WO2024023760A1

WO2024023760A1 - Gas scrubbing device and stockbreeding device provided with said gas scrubbing device

Info

Publication number: WO2024023760A1
Application number: PCT/IB2023/057640
Authority: WO
Inventors: Karel Van Den Berg; Korstiaan Cornelis BLOKLAND
Original assignee: Lely Patent N.V.
Priority date: 2022-07-29
Filing date: 2023-07-27
Publication date: 2024-02-01
Also published as: NL2032635B1

Abstract

A gas scrubbing device comprises a housing with an internal gas scrubbing space with a first supply for gas to be scrubbed with an acid, a first discharge for scrubbed gas, and a circuit for an acid solution, with a first supply line and discharge line for the acid solution, and a first pumping unit for pumping the acid solution round the circuit, and is further provided with a plasma reactor. This comprises a plasma housing with an internal plasma space, air supplying means for passing air through the plasma space, at least two electrodes and an electric power supply for generating a discharge between the electrodes in the air, and an absorber with an internal absorber space for the air that has gone through the plasma space, and provided with a second supply line and a second discharge line for the acid solution, which together form part of the circuit. The gas scrubbing device uses acid in gas scrubbing, which can be supplemented with nitric acid that is made from air by the plasma reactor. A stockbreeding facility with the gas scrubbing device is also provided.

Description

GAS SCRUBBING DEVICE AND STOCKBREEDING DEVICE PROVIDED WITH SAID GAS SCRUBBING DEVICE

The present invention relates in general to a gas scrubbing device for cleaning a gas stream, and more particularly to a gas scrubbing device comprising a housing with an internal gas scrubbing space for scrubbing a substance that reacts with acid out of a gas stream, with a first inlet for gas to be scrubbed, with a first discharge for scrubbed gas, and a circuit for an acid solution, with a first supply line for supplying the acid solution to the gas scrubbing space, a first discharge line in direct or indirect fluid communication with the first supply line for discharge, from the gas scrubbing space, of acid solution that has gone through the gas scrubbing space, and a first pumping unit for pumping the acid solution round the circuit.

Gas scrubbing devices of this kind are known per se. Thus, NL-2016618A describes a gas scrubbing device for withdrawing ammonia from a gas stream that is released above a resultant urine stream. In this known device, for example nitric acid is used for reacting with the ammonia.

Although known devices work well per se, there are drawbacks for example to the use of these acids. For example, transport and handling of these acids is dangerous. In addition, there is high energy consumption in their production, with considerable emission of for example CO2.

The present invention aims at least to mitigate said drawbacks, and for this purpose provides a gas scrubbing device according to Claim 1 , in particular a gas scrubbing device comprising a housing with an internal gas scrubbing space for scrubbing a substance that reacts with acid out of a gas stream, with a first inlet for gas to be scrubbed, with a first discharge for scrubbed gas, and a circuit for an acid solution, with a first supply line for supplying the acid solution to the gas scrubbing space, a first discharge line in direct or indirect fluid communication with the first supply line for discharge, from the gas scrubbing space, of acid solution that has gone through the gas scrubbing space, and a first pumping unit for pumping the acid solution round the circuit, further provided with a plasma reactor, comprising a plasma housing with an internal plasma space, air supplying means for passing air through the plasma space, at least two electrodes and an electric power supply for generating a discharge between the electrodes in said air, and an absorber with an internal absorber space for receiving and further treating air that has gone through the plasma space, and provided with a second supply line for supplying at least part of the acid solution to the absorber space, a second discharge line for discharging the acid solution from the absorber space, wherein the second supply line and the second discharge line form part of said circuit.

The invention is based on the idea that the acid can also be made in situ, so that there is no need for transport or handling of the acid. In this case, use is made of the known manufacture of in particular nitric acid, by having nitrogen oxides formed in atmospheric air by means of a plasma discharge in said air, which then cool down in the absorber and react with the acid solution, or at least the water therein, to form nitric and/or nitrous acid. Even if the amount of nitric and/or nitrous acid formed is less than the amount that is consumed in gas scrubbing, the number of times that the amount of acid has to be supplemented will become smaller, so that the advantage of the invention is still obtained.

Particular embodiments of the invention are described in the dependent claims, as well as in the part of the introduction to the description that now follows.

In some embodiments, the second discharge line is connected to the first supply line, and the first discharge line is connected to the second supply line. One large circuit is thus formed through both the gas scrubbing space and the absorber space. The entire acid solution can thus in each case be enriched with fresh acid in the plasma reactor.

Alternatively, the second supply line and the second discharge line form a second branch of the aforementioned circuit, besides a first branch that is formed by either the first supply line, or the first discharge line. It is then easier to take account of the situation that in practice a plasma reactor often has a much smaller capacity than the gas scrubbing device, and the amount of liquid that can reasonably flow through it is also much smaller. For example, by taking a line for the second branch that has a smaller cross-sectional area, it is possible to ensure that the flow rate in this second branch is sufficiently less than in the first or main branch through the gas scrubbing space. In addition, one or more valves, such as reducing valves or the like, may be provided. In particular, a second first pumping unit is provided, which is arranged for pumping the acid solution through the second branch. Thus, the amount of liquid through the plasma reactor can be controlled well, and it can even be reduced to zero, as will be explained later.

In some embodiments, the plasma reactor further comprises a control system for controlling the electric power supply, wherein the control system is arranged to be in control of the power supply if and so long as a predetermined criterion is fulfilled. A large amount of (electrical) energy is required for the plasma reaction. This energy is not always freely available, and the price for this energy may also vary considerably over time. Thus, it may be advantageous if the control system only switches on the supply when a criterion is fulfilled. When the supply is switched off, in particular when the criterion is not fulfilled, the optional second first pumping unit may also be switched off, or valves and the like may be closed completely, because the second branch does not then supply anything.

In particular, the gas scrubbing device further comprises an installation for generating electricity particularly a photovoltaic device and/or a wind turbine. With an installation of this kind, the required power can be self-generated, and it is easy to assess if, and in that case when, the predetermined criterion can be fulfilled. The alternative energy sources (photovoltaic systems, i.e. , solar panels, and wind turbines) in particular have generating capacities that may vary considerably, but which are somewhat predictable in the short term.

Attractive embodiments comprise the criterion that said installation generates at least a predetermined power. It will be clear that such a criterion is useful, because if the power is too low there may be a large decline in efficiency. Furthermore, it is often the case that when for example the installation for generating electricity itself is able to supply a lot of power, for example with strong solar radiation or high wind speed, the price of this electricity is also low, so that the use of the plasma reactor is relatively less expensive. Thus, a power meter may in particular be provided in the installation, giving an indirect indication of the price of electricity. The control system can thus determine, on the basis of the power measured by the power meter, whether the plasma reactor is switched on.

Advantageously, the control system is configured to switch on, as a function of a criterion, said power supply, or the plasma reactor, for generating nitric acid in the acid solution, wherein in particular the gas scrubbing device further comprises a storage device for acid solution, with an admission valve controllable by the control system and a reservoir for acid solution, wherein the control system is configured for storing acid solution. In these embodiments, the gas scrubbing device can prepare extra nitric acid in the acid solution, which will not be used directly for gas scrubbing. This extra nitric acid is either held in the acid solution in the circuit, or, depending on the particular arrangement, directed by the control system to said reservoir, to remain in storage there until the acid in the acid solution needs to be supplemented. Thus, surplus energy may be used to generate nitric acid in advance, for later use. The criterion will then advantageously also comprise that a minimum power is available, that the electricity costs fall below a certain minimum, and so on.

In particular, the acid solution comprises a solution of nitric acid, or a solution of nitric acid and nitrous acid. Thus, supplementary nitric and/or nitrous acid may be formed in the plasma reactor. This does not alter the composition of the solution, only the concentration. For example, a fertilizer with nitrates may be supplied thereby, as will be explained later. Alternatively, however, it also possible for example to supply a solution of sulphuric acid, citric acid or some other acid. This has the advantage that a reaction equilibrium in the absorber is influenced less by nitric acid/nitrate already present.

In a second aspect, the invention relates to a stockbreeding device with a gas scrubbing device according to the present invention, and comprising an accommodation space for livestock, with a barn floor and a storage space for storing at least a proportion of the manure and/or urine produced by the livestock, and an air exhausting device for extracting air from the accommodation space and/or the storage space, wherein the air exhausting device is arranged for delivering the extracted air to the aforementioned first supply, and wherein in particular the first discharge opens out to the ambient air.

In stockbreeding devices of this kind, a large amount of ammonia is released by the action of urease on urea, for example when urine and faeces come together. Thus, in the storage space for manure and/or urine, but also in the accommodation space, a relatively large amount of ammonia will be present in the air. This ammonia causes undesirable deposition of nitrogen in the environment, and it should thus preferably be removed from the air, which can take place efficiently with a gas scrubber with acid solution, such as that according to the invention. The advantage of being able to make up the amount of acid automatically is of course directly applicable in this stockbreeding system.

For more details regarding the stockbreeding system, reference should be made for example to NL-2016618 and W02022/002776, both from the applicant. It should be noted that in a number of the stockbreeding systems described there, the manure and the urine are collected and stored substantially separately. However, in practice it will be impossible to achieve 100% separation of in particular urine and urea, and ammonia and the like will therefore still be formed. Moreover, in principle all the particular features described above, with their advantages, are still applicable.

In some embodiments, the stockbreeding device is further provided with a supplementary gas scrubbing device, comprising a supplementary housing with a supplementary gas scrubbing space, and with a third supply line, connected to the supplementary gas scrubbing space, for second gas scrubbing liquid, which in particular is neutral to basic. This supplementary gas scrubbing space with the second circuit is intended to trap nitrogen oxides that are still present in the air that has gone through the absorber. After all, nitrogen oxides in the air are also undesirable substances, and measures are required to counteract emission of them. To make this trapping more effective than in the first gas scrubbing space, with acid solution, the solution used in this second circuit is advantageously neutral to basic. For this purpose, a discharge line and optionally a pump are provided in addition to the supply line.

In some embodiments, said second gas scrubbing liquid comprises substantially urine from said livestock, particularly urine collected from the barn floor, or manure moisture filtered from manure stored in the storage space. The pH of urine is generally between 7 and 8, so it is suitable as a liquid for the second gas scrubbing space. This urine may in particular be obtained from the barn floor. The barn floor comprises openings through which urine can trickle, to be collected under the floor. For this purpose, means may also be provided as described in the aforementioned NL- 2016618. It is alternatively also possible to obtain manure moisture by filtering slurry or manure collected separately from urine from the storage space, or even by pressing for separating into liquid and fibres. However, these last-mentioned liquids obviously contain more organic matter than urine, which may cause problems in gas scrubbing. This gas scrubbing will generally take place in a "packed bed" or the like, and organic matter may lead to blockage there, or at least a decrease in efficiency. Consequently, urine, advantageously urine that has been collected separately or filtered, is to be preferred in these embodiments.

In particular, the stockbreeding device further comprises a third discharge line for urine or manure moisture that has gone through the supplementary gas scrubbing space, wherein the third discharge line forms, by means of a second pumping unit, a circuit with the third supply line. In this case, the second gas scrubbing liquid (urine or manure moisture, with nitrates, in particular ammonium nitrate) may be returned to the storage space. There, the now acidified urine/manure moisture will be able to counteract further formation of ammonia as well as methane.

The invention will now be explained in more detail on the basis of the drawing, in which the single Figure 1 illustrates schematically an embodiment of a stockbreeding device according to the invention.

The stockbreeding device 1 comprises a gas scrubbing device 2 according to the invention and a stable 3, as well as a supplementary gas scrubbing device 42.

The stable 3 serves as accommodation space for example for cows 100, pigs etc., whose excrement ends up on the floor 4 in the form of heaps of manure 101. The floor 4 is provided with suitable openings (not shown), through which urine as well as manure moisture from the heaps 101 are collected and led away to a urine space 5 for urine and manure moisture 6, located under the floor. A manure space 7 for manure, i.e., the solid parts thereof, is also provided under the floor. A connecting opening 9, through which the superjacent air, or at least the gas mixture, can be exchanged, is provided between the urine space 5 and the manure space 7. A dung scraper 10, which may or may not be automatic, can push the heaps of manure 101 , or at least the solid parts thereof, across the floor 4, to discharge these via a discharge hole 11 into the manure space 7. Note that it is also possible to remove urine and manure together, such as to a slurry pit.

The gas scrubbing device 2 comprises a first gas scrubber, indicated generally with reference number 16, and a plasma reactor, indicated generally with reference number 35, as well as optionally a storage tank 26 for nitrogen-enriched liquid.

The plasma reactor 35 comprises a plasma housing 36 with a plasma space 37, into which ambient air is blown by an air blower 39 via a first air supply 38, and is blown out again via the first air discharge 34. In the plasma space 37, two or more electrodes, not shown separately here, are fitted, which by means of the power supply 40 can produce a discharge in the air. This discharge provides, in a manner known per se, ionization of the air, wherein nitrogen oxides (NO_X) may be formed, among other things.

The NO>rContaining air is then led to the absorber 28 via line 34, which also serves as second air supply. The absorber 28 comprises an absorber housing 29 with an absorber space 30, with a second supply line 33 for acid solution, and a second discharge line 32 for acid solution that has gone through the absorber space, as well as a second air discharge 41. In the plasma reactor 35, nitric acid is then formed according to the Birkeland-Eyde process from the nitrogen oxides that have formed (in particular NO, which reacts with O2 to form NO2), which react further with oxygen from the air and water in the acid solution to give HNO3.

The acid solution is advantageously already a nitric acid solution, for example from a reservoir with base solution, not shown separately here, and which is pumped by a first pump 31 through a connecting line 24, and via a three-way valve 23 to a first gas scrubber 16. This first gas scrubber 16 comprises a first housing 17 with a first gas scrubbing space 18, a first supply line 21 and a first discharge line 22, as well as a first scrubbed gas supply 19 and a first scrubbed gas discharge 20. The gas in question, which is to be scrubbed in the first gas scrubber, is extracted by a large fan or blower 15 from the stable 3 via the first gas discharge 13, and/or from the urine space 5 and/or the manure space 7 via the second gas discharge 14. The gas is in particular air with a relatively high proportion of ammonia (NH3). The ammonia from the gas reacts with the dissolved nitric acid to form ammonium nitrate. This is a suitable base fertilizer in itself. When the nitrogen content has risen sufficiently, for example as determined by an increase in density, and/or with a suitable change in acidity or electrical conductivity of the solution, determined in each case with an appropriate device, the control system may decide to send the liquid via the three-way valve 23 to the storage tank 26. After optional correction of pH, a usable liquid fertilizer is thus obtained. Of course, fresh acid solution should then be supplied to the gas scrubbing device 2. It is moreover in principle possible to choose an acid other than nitric acid, which has the advantage that the reaction equilibrium for receiving nitric acid in the absorber 28 is less affected by nitrate ions already present. For example, sulphuric acid solution may be used. On the other hand, the fertilizer will not then be a pure nitrate fertilizer, which may be a disadvantage in some cases.

The first gas scrubber 16 is, just like the other gas scrubbers described here, of any known type, such as a packed-bed scrubber, wherein gas to be scrubbed bubbles upwards through a descending column of scrubbing liquid in countercurrent. However, the type of gas scrubber is certainly not limited to this.

Because the acid solution of this first gas scrubber 16 is in each case enriched with nitrogen via the ammonia, and also becomes less acidic, it is advantageous to make up the amount of acid from the plasma reactor 35. Thus, the acid solution does not have to be supplemented with concentrated nitric acid (or another acid) so quickly, which ensures less risk as well as less handling and thus less work.

The air leaving the absorber 28 of the plasma reactor 35 via the second air discharge 41 may optionally be fed to a supplementary gas scrubber 42. This comprises a third air supply 43 connected to the second air discharge 41 and a third air discharge 44, both on a supplementary housing 45 with a supplementary gas scrubbing space 46. A third supply line is indicated with 47, and a third discharge line with 48, via which a second pump 49 pumps liquid away. In the example shown, the liquid is urine 6 from the urine space 5. This is neutral to slightly basic, so that any remaining nitrogen oxides from the air that has gone through the absorber 28 may also react and so be "washed away". The urine 6 is acidified thereby. Recycling of the acidified urine to the urine space 5 will counteract further formation of ammonia therein. Alternatively, manure moisture from slurry may also be used in place of urine 6, either as seepage moisture, or moisture pressed out of the slurry.

The plasma reactor 35 shown may thus contribute to the operation of gas scrubbing of gas obtained from stables and manure/urine storage, by forming nitric acid that is used in ammonia capture. However, this requires a lot of energy. It is thus advantageous if at least part of this energy is generated in situ by means of an electricity generating installation, such as with a photovoltaic device, in particular solar panels, or a wind turbine. Advantageously, the power supply 40 thus comprises said solar panels, and/or optionally a wind turbine. In particular, the control system 27 can switch on the power supply 40, and thus the plasma reactor 35, when the installation for generating electricity is generating at least a predetermined minimum power. Generally, the price for electricity will be low, because other installations will then probably also generate a lot of electricity, and the increased supply depresses the price. This is already a good proxy for the electricity price, and even if the electricity generating installation does not generate all the power required, the price to be paid for the nitric acid to be obtained will be relatively low.

To summarize, the stockbreeding device shown comprises a stable, wherein ammonia-containing air is extracted, and is stripped of ammonia via a gas scrubbing device, cf. the Lely Sphere® system. An acid solution is used in the gas scrubber, and is supplemented in a plasma reactor, with a plasma housing in which nitrogen oxides are formed by means of a discharge in air, which react with the acid solution in the absorber and add nitric acid there. Residual nitrogen oxides in the air are washed out by means of yet another gas scrubber, which makes use of (neutral to slightly basic) urine/manure moisture, which is itself recycled as acidified liquid to counteract formation of fresh ammonia. Overall, a device with long-lasting autonomous operation is obtained which purifies stable air, counteracts nitrogen emission and at the same time produces a very usable nitrogen fertilizer.

It will be clear that a person skilled in the art will be able to devise many variations of the stockbreeding device shown, as well as of the gas scrubbing device shown. Thus, the components indicated as optional may of course be omitted. It is also possible, instead of recycling the urine acidified in the supplementary gas scrubber 42 to the urine space 5, or the slurry pit in general, to use it elsewhere. In addition, instead of taking urine from the urine space 5 or a slurry pit, it may be taken directly from the floor 4, wherein the urine/manure moisture collected is first further acidified before it goes to the urine space 5.

Claims

1 . Gas scrubbing device, comprising:

- a housing with an internal gas scrubbing space for scrubbing a substance that reacts with acid out of a gas stream, with a first inlet for gas to be scrubbed, with a first discharge for scrubbed gas, and

- a circuit for an acid solution, with a first supply line for supplying the acid solution to the gas scrubbing space, a first discharge line in direct or indirect fluid communication with the first supply line for discharge, from the gas scrubbing space, of acid solution that has gone through the gas scrubbing space, and a first pumping unit for pumping the acid solution round the circuit, further provided with a plasma reactor, comprising

- a plasma housing with an internal plasma space, air supplying means for passing air through the plasma space, at least two electrodes and an electric power supply for generating a discharge between the electrodes in said air, and

- an absorber with an internal absorber space for receiving and further treating the air that has gone through the plasma space, and provided with a second supply line for supplying at least part of the acid solution to the absorber space, a second discharge line for discharging the acid solution from the absorber space, wherein the second supply line and the second discharge line form part of said circuit.

2. Gas scrubbing device according to Claim 1 , wherein the second discharge line is connected to the first supply line, and wherein the first discharge line is connected to the second supply line.

3. Gas scrubbing device according to Claim 1 , wherein the second supply line and the second discharge line form a second branch of said circuit, besides a first branch that is formed by either the first supply line, or the first discharge line, and wherein in particular a second first pumping unit is provided which is arranged for pumping the acid solution through the second branch.

4. Gas scrubbing device according to one of the preceding claims, wherein the plasma reactor further comprises a control system for controlling the electric power supply, wherein the control system is arranged to be in control of the power supply if and so long as a predetermined criterion is fulfilled.

5. Gas scrubbing device according to Claim 4, wherein the gas scrubbing device further comprises an installation for generating electricity, in particular a photovoltaic device and/or a wind turbine.

6. Gas scrubbing device according to Claim 5, wherein the criterion comprises that said installation generates at least a predetermined amount of power.

7. Gas scrubbing device according to one of the preceding claims, wherein the acid solution comprises a solution of nitric acid, or a solution of nitric acid and nitrous acid.

8. Stockbreeding device with a gas scrubbing device according to one of the preceding claims, and comprising

- an accommodation space for livestock, with a barn floor and a storage space for storing at least a proportion of the manure and/or urine produced by the livestock, and

- an air exhausting device for extracting air from the accommodation space and/or the storage space, wherein the air exhausting device is arranged for delivering the extracted air to the aforementioned first supply, and wherein in particular the first discharge opens out to the ambient air.

9. Stockbreeding device according to Claim 8, further provided with a supplementary gas scrubbing device, comprising a supplementary housing with a supplementary gas scrubbing space, and with a third supply line, connected to the supplementary gas scrubbing space, for second gas scrubbing liquid, which is in particular neutral to basic.

10. Stockbreeding device according to Claim 9, wherein said second gas scrubbing liquid substantially comprises urine from said livestock, particularly urine collected from the barn floor, or manure moisture filtered from manure stored in the storage space.

11. Stockbreeding device according to Claim 9 or 10, further comprising a third discharge line for urine or manure moisture that has gone through the supplementary gas scrubbing space, wherein the third discharge line forms, with a second pumping unit, a circuit with the third supply line.