WO2010089309A1 - Hydrocyclone arrangement, method for the operation thereof, and underflow nozzle therefor - Google Patents

Abstract

The invention relates to a hydrocyclone arrangement comprising an especially tangential infeed of the feed pulp, an overflow (19) for discharging fine grains, a conical/cylindrical underflow (1) for discharging coarse grains, and a sensor system (4, 11) for detecting the jet shape or the change in shape of the jet at the coarse-grained discharge end. According to the invention, means (3) for feeding additional water in a directed manner are provided in the area of the transition from the conical part of the underflow to the cylindrical part of the underflow. Furthermore, a throttle valve (7) is optionally formed on the overflow in order to influence the solid flow to the underflow in such a way that a single-jet discharge state approaching the state where the jet is dispersed in different directions is set when a transition from the single-jet discharge (5.1) to the dispersed-jet discharge (5.2) is detected at the underflow after the additional water feeding process has been activated.

Description

 HYDROCYCLONAL ASSEMBLY AND METHOD FOR THE OPERATION, AND

UNDERFLOW NOZZLE FOR THIS

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 with approach or extension piece according to the combination of features according to claim 8 and a method for m 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.

DE 199 63 284 A1 and PCT WO 00/25933 A1 show a hydrocyclone arrangement and a corresponding method for operating, wherein the hydrocyclone arrangement has an inlet of the feed sludge, an upper run and an underflow, wherein the inlet is guided by a pump into a receiving chamber becomes . 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 in T he common upper head collecting chamber open, the upper-head collecting chamber is designed as a pressure pot and an overflow collecting line with an adjustable Control valve and an associated control device for the adjustment of 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 control variable for the volume split can be derived by establishing a corresponding interaction with said control valve in the collecting line of the top stream 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.

DE 199 63 284 A1 states that this is given as the optimum operating point when, with free discharge of the coarse grain stream in the hydrocyclone underflow, the shape of the discharge jet turns from one 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. In order to determine the jet shape at the lower reaches, DE 100 27 976 C2 proposes to design a special arrangement for scanning the underflow jet, 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.

From FLSmidth Krebs, USA, under "www. krebs.com/product "introduced and offered an additional device for the reduction of fine sludge fractions in the lower reaches of a hydrocyclone, according to which a cylindrical intermediate piece containing a device for the tangential supply of washing water is inserted into the lower part of the hydrocyclone cone This dilution leads to a reduction of the fine particle concentration in the coarse grain discharge, but the desired positive effect of this water feed is limited, which is mainly due to the fact that only defined amounts of added water can be added Otherwise, more coarse grains are forced to the cyclone center and thus into the upper reaches, and undesirably a dilution occurs in the lower reaches. In the conical part, the additional water becomes over a relatively large radius which reduces the dilution effect, however, the erroneous discharge of coarse grains into the lower reaches can not be influenced.

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 Hydrozyklonanord- tion according to the feature combination 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 with a method according to the teaching of the claim 11, wherein the dependent claims comprise 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 fine grain discharge, a conical-cylindrical underflow for coarse grain discharge and a sensor for detecting the jet shape or the jet 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 Schwanku gene at the upper reaches a throttle valve or a throttle of defined size be formed to influence the flow of solids to the lower reaches, in such a way that after activation of the additional water supply in the field low screen angle, near the transition screen / strand is working.

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 feeding the 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 may be sealed by an annular Stülp, the Stülp 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 between Stülp and annular groove, an annular Zusatzwasserspeiseraum is formed. At Stülp is z. B. 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 annular ring for ease of manufacture 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 headwaters, the performance of an existing feed-feed pump may 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.

Hereby show:

Fig. 1 is a schematic diagram of the hydrocyclone arrangement according to the invention with control components for operating the hydrocyclone according to the invention;

Fig. 2 is a cross-sectional and a longitudinal sectional view of the nozzle-like holes provided with the underflow and symbolically represented angles of attack for the targeted introduction of the additional water and

Fig. 3 typical separation characteristics in the 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 additional 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 turbidity viscosity and thus also the sedimentation obstruction of the coarse grain.

Also, a misoriented coarse grain has to travel a further distance on the way to the upper run and can therefore be centrifigured again in the direction of 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 in 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 additional water are number, arrangement and alignment of the feed channels, which are preferably formed 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. H here is an essential idea of the invention is to effect a superposition 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 influenced in a targeted manner with a radial angle of attack α according to FIG. 2.

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 of attack β of the feed channels in either the positive or negative direction, as is also shown in Fig. 2, lower part of the image.

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 the case of 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. As a result, both better product yields and better product qualities are achieved 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 one underflow nozzle has to 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 comparison to an operation of the cyclone without regulated additional water flow, a reduction of the separation grain sizes is also possible.

Fig. 1 shows 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 Stellg songs, 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 strand returns to strand shape 5.1.

The countercurrent classification in the fluidized bed of the accumulated sediment is best achieved 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 an example of 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 (Pfeildarstell ments), which are arranged 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.

As shown in FIG. 2, this radial angle of attack α is measured to the tangent to the inner wall of the cyclone.

Fig. 2, bottom, shows a vertical section of the underflow nozzle. The Bohru can gene on two levels, eg. B. the level 100 and 200, be provided with an axial angle ß for the corresponding hole (turn arrow) 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. FIG. 3 shows typical separation curves for a hydrocyclone classified according to the invention.

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

claims 1. Hydrocyclone arrangement with a, in particular tangential inlet of the Aufgabetrübe, an upper course for the Feinkornaustrag, a conical cylindrical underflow for coarse grain discharge and a sensor for detecting the beam shape or the jet envelope on coarse grain discharge, characterized in that in the region of the transition from conical to cylindrical Part of the underflow means are provided to m directed feeding of make-up water, wherein the make-up water is provided via a control valve. 2. Hydrozyklonanordnung according to claim 1, characterized in that at the upper reaches a throttle valve is formed to influence the flow of solids to the underflow such that at a detected transition from strand to Schirmaustrag at the lower reaches after activating the Zusatzwasserzufü supply a close lying on the screen Strangaustragszustand or a discharge state is set with a low screen angle, wherein a regulator unit communicates with both the auxiliary water control valve and the upper-flow throttle valve. 3. Hydrocyclone arrangement according to claim 1 or 2, characterized in that the means for directionally supplying the 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 additional water directed to the center radial flow is generated, which accompanied by an axial upward flow directed to the center. 4. Hydrozyklonanordnung according to any one of the preceding claims, characterized in that the means for supplying the additional water are nozzle-like bores which are evenly spaced, one or more rows are arranged circumferentially at the lower reaches. 5. Hydrozyklonanordnung according to claim 4, characterized in that the nozzle-like bores have a relative to the underflow cross-section tangential orientation and have a radial (α) and an axial (ß) Anstellwinkel for defined flow generation. 6. Hydrozyklonanordnung according to claim 4 or 5, characterized in that the bores are sealed by an annular Stülp, wherein the Stülp simultaneously serves the water connection and the water distribution. 7. Hydrozyklonanordnung according to any one of the preceding claims, characterized in that the sensor comprises an optical detector for beam shape analysis and / or a vibration detector, the latter being directly acoustically coupled to the cyclone. 8. extension or extension piece for an underflow nozzle for a hydrocyclone with a nozzle cross-sectional profile, which changes in the axial direction from conical to cylindrical, characterized in that in the transition region between the conical and the cylindrical cross-section circumferentially and spaced nozzle-like openings are formed, which have a tangential-radial orientation in the center direction and an axial angle of attack. 9. underflow nozzle according to claim 8, characterized in that the nozzle-like openings are formed uniformly spaced in one or more rows and are in the region of an annular groove. 10. Unterlaufdüse according to claim 9, characterized in that the annular groove is sealingly surrounded by a Kreisringstulp, wherein formed between Stülp and annular groove an annular Zusatzwasserspeiseraum and the Stülp a Zusatzwassereinspeisung is arranged. 11. A method for operating a Hydrozyklonanordnung according to any one of claims 1 to 7, characterized in that continuously monitoring the beam shape at the coarse grain discharge to detect when activating the Zusatzwassereinspeisung a modified beam shape, which reduces the stabilization of the desired Strangaustrags the suspension pressure to underflow and For this purpose, an existing throttle valve opens at the upper reaches and / or a regulation of the additional water supply takes place. 12. The method according to claim 11, characterized in that the additional water quantity is regulated as a function of the suspension density and the grain size composition of the discontinued solids stream to be classified. 13. The method of claim 11 or 12, characterized in that when throttling the valve in the upper reaches to obtain the desired task throughput, the performance of a task-feed pump influenced, in particular increased.