EP0936948B1 - Centrifuge with an inside-out flow filter - Google Patents

Abstract

An invertable filter centrifuge for separating liquid-solids mixtures comprises a rotatingly driven centrifugal drum, an invertable filter cloth arranged on the centrifugal drum, a filtrate housing for receiving and discharging the liquid filtrate separated from the liquid-solids mixture by means of centrifugation with a filter cloth turned inwards into the centrifugal drum, a solids housing for receiving and discharging the solids (filter cake) separated from the liquid-solids mixture during further rotation of the centrifugal drum with a filter cloth turned outwards and an annular gap surrounding the edge of the centrifugal drum in the region of the filtrate housing and the solids housing. Protection means are provided on the invertable filter centrifuge, with the aid of which a flow of a gaseous blocking medium can be generated in the annular gap surrounding the edge of the drum, this flow preventing any undesired transfer of gaseous, liquid and/or solid substances between filtrate housing and solids housing.

Description

The invention relates to an inverting filter centrifuge for separation of liquid-solid mixtures with a rotating drive Centrifugal drum, with one on the centrifugal drum arranged, reversible filter cloth, with a filtrate housing for receiving and discharging the liquid-solid mixture by centrifuging in the centrifugal drum liquid filter, with the filter cloth a solid housing for receiving and discharging the liquid-solid mixture while rotating the centrifugal drum with the filter cloth separated solid (Filter cake) and with the edge of the centrifugal drum in the Area of the filtrate housing and the solid housing surrounding Annular gap.

An inverting filter centrifuge of this type is known from DE-37 40 411 A1 known.

In order to work with such a centrifuge as possible The centrifugal drum is usually used to achieve a large separation effect operated at the highest possible speed, which is too much high peripheral speeds at the edge of the drum. There with these centrifuges due to unavoidable imbalance the centrifugal drum occur so far between the rotating centrifugal drum and the stationary housing an annular gap is provided in the area of the filtrate and solids space, which also contain a flexible, elastic seal can (DE-34 30 506 C2). If now the centrifugal drum inside such an annular gap is set in rapid revolutions, the annular gap must be at least so large that at maximum Imbalance resulting tumbling movement of the drum not to one Touching the rotating centrifugal drum with stationary Housing parts leads. When using a seal in the annular gap due to the high peripheral speed of the Centrifugal drum and the heat generated when touched only touch lightly on rotating machine parts.

This is necessary in view of the tumbling movements of the drum The result of the annular gap is that between the filtrate housing and the solid housing no absolute sealing possible is.

Because the centrifugal drum rotates like a fan acts, arises in the filtrate housing, in which the closed Drum rotates during the filtering process, compared to the Solid housing an overpressure, which is basically for one Gas exchange between the filtrate and solid housing ensures. The when centrifuging through the holes in the drum jacket and liquid emerging through the filter cloth is in the Filtrate housing finely divided, i.e. the gas present there becomes enriched with liquid aerosols that pass through the annular gap can get into the solid housing. Although often between the filtrate housing and the solid housing an external so-called "Gas suspension line" is provided for pressure equalization between the two cases, it can still due to the turbulence prevailing in the filtrate housing Annular gap to an undesirable fluid transfer into the Solid housing come. Furthermore, in itself, of course also via the gas suspension line liquid aerosols into the Solid housing, as well as with filtered liquid saturated gas, which then undesirably in the solid housing can lead to condensation.

On the other hand, when turning the filter cloth and the then remove solids from this cloth the bottom piece carrying the filter cloth like a plunger in moved the solid housing into it. This creates in this Housing overpressure over the filtrate housing, at least as long as the filter cloth is still covered with solid and therefore pressure reduction cannot take place via the filter cloth. To turning the filter cloth inside out will turn the dry solid into the solid housing dropped. The gas is in this Housing through dust-like portions of the solid with solid aerosols enriched. Even if, as already mentioned, a gas compensation line is provided for pressure equalization is, due to the in the solid housing during the also when the centrifugal drum rotates prevailing turbulence an undesirable transfer of solids through the annular gap into the filtrate housing. Solid aerosols can also be used get into the filtrate housing via the gas suspension line.

An overflow of filtrate into the solid housing and vice versa of solids in the filtrate housing is due to the associated Contamination was highly undesirable, but was previously because of the annular gap between the centrifugal drum and the machine housing inevitable even if the annular gap is a seal contained.

It is an object of the invention to provide a generic inverting filter centrifuge to improve so that the purity of the separated Products disruptive transition from gaseous, liquid and solid substances between the filtrate and solid housing is prevented in both directions.

The task becomes with a generic inverting filter centrifuge solved by the invention in that on the inverting filter centrifuge Protective devices in the form of sealing gas generating devices are provided with the help of the drum edge surrounding annular gap is effective in two directions Purge gas flow can be generated, which is an undesirable Conversion of gaseous, liquid and / or solid substances into Direction towards the filtrate housing and / or solid housing effectively prevented by directly in the filtrate or Solid housing a positive or negative pressure can be generated.

The invention is therefore based on the general idea of a solution, at the annular gap between the filtrate housing and the solid housing to establish a gaseous medium flow, the one undesirable mass transfer between these housing areas excludes.

In the DE-37 40 411 mentioned above, an overpressure or underpressure directly in the centrifugal drum and not in the filtrate or Solid housing can be generated. The one in the centrifugal drum generated pressure can change in the normal operating state Inverting filter centrifuge, d. H. with a loaded filter cloth, not in surrounding filtrate housing so that the prevention a transfer of gaseous, liquid and / or solid This means that substances between the filtrate and solid housing are not is possible.

DE-83 31 079 U1 is a different type of centrifuge (Screw centrifuge) known in which on an area between the outer centrifugal drum surface and a solids collection housing a sealing gas can be applied, which one Should prevent leakage of solid. The application of the Sealing gas is carried out with an annular nozzle, which, in inverted filter centrifuges proves to be unfavorable. Preventing one Foreign matter escapes from a filtrate housing in the not described.

Fig. 1

schematisch eine Stülpfilterzentrifuge mit geschlossener Schleudertrommel;

Fig. 2

die Stülpfilterzentrifuge aus Fig. 1 mit geöffneter Schleudertrommel;

Fig. 3 und 4

Teilansichten im Bereich des strichpunktierten Kreises X in Fig. 1;

Fig. 5

eine abgewandelte Ausführungsform einer Stülpfilterzentrifuge mit geöffneter Schleudertrommel;

Fig. 6 und 7

Teilansichten abgewandelter Ausführungsformen von Stülpfilterzentrifugen im Bereich des strichpunktierten Kreises X in Fig. 1 und

Fig. 8

eine weiterhin abgewandelte Ausführungsform einer Stülpfilterzentrifuge mit geschlossener Trommel.

The following description of preferred embodiments of the invention serves in conjunction with the accompanying drawings for further explanation. Show it:

Fig. 1

schematically an inverting filter centrifuge with closed centrifugal drum;

Fig. 2

the inverting filter centrifuge from Figure 1 with an open centrifugal drum.

3 and 4

Partial views in the area of the dot-dash circle X in Fig. 1;

Fig. 5

a modified embodiment of an inverting filter centrifuge with an open centrifugal drum;

6 and 7

Partial views of modified embodiments of inverting filter centrifuges in the area of the dot-dash circle X in FIG. 1 and

Fig. 8

a further modified embodiment of an inverting filter centrifuge with a closed drum.

The inverted filter centrifuge shown in FIGS. 1 and 2 comprises a schematically indicated, (in each of these figures right, not visible) drive part of the centrifuge enclosing machine housing 1, in which on a stationary Machine frame 2 a hollow shaft 3 in bearings 4, 5 rotatably supported is. The hollow shaft 3 can via a (not shown) Engine are put into rapid circulation. It stretches themselves on the machine frame 2, the bearing 4 and one the machine housing 1 at the front, with the machine frame 2 tightly connected partition 6 and has an axially extending (also not shown) Keyway in which a wedge piece 9 is axially displaceable is. This wedge piece 9 is rigid with an inside of the hollow shaft 3 displaceable shaft 12 connected. The shaft 12 runs therefore together with the hollow shaft 3, but is in this axially displaceable.

At the end of the hollow shaft 3 protruding beyond the partition 6 is a pot-shaped centrifugal drum 16 with its bottom 17th flange-mounted. On its circular cylindrical side wall the centrifugal drum 16 has radially extending passage openings 18 on. On its end face opposite the bottom 17 the centrifugal drum 16 is open. On a flange-like Opening edge 19 is one by means of a retaining ring 21 Edge of an essentially circular cylindrical filter cloth 22 tightly clamped. The other edge of the filter cloth 22 is correspondingly sealed with a base piece 23 connected, which is rigid with the sliding, the bottom 17th freely penetrating shaft 12 is connected.

At the bottom piece 23 is about stud 24 with release a centrifugal chamber cover 25 is rigidly attached to an intermediate space, 1 the interior of the centrifugal drum 16 sealed by resting on the opening edge 19 and in Fig. 2 together with the bottom piece 23 by axially sliding out the shaft 12 from the hollow shaft 3 free of the centrifugal drum 16 is lifted off. 1, the filter cloth is 22nd turned inside out of the centrifugal drum 16, in FIG. 2 this cloth is turned inside out.

Connect to the machine housing 1 in the area of the centrifugal drum 16 a filtrate housing 10 and a solid housing 11 on. Both housings are sealed by corresponding walls completed. Near the opening edge 19 of the centrifugal drum 16 are the filtrate housing 10 and the solid housing 11 separated from each other by an annular end wall 14. The opening of this annular end wall 14 surrounds with release of an annular gap 15 the outer edge of the centrifugal drum 16. This annular gap is so large that the centrifugal drum can make small wobble movements at high speed, without the inside of those formed in the annular end wall 14 Touch opening. In addition, 15 known, circular self-contained seals 41 be arranged, made of elastic, highly flexible material exist, are embedded in the partition 14 and loose on Grind the outer edge of the drum 16 so that they tumble to the extent necessary (Fig. 4).

The filtrate housing 10 serves to receive and discharge a liquid filtrate, which the passage openings 18 of the Spin drum 16 and filter cloth 22 has penetrated. to The discharge of the filtrate is connected to the filtrate housing 10 Drain line 7 with shutoff valve 71 is provided. Via a discharge line 8 of the solid housing 11 can after Inverting the filter cloth 22 a deposited on this cloth filter cake present as a solid are discharged, wherein the line 8 can be tightly closed by a shut-off valve 81 is.

On the front of the (on the left of the drawing) Inverting filter centrifuge, a filling tube 26 is arranged, which for feeding one into its solid and liquid components suspension to be dismantled into the interior of the centrifugal drum 16 serves (Fig. 1) and in that shown in Fig. 2 Operating state in a bore 27 of the displaceable shaft 12 penetrates, the displacement of the shaft 12 and thus the Opening and closing the centrifugal drum 16 via (not shown, on the drawing also on the right) drive motors, e.g. hydraulic, done.

In centrifuging mode, i.e. during centrifugation the inverting filter centrifuge the position shown in Fig. 1 on. The displaceable shaft 12 is retracted into the hollow shaft 3, whereby the bottom piece 23 connected to the shaft 12 is near the bottom 17 of the centrifugal drum 16 and that Filter cloth 22 is inserted into the drum so that it is in the interior of which covers the passage openings 18. The spin chamber cover 25 has tightly on the opening edge 19th the centrifugal drum 16 placed. With rapidly rotating Centrifugal drum 16 is continuously closed via the filling tube 26 filtering suspension introduced. The liquid components the suspension pass through the filter cloth 22 and as a filtrate the through openings 18 into the filtrate housing 10 and are there from a baffle 36 in the with the filtrate housing 10 connected discharge line 7 passed. The solid particles the suspension are in the form of a filter cake from Filter cloth 22 retained.

With the centrifuge drum still rotating, usually slower 16 and after switching off the suspension supply on the filling pipe 26, the shaft 12 is now according to FIG. 2 (to the left) moved, causing the filter cloth 22 inside out and the solid particles of the filter cake adhering to it outwards in the direction of arrows 38 into the solid housing 11 are thrown out. Via the discharge line 8 Components of the filter cake removed.

In the position shown in FIG. 2, the filling tube 26 is replaced by a corresponding one Openings in the cover 25 or in the base piece 23 in the bore 27 penetrated the shaft 12. After dropping the solid particles forming the filter cake under the influence the centrifugal force will push the filter centrifuge back the shaft 12 back into the operating position according to FIG. 1 brought, the filter cloth 22 in the opposite Turns back in the direction. In this way the centrifuge is operating possible with continuously rotating centrifugal drum 16.

As already mentioned at the beginning, the rotating centrifugal drum works 16 in the filtrate 10 like a fan leading to one directed from the filtrate housing 10 into the solid housing 11 Pressure drop and thus to a gas flow from the filtrate housing 10 leads into the solid housing 11, whereby about the annular gap 15 undesirable substances, in particular liquid aerosols and evaporated liquid into the solid housing 11 can reach. To reliably prevent this Means or protective devices are provided for in the solid housing 11 to achieve a constant gas overpressure with whose help is a constant flow of a gaseous barrier medium, e.g. Air that can be generated through the annular gap an undesirable transfer of in particular gaseous and liquids from the filtrate housing 10 into the solid housing 11 prevented. For this purpose, for example a gas inlet connector 51 provided on the solid housing 11 a compressed gas source (pressure pump) connected in the direction of the arrow a gaseous medium, for example air or a introduces inert gas into the solid housing 11. The one in the solid housing 11 overpressure used can be, for example, 5 to 50, preferably 10 to 30 mbar. The filtrate housing 10 has a further nozzle 52, which in the simplest case is open to the atmosphere. Thus, 15 with the formation of a correspondingly directed gas flow Pressure equalization take place, with the gas flow passing of foreign particles from the liquid housing 10 in the Solid housing 11 prevented.

If - cf. 2 - the centrifugal drum 16 is opened, penetrates the bottom piece 23 connected to the filter cloth 22 as a plunger into the solid housing 11 and generated in this, at least for now, a strong overpressure that over the annular gap 15 for gas exchange from the solid housing 11 leads into the filtrate housing 10, again undesirable Foreign substances can be taken, namely in this case primarily solid aerosols. To prevent this from happening now over the pipe socket 51, 52 - cf. the respectively assigned Arrows in Fig. 2 - a compared to Fig. 1 in the opposite direction through the annular gap 15 flowing gas stream generated one excludes such undesirable transfer of material. In this Trap thus becomes a compressed gas source with the pipe socket 52 (Pressure pump) connected while the pipe socket 51 to the outside can lead to. Again, it is sufficient to generate a minor one Pressure difference in the above range.

When working according to both Fig. 1 and Fig. 2 are the shut-off valves 71, 81 in the discharge lines 7 and 8, respectively closed as needed.

1 and 2 show the filtrate housing 10 and Solid housing 11 by a running outside the housing "Gas suspension line" 53 connected to each other, shown in the Case contains a shut-off valve 54. At acquaintances Inverting filter centrifuges this shut-off valve 54 is missing, so that when working normally with the centrifuge when Differences in pressure of the type mentioned above a pressure equalization between filtrate housing 10 and solid housing 11, namely in both directions. It can because of of the missing shut-off valve 54 of course foreign particles from one housing get into the other housing. That is why in generating an overpressure in one as described above the housing 10 or 11 to avoid undesirable Foreign matter transfer, the shut-off valve 54 in the gas shuttle line 53 provided and during the generation of this overpressure kept closed.

3 and 4 are still for clarification once shown schematically and clearly. Fig. 3 shows corresponding to the circular area X in Fig. 1, the annular gap 15 between Partition 14 and the edge of the centrifugal drum 16. At 1, ie when the Centrifugal drum 16 is in the direction of arrow I in the Filtrate housing 10 directed gas flow generated, wherein Air can serve as a barrier medium, for example. If vice versa 2, the solid from the inverted filter cloth 22nd is thrown off, a flow of gaseous barrier medium caused by the annular gap 15 in the direction of arrow II. The same applies to an annular gap 15 with two annular the sealing strip 41 enclosing the centrifugal drum 16, as shown in Fig. 4.

Instead of on the socket 51 (FIG. 1) or on the socket 52 (FIG. 2) To connect pressure pumps, the corresponding, the pipe outlet 52 and 51 serving also on the gas outlet Vacuum lines (suction pumps) can be connected. At the Mode of action, namely the generation of a flow from a gaseous barrier medium in the annular gap 15 changes here Nothing.

5 shows a modified embodiment of a Inverting filter centrifuge, in which, however, compared to the embodiment 1 and 2, only the structure and arrangement of Gas suspension line 53 are changed. Except for the shutoff valve 54 in the gas shuttle line 53 this line includes yet another Shut-off valve 55. In addition, line 53 has another Branch 56 in the solid housing 11 with an additional Shut-off valve 57 and a dust or solid filter 58th

In principle, the inverting filter centrifuge according to FIG. 5 in the same way as with the inverting filter centrifuge according to the figure 1 and 2 can be worked. However, when solids discharge, thus with the centrifugal drum 16 open (FIG. 5) the barrier medium through the annular gap 15 in the direction of the filtrate housing 10 flows to the solid housing 11, it may be beneficial to the two Shutoff valves 54 and 55 to close as well as the Shut off pipe socket 51 tightly so that no gas escapes from it can. In this case, the shut-off valve 57 is then opened. The gaseous supplied via the pipe socket 52 Barrier medium flows out of the filtrate housing 10 via the annular gap 15 in the solid housing 11, from there via the open shut-off valve 57 in the dust filter 58, where solid particles are retained and finally via the gas suspension line 53 into an exhaust pipe 59. The exhaust pipe 59 can be a pressure control valve 61 included that of maintaining a certain Pressure in the overall system.

As already explained, the flow of the gaseous barrier medium in the annular gap 15 either in the desired direction by overpressure or by negative pressure in one of the filtrate housings or spaces forming the solid housing are generated. Also combinations of overpressure and underpressure in these rooms come into question.

That discharged from the solid housing 11 via the exhaust line 59 Gas can be reprocessed. If you are with a sealing gas flow works in the opposite direction, so the gas not from the solid housing 11, but from the filtrate housing 10 subtracts - with closed valves 54, 57 the valve 55 opened and the gas also for the purpose of processing inserted into the exhaust pipe 59. In this case for example the introduction of the gas via the pipe socket 51 into the solid housing 11, the pipe socket 52 is tightly closed.

Instead of the gaseous barrier medium with the formation of a corresponding one Pressure drop either into the filtrate housing 10 or initiate the solid housing 11, it can also directly fed to the annular gap 15 and from there directly into the relevant Housing space to be redirected. Is particularly cheap it, if, according to FIG. 6, the gas supplied both in introduces the filtrate housing 10 as well as into the solid housing 11 and thereby a double sealing effect against trespassing Foreign matter particles achieved. 6 shows this schematically two gas supply lines 62, 63 in the partition 14. In practice, numerous such lines 62, 63 go radially inside the partition 14 e.g. from a common Ring line and open in the annular gap 15, where they are the desired Generate sealing gas flows in directions I and II. The loop is with a gas source (pump) (not shown) connected.

In the modified embodiment according to FIG. 7 takes place of the two lines 62, 63 only a single line 64 provided in the partition 14, which in turn e.g. than radial Branch of a centrifugal drum 16 enclosing, with a ring line connected to a pump can be thought of. In in this case the two flows of the barrier medium go into directions I and II from a single opening opposite directions.

The annular gap 15 in FIG. 7 in turn contains two annular, the drum 16 enclosing sealing strips 41 which in the Partition 14 are attached. The introduction of the locking medium Via the line 64 takes place between the sealing strips 41 it is also possible to introduce the gaseous barrier medium in the annular gap 15 according to FIGS. 6 and 7 not after both Direction I and II, but depending on the working state the inverting filter centrifuge either only according to the direction I or only in the direction II.

One can see those shown in Figs. 6 and 7 in the directions I and II flowing gas flows either by overpressure generate in the lines 62, 63, 64, or also by negative pressure in the respective rooms that receive the currents, namely either the filtrate housing 10 or the solid housing 11th

8 finally shows a last embodiment of a Inverting filter centrifuge. If it is procedural and safety-related is permissible and appropriate from a cost point of view appears, the necessary for the sealing gas flow Pressure drop even without additional gas feed, as in the previous ones Described embodiments can be realized. So 8, for example, a suction pump P into the Gas suspension line 53 are switched on via a Liquid separator 91 and the open shut-off valve 55 Aspirated gaseous medium from the filtrate 10, when closed Shut-off valve 57 and open shut-off valve 54 in the solid housing 11 feeds and thus a constant, in closed flow of barrier medium through the annular gap 15 through (arrow I in Fig. 3 and 4) maintained. The pipe socket 51 is closed in this case.

When dropping the solids, i.e. with the centrifugal drum open is also arranged with the help of a line 53 Pump P generates a gas flow in the opposite direction (Arrows II in Figs. 3 and 4).

The invention could also be formulated as a method, for example in the sense that in the annular gap 15 a stream from a gaseous Barrier medium is generated, which is a transfer of foreign substances between filter and solid housing 10, 11 prevented.

Claims (13)

1. Invertible filter centrifuge for separating liquid-solids mixtures comprising a rotatingly driven centrifugal drum (16), an invertible filter cloth (22) arranged on the centrifugal drum (16), a filtrate housing (10) for receiving and discharging the liquid filtrate separated from the liquid-solids mixture by means of centrifugation with a filter cloth (22) turned inwards into the centrifugal drum (16), a solids housing (11) for receiving and discharging the solids (filter cake) separated from the liquid-solids mixture during further rotation of the centrifugal drum (16) with a filter cloth (22) turned outwards, and an annular gap (15) surrounding the edge of the centrifugal drum (16) in the area of the filtrate housing (10) and the solids housing (11), characterized in that protection means (51, 52, 62, 63, 64, P) in the form of blocking gas generating means are provided on the invertible filter centrifuge, with the aid of which a flow of blocking gas effective in two directions is generatable in the annular gap (15) surrounding the edge of the drum, said flow of blocking gas preventing any undesired transfer of gaseous, liquid and/or solid substances in the direction towards the filtrate housing (10) and/or solids housing (11) by an overpressure or underpressure being generatable directly in the filtrate housing or solids housing.
2. Invertible filter centrifuge as defined in claim 1, characterized in that the protection means comprise a pump (P).
3. Invertible filter centrifuge as defined in claim 2, characterized in that the pump (P) is connected to the filtrate and solids housings (10, 11) via pipe and control means (51, 52, 53, 54, 55, 57) and optionally generates overpressure in one of these housings (10; 11) so that the blocking gas flows through the annular gap (15) into the respective other housing.
4. Invertible filter centrifuge as defined in claim 2, characterized in that the pump (P) is connected to the annular gap (15) surrounding the edge of the drum via pipe and control means (62, 63, 64) and generates the flow of blocking gas directly in said gap.
5. Invertible filter centrifuge as defined in claim 4, characterized in that the pump (P) generates two flows (I, II) of a blocking gas in the annular gap (15), one of said flows being directed into the filtrate housing (10) and the other into the solids housing (11).
6. Invertible filter centrifuge as defined in claim 1, characterized in that the blocking gas is air or an inert gas.
7. Invertible filter centrifuge as defined in claim 1, characterized in that a seal (41) is arranged in the annular gap (15) between the edge of the rotating centrifugal drum (16) and a stationary machine housing part (14).
8. Invertible filter centrifuge as defined in claim 1, characterized in that an exhaust gas pipe (59) is provided, into which the blocking gas flowing out of the filtrate housing or solids housing (10, 11) is introducible.
9. Invertible filter centrifuge as defined in claim 8, characterized in that the exhaust gas pipe (59) contains a pressure-maintaining valve (61).
10. Invertible filter centrifuge as defined in claim 1, characterized in that a gas-shuttle pipe (53) with a check valve (54) is provided between filtrate housing (10) and solids housing (11).
11. Invertible filter centrifuge as defined in claims 2 and 10, characterized in that the pump (P) is arranged in the gas-shuttle pipe (53).
12. Invertible filter centrifuge as defined in claim 1, characterized by a solids filter (58) for the flow of blocking gas exiting from the solids housing (11).
13. Invertible filter centrifuge as defined in claim 1, characterized by a liquid separator (91) for the flow of blocking gas exiting from the filtrate housing (10).

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