Anode Life in the Laboratory

The laboratory layout is sketched in Fig. 15.4 The power supply is a 3-phase silicon controlled rectifier, SCR, controlled supply capable of delivering 200 A at 50 V. 

HF is supplied from a 100-Jb cylinder on an electronic scale which has a 10-g resolution. The cylinder is heated to 37°C with a band heater with two integral temperature sensors, one for control and an independent one for shutdown in case of overheating. From the cylinder, the HF passes through a throttling valve, a backup shutdown valve, and a control valve. A continuous nitrogen flow (actually the cathode reference flow) was added downstream of the control valve. 

The burner is operated on natural gas and air in a fuel-rich mode. Fluorine reacts with excess fuel to form HF and CF4. All of the air that goes through the containment cell (hood) is scrubbed with caustic before being released. (We considered destroying the fluorine by reaction with caustic, but our calculations suggested that this reaction was too slow.) 

The temperature control fluid is a 20% solution of commercial antifreeze in water. The fluid reservoir is a 20-liter insulated reservoir the fluid is kept above 60°C. Fluid from the reservoir is pumped through an electric heater to the jacket the fluid is heated to maintain the electrolyte temperature at 90°C. 

System control and data acquisition are done with a personal computer using Paragon software. About 150 input and output modules were used for the two laboratory cells. This is expensive and may seem excessive, but a lot of the inputs and outputs are used for safety purposes so that the cell can operate unattended 24 hr a day, 7 days a week to get good long-term data. 

---