross-section, while the external pipe 21 is upwards connected with an air exhaust 25.

In the first part of the internal pipe 21 , a moistening chamber 27 is provided, where in the vicinity of the air intake 24 there is provided one or more nozzles 32 that spray mist or droplets of water rearwards in the moistening chamber 27, i.e. in the opposite direction of the airflow through the apparatus 20. A ventilator 28 is disposed in the internal pipe 23, which has expanding cross-section downwards/outwards, i.e. is funnel-shaped, providing that the air from the moistening chamber 27 is sucked into the internal pipe 23 and is subsequently pressed through a klothoid diffuser 29.

When the air stream passes the klothoid diffuser 29, it will be deflected out against an internal side of the external pipe 21, which immediately after the double-walled pipe section 22 is connected with a cylindric separation chamber 26, if the diameter is greater than the diameter of the internal pipe 23 as well as the diameter of the part of the external pipe 21 constituting the moistening chamber 27.

Moistening of the particular impurities contained in the sucked in air stream thus occurs in moistening chamber 27, whereafter the particles are accelerated through the internal pipe 23 where they pass the ventilator 28 and are subsequently deflected forwards/outwards in the klothoid diffuser 29. The air stream decelerates in the separation chamber 26 where water droplets and particular impurities are deposited at the internal side of the separation chamber, and are led downwards along the inner wall of the external pipe 21 to the air intake 24, from where water and impurities are collected in the liquid collecting unit 33 while the cleansed air continues upwards and out through the air exhaust 25. Due to dimensional differences between the separation chamber 26, the moistening chamber 27 and a pipe section 34 mounted subsequently, pipe transition pieces 30, 31 are used.

The system 40 shown in Fig. 3 includes an apparatus 1 which, as indicated top right, is built into the ridge 61 of a stable building 60. The system 40 is shown with recovery of water. The nozzles 10 spray atomised water into the air stream, and the water runs by means of the force of gravity back down into the collecting unit 5, where the water is collected and conducted to a liquid reservoir 42 via drain 16 and piping 41.

The liquid is pumped onwards from the liquid reservoir 42 in pipe string 43 to a filter unit 44, where possible dust particles/air particles/unwanted organic substances are removed. T e liquid is conducted from filter unit 44 via pipe string 45 and a not shown pump onwards to the nozzles 10 which are in the moistening chamber 9 close to the air intake 2. The stable building 60 may include several apparatuses 1 and collecting units 5 that may be connected to a common liquid reservoir 42 and a common filter unit 44.

The apparatus 50 shown in Figs. 4 and 5 is constructed in principle like the apparatus

20 shown in Fig. 2, but unlike the latter the apparatus 50 is adapted for mounting in a mainly horizontal position, possibly with a very slight rearwards inclination so that precipitated water may run by itself back via an external drain pipe 68.

Unlike the apparatus 20, the apparatus 50 is adapted for use as a real air cleansing apparatus, that is the apparatus 50 is not connected to a discharge opening, by way of example in a roof, or is a part of a larger ventilation system. The apparatus 50 is by way of example mounted in a height of about 3 meters above the floor, by way of example in a pigsty or in an industrial plant, where the apparatus 50 continuously sucks in air through an air intake 52 to a moistening chamber 54, where the air, by means of a rearwards directed system of nozzles 56, is supplied with atomised water with a drop size of the magnitude 100 μm, as a dwell time of 1/3 second in the moistening chamber 54 is aimed at with the puφose of ensuring an efficient moistening of particles in the air.

There is reckoned with an average water consumption of the magnitude of about 100 1/min, of which about 90-95% is recycled, that is only about 5-10% supplementary water is added. Normally, an apparatus 20 according to the invention will have an air capacity of about 15,000 mVh, while the apparatus 50, in a smaller version, will have an air capacity of about 10,000 mVh.

The air flow through the apparatus 50 is shown with arrows 58, as a ventilator 60 disposed in a relatively short internal pipe 62 provides for sucking in the amount of air to be cleaned, and which is moistened in the combined moistening and cleaning chamber 54, from where the moistened air is pressed through the internal pipe 62 and a klothoid diffuser 64 mounted at the outlet of the internal pipe 62, and the design of which will be described in more detail below. At the passage of the air stream through the klothoid diffuser 64, water drops and particular impurities will be deflected and passed out against the inner wall of a separation chamber 66, so that the particular impurities, together with the water, are collected at the bottom of the separation chamber 66, from where it may be drained off through a drain pipe 68 which immediately before the air intake 52 is added possible excess water which is discharged from the bottom of the moistening chamber 54 through a vertical drain pipe 70, through which the contaminated water is conducted to a suitable cleaning facility, by way of example a biological cleaning plant, from where the cleaned water is recirculated to the nozzle system 56 of the apparatus 50.

Subsequent to the separation chamber 66, the cleansed air is discharged through an air outlet 72 to the room, by way of example a cowshed or pigsty, in which the apparatus 50 is mounted, etc. As supplement for the apparatus 50, the actual room may very well be provided with a ceiling mounted apparatus 20, cf. Fig. 2, which in that case provides for the necessary ventilation.

For application in air cleaning in the industry, by way of example in a foundry or similar works where there is a relatively high dust load, an apparatus 50 may correspondingly be suspended about 3 m above the floor, but in this case the air exhaust 72 may advantageously be connected with a pipe bend or a manifold and one or more downward leading pipes which are provided with an air distributor at the bottom.

The apparatus 50 according to the invention may thus in a known way operate according to the displacement ventilation principle, where the apparatus 50 all the time provides for displacing upwards the contaminated air and keeping the lowermost zone, in which the staff is staying, free from dust. Of course, such a displacement ventilation principle may also advantageously be used in pigstys where dry feed is used, and where it is known that the dust load is massive.

The klothoid diffuser 64 is not a genuine klothoid diffuser because it appears to be more suitable to work with a modified klothoid diffuser, the wing section (Fig. 6) being designed from a Nautilus spiral, where, as shown in Fig. 7, there is selected an internal sectional edge 74 and an external sectional edge 76, the opposite ends of which then are mutually connected along the Nautilus spiral face so that the wing profile 78 shown in Fig. 6 is formed.

By experiment it has furthermore appeared that the lower outer, external edge section 76 is to be set angularly about 5° relative to the direction of flow, as the centrifugal/spiral movement already imparted to the airstream at the outlet from the ventilator 60 may be utilised.

In the situation of use, the individual wings of the modified klothoid diffuser 64 are not adjustable, but in certain situations it has, however, appeared to be advantageous that the individual wings of the diffuser can be opened slightly so that the air flow through the diffuser may be increased with the intention of allowing a little more water particles to pass through the diffuser without being deflected and led away from the air stream.

This may particularly be applicable in case that the apparatus according to the invention is used for cleansing the air in very dry localities, and where it is desirable to kill two birds with one stone, namely cleansing the air while simultaneously humidifying the air. Possible localities where it may occur may by way of example be the wood and/or furniture industry, where the dust load can be massive, and where it may be advantageous to hold a very accurate air humidity.

Claims

1. Air cleansing apparatus including an air exhaust, a ventilator, a moistening chamber with a number of nozzles, an air intake and a liquid collecting unit, characterised in that a central part is entirely or partly designed as a double-walled pipe section, that is with an internal pipe and an external pipe, and that the apparatus furthermore includes an air diffuser which is disposed downstream of the ventilator at one end of the internal pipe.

2. Apparatus according to claim 1, characterised in that at least the internal tube has circular cross-section and is arranged coaxially in the external pipe.

3. Apparatus according to claims 1 - 2, characterised in that the external pipe forms the air intake at one end and forms the air exhaust at an opposite end.

4. Apparatus according to claim 3, characterised in that the external pipe at least forms a drainage zone communicating with the liquid collecting unit.

5. Apparatus according to claims 3 - 4, characterised in that the external pipe has outwards expanding cross-section at the air intake.

6. Apparatus according to claims 1 - 2, characterised in that the internal pipe downwards forms the air intake and is upwards connected to the air exhaust.

7. Apparatus according to claim 6, characterised in that the internal pipe together with the external pipe forms a draining zone.

8. Apparatus according to claims 1 - 7, characterised in that the internal pipe has expanding cross-section at one end.

9. Apparatus according to claim 1 , characterised in that the internal pipe and the external pipe are connected with an annular collar with a number of openings.

10. Apparatus according to claim 1, characterised in that the air difftisor includes a number of mutually adjustable uniform slats.

1 1. Apparatus according to claim 10, characterised in that the slats are formed with an approximately klothoid shape in the direction of flow and outwards.

12. Apparatus according to claim 1, characterised in that the nozzles are located in the moistening chamber immediately after the air intake and before the ventilator, where the nozzles are directed against the direction of flow.

14. Apparatus according to claim 1, characterised in that it includes a separation chamber disposed immediately after the air difftisor.

15. Apparatus according to claim 1 and 14, characterised in that the separation chamber includes a perforated section, preferably in the shape of a reticular pipe wall.