Last week, we discussed conductivity and how high levels can contribute to reduced slurry health. Now, we will discuss potential causes and what can be done about it.
Some common causes of high conductivity are:
♣ Increase in the number and strength of ions
♣ Bacteria
♣ Additions to the slurry
Most colloidal silica used in this industry is sodium stabilized. Sodium has a lower ionic strength than Iron, Calcium or Aluminum. As the concentration of ions increases in the slurry, especially higher strength ions, conductivity will increase.
One source of these higher strength ions is refractory flours. Some refractories have a high level of impurities that will leach out into the slurry. When this happens, the conductivity will rise and the pH will fall. The lower the slurry turnover rate, the greater the risk for slurry instability.
One way to remove these impurities is through the use of a rare earth magnet. There are a number of ways to install these magnets but, whichever method you choose, make sure they are easily accessible for cleaning. If you don’t clean the magnet on a regular basis, you will not reap the benefits. Start by checking it daily. As the build-up on the magnet decreases, the cleaning frequency can be reduced.
The presence of microbiological activity can also cause slurry conductivity to rise and pH to fall. If you experience this phenomenon, check for bacteria. If detected, treat with biocide, ammonium hydroxide or bleach.
However, using bleach to treat bacteria can have some other consequences including increased slurry conductivity, oxidation of polymers and reduction in shell hot strength. Do some investigation to identify the root cause of the bacteria. And then establish a regimen for preventing growth of bacteria in the slurries.
The unfortunate truth is there is no direct way to adjust conductivity, so it is important to take the appropriate steps to prevent slurry conductivity from climbing in the first place. But by following the tips above, you have the necessary tools to maintain conductivity levels in the optimal range.