EP3137220B1 - Hydrodynamic removal of dense materials from a slurry - Google Patents

Description

The invention relates to a device for the separation of heavy materials from a slurry of components of different density and different particle structure. Such a device is for example from the EP 0 138 475 A2 known. This discloses a device for hydrodynamic separation of heavy material from a slurry comprising a slurry receiving hydrocyclone (1), a separate heavy matter receiving separate storage chamber (7) and an actuator (11) for controlling the flushing water flow to the storage chamber. In a wet mechanical treatment of mixtures, eg waste, mechanically separated waste fractions or commercial residues, slurries, such as pulps or suspensions, the relevant amounts of sedimentable in water and sharp-edged materials, such as gravel, split, stones, ceramic or glass fragments or Contain metal particles that cause operational problems, such as deposits or wear in downstream process stages. The consequences are, for example, sediment layers in containers, which require elaborate emptying after a few years of operation, laying of pipelines which cause a high cleaning effort, or a strong wear of the machine technology due to the mostly abrasive properties of these materials.

Organic wastes suitable for fermentation may contain mineral heavy materials of 4% by weight ( Kübler, H., Hoppenheidt, K., Hirsch, P., Kottmair, A., Nimmrichter, R., Nordsieck, H., M., Mücke, W., Swerev (2000) Füll scale co-digestion of organic waste , Water Science & Technology 41, 195-202 ). Municipal biowaste contains relevant quantities of mineral heavy materials such as stones, broken glass, split or gravel or sand, which according to the investigations by Kranert et. al. ( Kranert, M., Hartmann A., Graul S. (1999) Determination of sand content in digestate. In: W. Bidlingmaier et al. (Ed.) Proceedings of the International Conference ORBIT 99 on Biological Treatment of Waste and the Environment, Part I, pp. 313-318 ) a proportion of the dry matter of the waste of partially over 25 wt.%. A substantial part of these mineral heavy materials is introduced into the pulp in a wet mechanical treatment of biowaste, which is then sent for biological recycling. Studies by Kübler et al. ( Kübler, H., Nimmrichter, R., Hoppenheidt, K., Hirsch, P., Kottmair, A., Nordsieck, H., Swerev, M., Mücke, W. (1998) Füll scale co-digestion of biowaste and commercial organic waste. Materials and Energy from Refuse. P. De Bruycker and J. Kretschmar (ed.), Technlogisch Instituut Antwerpen, P. 195-202 ) show that in the wet-mechanical treatment of biowaste, a pulp is formed, from which a hydrodynamic material separation still separates about 3% by weight of the wet mass of the treated waste as heavy materials.

In the operation of waste treatment plants, in which the sieved fraction smaller than 80 mm is fed to a wet treatment, a fraction of glass particles and mineral constituents of 12 to 14 wt.% Was determined in the wet mass of this fraction ( Rita, J., Braga, J., Mannall, C., Goldsmith, S., Kübler, H., Rahn, T., Schulte, S. (2015) Compost-like material or thermal valorisation-impact on MBT Plant economics and environmental aspects - case studies in Portugal and UK. In: M. Kühle-Weidemeier and M. Balhar (ed.) Energy and raw materials from residual and biowaste, Cuvillier Verlag Göttingen, P. 395-406 ).

In order to ensure a low-level recovery of the slurries or suspensions from the wet treatment, the readily sedimentable fractions are often separated from the suspension. For this purpose, heavy material separators are used. In addition to separating the contaminants, these heavy material separators must also minimize the discharge of the other constituents present in the slurry and to be utilized in the downstream process stages, for example fermentable organic substances. This can be done by a combination of hydrocyclone and classifying tube, which is located in the lower reaches of the hydrocyclone, for discontinuous discharge of the Separated heavy materials can be achieved. In order to reduce the discharge of the other components, the classifying tube is frequently supplied with rinsing liquid. As a result, a countercurrent is generated in the classifying tube, which frees the separated heavy materials from the other Bestanteilen the slurry.

Such a device is in the DE 195 05 073 A1 with a flat bottom hydrocyclone for separating heavy materials from a slurry made from waste materials. The flat-bottomed cyclone is followed by a classifying pipe to increase the selectivity of the heavy material separator. The separated heavy materials are collected in the lower reaches of the Classierrohres by means of a lock system with integrated chamber and discharged discontinuously. If, following emptying of the chamber, the shut-off valve is opened to the classifying tube, the content of the classifying tube and part of the contents of the hydrocyclone are discharged into the chamber at one go. On the other hand, it can happen that the heavy substances in the chamber become caked and thus make it difficult, if not impossible, to discharge them from the chamber. As a result, the zone of selective separation of the heavy material is disturbed and the selectivity of the separation result deteriorates. In said document is also referred to that the cleaning effect of Klassierrohrs improved when the classifying a rinsing liquid is supplied against the pressure prevailing in the hydrocyclone pressure and discharged through the upper reaches of the cyclone. As rinsing liquid service water or other liquid is provided.

In the operation of such hydrodynamic Schwerstoffabscheider the degree of separation of the sedimentable constituents and the discharge of other components is strongly influenced by the flushing water flow, which generates a counterflow in the classifying tube. In this case, the rinsing water flow in relation to the desired separation of the fractions have mutually opposite effects: Reducing the rinse water flow leads to an improved separation of easily sedimentable solids from the suspension, but increases the proportion the biologically recoverable components in the separated heavy fraction. These are thus withdrawn from the downstream process stages for the recovery of the suspension. On the other hand, increasing the flushing water flow has the opposite effect, namely that the proportion of biologically utilizable constituents in the separated heavy fraction is decreasing, but the separation of the readily sedimentable constituents from the suspension deteriorates. The Fig. 1 shows this contrarian effect based on operating results of a hydrodynamic heavy material separation process stage in a fermentation plant for 75,000 Mg / a of organic waste.

In order to limit the demand for fresh water and consequently also the amount of waste water, it is important, especially for economic as well as ecological aspects, to use process water as rinsing water, which is recirculated in the system (process water). This requires a process step that provides the process water in terms of pressure levels in the heavy material separator under sufficiently high pressure. From the point of view of costs and space requirements, the diameters of the process water pipes must be limited. In this case, it has been recognized by the inventor that in the prior art periodically high process water demand peaks occur in the heavy material separator itself as well as in other upstream or downstream units of the wet mechanical processing plant. As a result, there are always considerable pressure fluctuations in the process water supply of the classifying pipe.

The object of the invention is now to improve the degree of separation of the device and to reduce the contamination of the separated fraction. This object is achieved by a device according to claim 1, or by a method according to claim 13.

The basic idea of the invention, taking into account the above-described effects of the flushing water flow, is that depending on the requirement profile for plant operation, an optimum amount and pressure of the flushing water flow to the classifying tube determined and adjusted according to the flow rate of the rinse water. Furthermore, it is part of the invention to minimize the flushing water consumption to the storage chamber.

The control technique of the present invention takes into account the above-described significant pressure fluctuations in the rinse water supply of the classifier tube and the storage chamber. Thereby, the negative impact on the separation efficiency can be eliminated, whereby the separation quality of the separated heavy materials increases and a reduced Spülwasserbedarf is the result.

According to the invention, the adjustment of the flushing water flow relates, on the one hand, to the inlet to the classifying pipe and, on the other hand, to the storage chamber separated from the classifying pipe, into which the separated heavy materials are introduced. In other words, both the classifying pipe and the separate storage chamber are subjected to rinsing water. This is done in such a way that the inlet to the classifying pipe is regulated and the inlet to the storage chamber is controlled. While the control determines a comparison between the actual state and the target state and switches an actuator in response thereto, the control of the inlet to the storage chamber focuses on the detection of the actual state to switch a corresponding actuator.

to DE 195 05 073 A1 the adverse effect of the sudden emptying of the classifying tube has already been mentioned in the prior art. In order to prevent such a sudden emptying of the classifying tube into the separate storage chamber according to the invention, it is provided according to the invention to flood the storage chamber in a controlled manner following emptying with rinsing water. In this case, the required venting of the chamber takes place via a venting or overflow opening arranged at the upper end of the chamber. In order to minimize the flushing water needs of the storage chamber now and to solve the problem described above, that in a storage chamber which is only partially filled with rinse water, by opening the shut-off valve to the classifying tube disturbed the zone of selective separation of heavy material and the selectivity of the separation result be degraded According to the invention, the heavy material separator is equipped with a detection of the level of heavy material in the storage chamber for initiating its emptying and a detection of the rinsing water overflow during its filling with rinsing water.

The emptying of the storage chamber takes place only when the maximum level of heavy materials in the storage chamber is determined by measurement. Thus, a complete filling of the storage chamber is always ensured and thus minimizes the number of required emptying. The filling of the storage chamber with the rinse water is terminated only when process water is detected in the overflow of the storage chamber. Both features lead to a minimum need for rinse water.

• Um einen Rückstau der Schwerstoffe in das Klassierrohr zu vermeiden, der eine Verstopfung des Klassierrohres hervorrufen kann, muss die Entleerung der Speicherkammer ausreichend früh erfolgen. Dadurch ist die Speicherkammer bei Entleerung häufig nicht vollständig mit abgetrennten Schwerstoffen gefüllt. Um die gleiche Menge an Schwerstoffen abtrennen zu können, sind somit mehr Entleer-Befüll-Zyklen notwendig. Da die Speicherkammer vor Öffnen der Absperrarmatur zum Klassierrohr wieder mit Spülwasser gefüllt sein muss, führt eine höhere Anzahl von Entleer-Befüll-Zyklen zu einem höheren Spülwasserverbrauch.

This process of filling the chamber with process water can also be time-controlled and ensure a measured full storage chamber. The controller must be aware of the following facts:

• In order to avoid a backflow of the heavy materials into the classifying pipe, which can cause a clogging of the classifying pipe, the emptying of the storage chamber must take place sufficiently early. As a result, the storage chamber is often not completely filled with separated heavy substances when emptied. To be able to separate the same amount of heavy materials, more discharge-filling cycles are thus necessary. Since the storage chamber must be filled with rinse water again before opening the shut-off valve to the classifying pipe, a higher number of emptying-filling cycles leads to a higher flushing water consumption.

In another preferred embodiment, the emptying of the storage chamber is initiated by the detection of the maximum level of heavy materials and the supply of process water when filling the emptied storage chamber by detecting the overflow of process water from the chamber finished. The emptying of the storage chamber is carried out after detection of the maximum Schwofofffüllstandes by closing the shut-off valve to the classifying pipe and opening the lower shut-off valve of the storage chamber.

In an advantageous embodiment, the storage chamber is timed short rinse water pulses supplied to prevent caking of the bed of heavy materials in the storage chamber. Thus, the bed can completely fall out or be removed when opening the chamber.

• Fig. 1 die Konzentration an leicht sedimentierbaren mineralischen Stoffen in einer Abfallsuspension nach hydrodynamischer Schwerstoffabscheidung in 10 g/l (●) und Anteil der Organik in der Trockenmasse der abgetrennten Schwerstoffe (Δ) in Abhängigkeit der Erhöhung des Spülwasserstromes zeigt;
• Fig. 2 einen geregelten Spülwasserstrom zum Klassierrohr bei Einsatz eines Prozesswassers aufzeigt, das suspendierte Stoffe enthält, mit Einsatz eines Scheiben-Stellorgans mit integrierter Durchflussmessung
• Fig. 3 ein Schema einer erfindungsgemäßen Ausführung einer hydrodynamischen Schwerstoffabscheidung zeigt; und
• Fig. 4 Führungssprungantworten des Regelkreis bei einem Durchfluss von 500 l/h für Frischwasser und feststoffhaltigen Prozesswasser zeigt.

To control the flushing water flow to the classifying tube such actuators are combined with a flow meter for the rinse water. This flow meter must be suitable for solids containing water flows. The detection of the overflow of the solids-containing process water to fill the chamber by means of a capacitive proximity switch or infrared light barrier. The invention will be explained below with reference to the attached drawing, in which

• Fig. 1 the concentration of easily sedimentable mineral substances in a waste suspension after hydrodynamic separation of heavy material in 10 g / l (●) and proportion of the organic matter in the dry matter of the separated heavy materials (Δ) as a function of the increase of the rinsing water flow;
• Fig. 2 shows a controlled flushing water flow to the classifying tube when using a process water containing suspended matter, using a disc actuator with integrated flow measurement
• Fig. 3 a diagram of an embodiment according to the invention of a hydrodynamic heavy material separation shows; and
• Fig. 4 Control loop responses of the control loop at a flow rate of 500 l / h for fresh water and solids-containing process water.

For the production of rinse water, the process water for rinsing purposes is initially generated in-process by means of a solid-liquid separation during the treatment of mixtures. In particular, in the processing and recycling of organic waste producing a low-solids process water is problematic. This is because suspensions of organic waste contain fibrous as well as very fine-grained slimy constituents with a small difference in density. As a result, the process water production, with economical use of precipitants and flocculants, provides a rinse water with a considerable content of suspended matter of 1 to 10 g / l. Even a two-stage dewatering such as a combination of decanter centrifuge with polymer dosing and subsequent fine sieving of the centrate, for example by means of 250 μ m gap sieve, the concentration of suspended substances in the process water is often in the range of 0.5 to 4 g / l.

In order to achieve a uniform rinsing water supply, the choice of the actuator depending on the Aufschlämmanteils in the process water can be crucial. This is mainly due to a random partial laying by suspended in the process water substances in the actuator. As suitable actuators, actuators have discs of disks, which are adjusted against each other via an axis and the opposite movement of the free passage continuously changed, pinch valves, ball sector valves or ball valves proven.

Due to the already mentioned above to be handled by the pressure fluctuations in the process water supply of the relevant volume flow varies during the filling of the storage chamber accordingly. This has the consequence that appropriate time reserves are to be provided for the filling process to ensure complete filling of the chamber. These time reserves can lead to an unnecessarily large volume of process water, which must be treated and kept under pressure. In order to avoid this, the process water requirement for filling the chamber in an advantageous embodiment is minimized either by means of a level measurement in the storage chamber or by means of detection of the process water overflow from the storage chamber.

Fig. 3 shows a diagram of an embodiment according to the invention of a hydrodynamic heavy material separation consisting of hydrocyclone (1), classifying pipe (2) and storage chamber (3). In the embodiment according to the invention of this hydrodynamic heavy material separation, the rinsing water flow to the classifying pipe (4) is regulated and controlled to the storage chamber (5). In a preferred embodiment, the adjustment of the Spülwasseraufstromes in the classifying tube by means of an actuator (6), which is not easily laid by suspended materials and has a self-cleaning effect, as mentioned above.

In another preferred embodiment, the supply of process water during filling of the emptied storage chamber is controlled by a detection of the overflow of process water (7) from the chamber. For controlling the flushing water flow, the elements mentioned above as suitable actuators are combined in a preferred embodiment with a flow meter for the flushing water (8). This flow meter must be suitable for solids containing water flows. The detection of the overflow of the solids-containing process water (7) for filling the chamber can be done by means of a capacitive proximity switch or infrared light barrier.

Attempts to control the Spülwasseraufstrom in Classierrohr by means of a ball valve, brought already satisfactory results. The following table shows the development of the Spülwasseraufstromes over the experimental period. The set value of the flushing water upstream flow was 500 l / h. The correction of the Position of the ball valve made manually as specified. Periodically, the ball valve was fully opened for a short time in order to wash away solid deposits. duration of test Spülwasseraufstrom Flushing performed Current value Corrected value [Min] [L / h] [L / h] 0 500 500 No 15 481 498 No 30 487 502 No 45 469 500 No 60 451 505 No 75 425 500 Yes 90 458 500 No 105 490 503 No 120 473 505 No 135 498 498 No 150 479 500 No 165 466 497 No 180 453 502 No 195 438 497 Yes 210 489 501 No 225 473 498 No 240 478 503 No Ball sector valves, however, are even more superior to a ball valve for such controls of solids containing streams because the seals in the ball sector valve are less exposed to the abrasive heavies.

Motor control valves in a flat rotary valve design in the throttle body allow a linear flow change. In conjunction with an electric motor, such valves represent a proportional-regulating actuator, which ensures a constant flushing water flow even with solids-containing process water. In order to keep the flushing water flow as constant as possible even in the event of a power supply failure, the control is designed so that the previously assumed valve position is maintained in the event of a power failure.

Experiments with water on the control behavior of the upflow control by means of a flat rotary valve throttle device resulted in a quick adjustment at the start of the system and changes in the setpoint and a good control behavior for a balancing of pressure changes ( Fig. 4 ). Adjustment of the controller by Ziegler-Nichols method gives a good control result. Since the volume flow of the upflow water has a clear influence on the course of the control jump responses of the control loop, setting the controller at the set flow rate leads to the best control result. It showed that a proportional control (PI) control is sufficient and leads to a lower load on the actuator. A controller parameterised with fresh water does not show optimum control behavior in the case of solids-laden rinse water due to greater overshoot width and greater settling time ( Fig. 4 ). Consequently, the controller must be set with the flush water flow of the plant.

Fig. 2 shows the operating result of the hydrodynamic Schwerstoffabscheiders with regulated Spülwasserstrom to Klassierrohr when using a process water containing suspended matter, and a Flachdrehschieber throttle body in combination with an upstream magnetic-inductive flow measurement served. These system components enabled the supply of solids-containing process water to the classifying pipe to be kept relatively constant at the setpoint.

In general, relocation of the valves by suspended substances can not be completely ruled out. Therefore, in order to eliminate such misalignments, the actuator in an advantageous embodiment is deliberately driven up at short notice in order to completely relieve possible misplacement. This short-term full opening is time-controlled and favors the Einregeln a constant flushing water flow.

Experiments with fresh water as well as with process water showed that when filling the chamber in the overflow line of the phase change between venting air and overflowing liquid can be reliably measured by means of capacitive proximity switch or infrared light barrier.

Claims (19)

1. An apparatus for the hydrodynamic removal of dense material from a slurry,
   comprising a hydrocyclone (1) that receives the slurry, a classifying tube (2) adjoining the hydrocyclone, and a separate storage chamber (3) that receives the dense materials that have been separated out, a flow of flushing water to the classifying tube (2) controlled by means of a control circuit and an actuator being provided, and a flow of flushing water to the storage chamber (3) controlled by means of the actuator being provided, for which purpose a sensor is provided which introduces detection of the filling level of the dense materials and of a flushing water overflow of the storage chamber.
2. The apparatus according to Claim 1, characterised in that the actuator is a throttle
   device in which discs are adjusted relative to one another over an axis, and the movement of which in opposing directions changes the free passage.
3. The apparatus according to Claim 1, characterised in that the actuator is a flat rotary
   slide.
4. The apparatus according to Claim 1, characterised in that the actuator is a hose pinch valve.
5. The apparatus according to Claim 1, characterised in that the actuator is a ball sector
   valve.
6. The apparatus according to Claim 1, characterised in that the actuator is a ball valve.
7. The apparatus according to any of Claims 2 to 6, characterised in that a flow meter

   (8) is provided to measure the flow of flushing water to the classifying tube.
8. The apparatus according to Claim 7, characterised in that the flow meter (8) is a
   magnetically inductive flow meter.
9. The apparatus according to Claim 1, characterised in that means (7) are provided for
   detecting flushing water in an overflow on the storage chamber (3).
10. The apparatus according to Claim 9, characterised in that the means (7) for detecting
    overflowing flushing water have a capacitive proximity switch.
11. The apparatus according to Claim 9, characterised in that the means (7) for detecting
    overflowing flushing water have an infrared light barrier.
12. The apparatus according to Claim 9, characterised in that the means (7) for detecting
    the filling level of the dense materials have a vibration limit switch.
13. A method for the hydrodynamic removal of dense material from a slurry,

    - slurry being delivered to a hydrocyclone (1),

    - dense materials that are separated out then being conveyed into a classifying

    tube (2) into which flushing water is introduced for further separation,

    - the dense materials that are separated are then sedimented in a separate
    storage chamber,

    a flow of flushing water being delivered to the classifying tube in a controlled manner
    by means of a control circuit and an actuator, and the filling level of the storage chamber being detected by means of a sensor in order to flood the storage chamber with flushing water in a controlled manner from the detected filling level.
14. The method according to Claim 13, characterised in that the actuator or throttle
    device is fully opened for short intervals of time to control the flow of flushing water to the classifying tube in a time-controlled manner.
15. The method according to Claim 13 or 14, characterised in that the flow of flushing
    water to the classifying tube is controlled by means of a magnetically inductive flow
    meter.
16. The method according to either of Claims 13 to 14, characterised in that the flow of
    flushing water to the classifying tube is controlled with a PI controller.
17. The method according to any of Claims 13 to 16, characterised in that parameterisation of the control of the flow of flushing water to the classifying tube (2) takes place with the nominal flow with flushing water.
18. The method according to any of Claims 13 to 17, characterised in that the process of
    filling the storage chamber (3) with flushing water ends with detection of flushing
    water in the overflow.
19. The method according to any of Claims 13 to 18, characterised in that flushing water
    is temporarily delivered to the storage chamber in a time-controlled manner.

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