DE102007031984A1 - Reactor for high-voltage impulse-type disinfection of bacteria-contaminated liquids and method - Google Patents

Abstract

A reactor for the high voltage impulse disinfection of bacteria-contaminated liquids is presented: it has a convex, simple polygonal or round cross-section and a parallel electrode arrangement of two electrode bands that are perpendicular and mirror-symmetrical with respect to the longitudinal axis and electrically insulated from each other. One electrode is connected to an electrical reference potential and the other, the high voltage electrode, is connected to a high voltage electrical potential adjustable in duration and height, or the electrode assembly is coaxial with inner and outer conductors. On the high voltage potential can be acted upon electrode is a 100 to 300 micron thick ceramic layer. Both electrodes face each other with such a maximum distance that in case of application of high voltage potential by the high voltage between the two electrodes in each case no flashover forms, but also with a minimum distance, such that it at the exposed surface of the ceramic layer during the Anstehens of electrical high voltage potential at the high voltage electrode to form a maximum field strength of at least 1 MV / cm comes without sparkover.

Description

The The invention relates to a reactor for high voltage impulse technology Disinfection of bacteria-contaminated liquids and a procedure for operating the reactor.

to Water disinfection is becoming prevalent today Chlorine and its compounds used. This can be harmful to health Produce by-products that are difficult to biodegrade. This especially true if the polluted water is significant Contains quantities of organic substances. Therefore, increasingly chemical processes for water disinfection by physical processes replaced.

conventional Chemical disinfection can lead to unwanted toxic by-products, such as trihalomethane, THM, or bromine-chlorine compounds to lead. This is especially true when the water is very much organic Contains material.

The Use of ozone as the only disinfectant required very high doses to achieve effective disinfection. at Use of ozone creates significant amounts of toxic compounds, especially in the presence of bromides.

at the use of gamma, x-ray or Electron irradiation, the efficiency is usually very low and the Equipment and operating costs therefore very high, in particular, because effective radiation shielding is required.

UV radiation is in cloudy Water because of too low penetration depth is not effective and can also uncontrollable mutagenic changes of the bacterial genome.

Of the Invention has for its object to provide a reactor available with which a highly effective, high voltage impulse technology method for the disinfection of bacterially contaminated water, in general bacterially contaminated liquids, carried out can be. About that In addition, such a reactor should be technically and structurally simple Facility that is without additional peripheral Protective devices manages.

The The object is achieved by a reactor having the features of the claim 1 and the feasible Process according to the method steps of claim V1 solved.

The Invention introduces a reactor and a process, bacterial contaminated liquids, in particular bacterially contaminated water, using pulsed underwater corona discharges effectively disinfect or kill germs effectively.

Underwater corona discharges have been mainly to destruction investigated complex chemical substances. For these basic studies were mostly used tip plate arrangements. Such electrode configurations have short lifetimes because the electrode tips burn off quickly. Also, such electrode geometries can not be high Mass flow rates scale that for an industrial use for liquid disinfection are required.

The underwater corona discharge creates a non-thermal plasma channel, in the device here: many non-thermal plasma channels in which the electrons reach energies of a few eV. Electrons with these energies can split the water molecules / dissociate and ionize and thereby different, very reactive radicals, such ^as:. OH, ^H. , ^O. , HO ₂ ^. , and molecules: H ₂ O ₂ , H ₂ and O ₃ , produce. In addition, the plasma channel is a source of intense UV radiation and shock waves, which in turn leads to the production of free radicals. At the top of the plasma channel, electric fields of more than 200 MV / cm are achieved, which destroy the membrane of biological cells by electroporation. The combination of these effects leads to a very effective killing of microorganisms / germs and moreover to the destruction of toxic organic substances in the liquid, in the water.

The Invention solves the problem of splitting / germ destruction by generating a large number of corona channels, also known as streamer channels in technical language, at one with a thin porous ceramic layer coated anode.

According to claim 1, the reactor for the high voltage impulse disinfection of bacteria-contaminated liquids is constructed as follows:
It consists of a pipe section which can be flange-mounted on its two end faces and has a light, simply polygonal, but at least rectangular cross section or a light, simply convex, round cross section. A with respect to the longitudinal axis of the pipe section parallel electrode arrangement of two vertically and with respect to the longitudinal axis mirror image opposing, electrically insulated from each other electrode bands over most of the length of the pipe section and the polygonal cross section over at most the width of the polygon side. The lateral surfaces in polygonal cross-section are preferably flat.

The one electrode is connected to an electrical Be zugspotential, often ground potential, and the other, the high voltage electrode, connectable to a pulse-shaped, in the duration and height adjustable electrical high voltage potential. The high voltage electrode is covered on the exposed inward, or counter-electrode exposed surface with a porous ceramic layer.

Of the But the reactor can also from a respect to the longitudinal axis of the pipe section coaxial / concentric electrode arrangement of the at least electrically conductive inner wall, the outer conductor, and the coaxial inner conductor. Then one of them, preferably the outer conductor, on an electrical reference potential and the inner conductor to a in the Duration and height Adjustable electrical high voltage potential connectable. But also in this design, the high voltage electrode on the opposite electrode exposed area with a porous one Ceramic layer, as described above, covered. In all designs is the layer thickness of the porous Ceramic layer in the range of 100 to 300 microns. The two electrodes have have a distance to each other such that on the exposed surface of the Ceramic layer during the presence of the high voltage electrical potential at the high voltage electrode an electric field strength of at least 1 MV / cm without sparkover exists. Herewith is a receptive guide to the electrical and structural Dimensioning on a case-by-case basis to allow for planned throughputs, as planned, to be able to process. An embodiment is described below. It is essential that during the pulse duration no breakdown, d. H. a short circuit, takes place. However, many streamer during the High voltage pulse between and along the liquid to be processed padded Form electrode gap.

electrical are the high voltage pulse generator and the reactor on the one hand simply connected. For an electrically constantly changing one Load could then maybe electrical measures to protect the generator from problematic Reflections may be necessary. With only slightly changing load can such a reflection protection by impedance matching between Generator and reactor are easily solved.

Useful embodiments are described in the dependent claims 2 to 6:
For liquid inlet and outlet at least one connecting piece is attached to the two end regions of the reactor space. For diagnostics and analysis purposes, at least one additional connecting piece is located in the tube wall in the reactor area area (claim 2).

By a high voltage feedthrough in the pipe wall is the inner conductor with a high voltage pulse generator connected. The tube wall, at least the electrically conductive tube inner wall is connected to a reference potential, usually ground potential, so that at ground potential surrounding safety shields omitted can.

For the business It is advantageous if the ceramic layer reliably adheres to the inner conductor, as consistently in the streamer discharge also shock waves arise. This is still possible according to claim 4 support as the ceramic and the inner conductor material are not too different thermal expansion coefficients of the ambient temperature up to the operating temperature, preferably they are similar to equal.

Opposite the process liquid and the reaction products formed by the pulsation at least the inner surface be inert in the reactor space, or is the reactor of such materials be constructed (claim 5).

in the In case of coaxial electrode construction, there is a geometrically more extensive one Construction of only re the two electrode axes existing coaxiality and a Closer construction of the electrode coaxiality with position equality two similar ones Cross sections of the inner electrode and the clear width of the outer electrode. Both constructions of the coaxial, concentric reactor are required 6 characterizing described, namely that in the case of coaxial, concentric Electrode arrangement of the clear cross-section of the outer electrode is arbitrary to the cross section of the inner electrode, preferably however, the internal electrode cross section is characterized by radial compression with respect to the longitudinal axis the clear cross section of the outer electrode emerges and vice versa.

The method for high voltage impulse disinfection of bacteria-contaminated liquids according to claim 7 consists of the following steps:
The bacteria-contaminated liquid to be processed is either flowed through a tubular cavity or introduced into such a charging manner, which is constructed according to one of claims 1 to 6. The electrodes facing each other in the cavity form the clear area in which high-voltage pulsation of one of the two electrodes forms the pulsed electric field necessary for the processing. The high voltage bulbous electrode is the electrode coated with the porous ceramic layer. The contaminated, electrically-to-be-processed liquid becomes in flow-through or batch-wise operation during a high-voltage pulse of a plurality of the exposed ceramic caused thereby layer exposed outgoing electrical corona discharges along the potential overhead conductor. A pulsed electric field strength of at least 1 MV / cm is generated on the exposed ceramic surface at the potential-high electrode without provoking a flashover to the opposite electrode to the reference potential.

In the dependent Method claim 8 are proven Parameter areas for described an advantageous and long-term operation. Under consideration of the high voltage pulse generator and the lines to the reactor the rise times of the high-voltage pulse are below 100 ns and the pulse durations significantly over 100 ns, can also pulse rates of a few 10 Hz are driven.

Of the Reactor is a coaxial, length limited Electrode assembly. A qualitative specification of the electrode spacing is the avoidance of a single flashover and thus a short shot while the duration of the high voltage pulse. The decisive factor is the multiple radial streamer formation or tuft discharge in the electrode gap. The electrode distance is determined by the required volume throughput and given the pulse amplitude to be adjusted. For example 100 kV pulse amplitude and 200-300 ns Pulse duration is the electrode gap 3-5 cm. Because the specific resistance of the water layer is small against the specific resistance in the ceramic layer is - he is only by the conductivity the liquid determined in the pores of the ceramic -, much of the entire pulse voltage falls above the Ceramic layer off. For the occurrence of the streamer is a field strength of at least 1 MV / cm on the surface the ceramic required. For example, this is due to a 50-100 kV pulse in the example listed above Electrode distance reached.

When Generator for generating the high voltage pulses is a Blumlein arrangement suitable. Alternatively, a capacitor bank or a Marx generator be used as a high voltage pulse source. The impedance of the Generator is adapted to the impedance of the reactor to reflections to avoid in the generator. The pulse rate goes up to 10 Hz.

to Increase the production of oxidants during the pulsation Microgas bubbles flowed through the reactor. Oxygen and noble gases are suitable for example.

The chemical reactions that occur in underwater corona discharges are very similar to those of electron beam, X-ray, gamma ray and ultrasound treatment. The advantage of underwater corona treatment is the combination with other effects, such as UV radiation, shock waves, high electric fields, which leads to an increase in efficiency and in the lower equipment and operating costs. Furthermore, the advantage of the disinfection process is the high specific decontamination rates. Experimental results with bacteria of the strain Pseudomasputida show that for a reduction of the bacterial concentration by 6 orders of magnitude a specific electrical energy of 5.5 kWh / m ^{3 is} required. This result is due to the combination effect of oxidants, UV radiation, shock waves and strong electric fields generated by streamer discharges.

in the The following is the high voltage impulse underwater corona discharge for the disinfection of bacteria-contaminated liquids in an exemplary Reactor described. For this purpose, figures are shown in it technical schemes used. It shows:

1 the block diagram of the disinfection system for sterilization;

2 the reactor for sterilization

3 Frontal recording of a burning underwater corona discharge in the reactor.

The schematic representation in 1 shows an example of a plant for high-voltage pulse-technical disinfection of a bacteria-contaminated liquid, here water, which is introduced from a sewer pipe. On the left in the picture is shown in blocks:
The controlled power supply, the means for generating electrical high voltage pulses, here a Blumleingenerator, with Messsensorik, centrally the reactor in coaxial design, and connected to the reactor analysis device for studying the state of the process to be processed, bacteria-contaminated liquid by the action of underwater corona discharges. The two outputs of the Blumleinimpulsgenerators are connected to the reactor: The high voltage output is connected via the implementation of the reactor tube with the coaxially seated, ceramic-coated inner conductor. The reactor tube is made of stainless steel. A quartz window hermetically seals the interior of the reactor via a respective flange on the two end faces so that the processes in it can be visually observed. The two flanges have electrically conductive contact with the pipe wall, therefore, the reference potential of Blumlein pulse generator is electrically connected to the nearest flange. The nozzles for the introduction and discharge of the wastewater to be processed are not indicated, depending but the reactor interior is filled with it for the process. About the peristaltic pump samples are taken from the reactor room, flowed into the quartz cuvette for spectrophotometric examination and pumped back into the reactor room. The coaxially seated inner conductor is made of titanium and coated with the ceramic Almandine 200 microns thick via a primer layer. With regard to the coefficients of thermal expansion of the two materials are ideal, ie matched with respect to the expansion coefficient, namely the same, or almost the same.

In 2 By way of example, the reactor is shown constructively detailed. The essential exemplary reactor dimensions are listed below. The high voltage connection is designed here for <50 kV. In the two near-end areas are the nozzle through which the wastewater is introduced and discharged, so that the wastewater to be processed forcibly and in large quantities must flow through the effective electrode gap.

By way of example, the following dimensions are listed for these exemplary embodiments:
Length of the inner electrode 200 mm;
Diameter of inner electrode with circular cross section 6 mm;
outer diameter of outer electrode 30 mm;
thus electrode spacing 12 mm;
Almandine ceramic coating 200-300 μm.

The process was carried out with this exemplary embodiment:
Water with different bacterial concentrations and thus a conductivity range of the liquid to be processed in the range 0.5-1.5 mS / cm. The high voltage amplitude was in the range <50 kV, the pulse shape rectangular with a half width of 200-400 ns. In the laboratory reactor thus operated, a reduction of the bacterial concentration (Pseudomonas putida) by 6 logarithm stages, ie factor 1 000 000, was achieved with an energy input of 20 J / cm ³ .

At the non-central connection 26 and the central neck 27 the diagnostic device is flanged, which is not indicated here. The left side in the picture, with the reactor wall 2 , the outer conductor 2 , connected flange piece 14 has the spacer ring 5 for Innenelektrodenfixierun inserted. The inlet nozzle 4 for the liquid to be processed is welded on shell wall side. The picture on the right side, also with the reactor wall 2 , the outer conductor 2 connected flange piece 15 has on its mantle wall the outlet 4 and opposite the bushings 6 welded for high voltage. The frontal quartz glass windows 12 are each about the flange ring 13 and sealing rings 16 hermetically sealed to the reactor tube 2 via flange screw clamps 19 pressed. The electrodes 1 . 2 of the reactor space are arranged coaxially as in a Koaxialkabelstück and judge upon application of the inner electrode 1 with high voltage potential to the outer electrode 2 the radial electric process field. The outer conductor 2 , the reactor wall 2 , is connected to an electrical reference potential, here ground potential. The inner conductor 2 sits centered and is on one forehead over the support 11 worn and on the other, in the picture right front side over the designed as a plug-in device high voltage electrical feedthrough with its components:
By guide socket 6 , Screw sleeve 7 , Connecting bolt 8th , Insulation pipe 9 , Pin 10 to inner electrode 2 , held in a coaxial position. The high-voltage bushing closes the reactor chamber over the seals 20 and 21 gas and liquid tight hermetically from the environment.

Material separated with indicated seals in detail in the 2 shown.

4 Finally, the photographic snapshot shows the corona discharge and thus highlights the effect in the reactor chamber with annular light cross section.

Claims (8)

Reactor for the high-voltage impulse disinfection of bacteria-contaminated liquids, comprising: a tube section which can be flanged at its two end faces and has a light, simple polygonal, but at least rectangular cross-section or a light, simple convex, round cross-section, an electrode arrangement consisting of two parallel to one another and perpendicular to the longitudinal axis of the tube section the longitudinal axis mirror-inverted opposite, electrically insulated from each other electrode bands over most of the length of the pipe section and the polygonal cross section over at most the width of the polygon side, of which the one electrode to an electrical reference potential and the other, the high voltage electrode to an adjustable in the duration and height electric High voltage potential can be connected, or one with respect to the longitudinal axis of the pipe section coaxial / concentric electrode arrangement of the at least electrically conductive Inner wall, the outer conductor, and the inner conductor, one of which, preferably the outer conductor, to an electrical reference potential and the inner conductor to a in the duration and height adjustable Res electrical high voltage potential can be connected to a porous ceramic layer on the acted upon by high voltage electrode on the counter electrode exposed surface with a layer thickness in the range of 100 to 300 microns, both electrodes are on the one hand with such a maximum distance against that on the one hand upon application With high voltage potential through the high voltage between the two electrodes in each case no flashover and on the other hand with a minimum distance face that on the other hand on the exposed surface of the ceramic layer during the presence of the electrical high voltage potential at the high voltage electrode to form a maximum field strength of at least 1 MV / cm comes without sparking. Reactor according to claim 1, characterized in that that the reactor at least one each connecting piece in the two End areas or end faces of the pipe section for liquid inlet and outlet and at least one access for Has diagnostic facilities. Reactor according to claim 2, characterized in that that the reactor has a high voltage feedthrough through the wall of the blank, through through the coaxial electrode arrangement of the inner conductor can be connected to a high voltage pulse generator. Reactor according to claim 3, characterized in that that the ceramic layer applied to the inner conductor in the Temperature range from the environment to the stationary operating temperature at least a similar one CTE as the inner conductor has. Reactor according to claim 4, characterized in that that at least exposed in the reactor chamber surfaces across from the liquid to be processed and the process products are inert materials. Reactor according to one of Claims 1 to 5, characterized that in the case of coaxial, concentric electrode arrangement of clear cross-section of the outer electrode is arbitrary to the cross section of the inner electrode, preferably however, the internal electrode cross-section by radial compression with respect to the longitudinal axis from the clear cross section of the outer electrode emerges and vice versa. Method for high voltage impulse disinfection bacteria-contaminated fluids in a tubular shape Reactor, consisting of the process steps: a bacteria-contaminated, to be processed liquid will either flowed through a tubular cavity or introduced into such, in which two electrode bands as Wall elements along the cavity longitudinal axis electrically opposed to each other or by a tubular Cavity with concentric ring flowed light cross section or initiated in such, in which the outer wall and the axial rod as a coaxial conductor arrangement, electrically insulated from each other, facing each other radially, in which one of the two band electrodes or the inner conductor, the or the one with the exposed area a porous one Ceramic layer coated is, transient / pulsatile with a high voltage electrical potential adjustable maximum and adjustable duration and the respective Counter electrode is placed at reference potential to between the two Electrodes for the process necessary pulse-shaped electric field of at most 1 MV / cm at the exposed ceramic surface and thereby along the acted upon with high voltage potential Electrode emanating from the exposed ceramic surface streamer discharges to create, whereby the contaminated, to be processed liquid in flow or thrust operation of the electric field and the streamers are penetrated. Method according to claim 7, characterized in that that the high voltage pulse generator and the connected reactor are electrically dimensioned so that rise times of the high voltage pulse <100 ns and the Pulse duration> 100 ns are generated and generates a pulse rate up to several 10 Hz can be.