EP2393601B1 - Hydrocyclone arrangement, method for the operation thereof, and underflow nozzle therefor - Google Patents

Description

The invention relates to a hydrocyclone arrangement with an inlet of Aufgabetrübe, an upper course for the fine grain discharge, a conical-cylindrical underflow for coarse grain discharge and a sensor for detecting the beam shape or the jet envelope on coarse grain discharge according to the preamble of claim 1. Furthermore, the invention relates to an underflow nozzle Attachment or extension piece according to the combination of features according to claim 8 and a method for operating a hydrocyclone assembly according to the teaching of claim 11, wherein the dependent claims represent at least expedient refinements and developments.

Known hydrocyclones have a tangential inlet of the feed pulp in a cylindrical-conical process space and two discharges of the separation products in a fine grain overflow and coarse grain underflow. Such cyclones are used to classify polydisperse suspensions as close as possible to a desired particle size. The desired classification has physical limits. This concerns above all the solid particles in the micrometer range, which are discharged with the coarse grain with the aqueous medium, but also coarse grains, which are not completely separable in the underflow.

The DE 199 63 284 A1 as well as the PCT WO 00/25933 A1 show a Hydrozyklonanordnung and an associated method of operation, wherein the hydrocyclone assembly has an inlet of the feed pulp, an upper course and an underflow, wherein the inlet is guided by a pump in a receiving chamber.

The upper course is directed into a collection chamber and for the lower reaches a free outlet is available. According to the teaching there are several, preferably equally sized hydrocyclones provided and arranged spatially close to each other so that the headwaters of these hydrocyclones open into the common upper collecting chamber, the headbox is designed as a pressure pot and an overflow collecting line with an adjustable control valve and a associated control device for adjusting the volume split, namely the ratio of the flow rates of the upper and lower reaches, cooperates.

It exploits the fact that a hydrocyclone, depending on its operating state stores different amounts of solids in its conical lower section. Through the coupling of several hydrocyclones of smaller design in the overall hydrocyclone arrangement, the capacity is increased overall, the required structural complexity is low. From the collected mass of the stored sediment in the hydrocyclone cone, a controlled variable for the volume split can be derived by establishing a corresponding interaction with said control valve in the collecting line of the upstream flow of the hydrocyclone or hydrocyclone in the case of a hydrocyclone battery. The mass of the stored solid in the hydrocyclone cone determines to what extent coarse grain is separated into the fine grain discharge of the hydrocyclone overflow and thus increases the separation grain size of the hydrocyclone.

As optimal operating point is in the DE 199 63 284 A1 stated that this is given when, with free discharge of the coarse grain flow in the hydrocyclone underflow, the shape of the discharge jet turns from a strand to a so-called screen. As long as the strand shape can be observed in the lower reaches, sediment is still stored in the cone, which on the one hand means a high solids content or a high thickening in the lower reaches, on the other hand entails an at least partial spillage of this coarse-grained material in the lower reaches.

For the determination of the jet shape at the underflow, according to DE 100 27 976 C2 proposed to form a special arrangement for scanning the underflow, which is designed as a measuring probe. The measuring probe is located in a housing, wherein the housing has a flexible membrane on its side facing the beam or is terminated with such. The membrane is then subjected to deformation upon impact of the jet. An arranged inside the housing sensor can then detect the deformation, so that a conclusion on the corresponding beam shape or the beam shape change is possible.

The company FLSmidth Krebs, USA, presents and offers under "www.krebs.com/product" an additional device for the reduction of fine sludge content in the lower reaches of a hydrocyclone. According to this solution, a cylindrical intermediate piece is used in the lower part of the hydrocyclone cone, comprising a device for the tangential supply of washing water. This additional wash water dilutes the suspension with respect to the turbulently mixed fine particles contained therein. This dilution causes the fine particle concentration in the coarse-grain discharge to be reduced.

However, the desired positive effect of this water supply measure is limited, which is mainly due to the fact that only defined additional amounts of water can be added, otherwise more coarse grains are pushed to the cyclone center and thus in the upper reaches. Furthermore, an undesired dilution occurs in the underflow. In the conical part of the additional water is distributed over a relatively large radius, which indeed reduces the dilution effect, on the erroneous discharge of coarse grains in the lower reaches, however, can not be influenced.

According to the state of the art DE 10 41 431 B the controlled delivery of an auxiliary operating fluid into the conical hydrocyclone chamber is disclosed.

JP 50 064066 U discloses an underflow for a hydrocyclone with a cylindrical nozzle cross-sectional profile, with circumferentially formed nozzle-like openings, which have a tangential orientation and an axial angle of attack.

From the foregoing, it is therefore an object of the invention to provide an advanced hydrocyclone and a method for operating such an arrangement, which improves the separation so that both the erroneous discharge of fine grain in the lower course and the coarse grain is reduced in the upper reaches without the described Disadvantages of the prior art occur.

The object of the invention is achieved by a Hydrozyklonanordnung according to the combination of features according to claim 1, by a, retrofittable, approach or extension piece for or such extended underflow nozzle according to the combination of features according to claim 8 and a method according to the teaching of claim 11, wherein the subclaims include at least expedient refinements and developments.

Accordingly, it is assumed that a hydrocyclone arrangement with a, in particular tangential inlet of the feed pulp, which comprises an upper course for the Feinkornaustrag, a conical-cylindrical underflow for coarse grain discharge and a sensor for detecting the beam shape or the beam envelope on coarse grain discharge.

According to the invention, means for directional supply of make-up water are provided in the region of the transition from the conical to the cylindrical part of the underflow.

Furthermore, in particularly problematic task conditions with large fluctuations at the upper reaches of a throttle valve or a throttle of defined size may be formed to influence the flow of solids to the lower reaches, in such a way that worked after activating the additional water supply in the low screen angle, near the transition screen / strand becomes.

Ausgestaltend the make-up water is provided via a control valve, wherein a control unit is in effective connection with both the auxiliary water control valve and the upper-flow throttle valve.

The means for the directional supply of make-up water allow a superposition of given in the cyclone cross-flow classification with a countercurrent classification, for this purpose in the centrifugal field of the cyclone by the Make additional water is directed to the center radial flow, which is accompanied by a directed to the center axial upflow.

The means for supplying the make-up water are designed in particular as nozzle-like bores, wherein the nozzles are uniformly spaced, one or more rows are formed circumferentially at the underflow.

The nozzle-like bores have a tangential with respect to the underflow cross-section and have a radial and axial angle of attack for defined flow generation.

In one embodiment, the holes can be sealed by an annular forend, the forend simultaneously serves the water connection, the water distribution and water supply.

The sensor for steel mold analysis may comprise an optical detector and / or a vibration detector. The vibration detector is mounted directly on the hydrocyclone and is in acoustic communication with it. With such vibration detectors, it is possible to react very sensitively to the sediment level in the hydrocyclone cone.

The inventive, retrofittable underflow nozzle extension for known hydrocyclones has a nozzle cross-sectional profile, which changes in the axial direction from conical to cylindrical, wherein the discharge takes place at the cylindrical end.

The transition region between the conical and cylindrical cross-section has circumferentially and spaced nozzle-like openings which have a tangential-radial orientation in the center direction and an axial angle of attack to ensure the desired countercurrent classification in the centrifugal field of the hydrocyclone.

The nozzle-like openings may be uniformly spaced in one, but also in several rows and be in the region of a circumferential annular groove.

The annular groove is sealingly surrounded by a circular ring forend, wherein an annular additional water serving space is formed between the forend and the annular groove. The forend is e.g. a nozzle available to feed additional water accordingly. Due to the two-part design of the underflow nozzle with the special nozzle-like openings within an annular groove and the sealing annulus tulip a simple production is possible and ensures access to the nozzle-like openings at any time.

In the method according to the invention for operating the above-described hydrocyclone arrangement, the jet shape at the coarse-grain discharge is initially monitored continuously or at cyclic intervals in order to detect a changing beam shape when the additional-water feed is activated. To stabilize the desired strand discharge, it is possible to reduce the suspension pressure to the underflow. For this purpose, the throttle valve can be opened at the upper reaches and / or the Zusatzwassereinspeisung be regulated. By using optical sensors, the beam shape, in particular the beam angle can be determined very accurately. The aim is a dependent on the application case desired beam shape of the underflow discharge, preferably near the transition screen / strand.

The additional water quantity is generally regulated as a function of the suspension density and the grain size composition of the discontinued solids stream to be classified.

When throttling the valve at the upper reaches, the performance of an existing feed-feed pump can be increased at least temporarily to obtain the desired feed rate.

The invention will be explained below with reference to an embodiment and with the aid of figures.

Fig. 1

eine Prinzipdarstellung der erfindungsgemäßen Hydrozyklonanordnung mit Regelungskomponenten zum erfindungsgemäßen Betreiben des Hydrozyklons;

Fig. 2

eine Querschnitt- sowie eine Längsschnittdarstellung des mit den erfindungsgemäßen düsenartigen Bohrungen versehenen Unterlaufs und symbolisch dargestellten Anstellwinkeln zur gezielten Einbringung des Zusatzwassers und

Fig. 3

typische Trenncharakteristiken bei der Hydrozyklonklassierung.

Hereby show:

Fig. 1

a schematic diagram of the hydrocyclone arrangement according to the invention with control components for operating the hydrocyclone according to the invention;

Fig. 2

a cross-sectional view and a longitudinal sectional view of the provided with the nozzle-like holes according to the invention underflow and symbolically represented angles of attack for the targeted introduction of additional water and

Fig. 3

typical separation characteristics in hydrocyclone classification.

The approach according to the invention, which is to be explained again with the following exemplary embodiment, consists of specifically introducing additional water flow-oriented into the hydrocyclone, in particular pumping it in. It is crucial that the point of introduction is laid as far as possible in the direction of the underflow discharge. It is therefore necessary to arrange the make-up water connection to the underflow nozzle or a neck or extension piece, near the transition from the conical part to the cylindrical outlet of the corresponding underflow nozzle. In this area there is a dense fluidized bed of the sediment. With optimal dosing of make-up water, a fluidized bed countercurrent classification can be generated at this point, which leads both to a reduction of the fine grain and to an increased separation of the coarse grain in the underflow.

This makes it possible to achieve a very large effect with a relatively small amount of added water, since the radial cross section is substantially smaller than in the larger cone area above. The positive effect on the coarse grain separation is due to the following causes.

The displacement of the fine grain reduces cloudiness and cloudiness and thus also the sedimentation obstruction of the coarse grain.

Also, a misdirected coarse grain on the way to the headwaters has to cover a further distance and can therefore be centrifigured again towards the hydrocyclone wall. The thus designed hydrocyclone then reacts sensitively to make-up water, the further one moves in the direction of coarse grain discharge. There is in principle the risk that the additional water breaks through into the lower reaches and leads to an undesirable dilution of the coarse grain. There is also the danger of a breakthrough in the upper reaches with appropriate Fehlaustrag.

To avoid these disadvantages, a targeted control intervention is made, which will be explained in more detail.

Essential for the supply of make-up water are the number, arrangement and orientation of the feed channels, which are preferably designed as bores.

It should be noted that the introduction of additional water should be such that the cyclone flow is not disturbed in an undesirable manner. For this purpose, the largest possible number of supply channels or feed holes to be provided, which are arranged distributed in each case the same state and in several superimposed rows over the circumference of the underflow nozzle.

The basic orientation of the feed channels or feed holes follows the tangential flow in the cyclone. Here, an essential idea of the invention is to effect a superimposition of the cyclone taking place, preferably cross-flow classification by a countercurrent classification, which operates very segregated.

The prerequisite for a desired countercurrent classification in the centrifugal field of the hydrocyclone is the generation of a radial flow directed towards the center. This radial component of the additional water flow is α with a radial angle of attack Fig. 2 purposefully influenced.

Another prerequisite for the success of the countercurrent classification is that in the center of an axial upflow and on the wall provides an axial outflow for the removal of the separation products. This in turn is achieved by an axial angle β of the feed channels in either the positive or negative direction, as also in the Fig. 2 , lower part of the picture, is shown.

With regard to the operation of the hydrocyclone arrangement according to the invention, first a hydrocyclone monitoring takes place, specifically based on the form of the free underflow discharge. For application optical sensors can come here, which scan the discharge. However, vibration or vibration sensors are also suitable for reacting sensitively to the sediment level in the hydrocyclone cone.

The discharge jet of the underflow is in the form of either a screen or a strand. When working with make-up water, the discharge with a small screen angle or the strand discharge close to the transition to the screen offers optimum conditions. As is known, the solids content in the underflow at Schirmaustrag is higher, which leads to a lower erroneous discharge of fine grain.

Basically, results from the supply of additional water, a dilution of the lower reaches, whereby its shape tends more for Schirmaustrag. This is counteracted in critical cases by a throttle valve is opened in the upper reaches. In this way, it is possible to reduce the suspension pressure in the underflow nozzle and thus also the flow of solids in the lower reaches, so that again sediment is dammed and the Austragsstrahl returns to the strand shape.

The additional water quantity is here matched to the solids flow, the suspension density and the given grain size composition. Since in this regard the operating conditions inevitably change in the course of the use of the hydrocyclone, the additional water flow is also influenced by a valve in an advanced control. In schwankungsarmem task stream of effort can be reduced and subject only one of said valves a scheme, while the other valve is set to a constant value.

The control in the upper reaches has the advantage that in multiple circuits in hydrocyclone batteries, a valve is sufficient for all hydrocyclone overflows, if they are combined in a collecting pot. The supply or additional water control has the advantage that the cost of the valve on the cyclone is relatively low and that each individual cyclone is individually controlled.

The inventive hydrocyclone with control provides stable conditions in terms of fluidized bed height, fluidized bed density and countercurrent flow. The throttling of the valve in the upper reaches can lead to an increased pressure drop, which is accompanied by a lower throughput of the cyclone. This disadvantage can be counteracted by the pressure drop between inlet and upper reaches determined by means of a corresponding measuring device and an increase in the speed of the feed pump of the hydrocyclone is made.

The advantages of the described hydrocyclone arrangement according to the invention consist in the fact that the cyclone has greatly improved separation properties by means of a controlled addition of added water, as they correspond to a countercurrent classification. This achieves both better product yields and better product qualities with respect to a desired grain size composition. It can also flow diagrams and separation technologies are simplified because previously high Separation sharpness either by multi-stage cyclone circuits or the interconnection of cyclones were achieved with upstream classifiers.

The necessary technical or constructive changes to the cyclone itself are relatively small, since no new components are required and only an underflow nozzle must be modified accordingly. Thus, the presented teaching is also suitable for retrofitting existing systems.

The required regulatory effort is kept within limits, as can be used for the regulation of the water additive and for sensors on commercial products. In addition, compared to an operation of the cyclone without regulated additional water flow, a reduction of the separation grain sizes is possible.

Fig. 1 showed a schematic representation of a hydrocyclone.

The hydrocyclone body 15 merges into a funnel-shaped region 16, wherein the funnel-shaped region 16 is configured as underflow nozzle 1.

At the conical end of the underflow nozzle 1 holes 2 are formed to introduce additional water 3 under pressure.

The diameter of the underflow nozzle is selected so that the underflow is discharged strand-shaped without additional water.

After connecting the make-up water 3, the underflow discharge changes into the shield shape 5.2. The strand shape is provided with the reference numeral 5.1.

The additional water 3 is supplied via a valve arrangement 6 to the holes 2 for the additional water, wherein the additional water valve 6 is actuated via a first control unit 17.

The respective shape of the underflow jet 5.1 or 5.2 is determined either by means of an optical detector 4 or by means of a vibration detector 11. The corresponding detector 4 or 11 supplies the signals for the actuation of the actuators, namely the control valve 6 and the throttle valve in the upper reaches. 7

The throttle valve 7 in the upper reaches, which is never fully closed when the cyclone function, leads to a reduced suspension pressure on the underflow discharge and thus to a braked flow of solids to the underflow nozzle when opening. As a result, sediment is dammed again and the discharge line returns to the strand form 5.1.

The countercurrent classification in the fluidized bed of the accumulated sediment works best when the output line is close to the transition to the screen discharge. This detects the optical sensor 4 as an occasional penetration of the screen or the at least one vibration detector 11 by the registration of resonant vibrations of the hydrocyclone body 15; 16th

It should be noted in this context that in the countercurrent classification in the fluidized bed, in contrast to conventional hydrocyclones, the sharpest separation is achieved at Strandaustrag. Thus, it is advantageously possible to achieve high thickening and high selectivity even at high feed solids contents.

The presented regulation is necessary, since small variations of the properties of the feed sludge with regard to solids content and / or grain size composition disturb the countercurrent classification.

In relatively stable task conditions but the effort can be reduced to the effect that a constant throttling is specified in the upper reaches and the stabilization of the strand shape in the lower reaches is achieved solely by operating the control valve 6 for the Zulaufwasserstrom.

The feed pulp is conveyed by means of a feed pump 13 to the inlet 18 on the hydrocyclone body 15. The upper run with fine grain discharge is provided with the reference numeral 19.

Pressure measuring devices 12 determine the pressure conditions, in particular a pressure drop between inlet 18 and upper run 19. From this, the speed and thus the power of the feed pump 13 is adjusted with the aid of the second regulator 20, in particular increases in pressure drop.

By the reference numeral 10, a ring segment is indicated, which allows a uniform supply and feeding the make-up water to the holes 2.

The Fig. 2 shows by way of example the arrangement and the angle of attack of the selected holes in the underflow nozzle for additional water supply.

Fig. 2 , upper part of the picture, shows a horizontal section with recognizable eight holes (arrow representations), which are distributed at the same distance over the circumference of the nozzle.

The teaching according to the invention presupposes that the radial component of the flow required for countercurrent separation is generated by a radial angle of attack.

Like from the Fig. 2 can be seen, this radial angle of attack α is measured to the tangent to the inner wall of the cyclone.

Fig. 2 , below, shows a vertical section of the underflow nozzle. The bores can be provided on two levels, for example, the level 100 and 200, wherein an axial angle β for the corresponding hole (again arrow view) is selected. This axial angle β can have a positive, but also a negative sign. Depending on the choice of sign either the axial flow directed towards the lower reaches in the outer vortex or there is an increase in the axial flow of the inner vortex in the cyclone directed towards the upper flow. The appropriate choice of the angle of attack takes place in dependence on the respective Hydrozyklongeometrie.

The Fig. 3 shows typical separation curves in an inventively realized hydrocyclone classification.

The separation curves indicate the probability with which the individual particle sizes in the underflow are discharged.

As can be seen, an ideal separation would be characterized by a vertical c at the cut-off grain size d ₅₀ , which, however, does not correspond to physical reality.

The curve a for the typical course of the separation curve of a conventional cyclone shows the known deviations in both the fine grain and the coarse grain range with respect to the values for an ideal separation.

The curve b follows a typical course, as it is achieved by the use of controlled countercurrent separation in the cyclone. An approach to the ideal course can be observed in both the fine grain and the coarse grain range. This is due to the construction according to the invention and the operating method of the hydrocyclone. So it receives the hydrocyclone in terms of its release properties a new quality, which make it possible to develop other applications.

Claims (13)

1. Hydrocyclone arrangement having a, in particular, tangential inlet (18) of the feed slurry, an overflow (19) for the fine-grain discharge, a conically-cylindrically configured underflow (1) for the coarse-grain discharge as well as a sensor system (4; 11) for detecting the jet shape or the jet transition at the coarse-grain discharge,
   characterized in that
   means for the directed supply of make-up water are provided in the area of the junction from the conical to the cylindrical portion of the underflow (1), wherein the make-up water (3) is provided by a regulating valve (6).
2. Hydrocyclone arrangement according to claim 1,
   characterized in that
   a throttle valve (7) is formed on the overflow (19) to influence the solid matter stream to the underflow (1) such that upon a detected change from rope discharge (5.1) to umbrella discharge (5.2) at the underflow (1) upon activation of the make-up water supply a rope discharge state (5.1) close to the umbrella or a discharge state with a small umbrella angle is adjusted, wherein a regulator unit (17) communicates with both the make-up water regulating valve (6) and the overflow throttle valve (7).
3. Hydrocyclone arrangement according to claim 1 or 2,
   characterized in that
   the means for the directed supply of the make-up water (3) allow an overlapping of the cross flow classification given in the cyclone with a counterflow classification, wherein, for this purpose, a radial flow directed to the center is produced by the make-up water (3) in the centrifugal field of the cyclone which is accompanied by an axial upstream directed to the center.
4. Hydrocyclone arrangement according to one of the preceding claims,
   characterized in that
   the means for supplying the make-up water are nozzle type bores (2) which are arranged, in one or more rows, on the circumference at the underflow (1) in a regularly spaced-apart manner.
5. Hydrocyclone arrangement according to claim 4,
   characterized in that
   the nozzle type bores (2) have a tangential orientation with respect to the underflow cross-section and a radial (α) as well as axial (p) angle of inclination to generate a defined flow.
6. Hydrocyclone arrangement according to claim 4 or 5,
   characterized in that
   the bores (2) are sealed by a circular ring type cuff, wherein the cuff simultaneously serves the water connection and water distribution.
7. Hydrocyclone arrangement according to one of the preceding claims,
   characterized in that
   the sensor system includes an optical detector for the jet shape analysis (4) and/or a vibration detector (11), wherein the latter is directly acoustically coupled to the cyclone.
8. Attachment or extension piece for an underflow nozzle for a hydrocyclone, with a cross-sectional profile of the nozzle that changes in the axial direction from conical to cylindrical,
   characterized in that
   in the junction area between the conical and the cylindrical cross-section nozzle type openings are formed on the circumference and in a spaced-apart manner, which have a tangential-radial orientation in the center direction as well as an axial angle of inclination.
9. Attachment or extension piece for an underflow nozzle according to claim 8,
   characterized in that
   the nozzle type openings are formed in one or more rows in a regularly spaced-apart manner and are located in the area of an annular groove.
10. Attachment or extension piece for an underflow nozzle according to claim 9,
    characterized in that
    the annular groove is surrounded by a circular ring cuff in a sealing manner, wherein an annular make-up water feed space is formed between the cuff and the annular groove and a make-up water feeder is arranged at the cuff.
11. Method for operating a hydrocyclone arrangement according to one of claims 1 to 7,
    characterized in that
    the jet shape at the coarse-grain discharge is constantly monitored so as to detect a changed jet shape when activating the make-up water feed, wherein the suspension pressure to the underflow is reduced for stabilizing the desired rope discharge and, for this purpose, a provided throttle valve at the overflow is opened and/or a regulation of the make-up water feed takes place.
12. Method according to claim 11,
    characterized in that
    the make-up water quantity is regulated subject to the suspension density and the grain size composition of the fed solid matter stream to be classified.
13. Method according to claim 11 or 12,
    characterized in that
    upon throttling the valve in the overflow to obtain the desired feed flow-rate the capacity of a feed pump is influenced, in particular increased.

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