METHOD AND PLANT FOR TREATMENT OF MANURE, SOLID MANURE AND/OR LIQUID MANURE FROM LIVESTOCK

Abstract: A method for treatment of manure, solid manure and/or liquid manure may comprise the steps of: a) separation of manure, etc. in a fraction with a relatively high content of solid matter and a liquid fraction with a relatively low content of solid matter, b) treatment of the liquid fraction for the attainment of a gas phase containing NH3, c) oxidation of the gas phase containing NH3 into free nitrogen and/or compounds containing nitrogen oxide. Step b) may comprise boiling the liquid fraction, and compressing and subsequent condensing the gas phase containing NH3. Step c) may be carried out by catalysis. A plant for working the method may comprise separating means, boiling means for boiling the liquid fraction for the attainment of a gas phase containing NH3, oxidation means for oxidation of the gas phase containing NH3 into free nitrogen and/or compounds containing nitrogen oxide.

Description: METHOD AND PLANT FOR TREATMENT OF MANURE, SOLID MANURE AND/OR LIQUID MANURE FROM LIVESTOCK The invention relates to a method and a plant for treatment of manure, solid manure and/or liquid manure (stale) from livestock. In this description, solid manure means faeces from domestic animals without substantial contents of urine; liquid manure means urine (stale) from domestic animals without substantial contents of faeces; and manure means a mixture of faeces and urine (stale) from domestic animals. Furthermore, manure may contain litter, bedding, flushing water, etc. from a stable or barn. In the following, the substances mentioned are collectively designated "manure, etc.". From Dutch patent application No. NL 89/2933 a method and an apparatus for treatment of manure. The manure (1) is stripped with air (17) , which removes C0 2 and NH 3 from the manure. The manure is separated in a solid fraction (5) which is dried by means of hot air from a furnace (19) , and a liquid fraction (6) . To the liquid fraction lime is added (8) , whereby lime compounds (10) are deposited and fed back before the separator. The liquid fraction (11) is stripped once again (12) and carried away. The solid fraction is dried (18) , and the drying air is scrubbed (21) with water (22) containing acid (36) . Then, the air is being utilised as stripping gas, first for stripping of the liquid fraction (12) and then for stripping of the manure (2) . The used stripping air (33) is scrubbed (34) with water (22) containing acid (36) , and is then utilised as primary combustion air in the furnace (19) , whereby the odorants is being burned. Part of the dried, solid fraction (30) is utilised as fuel in the furnace (19) ; the ashes are carried back to the dried, solid fraction (32) , which is carried away (32) . From Dutch patent application No. NL 89/2932 a method is known for boiling down manure or the liquid fraction segregated from manure. The liquid fraction (2) is heated by injection of steam (53) from the evaporator (77) . The fraction is stripped (72) , the stripping being furthered by the heat. The fraction is heated again by steam injection (52) , and lime (40) is added, a high pH value furthering the stripping as well. The liquid fraction is boiled down in a multi-stage evaporator (77) being supplied with heat from a furnace (78) , which supplies drying air as well for drying the solid fraction, in the same way as disclosed for NL 89/2933. The drying air is scrubbed (75) , and acid scrubbing water is delivering heat to the stripping air (74) . From International application No. WO 93/6063 a method and an apparatus are known for the treatment of ani- mal dung, manure and stale. Dung, manure and stale are pumped (1) to a reactor (17) . Meanwhile suspended gypsum is added (37) . Air is added (18) , preferably stable air with a high content of C0 2 . Ammonia is bonded by adding carbonic acid and gypsum. Volatile compounds such as ammonia residues, methane, skatoles and mercaptanes are stripped away together with the oxygen-containing air (18) pouring out into the manure, etc. through a porous wall (4), and are burned by thermal catalysis or by means of a supporting fuel (11) . The stripping air is separated from the manure, etc. by means of a baffle plate (5) . Oxygen and carbon dioxide may optionally be supplied from batteries of gas cylinders (22, 31). Finally, from European patent application No. EP 785.176, a method and an apparatus are known for treatment of manure in small scale on a farm. The manure is separated in a solid an a liquid fraction (the stale) , and the solid fraction is composted with supply of air, optionally after being mixed with straw or the like. The liquid manure is filtered through straw or the like, which is subsequently composted. Thereafter the liquid manure is subjected to a nitrification and denitrification process according to Dutch patent appli- cation No. 95/336, following which the main part of it is evaporated. The nitrification and denitrification process seems not to be further specified in the European application even though it must be a very crucial part of the method, and there is every reason to believe that neither the method nor the apparatus will be able to function as intended. It is a purpose with the invention to provide a method for converting environmentally problematic sub- stances in solid manure, manure and/or liquid manure from livestock into substances which readily may be utilised locally in environmentally acceptable ways, be transported in concentrated form, or be discharged to the environment without environmental or other inconveniences. This purpose is met by the method according to the invention, the method being characteristic by the subject matter of claim 1. By the second, liquid fraction being treated for the attainment of a gas phase containing by far the chief part of the content of NH 3 in the manure, etc., a concentrate and a first, predominantly solid fraction are obtained, which both have a very low content of NH 3 , and therefore readily may be deposited or used as fertilisers or soil improvement agents as regards contamination with NH 3 . The first fraction is usable as a fuel or for pyrolysis . An advantageous embodiment of the invention is mentioned in claim 2. Under certain process conditions, this embodiment will permit that the gas phase containing NH 3 will be oxidised into a gas phase containing N0 X . By the gas phase containing NH 3 being oxidised into a gas phase containing N0 X , and NO x in the gas phase containing NO x being converted into free nitrogen and/or compounds containing nitrogen dioxide, conversion of NH 3 into non-problematic or exploitable nitrogen compounds is attained in a particularly advantageous way. The purpose mentioned is furthermore met by the plant according to the invention, the plant being characteristic by the subject matter of claim 34. By means of the separating means, the manure, etc., is separated into a first fraction with a relatively high content of solid matter and a second, liquid fraction with a relatively low content of solid matter. By means of the boiling means, the second, liquid fraction is boiled for the attainment of a gas phase con- taining by far the chief part of the content of NH 3 in the manure, etc., and a concentrate and a first, predominantly solid fraction, both having a very low content of NH 3 . An advantageous embodiment of the plant according to the invention is mentioned in claim 35. Hereby corres- ponding possibilities as mentioned for claim 2 are attained. By means of the oxidation means, the gas phase containing NH 3 is oxidised for the attainment of a gas phase containing NO x , and NO x in the gas phase containing NO x is reduced by means of the reduction means into free nitrogen and/or compounds containing nitrogen oxide . In this way, advantages corresponding to those mentioned for claim 2 are attained. By the subject matter of claims 3-9 and 36-40, it is attained that as much as possible of the content of solid matter in the manure, etc., is precipitated in an advantageous way, with very little risk of fouling of the means and apparatus utilised. By the subject matter of claim 10-11, a strongly reduced tendency to formation of foam is attained. By the subject matter of claims 12 and 41, an advantageous working temperature for the enzymes is attained in an economically justifiable way and, at the same time, as big a quantity as wanted of thermal energy can be utilised later in the process. By the subject matter of claims 13 and 42, it is attained that the conversion capacity of the enzymes is utilised optimally. By the subject matter of claims 14-17 and 43, it is attained that the gas phase containing NH 3 is liberated from the second, liquid fraction with an optimally low energy consumption, and a maximum possible portion of the NH 3 content of the second, liquid fraction is at the same time collected in the gas phase. By the subject matter of claims 18 and 44, it is prevented that the boiling side of the heat exchanger is boiling dry. By the subject matter of claim 19 it is attained that the heat exchanger can be designed with a steam collector, and so more compact and with a better heat transfer capability. By the subject matter of claims 20 and 47, a better concentration of the concentrate is attained. By the subject matter of claims 21 and 45-46, an improved liberation of the gas phase is attained. By the subject matter of claims 22-23 and 48-49, a particularly advantageous oxidising of NH 3 to NO x is attained. By the subject matter of claim 50 it is attained that heating, mixing and distribution of the gas phase containing NH 3 and supplementary air can take place concurrently and in the same component. By the subject matter of claims 24 and 51 it is attained that a particularly big fraction of the content of NH 3 in the manure, etc., is collected in the gas phase containing NH 3 . By the subject matter of claim 25 it is attained that a correspondingly smaller fraction of the reaction products from step d) have to be discharged, whereby also a smaller gas and heat exchange with the surroundings, and consequently a smaller loss of heat, take place. The heat saved can be utilised in the process. By the subject matter of claims 26-27 and 52 an efficient end cleaning of the waste-water is attained in a simple and advantageous manner before discharging. By the subject matter of claim 28 a particularly advantageous reduction of N0 X into free nitrogen or compounds containing nitrogen dioxide is attained. By the subject matter of claim 29 a necessary sup- ply of hydrogen to the gas phase containing N0 X is attained before step d) , without hydrogen having to be supplied from outside the plant. By the subject matter of claim 30 a supply of oxygen to the gas phase containing NH 3 is attained before step c) . By the subject matter of claims 31-33 it is attained that the conversion of NO x in step d) into either HN0 2 /HN0 3 or NH 4 N0 3 can take place with quite few modifications of the method and without adding ingredients from outside the plant. By the subject matter of claim 53, corresponding advantages as mentioned for claims 29-33 are attained. The invention will be explained in more detail below by means of embodiment examples and with reference to the drawings, in which: Fig. 1 as a schematic diagram shows an embodiment of a plant according to the invention, where the nitrogen contents of the manure, etc. is converted into free nitrogen, Fig. 2 in the same way shows an alternative embodiment of a plant according to the invention, where the nitrogen contents of the manure, etc., is converted into nitric acid or ammonium nitrate, and Fig. 3 in the same way shows an alternative embodi- ment of the plant in Fig. 1. Corresponding reference signs refer to same elements in Figs 1-3. The embodiments in Figs 1-3 are designed for treatment of 30 m 3 manure per day in average, being able to treat VA- m 3 /h in six days, following which the seventh day of the week may be used for cleaning the plant . Pig manure, for example, is supplied at 1 to a manure tank 2. The pig manure is preferably manure and flushing water from a piggery and will typically contain 4-6% TS (TS = Total Solid = total contents of solid matter) . By means of a pump 3, the manure is pumped to a press 4 which separates the manure into a first fraction with a relatively high content of solid matter, preferably around 40% TS, and a permeate with a relatively low content of solid matter, preferably around 1-3% TS . A suitable press is a standard screw press, type SP11 from the company Reine Econ A/S, N-4350 Naerbø, NO. This screw press is designed for separating manure and has a screw or worm, extending inside a tube and pressing the manure along through the tube, the wall of which constitutes a sieve with a certain mesh aperture. At the end of the tube, the latter extends into a conical mouthpiece, and at the end of the shaft of the screw, outside the mouthpiece, a valve is placed in the form of a spring- loaded, conical plate, rotating with the worm. By adjusting the bias of the spring, the degree of compaction - and thus the content of solid matter in the first fraction - can be con- trolled to some degree. The first fraction is self-composting and is carried away for composting at 5. After composting, the first fraction can be utilised as other compost for fertilising or soil improvement, without risk of undesir- able contamination of the environment with ammonia or other nitrogen compounds. However, as the solid matter in the first fraction contains around 70% combustible material, the first fraction is suitable for burning as well. In the embodiment in Figs 1-2, the permeate is carried to a vibration screen 6, where the permeate is filtered for the attainment of a second, liquid fraction ("manure juice") and a retentate (sludge). The second, liquid fraction contains typically below 1-2% TS, of which only about 10% is combustible material. A suitable vibration screen is manufactured by the company VAV Scan Vibro, DK-5700 Svendborg, DK. This screen has a screen area of 500x2000 mm and two adjustable 8 vibrators with eccentric weights, by means of which the screen can be given a wanted vibration pattern in both horizontal and vertical direction. By controlling the vibration pattern and the flow rate of the supply of the per- meate, the contents of solid matter in the retentate can be controlled to some extent. In the embodiments shown in Figs 1-2, the retentate is carried away at 7 for composting or burning, respectively, together with the first fraction. This requires a rela- tively high content of solid matter in the retentate, in order not to lower the content of solid matter in the first fraction, which again requires that the flow rate mentioned is reduced. If, however, a higher flow rate is wanted, whereby the content of solid matter will be lowered in the retentate, this can be carried back to the manure tank 2, where the low content of solid matter is of no importance. The second, liquid fraction is at 8 carried to a liquid tank 9. Subject to the freshness of the manure, the second fraction may contain varying amounts of substances such as proteins or lipides, which may imply risk of formation of foam. If the manure is fresh, that is less than 14 days old, it will in general only be slightly decomposed, and many of the substances mentioned will therefore form part of the retentate which is retained by the vibration screen. If the manure is older, it will often be decomposed so far that these substances are not retained and consequently, it is important that their foam forming properties will be eliminated. Even if the manure is fresh, substantial amounts of these substances may go through the separ- ating process and give rise to formation of considerable amounts of foam. In general, it is preferred that the manure is treated as fresh as possible, as hereby the largest amount of solid matter can be extracted for composting. With a view to counteracting formation of foam, enzymes may according to the invention be added to the liquid, preferably when it is contained in the liquid tank 9. The enzymes are preferably for decomposing fat, starch and/or proteins. Examples of suitable enzymes are: Alkalase for decomposing proteins, and Lipolase for decomposing fats, both supplied by the company Novo Nordisk A/S, Novo Alle, DK-2880 Bagsvaerd, DK. Preferably, the enzymes are added early in the process in order to obtain as long a residence time as possible, in the embodiment shown by dosing enzyme reagent from an enzyme reagent tank 10 to the liquid tank 9 by means of an metering pump 11, depending on the flow rate in the con- duit 8 and/or other relevant parameters. However, the enzymes may as well be added in other steps of the process, if suitable conditions for their action are hereby created. A controllable pump 12 pumps the second fraction along a conduit 15, the rate of the pump 12 being con- trolled to a desired flow rate in dependency of the signal from a flow meter 13. The desired flow rate may e.g. depend on the capacity of the remaining components of the plant, or the desired degree of purity of the end products from the treatment according to the invention. At 14, water may be added for start of the plant, the latter having to be filled with liquid before heating can be commenced. The correct working temperatures must be reached at the different locations in the plant, before manure juice (the second, liquid fraction) can be supplied. At a three-port directional valve 16 the flow of the second fraction is divided into two partial flows, passing through each their pair of heat exchangers with associated reactors. A first partial flow flows through the secondary side (the heat-receiving side) of a heat exchanger 17, where it is heated to a certain temperature, adequate to further the effect of the enzymes used, the temperature may e.g. be controlled by controlling the flow rate of the first partial flow, e.g. by adequate control of the flow rate in the conduit 15, as mentioned above, together with an adequate adjustment of the three-way valve 16. A typical temperature for enzymes commonly used is e.g. 70°C. 10 After the heat exchanger 17, the fist partial flow is carried to a first, preferably isolated reactor 18, the volume of which is adapted such that the residence time will be adequate for a favourable effect of the enzymes used. Subsequently, the first partial flow is carried along through the secondary side of the other heat exchanger 19 of the pair, where the partial flow is further heated to a temperature which is preferably near the boiling point, e.g. 90°C. The heat for the described heating comes from a sediment to be described in more detail below, and which is carried in counterflow through the primary sides (the heat supplying sides) of the two heat exchangers 19, 17. Hereby a desired cooling of the sediment is achieved as well. The other partial flow is in quite the same way carried through the secondary sides of the other pair of heat exchangers 20, 22, as well as another, preferably isolated reactor 21. In this case, the heat comes from a condensate to be described in more detail below, which is carried in counterflow through the primary sides of the two heat exchangers 22, 20. Hereby a desired cooling of the condensate is achieved as well. The ratio between the quantities in the two partial flows will in a typical plant according to the invention be around 1:6, the second partial flow carrying an amount about six times the amount in the first partial flow. The two partial flows of the second, liquid fraction is subsequently united at a point 23 where also a gas vent not shown in detail is installed, by means of which gas can escape from the second, liquid fraction. In this place, the second fraction will usually contain an amount of gas such as 0 2 , C0 2 , NH 3 and/or water vapour, owing to the heating performed. The discharged gases are carried by a conduit 24 to treatment together with the gas phase con- taining NH 3 , as it is explained below. Subsequently, the second, liquid fraction is carried on to a gas-liquid heat exchanger 58 where it is heated until near its boiling point by heat exchange with 11 discharge air from the N0 X conversion, as described in detail below. A typical temperature after this heating will e.g. be 97-98°C. The flow of the second, liquid fraction which thus by the measures described has been heated to near its boiling point, continues now to the boiling means 25. Firstly, the second fraction is supplied to a recirculation circuit where a circulation pump 26 pumps the second fraction through a flowmeter 27 and subsequently through three heat- ing elements 28 and into the boiling side 42 of a boiling heat exchanger 29, which preferably is a plate heat exchanger. In the heating elements 28, the second fraction is heated if necessary for the attainment of a temperature right below the boiling point. This heating may for example be necessary when starting up the plant, or after operating trouble. In the boiling side 42 of the boiling heat exchanger 29, the second fraction is subsequently boiled and at the same time recirculated in preferably upwards direction, so that steam and boiling liquid escape concurrently through a discharge conduit 30. Through a recirculation conduit 31, 37, preferably the major part of the boiling liquid is carried back through the heating elements 28 by means of the circulation pump 26, and back into the boiling side 42 of the boiling heat exchanger 29. In the recirculation circuit 30, 31, 37 there is preferably inserted a sedimentation tank 35, such that all the circulating, boiling liquid, or a partial flow thereof, is carried through the sedimentation tank 35 for the at- tainment of liberation of possible sediment 41 from the liquid. The sedimentation tank may be equipped with baffle plates known per se or means for reduction of turbulence and flow rate, in order to promote the sedimentation. The magnitude of the partial flow mentioned may e.g. be con- trolled by a manually operated three-way valve. The hot sediment is carried through a conduit 38 and through the two heat exchangers 19, 17 mentioned above, into the first 12 fraction 5 as shown or, alternatively, into the manure tank 2. The major part of the steam generated is carried on to a steam compressor 39. In the embodiment shown in Figs 1-2, this takes place through a conduit 33 in which a foam knife 32 or the like, or other mechanical means for disintegration of possible foam formations, may be inserted. However, the steam for the compressor 39 may as well be extracted from the top of the sedimentation tank 35, through the conduit 34 shown. The steam generated is mixed with air and NH 3 , as well as other gases such as H 2 S which may be expelled from the boiling liquid; these substances are collectively designated the gas phase containing NH 3 . Thanks to the strong- ly reduced solubility of NH 3 in water at elevated temperatures, by far the major part of the content of NH 3 of the second fraction will be collected in the gas phase containing NH 3 . In the steam compressor 39, the gas phase contain- ing NH 3 is being compressed to a slightly elevated pressure, whereby its temperature will increase until a little above the boiling point. In the present embodiment, the pressure increase is 12-16 kPa, and preferably around 16 kPa. The gas phase containing NH 3 is now carried into the condensing side 43 of the boiling heat exchanger 29. Thanks to the increase in temperature, the gas phase is now able to supply sufficient heat to maintain the boiling of the second, liquid fraction in the boiling heat exchanger 29. Hereby, the water vapour in the gas phase containing NH 3 may be superheated, and in order to avoid too much superheating, which may entail a risk of the second, liquid fraction sticking to the heating surfaces of the boiling side 42, water spray is according to the invention preferably added to the gas phase containing NH 3 before the steam compressor 39. Experiments have shown that injection of 0.4 1/min water will eliminate the risk of sticking to the heating surfaces. 13 During starting up of the plant, or in other situations where the temperature increase is insufficient, the gas may be carried back to the inlet port of the compressor 39 through a bypass conduit 72. During the heat release in the condensing side 43 of the boiling heat exchanger 29, a condensing of the water vapour in the gas phase containing NH 3 will take place, which will happen at a temperature a little above the boiling point of the second, liquid fraction, thanks to the elevated pressure in the condensing side 43 of the boiling heat exchanger caused by the steam compressor 39. In an experiment with the plant shown in the figures, temperatures of 97.5°C in the boiling side and 100.5°C in the condensing side was recorded. In practice, the pressure in the condensing side 43 will be nearest to the pressure in the surrounding atmosphere, since the steam compressor 39 will build up a slight vacuum on its inlet side where the flow resistance from areas with atmospheric pressure is considerably bigger than the corresponding resistance on the outlet side of the compressor. In the embodiment shown, the boiling heat exchanger is dimensioned for evaporating 1300 kg/h of the second, liquid fraction. As the temperature difference between the two sides of the heat exchanger is relatively small, around 2 °C, it is essential that the heat exchange surfaces are liberally dimensioned. In the embodiment shown, the heat exchanger is of the type A055 from the company APV Danmark, Kildemosevej 13, DK-5000 Odense C, DK, with a heat exchange surface of 111.7 m 2 . The mixture of the gas phase containing NH 3 and the condensate from the steam condensed in the condensing side 43 of the boiling heat exchanger 29 is carried to a condensate tank 44. Here, the gas phase containing NH 3 is liberated from the condensate. Possible settled sediment in the condensate tank 44 may be drained at intervals through a bottom valve 45. The gas phase containing NH 3 is carried on through a conduit 48, and the condensate is pumped on 14 through a conduit 47 by a pump 46. The gases escaped from the second, liquid fraction through the conduit 24 mentioned above are mixed into the gas flow in the conduit 48. The concentrations of nitrogen in the condensate flow in the conduit 47 are around 0.2%, and in the gas flow in the conduit 48 around lM-2%. The nitrogen quantities transported through the two conduits thus are substantially of the same order of magnitude . The condensate flow is carried through the con- duit 47 to a stripping tower or desorption column 49, where the condensate is being stripped of NH 3 with a suitable stripping gas, as will be explained below. By means of a pump 50, the stripped condensate is pumped through a conduit 51 to the pair of heat exchangers 22, 20 earlier men- tioned, where it delivers heat to the second, liquid fraction. The condensate thus cooled is subsequently carried to a ozone unit 52, where it is treated with ozone for the attainment of a reduced content of chemically or biologi- cally oxidable substances. The oxygen for production of the necessary ozone is supplied in the form of atmospheric air at 56, by means of a blower 55. Finally, the condensate is preferably carried to a UV unit 54, where it is treated with ultra-violet light for the attainment of a substantially reduced content of microorganisms . According to the invention, the condensate thus treated can by the measures described above be cleaned sufficiently to be drained as "clean waste-water", or used for e.g. cleaning of stables. If the parameters of the process are adjusted to give a little less efficient cleaning of the condensate, for example in order to gain savings in running the plant or to increase the capacity of same, the condensate, thus having achieved a somewhat higher nitrogen content, may be used for fertilising or combined irrigation and fertilising in the neighbourhood of the plant. The used stripping gas is carried from the desorption column 49 through a conduit 58 and is mixed into 15 the gas phase containing NH 3 from the conduit 48. The gas phase containing NH 3 , admixed the used stripping gas and the escaped gases mentioned above, is carried on to further treatment in a catalysis unit 59. A special heat exchanger 63 has according to the invention two inlets 65, 66 and two outlets 67, 68 on its secondary side (the heat receiving side) . The primary side of the heat exchanger 63 has one inlet port and one outlet port, as usual. The secondary side is adapted in such a way that two gas flows being let into the two inlet ports 65, 66, respectively, will be mixed in a certain way before they reach the two outlet ports 67, 68. This will be described in more detail below. At 61, atmospheric air is supplied which by means of a blower 62 is blown through the secondary side of a heat exchanger 78, where the air receives heat, please see below for more detail. The air thus heated, being preferably approximately 70 °C, is carried on through the conduit 64. By means of a blower 60, the gas phase containing NH 3 is blown to one 65 of the inlet ports on the secondary side of the heat exchanger 63. To the other inlet port 66, a first partial flow of the heated air from the conduit 64 is supplied. Thes^e two gas flows are separately carried through the heat exchanger 63, and are here heated to a desired temperature. After the heating, but before the gases reach the two outlet ports, the gases are subsequently mixed in such a way that approximately Vz of the gas phase containing NH 3 is carried to the outlet port 68, whereas the remaining % of the gas phase containing NH 3 is mixed with the air and carried to the outlet port 67. In the following, the embodiment in Fig. 1 will be described. In this embodiment, the catalysis unit 59 com- prises oxidation means and reduction means. A partial flow of the heated gas phase containing NH 3 from the outlet port 68 of the heat exchanger 63 is bypassed the oxidation means, as explained below. 16 At the point 69, three gas flows are united, viz. 1) the rest of the gas phase containing NH 3 from the outlet port 68; 2) the mixture of the gas phase containing NH 3 and air from the outlet port 67 on the secondary side of the heat exchanger 63; and 3) a remaining, second partial flow of the hot atmospheric air from the conduit 64. This second partial air flow may be adjusted by means of a valve 71. The gas flow l)-3) thus united is mixed in a static mixer 70, and is carried on through an electrical heating unit 73 to the oxidation means. In the embodiment shown in Fig. 1, the oxidation means are constituted by a third reactor 74 containing a catalyst for catalysis of the reaction: a NH 3 + b 0 2 → c NO x + d H 2 0 + Q - by which the gas phase containing NH 3 is being oxidised into a gas phase containing N0 X . A suitable catalyst is for example the type CK-307 "CATOX" from the company Haldor Topsøe A/S, Nymøllevej 55, DK-2800 Lyngby, DK, which requires a working temperature of approximately 280°C, or the type CK-428 "CATOX" from the same supplier, which requires a working temperature of 270 °C. The heat exchanger 63 is therefore preferably dimensioned for the attainment of such temperatures after admixing of the partial flow of the preferably approximately 70°C hot air from the conduit 64. If the desired temperature has not been reached, e.g. during starting up of the plant or because of operating trouble, the necessary, supplementary heating is performed by the heating unit 73. If other suitable catalysts are used, the plant must be dimensioned to their working temperatures. Suitable catalysts can thus be had, which will perform satisfactory at somewhat lower temperatures, e.g. down to around 240°C. By the oxidising, energy is released in the form of heat, typically around 5 kWh per kg N in the form of NH 3 , and the temperature is thereby increased to around 440 °C. After the oxidising, the gas phase containing NO x is admixed into the partial flow mentioned above of the gas phase containing NH 3 from the outlet port 68 of the heat 17 exchanger 63. The gas phase containing NO x is then carried through a static mixer 75 to reduction means. In the embodiment in Fig. 1, the reduction means are constituted by a fourth reactor 76 containing a cata- lyst for catalysis of the reaction: e N0 X + f NH 3 → g N 2 + h H 2 0 + Q - by which the gas phase containing N0 X is being reduced to a discharge gas containing N 2 and H 2 0. A suitable catalyst is for example the type DNX-931 "DENOX" from the company Haldor Topsøe A/S, Nymøllevej 55, DK-2800 Lyngby, DK. At the reduction, energy is likewise released in the form of heat, and the temperature of the discharge gas is hereby increased to around 500 °C. The hot discharge gas is carried to the primary side of the heat exchanger 63, where it delivers heat for heating of the gas phase containing NH 3 with warm air added, being thereby cooled to around 240°C. Following this, approximately % of the discharge gas thus cooled is carried to the heat exchanger 58, where it delivers more heat for the last heating of the manure to be fed to the boiling means 25. The temperature of the discharge gas has hereby dropped to around 100 °C in the embodiment shown of the plant according to the invention. The remaining V~ of the gas is carried to the humidification tank 80 to be described below, in order to be used as a stripping gas. The discharge gas is carried from the heat exchanger 58 on to the heat exchanger 78, where it delivers further heat for heating the air (61) to be added to the gas phase containing NH 3 . Hereby a condensing of the content of water vapour in the discharge gas into liquid water takes place . This condensed water from the heat exchanger 78 is carried through a conduit 81 to the humidification tank 80. The remainder of the discharge gas is discharged into open air at 79. In the humidification tank 80, a humidification of the V. mentioned of the discharge gas takes place, in such a way that it obtains a relative humidity of as near 100% as 18 possible. The condensate mentioned, coming through the conduit 81, is hereby carried to a sump in the bottom of the humidification tank. A circulation pump 83 circulates the hot condensate from the sump to a shower at the top of the humidification tank 80, and the likewise hot discharge gas is carried in counterflow through the thus created water spray, whereby it is cooled to around 100 °C as well as being humidified to as near 100% RH as possible. The hot discharge gas, thus humidified, is carried through a conduit 84 to the desorption column 49, where it strips the condensate flow from the boiling means for NH 3 , etc., as mentioned above. In the following, the embodiment in Fig. 1 will be described. In this embodiment, the catalysis unit 59 com- prises oxidation means only. At the point 69, three gas flows are united, viz. 1) the gas phase containing NH 3 from the outlet port 68; 2) the mixture of the gas phase containing NH 3 and air from the outlet port 67 on the secondary side of the heat exchanger 63; and 3) the second partial flow of the hot, atmospheric air from the conduit 64. Den second partial air flow can be adjusted by means of a valve 71. The gas flow l)-3) thus united is mixed in a static mixer 70, and is carried on through an electric heating unit 73 to the oxidation means. The oxidation means in the embodiment shown in Fig. 2 is quite like the oxidation means in the embodiment shown in Fig. 1 and described above, and the gas phase containing NH 3 is oxidised in quite the same way into a gas phase containing NO x . After oxidising, the gas phase containing N0 X is carried to the primary side of the heat exchanger 63, where it delivers heat for heating of the gas phase containing NH 3 and of the heated air mentioned. Subsequently, the gas phase containing NO x is carried to the heat exchanger 58, where it delivers more heat to a last heating of the manure which is to be fed to the boiling means 25. 19 After this heat delivery, the gas phase containing NO x is carried through a conduit 89 to a washing column 90, where the gas is washed with water which is recirculated through a conduit 91 by means of a circulation pump 92. By this washing, HN0 2 or HN0 3 is formed in this reaction: i H 2 0 + j N0 X → k HN0 X + Q The circulating water is being held at a temperature of nearly 100°C by means of the heat energy in the gas phase containing N0 X , which is furthering the process. The HN0 2 or HN0 3 formed is concentrated gradually in the circulating water and may be tapped continuously or periodically at 93. If the water content in the gas phase containing N0 X , coming from the oxidation means trough the conduit 89, is not sufficient to maintain the amount of circulating water in the conduit 91, water may be added during the operation of the plant, by means not shown. After the washing, the gas phase containing NO x is quite free from NO x , and has thereby been converted into a remaining discharge gas, substantially consisting of air with a very high humidity indeed. A partial flow of the hot and moist discharge gas is carried through a conduit 95 to the desorption column 49 for use as stripping gas, cf . the description of Fig. 1. The remaining part of the discharge gas is without problems discharged into free air at 94, after having delivered its remaining heat to the air (61) to be added to the gas phase containing NH 3 . Instead of production of the aqueous solution of an acid HNO x as described, the plant according to the invention will in the embodiment shown in Fig. 2 be usable for production of an aqueous solution of a salt such as ammonium nitrate, in that a partial flow of the gas phase containing NH 3 trough a conduit 96 may be supplied to the washing column. Hereby, this reaction as well will take place in the column: 1 NH 3 + m HN0 3 → n NH 4 N0 3 + Q The ammonium nitrate thus produced may be used for the production of artificial fertilisers. Production of other nitrates or nitrites will be possible as well by 20 means of the plant shown in Fig. 2. The person skilled in the art- ^ will be able to provide suitable solutions to this end. Apart from what is here mentioned, the plant in Fig. 2 is quite like the plant in Fig. 1. Below, the embodiment shown in Fig. 3 will be described. In this embodiment, the separation part differs from the embodiments in Figs 1-2, and as in Fig. 2, the catalysis unit 59 comprises oxidation means only. The separation part in Fig. 3 may readily be combined with the boiling and catalysis parts in Fig. 1 or Fig. 2, just as the catalysis part in Fig. 3 may readily be combined with the separation and boiling parts in Fig. 1 or Fig. 2. With the pump 3, the manure is pumped from the manure tank 2 to a reaction tank 97, where a flocculation and/or sedimentation agent such as a slightly cationic polymer is added. A suitable polymer is e.g. the type K-530C from the South Korean company Kolon; this type is intended for flocculation and sedimentation in the food industry. The powdered polymer is kept in a storage silo 99, from where it is carried by means of a pump 100 and/or a blower 101 to a mixing tank 102, which is equipped with mechanical agitation. Here, the powder is mixed with sedi- ment free manure juice, which is supplied through a conduit 103. The powder, dissolved in the manure juice is kept in a buffer tank 104, and from there it is pumped by a metering pump 105 to the reaction tank 97, which preferably likewise is equipped with mechanical agitation. Following this, a flocculation and sedimentation takes place, whereby the manure is separated into a supernatant of low content of solid matter, and a sediment. The supernatant is carried through a conduit 8 to the washing tank 9, and continues as described with reference to Fig. 1. The sediment is removed from the reaction tank 97 at 106, and is carried to a sludge press 98, which preferably is a belt press . In the embodiment shown of the plant according to the invention, the press preferably comprises 21 a tank for further settling of the sediment. The sediment is delivered to a conveyor belt formed as an endless sieve with a mesh aperture of 50-500 μm, preferably around 50 μm. The conveyor belt with the sediment is carried underneath another, corresponding belt, following which the belts are pressed together so that the moisture in the sediment is pressed out and escapes a filtrate, which through a conduit 107 is returned to the reaction tank 97. A partial flow of the filtrate is pumped to nozzles in the sludge press by a pump 108, and used for sluicing the belts. The retentate in form of a filter cake is now constituting the first fraction, and is via the connection 7 carried away for composting or burning at 5. The form of separating the manure described here has proven superior as regards certain types of manure. In particular, it has shown up that the flocculation removes foam forming substances from the manure juice in a particularly efficient way, so that the addition of enzymes as described above may be dispensed with. Correspondingly, a substantial simplification of the plant according to the invention can be achieved, in that the double heat exchangers 17, 19 and 20, 22 can be replaced by single heat exchangers 109-110 (cf. Fig. 3), and the isolated reactors can be dispensed with. The subsequent steps in the plant correspond to what is explained with reference to Figs 1 and 2. Under certain process conditions it is not possible to oxidise NH 3 to NO x by means of catalysis, and under these conditions, the CATOX catalyst in the reactor 74 will only oxidise the gas phase containing NH 3 to N 2 , i.e. free nitrogen, in the reaction: p NH 3 + q 0 2 → r N 2 + s H 2 0 + Q Such process conditions may e.g. be a high humidity in the atmosphere surrounding the plant, and/or a low con- centration of NH 3 in the manure juice. Such a low concentration may possibly occur in very fresh manure, where a large part of the nitrogen still exist as non-decomposed amino acids, which by flocculation and sedimentation will 22 segregate together with the first fraction. High atmospheric humidity is commonly occurring in tropic or sub- tropic countries. The embodiment of the plant according to the inven- tion in Fig. 3 is adapted to this end in that the oxidation means comprises the reactor 74 only, and the nitrogen formed is carried via the heat exchangers 63, 58 and 78 into free air at 79, in the same way as earlier explained. Besides what is here mentioned, the plant in Fig. 3 corresponds to the plants in Figs 1-2. The plants in Figs 1-3 are adapted to Cleaning In Place (CIP) , whereby a cleaning agent, which preferably is soda lye with addition of EDTA, is pumped through the conduits and components of the plant, and on the way degrading any deposits. To this end, the plant according to the invention comprises a CIP tank 85 for the cleaning agent, the tank being connected with the conduits of the plant in appropriate points by means of a flow pipe 86 and a return pipe 87. A CIP pump 88 as well as the rest of the pumps of the plant perform the necessary circulation, and a desired heating of the cleaning agent can be performed with the heating elements 28. At several places in the figures, by-pass conduits are shown, through which the various liquid and gas flows can be redirected, e.g. in connection with starting up, closing down or cleaning of the plant. The use of these conduits will not be a surprise to the person skilled in the art, and they do not contribute to the explanation of the invention, for which reason they are not commented more fully on in the present description. Even if oxidation of the gas phase containing NH 3 has only been mentioned in the foregoing as being performed by catalysis, nothing will prevent the oxidation to be performed in other ways. The gas phase containing NH 3 may e.g. be burned in a furnace delivering heat, or in a gas motor powering a generator and at the same time supplying waste heat through its cooling system. The first fraction (5) may e.g. be pyrolysed instead of being composted and the 23 pyrolysis gas may be burned in the same way as with the gas phase containing NH 3 . The ashes from the pyrolysis may e.g. be utilised as an artificial fertiliser. Even if above only treatment of manure, solid manure and/or liquid manure from livestock has been mentioned, nothing will prevent the method and the plant according to the invention to be used for other waste products. It will be a necessary condition, however, that the waste product contains or can be admixed water, and that the waste product contains nitrogen compounds. As examples of such waste products may be mentioned any kind of industrial waste water containing nitrogen compounds, such as waste water from slaughterhouses or potato starch factories. The claims are to be understood such that other forms of oxidation, etc., as well as treatment of other forms of waste water shall be protected by the claims.

Claims: 24 C L A I M S 1. A method for treatment of manure, solid manure and/or liquid manure (stale) , the method comprising the following steps: a) by treatment of manure and/or solid manure: separation thereof into a first fraction with a relatively high content of solid matter and a second, liquid fraction with a relatively low content of solid matter (by treatment of liquid manure (stale) , the liquid manure constitutes the second, liquid fraction) ; b) treatment of the second, liquid fraction for the attainment of a gas phase containing NH 3 , and a concentrate, a well as possibly a condensate; c) oxidation of the gas phase containing NH 3 into free nitrogen and/or compounds containing nitrogen oxide. 2. A method according to claim 1, wherein step c) comprise the steps : cl) oxidation of the gas phase containing NH 3 for the attainment of a gas phase containing NO x ; and c2) conversion of N0 X in the gas phase containing NO x into free nitrogen and/or compounds containing nitrogen oxide . 3. A method according to claim 1 or 2 , wherein step a) comprises the steps: a2) pressing of solid manure and/or manure, whereby a permeate escapes and the first fraction remains; a3) filtering the permeate, whereby the second, liquid fraction escapes as a filtrate and a retentate remains; and preferably a4) adding of the retentate to the first fraction. 4. A method according to claim 1 or 2 , wherein step a) comprises the steps: al) adding of a flocculation and/or sedimentation agent, preferably a slightly cationic polymer, to the solid manure and/or the manure, for the attainment of a solid phase and the second, liquid fraction; 25 a2) pressing of the solid phase, whereby a permeate escapes and the first fraction remains; a3) filtering of the permeate, whereby a filtrate escapes and a retentate remains; preferably a4) adding of the retentate to the first fraction; and preferably a5) adding of the filtrate to the second, liquid fraction. 5. A method according to claim 3 or 4 , wherein the pressing is performed in a mechanical press comprising a sieve . 6. A method according to any of the claims 3-5, wherein the filtering is performed on a vibration screen. 7. A method according to claim 3 or 4 , wherein the pressing and the filtering is performed as one process in a belt press. 8. A method according to claim 1 or 2, wherein liquid manure is treated in step b) and subsequent steps, and wherein a flocculation and/or sedimentation agent is added before the treatment in step b) , preferably a slightly cationic polymer, to the liquid manure, for the liberation of a solid phase. 9. A method according to claim 8, wherein the solid phase is added to the first fraction. 10. A method according to any of the preceding claims, wherein a foam reducing agent is added to the second, liquid fraction. 11. A method according to any of the preceding claims, wherein enzymes are added to the second, liquid fraction, preferably enzymes for degrading of proteins, starch or fat. 12. A method according to claim 11, wherein the second, liquid fraction after adding of enzymes is heated in at least two steps by counterflow heat exchange with the concentrate and/or a condensate of the gas phase containing NH 3 or a resultant thereof . 13. A method according to claim 12, wherein the second, liquid fraction is left standing at substantially 26 constant temperature between the two heating steps for the attainment of suitable operating conditions for the enzymes . 14. A method according to any of the preceding claims, wherein step b) comprises boiling of the second, liquid fraction, whereby the gas phase containing NH 3 is liberated. 15. A method according to any of the preceding claims, wherein the gas phase containing NH 3 is compressed and subsequently condensed to a condensate. 16. A method according to claim 15, wherein the condensation heat from the condensing is utilised for boiling the second, liquid fraction or the permeate. 17. A method according to claim 15 or 16, wherein the condensing and the boiling takes place in respective sides of a heat exchanger, preferably a plate heat exchanger . 18. A method according to claim 17, wherein liquid in that side of the heat exchanger, where the boiling takes place, is recirculated through the heat exchanger, preferably with a flow rate bigger than, and particularly preferred more than twice, the flow rate of the second, liquid fraction which is supplied to the heat exchanger for boiling. 19. A method according to claim 18, wherein the gas phase containing NH 3 as well as the concentrate from the recirculation circuit are liberated after the heat exchanger . 20. A method according to claim 18 or 19, wherein generally sediment-free liquid from the concentrate is fed back to the recirculation circuit after a sedimentation. 21. A method according to any of the claims 18-20, wherein any foam formations present are disintegrated by mechanical means. 22. A method according to any of the preceding claims, wherein the oxidation of NH 3 into N0 X in step c) takes place under the action of a suitable catalyst. 27 23. A method according to claim 22, wherein the temperature of the gas phase containing NH 3 is increased before step c) , preferably to 240°C or higher, e.g. by heat exchange with the reaction products from step c) or step d) . 24. A method according to any of the claims 15-23, wherein the condensate is stripped of NH 3 , and the stripping gas is preferably carried to the gas phase containing NH 3 before step c) . 25. A method according to claim 24, wherein at least a partial flow of the reaction products from step d) is utilised for the stripping of the condensate, preferably after humidifying. 26. A method according to claim 24 or 25, wherein the stripped condensate is treated with ozone for the attainment of a lowered content of chemically or biologically oxidable substances . 27. A method according to any of the claims 24-26, wherein the stripped condensate is treated with ultra- violet light for the attainment of a lowered content of micro-organisms . 28. A method according to any of the preceding claims, wherein the conversion of N0 X in step d) takes place under the action of a suitable catalyst. 29. A method according to claim 28, wherein N0 X is converted in step d) into free nitrogen, and a partial flow of the gas phase containing NH 3 is carried back to step d) after the heat exchange without being subjected to step c) . 30. A method according to claim 29, wherein atmos- pheric air is added to the remainder of the gas phase containing NH 3 . 31. A method according to claim 28, wherein NO x is converted into HN0 2 or HN0 3 in step d) , and step d) is performed in a washing column where the reaction products from step c) are washed with water, which is preferably recirculated. 28 32. A method according to claim 31, wherein step d) further comprises that HN0 2 or HN0 3 is reacted with a suitable base for the formation of a salt, e.g. NH 4 N0 3 or NaN0 3 . 33. A method according to claim 32, wherein at least a partial flow of the stripping gas and/or the gas phase containing NH 3 constitutes the base, and the salt formed is NH 4 N0 3 . 34. A plant for treatment of manure, solid manure and/or liquid manure (stale) from livestock, the plant com- prising: preferably separating means for separating manure and/or solid manure into a first fraction with a relatively high content of solid matter and a second, liquid fraction with a relatively low content of dry matter; - boiling means for boiling liquid manure or the second, liquid fraction, respectively, for the attainment of a gas phase containing NH 3 , and a concentrate; and oxidation means for oxidising the gas phase containing NH 3 into free nitrogen and/or compounds containing nitrogen oxide. 35. A plant according to claim 34, alternatively comprising: oxidation means for oxidation of the gas phase containing NH 3 for the attainment of gas phase containing NO x ; and furthermore comprising: reduction means for reduction of NO x in the gas phase containing N0 X into free nitrogen and/or compounds containing nitrogen oxide . 36. A plant according to claim 34 or 35, wherein the separating means comprise a mechanical press comprising a sieve, and a vibration screen. 37. A plant according to claim 36, wherein the press is a screw press. 38. A plant according to claim 36 or 37, wherein the sieve has a mesh aperture of 200-2000 μm, preferably 400-600 μm. 29 39. A plant according to any of the claims 36-38, wherein the vibration screen has a mesh aperture of less than 50 μm, preferably 5-30 μm. 40. A plant according to claim 34 or 35, wherein the separating means comprise a belt press. 41. A plant according to claim 40, wherein the belt has a mesh aperture of 50-500 μm, preferably around 100 μm. 42. A plant according to any of the claims 34-41, the plant further comprising pairs of heat exchangers, pre- ferably counter- flow heat exchangers for heat exchange of the second, liquid fraction with the concentrate and/or a condensate of the gas phase containing NH 3 or a reaction product thereof . 43. A plant according to claim 42, wherein a reac- tor for residence of the second, liquid fraction is connected between the two heat exchangers in a pair. 44. A plant according to any of the claims 34-43, wherein the boiling means comprise a boiling heat exchanger, preferably a plate heat exchanger, adapted for transferring heat from a condensing side to a boiling side, and a compressor, connected between the boiling side and the condensing side, for compressing steam liberated from the boiling side of the boiling heat exchanger, and supplying the compressed steam to the condensing side of the boiling heat exchanger. 45. A plant according to claim 44, wherein the boiling means further comprise a pump for recirculating the second, liquid fraction in a recirculation circuit comprising the boiling side of the boiling heat exchanger, the pump preferably having a capacity bigger than, particularly preferred more than twice, the capacity of the pumping means supplying the second, liquid fraction to the boiling means . 46. A plant according to claim 44 or 45, wherein the recirculation circuit further comprises liberating means for liberating the gas phase containing NH 3 as well as the concentrate from the recirculation circuit. 30 47. A plant according to any of the claims 44-46, wherein the recirculation circuit further comprise mechanical means for the disintegrating of foam formations. 48. A plant according to any of the claims 44-47, wherein, additionally, liberating means such as a sedimentation tank are connected to the recirculation circuit for liberating of a liquid phase rich in sediment from the recirculation circuit. 49. A plant according to any of the claims 34-48, wherein the oxidation means comprise a reactor with a catalyst suitable for reacting NH 3 with oxygen, for the attainment of NO x . 50. A plant according to claim 49, wherein the oxidation means further comprise a heat exchanger for heating the gas phase containing NH 3 before oxidation, preferably to 240°C or higher, by heat exchange with the reaction products from the oxidation or the reduction. 51. A plant according to claim 50, wherein the heat exchanger for heating the gas phase containing NH 3 contains one heat delivering circuit and two or more heat receiving circuits, and wherein at least two of the heat receiving circuits are connected with each other on their outlet side. 52. A plant according to any of the claims 34-51, the plant further comprising stripping means such as a desorption column for stripping the condensate of NH 3 . 53. A plant according to any of the claims 34-52, the plant further comprising means for treatment of the stripped condensate with ozone for the attainment of a lowered content of chemically or biologically oxidable substances, and/or ultra-violet light for the attainment of a lowered content of micro-organisms. 54. A plant according to any of the claims 34-53, wherein the reduction means comprise means such as washing columns or reactors containing catalysts suitable for converting NO x into free nitrogen compounds containing nitrogen oxide, in particular HN0 2 or HN0 3 .

Inventors: TANGE ANDERS, TANGE, ANDERS
Applicants: TANGE ANDERS, TANGE, ANDERS
Application year: 1998
Main classification: C05F3
IPC codes: C05F3