DESCRIPTION:

Technical field of the invention

The invention relates to a method for removing ammonia from stable air, wherein stable air in a livestock shed is led to the outside via an air scrubber and outside air is fed in, which air scrubber is provided with an inlet opening through which the stable air enters the air scrubber and an outlet opening through which the cleaned stable air is let out, into which air scrubber the stable air is passed over a cooling body and thereby contacts an outer surface of the cooling body and in which air scrubber this outer surface of the cooling body is moistened by a first fluid being a cleaning fluid.

Background of the invention

Such a method is known from EP 2 923 565 A. In this known method the outside air extracts heat from the cleaning fluid which circulates in the air scrubber and cools the stable air to be cleaned.

Summary of the invention

An object of the invention is to provide a method of the type described in the preamble, wherein more ammonia is removed from the stable air or the same amount of ammonia is removed from the stable air with less energy than with the known method. To this end, the method according to the invention is characterized in that a liquid with a pH of less than 5, preferably less than 4, is used as the cleaning fluid, and that the cooling body is cooled by a second fluid, which is different from the first fluid, being a cooling medium. The cleaning fluid not only has to remove dust particles from the air, as is the case with an air scrubber, but the cleaning fluid also has to bind the ammonia. By using a cleaning fluid with a low pH, ammonia is absorbed by the cleaning fluid, which also removes the ammonia from the air in the stable. The ammonia content results from the equilibrium between gaseous ammonia and ammonium in the cleaning fluid, this equilibrium being strongly influenced by the temperature (the lower the temperature, the more ammonium and the less ammonia can be in the cleaning fluid). So by cooling the filter material of the air scrubber, ammonia can be removed from the stable air more efficiently.

An embodiment of the device according to the invention is characterized in that a cooling body is used which comprises filter material. By moistening the filter material with cleaning fluid and letting the stable air to be cleaned flow past the filter material, the contact surface between the stable air to be cleaned and the cleaning fluid is increased, resulting in better cleaning.

In order to obtain a good heat transfer between the stable air to be cleaned and the outside air, an embodiment of the method according to the invention is characterized in that the cooling body is hollow and is cooled by contacting an inner surface of the filter material with the cooling medium.

A further embodiment of the device according to the invention is characterized in that a tube is used as the cooling body. The cleaning fluid can be passed through a tube without much resistance, so that a good heat transfer takes place. Preferably, a flat tube is used as the cooling body in order to increase the heat transfer surface.

A cost-effective embodiment is characterized in that outside air is used as cooling medium, which is sucked or blown from outside the stable into the stable through the hollow cooling body.

In order to further improve the efficiency of the cleaning process, a further embodiment of the method is characterized in that cleaning fluid is periodically sprayed onto the outer surface of the cooling body. The cleaning fluid is distributed over a large surface of the cooling body by the stable air flowing past the cooling body, and the stable air therefore comes into contact with the cleaning fluid over a large area, so that efficient cleaning is achieved. The time interval between spraying periods is preferably adapted to the degree of humidification of the stable air and/or of the cooling body, which is determined by sensors.

In order to further improve the efficiency of the cleaning process, a further embodiment of the method is characterized in that in the inlet opening and in the outlet opening the ammonia content of the stable air entering and leaving the air scrubber is measured and the quantity, the time interval and the pH value of the cleaning fluid to be sprayed is adjusted to the measured values. Brief description of the drawings

The invention will be further elucidated below on the basis of drawings in which embodiments of a device are shown with which the method according to the invention can be carried out. Herein is:

Figure 1 a schematic representation of a first embodiment of the device in vertical longitudinal section; and

Figure 2 the cooling body of a second embodiment of the device.

Detailed description of the drawings

Figure 1 shows a schematic vertical longitudinal section of a first embodiment of a device with which the method according to the invention can be carried out. The device is formed by an air scrubber 1 which is provided with an inlet opening 7 via which the stable air 3 enters the air scrubber and an outlet opening 9 via which the cleaned stable air 3 is let out. Filter material 15 is present in the housing of the air scrubber. Via the space between the filter material 15, stable air 3 is fed from the stable to the environment outside the stable, and the filter material 15 is cooled by a cooling medium 17. The cooling medium 17 hereby extracts heat via the filter material 15 from the stable air 3 flowing along the filter material 15. .

By using a liquid with a low pH, preferably lower than 4, as the cleaning fluid, the ammonia in the stable air is removed by the cleaning fluid. The filter material 15 is not continuously wetted, but periodically for efficiency reasons with cleaning fluid 13 for which, for example, acidified water can be used. The stable air 3 flowing along the filter material 15 thus comes into contact with the cleaning fluid over a large area. The cleaning fluid 13 is carried along and over the filter material 15 by the stable air 3 flowing in via the inlet opening 7 .

Wetting of the filter material 15 takes place discontinuously, wherein the degree of wetting and decrease in the amount of moisture in this area of the filter material 15 determine the time interval of the discontinuous spraying process. Optionally, the spraying of cleaning fluid, viewed over the length of the filter material 15, can be repeated by sprayers arranged above the filter material 15 at a distance from each other. The flushing area immediately after the inlet opening 7, in which the cleaning fluid 13 is sprayed onto the filter material 15, has a length of, for example, 1.5 meters. During rinsing, the ammonia-polluted stable air 3 will carry liquid particles along the longitudinal direction of the filter material 15 and deliver the cleaning fluid 13 to the filter material 15. The advantage of this is that few or no liquid particles at the end of the filter material 15 are taken outside by the stable air.

The filter material 15 has, among other things, the function of keeping the acidified water (cleaning fluid 13), which has to bind the ammonia from the stable air 3, constant within a certain temperature range. If the temperature of the water would increase too much, the molecules that bind the ammonia in the water will move faster, allowing them to escape from the water more easily and the ammonia will be released more easily into the stable air flowing by (increase vapor molecules). The filter material 15 has a certain minimum length (for example 7 to 8 meters) with the aim of achieving sufficient cooling capacity and to function as a moisture trap to prevent the acidified water particles from escaping from the unit.

The time interval between the spraying periods is continuously adapted to the degree of humidification of the stable air 3 and/or of the filter material 15. Furthermore, in the inlet opening 7 and in the outlet opening 9, the ammonia content of the stable air 3 entering and leaving the air scrubber is measured and the amount, time interval and pH value of the cleaning fluid 13 to be sprayed is adapted to the measured values.

The size of the flushing area (this is the area that is directly wetted by the nozzles), the spraying time and the pH value of the cleaning fluid can be varied depending on the conditions of the outside air (passing through the cooling bodies) and the stable air and on the temperature of the cleaning fluid. Control software determines an optimum between these key figures before control is regulated. By continuously measuring the ammonia concentration of the ingoing and outgoing stable air, the nozzles, fans, acidification of the cleaning fluid, etc. can be optimally controlled by means of driver software.

Figure 2 shows one of the cooling bodies 35 of a second embodiment of the device 21 according to the invention, with the air and liquid flows around it. This device 21 has a number of cooling bodies located next to each other at a mutual distance parallel to each other. A hollow flat tube is used as the cooling body 35 (the tube can also have a different shape, for example round, oval, etc.). The flat tube is preferably made of a material which is resistant to acids. Furthermore, the tube preferably has a small wall thickness and the tube is preferably made of a material that has a good thermal conductivity coefficient.

Contaminated stable air 23 is fed (sucked) along the outer surface of this cooling body, and at the same time a cleaning fluid 33 with a low Ph (preferably less than 4) is sprayed from above onto the cooling body 35. In this embodiment, water with sulfuric acid is used as the cleaning fluid 33. The ammonia in the polluted stable air 23 is absorbed in the cleaning fluid 33. At the bottom side of the cooling body 35, cleaning fluid 33b and ammonia in the cleaning fluid flows from the cooling body 35.

On the inside of the cooling body 35, outside air 37 flows inwards (suctioned or blown in). This outside air 37 always has a lower temperature than the polluted stable air 23. For this reason the cooling body 35 is cooled and the cleaning fluid 33 will therefore also cool down. Because the capacity to absorb ammonia increases at a lower temperature, the efficiency for absorbing ammonia increases.

Although the present invention is elucidated above on the basis of the given drawings, it should be noted that this invention is not limited whatsoever to the embodiments shown in the drawings. The invention also extends to all embodiments deviating from the embodiments shown in the drawings within the scope of the invention defined by the appended claims.