WO2006082561A1

WO2006082561A1 - Self-cleaning electrolyser

Info

Publication number: WO2006082561A1
Application number: PCT/IB2006/050341
Authority: WO
Inventors: Fritz Zimmermann; Serguei Zouikov; René Meier
Original assignee: Zimmermann Verfahrenstechnik Ag
Priority date: 2005-02-07
Filing date: 2006-02-01
Publication date: 2006-08-10
Also published as: CH697680B1

Abstract

The invention relates to a device and a method, which permit an electrolyte in a self-cleaning electrolyser to be treated in the most efficient, uniform manner.

Description

Self-cleaning electrolyzer

The present invention relates to a self-cleaning electrolyzer according to the preamble of patent claim 1.

Both mode of action and possible uses for the electrochemical treatment of water, aqueous solutions and other liquids suitable as electrolytes are known. The electrical polarization, or ionization of the electrolyte is used in the present case of cleaning, sterilization and decalcification.

The ionization of the water (electrolyte) has a disinfecting effect, d. H . existing germs are killed (cold sterilization). Another consequence of the electrolytic treatment of an aqueous solution is the formation of huge quantities of gas bubbles (about 3-5 million per cm ³ ) of, for B. Hydrogen, oxygen, ozone, etc. On the surface, these gas bubbles have an electric charge. As soon as the gas bubbles come into contact with microorganisms, they implode. The electrical discharge destroys the matter of microorganisms, whether they are alive or dead in the organic sense. In large-scale facilities such as hotels and commercial buildings, the sterilization becomes ever more important, since it was possible to prove the formation of Legionella in dead spaces of the piping system in plants operated with untreated water.

However, the ionization of water also causes a change in the crystalline form of the lime contained therein, which determines the "water hardness." Although the water hardness does not decrease, the lime in the new crystalline form no longer adheres to pipes and fittings.

For the treatment of the water (electrolyte), ie the practical production of ionized solutions, various construction forms and arrangements of devices (electrolysers) are used. Typical are so-called circular reactors, of which possible embodiments z. B. in EP 0 842 122 Bl. Recently, so-called flat reactors have been used variously, which can be installed in a space-saving plant. Due to their shape they are less expensive to install and can be adapted to the respective needs in a simple way by modular construction. These aforementioned and known electrolysers, both the known round and the new flat reactors liable to the lack of that they are not optimally designed in the process space, ie where the electrolysis takes place and the aqueous liquid is treated. For example, dead spaces contribute to never being sure that all the parts of the aqueous solution that passed through the electrolyser are actually processed. In fluidically unfavorable process spaces but also turbulent flows, which have the same effect on the uniform treatment of the electrolyte.

Even in test series, which serve to assess the mode of action in terms of sterility and influencing the crystalline lime structure in the aqueous solution, it has been shown that the quality of the treated solutions varies greatly. This is due to the uneven treatment of the aqueous solution in fluidically unfavorable process spaces of the known electrolysers. Dead spaces that are not inevitably flooded suddenly and irregularly empty in unpredictable cadences. Of course, those are in a dead room of the electrolyzer some time remaining parts of the electrolyte of a different quality than the regularly passing past the electrodes, or in the so-called "channeling" the electrolyzer passing in rapid direct passage parts.

The disadvantages of known electro-lyseurs are recognizable in the structure: they are equipped with electrodes which are simply immersed in the process space, ie in the liquid. This type of construction is chosen so that the electrodes can be easily replaced. One manufactures the electrodes of conductive material, since one wants to obtain the highest possible electrical power. These materials are usually easily worn because they undergo electrolytic corrosion from the process. For an electrolyser to be used over the long term, it is important to replace such electrodes easily.

The dead spaces and the turbulent flow, as they occur in round reactors around the electrodes, have a negative effect on the flow behavior of the electrolyte. The emptying of the dead spaces and the turbulent flow cause uneven quality of the treated electrolyte. Basically, the shape of the process space in circular reactors per se is not favorable for the flow behavior of the electrolyte.

If the process space, inlet and outlet of the electrolyzer are to be optimized in terms of flow, the electrodes become constructively part of the process space. They are thus usually less interchangeable, d. H . with each change of the electrodes, the electrolyzer z. B. be dismantled. To avoid this, the appropriate material must be used for the electrodes. The choice of the right material for the anode and the cathode is therefore of great importance. If possible, one would like to use electrodes that last for the entire life of the electrolyzer. Such electrodes are known. They are made of titanium and may even be provided with a surface protection. This material and a surface protection have for use as electrodes the disadvantage that they have large electrical resistances, so are poorly conductive. It is therefore necessary to make arrangements so that these electrodes are supplied with power uniformly over their entire length. You want to avoid that a voltage drop must be accepted. On the other hand, irregularities in the quality of the electrolyte are undesirable. The quality of the electrolyzer leaving the electrolyzer will have to be based on the least ionized parts, if one wants to give the user guarantees. It is therefore necessary to design such a plant so large that even the least treated portions of the liquid are still sufficiently processed and to meet a required quality standard. As a result, devices and thus the whole system larger, the demand for electricity increases. The economic viability of the facility is in question.

The present invention now has the object to improve a self-cleaning electrolyzer for the continuous, electrolytic treatment of water and / or aqueous solutions of the type mentioned in such a way that the advantages of the known devices are maintained, and by defined, laminar flow and uniform treatment of Liquid components improve the quality and safety in the design better. One wants to achieve a more uniform quality of the treated electrolyte with less energy. This object solves the presented self-cleaning electrolyzer for continuous, electrolytic treatment of suitable electrolytes such. B. Drinking and process water with the features of claim 1. Further inventive features will become apparent from the dependent claims and the advantages thereof are explained in the following description.

In the drawing shows:

Fig. 1 Perspective / view of an electrolyzer

Fig 2 section Y-Y through the electrolyzer

3 shows section X-X through the electrolyzer

Fig 4 Detail section X-X through the electrolyzer

Fig 5 elevation of the electrolyzer

Fig 6 Side elevation of the electrolyzer

Fig. 7 Floor plan of the electrolyzer

The figures represent preferred exemplary embodiment proposals, which are explained in the following description as examples.

An electrolyzer _1 of the inventive type is flat. In Fig. 1 z. B. a typical construction of this type shown. Two cover plates 30, 30 'laterally close off the entire package in the manner of a "sandwich construction" (FIGS. 3 & 4) .At these cover plates 30, 30', the electrodes 20, 20 'rest satisfactorily and without play the use of the electrolyzer 1 remains so, the gap between the electrodes 20, 20 'and the cover plates 30, 30' is sealed to the outside Electrodes 20, 20 'form the lateral delimitation of the process space 3. Together with the frame 4, they form the process space 3 (FIGS. 2-4). The entire package, cover plates 30, 30 'with outer seals 31, 31', electrodes 20, 20 'and the frame 4 with the process space seals 32, 32' is held together by means of screws 35 (Figure 5-7).

The process space 3 (FIG. 2) has a positive inclination in the angle OC in the direction of the outlet 6 between the inlet side and outlet side at the upper boundary 8 and the lower boundary 9 of the process space 3 relative to the horizontal. The process space 3 thus forms a chamber with a slight incline relative to the horizontal. The relatively narrow inlet 5 leads into the process space 3. This remains the same in cross-section over its entire length until it leads into the outlet 6. As long as the electrolyte is in the process chamber 3, there is no flow change and thus no turbulence.

In section XX (Figure 3, 4), the already briefly mentioned sandwich construction of the electrolyzer 1 is shown. On both sides of the electrodes 20, 20 'to the cover plates 30, 30' towards the outside seals 31, 31 'are arranged. In corresponding grooves of the cover plates 30, 30 'sealing profiles 34 are inserted for sealing against the electrodes 20, 20'. They keep the space between the cover plates 30, 30 'and the electrodes 20, 20' tight and closed. During assembly, care is taken to ensure that as little play as possible between the electrodes 20, 20 'and the covers 30, 30', and, if possible, that a vacuum is present. That this remains so during the life of the electrolyzer _1 is ensured by these outer seals 31, 31 '. Because the electrodes 20, 20 'are supported by the rigid cover plates 30, 30' against deflection, one can work in the process chamber 3 both with vacuum and with overpressure. In the case of overpressure, the electrodes 20, 20 'are supported on the cover plates 30, 30'. In the case of a vacuum in the process space 3, the resulting vacuum in the space between electrodes 20, 20 'and cover plates 30, 30' holds the electrodes 20, 20 'on the rigid cover plates 30, 30'. The electrolyzer 1 thus enables the pressure-free process control.

On the inner side facing the process space, 4 grooves are provided in the frame, which receive sealing profiles 34 for sealing between frame 4 and electrodes 20, 20 ', the so-called process space seals 32. These have the task of sealing the process space to the outside.

In order to uniformly supply the electrodes made of titanium over the entire length between inlet 5 and outlet 6, the latter is made over its entire length by means of current strips 21, 21 'of copper or other highly conductive material, over the largest possible area of the electrodes 20 , 21 'initiated. This contact surface should correspond to approximately 10% of the area of the electrodes 20, 20 ', which faces the process space 3 and is therefore in contact with the electrolyte. This avoids that the high resistance of the titanium-made electrodes 20, 20 'causes different electrical states. It would be detrimental to the process if different electrical states prevail at different locations in process space 3. On the other hand, the advantage of coated electrodes is the markedly long service life. Made of conventional material electrodes dissolve when they serve as an anode. This is even desirable in certain processes (e.g., AL production). A coating of titanium anodes avoids their dissolution during electrolysis. They are many times superior to conventionally used electrodes. Similarly good properties of the stability provide electrodes which are made of platinum. However, these are very expensive and therefore not economically viable.

During the process, the transformation of the crystalline form of the electrolyte in the process chamber 3 produces a type of sludge. In order to be able to remove it from time to time, the process space 3 below the outlet 6 has an emptying opening 7. With a special cleaning cycle this can be flushed out through the discharge opening 7.

In order to recognize the advantages of the device, various process steps must be described. In the basic function, the electrolyte in untreated form A is fed via the inlet 5 (product A) into the process space 3. As gently as possible and in laminar flow, the electrolyte to be treated traverses the process space 3 and flows through between the electrodes 20, 20 '(anode and cathode) and is thereby ionized. Via the outlet 6, the now treated electrolyte (educt B) leaves the process space 3.

The electrolyte should rise steadily but not too strongly between inlet 5 and outlet 6. The inlet 5 amount of electrolyte is said to "pierce" the contents of the process space 3 (Figure 3) between the upper limit 8 and the lower limit 9. For this purpose, the lead angle OC with respect to the horizontal must be at least 5 ° and at most 10 °.

Gases produced during the electrolysis process form fine bubbles during the action of the current. These can cause turbulence. As a result of the described design of the process space 3 and the laminar flow, these gas bubbles rise slowly and without causing turbulence in the process space 3 upwards. They pass through the same and reach the upper boundary 8 of the frame 4. Due to the inclination of the process space 3 and the flow of the electrolyte through the process space 13 in a laminar flow and gently flowing through the upper boundary 8, these bubbles slowly move in the direction of the upper boundary 8 Outlet 6 transported. They do not cause turbulence and also do not form gas bags. They then leave permanently together with the uniformly treated electrolyte the electrolyzer _1 through the outlet 6th To intensify the process, the untreated electrolyte (product A) can be fed CO ₂ into microbubbles. The resulting during the electrolysis, fine calcium crystals attach to these CO ₂ bubbles and can be easily removed as a flotate. In addition, with this addition of CO _2, the pH of the electrolyte (product A, starting solutions) can be adjusted or corrected. Especially in the treatment of water or aqueous solutions with too few minerals, this method allows the electrolyte in a higher degree of activation, without having to add other additives. A higher degree of activation and the addition of CO 2 cause the formation of a larger number of gas bubbles, which (as described in the introduction) play an important role in the purification process.

By using this self-cleaning electrolyzer 1, the control of the process becomes more reliable. The regulation takes place via the stabilization of the current. If z. B. the constantly measured conductance of the electrolyte changes, the electrolysis voltage at the electrodes 20, 20 'can be immediately influenced in order to keep the electrolysis current at the same level. By targeted modulation of the stabilized current, the pH and the redox values of the electrolyte can be specifically influenced.

This regulation makes it possible to set a desired quality of the treated electrolyte at outlet 6 (educt B) and to ensure its uniformity. The management of the process to obtain uniform quality is possible regardless of fluctuations in mineral content or conductivity of product A.

In order to avoid deposits on the electrodes 20, 20 ', they are regularly reversed during the process. On the surface of the electrode 20, 20 'used as a cathode, debris deposits, while the electrode 20, 20' acting as an anode self-cleans. If it is reversed regularly, the cleaning of the electrodes 20, 20 'is achieved. Cleaned electrodes ensure correct process control again.

Claims

claims

Self-cleaning electrolyzer (1) with process space (3) which is provided for the passage of an electrolyte with an inlet (5) and an outlet (6) and for total emptying with a discharge opening (7), characterized in that the process space (3) is closed off by a frame (4) and laterally by flat electrodes (20, 20 '), the flat electrodes (20, 20') being formed by cover plates (20, 20 ') which are likewise flat on the electrodes (20, 20'). 30, 30 ') are supported, with which the whole construction is held together in a sandwich.

2. Self-cleaning electrolyzer (1) according to claim 1, characterized in that an upper boundary (8) of the process space (3) with respect to the horizontal an angle OC of at least 5 ° and at most 10 °, so that from the side of the inlet ( 5) to the side of the outlet (6) towards the upper boundary (8) has a slope relative to the horizontal.

3. Self-cleaning electrolyzer according to claim 1, characterized in that a lower boundary

(9) from the side of the inlet (5) to the side of the outlet (6) has an angle OC to the horizontal of at least 5 ° and at most 10 °, so that from the side of the inlet (5) to the side of the outlet (5 6) towards the lower boundary (8) has a slope relative to the horizontal.

4. Self-cleaning electrolyzer (1) according to claim 1, characterized in that on the opposite side to the process space (3) of the flat electrodes (20, 20 ') are current strips (21, 21') which extend over the entire length of the electrodes ( 20, 20 ') and covering in terms of area at least 10% of the electrode surface which is free relative to the process space (3), ie forms the contact surface with the electrolyte.

5. Self-cleaning electrolyzer (1) according to claim 1, characterized in that the flat electrodes are made of titanium and whose surface is coated.

6. A process for the purification and decalcification of aqueous solutions with a self-cleaning electrolyzer according to claims 1 to 3, characterized in that the electrolyte passes the same laminar at a defined speed and this of all parts of the electrolyte of a preselected flow rate by a maximum of ± 20% deviates.

7. The method according to claim 5, characterized in that the aqueous solution before the inlet (5) in the process chamber (3) CO _{2 is} supplied.