Experiment 8: Formalizing Blender Methods + Continued Pulsing

Overview

The purpose of this experiment was to develop a more consistent method for preparing and blending the lime slurry that is added to the vertical columns and to the stock concentration. The desired outcome of this experiment was to provide insight into the importance of lime particle size on the performance of the experiment.

Procedure

An almost identical procedure was followed for this experiment as in Experiment 7. A lime slurry of 100 grams of lime plus 1 liter of tap water was prepared for each apparatus, as well as a lime slurry of 124.5 grams of lime prepared in 1 liter of tap water and then diluted further with 14 additional liters of water for the stock concentration. The difference between the two experiments is in the use of the blender to prepare the slurries.
For the 100 grams of lime that were to be fed into the vertical column, the blender was used for 5 minutes on "liquefy". Unfortunately, at the end of the 5-minute period for the second 100 gram slurry, the blender overheated and became inoperable. Therefore, the mixer had to be used to blend the remaining lime slurry needed for the stock concentration. It is suspected that the mixer does not provide the same particle uniformity that the blender does.

Results and Discussion

Despite the consistency in blender methods, the experiment performed approximately the same as it did in Experiment 7. Again, the 2.5 cm tube settler apparatus reached a pH of slightly greater than 12 while the 5 cm tube settler remained closer to 11.6. After approximately 4 hours, the 5 cm tube settler begins to steadily drop off. It then continues a pattern of steady decline followed by a spike every 6 hours, at the time of the lime pulse. The 2.5 cm tube settler apparatus doesn't drop below a pH of 12 until approximately 22 hours into the experiment. However, it then follows the same decreasing rise and fall curve with each lime pulse.
 
                                                                                                                                        Figure 1 - Experiment 8
The purpose of this experiment was to continue pulsing in a lime stock solution but to improve the uniformity of the slurries by using the same blender procedure for each slurry.