WO2012032142A1 - Method and device for electrokinetic disintegration of the cellular components of aqueous suspensions without pre-comminution necessitated by the method - Google Patents

Abstract

The invention relates to a device for electrokinetic disintegration of the cellular components of aqueous suspensions, comprising a flow tube (12, 14) having a tube wall which surrounds a longitudinal passage (15), at least one pair (18) of electrodes (32), and a device (16) which generates high voltage in the range of 30 to 300 kV and to which the electrodes (32) are connected such that an electrical field is generated between said electrodes, the passage (15) having two flat opposite inner faces (24) which are parallel to one another, and the electrodes (32) being disposed within the tube wall at a short distance from and parallel to the flat inner faces.

Description

METHOD AND DEVICE FOR THE ELECTROKINETIC DISINTEGRATION OF THE CELL COMPONENTS OF AQUEOUS SUSPENSIONS WITHOUT PROCEDURE PRE-REDUCTION Technical area

The invention relates to a method and a device for electrokinetic disintegration of the cell constituents of aqueous suspensions. The apparatus includes a flow tube having a tube wall enclosing a longitudinal passageway and at least one pair of electrodes and high voltage generating means to which the electrodes are connected to generate an electric field therebetween.

State of the art

In the anaerobic stabilization of aqueous suspensions, e.g. in wastewater treatment or biogas production from agricultural waste or with renewable raw materials, dissolved and undissolved compounds serve as the substrate of various microorganisms. These are capable of producing not only biomass from the suspension via a multistep biochemical conversion (hydrolysis - acidogenesis - aceticogenesis - methanogenesis) but also flammable gases, mainly methane and hydrogen, as part of the energy metabolism. In order to achieve the highest possible yield of such combustible gases [biogas], as well as to minimize the reaction volumes of the biochemical reaction, digests are often at temperatures above ambient temperature, usually between 35 ° C and 40 ° C (mesophile) or between 50 ° C and 55 ° C (thermophile). The stability of the operating parameters such as temperature, acid capacity, pH and mixing has a decisive influence on the quality of the process, ie the gas yield during the reaction and thus the eventual energy recovery from the starting material. In all systems of this type, therefore, large amounts of energy are used for the input of heat and mixing energy.

By electrokinetic disintegration, the viscosity of the suspension can be reduced and thus the pumpability can be increased, whereby the energy expenditure for pumping and circulating decreases. The overall efficiency of the system is thereby increased.

Another application is the treatment of aqueous suspensions in the food industry, such as those incurred in the fruit juice industry. Here can be increased by the treatment of product output.

In the paper industry, paper sludge can be uniformly applied to the paper machine by homogenization, thereby improving paper quality.

Since the process also damages pathogenic germs, it can also be used for disinfection.

It has been shown that the treatment of the media to be fermented with electric fields in the high voltage range, has very positive effects on their properties such as viscosity, tendency to foam and accessibility of the residual energy content of the material.

In principle, all aqueous media are suitable for treatment whose ingredients consist at least partially of cells or cell aggregates.

From WO 2006/121397 a device for electrokinetic disintegration of the cell components of aqueous suspensions of plant material of the type mentioned is known in which the electrodes are annular integrated into the pipe wall and part of the inside of the pipe wall, so that they are pumped with the suspension in Standing in contact. The electrodes are spaced apart in the flow direction of the suspension, and between them is a likewise annular isolation region. The cross section of the flow tube may be oval or rectangular. The voltage applied to the electrodes is 0.1 to 50 kV and has a pulse rate of 10 to 500 Hz. The generated field strength is 0.2 to 10 kV / cm, with the flow tube having a diameter of 1 to 20 cm. The conductivity of the treated suspension is 0.01 to 0.50 S / m, with a tomato suspension, an energy of 0.01 to 5.0 kJ / kg is introduced. A similar device is also known from WO 2006/017738.

From WO 00/13715 a device for the destruction of pathogenic microorganisms in liquids, including blood, is known, in which the cross section of the passage opening is between 2 and 40 mm ² , the cross-sectional opening is rectangular and to opposing electrodes a voltage of up to 100 V is created. The voltage has a frequency of 400 Hz to 1 MHz. In the treatment of human blood flows a current of up to 2 A.

Similar devices for the electrokinetic disintegration of cell components of aqueous suspensions are also known from JP2001-058179, JP2002-028685, WO 2006/096151, WO 02/04356 and DE 101 44 479, in which a pulsed electric field is used.

From EP 1 741 675 a device for water treatment is known in which electrodes are connected to a DC voltage source. The electrodes are immersed in the water to be treated.

From Andreas Zacherl, "Optimization of sewage and biogas production by disintegration in the electric field", The Wasserlinse, 10/2009, page 12, a disintegration device is known in which extends axially and centrally in the flow tube, a rod-shaped electrode which is electrically insulated , A high voltage of more than 10 kV is applied to the rod-shaped electrode. It can be DC or AC in the kHz range. The electric field has a radial structure. Such a device is also known from DE 20 2010 000 025. In this design, it can lead to blockages and blockages in the pipe system. This can be avoided by pre-shredding. This pre-shredding (e.g., macerator) reduces the overall efficiency because of the need to use a lot of energy for crushing and also increases the maintenance effort due to the wear associated with comminution.

In all known devices, the flow tube must have a large length or the suspension must be passed several times through the disintegration device in order to achieve optimum disintegration for the use of the suspension, for example in a biogas plant.

In the case of disintegration devices which operate with alternating voltage and in which the electrodes are in contact with the suspension to be treated, so that current flows, the disintegration effect is likely to be due to cavitation which arises when discharging at the surface of the electrodes.

In systems where disintegration is caused by a high-voltage DC field or AC field kV, application of an electric field higher than the cell's critical membrane potential will permanently destabilize the cell membrane and eventually destroy the cell membrane ,

Presentation of the invention

The invention has for its object to increase the effectiveness of the disintegration.

According to the invention, this object is achieved in a device of the type described above in that the passage opening has two opposite and mutually parallel, planar inner surfaces and that the electrodes are arranged within the tube wall at a small distance from and parallel to the flat inner surfaces.

In the method according to the invention, this object is achieved in that the electric field over the cross section of the passage opening is uniform.

Because the electrodes are flat and parallel to one another, the generated field strength over the cross section of the passage opening is substantially uniform.

Preferably, the passage opening has a rectangular cross section with flat inner surfaces and the electrodes extend substantially over the full width of the rectangular cross section of the passage opening. Thereby, the uniformity of the electric field is further improved.

Disintegration devices with an axial, central rod electrode have hitherto been used in practice, in particular. Immediately at the rod electrode, the field strength is very high and decreases radially outward. Cell components that move in the edge region of the passage opening, thereby experiencing a lower field strength and may not suffer disintegration. Among other things, this has the consequence that the suspension or the medium must be treated several times. In such a rod electrode holders are required at the end. These easily lead to blockages or blockages of the passage opening. The fact that the electrodes are integrated into the pipe wall in the integration device according to the invention, the passage opening is free, so that the risk of clogging or blocking by an axial, central rod electrode or its support no longer exists.

The electrodes are useful metal strips which are integrated into the wall of the flow tube and are insulated by a plastic layer of about 1 mm thickness of the free cross-section of the passage opening and thus of the suspension to be treated. The disintegration therefore takes place without current flow and only through the electric field, so that the power consumption is extremely low, and e.g. less than 50 watts.

Preferably, two or more electrode pairs of alternating polarity are arranged behind one another along the passage opening. By changing the polarity, the disintegration effect is also enhanced. The polarity of the electric field then changes along the flow tube.

Preferably, the disintegration device is constructed in such a way that a metal outer tube is spaced around an inner tube of glass fiber reinforced plastic, wherein the number of electrode pairs rests on the outside of the inner tube. The high voltage device is located in the space between inner tube and outer tube. The high voltage device preferably consists of two power supplies, each having a controllable positive or negative high voltage of e.g. generate up to 150 kV. Between the electrodes is then the double voltage, ie up to 300 kV. Preferably, the high voltage device generates DC voltage. However, AC voltage is also possible, the frequency being 1 Hz to 5 MHz, preferably 1 Hz to 5 kHz. These two power supplies are located on opposite sides of the inner tube. The remaining space between the inner tube and outer space is potted with plastic and may still be surrounded by a polypropylene tube, which acts as a protective screen. The metal outer tube serves as a heat sink for the high voltage device and at the same time as grounding of the device.

If the high-voltage device contains only a single power supply, one of the electrodes is at earth potential.

Overall, the flow tube of the disintegration device may be a tube element with a length of about 2 m, wherein the passage opening has a rectangular cross section of 7 by 12 cm. Two pairs of electrodes lie on the wider side of the rectangular cross section and the electrodes accordingly have a width of about 12 cm. Their length can be about 55 cm. At each end of the tubular element, a DN150 flange connection with reductions can be located on the rectangular cross-section of the passage opening.

The inventive method and apparatus for disintegration is for the treatment of suspensions such as excess sludge, primary sludge, circulating sludge, substrates from agriculture, waste from the food industry, etc. suitable. During the residence phase in the space between the electrodes, the physical and chemical properties of the suspension are positively influenced with regard to further processing. The suspension is better flowable and thus easier to pump. The tendency to foaming is reduced. Homogenization of the suspension can also be detected. In addition, an increased biogas yield in the anaerobic stabilization compared to untreated sludge is achieved. In the end, this also increases the degree of digestion, which in turn has positive effects on drainability and the chargeable disposal of residual sludge.

Brief description of the drawings

An embodiment of the invention will be explained below with reference to the drawing. Show it:
Figure 1 in a spatial representation and in section, the device for disintegration of digested sludge.
Figure 2 shows in section a part of the disintegration device with two pairs of electrodes.
3 shows the disintegration device in longitudinal section;
Fig. 4, the disintegration device rotated by 90 ° in longitudinal section;
Fig. 5, the disintegration device in section to 5-5 of Fig. 4 and
Fig. 6 shows a possible flow diagram of a plant in which the disintegration device is installed.

Best way to carry out the invention

The disintegration device 10 has a flow tube, which is formed from a circular cylindrical outer tube 12 and an inner tube 14, and in the space between the outer tube 12 and the inner tube 14, a high voltage device 16 and two pairs of electrodes 18, 20, located on the outside of the inner tube 14 lie.

The inner tube 14 has over almost its entire length a passage opening 15 of rectangular cross-section, so that the passage opening is bounded by flat inner surfaces 24. The aspect ratio of the rectangular cross section is about 1: 2. At each end, the inner tube 14 has only one flange connection 22, to which a reduction 26 adjoins the rectangular cross-section. The inner tube 14 is made of fiberglass-reinforced plastic. In the region of its rectangular cross-section, the inner tube 14 has a wide outer surface 28 and a narrow outer surface 30.

The electrodes 32 of the first and second pairs of electrodes 18, 20 are each metal strips, which are placed on the wide outer side 28 of the inner tube 14. The electrodes 32 of each electrode pair 18, 20 are each arranged opposite one another, wherein a distance of a few centimeters exists between the first electrode pair 18 and the second electrode pair 20.

In the space between outer tube 12 and inner tube 14, the high-voltage device 16 is further arranged, which consists of two power supplies 34, 36. Each electrode 32 is connected to a power supply 34, 36. The power supplies 34, 36 are each potted in a block and can generate a voltage of up to + or - 150 kV DC or AC voltage with 1 Hz to 5 MHz. In order to avoid punctures, it must be ensured that no air pockets remain in the power packs 34, 36 when casting. The voltage applied between the electrodes can then be up to 300 kV. The output voltage is linearly dependent on the input voltage within a control range of 30 kV to 150 kV. For the generation of DC voltage cascade circuits and for the generation of AC voltage transformers are used. The electrodes 32 are connected to the power supply units 34, 36 such that the electrode pairs 18, 20 have opposite polarity. Since the electrodes 32 are isolated from the suspension to be treated by the material of the inner tube, no conduction current flows but only displacement current. Due to the galvanic separation of the two electrodes no electron flow through the suspension or lines takes place. It comes so outside the high voltage device itself to no power consumption of the system. The power consumption of the power supplies is therefore only about 50 watts.

Incidentally, the space between the inner tube 14 and the outer tube 12 is filled with a potting compound 38, wherein the potting compound 38 is still surrounded by a polypropylene tube 40, which is located directly within the metal outer tube 12 and together with the potting compound as a protective screen before high voltage serves.

FIG. 2 shows in detail the region of the disintegration device 10 in which the two pairs of electrodes 18, 20 are located. Inside the inner tube 14, digested sludge 42 is pumped through. The electrodes 32 are located within the potting compound 38 and lie directly on the outside of the inner tube 14. The potting compound 38 surrounds the inner tube 14 and is enclosed in the polypropylene tube 40. The polypropylene tube 40 is in turn surrounded by the metal outer tube 12.

As mentioned, the two electrode pairs 18 and 20 are oppositely poled, so that when the digested sludge 42 flows through, the charges on the cell membrane of the cell components are forced to rearrange. This charge change leads to a high osmotic pressure, which dissolves the cell composite and destroys the cell membrane.

FIGS. 3 to 5 show the structure of the disintegration device 10 true to scale, wherein in particular it can be seen in FIG. 3 that the electrodes 32 extend over the entire width of the longer dimension of the rectangular cross section of the inner tube 14.

In the application of the disintegration device 10 according to the invention shown in FIG. 6, the suspension to be treated, which is digested sludge 42, is stored in a container 44 and pumped through the disintegration device 10 by a pump 46. The container 44 may be a storage container in which the digested sludge is buffered, in which case it is then sent through the disintegration device 10 several times a day. The container 44 may also be a fermenter or digester, the digested sludge then being sent through the disintegration device 10 only once a day, due to the size of the container 44.

LIST OF REFERENCE NUMBERS

10 disintegration device 12 outer tube 14 inner tube 15 passage opening 16 high voltage device 18 first electrode pair 20 second electrode pair 22 flange connection 24 inner surface 26 reduction

28 wide outside 30 narrow outside 32 electrodes 34, 36 power supplies 38 potting compound 40 PP pipe 42 digested sludge 44 containers 46 pump

Claims (10)

1. Device (10) for the electrokinetic disintegration of the cell components of aqueous suspensions

   a flow tube (12, 14) having a tube wall enclosing a longitudinal passage (15),

   with at least one pair (18) of electrodes (32), and

   with a device (16) for generating high voltage in the range of 30 to 300 kV, to which the electrodes (32) are connected, so that an electric field is generated between them,

   characterized,

   the passage opening (15) has two opposite and mutually parallel, flat inner surfaces (24),

   the electrodes (32) are arranged within the tube wall at a small distance from and parallel to the flat inner surfaces.
2. Apparatus according to claim 1, wherein the passage opening (15) has a rectangular cross-section.
3. Apparatus according to claim 1 or 2, wherein the electrodes (32) are planar.
4. Apparatus according to any one of the preceding claims, wherein the means (16) for generating high voltage generates DC voltage.
5. Apparatus as claimed in any one of the preceding claims, wherein the passageway (15) is free of any flow obstructing means, protrusions, brackets and the like.
6. A device according to any one of the preceding claims, wherein the spacing of the electrodes (32) is about 10 cm and one electrode has a voltage of +30 to +150 kV and the other electrode has a voltage of -30 to -150 kV.
7. Apparatus according to any preceding claim, wherein a plurality of pairs (18, 20) of electrodes (32) are disposed along the flow tube (12, 14) and the polarity of the electrodes (32) is alternating.
8. Process for the electrokinetic disintegration of the cell components of aqueous suspensions, wherein

   the aqueous suspension is passed through a flow tube (12, 14) having a tube wall enclosing a longitudinal passage (15),

   in the passageway through (15), a pair (18) of electrodes (32) disposed within the tube wall generates an electric field by means of high voltage in the range of 30 to 300 kV,

   characterized,

   the electric field is uniform across the cross section of the passage opening (15).
9. The method of claim 8, wherein high voltage is DC.
10. The method of claim 8 or 9, wherein the polarity of the electric field changes along the flow tube (12, 14).

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