KR20070108406A - Electrical circuit of an electrolyzer and method for reducing the electromagnetic fields in the vicinity of the electrolyzer - Google Patents

Abstract

Electrical circuit for reducing the electromagnetic fields in the vicinity of an electrolyzer, comprising a primary circuit supplying the electrolyzer and a secondary electrical circuit arranged in the vicinity of the primary circuit, for a current to flow in the opposite direction to that flowing in the main circuit in order to compensate for the electromagnetic fields generated by the latter.

Description

ELECTRICAL CIRCUIT OF AN ELECTROLYZER AND METHOD FOR REDUCING THE ELECTROMAGNETIC FIELDS IN THE VICINITY OF THE ELECTROLYZER}

The present invention relates to electrolysers, and more particularly to the electrical supply of such electrolysers.

The present invention more particularly relates to an electrical circuit for supplying a rectified current to an electrolyzer with bipolar electrodes.

Electrolyzers supplied with direct current, in particular electrolyzers with bipolar electrodes, are commonly used in the electrochemical industry. Such electrolysers are commonly used to electrolyze aqueous sodium chloride solutions with the intention of producing chlorine, aqueous sodium hydroxide or aqueous sodium chlorate solutions.

Given the high current density used in electrolytic cells with bipolar electrodes, rectified alternating current generally replaces direct current. Rectified alternating current usually has a phase that depends on the rectifier used for frequency and amplitude.

It is also known that electromagnetic fields generated by high electromagnetic fields, in particular rectified alternating currents, are harmful to the human body in excessive conditions because of the induced currents that occur in the body. It is therefore important to take measures to protect the attraction around industrial devices or to reduce the strength of the electromagnetic field there. In this regard, standards have been issued which require, on an industrial premise, to reduce the strength of the electromagnetic field. Among these standards, the European standard 89/391 / EEC is particularly strict.

It is an object of the present invention to provide an electrical circuit of a novel design that provides a high current in an industrial electrolyzer.

In particular, it is an object of the present invention to provide an electrical circuit in which the electromagnetic field around the electrolytic cell has been reduced to a value small enough to comply with the aforementioned European standards.

More specifically, it is an object of the present invention to reduce the intensity of the electromagnetic field on the passage along the side walls of electrolysers with bipolar electrodes.

Accordingly, the present invention relates to an electrical circuit for reducing an electromagnetic field around an electrolytic cell, comprising an electrical line comprising an electrolytic cell and one or more busbars for returning a current flowing in the electrolytic cell, and And a secondary electrical circuit disposed at least partially around the primary circuit such that the current flows in a direction opposite to the current flowing in the main circuit to cancel the electromagnetic field generated by the primary circuit. .

According to the invention, the secondary electrical circuit is arranged near the primary circuit. The current flow in the opposite direction of the secondary circuit is intended to induce a magnetic field that at least partially cancels the electromagnetic field generated by the current flow in the primary circuit. The secondary circuit must therefore be able to deliver a current of sufficient strength to achieve the desired cancellation. In order to obtain good electromagnetic cancellation, secondary circuits should be arranged as much around the primary circuit as possible. In order to obtain the optimum electromagnetic offset, taking into account the structural necessity of separating the two circuits at a certain position, one part of the secondary circuit should be attached to the electrolyzer and the other part is preferably a busbar or busbars. Recommended to be attached to In order to optimize the offset, certain pieces of the secondary circuit are generally distributed over a plurality of conductors connected in parallel. Through the control resistor, it is possible to power the secondary circuit using the power supply of the primary circuit. However, it is recommended that at least a portion of the secondary circuit lying around the return line be powered separately. The separate power supply also has the advantage that the frequency of the secondary current can be adapted to preferentially eliminate certain constant problem frequencies of the magnetic field produced by the electrolyzer. In general, it is recommended that the busbar or part of the secondary circuit placed around the busbars can carry a current (preferably five times stronger) than the current flowing in the part attached to the electrolyzer, where the current ratio Is a function of the distance between the busbar and the electrolyzer.

It is also recommended that the part of the circuit lying between the rectifiers and the electrolysis devices be configured to obtain good field cancellation. Therefore, care will be required to keep the current supply and return conductors close to each other. For this reason, it is recommended that such conductors are branched into a plurality of elements connected in parallel so that these conductors are interleaved with one another, for example in alternating and stacked layers of elements of each conductor.

The present invention applies to any type of electrolyzer, such as monopolar or bipolar mercury, diaphragm or membrane electrolyzers. However, the present invention is more particularly applied to electrolysers with substantially vertical bipolar electrodes. Such electrolysers are well known in the industry, which are commonly used to electrolyze metal halides, especially aqueous sodium chloride solutions. These electrodes are generally formed as a series of metal frames, each electrode comprising bipolar electrodes, which are placed side by side in the manner of a filter press (Modern Chlor-alkali technology, Vol. 3, SCI, 1986, Chapter 13, "Operating experience gained with the bipolar Hoechst-Uhde membrane cell"; Modern Chlor-alkali technology, Vol. 4, SCI, 1990, Chapter 20, "Hoechst-Uhde single element membrane electrolyzer: concept-experiences-applications"). The frames have customarily square or rectangular contours so that when the frames are laid side by side in the manner of a filter press, the frames could form the upper wall, the lower or base wall and the two side walls of the electrolyser. The electrolyzer is usually provided with direct current or, more generally, rectified alternating current. Direct current or rectified current flows from one terminal of the direct current power supply or rectifier through the electrode and then returned to the other terminal of the direct current power supply or rectifier through a current line placed outside the electrolyzer.

The electrical circuit according to the invention is preferably supplied with rectified alternating current. Three-phase alternating rectification provides a current with a base frequency (e.g., 6 x 50 Hz) that is six times higher than the fundamental frequency of three-phase current and a perfect harmonic spectrum.

In one recommended embodiment of the invention, the circuit comprises a power supply that uses two or more rectifiers to give currents whose current waveforms are phase shifted with respect to each other. The electrolysis electrical circuit is preferably supplied with a three phase alternating current.

The use of two or more mutually phase shifted rectifiers according to the present embodiment makes it possible to increase the frequency of vibration of the rectified current supplying the electrolyzer or electrolyzers. Given the strength and specific arrangement of the currents contained in the electrolyzer, the circuit according to the invention makes it possible to substantially reduce the electromagnetic field generated around the device.

In a preferred variant of this embodiment, the circuit comprises two rectifiers whose phase shift is close to 29 ° and 31 °, preferably close to 30 °. In this variant, a current with a base frequency of 12 times higher than the base frequency of the three phase current in which the current waveform is not rectified is obtained.

In another preferred variant of this embodiment of the electrical circuit, the circuit also includes one or more drain coils coupling the outputs of the two or more rectifiers. The drain coil is intended to achieve non-parallel reactance between the outputs of the rectifiers. The coil is preferably formed by combining iron plates and sheets, in order to limit heating losses. The outputs of the rectifiers enter in the opposite direction, causing current perturbation in one of the outputs to induce perverse perturbation in the current coming from the other output by reactance. When the two outputs overlap in parallel connection, less overall disturbed current is thereby obtained.

In a preferred variant of the electrical circuit according to the invention, the return current line comprises one or more busbars arranged above or below the electrolyzer. The choice of placing the busbar above or below the electrolyzer is determined by the assembly mode of the bipolar plates and the consideration of the configuration of the electrolyzer. As a variant, the above-described current line may include one busbar disposed under the electrolyzer and another busbar disposed above the electrolyzer. According to another variant, the electrolyzer may comprise a plurality of busbars under the electrolyzer and / or a plurality of busbars above the electrolyzer. In fact, when considering the maintenance and assembly of the electrolyzer, it is preferable that the above-described current line does not include a busbar on the electrolyzer.

Similar to others, the electrical circuit according to the invention is basically located along the side walls of the electrolyzer, especially along the side walls, on the passage normally present and used by operating and maintenance personnel, around the electrolyzer with bipolar electrodes. It is known to reduce the electromagnetic field.

In the electrical circuit according to the invention, the material of the busbars is not critical to the definition of the invention. Busbars are generally made of copper, aluminum or aluminum alloys.

In the electrical circuit according to the invention, the contour of the cross section of the busbar is not critical to the definition of the invention. The busbars may be, for example, square, rectangular, circular or polygonal.

In a first particular embodiment of the electrical circuit according to the invention, the busbar has a rectangular contour and is adapted such that the wide sides are substantially horizontal. Similar to others, it has been observed that selecting the busbars of rectangular portions arranged horizontally above and / or under the electrolyzer reduces the size of the electromagnetic field around the electrolyzer. It is also observed that when the ratio between the thickness and width of the busbars is small, the decrease in the electromagnetic field around the electrolytic cell is proportionally greater. In practice, it is therefore preferred to use metal plates for busbars. As a variant, a plurality of metal plates arranged side by side under and / or over an electrolytic cell may be used.

Similar to others, it is also observed that the size of the electromagnetic field around the cell is reduced when the busbar is placed close to the wall of the cell.

In a second embodiment of the electrical circuit according to the invention, the busbars are thus arranged immediately near the wall of the electrolytic cell. In this embodiment of the invention, the wall of the electrolytic cell is a lower or base wall or upper wall of the electrolytic cell, depending on whether the busbar is located under or above the electrolytic cell. In this embodiment of the present invention, the expression "near the wall of the electrolytic cell" means that the distance between this wall and the busbar is approximately equal to five times (preferably three times) the thickness of the busbar. Preferably, this distance does not exceed the thickness of the busbars.

In a preferred variant of the aforementioned second embodiment of the invention, a busbar is attached to said wall of the electrolytic cell. In this preferred embodiment of the invention, the busbar is advantageously a metal plate, with one of the wide sides of the metal plate attached to the wall, and only electrical insulators of the required thickness separating the bar from the wall. The metal plate may be attached to a portion of the surface area of the wall. Preferably, the metal plate should be attached to substantially all of the surface area of the wall.

In a third specific embodiment of the invention, the above-mentioned electrical line also includes two additional busbars, each arranged immediately near the two side walls of the electrolyzer. In this embodiment of the invention, the expression “near immediately” corresponds to the definition given for this expression in the second embodiment described above.

Similar to others, the presence of additional busbars reduces the size of the electromagnetic field around the electrolyzer.

In a third embodiment according to the invention, the additional busbars may have any shape compatible with the configuration of the electrolyzer. Busbars may have, for example, square, rectangular, polygonal, oval or circular contours. Additional busbars may also have the same contour or different contours, and may have the same dimension or different dimensions. In practice, however, additional busbars preferably have the same contour and the same dimensions. It is also preferred that further busbars have a rectangular contour and additional busbars are each attached to the two side walls of the electrolyzer through their wide sides.

In the third embodiment of the invention described, the respective dimensions of the additional busbars and the dimensions of the respective busbars, arranged under and / or above the electrolyzer, are in such a way that current is intended to be distributed between these busbars. Is determined as a function of.

In a particularly preferred, fourth embodiment of the invention, the return current line of the electrical circuit is positioned to generate an electromagnetic field that is substantially symmetrical with respect to the vertical center plane of the electrolyzer. The object of this embodiment (generating an electromagnetic field substantially symmetrical with respect to the vertical center plane of the electrolytic bath) is achieved by the approximate dimensioning and placement of each busbar. The choice of the optimal dimension and the optimal position is determined by one skilled in the art, in particular as a function of the dimensions and shape of the electrolyzer. In practice, this result may generally be obtained by placing the busbar or busbars symmetrically with respect to the vertical center plane of the electrolyzer.

The electrical circuit according to the invention substantially reduces the electromagnetic field around the electrolyzer with bipolar electrodes.

The invention also provides a method for reducing an electromagnetic field around an electrical circuit of an electrolyzer comprising a primary electrical circuit, the electrical circuit comprising an electrical line comprising an electrolyzer and one or more busbars for returning current flowing through the electrolyzer. And a primary electrical circuit comprising by itself, the method comprising passing a current through a secondary electrical circuit disposed around the primary electrical circuit in a direction opposite to the current flowing through the primary electrical circuit. do.

According to a preferred variant of the method according to the invention, the primary circuit comprises a power supply that uses two rectifiers to give a current whose phase is phase shifted by 30 ° with respect to each other.

In a preferred form of this variant, the primary circuit also comprises a drain coil coupling the outputs of the two rectifiers.

The electric circuit according to the invention applies in particular to electrolyzers for the continuous electrolysis of aqueous solutions or water, such as alkali metal halogens, in particular aqueous sodium chloride solutions. In a preferred embodiment of the invention, the electrolytic cell thus comprises a conduit for the continuous suction of the aqueous solution electrolyte and a conduit for the continuous release of the aqueous solution electrolyte.

The present invention is particularly applied to an electrolytic cell for producing sodium chlorate by electrolyzing an aqueous sodium chloride solution. The present invention is particularly applicable to electrolysers for producing aqueous sodium hydroxide solution and chlorine by electrolysis of aqueous sodium chloride solution, which include cationic selective permeation membranes sandwiched between bipolar electrodes.

The electrical circuit according to the invention is applied to an electrolysis device which combines one or more electrolysers with vertical bipolar electrodes.

The invention therefore also relates to an electrolysis device comprising at least one electrolytic cell with bipolar electrodes, which is connected to an electrical circuit according to the invention. The device according to the invention may comprise a single electrolyzer or a plurality of electrolyzers which are electrically connected in series or in parallel.

The invention relates in particular to the use of the present apparatus for producing aqueous sodium hydroxide solution and chlorine.

The features and details of the invention will become apparent from the following description of the accompanying drawings which illustrate certain embodiments of the invention.

1 is a plan view showing a general layout of an electrolysis device according to a particular embodiment of the invention.

2 is a schematic drawing of a longitudinal section of another particular embodiment of an electrolysis device according to the invention.

FIG. 3 is a view showing a vertical section on plane III-III of FIG. 2.

4 is a view, similar to FIG. 3, of another embodiment of the apparatus according to the invention.

5 is a preferred variant of the device of FIG. 4.

6 and 7 are similar to FIGS. 4 and 5, but also showing a secondary circuit.

In these figures, the same elements are given the same reference numerals.

The electrolysis device outlined in FIG. 1 comprises electrolysers 1, 2 and 3 designed for the production of chlorine, hydrogen and sodium hydroxide by electrolyzing an aqueous sodium chloride solution. The electrolyzers 1, 2 and 3 are of a type with vertical bipolar electrodes. The electrolysers are formed by placing the vertical rectangular frames 4 side by side, each vertical rectangular frame 4 comprising a vertical bipolar electrode (not shown). The frames 4 are placed side by side in the manner of a filter press. Cation selective permeation membranes are alternately sandwiched between the frames 4 to delimit the anode and cathode chambers. The anode chambers of the electrolyzers 1, 2 and 3 are connected with a conduit (not shown) for the continuous suction of the aqueous sodium chloride solution. The chambers are connected with a manifold (not shown) for the continuous release of chlorine. The cathode chambers of the electrolyzers 1, 2 and 3 are each connected with two manifolds (not shown) which are used for the continuous release of hydrogen on the one hand and for the continuous release of the aqueous sodium hydroxide solution on the other hand.

The electrolysers 1, 2 and 3 are arranged on the one hand with conductive bars 6 sandwiched between the electrolysers 1, 2 and 3 and on the other hand return outside the electrolysers 1, 2 and 3. It is electrically connected in series via the drain coil 19 to the two rectifiers 5a and 5b by an electrical circuit comprising a current line 7. The rectifiers 5a and 5b are supplied with a 30 ° phase shift by the AC power source 18.

In the electrolysis device outlined in FIG. 1, each of the three electrolyzers 1, 2 and 3 comprises for example 30 to 40 basic electrolysis cells, the electric power supply being for example 8 to 20 Includes a 520V dc rectifier capable of delivering a current of kA. As a function of the surface area of the electrodes, this may result in an anode current density of 2.5 to 6 kA / m 2 of the anode area. These numerical values, however, are merely indicative and do not limit the scope of the invention and the following claims.

When closing the bipolar switch, the rectified current flows continuously in the electrolysers 1, 2 and 3 to the return line 7 and through its bipolar electrodes. This current generates an electromagnetic field around the device.

According to the invention, the secondary circuit comprising the fragments 17a and 17b is arranged near the electrolysers and the return line.

The electrolysis device outlined in FIGS. 2 and 3 shows a particular embodiment of the invention. The secondary circuit does not appear in the figures. Only the electrolyzer 3 is shown in these figures. In the apparatus of FIGS. 2 and 3, the return current line 7 comprises two busbars 9 and 10 arranged under the lower wall 11 of the electrolytic cell 3. Busbars 9 and 10 are prismatic bars of metal which are good electrical conductors (preferably copper or aluminum). These bars are arranged symmetrically on one side of the vertical center plane X-X of the electrolytic cell. The bars 9 and 10 are also arranged near the lower wall 11 of the electrolytic cell 3. The effect of arranging the busbars 9 and 10 in the manner shown schematically in FIG. 3 follows the side walls 13 of the electrolyzer 3 and determines the magnitude of the electromagnetic field on the passage 12 intended for the manpower of the electrolyzer. To reduce.

Similar to others, it is observed that the strength of the electromagnetic field on the passage 12 decreases proportionally when the bars 9 and 10 are close to the lower wall 11 and the central plane X-X. It is also observed that the intensity of the electromagnetic field on the passage 12 is reduced by reducing the ratio between the width and the thickness of the bars 9 and 10. It is therefore preferable to use horizontal plates or sheets for the busbars 9 and 10.

In the embodiment outlined in FIG. 4, where the secondary circuit also does not appear, the return current line 7 comprises a metal plate or sheet 14 attached to the lower wall 11 of the electrolytic cell and substantially covering all of the walls. do.

In the arrangement of FIG. 5, the current line 7 is a metal plate 14 which is applied to the lower wall 11 of the electrolyzer 3 and two additional buses which respectively follow the two side walls 13 of the electrolyzer 3. Bars 15 and 16. The two further busbars 15 and 16 are preferably metal plates or sheets attached to the side walls 13.

In the apparatus of FIGS. 6 and 7, similar to FIGS. 4 and 5, circuits 17a and 17b are shown. An electric current flows in the conductor 17b in a direction opposite to that flowing in the plate 14. The same principle applies to the conductor 17a and the plates 15 and 16.

Claims (14)

As an electric circuit for reducing the electromagnetic field around the electrolytic cell (1, 2, 3), A primary electrical circuit, comprising by itself an electrical line 7 comprising the electrolyzer and one or more busbars 9, 10, 14 for returning the current flowing in the electrolyzer, and Secondary electrical circuits 17a, 17b, which are at least partially disposed around the primary circuit so that the current flows in a direction opposite to the current flowing in the main circuit to cancel the electromagnetic field generated by the primary circuit; Including, electrical circuit. The method of claim 1, The bus bar (9, 10, 14) is arranged under and / or above the electrolytic cell (3). The method of claim 1, The bus bar (14) is characterized in that it is attached to the wall (11) of the electrolytic cell (3). The method of claim 3, wherein The wall is characterized in that the base wall (11) of the electrolytic cell. The method according to claim 3 or 4, The busbar is a metal plate (14), wherein one of the wide sides of the metal plate is attached to the wall (11). The method according to any one of claims 1 to 5, The electrical line (7) further comprises two additional busbars (15, 16), the additional busbars being respectively attached to the two side walls (13) of the electrolytic cell (3). The method according to any one of claims 1 to 6, The electric line (7) is characterized in that it is positioned to produce an electromagnetic field that is substantially symmetrical with respect to the vertical center plane (X-X) of the electrolytic cell. The method according to any one of claims 1 to 7, Wherein said electrolyzer comprises a conduit for continuous intake of aqueous electrolyte solution and a conduit for continuous release of aqueous electrolyte solution. The method of claim 8, The electrolyser comprises two membranes capable of selectively permeating cations, sandwiched between bipolar electrodes. The method according to any one of claims 1 to 9, The primary circuit comprises a power supply using two rectifiers (5a, 5b) to deliver current in which the current waveforms are phase shifted with respect to each other. The method of claim 10, An electrical circuit further comprising a drain coil (19) coupling the output of said two rectifiers. As a method for reducing the electromagnetic field around the electric circuit of the electrolytic cells 1, 2, 3, The electrical circuit comprises a primary electrical circuit which itself comprises an electrical line 7 comprising an electrolytic cell and one or more busbars for returning a current flowing in the electrolytic cell, The method passes the secondary electric circuit (17a, 17b) disposed in the periphery of the primary electrical circuit in a direction opposite to the current flowing in the primary electrical circuit. The method of claim 12, Wherein the primary circuit comprises a power supply that uses two rectifiers to deliver currents whose current waveforms are phase shifted by 30 ° relative to each other. The method of claim 13, The primary circuit further comprises a drain coil (19) for coupling the outputs of the two rectifiers.

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