WO1998048917A1

WO1998048917A1 - Device and filtering method for separating substances from suspensions

Info

Publication number: WO1998048917A1
Application number: PCT/DE1998/001153
Authority: WO
Inventors: Peter Lüth
Original assignee: Lueth Peter
Priority date: 1997-04-25
Filing date: 1998-04-23
Publication date: 1998-11-05
Also published as: DE19717448A1; AU8207598A

Abstract

The invention relates to a device and a method for separating substances from suspensions. A suspension (4), whose liquid phase can also contain an emulsion, is placed in a filter drum (2) or a filter tube. Particles are separated from the fluid phase according to size or constituents by continuous external rinsing so as to avoid formation of an impermeable filter cake (6) or clogging of the filter medium (1).

Description

Device and filtration method for separating substances from suspensions

description

The invention relates to a device and a method for the filtration of suspensions, the liquid phase of which can also consist of an emulsion.

Areas of application are e.g. microbiology, food technology, pharmacy, chemistry or mineralogy.

It is known that the filtration of suspensions or slurries (hereinafter called suspensions), which contain small particles of different sizes, is problematic with conventional methods.

When attempting to separate constituents from suspensions, the liquid phase of which may also consist of an emulsion, an impermeable layer (filter cake) forms very quickly on the filter medium, which is no longer passed by the particles to be separated or the liquid phase of the suspension can.

There are several methods to solve this problem. In pressure filtration, for example, there is the possibility of increasing the surface area of the filter medium by constructing so-called filter cartridges. Backflushing can remove the filter cake from time to time. This so-called pressure filtration fails, however, when it comes to a suspension with very small particles (e.g. 1 - 500 μm) and a high solids content, the smallest fraction of the solid phase or a certain component of the liquid phase (in the event that this consists of a Emulsion) to separate because the filter medium stuffs. Other methods in which the filter cake formed in the pressure filtration is rinsed off by the filter medium (published application DE 4110999 AI, WO-A-92/21427 and WO-A-92/06766) have so far not proven successful in practice.

To avoid the disadvantages mentioned, the cross-flow method was developed, in which the suspension flows past the filter medium. In this way, the constituents to be filtered move through the filter medium without exerting a strong pressure on the filter medium from the suspension. The movement of the components to be separated from the suspension through the filter medium is more or less random. However, it only takes place until a balance has been reached. The filtration can therefore never be carried out completely. In addition, the method has the disadvantage that it takes a very long time and is only suitable for relatively small amounts of suspension. The cross-flow process also does not allow continuous operation.

It is also known to combine the principle of cross-flow filtration with the effect of an azimuthal flow in the suspension, which is triggered by rotating disks. This dynamic microfiltration should make it possible to decouple the factors determining the separation (transmembrane pressure difference, azimuthal flow and residence time) in a product-specific manner and thus prevent the suspended particles from attaching to the filter medium (information from Pall Filtrationstechnik GmbH). However, our own experiments with this technology have shown that the filter medium clogs up sooner or later and has to be laboriously cleaned or replaced. It is also not possible with this technology to separate the separating components completely from the suspension or to ensure a continuous operation. It is therefore not possible with this method to completely clean a suspension of, for example, bacterial contaminants in biotechnology.

The problem underlying the invention is that the separation of particles or individual liquid constituents from suspensions is not effectively solved with conventional filtration processes. Filtration is either very complex, can only be carried out with relatively small amounts of suspension or takes a very long time.

The invention was therefore based on the object of developing a device and a method which allows substances to be almost completely removed from suspensions, these substances in particular being small particles <500 μm, such as bacterial particles. The process should also work continuously and be effective with regard to the materials used.

The invention is achieved according to claims 1 and 8, subclaims 2 to 7 and 9 and 10 are preferred variants.

The device according to the invention for the filtration of substances from suspensions is characterized by a closable trough, in which there is a drum, the outer surface of which is covered with a filter medium, and which has a closable insertion part for the suspension, and a protruding into the trough on which Drum-directed feed device which is provided with one or more nozzles for a detergent, an outflow device for the filtrate leading from the tub and optionally a separator with a possibly upstream pump, which has a discharge line for separated components and is connected to the detergent supply device for returning liquid to rinsing.

The detergent is applied continuously to the entire surface of the drum by appropriately arranging the nozzles by pouring, spraying or spraying.

With this device according to the invention, large quantities of small particles, e.g. Fungus spores, or certain components of the liquid phase are almost completely separated from the suspension in question, without the filter medium becoming blocked. In the event of a continuous accumulation of the suspension to be processed, the method is also suitable for ensuring a continuous separation of the corresponding suspension components. By using a separator, the liquid consumption (e.g. water, oil, alcohol etc.) can be limited to a minimum amount. This means that it is not necessary to continuously dilute the suspension for a successful filtration process.

Particles are separated from the solid phase of suspensions or the solid phase is divided into 2 fractions. In addition, if the liquid phase of the suspension consists of an emulsion of different constituents of different densities, constituents of the liquid phase can also be separated from the suspension without affecting the solid phase. The method can thus be used both for cleaning a suspension of undesired constituents and for obtaining Recyclable materials from both the solid and the liquid phase can be used.

The invention is explained in more detail with reference to Figures 1 to 3. The pictures show:

Fig. 1: Functional principle of the device with

Filter drum Fig. 2: Filter drum with inlet and outlet pipe Fig. 3: Filter drum in the form of a filter pipe in the

Longitudinal section

The principle of operation is shown in Figure 1. The jacket of a horizontally rotating drum 2 is covered with a filter medium 1. Depending on the size of the particles to be separated or retained, this filter medium has mesh sizes or pore sizes of different sizes (eg 10 μ for separating small fungal spores). It usually consists of a layer, preferably metal or synthetic fiber, which can easily be penetrated by a liquid from the outside of the drum. The drum has an opening 3, which can be firmly closed with a lid, for filling in the suspension 4. The jacket is sprayed, sprayed or poured from the outside with the cleaned liquid phase of the suspension (for example water) in such a way that the entire jacket surface is conditional by the rotation of the drum, is swept during one revolution. The result of this is that the filter cake 6 which forms on the inside of the jacket is continuously removed again by the liquid which presses through the filter medium from the outside, or is not even given the opportunity to form. Due to the liquid penetrating through the jacket, the suspension, which is continuously reduced by the outflow of the filtrate 7 containing the constituents to be separated, is continuously refilled. The filtrate is a separator 8 for liquid-solid or liquid Sig-liquid separation (for example from Westfalia Separator AG), where the components 9 to be separated are separated from the filtrate and collected. The remaining liquid is fed back into the filter drum by using it here again to flush the filter medium. In this way, components can be separated from the suspension with a minimum of liquid. The process can be continued until the components to be separated are completely separated from the suspension. In the case of separation of small particles from the suspension, this is expressed by an increasing clarification of the filtrate flowing off the filter drum. The filter drum hangs in a trough 10, in which the outflowing filtrate is collected and passed to the separator via an outflow 11, which can be connected to a pump 12. The trough is closed with a lid 13 so that no contaminants can get into the trough from outside and thus into the outflowing filtrate. After the end of the filtration, the opening 3 in the drum jacket is exposed and the suspension remaining in the drum can be rinsed out of the drum while the drum is still rotating and further liquid supply, and can either be collected in a separate container or properly disposed of in accordance with the objective.

It is again emphasized that the filter drum is sealed airtight to the outside during operation. No air can penetrate or escape through the meshes (pores) of the filter medium, as these are filled with the suspension. The entry of the jet into the filter drum results in a slight increase in the air pressure in the drum, which causes the suspension with the particles to be separated (or dissolved or emulsified substances) on the entire surface of the filter medium, which follows the cleaning jet, is pressed out. Effective filtration is only possible by increasing the air pressure in the filter drum. The film of the suspension adhering to the entire inside of the drum shell is pressed outwards through the filter medium. This process is shown schematically in Fig. 2.

Another variant of the device according to the invention, which consists in loading the drum with the suspension or emptying it again after the filtration, is shown in FIG. 3.

The drum 2 is rotatably supported on the end faces on the filler pipe 3 and the discharge device 11, which is an emptying pipe. The tubes, which also act as an axis around which the drum rotates, are sealed off from the drum by means of oil seals 14, so that the suspension 4 cannot escape here. Both tubes are provided with a valve 15 which can be kept closed during the filtration. For complete emptying of the drum after the filtration, a cleaning or rinsing liquid can be added via the filler pipe, which is drawn off again via the emptying pipe.

Filling and emptying of the drum by means of axially arranged pipes can also be realized in that the pipes act as a shaft via which the torque is transmitted to the drum.

In a third variant of the device, which allows continuous operation, the filter drum 2 is extended to a filter tube. The outer surface of the filter tube is covered with the filter medium 1. A screw conveyor runs in the pipe 16. The shaft of the screw conveyor can be designed as a hollow shaft, whereby the suspension 4 is continuously fed to the filter tube (Fig. 4). The horizontal rotation of the filter tube now frees the suspension from the constituents to be separated, and it is conveyed to the removal side 17 by the screw conveyor rotating separately to the filter tube. The cleaned suspension is discharged via the drain 18 and, depending on the objective, either collected in a separate vessel or properly disposed of.

During the filtration, the filter medium is continuously flushed over the entire area from the supplied rinsing liquid 5 via the nozzles 19 by the horizontal rotation of the filter tube. In the tub 10, the filtrate penetrating through the filter medium and containing the constituents to be separated is collected and fed via the outlet 11 to a separator 8 for liquid-solid or liquid-liquid separation, where the constituents to be separated are separated from the filtrate and collected become. The remaining liquid is fed back into the filter tube as rinsing liquid.

The new device and the method that can be carried out with it can also be operated without a separator for the purpose of cleaning a suspension (e.g. of bacterial contaminants). In this case, the filter drum or the filter tube must be constantly supplied with new liquid (in the best case, water), and the filtrate flowing off is immediately properly disposed of.

embodiments

example 1

The mushroom Coniothyrium minitans was cultivated on a growing medium consisting of wheat bran pellets. fourth. In order to release the conidia (pycnidiospores of the fungus) that form in closed fruiting bodies (pycnidia) and have a diameter of about 6 μm, the substrate was mechanically dispersed in water after the culture. As a result, a suspension was obtained consisting of the remains of the wheat bran, fungal mycelium, the fragments of the fruiting bodies and the conidia of the mushroom. The particle size in the suspension varied greatly. While the smallest particles (the conidia) were approx. 6 μm in diameter, the largest particle diameters of approx. 500 μm were measured. The mass fraction of the conidia in the suspension, based on the total dry mass, was about 5.4%. The density of the conidia in the suspension at the beginning of the filtration process was 1.7 × 10 ^β per ml. A filter drum with a diameter of 450 mm and an axis length (cylinder length) of 250 mm was used for the filtration. The jacket of the drum was covered with a filter mesh made of stainless steel wire (weave: armored tress) with a nominal filter fineness of 17 μm.

5000 ml of the suspension described with a dry matter content of 15% were used for the filtration. The drum was driven at a speed of 25 rpm. To flush the drum jacket, a water jet was sprayed onto the filter medium using a wide jet nozzle at a pressure of 0.5 bar. When the drum rotates, the jet sweeps over the entire surface. The water supply was carried out with a throughput of 260 liters / hour. The attempt lasted 25 minutes. During this time, the continuously draining filtrate turned from initially dark brown (the conidia of C. minitans have a dark brown color) to crystal clear at the end of the filtration process. No conidia could be detected in the filtrate that last drained using the method used, while the filtrate flowing off at the beginning of the experiment had a concentration of 1.1 x 10 ^-7 conidia / ml. The amount of suspension remaining in the drum (3520 ml with a solids content of 19.9%) had a concentration of 4.2 × 10 ^A conidia / ml. The overall distribution of the conidia was as follows:

Starting suspension: 1.7 x 10 in 5000 ml

= 8.3 x 10 ¹¹ conidia

Final suspension: 4.2 x 10 ⁴ in 3520 ml

= 1.5 x lθ ⁸ conidia

Filtrate: 7.7 x 10 ⁶ in 108000 ml *

8.3 x 10 ^{13 "} conidia

*) The filtrate was not worked up further with a separator after the filtration.

The number of conidia remaining in the suspension was so small that no difference between the initial conidia amount and the conidia amount in the filtrate could be detected. The proportion of impurities in the filtrate (small particles that were not conidia) was 6.8%.

Example 2

The fungus Talaromyces flavus was grown on a growing medium consisting of rye grains. In order to release the ascospores of the fungus, which form in fruiting bodies, the so-called Kleistothezien, the mushroom-covered culture substrate was mechanically dispersed 42 days after the culture batch with the addition of water. A suspension was formed which, in addition to the ascospores of the fungus, also contained residues of the culture substrate as well as mycelium and fragments of the Kleistothezia. The pentosans originating from the cell walls of the rye were also dissolved in the liquid phase of the suspension. Pentosans (Mixture of xylose and arabinose) are cellulose-like compounds which, as mucilages, lead to a high viscosity in a concentrated suspension, which can considerably disrupt the further technological process of processing the ascospores. The aim of the experiment was therefore to separate the pentosans from the suspension. The ascospores of Talaromyces flavus should remain in the suspension.

The detection of the pentosans was carried out by detecting the xylose dissolved in the water by means of an orcine reaction in an acidic environment, the amount of xylose being able to be determined on the basis of the intensity of a color reaction. The xylose fraction is representative of the total pentos fraction.

The filter drum used had the same dimensions as in Example 1. The drum shell was covered with a filter made of stainless steel wire mesh (weave: body tress) with a nominal filter fineness of 2 μm. For the filtration, 5000 ml of the suspension described were filled into the drum with a dry matter content of 16.2%. In this amount, a xylose content of 38.7 g was determined. Furthermore, a spore concentration of 9.4 x 10 ⁷ per ml suspension was determined. The other test parameters were the same as in Example 1. The evaluation was carried out on the basis of the measurement of the spore concentration and the xylose content of the suspension still present in the drum after the test procedure. Previously, this, which had been reduced to 4390 ml by the filtration process, was made up to 5000 ml again by adding clear water. The xylose content was reduced to 0.7 g (1.8% of the starting amount). The concentration of the ascospores in the suspension decreased to 9.2 x 10 ⁷ spores / ml, which is negligible in the practical application of the method. Reference list

1 filter medium

2 drum

3 Feeding device for suspension

4 suspension

5 Detergent supply

6 filter cakes

7 flowing filtrate

8 separator

9 constituents separated from filtrate

10 tub

11 Drainage device for filtrate

12 pump

13 tub cover

14 Sim rings

15 valves

16 screw conveyor

17 Removal side of the filter tube

18 derivative

19 nozzles

Claims

claims

1. Device for the filtration of substances from suspensions characterized by a closable trough (10), in which there is a drum (2), the outer surface of which is covered with a filter medium (1), and a closable insertion part (3) for the suspension has, as well as a protruding into the tub, directed towards the drum (2) feed device (5) for a detergent, which is provided with one or more nozzles, so that the detergent is continuously applied to the entire surface of the drum, one from the tub leading drain device (11) for the filtrate.

2. Device according to claim 1, characterized in that it additionally contains a separator (8), optionally with an upstream pump (12), which has a discharge line (9) for separated components and which is connected to the detergent supply device.

3. Apparatus according to claim 1 and 2, characterized in that the drum (2) is cylindrical, closed by a cover over the opening for the suspension introduction (3) and is arranged to rotate horizontally.

4. Apparatus according to claim 1 and 2, characterized in that the drum (2) is cylindrical and rotatable on one side via an axially arranged insertion tube (3) and rotatable on the other side via an axially arranged emptying tube (11) in the tub is hung up the Pipes are sealed by oil seals (14) and each have a valve (15).

5. Apparatus according to claim 1 and 2, characterized in that the drum (2) is constructed as a filter tube, in the interior of which there is a screw conveyor (16) for conveying the suspension, the shaft of which as a hollow shaft (3) for introduction (3) the suspension is formed and which is not connected to the jacket of the filter tube (2), whereby the speed of the screw conveyor can be regulated independently of the speed of the filter tube and the feed device for the rinsing liquid has as many nozzles (19) as are necessary, the whole To spray the outer surface, the filter tube having an extra drain (18) for the cleaned suspension.

6. Device according to one of claims 1 to 5, characterized in that the filter means (1) is a conventional filter layer made of different materials with a mesh or pore size, which depends on the size of the particles to be separated or retained.

7. The device according to claim 6, characterized in that the filter means is a metal or synthetic fiber fabric.

8. Filtration process for separating particles or liquid constituents from a suspension, the liquid phase of which can also consist of an emulsion by means of a device according to one of claims 1 to 7, characterized in that the suspension in question is in the drum, and the outer surface of the filter medium by adding liquid is continuously flushed out by forcing a liquid which partially or completely corresponds to the liquid phase of the suspension from the outside through the filter medium, that the filtrate emerging through the filter medium is collected in the tub and discharged through the filtrate drainage device, then optionally a separator is fed, with the help of which the constituents to be obtained are separated therefrom, and the remaining filtrate liquid after separating the constituents to be separated is fed back to the drum, where it is used again to rinse the filter medium.

9. The method according to claim 8, characterized in that the suspension is removed again after the filtration.

10. The method according to any one of claims 7 to 9, characterized in that the particles to be separated from a suspension are fungal spores.