Filtration and emulsification device

Abstract

The invention relates to a device for the microfiltration, ultrafiltration, or nanofiltration and/or the emulsification of liquids. The device has at least one rotatable membrane medium, which has a filtrate/permeate side or a side facing a dispersed phase and a concentrate/retentate side or a side facing a coherent phase and which can be rotated in a container in order to produce a vacuum on an unfiltered liquid side or the side facing the coherent phase on partial regions of the at least one rotatable membrane medium in the container in small time segments at a frequency of 1-100 Hz. Said container has at least one feed for an unfiltered liquid or the coherent phase, at least one overflow for an unfiltered liquid or an emulsion, and at least one rotatable channel for filtrate/permeate drainage or feed of the dispersed phase, and a suction device, in particular in the manner of a suction strip or nozzle plate. The suction device has at least one suction strip or nozzle plate arranged parallel to the rotatable membrane medium or is such a suction strip or nozzle plate, which is attached at a distance of less than 0.1 to 10 mm from the membrane medium, and thus cleans non-permeating materials collected on the unfiltered liquid side during a filtration process from a surface of the membrane medium, or promotes drop formation of the dispersed phase exiting from a membrane surface on the side facing the coherent phase during an emulsification process. The invention further relates to uses of the device.

Claims

1. A device for treatment of substances, comprising: at least one membrane medium comprising a first side configured to face an unfiltered phase of a substance and a second side configured to face a filtered phase of the substance; and a housing in which the at least one membrane medium is stationary or adapted to be rotated, the housing comprising: at least one feed inlet for the unfiltered phase of the substance, at least one overflow outlet for the unfiltered phase of the substance, at least one rotatable channel for drainage of the filtered phase of the substance, and a suction device configured to produce vacuum on regions of the at least one membrane medium on the side facing the unfiltered phase of the substance, the suction device comprising at least one suction slot arranged parallel to the at least one membrane medium at a distance of 0.1 mm to 0.5 mm from the membrane medium, wherein the at least one membrane medium is a plurality of membrane media each associated with a respective membrane support element and the suction device comprises a plurality of suction elements each associated with a respective membrane medium, and wherein the membrane support elements and the suction elements are alternately stacked on top of each other onto a sleeve shaft.

2. The device of claim 1, wherein the sleeve shaft is a rotatable sleeve shaft comprising one or more tappets, each of the one or more tappets engaging with the membrane support elements.

3. The device of claim 1, further comprising a tie rod to link the suction elements and the membrane support elements to the device.

4. A device for treatment of substances, comprising: at least one membrane medium comprising a first side configured to face an unfiltered phase of a substance and a second side configured to face a filtered phase of the substance; and a housing in which the at least one membrane medium is stationary or adapted to be rotated, the housing comprising: at least one feed inlet for the unfiltered phase of the substance, at least one overflow outlet for the unfiltered phase of the substance, at least one rotatable channel for drainage of the filtered phase of the substance, and a suction device configured to produce vacuum on regions of the at least one membrane medium on the side facing the unfiltered phase of the substance, the suction device comprising at least one suction slot arranged parallel to the at least one membrane medium at a distance of 0.1 mm to 20 mm from the membrane medium, wherein the at least one membrane medium is a plurality of membrane media each associated with a respective membrane support element and the suction device comprises a plurality of suction elements each associated with a respective membrane medium, and wherein the membrane support elements and the suction elements are alternately stacked on top of each other onto a sleeve shaft.

5. The device of claim 4, wherein the sleeve shaft is a rotatable sleeve shaft comprising one or more tappets, each of the one or more tappets engaging with the membrane support elements.

6. The device of claim 4, further comprising a tie rod to link the suction elements and the membrane support elements to the device.

Description

(1) Preferred exemplary embodiments of the invention are explained below:

(2) Example 1: filtration of low-fat milk: a microsieve (filter medium) with a pore size of 0.9 microns and a membrane strength of approx. 1 micron and an open surface of >20% is installed in a revolving disc, the filter carrier, at a distance of about 5 cm from the rotational axis. The filter receptacle was filled with low-fat milk at 18-23 C. and a constant TMP of 0.1 bar was set, while the disc with the filter medium is rotated at a constant speed of 20 cycles per second. The initial filtration capacity or filtration flow (flux) was close to 8,000 L/m.sup.2/h, but decreased to less than 500 L/m.sup.2/h within several seconds. Such a reduction of the filtration capacity is typical in the state of the art with a filtration apparatus in which said type of filter medium is used. When the suction strip or nozzle plate according to the invention was used in such a way that the filter medium was periodically cleaned locally, the flux was restored to more than 5,000 L/m.sup.2/h.

(3) However, if the high-frequency flow reversal with suction strip or nozzle plate according to the invention is used from the start, the stable generation of permeate quantities of 18-30 m.sup.3/m.sup.2/h at pressures of up to a max. of 0.15 bar and with rotational speeds of 10-20 cycles per second was possible over 4-6 hours. This method allows the reduction of the bacterial load in low-fat milk, measured in CFU (colony-forming units) by 4-6 log stages. Here, the slot has a width of 0.5 mm and a distance of approximately 500 m as contrasted to the filter medium. The circumferential velocity is close to 25 cm and the effective filtration time is almost 99.7%.

(4) Example 2: unskimmed milk: the device according to the invention described above and a microsieve used as filter medium with a pore diameter of 0.9 microns was used to filter unskimmed milk with a fat content of 3.6% at 50 C. With rotational speeds of 20-30 cycles per second and the same number of backpulsing intervals, the stable filtration of 9-12 m.sup.3/m.sup.2/h was possible with pressures close to 0.2 bar over a period of 4 hours.

(5) Example 3: filtration of beer: here, a microsieve (filter medium) having a pore size of 0.6 microns is installed in a revolving disc at a distance of about 5 cm from the rotational axis. The filter receptacle was filled with unfiltered beer at 5 C. and a constant TMP of 0.1 bar was set. The rotation of the disc with the filter medium was set to a constant speed of 10 cycles per second. The initial filtration capacity (flux) is close to 12,000 L/m.sup.2/h, but decreases to less than 1,000 L/m.sup.2/h within ten seconds. If the aspiration through a suction strip or nozzle strip was added, such that the filter medium was periodically locally cleaned, it was possible to restore the average flux to a value of 8,000 L/m.sup.2/h. Here, the slot has a width of 0.8 mm and a distance of approximately 500 m as contrasted to the filter medium. The circumferential velocity is close to 25 cm and the effective filtration time is almost 99.5%.

(6) Example 4: emulsification: it is known that ceramic membranes have been studied extensively for emulsification applications with a non-rotating membrane device. Typical dispersed phase streams of an oil during the preparation of an oil-in-water emulsion by means of a ceramic membrane having an average pore size of 0.8 micrometers are 30-100 L/m.sup.2/h at an operating pressure of 3-10 bar. In that case, the average emulsion droplet size is typically a few micrometers, with a broad drop size distribution.

(7) With a device according to the invention, in which rotating microsieve membranes having slot-shaped pores with a pore size of 0.8 microns were used, it was possible to generate flows of a sunflower oil for the preparation of an oil-in-water emulsion of 3,000-5,000 L/m.sup.2/h with an operating pressure of only 0.3 bar at 40 rotations per second in the coherent aqueous phase. Surprisingly, emulsion droplets with an average size of close to 1.6 micrometers were found, with a standard deviation of the size distribution of 0.2 micrometers.

(8) FIG. 4 shows the flux if the nozzle or suction strip are operated and a local reverse flow according to the invention, as a function of the suction pressure (or energy), which is generated above the microsieve surface in order to remove particles and coatings. In this fashion, it was possible to measure an average beer filtration capacity of nearly 6,000 L/m.sup.2/h (with a TMP of 0.1 bar and at 5 C.), which was maintained for more than 16 hours.

(9) FIG. 5 shows a rotating filtration device 81, with a plurality of microsieves 82 lined up in parallel rotating in it, equipped with an integrated nozzle or suction strip 83, having an inlet, overflow and filtrate outlet 84, 85 to collect the filtrate stream 86. It can be seen that the suction device comprises various suction extensions extending between the microsieves. The concentrate liquid, which is rich in covering layer, is removed directly from the microsieves 87 at periodic intervals, during every rotation.

(10) The rapid-onset and high efficiency of the high-frequency flow reversal is illustrated below with reference to FIG. 13, wherein the setting of the pull was first reduced by 40%, then by 60% and subsequently raised back to 100%, depending on the pumping capacity with two different test fluids (low-fat milk with different fat contents, referred to as test 1 and test 2). It is clearly visible how quickly and stronglyby much more than 90%the flux decreases, especially when the pumping capacity is reduced to 40% (see reference no. 201) and how it recovers with the restoration of the original pumping capacity (100%) and thus the pull acting on the membrane surface (cp. reference no. 202), when the covering layers are effectively removed again. The diagram illustrates how quickly the filtration capacity collapses and how efficiently the flow reversal works. If the suction capacity is reduced by 60%, the flux decreases by more than 95%. As soon as the suction capacity is increased again, the covering layer is again removed immediately; the original filtration capacity (measured by the flux) is restored.

(11) Similarly, the invention can be used in a normal (non-rotating, also known as stationary) filter system, where a plate can be provided with a number of slots, which can be arranged movable with respect to the filter medium.

(12) Above, the invention has already been described with reference to the Figures. It should be noted that the exemplary embodiments illustrated in the Figures are for illustration purposes only and do not represent any restrictions of the claimed invention. In the Figures:

(13) FIG. 1 shows a schematic representation of a cross-section through a microsieve during filtration. A standard situation is shown, such as it already occurs after a short filtration time. A filter cake, a covering layer, has accumulated above the filter medium, blocking the pores.

(14) FIG. 2 shows a schematic sectional view of the invention. Compared to FIG. 1, it shows how the filter medium surface is cleaned and the blocked pores become unblocked again;

(15) FIG. 3 shows an alternative embodiment of the invention;

(16) FIG. 4 shows a flux in a filter device according to the invention;

(17) FIG. 5 shows a further exemplary embodiment in the form of a rotating, horizontally arranged stack of filter media and an analogously designed suction device;

(18) FIG. 6 shows a perspective representation of an exemplary embodiment for the scaling of the invention, comprising two multipliable and pluggable basic elements;

(19) FIG. 7 shows a top view (left), a section (middle) and a perspective representation (right) of the rotatable membrane support element;

(20) FIG. 8 shows the membrane support element having filigree support diaphragms arranged in the shape of an involute to a circle;

(21) FIG. 9 shows a top view (left), a side view (middle) and a bottom view (top right) as well as a perspective representation (bottom right) of the stationary backpulsing and membrane-protective element;

(22) FIG. 10 shows a top view of a rotatable sleeve shaft as filtrate/permeate drainage channel;

(23) FIG. 11 shows a top view of an exemplary embodiment of an emulsification device (basic module);

(24) FIG. 12 shows a cross-section of the emulsification device in FIG. 11; and

(25) FIG. 13 shows a diagram illustrating the filtration flux over time of two different test liquids depending on the pumping capacity.