HYDRODYNAMIC REMOVAL OF DENSE MATERIALS FROM A SLURRY

Abstract

The invention relates to a device and to a method for the hydrodynamic removal of dense materials from a suspension, said device comprising a hydrocyclone (1), which holds the suspension, a classifying tube (2), which adjoins the hydrocyclone, and a storage chamber (3), which holds the removed dense materials, wherein a flushing water flow to the classifying tube (2) and a flushing water flow to the storage chamber (3) are provided, which can be controlled in a closed-loop or open-loop manner by means of a control element provided at the feed to the classifying tube and a control element provided at the feed to the storage chamber, respectively.

Claims

1. An apparatus for the hydrodynamic removal of dense material from a slurry, comprising: a hydrocyclone that receives the slurry, a classifying tube adjoining the hydrocyclone, and a separate storage chamber that receives dense materials that have been separated out from the slurry, a flow of flushing water to the classifying tube controlled via control circuit and an actuator and a flow of flushing water to the storage chamber controlled via the actuator, a sensor being positioned to detect a filling level of the dense materials and a flushing water overflow of the storage chamber.

2. The apparatus according to claim 1, wherein 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 a free passage.

3. The apparatus according to claim 1, wherein the actuator is a flat rotary slide.

4. The apparatus according to claim 1, wherein the actuator is a hose pinch valve.

5. The apparatus according to claim 1, wherein the actuator is a ball sector valve.

6. The apparatus according to claim 1, wherein the actuator is a ball valve.

7. The apparatus according to claim 2, wherein a flow meter is positioned to measure the flow of flushing water to the classifying tube.

8. The apparatus according to claim 7, wherein the flow meter is a magnetically inductive flow meter.

9. The apparatus according to claim 1, wherein means are provided for detecting flushing water in an overflow on the storage chamber.

10. The apparatus according to claim 9, wherein the means for detecting overflowing flushing water have a capacitive proximity switch.

11. The apparatus according to claim 9, wherein the means for detecting overflowing flushing water have an infrared light barrier.

12. The apparatus according to claim 9, wherein the means 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, comprising: delivering slurry to a hydrocyclone, separating out dense materials from the slurry for conveying the separated out dense materials into a classifying tube into which flushing water is introduced for further separation, sedimenting the dense materials that are separated in a separate storage chamber, and delivering a flow of flushing water to the classifying tube in a controlled manner by means of a control circuit and an actuator, and a detected filling level of the storage chamber detected by means of a sensor in order to flood the storage chamber with flushing water in a controlled manner based on the detected filling level.

14. The method according to claim 13, wherein the actuator is a throttle device that 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, wherein the flow of flushing water to the classifying tube is controlled by means of a magnetically inductive flow meter.

16. The method according to claim 13, wherein the flow of flushing water to the classifying tube is controlled with a PI controller.

17. The method according to claim 13, wherein parameterisation of the control of the flow of flushing water to the classifying tube takes place with nominal flow of the flushing water.

18. The method according to claim 13, comprising: ending the filling the storage chamber with flushing water in response to detection of flushing water at an overflow.

19. The method according to claim 13, wherein flushing water is temporarily delivered to the storage chamber in a time-controlled manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the invention is explained below with reference to the attached drawings. It should be understood that like reference numbers used in the drawings may identify like components. The drawings include:

[0023] FIG. 1, which is a graph illustrating the concentration of easily sedimentable mineral materials in a waste suspension after hydrodynamic separation of dense materials in 10 g/l (.circle-solid.) and the portion of organic material in the dry mass of the dense materials that have been removed () dependently upon the increase in the flow of flushing water;

[0024] FIG. 2, which is a graph illustrating a regulated flow of flushing water to the classifying tube when using a process water that contains suspended materials, with the use of a disc actuating element with integrated flow measurement;

[0025] FIG. 3, which is a schematic diagram of an embodiment according to the invention of an apparatus for hydrodynamic dense material separation; and

[0026] FIG. 4, which is a graph illustrating a guidance jump responses of the control circuit with a flow of 500l/h for fresh water and process water that contains solids.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0027] For the production of flushing water when processing material mixtures the process water for flushing purposes is first of all generated as part of the process by means of solid/liquid separation. In particular when processing and recycling organic waste the generation of process water with a low solid content is problematic. This is due to the fact that suspensions from organic waste contain fibrous as well as very fine-grained slimy components with a small density difference. This leads to the process water extraction providing a flushing water with a considerable content of suspended materials of 1 to 10 g/l with the commercial use of precipitating and flocculating agents. Also with two-stage dewatering, such as a combination of a decanter centrifuge with polymer metering and then fine screening of the centrate, e.g. by means of a 250 m slotted screen, the concentration of the suspended materials in the process water is often in the region of 0.5 to 4 g/l.

[0028] In order to achieve an even supply of flushing water the choice of actuator depending on the portion of slurry in the process water may be decisive here. This is especially due to random partial displacement by the materials suspended in the process water in the actuator. Actuators comprised of discs which are adjusted relative to one another about an axis and the opposing movements of which change the free passage with infinite variation, hose pinch valves, ball sector valves or ball valves have proven to be suitable as actuators.

[0029] Due to the aforementioned pressure fluctuations in the supply of process water to be managed by the inventor, in this regard the volumetric flow varies accordingly when filling the storage chamber. The result of this is that appropriate amounts of time are to be set aside for the filling process in order to ensure total filling of the chamber. These time reserves may lead to unnecessarily large volumes of process water which must be processed and kept at pressure. In order to avoid this, the amount of process water required to fill the chamber in an advantageous embodiment is minimized either by means of a filling level measurement in the storage chamber or by means of detection of the process water overflow from the storage chamber.

[0030] FIG. 3 shows a diagram of an embodiment according to the invention of an apparatus for hydrodynamic separation of dense materials comprising a hydrocyclone (1), a classifying tube (2) and a storage chamber (3). In the embodiment according to the invention of this apparatus for hydrodynamic separation of dense materials the flow of flushing water to the classifying tube (4) is regulated and guided to the storage chamber (5). In a preferred embodiment the flow of flushing water into the classifying tube is set by means of an actuator (6) which is not easily displaced by suspended materials and has a self-cleaning effect, as specified above.

[0031] In another preferred embodiment the supply of process water when filling the emptied storage chamber is controlled by detection of the overflow of process water (7) from the chamber via a detector or a detection mechanism. In order to regulate the flow of flushing water the elements specified above as appropriate actuators are combined with a flow meter for the flushing water (8) in a preferred embodiment. This flow meter must be appropriate for water flows which contain solids (e.g. slurries). The overflow of the process water (7) that contains solids for filling the chamber may be detected by means of a capacitive proximity switch or an infrared light barrier in some embodiments.

[0032] Attempts to control the upwards flow of flushing water within the classifying tube by means of a ball valve was found to provide satisfactory results. The following table 1 shows the development of the upwards flow of flushing water over the trial period. The nominal value of the upwards flow of flushing water was 500 l/h. The positioning of the ball valve was corrected manually here as required. The ball valve was periodically fully opened for a short time in order to flush away solid accretions.

TABLE-US-00001 TABLE 1 Trial Upwards flow of flushing water Flushing duration Current value Corrected value process [min] [l/h] [l/h] performed 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

[0033] However, for such controls of material flows that contain solids ball sector valves are superior to a ball valve in terms of construction because the seals in the ball sector valve are exposed less to the abrasive dense materials.

[0034] Motor regulating valves in a flat rotary slide construction in the throttle device enable a linear flow change. In association with an electric motor such valves constitute a proportional regulating actuator which also ensures a constant flow of flushing water with process water that contains solids. In order to keep the flow of flushing water as constant as possible when the flow supply stops, the regulation is designed such that if there is power failure, the previously adopted valve position is maintained.

[0035] Experiments with water to consider the regulating characteristics of the regulation of upwards flow by means of a flat rotary slide throttle device showed rapid adjustment at the start of the system and with changes to the nominal value as well as good regulating characteristics for the correction of pressure changes (FIG. 4). The setting of the regulator by means of the Ziegler Nichols method gives a good regulating result. Since the volumetric flow of the upwards flow of water has a clear effect upon the guiding jump response sequence of the control circuit, adjustment of the regulator with the nominal flow leads to the best regulating result. It was shown here that a PI (Proportional Integral) controller is sufficient and leads to less stressing of the actuator. A regulator paramaterized with fresh water does not show optimal regulating characteristics with flushing water charged with solids due to the greater overshoot width and the greater correction time (FIG. 4). Consequently, the regulator must be set with the flow of flushing water of the operational plant.

[0036] FIG. 2 shows the operational result of the hydrodynamic dense materials separator with a regulated flow of flushing water to the classifying tube when using process water that contains suspended materials and uses a flat rotary slide throttle device in combination with an upstream magnetically inductive flow measurement. By means of these system components the supply of process water containing solids to the classifying tube could be kept relatively constant at the nominal value.

[0037] In general, displacement of the valves by suspended materials cannot be entirely ruled out. Therefore, in order to eliminate such displacement, in one advantageous embodiment the actuator is deliberately moved fully forwards for a short period of time so that any possible displacement is entirely eliminated. This short-term full opening takes place in a time-controlled manner and assists with the re-setting of a constant flow of flushing water.

[0038] Experiments with fresh water and also with process water showed that upon filling the chamber in its overflow pipe, the phase change between the ventilation air and the overflowing liquid can be measured reliably by means of a capacitive proximity switch or an infrared light barrier.

[0039] While certain exemplary embodiments of the apparatus for hydrodynamic dense material separation and methods of making and using the same have been shown and described above, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.