STARprobe TM. A new technology allowing simultaneous measurements of four cryolitic bath properties in only 5 minutes:

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1 A N e w T e c h n o l o g y A l l o w i n g S i m u l t a n e o u s M e a s u r e m e n t s o f F o u r C r y o l i t i c B a t h P r o p e r t i e s i n O n l y 5 M i n u t e s STARprobe TM

2 STARprobe TM A new technology allowing simultaneous measurements of four cryolitic bath properties in only 5 minutes: 2

3 Introduction Measurements of bath temperature and bath composition are critical to potroom operations. Temperature measurements and bath sampling for chemical analysis are carried out separately: STARprobe TM regroups conventional procedures of temperature measurement and bath sampling/analysis. STARprobe TM was specifically developed for potroom use to provide all critical REAL TIME information necessary for effective pot control. 3

4 How the STARprobe TM Works STARprobe TM uses Differential Thermal Analysis (DTA). This method measures the temperature difference of the sample versus a reference, caused by thermal events in a material. When a cryolitic melt is cooled from liquid state to a solid state: It goes through several phase transformation/changes. The phase changes are accompanied by specific heat releases (Hi). The amount of heat released can be directly related to the composition of the melt. DTA = Sample Thermocouple 1 ( TC1 ) - Reference Thermocouple 2 ( TC2 ) 4

5 Temperature, C Probe tip is the core of STARprobe TM and consists of: Patented design with reliable measurements based on DTA principle. Specified type K T/C offering accurate temperature (better than ± 0.4%), fast response time and, most important of all, able to withstand molten bath for multiple uses Temperature, sample Temperature, reference 5

6 Delt T (TC1-TC2) Cryolite ratio Bath ratio (%XS AlF 3 ): Cryolite ratio is fundamentally a function of the cooling curve characteristics. The differential temperature for cryolite phase (peak 1) increases, and that for chiolite phase (peak 2) decreases when bath ratio increases Peak Peak Tliq Bath Temperature, C Ra 1.00 Ra 1.10 Ra 1.20 Ra

7 STARprobe TM Components 1) Reusable probe tip 2) Lance and stand assembly 3) Electronic probe head data acquisition, system monitoring and wireless communication 4) Interface computer and software 5) Wheeled cart including power supply

8 1) Reusable probe tip 8

9 2) Probe lance and stand assembly 9

10 10 Tablet PC In measurement A probe in pot

11 3) Probe head Physically connected to probe tip, collects temperature data from probe. Transmits (via wireless radio) data to tablet PC. Receives (via wireless radio) instructions from tablet PC. Displays status of measuring sequence. 11

12 4) Tablet PC (the brain) Controls two probe heads. Collects analysis data. Transmits results to server (optional). 12

13 5) The cart Stand for tablet, probes and tips Power supply by batteries

14 Using the STARprobe TM Designed to be used by potroom operators. One operator uses the tablet PC and 2 probe heads simultaneously. Simple sequence to perform the measurement: Insert probe in molten bath and wait for temperature to equilibrate. Remove probe from molten bath and allow to cool. Reheat probe for cleaning. The probe is reused for the next measurement. 5 minutes average per measurement. 14

15 Video 15 Tablet PC In measurement A probe in pot

16 STARprobe TM Based Pot Control Benefits associated to the use of STARprobe TM % current efficiency 35 mv voltage savings 5% AlF 3 savings Labor savings for sampling/analysis Improved understanding by operators 16

17 Conclusion STARprobe TM allows real-time measurement of Superheat, Temperature, Alumina concentration and Ratio (excess AlF 3 ). Measurements have shown to be equivalent for all four parameters. STARprobe TM has been successfully deployed in most of Alcoa s plants. Higher pot performance reduced pot power consumption, reduced chemical consumption, and increased current efficiency has been achieved by using STARprobe TM and the integrated STARprobe TM based pot control. 17

18 QUESTIONS? 18