NL1017983C2 - Manure incineration method, comprises drying manure prior to incineration with exhaust gases from incinerator - Google Patents

Abstract

Manure with a relatively high dry solids content is burnt in an incinerator (2) and the resulting exhaust gases are transferred to a manure dryer (3), where they are preferably passed through the manure in order to remove moisture. Particles of manure are filtered from the exhaust gases, the dried manure is removed from the dryer and the ash is removed from the incinerator. An Independent claim is also included for the process apparatus.

Description

Title: Method for burning manure.

The invention relates to a method for burning manure.

Manure surpluses are a persistent problem in livestock farming. Over time, different processing methods have been proposed for reducing such surpluses. One of the options is the incineration of relatively dry manure. To this end, liquid manure is introduced into a separator, where a highly liquid fraction is separated, so that a relatively solid fraction remains. This relatively solid fraction can then be further evaporated, for example in a manure drying device, where dry and preferably warm air is passed along the manure, so that this air can absorb and remove moisture from the manure. The dry manure thus obtained can be further processed by burning into a mineral-rich ash. Thanks to the high combustion temperatures, this ash is germ-free and therefore suitable for export to countries with a shortage of such minerals. Burning dry manure can therefore better regulate mineral surpluses and shortages.

Despite the above advantages, the burning of dry manure does not take place on a large scale. This is on the one hand due to an insufficient availability of dry manure. On the other hand, the flue gases emitted by the current combustion methods exceed the emission standards laid down in environmental legislation. As a result, an expensive cleaning installation is required for cleaning the flue gases, as a result of which the combustion installations, at least at farm level, are not economically viable.

It is an object of the invention to provide a method for burning dry manure, wherein the aforementioned disadvantages are eliminated, while maintaining its advantages. To that end, a method according to the invention is characterized by the features of claim 1.

Combining the burning of manure with drying manure according to the invention offers the following advantages. Firstly, the flue gases released during incineration are cleaned in the manure drying device, during the flow of the manure and / or possibly other filter systems present in the drying device. As a result, the emission of harmful flue gases decreases and the installation will run less quickly against the set emission standards and preferably remain entirely below that. A less expensive flue gas cleaning installation is therefore required, whereby an economically viable combustion installation is obtained.

Furthermore, the efficiency of the manure drying device increases, because the heat from the flue gases contributes to drying the manure. The heat increases the moisture-absorbing capacity of the air and thus the drying capacity of the manure-drying device. Theoretically, the moisture-absorbing capacity can even increase by at least a factor of four.

The efficiency of the incineration plant also increases, since the heat in the flue gases, which was previously lost, is usefully employed in the above method.

In addition, greater outlets for the manure are obtained. The mineral ash remaining after incineration meets the export requirements and can therefore be exported to countries with a mineral deficiency. Finally, the process is more environmentally friendly because less energy is lost and because fewer harmful substances are emitted.

In an advantageous embodiment, a method according to the invention is characterized by the features of claim 2.

By supplementing the flue gases released during the combustion with air from outside the device, a sufficient amount of gas-air mixture is obtained for drying the manure in the manure-drying device. To keep the temperature of the gas-air mixture at a desired value, it is advantageous to use air from neighboring stables. This stall air has already been heated by the animals staying in the stable 5. In addition, stable air in comparison with the outside air generally has a lower humidity, so that it can absorb more moisture. For moving the stall air to the drying device, use can furthermore be made of air circulation means already present in the stall.

Furthermore, a part of the heat released during the manure combustion can be used to heat the mixture of flue gases and stable air or outside air to a temperature suitable for the manure drying device.

In a further advantageous embodiment, a method according to the invention is characterized by the features of claim 5.

Capturing ammonia-rich air in the manure drying device and subsequently adding it to the manure burning process offers the advantage that on the one hand the ammonia content of the air in the drying device decreases. On the other hand, during the combustion process the ammonia causes a chemical reaction known per se from practice, as a result of which the emission of nitrogen oxides is limited.

The invention also relates to a device for burning manure, characterized by the features of claim 10.

With such a device, manure can be processed in an environmentally friendly and energetic manner, in particular with a method according to the present invention.

In a further embodiment, a device according to the invention is characterized by the features of claim 12.

By equipping the manure drying device with a number of filters 30, the gas-air mixture containing the moisture taken from the manure can be further cleaned before being discharged outside. Possible filters for removing unwanted components from the air and the flue gases are, for example, a biofilter, a biotrickling filter, chemical filters, with the help of acid water, and dust collection filters. With these filters, which are known per se, the flue gases are stripped of, among other things, nitrogen oxides (NOx), dust particles and other contaminants. An additional advantage is that when the flue gases raise the temperature of the biotrickling filter, its operation is improved. The optimum operating temperature of such a filter is around 35 ° C.

In an advantageous embodiment, a device according to the invention is further characterized by the features of claim 16.

The heat generated during the incineration can be used on site for heating cowsheds and homes, or can be supplied to an existing energy circuit by means of, for example, a heat buffer. In addition, it is possible to use part of the heat, as already indicated above, to heat the gas-air mixture that is passed through the manure-drying device, so that the moisture-absorbing capacity increases.

In particular if the heat generated is intended for use within a cattle farm, it is preferable to provide the device with a storage tank for liquid or partially dried manure with sufficient storage capacity to store manure production over a longer period, preferably at least six months. store in wet or partially dried form. This gives the freedom to operate the incineration plant 25 only when there is a need for the extra heat generated by the manure combustion.

Further advantageous embodiments of a combustion device according to the invention are described in the further subclaims.

1017983 * 5

To clarify the invention, an exemplary embodiment of a combustion installation and method according to the present invention will be described with reference to the drawing. The single figure schematically shows a combustion device 5 according to the present invention.

In this description dry manure is understood to mean at least manure with a relatively high content of dry matter, for example more than 50%, while liquid manure is understood to mean manure with a dry matter percentage of less than 20%. Manure with an intermediate percentage of dry matter, ie between 20% and 50%, is called stackable manure. Incineration of manure is possible at dry matter percentages from around 30%. Said percentages are volume percentages. Dry matter in this context is to be understood as at least comprising all relatively solid parts which are present in liquid manure and can be separated therefrom with the aid of a separator or by drying.

Figure 1 shows schematically a combustion device 1 for dry manure suitable for a method according to the invention. The combustion device 1 comprises a combustion installation 2 and a manure-drying device 3. Such a manure-drying device 3 is known, for example, from Dutch patent application 1010772, which patent application is deemed to be incorporated herein by reference, at least as regards the drying device described therein. The manure-drying device 3 is provided with a mixing tank 4, in which flows of manure are mixed with different percentages of dry matter, which are supplied from different stages of the manure-drying process, to which reference is made in more detail later, via first, second and third manure feed means 5, 10 and 22. The mixture thus obtained is introduced via first manure discharge means 7 into a mechanical separator 6. In such a separator, for example of the FAN Separator type, supplied by Fan Separator GmbH in Germany, the mixture is separated into manure with a relatively high percentage of dry matter and manure with a lower percentage of dry matter. The separator 6 is connected via said second supply means 10 to the mixing tank 4 for returning a portion of the manure with a relatively low percentage of dry matter.

Furthermore, the separator 6 is connected via second manure removal means 11 to drying platforms 12 arranged one above the other in the manure drying device 3 for discharging the further manure with a relatively high percentage of dry matter to those platforms 12. Optionally, stackable manure can also be supplied directly from the mixing tank 4, without the intervention of the separator 6, to the manure-drying device 3, via fourth manure feed means 8.

First and second air supply means 14, 15 are provided around the drying platforms 12. Outside air or air from neighboring stables 15 is supplied by the first air supply means 14, hot air is supplied from the combustion plant 2 in the form of flue gases by the second air supply means 15. For mixing the supplied air and the flue gases, fans 16 are provided, with which the gas-air mixture can also be passed along and through the manure displayed on the drying platforms 12, so that moisture from the manure is absorbed into the gas-air mixture. Furthermore, first air discharge means 18 are provided, which carry the moisture-saturated gas-air mixture along and through a number of filter systems 19, in which the air mixture is stripped of undesired components.

Above a first, upper drying platform 12a, second air discharge means 20 are provided for capturing and transporting ammonia-rich air to the combustion plant 2. A lower drying platform 12d is in communication with the aforementioned third manure feed means 22 with which a part of the dry manure can be returned to mixing tank 4 and third manure removal means 23 for discharging the remaining manure to processing means 25, such as a pressing press or a pelletizer. These process the dry manure into a form suitable for storage and incineration. The processing means 25 are connected to a storage tank 26 for dry manure, from which the incineration plant 2 is fed via supply means 27. This combustion installation 2, for example of the fluidized bed or pulse burner type, is connected to ash discharge means 28 for discharging mineral-rich combustion ash and the second air supply means 15 for collecting flue gases in and subsequently moving it from the combustion installation 2 to the drying device 3. Furthermore, the combustion installation 2 comprises at least one discharge channel 30 for dissipating heat generated during the combustion to, for example, a district heating circuit 31, preferably via a heat exchanger (not shown).

The device according to Figure 1 can be used as follows.

Liquid manure with, for example, a percentage of dry matter between 4 and 10% is brought from, for example, stables or a slurry pit via the first manure feed means 5 to a mixing tank 4. For the separator 6 to function properly, it is preferred that manure supplied therein from the mixing tank 4 comprises a percentage of dry matter which is preferably between approximately 6 and 15%. This is achieved by mixing the liquid manure in mixing tank 4 with dry manure originating from the drying device 3, which has a relatively high percentage of dry matter, for example between 85 and 95% and / or with liquid manure returned from the separator 6 with a relatively low percentage of dry matter, for example between 2 and 5%. The ratio between the amounts of added manure with different percentages of dry matter is matched to each other in such a way that the resulting manure mixture comprises the desired 6 to 15% dry matter. Dry matter, such as straw, may be added from outside to achieve the desired dry matter percentage. An additional advantage of this mixing is that the part separated in the separator 6 does not have to be discharged from the device with the low dry matter percentage, the so-called thin fraction.

The manure is then introduced from mixing tank 4 into the mechanical separator 6, where it is separated into a part of liquid manure 5 with a low dry matter percentage between 2 and 5%, which part, as mentioned above, is returned as a thin fraction to the mixing tank 4, and a part of stackable manure with a higher percentage of dry matter, for example 30%, which part is conveyed via the second manure removal means 11 towards the manure drying device 3. It should be noted, moreover, that the stackable manure to be supplied to the manure drying device 3 is also can be formed directly in the mixing tank 4, without the intervention of a separator 6, by mixing suitable amounts of liquid and dry manure in the mixing tank 4. The stackable manure thus obtained can then be supplied directly from the mixing tank 4 to the manure drying device 3 via fourth manure feed means 8, which are shown in the accompanying drawing with a broken line, to indicate that this is an alternative.

In the manure drying device 3 the manure, through the aid of transport means (not shown), successively passes through a number of drying platforms 12. Along and through these platforms 12 a relatively dry air mixture is guided, which is supplied via the first and second air supply means 14, 15. The air mixture comprises on the one hand outside air or stable air and on the other hand flue gases from the incineration plant 2. The heat of the flue gases increases the moisture-absorbing capacity of the air mixture. This allows more moisture to be absorbed from the manure, so that the percentage of dry matter in the manure increases. The manure contributes to the cleaning of the flue gases, because the manure acts as a dust filter.

The moisture-saturated air mixture is discharged via the first air discharge means 18, which guide the mixture through various filter systems 19 known per se, such as a chemical filter or a biotrickling filter. With the aid of these filters, the air mixture is further cleaned, such as removing dust particles and environmentally unfriendly components such as nitrogen oxides. Furthermore, ammonia-rich air is captured by the second air discharge means 20 above the first drying platform 12a, the usefulness of which will become clear later in this description.

After running through the drying device 3, the manure has, depending on, inter alia, the residence time in the drying device, a percentage of dry matter between 85% and 95%. A portion of this dry manure is, as already indicated above, returned to the mixing tank 4 to maintain the desired percentage of dry matter in this tank. The remaining part is discharged to processing means 25, which bring the dry manure into a form suitable for incineration. Incidentally, it should be noted that burning manure is already possible with manure with a percentage of dry matter from around 30%. The above-mentioned percentages of dry matter should therefore only be seen as preferred values and in no way be construed as being restrictive. Optionally, the manure can then be stored in a storage buffer 26 until further use.

From the processing means 25 or the storage buffer 26 the dry manure is brought to the incineration plant 2. This combustion installation 2 can be a conventional stove, but preferably comprises a fluidized bed or pulse burner, with which an optimum combustion can be realized. During the burning, the ammonia-rich air collected from the drying device is added. This results in a chemical reaction known per se, which reduces the emission of nitrogen oxides.

The heat released during incineration is collected, for example by heating water with it. This heat can be used within the cattle farm, for example for heating the T0T7988 stables and the like, or be transferred to a larger energy network, for example a district heating circuit. The ash, which is free from germs, vermin and the like due to the high combustion temperatures, can be exported as a mineral-containing product to areas with a mineral deficiency.

It will be clear that the invention is not limited to the exemplary embodiments shown in the description and the drawing. Many variations thereof are possible within the scope of the invention as set forth in the claims.

The described process can thus be carried out continuously, which is favorable for reducing the manure surpluses. However, the combustion process can also only be started if there is a need for the extra heat that is released during this combustion. It is thereby important to provide sufficient storage capacity for liquid and / or dry manure to bridge the period in which the installation is stationary.

Furthermore, the incineration plant can be equipped with additional flue gas cleaning means in order to further minimize the emission of nitrogen oxides. The drying device 20 can likewise be provided with additional or other filters than those already mentioned for cleaning the air mixture used for drying the manure. Furthermore, it is possible to connect several drying devices to one incineration plant.

The same process can also be carried out with a different drying device than the device described above, wherein the manure successively traverses a number of drying platforms. The same applies to the mechanical separator and incinerator; they may deviate in terms of type from those described above. The stated percentages of dry matter can also differ at the different stages of the process from the values stated in the above description.

f017983 · 11

These and comparable variations are understood to fall within the scope of the invention as set forth in the claims.

1017983 *

Claims (19)

Method for burning manure, comprising the following steps: burning manure with a relatively high percentage of dry matter in an incineration plant (2), 5. collecting flue gases emitted during combustion and transferring them to a manure drying device (3), drying of manure present in the manure drying device (3) by passing the flue gases along, preferably through this manure, wherein the flue gases absorb and remove moisture from the manure and the manure filters dust particles 10 from the flue gases, discharge of the manure drying device (3) dried manure; and removal of ash remaining after incineration from the incineration plant (2). 2. Method according to claim 1, wherein the flue gases, before being passed through the manure drying device (3), are mixed with air supplied from outside the manure drying device (3). Method according to claim 2, wherein the supplied air comes from a shed. 4. Method as claimed in any of the foregoing claims, wherein the flue gases or the mixture of flue gases and air with moisture absorbed therein from the manure is furthermore passed through at least one filter (19) which further cleans the flue gases or the gas-air mixture. 5. Method as claimed in any of the foregoing claims, wherein ammonia-rich air is collected from the manure-drying device (3) and introduced into the manure-burning process, such that this ammonia-rich air limits the formation of nitrogen oxides by means of a chemical reaction. f017983 · Method according to one of the preceding claims, wherein the dry manure discharged from the manure drying device (3) and manure supplied to the incineration plant (2) are at least 30%, more in particular at least 50% and preferably at least about 80% dry matter. A method according to any one of the preceding claims, wherein the heat produced during the combustion is collected and delivered to an energy network. 8. Method as claimed in any of the foregoing claims, wherein the heat generated during the combustion is applied within the animal husbandry. 9. Method according to claims 2-8, wherein at least a part of the heat generated during the combustion is used to heat up the air with which the flue gases are mixed. Device for burning manure, comprising a combustion installation (2) and a manure-drying installation (3), wherein the combustion installation (2) is provided with supply means (23, 27) for manure with a relatively high percentage of dry matter, discharge means (28 ) for removing ash remaining after combustion and means (20) for collecting and transporting flue gases emitted during combustion to the manure drying device (3), wherein the manure drying device (3) is provided with means for supplying manure with a relatively low dry matter content, blowing means (16) for passing the flue gases along, preferably through the manure present in the manure drying device (3), such that the flue gases can absorb moisture from the manure and the manure can capture dust from the flue gasses, and furthermore means (18) are provided for discharging the moisture-saturated flue gasses and means (23) for discharging the flue-drying device in the manure-drying device (3) dried manure to the incineration plant (2). §017983 « Device as claimed in claim 10, wherein the device further comprises air suction means (14) for sucking in stable air or outside air and mixing means (16) for mixing the sucked-in air and the flue gases coming from the incineration plant (2) into a flue gas in the manure drying device (3) gas-air mixture to be used. Device as claimed in claim 10 or 11, wherein the device further comprises at least one filter (19) for further cleaning the air mixture and the manure moisture contained therein. Device according to claim 12, wherein the at least one filter 10 (19) comprises a biotrickling filter for filtering out nitrogen oxides, an air cleaning filter for filtering out dust particles and a chemical filter for filtering out ammonia. Device as claimed in any of the claims 10-13, wherein the combustion installation (2) comprises additional flue gas cleaning means. Device as claimed in any of the claims 10-14, wherein the manure drying device (3) comprises an exhaust system (20) for capturing ammonia-rich air present in the manure drying device (3) and means for transporting and introducing it into the manure combustion plant (2) ). Device according to one of claims 10-15, wherein the combustion installation (2) is connected to a heating circuit (31) for the removal of heat generated during the combustion. 17. Device as claimed in any of the claims 10-16, wherein buffers are provided for the storage of ash from the incineration plant and for the storage of manure for the manure-drying device (3) and / or for the incineration plant (2). 18. Device as claimed in any of the claims 10-17, wherein the device comprises processing means (25) for relatively dry manure, which bring the dried manure into a form suitable for incineration in the incineration plant (2). 1017981 « Device according to one of claims 10 to 18, wherein the combustion installation (2) comprises a fluid bed burner or pulse burner. 1017983 ·