Experiment 7: Pulsing in a Stock Solution of Lime

Overview

The purpose of this experiment was to test pulsing lime into the two apparatuses. Because both apparatuses fail after a shorter time than desired, it was hypothesized that the lime initially added to the apparatus (100 grams) eventually reached a point where it would no longer properly dissolve and raise the pH. Thus, more lime was needed as the experiment progressed. However, adding 100 grams each time would severely overwhelm the system. The following calculations were performed to determine the appropriate amount of lime that needed to be pulsed in every 6 hours:
INSERT MATHCAD CALCULATIONS HERE

Procedure

For the apparatuses, the same procedure was followed as outlined in the materials and methods page. Two 100 gram samples of lime slurry were prepared by blending them in the blender on the "liquefy" setting. These were then fed into each apparatus via the vertical column. The water used was tap water and A1 had a flow rate of 30 mL/min and A2 had a flow rate of 40 mL/min.

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For this experiment, the lime slurry in the bucket was not blended using the blender but rather using the mixer. The mixer stayed in the bucket throughout the course of the experiment and Process Controller was configured to turn the mixer on for two minutes before the pump was configured to run. Thus, the stock solution would mix for two minutes and then be pumped for one minute at 380 mL/min. This repeated every six hours.

Results and Discussion

As the first pulsing experiment, the apparatuses behaved approximately as expected. However, neither apparatus ever reached saturation (pH = 12.6) which could have been due to a number of things, including on-going difficulties with the pH probes.

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