METHOD FOR TRANSPORTING PASTOUS MATERIAL

Description

[0001] The invention relates to a method for conveying pasty material, e.g. sludge or shredded food waste or the like, with a system comprising an eccentric screw pump having a stator, a rotor rotating in the stator, a suction housing connected to the stator (suction side) with a filling opening and preferably a pressure housing connected to the stator (pressure side) with an outlet opening.

[0002] Such an eccentric screw pump is a pump from the group of rotating positive displacement pumps, which are used to convey a wide variety of media, especially highly viscous liquids, in a wide variety of industries. The media or liquids to be conveyed often contain high solids content. Within the scope of the present invention, the eccentric screw pump is used to convey pasty materials and, consequently, highly viscous liquids with (high) solids content.

[0003] The stator consists, for example, of elastic or elastomeric material and is generally surrounded by a one-piece or multi-piece stator casing or stator housing. The eccentric screw pump has a drive for the rotor and preferably a coupling rod arranged in the suction casing, which is preferably connected to a drive-side shaft via a drive-side joint and to the rotor via a rotor-side joint, wherein the coupling rod realizes the eccentricity for the rotating movement of the rotor. An eccentric screw pump is preferably used as a hopper pump, in which a filling hopper is connected to the filling opening. In such an embodiment for the conveyance of pasty or highly viscous media with a solid content, the coupling rod is preferably equipped with conveying tools, e.g.with a screw conveyor or with conveyor paddles, which support the transport of the material from the area of ​​the filling opening to the area of ​​the rotor.

[0004] In practice, there is a need to transport pasty materials or media, such as dewatered sludge, over long distances. This poses significant challenges, for example, for municipal wastewater treatment plants. Due to the high viscosity and abrasiveness of this material / medium, a significant pressure drop in the conveying line must be overcome. These pressure drops scale directly with the length of the conveying line, making conveying over distances in the range of kilometers extremely difficult. The pumping solutions commonly used must build up high pressures to overcome the pressure drops, meaning they are limited to a maximum conveying distance based on their pressure rating. In addition, the load on the pumps is very high at high backpressure, resulting in frequent maintenance cycles due to wear on the rotor-stator geometry and / or the joints, which are time-consuming and costly.When using eccentric screw pumps for such long conveying distances, correspondingly large, heavy eccentric screw pumps must be used, which require considerable maintenance effort and corresponding costs.

[0005] Alternatively, sequential conveying solutions with multiple drives, such as conveyor belts or screw conveyors, are used in practice. The disadvantages of these are, on the one hand, high energy consumption and maintenance costs, and, on the other hand, often an open design with corresponding odor nuisance or even re-dilution (dried sludge) due to rain. Such conveying solutions are also inefficient for vertical or angled transport. The use of closed pipelines generally requires the use of multi-stage progressing cavity pumps or, alternatively, piston pumps, which are suitable for highly viscous media and high pressures. However, due to the high backpressure, they require a relatively high drive power and thus high energy consumption and maintenance costs.

[0006] Furthermore, pneumatic conveying, and in particular so-called plug conveying, is known in practice, although this is primarily used for the transport of (loose) bulk materials. Such a method and device for the pneumatic conveying of bulk materials is known, for example, from WO 01 / 02274 A2. The bulk material is conveyed from a low to a higher level, with the bulk material first being conveyed essentially horizontally, then pneumatically lifted, and subsequently pneumatically conveyed further. The initial conveying takes place in the form of discrete plugs of bulk material spaced apart by gas cushions, and the lifting of the bulk material takes place in the form of a largely continuous bulk material flow.

[0007] A conveying system with a pipeline for the fluidic transport of short, uniform plugs of granular or powdery material is also known, for example, from DE 33 19 076 A1. This system consists of a conveying line and branch lines running parallel to it. Furthermore, a feed device (e.g., a pump) is provided, which has a sealing device against the pipeline pressure generated by a fluid pressure source. The feed device can, in principle, also be designed as an eccentric screw pump with a rotor and stator. In any case, a material receiving chamber is connected downstream of the pump, at the beginning of which a connection for the fluid pressure source is provided, so that the conveying line can be continuously pressurized with fluid pressure via the inlet-side receiving chamber.In addition, at least one opening is provided in the downstream conveying line for the material plug transport, allowing a portion of the fluid to enter the conveying line. When using an eccentric screw pump, it is also proposed to provide a rotary valve in the outlet-side receiving chamber. This valve not only serves to better seal the pump against the pressure prevailing in the conveying line, but also to crush the material emerging from the pump.

[0008] Devices for conveying moist and mushy material in pipelines in the sense of plug transport are also known from DE 874 877 and DE 559 237.

[0009] JP 2013 112456 A discloses a method for conveying pasty material, using a system that has a screw conveyor with a filling opening and an outlet opening. The system also includes a pneumatic conveying line connected to the outlet opening of the screw conveyor in such a way that the material to be conveyed is pressed into the conveying line by the screw conveyor as a material strand. A pressure medium supply is connected to the conveying line via a controlled valve, with the valve being controlled in such a way that pressure pulses of a predetermined duration are injected into the conveying line at intervals. These pulses separate material plugs of a limited length from the material strand and transport them through the conveying line.

[0010] Finally, DE 42 03 571 A1 describes a mobile device for producing lightweight concrete with a screw mixer and a screw pump, to which a pressurised chamber of a compressed air mixing and conveying machine is connected via a connecting line.

[0011] Based on the prior art, the invention is based on the technical problem of creating a method with a system which enables a flawless and efficient conveyance of pasty material even over long distances with a cost-effective and low-maintenance design.

[0012] To achieve this object, the invention teaches a method according to claim 1.

[0013] The invention is based on the finding that by combining an eccentric screw pump and a so-called pneumatic dense phase conveyor, pasty material, i.e. highly viscous liquids or media, can be transported economically and efficiently even over long distances without the need for particularly large eccentric screw pumps. The material is pressed directly into the conveyor line by the eccentric screw pump, forming a compressed (continuous) material strand. With the pressure media supply integrated into the conveyor line, pressure pulses are injected into the conveyor line at time intervals, thereby separating material plugs from the material strand. These material plugs are transported in the conveyor line along the conveying direction (at a distance from one another) with the help of the pressure pulses or the pressure generated in the conveyor line.In this case, there is no permanent pressurisation of the conveying line with a pressure medium, e.g. compressed air, but rather the described pressure pulses are simply generated in the conveying line, which, due to the design, act both in the conveying direction and against the conveying direction and thus in the direction of the pump. However, since the eccentric screw pump is characterized by a closed sealing line and the material from the eccentric screw pump is compressed and consequently pressed into the conveying line under pressure, the pressure pulses entering the conveying line can only "evade" in the conveying direction and thus transport the resulting material plugs - supported by the effect of the eccentric screw pump - in the conveying direction. Furthermore, it is within the scope of the invention to provide not only one pressure medium supply, or not only at one point orNot only can a pressure medium be injected into the delivery line using a valve, but there is also the option of injecting pressure pulses into the delivery line at several points, and in particular at several points distributed over the length of the delivery line, e.g. via several valves distributed over the length of the delivery line.

[0014] A pressure measuring device is preferably connected to the delivery line. In addition, the system has a control device which is connected to the pressure medium supply valve and, on the other hand, preferably to the pressure measuring device, so that the control device can control the valve as a function of the pressure in the delivery line measured by the pressure measuring device. During operation, the pasty material is therefore compressed in the pressure line by the eccentric screw pump, so that the pressure in the delivery line measured by the pressure measuring device gradually increases. When a predetermined pressure threshold value is reached or exceeded, which can be stored, for example, in the control device, the valve is opened, and the pressure pulse thus injected into the delivery line separates the material plug and conveys it along the conveying direction through the delivery line.During the pressure media injection, the pressure rises briefly, but then immediately drops again as the sludge plug separates. As the material is continuously fed in again with the progressing cavity pump, the pressure in the conveying line (slowly) rises again until another pressure media injection occurs.

[0015] Depending on the properties of the pasty material to be conveyed, it may be advantageous to support the conveying process by simultaneously injecting a lubricant to reduce pipe friction and in this way permanently reduce the pressure in the entire conveying line to a very low pressure level, below 5 bar, preferably below 4 bar. The use of such a lubricant is advantageous, for example, when conveying sludge, and in particular dried sludge. For this purpose, it is preferably provided that a lubricant supply is connected to the conveying line, preferably between the eccentric screw pump and the pressure media supply (the opening of the supply into the conveying line). With this lubricant supply (before the pressure media supply), a lubricant can be injected, preferably continuously (or quasi-continuously), into the pressure line or into the area of ​​the material strand.In this way, the material, and thus also the material plug, is additionally coated with a lubricant, thus reducing pipe friction for dense phase conveying and optimizing the energy efficiency of the overall system. The lubricant can be, for example, a known polymer solution. Alternatively, water can also be used as a lubricant. Furthermore, it is possible to inject the lubricant into the conveying line circumferentially, e.g., with several injection points distributed around the circumference, so that a comprehensive lubricant layer or a lubricant layer surrounding the material plug (boundary layer) is created.

[0016] By combining (progressive cavity) pump conveying and dense-phase pneumatic conveying, the pressure in the entire conveying line is permanently reduced to a very low pressure level. This pressure level results directly from the force required to initially move the material plug. Once the static friction force is overcome, the material plug is accelerated by the incoming and expanding compressed air (pressure medium), causing the pressure level in the line to drop again. Optionally, the maximum pressure level in the line can be influenced by varying the amount of lubricant used, e.g., polymer solution, and the length or weight of the material plug. This allows an energy-optimized operating point to be set during commissioning.

[0017] In principle, it is also within the scope of the invention to operate without additional lubricant supply, especially if the material used allows this. For example, when conveying shredded food waste, which is also contemplated by the invention, the need for corresponding lubricants can be dispensed with due to the good friction properties.

[0018] The eccentric screw pump is preferably designed as a hopper pump, with a filling hopper connected to the filling opening. In such a hopper pump, it is preferably provided that the coupling rod, which is arranged between the drive and the rotor and implements the eccentricity, is equipped with conveying tools, e.g., a conveyor screw or paddles or the like.

[0019] Through the inventive combination of pump conveying and pneumatic dense-phase conveying (optionally with simultaneous lubricant injection), the pressure in the entire conveying line can be permanently reduced to a very low pressure level, below 5 bar, preferably below 4 bar, as already mentioned. Building on this, the invention proposes, in a particularly preferred embodiment, the use of correspondingly small, maintenance-optimized eccentric screw pumps. These are eccentric screw pumps in which the elastic stator can be easily and quickly replaced without removing the suction housing and without removing the pressure housing, and / or in which the rotor can be easily and quickly replaced without removing the suction housing and without removing the pressure housing, preferably also without the use of additional equipment.In practice, such maintenance-optimized pumps are generally designed for relatively low pressures. The inventive concept, in which the pressure level in the delivery line is limited to relatively low values, now enables the use of precisely such maintenance-optimized pumps, so that the combination of such a progressing cavity pump with pneumatic dense-phase conveying as plug conveying takes on particular importance. The low pressure level increases the service life of the components, allowing for extended maintenance intervals due to the lower stress on the components. Furthermore, maintenance effort is reduced, as stator and / or rotor replacement can be carried out quickly without dismantling the line and usually without additional lifting and crane equipment.

[0020] For a simple stator and / or rotor change, an eccentric screw pump is particularly suitable, in which the (elastic) stator is a longitudinally split stator consisting of at least two stator shells. In addition, the stator shell surrounding the elastic stator can be a longitudinally split shell consisting of several shell segments, which may optionally form a stator clamping device for the elastic stator. Such an eccentric screw pump is known, for example, from DE 10 2008 021 920 A1, DE 10 2010 037 440 B4, DE 10 2014 112 552 B4 or DE 10 2014 112 550 B4. Eccentric screw pumps of this type can preferably be used. For a simple rotor replacement, an embodiment is preferably proposed in which the rotor can be replaced independently of the joints of the coupling rod, for example by B. the rotor is detachably connected to the coupling joint via a detachable separation point (see e.g. DE 10 2010 037 440 B4).

[0021] In principle, however, eccentric screw pumps of other designs and maintenance-optimized eccentric screw pumps of other designs are also considered within the scope of the invention.

[0022] Optionally, the progressing cavity pump can be equipped with a material shredding device. This is advantageous when the material fed to the progressing cavity pump needs to be shredded before being conveyed by compressed air and, if necessary, before being transported through the pump. Such a shredding device, also known as a macerator, can be integrated into the progressing cavity pump, for example, preferably located upstream of the stator / rotor.

[0023] Overall, within the scope of the invention, pasty media can be transported over long distances. The length of the conveying line is preferably more than 25 meters, e.g. more than 50 meters, in particular more than 100 meters, particularly preferably more than 200 meters. A storage facility, e.g. a silo or the like, can be connected to the end of the conveying line. Reducing the pressure level to the values ​​described enables the use of the Easy Maintenance pumps already described. In addition, due to the low pressure level, wear can be reduced, thus increasing the service life of the components and extending maintenance cycles. The space required by the individual components is small. Likewise, operating costs are low due to the low energy consumption and long maintenance cycles and inexpensive spare parts. In addition, the overall investment costs can be reduced, since the low pressure level allows the use of cost-effective piping, i.e.It is possible to work with thinner-walled and cheaper pipelines. An automated system including process monitoring can be implemented, which can be integrated into existing automation and control systems via common bus interfaces. Furthermore, occupational safety benefits arise due to the lower component weight, which means fewer people are required for maintenance. With small pumps, maintenance can be performed by a single person without additional lifting or crane equipment.

[0024] The invention is explained below with reference to drawings which merely represent exemplary embodiments. Fig. 1A to 1D a system in a simplified view in different functional positions, Fig. 2 a modified version of the system according to Fig. 1A , Fig. 3 an operating diagram of a plant according to Fig. 1A to 1D , (pressure in the delivery line as a function of time), Fig. 4 an embodiment of an eccentric screw pump of the system according to Fig. 1A to 1D .

[0025] The figures show a system for conveying pasty material, e.g. (dewatered) sludge or shredded food waste.

[0026] The Figures 1A to 1D show a first embodiment of such a system in various functional positions, whereby this system can be used, for example, for conveying pasty material M in the form of dewatered sludge.

[0027] In contrast, Fig. 2 a second embodiment which can be used, for example, for conveying pasty material M in the form of shredded food waste.

[0028] The system comprises an eccentric screw pump 1, which has a stator 2 (made of elastic material) and a rotor 3 rotating in the stator. Furthermore, the eccentric screw pump has a suction housing 4 connected to the stator on the suction side with a filling opening 5 and a pressure housing 6 connected to the stator on the pressure side with an outlet opening 7. The pump is provided with a drive 9 for the rotor 3. Further details on the construction of such an eccentric screw pump 1 will be explained below with reference to the Fig. 4 explained.

[0029] The system further comprises a pneumatic conveying line 8 (directly) connected to the outlet opening 7 of the eccentric screw pump 1. This conveying line 8 is connected to the outlet opening 7 or to the pressure housing 6 in such a way that the material M to be conveyed is pressed into the conveying line as a compressed material strand by the eccentric screw pump 1. A pressure medium supply 10 is also connected to the conveying line 8 via a valve 11. In the exemplary embodiment, this is designed as a compressed air supply 10, with which pressure pulses can be injected into the conveying line 8 at time intervals. With these pressure pulses, material plugs MP of a limited length can be severed from the compressed material strand and transported through the conveying line 8. This will be discussed in more detail below. A reservoir, e.g.a silo 20 is connected so that the material M fed to the eccentric screw pump 1 is conveyed through the eccentric screw pump 1 and the conveying line 8 into the silo 20, namely over a relatively long transport distance of, for example, more than 100 meters.

[0030] A pressure measuring device 15 is also connected to the delivery line 8. Both the pressure measuring device 15 and the compressed air valve 11 are preferably connected to a control device (not shown). The pressure medium supply 10 can comprise a compressor 12, an air chamber 13, and a compressed air line 14.

[0031] In addition, in the embodiment according to Figures 1A to 1DA lubricant supply 16 is connected to the delivery line 8, which in the exemplary embodiment comprises a pump 17 and a line 18. The lubricant supply or the connection of the lubricant supply 16 to the delivery line is arranged between the eccentric screw pump and the compressed air supply 10 or the connection of the compressed air supply 10 to the delivery line 8. With the aid of this lubricant supply 16, a lubricant, e.g., a polymer solution, can be injected into the pressure line 8 or into the area of ​​the material strand.

[0032] In the exemplary embodiment, the eccentric screw pump 1 is designed as a hopper pump, with a filling hopper 21 connected to the filling opening 5. Details are given in Fig. 4 which will be discussed below. The system shown in Figures 1A to 1D is operated as follows:

[0033] The eccentric screw pump 1 is fed with the material to be pumped, e.g., dewatered sludge, via the hopper 21. The sludge M is compressed by the hopper pump 1 into the delivery line or pressure line 8 (see Fig. 1A ). At the same time, the conveying line is (continuously) supplied with a lubricant, e.g., a polymer solution, via the lubricant supply 16. During the compressed feeding of the sludge into the conveying line 8, the pressure in the conveying line 8, monitored by the pressure measuring device 15, gradually increases. When a predefined pressure threshold value ( Fig. 1B ) by opening the valve 11 a compressed air pulse is injected into the conveyor line 8 and thereby a material plug MP of limited length is separated from the compressed material strand and transported through the conveyor line 8 ( Fig. 1C ). A comparative analysis of the Figures 1C and 1Dindicates that in this way the pressure in the delivery line drops again and the described process starts again with Fig. 1A .

[0034] The functionality can also be explained by Fig. 3 which graphically represents the pressure curve at the injection point of the delivery line 8. The diagram shows the pressure p in the delivery line, measured with the pressure measuring device 15, ie in the area of ​​the injection point 10, as a function of time t. Starting with time 0, it is initially apparent how, in the course of feeding the material into the delivery line 8, Fig. 1A the pressure p rises and (after just over two minutes) reaches the pressure threshold ps (corresponding to Fig. 1B). At this point, the pressure pulse is injected so that the pressure p rises abruptly to a value of approximately 4 bar and then immediately drops again to a value well below the pressure threshold ps (corresponding to Figures 1C and 1D ). In the exemplary embodiment, the pressure p in line 8 drops by approximately 1 bar below the pressure threshold. Subsequently, a new sludge plug is pumped into the line with the eccentric screw pump over a period of several minutes until another compressed air injection takes place. Fig. 3 States a), b), c) and d) shown correspond to those shown in the Figures 1A to 1D depicted states.

[0035] In the embodiment according to Fig. 1A to 1D It is shown that a lubricant is injected to reduce pipe friction for dense phase conveying and thus improve the energy efficiency of the overall system.

[0036] In contrast, Fig. 2A second embodiment in which the lubricant supply is omitted. This embodiment is suitable for materials that already possess sufficient friction properties, e.g., shredded food waste or pasty food pulp. The system is used, for example, to convey food waste over long distances, e.g., to a remote biogas plant. The food waste or food pulp is conveyed via a long conveyor line 8 into the illustrated storage unit 20.

[0037] Several process steps for the preparation of food waste for incineration in a biogas plant can be integrated into this system in a very small space. The eccentric screw pump 1 is again designed as a hopper pump, which differs from the Fig. 1AIt differs from the eccentric screw pump shown in the drawing in that it additionally provides a comminution device 19, which in the exemplary embodiment is integrated into the eccentric screw pump, e.g. between the hopper 21 and the stator 2. It is designed as a cutting tool or is equipped with a cutting tool, so that first the introduced material, e.g. whole fruits or vegetables or leftovers, is crushed and then compressed into the pressure line 8 as a pasty food pulp. Apart from the lubricant supply, the system is constructed in the same way as in Figures 1A to 1D and it is also operated in the same way.

[0038] As already mentioned, the eccentric screw pump in the exemplary embodiments is preferably designed as a hopper pump. One possible embodiment is shown in Fig. 4The drive 9 operates via a coupling rod 22 on the rotor 3, wherein the coupling rod 22 in the exemplary embodiment is provided with a conveying tool 26, e.g., a screw, to assist in conveying the material into the area of ​​the rotor or stator. The coupling rod 22 is connected to the drive or a drive shaft or connecting shaft 24 via an input-side joint 23 and to the rotor 2 via a rotor-side joint 25, so that the eccentric movement of the rotor 3 is enabled or realized via the coupling rod 22 and the joints 23, 24.

[0039] The eccentric screw pump 1 is designed as a so-called easy-maintenance pump, in which both the stator 2 and the rotor 3 can be replaced without removing the suction housing 4 and without removing the discharge nozzle 6 or the connected lines, and in particular also without removing the hopper 21. For this purpose, in the exemplary embodiment, the stator 2 is designed as a longitudinally split stator, consisting of, for example, two stator halves. Details are not shown. The stator casing 27 surrounding the elastomeric stator preferably consists of several casing segments, which on the one hand form a stator clamping device and on the other hand enable simple disassembly and simple stator replacement. In addition, the rotor 3 can be connected to the rotor-side coupling joint via an additional separation point, so that the rotor 3 can be replaced without separating the joint.Details are not shown here either, but the concepts known from DE 10 2010 037 449 B4, DE 10 2014 112 550 B4, DE 10 2014 112 552 B4 or DE 10 2008 021 920 A1 can be used overall.

Claims

1. A method for conveying paste-like material (M), e.g. sludge or comminuted food wastes using a plant which has a progressive cavity pump (1), which has a stator (2), a rotor (3) rotating in the stator (2), a suction housing (4), which is connected to the stator, having a filling opening (5) and an outlet opening (7), and has a pneumatic conveying pipe (8) which is connected in such a manner to the outlet opening (7) of the progressive cavity pump (1) that the material (M) to be conveyed using the progressive cavity pump (1) is pressed as a compressed material strand into the conveying pipe (8), and also has a control device, wherein a pressure medium supply (10) is connected to the conveying pipe (8) by means of at least one valve (11), wherein the control device is connected to the valve (11) of the pressure medium supply and the valve (11) is controlled in such a manner using the control device that pressure pulses are injected into the conveying pipe (8) at time intervals, wherein material plugs (MP) of limited length are separated from the compressed material strand using the pressure pulses and transported through the conveying pipe (8), wherein the plant is controlled in such a manner that the pressure in the conveying pipe does not exceed an upper pressure limit value of 5 bars, wherein - a pressure measuring device (15) is connected to the conveying pipe (8), which pressure measuring device is connected to the control device so that the valve (11) is controlled depending on the pressure in the conveying pipe (8) that is measured using the pressure measuring device (15), wherein the pressure pulses are generated depending on the pressure in the conveying pipe (8), specifically when a specified pressure threshold value is reached or exceeded in each case, or - wherein the pressure pulses have a specified duration in each case.

2. The method according to Claim 1, wherein the progressive cavity pump (1) is designed as a hopper pump, wherein a feed hopper (21) is connected to the filling opening (5), wherein the coupling rod (22) is preferably provided with conveying tools (2) between drive (9) and rotor (3).

3. The method according to Claim 1 or 2, wherein the conveying pipe (8) has a length of more than 25 metres, particularly more than 100 metres, preferably more than 200 metres, wherein a material store, e.g. a silo (20) is preferably connected to the end of the conveying pipe.

4. The method according to one of Claims 1 to 3, wherein a lubricant supply (16) is connected to the conveying pipe (8), preferably between progressive cavity pump (1) and pressure medium supply (10), using which a lubricant, e.g. water or a polymer solution, is injected into the pressure line (8).

5. The method according to one of Claims 1 to 4, wherein the elastic stator (2) is replaceable without removing the suction housing (4) and / or the pressure housing (6), e.g. is designed as a longitudinally split stator (2).

6. The method according to one of Claims 1 to 5, wherein the rotor (3) is replaceable without removing the suction housing (4) and / or the pressure housing (6), e.g. wherein the rotor (3) has a point of separation or housing opening in the region of the joint.

7. The method according to one of Claims 1 to 6, wherein the pressure pulses in each case have a specified duration of 1 second to 20 seconds and / or wherein the duration of the pressure pulses is controlled in each case in a variable manner depending on the pressure in the conveying pipe.

8. The method according to one of Claims 4 to 7, wherein a lubricant is injected into the conveying pipe (8), wherein the quantity of the injected lubricant is preferably controlled depending on the pressure in the conveying pipe.

9. The method according to one of Claims 1 to 8, wherein the material poured into the filling opening (5) of the progressive cavity pump (1) is comminuted, preferably before it reaches the conveying pipe (8), preferably in the progressive cavity pump (1) upstream of the stator (2).

10. The method according to one of Claims 1 to 9, wherein the plant is controlled in such a manner that the pressure in the conveying pipe does not exceed an upper pressure limit value of 4 bars.