APPARATUS FOR FERMENTATION OF ORGANIC MATERIAL

Abstract: An apparatus for fermentation of organic material, for instance manure or sewage water, which is transported substantially horizontally through a fermentor (1). The apparatus is characterized by a rotatable screw (12), provided with blades, which screw carries out the horizontal transports, and by a device for internal heating of the screw blades, at least along a part (19) of the screw elongation.

Description: Apparatus for fermentation of organic material This invention relates to an apparatus for fer¬ mentation of organic material, which is trans¬ ported substantially horizontally through a fer¬ mentor. An apparatus of this kind is known, for example from the French Patent Specification No. 732738. According to this the material is pushed through the feππentor by gaseous pressure and is heated under its way through the vessel by an internally heated, rotatable pipe coil, which is provided peripherally with blades for stirring the material. This invention relates to an improvement of the known device with the object to increase the heating efficiency and is characterized by a ro- tatable screw, provided with blades, which screw carries out the horizontal transport, and by a device for internal heating of the screw blades, at least along a part of the screw elongation. The advantage with s * aid screw is that its blades give a large heat transfer area and that this area moves in relationship to the material, which is transported and mixed by the screw. These both circumstances give rise to the desired improve-- ent of the heat transfer efficiency. A further advantage with the invention lies in the following circumstance. For instance when fermenting manure anaerobically gas bubbles con- OMPI taining methane are developed- These lift solid particles to the manure surface, so that there is formed a solid mat. The good mixing, that the screw carries out, prevents the formation of this mat and makes the gas bubbles get free from the par¬ ticles and collect in the upper part of the fer¬ mentor. From there the gas can be discharged. A further advantage with the transport screw is, that this will efficiently prevent solid material from being accumulated in the fermentor plugging this with the time. The design of the screw makes it prevent the formation of short circuit flows, which could mean lower efficiency in the fermenta¬ tion process. As the heat requirement of the fer- mentation process normally prevails in the start end of the fermentor, where the organic material is fed, it can be su ficient to heat the transport screw blades substantially at the inlet of the fer¬ mentor. Setting of the desired temperature, for instance 35°C for anaerobic fermentation, can be done by regulating the temperature and/or the flow of the medium, that is used for heating, such as warm water. A further improvement of the heating of the con- tent of the fermentor can be obtained by one or a plurality of pipes, oriented in the axial direc¬ tion of the screw and preferably rotatable with - the screw, provided for internal heating. These pipes can be fastened to the screw at the peri- phery, serving to carry the screw. It may be desirable to inoculate the material. OMPI entering the fermentor, with microorganisms to ' accelerate the start of the fermenting process. According to one further characterizing feature of the invention this can be achieved by designing the fermentor with a space, located outside the periphery of the screw, which stretches along the screw, which space allows recirculation of fer¬ mented material to the material inlet to the fer¬ mentor. The recirculation is carried out auto- matically by returning part of the material, that has reached the gable of the fermentor at the out¬ let end for the material, moving it outside the screw periphery back towards the inlet side. The invention shall now be explained more in de- tail, reference being made to the enclosed drawing, which shows, by way of example, an embodiment of the apparatus in question. To be more exact figure 1 shows a longitudinal sectional view of the fer¬ mentor and figure 2 a cross sectional view of the same apparatus, seen from the left. It is provided that methane gas shall be produced by anaerobic fermentation of manure. Figure 1 just shows the both ends of an elongated closed fermentor 1. This is provided with a not shown external heat insulation. Manure is fed thorugh a pipe 2 to an inlet chamber 3, provided with a cap 4, in order that the inner parts of the chamber may be available if needed. From a bottom space 5 in the chamber 3 manure flows further into the fermentor 1, and after having passed this into a bottom space 6 in an outlet chamber 7. Fermented manure then leaves this chamber through a weir outlet 8. In the fermentor there is formed methane OMPI ,, Y WIIPPOO _ gas, which fills a space 9 above the manure sur¬ face 10 in the fermentor 1. In the chambers 3 and 7 a manure level will establish, which is higher than the level 10 and which is determined by the gas pressure in the space 9. The developed methane gas is discharged under a certain overpressure through a pipe 11. A transport screw 12 is sup¬ ported by a rectangular frame 13, consisting of pipes, which frame is welded to the periphery of the screw. The frame is supported at the gables of the fermentor of bearings 14 and 15. The latter bearing is firmly connected to shaft tap 16, which by a motor brings the frame 13 and thus also the screw 12 into rotation. Hot water is fed to the device through a channel 17, which goes through the shaft tap and the bearing 15. In the frame 13 there is provided a blocking wall 18, which in the shown position of the frame directs water up-- wards through the frame. As is indicated in the figure the left part 19 of the blade of the screw 12 is hollow, and water can - via a connection - reach this hollow blade part f om the frame 13. A blocking wall 20aprevents water from flowing fur¬ ther to the left in the upper part of the frame. According to the figure the cavity of the screw blade ceases after one blade turn and the water flows through a new connection once more into the frame 13 and continues in the frame to the block¬ ing wall 18. Here the water reaches an outlet channel 20 and leaves the apparatus. The frame 13 is provided, at the outlet end, with baffles 21, which help keeping the outlet free and discharge the fermented manure into the space 6. Also the C hamber 7 has a cap, denoted 22, which shall again make the inner parts of the chamber available. The i - chamber 7 and the left gable of the fermentor are also for similar reasons arranged detachable from 5 the rest of the fermentor by a screw joint 23. In figure 2 corresponding parts have the same re¬ ference numbers as in figure 1. Furthermore, there are shown in figure 2 two rods which support the chamber 7. Furthermore the figure shows a space 25 10 between the periphery of the screw 12 and the inner side of the fermentor 1. Through this space part of the fermented manure is recirculated from the left gable of the fermentor to the right one, thus inoculating the fresh entering manure with 15 microorganisms. As well the screw 12 as the frame 13.by rotation break the mat, that would otherwise be formed below the surface 10, especially through the flotating action, that the ascending gas bubbles 20 perform on the solid particles of the manure.

Claims: Claims 1. An apparatus for fermentation of organic mate¬ rial, which is transported substantially horizon¬ tally through a fermentor (1), c h a r a c t e ¬ r i z e d b y a rotatable screw (12) provided with blades, which screw carries out the horizontal transport, and by a device for internal heating of the screw blades, at least along a part (19) of the screw elongation. 2. An appratus according to claim 1, c h a r a c- t e r i z e d i n that the blade or the blades are arranged to be heated, primarily, at the material inlet end of the fermentor (1) . 3. An apparatus according to claim 1 or 2, c h a r a c t e r i z e d b y one or a plu- rality of pipes (13) oriented in axial direction of the screw (12) and preferably rotatable with the screw, provided for internal heating. 4. An apparatus according to claim 3, c h a ¬ r a c t e r i z e d, i n that the pipes (13) are arranged at or in the vicinity of the peri¬ phery of the screw (12) . 5. An appratus according to any of the preceeding claims, c h a r a c t e r i z e d i n that the fermentor (1) is provided with a space (25) located outside the periphery of the screw (12) which stretches along the screw, which space allows recirculation of fermented material to the material inlet of the fermentor. O

Inventors: CARLSSON TORSTEN LENNART TEODO, OESTER AKE RAFAEL, WIKHOLM BERT STEFAN, CARLSSON TORSTEN LENNART TEODOR
Applicants: ALFA LAVAL AB, CARLSSON TORSTEN LENNART TEODO, OESTER AKE RAFAEL, WIKHOLM BERT STEFAN, CARLSSON TORSTEN LENNART TEODOR
Application year: 1982
Main classification: C02F11
IPC codes: B01F15, C02F3, C12M1