Electrolyzer, Insert for an Electrolyzer, Supply Pipe for an Electrolyzer and Discharge Pipe for an Electrolyzer

The invention relates to an electrolyzer having a plurality of cell elements and having a supply pipe and a discharge pipe for supplying and discharging an electrolyte to and away from the cell elements. The invention further relates to an insert for such an electrolyzer, a supply pipe for such an electrolyzer and a discharge pipe for such an electrolyzer.

During electrolysis, redox reactions which are related to materials conversions can be enforced by impressing an electrical current through suitable cell elements. A device for this purpose is referred to as an electrolyzer and can be used to produce important basic substances of the chemical industry. In many cases, anode and cathode half-spaces are separated by means of diaphragms (or membranes) which allow electrical conductivity (ion and/or proton exchange) but prevent mass transfer. If liquid electrolytes are used in electrolyzers which are altered or consumed by the materials conversion, these may be continuously renewed during the process by means of corresponding supply lines and discharge lines. The materials conversion rates for given cell elements are typically given narrow limits due to current density constraints. For large-scale use, the active cell element area must therefore be increased in order to increase the materials conversion rates. This may be achieved by enlarging the cell elements or by simultaneously operating a plurality of smaller cell elements. A technically sensible and frequently applied method is the arrangement of many (identical) cell elements into a stack. In this context, the electrical connection of the cell elements of a stack represents a series connection, i.e., the anode of a cell element N is connected to the cathode of the cell element N+1, and the cathode of the cell element N is connected to the anode of the cell element N−1 in an electrically conducting manner. The series connection also multiplies the low cell element voltage from a few volts to, for example, several hundred volts. The hydraulic interconnection of the cell elements of a stack for delivering fresh electrolytes, on the other hand, represents a parallel connection. By hydraulically interconnecting the cell elements to form a stack, additional and undesirable electrically conductive connections are created between all of the cell elements. During operation of the stack of cell elements, i.e., application of an electrical voltage or impressing of an electrical current from the first to the last cell element, an electrical working current flows through all of the cell elements. However, undesirable so-called electrical stray currents additionally flow in the various parallel current paths. These electrical stray currents lead, in particular at the first and last cell elements of a stack, to local excessive current density elevations close to the supply lines and discharge lines of the electrolytes. This may lead to premature ageing and destruction of the membranes and to failure of the entire stack.

A reduction in the electrical stray currents may be achieved by increasing the electrical resistances of the supply lines and discharge lines of the electrolytes. The previous solution provides for the supply lines and discharge lines to be extended, consequently resulting in an increase in resistance with a constant cross-sectional area. However, the line extensions adversely lead to increased flow resistances and increased material needs for manufacture.

The object of the invention is achieved by an electrolyzer having a plurality of cell elements and having a supply pipe and a discharge pipe for supplying and discharging an electrolyte to and away from the cell elements, wherein, at least in sections, the supply pipe and/or the discharge pipe have at least two sub-lines designed to be galvanically isolated from one another, wherein the sub-lines are designed as eccentric sub-lines and are configured such that a current path extension of the current paths of electrical stray currents is effected in the supply pipe and/or the discharge pipe.

In this context, a supply pipe or discharge pipe is understood to mean an elongate hollow body having a length substantially greater than its diameter. Unlike a hose, a pipe is manufactured of a relatively inflexible material. Thus, the supply pipe and the discharge pipe may be designed to be rigid such that manual deformation as in the case of a hose, such as, for instance, a corrugated hose, is impossible, but instead a tool insert is required to do so.

In other words, by means of the at least two sub-lines at least in sections designed to be galvanically isolated from one another, the plurality of cell elements forming a stack are divided into at least two cell element groups which are better electrically insulated from one another. Thus, a current path extension is achieved for at least some of the electrical stray currents, which, due to the extension, give rise to a higher ohmic resistance, without there being an extension of the supply pipe and/or discharge pipe, which in turn would give rise to increased flow losses.

By having the sub-lines designed as eccentrically disposed sub-lines, a particularly stable construction with optimized utilization of the cross-sectional area of the supply pipe or the discharge pipe is made possible. In this context, the term eccentric is understood to mean outside a circle center or center of rotation, hence, for instance, arrangements in which the sub-lines are not arranged as concentric circles or rings with respect to one another.

According to one embodiment, at least one of the sub-lines is designed to form a comb structure. As such, the sub-lines with their respective cross-sectional areas form a regular pattern with the cross-sectional areas as the cell elements. The respective cross-sectional areas may have any basic shape, for instance, be designed to be triangle-shaped, quadrangle-shaped, or even circular. Such a comb structure leads to a particularly stable construction without any additional stabilizing elements.

According to a further embodiment, at least one of the sub-lines has a hexagon-shaped cross-sectional area. As such, the respective cross-sectional areas form a honeycomb structure which is at the same time particularly stable and provides maximized cross-sectional areas.

According to a further embodiment, the sub-lines are each designed to provide an equal cross-sectional area. Thus, it is ensured that the same amount of electrolyte per unit of time may be delivered to each cell element group. A particularly simple construction is thus made possible, since each of the cell element groups may have the same number of cell elements.

According to a further embodiment, the sub-lines extend in the supply pipe with a predetermined length in the direction opposite to the electrolyte flow direction and/or in the discharge pipe with a predetermined length in the direction of the electrolyte flow direction. Thus, the current path extension may be increased once again.

According to a further embodiment, at least one of the sub-lines is formed by a passage extending through an insert in the supply pipe and/or discharge pipe. Thus, the sub-lines may be formed in a particularly simple manner by an integral and/or materially uniform member.

According to a further embodiment, at least one of the sub-lines is formed by a groove extending parallel to the passage. In other words, while the other sub-lines are completely jacketed by the insert, the sub-line formed by the groove is only partially jacketed by the insert. Rather, the insert and the pipe jacket of the supply pipe or discharge pipe together form a jacket of that passage. Thus, a further sub-line may be formed in a particularly simple manner.

According to a further embodiment, the insert has at least one tube section and an annular element associated with each tube section, wherein the respective annular element extends radially outwards from the respective tube section and terminates at least one sub-line each. For instance, the insert may be designed to be integral and/or materially uniform, and thus makes it possible to form the plurality of sub-lines by installing only one member.

The invention further encompasses an insert for such an electrolyzer, a supply pipe and a discharge pipe for such an electrolyzer.

Reference is initially made to, where an electrolyzeris depicted.

In the present exemplary embodiment, the electrolyzerhas a plurality of cell elementsforming a stackand electrically connected in series. Further, in the present exemplary embodiment, the electrolyzerhas a supply pipeand a discharge pipe, each with circular cross-sectional areas, using which electrolyte may first be supplied to the cell elementsand then be discharged from the cell elements. To accomplish this, both the supply pipeand the discharge pipeeach have a plurality of outlet and inlet openings (not depicted).

In order to effect a current path extension of the current paths of electrical stray currents, in the present exemplary embodiment, an insertis inserted into each of the supply pipeand the discharge pipe.

The construction of an exemplary embodiment of the insertwill now be explained with additional reference to.

In the present exemplary embodiment, the inserthas 19 pipe sectionstoeach forming a sub-lineto. Deviating from the present exemplary embodiment, the number of tube sectionstomay also be different.

Further, in the present exemplary embodiment, each of the sub-linestohas a hexagon-shaped cross-sectional area and as such forms a comb structure or honeycomb structure. In other words, in the present exemplary embodiment, the sub-linestoare each formed by a passagetoextending through the insertalong their main direction of extension and, in the present exemplary embodiment, each designed to be a straight line and parallel to one another.

The passagestoor webs connecting the passagestomay form flow-optimized inlet regions by means of roundings.

Homogenization of the electrolyte distribution may be achieved by means of optimized cross-sectional areas of the supply and discharge lines of the respective cell element of the stack, along with an adjustment of the flow resistance, i.e., deviations from the even comb structure, and/or by means of optimized entry areas.

Furthermore, the sub-linestoare designed to be eccentrically disposed sub-linesto, i.e., they are located outside a circle center or center of rotation. In other words, in the present exemplary embodiment, the sub-linestoare not arranged as concentric circles or rings with respect to one another.

In the present exemplary embodiment, one of the sub-linesis further formed by a grooveextending parallel to the passagestoand forming a further passage

The sub-lineformed by the grooveis only partially jacketed by the insert. Rather, the insertand the pipe jacket of the supply pipeor discharge pipetogether form a jacket of that passage

Each of the sub-linestoterminates at an annular elementtosealing the respective sub-linetowith respect to the supply lineor discharge line. As such, with each of the sub-linesto, electrolyte may be delivered to one cell element group each of the stack, or electrolyte is discarded. In the present exemplary embodiment, electrolyte is delivered to a first cell element group in the electrolyte flow direction E through the sub-linesformed by the groove, or electrolyte is discarded.

In the present exemplary embodiment, the insertis designed to be integral and/or materially uniform. In particular, in the present exemplary embodiment, the insert—as well as the supply pipeand the discharge pipe—is manufactured of an electrically insulating material.

Reference is now additionally made to, where it is depicted that, in the inserted state in the supply pipeor the discharge pipe, the respective annular elementstocome into contact with the inner wall of the supply pipeor the discharge pipeand thus provide a closure which, in the present exemplary embodiment, closes off one of the sub-linesto, wherein seals for sealing may additionally be provided in this case. Small leakages of the insertbetween adjacent cell element groups of the stack may be tolerated, leading to a simple sealing concept.

In the present exemplary embodiment, the supply pipeand the discharge lineare designed to be rigid in the section in which the respective insertsare located and are flexible in comparison thereto in the remaining section.

In the present exemplary embodiment, the respective cross-sectional areas of the sub-linestoare of the same size. Thus, a largely homogeneous distribution of electrolytes to all of the cell element groups of the stackmay be achieved.

For instance, electrolyte is thus delivered to a stackhaving 20 cell elements.

Furthermore, in the present exemplary embodiment, the insertsrespectively inserted into the supply pipeand the discharge pipeextend, in the case of the supply pipe, with a predetermined length L in the direction opposite to the electrolyte flow direction E and, in the case of the discharge pipe, with the predetermined length L in the direction of the electrolyte flow direction E. In the present exemplary embodiment, the respective lengths L are of the same size. Deviating from the present exemplary embodiment, however, they may also be of different sizes.

In the present exemplary embodiment, the length L has a value in the range of from 0.5 m to 3 m, for instance 2 m.

Inserting the insertseparates the individual sections of the stack. This forces electrical stray currents emerging from rear sections and entering front sections into extended current paths S. The extended current paths S are related to an increased ohmic resistance, consequently reducing the electrical stray current intensities. A maximum of the electrical stray current density may thus be reduced by 70% (to 30%).

In other words, an electrical series connection and, at the same time, a hydraulic parallel connection are thus provided, while at the same time having a particularly compact design.

Thus, a current path extension is achieved for at least some of the electrical stray currents, which, due to the extension, gives rise to a higher ohmic resistance, without there being an extension of the supply pipeand/or discharge pipe, which in turn would give rise to increased flow losses. At the same time, an insertis provided which is easy to manufacture and is particularly stable due to the comb structure.