A FERMENTER FOR FERMENTING ANIMAL MANURE UNDER AEROBIC CONDITIONS, A DEVICE AND A METHOD FOR FERMENTING ANIMAL MANURE UNDER AEROBIC CONDITIONS, USING SUCH A FERMENTER

Abstract: A fermenter for fermenting animal manure under aerobic conditions, which fermenter comprises a cylindrical tube, which is rotatable about its longitudinal axis, wherein the cylindrical tube is subdivided over substantially the entire length of the tube into at least two separate compartments, which compartments are made up of a partition which extends over substantially the entire length of the tube. The present invention furthermore relates to a device and a method for fermenting animal manure under aerobic conditions, using such a fermenter.

Description: A fermenter for fermenting animal manure under aerobic conditions, a device and a method for fermenting animal manure under aerobic conditions, using such a fermenter. The invention relates to a fermenter for fermenting animal manure under aerobic conditions, which fermenter comprises a cylindrical tube, which is rotatable about its longitudinal axis. The present invention furthermore relates to a device for fermenting animal manure under aerobic conditions, which device comprises a rotatable cylindrical fermentation unit, means for supplying and discharging air and means for supplying and discharging material to be fermented. The present invention furthermore relates to a method for fermenting animal manure under aerobic conditions, using a cylindrical tube which is rotatable about its longitudinal axis. A cylindrical fermenter of this kind is known from European patent application No. 0 685 441. According to said European patent application, the fermenter is mounted on a lorry in such a manner as to be rotatable about its longitudinal axis, whereby the fermenter is subdivided into chambers in a direction transversely to its longitudinal axis by means of perforated partitions. Each chamber thus formed is in turn subdivided into four subchambers in the direction of its longitudinal axis by means of perforated partitions, wherein each chamber is provided with an inlet and outlet opening, which is provided with a pivoted cover. The perforations allow the bacteria to migrate from one chamber to another and provide uniform gas conditions, wherein the partitions, which are mounted transversely to the longitudinal axis, prevent the contents to be fermented from being moved from one chamber to another. The drawback of such a fermenter is that partial discharge of compost and supply of material to be composted must take place periodically for each chamber separately. In addition, the overall efficiency of the aerobic fermentation is insufficient, due to the fact that there is no mutual exchange of the contents of the individual chambers that are present in the whole rotatable fermenter. A drum for aerobic fermentation of organic waste products which is rotatable about a substantially horizontal axis is also known from Dutch patent No. 98 394. According to a special embodiment described therein, the interior space of the drum, at least the central part thereof, is subdivided by radial longitudinal partitions into a number of separate spaces, which are open at their ends, and to each of which air is separately supplied in transverse direction. The provision of such longitudinal partitions in a central part of a rotating drum only leads to accumulation of the material to be fermented, so that lumps are formed. Such lumps result in anaerobic fermentation, which in turn leads to the formation of the undesirable biogas. In addition, such longitudinal partitions are curved in such a manner that supply lines for air can be provided therein. In practice it has become apparent, however, that because of the curved shape of the longitudinal partitions, an adequate separation of the individual spaces cannot be obtained, as a result of which the material to be aerobically fermented is not advantageously distributed over the various spaces, which affects the efficiency of the aerobic fermentation. Moreover, longitudinal partitions of this kind will result an undesirably decreased net volume being available for the fermentation process. A cylindrical tube which is rotatable about its longitudinal axis and which is used for fermenting animal manure under aerobic conditions, is also known from US patent No. 5,407,809. According to said US patent, the cylindrical tube, which is rotatable about its longitudinal axis, consists of a number of partitions, which are provi ded in regularly spaced-apart relationship over the cross-section of the tube. Each partition has a variable surface area, which varies from 60% to 100% of the cross-sectional area of the tube, and it is disposed in such a manner with respect to another partition, that the material to be fermented and the air to be supplied to the tube must traverse a non-linear path through the tube. During fermentation, the air is passed through the tube in the opposite direction to the material to be fermented, whereby the regularly spaced partitions cause the air to swirl through the tube. The tube is provided with so-called longitudinal ribs along the entire inner circumference thereof, so as to effect a proper mixing during rotation in each tube compartment, which is made up of two partitions which are disposed a specified distance apart. Such ribs prevent the formation of large lumps of material to be fermented, and thus they have a certain abrasive effect. One drawback of such a cylindrical tube which is rotatable about its longitudinal axis is the fact that the residence times in each compartment made up of partitions being disposed in the transverse direction of the tube vary greatly. As a result of the "swirling" path in the rotatable tube, the material to be fermented will be transported through the tube with varying residence times in each compartment. The result of this is that generally the material which is discharged from the tube will still contain fermentable components, which is undesirable in practice. Moreover, it is known that large lumps of material to be fermented do occur, in spite of the presence of the longitudinal ribs, as a result of which the material to be fermented and the air being supplied will not be thoroughly mixed. It is an object of the present invention to overcome the above problems, and to provide a fermenter for fermenting animal manure under aerobic conditions, which fermenter provides a residual material of a constant quality, in particular having a low moisture content and a small residual amount of materials to be fermented. In addition to that, it is an object of the present invention to provide a fermenter for fermenting animal manure under aerobic conditions, wherein the fermenter is not subdivided in its transverse direction into separate compartments, which compartments only allow the exchange of bacteria and gaseous components. Another object of the present invention is furthermore to provide a device and a method wherein the amount of air which is required for the aerobic fermentation is used economically, and wherein the energy consumption is furthermore minimised. Although the present description constantly refers to the processing of animal manure, it will be apparent to those who are skilled in the art that each material which can be aerobically fermented, such as organic household waste, garden waste, auction mart waste, sludge and the like, can be processed by means of the method and the device according to the present invention. Thus, the present invention is by no means limited to the processing of animal manure. According to the present invention, the fermenter for fermenting animal manure under aerobic conditions as referred to in the introduction is characterized in that said cylindrical tube is subdivided over substantially the entire length of the tube into at least two separate compartments, which compartments are made up of a partition which extends over substantially the entire length of the tube. In a preferred embodiment of the fermenter according to the invention, the cylindrical tube is subdivided, over substantially the entire length thereof, into four separate compartments, wherein said compartments are made up of partitions which extend over substantially the entire length of the tube. By providing four separate compartments, which extend over substantially the entire length of the tube, the capacity of the rotating fermenter is increased, because there is a better contact between the air and the material to be fermented in each compartment than in the rotatable fermenters as known from the above-described prior art. In addition, the formation of lumps will be limited when "small" compartments are used, since there will be constant collisions with the wall of the cylindrical tube and with the partition extending along the longitudinal axis. Furthermore, a close contact will be effected in each compartment between the material to be fermented and the air being supplied in the opposite direction. In another preferred embodiment, the partitions are provided with openings. By providing the partitions, which extend over substantially the entire length of the tube, with openings, a certain exchange of material to be fermented will be effected between the individual compartments. Material having smaller dimensions than the openings will be exchanged between the compartments, whilst the material to be fermented that has larger dimensions than the openings will remain behind in each compartment. Since there is a certain exchange between the compartments, the fermentation process in the various compartments will take place more uniformly than in the embodiment according to the above- described prior art, in particular as described in European patent application No. 0 685 441, wherein no exchange of the material to be fermented between the individual chambers is possible at all. In addition, the presence of openings will ensure that large lumps of material to be fermented will be reduced by the abrasive effect of such openings, so that there will be a more optimum fermentation and a more optimum exchange of material between the compartments. A grid may be used as the apertured partition, for example. The openings in the partitions preferably have sharp edges. Such sharp edges provide a slight grinding effect, whereby large particles are converted into small particles, which small particles have an advantageous effect on the aerobic fermentation process. The size of the openings preferably decreases in the longitudinal direction of the tube, because an exchange of the material to be fermented is in particular desired on the side where the fresh material to be fermented is supplied. In addition, due to the abrasive effect of the presence of the openings, the material to be fermented will have more uniform dimensions at the end of the cylindrical tube than at the beginning of the tube, so that the presence of smaller openings ensures that not all of the material to be fermented is transported from one compartment to the other. In another preferred embodiment of the fermenter according to the present invention, the size of the openings increases in a direction from the wall towards the centre of the tube. Since the cylindrical tube is rotatable about its longitudinal axis, the material to be fermented will be moved to the wall of said cylindrical tube under the influence of the centrifugal force. Consequently, it is desirable for the size of the openings to increase in a direction from the wall towards the centre, in order to obtain a certain exchange between the compartments. In order to prevent the partitions, which extend over substantially the entire length of the tube, from deflecting, or breaking if it comes to the worst, under the influence of the material to be fermented, one or more stiffening elements are provided in regularly spaced-apart relationship along the wall of the tube, which stiffening elements extend over the entire transverse circumference of the tube. It should be understood, however, that such stiffening elements do not correspond with the partitions used in US patent No. 5,407,809, or with the partitions which are known from European patent application No. 685 441, which are mounted transversely to the longitudinal axis of the rotatable fermenter. The fact is that the stiffening elements which are used in a special embodiment of the present invention by no means function to reduce the transport of the material to be fermented over the longitudinal axis of the rotatable fermenter to an essential extent. The present invention furthermore relates to a device for fermenting animal manure under aerobic conditions, which device comprises a rotatable, cylindrical fermentation unit, means for supplying and discharging air and means for supplying and discharging the material to be fermented, which device is according to the present invention characterized in that at least one rotatable fermenter as described above is used. In a preferred embodiment of the device according to the present invention the device comprises at least two rotatable cylindrical fermenters, which cylindrical fermenters are subdivided, over substantially the entire length thereof, into at least two separate compartments, which are made up of a partition which extends over substantially the entire length of the tube. In the embodiment wherein two such cylindrical tubes being rotatable about their longitudinal axes are used, the material which is discharged from one fermenter serves as the material to be supplied to the other fermenter, whereby the air flow in each cylindrical tube takes place in the opposite direction to the direction of transport of the material to be fermented. Although such a device may also consist of only one cylindrical fermenter being rotatable about its longitudinal axis, it is preferred, for reasons of fermentation and drying efficiency, to use at least two such rotatable fermenters. The fermentation process requires a particular residence time in the tube, and the use of two separate fermenters makes it possible to use tubes which have a length which is still feasible in practice. In specific embodiments it is preferred to dispose the cylindrical tubes at an angle in order to promote the transport of the material to be fermented in the fermenter being rotatable about its longitudinal axis, so that the transport inside the fermenter will take place under the influence of gravity. In the embodiment wherein at least two rotatable cylindrical fermenters are used, the angle at which the first fermenter is disposed is preferably smaller than the angle at which the second fermenter is disposed. Experiments have shown that the fermentation process, which is a relatively slow process in comparison with the drying process, mainly takes place in the first fermenter, so that the residence time must be longer than in the second fermenter, where the drying process mainly takes place. The influencing of the residence time in the fermenter is thus effected by changing the angle at which the cylindrical fermenters are disposed. In addition to that it is possible, however, to influence the residence time in the fermenter by changing the rotation speed of the fermenter, or by changing the speed at which the material to be fermented is supplied to the fermenter. In practice it has become apparent that horizontally disposed, rotatable fermenters provide adequate internal transport of the material to be fermented, because the rotation of the fermenter and the change in the consistency of the material to be processed, which is caused by the fermentation process, contribute to the internal transport. In another special embodiment of the device according to the present invention, the device comprises three rotatable cylindrical fermenters, wherein the material which is discharged from the first fermenter serves as the material to be supplied to the second fermenter, and wherein the material which is discharged from the second fermenter serves as the material to be supplied to the third fermenter. Thus, it is possible to effect the total residence time which is desired in order to obtain a residual material of a constant quality as described above, using three rotatable fermenters having practically feasible dimensions. The present invention furthermore relates to a method for fermenting animal manure under aerobic conditions, which method is characterized in that a cylindrical tube which is rotatable about its longitudinal axis is used as a fermenter, which cylindrical tube is subdivided, over substantially the entire length thereof, into at least two separate compartments, which compartments are made up of a partition which extends over substantially the entire length of the tube. In a preferred embodiment of the method according to the present invention, the material to be fermented is continuously suppl ied to the rotatable cyl indrical fermenter, wherein the air flow takes place in the opposite direction to the direction of transport of the material to be fermented in the tube, and wherein fermented material which is discharged from one tube is supplied to the other rotatable fermenter if the special embodiment comprises more than one rotatable cylindrical fermenter. When such a method is used, a thorough mixing of the material to be fermented and the air, which is essential for the aerobic fermentation process, is obtained. Since the cylindrical tube is subdivided, over substantially the entire length thereof, into at least two separate compartments, there is a proper ratio between the amount of air which is being supplied and the amount of material to be fermented, which has a positive effect on the fermentation and drying process. Preferably, the air from the first rotatable fermenter is reused as inlet air for the first rotatable fermenter, whereby a specified amount of the circulation air may be exhausted and fresh air may be admixed. Since the fermentation process will mainly take place in the first rotatable fermenter, which fermentation process will cause a temperature increase in the material to be fermented to a value of about 35 - 80 ° C, due to the action of the aerobic bacteria, it is preferred to maintain a stable temperature conditions in the first fermenter. Since the relatively hot air issuing from the first fermenter is resupplied to the same fermenter, stable temperature conditions are provided, which has a positive effect on the fermentation process. The circulation air can be partially exhausted, with fresh air being admixed, in order prevent an accumulation of undesirable constituents in the circulation air in the first fermenter. In addition, the material that has already been fermented in the first fermenter must be prevented from being moisturized by the recirculated air. It should be understood that the present invention is suitable for fermenting and drying any material that is fermentable, such as garden and kitchen waste, auction mart waste, sludge and animal manure, with chicken manure being preferred in view of its high dry matter content. The essence of the present invention is the fact that the cylindrical tube, which is used for the fermentation of (preferably) animal manure under aerobic conditions, is subdivided, over substantially the entire length thereof, into at least two separate compartments, which compartments are made up of a partition which extends over substantially the entire length of the tube. In a particularly preferred embodiment, the partition is provided with openings which allow an exchange of material between the individual compartments. The present invention is by no means limited, however, to a device which comprises two or three such rotatable cylindrical fermenters, whereby it should be noted that the desired residence time in the fermenter can be determined by routine experiments carried out by persons who are skilled in this field of the art. The present invention will be explained in more detail hereafter with reference to the accompanying figures. Figure 1 diagrammatically shows a fermentation device according to the present invention, which consists of three rotatable cylindrical fermenters. Figure 2 is a diagrammatic cross-sectional view along line 11— 11 of the fermentation device of Figure 1. Figure 3 is a detail view of a single rotatable cylindrical fermenter according to the present invention, which comprises partitions in the form of a grid. Figure 4 is a cross-sectional view of the rotatable fermenter of Figure 3. Figure 5 is a diagrammatic, perspective view of a rotatable cylindrical fermenter, which comprises four compartments wherein mutual exchange of material to be fermented can take place. Figure 6 diagrammatically shows a fermentation device which corresponds with the fermentation device which is shown in Figure 1, with this difference that two rotatable cylindrical fermenters are used. Figure 7 is a diagrammatic cross-sectional view along line VII-VII of the fermentation device of Figure 6. Figure 8 diagrammatically shows a special embodiment of a drive unit for a rotatable cylindrical fermenter. Figure 9 is a diagrammatic, cross-sectional view along line IX-IX of the drive unit of Figure 8. Example Figure 1 shows a fermentation device 1, which fermentation device 1 comprises three separate, rotatable cylindrical fermenters 2, 3, 4. Each fermenter 2, 3, 4 is subdivided, over substantially the entire length thereof, into four separate compartments, which compartments are made up of partitions which extend over substantially the entire length of the tube. Thus, cylindrical tube 2, which is rotatable about its longitudinal axis, is subdivided, over substantially the entire length of tube 2, into four separate compartments 20, 21, 30, 31 by partitions 7, 26. For the sake of clarity only partition 7 is shown in Figure 1, whilst Figure 2 shows a cross-section of cylindrical tube 2, wherein partitions 7, 26 can be clearly distinguished. Cylindrical tube 3, which is rotatable about its longitudinal axis, is similarly subdivided by partitions 8, 27 into four separate compartments 22, 23, 32, 33, of which only compartments 22, 23 are diagrammatically shown in Figure 1. Cylindrical tube 4 is similarly subdivided by partitions 9, 28 into four separate compartments 24, 25, 34, 35, whereby for the sake of clarity only compartments 24, 25 are diagrammatically shown in Figure 1. The material 5 to be fermented is supplied to the upper cylindrical tube 2 via supply element 6. Supply element 6 ensures that the material 5 to be fermented is evenly supplied to each individual compartment 20, 21, 30, 31 of tube 2. For the sake of clarity, only compartments 20, 21 are shown in Figure 1, whereby the mass flows of the material to be fermented in said compartments are diagrammatically indicated by hatchings. The material 5 to be fermented which is supplied to cylindrical tube 2 will undergo aerobic fermentation under the influence of the air 15 that is supplied. The aerobic reaction will cause the temperature of the material to be fermented in tube 2 to increase to a value of about 40 - 45 ° C. It is preferred to resupply air 15 to tube 2, in order to maintain stable temperature conditions in tube 2. The air 15 which is supplied to tube 2 exits tube 2 via opening 19, after which it is carried back to the inlet of tube 2 via pipe 18, in which a fan (not shown) may be provided. In order to prevent accumulation of undesirable constituents in the air thus recycled, it is also possible to exhaust an amount of air via valve 17. In addition to that it is possible to admix an amount of "fresh" air to the air 15 being resupplied to tube 2, which is done by setting valve 16 so that a specified amount of air from outside the fermentation device 1 is drawn into tube 2. The material being discharged from tube 2 is then supplied to rotatable cylindrical tube 3 via supply element 10. Supply element 10 is of a different type than the supply element 6 which is used in cylindrical tube 2. Since each cylindrical tube 2, 3, 4 is rotatable about its longitudinal axis, supply element 10 is suitable for filling each individual compartment in an even manner, since each individual compartment is placed in front of the opening of supply element 10 at a certain point in time as a result of the rotation of tubes 2, 3, 4. The fermentation device which is shown in Figure 1 is not limited to supply element 6 or supply element 10, however. Instead of using supply element 6, it is thus also possible to provide a supply element corresponding with supply element 10 near tube 2. The same applies with regard to tube 3 and tube 4, respectively. The use of a supply element 6 also ensures that the air which is supplied in the opposite direction to the direction of flow of the material to be fermented can easily exit the rotatable fermenter. Cylindrical tube 3 is subdivided, over substantially the entire length thereof, into four separate compartments 22, 23, 32, 33, which are made up of partitions 8, 27 (also refer to Figure 2) which extend over substantially the entire length of tube 3. For the sake of clarity only compartments 22, 23 are diagrammatically shown in Figure 1, whereby the mass flows of the material to be fermented in said compartments 22, 23 are diagrammatically indicated by hatchings. After the material has exited cylindrical tube 3, it will land in cylindrical tube 4 via supply element 11. In this embodiment, cylindrical tube 4 is subdivided into four separate compartments 24, 25, 34, 35 by two partitions 9, 28 which extend over substantially the entire length of the tube, whereby for the sake of clarity only compartments 24, 25 are diagrammatically shown in Figure 1. Air 12 is supplied to cylindrical tube 4, which air 12 mainly serves to dry the materials which are present in tube 4. The air 12 exits tube 4 via opening 13, and possibly also via supply element 11, after which it is supplied to tube 3, whereby air 12 exits tube 3 via opening 29, and possibly also via supply element 10, after which it is discharged via opening 14. It is desirable to mount a partition (not shown) between tube 4 and tube 3, in order to ensure that the air 12 issuing from tube 4 is carried into tube 3. Such a partition prevents air which issues from tube 4 from flowing past tube 3 and being directly discharged via opening 14. Experiments have shown that cylindrical tube 2 mainly functions to ferment material 5, whilst cylindrical tubes 3, 4 mainly function to dry the material that has already been fermented in tube 2. A certain amount of fermentation may also take place in tube 3 as well as in tube 4, however. Furthermore, in addition to said fermentation, also a certain amount of drying will take place in tube 2. The fermented and dried material exits tube 4 and it is stored or possibly undergoes further processing for special purposes like compost. Although the rotatable tubular fermenters 2, 3, 4 are shown in a horizontal position in Figure 1, it is also possible, of course, to use a slightly inclined position in order to influence the transport of material 5 in each fermenter 2, 3, 4. Figure 2 shows a diagrammatic cross-section of the fermentation device 1 which is shown in Figure 1. Cylindrical tube 2, which is rotatable about its longitudinal axis, is rotated by means of rotatable rollers 36, 37. Cylindrical tube 2 is subdivided into four separate compartments 20, 21, 30, 31 by means of partitions 7, 26, which extend over substantially the entire length of the tube. Cylindrical tube 3, which is rotatable about its longitudinal axis, is subdivided into four separate compartments 22, 23, 32, 33 by means of partitions 8, 27, which extend over substantially the entire length of the tube. Cylindrical tube 3 is rotated by rotatable rollers 38, 39. Cylindrical tube 4, which is rotatable about its longitudinal axis, is subdivided into four separate compartments 24, 25, 34, 35 by means of partitions 9, 28, which extend over substantially the entire length of the tube. Cylindrical tube 4 is rotated by rotatable rollers 40, 41. For the sake of clarity the flows of the material to be fermented are not shown in Figure 2. It should be understood, however, that the fermentation device according to the present invention is not limited to the specific embodiment comprising three cylindrical tubes, which each comprise four compartments extending over the length of the tube. Figure 3 is a diagrammatic detail view of a single rotatable cylindrical fermenter 42, which comprises partitions 44, 52 in the form of a grid. The material 5 to be fermented is supplied to the separate compartments 48, 49, 50, 51 of cylindrical tube 42 via supply element 43. Since the partitions 44, 52 are in the form of grids, an exchange of material will take place between the individual compartments 48, 49, 50, 51. For the sake of clarity it is also indicated that air 15 which has been supplied to cylindrical tube 42 is resupplied to fermenter 42 via pipe 18. The recirculation air may be admixed with "fresh" outside air by suitably adjusting valve 16, as already described with reference to Figure 1. Furthermore, it is possible to exhaust at least part of the air 15 via a discharge valve (not shown) after it has exited fermenter 42. It should be understood, however, that cylindrical tube 42, which comprises partitions 44, 52 provided with openings 47, is not limited to such a manner of reusing air. Figure 4 shows a diagrammatic cross-section of the cylindrical tube 42 of Figure 3. Cylindrical tube 42 is rotated by rotatable rollers 45, 46. Since grids 44, 52 are used as partitions, it will be apparent that an exchange of material to be treated takes place between the individual compartments 48, 49, 50, 51. Figure 5 is a perspective view of the rotatable cylindrical fermenter 42 which is used in Figures 3, 4. Grids 44, 52 are provided with openings 47, via which openings 47 an exchange of material takes place between the individual compartments 48, 49, 50, 51. In a preferred embodiment of the partitions 44, 52 provided with openings 47, the size of openings 47 may decrease in the longitudinal direction of tube 42, which means that the openings 47 which are present at the beginning of fermenter 42, where material to be fermented is supplied, must be larger than the openings which are present at the end of fermenter 42, where material is discharged. In addition to that, the partitions 44, 52 provided with openings 47 may be configured in such a manner that the size of openings 47 increases in a direction from the wall towards the centre of tube 42, which means that the openings 47 which are present in the centre are larger than the openings 47 which are present near the wall of the fermenter 42. Figure 6 shows a fermentation device 1 which corresponds with the fermentation device 1 which is shown in Figure 1, with this difference that the fermentation device 1 which is shown in Figure 6 comprises two separate rotatable cylindrical fermenters 2, 3, whilst the fermentation device 1 which is shown in Figure 1 comprises three separate rotatable cylindrical fermenters 2, 3, 4. The reference numerals used in Figure 1 correspond with those which are used in Figure 6. Although the supply element 10 which is used with fermenter 3 is different from the supply element 6 which is used with fermenter 2, it should be apparent that the fermentation device 1 shown in Figure 6 is not limited to such specific supply elements 6, 10. It is also possible to use supply element 10 for fermenter 2. Figure 7 is a diagrammatic cross-sectional view of the fermentation device 1 which is shown in Figure 6. Figure 7 substantially corresponds with Figure 2, with this difference that Figure 7 shows two separate rotatable cylindrical fermenters 2, 3. Also with regard to Figure 7 it applies that the reference numerals used in Figure 2 correspond with those which are used in Figure 7. Figure 8 diagrammatically shows a rotatable cyl indrical fermenter 53. The rotatable cylindrical fermenter 53 is rotatable about its longitudinal axis, using conveyor belt 55, which conveyor belt is provided along the circumference of rotatable fermenter 53. Conveyor belt 55 is driven by means of transmission element 58, which is connected to drive unit 57 via shaft 56. Rotatable rollers 54 function to support rotatable fermenter 53. Figure 9 is a diagrammatic, cross-sectional view of the rotatable fermenter 53 of Figure 8. Conveyor belt 55 is provided along the circumference of rotatable fermenter 53, and it can be rotated by means of transmission element 58, which is connected to drive unit 57 via shaft 56. Although the rotatable fermenter 53 of Figure 9 is divided into four separate compartments, it should be understood that the present invention is not limited to such a specific distribution of the compartments. Experiments have shown that chicken manure having a dry matter content of 45% can be fermented and dried to a material having a dry matter content of 82% by using a fermentation device 1 as described above. It is possible to supply air having a higher temperature so as to promote the drying process, which mainly takes place in cylindrical tubes 3, 4, in particular in the device 1 which is shown in Figure 1. Although the fermentation device 1 which is described in the present example is built up of three cylindrical tubes 2, 3, 4, which cylindrical tubes 2, 3, 4 each comprise four compartments, which extend over substantially the entire length of the tube, the present invention is not limited to such an embodiment. It is possible within the scope of the present invention to use only one cylindrical tube which is rotatable about its longitudinal axis, which tube is subdivided over substantially its entire length into at least two separate compartments. In addition to that it is possible to arrange the cylindrical tubes one behind the other instead of using the arrangements which are diagrammatically shown in Figures 1, 2, 6 and 7, wherein the cylindrical tubes are arranged one above the other.

Claims: CLAIMS 1. A fermenter for fermenting animal manure under aerobic conditions, which fermenter comprises a cylindrical tube, which is rotatable about its longitudinal axis, characterized in that said cylindrical tube is subdivided over substantially the entire length of the tube into at least two separate compartments, which compartments are made up of a partition which extends over substantially the entire length of the tube. 2. A fermenter according to claim 1, characterized in that said cylindrical tube is subdivided, over substantially the entire length thereof, into four separate compartments, wherein said compartments are made up of partitions which extend over substantially the entire length of the tube. 3. A fermenter according to claims 1 - 2, characterized in that said partitions are provided with openings. 4. A fermenter according to claim 3, characterized in that the size of the openings decreases in the longitudinal direction of the tube. 5. A fermenter according to claim 3, characterized in that the size of the openings increases in a direction from the wall towards the centre of the tube. 6. A fermenter according to claim 1, characterized in that one or more stiffening elements are provided in regularly spaced-apart relationship transversely to the longitudinal axis of the tube, which stiffening elements extend over the entire transverse circumference of the tube. 7. A device for fermenting animal manure under aerobic conditions, which device comprises a rotatable, cylindrical fermentation unit, means for supplying and discharging air and means for supplying and discharging the material to be fermented, characterized in that at least one rotatable fermenter according to claims 1 - 6 is used. 8. A device according to claim 7, characterized in that the device comprises at least two rotatable cylindrical fermenters according to claims 1 - 6, wherein the material which is discharged from one fermenter serves as the material to be supplied to the other fermenter, and wherein the air flow in each cylindrical tube takes place in the opposite direction to the direction of movement of the material to be fermented. 9. A device according to claims 7 - 8, characterized in that said cylindrical fermenters are disposed at an angle. 10. A method for fermenting animal manure under aerobic conditions, using a cylindrical tube which is rotatable about its longitudinal axis, wherein air is supplied to said cylindrical tube, characterized in that at least one rotatable fermenter according to claims 1 - 6 is used. 11. A method according to claim 10, characterized in that at least two rotatable fermenters according to claims 1 - 6 are used, wherein the material to be fermented is continuously supplied to one rotatable cylindrical fermenter, wherein the air flow takes place in the opposite direction to the direction of transport therein of the material to be fermented, and in that the material thus fermented, after being discharged from one fermenter, is supplied to the other rotatable fermenter. 12. A method according to claims 10 - 11, characterized in that the air from the first rotatable fermenter is reused as inlet air for the first rotatable fermenter. 13. A method according to claim 10 - 12, characterized in that the residence time in the first rotatable fermenter is longer than in the second rotatable fermenter. 14. A method according to claims 10 - 13, characterized in that the temperature in the first tube ranges between 35 - 80 ° C.

Inventors: JACOBS JOHANNES JOSEPH, JACOBS, JOHANNES, JOSEPH
Applicants: JACOBS JOHANNES JOSEPH, JACOBS, JOHANNES, JOSEPH
Application year: 1998
Main classification: C05F17
IPC codes: C05F17