WO2009021588A2

WO2009021588A2 - Mixture of filter aids for use in precoat filtration and also processes for precoat filtration of liquids

Info

Publication number: WO2009021588A2
Application number: PCT/EP2008/005827
Authority: WO
Inventors: Andreas Zeller
Original assignee: Khs Ag
Priority date: 2007-08-16
Filing date: 2008-07-17
Publication date: 2009-02-19
Also published as: DE102007038828A1; WO2009021588A3

Abstract

The present invention relates to a mixture of filter aids for use in precoat filtration of liquids, and a process for precoat filtration using such a mixture. The above-mentioned mixture is characterized by a) fibres having a fibre length up to approximately 300 μm in a concentration of approximately 80% by weight up to approximately 100% by weight and, if appropriate, b) fibres having a fibre length of greater than 300 μm and up to approximately 700 μm in a concentration of approximately 1% by weight up to approximately 20% by weight.

Description

Mixture of filter aids for use in precoat filtration and precoat filtration of liquids

The invention relates to a mixture of filter aids for use in the precoat filtration of liquids and an associated method for precoat filtration.

Liquids such as, for example, drinks and, in particular, beer have, after their preparation, admixtures of solids which can be attributed to turbidity, which inevitably occurs during production. In order to filter out these turbid matter or solid admixtures, so-called precoat filtration has proven to be particularly favorable. In this procedure, a porous filter cake is formed on, for example, a horizontal disk filter, which retains the turbid substances in a physical-mechanical way.

The addressed horizontal disc filter or horizontal screen thus acts as a basis for the forming filter cake. This is mostly a precoat layer of specifically intended to be cleaned liquid, the unfiltered, metered filter aid, which may be, for example, diatomaceous earth. The filter aid settles on the basis, because the liquid to be filtered or the unfiltered in the example flows through the filter cake and a usually net-like filter bottom in a Filtratraum and can then be withdrawn as filtered liquid. In this way, the filter cake built up predominantly from the filter aid forms a sufficiently porous structure to pass the subsequently clarified liquid. DE 103 40 366 A1, DE 198 04 494 A1 or DE 39 00 934 A1 describe such filter systems.

In contrast, in the pores or capillaries of the filter cake in the course of filtration, the turbid substances are retained. These are increasingly due to addition of the aforementioned openings, so that the filtration process from a certain minimum permeability no longer needs to be continued and the filter cake must be removed. In addition, the attachment described is automatically associated with an increase in pressure differences between on the one hand the Unfiltratraum and on the other hand, the filtrate. Since diatomaceous earth, for example, is increasingly criticized as a filter aid, because its use is said to harm certain consumer health risks and, moreover, disposal becomes increasingly critical, in the past it has already resorted to cellulose as a renewable raw material for use as a filter aid, as described in DE 198 04 882 A1 is described. In fact, cellulose can be used with virtually no harmful effects and can easily be disposed of or reintroduced into a natural cycle. Thus, the aforementioned German Offenlegungsschrift describes a filter aid from a mixture of exclusively natural organic components.

In addition, EP 0 460 499 B1 has disclosed a mixture of filter aids of different morphological and physical properties. In fact, a chemically resistant mixture component of a fibrous or granular structure and additionally one based on plastic and / or cellulose fibers is used. This is intended to maintain the filtration-active structure of the filter aids used in their regeneration, so that the filtration properties do not change despite repeated use.

Also relevant to the prior art is DE 10 2004 062 617 A1, which deals with a filter aid which is composed of a base material mixed with active ingredients. The base material is a cellulose fiber while the active ingredients are at least one cellulosic fiber having an average fiber length and fiber thickness other than the base material. In addition, a thixotropic agent in the form of polyethylene fibers is used.

The state of the art can not convince in all matters. Because the previous filter aid mixtures and the filter cake formed therefrom have a too rapid differential pressure increase and thus a relatively low filter performance.

In fact, the pores and capillaries of the filter cake settle relatively quickly through the turbidity, so that it to the already described

Differential pressure rise and ultimately the uselessness of the filter cake comes in total. This is the case in the prior art after a short time, so that the filter cake by, for example, backwashing from the base (For example, a filter cartridge) blasted and removed from a filter tank must be. This is time consuming and leads to production interruptions, for example in beer production. In addition, it has been found that the previous mixtures of filter aids do not sufficiently reduce the turbidity within the liquid or that there are still too many turbid substances in the filtered liquid or in the filtrate space. The invention aims to remedy this situation.

The invention is based on the technical problem of specifying a mixture of filter aids for use in the precoat filtration of liquids, which is characterized by an increased filter performance and sufficient turbidity reduction compared with the prior art.

To solve this technical problem, a mixture of filter aids, in particular cellulose-based for use in the precoat filtration of liquids is characterized by

a) fibers having a fiber length up to about 300 microns in a concentration of about 80 wt .-% up to about 100 wt .-% and optionally

b) fibers having a fiber length of more than 300 μm and up to about 700 μm in a concentration of about 1% by weight up to about 20% by weight

as mixture components.

Thus, the invention deliberately makes use of a mixture of different fibers with different fiber lengths, wherein deliberately different ranges have been chosen for the fiber lengths than, for example, in the context of EP 0 460 499 B1. This also applies in contrast to DE 10 2004 062 617 A1. In fact, the mixture according to the invention of the fibers predominantly uses those having a fiber length of up to about 300 μm. Only 1/5 or less of the concentration of the mixture of the fibers or the filter aid as a whole is occupied by fibers having a fiber length in the range of more than 300 microns and a maximum of 700 microns. In this composition of the mixture of the fibers with the described lengths has surprisingly been found that a special suitability for the filtration is observed and overcome the aforementioned problems.

On the one hand, the respective fibers forming the mixture are able to provide a filter cake of low porosity in order to be able to effectively retain the low-volume turbidity substances and / or yeasts in beer in the example case. On the other hand, a low filter performance is reliably avoided because the present with a maximum fiber length to a maximum of 1/5 in the mixture blocking of the filter cake is avoided and keep these fibers virtually unchanged channels into the interior of the filter cake and define. In other words, the pores in the filter cake are used over the entire cross-section and the entire thickness and, in particular, near-surface layer areas do not settle with turbidity, which would mean a rapid rise in differential pressure and a low filter performance.

According to an advantageous embodiment, the mixture component a) with the fibers of a fiber length up to about 300 microns over a fiber thickness of up to 20 microns. In contrast, the mixture component b) covering fibers with a fiber length of more than 300 microns up to about 700 microns, equipped with fibers of a fiber thickness of more than 20 microns and up to about 40 .mu.m, in particular up to about 30 microns , In this way, the effect described above is still supported by the mixing component a), which mainly supplies the small pores and capillaries, and the associated fibers have a relatively small fiber thickness in order to be able to assume the random arrangement required for this purpose. In contrast, the longer fibers of the blend component b) are equipped with larger fiber thicknesses in order to support the effect as through passageways in inner layers of the filter cake as it were.

The mixture component a) may be one which in turn is composed of two or even more subcomponents. It has proved to be beneficial when the mixture component a) from

a1) fibers with a fiber length of more than 100 microns and up to about 200 microns in a concentration of 20 to 60 wt .-% and a2) fibers having a fiber length of up to about 100 μm in a concentration of 1 to 30% by weight

in each case based on the mixture as a whole.

Furthermore, the invention recommends that the abovementioned subcomponent a2) of the mixture component a) only contains fibers up to a fiber length of up to about 50 μm. It is very particularly preferred if the subcomponent a2) in question is composed essentially of fibers having a fiber length of about 30 μm and about 23 μm.

As subcomponent a1) of the mixture component a), the invention recommends predominantly to use such fibers having a fiber length of about 120 μm and fibers having a fiber length of about 200 μm. In other words, the subcomponent a1) is composed, according to a particularly preferred embodiment, essentially of fibers of the fiber length of about 120 μm and those of the fiber length of about 200 μm. In sub-component a2) also a fiber mixture of predominantly fibers of the fiber length of about 30 microns and those of the fiber length of about 23 microns is used. In other words, the two subcomponents a1) and a2) of the mixture component a) are in turn composed of mixtures of two fibers of different fiber lengths in the specified dimensions.

The fibers of the mixture component b) are usually equipped with a maximum fiber length of about 600 microns. In fact, at this point predominantly only fibers of the fiber length in question of approximately 600 μm are used for the mixture component b) and no further fibers thereof deviate in fiber length.

The mixture according to the invention of the described filter aids can be used in such a way that the fibers according to a) and those according to b) are each used together as a mixture in a filtration stage. In most cases, two filtration stages are used, which can make use of a matching mixture of the fibers according to a) and the fibers according to b). But it is also possible, the two filtration stages with mixtures of the fibers according to a) and according to b) in different composition within the described ranges.

In addition, it is within the scope of the invention to use the filter aids or fibers according to a) in a filtration stage and the fibers according to b) in another filtration stage. In this respect it can be explained that the mixture described and claimed for protection need not necessarily contain fibers according to a) and those according to b). But it can be used in example, a first filtration stage or in the first filtration filter aid, which is equipped only with fibers according to a). In the second filtration or in the second filtration stage then only fibers according to b) may be used. As a rule, however, a mixture of fibers according to a) and fibers according to b) are used in the second filtration.

If several filtration stages are used, the sum of the mixture components, ie the fibers according to a) and those according to b) or only the fibers according to a) each covers a range of 100% by weight per filtration stage. In this case - as already stated - in the first filtration and in the second filtration with a mixture of fibers a) and b) are used, each of which accounts for 100 wt .-% of the filter aid in the respective filtration stage. Alternatively, it is also conceivable that in the first filtration only fibers according to a) to 100 wt .-% determine the filter aid, while the second filtration resorted to a mixture of fibers according to a) and b) to 100 wt .-% as a filter aid ,

The fibers for the mixture according to the invention are in particular produced on a cellulose basis. D. h., It come for both the fibers a) and the fibers b) predominantly those of cellulose, ie cellulose fibers are used. In principle, however, it is also conceivable and is covered by the invention to resort to fibers made of plastic. That is to say, the fibers according to a) and the fibers according to b) can also be plastic fibers. Of course, mixed forms are also conceivable, d. H. the fibers according to a) are cellulose fibers while the fibers according to b) are synthetic fibers and vice versa.

The invention also provides a process for the precoat filtration of liquids, in which a mixture of filter aids as described above is used. In this process, the individual Mixing components a) and b) respectively a1) and a2) and b) before being used in each case by stirring either individually or together dissolved in water. As a result, individual suspensions or a total suspension are formed in each case, which is added to the liquid to be filtered.

In this case, the individual suspensions in different stages or together of the liquid to be filtered, the unfiltered be added. In addition, it has proven useful if the suspension in question (single suspension and / or total suspension) of water and the one or more mixture components is additionally subjected to shearing during their production. This shearing impingement can advantageously be achieved and, as it were, achieved automatically so that the suspension is circulated during its production and in this case undergoes a corresponding impingement by a centrifugal pump. By virtue of the wings for the liquid transport which are obligatorily provided in a centrifugal pump, the shearing forces described are exerted on the fibers and the partly lumpy cellulose is dissolved properly in the water.

This is especially true in the case that, according to an advantageous embodiment, the fibers of the mixture component a) or the fibers of the mixture component b) or both fibers are designed to be fibrillated, that is, have a split shape. Such spiked or fibrillated fibers form a matting precoat layer and a correspondingly designed filter cake. This is characterized by a special mechanical stability.

Overall, applies to the filter aid according to the invention or the filter cake produced therefrom, that this can be regenerated much easier than, for example, kieselguhr and represents a real alternative to the relevant filter aid (kieselguhr). In fact, the fibers can be easily regenerated into lye, in particular cellulose-based, more than once. In addition, the disposal succeeds easily, can be implemented for example by composting, as part of a biogas plant in the gasification or combustion.

In the following, the implementation of the method will be explained in more detail with reference to an exemplary embodiment. The single FIGURE shows a filter device for Precoat filtration of liquids, in particular beer, with the aid of filter aids preferably based on cellulose.

In the figure, two filters 1, 2 connected in series are shown, each of which is a filter vessel 1, 2. The filter tanks 1, 2 may in each case be constructed as described in DE 103 40 366 A1. In fact, the filter vessel 1, 2 have a central distribution pipe, in which a

Liquid line 4 opens. As filter so-called plate filter 3 come

Use, which are only indicated by way of example and wear the precoat or serve to build the filter cake. Both filters 1, 2 form through their

Series connection one behind the other a so-called tandem filtration.

In order to be able to form the precoat layer for forming the filter cake on a base or the plate filters 3 in the example, a suspension of water and the previously described filter aid or the mixture of filter aids is added through the respective liquid line 4 and a certain time on the Pumps 9 and 10 conveyed in a circle until the required layer is built on filter aid. In an alternative alluvial process eliminates the circulation pump 9 with the associated conduction path, and the circulation flow is funded solely by the pump 10 on the dashed lines shown conduit 11, wherein the corresponding suspension is added in front of the filters 1 and 2.

For the purpose of metering the respective liquid line 4 so-called buffer container 5 associated with which the filter aid or the mixture of the

Store filter aids respectively the suspension and into the liquid line

4 meter. For this purpose, a respective feed pump 6, which the suspension in the

Liquid line 4 (regulated) initiates. In the buffer container 5 rotates one each

Stirrer, in particular a bar stirrer, which ensures that the introduced into the water buffer container 5 introduced fibers are dissolved. In addition, one provides

Centrifugal pump 7 in the example case that the gradually forming suspension in the buffer tank 5 is recycled.

Thus, in this process, no suspension enters the liquid line 4, a switching valve 8 is provided between this circulation or the buffer tank 5 and the feed pump 6, which during this process the Buffer tank 5 and the circulation of the feed pump 6 and thus the liquid line 4 separated. The described stirring or the circulation is carried out for about one hour.

In the first filter 1 a so-called first filtration can be carried out in order to reduce the turbidity unavoidable in beer. As part of this Erstfiltration a mixture of fibers according to a) and those according to b) is used. But it is also possible to work at this point only with fibers according to a), as will be expressed below in the context of embodiment 3.

The subsequently filtered liquid leaves the filter 1 via a non-filtrate channel, which opens into a further liquid line 4 between the filter 1 and the filter 2. In this way, the already filtered in the filter 1 liquid passes through the further liquid line 4 into the filter 2, in which the second filtration takes place. At this point, a mixture of filter aids with fibers according to a) and b) is used throughout. Here, the number of yeast cells necessarily present in the beer is reduced to almost zero or zero, and the required turbidity is also set. Both buffer containers 5 work for the construction of the precoat layer or of the filter cake on the base or the plate filters 3 with the above-described mixture of cellulose fibers of different fiber length and possibly different fiber diameter.

In the following examples, various cellulose fibers are described, which are characterized by the numbers 1 to 6 and differ essentially by the fiber length and the fiber diameter.

Embodiment 1

As a particularly suitable mixture composition for the filter aid according to the invention, the following mixture components have been found

Embodiment 2:

Particular preference is given to a first filtration followed by a second filtration, which makes use of the subsequently described mixture components in the concentrations indicated:

The mode of action of the mixtures used in the context of the embodiment 2 in the context of Erstfiltration and second filtration is particularly clear on the basis of the measurement protocols according to FIGS. 2 and 3. Here, Fig. 2 shows the filtration process in the first filtration, ie in the filter 1 of the filter system according to Fig. 1. On the Y-axis, the turbidity in the unit EBC (European Brewery Convention) is shown on the left. The specified angles of 25 ° and 90 ° correspond to the measuring angle for the described turbidity measurement. This is how diatomaceous earth turns out Values between 0.3 to 0.9 EBC, whereas cellulose corresponds to 0.6 to 0.7 EBC.

Also on the left Y-axis, the flow through the respective filter, as part of the Erstfiltration through the filter 1, shown, in hectoliters per hour: 10 (hl / h / 10). The X-axis represents the time in hours. The differential pressure is shown on the right Y axis.

It can be seen that during the first filtration the differential pressure in bar rises slowly and even after 8 hours has just exceeded values of 0.5 bar. As desired, the haze at 25 ° and that at 90 ° decrease, i. h., the desired filtering effect is observed.

In FIG. 3, the conditions in the second filtration are therefore shown in the filter or filter vessel 2. Also in this case, the flow remains substantially constant and is expected only after 7 to 8 hours with a relevant increase in the differential pressure.

Claims

claims

1. Mixture of filter aids for use in the precoat filtration of liquids, e n c e c e m e n d a c e m e n d

a) fibers having a fiber length up to about 300 microns in a concentration of about 80 wt .-% to about 100 wt .-% and optionally

as mixture components.

2. Mixture according to claim 1, characterized in that the mixture component a) has a fiber thickness up to about 20 microns and the mixture component b) such from more than 20 microns and up to about 40 microns, in particular up to about 30 microns , having.

3. Mixture according to claim 1 or 2, characterized in that the mixture component a) consists of two or more subcomponents and namely as follows:

a1) fibers having a fiber length of more than 100 μm and up to about 200 μm in a concentration of about 20% by weight to about 60% by weight,

a2) fibers having a fiber length of up to 100 μm in a concentration of about 1% by weight to about 30% by weight

in each case based on the mixture as a whole. 2

4. Mixture according to claim 3, characterized in that the subcomponent a2) of the mixture component a) only contains fibers up to a fiber length of up to about 50 microns.

5. Mixture according to claim 4, characterized in that the subcomponent a2) of the mixture component a) consists essentially of fibers having a fiber length of about 30 microns and those having a fiber length of about 23 microns.

6. Mixture according to one of claims 3 to 5, characterized in that the subcomponent a1) of the mixture component a) consists essentially of fibers having a fiber length of about 120 microns and those having a fiber length of about 200 microns.

7. Mixture according to one of claims 1 to 6, characterized in that the fibers of the mixture component b) have a maximum fiber length of about 600 microns.

8. Mixture according to one of claims 1 to 7, characterized in that as fibers such plastic, cellulose or mixtures are used.

9. Mixture according to one of claims 1 to 8, characterized in that the fibers according to a) and the fibers according to b) are used in each case in a filtration stage in a multi-stage filtration.

10. Mixture according to one of claims 1 to 9, characterized in that only the fibers according to a) are used in a filtration stage and a mixture of fibers according to a) and b) in another filtration stage in a multi-stage, in particular two-stage, filtration.

11. A method for precoat filtration of liquids by means of a mixture of filter aids according to any one of claims 1 to 10, wherein the individual mixture components a) and b) before use by stirring either individually or jointly dissolved in water.

12. The method according to claim 11, characterized in that a suspension of water and the one or more mixture components a) and b) is applied additionally shearing in the course of their production.

13. The method according to any one of claims 11 or 12, characterized in that different mixtures according to a) and b) are used in the filtration stages in a two-stage filtration, wherein the proportion of fibers to b) in the second stages by 5% to 15% and in particular increased by 10%, and the proportion of the fibers according to a) is lowered by the same value in the second stage.

14. The method according to claim 13, characterized in that the reduction of the proportion of the fibers according to a) exclusively or almost exclusively fibers according to a1) and the proportion of fibers according to a2) remains unchanged or virtually unchanged.