WO2007143853A1

WO2007143853A1 - Shredder for organic sludges, fertilizers and the like

Info

Publication number: WO2007143853A1
Application number: PCT/CA2007/001071
Authority: WO
Inventors: Jules DÉPAULT
Original assignee: Les Equipements Pro-Jet Inc.
Priority date: 2006-06-15
Filing date: 2007-06-15
Publication date: 2007-12-21

Abstract

A shredder (10) for reducing the size of solids in sludge has a casing (14) with an axial opening (26) for receiving the sludge and at least one tangential exit (38) for expelling the sludge. A primary rotor (80) having a first plurality of blades (84) draws at least a portion of the sludge into the casing (14) via the opening (26) to initially reduce the size of the solids. A secondary rotor (100) positioned within the casing (14) and having a second plurality of blades (102) draws the sludge into the casing (14) through the opening (26) and expels the sludge from the casing (14) via the at least one tangential exit (38). A plurality of teeth (54, 62, 66) disposed within the casing (14) cooperate with a forward portion (104) of each of the second plurality of blades (102) to further reduce the size of the solids.

Description

SHREDDER FOR ORGANIC SLUDGES, FERTILIZERS AND THE LIKE

FIELD OF THE INVENTION

The present invention relates to a shredder for reducing the size of solid materials contained in sludges to improve pumping same. More specifically, the present invention is concerned with shredding and pumping organic sludges, for example reservoirs or manure pits.

BACKGROUND OF THE INVENTION

Agriculture, industries and municipalities process a significant quantity of wastewater. Organic and inorganic waste products are contained in wastewater. Thus, wastewater becomes a sludge including various solid organic material when it is collected for being treated and transformed into a useable substance.

Sludges carrying solid material that may come from animal manure, human manure, dead animals, crop residues from agriculture, industrial organics residues, municipal wastes, slaughter house sludge, and others are more difficult to pump and to transport via a piping system than water or other low viscosity fluids. The solid material contained in the pumped sludge can choke or block the pipes used to channel the sludge. Reducing the size of the solid material contained in sludges can prevent blockage of the pipe and requires less pumping energy.

Efficiently composting organic solids in sludges is another parameter in sludges treatment. The proportion of the outside surface in respect to the volume of a solid is an important parameter effecting the composting speed of an organic solid. Significant size solid organic materials have a low surface-to-volume ratio. Low surface-to-volume ratio organic solids take a long time to compost as opposed to high surface-to-volume ratio organic solids that are composting more quickly. Reducing the size of a solid therefore increases the surface-to-volume ratio thus improving the composting cycle of organic solids.

Shredding solid organic matters contained in sludges requires tremendous mechanical actions. The shredder and the pump must deal with unsteady flow due to the constant change in the density of the sludge. This change in density is caused by the solid fraction contained in the sludge. Solid matter is generally denser than the carrier fluid. This constant change in the sludge's density causes significant vibrations in the shredder. Vibrations may produce major mechanical damage to the shredder. The drive unit of the shredder and the means powering the shredder are also subject to damage due to the shredder's vibration.

Another issue arises with the use of a shredder utilized for reducing the size of long solid material such as ropes or straws that are contained in sludges. These relatively long solid materials might stay stuck on the blades of the shredder and cause significant loss of productivity.

The present invention seeks to meet these needs and other needs.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a shredder for reducing the size of solids in a sludge, the shredder comprising: a casing having an axial opening for receiving the sludge therein and at least one tangential exit for expelling the sludge therefrom; a primary rotor positioned adjacent the opening and having a first plurality of blades rotatable about an axis concentric with the opening for drawing at least a portion of the sludge into the casing via the opening and for initially reducing the size of the solids in the sludge; a secondary rotor positioned within the casing and having a second plurality of blades rotatable about the axis for drawing the sludge into the casing through the opening and expelling the sludge from the casing via the at least one tangential exit; and a plurality of teeth disposed within the casing, the teeth cooperating with a forward portion of each of the second plurality of blades to further reduce the size of the solids.

The invention as well as its numerous advantages will be better understood by reading of the following non-restrictive description of preferred embodiments made in reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a shredder, according to a preferred embodiment of the present invention. Fig. 2 is an exploded perspective view of the shredder of Fig. 1.

Fig. 3 is front elevational view of the shredder of Fig. 1 , with the front cover removed.

Fig. 4 is an rear perspective view of the second rotor in the shredder of Figure 1.

Figure 5 is an rear elevational view of the shredder of Figure 1.

DESCRIPTION OF PREFERED EMBODIMENTS

Referring to Fig. 1 , there is shown a shredder 10 for reducing the size of solids in a sludge. The shredder 10 includes a casing 14 with an axial opening 26 for receiving the sludge therein and at least one tangential exit 38 for expelling the sludge therefrom. A primary rotor 80 is positioned adjacent the opening 26 and has a first plurality of blades 84 rotatable about an axis 70 concentric with the opening 26 for drawing at least a portion of the sludge into the casing 14 via the opening 26 and for initially reducing the size of the solids in the sludge. A secondary rotor 100 is positioned within the casing 14 and has a second plurality of blades 102 rotatable about the axis 70 for drawing the sludge into the casing 14 through the opening 26 and expelling the sludge from the casing 14 via the at least one tangential exit 38. A plurality of teeth 54 are disposed within the casing 14 and cooperate with a forward portion 104 of each of the second plurality of blades 102 to further reduce the size of the solids

Preferably, the casing 14 is also adapted to be connected to a reservoir, or to a tank, or to an external manure pit, to shred and extract sludges contained. Various fasteners removably connect the casing 14 of the shredder 10 to the reservoir or manure pit. An illustrative agricultural application is provided with a seal member (not shown) installed between the casing 14 and the reservoir to prevent any leak. The shredder 10 may be positioned at any angle on the reservoir as long as the shredder 10 is in fluidic communication with the interior of the reservoir. Normally, the shredder 10 is installed low on the reservoir for shredding and extracting all of the sludge therein.

Rotation of the shredder's moveable parts can be induced by different power sources such as hydraulically actuated mechanisms, mechanical and electrical systems. The choice of the power source is made in accordance with the specific use of the shredder 10. A static industrial application will have requirements that are substantially different to agricultural applications. Industrial applications generally use an electric motor or an internal combustion engine, with or without clutch or transmission means including hydraulic systems, to procure movement of the rotating parts of the shredder 10. Rotational speeds of an electric motor in industrial applications may be up to 3600 RPM for better efficiency. Conversely, the shredder 10 may be mounted on a wheeled reservoir or onto a fixed manure pit for agricultural applications. A tractor's power take off (PTO) can serve as power unit for the shredder 10 in agricultural applications. The rotation speed of a tractor PTO is normally about 540 RPM. Higher rotational speeds may be available on large tractors, such as 162 HP and up, and a PTO speed of about 1100 RPM may be used. Rotational speed of the power source is one of the numerous design criterion. The illustrative embodiment is sized and designed for optimal rotational speed of about 1100 RPM. However, better results are obtained with rotational speed above 1000 RPM. The selection of the power source may vary and still be encompassed by the present invention. The power connection between the power source and the rotors 80, 100 may be made via a drive shaft.

Preferably, the casing 14 is made of sheet of steel material. The thickness of the material must be sufficient to sustain the loads applied on the shredder. The casing 14 may be made of any type of non-ferrous alloy or be molded using cast iron without departing from the scope of the invention. The shape of the casing 14 defines the dimension and the shape of the internal cavity of the shredder 10. Two flat covers 22 are disposed parallel on each side of the central wall portion 18 of the casing 14. The flat cover 22 on the side of the casing 14 adapted for being mountable onto the mobile reservoir or fixed manure tank is provided with an axial opening 26. Covers 22 cooperate with other internal parts of the shredder 10 to obtain the desired hydraulic effect. The distances between the internal walls of the casing 14, the covers 22 and the secondary rotor 100 influence the shredding and the pumping efficiency of the shredder 10.

All moving parts in the shredder 10 are rotating about an axis 70 that is normal to the cover 22. The shredder 10 in the illustrative embodiment uses two rotors: a primary rotor 80 and a secondary rotor 100. The primary rotor 80 axially extends outside the casing 14, through the axial opening 26, to perform a preliminary coarse shredding of the solid matter contained in the sludge. The secondary rotor 100 is disposed downstream from the axial opening 26, inside the casing 14, to perform a finer shredding once the sludge has passed the primary rotor 80.

The primary rotor 80 includes a plurality of blades 84 radially disposed about a key lock shaft 140 disposed along the axis 70 and positioned at a distance from the cover 22. The blades 84 may be axially staggered along the shaft 140. The primary rotor 80 is fastened to the secondary rotor 100. A left-hand thread (not shown) on the central axis of the primary rotor 80 is utilized for securing the secondary rotor 100. A left-handed thread is preferred considering the counter clockwise rotation of the rotors that could lead to unscrew the secondary rotor 100 from the primary rotor 80. The action of the shredder 10 will not unscrew the primary rotor 80 seated on a left-handed threaded portion. In the illustrative embodiment, an even number of blades 84 disposed on two distinct planes is provided. Each blade 84 has a curved portion 96 and a protrusion portion 88 disposed on the distal end of each blade 84. The curved shape 96 of the blade 84 prevents linear debris, like rope or hay to get stuck on the blade 84. Any material stuck on the turning blade 84 would diminish the efficiency of the shredder 10. The curve 96, combined with the centrifugal force, help unhook the debris from the blade 84. The radius of the curve 96 on the blade 84 should not be too small because a small radius would diminish the grinding/cutting effect of the blade 84. The edge of the blade 84 may be sharpened to improve the cutting efficiency.

The protrusion portion 88 extends from the distal end of the blade 84 for progressively grinding the solid material entering the shredder 10 and reduces strong instantaneous shock between the blade 84 and the solid material in the sludge. The radial angle of the protrusion 88 on each blade is arranged to move sludges toward the axis 70 to eventually be forced in the casing 14 through the axial opening 26. The angle between the curved portion 96 and the protrusion 88 is preferably an obtuse angle.

Additionally, as best shown in Fig. 2, the radius 92 of each of the blades 84 is preferably different. Each blade 84 may also have a unique length to ensure the protrusion portion 88 of one blade 84 does not pass in the "trace" of the protrusion portion 88 on the preceding blade 84. The shredding action of each of the protrusion portion 88 is thus maximized when attacking a large piece of solid material contained in the sludge. The size and the weight of each blade 84 may vary for balancing the primary rotor 80.

The secondary rotor 100 is disposed in the casing 14 and rotates about axis 70. The rotation of the secondary rotor 100 inside the casing 14 shreds and grinds the solid particles remaining in the sludge after the action of the primary rotor 80. As best shown on Fig. 2, the secondary rotor 100 includes a plurality of blades 102. Each blade 102 radially extends from the axis 70. The blade 102 includes a forward portion 104 having an angled portion 108 and a blade wall 112 disposed on the distal end of the blade 102. The secondary rotor 100 may have a diameter of between 100 mm to 1000 mm selected according to the task to be performed and the power unit available. The centrifugal force generated by the rotation of the secondary rotor 100 inside the casing 14 draws the sludge through the axial opening 26. The forward portion 104, the angled portion 108 and the blade wall 112 improve the efficiency of the blades 102. Forward portion 104 of the blade 102, in cooperation with cutting edge tooth 66 disposed on the cover 22 and radially extending in the axial opening 26, cuts the solid material entering the casing 14. The angled portion 108 shaping the forward portion 104 of the blade 102 is illustratively of about 22° to ensure enough sludge enters the casing with each blade 102. The angled portion 108 also defines the proper attack angle cooperating with the cutting edge tooth 66. Additionally, the blade wall 112 is perpendicularly connected on the trailing side of the distal end of each blade 102. The extended surface provided by the blade wall 112 facing the casing 14 improves the control of the sludge leaking out between the distal end of the blade 102 and the casing 14. Undesired swirling or cavitation of the sludge in the surrounding of the distal end of each blade 102 causing a pressure drop is also improved.

Referring to Figures 3 and 4, it can be appreciated that a plurality of peripheral teeth 54 are disposed in the casing 14. The teeth 54 are disposed in proximity of the distal end of the blade 102 and the blade wall 112 with which they are cooperating to increase shredding capacity. Each tooth 54 is axially shorter than the axial length of the blade wall 112. An axially staggered 58 arrangement of the teeth 54 is provided in the casing 14 for improving shredding of sludges each time the tip of a blade 102 passes next to a tooth 54. The number of tooth 54 is preferably identical to the number of blades 102 to reduce the vibration generated by the rotation of the secondary rotor 100. The teeth 54 are radially equally disposed about the axis 70 such that each blade 102 meets a tooth 54 at the same moment.

All teeth 54 are hardened and are either welded or fastened on the internal wall of the casing 14. Two cutter teeth 62, having a slightly different shape than teeth 54, are used for cutting and shredding the solid matter carried by the sludge. Both cutter teeth 62 are disposed at 180° from each other, about the axis 70 near inlets

34, 46 of exit channels 30, 42. The cutter teeth 62 separate the flow of sludge rotating with the secondary rotor 100 toward each exit channel 30, 42 thus improving the pumping efficiency of the shredder 10. These hardened cutter teeth

62 are preferably fastened on the internal wall of the casing 14 to facilitate their replacement when needed.

As best shown on Figure 3, the casing 14 preferably defines two exit channels 30, 42 having their respective inlets 34, 46 disposed at 180° about the axis 70. The inlets 34, 46 are oppositely disposed to reduce the vibrations generated by the pumping of the sludge. The two inlets 34, 46 equally disposed in the casing 14 and tangent with the external diameter of the secondary rotor 100 provide a more balanced resistance as opposed to having only a single inlet forcing the sludge out of the casing 14. The vibration is reduced and all mechanical parts are submitted to less stress. Having two exit channels 30, 42 in the casing 14 also increase the sludge output rate of the shredder 10. In the illustrative embodiment both exit outlets 38, 50 are located on the same side of the casing 14. The casing 14 defines separate internal passages routing both exit channels 30, 42. A collector tube (not shown) receiving the sludge coming out the casing 14 may be connected on a single side of the casing 14 on both outlets 38, 50. A limited number of collector tubes is required when the outlets 38, 50 are concentrated at the same place around the casing 14. Referring to Figs. 2 to 4, the secondary rotor 100 further includes a base plate 116 disposed normal to the axis 70. Base plate 116 is supporting the back portion of the blades 102 on its forward side 124. The rearward side 126 of the base plate 116 is rotatably maintained next to the back cover 22 of the casing 14. A series of vanes 120, disposed on the rearward side 126 the base plate 116, pushes the sludge radially outwardly toward the teeth 54. By this motion of the vanes 120, the sludge, and the solid matter contained therein, are prevented from building-up between the secondary rotor 100 and the back cover 22.

Referring to Figs. 3 and 5, drain plugs 130 are disposed on the casing 14 for purging the fluid remaining in the first exit channel 30 and in the second exit channel 42. The position of the plugs 130 may vary depending on the position and the orientation of the casing 14. Ideally the plugs 130 are disposed on the lowest portion of the casing 14 to remove any sludge remaining in the casing 14 when the shredder 10 is stopped.

Although preferred embodiments of the present invention have been described in detail herein and illustrated in the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments and that various changes and modifications may be effected therein without departing from the scope or spirit of the present invention.

Claims

1. A shredder (10) for reducing the size of solids in a sludge, the shredder comprising: a casing (14) having an axial opening (26) for receiving the sludge therein and at least one tangential exit (38) for expelling the sludge therefrom; a primary rotor (80) positioned adjacent the opening (26) and having a first plurality of blades (84) rotatable about an axis (70) concentric with the opening (26) for drawing at least a portion of the sludge into the casing (14) via the opening (26) and for initially reducing the size of the solids in the sludge; a secondary rotor (100) positioned within the casing (14) and having a second plurality of blades (102) rotatable about the axis (70) for drawing the sludge into the casing (14) through the opening (26) and expelling the sludge from the casing (14) via the at least one tangential exit (38); and a plurality of teeth (54, 62, 66) disposed within the casing (14), the teeth (54, 62, 66) cooperating with a forward portion (104) of each of the second plurality of blades (102) to further reduce the size of the solids.

2. The shredder of claim 1 , wherein the casing (14) includes a cutting edge tooth (66) disposed on a cover (22) of the casing (14), the cutting edge tooth (66) radially extending in the opening (26).

3. The shredder of claim 1 , wherein each of the second plurality of blades (102) includes an angled portion (108) and a blade wall (112) perpendicularly disposed on a distal end of each second blade (102).

4. The shredder of claim 1 , wherein the casing (14) includes a plurality of peripheral teeth (54) disposed in a central wall portion (18) of the casing (14) in proximity of a distal end of the second blades (102).

5. The shredder according to any one of claims 1 to 4, wherein the casing (14) includes at least two tangential exits (38, 50).

6. The shredder of claim 5, wherein the casing (14) includes two exit channels (30, 42) respectively communicating with the two tangential exits (38, 50), the two exit channels (30,42) having respective inlets (34, 46) oppositely disposed to one another to reduce vibrations generated by when pumping of the sludge.

7. The shredder of claim 6, wherein the inlets (34, 46) of the two exit channels (30,42) are disposed at about 180 degrees to one another.

8. The shredder of claim 6 or 7, wherein the casing (14) includes two cutter teeth (62) respectively positioned near the inlets (34, 46) of exit channels (30, 42) for improving a pumping efficiency of the shredder (10).

9. The shredder of claim 6, 7 or 8, wherein the casing (14) includes drain plugs (130) for purging fluid remaining in the exit channels (30, 42).

10. The shredder of claim 1 , wherein the secondary rotor (100) includes a base plate (116) disposed normal to the axis (70) for supporting a back portion of the second blades (102).

11. The shredder of claim 10, wherein a rearward side (126) of the base plate (116) includes a series of vanes (120) for pushing the sludge radially outwardly with respect to the axis (70).

12. The shredder of claim 1 , wherein each of the first blades (84) of the primary rotor (80) has a curved portion (96) and a protrusion portion (88) disposed on a distal end of the curved portion (96) and defining an obtuse angle with respect to the curved portion (96).

13. Use of the shredder (10) of any one of claims 1 to 12 for pumping sludge from a mobile reservoir.

14. Use of the shredder (10) of any one of claims 1 to 12 for pumping sludge from a manure pit.