Apparatus,systems and methods for an aluminium production system

Abstract

A measurement apparatus for an aluminum production system is described. The measurement apparatus 100 comprises a sensor assembly configured to contact an anode rod 20 of the aluminium production syst

Description

The Hall-Heroult electrolysis process, whereby aluminium is extracted from its oxide, alumina, is a major production route for aluminium. Carbon anodes used in this process are suspended via an anode rod or stem in a cell or pot in which electrolysis take place. As the bottom surfaces of the anodes are consumed during electrolysis, the anodes will be lowered vertically into the pot. An aluminium smelter will typically consist of a large number of pots, each of which typically contain a number of anodes. If the alumina concentration drops too low in a pot, a phenomenon known as the anode effect may occur, resulting in a decrease in the rate of aluminium production, significant heat generation, and an increase in the emission of greenhouse gases such as perfluorocarbons (PFCs). In particular, the anode effect results in strong emissions of Carbon tetrafluoride and Hexafluoroethane gases, both of which are known to have a particularly negative effect on the climate Maintaining a constant and controlled distribution of electric current is important to avoid the anode affect phenomenon. Furthermore, having a well-controlled current distribution also contributes to stable electrolysis, reducing the impurities that the aluminium receives as a result of potential unwanted side effects of the electrolysis. A well-controlled current distribution can also assist in maintaining uniform wear on the anodes, providing improved lifespan of the anodes and the cell, and can also result in increased energy efficiency due to improved stability of the cell and the reduced resistive losses of each anode. During electrolysis, current is supplied to the cell through the carbon anodes. When the cell is subjected to increased currents, a higher yield can be obtained in an aluminium smelter. However, at increased currents the cell also has reduced stability and has a higher likelihood of experiencing the anode effect. Having a means of obtaining regular measurements of the current at individual anodes is beneficial as it can contribute to maintaining a controlled current distribution at these increased current values. Furthermore, measuring the current at individual anodes will also facilitate in the early detection of the onset of the anode effect and other negative events such as anode cracking or dropping of the carbon anode. Measuring the current at individual anodes has proven to be difficult in practice in production operations due to the high temperatures involved, the low voltage signals which must be detected, the high energy requirements for obtaining such measurements, and the fact that the anodes have to be vertically lowered and replaced altogether every 30 days. Currently, the conventional practice typically involves measuring the overall current in each pot, and performing occasional manual measurements of the individual anode current, for example every 36 hours. Whilst different systems have been proposed for measuring the current at individual anodes, these systems all have limitations of some kind, impacting their use in industry. US 4,786,379 describes a method and apparatus for measuring the current distribution at anodes in an alumina reduction cell. The apparatus includes a sensor assembly and a means for transmitting and receiving data from the sensor assembly to a remote computer system. The sensor assembly comprises two arms which are connected at a pivot. Two pins are attached to one of the arms, and these act as positive and negative connections to the anode stem, between which the voltage is measured. The two arms act as a pair of gripping arms and enable the pins to be mounted and dismounted from the anode stem. The sensor assembly includes an adjustment screw on one of the two arms for maintaining a locked grip and connection with the anode stem. CN 2578341 Y describes a current distribution measuring device for an anode which is composed of a U-shaped steel channel. The U-shaped channel is fitted around the anode guide rod using a tension spring 14. By measuring the rivet cap voltage drop, the current value of the anode guide rod can be obtained. Whilst these known measuring devices provide a solution for measuring the current distribution in an anode rod, these devices will require repositioning when the vertical position of the anode rod is changed, such as when it is lowered over time, and will also need to be removed and fitted to a new anode rod when it is time for replacement. CN 201809454 II describes a current distribution measurement device which includes a current measuring probe, for an aluminium electrolytic cell. The current measuring probe measures the current distribution in an anode guide rod which is fixed on a busbar. The measurement device is mounted via a universal joint on the top of a J-shaped fixing frame. The inner dimensions of the J-shaped fixing frame match the outer dimensions of the busbar, onto which the J-shaped frame is sheathed and clamped. Whilst CN 201809454 II describes a solution for measuring the current distribution in an anode rod, this solution has the disadvantage that the measuring device is mounted on the busbar and, unless it is manually moved, will remain in contact with the anode guide rod if the anode guide rod is repositioned. As such, the sensor assembly may become damaged or may become dislodged in circumstances where the anode rod is moved during operation. Known methods attempt to solve different issues associated with measuring the current distribution in individual anode rods. However, none of these methods provide a cost-effective solution which can effectively be used on a large scale across a number of anode rods in an aluminium smelter. Summary of the invention It is amongst the aims and objects of the invention to provide an apparatus and method for performing measurements on anode rods, which addresses one or more problems of known apparatus and methods. It is amongst the aims and objects of the invention to provide an improved apparatus and method for performing measurements on anode rods with improved reliability and improved cost-effectiveness. It is amongst the aims and objects of the invention to provide an improved apparatus and method which more efficiently determines the current at an anode rod, in comparison to known apparatus and methods. It is amongst the aims and objects of the invention to provide an improved apparatus and method which more accurately determines the current at an anode rod, in comparison to known apparatus and methods. It is amongst the aims and objects of the invention to provide an improved apparatus and method for determining the current at an anode rod. It is amongst the aims and objects of the invention to provide an improved apparatus and method for performing measurements across the large number of anode rods typically found within an aluminium smelter. Further objects and aims of the invention will become apparent from the following description. According to a first aspect of the invention, there is provided a measurement apparatus for an aluminium production system, the measurement apparatus comprising: a sensor assembly configured to contact an anode rod of the aluminium production system; and a mounting arrangement configured to mechanically attach the sensor assembly to an anode rod clamp, the anode rod clamp being removably connected to an anode beam of the aluminium production system; wherein the mounting arrangement is configured so that the sensor assembly is in contact with the anode rod at a measurement position when the anode clamp is clamped onto the anode rod to support the anode rod in the aluminium production system, and the mounting arrangement is configured so that the sensor assembly is released from the measurement position when the anode clamp is in an unclamped condition in which the anode clamp does not support the anode rod. The measurement apparatus may be configured such that operating the anode clamp to clamp the anode rod brings the sensor assembly into the measurement position in contact with the anode rod. The measurement apparatus may be configured such that loosening of the anode clamp enables the sensor assembly to be brought out of a measurement position on the anode rod. The measurement apparatus may be configured such that loosening of the anode clamp brings the sensor assembly out of a measurement position on the anode rod. Alternatively, the measurement apparatus may be configured such that loosening of the anode clamp reduces a contact force between the sensor assembly and the anode rod in the measurement position. In this arrangement, a reduced force between the sensor assembly and the anode rod may enable the anode rod to be moved with respect to the sensor assembly. The measurement apparatus may be configured to apply a force to the sensor assembly that presses the sensor assembly against the anode rod. The force may be sufficient to allow reliable measurements to be obtained from the sensor assembly. The mounting arrangement may be configured to transfer a force from a movable part of the anode clamp to the sensor assembly. The movable part may be a part of clamp member. The clamp member may move during operation of the clamp. Closing the clamp may direct a force through the mounting assembly to the sensor assembly in a direction towards the anode rod. Opening the clamp may direct a force through the mounting assembly to the sensor assembly in a direction away from the anode rod. Alternatively, or in addition, opening the clamp may reduce the magnitude of a force through the mounting assembly to the sensor assembly in a direction towards the anode rod. The mounting arrangement may allow for variations in the position of the surface of anode rod, whilst maintaining the sensor assembly in contact with the anode rod and limiting the force that the anode rod exerts on the sensor assembly. The mounting arrangement may be at least partially compliant in a direction between the anode clamp and the sensor assembly. This may have the effect of limiting the force exerted on the sensor assembly by the anode rod when the anode clamp is in a clamped condition. The measurement apparatus may comprise a biasing mechanism configured to bias the sensor assembly towards the anode rod. The mounting arrangement may be configured to transfer a force from a movable part of the anode clamp to the sensor assembly via the biasing mechanism. At least one sensor may comprise a biasing mechanism, such as a spring, configured to assist in maintaining contact between the at least one sensor and the anode rod at the measurement position. The mounting arrangement may comprise an arm disposed between the anode clamp and the sensor assembly. The arm may be at least partially telescopic. The arm may be biased towards an extended condition. The force may act substantially longitudinally through the arm of the measurement apparatus. The arm may be longitudinally extendable and may be biased towards an extended condition. The force may act substantially as a turning moment on the arm. The arm may be connected to the anode clamp by an extendable hinge joint, and may be biased towards an extended condition. The sensor assembly may comprise a body, and may comprise at least one sensor on or in the body. The at least one sensor may be configured for measuring or determining at least one of thermal flux, voltage drop, current, current flow, temperature, vibrations, sound, surface acoustic waves, strain, rotational force, and / or magnetic fields. The sensor assembly may comprise a first upper voltage sensor and a second lower voltage sensor. A current flow through the anode rod may be determined from the voltage difference between the first upper voltage sensor and the second lower voltage sensor. The measurement apparatus may be configured so that the upper and lower voltage sensor contact with a respective upper and lower point on the anode rod, in the measurement position. The sensor assembly may comprise at least one temperature sensor. The sensor assembly may comprise at least one temperature sensor for measuring the temperature at least one location on the anode rod. The at least one temperature measurement may improve the accuracy of the determined current flow. The measurement apparatus may allow for lateral movement of the anode rod, whilst maintaining the sensor assembly in contact with the anode rod and limiting the force that the anode rod exerts on the sensor assembly. In the unclamped condition, the sensor assembly may be released from the anode rod such that the sensor assembly is no longer in contact with the anode rod. In an alternative embodiment, in the unclamped condition, the sensor assembly may maintain contact with the anode rod but may be released from the anode rod through a reduced force applied to the sensor assembly by the biasing mechanism. The force in this unclamped condition may be a reduced force in comparison to the force applied to the sensor assembly by the biasing mechanism in the measurement position. The mounting arrangement may be configured so that the sensor assembly is mechanically attached at a distance below the anode rod clamp of the aluminium production system. The mounting arrangement may comprise two mounting arms that are connected between the anode clamp and opposing sides of the sensor assembly. The measurement apparatus may comprise an electronics package which powers and / or controls the sensor assembly. The electronics package may be contained within or connected to the sensor assembly, the mounting arrangement and / or the anode rod clamp. The electronics package may be self-contained. The electronics package may comprise a battery. Alternatively, the electronics package may be configured to harvest energy from the surrounding environment. The electronics package may be configured to harvest energy from light, such as through the use of a photovoltaic cell. Alternatively, the electronics package may be configured to harvest energy from magnetic fields or from temperature differences in the surrounding environment. Alternatively, the electronics package may be configured to harvest the energy resulting from the voltage difference between the first upper voltage sensor and the second lower voltage sensor, or harvest the energy resulting from the voltage difference between the anode clamp and the second lower voltage sensor. The measurement apparatus may be configured to transmit data wirelessly to a receiver. The measurement apparatus may comprise a sensor body antenna. The sensor body antenna may transmit data wirelessly to the receiver. The sensor body antenna may be connected to or contained within the sensor assembly, the mounting arrangement and / or the anode rod clamp. The measurement apparatus may be configured to communicate and / or transmit data wirelessly to other measurement apparatus within a system of measurement apparatus. The measurement apparatus may be configured to communicate and / or transmit data wirelessly to a receiver, controller or control room. According to a further aspect of the invention, there may be provided a system comprising a plurality of measurement apparatus according to the first aspect of the invention, configured to be connected to a plurality of anode rod clamps in an aluminium production system. The plurality of measurement apparatus may be configured to communicate with one another other. The plurality of measurement apparatus may be configured to communicate with one another as a wireless network. The plurality of measurement apparatus may be configured to communicate with a controller, receiver or control room. The plurality of measurement apparatus may be configured to communicate with the controller, receiver or control room as a wireless network. The plurality of measurement apparatus may be configured to transmit data to the controller or control room. The measurement apparatus is an improved apparatus for more accurately determining the current at an anode rod, in comparison to known methods. As such, the measurement apparatus provides improved accuracy in detecting the onset of the anode effect or other anode related issues. Embodiments in which the plurality of measurement apparatus are configured to communicate with one another, or are configured to communicate with the controller, receiver or control room, have the advantage of facilitating further improvements in the accuracy of detecting the onset of the anode effect or other anode related issues. An improved accuracy in detecting the onset of the anode effect, or other anode related issues, has the benefit that steps can be taken to counteract the anode effect or the occurrence of these other anode related issues. Embodiments of the further aspect of the invention may include one or more features of the first aspect of the invention or their embodiments, or vice versa. According to a second aspect of the invention, there may be provided a mounting arrangement for a measurement apparatus in an aluminium production system, the mounting arrangement comprising: a support structure configured to mechanically attach a sensor assembly to an anode rod clamp of the aluminium production system; wherein the mounting arrangement is configured so that the sensor assembly is in contact with the anode rod when the anode clamp is in a first condition in which it is clamped onto the anode rod and supports the anode rod in the aluminium production system, and the mounting arrangement is configured so that the sensor assembly is released from the anode rod when the anode clamp is in a second condition in which the anode clamp does not support the anode rod. Embodiments of the second aspect of the invention may include one or more features of the previous aspects of the invention or their embodiments, or vice versa. According to a third aspect of the invention, there may be provided a method for performing measurements on an anode rod used in the production of aluminium, using a sensor assembly connected to an anode clamp, the anode clamp having a first mode of operation in which it is in contact with the anode rod and supports the anode rod through its connection to an anode beam, and having a second mode of operation in which the anode clamp does not support the anode rod, wherein in the first mode of operation the sensor assembly contacts a surface of the anode rod and is released from the surface of the anode rod in the second mode of operation, wherein the method comprises: performing a measurement on the surface of the anode rod in the first mode of operation of the anode clamp; loosening the anode clamp to bring the sensor assembly into its second mode of operation; and changing the vertical position of the anode rod relative to the anode clamp and anode rod in the second mode of operation. Embodiments of the third aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. According to a fourth aspect of the invention, there is provided a method of installing a measurement apparatus in an aluminium production system, the method comprising: mechanically attaching a mounting arrangement and sensor assembly to an anode rod clamp of the aluminium production system; clamping the anode rod clamp onto an anode rod of the aluminium production system so that the anode rod is supported by the clamp; wherein clamping the anode rod clamp brings the sensor assembly into contact with the anode rod at a measurement position. Embodiments of the fourth aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. According to a fifth aspect of the invention, there is provided a method of configuring an aluminium production system, the method comprising installing a measurement apparatus in an aluminium production system according to the method of the previous aspect of the invention; opening the anode rod clamp so that the anode rod is not supported by the clamp; wherein opening the anode rod clamp releases the sensor assembly from the anode rod; changing the vertical position of the anode rod relative to the anode clamp; clamping the anode rod clamp onto an anode rod of the aluminium production system so that the anode rod is supported by the clamp in the changed vertical position; wherein clamping the anode rod clamp brings the sensor assembly into contact with the anode rod in the changed vertical position. Embodiments of the fifth aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. According to a sixth aspect of the invention, there may be provided a method of performing measurements on an anode rod during the production of aluminium, the method comprising installing a measurement apparatus according to any previous aspect of the invention, and measuring or determining at least one of voltage, current, temperature, thermal flux, vibration, sound, surface acoustic waves, strain, rotational force, or magnetic fields using the measurement apparatus. Embodiments of the sixth aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. According to a seventh aspect of the invention, there is provided a method of performing measurements on an anode rod during the production of aluminium, the method comprising configuring an aluminium production system according to any previous aspect of the invention, and measuring or determining at least one of voltage, current, temperature, thermal flux, vibration, sound, surface acoustic waves, strain, rotational force, or magnetic fields using the measurement apparatus. Embodiments of the seventh aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. According to an eighth aspect of the invention, there may be provided a method of performing measurements on an anode rod used in the production of aluminium, using a sensor assembly connected to an anode clamp, the anode clamp having a first mode of operation in which it is in contact with the anode rod and supports the anode rod through its connection to an anode beam, and having a second mode of operation in which the anode clamp does not support the anode rod, wherein in the first mode of operation the sensor assembly contacts a surface of the anode rod and is released from the surface of the anode rod in the second mode of operation, wherein the method comprises: performing a measurement on the surface of the anode rod in the first mode of operation of the anode clamp; loosening the anode clamp to bring the sensor assembly into its second mode of operation; and changing the vertical position of the anode rod relative to the anode clamp and anode rod in the second mode of operation. Embodiments of the eighth aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. According to a ninth aspect of the invention, there is provided an aluminium production system, the aluminium production system comprising: an anode rod; an anode rod clamp removably connected to an anode beam; a sensor assembly configured to contact the anode rod; a mounting arrangement mechanically attaching the sensor assembly to the anode rod clamp; - wherein the sensor assembly is in contact with the anode rod when the anode clamp is in a first condition in which it is clamped onto the anode rod and supports the anode rod, and the sensor assembly is released from the anode rod when the anode clamp is in a second condition in which the anode clamp does not support the anode rod. Embodiments of the ninth aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. According to a tenth aspect of the invention, there may be provided a measurement apparatus for an aluminium production system, the measurement apparatus comprising: a sensor assembly configured to contact an anode rod of the aluminium production system; a mounting arrangement configured to mechanically attach the sensor assembly to an anode rod clamp of the aluminium production system; - wherein the measurement apparatus is configured so that the tightening of the anode clamp brings the sensor assembly into a measurement position in contact with the anode rod; and - wherein the measurement apparatus is configured so that the loosening of the anode clamp enables the sensor assembly to be brought out of a measurement position on the anode rod. The measurement apparatus may be configured so that the loosening of the anode clamp brings the sensor assembly out of a measurement position on the anode rod. Alternatively, the measurement apparatus may be configured so that the loosening of the anode clamp reduces a contact force between the sensor assembly and the anode rod in the measurement position. In this arrangement, the reduced force between the sensor assembly and the anode rod may enable the anode rod to be moved with respect to the sensor assembly. Embodiments of the tenth aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. According to an eleventh aspect of the invention, there is provided a method of performing measurements on an anode rod used in the production of aluminium, using a measurement apparatus according to any previous aspects of the invention. Embodiments of the eleventh aspect of the invention may include one or more features of the previous aspects of the invention, or their embodiments, or vice versa. Brief description of the drawings There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which: Figure 1 is a schematic representation of an aluminium production system incorporating a measurement apparatus according to an embodiment of the invention; Figure 2A is a side view and Figure 2B is a front view of a measurement apparatus according to an embodiment of the invention; Figure 3A is an isometric view and Figure 3B is a top view of the measurement apparatus of Figures 2A to 2B connected to an anode clamp in a measurement position; Figure 4A is a top view and Figure 4B is a front view of the measurement apparatus of Figure 2A and 2B connected to an anode clamp in a released condition; Figure 5A is a side view and Figure 5B is a front view of a measurement apparatus, according to an alternative embodiment of the invention; Figure 6A is an isometric view of the measurement apparatus of Figures 5A and 5B connected to an anode clamp and in a measurement position; Figure 6B is a side view of the measurement apparatus of Figures 5A and 5B connected to an anode clamp and in a released condition; Figure 7A is a side view and Figure 7B is a front view of a measurement apparatus, according to an alternative embodiment of the invention; Figure 8A is an isometric view of the measurement apparatus of Figures 7A and 7B connected to an anode clamp and in a measurement position; and Figure 8B is a side view of the measurement apparatus of Figures 7A and 7B connected to an anode clamp and in a released condition. Detailed description of preferred embodiments Referring firstly to Figure 1, there is shown generally at 10 an aluminium production system. The aluminium production system 10 comprises an anode rod or stem 20 which supports a carbon anode 30 in an electrolyte bath 40. An anode clamp 150 is connected via a beam bracket 70 to an anode beam 50, and supports the anode rod 20 at a particular vertical height in the electrolyte bath 40. As the bottom surfaces of the anodes 30 are consumed during electrolysis, the anodes 30 will be lowered vertically into the bath 40. The anodes 30 together with the anode rods 20 will also have to be occasionally replaced altogether. A measurement apparatus 100 is connected to the anode clamp 150 and is configured for performing measurements on a surface of the anode rod 20. An exemplary measurement application is a measurement of the voltage drop over a portion of the anode rod 20, from which a current flow through the anode rod 20 can be determined. Embodiments of the invention are described in this context. In addition, in the described embodiments of the invention, a measurement of temperature is taken at the surface of the anode rod 20 which can be used to improve the accuracy of the current flow calculation. Figure 2A is a side view of the measurement apparatus 100 and Figure 2B is a front view of the measurement apparatus 100. The measurement apparatus 100 comprises a sensor assembly shown generally at 110 and a mounting arrangement shown generally at 120. In this embodiment, the sensor assembly 110 comprises a first voltage sensor 111 and a second voltage sensor 112 positioned respectively towards upper and lower ends of a sensor body 113. The sensor body 113 also comprises a temperature sensor 115 which is connected to the sensor body 113 via a spring 116, the spring functioning to press the temperature sensor against the surface of the anode rod 20 during use. A sensor body antenna 117 is connected to an outer surface of the sensor body 113. The mounting arrangement 120 comprises a first arm 125 and a second arm 130. The first arm 125 is connected to the sensor body 113 at one end at a sensor body hinge joint 127 and is connected to a first clamp connector 135 at its other end. One end of the second arm 130 connects to the first arm substantially perpendicularly, at approximately the middle point of the first arm 125. The opposing end of the second arm has a second connector 140. The first arm is configured to be positioned between a movable part of the anode clamp (to which the first connector is joined) and the sensor assembly, and functions to direct a force from the anode clamp to push the sensor assembly towards the anode. The second arm supports the measurement apparatus below the anode clamp, by joining the second connector to the anode clamp. The first arm 125 has a telescopic element 126 which enables the mounting arrangement to compensate for variations in the position of the surface of anode rod, whilst maintaining the sensor assembly in contact with the anode rod and limiting the force that is exerting the sensor assembly. The telescopic element 126 is operable to extend and retract with respect to the main arm 125, and contains a biasing mechanism, such as a spring (not shown), which biases the element 126 to an extended condition and therefore pushes the sensor assembly towards the anode rod. Figure 3A and Figure 3B, and Figure 4A and 4B, illustrate the measurement apparatus 100, the beam bracket 70, and the anode clamp 150 connected together during use. Figures 3A and 3B illustrate the measurement apparatus 100 and anode clamp 150 in use in a clamped condition. In contrast, Figures 4A and 4B illustrate the measurement apparatus 100 and anode clamp 150 in use in a released condition. The anode clamp 150 comprises a first clamp member 155 and a second clamp member 160. The first clamp member 155 has a first clamp outer portion 156 and a first clamp inner portion 157. The second clamp member 160 has a second clamp outer portion 161 and a second clamp inner portion 162. The inner portions 157 and 162 of the first clamp member 155 and the second clamp member 160 are pivotally connected via a connection rod 175. The outer portions 156 and 161 of the first clamp member 155 and the second clamp member 160 are threadedly connected via a threaded adjustment rod 170 with an adjustment nut 171. The beam bracket 70 comprises a first supporting member 75 and a second supporting member 80. The first supporting member 75 and the second supporting member 80 define an upper surface with a concave shape. The anode clamp 150 is connected to the first supporting member 75 and the second supporting member 80 of the beam bracket 70 via the connection rod 175. The connection rod 175 is supported in the concave shape defined by the first and second supporting member 75 and 80. The measurement apparatus 100 is connected to the anode clamp 150 via the first connector 135 and the second connector 140. The first connector 135 is connected to the outer potion 161 of the second clamp member 160. The second connector 140 is connected to the connection rod 175. A user or external operator or controller can operate the anode clamp 150 through the rotation of the adjustment nut 171. Rotation of the adjustment nut 171 and rod 170 in one direction causes the clamp outer portions to be separated, which moves clamping faces of the inner portions towards the anode rod to a clamping condition. Rotation of the adjustment nut 171 and rod 170 in the opposite direction causes the clamp outer portions to be separated, which moves clamping faces of the inner portions away from the anode rod to an unclamped condition. During clamping, as the outer portions 156 and 161 of the first clamp member 155 and the second clamp member 160 are moved in opposing directions away from each other, the inner portions 157 and 162 of the first clamp member 155 and the second clamp member 160 will be moved in a direction towards the surface of the anode rod 20. As the inner portions 157 and 162 of the first clamp member 155 and the second clamp member 160 are pivotally connected via the connection rod 175, the outer portions 156 and 161 will be moved in opposing directions away from each other whilst also being rotated in a direction towards the anode rod 20. In the clamped condition, shown in Figures 3A and 3B, the anode clamp 150 is clamped to the anode rod 20 and supports the weight of the anode rod 20. The inner portions 157 and 162 of the first clamp member 155 and the second clamp member 160 are engaged with a surface of the anode rod 20. Through the connection of the anode clamp 150 to the beam bracket 70 via the connection rod 175, a supporting force is provided to support the weight of the anode rod 20. In use in an aluminium production system 10, the carbon anode 30 is supported at a particular vertical height in an electrolyte bath 40. In the clamped condition, the sensors 111, 112 and 115 of the sensor assembly 110 are in contact with the anode rod 20. The measurement apparatus 100 is brought into the measurement position, with the sensor assembly 110 in contact with the anode rod 20, by operating the anode clamp 150. The sensor assembly 110, being mechanically linked to a movable part of the clamp, is moved into contact with the anode rod 20. As the sensor assembly 110 is brought into contact with the anode rod 20, the sensor body hinge joint 127 allows for rotation of the sensor body 113 so that it remains parallel to the surface of the anode rod 20 and enables each of the sensors 111, 112 and 115 to be in contact with the anode rod 20. The mounting arrangement is laterally compliant, in this case by virtue of the telescopic element and biasing mechanism, which allows for variations in distance between the outer clamp member (to which the first connector is attached) and the surface of anode rod when the anode clamp is in a clamped condition. The first arm, when fully extended, ensures that the mounting arrangement is longer than a typical distance between the clamp and the anode rod, so that the biasing means is partially compressed when the anode clamp is in a clamped condition. This helps maintaining the sensor assembly in contact with the anode rod and limits the force that the anode rod exerts on the sensor assembly. With the sensor assembly in contact with the anode rod, measurements can be performed on the surface of the anode rod 20. As an example, a voltage drop can be measured between the first voltage sensor 111 and the second voltage sensor 112, from which a current at the anode rod 20 can be determined, and a temperature can be measured using the temperature sensor 115. A sensor body antenna 117 transmits data wirelessly to a receiver (not shown). The receiver may be located at the cell or pot of the anode or may be located at another location. The receiver may receive data from a number of measurement apparatus attached to a number of anode clamps 150 within an aluminium smelter. There may also be additional components (not shown) of a sensor and data system which power and / or control the operation of the sensors 111, 112 and 115 and the sensor body antenna 117. These additional components may be attached to the sensor body 113, and / or at least some may be mounted or housed to other parts of the mounting arrangement 120 or anode clamp to avoid making the sensor assembly bulky, or to protect the components from exposure to extreme conditions. Figures 4A and 4B shows the anode clamp 150 opened and the sensor assembly 110 released from the surface of the anode rod 20. The unclamped condition allows for the vertical height of the anode rod to be adjusted and also allows for the anode rod 20 to be replaced. The measurement apparatus 100, being mechanically coupled to a movable part of the clamp, is moved during opening of the clamp, and the sensor assembly 110 is released from the surface of the anode rod 20. A user or external operator or controller can operate the anode clamp 150 by rotating the adjustment nut 171. As the outer portions 156 and 161 are moved towards each other, they will also be rotated in a direction away from the anode rod 20, reducing the force imparted by the sensor assembly 110 on the anode rod, and ultimately bringing the sensor assembly out of contact with the anode rod 20. However, in alternative embodiments the sensor assembly 110 may maintain contact with the anode rod in the unclamped but may be effectively released from the anode rod 20 through a reduction in the force that is applied to the sensor assembly 110 by the biasing mechanisms. The force applied by the biasing mechanisms may be reduced sufficiently to allow the vertical movement or replacement of the anode rod 20, without causing damage to the measuring apparatus 100. The invention has the advantage that the measurement apparatus 100 may be automatically released from the surface of the anode rod 20 when the anode rod 20 is repositioned or replaced by operating the anode clamp. Damage to the measurement apparatus 100, such as to the sensors 111, 112 and 115, is minimised or reduced during the process of anode rod 20 repositioning or replacement, without an additional active step of removing or disconnecting the sensors, as required in the prior art. The invention makes use of the existing anode clamp 150, to mount and dismount the measurement apparatus 100. By using the tightening and loosening of the anode clamp 150 to release the measurement apparatus 100 from the anode rod 20, no additional user intervention is required. In addition, as the position of the sensor assembly 110 and sensors 111, 112 and 115 is fixed relative to the anode clamp 150, the sensors 111, 112 and 115 will have a set position, even after the re-positioning or replacement of the anode rods 20. Whilst in the described embodiment, the sensor assembly 110 comprises a first voltage sensor 111, a second voltage sensor 112, and the temperature sensor 115, in alternative embodiments additional or alternative sensors may be included in the sensor assembly 110. For example, sensors could be included allowing thermal flux, vibrations, sound, surface acoustic waves, strain and rotational force, or magnetic fields to be measured. The temperature measurement performed by the temperature sensor 115 may be used to improve the accuracy of the current flow calculation. Alternatively, the temperature may be measured at more than one location on the anode rod 20 in order to further improve the accuracy of the current flow calculation, to identify thermal deviations from anode rod 20 malfunctions, or to calculate thermal flux in the anode rod 20. Figures 5A and 5B illustrate a measurement apparatus 200 according to an alternative embodiment of the invention. The measurement apparatus 200 is similar to the measurement apparatus 100, with like features indicated by like reference numerals incremented by 100. In common with measurement apparatus 100, measurement apparatus 200 comprises a mounting arrangement 220 which comprises a first arm 225 and a second arm 230. The first arm 225 is connected to the sensor body 213 at one end and is connected to a first connector 235 at its other end. In contrast to measurement apparatus 100, the second mounting arm 230 connects to the first mounting arm 225 at the end of the first mounting arm 225, and the first mounting arm connects to the sensor body 213. The second mounting arm 230 comprises a first mounting arm portion 230a and a second mounting arm portion 230b. Furthermore, in contrast to the measurement apparatus 100, the first mounting arm 225 comprises a bracing arm 300 and the first connector 235 has an open shape which defines a bearing surface 310. The first mounting arm 225 may additionally comprise a spring or a biasing mechanism (not shown) to provide an outward force on the bracing arm 300. As with the measurement apparatus 100, there may also be additional components (not shown) to power and / or control the operation of the sensors 111, 112 and 115 and the sensor body antenna 117. These additional components may be attached to the sensor body 213 the mounting arrangement 220, such as on the first connector 235, or may be connected to the anode clamp 150. Figure 6A and 6B illustrate the measurement apparatus 200 connected to the anode clamp 150. The measurement apparatus 200 is connected to the anode clamp 150 via the first connector 235 and the second connector 240. The first connector 235 connects to the second clamp member 160 via the bearing surface 310. The second connector 240 connects to the inner portion 162 of the second clamp member 160. Figure 6A illustrates the measurement apparatus 200 in use in a measurement position and Figure 6B illustrates the measurement apparatus 200 in in an unclamped condition. In the measurement position the anode clamp 150 is clamped to the anode rod 20 and supports the weight of the anode rod 20, and the sensors 211, 212 and 215 of the sensor assembly 210 are in contact with the anode rod 20 such that measurements can be performed on the surface of the anode rod 20. In the unclamped condition, the anode clamp 150 and the sensor assembly 210 are released from the surface of the anode rod 20, allowing for the movement or replacement of the anode rod 20. In common with measurement apparatus 100, the measurement apparatus 200 is brought into the measurement position or released condition through the operation of the anode clamp 150, through the rotation of the adjustment nut 171. In the measurement position of the measurement apparatus 200, a force provided by the spring or biasing mechanism (not shown) on the bracing arm 300 facilitates maintaining contact with an appropriate contact force between the sensors of the sensor assembly 210 and the surface of the anode rod 20. In addition, the biasing mechanism provides a limit to the force that can be applied to the sensors 211,212 and 215 in the measurement position, and allows for variation in distance between the clamp and the anode rod surface. Figure 7A and 7B illustrate a measurement apparatus 400 according to an alternative embodiment of the invention. The measurement apparatus 400 is similar to the measurement apparatus 100, with like features indicated by like reference numerals incremented by 300. In common with measurement apparatus 100 and 200, measurement apparatus 400 comprises a mounting arrangement 420 and a sensor assembly 410. However, the mounting arrangement 420 has a number of differences to the mounting arrangements 120 and 220. In particular, the mounting arrangement 420 comprises a first mounting member 510 and a second mounting member 520, connected via a sliding hinge joint 515 comprising an upper hinge and a lower hinge. The first mounting member 510 is connected to an end portion of the sensor body 413 and the second mounting member 520 connects the mounting arrangement 420 to the anode clamp 150. A torsion spring 525 is connected between a surface of the hinge joint 515 and an upper surface of the sensor body 413, and tends to extend the sliding hinge joint. In an alternative embodiment, the torsion spring 525 may be a coil spring or another appropriate biasing mechanism. The torsion spring 525 may be configured so that it is partly compressed when the hinge joint is fully extended, so that it therefore always exerts a torque force on the sensor body 413. Figure 8A and 8B illustrate the measurement apparatus 400 connected to the anode clamp 150. In contrast to the measurement apparatus 100 and the measurement apparatus 200, the measurement apparatus 400 is not connected to the outer portion 161 of the second clamp member 160, or in the case of apparatus 200 is not connected at a location nearby to the outer potion 161 of the second clamp member 160. In contrast, the measurement apparatus 400 is connected to the anode clamp 150 by coupling of the upper hinge joint to the second mounting member 520 at the inner portion 162 of the second clamp member 160. Figure 8A illustrates the measurement apparatus 400 in use in a measurement position and Figure 8B illustrates the measurement apparatus 400 is use in an unclamped condition. In the measurement position the anode clamp 150 supports the weight of the anode rod 20, and the sensors 411,412 and 415 are in contact with the anode rod 20, such that measurements can be performed on the surface of the anode rod 20. In the unclamped condition, the sensor assembly 410 is released from the surface of the anode rod 20, allowing for the movement or replacement of the anode rod 20. In common with measurement apparatus 100, the measurement apparatus 400 is brought between measurement and release conditions through the operation of the anode clamp 150, through the rotation of the adjustment nut 171. The anode clamp 150 and the sensor assembly 410 are brought into contact with the anode rod 20 through the movement of the inner portions 157 and 162 of the first clamp member 155 and the second clamp member 160 in a direction towards the surface of the anode rod 20. The anode clamp 150 and the sensor assembly 410 are released from the anode rod 20 through the movement of the inner portions 157 and 162 in a direction away from the surface of the anode rod 20. In the measurement position, the upper hinge joint has been brought towards the lower hinge joint and the torsion spring 525 has been compressed between the force from the clamp and the force from the anode rod surface acting through the sensor assembly. The torsion spring applies a force to the sensor assembly 410 in the measurement position that presses the sensor assembly 410 towards the anode rod 20. As the clamp moves towards an unclamped condition, the upper hinge joint moves away from the lower hinge joint to reduce the force applied by the torsion spring to the anode rod via the sensor assembly. The sensor assembly 410 is released from the anode rod 20 through the operation of the anode clamp 150. As shown in Figure 8B, in the unclamped condition the sensor assembly 410 is released from the anode rod 20 such that the sensor assembly 410 is no longer in contact with the anode rod. However, as previously described for earlier embodiments, the sensor assembly 410 may maintain contact with the anode rod 20 in the unclamped condition but may be effectively released from the anode rod 20 through a reduction in the force that is applied to the sensor assembly 410 by the torsion spring 525. This reduction in force will occur as the second clamp inner portion 162 moves in a direction away from the anode rod 20 during operation of the anode clamp 150. The invention provides a measurement apparatus for an aluminium production system. The measurement apparatus comprises a sensor assembly configured to contact an anode rod of the aluminium production system and a mounting arrangement configured to mechanically attach the sensor assembly to an anode rod clamp of the aluminium production system. The mounting arrangement is configured so that the sensor assembly is in contact with the anode rod at a measurement position when the anode clamp is clamped onto the anode rod to support the anode rod in the aluminium production system. The mounting arrangement is configured so that the sensor assembly is released from the measurement position when the anode clamp is in an unclamped condition in which the anode clamp does not support the anode rod. The invention makes use of an already present mechanical component in aluminium smelters, the anode clamp, to mount the measurement apparatus. Furthermore, the invention makes use of a process already occurring - the tightening and loosening of the anode clamp - to bring the measurement apparatus into and out of contact with the anode rod. Therefore, this provides a cost-effective solution for mounting a measurement apparatus, and for bringing the measurement apparatus into and out of contact with the anode rod, which minimises the need to introduce additional mechanical or electrical components or mechanisms. As the invention makes use of the automated tightening and loosening of the anode clamp, manual operations are not required to reposition the measurement apparatus when the anode rod is re-positioned or replaced. This therefore removes the need for this costly and potentially dangerous task. Furthermore, as the position of the sensor assembly and sensors is positioned relative to the anode clamp, the position of which is at a set height within in aluminium smelter, the sensors will have a set position, even after the re-positioning or replacement of the anode rods. This has the benefit that recalibration of the sensor position is typically not required following the re-positioning or replacement of the anode rods, providing improved accuracy in the measurements that are obtained. The invention is advantageous as it provides a method for performing measurements on an anode rod which does not require that sensors are integrated into the anode rod, which is an approach commonly seen in the field. It is beneficial to avoid such approaches as these approaches require that costly modifications are made to the anode, such as inserting internal wiring and milling of the anode. Furthermore, in industrial settings there are commonly many anode rods in stock, and therefore where sensors are integrated into the anode rods, there will be a lot of sensors not giving any valuable data. In addition, it is beneficial to have the measurement apparatus separate to the anode rod as the anode rod has to go through harsh environments during production and during the replacement process. The invention facilitates measuring individual anode currents across the large number of anodes typically found in aluminium plants by providing an apparatus and method with reduced complexity, which removes manual tasks, and lowers investment and operational costs in comparison with known techniques. The invention provides a method for determining individual anode current in real time. Having a method which allows for the regular determination of the individual anode current may provide early detection of the onset of the anode effect and other negative events such as anode cracking or dropping of the carbon anode. As such, this facilitates for early mitigating actions to be taken, reducing or eliminating issues associated with the anode effect, leading to higher production output, reduced electricity consumption, reduced anode wear and reduced greenhouse gas emissions. Furthermore, having a method which allows for the regular determination of the individual anode current facilitates improved control of the current distribution through the anode and cell. This can contribute to increased energy efficiency in the cell and anode, an improved quality in the aluminium that is produced, an extended lifetime of the anode and cell, and the ability to use increased currents and benefit from associated higher yields of aluminium. Various modifications to the above-described embodiments may be made within the scope of the invention.

Claims

251 Claims23 1. A measurement apparatus for an aluminium production system, the measurement4 apparatus comprising:5 a sensor assembly configured to contact an anode rod of the aluminium production6 system; and7 a mounting arrangement configured to mechanically attach the sensor assembly to8 an anode rod clamp, the anode rod clamp being removably connected to an anode9 beam of the aluminium production system;10 wherein the mounting arrangement is configured so that the sensor assembly is in11 contact with the anode rod at a measurement position when the anode clamp is12 clamped onto the anode rod to support the anode rod in the aluminium production13 system, and the mounting arrangement is configured so that the sensor assembly is14 released from the measurement position when the anode clamp is in an unclamped15 condition in which the anode clamp does not support the anode rod.1617 2. The measurement apparatus according to claim 1, configured such that operating18 the anode clamp to clamp the anode rod brings the sensor assembly into the19 measurement position in contact with the anode rod.2021 3. The measurement apparatus according to claim 1 or claim 2, configured such that22 loosening of the anode clamp enables the sensor assembly to be brought out of a23 measurement position on the anode rod.2425 4. The measurement apparatus according to any preceding claim, configured such that26 loosening of the anode clamp brings the sensor assembly out of a measurement27 position on the anode rod.2829 5. The measurement apparatus according to any of claims 1 to 3, configured such that30 loosening of the anode clamp reduces a contact force between the sensor assembly31 and the anode rod in the measurement position.3233 6. The measurement apparatus according to any preceding claim, wherein the34 mounting arrangement is configured to transfer a force from a movable part of the35 anode clamp to the sensor assembly.

7. The measurement apparatus according to any preceding claim, wherein themounting arrangement is at least partially compliant in a direction between the anode clamp and the sensor assembly.

8. The measurement apparatus according to any preceding claim, comprising a biasing mechanism configured to bias the sensor assembly towards the anode rod.

9. The measurement apparatus according to claim 8, wherein the mounting arrangement is configured to transfer a force from a movable part of the anode clamp to the sensor assembly via the biasing mechanism.

10. The measurement apparatus according to any preceding claim, wherein the mounting arrangement comprises an arm disposed between the anode clamp and the sensor assembly.

11. The measurement apparatus according to claim 10, wherein the force acts substantially longitudinally through the arm.

12. The measurement apparatus according to claim 10 or claim 11, wherein the arm is longitudinally extendable and is biased towards an extended condition.

13. The measurement apparatus according to claim 10, wherein the force acts substantially as a turning moment on the arm.

14. The measurement apparatus according to claim 13, wherein the arm is connected to the anode clamp by an extendable hinge joint, and is biased towards an extended condition.

15. The measurement apparatus according to any preceding claim, wherein the sensor assembly comprises a body and at least one sensor on or in the body, the at least one sensor configured for measuring or determining at least one of thermal flux, voltage drop, current, current flow, temperature, vibrations, sound, surface acoustic waves, strain, rotational force, and / or magnetic fields.

16. The measurement apparatus according to any preceding claim, wherein the sensor assembly comprises a first upper voltage sensor and a second lower voltage sensor.

17. The measurement apparatus according to any preceding claim, wherein the sensor assembly comprises at least one temperature sensor.

18. The measurement apparatus according to any preceding claim, further comprising an electronics package which powers and / or controls the sensor assembly.

19. The measurement apparatus according to claim 18, wherein the electronics package is configured to harvest energy from the surrounding environment.

20. The measurement apparatus according to any preceding claim, wherein the measurement apparatus is configured to transmit data wirelessly to a receiver.

21. A method of performing measurements on an anode rod used in the production of aluminium, using a measurement apparatus of any preceding claim.

22. A method of installing a measurement apparatus in an aluminium production system, the method comprising:mechanically attaching a mounting arrangement and sensor assembly to an anode rod clamp of the aluminium production system;clamping the anode rod clamp onto an anode rod of the aluminium production system so that the anode rod is supported by the clamp;wherein clamping the anode rod clamp brings the sensor assembly into contact with the anode rod at a measurement position.

23. A method of configuring an aluminium production system, the method comprising installing a measurement apparatus in an aluminium production system according to the method of claim 22;opening the anode rod clamp so that the anode rod is not supported by the clamp; wherein opening the anode rod clamp releases the sensor assembly from the anode rod;changing the vertical position of the anode rod relative to the anode clamp;28 10 25clamping the anode rod clamp onto an anode rod of the aluminium production system so that the anode rod is supported by the clamp in the changed vertical position;wherein clamping the anode rod clamp brings the sensor assembly into contact with the anode rod in the changed vertical position.

24. A method of performing measurements on an anode rod during the production of aluminium, the method comprising configuring an aluminium production system according to claim 23, and measuring or determining at least one of voltage, current, temperature, thermal flux, vibration, sound, surface acoustic waves, strain, rotational force, or magnetic fields using the measurement apparatus.

25. An aluminium production system, the aluminium production system comprising: an anode rod;an anode rod clamp removably connected to an anode beam;a sensor assembly configured to contact the anode rod;a mounting arrangement mechanically attaching the sensor assembly to the anode rod clamp;- wherein the sensor assembly is in contact with the anode rod when the anode clamp is in a first condition in which it is clamped onto the anode rod and supports the anode rod, and the sensor assembly is released from the anode rod when the anode clamp is in a second condition in which the anode clamp does not support the anode rod.s

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