Abstract:
The invention relates to a device for delivering thick matter. The device comprises: a delivery cylinder ( 20 ); a material feed space ( 16 ), which is connected to the delivery cylinder ( 20 ) on the entry side; a delivery line ( 18 ), which is connected to the delivery cylinder ( 20 ) on the exit side; a delivery plunger ( 12 ), which can be displaced to-and-fro through the material feed space ( 16 ) and the delivery cylinder ( 20 ), and; a closing element ( 22 ), which is placed at the exit location of the delivery cylinder ( 20 ) or inside the delivery line ( 18 ) and which can be displaced between an open position and a closing position. In order to be able to separate foreign substances, which are contained in the flow of thick matter, out of the flow of thick matter before the actual processing step for the useful substances, the invention provides that the delivery cylinder ( 20 ) is perforated at least over a portion of its cylinder jacket ( 24 ). These measures make it possible to obtain a device that combines the features of a thick matter pump, a sieve and a press.

Description:
This is a U.S. national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/EP2006/007868, filed Aug. 9, 2006, and claims benefit of German Patent Application No. 10 2005 040 014.0, filed Aug. 23, 2005. The International Application was published in German on Mar. 1, 2007 as WO 2007/022867 under PCT Article 21(2). 
     The present invention relates to a device for conveying thick matter, including a delivery cylinder, a material feed space connected to the inlet side of the delivery cylinder, a delivery line connected to the outlet side of the delivery cylinder, a delivery piston which is reciprocatable through the material feed space and the delivery cylinder, and further including a closure member which is located at the outlet side of the delivery cylinder or in the delivery line and is movable between an open position and a closed position. 
     BACKGROUND 
     European Patent EP-B 681672 describes a device which is designed for conveying thick matter containing shredded scrap metal. In that device, the thick matter is fed to the delivery device via the material feed space and is moved by the delivery piston into the delivery cylinder, from where it is forced through the delivery line. The closure member provides that, during each stroke, the thick matter is first compressed in the delivery cylinder before it is forced into the delivery line while the closure member is open. This device conveys the thick matter through the delivery conduit along with the foreign substances contained therein, including scrap metal and similar solids. 
     In principle, this device can also be used to convey biogenic wastes, which generally contain not only organic components, but also considerable amounts of foreign substances. The foreign substances must be removed from the material flow for a subsequent processing step. As long as the waste is in a relatively dry form, the separation of foreign substances is mostly done by hand. However, in the case of wet organic waste, the method chosen is that of shredding. In the treatment of food remains, for example, one uses hammer mills capable of shredding foreign substances, such as knife handles, to particles of less than 10 mm in size. Thick matter that is conditioned in this way can indeed be transported by a thick matter pump of the type specified at the outset. However, the disadvantage here is that the foreign substances are still contained in the material flow. The material separation problem is not solved in this manner, but shifted to a process step at the end of the transport process. This is the procedure used, for example, for food waste substrate which is fed to a fermenter and which still contains foreign substances such as shredded plastic packaging, cans, tubes, knives, forks. There, the organic matter is indeed degraded in the fermentation residue, but the shredded foreign substances contained in the sludge must still be removed if the sludge is intended for use as an organic nitrogen fertilizer. Without separation, the only possible method of disposal is by burning. 
     SUMMARY 
     In view of the above, it is an aspect of the present invention to improve a known device for conveying thick matter in such a way that the foreign substances are separated from the material flow before the actual processing step for the useful substances. 
     The present invention provides a device for conveying a mixture of substances including at least one mixture component predominantly having a viscous consistency and at least one mixture component predominantly having a solid, particle-like consistency. The invention includes a delivery cylinder having perforations over a portion of a lateral wall thereof and configured to separate, through the perforations, at least one of the mixture components from the mixture of substances. The delivery cylinder is connected, via a pipeline provided on an outside of the perforated lateral cylinder wall, to a processing station for the separated at least one mixture component. A material feed space is connected to an inlet side of the delivery cylinder. A delivery line is connected to an outlet side of the delivery cylinder. A delivery piston is reciprocatable through the material feed space and the delivery cylinder. A closure member is disposed at the outlet side of the delivery cylinder or in the delivery line and movable between an open position and a closed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be explained in more detail below with reference to an exemplary embodiment schematically shown in the drawing, in which: 
         FIG. 1  is a schematic view of a single-piston pump for preparing and conveying biogenic wastes; 
         FIGS. 2   a  through  c  are, respectively, a side view, a longitudinal sectional view, and a cross-sectional view of the perforated lateral wall of the delivery cylinder; 
         FIG. 3  is a view showing an extension section which is arranged in a meandering pattern and is intended to be integrated into the return section of the pump circuit of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is based on the idea of developing a device that combines the features of a thick matter pump, a sieve and a press. In a device of the type specified at the outset, in order to achieve this, the delivery cylinder is perforated at least over a portion of its lateral wall. In this case, the device provides a press for the thick matter that is conveyed by the delivery piston from the material feed space into the delivery cylinder while the closure member is closed. 
     The perforated lateral cylinder wall constitutes a sieve unit through which the useful liquid substances are passed to the outside and into a collecting duct under the action of the pressure developed by the press. Subsequently, while the closure member is open, the foreign substances are forced into the delivery line in the manner of a pump. 
     In an advantageous embodiment of the present invention, the perforations of the lateral cylinder wall are in the form of a grid of holes. More specifically, the perforations are arranged in a portion of the lateral cylinder wall that is swept by the delivery piston during reciprocation. It has proven advantageous if the cross-sectional area of the holes forming the perforations is smaller on the inside than on the outside of the lateral wall. In order to prevent premature wear, the lateral wall of the delivery cylinder is expediently made from a material that is hardened on the inner side. 
     In a preferred embodiment of the present invention, a slide is disposed in the area of the lateral cylinder wall, said slide being movable relative to the lateral cylinder wall between a closed position, in which the perforations are sealed, and an open position, in which the perforations are left open. 
     Advantageously, the lateral cylinder wall is surrounded by a tubular slide. The slide is movable axially with respect to the lateral cylinder wall. In one advantageous embodiment of the present invention, the lateral cylinder wall is perforated over at most half its length, while the slide has a closed shell and is moved by half the length of the lateral cylinder wall from the open position to the closed position. 
     In principle, however, the slide may also have a grid of holes and closed areas therebetween, said grid being complementary to the grid of holes of the lateral cylinder wall. In this case, it is possible for the slide to be moved or rotated between the open position and the closed position in an axial or circumferential direction with respect to the lateral cylinder wall by half the grid spacing of the grid of holes. This results in a relatively small rotational or translational movement of the slide as compared to the embodiment where half the cylinder length is used. 
     In principle, it is also possible to use a sealing device having a separate sealing member for each perforation hole. Such a sealing member may, for example, be in the form of a plug or a sealing cone. 
     In another preferred embodiment of the present invention, a control unit is provided for coupled control of drive mechanisms for moving the piston, the closure member and/or the slide. In order to achieve this, the controller conveniently provides a sequence control system for controlling the drive units of the piston, of the closure member, and of the slide. 
     In this connection, it is advantageous if, in response to displacement signals produced by the piston, the control unit causes the closure member to perform a closing movement and/or if, in response to output signals of a pressure sensor located upstream of the closure member in the delivery cylinder or in the delivery line, the control unit causes the closure member to perform an opening movement. 
     Similarly, the slide may also have a drive mechanism that is controllable by the control unit. In this case, the control unit will respond, for example, to displacement signals of the delivery piston by causing the slide to perform an opening movement as the delivery piston moves into the delivery cylinder, while it will respond to a pressure signal of the pressure sensor by causing the slide to perform a closing movement when the pressure exceeds a predetermined threshold. 
     Advantageously, to ensure that the perforation holes are always open for the passage of the useful substances therethrough, a cleaning device is provided which applies compressed air or pressurized water to the perforation holes. Apart from that, clogging of the perforation holes with filter cake is also reliably prevented because the passing piston automatically cleans the cylinder surface during each stroke. 
     The pressure at which the closure member is opened can be adjusted by the piston travel and makes it possible to squeeze out the particles that are present in a particular case, and thereby to maintain a high level of functional reliability. Moreover, in accordance with one advantageous embodiment of the present invention, the delivery line feeds into a return section which leads back to the material feed space and is preferably in the form of a bioreactor. The return section may have a heating means disposed therein which heats the material being conveyed. In order to prolong the residence time, the return section may have an extension section disposed therein which is preferably arranged in a meandering pattern. 
     Moreover, a pipeline leading to a processing station may be connected on the outside of the perforated lateral cylinder wall. The useful substances forced out through the perforations can be delivered to the processing station through this pipeline. Thus, the pump is provided with the function of a two-phase pump. 
     The device of the present invention is particularly suitable for carrying out a method for conveying mixtures of substances containing different components, at least one of the mixture components predominantly having a viscous consistency and at least one other mixture component predominantly having a solid, particle-like consistency. In accordance with the present invention, the mixture of substances is forced into a compression chamber while pressure is being built up. In the process, the mixture components predominantly having a viscous consistency and the mixture components predominantly having a solid, particle-like consistency are separated by the pressure developed in the compression chamber, thereby producing different flows of material. The division into different material flows is preferably accomplished by the fact that the mixture components predominantly having a viscous consistency are forced by the pressure out of the compression chamber and into a first delivery path through relief openings in a boundary wall, and that the mixture components predominantly having a solid, particle-like consistency are forced out of the compression chamber and into a second delivery path after a closure member is opened. The opening of the closure member is conveniently triggered when the pressure in the compression chamber exceeds a predetermined limit value. Advantageously, during a stroke of the piston, the predominantly viscous components of the mixture are forced through perforations in the cylinder wall while the closure member is in a closed position, while the predominantly particle-like, solid components of the mixture are forced into a delivery line downstream of the cylinder after the closure member is opened. 
     The device illustrated in the drawing is designed for preparing and conveying thick matter containing a liquid or pasty useful component and solid foreign components. As is typical of a single-piston pump, the device includes a plunger-like delivery piston  12  which is coupled to a hydraulic piston  11  of a hydraulic cylinder  10 , a material feed space  16  which can be charged with thick matter via a feeding duct  14 , a delivery cylinder  20  which is connected to material feed space  16  on the inlet side and to a delivery line  18  on the outlet side, and further includes a gate-like closure member  22  which is located on the outlet side of delivery cylinder  20  and which is movable between a closed position and an open position in a direction transverse to the delivery cylinder. Lateral cylinder wall  24  of delivery cylinder  20  has perforations  26  which are in the form of a grid of holes and which, on the outside of lateral cylinder wall  24 , open into a collecting duct  28 . A pressure sensor  42  may be included in the delivery cylinder  20  upstream of the closure member  22 . In the exemplary embodiment shown, the material is supplied to feeding duct  14  via a hopper  30  and a screw conveyor  32 . 
     In a device of this type, the sequence of a pumping cycle is as follows:
     a) At the beginning of the cycle (see  FIG. 1 ), delivery piston  12  is in a position where it is retracted into hydraulic cylinder  10 . Material feed space  16  is filled via feeding duct  14  to a level above the piston diameter, while closure member  22  is in a closed position.   b) Then, hydraulic piston  11  and delivery piston  12  together begin to move toward closure member  22 , causing the material in the material feed space to be pushed into delivery cylinder  20 . A pressure P builds up in delivery cylinder  20 , causing liquid and pasty components to be forced out through perforations  26  in lateral cylinder wall  24 . At the same time, the passing delivery piston  12  cleans the inner surface of lateral cylinder wall  24  of filter cake. In the material remaining in delivery cylinder  20 , the pressure increases to a predetermined limit pressure P limit , which can be adjusted for each particular product. The limit pressure may, for example, be selected such that packaging containers present in the material being conveyed will burst and release their contents. The useful material fraction that is forced through perforations  26  flows into collecting duct  28  from where it is fed to a subsequent processing stage.   c) Once limit pressure P limit  is reached, it is maintained for a short period of time.   d) Then, closure member  22  opens. This causes the pressure to decrease, thereby allowing delivery piston  12  to move further to its end position within delivery cylinder  20 . The foreign fraction still present in delivery cylinder  20  is moved by delivery piston  12  into delivery line  18  for further processing.   e) Closure member  22  returns to its closed position.   f) Hydraulic piston  11  and delivery piston  12  return together to their original position. At the same, material feed space  16  is refilled via feeding duct  14 .   

     The sequences of motion of delivery piston  12  and of closure member  22  are controlled by a control unit  40  in a coupled fashion in the manner of a sequence control system by means of suitable drive units. 
     The procedure described can be repeated several times, depending on the raw material to he processed. In the case of biogenic substances, it may be useful to interpose a bioreactor in the form of a hydrolysis stage. To this end, a return section  34  leading back to feeding duct  14  is used which may include a meandering extension section  36 , depending on the desired residence time. The return section may have a heating means  44  disposed therein which beats the material being conveyed. 
     As can be seen from  FIGS. 1 and 2   a , perforated lateral cylinder wall  24  is surrounded by a tubular slide  38 , which is movable relative to lateral cylinder wall  24  between a closed position, in which perforations  26  are sealed, and an open position, in which the perforations are left open. In the advantageous embodiment shown in  FIG. 2   a , the lateral cylinder wall is perforated over about half its length, while the slide has a closed shell and is moved by half the length of the lateral cylinder wall from the open position to the closed position. 
     In the embodiment illustrated. in  FIG. 1 , slide  38  has a grid of holes and closed areas therebetween, said grid being complementary to the grid of holes of the lateral cylinder wall. In this case, it is possible for the slide to be moved or rotated between the open position and the closed position in an axial or circumferential direction with respect to the lateral cylinder wall by half the grid spacing of the grid of holes. This results in a relatively small rotational or translational movement of slide  38  as compared to the embodiment of  FIG. 2   a .  FIG. 1  indicates that the slide is also controlled by control unit  40 . To this end, control unit  40  provides a sequence control system for controlling the drive unit  10 ,  11  of delrvery piston  12 , the drive unit  46  of closure member  22 , and the drive unit  48  of slide  38 . 
     An embodiment of the invention is summarized as follows: The present invention relates to a device for conveying thick matter. The device includes a delivery cylinder  20 , a material feed space  16  connected to the inlet side of delivery cylinder  20 , a delivery line  18  connected to the outlet side of delivery cylinder  20 , a delivery piston  12  which is reciprocatable through material feed space  16  and delivery cylinder  20 , and further includes a closure member  22  which is located at the outlet of delivery cylinder  20  or in delivery line  18  and is movable between an open position and a closed position. In order to allow the foreign substances contained in the flow of thick material to be separated from said material flow before the actual processing step for the useful substances, it is proposed, in accordance with the present invention, that delivery cylinder  20  be perforated at least over a portion of its lateral wall  24 . With these measures, a device is obtained which combines the features of a thick matter pump, a sieve and a press.