Method for replacing a selected anode and anode changing assembly

Abstract

The invention relates to a method for replacing a selected anode, wherein a plurality of anodes (5) are located in an electrolytic cell (100) each comprising a rod detachably fixed to an anode frame (4) and at least one anode block (5a) located inside a reduction pot (2) during an operating time, the method comprises the steps of: - determining or evaluating, if one of the anodes (5) is a selected anode and needs to be replaced; - detaching and removing the selected anode by using a handling tool (1 a); - selecting and grabbing a new anode by using the handling tool (1a); - setting the new anode into the electrolytic cell (100) and placing and fixing the new anode at a mounting height, wherein the mounting height is determined by a predictive algorithm (G) by collecting and processing -- anode information (IA) characterizing the at least one selected anode and / or the at least one new anode, and -- process information characterizing the electrolytic reduction process at least during the operating time (tO) while the at least one selected anode was in the reduction pot (2).

Description

[0001] The present invention relates to a method for replacing a selected anode located in an electrolytic cell for the producing of aluminum by electrolytic reduction and an anode changing assembly, in particular a pot tending machine or a service unit, for carrying out the method.

[0002] In an aluminum factory a very important part of the production process are the anodes being located inside a reduction pot containing a molten electrolytic bath and molten aluminum. The anodes are consumed during the electrolytic reduction processes, wherein for each ton of aluminum produced approx. 500 kg of anode material is being consumed. Consequently, the consumed anodes must be replaced by new ones from time to time, e.g., around every 20 to 30 days, depending on process parameters.

[0003] Thereby, about 20 to 40 anodes are located inside one reduction pot, wherein the anodes are arranged in a certain distance to each other and each anode is supported by a superstructure above it. Each of the anodes are releasably fixed to an anode frame on the superstructure via a fastener, e.g., an anode connector, wherein the fastener is holding a rod or stem attached to the top surface of the respective anode via an attachment element, e.g., a multipode. The mounting height of the anode can be modified by adjusting the position of the rod relative to the fastener on the anode frame before fixation.

[0004] For replacement of a selected or worn anode, the assigned rod can be lifted by an anode changing assembly, in particular a pot tending machine or a service unit, after releasing the respective rod from the superstructure. Therefore, the pot tending machine comprises an overhead crane and tools attached thereto having at least anode clamps or anode wrenches for grabbing the rod. Alternatively, a service unit might be used to change the anode, e.g., a vehicle on wheels being able to drive on the shop floor and having several tools for grabbing an anode for its replacement. After the selected or worn anode has been carried away by the pot tending machine or the service unit a new anode is fastened to the superstructure via the pot tending machine or service unit. To not disturb the reduction process in the reduction pot when replacing a selected or worn anode, only one or two anodes are changed at a time.

[0005] Hence, in a reduction pot each anode is normally at a different stage of consumption and having a different thickness. Thereby, the mounting height of the new anode is chosen such that its bottom surface is at the same level as the bottom surfaces of all the other anodes in the reduction pot to ensure a flat anodic level and a constant distance between the anode and the cathode over the entire reduction pot. Hence, when replacing a selected or worn anode, the new one must be placed at a higher position to compensate the thickness difference between the old anode, having a reduced thickness, and the new anode. As the bottom surface of the anode is not visible during operation this leveling is normally done by setting both, the old and the new anode, on a reference plane on the ground and using a vernier to mark the height difference by manually drawing reference chalk lines, which is a complex, time consuming and failure-prone process. However, measuring both anode heights individually to define their height difference is anyway necessary as one cannot rely on theoretical dimensions of the respective anodes considering the variability in the dimensions of the (old and new) anodes, that might result from the fabrication process of the respective anode, and as the exact consumption of the old anode is not known.

[0006] Other replacement methods are known that use optical sensors for measuring the constructive properties of the selected or worn anode during lifting it out of the reduction pot and of the new anode during lowering it into the reduction pot in order to calculate the correct height to choose for the new anode, as described in DE 28 19 351, US 4,221,641, US 7,422,675 for example. Also, other sensing methods are known, as described in US 4,540,474 or US 2008 / 0251392A1 for example.

[0007] But, even with those measurement methods, the replacement operation of an anode is complex and time consuming. Further, such solutions cannot always be retrofitted onto an existing pot tending machine and / or need to be maintained regularly and need to be taken special care of due to its fragility.

[0008] Accordingly, it is the object of the present invention to provide an easy, fast and secure way to replace a selected anode, in particular a worn anode, located inside a reduction pot of an aluminum smelter, with a new anode, ensuring a consistent distance between the anode and the cathode over the entire reduction pot after replacement.

[0009] This object is achieved by a method and an anode changing assembly, in particular a pot tending machine or a service unit or another device, according to the independent claims. Preferred embodiments are referred to in the subclaims.

[0010] Hence, according to the invention, a method for replacing one or several (typically one or two) selected anode(s) located in an electrolytic cell for the producing of aluminum by electrolytic reduction is provided, wherein a plurality of anodes are located in the electrolytic cell side by side and each of the anodes comprises a metallic rod detachably fixed to an anode frame of the electrolytic cell via a fastener, e.g., an anode connector, and one or two anode block (carbon block) attached to the rod of the respective anode.

[0011] The respective anode(s) is / are individually fixed to the anode frame (via the rod and fastener) in a certain mounting height such that the anode block is located inside a reduction pot or crucible of the electrolytic cell, where the electrolytic reduction process is carried out. The claimed method comprises at least the steps of:- determining or evaluating, if at least one of the anodes in the electrolytic cell is a selected anode that needs to be replaced, e.g., because a predetermined schedule indicates that the respective anode(s) needs to be replaced and / or a block thickness of the anode block(s) of the respective anode(s) falls below a predetermined thickness threshold and / or the operating time (overall time spent in the reduction pot) of the respective anode(s) exceeds a predetermined maximum time; detaching and removing the selected anode(s) from the electrolytic cell by using a handling tool of an anode changing assembly, e.g., a pot tending machine or a service module or a similar device, having a height adjustable anode clamp. In the case there are two selected anodes in a pot, they are adjacent to each other and are changed simultaneously and the anode changing assembly is fitted with two height adjustable anode clamps.

[0012] In particular, before or during detaching and removing the selected anode(s) from the electrolytic cell the following steps are carried out: placing the handling tool of the anode changing assembly close to and / or above the rod(s) of the determined selected anode(s); gripping or clamping the rod(s) of the determined selected anode(s) using the at least one height adjustable anode clamp of the handling tool, wherein, for example, the at least one anode clamp is lowered onto the upper end of the rod(s) of the determined selected anode(s) by a height adjustment device until the at least one anode clamp engages a clamping surface, e.g., inside a clamping hole in the upper end of the respective rod; determining a (relative) mounting height of the selected anode(s) in the electrolytic cell, e.g., in relation to a reference point located on the superstructure or the anode frame of the electrolytic cell or a fixed point on the anode changing assembly; detaching and removing the selected anode(s) from the electrolytic cell, e.g., by releasing the fastener, and disposing the selected anode(s).

[0013] Afterwards, the following steps are carried out: selecting and grabbing one or several (typically one or two) new anode(s) by using the handling tool of the anode changing assembly, e.g., by placing the handling tool of the anode changing assembly close to the rod(s) of the new anode(s) outside the electrolytic cell, e.g., in an exchange location for storing new anodes, and gripping the rod(s) of the respective new anode(s) using the at least one height adjustable anode clamp of the handling tool, e.g., lowering the at least one anode clamp onto the upper end of the rod(s) of the new anode(s) by the height adjustment device until the at least one anode clamp engages a clamping surface, e.g., inside a clamping hole in the upper end of the respective new rod; setting the new anode(s) into the electrolytic cell and placing and fixing the new anode(s) at a mounting height, wherein the mounting height is determined by a predictive algorithm by collecting and processing -- anode information characterizing the selected anode(s) and / or the new anode(s), and -- process information characterizing the electrolytic reduction process at least during the operating time while the selected anode(s) was / were in the reduction pot.

[0014] Thereby, for example, the mounting height for the new anode(s) might be determined in dependence on the determined mounting height of the selected anode(s) (already being detached and removed) and a (predicted) consumption thickness of the selected anode(s), i.e., the amount of material that (predictively) has been removed from the anode block(s) of the selected anode(s) during the operation time, wherein this consumption thickness of the selected anode(s) is predicted based on the operating time of the selected anode(s) determined accordingly and at least an overall current flowing through the corresponding reduction pot during this operating time, the overall current being predetermined based on operation conditions and being constantly monitored and saved over time.

[0015] One of the benefits of this method is that the offset or difference in the spatial dimensions, in particular the block height, between the respective selected anode and the respective new anode is determined based on a virtual or predictive quantity, namely the predicted consumption thickness, that is not measured directly. Rather, it was found that the consumption of an anode block is mainly given by the operating time of the respective selected anode or its time spent in the reduction pot factored by the overall current flowing through the reduction pot during the electrolytic reduction process. As these quantities can be constantly measured throughout the reduction process, the amount of material that has been removed from the anode block of the respective selected anode during the operation time can be predicted.

[0016] Further, variations of the initial spatial dimensions of an anode can be considered by additionally loading anode information about the new anode(s) as well as the selected anode(s). So, when calculating the mounting height for the new anode(s), these dimensional variations, e.g., due to production tolerances, can be taken into account in addition to the predicted consumption thickness of the selected anode(s). This improves the precision of the positioning of the new anode(s) further, such that time-consuming re-adjustments can be omitted and the electrolysis process itself can be optimized.

[0017] Thus, the anode changing assembly is able to collect various process information or anode information characterizing the electrolysis process or the respective anode(s), wherein these units of information are usually individual for the respective reduction pot and the anodes therein. Said process information might include, for example, the operation time and / or at least a time progression (history) of the overall current flowing through the reduction pot and / or of the electric voltage applied between the anode(s) and the cathode throughout the operation time and / or a feeding parameter characterizing the amount of alumina fed into the respective reduction pot during the operation time and / or a movement parameter specifying the amount of (vertical) movement (into or out of the respective reduction pot) of the anode frame during the operation time and / or a resetting parameter specifying whether the respective anode has been reset into the reduction pot during the operation time and / or any other parameter that might have an influence on the removal of material from the anode block. Further, the anode information might include, for example, at least the spatial dimensions of the selected / new anode(s) and / or the weight of the selected / new anode block(s). Further process information and / or anode information might be provided.

[0018] These various process information and anode information might be processed by a processing unit assigned to the anode changing assembly, wherein the processing unit might be arranged locally on the or adjacent to the anode changing assembly or away from the anode changing assembly, e.g., as a cloud-based computing system (laaS, PaaS, SaaS) or any other computing system. The processing unit is able to receive said units of information via corresponding signal interfaces and / or can determine certain information by itself (e.g., based on collected information). By analyzing the process information and / or anode information in a well-known environment the processing unit can build up a predictive model or predictive algorithm. After enough process information and / or anode information have been harvested or collected, the predictive algorithm can be used to operate the anode changing assembly. By constantly comparing newly collected process information and / or anode information with forecasts while operating the anode changing assembly using the predictive algorithm, observed errors can be used to continuously adjust or adapt the predictive algorithm.

[0019] In particular, as the consumption of an anode block over time can be determined by the predictive algorithm based on the collected process information and anode information, the predetermined schedule that is normally used for planning the time to replace the anodes can be optimized. Hence, the point in time for replacing a specific anode can be specified more precisely, further improving the electrolytic reduction process and saving cost.

[0020] Features and advantages of the present invention will become apparent upon reading of the following detailed description along with the accompanied drawings, wherein: Fig. 1shows a cross-sectional view of a pot tending machine and a reduction pot; Fig. 2shows a detailed view of an anode inside the reduction pot of Fig 1; Fig. 3shows a flow chart of an embodiment of the method for replacing an anode; and Fig. 4A-4Cshow the different stages of the replacing process.

[0021] Fig. 1 is a schematic view of an electrolytic cell 100 for the production of aluminum by an electrolytic reduction process, the electrolytic cell 100 comprising a reduction pot 2, a superstructure 3, an anode frame 4 and a plurality of anodes 5 or anode assemblies, two of which are shown. As usual, the pot 2 comprises at least a casing 6, a lining 7, a cathode unit 8 having a cathode rod 8a and a cathode block 8b, and removable hoods 9 for covering the pot 2. Each of the anodes 5 or anode assemblies is composed of one or two anode block(s) 5a (carbon block) having a certain block thickness T5a (in vertical direction) and one metallic rod 5b attached to a top surface 5c of the anode block(s) 5a via an attachment element 5e, e.g., via a "multipode", as shown in Fig 2. In case the anode 5 comprises two carbon blocks 5a attached to a single metallic rod 5b, their block thickness T5a is considered as being the same. The metallic rod 5b further comprises a clamping hole 5f (or any other type of shape that allow to clamp the anode rod 5b) having any cross-section for clamping the anode 5 by a handling tool 1a of an anode changing assembly 1, e.g., a pot tending machine 40 or a service unit 60, as described below. The whole anode 5 has a certain anode height H5, composed of the block thickness T5a, a rod height H5b of the rod 5b and an attachment height H5e of the attachment element 5e, wherein the rod height H5b of the rod 5 is measured, for example, up to the top surface 5g of the clamping hole 5f.

[0022] The anodes 5 are releasably fixed to the anode frame 4 via its rods 5b by a mechanical fastener 10, e.g., an anode connector, which presses the respective rod 5b against the anode frame 4. The mounting height is chosen in such a way, that a bottom surface 5d of each anode block 5a is located in the interior 11 of the pot 2 formed by the lining 7 and the cathode unit 8. During the electrolytic process, the interior 11 contains at least a molten electrolytic bath 30 and molten aluminum 31, wherein the bottom surface 5d of each anode block 5a is immersed in the molten electrolytic bath 30. Further, the bottom surface 5d of each anode block 5a in the interior 11 is spaced apart from the top of the cathode block 8b by a predetermined distance, such that the bottom surface 5d of each anode block 5a lies approximately at the same anodic level L inside the reduction pot 2. As a result, a uniform electric voltage V is provided between the cathode block 8b and each of the anode blocks 5a within the reduction pot 2 leading to a uniform distribution of the overall current CO among all the anodes 5 within the same reduction pot 2.

[0023] Thereby, the overall current CO is predetermined and provided by a current source 13 and the electric voltage V provided between the cathode block 8b and the respective anode block 5a can be measured by a voltage measurement device 14, e.g., located between a first electrical conductor 12a connected to the anode frame 4 and a second electrical conductor 12b connected to the cathode unit 8. The voltage measurement device 14 might be used to measure the electric voltage V for the given overall current CO to monitor if an actual resistance calculated by ohm's law equals approximately to a predetermined target-resistance that ensures an optimized reduction process. Thereby, the actual resistance can be adjusted by changing the height of all the anodes 5 in the reduction pot 2, e.g., after replacement of one or several anodes 5, wherein this height adjustment of all the anodes 5 together is done by vertically moving the anode frame 4, for example.

[0024] During the electrolytic reduction processes the anode blocks 5a are constantly consumed, wherein for each ton of aluminum produced approx. 500 kg of anode material is being consumed mainly from the bottom surface 5d of the anode block 5a. Typically, when an anode block 5a is at its end of life, its block thickness T5a has been reduced by around 300 to 400mm from its initial block thickness T5ai. This also reduces the electrical resistance of the respective anode block 5a, which can be monitored via the voltage measurement device 14. Further, the change in electrical resistance may result in a change in the uniform distribution of the given overall current CO among all the anodes 5 within the same reduction pot 2.

[0025] As the anodes 5 are constantly consumed through the electrolysis process, a selected anode 5S has to be replaced by a new anode 5N from time to time, e.g., around every 28 days, depending on process parameters. Thereby, an anode 5 in the reduction pot 2 is treated as a selected anode 5S based on a predetermined schedule which indicates that or when the respective anode 5 needs to be replaced. The predetermined schedule might be set in advance and considers, for example, when the block thickness T5a of the anode block 5a of the respective anode 5 will approach or reach a predetermined thickness threshold TT and / or further considers that a stable and efficient work organization and a stable electrolysis process will be ensured, also including some buffer times to account for potential disruptions during the common workflows.

[0026] The replacement process is done according to the method as claimed by predictively gauging an anode 5S and determining the mounting height of the new anode 5N based on this prediction. The overall process sequence of this method is exemplarily shown in the flow chart of Fig 3: In a first step ST1, the status of the anodes 5 in the reduction pot 2 is checked, i.e., it is determined or evaluated, if one or more of the anodes 5 inside the reduction pot 2 is a selected anode 5S and needs to be replaced. This can be done continuously or at specific time intervals throughout the electrolysis process, e.g., based on said predetermined schedule, wherein the status check can be done manually or automatically.

[0027] One possibility of setting said schedule is to consumption or operation time to that is assigned to the respective anode 5, i.e., the time the respective anode 5 already spent inside the reduction pot 2. If the operation time to exceeds a predetermined maximum time tMax, e.g., 25 days, the schedule indicates that the respective anode 5 needs to be replaced as it is assumed that the block thickness T5a is approaching the predetermined thickness threshold TT. Hence, a predetermined maximum time tMax for the respective anode 5 is loaded from a look-up table or the like, wherein the maximum time tMax might be determined in prior experiments. Further, the schedule considers a stable work organization, i.e., it is checked whether the replacement of the anode 5 at a later point in time, which suits the work organization of the electrolysis plant, would lead to an operation time to of the respective anode 5 which exceeds the predetermined maximum time tMax.

[0028] In case the respective anode 5 is treated as a selected anode 5S considering the operation time to as explained, a replacement signal SR is triggered manually, e.g., by an operator manually monitoring the schedule, or automatically, e.g., by a processing unit 20 automatically monitoring the schedule. Afterwards, the replacement process for the respective anode 5 can start. Thereby, the processing unit 20 can be arranged locally on the or adjacent to the anode changing assembly 1 or away from the anode changing assembly 1, e.g., as a cloud-based computing system (laaS, PaaS, SaaS) or any other computing system.

[0029] Alternatively, the schedule for checking the status of the respective anode 5 can be set by using a predictive algorithm G that is implemented on said processing unit 20, e.g., as a software or hardware implementation. The predictive algorithm G is adapted to determine a predicted block thickness T5ap of each anode 5 located in the reduction pot 2, as described later. Based on said predicted block thickness T5ap the predictive algorithm G can determine the point in time during operation when the predicted block thickness T5ap of a certain anode 5 will fall or falls below the thickness threshold TT. Consequently, this prediction can be used to set the schedule precisely specifying when the respective anode 5 needs to be replaced and, thus, is to be treated as a selected anode 5S. In addition, also in this embodiment, a stable work organization is considered when setting the schedule based on the predictive model.

[0030] Hence, throughout the electrolysis process, the status of an anode 5 is constantly checked via a prediction of the consumption (or of the thickness) of the respective anode 5 or anode block 5a. In case the respective anode 5 is treated as a selected anode 5S considering this prediction to set the schedule, a replacement signal SR is triggered manually, e.g., by an operator manually monitoring the schedule, or automatically, e.g., by the processing unit 20 automatically monitoring the schedule. Afterwards, the replacement process for the respective anode 5 can start.

[0031] For predicting the consumption (or the thickness) of the respective anode 5 or anode block 5a, the processing unit 20 can receive various input signals SI via an input interface 21, wherein the input signals SI are processed by the predictive algorithm G for determining the predicted block thickness T5ap of a selected anode 5. The input signals SI may contain, for example, anode information IA assigned to each of the anodes 5 located in the reduction pot 2 and process information IP as, for example, the overall current CO given by the current source 13, and / or the electrical voltage V measured by the voltage measurement device 14 during a specified operation time tO, and / or a feeding parameter FP specifying the amount of alumina that is fed or is supposed to be fed into the respective reduction pot 2 during a specified operation time tO, and / or a movement parameter MP specifying the amount of (vertical) movement (into or out of the respective reduction pot 2) of the anode frame 4 during a specified operation time tO, e.g., when adjusting the actual resistance by changing the height of all the anodes 5 in the reduction pot 2, and / or a resetting parameter RP specifying whether the respective anode 5 was reset into the respective reduction pot 2 during a specified operation time tO, e.g., because the respective anode 5 was not properly loaded into the reduction pot 2 and / or to the anode frame 4, and / or any other parameter having an influence on the consumption or on the removal of material from the respective anode block 5a and therefore might be useful for the predictive model.

[0032] The anode information IA assigned to the respective anode 5 might be, for example, a carbon density r5a of the anode block 5a, initial spatial dimensions D5 (initial block thickness T5ai of the anode block 5a, initial block volume V5ai of the anode block 5a, rod height H5b, attachment height H5e of the attachment element 5e, initial anode height H5i, etc.) of the respective anode 5, an initial weight W5ai of the anode block 5a, a positional specification P5 of the respective anode 5, e.g., "in the middle", "on the side", and the operating time tO, i.e., the time the respective anode 5 already spent and / or is supposed to spend inside the reduction pot 2. In case the anode 5 comprises two carbon blocks 5a attached to a single metallic rod 5b as described before, the collected data or anode information IA of two carbon blocks 5a are combined accordingly, for example.

[0033] Alternatively, the operating time tO is not transmitted to the processing unit 20, but the processing unit 20 or the predictive algorithm G is determining the operating time to of the respective anode 5 by itself, e.g., counting the time after receiving a respective trigger signal that specifies that the respective anode 5 has been inserted into the reduction pot 2 for operation. If further information about the electrolysis process and the anodes 5 located inside the reduction pot 2 are known, they can also be transmitted to the processing unit 20 via the input signal SI and taken into consideration by the predictive algorithm G.

[0034] The respective information (IA, IP) provided or available to the predictive algorithm G allow to predict the amount of anode material that has already been or will be consumed from the respective anode 5 during a specified operating time tO. In case of setting the schedule, this operating time tO is the time in question, which the anode 5 is supposed to spent inside the reduction pot 2 before it needs to be replaced. In case of determining an actual state of the anode 5, the specified operating time tO is the time the anode 5 already spent inside the reduction pot 2.

[0035] In this context, the predictive algorithm G is able to determine a consumption parameter PC for every anode 5 in the reduction pot 2 based on the information (IA, IP) provided or available. This consumption parameter PC is a virtual or predictive measure on the change in the spatial dimension of the respective anode block(s) 5a, in particular, on the change in the block thickness T5a from its initial block thickness T5ai, as during the electrolysis process material is mainly removed from the bottom surface 5d of the respective anode 5.

[0036] Especially, said consumption parameter PC is dependent on the specified operation time to of the respective anode 5 in the reduction pot 2 factored by the given overall current CO flowing through the reduction pot 2 throughout the operation time tO. Further, the feeding parameter FP, i.e., the amount of alumina that is already fed or will be fed into the respective reduction pot 2 during the specified operation time to influences the consumption of the anode 5. Also, the movement parameter MP, i.e., the amount of (vertical) movement (into or out of the respective reduction pot) of the anode frame 4 during a specified operation time tO, and / or the resetting parameter RP, i.e., whether the respective anode 5 was reset into the respective reduction pot 2 during a specified operation time tO, influences the consumption of the anode 5.

[0037] Hence, the consumption of the respective anode 5 is mainly influenced by these parameters tO, CO, FP, MP, RP resulting in the following integral equation for the consumption parameter PC: PC = ∫ 0 tO f CO t , FP t , MP t , RP t , k dt with f being a predetermined functional equation, e.g. a polynomial function, comprising adaptive proportionality factor(s) k for considering the properties of the respective anode 5, e.g., above mentioned carbon density r5a of the anode block 5a, the initial spatial dimensions D5 (initial block thickness T5ai of the anode block 5a, initial block volume V5ai of the anode block 5a, rod height H5b, attachment height H5e of the attachment element 5e, initial anode height H5i, etc.) of the respective anode 5, the initial weight W5ai of the anode block 5a, the positional specification P5 of the respective anode 5, e.g., "in the middle", "on the side". Further anode properties and / or process conditions may have an influence on the proportionality factor k and / or the type of functional equation f.

[0038] As the consumption parameter PC is linked to the consumption of the respective anode 5, it can be used to determine the predicted block thickness T5ap of the respective anode 5 that is currently existent or that is supposed to be existent throughout the specified operation time tO, as follows: First, a consumption thickness T5ac is determined in dependence of the consumption parameter PC, i.e., the amount of material that has already been removed or that is supposed to be removed from the bottom surface (s) 5d of the respective anode block(s) 5a during the specified operation time tO. Depending on the type of functional equation f (of the consumption parameter PC) and / or the definition of the proportionality factor k in the functional equation f, the consumption thickness T5ac might directly be given by the consumption parameter PC, i.e., T5ac = c . PC with the conversion parameter c being 1. Alternatively, the conversion factor c is unequal to 1, e.g., having a value that is obtained by prior experiments. Secondly, this consumption thickness T5ac is subtracted from the initial block thickness T5ai of the respective anode 5 for determining the predicted block thickness T5ap that is currently existent or that is supposed to be existent throughout the specified operation time tO, i.e., T5ap = T5ai - T5ac. Thereby, the initial block thickness T5ai of the respective anode block 5a is included in the initial spatial dimensions D5 received via the input signal SI, as described above.

[0039] Hence, in the first step ST1 the consumption parameter PC can be used to determine or to evaluate, if an anode 5 is a selected anode 5S by prior setting of the schedule based on when the predicted block thickness T5ap of that anode 5 will fall or falls below the predetermined thickness threshold TT linked to that anode 5. This is done for every anode 5 in the reduction pot 2 individually, using the received process information IP and / or anode information IA assigned to the respective anode 5.

[0040] If the respective anode(s) 5 is / are treated as a selected anode(s) 5S, the replacement signal SR is created or triggered manually, e.g., by an operator monitoring the schedule, or automatically, e.g., by the processing unit 20 monitoring the schedule. The replacement signal SR is containing the information that the respective anode(s) 5 is a selected anode(s) 5S and needs to be replaced. Equivalently, a threshold value PCW for the consumption parameter PC may be specified for the respective anode 5. If the determined consumption parameter PC exceeds this threshold value PCW (i.e., the consumption is too high), the replacement signal SR for replacement of the respective anode(s) 5 is created or triggered.

[0041] Optionally, to train or build the predictive algorithm G or the implemented predictive model for calculating the consumption parameter PC, the anode change operations are carried out with the original method in an initial step ST0, i.e., individually measuring the actual anode height H5 of the selected anode 5S and an initial height H5Ni of the new anode 5N and calculate their height differences. Further, process information IP are monitored during replacement and / or during the electrolysis process in this initial step ST0 e.g., the electric voltage V and / or the overall current CO, etc.. This initial phase is used to collect and record as much information about the process and the changing operation as possible and combine or link all the collected data to set up the parameters or variables for calculating the consumption parameter PC or the consumption thickness T5ac, i.e., the proportionality factor(s) k, and / or the conversion parameter c, and / or an corrective term X for calculating a mounting height H5N of the new anode 5N (as described later), and / or the functional equation f.

[0042] This machine learning process of the predictive algorithm G, once stabilized after a certain predetermined learning time, for example, will allow to use the calculation method of the consumption parameter PC or of the consumption thickness T5ac with confidence without the need to measure the actual anode height H5 of the selected anode 5S and the initial height H5Ni of the new anode 5 anymore.

[0043] In a second step ST2, if a replacement signal SR is existent and one or more selected anode(s) 5S is / are determined, the handling tool(s) 1a (one for each selected anode 5S) of the anode changing assembly 1, e.g., of the pot tending machine 40 or of the service unit 60 is / are placed close to the rod(s) 5Sb of the selected anode(s) 5S determined in the first step ST1, as shown in Fig. 4A in more detail for a pot tending machine 40. Further, the hood 9 of the reduction pot 2 located next to the respective selected anode(s) 5S is removed.

[0044] In a third step ST3, the rod(s) 5Sb of the respective selected anode(s) 5S is / are gripped using the handling tool(s) 1a of the pot tending machine 40 or of the service unit 60, the handling tool(s) 1a each having an anode clamp 1b besides other tools (not shown). The handling tool(s) 1a is / are attached to a trolley 43 of the pot tending machine 40 being movable on a main structure 44. In case of a service unit 60, the handling tool(s) 1a might be attached to any kind of pivoting mechanism or the like, e.g., a pivotable arm, for positioning the handling tool(s) 1a.

[0045] This allows to precisely position the anode clamp(s) 1b of the respective anode changing assembly 1; 40, 60 above the selected anode(s) 5S and to approach the rod(s) 5Sb of the selected anode(s) 5S from above, as shown in Fig. 4B. Thereby, the anode clamp(s) 1b is / are lowered onto the upper end of the rod(s) 5Sb of the respective selected anode(s) 5S by a height adjustment mechanism 1c, e.g., by a telescopic mechanism or other hoisting mechanism. Once the anode clamp(s) 1b reach(es) the upper end of the respective rod(s) 5Sb, the rod(s) 5Sb is / are clamped. Thereby, the anode clamp(s) 1b is / are engaging the clamping holes 5f at the upper end of the rod(s) 5Sb of the selected anode(s) 5S, touching the top surface 5g of the clamping hole 5f for picking the rod(s) 5Sb of the selected anode(s) 5S in an upward movement of the handling tool 1a.

[0046] In a fourth step ST4, a mounting height H5S of the selected anode(s) 5S in the electrolytic cell 100 is determined. This is done, for example based on the height of the respective anode clamp(s) 1b. The height of the respective anode clamp(s) 1b is set or adjusted by a control unit 50 controlling the height adjustment mechanism 1c based on control signals SC. The control signals SC are created based on calculated or predetermined target values for the height of the respective anode clamp(s) 1b. The control signals SC are created in the processing unit 20, for example, and are transmitted to the control unit 50 afterwards. Hence, during the height adjustment of the respective anode clamp(s) 1b, the control unit 50 processes actual values or target values that are linked to the height of the respective anode clamp(s) 1b, wherein these values are preferably relative values in relation to any reference.

[0047] Once the respective anode clamp(s) 1b grabs the rod(s) 5Sb of the selected anode(s) 5S, these processed actual values or target values are also characterizing the mounting height H5S of the respective selected anode(s) 5S. The height at which the respective anode clamp(s) 1b grabs the rod(s) 5Sb of the selected anode(s) 5S can be detected via load cells, for example, as up from the point in time when the respective anode clamp(s) 1b is / are lifted in tension the respective anode clamp(s) 1b is / are touching the top surface 5g of the clamping hole(s) 5f. The mounting height H5S of the selected anode(s) 5S results from the (relative) height valid at this point in time when the system is in tension. This (relative) height of the respective anode clamp(s) 1b can be measured by a height measurement device measuring the vertical position of the respective anode clamp(s) 1b in relation to a certain reference. The height measurement device may, for example, be an encoder on the respective handling tool(s) 1a.

[0048] Another way of determining the mounting height H5S of the selected anode(s) 5S is by optically measuring a distance(s) D between a fixed point PF on the handling tool(s) 1a, in particular on the respective anode clamp(s) 1b, and a reference point PR on the anode frame 4 or on the superstructure 3, while the anode clamp(s) 1b grabs the selected anode(s) 5S from above. This measured distance(s) D characterizes the mounting height(s) H5S of the selected anode(s) 5S, e.g., in relation to the anode frame 4. The distance measurement can be carried out via optical measurement methods, for example, by a distance measurement device 46 attached to the handling tool(s) 1a at the fixed point PF, as shown in Fig. 4B.

[0049] After grabbing the rod(s) 5Sb and determining the mounting height(s) H5S of the selected anode(s) 5S, the fastener(s) 10 fixing the selected anode(s) 5S to the anode frame 4 is / are detached in a fifth step ST5, for unfixing the rod(s) 5Sb and the selected anode(s) 5S. In a sixth step ST6 the selected anode(s) 5S is / are removed from the reduction pot 2 by lifting the anode clamp(s) 1b via the height adjustment mechanism 1c and by moving the trolley 43 and the overhead crane 44 of the pot tending machine 40 or by moving the service module 60, e.g., on the floor. The selected anode(s) 5S is / are brought to a storage location for storing selected anodes 5S.

[0050] In a seventh step ST7, one or more new anode(s) 5N is / are gripped using the anode clamp(s) 1b of the respective handling tool(s) 1a, i.e., by approaching the anode clamp(s) 1b to the upper end of the rod(s) 5Nb of the new anode(s) 5N from above. The new anode(s) 5N is / are located in an exchange location for storing new anodes 5N. In an eighth step ST8, anode information IA concerning the selected anode(s) 5S and the new anode(s) 5N are loaded and processed by the predictive algorithm G and / or the processing unit 20. These anode information IA contain: the initial spatial dimensions D5N of the new anode 5N (initial block thickness T5Nai of the anode block 5Na of the new anode 5N, initial block volume V5Nai of the anode block 5Na of the new anode 5N, rod height H5Nb of the rod 5Nb of the new anode 5N, attachment height H5Ne of the attachment element 5Ne of the new anode 5N, initial height H5Ni of the new anode 5N, etc.), which are (manually or automatically) measured in the rodding shop before, and the initial spatial dimensions D5S of the selected anode 5S (initial block thickness T5Sai of the anode block 5Sa of the selected anode 5S, initial block volume V5Sai of the anode block 5Sa of the selected anode 5S, rod height H5Sb of the rod 5Sb of the selected anode 5S, attachment height H5Se of the attachment element 5Se of the selected anode 5S, initial height H5Si of the selected anode 5S, etc.).

[0051] The anode information IA of the respective anode(s) 5N, 5S might be transferred to the processing unit 20 via the input interface 21, e.g., from an external data storage device; or via a RFID-system having a transponder located on the respective anode(s) 5N, 5S, with the anode information IA stored on the transponder, and a receiver connected to the input interface 21; or via any identification system that allows to identify a specific anode 5N, 5S and make the link to its specific anode information IA. Thereby, the anode information IA of the selected anode(s) 5S might already been transferred to the processing unit 20 earlier, e.g., in step ST1 or even before, when it was initially installed (as a new anode(s) 5N before consumption). Further, process information IP are transferred to or loaded by the processing unit 20 that characterizes the reduction process while the selected anode(s) 5S was / were in the reduction pot 2.

[0052] In a ninth step ST9 the mounting height H5N for the new anode(s) 5N is / are calculated based on the mounting height(s) H5S of the selected anode(s) 5S (see fourth step ST4) and at least on the consumption thickness T5Sac = c · PC or the predicted block thickness T5Sap = T5Sai - T5Sac of the anode block(s) 5Sa of the selected anode(s) 5S that is / are determined based on the consumption parameter PC (k, tO, CO, FP, MP, RP) as described above (step ST1), i.e., based on a virtual or predictive measure of the change in the spatial dimensions of the selected anode(s) 5S. In this case, the specified operating time(s) to that the predictive algorithm G uses to determine the consumption parameter(s) PC according to the abovementioned integral equation is / are the actual time(s), the selected anode(s) 5S has / have spent in the reduction pot 2. This is / are an anode information IA that is known to the processing unit 20. The processing information IP (CO, FP, MP, RP) used to determine the consumption parameter(s) PC are also know to the processing unit 20.

[0053] Thereby, the mounting height(s) H5N for the new anode(s) 5N is / are calculated as follows: H5N = H5S + T5Sac PC + X with X being a corrective term, considering, for example, differences between the initial block thickness T5Nai of the new anode(s) 5N and the initial block thickness T5Sai of the respective selected anode(s) 5S, and / or differences between the rod height H5Nb of the new anode(s) 5N and the rod height H5Sb of the respective selected anode(s) 5S, and / or differences between the initial height H5Ni of the new anode(s) 5N and the initial height H5Si of the selected anode(s) 5S, and / or other differences between the initial spatial dimensions D5N of the new anode(s) 5N and the initial spatial dimensions D5S of the respective selected anode(s) 5S, and / or differences in a predetermined offset to account for any "warm up"- phenomena and / or settling of the fixation of the new anode(s) 5N and the selected anode(s) 5S. This offset could be different for the new anode(s) 5N and the selected anode(s) 5S depending of the anode position of the respective anode(s) 5N, 5S in the pot 2 or other parameters deemed pertinent like the density of the new anode block.

[0054] In a tenth step ST10, the new anode(s) 5N is / are set into the reduction pot 2 at the position that was initially occupied by the respective selected anode(s) 5S and in the calculated mounting height(s) H5N for the respective new anode(s) 5N, as shown in Fig. 4C, such that the bottom surface 5Nd of the respective new anode(s) 5N is at the same anodic level L as the respective selected anode(s) 5S (and ideally all the other anodes 5 in the reduction pot 2) possibly considering an offset to account for any "warm up" phenomena and / or settling of the fixation of the new anode 5N.

[0055] Comparable to the determination of the mounting height H5S of the respective selected anode(s) 5S in the fourth step ST4 this is done, for example, by constantly monitoring the height of the anode clamp(s) 1b that is adjusted by the control unit 50 via the height adjustment mechanism 1c. During the height adjustment of the anode clamp(s) 1b, the control unit 50 processes actual values or target values that are linked to the height of the anode clamp(s) 1b. So, when lowering the new anode(s) 5N, these processed actual values or target values can be used to determine, if the calculated mounting height(s) H5N for the respective new anode(s) 5N has / have been reached, e.g., the measurement of the load cell is indicating to a relaxation at a certain (relative) height, from which the anode clamp(s) 1b is / are detached from or is / are not touching the upper surface 5f of the clamping hole(s) 5e anymore. This (relative) height of the anode clamp(s) 1b can be measured or monitored by the height measurement device, e.g., the encoder, as in the fourth step ST4, wherein the same measurement parameters are used in order to avoid inaccuracies. In this way, a height of the anode clamp(s) 1b can be set that corresponds to the calculated mounting height(s) H5N for the respective new anode(s) 5N.

[0056] Alternatively, the mounting height(s) H5N of the new anode(s) 5N can be set by monitoring the distance(s) D between the fixed point PF on the handling tool 1a, e.g., the anode clamp(s) 1b, and the reference point PR on the anode frame 4 or on the superstructure 3, while the anode clamp (s)1b is / are grabbing the respective new anode(s) 5N from above and during the height adjustment mechanism 1c is lowering the anode clamp(s) 1b into the reduction pot 2. Thereby, the fixed point PF and the reference point PR should be the same as for determining the mounting height(s) H5S of the selected anode(s) 5S in the fourth step ST4, to avoid inaccuracies. The respective new anode(s) 5N is / are lowered until the calculated mounting height(s) H5N is / are reached, e.g., the currently measured distance(s) D corresponds to or characterizes the calculated mounting height(s) H5N for the respective new anode(s) 5N, e.g., in relation to the anode frame 4.

[0057] In an eleventh step ST11 the rod(s) 5Nb of the new anode 5N is / are fixed by the fastener(s) 10 once the mounting height H5N of the new anode(s) 5N is / are reached, such that the bottom surface(s) 5Nd of the anode block(s) 5Na of the new anode(s) 5N lies approximately at the same anodic level L as the bottom surfaces 5d of all the other anodes 5 in the reduction pot 2. Afterwards, the handling tool(s) 1a is / are raised.

[0058] Afterwards, the process starts from the beginning, for determining further selected anodes 5S and replacing them with new anodes 5N, successively using the described method.

[0059] Optionally, in a twelfth step ST12, the replacement process might be evaluated, e.g., by monitoring process information IP during replacement and / or during the electrolysis process, e.g., the electric voltage V and / or the overall current CO. If, during this evaluation, deviations from target values or expected values for these process parameters are determined, the proportionality factor(s) k for calculating the consumption parameter PC and / or the conversion parameter c for calculating the consumption thickness T5Sac of the selected anode 5S and / or the corrective term X for calculating the mounting height H5N for the new anode 5N, and / or the functional equation f, and / or process parameter, e.g., the overall current CO, might be adapted or adaptively adjusted based on the determined deviations. This could also include additional measurements of the actual height H5 of the selected anode 5S using the methods according to the state of the art, i.e., individually measuring the actual anode height H5 of the selected anode 5S and an initial height H5Ni of the new anode 5N and calculate their height differences, like when training or building up the predictive algorithm G during the initial step ST0. This evaluation or adaptation can be carried out over a certain period of time for improving the predictive model / predictive algorithm G and providing a precise forecast of the consumption thickness T5Sac of the selected anode(s) 5S and the mounting height(s) H5N of the new anode(s) 5N. In this way, the predictive algorithm G can learn or be trained by a machine learning process. Further, the electrolysis process can be improved in general.List of reference signs

[0060] 1pot tending assembly 1ahandling tool of the pot tending assembly 1 1banode clamp 1cheight adjustment mechanism 2reduction pot 3superstructure 4anode frame 5anode 5aanode block of the anode 5 5brod of the anode 5 5ctop surface of the anode block 5a 5dbottom surface of the anode block 5a 5eattachment element of the anode 5 5fclamping hole in the rod 5b 5gtop surface of the clamping hole 5f 5Nnew anode 5Naanode block of the new anode 5N 5Nbrod of the new anode 5N 5Ndbottom surface of the anode block 5a of the new anode 5N 5Neattachment element of the new anode 5N 5Sselected anode 5Saanode block of the selected anode 5S 5Sbrod of the selected anode 5S 5Sdbottom surface of the anode block 5a of the selected anode 5S 5Seattachment element of the selected anode 5S 6casing 7lining 8cathode unit 8acathode rod 8bcathode block 9hood 10fastener 11interior of the pot 2 12afirst electrical conductor 12bsecond electrical conductor 13current source 14voltage measurement device 20processing unit 21input interface 30molten electrolytic bath 31molten aluminum 40pot tending machine 43trolley 44main structure 46distance measurement device 50control unit 60service unit 100electrolytic cell cconversion parameter COoverall current Ddistance D5initial spatial dimension of the anode 5 D5Ninitial spatial dimension of the new anode 5N D5Sinitial spatial dimension of the selected anode 5S ffunctional equation FPfeeding parameter Gpredictive algorithm H5anode height of the anode 5 H5brod height of the rod 5b of the anode 5 H5eattachment height of the attachment element 5e of the anode 5 H5iinitial height of the anode 5 H5Nmounting height of the new anode 5N H5Nbrod height of the rod 5Nb of the new anode 5N H5Neattachment height of the attachment element 5Ne of the new anode 5N H5Niinitial height of the new anode 5 H5Smounting height of the selected anode 5S H5Sbrod height of the rod 5Sb of the selected anode 5S H5Seattachment height of the attachment element 5Se of the selected anode 5S H5Siinitial height of the selected anode 5S IAanode information IPprocess information kproportionality factor Lanodic level MPmovement parameter P5positional specification of the respective anode 5 PCconsumption parameter PCWthreshold value of the consumption parameter PFfixed point PRreference point r5acarbon density of the anode block 5a RPresetting parameter SCcontrol signal SIinput signal SRreplacement signal tMaxmaximum time tooperation time of the respective anode 5 T5ablock thickness of the anode block 5a T5acconsumption thickness of the anode block 5a of the anode 5 T5Sacconsumption thickness of the anode block 5Sa of the selected anode 5S T5aiinitial block thickness of the anode block 5a of the anode 5 T5Naiinitial block thickness of the anode block 5Na of the new anode 5N T5Saiinitial block thickness of the anode block 5Sa of the selected anode 5S T5appredicted block thickness of the anode block 5a of the anode 5 T5Sappredicted block thickness of the anode block 5Sa of the selected anode 5S TTthickness threshold Velectric voltage V5aiinitial block volume of the anode block 5a of the anode 5 V5Naiinitial block volume of the anode block 5Na of the new anode 5N V5Saiinitial block volume of the anode block 5Sa of the selected anode 5S W5aiinitial weight of the anode block 5a Xcorrective term

Claims

1. Method for replacing at least one selected anode (5S) located in an electrolytic cell (100) for the producing of aluminum by electrolytic reduction, wherein a plurality of anodes (5) are located in the electrolytic cell (100) each of the anodes (5) comprising a rod (5b) detachably fixed to an anode frame (4) of the electrolytic cell (100) and at least one anode block (5a) attached to the rod (5b) of the respective anode (5) and located inside a reduction pot (2) of the electrolytic cell (100) during an operating time (tO), the method comprises the steps of: - determining or evaluating, if at least one of the anodes (5) in the electrolytic cell (100) is a selected anode (5S) and needs to be replaced (ST1); - detaching and removing the at least one selected anode (5S) from the electrolytic cell (100) by using a handling tool (1a) of an anode changing assembly (1) having at least one height adjustable anode clamp (1b) (ST5, ST6); - selecting and grabbing at least one new anode (5N) by using the handling tool (1a) of the anode changing assembly (1) (ST7); - setting the at least one new anode (5N) into the electrolytic cell (100) and placing and fixing the at least one new anode (5N) at a mounting height (H5N), wherein the mounting height (H5N) is determined by a predictive algorithm (G) by collecting and processing -- anode information (IA) characterizing the at least one selected anode (5S) and / or the at least one new anode (5N), and -- process information (IP) characterizing the electrolytic reduction process at least during the operating time (tO) while the at least one selected anode (5S) was in the reduction pot (2) (ST9, ST10, ST11).

2. Method according to claim 1, wherein before detaching and removing the at least one selected anode (5S) from the electrolytic cell (100) by using the handling tool (1a) of the anode changing assembly (1) the following steps are carried out: - placing the handling tool (1a) of the anode changing assembly (1) close to the rod (5Sb) of the determined at least one selected anode (5S) (ST2); - gripping the rod (5Sb) of the determined at least one selected anode (5S) using at least one height adjustable anode clamp (1b) of the handling tool (1a) (ST3).

3. Method according to claim 1 or 2, wherein selecting and grabbing at least one new anode (5N) by using the handling tool (1a) of the anode changing assembly (1) comprises the steps of: - placing the handling tool (1a) of the anode changing assembly (1) close to the rod (5Nb) of the at least one new anode (5N) outside the electrolytic cell (100) and gripping the rod (5Nb) of the at least one new anode (5N) using the at least one height adjustable anode clamp (1b) of the handling tool (1a) (ST7).

4. Method according to any one of the preceding claims, wherein determining or evaluating, if at least one of the anodes (5) in the electrolytic cell (100) is a selected anode (5S) and needs to be replaced (ST1), includes determining if or when the operating time (tO) of the respective anode (5) exceeds a predetermined maximum time (tMax).

5. Method according to any one of the preceding claims, wherein determining or evaluating, if at least one of the anodes (5) in the electrolytic cell (100) is a selected anode (5S) and needs to be replaced (ST1), includes determining a predicted block thickness (T5ap) of the at least one anode block (5a) of the respective anode (5), e.g., by the predictive algorithm (G), wherein the predicted block thickness (T5ap) is determined in dependence on the operating time (tO) the respective anode (5) has been or will be in the reduction pot (2), and at least an overall current (CO) flowing through the at least one anode block (5a) of the respective anode (5) during this operating time (tO), and in particular, includes determining if or when the predicted block thickness (T5ap) of the at least one anode block (5a) of the respective anode (5) is approaching or is equal to a predetermined thickness threshold (TT).

6. Method according to any one of the preceding claims, wherein the mounting height (H5N) for the at least one new anode (5N) is determined by the predictive algorithm (G) in dependence on - a mounting height (H5S) of the at least one selected anode (5S) determined before removing the respective selected anode (5S) from the electrolytic cell (100) (ST4), and - a consumption thickness (T5Sac) of the at least one selected anode (5S) (ST9), wherein the consumption thickness (T5Sac) of the at least one selected anode (5S) is predicted based on the collected anode information (IA), e.g., the operating time (tO) the respective selected anode (5S) has spent in the reduction pot (2), and the collected process information (IP), e.g., at least an overall current (CO) flowing through the anode block (5Sa) of the respective selected anode (5S) during the operating time (tO).

7. Method according to claim 6, wherein determining the mounting height (H5S) of the at least one selected anode (5S) in the electrolytic cell (100) (ST4) includes measuring a distance (D) between a fixed point (PF) on the respective selected anode (5S) or on the handling tool (1a), while the anode clamp (1b) grabs the respective selected anode (5S) from above, and a reference point (PR) on the anode frame (4) or on a superstructure (3) of the electrolytic cell (100), wherein the measured distance (D) characterizes the mounting height (H5S) of the respective selected anode (5S), e.g., in relation to the anode frame (4) or the superstructure (3).

8. Method according to claim 6 or 7, wherein determining the mounting height (H5S) of the at least one selected anode (5S) in the electrolytic cell (100) (ST4) includes determining the height of the anode clamp (1b), while the anode clamp (1b) grabs the respective selected anode (5S) from above, e.g., via signal processing of a height adjustment mechanism (1c) during height adjustment of the anode clamp (1b).

9. Method according to any one of the claims 6 to 8, wherein predicting the consumption thickness (T5Sac) of the respective selected anode (5S), for determining the mounting height (H5N) for the respective new anode (5N), includes determining a consumption parameter (PC), wherein the consumption parameter (PC) is dependent on the operation time (tO) of the selected anode (5S) factored by the overall current (CO) flowing through the at least one anode block (5Sa) of the respective selected anode (5S) during the operating time (tO).

10. Method according to claim 9, wherein the consumption parameter (PC) is defined by PC = ∫ 0 tO f CO t , FP t , MP t , RP t , k dt with f being a predetermined functional equation comprising a proportionality factor k for considering the properties of the respective selected anode (5S) and / or a feeding parameter (FP) and / or a movement parameter (MP) and / or a resetting parameter (PR).

11. Method according to claim 10, wherein the proportionality factor (k) and / or the functional equation (f) is dependent on the anode information (IA) characterizing the respective selected anode (5S), e.g., dependent on - at least one initial spatial dimension (D5S) of the respective selected anode (5S) that is selected from the group consisting of: an initial block thickness (T5Sai) of the anode block (5Sa) of the selected anode (5S), an initial block volume (V5Sai) of the anode block (5Sa) of the selected anode (5S), a rod height (H5Sb) of the rod (5Sb) of the selected anode (5S), attachment height (H5Se) of the attachment element (5Se) of the selected anode (5S), an initial anode height (H5Si) of the selected anode (5S), and / or - an initial weight (W5ai) of the anode block (5Sa) of the selected anode (5S), a positional specification (P5) of the selected anode (5S).

12. Method according to claim 10 or 11, wherein the proportionality factor (k) and / or the functional equation (f) is set or adapted or adaptively adjusted, if a process value, in particular, the overall current (CO) and / or a measured electric voltage (V) between a cathode unit (8) and the respective anode (5) of the electrolytic cell (100), deviates from an expected value after setting the at least one new anode (5N) into the electrolytic cell (100) in the calculated mounting height (H5N) for training the predictive algorithm (G).

13. Method according to any one of the claims 6 to 12, wherein a corrective term (X) is considered when determining the mounting height (H5N) for the respective new anode (5N) in dependence on the determined mounting height (H5S) of the respective selected anode (5S) and the consumption thickness (T5Sac) of the respective selected anode (5S).

14. Method according to claim 13, wherein the corrective term (X) is dependent on differences between initial spatial dimensions (D5N) of the respective new anode (5N), included in the anode information (IA) characterizing of the respective new anode (5N), and initial spatial dimensions (D5S) of the respective selected anode (5S), included in the anode information (IA) characterizing the respective selected anode (5S), in particular, - differences between an initial block thickness (T5Nai) of the respective new anode (5N) and an initial block thickness (T5Sai) of the respective selected anode (5S), and / or - differences between a rod height (H5Nb) of the respective new anode (5N) and the rod height (H5Sb) of the respective selected anode (5S).

15. Method according to claim 14, wherein the corrective term (X) is set or adapted or adaptively adjusted, if a process value, in particular, the overall current (CO) and / or a measured electric voltage (V) between a cathode unit (8) and the respective anode (5) of the electrolytic cell (100), deviates from an expected value after setting the respective new anode (5N) into the electrolytic cell (100) in the calculated mounting height (H5N) for training the predictive algorithm (G).

16. Pot tending assembly (1), comprising a handling tool (1a) with at least one height adjustable anode clamp (1b), and a processing unit (20) adapted to carry out the method according to any one of the preceding claims, wherein the pot tending assembly (1) is a pot tending machine (40) or a service unit (60), for example.

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