Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B15/00—Operating or servicing cells
  • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B15/00—Operating or servicing cells
  • C25B15/02—Process control or regulation
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
  • C02F2001/46152—Electrodes characterised by the shape or form
  • C02F2001/46157—Perforated or foraminous electrodes
  • C02F2001/46161—Porous electrodes
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/4611—Fluid flow
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/46115—Electrolytic cell with membranes or diaphragms
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/4618—Supplying or removing reactants or electrolyte

Definitions

• the invention relates to a method for generating a uniform flow through an electrolyte space of an electrolysis cell and an electrolysis cell.
• Electrolysis is of great importance in the chemical industry. Areas of application for electrolysis are, for example, the synthesis of chlorine by chlor-alkali electrolysis or hydrogen chloride electrolysis, electrolytic chromic acid regeneration, electrochemical production of sodium dithionite as well as electrochemical wastewater treatment and metal separation to obtain pure metals.
• the active electrode surface consists of a soot-based gas diffusion layer, which is activated with special methods, saturated with ionomers and hydrophobized in order to offer the reaction gases a reaction surface many times larger than would correspond to the dimensions of the gas diffusion layer.
• the oxidation of sugars to sugar acids is carried out in a special stirring reactor equipped with anode grids.
• cathodes For the reduction of phthalic acid to dihydrophthalic acid, cathodes are used, which are imprinted with a groove structure to increase sales.
• the so-called Swiss Roll Cell was developed for reactions catalyzed by nickel oxide.
• the anode and cathode are wound in a spiral.
• Electrodes whose active surface is larger than their purely geometric dimensions are often referred to as three-dimensional electrodes.
• lamellar constructions are also known which have been composed, for example, of strips with metallic glasses.
• inorganic electrolysis such three-dimensional electrodes are used, for example, to separate metal traces from waste water.
• felt-like electrodes or electrodes made of particle beds are used, for example.
• electrodes in the form of a mesh-like construction can be used for the production of sodium dithionite.
• the design of the overall electrode and the electrolyte space based on the flow field is relatively uncritical in some cases, such as for example in chlor-alkali electrolysis using the membrane process, in which two gas-developing grid electrodes separated by a membrane face each other.
• the mammoth pump effect created by the developing gas bubbles ensures that the two electrolyte compartments are sufficiently evenly distributed. Neither a strong nor a defined circulation of the electrolytes is necessary.
• electrolysis in which high selectivity with high turnover is a critical variable, problems occur with electrolysis cells without defined hydrodynamics.
• the reaction liquid In order to avoid dead spaces in which uncontrolled formation of secondary components can occur and to achieve optimum utilization of the electrode surface, the reaction liquid must be distributed as evenly as possible in the electrolyte space and in this way the most homogeneous current density distribution possible. For this purpose, it is necessary to influence the liquid flows outside the immediate vicinity of the electrode surface. Dead spaces are, for example, gas cushions (ie stuck gas bubbles) or areas in which there is no liquid flow. Such areas arise, for example, from eddies, backflow or accumulation at obstacles in the flow path.
• the object of the present invention is to provide a method which ensures a uniform flow through an electrolyte space of an electrolysis cell and thus a narrow residence time distribution.
• the solution to the problem consists in a method for producing a uniform flow through an electrolyte space of an electrolysis cell, in which a maximum deviation from the average flow rate of less than 1% to 25% is generated by suitable design measures.
• At least two electrolyte spaces preferably form an electrolysis cell.
• At least one electrolyte space is an anolyte space and at least one electrolyte space is a catholyte space.
• An anolyte space and a catholyte space are adjacent and separated from one another by at least one membrane.
• the maximum deviation from the mean flow velocity is preferably obtained by building up an additional pressure drop. This is preferably 1 to 10 times the pressure difference in the entry area of the electrolyte space (i.e. the pressure loss in the entry area between the inlet to the entry area and the electrode in the electrolyte space if no additional pressure loss is applied).
• the calculation is carried out using equation (1):
• the inflow into the inlet area of the electrolyte space takes place in such a way that the volume flow entering is approximately uniformly divided into two partial flows with opposite main flow direction in the inlet area. This is particularly the case when the inflow is centered on the electrolyte space in relation to the width of the electrolyte space.
• the width of the electrolyte space is the dimension that is perpendicular to the main flow direction in the electrolyte space and perpendicular to the main direction of the electric field (gap width).
• ⁇ pov additional pressure loss
• ⁇ pv friction pressure loss in the inlet area
• p d y n dynamic pressure in the inlet area
• ⁇ pE total pressure loss in the electrolyte space
• A maximum deviation from the mean flow velocity, where 0 means no deviation and 1 means a deviation of 100%.
• the center of the electrolyte space refers to the center of the cross section perpendicular to the direction of flow on the upstream side of the electrode.
• the additional pressure loss is generated by pressure loss elements (i.e. constructive measures by means of which an additional pressure loss is generated) in the entry and / or exit area of the electrolyte space.
• the entry area is the area between the inlet to the electrolyte space and the electrode.
• the exit area is accordingly the area between the electrode and the outlet from the electrolyte space.
• the entry area can be designed, for example, as a distributor and the exit area as a collector.
• the pressure loss elements preferably produce a reduction in the flow cross section.
• the pressure loss elements are internals in the inlet area and / or outlet area of the electrolyte space.
• the pressure loss elements in the inlet area and / or in the outlet area Due to the pressure loss elements in the inlet area and / or in the outlet area, differences in the flow velocity, e.g. caused by pressure gradients in the entry area or in the exit area.
• the pressure gradients result e.g. B. from the fact that the inlet to the inlet area is arranged perpendicular to the flow direction in the electrode.
• the liquid is deflected in the entry area.
• the entrance area is closed on the side opposite the inlet.
• the liquid initially flows in the direction specified by the inlet.
• the liquid builds up on the side opposite the inlet, which increases the pressure. Due to the increased pressure, the liquid is then deflected into the electrode.
• the use of the at least one pressure loss element ensures that the pressure is evenly distributed after flowing through the pressure loss element. This leads to an even flow rate.
• pressure loss elements are therefore arranged in the outlet area for uniform distribution in the electrolyte spaces.
• a uniform flow rate can also be achieved if the inlet into the inlet area is opposite the inlet of the electrolyte space and the inlet area widens in the form of a diffuser. Due to the small opening angle of diffusers, however, a lot of space is required for this, which is often not available for installing the electrolysis cell. The slow transition from one cross-section to the other in the diffuser leads to long dwell times and a correspondingly large hold-up.
• the use of pressure loss elements in the inlet area and / or in the outlet area enables a space requirement that is significantly reduced compared to the use of diffusers by arranging the inlet at any point in the inlet area and the outlet at any point in the outlet area. At the same time, the smaller volume of the entrance area and the exit area reduces the hold-up.
• the pressure loss element is arranged between the inlet and the electrolyte space or between the electrolyte space and the outlet.
• electrolysis cells each comprising an anolyte space and a catholyte space
• the liquid is fed into the individual electrolysis cells via a distribution system, which preferably comprises a channel, from each of which an inlet to the entry area branches off to each electrolyte space.
• a distribution system which preferably comprises a channel, from each of which an inlet to the entry area branches off to each electrolyte space.
• the outlet area is connected to an outlet which opens into an outlet channel.
• Internals are known to the person skilled in the art which, on account of their structural conditions, can serve as pressure loss elements.
• Perforated sheets are an example of a pressure loss element.
• the openings in the perforated plates can have any cross section. Preferred openings in the perforated plates are bores.
• plates with at least one channel accommodated therein are also suitable as pressure loss elements. If there are several channels, these are preferably arranged parallel to one another. In a preferred embodiment, the channels have a circular cross section, since this is easiest to manufacture with conventional tools.
• the channels can also be elliptical or in the form of a polygon with at least three corners. Any other cross-sectional geometry known to the person skilled in the art is also conceivable for the channels accommodated in the plates.
• a gap in the pressure loss element is also preferred.
• the pressure loss elements are designed as a fabric or as a foam structure or as a plate with capillaries accommodated therein.
• the flow can emerge from the pressure loss element in the form of a jet.
• This beam should not pass directly into the working electrode which is connected downstream of the pressure loss element, since otherwise a high pressure loss is generated in the working electrode by the beam. For this reason, a calming section for distributing the emerging jet is provided between the pressure loss element and the working electrode.
• the exit area is essentially designed like the entry area, the design can be carried out essentially as for the entry area. In the exit area, however, the friction effects often dominate. It has also been shown that the uniform outflow from the electrolyte spaces often requires greater pressure losses in order to make the flow more even.
• the pressure loss resulting from the flow through the electrode must also be taken into account when dimensioning the pressure loss elements.
• the electrolyte space with the porous electrode can be the analysis space or the catholyte space, depending on the use of the electrolysis cell.
• the pressure level required in the electrolyte spaces for pressing the membrane against the porous electrode is preferably achieved by setting a counterpressure in the outlet area.
• the back pressure in the outlet area should be selected so that the pressure in the electrode space with the porous electrode is lower at every point than the pressure in the other electrolyte space.
• FIG. 1 shows a section through an electrolysis cell
• FIG. 2 shows a section through a catholyte space of an electrolysis cell
• FIG. 3 shows a section through a cell stack
• FIG. 4 shows a section of a catholyte space with distributor and pressure loss elements accommodated therein
• FIG. 5 shows a section of a catholyte compartment with distributor and a pressure loss element with capillaries
• FIG. 1 shows a section through an electrolysis cell.
• An electrolytic cell 1 comprises an anolyte space 2 and a catholyte space 3.
• an anode 4 in the form of a plate is accommodated in the anolyte space 2.
• the wall 14 of the anolyte space 2 can also be designed as a bipolar plate and thus take over the function of the anode 4.
• a cathode 5 is accommodated in the catholyte space 3, which has a porous structure and fills the entire catholyte space 3.
• the catholyte space 3 is separated from the anolyte space 2 by a membrane.
• the membrane 6 is fixed against the cathode 5.
• the pressure in the anolyte compartment 2 is preferably higher at every point than in the catholyte compartment 3.
• the membrane 6 is pressed against the cathode 5. In this way, bypasses between the cathode 5 and the membrane 6 are avoided and the entire catholyte flows through the cathode 5 designed as a porous structure.
• the anolyte is supplied to the anolyte space 2 from an inlet area designed as an anolyte distributor 10 via a pressure loss element 9.1.
• the anolyte flows via a further pressure loss element 9.3 into an outlet area designed as a collector 12.
• the direction of flow of the anolyte is identified by an arrow with reference number 7.
• the catholyte flows from an inlet area designed as a catholyte distributor 11 via a pressure loss element 9.2 into the catholyte space 3, flows through the electrode 5 there and finally flows through a pressure loss element 9.4 into an outlet area designed as a camolyte collector 13.
• FIG. 2 shows a section through a catholyte space of an electrolysis cell.
• the catholyte space is rotated by 90 ° in comparison to FIG. 1.
• the catholyte either passes through a central inlet 15 or a side inlet
• Figure 3 shows a section through a cell stack.
• a cell stack 19 comprises at least two electrolysis cells 1. However, depending on the required throughput, any number of electrolysis cells 1 can be connected to form a cell stack 19.
• anolyte spaces 2 and catholyte spaces 3 alternate.
• anolyte space 2 and catholyte space 3 are separated by membrane 6.
• Two electrolysis cells are separated by the wall 14, which can be designed, for example, as a bipolar plate.
• the electrolyte flows through the pressure loss element 9.1, 9.2 and thus reaches the anolyte space 2 or catholyte space 3.
• the electrolyte flows through the pressure loss elements 9.3, 9.4 and thus reaches the collector 12, 13 assigned to each anolyte space 2 or catholyte space 3.
• the direction of flow of the electrolyte is indicated here by arrows 7, 8.
• the electrolyte can also flow through the electrolytic cell 1 in the opposite direction from top to bottom.
• the electrolysis cell 1 can also be arranged such that the distributors 10, 11 and the collectors 12, 13 are at one level.
• the electrolysis cell 1 can also be inclined at any angle.
• Figure 4 shows a section of a catholyte compartment with distributor and pressure loss element.
• a calming section 21 is formed behind the pressure loss element 9.2.
• the liquid jet passing through the opening 23 widens in accordance with the flow direction indicated by the arrow 22.
• the calming section 21 a uniform liquid distribution with an almost constant pressure and thus with the same entry speed into the cathode 5 is achieved.
• a calming section 21 is preferably interposed between the porous cathode 5 and the pressure loss element 9.4. This ensures that a build-up of the liquid at the impermeable areas of the pressure loss element 9.4 does not lead to a build-up in the porous cathode 5, but rather that a uniform flow rate is obtained in the cathode 5 as far as the calming section 21.
• a calming section 21 between the porous anode 4 and the pressure loss element 9.3 must also be provided here analogously to the porous cathode 5.
• the openings 23 in the pressure loss element 9.1, 9.2, 9.3, 9.4 can be holes in a perforated plate, for example.
• the openings 23 can also have any other cross section.
• the opening 23 can, for example, also be a gap over the entire length of the electrolyte space.
• length is to be understood as the greater extent of the electrode perpendicular to the flow direction of the electrolyte.
• capillary 24 can also be accommodated in the pressure loss element 9.1, 9.2, 9.3, 9.4.
• the pressure loss in the pressure loss element 9.1, 9.2, 9.3, 9.4 is primarily generated by frictional forces.
• tissue or foam structures as well as fillers or structured packings are also suitable as pressure loss elements 9.1, 9.2, 9.3, 9.4.
• a plate electrolysis cell has a cross-section of 5 mm x 500 mm.
• a distributor of 20 x 20 x 500 nm is provided for the distribution of the electrolyte.
• the volume flow of the electrolyte is 720 17h with an electrolyte density of 1000 kg / m 3 .
• the flow should be evened out by a pressure loss element with holes.
• the maximum deviation from the mean flow velocity should be 5%.
• the mis-distribution is said to be determined by inertia.
• a maximum flow velocity v of results from the volume flow and cross-section of the distribution channel
• Equation (1) then results in a required pressure loss across the pressure loss elements of 12.2 mbar for the desired deviation of 5%.
• a pressure loss only takes into account the given pressure loss coefficient at a flow velocity in the opening V ⁇ of

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Metallurgy (AREA)
• Materials Engineering (AREA)
• Automation & Control Theory (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

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• 2004
  • 2004-04-22 DE DE102004019671A patent/DE102004019671A1/de not_active Withdrawn
• 2005
  • 2005-04-18 JP JP2007508806A patent/JP2007533855A/ja not_active Withdrawn
  • 2005-04-18 EP EP05734841A patent/EP1743051A2/de not_active Withdrawn
  • 2005-04-18 CN CNA2005800206484A patent/CN1973062A/zh active Pending
  • 2005-04-18 US US11/587,056 patent/US20070221496A1/en not_active Abandoned
  • 2005-04-18 WO PCT/EP2005/004074 patent/WO2005103336A2/de active Application Filing

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